ISIJ International, Vol. 31 (1991), No. 5, pp. 449 457

Review

Preheating Techniques to Manufacture Metallurgical Coke

M.A. D[EZ, R. ALVAREZ1),M. SIRGAD02)and H. MARSH

Northern CarbonResearchLaboratories, Departmentof Chemistry, BedsonBuilding, University of Newcastle uponTyne, Newcastle upon

1) Institute Nacional del Carb6n (lNCAR) CSIC 33080Oviedo Spain ' ' '

, . . . ,, , .2) ENSIDESA,Avlles, Spaln.

Tyne, NEI 7RU, U.K.

(Received on October 5, Ig90; accepted in the final form on November16, 1990)

Recently, reserves of good coking coa[s have becomeless available and comparatively moreexpensive. Resources

are being extended by the use of coal blends with difterent coking properties and/or selective additives. Coal preheating

technology emergedas a technique to overcomesomeof these problems. It has several advantages including: in-

creases in coke oven productivity, improvements in quality of metallurgical coke, greater uniformity of charge, Iess air

pollution by using a closed charging system, Ievelling of the charge, a saving in energy becausedry coal is moreefficient in

the preheater than in a coke oven, and the possibility of using poorer and cheaper coking poals. Thedisadvantages of

this technique are the handling of fine and hot coal, the carry-over and the preheater fines.

Currently, the preheating process is being re-considered in combination with dry-cooling of coke in a European

Research Project called "JumboCoking Reactor", which is based on past and current experience of development of

moderncokemakingtechnology.

This study reviews preheating technology as a meansto widen the range oi coking coals including not only the high-

volati[e coals which are moreabundant, but also semi-anthracite and petroleum coke. A6t Experimental CokeOvenand

a 2tfh Preheating Pilot Plant (Precarbon Process) were used.

KEYWORDS:carbonization; preheating; future of carbonization; coke quality.

1. Introduction

In the 1950s, there was a considerable and special

interest to develop newcarbonization technologies as

a wayof utilizing coals of poor coking properties and

so to increase the range of coals that could be used

for cokemaking. Main reasons were previous fore-

casts about pessimistic future shortages of goodcoking

coals and increases in the demandfor iron and steel.

Coal preheating technology emergedas a promising

technique and it was received enthusiastically. Thedrying process of coals could be performed more efli-

ciently in the preheater before charging than in the

coke oven, to be used only for carbonizations.

The preheating of coal prior to carbonization wasintroduced by the coking industry at a number of

commercial plants around the world in the late 1970s,

but the trend declined in the 1980s.

However, currently and in the near future, pre-

heating will again be considered in combination with

dry-cooling of coke in an ambitious EuropeanEureka

Project under Germanleadership.

Three preheating processes reached the stage of

industrial application and have all been described in

the technical literature. 1,2) Acomparison of preheat-

ing systems wasmadeby Graham.8)Thermocharge4~7) and Precarbon8~12) use an en-

trainment type unit for preheating the coal in twostages and a gravity method for charging the pre-

heated coal to the ovens. In the Thermochargesys-

tem the hot coal is charged from a specially designed

charging car and in the Precarbon system the hot coal

moves along a chain conveyor and into a special

charging unit. Further developments of the initial

Precarbon system have been carried out.13)

To simplify the Precarbon preheating technology,

a single stage plant with a larry car was operating in

the coke oven plant at USSteel's Fairfield works.14)

Coaltekl5-18) uses for preheating a hybrid unit fluid

bed-entrainment type and for charging the preheated

coal to the oven a system in which coal is fed into the

ovens through a pipeline, using, originally, super-

heated steam as the carrier medium, although later

nitrogen has also been used.19)

2. Advantagesof Preheating

The main advantages that have been claimed for

the preheating technique are :* An increase in oven throughput (productivity)

due partly to the greater weight of dry coal charged

to the oven and partly to the reduction in car-

bonising time. The increase in throughput can

range from about 30 wto/o for the higher rank coals

to 50 wto/o for the lower rank coals, comparedwith

the use of wet coal of 10 wto/o moisture. Alterna-

tively, a lower flue temperature can be used to ob-

tain the sameproductivity as for a wet charge.

* An improvement in coke strength in terms of

all the conventional parameters of quality. Theimprovement in resistance to abrasion (MIO mdex)

can be explained by the increase in bulk density of

the charge. This differs from normal carbonizing

conditions whenan increase in bulk density of the

charge decreases the coarse breakage resistance

(M40 mdex). Surprisingly, this is not brought

449C1991 ISI J

ISIJ International, Vol. 31 (1991), No. 5

about by preheating. Factors other than chargebulk density affect breakage resistance. Two ofthese20,21) are a better mineral matter distributionand changesin thermal conditions of carbonization.The reduced rate of heating of preheated coal inthe oven leads to an increase in the width of theplastic zone (300-500'C) and semi-coke zone (500-700'C), so improving the coke breakage resistance.In general, degrees of improvement are larger thelower the rank of the coal.

* Widening the coking coal range. The propor-tion of poorer and cheaper coking coals can be in-creased without impairment of coke quality.

