Complete gasification

Gasification. The extent of carbon removal from coal by pyrolysis is relatively limited. As a result, the yields of secondary fuels having increased H/C ratio are not large. Essentially complete control of the amount of carbon removed can be achieved, however, by complete gasification of coal with an oxygen-containing gas and steam ... 

Combustion with complete gasification occurs when an AP pyrolant is composed of l2ip(0.86) and bi3I((0.14). The mass fraction of hydrogen chloride (HCl) among the combustion products is about 0.3. It is well known that HCl molecules combine with water vapor in the atmosphere to generate a white smoke. It is for this reason that AP pyrolants act as white smoke generators in a humid atmosphere. 

A model Is presented for char gasification with simultaneous capture of sulfur In the ash minerals as CaS. This model encompasses the physicochemical rate processes In the boundary layer, In the porous char, and around the mineral matter. A description of the widening of the pores and the eventual collapse of the char structure Is Included. The modeling equations are solved analytically for two limiting cases. The results demonstrate that pore diffusion effects make It possible to capture sulfur as CaS In the pores of the char even when CaS formation Is not feasible at bulk gas conditions. The model predictions show good agreement with experimentally determined sulfur capture levels and reaction times necessary to complete gasification. 

At temperatures lower than 550 °C, soot and tar are formed. For the experiments in the miniature plant generally a closure of the carbon balance better than 96 % could be achieved. The results show that at temperatures higher than 550 C a complete gasification of glucose without the formation or only with traces of solid and oily byproducts can be obtained. Residence times are up to 2 min. Samples of the aqueous effluent (residual TOC) contained some phenol and phenol derivatives. 

The observed results show that a nearly complete gasification of the used model compounds can be achieved at temperatures of 600 C. The screening experiments with the real feedstock confirm the experiments done at the University of Hawaii. Compared to the traditional gasification process the following advantages for the hydrothermal gasification of wet biomass / organic waste feedstock can be expected ... 

The biomass gasifleation processes so far proposed require operation at temperatures higher than 600 C or the use of expensive metal catalysts. Dr. Antal s group achieved complete gasification by conducting supercritical water gasifleation at... 

Complete gasification consists of the pyrolyzer reaction and an additional exothermic reaction of the fixed car-... 

Another method commonly used for the conversion of methane is partial oxidation, shown in Reaction 2.9, which may or may not be catalytic. The reaction will be accompanied by complete gasification. 

Osthaus, K. H., Intern. Conf. Complete Gasification Mined Coal, Liege, 1954, 255. 

The main chemical equilibrium reactions for complete gasification e.g. at 1200 °C are compiled in Table 8.5. 

Two-stage gasification Partial gasification or pyrolysis in a first step followed by complete gasification of the resultant char in a second step. 

Here we assume that solid B is sufficiently pure that complete gasification takes place and that negligible quantities of solid residue remain. Cases where appreciable quantities of solid residue are left after reaction (e.g., the combustion of coals of high ash content) are treated in a subsequent section. 

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