Coking option

Exxon was the first to investigate the suitabiUty of a wide range of different U.S. coals for conversion. Operation of the EDS process was demonstrated in a 230 t/d unit in Baytown, Texas that had a start-up in May of 1980. Data on the response of a variety of coals to once-through and bottoms recycle operations are shown in Eigure 4. Eigure 5 presents typical Hquefaction product distributions for the system operated both with and without the Elexicoking (fluidized-bed coking) option. 

Average Annual Charge Rates, Million B/D Primary distillation 15.3 16.7 Coking Option 18.0 Hydro- Processing Option 18.0... 

Table 7 also shows these hydrogen requirements as 0.21 Quad/year in 1980 and 0.46 Quad/year in the year 2000 (coking option) or 1.41 Quad/year (hydroprocessing option). Assuming these quantities of hydrogen are produced by steam reforming, the reformer feed stock requirements would increase from 149 thousand B/D crude oil equivalent in 1980 to 326 thousand B/D in the year 2000 option) or 1001 thousand B/D for the year... 

Coal can be converted to gas by several routes (2,6—11), but often a particular process is a combination of options chosen on the basis of the product desired, ie, low, medium, or high heat-value gas. In a very general sense, coal gas is the term appHed to the mixture of gaseous constituents that are produced during the thermal decomposition of coal at temperatures in excess of 500°C (>930°F), often in the absence of oxygen (air) (see Coal CONVERSION PROCESSES, gasification) (3). A soHd residue (coke, char), tars, and other Hquids are also produced in the process ... 

The high capital cost, about 1500/kW, is the principal deterrent to growth of the IGCC concept. The abiUty to remove up to 99% of the sulfur species from the combustion products make the IGCC an environmentally desirable option as make calcium carbide (see Carbides), from which acetjiene is made. Synthesis gas for methanol and ammonia production is also made from gasification of coke. 

However, this mode of flow usually is limited to conveying distances of L < 500 m. The Group D materials that possess wide size distributions (especially a considerable amount of fines) and/or unusual particle shape (e.g., crushed coal, petroleum coke, crushed bath, rice hulls) usually are not suited to low-velocity conveying. In these cases, the options are dilute-phase or single-slug dense-phase (i.e., these materials usually are too coarse for bypass conveying). However, when long distances are involved, dilute-phase may be the only practical option. 

Geosits, R. and Mohammad-Zadeh, Y., Coke Gasification Power Generation Options and Economics. Power-Gen Americas, Dallas, TX, November 1993. 

Sulfur removal, as currently practiced in the petroleum industry, can be achieved using three options. The first option involves the use of thermal methods such as the various cracking techniques that concentrate the majority of the sulfur into the nonvolatile products, i.e., coke. Such processes are located in the conversion section of a refinery (Figure 4-1). The remainder of the sulfur may occur in the... 

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