* Improvementin the yield of coke in the usefulsize range for the blast furnace. The proportionof coke in the useful size range for the blast furnaceis generally increased.22)

* High operational flexibility because control ofthroughput can be achieved by adjustment of thepreheated coal temperature and depending onchoice, both preheated andwet coal can be charged.

* Moreuniformity of charge throughput of theoven. Elimination of the water from the ch,argeprovides more uniform heating conditions for the

ovens as vvell as le likelihood of " green " pushes.Thermal shock to the refractory brickwork is alsoreduced.

* Improvementof environnrent protection. Lessair pollution, becauseofthe use ofa closed chargingsystem (at least with pipeline and chain conveyorcharging) and removal of the need for mechanicallevelling of the wet charges. There are reducedpollution emissions during the pushing operationbecause the charge is moreevenly carbonized.

* Energy saving. A net saving of 8-12 o/o in the

energy used to produce coke by preheating hasbeen proposed.23)

This energy saving camefrom the reduction incarbonizing time and temperatures and also, be-

cause the entrainment type of preheater is a moreefficient dryer of coal than the coke oven (steamleaves at a lower temperature).

It has been shownthat the two-stage preheatersused in the Thermochargeand Precarbon systemsare more efficient than the single-stage Cercharpreheater.24)

* A reduction in capital andoperating costs pertonne of coke produced. This depends largely

on the balance between additional capital costs ofthe preheater and the increase in throughputreached and whether or not cheaper coals are used.

A comparison of coal preheating (Precarbon s~s-

tem) and partial briquetting techniques has beenmade,11) and concludes that the capital costs of acoal preheating plant are higher than those incurredby partial briquetting. Thesehigher costs seemtobe compensated by the increase in throughputachieved. With the Precarbon process, calcula-tions have demonstrated the economic efiiciency ofusing preheated coal whenusing batteries of 4.5 mheight in comparison with the alternative of build-ing new coke oven batteries with larger capacity

(7.5 movens and wet coal).25)

Finally, although most of the beneflts can be quan-tified in terms ofmoney, manpowerand energy, thereare other benefits very difficult to quantify, such as theconsiderable improvemen+in blast f' urnace operationby using the more consistent and improved coke pro-duced from preheated coal.

3. Drawbacks

Given all the above benefits, it maywell be askedwhy, after at least two decades of development, pre-heating is not used througkiout the world morewidelythan at present (the appearance ofpublications on the sub-

ject has declined recently). Despite muchapparent en-thusiasm by research workers, contractors and at least

somecommercial users ofpreheating, the technique is

by no meansgenerally applied at coking plants. Thisis due mainly to economic factors such as the declinein coke demand. But, there are also reasons of amore technical kind. Hesitation to introduce a newtechnique that certainly adds to the complexity ofcoke oven operation must play a large part in pre-venting a morewidespread adoption of preheating.

In a survey of BCRAresearch on preheating)26) themain disadvantages are stated to be the problem ofhandling hot coal (the pollution and oxidation risks),

carry-over, and the fines from the preheating andhandling plant. The use of a charging car carriesrisks of pollution during the filling of the hoppers andof erratic coal flow; in pipeline charging with steam(nitrogen is nowpreferred, however), the plugging of noz-zles and condensation present problems. Difliculties

in the use of chain conveyors for transporting the hotcoal arise from increased resistance to motion, falls ofcoal at steep angles, rapid wear, inadequate sealing,

and troublesome maintenance. Further problems in-clude26) : the high rate of gas evolution during charg-ing; the danger of over-filling the oven; the possibilityofgenerating an explosive mixture in the charging carhoppers; the pressure rise in the oven and the greaterdifliculty in controlling the level of the charge in pipe-line charging; the smaller shrinkage of the charge(necessitating an adjustment to the vertical heat distribution

in the flues) ; and the solids carry-over, which is ad-versely affected by air ingress during gravity chargingand depends on operating conditions and pipe entryconfiguration in pipeline charging.

Germanworkers27) consider the drawbacksas beingthe need for additional equipment (with its cost and the

greater complexity of operation) and the carry-over prob-lem (leading to a fall in the tar quality and the danger ofblockage of gas mains). The latter can be minimisedby adding a binder to the coal or dealt with by the

use of a separate " charging main "; but these meanrespectively a smaller increase in the bulk density ofthe charge and an increase in cost. According tothese workers, carry-over is better avoided by com-bining preheating with stamp-charging.

Of these drawbacks, the carry-over is perhaps the

most important. Several studies28~31) have been de-voted to the control of carry-over and techniques to

450

ISIJ International, Vol. 3l (1991), I¶o. 5

reduce it.

A few coking plants have abandonedpreheatingafter initial enthusiasm and in 2instances reasons havebeen published. At the Redcar works of the British

Steel Corporation, where a whole series of disasters

due to poor engineering led to irretrievable damagetonewly-built coke ovens using the Coaltek preheatingand pipeline charging system, the reasons given32) for

returning to wet charges for rebuilt plant were:(a) There was a need to guarantee the perform-

ance and lifetime of the ovens.(b) The economic advantage in using local high-

volatile coals (which anyway had deteriorated in quality)

had disappeared because of the availability of cheapimported coals.

