Liquefaction indirect

Gary J Stiegel, M S , P.E., Program Coordinator, Federal Energy Technology Center (Pittsburgh), U.S. Depaiiment of Energy. (Indirect Liquefaction)... 

Status of Indirect Liquefaction Technology The only commercial indirect coal liquefaction plants for the production of transportation fuels are operated by SASOL in South Africa. Construction of the original plant was begun in 1950, and operations began in 1955. This plant employs both fixed-bed (Arge) and entrained-bed (Synthol) reactors. Two additional plants were later constructed with start-ups in 1980 and 1983. These latter plants employ dry-ash Lurgi Mark IV coal gasifiers and entrained-bed (Synthol) reactors for synthesis gas conversion. These plants currently produce 45 percent of South Africa s transportation fuel requirements, and, in addition, they produce more than 120 other products from coal. 

The indirect liquefaction basehne design is for a plant of similar size. Unhke the direct hquefaction basehne, the design focuses on producing refined transportation fuels by use of Sheh gasification technology. Table 27-17 shows that the crude oil equivalent price is approximately 216/m ( 34/bbl). Additional technological advances in the production of synthesis gas, the Fischer-Tropsch synthesis, and product refining have the potential to reduce the cost to 171/m ( 27/bbl) (1993 US dollars), as shown in the second column of Table 27-17. 

At the current stage of development, direct and indirect liquefaction technologies loc equally attractive economically, and botn have the potential for significant cost improvements. 

Indirect liquefaction, 6 828 Indirect mode of operation, in separating nonideal liquid mixtures, 22 303, 306-307... 

We will examine three synthetic fuel scenarios and compare their implications regarding sulfur availability with the current and projected market for sulfur to the year 2000. The analysis will consider three production levels of synthetic fuels from coal and oil shale. A low sulfur Western coal will be utilized as a feedstock for indirect liquefaction producing both synthetic natural gas and refined liquid fuels. A high sulfur Eastern coal will be converted to naphtha and syncrude via the H-Coal direct liquefaction process. Standard retorting of a Colorado shale, followed by refining of the crude shale oil, will round out the analysis. Insights will be developed from the displacement of imported oil by synthetic liquid fuels from coal and shale. 

The plant processes 26,840 TPSD of low sulfur North Dakota lignite. The sulfur is 1.3 wt%/DAF coal. The coal analysis is shown in Table II. Output from the plant is 268,700 MM Btu/day of SNG, equivalent to 45,000 BOE/day. Total production of by-product elemental sulfur is 161 tons/day. This represents 78 wt% of total sulfur input from the coal feedstock. Since goal gasification and indirect liquefaction facilities are most likely to use Western low sulfur lignite or subbituminous coals, this represents the low sulfur case for coal conversion. 

Figure 3. Indirect liquefaction or SNG from coal plant.

Indirect liquefaction of coal and conversion of natural gas to synthetic liquid fuels is defined by technology that involves an intermediate step to generate synthesis gas, CO + H2. The main reactions involved in the generation of synthesis gas are the coal gasification reactions. Combustion... 

Indirect liquefaction Combination of a synthesis gas composed of carbon monoxide and hydrogen over a suitable catalyst to form liquid products such as gasoline and methanol. 

The principal method of indirect liquefaction is to react carbon monoxide and hydrogen produced by coal gasification in the presence of a catalyst to form hydrocarbon vapors, which are then condensed to liquid fuels. This procedure for synthesizing hydrocarbons is based on the work of Fischer and Tropsch in Germany in the 1920s. Just prior to and during World War II, Germany produced... 

FIGURE 4 Indirect liquefaction of coal. [Reprinted with permission from Probstein, R. F., and Hicks, R. E. (1990). Synthetic Fuels, pH Press, Cambridge, MA.]... 

The three principal routes by which liquid fuels can be produced from coal have been noted to be pyrolysis, direct liquefaction, and indirect liquefaction. A clean fuel that is a solid at room temperature can also be produced by direct liquefaction processes. 

The last major category for the manufacture of liquid fuels is the indirect liquefaction procedures. The most extensive production of synthetic liquid fuels today is that being carried out by Fischer-Tropsch reactions at the South African Sasol complexes, with a combined output of over... 

Of the indirect liquefaction procedures, methanol synthesis is the most straightforward and well developed [Eq. (6)]. Most methanol plants use natural gas (methane) as the feedstock and obtain the synthesis gas by the steam reforming of methane in a reaction that is the reverse of the methanation reaction in Eq. (5). However, the synthesis gas can also be obtained by coal gasification, and this has been and is practiced. In one modern low-pressure procedure developed by Imperial Chemical Industries (ICI), the synthesis gas is compressed to a pressure of from 5 to 10 MPa and, after heating, fed to the top of a fixed bed reactor containing a copper/zinc catalyst. The reactor temperature is maintained at 250 to 270°C by injecting... 

An indirect liquefaction procedure of relatively recent origin is the Mobil M process for the conversion of methanol to gasoline following the reaction... 

A sizeable amount of work expended in Fischer-Tropsch in both catalyst research as well as pilot plant studies and design. Much of the design work in the SASOL I indirect liquefaction plant in South Africa and the pilot plant in Louisiana, Missouri, was obtained from the bank of information that was generated at PETC. 

We have our work divided into process engineering, process chemistry, catalysis, and support technology. As an example, one of the indirect liquefaction projects, tube wall reactor, deals with the design and operation of high thermal efficiency catalytic reactors for syn-gas conversion. Other activities are coal liquefaction properties of coal minerals, the role of catalysts, coal liquid product stability, and environmental impact—to name a few. 

So if you don t consider it a broad application for everybody, but instead a single demonstration of a type, be it direct liquefaction or indirect liquefaction process, I think this is a very likely thing and something that we intend to pursue. 

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 indirect liquefaction processes include Fischer-Tropsch and coal to methanol. Both processes have operated on a commercial scale. For the past 25 years, a Fischer-Tropsch facility has operated in South Africa. Presently the South Africans are constructing an advanced and larger facility. Coal-to-methanol plants existed in the United States, but were replaced by natural gas-to-methanol facilities because it was more economical to do so. 

Because of the advanced stage of development of indirect liquefaction resource applications in DOE are aggressively pursuing the commercialization of the indirect processes. 

Why is it, if indirect liquefaction processes are technically proven, the demand exists and is getting stronger for petroleum substitutes and there is so much coal available to us that people aren t standing in line to build coal liquefaction facilities in the United States today The answer is fairly simple. There are so many uncertainties associated with commercialization — not only technological, but also institutional, legal and regulatory— that the large capital investments required seem too risky to make. Coal liquefaction facilities are capital-intensive with cost in excess of 1 billion. 

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