SAJJAD KHUDHUR ABBAS

Ceo , Founder & Head of SHacademyChemical Engineering , Al-Muthanna University, Iraq

Oil & Gas Safety and Health Professional – OSHACADEMY

Trainer of Trainers (TOT) - Canadian Center of Human

Development

Episode 3 : Production of

Synthesis Gas by Steam

Methane Reforming

History of Synthesis Gas

• In 1780, Felice Fontana discovered that

combustible gas develops if water vapor is

passed over carbon at temperatures over 500

°C. This CO and H2 containing gas was called

water gas and mainly used for lighting

purposes in the19th century.

• As of the beginning of the 20th century,

H2/CO-mixtures were used for syntheses of

hydrocarbons and then, as a consequence,

also called synthesis gas.

• Haber and Bosch discovered the synthesis of ammonia

from H2 and N2 in 1910 and the first industrial ammonia

synthesis plant was commissioned in 1913.

• The production of liquid hydrocarbons and oxygenates

from syngas conversion over iron catalysts was

discovered in 1923 by Fischer and Tropsch.

• Much of the syngas conversion processes were being

developed in Germany during the first and second

world wars at a time when natural resources were

becoming scare and alternative routes for hydrogen

production, ammonia synthesis, and transportation fuels

were a necessity.

• In 1943/44, this was applied for large-scale production

of artificial fuels from synthesis gas in Germany.

To this day, however, methanol

and ammonia are still produced

from syngas using essentially the

same processes originally

developed and, apart from

hydrogen production, constitute

the major uses of syngas.

What is synthesis gas ?

In its simplest form, syngas (also called producer gas, town gas, blue water gas, and synthesis gas) is composed of carbon monoxide (CO) and hydrogen (H2). The name comes from its use.Syngas is combustible and often used as a fuel of internal combustion engines. It has less than half the energy density of natural gas.

syngas can be produced from any hydrocarbon

feedstock, including: natural gas, naphtha, residual oil, petroleum coke, and coal.The lowest cost routes for syngas production, however, are based on natural gas, the cheapest option.The choice of technology for syngas production also depends on the scale of the synthesis operation.

Syngas production from solid fuels can require an

even greater capital investment with the addition of feedstock handling and more complex syngas purification operations.The syngas composition, most importantly the H2/CO ratio, varies as a function of production technology and feedstock.Steam methane reforming yields H2/CO ratios of 3/1, while coal gasification yields ratios closer to unity or lower.

Physical Properties of Hydrogen (H2):

With only one proton and one electron, hydrogen is the lightest of all chemical

elements. At ambient temperature, molecular hydrogen, H2, is a colourless and

odorless gas.

hydrogen condenses to a colorless liquid, it freezes at –259.15 °C.

H2 is14 times lighter than air.

ValueUnitproperty

2.016g mol–1Molar mass

898J mol–1Heat of vaporization

Properties at 273.15 K, 101.3 kPa

0.0899kg m–3Density

0.1645W m–1 K–1Thermal conductivity

Cp = 22.0, Cv = 6.51J mol–1 K–1Molar heat

ValueUnitProperty

Boiling point (101.3 kPa)

20.37KTemperature

70.00kg m–3Density (liquid)

1.319kg m–3Density (gas)

Liquid at boiling point (101.3 kPa)

Cp = 22.0, Cv = 6.51J mol–1 K–1Molar heat

–7918J mol–1Enthalpy

0.117W m–1 K–1Thermal conductivity

Gas at boiling point (101.3 kPa)

Cp = 23.49, Cv = 12.8J mol–1 K–1Specific heatcapacity

–7020J mol–1Enthalpy

0.0185W m–1 K–1Thermal conductivity

Critical Point

33.00KTemperature

1339kPaPressure

30.09kg m–3Density

Chemical properties of hydrogen

In air, H2 combusts to water with a hardly visible, weakly bluish flame. Hydrogen combines with almost any other element. Metal compounds with negatively charged hydrogen are called metal hydrides (e.g. CaH2, NaH, LiH).Hydrogen has a reducing effect on a lot of metal oxides when heated. Thus CuO with H2, for example, reacts to Cu

and H2O. Hydrogen has a reducingeffect on a lot of metal oxides when heated.

Physical and Chemical Properties of Carbon Monoxide (CO):Carbon monoxide is colourless, odourless and tasteless. It is

highly toxic,poorly soluble in water (solubility: 23 mL L–1 at 20

°C and 1 bar).

ValueUnitProperty

28.010g mol–1Molar mass

10.9 – 76% Volume

fraction

Explosion range

(in air at 101.3 kPa)

Properties at 273.15 K, 101.3 kPa

1.250kg m–3Density

Cp = 29.05,Cv =

20.68

J mol–1 K–1Molar heat

0.02324W m–1 K–1Thermal

conductivity

ValueUnitProperty

Boiling point (101.3 kPa)

81.65KTemperature

Melting point (101.3 kPa)

74.15KTemperature

Critical point

132.29KTemperature

3496KpaPressure

301kg m–3Density

Chemical properties of CO

Together with air, carbon monoxide forms explosive mixtures in the concentration range of a CO-volume fraction of (10.9-76%).In engineering, it is obtained by separation from synthesis gas.The reason for its toxicity is it’s property to displace the oxygen from the hemoglobin-complex of blood, since the affinity of hemoglobin (Hb) to CO is about 300 times higher than to O2. The hemoglobin of a heavy smoker of cigarettes can reach a CO-saturation of up to 15% in the course of a day.

