)) EUROPE SICILIAN SULFUR
m Technology gets economic assistance to he&
industrialize Italy's problem area
GERLANDO MARULLO FRANCESCO TRAINA
Modem, efficient processes ore often unsuited to underdeveloped areas,
where social or
political
factors con easily outweigh the purely
technological.
Sometimes
these factors dictate that low grade indigenous raw materials be used; the role of technology is to find o way to use them.
This i s the
case with sulfur in Sicily. We
present our
international
readers with Sicily's problem and how the islanders ore approaching it.
Perhaps their
approach
will
be pertinent to other ports of the world with similar problems.
20
INDUSTRIAL AND ENGINEERING CHEMISTRY
sulfur ore has been exploited in Sicily Lowfor grade many centuries. It has had its good times and its bad times. The current Sicilian sulfur crisis began when high grade sulfur deposits in the US. were commercialized about the turn of the century. Since then, except for short periods of high demand, the last of which was during the Korean War, the crisis has continued to get worse and has reached today an exceptionally grave position. Not only is the U.S.A. a serious competitor, but other countries have, in the past decade, become large producers of sulfur. Mexico, Poland, France (Lacq), and Alberta, Canada, have found either sulfur domes or sour gas deposits. And petroleum refiners all over the industrialized world have begun to recover great quantities of sulfur from their refinery gases. Because of these tough competitors, plus rhe difficulty of producing at a competitive cost in Sicily, the Sicilian sulfur producers do not object in principle to valid help. They have been subsidized for many years; now they are getting special assistance through local, national, and Common Market initiative
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.
The Montecatini subsidiary Akragas uses low grade sulfur ore in its plant at Porto Empedocle, Sicily
A Short History
Shortly after the first world war, a few people foresaw a possibility of salvation in the use of sulfur ores to make sulfuric acid. A first attempt, although indirect, was carried out by the proprietors of the Cozzo Disi mine, who thought to use the SO2 from their Gill furnace to make sulfuric acid. The attempt aimed at recovering the SO2 which was being discharged into the air during the ore processing, but it was not successful. Gill furnace gas is at low temperature, high in humidity, and loaded with solids; thus it is unsuitable for good performance in the Glover tower used to denitrate acid coming from the Gay-Lussac tower. An attempt to raise the gas temperature, leading to an increase in air content, led to a strong reduction in yield of the Gill furnace, so the project was abandoned. T h e problem was taken up again later by an Italian professor, Giuseppe Oddo, who first suggested burning the ore directly. He also suggested using the fines, which could not be charged to traditional fusion processes.
At that time, the fines, pieces smaller than a walnut, were mixed with clay and dried in the sun before being fed to the furnaces. This procedure yields mediumsized blocks called “panotti di sterri,” which could be used in melting devices but which had the disadvantages of residual moisture and of clay plus the fact that they were dried in the sun-possible only in good weather. Therefore, Professor Oddo’s suggestion had to aM ait development of a furnace which could use the sterri directly and would assure, on the one hand, complete combustion of the ore and avoid, on the other hand, sulfation of the calciferous gangue. For good combustion of the sulfur, which distills from the gangue, large volumes of air are necessary; otherwise unburned sulfur is entrained in the gas stream. But to avoid sulfation, contact between the gangue and the Son-laden gas must be prevented. T h e latter disadvantage is what happens in a fluidized bed furnace where intimate contact leads to considerable sulfation. Montecatini, interested in Sicily for both mining and fertilizer manufacture and needing sulfuric acid for its superphosphate fertilizer production, solved the problem by adapting the shelf-combustion furnace normally used for pyrites roasting. Only two shelves, in a high combustion chamber, are necessary. Sulfur distills from the hot ore on the shelves; the sulfur vapor limits contact of SO2 with the gangue. This sort of furnace gives good combustion of both rich ore (30 to 4070 sulfur) and average ore (20 to 25% sulfur). T h e combustion yield is very high: 97 to %yo’,. Akragas (a Montecatini subsidiary), in its plant at Porto Empedocle, uses a shelf combustion furnace of this type. T h e plant was built in 1956 and has a conventional contact unit to convert the SO2 to sulfuric acid. Also, in 1956, Sincat, a subsidiary of Edison, built a big plant at Priolo, using a fluidized bed furnace. Total capacity of the two plants is now 1000 tuns per day, all using Sicilian ore. Compared to the pyrites roasting, the ore roasting process costs less to operate, gives a vapor richer in SOz, and requires only a small gas purification system; however, because the heat of combustion is lower, it yields only 50 to 6070 of the steam and an ash of little value. T h e ash has found use as a paving material, since mixed with water and dried, it provides a durable material, but its price must be very low. But the fundamental factors influencing process economics are costs of ore extraction and ore transport from the mine to the plant. Transporting a 25% sulfur ore 60 km. (36 miles) adds about 3400 lire (about $5..50) per ton of sulfur to the costs. Obviously, transporting a richer ore will cost proportionately less, but the availability of richer ore is becoming smaller as mining continues. Further, enriching the ore at the mina head is not always possible or economic. Basically, there are two types of Sicilian ore. In one, crystalline sulfur appears on the gangue and, being more fragile, is selectively pulverized by grinding to give a rich fines fraction plus VOL. 5 4
