Gasification solids mixtures

Recent research in homogeneous catalysis emphasized the identification and development of transition metal complexes for the conversion of synthesis gas (CO -I- H2) , which is produced from natural gas or from coal and other hydrocarbon sources by gasification. Solid catalysts are known for conversion of CO + H2 into methanol, into mixtures of hydrocarbons (Fischer-Tropsch products), or into other products (see... 

Coal can be converted to gas by several routes (2,6—11), but often a particular process is a combination of options chosen on the basis of the product desired, ie, low, medium, or high heat-value gas. In a very general sense, coal gas is the term applied to the mixture of gaseous constituents that are produced during the thermal decomposition of coal at temperatures in excess of 500°C (>930°F), often in the absence of oxygen (air) (see Coal CONVERSION processes, gasification) (3). A solid residue (coke, char), tars, and other liquids are also produced in the process ... 

Pyrolysis is the degradation of macromolecular materials with heat alone in the absence of oxygen [45]. The development of pyrolysis processes for the production of liquids has gained much attention in the last decade because they offer a convenient way to convert low-value woody residues into liquid fuels and value-added products. Biomass pyrolysis is of growing interest as the liquid product can be stored and easily transported [46]. Pyrolysis processes yield a mixture of gas, liquid, and solid products. If pyrolysis is practiced alone, that is, without a subsequent gasification step (see Section 16.4.3), the process conditions are usually chosen to maximize liquid product yields. 

Modelling studies for the moving bed were made at two gas compositions, a hydrogen rich composition containing 50% H2 and 20% CO with 10% H20 and 5% CO2, and a CO rich gas mixture containing 50% CO and 20% H2 with 5% H2O and 20% C02. Most results were obtained with the latter mixture, which is representative of gas produced from coal gasification, which is likely to have a major application for reduction processes in the future.Pellets of 8mm diameter were modelled unless otherwise indicated.Temperatures were varied from 873 to 1273K while gas flows and solid flow rates are typical of those used commercially. 

Minowa et al. [17] at the National Institute for Resources and Environment, Japan, proposed treatment of city garbage at ten cratures lower than 200 C to "liquidize the garbage. This operation is different from conventional liquidization because the product material is not oil but a biomass slurry that can be obtained at much lower temperature. Specifically, they were able to liquidize a mixture of cabbage, steamed rice, clam shells, dried sardines, and butter en loyed as a garbage model by treating it in an autoclave. The product was a slurry, and solid conqronents were found to precipitate with time. However, when they operated at 150 C for 1 hour, the solid components could be suspended for more than several hours. They proposed that this process could be applied as an effective pretreatment for supercritical water gasification,... 

Approximately 2 g. of the desired model compounds were heated in a stream of dry nitrogen (pyrolysis) or of a mixture of 92 % nitrogen and 8% oxygen (gasification). The sample was placed in a combustion boat of porcelain. The boat was heated in a quartz tube which was placed in an electrically heated furnace. The furnace was heated with 50 C/min to the desired temperature which was kept for 30 minutes, and the sample was cooled under nitrogen and weighed. The fraction of solid residue left in the vessel was calculated and analysed on its chlorine content. 

Conventional gasification requires separation of hydrogen and CO2 from the fuel gas mixture. This can be accomplished through chemical or physical sorbents or through membrane separation. As mentioned earlier, at low temperatures, physical and chemical adsorption is commonly used to separate hydrogen from the gas stream. Many of the zero-emission plants, however, could improve efficiency dramatically if CO2 capture could be achieved at high temperatures. Solid chemical sorbents, such as CaO, have been considered potential candidates. 

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