Uses of syngas

1. Syngas can be used to produce a variety of chemicals like ammonia and methanol.

2. Syngas itself can be used as a fuel in internal combustion engine.

3. Syngas is also used as an intermediate in producing synthetic petroleum for use as a fuel or lubricant via the Fischer–Tropsch process and previously the Mobil methanol to gasoline process.

4. syngas can be used to produce organic molecules such as synthetic natural gas (SNG-methane).

At these days, synthesis gas is mainly used for production of the

products listed:

UsesProduct

AmmoniaH2 and N2

Formic acidCO

Acetic acidH2 and CO

MethanolMixtures of (H2, CO and CO2)

Production of Synthesis Gas from Hydrocarbons:In the production of synthesis gases from hydrocarbons, the components hydrogen and carbon monoxide usually appear as complementary products, carbon dioxide can be obtained as a by-product.

There are Several Methods to Production the

Synthesis Gas from Hydrocarbons :1.Steam Reforming

2.Partial Oxidation (PO ).

3.Autothermal Reforming ( ATR).

The Process Selection depends on Two factors:1. The desired product composition (H2/CO ratio ).2. The feedstock available like natural gas, residual gases

from refineries,LPG(Liquefied Petroleum Gas), naphtha, heavy oils, distillation residues, pitch and coal.

The selected process in this project is Production Synthesis Gas by steam reforming of Methane Gas due to ratio (H2/CO)is equal to 3/1 and the feed is

methane gas. the economic cost of the steam must be taken into account

The Advantages of (SMR):

Steam reforming of natural gas are :

EfficientEconomicalwidely used process for hydrogen and monoxide

productionprovides near- and mid-term energy security and

environmental benefitsThe SMR produces a H2/CO ratio equal to three

We choose methane as a feed because of :

• Methane is a wide distribution in nature.

• cheap

• Make a Less problems with the reformer.

• Make a longer age for reformer than other

feed stockes.

MethaneMethane is a chemical compound with the chemical formula CH4 (one

atom of carbon and four atoms of hydrogen). It is the simplest alkane and

the main component of natural gas.

Methane is a colorless, odorless gas with a wide distribution in nature. It is

the principal component of natural gas, a mixture containing about 75%

CH4, 15% ethane (C2H6), and 5% other hydrocarbons, such as propane

(C3H8) and butane (C4H10).

ValueUnitProperty

CH4Molecular formula

16.04g mol-1Molar Mass

0.656g cm-3Density at 25 °C , 1

atm

0.142mPa.sViscosity at -170 °C

5.34J g-1 k-1Specific heat

capacity at -100 °C

-182 °CMelting point

43.4cm s-1Flame Velocity

Critical Values

- 82.5°CTemperature

4.67MPaPressure

0.162g cm-3Density

Sources of Methane

Natural sources

1.Wetlands2.Oceans3.Geological sources4.Wild animals5.Wildfires

Non Natural sources(Artificiality)

1.Oil and Gas System2.Landfills3.Wastewater4.Coal Mines5.Agriculture

Steam Reforming (Tubular Reforming)

Steam Reforming Methane (SMR) has been used for several decades

since it has been developed in 1926 and over the years substantial

improvements have been introduced. SMR process consists of gas

feed pre-heating and pre-treatment, reforming.

Steam reforming of methane is the main industrial route to produce

synthesis gas (a mixture of hydrogen and carbon monoxide).

In the steam reforming process, a light hydrocarbon feedstock (such

as natural gas, refinery gas, LNG, or naphtha) is reacted with steam

at elevated temperatures(typically 700° C to 900° C), and elevated

pressures (15 to 30 bar) in nickel-based catalyst filled tubes to

produce a synthesis gas. This gas consists primarily of hydrogen and

carbon monoxide. , but other gases such as carbon dioxide and

nitrogen, as well as water vapor are also present.The typical steam to

carbon ratio falls in the range of (2.8 to 3.2 to 1).

steam reforming (SR) is highly endothermic and it is carried

out at high temperature (700 - 900 ºC) and at pressures

between 15 and 30 bar.

The standard enthalpies of reaction (at 298 K) are given in brackets.

The most important reactions in steam reforming (SR) of methane are:

1. CH4(g) + H2O(g) ↔ CO(g) + 3H2(g) (∆H = +206 kJ/mol)

2. CO(g) + H2O(g) ↔ CO2(g) + H2(g) (∆H = -41 kJ/mol)

Reactions and thermodynamics

CatalystAll tubular reformers use catalyst inside the

tubes in order to reduce the operating

temperature. This is important in order to

reduce the tube stresses resulting from high

pressure and high temperatures The Ni-

catalyst is needed since methane is a very

thermodynamically stable molecule even

at high temperatures. nickel catalyst filled

tubes to produce a synthesis gas.

Ni-catalyst is often in the form of thick-

walled Raschig rings, with 16 mm in

diameter and height, and a 6 – 8 mm hole

in the middle.

Challenges

During the production of Synthesis gas, CO2

is also produced. The SMR process in

centralized plants emits more than twice the

CO2 than hydrogen produced. To avoid

emission of CO2 into the atmosphere, CO2

can be concentrated, captured, and

sequestered.

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