Processes based on coal

Cormos, C. C., Starr, F., Tzimas, E. and Peteves, S. (2008). Innovative concepts for hydrogen production processes based on coal gasification with C02 capture. International Journal of Hydrogen Energy, 33 (4), 1286-1294. 

A more promising way of obtaining more uniform degradation products is pyrolysis at high temperature. Synthesis gas is obtained at ever higher temperatures (700-1000°C), but according to Nimz, at the present it is not competitive with the corresponding processes based on coal (2). 

Although the Fischer-Tropsch process (based on coal) has been uneconomic for many years compared to oil-based routes, the peculiar political situation of South Africa allied with its large reserves of cheap coal led it to continue operating this process. Indeed, the experience gained led in the 1970s to the building of a second-generation plant, (the scheme for this SASOL II plant is shown in Fig. 2.4" ) and a SASOL III plant is now on stream. 

U.S. Development (30). A consortium of U.S. integrated steel companies is currently developing an advanced steel-making process based on coal, oxygen, and iron ore. A large (120 t/d) pilot plant is under construction at a USX facility near Pittsburgh, Pennsylvania. Though process details are not public, the process is likely to be similar to the COREX process and produce excess coal-derived fuel gas. 

Processes based on coal feedstock are similar to the partial oxidation process for heavy oil, and usually include a nitrogen wash stage to produce a similar... 

Newer coal-based methods of acetylene manufacture under development include the AVCO process, based on the reaction of coal in a hydrogen plasma. Finely divided coal is passed through a hydrogen plasma arc generating temperature gradients of up to 15,000 K. About 67% of the coal is consumed, yielding char and acetylene in concentrations up to 16%. An energy requirement of 9.5 kW h/kg acetylene has been reported (33). 

Occidental Petroleum Coal Conversion Process. Garrett R D Co. (now the Occidental Research Co.) developed the Oxy Coal Conversion process based on mathematical simulation for heating coal particles in the pyrolysis unit. It was estimated that coal particles of 100-mm diameter could be heated throughout their volumes to decomposition temperature (450—540°C) within 0.1 s. A large pilot faciUty was constmcted at LaVeme, California, in 1971. This unit was reported to operate successfully at feed rates up to 136 kg/h (3.2 t/d). 

The quahty of naphthalene required for phthaUc anhydride manufacture is generally 95% minimum purity. The fixed plants do not require the high (>98%) purity naphthalene product and low (<50 ppm) sulfur. The typical commercial coal-tar naphthalene having a purity ca 95% (freezing point, 77.5°C), a sulfur content of ca 0.5%, and other miscellaneous impurities, is acceptable feedstock for the fixed-bed catalyst process based on naphthalene. 

The methanation reaction is currently used to remove the last traces (<1%) of carbon monoxide and carbon dioxide from hydrogen to prevent poisoning of catalysts employed for subsequent hydrogenation reactions. Processes for conversion of synthesis gas containing large quantities of carbon monoxide (up to 25%) into synthetic natural gas have been investigated to serve plants based on coal-suppHed synthesis gas. 

The KEN-FLOTE column (11) is one of several column flotation processes based on a countercurrent principle. The feed slurry containing reagents is iatroduced iato the column just below the froth zone. Air is iujected at the bottom of the column via an air sparger. Wash water is sprayed within the froth zone to reject the entrained impurities from the froth. Test results on this column iadicate that a 6% ash product coal having a combustible-recovery of 75—80% can be obtained. A 70—80% pyrite reduction is also claimed. Figure 2 shows the operation of such a column. 

The petroleum industry is now the principal suppHer of ben2ene, toluene, the xylenes, and naphthalene (see BTX processing Feedstocks). Petroleum displaced coal tar as the primary source for these aromatic compounds after World War II because it was relatively cheap and abundantly available. However, the re-emergence of king coal is predicted for the twenty-first century, when oil suppHes are expected to dwindle and the cost of producing chemicals from coal (including new processes based on synthesis gas) will gradually become more competitive (3). 

Immiscible wetting in mixers Sol-gel processes Pellet flocculation <0.3 Low Up to 10 ton/hr Wet processing based on flocculation properties of particulate feed Coal fines, soot and oil removal from water Metal dicarhide, silica hydrogels Waste sludges and slurries... 

During the 1800s, benzene was of limited commercial value, finding use mainly as a solvent. But after the invention of the internal combustion engine and the automobile, it was found that motors ran better when the fuel contained benzene. This added a new economic incentive to recover all of the benzene possible from the steel industry s coke ovens. However, just prior to World War II, the importance of benzene as a chemical intermediate started to be recognized. These dual incentives (gasoline and chemical intermediate) led to new and improved benzene processes based on petrochemistry rather than coal. 

Although the comparisons are by no means exact, a process based on short-contact time dissolution and catalytic upgrading would appear to have potential for significantly higher yields of high quality liquids from coal. 

The CTL process, as described by Equation 17.1, required approximately 58 kJ/mol of energy, whereas the process based on a methane feed, described by Equation 17.2, produces approximately 20 kJ/mol of energy. The energy required by the CTL process can be supplied by combusting a further quantity of coal (considered as C). This will also mean a further production of carbon dioxide. 

The idealized target for a two-stage process based on current processes can be determined. First, coal is gasified to produce syngas in a two one ratio (H2and CO), and second, the syngas is converted to hydrocarbons (Fischer-Tropsch synthesis) ... 

GFETC A coal gasification process based on a slagging gasifier, developed for the U S. Department of Energy, at Grand Forks, ND. 

Otto-Rummel A coal-gasification process based on a double shaft furnace, developed in Germany by Dr. C. Otto Company. 

Riley-Morgan A coal gasification process, based on a cylindrical gas-producer developed by C. H. Morgan in Worcester, MA, in 1880. By 1964, the Morgan Construction Company had installed more than 9,000 such units in a number of industries worldwide. In 1971 the... 

Ruhrkohle/VEBA Oel-hydrogenation A coal liquifaction process based on the IG-Hydrogenation process. 

The H-Cocd Process, based on H-Oil technology, was developed by Hydrocarbon Research, Inc. (HRI). The heart of the process was a three-phase, ebullated-bed reactor in which catalyst pellets were fluidized by the upward flow of slurry and gas through the reactor. The reactor contained an internal tube for recirculating the reaction mixture to the bottom of the catalyst bed. Catalyst activity in the reactor was maintained by the withdrawal of small quantities of spent catalyst and the addition of fresh catalyst. The addition of a catalyst to the reactor is the main feature which distinguishes the H-Coal Process from the typical process. 

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