Manufactured Gas History and Processes

Abstract

Thousands of manufactured gas plants operated in the United States for more than 150 years and were important to the industrial and social development of the country. There are many people who have contributed to the development of economical methods of manufactured gas production. While there were other factors, the decline in the use of manufactured gas was largely due to improvements in the long-distance transmission of natural gas, the development of oil-burning equipment, and the availability of electricity. The decline in manufactured gas use changed the gas utility industry from a manufacturing industry to a gas distribution industry. An understanding of the historically important processes can assist in the study of former gas plant sites since the raw materials, reactors, and appurtenances employed and the residuals produced can vary with the production process employed. A recent paper published in Environmental Forensics by Murphy et al., 2005 grouped historical and process aspects of manufactured gas production processes together while focused on evaluating accidental versus intentional disposal at manufactured gas plant sites. This paper separately reviews the raw materials, processes employed, gases produced and residuals generated by each of the historically important town gas processes in order to emphasize the differences between the processes. Gasification processes and the associated fuel gas produced include: producer gas consisting of carbon monoxide and hydrogen; carburetted water gas consisting of hydrogen, carbon monoxide and illuminants, and oil gas consisting of hydrogen and methane with lesser amount of carbon monoxide and illuminants. Coal gas is produced from the carbonization of coal and consists of hydrogen, methane, carbon monoxide, and illuminants. Each of the town gas processes discussed (i.e., coal gas, oil gas and carburetted water gas) contained water vapor, tar, naphthalene and hydrogen sulfide as impurities. The removal of these impurities resulted in residuals containing these components. Water vapor was removed as condensate. Tar-water emulsions were common to oil gas and carburetted water gas processes that used heavy oils or asphaltic-based oils. Emulsions were not common from processes that used lighter oils or from coal gas processes. Carburetted water gas tars are similar to oil gas tars but are lower in filterable carbon. Unlike coal gas tar, carburetted water gas and oil gas tars do not contain tar acids, nor is ammonia liquor produced in these processes. Much of the naphthalene would be removed with the tar. Additional naphthalene could be removed with wash oil. In the oil gas process, naphthalene was removed using a wash oil and the used wash oil was recycled into the gas-making oil. Town gas purifier wastes generally contained sulfides, but cyanide-bearing purifier wastes were common only to coal gas processes. Lampblack was generated in significant quantities only from the oil gas process. Coal gas processes produced coke. Petroleum ash was generated from the oil gas process. Coal ash and clinker were generated in the producer gas and carburetted water gas process, but not from the oil gas or coal gas processes.