Coal solvent

A more complex reaction model was proposed from the results of a kinetic study of thermal liquefaction of subbituminous coal. Data were obtained over a temperature range of 673 to 743 K (752 to 878°F) at 13.8 MPa (2000 psia) by using two solvents, hydrogenated anthracene oil (HAO), and hydrogenated phenanthrene oil (HPO), at a coal-solvent ratio of 1 15. Results were correlated with the following model ... 

Gasoline, coal solvent extn, hydrocracked naphtha... 

About one half of the coal samples used in the above study (61) have been investigated by workers in Gulf Research and Development Company, using a continuous flow reactor (63). The throughput was about 1 kg./h of coal/solvent slurry, the solvent was a partly hydrogenated anthracene oil, temperatures of 440 and 455°C were used, and the system was pressurized with hydrogen to 20.69 MPa. 

Digestion 400°C, 60 minute residence time Coal Solvent ratio 1 4... 

Figure 5. Influence of digestion time and temperature on extraction yield. Coal = Beynon solvent = anthracene oil coal solvent ratio = 1 4.

Digestion conditions 400°C 60 minute residence time Coal solvent ratio 1 3... 

THF Conversion. Tetrahydrofuran (THF) conversion was calculated from the difference between the initial and the final solubilities of the total coal-solvent slurry in THF. It was assumed that all of the solvent and none of the starting coal was soluble in THF. THF conversions were calculated on an MAF coal basis and adjusted for the coal not recovered from the autoclaves. The filter cake resulting from filtration of the product at 250 C was continuously extracted with THF for up to 3 days. 

Figure 1. Liquefaction yields vs. maximum fluidities in the fused state of coal (%), solvent (SRC pitch benzene soluble) (O), pyrene ((B), no solvent. Coal.sol-vent ratio = 1 3 reaction temperature = 390°C(8).

Figure 2. Variation in atomic H/C ratio versus chloroform-soluble yields from subbituminous (PSOC-1403) and bituminous (PSOC-1266) coals (solvent-free hydrogenation 300-400°C 5-180 min 1% wt sulfided Mo 7 MPa H2 cold) (data from refs 7 and 8).

A direct liquefaction technique, the SRC process involves mixing dried and finely pulverized coal with a hydrogen donor solvent, such as tetralin, to form a coal-solvent slurry. The slurry is pumped together with hydrogen into a pressurized, vertical flow reactor. The reactor temperature is about 825°F (440°C) and pressures range from 1,450 to 2,000 psi. A residence time in the reactor of about 30 minutes is required for the carbonaceous material to dissolve into solution. From the reactor, the product passes through a vapor/liquid separation system. The slurry solids remaining in the reactor are then removed and filtered. Various filtration techniques have been developed to remove solids from recoverable oil. 

The low yield of oil and the coal/solvent ratio in slurry are important factors that influence the cost of coal-derived oil. 

Figure I. Determination of coal/solvent ratio for optimum extraction...

To find the optimum ratio of coal/solvent (C/S), a series of solubility experiments were performed at constant temperature and time but with different C/S. It was found that at ratios smaller than 1 8 the quantity of coal dissolved did not increase (Figure 1). All kinetic studies were made at ratios of 1 10 to ensure that excess solvent was always present. 

Figure 9 Effect of Coal/Solvent Ratio on Amount and...

Summary of Experiments. Fifteen coal liquefaction experiments were done using two coals and two solvents supplied by Mobil Research and Development Corporation. Each coal-solvent combination was tried at conditions designed to give conversions to pyridine solubles of about 65 and 80 percent of MAF coal. 

MAF Coal Conversions to Pyridine Solubles. MAF coal conversions, based on ash analyses, are shown for each coal-solvent combination in Figure 3. Subbituminous coal is converted more slowly, resulting in lower conversions at identical reaction severities than bituminous coal. Maximum conversions are higher with bituminous coal, approaching 90 percent on an MAF basis for the Monterey coal compared to about 75 percent for Wyodak coal. 

One of the methods used in the production of liquid fuels from coal is to heat coal in the presence of solvents in order to dissolve and stabilize low molecular weight fragments. Many studies (1-6) have been devoted to elucidating the chemical mechanism of product formation in hydrogen donor and non-donor solvents. In most of these studies, the time dependence of the product yield was used as a measure of the rates of reaction, or the product yield was correlated with the solvent, the rank of the coal or other properties of the coal. In order to gain a better understanding of the nature of the coal-solvent interactions, we... 

Equipment. The liquefaction of coal was studied In a 1 liter magnetically stirred stainless steel autoclave. The autoclave was equipped with a thermowell a gas Inlet port connected to a synthesis gas (Hg C0 ratio of 1 1), or to a hydrogen cylinder and to a pressure gauge a port for connection to a rupture disk assembly and a port for gas discharge. The vertical magentlc rod with dashers stirred the coal, solvent and ash or catalyst particles. The autoclave temperature was measured by a thermocouple placed Into the thermowell. 

Coal-solvent interactions leading to swelling and dissolution of the coal (11, 12). 

Table IX. Trace and Minor Element Concentration Ratios Feed Coal/Solvent-Refined Coal...

Nature of the Free Radicals in Coals, Pyrolyzed Coals, Solvent-Refined Coal, and Coal Liquefaction Products... 

Figure 1. Percentage of coal solvent-extractable vs, lithotype...

Material Coalings Solvent Redox couple Refs. 

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