Non recovery-heat recovery cokemaking - a review of recent developments

Jorge Madias, Mariano de Cordova

Consultants

Metallon

[email protected]

Non-recovery/Heat recovery Cokemaking:

A Review of Recent Developments

mailto:[email protected]

Content

Introduction

Equipment

Blend design & Coke quality

South American experience

Conclusions

Introduction

Australia: two plants

Brazil: two plants

Colombia: two plants

China: thirteen plants

India : eight plants

USA: four plants

Introduction

Main features of conventional and heat-

recovery cokemaking

Equipment

Suppliers

SunCoke (USA)

Beijing SinoSteel Industry & Trade - SSIT (China)

Sesa Goa (India)

Uhde (Germany)

CISDI / MMC (China)

in-house knowledge

Shanxi Sanjia in China

Bla, India

Ilawarra, Australia

Carbocoque, Colombia

Equipment

Comparison

Process Charge preparation Charge Refrac

tories

Discharge Dimensions

(m)

SinoSteel stamped charging top fall to wagon 28-40 x 32-

44 x 0.56

(vertical)

SESA Goa standard top alumin

ous

fall to wagon 2.7 x 10.8

vibrocompaction horizontal

Uhde stamped charging

(charging machine

does not enter into

the oven)

horizontal silica push to wagon 3.8 x 15.0

SunCoke standard horizontal

(PCM)

silica fall to wagon 3.7 x 14.0

SJ-96 With cold oven manual alumin

ous

inside cooling,

manual

3 x 22.6

Equipment

SunCoke

First to include a power station to recover heat in

the off-gas

23 refractory brick shapes

Coal blend charged through one side, by means

of a Pusher Charger Machine (PCM) moving over

rails close to the ovens

Temperature, pressure and inner combustion are

controlled in the ovens

Equipment

SunCoke

Coke withdrawal with same PCM

All water used for coke quenching is recovered,

except evaporation loss

Process hot gas, after going through the bottom of

the oven, goes up to the duct

Gas to boilers, for steam production

Gas to the stacks

Desulphurization by aspersion of lime slurry on the gas

More than 80% SO2 generated during coking is

eliminated, with calcium sulfate/sulfide as a waste

Equipment

SunCoke

Equipment

SinoSteel: Horizontal & vertical ovens

Horizontal

Oven roof is a 120o arch structure

Adjustable primary air inlets are evenly installed in the

arch

Four linked arches are used at the oven bottom

On the base of the arches, adjustable secondary air

inlets are installed

Flues inside wall and bottom can be coordinated

A ventilation layer between the foundation of the oven

and the sole prevents the base plate from overheating

Main wall is equipped with suction-adjusting facilities

Equipment

SinoSteel (horizontal ovens)

Equipment

SinoSteel (vertical ovens)

First one built in 2002 in China

Less land and 20-30% less construction work

Separation between coking chamber and

combustion chamber avoids the burning of the

coke that may occur in horizontal oven

Heat comes only through refractories, as in

conventional batteries

Two layers of air cooling channels at the bottom of

the batteries

Foundation temperature between 100-150 oC

Equipment

SinoSteel (vertical)

Equipment

SinoSteel (vertical)

Typical technical parameters, 0.2 – 0.6 Mtpa plant Value Value

Carbonization

chamber height

(mm)

3200 – 4400 Partition wall

thickness (mm)

100

Carbonization

chamber length

(mm)

12570 Thickness of the

oven sole (mm)

1182

Average width

(mm)

560 Useful height (mm) 2800 - 4000

Center distance

(mm)

1180 Center

temperature (oC)

1000 +/- 50

Charge weight (t) ≈24 Pushing coke (t) ≈18

Cake bulk density

(t/m3)

1,0 – 1,1 Off-gas (Nm3/h) 350000

Coking time (h) 38 Off-gas

temperature (oC)

950 +/- 50

Number of ovens 4 x 35 Power plant 2 x12 MW

Equipment

SinoSteel

After desulphurization and dust extraction

treatment in the power plant, SO2 < 100 mg/Nm3

and PM10 < 50 mg/Nm3

Environmental equipment includes gas

desulfurization and dust extraction for coal

charging and coke crushing

Equipment

Sesa Goa Ovens are narrower than

SunCoke. This makes

possible to use roman

arch for the roof

Aluminous refractories

(better behavior under

oxidizing atmosphere,

better resistance to

thermal shock and less

volume changes upon

cooling, when there is

some delay in recharging

the oven)

