Coal liquefaction slurry

Fig. 33 Actual temperature profile in coal liquefaction slurry column compared with the model of Shah and Parulekar (from [177]) e plant data...

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. 

Products Company and Davison (W.R. Grace) Catalysts) and Hydrocarbon Technologies, Inc. ART provides non-zeolitic catalysts for ebullating residue hydrocracking and fixed bed pretreating HDT [140], A nanoscale iron based, slurry catalyst is recommended for coal liquefaction, while a molecule-sized and chemically in situ generated catalyst is employed for the high conversion of asphaltenic fractions or heavy oils [141],... 

The development of three-phase reactor technologies in the 1970 s saw renewed interest in the synthetic fuel area due to the energy crisis of 1973. Several processes were developed for direct coal liquefaction using both slurry bubble column reactors (Exxon Donor Solvent process and Solvent Refined Coal process) and three-phase fluidized bed reactors (H-Coal process). These processes were again shelved in the early 1980 s due to the low price of petroleum crudes. 

Coal liquefaction, 6 765-766, 832-869 coprossing, 6 856-858 direct, 6 833-858 indirect, 6 858-867 use of steam in, 23 239-240 Coal mining, 6 744-745 Coal-oil coprocessing, 6 833, 856-857 Coal petrography, 6 706-709 Coal petrology, 6 706 Coals, ash properties of, 72 324t Coal slurry pipelines, 6 748 Coal tar... 

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. 

The H-Coal and CFFC Processes are unique In the sense that first-stage liquefaction is achieved by circulating the coal-donor slurry through an "ebullated" (i.e., partly fluidized) bed of uniformly sized catalyst pellets. 

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. 

SELECTION OF CEFiAMIC PIPING FOR COAL SLURRIES IN A COAL LIQUEFACTION PLANT 827... 

Coal liquefaction Fischer-Tropsch synthesis Synthesis of methanol Hydrogenation of oils Alkylation of methanol and benzene Polymerization of olefins Hydrogenation of coal oils, heavy oil fractions, and unsaturated fatty acids Adsorption of S02 in an aqueous slurry of magnesium oxide and calcium carbonate S02 or removal from tail gas Wet oxidation of waste sludge Catalytic desulfurization of petroleum fractions Wastewater treatment... 

In route 2, the direct liquefaction approach, coal is slurried with a process solvent and the slurry is pumped into a pre-heater/reactor and heated to temperatures of 750-850°F at a pressure of 1500-3000 psi of hydrogen. A catalyst can be used either in the reactor itself or external to the reactor to hydrogenate the process solvent. Almost all the organic constituents of the... 

The recovery, regeneration, and repeated reuse of the active catalyst are of prime importance in substantially reducing the overall cost of coal liquefaction. The used catalysts usually remain in the bottoms products, which consist of nondistillable asphaltenes, preasphaltenes, unreacted coal, and minerals. The asphaltenes and preasphaltenes can be recycled with the catalyst in bottoms recycle processes. However, unreacted coal and minerals, if present in the recycle, dilute the catalyst and limit the amount of allowable bottoms recycle because they unnecessarily increase the slurry viscosity and corrosion problems. Hence, these useless components should be removed or at least reduced in concentration. If the catalyst is deactivated, reactivation becomes necessary before reuse. Thus, the design of means for catalyst regeneration and recycle is necessary for an effective coal liquefaction process. Several approaches to achieving these goals are discussed below. 

This term is restricted here to equipment in which finely divided solids in suspension interact with gases. Solids fluidized by liquids are called slurries. Three phase fluidized mixtures occur in some coal liquefaction and petroleum treating processes. In dense phase gas-solid fluidization, a fairly definite bed level is maintained in dilute phase systems the solid is entrained continuously through the reaction zone and is separated out in a subsequent zone. 

Gas-liquid bubble columns and gas-liquid-solid slurry bubble columns are widely used in the chemical and petrochemical industries for processes such as methanol synthesis, coal liquefaction, Fischer-Tropsch synthesis and separation methods such as solvent extraction and particle/gas flotation. The hydrodynamic behavior of gas-liquid bubble columns and gas-liquid-solid slurry bubble columns are of great importance for the design and scale-up of reactors. Although the hydrodynamics of the bubble and slurry bubble columns has been a subject of intensive research through experiments and computations, the flow structure quantification of complex multi-phase flows are still not well understood, especially in the three-dimensional region. In bubble and slurry bubble columns, the presence of gas bubbles plays an important role to induce appreciable liquid/solids mixing as well as mass transfer. The flows within these systems are divided into two... 

HDN as applied to coal liquefaction can be performed either during the liquefaction process itself or by hydrotreatment of the released oil. In H-Coal and Synthoil processes4 19,68d the coal is directly in contact with CoMo or NiMo catalysts in the H-Coal process, a slurry of H2, coal, ex-coal oil, and... 

Shinn (1982) developed a mechanically agitated slurry reactor with induction heaters for coal liquefaction. While the induction heaters required large power input, they allowed the slurry to heat up to 400-450°C in few minutes, thus cutting down the heat-up period. In the use of such reactors, the effects of induction heating on the metal degradation and failure need to be carefully considered. Except for the induction heating system, the rest of the reactor was a conventional slurry reactor. The concept of induction heating is more practical for smaller-size reactors. 

When the catalyst is available in a small amount, a microreactor assembly is often used (Miller, 1987). This is a simple T-type reactor heated by a fluidized sand bath. The mixing is provided by mechanical agitation that shakes the reactor up and down within the fluidized bed. Because of the small amount of slurry, and an effective heat transfer in the fluidized sand bath, the heat-up period in such a reactor is small. The nature of mechanical agitation is, however, energy-efficient. The reactor provides only a small sample for the product analysis, which makes the usefulness of the reactor for detailed kinetic measurements somewhat limited. The reactor has been extensively used for laboratory catalyst screening tests in coal liquefaction. 

Direct coal liquefaction (DCL) refers to the process of converting coal to liquid products by mixing ground coal with a recycled process solvent and/or petroleum-derived residual oil and reacting the slurry in a hydrogen atmosphere at 750-850°F (400-450°C) and 1000-2500 psig (7-17 MPa). Under these conditions, the coal structure breaks down into... 

While current applications include hydrogenation and fermentation, slurry bubble columns have recently been the subject of renewed study for use in two areas of hetergeneous catalysis, SRC coal liquefaction and the Fischer-Tropsch reaction to produce hydrocarbons from synthesis gas. 

NEDOL [New Energy Development Organization Liquefaction] A coal liquefaction process in development in Japan by the New Energy and Industrial Technology Development Organization (NEDO), Tokyo. Crushed coal is mixed with a pyrite catalyst and slurried in a hydrogenated heavy oil. Liquefaction takes place at 450°C, 170 bar. The overall oil yield is 59%. The used solvent is hydrogenated and recycled. Piloted in Kashima, Japan, in 1997 to 1998. Two Chinese companies were licensed to build test units in 2006. 

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. 

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