i

THE COPPERBELT UNIVERSITY

SCHOOL OF TECHNOLOGY

CHEMICAL ENGINEERING DEPARTMENT

HYDROCHLORIC ACID PLANT

DESIGN

i

THE COPPERBELT UNIVERSITY

SCHOOL OF TECHNOLOGY

CHEMICAL ENGINEERING DEPARTMENT

HYDROCHLORIC ACID PLANT DESIGN

PREPARED BY:

1. MUTAMBANSHIKU LYASHI ARREN 98715747

2. ROMANSHI EMMY

3. SHIMOONJE HANS K 99229633

4. SICHALI RONNY KAPYELA 98611062

SUPERVISED BY:

Mr J.J. KANYEMBO

This paper is prepared in partial fulfilment leading to the award of a Bachelor of

Engineering (BEng) in Chemical Engineering.

i

LETTER OF TRANSMITTAL

The projects co-coordinator,

Chemical Engineering department,

Copperbelt University,

P.O BOX 21692,

Kitwe.

25th November 2005

Dear Sir,

RE: SUBMISSION OF DESIGN PROJECT.

We refer you to your request for a report on the design of a Hydrochloric acid plant as partial fulfillment for the award of a degree in Chemical Engineering.

We submit this report with the view that it meets the standards necessary for the assessment of this course (CE-500).

It is our sincere hope that this report will meet your expectations.

Yours faithfully,

Sichali Ronny Kapyela .................................................

Mutambanshiku Lyashi Arren ...............................................

Romanshi Emmy .................................................

Shimoonje Hans ...................................................

ii

DECLARATION

I Sichali Ronny having read the University Regulations on cheating plagiarism,

do by here declare that to the best of my knowledge the work contained in this

presentation is of my own working and that all material used print, electronic and

verbal have been dually acknowledged.

The examiners cannot, however, be held responsible for the views expressed,

nor the factual accuracy of the contents.

Sichali Ronny Kapyela

……………………………………………..

Mr J.J Kanyembo

(Supervisor)

…………………………………………………….

iii

DECLARATION

I Mutambanshiku Lyashi Arren having read the University Regulations on

cheating plagiarism, do by here declare that to the best of my knowledge the

work contained in this presentation is of my own working and that all material

used print, electronic and verbal have been dually acknowledged.

The examiners cannot, however, be held responsible for the views expressed,

nor the factual accuracy of the contents.

Mutambanshiku Lyashi Arren

……………………………………………..

Mr J.J Kanyembo

(Supervisor)

…………………………………………………….

iv

DECLARATION

I Romanshi Emmy having read the University Regulations on cheating

plagiarism, do by here declare that to the best of my knowledge the work

contained in this presentation is of my own working and that all material used

print, electronic and verbal have been dually acknowledged.

The examiners cannot, however, be held responsible for the views expressed,

nor the factual accuracy of the contents.

Romanshi Emmy

……………………………………………..

Mr J.J Kanyembo

(Supervisor)

…………………………………………………….

v

DECLARATION

I Shimoonje Hans having read the University Regulations on cheating plagiarism,

do by here declare that to the best of my knowledge the work contained in this

presentation is of my own working and that all material used print, electronic and

verbal have been dually acknowledged.

The examiners cannot, however, be held responsible for the views expressed,

nor the factual accuracy of the contents.

Shimoonje Hans

……………………………………………..

Mr J.J Kanyembo

(Supervisor)

…………………………………………………….

vi

ACKNOWLEDMENTS

RONNY SICHALI’S ACKNOWLEDGEMENT

I would like to take this opportunity to thank the almighty Jehovah GOD, without

who non-this would have been possible.

To my project supervisor, Mr J.J Kanyembo, for the guidance and patience

during the duration of this project, to you sir, I say thank you very much.

To my mum, Karen Sichali-Sichinga for the encouragement and believing in me.

Thanks a million, love you.

I would also like to thank the Sichali family for moral and financial support. And to

my sponsors, GRZ through the bursaries department.

A big thank you to some very good friends; Kabuswe Bwalya, Simon Bwalya and

family, Elias, Mr and Mrs C Bwembya, Lumbwa Kafwimbi, and to all my friends

thanks for being there.

MUTAMBANSHIKU’S ACKNOWLEDGEMENT

My thanks to the project supervisor Mr.J.J.Kanyembo and staff in the Chemical

Engineering Department. Thank you to the project team; Ronny, Hans, Emmie

and myself for the intellectual and fruitful arguments. My thanks go to my

classmates whose suggestions added value to this work.

My special thanks go to my family the driving force to this mission.

My special, special thanks to Jehovah God for the vision that He rekindles each new

day.

SHIMOONJE HANS’ ACKNOWLEDGEMENTS Firstly I would like to give thanks to the almighty God for blessing me with my

abilities and for carrying me this far.

I would also like to give passionate acknowledgements firstly to my mother, Mrs.

R.J Shimoonje, for her unconditional and undying support and love in all my

endeavors, and to my late father, Mr. J.M Shimoonje for laying a solid

vii

educational foundation on my life and for all the inspirational and motivational

words that I still carry deep within me.

To my brothers Hector, Shachillu and Mbaze, thank you for your love, it keeps

me going. To my sister Trina thanks for your love and financial support, I will

never forget!

To my group members, Arren, Ronny and Issa, your criticism has added to my

intellectual growth and working with you has opened my mind to new ideas, to

you I say thank you and job well done.

To my friends T.K, Martin, Yanda, Gilbert, Davies Z,Goli, Luke and Maimbo, the

memories we share I hold close to my heart, thank you for everything.

Last but not least , to our supervisor Mr. J.J Kanyembo thank you for all the

guidance and criticism which played a key role in shaping this report.

viii

ABSTRACT

The aim of this project is to design a plant that will be producing 150 tons a day

of Hydrochloric acid, with a quality of 20 ºBe´. Given Sodium Chloride NaCl

(Common salt) and Sulphuric Acid H2SO4 of 60 ºBe´ quality as raw materials.

This will include determining whether the project is viable or not through costing

and equipment sizing.

As the country currently has no HCl plant this project is worth carrying out as it

may provide not only local source for HCl required in Chemical and allied

industries, but also employment for the local people.

The production will be carried though the reacting of raw materials given, by heating

them to a required temperature and subsequent absorption of the gas

ix

TABLE OF CONTENT

Item age number

Letter of transmittal .............. I

Declarations .............. ii

Acknowledgments .............. vi

Abstract .......... vii

Table of contents ........... ix

List of tables ........... xii

List of figures and diagrams ............ xii

Chapter one

1.0 Introduction .............. 1

1.1 Process of design .............. 2

1.2 Uses of HCl .............. 4

Chapter two

2.0 Reactor (furnace design) ................... 5

2.1 Design objectives .................... 6

2.2 Process design ................. 6

2.2.1 Physical properties .................. 6

2.2.2 Process description .................. 8

2.3 Material balance ................ 10

2.3.1 Component balance .................. 11

2.4 Muffle furnace .................. 12

2.4.1 Operating conditions ...................... 12

2.4.2 Reaction kinetics .................... 12

2.5 Energy balances around the furnace ................. 16

2.5.1 Heat of reactions conversion for furnace duty..... 16

2.5.2 Furnace duty and fuel quantity .................... 17

2.5.3 Air and fuel analysis .................. 19

x

item page number

2.6 Selection of fuel .................... 20

2.7 Type of fuel ................... 21

2.8 Process control .................. 22

2.9 Mechanical design (muffle furnace) .................. 22

2.10 Costing of muffle furnace ................. 23

Chapter three

3.0 cooling of hydrogen chloride gas .................. 25

3.1 Introduction .................... 26

3.1.1 Advantages of the Trombone Cooler………….. 27

3.1.2 Industrial Applications ………….. 28

3.2 Process design ………… 28

3.2.1 Heat Flow through A Trombone Cooler ………… 28

3.2.2 Calculation of Outside Film Coefficient ………. 29

3.2.3 Heat load ……….. 30

3.2.4 Pressure drop …………. 35

3.3 Summary of process design …………. 36

3.4 Mechanical design ………….. 37

3.5 Unit Costing of Cooler …………… 38

Chapter four

4.0 Absorption column design …………… 40

4.1 Introduction …………… 41

4.2 Process Design …………… 43

4.2.1 Column diameter …………… 43

4.2.2 Selection of plate type …………… 43

4.3 Material balance ……………. 45

4.4 Equation of the operating line ……………. 47

4.4.1 Column diameter Calculation …………….. 50

xi

item age number

4.5 Unit Costing and Evaluation ……………. 53

Chapter five

5.0 site selection and safety ……………. 55

5.1 Occurrences of raw materials …………… 55

5.2 Site selection …………… 55

5.4 Safety factors …………… 56

Chapter six

6.0 project evaluation and cost ................. 58

6.1 Introduction ............... 58

6.2 Fixed and installation cost ………….. 59

6.2.1 Physical plant cost (PPC) …………. 60

6.2.2 Fixed capital cost (FCC) ………….. 60

6.2.3 Cost (expenditure) ………….. 60

6.2.4 Income per year ………….. 60

Conclusion …………. 64

Recommendations ………….. 67

Reference ……………. 69

Appendix …………… 71

xii

List of tables

Item Page number

Properties and composition of fuel selected table 2.1 18

Fuel air combustion analysis table 2.2 18

Fuel air combustion analysis table 2.3 19

Hydrocarbon fuel cost table 2.4 21

Furnace dimensions summary table 2.5 23

Solubility of HCl in water at 760mmHg table 4.1 41

Mechanical description table 4.2 52

Summary table cost evaluation table 6.1 61

Process design summary table 6.2 62

Mechanical design and costs summary table 6.3 63

LIST OF FIGURES AND DIAGRAMS

Item page number

Overall material balance diagram 2.1 10

Component material balance around the furnace fig 2.1 11

Energy balance around the furnace diagram 2.2 16

Trombone cooler Diagram 3.1 27

Falling film absorber Diagram 4.1 42

Summary of outcome of calculations diagram 4.2 47

Dimensions diagram 4.3 52

1

CHAPTER ONE

1.0 INTRODUCTION

Basilius Valentinus is credited with the production of hydrogen chloride in the

fifteenth century. Its commercial production awaited the Leblanc process for

sodium carbonate in which hydrogen chloride and salt cake are co products. For

a time, the gas was merely vented to the atmosphere, but legislation was

enacted prohibiting its indiscriminate discharge, and thus necessitating its

recovery.