(c) The type of coal blend being used to producehigh-quality, unreactive coke for the giant Redcarblast furnace was possibly not ideally suited to pre-heating.

(d) Preheating meant relatively high manninglevels and maintenance costs (the effect of which was to

increase the cost of the coke if high output wasnot consistently

maintained).

At Iscor's Pretoria works in South Africa, an early

version of the Otto-Simon Carves Thermochargesys-

tem was installed, but prehating has since been aban-doned as uneconomic (running costs were high, the

coke reactivity tended to increase and tar quality andpollution posed fairly severe problems). Partial bri-

quetting of the charge has been preferred as a meansof improving the coke quality. It should also benoted in this context that Nippon Steel has selected

Precarbon at its Muroranplant. Elsewhere, at Oita,

Kawasaki plant at Chiba and NKKplant at Fuku-

yamapartial drying to a controlled moisture contentof the charge (4 to 5wto/o moisture) is used withheat from CDQ. This is a simpler technology withbenefits qualitatively similar to several of those ofpreheating.

4. Conclusions about the Preheating Process

The first conclusion to be drawn from this reviewis that at least someof the advantages need qualifica-

tion; there is rather less ground for optimism thansuch a list suggests. Thus the increase in productivityattainable maybe limited by the nature of the coa]

charged because of restraints imposed by coal rank,swelling pressure, coke shrinkage, and/or coke quality,

as well as by the methodof charging. To obtain the

greatest benefit in terms of coke quality, the poorercoking, higher volatile coals must be used; with coals

of better coking capacity, somedeterioration in quality

mayeven be experienced. Third, the high mobilityof hot, dry coal does not necessarily meana com-pletely uniform and level charge in the oven, partic-

ularly with pipeline charging; adjustment of the heat-

ing of the ovens maybe needed to compensate for

segregation, and without a mechanical leveller, oc-casional piling-up of coal has to be tolerated. Again,the avoidance of air pollution during charging is

achieved only by good sealing arrangements and. at

the expense of carry-over and its attendant problems.Lastly, the savings in energy comsumptionand costsof coke production do appear to be very variable, oreven non-existent in unfavourable circumstances.

There is no doubt that the addition of preheatingmakescoke oven operation more complex and moresensitive to disturbances. Most commissioning andoperating problems of an engineering kind can be

overcomeby careful attention to design' and materials,

or by minor modiflcations; with past experience as abasis, modern installations should not be subject to

so manyfaults as were the older ones. But the provi-sion of numeroussafety features, instruments and con-trols, a high standard of maintenanceandwell-trained

operators are essential. Standby preheating equip-

mentmust be installed.

Thus one major drawback, if it can be regafded assuch, to the use of preheating is the need for steadyoperation, high-quality supervision and regular atten-tion to maintenanceof both preheating plant andcoke

ovens as well as properly standardised operating pro-cedures. Froman economic point of view, it is im-portant to be sure that the demandfor coke from the

plant does not decrease signiflcantly in the short to

mediurn term, and that the coals to be used will in-

deedcontinue to be cheaper than others that could becarbonized in wet charges to makecoke of the samequality. Installation of preheating plant for onlyshort-term use would hardly be justifiable.

To sumup, there are indeed drawbacks to the pre-heasing of coal for cokemaking, but it seemsthat in

manysituations these can be tolerated or are insufn-

cient to mitigate against the use of the technique:Clearly, each instance needs individual assessmentand

very careful consideration of manyfactors.

5. Development of CokemakingTechnologyPresent andFuture

5.1. Combination Coke Dry Qjuenching (CDQ)-Coal Pre-

heating Process

Dry cooling (quenching) of coke is a well-estab-

lished technology in the cokemakingindustry33) havingbeing practised widely in the USSRand Japan but

not yet to any significant extent in the western world.

The existing conventional coking process is very

poor in terms of energy efliciency and one meansto

increase this efliciency is the recovery of most of the

large amount of energy which emerges as sensible

heat of the coke, energy which is otherwise wasted in

the normal process of cooling by quenching with

water. Dry cooling plants are built not only to re-

cover energy, but also to protect the environmerlt.

Further advantages are low reactivity, improved sta-

bility and abrasion resistance, and also moreuniformsize distribution of coke.34,85)

The main drawback of coke dry cooling (quench-

ing) (CDQ)is the higher cost for the installation in

comparison with wet quenching and the assessmentof the possible application of dry cooling dependsonthe prospects of energy utilization and' its evaluation;

A study of energy utilization possibilities has been

451

ISIT International, Vol. 31 (1991), No. 5

madein Germany.36)The combination of coal preheating and coke dry

cooling has practical advantages in relation to effi-

ciency of utilization of the energy recovered and tosafety in operation. Barker et al.24) published a paperconcerned with this combination and the meanswhereby it maybe effective in practice. The energycycle of cokemakingwould thus be morenearly closed.

