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By R G. Reddy, A Yahya

The sulfur distribution ratio (Ls) is an expression of the amount of sulfur in slag to the amount of sulfur in molten metal. The sulfide capacities calculated from Reddy-Blander (RB) model were used to calculate the sulfur distribution ratio (Ls). A new Reddy model for sulfur distribution ratio (Ls) was developed for modelling Ls for ironmaking, steelmaking, and secondary steelmaking conditions. Besides calcium oxide, the major component in the ladle furnace (LF) slags is alumina. The Ls was calculated for typical LF slags as a function of temperature and composition. The model calculated Ls values are in good agreement with the experimental and industrial slags data. The extremely low oxygen potential in these furnaces after fully-killed steel is favourable for desulfurisation. For any given slag’s composition and temperature, its sulfide capacity can be calculated a priori. The equilibrium sulfur distribution ratio between this slag and liquid metal in a particular vessel can also be calculated a priori. The Ls for ladle furnace (LF) slags is about twice those for blast furnaces (BF) slags and ten times those of basic oxygen furnace (BOF) slags. The desulfurisation of pig iron in BF and desulfurisation of steel in LF during secondary steelmaking are recommended. Steel desulfurisation in steelmaking furnaces is not effective. Since the model used to calculate the sulfur distribution ratio (Ls) is a priori, it is a useful tool for the iron and steel makers in improving the product quality and optimisation of the industrial furnace operations.

Aug 21, 2024

By N. A. Warner

Fundamental studies on the reaction of limestone or dolomite at high temperature with S02 are extended to the realm of large scale primary copper smelting. Whereas flue gas desulfurisation in the electric power utility industry is concerned with S02 concentrations normally less than 0.5 percent, high temperature smelting gases can have S02 levels approaching 100 percent. The reaction involved is very exothermic so proposals are made in this paper for returning the heat generated in sulfur fixation directly back to the copper smelting process. This integration leads to metal production with lower energy requirements than current technology. The anhydrite reaction product can either be disposed of locally with minimum adverse environmental impact or upgraded to a value-added product. It is assumed, of course, that no viable market exists to support sulfuric acid production.

Jan 1, 1996

By Geo Ashley

THE following paper is intended to be suggestive only, and to open the way for discussion and further observation. Its preparation was requested only two days before the time limit set for the submission of the papers comprising this symposium. Thus no time existed for detailed studies so it is largely a memorandum of such facts as have come incidentally to the notice of the writer in the study of coal in the field. The field study of sulfur in coal has received very little special attention or description from coal students. The presence of sulfur concretions is noted in hundreds of descriptions, and certain benches of a coal bed may be described as "sulfury" or the presence and position of sulfur bands may be noted in coal sections in connection with sampling. It may be accepted that some sulfur is present in all coal. The amount varies greatly in different regions, in different beds, and in the same bed in different areas. The anthracite of Rhode Island comes the nearest of any coal known to the writer of being free from sulfur, several analyses of that coal showing less than 0.1 per cent. Subbituminous coals in Colorado in a few places have close to 0.2 per cent. of sulfur on the dry-coal basis and in other states subbituminous coals approach this lower limit. Bituminous coals seldom run under 0.4 per cent. of sulfur on the dry basis, though in a few places dry bituminous coals in Colorado and Washington have between 0.3 and 0.4 per cent. The better known bituminous coals have almost everywhere over 0.4 per cent. The best of the Pocahontas and New River coals run close to 0.4 per cent., but there is very little commercial coal in Pennsylvania, Ohio, Indiana, Illinois, Kentucky, or the other states that runs under 0.5 per cent. on the dry basis. From these minimum figures, the amount will range up to 5 or 6 per cent. or higher if visible sulfur is not excluded. It must be remembered that the usual -analysis of a coal bed is not intended to give the total proportion of sulfur in the bed but the amount in the coal after the removal of the more obvious and larger sulfur masses.

