Liquid liquefaction process

ESTIMATED YIELD AND COMPOSITION OF LIQUID PRODUCTS FROM LIQUEFACTION PROCESSES... 

A comparison of potential yields from a combined SCT dissolution plus upgrading scheme with yields from other liquefaction schemes shows that the SCT scheme has potential to give significantly lower gas and higher liquid yields. This results in a more efficient utilization of hydrogen in the liquefaction process. 

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. 

Pyrolysis and liquefaction processes take an intermediate position in the sense that they maintain some larger molecular characteristics. Pyrolysis is a process in which the biomass material is quickly heated. The thermal cracking process, de-polymerizes waste or dry biomass and produces a liquid of complex composition (Fig. 1.17). 

Catalytic coal liquefaction processes do not specifically use hydrogen donor solvents although coal is introduced into the liquefaction reactor as a slurry in a recycle liquid stream. Catalyst is used as a powder or as granules such as pellets or extrudates. If powdered catalyst is used, it is mixed with the coal/liquid stream entering the reactor. Pelleted catalyst can be used in fixed bed reactors if precautions are taken to avoid plugging with solids or in fluidized bed reactors. In the latter case, the reacting system is actually a three phase fluidized bed, that is, catalyst particles and coal solids, as well as liquid, are fluidized by gas. 

A modification of the pyrolysis process, developed by Hoppe-Seyler in 1871, involved the addition of water and alkali to biomass which was converted into oil, gas, water-soluble components, and carbonaceous material. " The addition of carbon monoxide and hydrogen in the liquefaction process allowed the production of liquid fuels from biomass. Asphalt substitutes have also been prepared from biomass under liquefaction conditions. ... 

An enormous amount of work both at bench scale and at pilot plant scale have been conducted to study the production of liquid and gaseous hydrocarbons from coal. Since most of the analytical methods are either very time consuming or very specialized, almost all the data available on the coal liquefaction process are based on distillation data or on the assumption that all products which are not insoluble solids are converted. It is known that products of liquefaction vary based on coal, reaction conditions, and media of reaction hence, conversion and yield may be based on very different products. 

The type of quantitative analytical data which are needed for modelling and kinetic studies on coal liquefaction process could not be obtained by using general analytical techniques. We have developed a new analytical approach for obtaining qualitative information as well as quantitative data on coal liquid species. Coal liquefaction produces smaller molecules from coal which is composed of larger molecular species or a matrix of larger molecular species in which smaller species are entrapped. 

One of the major results of SEC-GC-MS studies is the discovery of an orderly pattern, by which various isomers and homologs of similar chemical species exist in coal liquids. For example almost any direct coal liquefaction process produces very similar species, which differ from each other by size and extent of isomerization but with an orderly distribution pattern. Alkanes... 

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. 

Three types of direct coal liquefaction processes have emerged to convert coals to liquid hydrocarbon fuels 8... 

Solid/liquid separation is usually required at the interface of the primary and secondary stages to allow optional upgrading of the crude coal liquids of the primary liquefaction stage, by removing mineral matter, unreacted coal, heavy products, and catalysts (111, 112). Distillation, anti-solvent extraction, and centrifugation have been conventionally employed in liquefaction processes (113, 114). 

Coal and its derived liquids contain a number of catalyst poisons or poison precursors, which inevitably and severely deactivate the catalysts during the liquefaction process. The catalysts are deactivated via three major routes... 

Liquefaction. Since the 1970s attempts have been made to commercialize biomass pyrolysis for combined waste disposal—liquid fuels production. None of these plants were in use in 1992 because of operating difficulties and economic factors only one type of biomass liquefaction process, alcoholic fermentation for ethanol, is used commercially for the production of liquid fuels. 

The literature abounds with reports of the fractionation of extracts from coal, more specifically to the liquids and solids produced by various coal liquefaction processes (Speight, 1994, and references cited therein). However, to accomplish the subfractionation of the coal extracts, it is preferable to apply (with any modifications noted) a suite of the standard test methods that are often applied to petroleum and its residua. However, before application of any subfractionation procedure to coal extracts, it may be necessary to stabilize the extracts (at a fixed temperature and pressure) to ensure that losses of potentially volatile constituents do not occur during the subfractionation procedure. Once the extracts have been stabilized, it is in order to proceed. 

Grassmann diagram for the Linde liquefaction process of methane. One thousand exergy units of compression energy result in 53 exergy units of liquid methane. The thermodynamic efficiency of this process is 5.3%. The arrowed curves, bent to the right, show the losses in the various process steps. 

Although the first major use of coal liquids will be as boiler fuels, it is clear that in order to make the largest impact on the U.S. liquid fuel demand, products from direct liquefaction have to be upgraded to quality liquid fuels for both transportation and home heating oil uses. The products coming from the all-distillate coal liquefaction processes such as H-Coal Syncrude, SRC-II and Donor Solvent, along with shale oil production will be candidates for use as refinery feedstock. 

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