Protean Brimstone

Minerals and Men, by James F. McDivitt, is a new paperback book sponsored by Resources for the Future and shortly to be published by Rand McNally (see page 4). It is intended for general reading, blending some geological facts with dollars and cents requirements, some technological developments with foreign trade requirements. Taking each major mineral in turn, the author distinguishes its dominant characteristics as a resource and as a commodity, and by this means illustrates the intricate relationships between such factors, common to all minerals, as fixed sanitation, exhaustion of reserves, changing patterns of supply, competition between primary and by-product production, and the role played by technology. This last factor is dominant among the characteristics of the sulfur industry, the story of which is extracted here from the book.

Sulfur is one of the nonmetallic materials which would be classed as an industrial mineral rather than a rock. In industry it has considerable importance, this brimstone of the ancients and spring tonic of our American forebears has become a key raw material for one of the fastest growing and most important segments of our economy—the chemical industry.

The value of sulfur production in this country in 1960 was over $115 million—a figure exceeded among metals only by iron ore, copper, and uranium—yet we hear relatively little of sulfur for most of it goes into the early stages of industrial processing. Some 80 percent is converted into sulfuric acid. Over 40 percent of the sulfuric acid produced in the United States is used in the manufacture of fertilizer. Other branches the chemical industry consume an additional 30 percent, and petroleum refining, iron and steel, and other branches of mineral processing also require significant amounts. These behind-the-scenes uses are steadily increasing to the extent that the demand for sulfur has more than tripled in the last twenty years.

At the close of the last century, 95 percent of the world's elemental sulfur came from the mines of Sicily. High price and limited production from this natural monopoly restricted the use of sulfur but at the same time stimulated the search for new sources. The first such source put to general use was pyrite—an iron sulfide which is quite common throughout the world and which today accounts for an important part of world sulfur production. This development began over one hundred years ago and subsequently served to lessen the hold of the Italian sulfur producers for some uses.

The great advance came after 1891, when Herman Frasch patented a process for recovering the sulfur which forms as a cap over some of the salt domes or plugs deep beneath the Gulf Coast of Texas, Louisiana, and Mexico. The process was so successful that it completely changed the pattern of the sulfur industry. Italian control was broken for all time and the economy of Sicily, which was not strong even at the best of times, suffered a serious blow. Although the Frasch process may have been an unfortunate invention for Sicily, it was a stroke of technological luck for the world, for Sicilian production could have supplied only a fraction of the sulfur the world has since consumed. The deposits of Sicily were not exhausted. Indeed, they still produce important quantities of sulfur, as they have for several hundred years, and in this they serve to illustrate that the death of a mineral deposit is not a sudden and drastic end but, rather, a slow tapering off which can continue indefinitely. In this case a traditional source of a mineral raw material was replaced by a completely new source made available by a significant breakthrough in technology. Sulfur from this new source was cheaper, vastly more abundant, and capable of meeting the growing demands of our rapidly industrializing society at just the time when that need was becoming acute.

The Gulf Coast sulfur-bearing salt domes are remarkable geologic structures which so far are unique in the world. They form an almost limitless reserve of salt, they have yielded vast quantities of oil, and during this century they have also supplied the bulk of the world's sulfur. Sulfur melts at about 240° Fahrenheit. The Frasch process takes advantage of this through pumping water heated above this temperature into the sulfur-bearing formation. The sulfur melts away from the adjacent rock and impurities, and is pumped to the surface, where it solidifies in almost chemically pure form.