Jan 9, 1919

By D. Silva-Galvan, R. D. Morales, S. Gonzáelez-López, A. Romero-Serrano, G. Plascencia-Barrera, F. Chavez-Alcala

This work is focussed on lead decopperising by two techniques: conventional top addition of sulfur and injection of sulfur powder. It is found that the first method proceeds under equilibrium conditions and the second one depends on kinetic considerations. Experiments were carried out using 15 kg lead baths at two temperatures, 340°C and 380°C. The carrying gas used for the injection trials was nitrogen at flow rates of 6.3 and 18.6 L min- 1• The results show that 'decopperising process is more efficient at temperatures close to the melting point of lead for the sulfur top addition process, whereas high temperatures produce better copper removal for the injection of sulfur powder. Besides, the sulfur injection with the higher nitrogen flow rate (18.6 L min-1) produced higher decopperising rates. Thermodynamic and kinetic models are used to simulate this lead refining process.

Jan 1, 2000

By S Karosiya, A Sharma, M Jain, N N. Viswanathan, M M. Pande, D Kumar, S Kumar

Desulfurisation of steel during ladle refining is governed by both thermodynamics and kinetics. For effective desulfurisation, thermodynamically, a low partial pressure of oxygen at the steel-slag interface and highly basic slag which possess a large sulfide capacity are desired. Kinetically, the mass transfer coefficient of sulfur in the liquid steel and in the slag determines the rate of desulfurisation. A fast desulfurisation rate is achieved by maintaining sufficiently strong argon stirring of the melt. In the present work, sulfur mass balance for steel and slag was performed after the desulfurisation treatment for several industrial heats. The decrease in the sulfur quantity of the liquid steel was more than the increase in the sulfur quantity of the slag. The discrepancy in the sulfur mass balance suggests that the sulfur could be transferred to: (a) the gas (via slag) phase; or to (b) the refractory (crucible) phase. The preliminary investigation of the refractory samples taken at slag-refractory and steel-refractory interface showed no interaction of sulfur with the refractory. Therefore, the possibility of sulfur transfer to the gas phase was verified by carrying out melting experiments of sulfur containing slag in an argon/air atmosphere. Sulfur containing slag was initially melted in an MgO-C crucible under an argon atmosphere followed by creating the air atmosphere just above the melt. Careful sampling and analysis from the cold spots of the crucible, much above the melt surface, revealed formation of a fibrous structure. Scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS) analysis of these fibrous deposits confirmed the presence of oxides and sulfides. Oxidation of sulfur containing slag under air atmosphere was also performed using a thermogravimetric analysis (TGA) set-up. It showed a constant sulfur loss in the range of 1300– 1500°C. Thermodynamic calculations carried out using FactSage™ ver 8.3 for these experimental conditions are in good agreement with the observed results.

Aug 21, 2024

By David B. George

Kennecott recently completed an $880 million modernization and expansion of its smelter and refinery to process all concentrates from the Bingham Canyon mine. This is the first application of Kennecott-Outokumpu Flash Converting. Molten material movement by overhead cranes is eliminated and high levels of oxygen enrichment result in very low process gas volumes and exceptionally control of sulfur oxide emissions. All existing in-plant hygiene, safety, and environmental regulations will be met and the smelter is positioned for anticipated more stringent future regulations. Sulfur capture is 99.9 percent resulting in sulfur dioxide emissions less than the 112 kg/hr Air Permit limit, making the smelter the cleanest in the world.

Jan 1, 1996

By R. B. Anderson

SULFUR poisoning of iron catalysts in the Fischer-Tropsch synthesis was investigated at the Bureau of Mines, because synthesis gas produced from coal contains sulfur compounds. Tests of two typical iron catalysts with synthesis gas containing known concentrations of H2S were made to determine catalyst life as a function of sulfur concentration to ascertain the type of gas purification required. Fixed beds of activated steel turnings and a fused iron oxide catalyst were investigated in sulfur poisoning tests at 21.4 atmospheres with IH2+100 gas containing 6.9, 23, or 69 mg S as H2S per cubic meter (0.3, 1.0, and 3.0 gr per 100 cu. ft.). In tests of reduced catalysts at constant temperatures, more than 80 percent of the activity was lost when 0.5 mg S/g Fe was introduced. Poisoning of nitrided or carbided fused iron oxide catalysts to a given extent required more than twice as much sulfur than for the corresponding reduced catalyst. When the synthesis temperature was increased to compensate for loss in activity, tests of the fused iron oxide catalysts at constant productivity could be continued for 19 to 98 days. The tests were terminated by clogging of the reactor, presumably caused by carbon deposition. One objective of the present work was to determine if synthesis gas, purified by the Bureau of Mines' hot-potassium carbonate process for removing H2S, OOS, and CO2, is suitable for synthesis on iron catalysts. The sulfur content of the gas purified by tills process is in the range of concentrations used in the present work. In constant-productivity tests of nitrided fused iron oxide catalysts with synthesis gas containing 6.9 mg S/m3, catalyst lives are nearly long enough for serious consideration of tills mode of operation. However, factors relating to selectivity and stability of the catalyst indicate that this type of operation is impractical for a commercial process. On this basis additional gas purification, such as iron oxide boxes following a hot potassium carbonate scrubber, is desirable.

