The manufactured gas industry experienced a range of technological improvements throughout the nineteenth century. Organic solids and liquids emit flammable vapors when heated in an oxygen-poor environment. In the absence of oxygen, these substances will not burn, and these vapors can be collected and used elsewhere as fuel. The flammable vapors comprising gas made from coal are principally hydrogen, carbon monoxide and methane. All of these gases are capable of adding oxygen to their structures, which will then emit energy in the form of heat and light. However, there are some dangers in relation to supplying gas this way. For instance, carbon monoxide although flammable is toxic, and was consequently notorious in the past as a means of committing suicide - it was also frequently the cause of accidental asphyxiation.
Generally coal was the dominant feedstock for the production of manufactured gas; although from around 1870 an abundance of refined petroleum products triggered construction of gasworks that used a mixture of oil and coal. One of the lighter distillates of crude oil, naphtha was especially attractive because it had no alternative market and because the resultant oil gas contained less carbon monoxide and sulphuric impurities than coal gas. Today, a number of the manufactured gasworks that survive produce gas from naphtha, rather than coal, and mix it with natural gas, such as in Hong Kong and Singapore. In choosing the feedstock, companies considered the regional availability and comparative costs; while entrepreneurial whims and the inertia of sunken investments also influenced decisions.
The original basic design of the gaslight apparatus used in the nineteenth century was established by Boulton and Watt and Samuel Clegg in the period from 1805 to 1812. Additional improvements were later undertaken by the Gas Light and Coke Company of London, as well as a growing number of gas engineers after 1812. Boulton and Watt contributed the basic designs of what were to become known as the condenser, the retort and the gasometer. Others inventors and engineers were later to improve them and to introduce lime purification and the hydraulic main (another purifier). The retort-bench was a construction where the retorts were situated, which in turn was used for the carbonization of the coal feedstock and the creation of coal gas. Over the years, advances were made that transformed the retort-bench from iron vessels containing coal located over an open fire to a highly efficient, partially automated plant for the carbonization of large amounts of coal.
From the retort bench, the gas was passed through a tar/water ‘trap’ (similar to a trap in plumbing) called a ‘hydraulic main’, where coal tar was extracted and the gas was cooled. The gas would then continue on to the condenser, which was either an atmospheric or water-cooled condenser, with the condenser often consisting of odd lengths of pipe and connections. Manufactured coal gas that came directly from the retort-bench was a noxious collection of chemicals, and removal of the most dangerous components was necessary for improving the quality of the gas, for preventing damage to equipment and for extracting chemicals that could be sold as by-products. For instance, tar in the gas could gum up the pipes (and could also be sold as a by-product), ammoniacal vapors might lead to corrosion of equipment and pipes, naphthalene vapors could block the gas pipes and carbon dioxide was known to decrease illumination. The most hazardous substance in the raw coal gas was the sulfuret of hydrogen (hydrogen sulfide, H2S); therefore, its removal was particularly important.
Gas storage facilities were constructed of a variety of materials including stone, brick, concrete, steel and wrought iron. These facilities, or gasometers as they came to be known, increased in size throughout the nineteenth century and became very well-known landmarks in many cities, simply because of their sheer size (as shown in Pictures 3.2 and 3.3).
Throughout the nineteenth century, no clear demarcation existed between gas production, transmission and distribution. Gas was produced from coal in one or more gasworks in each urban center; and usually the same firm that produced the gas also operated the distribution pipeline network. However the increasing scale economies (and capital-intensive nature) of the gasworks, coupled with the expense of duplicating a distribution pipe network, made it difficult to sustain any sort of competition in gas markets. In addition, gas could only be stored for limited time periods and was expensive to transport. Gas manufacturing and distribution technology was at that time one that yielded small local networks, and were most effective in densely populated urban centers. It was not until the discovery of large reserves of natural gas and the introduction of pipeline technology developments that allowed for transport over long distances was there a strong push for regional or national government intervention. Transporting gas over long distances was difficult because the pipes often leaked too much gas, and it was expensive to create the sort of pressure needed to transport it. Quite simply, it was cheaper to transport coal (or oil) over long distances and then convert it into gas close to consumers than to produce it at a central location, say at the coal or oil fields. This meant that from very early on, the conditions of monopoly arose, along with responding demands for regulation.