In 1979, Stahlwerke Peine-Salzgitter AG, DidierEngineering GmbHand Dr. C. Otto & Companyadopted this idea, using as carrier gas blast furnace

gas and decided to try it out in a pilot plant atSalzgitter.37) The namegiven to the process was" CombiCoke"

The CombiCokepilot plant was successfully op-erated over a test period of I I monthsand the proc-ess did not cause any particular technical problems.The combination of CDQand preheating processbecomessimple because steam is not condensedandremains in the gaseous heat carrier.38) Fig. I repre-sents this kind of combination. Since steam is con-tinuously generated during coal drying, the circulating

gas consists mainly of steam. As a consequenceex-cessive steam has to be removedfrom the circulating

gas so avoiding environmental problems.Cokeburn-off causedby the water-gas reaction was

minimised following application of ideas from labora-

tory scale studies with a thermobalance at the Engler-Bunte Institute of the University of Karlsruhe39) andseveral tests carried out in a semi-technical CDQ_-device at Bergbau~ForschungGmbH40)based on thekinetic parameters measured in the laboratory tests.

Fig. 2 shows the schemeof the semi-technical ap-paratus constructed for CDQwith steam; the heattransfer to the coal preheater is simulated by a heatexchanger. The CDQ-chamberhas a diameter of0.5 mand consists of 3zones: prechamber, co-currentand countercurrent zone.

Theenergy saving proposed for this combination of

CDQand Coal Preheating process is illustrated inFig. 3. This combination wili be used in a researchproject : " CokingJumboReactor "

5.2. JVlew CokemakingSystem: JumboCoking Reactor

The state-of-the-art of coking technology duringthe 1970s is summarisedin Table I and of the 1980sin Table 2 for a capacity of 2mty coke, taken bothtables from the G. Nashanpaper presented in theIst International Cokemaking Congress.41) In thelater 1980s. Ruhrkohle AGbuilt the largest cokingplant in the world, i.e., Kaiserstuhl 111,42) and havingcoke oven dimensions based upon experiences of op-eration of wide oven chambers at the Bergbau-ForschungGmbHProsper Testing Plant,43) RAGnewProsper Coking works,44) and Mannesmannr6hrenWerkeAGnewHuckingen CokeOvenPlant.45)

Theseprojects above represent significant improve-ments in cokemaking technology, especially for emis-sion control in terms of the numberof pushed ovens/24 h, and sealing for a specific output. Environmen-tal compatibility and profitability of processes for cokeproduction must be moredemandingand for this rea-

i] LL~~~~~~2L][~'I

Generator

l 100'C

r~Z~~Z~~rl[~~~LJ

Exc' steam

Cokel 100'C

Coal80'c Coal

20'c

steamCycle

Coke150'C

Fig. I .Schemefor direct combination CDQlcoal preheat-

ing using steam as the heat carrier.88,

Ilac8ladescent Col,e 8OIglh

Ptechamber2.35 m

CQunter4un~rt2.55 m

ColEeBu!nHDff0.4 * 0.6 ~,

Fig. 2,

b.5i

1-1~t"'

50p

bo6bf

l zo'C

650'C

l 20'C76 m3lh

CoolingAir

Heat E:ehanger

w.steCoeled

Stealn

Col,e

Schemeof the semi-technical test plant for coke dryquenching (CDQ,) by steam.B8]

CokePl8nt vith WetCo•]Ch•r8,,Ig llnd Wetgucochlp,

ElectTicity steaulCOl,Wh 134 l,g

4B~

192!n:3 =CokePlant

Gasor Sale

Underfidng288m3

G8!,

CokeP,luat with a CombinatlonCDg/CoalPreheathg

Electrlclty83 l,Wh

UnderflrtngGas

All Values Related to It of CokeCd.b.)

80OMJ

351 m3(+ 63m3J

Fig. 3. Thermal efnciency of a coke plant with wet coal

charging and wet quenching and with a combina-tion CDQrCoalpreheating process.38)

son, Ruhrkohle AGtogether with the former Bergbau-ForschungGmbHandcoke plant builder in Germanyadvancedplans for a newcoking system41) :

452

ISIJ rnternational, Vol. 31 (1991), No. 5

Table l. State-of-the-art in 1970s (" Old design ").

Plant and operational data for a capacity of

2 mty coke.41)

Coking plant

Small Medium LargeOhgishima

Dimensions (usable) :Height (m)Length (m)Width (m)

Useful volume (m8)Productivity coke/Oven (t)

Numberof ovensTotal oven openingsLength of sealing faces (km)Numberof pushed ovens/dTotal of opening cycles/d

Length of sealing faces tobe cleaned (km/d)

4.50

l I .70

O.45

22. l

12.7

322

2898l0.5

430

3870

14.0

6.OO

l4.20

O.45

36. 4

21 .3

l87

14966.9

257

2056

9.5

7.6S

I6.40

O.43

52. 2

32. O

123

9845.1

171

l 368

7.2

Table 2. State of the art m1980s (" Newdesrgn ")

Plant and operational data for a capacity of

2 mty coke.41)

Coking plant

KaiserstuhlHuckingen Prosper 111

Dimensions (usable) :Height (m)Length (m)Width (m)

Useful volume (m3)Productivity coke/Oven (t)

Numberof ovensTotal oven openingsLength of sealing faces (km)Numberof pushed ovens/dTotal of opening cycles/d

Length of sealing faces tobe cleaned (km/d)

7.850

l7.200

O.550

7043

. O220

10806.0

128

1152

5.6

7.100

l5.900

O.590

62. 3

39. 8

142

l 2786.2

138

l 242

6.0

7.630

18.0000.610

78. 9

48. 7

l20

l 0805.5

ll5

l 035

5.3

* Combining preheating process and dry cooling(quenching).

