Table 6.29. Cost of steam generation using highBtu gas from coal Basis: lo6 lb/hr of steam at 75OoF, 650 psia; estimated cost of boiler = $15 X lo6 ~
Annual cost (10%
Unit cost (e/1O6 Btu)
Capital charges at 22.2%fmed charge rate
3.33
42
Operating and maintenance (excluding fuel cost) Unit fuel cost at production site LUIgi US. developmental
0.31
3
Shipping cost
239 219 Houston
New Orleans
18
12
Delivered fuel cost LUIgi U.S. developmental
257 237
251 231
Steam cost (at 85%boiler efficiency) Lurgi U.S. developmental
347 324
340 317
6.6 LIQUEFACTION AND CLEAN BOILER FUELS FROM COAL 6.6.1 General Descripti~n'*~''~~
The production of synthetic liquid fuels from coal involves the development of technology in two areas: conversion of coal to liquids by hydrogenation and production of hydrogen from coal at a lower cost than that available from existing technology. The main problem in the conversion of coal to liquids is to transforma low-hydrogencontent solid into a liquid containing substantially higher amounts of hydrogen. The extent of the hydrogen addition is illustrated in Table 6.30. In normal petroleum refining,the hydrogen consumption may be in the order of 500 to 1500 scf/barrel, depending on the specific type of processing used and the properties of the refinery feedstock. Experience in coal liquefaction has shown that much more hydrogen processing is needed, requiring large amounts of hydrogen and severe processing conditions. To convert the organic material in coal to a petroleum-like liquid theoretically requires about 5000 scf/ barrel. This amount of hydrogen would suffice to remove the sulfur, oxygen, and nitrogen compounds and yield a liquid containing about 13%hydrogen without producing any substantial amounts of light hydrocarbon gases. In practice, the hydrogen consumption is much higher, rangingfrom6000 to 10,000 scf/ barrel, due primarily to a substantial production of light hydrocarbon gases and to loss of hydrogen into the unliquefied solid residue. As a result, the production of hydrogen represents a major factor in coal liquefaction and the processing of coal liquids. Other problems arise from the nature of coal itself. The presence of organic nitrogen compounds inhibits many of the reactions in converting the coal liquids. Further, the presence of ash has several 129. US.Energy Outlook: Coal Availability, National Petroleum Council, 1973. 130. H. C. Hottel and J. B. Howard, New Energy Technology: Some Facts and Assessments, M1T Press, 1971.