Coal-to-liquids processes

Cherry, R.S. (2006), Use of a High Temperature Gas Reactor in a Coal-to-liquids Process, INL Work for Others, INL EXT-06-11667, August. 

Figure 4 Coal-to-liquid process coupled to a nuclear energy source...

The second process utilizing coal is the conversion of coal-to-liquids. The coal to liquids process was originally developed to convert hvc bituminous coal from the Western Kentucky Hamilton Hines of Island Creek Coal Co., also a subsidiary of Occidental Petroleum Corporation, into liquid fuels. A typical analysis of the coal is shown in Table V. 

The optimum yield of liquid product is obtained in the coal-to-liquids process at approximately 1075 F. A typical product distribution for coal-to-liquida processing using this coal is 56% char, 35% tar, 7% gas, and 2% water. The residence time for this process is also kept as short as possible which maximizes the yield and prevents further cracking of the liquid product. The effect of flash pyrolysis on the liquid yield is shown by the fact that the tar and light oil yield for this coal from... 

Typical char analyses from the coal-to-liquids process are shown in Table VII. 

TABLE VII CHAR FROM THE COAL-TO-LIQUID PROCESS ... 

During the late seventies and early eighties, when oil prices rose after the 1973 war, extensive research was done to change coal to liquid hydrocarbons. However, coal-derived hydrocarbons were more expensive than crude oils. Another way to use coal is through gasification to a fuel gas mixture of CO and H2 (medium Btu gas). This gas mixture could be used as a fuel or as a synthesis gas mixture for the production of fuels and chemicals via a Fischer Tropsch synthesis route. This process is... 

Coal is the main energy reserve for many countries. In order to ensure energy security, many of these countries are looking at implementing large-scale coal-to-liquid (CTL) plants. Current CTL Fischer-Tropsch (FT)-based processes at best have a carbon efficiency near 45% that is, less than half the carbon that is fed to the process ends up as hydrocarbon fuels. This has large implications for the environment, in that more than half of the carbon in the feed to the CTL ends up... 

The overall coal-to-liquid fuels process can be described as follows ... 

Three types of direct coal liquefaction processes have emerged to convert coals to liquid hydrocarbon fuels 8... 

Early developments for producing liquid fuel from coal which can be found in many countries took place in the 1840s in Germany and England. They were the first steps of the petrochemical industry. These processes produced kerosene to fuel German airplanes during World War II and supplied up to 90% of the demand in liquid fuels at that time. Sasol s plants in the Republic of South Africa are the only industrial coal-to-liquid production capability that remains today with an annual production of 7.5 M tonnes of liquid fuels (gas oil, kerosene) and chemical products. 

Analyses of coals which have been processed in the continuously operated pilot plants are listed in Table 1. Process liquid yields from the liquefaction step for these coals are shown in Figure 4 for different residence times in the liquefaction reactor. Longer residence time increases conversion of coal to liquids, but also increases hydrocracking of liquids to gas. 

In the field of coal liquefaction, many processes exist to convert coal to liquid and gaseous products. These processes can be categorized as direct and indirect liquefaction. 

The FTS converts synthesis gas into mostly liquid hydrocarbons [12-15]. Depending on the origin of the synthesis gas, the overall process from carbon feedstock to liquid product is called gas-to-liquids (GTL), coal to liquids (CTL), or biomass to liquids (BTL). The product spectrum, however, is broader than liquid hydrocarbons alone and can include methane and alkanes, C H2 +2 (with n from 1 — 100), alkenes or olefins (C H2 n > 2), and to a lesser extent, oxygenated products such as alcohols. Hence the FTS offers the opportunity to convert gas, coal, or biomass-derived syngas into transportation fuels, such as gasoline, jet fuel, and diesel oil, and chemicals, such as olefins, naphtha, and waxes. The reactions need a catalyst, which in commercial applications is either based on cobalt or iron. 

Direct coal liquefaction (DCL) refers to the process of converting coal to liquid products by mixing ground coal with a recycled process solvent and/or petroleum-derived residual oil and reacting the slurry in a hydrogen atmosphere at 750-850°F (400-450°C) and 1000-2500 psig (7-17 MPa). Under these conditions, the coal structure breaks down into... 

CTL [Coal To Liquids] A general name for processes that convert coal to liquid hydrocarbons, usually for use as fuels. Sasol was building a prototype reactor in Sasolburg, South Africa, in 2006. The first U.S. plant is scheduled to be built in Gilberton, PA, for completion in 2009. 

---