* Instead ofmulti-chamber system, a singl.e reactor.* Instead of flexible heating walls, rigid, pressure

stable horizontally supported heating walls.

* Instead of heating flues, to supply heat to twochambers, with independent systems of heating for

each reactor.* The supply of heat to the single reactor will be in-

dividual and proportional to demand.* Instead of reducing the emissions by costly mea-

sures for elimination of damage,emphasis will begiven to the prevention of causes of damage.

* Instead of recovering classical by-products, it will

be alternatively possible to produce and furnish

hydrogen or synthesis gas.* Instead of three-shift working operation, a possible

change to two-shift.

Aschemeof the " JumboCoking Reactor " systemcan be seen in Fig. 4.41) Twobasic proposals for the

design of the "Jumbo Coking Reactor" have beenworked out: with underneath-arranged regeneratorand with side-arranged regenerator.

Plant and operational data for the " JumboCokingReactor " for a capacity of 2mty coke are in Table3.41) Possible beneflts can be seen comparing datafrom Table 3 with data corresponding to the state-

of-the-art in 1980s (Table 2).

To explore the possibilities of the " JumboCokingReactor ", Eureka Project wasaccepted by the Euro-

pean Communityon the Ist June, 1990 in Romewiththe leadership of the GermanCoking Industry and the

cooperation of other European companies on asmaller scale.

6. Spanish Experience on Preheating Process

At the begining of 1980 a coal preheating pilot

plant, Precarbon system, was built by the SpanishSteel Company(ENSIDESA)on the premises of the

Fig. 4.

Schemefor the " JumboCoking Reactor ",41)

CokingReactor

IndividuallyControlled

CokeDryQuenching

GasTreatment

CokeGasSynthetic GasHydrogen

453

ISIJ International, Vol. 31 (1991), No. 5

Table 3. State-of-the-art in future-oriented "JumboCoking Reactor "

Plant and operational data for a capacity of

2 mty coke.41)

Stu dy

Basis Feasibility

Dimensions (usable) :Height (m)Length (m)Width (m)

Useful volume (m3)

Productivity coke/Ovens (t)

Numberof ovensTotal oven openingsLength of sealing faces (km)Numberof pushed ovens/dTotal of opening cycles/d

Length of sealing faces to becleaned (km/d)

1O.OO

19.00

O.85

l50. O

lOO. O

55llO

2.455

llO

2.4

l2.50

25.OO

O.85

255. O

165. O

3366

1.8

3366

l .8

Spanish National Coal Institute (INCAR), Iocated inthe vicinity of Oviedo. This preheating plant wason-line with the INCARCoking Test Plant (Fig. 5)

which comprises 4ovens of equal length (6.5 m) andheight (2.8m) to arch but of different widths from300 to 450mm. The heating system is independentfor each oven and the coal capacity is from 4 to 6t.

Although the initial prospects to introduce coalpreheating in Spain have not been fullfilled becausethere wasneither the anticipated increase in coke de-

mandnor the shortages in good coking coals; also inthe Spanish situation there are no cheaper coals avail-

able.

Someresearch work has been carried out withECSCand Spanish Governmentsupport.

At INCAR,studies are devoted to widen the rangeof coking coals, not only of traditional and moreade-quate high volatile coals, but also to include low vola-tile (semi-anthracite) and petroleum coke. Asimilarstudy was presented at the Ist International Coke-making Congress,46) but currently a difference is tokeep the volatile matter of the blend at the samelevel

or below that of a reference base-blend. An indus-trial blend, producing a good quality coke for theblast furnace, does not reduce the specific output ofthe process by increasing volatile matter of the blendas would be got by adding high volatile coals.

6. 1. Installations Used

A 2t/h preheating pilot plant, Precarbon process(diagram in Fig. 6), and the 6t oven of the INCARCoking Test Plant were used. This plant has also

by-products recovery, gas holder, oxygen analyzers,

gas recording calorimeter and gas chromatograph online, and coal storage, crushing and blending facilities.

6. 2. Experimental Procedure andResults

Table 4shows characteristic data of the coals andpetroleum coke used, as received. Coal blend A is

typical for the Spanish Steel Company-ENSIDESA-producing a goodcoke quality for the blast furnace.It is complex because it uses more than 15 different

Fig. 5. Preheating plant at Spanish National Coal (INCAR).

Table 4. Characteristics of industrial base-coal blend

and additives used.

Base-coal Coal Coal Petroleumcokeblend A B C

Moisture (wto/o)

Ash (d.b.) (wto/o)

Volatile matter (d,b,)(wto/o)

Sulphur (d.b,) (wto/o)

Swelling index

Arnu (a+b)Meanreflectance (o/o)

St, deviation

9.28,l

25, 7

O,88

7,580

I ,15

O,32

6.88.2

32. 2

l .05

882

O.85

O.07

9.48.0

2.3

0.77

o

2.33

o.57

9.5

l .O

11.8

l .40

O

(d,b.): dry basis,

coals. Coals Band Care Spanish high volatile coal

and semi-anthracite, respectively.