The developed world today describes this era as the information age following

successes of industrialization age; however, this idea has landed the least

developed countries on an unfair field of play. Though the theory of quantum leap

do apply in certain quotas but its not so in other quotas. There are no short cuts

to credible achievement or success as success should have a traceable root thus

has to be worked for. The labor of industrialization has built strong economies in

the developed countries. In particular, the chemical and allied industries have

been described to be the backbone of these successful economies.

The need for industrialization in developing countries and Zambia in particular is

therefore very obvious. Since 1964, Zambian industrialization process has

suffered a lot of set backs because of changes in both the political and economic

development. This has been seen by the closure of many manufacturing

industries and mines in particular. The few existing manufacturing plants driving

the Zambian economy are now being recapitalized by foreign investment and

others are still calling for recapitalization whose operations are far below their

capacity for instance Nitrogen Chemicals of Zambia (NCZ) plant. The status quo

of the industrialization crusade in Zambia is a challenge to the technocrats. The

need for new and viable projects in chemical and allied industries should be

regarded not only as a challenge but as an opportunity for economic growth.

This is report is on a project whose objective is to design a plant to produce 150

tones per day of hydrochloric acid (20oBe’) from sodium chloride and sulphuric

acid (60oBe’).There is no existing plant in Zambia producing hydrochloric acid

2

despite its wide application in both local and regional industries This report will

discuss the plant design of the commercial production of hydrochloric acid.

What is hydrochloric acid? Hydrochloric acid is a solution of hydrogen chloride

(HCl) in water. In industry it is referred to as the spirit of salt where it attracts a

wider application which will be discussed in detail later in the report. There are

four major known processes used commercially to produce hydrogen chloride

and hydrochloric acid. (1) the salt-sulphuric acid process, (2) the Hargreaves

process-salt, sulphur dioxide, air and water-vapor used as reactants, (3)synthetic

process or thermal process- combustion of hydrogen and chloride mixture, (4)the

by-product of organic chlorinations such as methane and benzene.

1.1 Process of design

The design approach to the stated objective will be the salt-sulphuric acid

process because of the specified raw materials in the design question. The HCl

plant will have three (3) main units and service equipment namely the furnace

(reactor), the cooler and the absorber and a compressor as a service unit. The

report will consider discussing each unit as an individual chapter. However, each

unit chapter will adopt the same outline of detailed discussion under the

subsections namely; the process design, mechanical design and unit costing.

The furnace which will be the reactor, the heart of the plant will be discussed in

chapter two. The physical properties of raw materials and products will be

discussed. The process description, the reaction chemistry, the reaction kinetics,

the material and energy balances, the type and analysis of fuel and its choice will

all be discussed in this chapter. Product gas temperature will be expected to

exceed that allowable for absorption. Methods of cooling do vary with

temperature volume of gas to be processed. Chapter three discusses in detail

the suitable type of cooling for the duty. Chapter four discusses in detail the

absorption of HCl gas in the absorber to produce the final product HCl acid.

Hydrogen chloride exerts a destructive action on the mucous membrane and

skin. For instance, exposure to HCl gas or acid may result in chemical burns or

3

dermatitis. Chapter five discusses safety, health and environment (SHE) in detail.

In order for the process to produce the HCl (20oBe’) with consistence, raw

materials and operating conditions must be adhered to. This important aspect

would be possible with a process control in place. Chapter six discusses briefly

the process control and the loop will be indicated on the overall plant design flow

sheet.

The overall plant costing versus the projected sales volume of the product and

the by product to ascertain the viability of the project will be discussed in detail in

chapter seven.

As earlier mentioned HCl attracts a wider industrial application, chapter eight will

discuss in detail its uses. The occurrence of raw materials and factors influencing

site selection will be discussed in detail in chapter nine.

It is the hope of the design project team that the report will have a conceptual

approach to provide workable solution to the design question.

4

1.2 Uses of HCl

A strong inorganic acid used in many industrial processes.

Regeneration of ion exchangers resins.

pH control in food, pharmaceutical, drinking water and neutralizing waste

streams. It is used to control the pH of the process streams.

Pickling is an essential step in metal surface treatment, to remove rust or

iron oxide scale from iron or steel before subsequent processing, such as

extrusion, rolling and galvanizing among many other techniques.

In the production of inorganic compounds such as flocculants and

coagulants useful in wastewater treatment, drinking water production, and

paper production.

Production of organic compounds; vinyl chloride for PVC and other

pharmaceutical products.

Leather processing, household cleaning and building construction.

Diluted to 10% to 12% strength is recommended for household purposes,

mostly cleaning.

Used as a form improver in the production of washing detergents.

5

CHAPTER TWO

2.0 REACTOR (FURNACE DESIGN)

NOMENCLATURE

νs volume of solid, m

h height of reactor,m

d diameter of reactor,m

νNaCl volumetric flow rate of sodium chloride, m3/s

ρNaCl density of sodium chloride, kg/m3

mNaCl mass flow rate of sodium chloride, kg/s

ө uncorrected residence time, s

к correcting factor for particles of nominal diameter 53-63microns

tr corrected residence time for a single particle, s

rA reaction rate for reactant A,

К reaction rate constant

CAO initial concentration of reactant A, kmol/m3

CBO initial concentration of reactant B, kmol/m3

CA final concentration of reactant A, kmol/m3

CB final concentration of reactant B, kmol/m3

νH2SO4 volumetric flow rate of sulphuric acid, m3/s

ρH2SO4 density of sulphuric acid, kg/m3

mH2SO4 mass flow rate of sulphuric acid, kg/s

XA fractional conversion of reactant A

FAO Initial molar flow rate, kmol/s.

τ residence time for the reaction mixture, s

Q heat added by fuel, kW

mf mass flow rate fuel,kg/s

CV calorific value of fuel, MJ/kg

6

2.1 design objective

To design a plant to produce 150 tones per day HCl (20oBe’) from

NaCl and H2SO4 (60oBe’).

This section of the project deals with the sizing of a furnace in which the raw

materials solid sodium chloride and liquid sulphuric acid will react to produce

hydrochloric acid gas the desired product and solid sodium sulphate a by-

product. The sizing will be based on reaction kinetics and the material balance.

The reaction requires a long reaction time and a high temperature. This is

achieved in a muffle furnace with a body of hearth which is heated with oil

burners to 550-660oC.

2.2 process design

ASSUMPTIONS

The process is a steady state flow

The process is endothermic and adiabatic.

The reactor is a non-catalytic CSTR.

The reactants are uniformly mixed.

The system is homogeneous on this basis.

The muffle furnace efficiency is 100%.

2.2.1 Physical Properties

Sulphuric Acid (H2SO4),

Colorless, viscous liquid, specific gravity of 1.835 and boiling point is 270oC. It is

a strong acid.

Feed conditions

Temperature = 20oC

Quality = 60oBe’

Specific gravity = 1.705

Flow rate = 3174.13kg/h

Enthalpy = -887.13kJ/mol

7

Sodium chloride (NaCl)

Ionic crystal, colorless and has closed packed lattices.

Specific gravity, 1.1978.

Specific heat, 12359 Cal/mol.

Lattice energy, 182 Cal/mol.

Solubility in water, 35.7g/100g in water at 0oC, 39.8g/100g in water at 100oC.

Temperature = 50oC

Flow rate = 3789.52kg/h

Enthalpy = -411.38kJ/mol

Product conditions from the furnace

Hydrochloric (HCl) gas,

Colorless or slightly yellow, fuming gas, suffocating odor, very soluble in water; in

alcohol and ether and its non-flammable

Specific gravity = 1.16.