Jan 1, 1965

By Albert W. Deurbrouck

The coal reserves in the United States are estimated to be in excess of 300 billion recoverable tons, and current projections of energy requirements indicate our increased dependence upon these reserves. The Department of Energy's Energy Outlook for 1984 projects that coal consumption in the United States will increase from 737 million tons in 1983 to 958 million tons in 1990, and then to 1,110 million tons in 1995 (Table 1). As shown in this table, the future utilization of coal in the United States is closely tied to the electric utility market, a market that consumes about 85% of the coal produced. Be- cause of this dependence on the utility market, the uncertainties of new environmental regulations, particularly those concerning sulfur emissions, could have a significant adverse impact on future coal demands in the United States. SULFUR IN U.S. COALS Most of the Nation's coal reserves contain too much sulfur to be fired directly and meet existing emission control standards. In Table 2, the sulfur contents of the coals of the eastern United States are summarized by sulfur levels according to regions. While the coals of some of the eastern regions are predominantly high in sulfur content, it is important to recognize that large tonnages of coal with relatively lower sulfur content are available in these regions. Furthermore, an often significant portion of the sulfur occurs in the form of iron sulfide (Fes2 or pyrite). Because pyrite occurs as discrete particles of high specific gravity, it can often be removed by simple, inexpensive physical coal beneficiation techniques after being liberated by stage crushing. The potential for physical removal of pyrite by conventional specific gravity processes combined with stage crushing is summarized in Table 3 on a regional basis.

Jan 1, 1986

By A. F. Baker, E. R. Palowitch, A. W. Deurbrouck

As air-pollution regulations become increasingly more stringent, increased significance is being placed on the amount of sulfur present in coals used for steam generation. These regulations are aimed at minimizing the pollution of the atmosphere with noxious gases such as the sulfur oxides that are formed and emitted when coal is burned. Two meet these future requirements, a definite need exists to reduce the sulfur content of some of the coals used for steam generation. Reducing pyritic sulfur involves liberating the pyrite from the coal and then removing it. The specific gravity of pyrite is high (5.0) compared to that of coal (about 1.2, mineral-free), and standard coal-washing devices, such as wet concentrating tables, will efficiently remove pyrite particles larger than about 100 mesh. Particles below this size will be entrained in the table water and will be carried into the clean coal product. Techniques such as froth flotation are of little benefit for pyrite reduction because the flotation characteristics of pyrite are similar to those of coal.

Jan 6, 1966

By Hengwei Yan, Zhanwei Liu, Wenhui Ma, Ping Xiong

The sulfur in high-sulfur bauxite not only pollutes the environment but also harms alumina production. This study investigated the removal of sulfur from high-sulfur bauxite by adding Zn or ZnO during the Bayer process. The results showed that the different valence sulfur (S2−, S2O3 2−, SO3 2−, and SO4 2−) in sodium aluminate solution can be effectively removed by adding Zn during the digestion process. Adding ZnO removes the S2− in liquor, but the other sulfur compounds (S2O3 2−, SO3 2−, and SO4 2−) are not affected. The mechanism of sulfur removal has been elucidated, where the S2O3 2−, SO3 2−, and SO4 2− are first reduced to S2−, and after adding Zn, the S2− enters into red mud in the form of ZnS. The ZnO then reacts with S2− to generate the ZnS that enters into red mud. Thus, this is a new and effective method of sulfur removal by adding Zn during the digestion process. The results shed light on the removal of sulfur from high-sulfur bauxite during alumina production.