Table 5shows the data of the coal blends, cokingconditions, and coke quality. The industrial coal

blend A is included as reference. Coal bulk densityis between740-750 kg m~3for wet charge and around760 kg m~3for preheated charges. Preheating tem-perature was 220:!15'C. Hot combustion gases wereproduced by burning coke oven gas with air. In all

cases coke pushing was I h after reaching I OOO'Cin

the centre of the charge. Cokesamples were takenin the wharf exit, with the minimumhandling as is

commonpractice at INCAR.The philosophy of the study was to compare in-

dustrial base-coal blend A wit.h blends produced byadding different amounts of high and low volatile

coals and petroleum coke andby reducing the averageof the coal blend A to 50 wto/o' In all cases, thevolatile matter of the prepared blends was lower than

or equal to the base-coal blend A.Additives impair the coke quality in terms of

454

ISI J International, Vol, 31 (1991), No. 5

1:

2:

3:

4:

5:

6:

7:

8:

9:

lO:

a:b:

d:

FeedbunkerDrying columnCyclonesPreheating columnCombustionchamberHot bunkerChain conveyorConnection chute

CokeovensWetscrubber

Wetcoal

COGCombustionair

Heat carrier gasWastegas

3

7

6 4

3

21

3 IO

a

e

8 d

i A

/ /

Fig.

5

6. Schemeof 2t/h precarbon pilot plant.

b

Table 5. Characteristics of blends, coking conditions and properties of resultant cokes.

ChargeBl.ENDCOMPOS1110N

Base-coal blend ACoal BCoal CPelroleum coke

BLENDANALYSTSMolsturc [wi. o~])

Ash (d.b.] (wt. o~,)

Volatlle matter [d.b.] (wi.

Sulphur [d.b.) [wt. 9,))

Swelllng IndexArnu (a + b)

COALSIZE AI,YSIS

olo)

>3nun

( 0.5 mmCARBONIZATIONCONDITIONS

Meanflue temperature ('C)

Coklng time (h:min]

COr(EANAI,YSISAsh (d.b.) [wi, o~)]

VolaUle matter (d.b,) (wi.

Sulphur [d.b.) (wt. %)CO,(ESIZE ANALYSIS

%)

> eomm80-20 mm

20mm120IIO

w P w P w w w W w P w W PPPI'i)I)wlOO 9O 90 eo eo eo eo 70 70 70 70 OO 50 50 50eo eo eo SO

6,3 6.3 12.6 12.6 12.6 12.6 18,9 18.9 18.9 18,9 25,2 25.2 25.2 25,2 31.5 31.5 31.5 31.5

7.4 7.4 11, I I I . I - - 14.8 14,8 - 18.5 18.5

3.7 3,7 7.4 7,4 11. I I I . I 14.8 14,8 18,5 rs,5 -

6.9 -7.7 -8,4 - 7.9 -7.9 -7. 3 -ll.5 - 7. I -g,2 6,8 -

8,1 7,8 7.0 7,4 7,0 8,0 8,0 7.4 6,8 8.3 8.4 7.4 6,2 8,5 7.7 7.0 6,3 8.7 7,7

25.7 25.4 25.4 25,2 24,7 25,7 24.9 25.S 24.9 25,6 24.1 25.2 24,9 25,2 24.2 24.7 24.1 24,8 24.7

0.88 O.go 0.88 0,92 0,87 0,90 0,87 0.96 0,94 0,91 0.89 1.04 l.oo 0.88 0.88 I.03 0.99 0.9Q o.eo

7 4,5 5 5 55.5 4.5 77 66 77 77.5 7.5 7.5 7850 42 37 27 42 3154 26 39 2666 44 55 45 47 41 51 33eo

12.7 I0,5 12.7 12,5 11,8 I0,6 15.3 8,6 5,8 9.8 9,6 9,7 7.0 Il.o 7,8 12.2 3.9 14.0 13.1

79, 1 82. 1 80.0 78, 8 82, 2 82, 8 77, 1 84.0 88, 1 8~, 7 84.3 ee, 8 87. 3 77. 6 86, 5 79.9 92.2 76,4 78, 536,8 38,0 56.0 33.2 592 41 9 488 379 59 6 358 52 6 36 1 58 8 31 4 608 358 679 31 3 52 7

1230 1265 1270 1245 1255 1220 1240 1240 1260 1225 1225 12eo 1240 1245 12eo 1245 1235 1240 124018:20 17:20 13:07 17:27 13:07 18:54 13:40 18:04 13:42 19:05 14:26 18:00 13:42 18:18 13:59 18:30 14:20 19:lo 14:oe

l o, 2 1o. 3 9.7 9, 9 9, 4 1o, 4 1o. 3 9.6 9, 2 1o, 8 1o. 1 9. 1 8,9 10,8 1o. 1 9, 1 8,9 11. I I0.4