Melting point = -114oC

Boiling point = -85oC

Solubility= 72g/100g in water (20oC)

Temperature = 537oC

Quality = 20oBe’

Specific gravity = 1.16

Flow rate = 2364.4kg/h

Enthalpy = -92.31kJ/mol

Sodium sulphate (Na2SO4) (s)

Temperature = 527oC

Specific gravity =

Flow rate = 4599.24kg/h

8

Enthalpy = -1382.81kJ/mol

Reaction Chemistry

Common salt, sodium chloride and 60oBe’ sulphuric acid react readily to form

hydrogen chloride and the acid sulphate, NaHSO4, at temperatures in the range

of 148.9oC and finally the normal salt, Na2SO4 at 527.8oC. The reactions are

endothermic and are represented as follows:

NaCl (s) + H2SO4 (l) →NaHSO4(s) + HCl (g)

NaCl (s) + NaHSO4(s) →Na2SO4(s) + HCl (g)

2NaCl (s) + H2SO4 (l) →Na2SO4 (s) + 2HCl (g)

2.2.2 Process description

The sodium chloride is ground in a mill, mixed with current of hot compressed air

to 50oC and liquid sulphuric acid are charged through a feed inlet through the

cover of the furnace. This is an externally heated furnace in which the process

stream is heated primarily by radiactive and conductive heat transfer from the

flame and hot gases and is known as Continuous Mechanical Muffle furnace.

This furnace as it is referred to comprise the combustion chamber, the work

space, the stationary circular muffle with a bottom concave pan and a domed

cover separated by a cylindrical mantle or steel column and the plough mounted

on rotating arms fixed to a central under driven shaft.

The combustion chamber is where the fuel/air combustion takes place to produce

combustion gases, CO2 and H2. Hot flue gases are circulated around the muffle.

The work space which is sufficiently tight to keep out contaminants is where the

actual decomposition of the reactants takes place to produce HCl gas and solid

Na2SO4.This is an externally heated furnace in which the process stream is

9

heated primarily by radiative and conductive heat transfer from the flames and

hot gases (combustion gases) above the dome and the pan transmit the required

heat for the reaction by radiation from the cover and by conduction through the

pan (there is no direct contact between the combustion gases and the

reactants/products). The reaction mass is agitated by the ploughs. The rotating

ploughs move the reacting mass toward the periphery of the pan where the salt

cake, sodium sulphate is discharged. Hydrogen chloride (30- 36% by weight) and

air are withdrawn from an outlet in the cover and transferred to coolers and

absorbers.

Combustion chamber temperatures of about 1202oC (1475K) are used for

heating. The reaction between sodium chloride and sulphuric acid takes place at

temperatures ranging 500 to 550oC. The product hydrogen chloride gas is

discharged at temperature 537oC and the byproduct sodium sulphate is

discharged from the hearth at about 527oC.

10

2.3 Material balance

Overall material balance diagram 2.1

OVERALL

MATERIAL BALANCE

2NaCl(s) + H2 SO4 (l) → Na2SO4 (s) + 2HCl (g)

(98) (117) (142) (73)

Na2SO4 (S)

HCl(g)

NaCl (s)

H2SO4 (l)

Basis: 150t/day of HCl (20oBe’)

(150 x 1000) / 24 = 6250kg/h HCl acid

But the amount of HCl gas which is leaving the reactor (furnace) to be absorbed

with water at 95% efficiency is obtained by:

Consider solubility ratio of 0.561: 1 that is HCl/water ratio

(0.561/1.561) x 6250 = 2246.15kg/h HCl to be absorbed in water

Therefore at 95% efficiency of the absorber, this implies that

95% HCl acid leaving the absorber = 2246.15kg/h giving 35.9% by wt HCl acid

100% HCl gas entering the absorber = x

x = (100 x 2246.15)/95 = 2364.4kg/h

This value serves as a basis for the material balance at the reactor

11

2.3.1 component balance

Component material balance around the furnace fig 2.1

NaCl (s)

HCl (gas)

H2SO4(l)

Na2SO4(s)

Basis: 2364.4kg/h of HCl gas

Feed:

H2 SO4 (l): (98/73) x 2364.4 = 3174.13kg/h

NaCl (s): (117/73) x 2364.4 = 3789.52kg/h

Product:

HCl (g): 2364.4kg/h

% wt: [2364.4/ (3174.13 + 3789.52)] x 100 = 33.95%

(It is within the expected value ranging between 30-36% for the

conventional sulphate process)

By-product

Na2SO4 (s): (142/73) x 2364.4 = 4599.24kg/h

12

2.4 Muffle Furnace

2.4.1 Operating Conditions

Combustion chamber:

Temperature = 1202oC

Pressure = 6.8atm

Work space:

Temperature = 500-550oC

Pressure = 1.5atm

Reaction kinetics

Diameter of the reactor = 3m

Height of the reactor = 6m

Average particle diameter of NaCl(s) = 53-63 microns.

Residence time,

2.4.2 Reactor kinetics

H2 SO4 (l) + 2NaCl(s) → Na2SO4 (s) + 2HCl (g)

particlesNaClforfactortimereactiontheiswhere

st

micronsdiameteraverageofparticlesforttimeresidence

sv

s

smm

NaClofratefeedvolumetric

mhd

reactortheinsolidofvolume

r

r

Nacl

s

min42896.0482

,6353 ,

48210788.8

424.0

/ 10 788.88.11973600

52.3789

424.001.04

63

4

,

4

34-

322

13

Since sulphuric acid is more expensive than sodium chloride (natural salt), it is

taken as a limiting reagent and the basis for the calculations in reactor kinetics,

Let A, and B represent sulphuric acid and sodium chloride respectively.

2

BAA CkCr

3

3

/48.205.58

8.1197

/39.1798

1705

42

42

mkmolM

lC

mkmolM

C

NaCl

NaCBo

SOH

SOH

Ao

14

0001665.0

98.010997.8

/10809.4

71.18

10997.8

/10997.8

983600

13.3174

/0001665.0

2984.03742.0005.0

/9277.098.039.17248.202

/3478.098.0139.171

3

34

3

3

3

2

3

3

A

AAo

o

Ao

Ao

o

Ao

Ao

A

A

AAoBoB

AAoA

r

XFV

smV

C

FV

skmolF

smkmolr

r

mkmolXCCC

mkmolXCC

15

The conversion of the reaction is at 0.98

min3.18

10809.4

01.09.52

9.52

0001665.0

98.010997.8

/10809.4

71.18

10997.8

/10997.8

983600

13.3174

/0001665.0

2984.03742.0005.0

/9277.098.039.17248.202

/3478.098.0139.171

4

3

3

34

3

3

3

2

3

3

o

A

AAo

o

Ao

Ao

o

Ao

Ao

A

A

AAoBoB

AAoA

V

V

mV

r

XFV

smV

C

FV

skmolF

F

smkmolr

r

mkmolXCCC

mkmolXCC

16

2.5 Energy balance around the furnace

energy balance around the furnace diagram 2.2

The reference state is 22oC and 1atm

2.5.1 Heat of reactions conversion for furnace duty evaluation…..

2NaCl(s) + H2 SO4 (l) → Na2SO4 (s) + 2HCl (g)

-411.38kJ/mol -887.13kJ/mol -1382.81kJ/mol -92.31kJ/mol

H2 SO4 (l):

[3174.13/3600]/98*[-887.13*103] = -7981.48kW.

ENERGY BALANCE

AROUND THE FURNACE

2NaCl(s) + H2SO4 (l) HCl(g) + Na2SO4

• The reference state is 22oC and 1atm

Qin

(ΔH) Flue gas

(ΔH) HCl(g)(ΔH) NaCl(s)

(ΔH) H2SO4 (l)

(ΔH)Na2SO4(s)

enthalpy

feeds

enthalpy

products

added

heat

17

2NaCl(s):

[3789.52/3600]/58.5*[-822.73*103] = -14804kW.

Na2SO4:

[4599.24/3600]/142*[-1382.81*103] = -1248.87kW.

2HCl:

[2364.4/3600]/36.5*[-184.62*103] = -3322.04kW.

2.5.2 Furnace duty and fuel quantity…..

Furnace duty = Heat added by fuel

Heat added by fuel, Q = (Heat in Products)-(Heat in Reactants)

= -4570.91-(-22785.48)

= 18214.57kW

Therefore, quantity of HFO required for this duty is:

Q = CV*mf

Where mf = mass flow rate of fuel (HFO), kg/s

CV = calorific value of fuel, kJ/kg

mf = 18214.57kJ/s*[1/42.9*103kJ/kg] = 0.425kg/s (1528.49kg/h) or 63.68tpd

Volumetric flow = [1528.49kg/h]/[960kg/m3] = 1.59m3/h (1592.18l/h)

18

Table Showing Properties and Composition of Fuel Selected table 2.1

Fuel

Relative

Density

Composition % by

mass

Calorific

value

(MJ/Kg)

C H O N S Ash Gross Net

Heavy

Fuel

Oil

0.96

85.4

11.4

2.8

1.0

0.5

1.5

42.9

40.5

table 2.2

3.169TOTAL

0.025__0.025Ash

0.010.005 S(S)+ 02(g) S02(l)

0.005S

0.01__0.01N

_- 0.028_ 0.028O

1.0260.9122H2(g)+ 02(g) 2H20(l) 0.114H

3.132.28 C(s)+ O2(g) CO2(g)0.854C

Products per Kg

of fuel

Oxygen required

Per Kg of fuelCombustion equationMass / kg

fuel

Component

element

FUEL AIR COMBUSTION ANALYSIS

19

table 2.3

2.5.3 Air and fuel analysis

100.0100.0Wet:0.5906

Dry: 0.5336

100.0Wet:17.20

Dry:16.17

total

0.040.030.0002640.00060.01S02

83.2875.30.44442872.312.43N2

3.373.00.018323.50.60102

9.70.057186.01.026H2O

13.3112.00.0714418.23.13CO2

% by Vol.

