Pyrolysis processes carbonization

Chemical recovery ia sodium-based sulfite pulpiag is more complicated, and a large number of processes have been proposed. The most common process iavolves liquor iaciaeration under reduciag conditions to give a smelt, which is dissolved to produce a kraft-type green liquor. Sulfide is stripped from the liquor as H2S after the pH is lowered by CO2. The H2S is oxidized to sulfur ia a separate stream by reaction with SO2, and the sulfur is subsequendy burned to reform SO2. Alternatively, ia a pyrolysis process such as SCA-Bidemd, the H2S gas is burned direcdy to SO2. A rather novel approach is the Sonoco process, ia which alumina is added to the spent liquors which are then burned ia a kiln to form sodium aluminate. In anther method, used particulady ia neutral sulfite semichemical processes, fluidized-bed combustion is employed to give a mixture of sodium carbonate and sodium sulfate, which can be sold to kraft mills as makeup chemical. 

Goal Processing to Synthetic Fuels and Other Products. The primary approaches to coal processing or coal conversion are thermal decomposition, including pyrolysis or carbonization (5,6), gasification (6), and Hquefaction by hydrogenation (6). The hydrogenation of coal is not currently practiced commercially. 

Process development on fluidized-bed pyrolysis was also carried out by the ConsoHdation Coal Co., culminating in operation of a 32 t/d pilot plant (35). The CONSOL pyrolysis process incorporated a novel stirred carbonizer as the pyrolysis reactor, which made operation of the system feasible even using strongly agglomerating eastern U.S. biturninous coals. This allowed the process to bypass the normal pre-oxidation step that is often used with caking coals, and resulted in a nearly 50% increase in tar yield. Use of a sweep gas to rapidly remove volatiles from the pyrolysis reactor gave overall tar yields of nearly 25% for a coal that had Eischer assay tar yields of only 15%. 

Montaudo and co-workers have used direct pyrolysis mass spectrometry (DPMS) to analyse the high-temperature (>500°C) pyrolysis compounds evolved from several condensation polymers, including poly(bisphenol-A-carbonate) [69], poly(ether sulfone) (PES) and poly(phenylene oxide) (PPO) [72] and poly(phenylene sulfide) (PPS) [73]. Additionally, in order to obtain data on the involatile charred residue formed during the isothermal pyrolysis process, the pyrolysis residue was subjected to aminolysis, and then the aminolyzed residue analysed using fast atom bombardment (FAB) MS. During the DPMS measurements, EI-MS scans were made every 3 s continuously over the mass range 10-1,000 Da with an interscan time of 3 s. 

These adsorptions appear to be inconsistent with the evolution of carbon dioxide and other volatiles out of the charring solid in the pyrolysis process. The adsorptive properties develop as pyrolysis frees sites for adsorption debris escaping from thermally decomposing lignocellulosics leaves the char residue with a highly reactive, eagerly adsorbing inner surface. 

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. ... 

Furthermore, not all applications will need or benefit from the availability of phase pure SiC. For example, in polymer infiltration and pyrolysis processing of composites, the reinforcing material frequently is oxidized at the surface. Thus, an SiC precursor that produces excess carbon may be required to ensure that the oxide surface layer is reduced off during processing so that good interfaces are obtained. 

Pyrolysis units are expected to have minimal air pollution impacts because most of the pyro-gas generated in the pyrolysis process is burned as fuel in the process. During burning, the organic compounds are destroyed. Assuming complete combustion, the decomposition products are water, carbon dioxide, carbon monoxide, sulfur dioxide and nitrogen oxides ... 

Modification of porous inorganic materials by carbon makes it possible to obtain porous carboniferous composites with high thermal and chemical stability and strength. To introduce carbon into pores, both gas phase pyrolysis and carbonization through thermochemical solid-phase reactions are employed. The formation of carbon structures depends on carbonization conditions process rate, precursor concentration, presence of catalyst, etc. [1-3]. Phenolic resins, polyimides, carbohydrates, condensed aromatic compounds are most widely used as polymeric and organic precursors[4-6]. 

After pyrolysis, the carbon body is further densified by liquid pitch, resin impregnation, or CVD. Studies were undertaken to understand the role of the matrix, pores, and cracks, and fiber-matrix interactions in this material as it is stressed. The intent was to determine whether processing differences could alter the fracture behavior and possibly improve the physical characteristics ... 

Heating wood to temperatures slightly above 100°C initiates some thermal decomposition. A more active decomposition takes place above 250°C, and for industrial applications temperatures up to 500°C may be used. Above 270°C, thermal decomposition does not require any external heat source because the process becomes exothermic. The thermal decomposition of wood is usually called pyrolysis or carbonization. A number of other terms such as wood distillation, destructive distillation, and dry distillation are used interchangeably for this type of processing. 

Pyrolysis conditions determine the extent to which the coal is carbonized and the nature of the liquid and gaseous products. Coal pyrolysis processes are generally classified as low temperature (<700°C), medium temperature (700-900°C), or high temperature (>900°C). A number of reviews on advanced pyrolysis processes are available.30-31 Two highly developed pyrolysis processes were the COED process, developed by FMC Corporation, which used a series of fluidized beds operating at successively higher temperatures, and the TOSCOAL process, which used a horizontal rotating kiln. 

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