O.6 0,3 0.4 o. I O. I 0.2 0,4 0.6 0.3 0,3 0.3 0.3 0,5 0,5 0.3 0.4 0.7 0.5 0,4

0.75 0,87 0,87 0.88 0.89 0.87 0,86 0.94 0.98 0,87 o.e6 0,96 l.ol O.e8 0,87 l.ol 0.97 0,92 0.89

54.2 52.8 37.9 5e,4 34,8 54, 1 52. 1 54.8 46.2 56,9 50. 1 49,9 46.4 58. 5 40. 5 58. 5 so.6 63.7 46, l40,8 43.4 5e. 5 42, 1 61, 6 41, 3 45. 2 40.7 49, 3 37. 1 47.0 43.6 49.7 34.4 55.8 S5,2 45.4 31.2 50, l

5.0 3.8 3.6 4.5 3,6 4.6 2,7 4.5 4,5 6,0 2.9 6.5 3.9 7.1 3.7 6.3 4.0 5,1 3.8

75.4 75.3 75.9 74. 1 75.7 74.0 76.4 73.6 75.8 72.7 75.9 71.3 75,7 69,9 75.9 69.7 75.7 e8.6 74.6

22. O 22.3 21.4 23, 1 21, 5 23, 3 20.9 23, 7 21.2 24.7 21.4 25. 6 21.7 26.5 21.4 27. 1 21.9 28.0 22. 5

W:Wetcharge: P: Preheated charge: (d,b.): dry basis.

mechanical strength (IRSID indices: 120 and Ino)

from charges of wet blends in all cases. This effect is

more markedwhen the proportion of the industrial

base-coal blend Adecreases from 80 to 50 wto/o (Fig.

7).

Preheating reduces the volatile matter of the coal,

the Arnu dilatation and the coking time but increases

notoriously the -0.5mmcoal size (Table 5). Pre-heating produces coke of slightly better quality fromall blends comparedwith coke from the base-coal

blend A, with the marginal exception of the blend

containing 50 wto/o of base-coal blend A, 31.5 wto/o

coal B (Spanish high volatile coal) with 18.5wto/ocoal C (semi-anthracite) (Table 5and Fig. 7).

At the same time, the production of coke in theuseful size range (20-80 mm)for blast furnace opera-tion increased always by using the preheating process(Table 5).

In conclusion, preheating can be used to widen the

range of coking coals not only to the high-volatile

coals but also together to include such low volatile

inerts as semi-anthracite and petroleum coke.

'455

ISIJ International, Vol. 31 (1991), No. 5

12Q78

76

74

72

70

e

68eo 90 1roIOO40 50 OO 70

Base-coal blend A(wt. olo]

eo

5)

6)

7)

8)

9)

lO)

li)

12)

IIO

28

26

24

22

20

e

40 CO 70 so eo mo I lOSO

Base-coal blend A(wt. olo]

I Coal Band petroleum coke. Preheated charge[1 Coal Band petroleurn coke. Wetcharge

A Coal Band Coal C. Preheated charge

A Coal Band Coal C. Wetcharge

O 100 wto/o ofindustrial base-coal blend A. Wetcharge

Fig. 7. Variation of IRSID indices of cokes from blends

with different contents of industrial base-coal blend

Aand addi.tives.

Acknowledgements

The authors are very grateful to Dr.-Ing. G.Nashanand Dr.-Ing. W.Rohdefor their permission topublish flgures from their papers presented to the Ist

International CokemakingCongress in Essen in 1987.

Also the authors thank ECSCfor the financial sup-port (Project 7220-EB1752). M.A.D. is grateful for

support from the Consejo Superior de Investi.gaciones

Cientificas, C.S.1.C., (Spain) to enable her to studyin the Northern CarbonResearchLaboratories.

REFERENCESl) J. Dartnell: IISI. Committee on Technology, IISI,

Brussels, June 1980, Vol. 1, 69100.2) W. Eisenhut: Chemistry of Coal Utilization, 2nd Supple-

mentary Volume,John Wiley and Sons, NewYork, (1981),

889892.

3) J. P. Graham: Conference on " Coal, Coke and TheBlast Furnace ", Royal Soc. London, Middlesbrough, (JLlne

1977), I17-123.

4) R. H. Chambersand L. A. Watson: Ironmaking Proc.,

Vol. 33, AIME, (1974), 233.

13)

l4)

15)

16)

17)

18)

19)

20)

21)

22)

23)

24)

25)

26)

27)

28)

29)

30)

31)

32)

33)

34)

35)

36)

37)

38)

J. McN. Bruce and W. Staniforth: Ironmaking Proc.,

Vol. 36, AIME, (1977), 62.

R. Pitt: Steel Times Int., (1981), June, 75.

W. Staniforth and D. B. Corry: Coke Oven Managers'Assoc. Year Book, COMA,Mexborough, U.K., (1983),

125-147.

K. G. Beck: Coke Oven Managers' Assoc. Year Book,

COMA,Mexborough,U.K., (1974), 230-242.C. Flockenhaus, J. F. Meckel, D. Wagnerand W. Rohde,lronmaking Proc., Vol. 37, AIME, (1978), 549.

D. Habermehland W.Rohde: Ironmaking Proc., Vol. 38,

AIME, (1979), 426.

