Charge of coke

Compared to conventional cold blast operation with one row of tuyeres, the increase in tapping temperature obtained for a given charge of coke, can be expected to be as follows blast enrichment + 15 °C... 

The handling, transport and charging of coke results in the production of coke breeze. Specific measures may be adopted for the collection and recycling of this material e.g. collection systems below conveyor belts or, at charging points. 

Another thermally efficient kiln is the modem mixed-feed vertical kiln ia which coke is admixed with 8.5—20 cm lump limestone and charged into the top of the vertical kiln by a mobile, overhead charging system. However, use of this kiln is waning since the quaUty of mixed-feed kiln lime does not equal that of the other three kilns described above, owing to ash contamination from the coke and poorer reactivity and to the higher cost of coke in most areas. 

Blast furnaces are charged through the top with coke, flux (usually iron metal and siUca), and scrap while air is iajected through tuyeres continuously at the bottom just above the black copper. The coke (100 kg/1 slag) bums to maintain furnace temperatures of 1200°C, provides the reductant, and maintains an open border. A charge of 10 t/h is typical. The furnace produces a molten black copper that contains about 80% copper. The 2iac, lead, and... 

The passing of the Clean Air Act in the United Kingdom in 1956 resulted in a revival of interest in low temperature carbonization to produce a very reactive coke suitable for open fires. In the CoaUte process, the coal is heated at 600—650°C for 4 h in small retorts each hoi ding 6—7 metric tons (5). The Rexco process employed large internally heated retorts in which charges of 34 metric tons were heated to 700—750°C for 6 h, but is no longer in operation in the United Kingdom (6). 

Further down, ca 75 cm below the electrode tips, the mix is hot enough (2200—2500°C) to allow the lime to melt. The coke does not melt and the hquid lime percolates downward through the relatively fixed bed of coke forming calcium carbide, which is Hquid at this temperature. Both Hquids erode coke particles as they flow downward. The weak carbide first formed is converted to richer material by continued contact and reaction with coke particles. The carbon monoxide gas produced in this area must be released by flowing back up through the charge. The process continues down to the taphole level. Material in this area consists of soHd coke wetted in a pool of Hquid lime and Hquid calcium carbide at the furnace bottom. 

Catalysts in this service can deactivate by several different mechanisms, but deactivation is ordinarily and primarily the result of deposition of carbonaceous materials onto the catalyst surface during hydrocarbon charge-stock processing at elevated temperature. This deposit of highly dehydrogenated polymers or polynuclear-condensed ring aromatics is called coke. The deposition of coke on the catalyst results in substantial deterioration in catalyst performance. The catalyst activity, or its abiUty to convert reactants, is adversely affected by this coke deposition, and the catalyst is referred to as spent. The coke deposits on spent reforming catalyst may exceed 20 wt %. 

Coke Production. Coking coals are mainly selected on the basis of the quaUty and amount of coke that they produce, although gas yield is also considered. About 65—70% of the coal charged is produced as coke. The gas quaUty depends on the coal rank and is a maximum, measured in energy in gas per mass of coal, for coals of about 89 wt % carbon on a dry, mineral matter-free basis, or 30% volatile matter. 

The installation costs for a single impressed current anode of high-silicon iron can be taken as Kj = DM 975 (S550). This involves about 5 m of cable trench between anodes so that the costs for horizontal or vertical anodes or for anodes in a common continuous coke bed are almost the same. To calculate the total costs, the annuity factor for a trouble-free service life of 20 years (a = 0.11, given in Fig. 22-2) should be used. For the cost of current, an industrial power tariff of 0.188 DM/kWh should be assumed for t = 8750 hours of use per year, and for the rectifier an efficiency of w = 0.5. The annual basic charge of about DM 152 for 0.5 kW gives about 0.0174 DM/kWh for the calculated hours of use, so that the total current cost comes to... 

There are two process routes for making steel in the UK today the electric arc furnace and the basic oxygen converter. The latter requires a charge of molten iron, which is produced in blast furnaces. The raw materials for producing molten iron are iron ore, coking coal, and fluxes (materials that help the chemical process) - mainly limestone. 

Figure 14. First- and second- cycle constant-current charge/discharge curves of coke (Conoco) in LiN(S02CF,)i / ethylene carbonate / dimethyl carbonate as the electrolyte (Cirr irreversible specific charge Crcv = reversible specific charge) [2. ...

Estimates also were made for 65 coke plants in 12 states. Coke ovens produce benzene as a by-product, but not all of it can be recovered. It has been estimated that benzene contributes about two-thirds of one percent of the coal gas generated. Potential points of emissions from one type of coke battery are illustrated in Figure 7. Emissions from coke ovens were derived from estimated emission factors (based on coke oven product assays and benzene yields) and coal charging rates. 

Most of the oxides are reduced to molten iron by CO, although some are reduced by coke directly. Carbon dioxide, a reaction product, reacts with excess coke to provide more CO to reduce the next charge of iron ore. 

Figure 67. Effect of coke particle size on the charge capacity at various temperatures. (Reproduced with permission from ref 513 (Figure 8). Copyright 2000 The Electrochemical Society.)...

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