There are over two hundred salt domes in the Gulf Coast area of Texas, Louisiana, and Mexico but few of these are sulfur-bearing. First one, then two, and now five major producing companies have used the Frasch process to recover sulfur from the two dozen domes that have yielded commercial quantities. It is upon these few locations in this limited area that the country and, in fact, the world, has depended for a major part of its supply of elemental sulfur during this century. But, as with all mineral deposits, the supply is not unlimited. Although the sulfur in the domes is abundant and will continue to contribute to our needs for a long time, there is already evidence that a depletion of reserves will force a halt to expanding production. Some of the domes have already been exhausted and have closed down; production on others is declining. In 1960 three new Frasch mines were opened but two old ones were closed and there are no more known sulfur-bearing domes to drill. The most recent large development is some six miles from the shore in 45 feet of water. Unless further development in the Gulf waters is successful, it would appear that the most productive period of the sulfur domes is over.

Again the world is faced with potential mineral shortage. Again the stimulus provided by this potential shortage, combined with technology, has seen to it that a new and important source has been developed at the right moment. This rather dramatic act has been played so many times during the history of mineral development that the outcome can be predicted with some confidence.

As in one part of the world production of sulfur from the great salt domes begins to level off and decline, in quite different parts of the world there is a growing production of sulfur from sour gas, a form of natural gas containing sulfur which must be removed before the gas becomes a marketable product. Such gas reserves occur at Lacq in southwestern France, where they are important to the growing industrial economy of France, and in the provinces of Alberta and British Columbia in Canada, where they provide fuel for a large segment of the west coast of North America. Production of natural gas from these fields automatically means the by-production of sulfur. The fact that sulfur can be sold—in some cases providing as much as 50 percent of the total value of production—is a source of considerable satisfaction to the gas companies, for this is a bonus which does much more than cover the cost of separation.

These are the main areas of sour gas production. Sulfur is also recovered from natural gas in other areas, as for example in Wyoming, but in lesser quantities. The gas fields have been developed during recent years and are only now moving towards full production. Lacq, which in 1960 produced 800,000 tons of sulfur, in 1962 had the capacity to produce 1.4 million tons; Western Canada, which in the early fifties produced only a few thousand tons of sulfur from gas, produced over 400,000 tons in 1960 and had the capacity to produce over 2 million tons a year at the end of 1962.

By comparison, total free world production in all forms in 1960 was about 18 million tons of sulfur equivalent, of which 6 million was from Frasch process operations, about 1 million from sulfur ores, 2.8 million recovered as a by-product from the purification of natural and refinery gas, and some 8 million from pyrites. The pyrites are sulfide ores from which sulfuric acid is produced directly without going through an elemental sulfur stage, thus we talk of sulfur equivalent. In sulfur, then, the increased demands of the growing market will be met not by increased production from the salt domes (unless some of the domes recently discovered in the middle of the Gulf are found to contain recoverable sulfur), but rather by new or increased production from natural gas fields and by increased production from other sources such as pyrite and other sulfide ores.

The fact that the new sulfur from sulfur gas is by-product material involves certain complications. The natural gas market is the controlling factor in drilling and operating the gas wells, but because this market is rapidly growing, the supply of sulfur from sour gas should continue to increase. In producing natural gas the sulfur cannot be ignored. It must be removed as an objectionable constituent. Thus sulfur from this source will exist whether there is a market for it or not, and since its cost of production is low it could be sold for whatever price it would bring, thereby disrupting the market. However, this is unlikely to happen. It is much more probable that the development of this new source of sulfur, with the consequent shift in the pattern of sulfur supply, will avert a world-wide shortage.

One might ask what would have happened if sour gas had not come along at this critical moment. Here, as is true with the metals, this is an economic problem as much as it is is a problem of raw materials. There is no shortage of sulfur-bearing minerals in the earth. The supply of sulfur in various forms of sulfide is great and much of this material is already being mined, for many of the metallic ores of copper, lead, and zinc are sulfur-bearing. The supply of gypsum and anhydrite, two forms of calcium sulfate, in the United States and the world is almost unlimited and can, under proper economic stimulus, be looked upon as a potential source of sulfur. Anhydrite in fact is being used in in the production of sulfuric acid in Germany today. These materials are not being more widely used today because better and cheaper sources of sulfur are available. They do exist and they can be used if and when they are needed.