Equipment

Sesa Goa

Simultaneous vibration and compaction, within a box, in

three successive layers, for higher charge density

24 plates covering the full surface of the “cake” are

actuated during two minutes for each layer

Up to 70% semi soft coal

Equipment

Uhde

Redesign and building of two ovens at Illawarra

Coke Co., Australia

Tunnel for off-gas runs laterally below the oven

floor level, instead of over the ovens

Charge and discharge are carried out with two

different machines

Equipment

Uhde The charge being previously stamped, there is no need for

the machine to enter into the oven, avoiding water cooling

and water to humidify coal

For discharge there is no fall of the coke, keeping the cake

without breaking, thus favoring lower emissions

Equipment

Uhde

Thermal modeling exercise

ovens must be kept at as high a temperature

as possible if the optimum gross coking times

are to be achieved

so, VM% is limited, to achieve an adequate

heat balance with a 1 m bed height, density

>1050 kg/m3 and gross coking time<60 h

therefore, heat recovery coke oven must be

airtight

Equipment

Uhde

Thermal modelling conclusions

Adjustment of the primary and

secondary air flow at the right

point in time is key to

temperature regime in the oven

Supplying primary air through

the oven top promotes surface

heating of the charge in ovens

longer than 10 m and is an

advantage over air supplied

through the oven doors at the

sides


Non-recovery /heat recovery batteries produce

a quality coke for blast furnaces, cupolas,

ferroalloy smelters, etc.

high quality coke for blast furnace operation with

high PCI, where better properties are needed

standard coke based on blends with some

proportion of non coking coal


Shanxi Sanjia (China) reported a coke quality

with ASTM stability and hardness, as well as

CSR, equal or larger than 70

22.5% volatile matter, reflectance of 1.31 %

and a high fluidity (7782 ddpm), due to

influence of a local high range coal with

excellent plastic properties

Oven size must be of help: low heating rate

(better wetting, bonding, and lesser differential

stresses, more formation of pirolitic carbon)


JSW Steel, India

To increase percent of non-coking coals,

obtaining a coke with reasonable quality for their

blast furnaces

Optimizing coal humectation and using

vibrocompaction, a charge density of 1.1 kg/dm3

was achieved

Up to 35% of non-coking and weakly-coking coals

Coke: CSR >64%, reactivity <25% , M10 <6%


Volatile matter in the blend

is an important parameter

in non-recovery

cokemaking, as the energy

required by the process is

contributed by their

combustion

A certain minimum content

is required. But if VM is too

high, coke may have high

porosity, being too reactive

to CO2 and with low post-

reaction strength


SunCoke’s IHCC 1998 – 2000

Start-up with 30% volatile matter (dry basis), 3097

ddpm maximum fluidity and 1.11% maximum

vitrinite reflectance

Then the blend evolved to less fluidity (200

ddpm), less volatile matter (22%) and higher

reflectance (1.42%), with an important content of

low volatile coal, which would resulted in wall

damaged in a conventional battery, due to

expansion at the end of coking typical of these

coals. Coke quality continued to be high, despite

of the changes


Coqueria Sol, Serra, Brazil (SunCoke)


Some features of ThyssenKrupp CSA non-

recovery coking plant (CISDI/MCC)

Ítem Description

Coke capacity, dry basis (Mtpa) 2.05

Coal handling capacity, dry basis (Mtpa) 2.70

Number of ovens 432 (3 batteries of 144 ovens each)

Power generation capacidad (MW) 175

Own personnel (operation and

maintenance)

230

Área ocuppied by batteries and ancillary

equipment

370.000 m2

Latin American experience

Carbocoque, Lenguazaque, Colombia (own

design and construction)

Conclusions

Non-recovery/heat recovery oven batteries are expanding in

Australia, Brazil, China, Colombia, India and the USA

They demand smaller investment and they are less polluting,

because of the operation with negative pressure

With the same coal blend, better coke quality is obtained

More coals may be used, including low volatile expansible

coals, low caking coals and other carbon-based raw materials

More flexibility in the use of these coals is obtained through

compacted charging

Oven design by different suppliers starts to have some

common features

Jorge Madias and Mariano de Cordova

Consultants

metallon

[email protected]

Thank You

mailto:[email protected]

Non recovery-heat recovery cokemaking - a review of recent developments

Engineering

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