Coal under atmospheric pressure

The liquefaction mechanism was discussed by distinguishing the fusible coal from non-fusible one. The importance of solvolytic hydrogen transfer is pointed for the liquefaction of non-fusible coal under atmospheric pressure. 

The present authors studied the solvolytic liquefaction process ( ,7) from chemical viewpoints on the solvents and the coals in previous paper ( 5). The basic idea of this process is that coals can be liquefied under atmospheric pressure when a suitable solvent of high boiling point assures the ability of coal extraction or solvolytic reactivity. The solvent may be hopefully derived from the petroleum asphaltene because of its effective utilization. Fig. 1 of a previous paper (8) may indicate an essential nature of this process. The liquefaction activity of a solvent was revealed to depend not only on its dissolving ability but also on its reactivity for the liquefying reaction according to the nature of the coal. Fusible coals were liquefied at high yield by the aid of aromatic solvents. However, coals which are non-fusible at liquefaction temperature are scarcely... 

In the present study, the liquefaction activities of pyrene, its derivatives, and decacyclene with coals of several ranks are studied to ascertain the previous ideas of liquefaction mechanism and to develop novel liquefaction process under atmospheric pressure. The coals used in the present study are non-fusible or fusible at relatively high temperature, and then gave small liquefaction yield with pyrene of a non-solvoly-tic solvent at 370°C. 

West-Kentucky, and Itmann coals of three different ranks were sufficiently liquefied with hydropyrene under atmospheric pressure at 370°C regardless of their fusibility. The analyses of hydropyrene and the coal before and after the liquefaction clearly indicate the hydrogen transfer from the solvent to the coal substance. Lower rank coals look to show rather higher reactivity in such liquefaction, probably because their constituent molecule may have smaller condensed ring. 

Stoic Also called Foster Wheeler-Stoic and FW-Stoic. A two-stage, nonslagging coal gasification process, operated under atmospheric pressure and using air as the oxidant. Initially developed by Stoic Combustion Limited Pty, South Africa licensed and further developed by Foster Wheeler Corporation, United States. First used in South Africa in 1950 now widely used in Europe, the United States, and South Africa. 

ACGP [Advanced Coal Gasification Process] A coal gasification process developed in South Africa by Kynoch Fertilizer and Babcock Wilcox as a replacement for the KBW process. Unlike the KBW process, it operates under atmospheric pressure. ACGP had not been commercialized by 2006. 

By passing gases from the distillation of coal under a pressure of 400 atmospheres over metallic oxides, such as ferric oxide, at a temperature of 300° to 600° C., it is claimed that alcohols may be obtained.811 However, by using methane or gases containing methane in a similar manner only higher hydrocarbons are formed.811 ... 

Q, is the desorption quantity at the gas desorption time t 2- the ultimate desorption quantity of the coal particles under atmospheric pressure d is diameter of the coal particles D is the gas effective diffusion coefficient. 

Coals that soften and then swell prior to coke formation under atmospheric pressure do not always behave similarly when heated in vacuo. In fact, the reduced pressure actually decreases the degree of softening and swelling. On the other hand, if coal is heated under pressure, the softening and swelling increase and a firmer coke is produced, but to obtain an appreciable effect, higher pressures (on the order of 100 psi and more) may be necessary. 

The first process was studied by Berthelot in 1867 and was further developed in Germany by Bergius in 1910. The early Bergius process involved the reaction of H2 under atmospheric pressure with pulverized coal suspended in an oil heated to about 450°C in the presence of a catalyst such as stannous formate or Mo. The liquid oil product is separated from the solid residue and processed as ordinary crude oil. Modem developments in this coal liquefaction approach include (1) Exxon Donner Solvent (EDS) process, (2) the HRI H-Coal process, and (3) the Gulf Solvent Refined Coal SRC-II process. The major improvement of these processes over the Bergius process is in the catalyst used, allowing for milder reaction conditions. 

In the Koppers-Totzek process, the polarized coal is rapidly partially oxidized with oxygen and steam at essentially atmospheric pressure under slogging con-... 

The combustion of pulverized coal at both atmospheric and higher pressure has been studied by Hazard and Buckley (4G), using three sizes of burners. The coal is pulverized to 93% through a 200-mesh screen. Experiments on burning pulverized coal under pressure have also been described (7G). 

Aqueous Na3C03 Treatments. Two samples of treated Illinois No. 6 run-of-mine coal were studied. One sample was treated in an autoclave under a pressure of 600 psi for one hour with 1.0 M Na2C03 at 250 C in a nitrogen atmosphere and washed subsequently wTth not... 

A process pioneered by the National Coal Board in England that has not reached the fully developed stage but that has considerable potential is supercritical gas extraction. In this process the coal is pyrolized at a relatively low temperature, around 400°C, in the presence of a compressed supercritical gas, that is, a gas whose temperature is above the critical temperature at which it can be liquefied. Suitable gases are, for example, a number of petroleum fractions. Under these conditions at high pressures, around 10 MPa, the gas density is like that of a liquid, and the gas acts like a strong solvent that causes the liquids to volatilize and be taken up by the vapor. By transferring the gas to a vessel at atmospheric pressure, the density of the solvent gas is reduced and the extracted... 

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