Dry basis

% by Vol.

Wet basis

Kmol per

Kg Fuel

M

Kg/Kmol

%

By MASS

Mass per

Kg FuelPRODUCT

FUEL AIR COMBUSTION ANALYSIS

hKg

hfuelKgfuelKgflueKgoutgivengasflue

hKg

fuelhKgfuelkgairKgfurnacetofiredAir

Therefore

Kg fuel Kg air / .

.% .

ratiostioc A/F%excess ratiostoic A/F Actual A/F

.atiotric A/F rstoichiome

fuel kg air/kg..

.of Fuel ed per Kg Air requir

f Air is % excess oAssume

/68.24715

/ 49.1528 / 17.16

/19.25923

/49.1528 / 96.16

,

1916

4913209913

1

3913

49132330

1693

suplied.20

20

2.6 Selection of fuel

For selecting a particular type of fuel, the following factors are taken into

consideration:-

1. Suitability to process.

2. Supply position. Supply position with regard to availability in sufficient

quantity will be considered. Reliability of supply is also taken into consideration.

Factors which may affect the reliability of fuel supply are: life of reserves,

international politics, wars, labor difficulties and weather disturbances.

3. Cost of fuel. Cost of fuel depends on the following factors:-

(i) Cost of fuel per unit of calorific value (C.V.).

(ii) Cost incurred in its tapping and transport.

(iii)Efficiency of utilization. A fuel may be utilized efficiently only with a particular

set of equipment. For example efficiency of the fuel in the furnace can be

achieved if heat recovery equipment is incorporated in the plant.

(iv) Maintenance of equipment. Cost of maintenance, storing, handling and

burning of fuel must be considered. Such cost is higher in the case of coal than in

case of oils.

(v)Labor and convenience. For example, labor is required for moving the fuel

when the coal is burnt while no such labor is required for gaseous and liquid

fuels.

(vi) Refuse handling and burning quality. When coal is burnt some labor is

required to remove ash. No such labor is required when oil or gas is burnt.

Whether it burns efficiently and without smoke.

(vii) Auxiliary power. Cost of auxiliary power required with a particular type of fuel

is taken into consideration. For example, power is required for conveying coal or

for pulverizing or pumping coal; power is required for supply of air or steam for

atomization of oil, and for supplying air of combustion.

21

2.7 Types of fuel

Basically there are three types of fuel to select from namely coal, diesel or heavy

fuel oil (HFO).

Hydrocarbon fuel cost table 2.4

FUEL CV

MJ/t

DENSITY

Kg/l

COST

US $

COST

ZM K

Diesel 51700 0.87 509.04 2,063,027.13

HFO 42400 0.96 265.00 1,073,986.70

Coal 30400 1.10 135.29 548,300.61

Muffle furnace does not favor the use of coal because of its ash accumulation

nature. Therefore, the choice is reduced to either HFO or diesel but despite the

higher CV of diesel than HFO, the cost implications disadvantage its choice for a

suitable fuel. HFO is a residue fuel from the refinery and costs less and able to

meet the energy demand for the design.

22

2.8 Process control

The salt is dosaged by means of a belt weigher, the quantity of acid is

measured by flow measurement and controlled by an electropneumatic

positioner.

Based on raw material analyses, the quantity ratio of the materials is then

controlled by a human operator.

The reaction between sulphuric acid and potassium chloride requires a

long reaction time and a high temperature.

Producing sulphate that is free of sulphuric acid and hydrochloric acid

requires equivalent amounts of acid and salt.

The furnace will have both the temperature and pressure sensors installed

to ensure operating conditions are monitored and adhered to.

2.9 Mechanical design (muffle furnace)

The continuous mechanical muffle furnace is primarily a stationary circular muffle

comprising a bottom concave pan (hearth). It consists of a circular refractory

hearth, up to 6m in diameter, with a silicon carbide hearth. And a domed cover

separated by a cylindrical mantle. The external structure has a steel shell with

two main access doors. The muffle furnace consists of basically two apartments.

The 1st apartment is the combustion chamber where the fuel/air combustion

takes place. The 2nd apartment is the work space where the reaction between the

reactants (sodium chloride and sulphuric acid) to produce desired product (HCl

gas) and by-product (Na2SO4) takes place.

The 1st apartment- combustion chamber is has an acidic refractory lining to

protect the steel shell high temperature combustion gases and their acidic

nature.

The 2nd apartment- work space comprises a circular refractory hearth with a

silicon carbide hearth. The acidic refractory lining is used because of the acidic

nature of the feed material and the product material.

23

The muffle would be cast iron with refractory lining and steel enclosure supported

on steel columns.

The internal diameter of the furnace is 3m with a refractory lining of thickness

10cm. Muffle thickness is 3cm. The combustion chamber spacing 1.5m and shell

thickness of 3cm (includes corrosion allowance). The overall shell diameter is

3.34m.

The depth of the reaction volume is 6m. The overall height of the furnace is

10.78m.

Furnace dimensions summary table 2.5

ITEM DIAMETER (m)

HEIGHT (m)

Work space (depth)

1x 3.0

1 x 6.0

Refractory thickness

6 x 0.1

6 x 0.1

Muffle thickness

4 x 0.03

4 x 0.03

Support (columns)

0.5 x 2

0.5 x 2

Combustion space

1.5 x 2

1.5 x 2

Shell thickness

0.03 x 2

0.03 x 2

OVERALL

7.28

10.78

24

2.10 COSTING OF MUFFLE FURNACE The cost of furnace is based on the furnace energy demand. Furnace duty = Heat added by fuel

= 18214.57kW Ce = CSn

Where Ce = purchased equipment cost, ₤.

S = characteristic size parameter, KW.

C = constant taken from table.

n = index for the type of equipment

= 220 x 18214.57 0.77 = 419,695.958

= ₤ 419,695.96 (ZK 292,347,614.90)

Exchange rate as at 23.11.05 ZK 6,969.57 is equivalent to £ 1.00 (British Pound) ZK 4,052.78 is equivalent to $ 1.00 (US Dollar)

25

CHAPTER THREE

3.0 COOLING OF HYDROGEN CHLORIDE GAS

NOMENCLATURE

Q heat load ,W

U overall heat transfer coefficient,W/m2o

C

A effective heat transfer area,m2

T temperature ,oC

FT temperature correction factor

Өln log mean temperature difference

G,G mass velocity

H heat transfer coefficient,W/m2o

C

hi inside(tube-side) heat transfer coefficient,W/m2o

C

ho outside heat transfer coefficient

Do outside diameter ,m

Di Inside diameter ,m

C OPH 2 heat capacity of water,Kj/KgK

C OPH 2 heat capacity of hydrochloric acid gas,Kj/KgK

Өcorr corrected temperature ,oC

m mass flowrate ,Kg/s

Re Reynolds’s number

µ viscocity,Ns/m2

M mass flowrate ,Kg/s

Ρ density,Kg/m3

∆P pressure drop, Kpa

U velocity, m/s

jf dimensionless friction factor

m

W

- viscosity correction factor

L,I length m

26

3.1 Introduction

Product gas temperatures from the reactor (furnace) exceed those allowable for

absorption. The method used for absorption varies with the temperature and

volume of the gas being processed. Some cooling is achieved in the pipeline

carrying the gas from the generating unit to the cooler or cooler-absorber. In the

cast-iron or steel flue carrying the high-temperature gas from the salt-sulphuric

acid process, some heat is removed by radiation to the atmosphere. In synthesis

plants using impervious graphite or silica coolers, the pipe may be cooled with

external water sprays.

Generally, the high-HCl low-volume gases are cooled in tubular equipment, and

the low-HCl high-volume gases by heat interchange with concentrated

hydrochloric acid in packed towers. For this design particular design the cooling

was achieved by a tubular exchanger known as the Trombone Cooler. Other

names for the trombone cooler include trickle coolers or cascade coolers.

Trombone coolers are S-shaped bends, consisting of a bank of standard pipes

one above the other in series and over which water trickles downward, partly

27

evaporating as it travels (see diagram below)

Trombone cooler Diagram 3.1

Tubes are made out of impervious ceramic material for cooling corrosive gases

at atmospheric pressure, such as HCl and NO2 that may be cooled by exterior

water or may be jacketed. Trombone coolers are also available in cross-flow

types and banks of impervious graphite tubes have been used which are

submerged in running water. Packed columns may also be used for the low

volume gases.

3.1.1 Advantages of the Trombone Cooler

Its pipes are made of ceramic material which offers a very good

resistance to high temperature corrosive gases.

It does not consist of a lot of components hence it is easier to design

than most other types of coolers.

28

It’s relatively cheaper to design compared to other types of coolers.