Jun 24, 2020

By Gregory R. Wessel

Sulfur is a nonmetallic element widely distributed in nature and of great physical and economic importance. It is the 14th most abundant element in the Earth's crust (0.06%) and an important constituent of animal and plant life. Sulfur has been known and used since ancient times for a number of medicinal and industrial uses. At present, most sulfur is used to generate sulfuric acid that is used in a wide variety of industrial processes, particularly the production of fertilizer. Because of this, sulfuric acid (and hence sulfur) consumption is often regarded as a good index of a nation's industrial development. In the past, sulfur was mined from surface occurrences in several geologic environments, and was used in relatively small amounts. With time, the uses of sulfur and sulfuric acid expanded, as has the need for larger quantities of these commodities. Sulfur is now mined from both surface and underground deposits, and is recovered as a byproduct from a number of industrial processes. Despite valiant efforts and years of work by sulfur explorationists and others, many aspects of sulfur mineralization remain controversial. Almost as controversial is the spelling of the word sulfur. The English spelling sulphur commonly is used outside America and in the American sulfur mining industry, but sulfur is the correct American spelling as approved by the American Chemical Society, the American Geological Institute, and many others. Those new to the American sulfur industry often find it puzzling to be reprimanded for using the correct American spelling. Sulfur resources are abundant and widespread, but the extent to which they can be classified as reserves is constrained by pre- vailing prices and extraction technologies. At present, sulfur can be economically mined from very few deposits. The sulfur industry is roughly divisible into two sectors: voluntary (or discretionary) and involuntary (or nondiscretionary). In voluntary production, the mining of sulfur or pyrites is the sole objective, and the recovery of the resource is as complete as economic conditions will allow. During involuntary production, sulfur or sulfuric acid (termed recovered sulfur) are produced as byproducts, and the quantity of the output is dictated by the demand for the primary product. Voluntary sulfur now accounts for only about 35% of the elemental sulfur produced worldwide, and most inves- tigators believe that voluntary sulfur will be less important in the future. Sulfur sources and products are described as follows (after Barker, 1983): Sulfur Sources: Combined sulfur-sulfur that occurs in nature combined with other elements, commonly referring to sulfides and sulfates. Cupriferous pyrites-pyrite containing minor amounts of cop- per sulfides. Hydrogen sulfide-a toxic gas that occurs in petroleum and natural gas. Involuntary sulfur-sulfur produced as a byproduct in response to legislative or process mandates. Native sulfur-naturally occurring elemental sulfur. Nonferrous metal sulfides-opper, lead, zinc, nickel, and molybdenum sulfides that are processed for their metal content. Organic sulfur complex organic sulfur compounds that occur in petroleum, coal, oil shale, and tar sands. Pyrites-iron sulfide minerals that include pyrite, marcasite, and pyrrhotite. Sulfate sulfur-sulfur contained in anhydrite and gypsum. Voluntary sulfur-sulfur produced in response to market demand. Basic Sulfur Products: Acid sludge-contaminated sulfuric acid usually returned to acid plants for reconstitution. Brimstone-synonymous with crude sulfur. Bright sulfur-crude sulfur free of discoloring impurities and bright yellow in color. Broken sulfur-solid crude sulfur crushed to -8 in. Byproduct sulfuric acid-sulfuric acid produced as a byproduct of a metallurgical or industrial process, generally relating to combined sulfur sources. Crude sulfur-commercial nomenclature for elemental sulfur. Dark sulfur-crude sulfur discolored by minor quantities of hydrocarbons, ranging up to 0.3% carbon content. Elemental sulfur-processed sulfur in the elemental form produced from native sulfur or combined sulfur sources, generally with a minimum sulfur content of 99.5%. Formed sulfur-elemental sulfur cast or pressed into particular shapes to enhance handling and to suppress dust generation and moisture retention. Frasch sulfur-elemental sulfur produced from native sulfur sources by the Frasch mining process. Liquid sulfur-synonymous with molten sulfur. Liquid sulfur dioxide-purified sulfur dioxide compressed to the liquid phase. Molten sulfur-crude sulfur in the molten state. Prilled sulfur-solid crude sulfur in the form of pellets produced by cooling molten sulfur in air or water. Recovered sulfur-elemental sulfur produced from combined sulfur sources (including byproduct hydrogen sulfide, but sometimes referring only to sulfur from fossil fuels) by any method. Slated sulfur-solid crude sulfur in the form of slate-like lumps, produced by allowing molten sulfur to solidify on a moving belt. Specialty sulfur-prepared or refined grades of elemental sulfur that include amorphous, colloidal, flowers, precipitated, wettable, flour, and paste sulfur. Sulfur ore-unprocessed ore containing native sulfur.

