This paper is an update of a previous publication in Spanish [1]. One of the current trends in the production of metallurgical coke is the comeback of non-recovery ovens. This is driven by less interest in byproducts, smaller investment per annual ton, better environmental performance. The development took place particularly in China, India, USA, Brazil, Australia and Colombia [2]. In the USA, one important factor promoting this technology was that EPA declared it as Maximum Achievable Current technology in 1990. This technology arises from the classic beehive ovens which supplied since the XVIII century the coke for the industrial revolution. Those ovens were manually operated, with small heat recovery, just for heating the oven. Now, non-recovery ovens are modern construction, with highly mechanized operation, and automated to a certain degree. Gases generated by the combustion of the volatile matter are sent through downcomers and further burnt to heat the oven bottom and sides; in many cases, mostly when the plant is built within or closed to a steelmaking facility, the hot gas is used for vapor generation and electric power production. Main differences between conventional and non-recovery/heat recovery processes are shown in figure 1. In conventional process, the coal charged receives the heat indirectly through the furnace walls, by combustion of external gas; inside the oven, positive pressure develops. Gas generated in the coking process is sent to the by-products plant. In non-recovery ovens, coking proceeds from the top through direct heating by the partial combustion of the volatile matter over the coal bed, and from the bottom by heat coming from full combustion of gases escaping from the oven. In these plants, the offgas is treated and sent to the stack, in many cases after recovering sensible heat to produce vapor and electric power. Installed capacity for these furnaces was esteemed in 2005 in 22 M metric tons per year, probably including beehive ovens [2]. In table 1, some of the non-recovery coke plants currently operating are listed. Some plants belong to companies with coal mining as its core business; others are independent coke producers, purchasing coal and selling coke; then there is some joint ventures between coke producers and steelmakers, and finally, captive coke plants belonging to steel companies.

1. Jorge Madias, Mariano de Cordova
Consultants
Metallon
jorge.madias@metallon.com.ar
Non-recovery/Heat recovery Cokemaking: A Review of Recent Developments

2. Content
Introduction
Equipment
Blend design & Coke quality
South American experience
Conclusions

3. Introduction
Australia: two plants
Brazil: two plants
Colombia: two plants
China: thirteen plants
India : eight plants
USA: four plants

4. Introduction
Main features of conventional and heat- recovery cokemaking

5. 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

6. Equipment
Comparison
Process
Charge preparation
Charge
Refractories
Discharge
Dimensions
(m)
SinoSteel
stamped charging
top
fall to wagon
28-40 x 32- 44 x 0.56 (vertical)
SESA Goa
standard
top
aluminous
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
aluminous
inside cooling, manual
3 x 22.6

7. 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

8. 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

9. Equipment
SunCoke

10. 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

11. Equipment
SinoSteel (horizontal ovens)

12. 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

13. Equipment
SinoSteel (vertical)

14. 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

15. 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

16. 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)

17. 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

18. 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

19. 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

20. 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

21. 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

22. Blend design & Coke quality
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

23. Blend design & Coke quality
 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)

24. Blend design & Coke quality
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%

25. Blend design & Coke quality
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

26. Blend design & Coke quality
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

27. South American experience
Coqueria Sol, Serra, Brazil (SunCoke)

28. South American experience
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

29. Latin American experience
Carbocoque, Lenguazaque, Colombia (own design and construction)

30. 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

31. Jorge Madias and Mariano de Cordova Consultants metallon jorge.madias@metallon.com.ar
Thank You