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a barren main cut. In the other, the sulfur and gangue are intimately interdispersed according to a microstructure, and mechanical selection is not possible. By analogous reasoning, it is not always possible to enrich by flotation either. Despite such marginal considerations, the substantial fact remains that the direct use of ore to make sulfuric acid represents the least uneconomic system to resolve the Sicilian sulfur crisis. This crisis is now more critical than ever and has the interest of responsible private and public organs, the Regional Government, the National Government, and even the European Parliament. T h e legislative measures coming from the Regional and National Governments up to 1957 aimed at subsidizing the sulfur industry with either very low interest rates or written-off capital. This approach meant very large tax burdens on the governments but had one great advantage: T h e industry survived and its workers were employed. A New Course
I n 1959 the Regional Government, having received a report from a study commission of Italian experts from all interested sectors, determined a new course of action aimed at economic reorganization of the industry and putting the reorganized industry on its feet. T h e approaches are outlined in Regional Laws 13-3-59 No. 4 and 4-8-60 No. 32 as follows: -Reorganization to be attained in five years -Subsidies without interest, amortized over 10 years, to come from a rotating fund of 22,500 million lire ($36 million) supplied by the Mineral Credit Section of the Bank of Sicily -Social benefits for workers dismissed during the reorganization -Ccntribution of 2070 of the cost of plants built to put the industry on its feet, with emphasis on sulfuric acid plants -Contributions up to 4y0 on contracts for chemical plant construction for plants using the products of the sulfur industry -Special contributions for up to three years to chemical plants using either the ore or the ore concentrates -Miscellaneous benefits According to the law, the program may cost a tetal of 28,230 million lire ($45million). The governmental initiative, plus the activities of the large companies (Montecatini and Edison), has encouraged the mine grantees to embrace the program and revitalize thek operations. Thcy formed a conAUTHORS D r . Gerlando Marullo is General Manager of
Research at the G. Donegani Research Institute of the Montecatini Society in AVoLbara, Itaiy. He was born in Sicily and received a doctorate in industrial engineering from the Polytechnic Institute of M i l a n . D r . Francesco Traana is Head of the Cntalyst Research Dejiartment at /he same injtitute. He was barn in Sicily also, and rcceiz’ed a doctorate ir, chemistry at the Unirersify of Palemo. 22
INDUSTRIAL AND ENGINEERING
CHEMISTRY
sortium (“Consorzio Industrie Zolfifere”), wi?h public deed, to handle sulfur products not contracted to Ente Zolfi Italian0 (handles ore sales and exports), and created another company, between the consortium and the mines, to set u p the ne\\’ industrial plants. T h e consortium itself put up more than 90% of the capital. Through this combination, the consortium provides the company with an assured supply of the necessary raw materials, while the company provides the consortium with the profits of’ the chemical industry that will subsidize the mines activity. Next, the consortium presented to the Minister of Industry and Commerce and to the President of the Regional Government a detailed plan which foresees a total investment of 8 billion lire ($12.8 million) for these uses : --Construction of two contact sulfuric acid plants, one of 400 tons per day at Porto Empedocle, the other of 600 tons per day in the industrial zone of Catania. The two plants together will consume a little more than 500,000 tons of 257, sulfur ore -Prcviding 80% of the acid produced to the industrial complex already operating in Sicily, which has already agreed to take it -Construction in the industrial zone of Catania of a plant for ammonium sulfate with 100 tons-per-day capacity. The necessary 25 tons per day of ammonia will come from plants already existing in Sicily, in exchange for sulfuric acid Also, when the reorganization of the industry is complete, the cost of sulfur at the mine should not be higher than 13,000 lire per ton ($20.80). Moreover, ore transport costs will be held t u a minimum because the two acid plants (at Porto Empeclocle and Catania) were located at these places on the basis of minimum distance from the mines. ,411 this adds up to a new force in Sicily: T h e salvation of the sulfur industry, demanded by compelling socioeconomic reasons, is no longer dependent on sterile subsidies but on the vitality of technology aided by serious programs in which economic help acquires a ncrmal catalytic function. This is the spirit which animates the resolution by the European Common Market on March 2, 1960. Violating the basic goals of Treaty of Rome, the resolution isolates the Italian sulfur market for six to eight years, provided that Italy pledges to re-equilibrate the situation. It was also agreed that the program to put the industry o n its feet would be financed by the European Investment Bank. This recovery work started in the second half of 1962. T h e responsible Italian and European authorities intend with their intervention not to subvert the normal economic processes but to stimulate with adequate means the industrialization of a depressed area. The sulfur problem is destined to exhaust itself when most of the ore is used up, but the industrialization will remain. The Sicilian situation represents an example of general validity for other areas with similar necessities.