Jan 1, 1994

By N. Duru, C. Nesbitt

During the cyanide leaching process, gold and silver ores that come from the transition zones, which typically contains low levels of sulfide, may produce one or more of the following reduced sulfur species: sulfide ( HS−), polysulfides ( Sn 2−), thiocyanate ( SCN−), thiosulfate ( S2O3 2−), trithionate ( S3O6 2−), tetrathionate ( S4O6 2−), pentathionate ( S5O6 2−), hexathionate ( S6O6 2−). The actual speciation of the reduced sulfur species in the circuits will primarily depend on the redox potential, pH, cyanide levels, and existing sulfur species in recycled process water, as well as the presence of other reactive metal species. The development of an accurate analytical method for sulfur species in cyanide leaching units of gold ores where sulfur speciation occurs has an important role in explaining the metal recovery deviations. This study presents the speciation of sulfur species and the development of ion chromatography method to analyze reduced sulfur species thiocyanate ( SCN−), thiosulfate ( S2O3 2−), trithionate ( S3O6 2−), tetrathionate ( S4O6 2−) in cyanide leaching circuits for gold ores. The method developed has resulted in precise quantification of target sulfur species in leach solutions. Method development and validation results were illustrated on analytical graphs containing each species’ peak number, retention time (min), type, width (min), area (mAU*s), height (mAU), and area distribution (%) of the peak.

Mar 2, 2024

By C. Nesbit, N. Duru

During the cyanide leaching process of gold and silver, ores that come from the transition zones which typically con-tains low levels of sulfide may produce one or more of the following reduced sulfur species: sulfide (HS ), polysulfides (Sn ), thiocyanate (SCN ), thiosulfate (S2O3 ), trithionate (S3O6 ), tetrathionate (S4O6 ), pentathionate (S5O6 ) and hexathionate (S6O6 ). The actual speciation of the reduced sulfur species in the circuits will primarily depend on the re-dox potential, pH, cyanide levels and existing sulfur species in recycled process water, as well as the presence of other reac-tive metal species. Development of an accurate analytical method for sul-fur species in cyanide leaching units of gold ores where sul-fur speciation occurs has an important role in explaining the metal recovery deviations. This study presents the speciation of sulfur species and development of an ion chromatography method to analyze the reduced sulfur species thiocyanate, thio-sulfate, trithionate and tetrathionate in cyanide leaching circuits for gold ores. The method developed has resulted in the precise quantification of target sulfur species in leach solutions.

Jun 1, 2024

By S Juras

To our geologists at Eldorado Gold Corporation, the release of the gold assays on a new ore zone causes a flurry of excitement. But to our metallurgists, that news is often greeted with the question ‘What’s the sulfur grade’? In our company, we operate and manage projects whose end-product will either be auriferous sulfide flotation concentrate or gold doré. Almost all of the steps in the ore processing are related to sulfur (in this paper specifically sulfide sulfur). So why do we geologists wait until late in a project or into production before collecting sulfur data for mine planning and ore control purposes?Gold deposits associated with sulfides commonly use a metallurgical process that begins with a flotation step to recover gold into a smaller mass known as flotation concentrate. Often, this step solely targets the sulfide minerals with gold only coming along for the ‘ride’. As a result, the gold grade in the concentrate is primarily influenced by the ratio of gold to sulfur in the feed. Should this concentrate require a refractory process downstream (eg pressure oxidation), knowing sulfur grade is critical as sulfur controls heat balance in the process. Regardless, we need sulfur models to be as robust as gold models, and created much earlier in the project evaluation process.Sulfur models require quality data collected at the same density as gold samples. Analytical methods must match expected grade ranges and quality assurance quality control (QA/QC) protocols and must be of the same integrity as in use for gold. Sulfur models will then be created by their own data analyses, interpolation protocols and validation. Furthermore, ore control systems should be designed for regular sulfur monitoring to ensure and enhance downstream value. Given time it should become habitual for geologists to likewise ask, ‘And what’s the sulfur grade’, or more specifically, ‘What’s the gold to sulfur ratio’?CITATION:Juras, S, 2017. Sulfur – the new geometallurgical grade in gold-sulfide deposits, in Proceedings Tenth International Mining Geology Conference 2017, pp 199–202 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 20, 2017