3.1.2 Industrial Applications

Trombone coolers have been used extensively in the following industries

heavy chemical

brewing

Coke

petroleum and

ice-making industries.

3.2 Process design

3.2.1 Heat Flow Through A Trombone Cooler

When calculating the heat flow through ceramics the resistance of the pipe wall

must be included. The basic design equation is

Q = UA∆T

Where,

Q = heat load,W

U = overall heat transfer coefficient,W/m2oC

A = the effective heat transfer area,m2

The trombone cooler presents two problems:

(1) the evaluation of the outside film coefficient and

(2) calculation of the cross flow true temperature.

Temperature difference in the Trombone Cooler

Bowman, Mueller, and Nagle have prepared correction factors FT by which the

true temperature difference ∆t can be obtained as the product

FT x LMTD

for both the return-bend and helical types of trombone arrangement.

29

3.2.2 Calculation of Outside Film Coefficient

In calculating the outside film coefficients, the following assumptions are made:

(1) no evaporation occurs from the surface of the water although it is exposed to

the atmosphere.

(2) half of the liquid flows down each side of the pipe in streamline

flow. The criterion of streamline flow is a Reynolds’s number,

'4G, of less than

2100,

where G = L

m

2, m is the water rate in kilograms per hour, and L is the length

of each pipe in the bank in meters. The equation for the transfer coefficients

within ±25% is given by the dimensional equation

h = 65

Do

G' 1/3

where Do is the outside diameter of the pipe in meters. When the value of the

Reynolds’s number exceeds 2100,it is to be expected that the rates will be

somewhat higher. Any appreciable evaporation will also increase the film

coefficient. Large fouling factors and low outlet-water temperatures are

recommended, particularly when the water has a large mineral content.

30

3.2.3 Heat load

It is desired to cool gaseous hydrochloric acid from the reactor temperature of

5370C to 60OC before it is fed into the absorption column. The mass flowrate of

the gaseous HCl is 2364 Kg/hr. In cooling the gas, the temperature of water is

raised from 20oC to 90oC.The process design was carried out as follows:

CHcl @Tav =

2

60537 = 0.84Kj/Kg

CH20 @ tav =

2

2090 = 4.2 Kj/Kg

Heat load of cooler,

Q = m OH2 x Cp OH2

x ∆T

= 3600

2364 x 0.84 x (537 – 60)

= 263.1KW

Cooling water flow,

mH2O = )( 12 ttm

Q

hcl

= )2090(2.4

1.263

= 0.89 Kg/s

= 3204 Kg/hr

Log Mean Temperature Difference(LMTD),

Өln =

)(

)(ln

)()(

12

21

1221

tT

tT

tTtT

=

)2060(

)90500(ln

)2060()90500(

31

=

40

410ln

40410

= 159oC

Correction factor FT,

R = 2060

60500

= 6.3

This value is out of range of fig.20(Kern pg728) so the reciprocal is used,

R

1= 0.16

S = 20500

20900

= 0.15,use RS = 0.95

@ (R

1, RS) FT = 0.9

Corrected temperature,

Өcorr = FT∆Өln

= 0.9 x 159OC

= 143.1oC

Tube-Side Coefficient:

Using 3in. IPS pipes(Kern Table11 Pg 844),

Flow area per pipe ,

ta = 7.38in2

All pipes in series therefore,

Total flow area = 144

38.7

= 0.052ft2 (0.0048m2)

32

Mass velocity,

Gt = ta

m=

0048.0

2364

D = 3.068in x 0.0254m/in = 0.078m

@ Tav = 280oC,

hcl = 0.25 x 10-4Nsm-2 {fig 15,p825}

Reynolds’s number,

Re =

tDG

Friction factor jH = 790

Thermal conductivity Khcl = 0.12W/oC {kern table 5,p801}

3/1

k

c= (0.84 x 0.25 x 10-4 / 0.12)1/3 = 0.06

inside coefficient,

hi =

3/1

k

c

a

kj

t

H

= 790 x

078.0

12.0x0.06= 72.9 W/m2oC

outside coefficient,

hio= hi x OD

ID = 72.9 x

50.3

068.3 = 63.9 W/m2oC

Overall heat transfer coefficient without fouling,

Uclean = ioi

ioi

hh

hh

=

)9.639.72(

)9.639.72(

x = 34.1 W/m2oC

33

Allowing a dirt coefficient of Rd = 0.01,overall coefficient with fouling becomes,

hd = 01.0

1 = 100

overall coefficient with dirt is given by,

Udirt = )(

)(

dclean

dclean

hU

xhU

= )1001.34(

)1001.34(

x

= 25.4 W/m2oC

Overall heat transfer area is given by

A = )( corrd xU

Q

= )1.1434.25(

101.263 3

x

x = 72.4m2 (779ft2)

from table 11 Kern p844,

external surface/lin ft = 0.917

therefore,

number of pipe lengths = )8917.0(

779 2

inx

ft = 106tubes

Outside Coefficient:

02Hm = 2988Kg/hr = 6587lb/hr

OH2 @ 55oC= 0.00034lb/ftsec = 1.22lb/fthr

34

Mass velocity,

G = L

m OH

2

2 = )82(

6587

x = 411.7kg/hrm2

Reinhold’s number,

Re =

'4G

= 22.1

7.4114x

= 1350 (streamline flow)

Outside diameter,

Do = 12

5.3 = 0.292 ft ftin 12.1{ }

Coefficient given as,

ho = 65

3/1

'

oD

G

= 65

3/1

292.0

7.411

= 729W/m2oC

35

3.2.4 Pressure drop

Tube-Side Pressure Drop

The pressure drop suffered by the gas in flowing through the entire tubular length

of the cooler is given as,

∆Pt = 8jf

id

L' ρ 2

2tu

m

w

Where,

∆Pt = pressure drop in tubes, Pa

jf = dimension friction factor = 1.7

L’ = effective pipe length = 8in x 90tubes

di = tube inside diameter= 3.068in

ρ = density of fluid,kg/m3 ≈ 600kg/m3

2

tu = tube-side velocity, m/s =

G = 0.0058m/s

m

w

= viscosity correction factor ,m= -0.14 for turbulent flow.

Therefore,

∆Pt = 8 x 1.7 x

3

890x x 600 x

2

0058.0 2

x 14.0

4

4

10215.0

1025.0

x

x

≈ 0.03 Kpa

36

3.3 Summary of process design:

Overall heart transfer coefficient = 25.4W/m2oC

Heat transfer area ,A =72.4m2

Tube-side coefficient, hi =72.9w/m2oC

Outside coefficient, ho =729W/m2oC

Total number of tubes required =106

Reynolds’s number, Re =1350

37

3.4 Mechanical design

Stoneware ceramic has the following physical properties which make it the best

choice for this particular construction:

Tensile strength = 28.6 Kpsi

Compressive strength = 325kpsi or 2241

Young’s modulus = 45 x 10-6

Shear Modulus=45 x10-6Mpa

Fracture toughness= 3.7Mpa m

Hardness = 1160 kg/mm2

With these properties the heat exchanger will have the following notable

attributes:

High durability

High resistance to corrosion

Low maintenance costs

38

3.5 Unit Costing

The material chosen to construct the tubes of the cooler is ceramic material

known as stoneware. From chemical engineering vol.6,table …,

cost per unit volume,m3,of stoneware = £620,

The cost of construction the equipment was performed as follows,

Volume of 1 tube = pi 4

)( 2

12 dd l

Where ,

l = length of one tube = 8in = (8 x.0.0254)m

therefore,

volume of 1 tube= 3.142 x 4

)078.0( 2

x (8 x 0.0254)

= 1.5m3

Total volume = 1.5m3 / tube x 106tubes

= 159m3

Purchase cost = 159m3 x £620

= £98,580

therefore,

Cost of construction = purchase cost x material factor

= 98,580 x 0.03

= £2957.40

39

The exchange rate for the pound by mid-1998 was taken as,

1£ = K6969.57

Hence,

Cost of construction = 2957.40 x 6969.57

= K20, 611, 806

≈ K 21, 000,000

40

CHAPTER FOUR

4.0 ABSORPTION COLUMN DESIGN

Nomenclature

A Heat transfer area

at Area of the tubes

a’t lin surface area of a tube

L(b) Baffle spacing

Cp Heat capacity at constant pressure

Ds Shell diameter

di Tube inside diameter

do Tube outside diameter

g Gravitational acceleration

Hgf Sensible heat of vapour

ho Heat transfer coefficient

j Heat transfer factor

Nb Number of baffles

N Number of tubes

P Total pressure

ΔPs Shell pressure drop

ΔPr Tube pressure drop due to tube resistance

ΔPt Tube pressure drop due to fluid flow

Q Heat transfer in unit time

Vv Vapour velocity

Vl Liquid velocity

W Mass flow rate of fluid

μ Viscosity of bulk fluid

ρ Fluid density

41

4.1 Introduction

Absorption or gas absorption is a unit operation used in chemical industry to

separate gases by washing or scrubbing a gas mixture with a suitable liquid. One

or more of the constituents of the gas mixture will dissolve or be absorbed in the

liquid and can thus be removed from the mixture.