K. G. Beck and J. F. Meckel: Ironmaking Steelmaking, 3(1980), Ill.

A. Suzawa, H. Kamoya,O. Mikumi, N. Noguchi and H.Matsuoka: IISI Committeeon Technology, IISI, Brussels,

June 1990, Vol. 1, 29-68.

W. Rohde: CokeOvenTechniques, Graham& TrotmanLtd., Luxembourg, (1981), 172-184.

D. Stalherm: Iron andSteel Eng., (1982), May, 25.

D. G. Marting and R. Marcellini: Rev. M~tall., (1976),

June, 46.

D. Crocker: Ironmaking Proc., Vol. 38, AIME, (1979),

455.

British Carbonization Res. Assoc. (B.C.R.A.) : Carboniza-tion ResearchReport 79, Chesterfield, Dec. 1979.

H. D. Hatters, J. L. Sundholmand R. F. Wall: Ironmak-ing Proc., Vol. 42, AIME, (1983), 321.

P. S. Allen and S. I. Pettifor: Coke Oven Managers'Assoc. Year Book, Mexborough,U.K., (1984), 136160.D. Gregory and J. Goleczka: Coke Oven Managers'Assoc. Year Book, Mexborough,U.K., (1977), 181202.S. Delessard and G. Prudhon: Ironmaking Proc.. Vol. 41,

AIME, (1982), 456.

J. P. Grahamand H. C. Wilkinson: Coke Oven Man-agers' Assoc. Year Book, Mexborough.U.K., (1980), 161-181.

P. B. Taylor and K.S.B. Rose: EnergyAudit Series No. 9,

The CokeMaking Industry, Dept. of Energy and Dept. of

Industry, (1979).

J. E. Barker, .J. McN. Bruce and R. Kemmetmuller: J.

Inst. Fuel, 91 (1978), 90,

W.RohdeandK. G. Beck: Rev. Me'tall., (1976), June, 495.

J. P. Grahamand V. J. Pater: Ironmaking Proc., Vol. 38,

AIME, (1979), 442.

G. W. Lask, H. Petak andJ. Echterhoff: Stahl. Eisen, 100(1980), I177-1183.British Carbonization Res. Assoc. (B.C.R.A.) : Carboniza-tion ResearchReport 62, Chesterfield. December1968.

British Carbonization Res. Assoc. (B.C.R.A.): Carboniza-

tion ResearchReport 92, Chesterfield, December1980.

Traitement des mixtes dans les cokeries modernes, SEMEUR-8386,(1982),

A. I. Aktay: Ironmaking Proc., Vol. 42, AIME, (1983),

383.

J. P. Guerin and M. M. Bowness: Ironmaking Proc., Vol.

42, AIME, (1983), 291.

H. Bertling and H. Baer : Glackauf, 119 (1983), 631.

Y. Miura, H. Haraguchi, J. Nishi and Y. Kogushi: Trans.

lron Steel h~st. Jpn., 21 (1981), 632.

J. E. Baker andJ. W.Patrick: Fuel, 64 (1985), 178.

H. Bertling and H. Baer: Glackauf, 119 (1983), 1203.

E. Teicher, J. EnB, J. F. Meckel and J. Tietze: Ironmak-ing Proc., Vol. 43, AIME., (1984), 29.

K. Hedden, H. Bertling, K. G. Beck. W. Rohdeand P.

Arendt: Ist Int. CokemakingCongress, Essen, Vol. 2,

European CokmakingComm.,Verlag Gluckauf GmbH,(1987), K3.

456

39)

40)

41)

42)

43)

ISIJ International. Vol. 3l

K. Hedden,J. Hess, K. Kaltenmaier and P. Missal : Gwf-

gas erdgas, 127 (1986), 149. 44)

W.Rohde, P. Arendt and K. G. Beck: Gwf-gaserdgas, 127(1986), No. 4, 145.

G. Nashan: Ist International CokemakingCongress, Essen, 45)

Vol. 1, European CokemakingComm.,Verlag Gluckauf

GmbH,(1987). A2.D. Breidenbach, W. Rohde, R. Beckmann,H. Dtrseln. W. 46)

Holz, D. Stalhermand and F. Wackersbarth: Ist Interna-tional Cokemaking Congress, Essen, Vol. 2, EuropeanCokemakingComm.,Verlag Gluckauf GmbH,(1987), F3.

W. Rohde, D. Habermehland K. G. Beck: Ironmaking

(1991). No. 5

Proc., Vol. 45, ISS-AIME, Warrendal, PA, (1986), I13.

W.Holz, F. Sch6nmuth,D. Stalherm and F. Wackerbarth:lronmaking Proc., Vol. 45, ISS-AIME, Warrendal, PA,(1986), 133.

R. Beckman,H. Bonnekamp,G. Winzer, H. Durselen. D.Heeseand G. Meyer: Ironmaking Proc., Vol. 45, ISS-

AIME,Warrendal, PA, (1986), 119.

R. Alvarez, E. Alvarez, C. Suzirez, F. M6ndezde And~s,E. Fern~ndez and M. Sirgado : Ist International Coke-making Congress, Essen, Vol. I, European CokemakingComm.,Verlag Gluckauf GmbH,(1987), E5.

457