Hydrogasification product gases

Hydrogen and pre-treated biomass are fed to the hydrogasification reactor. The produced gas passes a high-temperature gas clean-up section for removal of contaminants, followed by a final methanation step for the conversion of residual CO. Removal of H2O from the product gas of the methanation step, results in SNG as the final product. 

At 850 C and 30 bar, beside 100% formation of the pyrolysis products C2H4, CO, and CO2, more than 95% of ethane, and about 80% of methane were formed within the first 10 minutes. After that only methane, and in much less extent ethane, continued to be formed, through the hydrogasification of char. Figure 6 presents the mean concentration of the main carbon-containing components in the product gas as a function of pressure. It can be seen how the concentration of CO, CO2, and C2H4 decreases with pressure, while the concentration of CH4 and CjH increases with pressure. 

Because it requires many possible variables, such as temperature, pressure, the nature of chemical reaction, and the character of the solid surface, and because it incorporates many constants which require experimental evaluation, the general mathematical model to estimate the product gas distribution for different levels of carbon conversion can become exceedingly complicated. Practical application of this model is particularly difficult when a choice has to be made between reaction mechanisms, each of which can generate complex functions with a sufficient number of arbitrary constants to fit any given experimental curve. The purpose of the work discussed in this paper was to study the influence of temperature and the partial pressure of hydrogen and steam on the rate of steam-hydrogen and coal char reactions based on the previous pilot plant data obtained at IGT (10, 11) and to develop a correlation to estimate the performance of a hydrogasification reactor in terms of its product gas distribution for different levels of carbon conversion. 

Reactors may also be designed to operate either at atmospheric pressure or at high pressure. In the latter type of operation, the hydrogasification process is optimized and the quality of the product gas (in terms of heat, or Btu, content) is improved. In addition, the reactor size may be reduced and the need to pressurize the gas before it is introduced into a pipeline is eliminated (if a high-heat-content gas is to be the ultimate product). However, high-pressure systems may have problems associated with the introduction of the coal into the reactor. 

In general terms, as the molecular weight of the feedstock is increased, similar operating conditions of hydrogasification lead to decreasing hydrocarbon gas yields, increasing yields of aromatic Hquids, with carbon also appearing as a product. 

Coal can be processed to H2 by heat from a high temperature, gas-cooled reactor at a process efficiency of 60—70%. Process steps are coal hquefaction, hydrogasification of the Hquid, and steam reforming of gaseous products (179). 

Direct production of methane from coal is called coal hydrogasification. Several technologies have been developed to make city gas from coal. The main reaction in coal hydrogasification is... 

The calorific value of the product from hydrogasification is lower than that from single methanation, particularly with high carbon/hydrogen feedstocks because of the additional steam required. However, by adding a final metlianator. the calorific value can be increased to that obtained from double methanation, again with increased capital cost and reduced efficiency. This process (Fig. 2) is used in the first operational SNG plant in the United States at Harrison, N.J. Typical gas analyses are given in Table 4. 

At the hydrogasification conditions used, about 90% of the 360°C endpoint feed oil is gasified, yielding a raw gas containing about 52% methane and 10% ethane, with the remainder principally hydrogen. About 60% of the liquid products is benzene. Total liquid products are removed... 

In this process, gasification is carried out in the presence of hydrogen. Most of the research on hydrogasification has targeted methane as the final product. One approach involves the sequential production of synthesis gas and then methanation of the carbon monoxide with hydrogen to yield methane. Another route involves the direct reaction of the feed with hydrogen (Feldmann et al,... 

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