In some systems this gaseous constituents forms a physical solution with the

liquid or the solvent and in other cases, it reacts with the liquid chemically the

purpose of such scrubbing operations may to the following:

i) gas purification

ii) product recovery

iii) production of solution of gases for various purposes

Gas absorption is carried out in vertical countercurrent columns. The solvent is

fed at the top of the absorber. Whereas the gas mixture enters from the bottom

Hydrochloric acid can be produced to any specification, ranging from technical or

chemical quality to foodstuffs quality. Weak acid can be fed into the absorber as

absorbing liquids and brought up to the required acid concentration.

Solubility of HCl in water

HCL is a relatively stable compound with slight evidence of dissociation at

temperatures above 1500°c it is completely miscible with water foaming a max

building azeotropic that boils at 108.58°c at 1 atm and contains 20.22%

Solubility of HCl in water at 760mmHg table 4.1

Temp 0 30 40 50 60

Solubility, g HCl / 100g H2O 82.31 67.30 63.07 59.59 56.10

The classical equipment for hydrogen chloride absorption was a system of

cellarius focrills or woulfe modern time’s use cooled – absorption towers.

The cooling – absorber is essentially a vertical shell and tube heat exchanger of

impervious graphite or glass such as the one shown below.

42

Diagram 4.1 Falling film absorber

Production of hydrochloric acid in a concentration of 1 to 40 % HCl acid from

chlorine and hydrogen, using water or weak hydrochloric acid as the absorbing

liquid. System of failing – film cooler – absorbers has been used for recovering

hydrogen chloride from gases as dilute as 5 – 10 % HCl. This is accomplished by

increasing the mass – transfer surface, by adding one or two absorbers and

possibly increasing the length of the tubes.

The absorption of HCl in water however generates heat as the process is highly

exothermic. This makes the falling firm cooler – absorber ideal.

However there is not enough information available for the design of the type of

absorber. Therefore a sieve plate water cooled tower will be opted for.

43

4.2 Process Design

Plate spacing

The overall height of the column will depend on the plate spacing. Plate spacing

from 0.15m (6in) to 1m (36in) are normally used. The spacing chosen will depend

on operating conditions.

Closed spacing is used with small – diameter columns and where head room is

restricted as it will be when a column is installed in a building.

4.2.1 Column diameter

The principal factors that determine the column diameter is the vapor from rate.

The vapor velocity must be below that which would cause excessive liquid

entrainment or a high pressure drop. The equation given which is based on the

well known sounders and Brown equation Lowenstein (1961) can be used to

estimate the maximum allowable superficial vapor velocity and hence the column

area and diameter.

Uv - must allowable vapor velocity

Lt – plate spacing

D – diameter

4.2.2 Selection of plate type

Principal factors to consider when comparing the performance of bubble cup,

sieve and valve plates are cost, capacity, operating, efficiency and pressure

drop.

Cost.

212

)()047.027.0171.0(

v

vlltlU tv

pvUu

VwD

4

44

Bubble cup plates are appreciably more expensive than sieve or valve plates the

relative cost will depend on the material of construction used for mild steel the

ratio is;

Bubble – cup: sieve: valve plates

3.0: 1.5: 1.0

Capacity.

There is little difference in capacity rating of the three types (the diameter of the

column required for a given flow rate) the ranking is sieve, valve and bubble.

Operating.

By operating range it means the range of vapor and liquid rate over which the

plate will operate satisfactorily (this is the most significant) some flexibility will

always be require in an operating plant to allow for changes in production rate

and to cover start – up and shut down conditions.

The ratio of the highest to the lowest is termed as the turn down ratio.

Bubble – Cups have a partial liquid seal and can therefore operate efficiently at

very low vapor rates.

Sieve plates rely on the flow of vapor through the hole to hold the liquid on the

plate and can not operate at very low vapor rates. But with good design sieve

plates can be designed to give a satisfactory operating range typically from 50 –

120%

Valve plates are intended to give greater flexibility than sieve plates at a lower

cost than bubble – cups.

Efficiency.

The Murphree efficiency of the three types of plates will be virtually the same

when operating over their design flow range and no real distribution can be made

between them.

Pressure drop.

The pressure drop for the design of columns. The plate pressure drop will

depend on the detailed design of the plate but in general. Sieve plates give the

45

lowest pressure drop followed by valve plates with bubble – cup giving the

highest.

Summary

Sieve plates are the cheapest and are satisfactory for most applications.

4.3 Material balance

For an inlet temperature of 60°c the solubility is 56.10g HCl / 100g H2O

Overall material balance around.

Given that the amount of product is 150 ton/day

As the basis and at a temperature of 60°c

hrkgdayhrs

tonkgton/6250

/24

/1000*150

46

Ratio since the solubility at 60°c is 56.10g HCl/ 100g water.

HCl: H2O

56.1: 100

0.561: 1

HCl in (y kg/hr)

Total ratio = 1+ 0.561 = 1.561

H2O into absorber (x kg/hr)

Assuming an efficiency of 95% for the HCl y will be as follows,

The HCl loss in the out let purge will therefore be.

hrkgy

y

/2.2246

6250*561.1

561.0

hrkgx

x

/84.4003

6250*561.1

1

hrkgy

y

y

/4.2364

095

2.2246

2.224695.0

HCl.2H2O

(6250

kg/hr)

HCl

Y kg/hr

Water

X kg/hr

47

Summary of outcome of calculations diagram 4.2

4.4 Equation of the operating line

Assuming is solubility

hrkg /2.1182.22464.2364

48

nn

nn

nnnn

nnnn

nnnn

yy

xx

G

L

xxGyyL

GxGxLyLy

LyGxGxLy

1

1

11

11

111

)()(

49

Material balance

Based on the figure above

Equation of the absorber is them and by

Dividing through out by G

Therefore equation of the operating line becomes

Were liquid L = 6250kg/hr and gas G = 2364.4 kg/hr

Therefore the equation reduces to

Values obtained from the above equation. And these are plotted on a graph.

X 0.1 0.5

Y 0.389 0.546

LB

LxBxVyo

11

101

110

110

LxGyLxGy

LxLxGyGy

LxGyLxGy

nn

nn

nn

01

101

)( yxxG

Ly

xG

Lyx

G

Ly

nnn

nn

01 yxG

Lyn

35.064.2

4.2364

6250

1

01

xy

yxy

n

n

50

The above graph gives two stages

Mechanical design

Based on the vapor flow rate of 2364.4kg/hr

Therefore basis = 2364.4 kg/hr

4.4.1 Column diameter Calculation

Most of the above factors that affect column operation are due to vapor flow

conditions: either excessive or too low. Vapor flow velocity is dependent on

column diameter. Weeping determines the minimum vapor flow required flooding

determines the maximum vapor flow allowed, hence column capacity. Thus if the

column diameter is not sized properly, the column will not perform well. Not only

will operational problems occur, the desired operational duties will not be

achieved.

51

State of Trays and Packings.

Since actual number of trays required for a particular separation duty is

determined by the efficiency of the plate and the packings, if packings are used.

Thus any factors that cause a decrease in tray efficiencies are affected by fouling

wear and tear, corrosion and the rates at which these occur depends on the

properties of the liquid being processed. Thus appropriate material should be

specified for tray construction.

Weather Conditions.

Most distillation columns are open to the atmosphere, although many of the

columns are insulated, changing weather conditions can still affect the operation.

Thus the reboiler must be appropriately sized to ensure that enough vapors can

be generated during cold or windy spells and that it can be turned down

sufficiently during hot seasons. The same applies to condensers.

These are some of most important factors that can cause poor distillation column

performance. Other factors include changing operating conditions and throughputs,

brought about in changes in up stream conditions and changes in the demand of the

products. All these factors including associates control systems should be considered at

design stage because once a column is built and installed nothing much can be done to

rectify the situation without incurring significant costs. The control of distillation column

will be looked at later

Column diameter

Were Vm – is the maximum allowable flow

pL – liquid density

UL – vapor calculated

Therefore the column diameter will be

Column height (m)

It is given by the number of plates x spacing + 2 x spacing

The number of plates is 2

52

dimensions diagram 4.3

Mechanical description table 4.2

Item Actual calculated value Nearest number estimation

Column diameter (m) 0.9605m 1m

Column height (m) 4.8m 5m

Number of plates 2 2

4.5 Unit Costing and Evaluation

mh

h

h

8.4

4.24.2

2.122.12

53

Ce = CSn

Where

Ce – purchased equipment cost

C – cost constant from appendix 1

S – characteristic size diameter appendix 1

n – index for that type of equipment

Data (adsorption column)

Dc – 0.96309 m

Hc – 4.8m

Area of column therefore A (m2)

Cost of shell

Material factor at (s.s) stainless steel = 2.5

Cost = 7.5 x 1000

= $ 7 500

Therefore cost

= 7500 x 2.5

= $ 18 750

Cost of the two plates

From appendix 2 (fig 6.7)

Bare cost = $ 1 600

Material factor – 1.7

Installed cost = bare cost + material factor

= 1600 x 1.7

= $ 2 720 / plate

= $ 2 720 x 2

2631.3

4

8.496309.0

4

mA

A

dhA

54

= $ 5 440

Total cost for the absorption column will be

Cost of shell + cost of plates

= 18 750 + 5 440

= $ 24 190

Conversion in Kwacha based Bank Of Zambia exchange rate obtained from The

Time of Zambia news paper dated 02/11/2005

$1 – K4 321.11

= 43211.1 x 24190

= K 104,527,650.9

= K 104.53 million

55

CHAPTER FIVE

5.0 SITE SELECTION AND SAFETY

5.1 Occurrences of raw materials

Sodium chloride occurs in solution in sea water.

