foundry coke without coal - more than half a century of production in argentina
TRANSCRIPT
Foundry coke without coal: more than half a century of production
in Argentina
Jorge Madias Mariano de Cordova
San Nicolas, Argentina
Content• Introduction• Raw materials• Blend design• Coke plant operations• Coke quality• Conclusions
Introduction
• Foundry coke is produced in Argentina using domestic raw materials, with any coal at all
• This way to produce coke was developed as a substitute for coke imports, in the sixties
• Reasons– Availability of domestic low S petroleum coke– Availability of domestic coal tar pitch– Lack of domestic coking coals
• Produced in non-recovery coke ovens
Raw materials
• Petroleum coke– Production in four oil refineries• YPF Lujan de Cuyo (Mendoza) and La Plata (Buenos
Aires): 0.93 Mt/year• Esso Campana (Buenos Aires): 0.35 Mt/y• Shell Avellaneda (Buenos Aires): 0.2 Mt/year• Annual production in the order of 1.5 Mt• Due to the crude oil quality, pet coke sulfur content is
in between 0.5 and 1%
Raw materials
• Petroleum coke• Foundry coke producers must compete with other
industries for the supply– the conventional slot oven batteries at Ternium Siderar, San
Nicolas, Buenos Aires, using up to 40% petroleum coke in the coal blend
– Copetro, a coke calciner for the production of anodes for the aluminum industry
– Ferroalloys producers, for use as a reductant at submerged arc furnaces
– Other smaller markets
Raw materials
• Coal tar pitch– Produced in Carboquimica del Parana, Ramallo,
Buenos Aires, departing from coal tar supplied by Ternium Siderar steel plant
– Tar is heated to temperatures up to 400 oC in specially designed distillation stills
– This removes moisture, naphtalene, light creosote oil and heavy creosote oil from the coal tar
– The resultant product is the coal tar pitch
Raw materials
– Pitch substitutes (when domestic pitch is scarce)• Imported pitch (Colombia, 200 l drums)• Oxidized asphalt 120/5
– produced in batch reactors where hot liquid asphalt is air injected and then dumped to a pool
– cut in big pieces after solidification.– cut into small pieces in a special cutting machine– incorporated to the blend, before grinding
• Asphaltite– Mined in Mendoza and Neuquen states
Raw materials
• Coke fines– Recycled to the coking blend to improve coke size
by acting on the fissuring network structure• Additions for higher ash (for low
recarburization in cupolas)– Imported coking coals (in the past)– Domestic high-ash Rio Turbio steam coal– Sand– Soil
Blend design• Typical– 80% petroleum coke– 17% coal tar pitch– 3% coke breeze
• The lower the pitch content, the lower the coke cost
• Compared with coal-based coking blends, ash is much lower, fixed carbon is higher and volatile matter is more or less the same
Blend design
• Alternative design (to replace pitch)– with oxidized asphalt: 27%• Careful oven control to avoid fast fissuring bringing
about too small coke size)
– with asphaltite• Limited to 5% due to high Sulfur content• For SAFs producing CaC2, 30-35% asphaltite, 5-10% coal
tar pitch, balance pet coke have been used
Blend design
• Coking mechanism differs somewhat from coal-based blends
• Pitch softens at much lower temperature than coking coals
• Grinding and mixing are key to coke quality, as inert and active components are not intimately mixed as in coking coal
Coke plant operations
• Six sites belonging to five companies– Las Palmas S.R.L.– MECAF Argentina
S.R.L. – SIDYMETAL S.A.– Minera Lujan S.R.L.– PROCAMET S.A.
Coke plant operations
• Typical process flow
Coke plant operations
• Non-recovery coke ovens– Rectangular plant
view– Arched roof– Low alumina
refractories
Coke plant operations
Coke plant operations
• The total number of ovens could be estimated in 120
• Just four of them are of the heat-recovery type, with sole heating by off gas
• Supposing continuous four-day operation and four metric tons of coke per oven, annual capacity would be around 40,000 t
• Some production is exported to Chile, Uruguay and Brazil
Coke quality• Typical specifications
Product Volatile matter (%)
Ash (%) Moisture (%)
Sulfur (%) Fixed carbon (%)
Size >70 mm (%)
High recarb./Low S
1.7 1.5 4 0.6 96 min 95
Medium recarb./Low S
2.5 5 4 0.6 93 min 95
Low recarb.
2.5 9 4 0.7 89 min 95
Medium recarb./Medium S
2.5 5 4 1.0 93 min 95
Coke quality
• Control at coke plant– size, moisture, proximate analysis, sulfur and in
some cases, ASTM tumbler test– Occasionally, MICUM tests and reactivity
determinations have been carried out by third parties
Coke quality
• Most foundries evaluate this coke based on visual aspect at arrival and behavior during cupola operation; some of them request proximate analysis to commercial labs
• Just the larger ones, dedicated to the automotive industry, carry out some testing (moisture, proximate analysis, sulfur)
• In operation, the low ash content must be taken into account
Conclusions
• Due to lack of coking coals and availability of low S pet coke and coal tar pitch, the foundry coke industry opted for a coal-less coke production in Argentina more than 50 years ago
• Coke plant operations has to adapt to the particular raw material base
• A low-ash high quality coke is obtained
