Carbon monoxide coal conversion

Several important chemical reactions for the conversion of coal to methane are shown in Table 2. Steam conversion involves the reaction of coal with steam to produce hydrogen and carbon monoxide. Hydrogen conversion is a reaction in which coal and hydrogen react to form methane. Oxygen conversion produces hydrogen and carbon monoxide by partial oxidation of coal. Methan-ation involves a reaction in which methane and water are produced from carbon monoxide and hydrogen. The water gas shift reaction between carbon monoxide and steam produces carbon dioxide and hydrogen. 

Synthetic oil is feasible and can be produced from coal or natural gas via synthesis gas (a mixture of carbon monoxide and hydrogen obtained from incomplete combustion of coal or natural gas). However, these are themselves nonrenewable resources. Coal conversion was used in Germany during World War II by hydrogenation or. 

The conversion of coal to gas on an industrial scale dates to the early nineteenth century (14). The gas, often referred to as manufactured gas, was produced in coke ovens or similar types of retorts by simply heating coal to vaporize the volatile constituents. Estimates based on modem data indicate that the gas mixture probably contained hydrogen (qv) (ca 50%), methane (ca 30%), carbon monoxide (qv) and carbon dioxide (qv) (ca 15%), and some inert material, such as nitrogen (qv), from which a heating value of approximately 20.5 MJ/m (550 Btu/fT) can be estimated (6). 

In Germany, large-scale production of synthetic fuels from coal began in 1910 and necessitated the conversion of coal to carbon monoxide and hydrogen. 

The methanation reaction is currently used to remove the last traces (<1%) of carbon monoxide and carbon dioxide from hydrogen to prevent poisoning of catalysts employed for subsequent hydrogenation reactions. Processes for conversion of synthesis gas containing large quantities of carbon monoxide (up to 25%) into synthetic natural gas have been investigated to serve plants based on coal-suppHed synthesis gas. 

The process will adversely affect air quality by releasing nitrogen oxides, sulfur oxides, carbon monoxides and other particulates into the atmosphere. Better control of the conversion conditions and better control of emissions can make the process cleaner, yet technology cannot do anything to curb carbon emissions. Since much of the carbon in coal is converted to carbon dioxide in the synthesis process, and is not part of the synthetic fuel itself, the amount of carbon dioxide that will be released to the environment during combustion is 50 to 100 percent more than coal, and around three times more than natural gas. 

In run 19, where considerable carbon monoxide conversion was obtained in both stages, the recycle ratio was 1.48 scf recycle gas per scf feed gas. Recycle ratios in the other tests varied from 1.14 to 1.30. The design recycle ratio is 1.67 for lignite coal feed with hydrogen/steam synthesis gas. 

Some chemical processes use energy directly to drive the transformation. For example, the conversion of iron ore, iron oxide, to iron metal requires chemical energy to remove the oxygen atoms. In early times the iron ore was heated with charcoal in more recent times it is heated with refined coal (coke), but in both cases the result is conversion of coal or wood into carbon monoxide, which is toxic but can be burned to carbon dioxide to generate needed heat. There is now interest in devising processes that do not use carbon in this way, but use electrical energy to avoid the production of carbon oxides. 

This paper touches on the chemistry of coal gasification and liquefaction comments on the current status of conversion processes and the influence of coal properties on coal performance in such processes and examines the contributions which coal conversion could make towards attainment of Canadian energy self-sufficiency. Particular attention is directed to a possible role for the medium-btu gas in long-term supply of fuel gas to residential and industrial consumers to linkages between partial conversion and thermal generation of electric energy and to coproduction of certain petrochemicals, fuel gas and liquid hydrocarbons by carbon monoxide hydrogenation. 

Another important use of methane is its conversion into synthesis gas (or syn-gas), a mixture of hydrogen gas and carbon monoxide as shown in Figure 17.1. Syn-gas can also be derived from coal. When this occurs, it is called water gas. Interestingly, the reaction of methane giving carbon monoxide and hydrogen can be reversed so that methane can be produced from coal through this route. 

---