Also occurs in dry deposits as rock salt and brine.

There are sodium chloride deposits in Kaputa and Mkushi districts in

Zambia It can be acquired from neighboring Congo D.R., Mozambique

and Angola.

Sulphuric acid can be obtained from Mbwana Mkubwa acid plant in Ndola

or KCM acid plant in Kitwe.

5.2 Site selection

The plant will best be located in Ndola, because of the following factors;

It is a central town in terms of the acquisition of factors of production; raw

materials, labor and transport net work.

Sulphuric acid will be acquired from Bwana Mkubwa and Konkola Copper

(Kitwe) mines.

Sodium chloride deposits in Kaputa and Mkushi districts in Zambia are

accessible and easily are transported to Ndola.

The energy source electricity, coal, diesel or oil is easily accessible

because of the already existing national power grid and both the rail and

road network.

It will be located near Kafubu River as source industrial water and for

treated wastewater disposal.

Since Ndola is a central town ,our product and by product can find ready

market in the following industries:

The main product hydrochloric acid will find market in the mines, cement

industry, textile industry, and leather industry.

The by-product, sodium sulphate which is used in glass manufacturing, for

example the coming back into life of Kapiri glass factory.

56

Sodium sulphate is used by detergent manufacturing companies as a

‘builder’ and in dyeing to standardize dyes, therefore Ndola is nearby for

marketing.

5.4 SAFTY FACTORS

A report prepared By: U.S. Office of Air Quality Planning and Standards, Air

Quality Strategies and Standards Division, Integrated Strategies and Economics

Group, Research Triangle Park, North Carolina out lines the hazardous

associated with HCl gas and acid.

There are Regulatory issues such as national emission standards for hazardous

air pollutants (NESHAP) for hydrochloric acid (HCl) production facilities, including

HCl production at fume silica facilities. The EPA has identified these facilities as

major sources of hazardous air pollutant (HAP) emissions; primarily HCl.

Hydrochloric acid is associated with a variety of adverse health effects. These

adverse health effects include chronic health disorders (e.g., effects on the

central nervous system, blood, and heart) and acute health disorders (e.g.,

irritation of eyes, throat, and mucous membranes and damage to the liver and

kidneys).

The production processes NESHAP affect are processes that routes a gaseous

stream that contains HCl to an absorber, thereby creating a liquid HCl product.

Among these various processes are:

i) Organic and inorganic chemical manufacturing processes that produce

HCl as a byproduct;

ii) The reaction of salts and sulfuric acid (Mannheim process);

iii) The reaction of a salt, sulfur dioxide, oxygen, and water (Hargreaves

process);

iv) The combustion of chlorinated organic compounds;

v) The direct synthesis of HCl through the burning of chlorine in the

presence of hydrogen

It is important to note that most HCl production is as a by-product of other

processes such as aliphatic and aromatic hydrocarbon chlorination, the

57

phosgenation of amines for isocyanates, and halogenations for making

chlorofluorocarbons. Only about 5 percent of HCl is produced as primary product.

Production from the U.S. HCl industry is roughly 4.2 million tons/year as of 1997.

Most of the production is captive capacity; that is, the HCl is produced as an

intermediate product to be used in final output. Given that about 5 percent of HCl

produced in the U.S. is as primary product, this means that only about 200,000

tons of primary HCl output is generated in a typical year.

It’s therefore imperative that safety attire be emphasized at all times, it the

responsibility of there company as well as the workers for such a plant to ensure

that safety attire are worn, in addition to the regulatory bodies assigned to the

tusk.

58

CHAPTER SIX

6.0 PROJECT EVALUATION AND COST

6.1 Introduction

The use of HCl in the production of other chemicals is the major way in which

HCl is used in the U.S. Thirty percent of HCl produced in the U.S. goes into

production of other chemicals. The next most common uses of HCl are steel

pickling (20 percent), oil well acidizing (19 percent), and food processing (17

percent). Other uses for HCl include semiconductor production and regeneration

of ion-exchange resins for water treatment.

The U.S. imports and exports very little HCl. In 1997, the U.S. imported 85,000

tons of HCl, or only 2 percent of U.S. capacity. During that same year, the U.S.

exported 60,000 tons of HCl or only 1.5 percent of U.S. production capacity.3

hence, the U.S. imports as much or more HCl as it exports, but the trade balance

is negligible compared to the output consumed within the U.S. Most of this trade

is with Canada.

The growth in U.S. HCl production averaged about 4.2 percent per year from

1993 to 1998. Growth has averaged roughly 3 percent per year from 1985

through 1998, so there has been some increase in production growth in the

decade of the 1990's.4 Prices for HCl have increased considerably from 1992 to

1998. These prices generally ranged from $40/ton to $57/ton in 1992 and 1993,

but rose to over $90/ton in 1998 due to railroad disruptions that occurred late in

1997 and continued into 1998. Projected growth is expected to be about 2.5

percent per year through 2003, though this amount could be an underestimate if

continued strength in oil drilling leads to additional demand for HCl.

As of 2003 the price of HCl acid stood at $92.25 /ton therefore the estimated

revenue from the sales of HCl acid is about

$92.25 /ton x 150 ton/day x 350 days/year = $4, 843, 125. /year

In kwacha $4, 843, 125 X K4, 052.00 = K19, 624, 342, 500. /year

59

6.2 Fixed and installation cost

Using the factorial method of overall project estimation we can estimate the cost

of this project and determine of it’s viable or not. This is based on the following,

Taking into consideration of the PCE at $ 36,340.87

item PCE

f1 – equipment erection 0.4

f2 – Piping 0.7

f3 – instrumentation 0.2

f4 – Electrical 0.1

f5 – Building process 0.15

f6 – Utilities 0.5

f7 – storage 0.15

f8 – site development 0.05

f9 – ancillary building 0.15

Total 3.40

PCE which is the purchased cost is total of cost of all the major units

PCE = $ 36,340.87

PCE = K 417.88m

6.2.1 Physical plant cost (PPC)

PPC = PCE (1+ f1 + …. + f9)

PPC = 36,340 x 3.40

PPC = $ 123,556

6.2.2 fixed capital cost (FCC)

Item PPC

f10 – design and engineering 0.3

f11 – constructor’s fee 0.05

f12 – contingency 0.1

Total 1.45

60

FCC = PPC x 1.45

FCC = 123,556 x 1.45

FCC = $ 179,156.2

Simple mathematics

6.2.3 Cost (expenditure)

Cost (expenditure) = $ 179,156.2

Or = 179,156.2 x 4053 = K 726,119,268.

K 726.12m

This is what it will cost just the project to start running and buy all the equipment

needed. Plus variable cost which are about 10% of FCC = $ 17,215.62

Therefore total cost for one year = $ 196,371.82

6.2.4 Income per year

From HCl sold in one year = $4, 843, 125. /year

The by product sold in one year will be

Na2SO4 = $ 60 / ton

Production is at = 4.6 ton/hr or 39,744 ton/year

Therefore 39744 ton x $ 60 = $ 2,384,640/ year

Total income is $ 7, 227, 765/year

The pay back time for this project will be in the first month of sales and

production. See summary table below.

61

Summary table cost evaluation table 6.1

Expenditure for given month sales or income for given month

Month/year Fixed cost $ Variable cost $ Sales $ Operating cost $

1m 19,259.34 963 0 0

2m 104,297.0 10,430 0 0

3m 36,340.87 3,634 0 0

4m 50,800.00 25,343 602,313.75 12,046.28

5m 0 25,343 602,313.75 12,046.28

6m 0 25,343 602,313.75 12,046.28

2y 0 433,665.9 7,227,765 72,277.65

3y 0 433,665.9 7,227,765 72,277.65

4y 0 433,665.9 7,227,765 72,277.65

5y 0 433,665.9 7,227,765 72,277.65

6y 0 433,665.9 7,227,765 72,277.65

7y 0 433,665.9 7,227,765 72,277.65

Total cost 210,696.34 2,693,052. 45,173,531.25 469,804.74

Grand total Expenditure = $ 3,373,553.08 Income = $ 45,173,531.25

Profit Up to year 7 $ 41,799,977.92

The pay back time for this project is 4 months just in the first month of sales

and production. with the total investment being $ 263,112.62 for the plant to be

complete and start running.

Therefore it’s a viable project with a good pay back time.

