South African coal

The chapter by Eisenlohr et al. deals with the results of large scale pilot operations using a newly developed high-nickel catalyst with hot-gas recycle for temperature control. This and other work, conducted by Lurgi Mineraloeltechnik GmbH, with South African Coal and Oil Limited (SASOL), are the bases of the methanation process which Lurgi is proposing for commercial plants. 

South African Coal, Oil, and Gas Corp., Sasolburg, South Africa... 

Consequently, two semicommercial pilot plants have been operated for 1.5 years. One plant, designed and erected by Lurgi and South African Coal, Oil, and Gas Corp. (SASOL), Sasolburg, South Africa, was operated as a sidestream plant to a commercial Fischer-Tropsch synthesis plant. Synthesis gas is produced in a commercial coal pressure gasification plant which includes Rectisol gas purification and shift conversion so the overall process scheme for producing SNG from coal could be demonstrated successfully. The other plant, a joint effort of Lurgi and El Paso Natural Gas Corp., was operated at the same time at Petrochemie Schwechat, near Vienna, Austria. Since the starting material was synthesis gas produced from naphtha, different reaction conditions from those of the SASOL plant have also been operated successfully. 

H. Roberts (South African Coal, Oil, and Gas Corp.) May I say that for the pilot plant we used a reciprocating compressor which would operate only at near ambient temperature. So we simulated the operation of the hot recycle compressor by adding high pressure steam on the delivery side of the reciprocating compressor. We did not use a hot recycle compressor in the pilot plant. 

South African Coals and Their Behavior During Liquefaction... 

South African coals differ from most Northern Hemisphere coals in their geological age, unusual petrology and their high mineral matter content. If these coals are to be used for conversion to synthetic fuels then criteria must be found to enable predictions of their behaviour under liquefaction conditions to be determined. This paper describes the hydrogenation of a number of South African coals using two different techniques, to ascertain whether well known coal properties can be used to predict their hydrogenation behaviour. 

LIQUEFACTION BEHAVIOUR OF A SELECTION OF SOUTH AFRICAN COALS... 

There is also intercorrelation between the volatile matter and the H/C atomic ratio for the South African coals studied. 

The different slopes for the lines of best fit for total reactives and vitrinite + exinite reflects the special petrology of the majority of South African coals used in this study (see Table III). For these coals the reactives contain a high proportion of semi-fusinite in the inertinite. 

For American and European coking coals the behaviour of semi-fusinite is generally less important since only small quantities of this maceral are usually present. However, South African coal used in coke oven-blends contains as little as 40 per cent vitrinite and as much as 45 per cent reactive semi-fusinite (12). The partial reactivity of the semi-fusinite fraction during liquefaction of Australian coals has been reported by Guyot et al (13). They found that the low reflecting inertinite in two coals up to (a reflectance from 1.40 to 1.49) was reactive. This agrees with the results of Smith and Steyn (12) who consider that the semi-fusinite fraction in South African coals up to V- 5 (1.50 - 1.59) can be reactive to coking. 

The results obtained from the float/sink fractions are shown in Figure 11. It could be that the increase in oil yield obtained with the higher mineral matter fractions is due to the increase in sulfur content that varies from 0.5 per cent in the 1.4 float to 9 per cent in the 1.65 sink fraction. The significance of these results, at least as far as South African coals are concerned, is that a high mineral matter content does not necessarily mean poor performance during coal liquefaction. 

The iron sulphide in South African coals is a mixture of pyrite and marcasite (18). Although marcasite is known to transform into pyrite at elevated temperatures, separate spiking experiments were performed to see if pyrite or marcasite would show a preferential catalytic effect. The addition of pyrite and marcasite minerals (-200 mesh), to the coal showed equivalent total conversions, and yields of oil and asphaltene. 

The close pricing relationships between fuel grade petroleum coke and at least one coal sold in the world markets are shown in Figure 11. South African coal was chosen to illustrate this relationship because it is widely... 

Figure 11. Price of U.S. green coke and South African coal.

As shown, petroleum coke sells at a discount to South African coal (as well as coal from other regions that is sold primarily through spot transactions). There are several reasons for this discount ... 

Petroleum coke has a higher sulfur content than South African coal. 

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