Liquefaction systems

The last entry in Table 7.5 allows comparison of membrane processing with an expanded liquefaction system. There is little to choose between the two. However, to match the recovery obtained by the membranes required very low liquefaction temperatures. 

In liquefaction systems wood and wood wastes are the most common fuelstocks. They are reacted with steam or hydrogen and carbon monoxide to produce liquids and chemicals. The chemical reactions that take place are similar to gasification but lower temperatures and higher pressure are used. Liquefaction processes can be direct or indirect. The product from liquefaction is pyrolytic oil which has a high oxygen content. It can be converted to diesel fuel, gasoline or methanol. 

Figure 6.36 Hampson-Linde gas liquefaction system schematic diagram.

Figure 6.38 is the Claude gas liquefaction system, a modification of the Hampson-Linde gas liquefaction system. The Claude system has a turbine in the expansion process to replace a part of the highly irreversible throttling process of the Hampson-Linde system. From state 1 to state 10, the Claude system processes are the same as those of the Hampson-Linde system. After the gas is cooled to state by the regenerative cooler (heat... 

Mueller, J. J., et al., Application of advanced materials and fabrication technology to let down valves for coal liquefaction systems, Electrical Power Research Institute Report, AF-305, January 1977. 

Tig. 5. Propane-mixed-refrigerant liquefaction system for producing LNG. L.P, = low pressure H.P. = high pressure MR = mixed refrigerant... 

Ohio for Union Carbide s Linde Division. The system is designed to produce 9 MMSCFD of hydrogen. The purity is 99.9999% since only 1 ppm total impurities can be tolerated in a liquefaction system downstream of the POLYBED unit. Several other hydrogen plants which integrate steam reforming with POLYBED PSA are in various stages of design and construction (2) ... 

A thermodynamic measure of the quality of a low-temperature refrigeration and liquefaction system is its reversibility. The second law, or more precisely the entropy increase, is an effective guide to the degree of irreversibility associated with such a system. However, to obtain a clearer picture of what these entropy increases mean, it has become convenient to relate such an analysis to the additional work required to overcome these irreversibilities. The fundamental equation for such an analysis is... 

TABLE II Comparison of Several Liquefaction Systems Using Air as the Working Fluid"... 

Air liquefaction system Liquid yield (y = riif/m) Work per unit mass liquefied, (kj/kg) Figure of merit... 

Calculations were carried out for unit mole of carbon in feed coal (MAF basis). Since the empirical formula of feed coal is denoted by CHo.8390o.o96N0.018s0.019 its molecular weight per unit mole of carbon is 15.236. In the present exergy analysis, the exergy input to the liquefaction system is 528.71 kj, which corresponds to the exergy value of 1 mol-C of feed coal, as shown in Table V. 

In this way, we know that the coal liquefaction system constitutes a structure of multi-target system. In addition to these subtargets, the coal liquefaction system attaches an accomodate system which includes oxygen prdduction, hydrogen production, power production, and utilities. 

This simplest kind of liquefaction system, known as the Linde process, is shown in Fig. 9.9. After compression, the gas is precooled to ambient temperature. It may even be further cooled by refrigeration. The lower the temperature of the gas entering the throttle valve, the greater the fraction of gas that is liquefied. For example, evaporating a refrigerant in the precooler at -40(°F) gives a lower temperature into the valve than if water at 70(°F) is the cooling medium. 

The H-Coal process produces approximately 3-3.5 barrels of liquid product for each ton of coal.42 Tests showed that the process is best suited for high-volatile bituminous coal the use of low-rank coals significantly reduced throughput and distillate yields. The successful performance of the ebullated bed reactor in the H-Coal process led to its later use in two-stage liquefaction systems. 

The specific reaction ( activation ) conditions for the conversion of catalyst precursors to unsupported catalysts have a direct effect on the catalytic activity and dispersion. The importance of reaction intermediates in decomposition of ammonium heptamolybdate and ammonium tetrathiomolybdate, and the sensitivity of these intermediates to reaction conditions, were studied in coal liquefaction systems. Recent results indicate that optimization of activation conditions facilitates the formation of a highly dispersed and active form of molybdenum disulfide for coal liquefaction. The use of the catalyst precursors ammonium heptamolybdate, ammonium tetrathiomolybdate, and molybdenum trisulflde for the conversion of coal to soluble products will be discussed. 

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