62

Process design summary table 6.2

FLOW- RATE(kg/h)

ENERGY (kW)

TEMP. oC)

PRESSURE (atm)

FURNACE

Sodium chloride 3774.13 -14804 50 1.0

Sulphuric acid 3174.13 -7981.48 20 1.0

HCl(gas) 2363.4 -3322.04 537 1.5

Sodium sulphate 4599.2 -1248.87 527 1.0

FUEL (HFO) 1528.49 18214.57 6.5

COOLER

Process Stream: -

HCl (gas) (inlet) 2363.4 - 537 1.5

HCl (gas) (outlet) 2363.4 - 60 1.4

Service Stream:

H2O (inlet) 3204 - 22 1.0

H2O (outlet) 3204 - 90 1.0

COMPRESSOR

HCl (gas) in 2363.4 - 60 1.4

HCl (gas) out 2363.4 - 61 1.5

ABSORBER

HCl(gas) 2363.4 - 60 1.5

H2O 4003.98 - 22 1.0

HCl (vent) 118.2 - 62 1.1

HCl(aq) 6250.0 - 60 1.5

63

Mechanical design and costs summary table 6.3

Item/ units units Furnace Cooler Absorber

Diameter m 7.28 0.0078 0.9605

Height m 10.78 4.8

Length m - 0.02032 -

Area m2 - 72.4 -

# Tubes Nil - 106 -

# Plates Nil - - 2

Material of

Construction

Nil Refractory

brick & steel

Stone ware

ceramics

Stainless

steel

Cost of unit $ 6,969.57 5,181.3 24,190

Cost of unit K (m) 292.35 21.0 104.53

Sales HCl K / year 19,629,185,625m

Sales Na2SO4 K / year 9,664,945,920m

Total sales K 29,294,131,545m

64

CONCLUSION

To design a plant which will be producing 150tpd HCl (20oBe’) from sodium

chloride and H2SO4 (60oBe’), the salt-sulphuric acid process has been adopted

because of the specified raw materials in the question. Although there are three

other methods used to produce HCl but there use in the question is not favored

because of other raw materials used in other processes.

The design process adopted for this design question uses three (3) main units

and service equipment namely the furnace (reactor), the cooler and the absorber

and a compressor as a service unit. The muffle furnace is operated at 500 to

550oC in the work space heated by indirect heat from the combustion chamber

operating at temperature as high as 1205oC. The furnace is operated at 1atm.

Heavy fuel oil is suitable for the muffle furnace. The reaction volume of the

reactor is 52.8m3 and the residence time is 18.3minutes. The duty of the furnace

is 18214.57kW. The cost of the furnace based on the energy demand is

£419,695.96 (ZK 292,347,614.90).

HCl gas leaves the furnace at 537oC temperature which exceeds that suitable

absorption temperature of 60oC. For this particular design the cooling has been

achieved by a tubular exchanger known as the Trombone Cooler and operates at

atmospheric pressure. Total heat transfer area for the trombone cooler is 72.4m2

giving a total number of 106 tubes. The cost of the trombone cooler is £ 2,957.40

(ZK 21,000,000.00).

At the cooler there is a pressure drop in the flow of HCl gas and therefore a

compressor has been used to compensate for pressure loss prior to absorption

form 1.4atm to 1.5atm. Gas absorption is carried out in a vertical countercurrent

column. The solubility of HCl in water at 60°C is 56.10g HCl/ 100g water. The

column diameter is 0.96m and height of the absorber is 4.8m and the number of

plates is 2. The cost for the absorption column is K 104.53 million.

Plant location has been influenced by raw material availability, other factors of

production and main product and by-product market forecast. Other than

importing sodium chloride from Congo DR, Mozambique and South Africa, it can

65

also be sourced locally form Kaputa and Mkushi districts. Sulphuric acid will be

sourced from Mbwana Mkubwa acid plant in Ndola or KCM acid plant in Kitwe.

The plant will best be located in Ndola, because it central to sources of raw

materials and product market. Environmental, safety and health (SHE) issues

have been considered for instance plant location is far from the residential areas

because of the dangers hydrogen chloride gas and acid pose on human tissue,

potentially damaging respiratory organs, eyes, skin and intestine. Plant location

near the stream which provides service water through out the year makes it

possible to treat waste streams before they are disposed to the environment.

Quality assurance of the project has been taken into account by incorporating a

process control system to monitor that specific operating conditions are adhered

to, namely, raw material flow rates, operating temperature and pressure at the

furnace, the temperature of process and service streams at the cooler and the

flow rates and temperatures of water and HCl gas at the absorber.

HCl acids attracts a wider application in industry among these include;

Regeneration of ion exchangers resins. pH control in food, pharmaceutical,

drinking water and neutralizing waste streams. It is used to control the pH of the

process streams. Pickling is an essential step in metal surface treatment. The by-

product sodium sulphate also attracts a wider application in industry among

these include glass manufacturing, detergent manufacturing used as form builder

and in some types of cement it is used for cement setting property a substitute

for gypsum.

Using the factorial method the overall project cost has been estimated taking into

account the costs for equipment erection, piping, instrumentation, electrical,

building process, utilities, storage, site development and ancillary building, to

determine its viability.

The total investment cost is $ 251,066.34 (ZK 1,017,320,809.68) and operating

cost for plant start up is $12,046.28 (ZK 48,811,526.56). The plant grand total

cost is $263,112.62 (ZK 1,066,132,336.24)

The unit price of HCl is $92.25 /ton and the total HCl sold in one year is $4, 843,

125. /year (ZK 19,624,342,500.00/year). The unit price of Na2SO4 (by-product) is

66

$ 60 / ton and the total Na2SO4 is $ 2,384,640/ year (ZK 9,662,561,280.00/year).

The projected sales volume gives a grand total income of $ 7, 227, 765/year

(ZK 29,286,903,780.00/year). The pay back time for this project is 4 months just

in the first month of production and sales. Therefore, this project is viable.

67

RECOMMENDATIONS

A detailed analysis of this report reveals that the costs of implementation of this

project are outweighed by the various benefits that it has to offer hence the

project team recommends this project as a viable project and worth undertaking.

This project has the potential to add major growth to the Zambian economy.

Therefore, if this project were to be undertaken, the project team recommends a

subsidy, by government, on certain materials of construction. This can be

achieved by reduction of import duty on those materials that have to be imported

from outside the country.

Additionally the team also recommends that government makes available

research scholarships for Zambian chemical engineers to expose them to heavily

industrialized countries where technology such as HCl production is a practical

reality. This would result in highly competent Zambian engineers and hence get

rid of the dependency on expatriates.

As with any other plant design, this undertaking is heavily material dependent

hence special factors pertaining to site selection have to be considered in order

to optimize on transportation costs. The plant must be centrally located in terms

of easy access to market as well as easy access to raw materials and thus Ndola

has been recommended.

Safety factors, however, should also to be observed as pertaining to the location

of the plant, bearing in mind that hydrochloric acid is a hazardous air pollutant

(HAP) associated with a variety of adverse health effects. Therefore, the plant

must be located at a healthy distance away from residential areas to allow for

dilution in case of accidents and effluent and emission standards should strictly

be observed.

68

To the department, we would first of all like to commend you for a job well done

on the supervision and guidance of the projects, and at list we are now seeing an

increase in the number of project the are practical and an involvement of

industries in the projects, this is good as it will increase cooperation between the

University and the industry.

We would like to recommend the following;

i) Some of the small scale projects done by students are manageable

financially; the department should try and actually do some of these

projects for income generation.

ii) We recommend that the projects done by previous students be made

available to the student by means of a department library or the library it

self, after all what power does knowledge have if it can’t be shared.

All in all we commend you for job well done given the conditions.

69

REFERENCE

Chattopadhyah P, (1998) Unit Operations Of Chemical Engineering vol. 1.

New Delhi: Khanna publishers.

Chattopadhyah P,(2001) Unit Operations Of Chemical Engineering vol. 2

New Delhi: Khanna publishers.

Corporate author, (2005) Chemical Engineering resource page,

www.chemiresouces.com. Extracted 11/10/2005, 14:36.

Corporate author, Energy Regulation Board news letter 2004, government

publishers. Lusaka Zambia.

Corporate author, (2005), GRAPHITE HYDROCHLORIC ACID (HCL ACID)

SYNTHESIS UNIT, http://www.ptcexports.com/index.htm, extracted 10/11/2005.

17:08

Corporate author Ministry of Energy, (2004), ZAMBIA ENERGY POLICY

DOCUMENT 1994. Government publishers. Lusaka Zambia.

Corporate author, (2005), GRAPHITE FALLING FILM ABSORBERS,

http://www.ptcexports.com/index.htm, extracted 10/11/2005. 17:56

Corporate Author, (1965) Encyclopedia Of Chemical Technology, New York

2nd Inter-science publishers, a division of John Wiley & sons Publishers inc,

Consultant Michael J. Ervin and Associates and published in, (2005), FUEL

FACTS .www.mjervin.com, Visit M.J. Ervin and Associates' website extracted

2710/2005 17:30

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Coulson and Richardson, (1999) Chemical Engineering vol. 2. 3rd edition,

Butterworth: Oxford Heinemann, Jordan hill.

Coulson and Richardsons, (1999) Chemical Engineering vol. 6. 3rd edition,

Butter worth: Oxford Heinemann, Jordan hill.

Kern Donald Q, (1997) Process Heat Transfer. 2nd edition, New Delhi: Tata

McGraw – hill publishing company.

Perry Robert H, (1999) Perry’s Chemical Engineers’ Handbook 7th edition,

New York: McGraw-Hill Companies, Inc.

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71

APPENDIX

Appendix 1

Muffle Furnace

72