Water gas

Water gas is a method of hydrogen production that combines steam and coke gas In the following chemical reaction:

CO + H₂O → CO₂ + H₂

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In 1873, Professor Thaddeus S. C. Lowe developed and patented a process by which large amounts of hydrogen gas could be generated for residential and commercial use in heating and lighting. Unlike the common coal gas, or coke gas which was used in municipal service, water gas provided a more efficient heating fuel.

The process was discovered by the passing of high-pressure steam over hot coal, the major source of coke gas. Lowe's process improved upon the chimney systems by which the coal could remain superheated thereby maintaining a consistently high supply of the gas. This process created a thermo-chemical reaction of applying hydrogen, in the steam, to carbon monoxide, in the coke gas. The reaction produced carbon dioxide and pure hydrogen which after a process of cooling and "scrubbing," passing through water vapor, left just a pure hydrogen gas.

The process spurred on the industry of gas manufacturing, and gasification plants were established quickly along the Eastern seaboard of the United States. Similar processes, like the Haber Process, led to the manufacture of ammonia (NH₃) by the combining of nitrogen, found in air, with high volumes of hydrogen. This spurred on the refrigeration industry which long used ammonia as its refrigerant. Prof. Lowe also held several patents on artificial ice making machines, and was able to run successful businesses in cold storage as well as products which operated on hydrogen gas.

UK Usage

It appears that the term Water Gas has different meanings in the USA and the UK. In the UK it means a mixture of carbon monoxide and hydrogen obtained by passing steam over red-hot coke:

C + H₂O → CO + H₂

The reaction is endothermic so the coke must be continually re-heated to keep the reaction going. This was usually done by alternating the steam stream with an air stream.

UK water gas had a lower calorific value than coal gas so the calorific value was often boosted by passing the gas through a heated retort into which oil was sprayed. The resulting mixed gas was called carburetted water gas.

These are useful gases but require careful handling because of the risk of carbon monoxide poisoning.

See also

• Syngas
• Town gas
• Water gas shift reaction
• Wood gas