Liquefaction products, coal

It has been proposed (17) that the portion of coal which is mobile under liquefaction conditions, contributes to the stabilization of thermally-generated radicals. Thus, coals which are highly fluid or contain large contents of extractable material might be expected to provide hydrogen and thus promote conversion. Collins has reported that vitrinite is a better donor of hydrogen than is Tetralin (20). Our own measurements of the aromatic content and elemental analyses of the coals (16,21) (or coal products) before and after conversion at short time are insufficient to confirm or deny the supposition that coal acts as its own H-donor even at short times. 

Fully-deuterated xetralin was used to study the mechanisms of coal liquefaction. Experiments were conducted with xetralin-di2, deuterium g s and bituminous coal at 400°C and at 15.2-20.7 MPa. The recovered solvent and solvent-fractionated coal products were analyzed for total deuterium content and for deuterium content in each structural position. 

Table VI liststhe calculated Px,y/Fy vaiues for the three soluble coal products from E10 and E19. The values range from 0.58 to 1.63. The a-alkyl regions in E10 and E19 have Px,y >fy which indicate that in liquefaction experiments conducted with a donor solvent, preferential incorporation occurs in the a-alkyl position.

We will consider three processes in more detail to show how the sulfur in the original feedstock material (coal or oil shale) is recovered as elemental by-product sulfur. In this way yields of sulfur per barrel of product can be computed. The three processes will illustrate examples of coal gasification for production of SNG, methanol or indirect liquids, direct liquefaction for production of naphtha and synthetic crude oil and finally, oil shale retorting for production of hydrotreated shale oil. 

It is not necessary or even desirable to achieve highly upgraded coal products in this initial liquefaction step as a sufficiently depolymerized and hydrogenated product can be further upgraded in a secondary step through hydrocracking and hydrorefining. 

More recently, there has been much concern about the possible effects of the mineral matter in coal on processes used to convert coal to other fuels such as gasification, liquefaction, and production of clean solid fuels. Not only is removing and disposing of the mineral matter a problem, but also the possible chemical effects such as catalyst poisoning, which might be expected in the methanation of gas from coal, should be considered. 

Effect of Recycle on Liquefaction and Product Distribution. It Is Important that the product oil from a coal liquefaction process should have a low viscosity so that It could be used for preparing coal-oll slurries for recycling In a continuous liquefaction process. The product oil should also exhibit reactivity or solvency for the coal so that the viscosities do not deteriorate with prolonged recycling operation. 

Within this context, the quantitation and speciation of organically bound trace metals in coal liquefaction soluble products presents a real challenge. Quantitative trace element methods in the solid state on liquefaction... 

Combustion, carbonization, gasification, and liquefaction are considered the four grand processes in the utilization of coal. In general terms, 92% of the coal production is used as fuel and 8% is carbonized to produce metallurgical coke. Coal combustion is carried out in thermal utilities for electricity production, co-generation plants, and cement factories. Coal combines with oxygen from the air giving carbon dioxide and heat ... 

Texaco Research and Development Coordinating author plus Introduction and sections on Coal Production and Consumption, Origin and Classification, Coal Composition and Structure, Pyrolysis, and Gasification (2) Center for Applied Energy Research, University of Kentucky Coal Mining and Preparation (3) Advanced Fuel Research Combustion (4) Center for Applied Energy Research, University of Kentucky Direct Coal Liquefaction (5) Eastman Chemical Company Petrochemical Feedstocks. 

Figure 17.28 shows a schematic of the SRC-I process. The feed coal is crushed and mixed with a recycle solvent and hydrogen prior to entering the preheater. The preheater effluent, at 700 to 750°F (370-400°C), then is fed to the dissolver unit, or thermal liquefaction unit (TLU), which operates at 840 to 870°F (450-465°C). There is no upgrading step, as the desired product is a solid at room temperature and not a distillate. The solids removal from the liquid slurry is accomplished by critical solvent de-ashing (CSD). The solids-free resid from the CSD was separated by vacuum distillation into a recycle solvent (the light fraction) and a solvent refined coal product (the bottoms). 

Liquefaction. Liquefaction of coal to oil was first accompHshed in 1914. Hydrogen was placed with a paste of coal, heavy oil, and a small amount of iron oxide catalyst at 450° and 20 MPa (200 atm) in stirred autoclaves. This process was developed by the I. G. Earbenindustrie AG to give commercial quaUty gasoline as the principal product. Twelve hydrogenation plants were operated during World War II to make Hquid fuels (see CoAL... 

Background Indirect coal liquefaction differs fundamentally from direct coal hquefaction in that the coal is first converted to a synthesis gas (a mixture of H9 and CO) which is then converted over a catalyst to the final product. Figure 27-9 presents a simplified process flow diagram for a typical indirect coal hquefaction process. The synthesis gas is produced in a gasifier (see a description of coal gasifiers earlier in this section), where the coal is partially combusted at high temperature and moderate pressure with a mixture of oxygen and steam. In addition to H9 and CO, the raw synthesis gas contains other constituents (such as CO9, H9S, NH3, N9, and CHJ, as well as particulates. 

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. 

In addition to supplying transportation fuels and chemicals, products from coal liquefaction and extraction have been used m the past as pitches for binders and feedstocks for cokes [12]. Indeed, the majority of organic chemicals and carbonaceous materials prior to World War II were based on coal technologies. Unfortunately, this technology was supplanted when inexpensive petroleum became available dunng the 1940s. Nevertheless, despite a steady decline of coal use for non-combustion purposes over the past several decades, coal tars still remain an important commodity in North America. 

These reactors contain suspended solid particles. A discontinuous gas phase is sparged into the reactor. Coal liquefaction is an example where the solid is consumed by the reaction. The three phases are hydrogen, a hydrocarbon-solvent/ product mixture, and solid coal. Microbial cells immobilized on a particulate substrate are an example of a three-phase system where the slurried phase is catalytic. The liquid phase is water that contains the organic substrate. The gas phase supplies oxygen and removes carbon dioxide. The solid phase consists of microbial cells grown on the surface of a nonconsumable solid such as activated carbon. 

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