By D. D. Harbuck

The U.S. Bureau of Mines investigated germanium and gallium extraction from an ore containing 0.089% Ge and 0.036% Ga. While previous researchers concluded that a reducing agent such as 502 is needed to extract germanium and gallium from such ore, this research showed that high extractions (87% Ge, 97% Ga) were possible using sulfuric acid alone, if the acid concentration were properly controlled. This control was achieved using a two-stage counter-current leach circuit. Microprobe analyses revealed that the non-extracted germanium is in solid solution with quartz, and therefore cannot be leached with 502 or sulfuric acid.

Jan 1, 1991

By A. Kontopoulos

The extraction of nickel and cobalt from low-grade greek laterites by sulfuric acid leaching has been studied. Batch and continuous mini-plant atmospheric leaching as well as pressure leaching techniques were employed. Atmospheric leaching at temperatures as high as 95 OC generally resulted in low Ni extractions (up to 82%), high acid consumption (650-850 kg/t ore or 80-100 kg/kg Ni) and high Fe co-dissolution (30%). Pressure leaching at 260 OC increased Ni extraction to over 98%, with minimal Fe co-dissolution (2.5%); acid consumption was 300 kg/t ore (31 kg/kg Ni). Detailed experimental results and conceptual flow sheets for atmospheric and pressure leaching are presented.

Jan 1, 1991

By R. H. Rubisov

Sulphuric acid pressure leaching of nickeliferous laterites has attracted considerable attention from the nickel industry during the past five years. The process is especially advantageous for limonitic laterites that mostly contain goethite, because iron precipitates releasing acid and thus rendering low acid consumption. It is also applicable to mixtures of limonites and saprolites, although at higher acid consumption due to magnesium. Effective process design requires the solubility of metals that precipitate during the process to be known. In the present work, determination of metal solubilities is based on a simple speciation program that assumes the presence of only one dominant complex for each metal. The thermodynamic data for the precipitation reactions are extracted from high-temperature experiments with monometallic systems published previously. The validity of the approach is then tested against mixed bimetallic systems, and finally applied to calculate the solubility of aluminium, iron and magnesium in laterite leaching effluents "at temperature". In both cases of limonitic feed and limoniticfsaprolitic blends, the prediction closely follows metal solubilities measured experimentally at temperatures from 230 to 270°C and at terminal he acidities ranging from 10 to 75 g/L.

Jan 1, 1999

By B. C. Haydon

Manganese silver ores are well known to be refractory towards cyanidation. Various processes have been suggested for improving the amenability of these ores. A sulfurous acid pre-leach is one such process. This paper traces the development and implementation of the sulfurous acid pre-leach process for the retreatment of manganese silver tailings at Tonopah, Nevada. An account of the test work program is presented, followed by a description of the operating plant and specimen metallurgical performance. The paper also summarizes the history of the Tonopah tailings, their mineralogy and makes reference to previous application of the sulfurous acid pre-leach process.

Jan 1, 1984

By Brad Gunn

Our program has been dictated by the necessity of broadening our markets through converting potash chemicals to fertilizers more in demand than potassium chloride. To this end, we have undertaken studies on methods of preparing potassium sulphate or potassium magnesium sulphate by rather simple conversion. When mixtures of sodium and magnesium sulphates are reacted with potassium chloride, the ratio of sodium to magnesium is quite pertinent. A range of ratios has been selected and the conversions of potassium chloride to sulphate have been assessed by cyclic operations. Results from experimental procedures for producing potassium nitrate are also avail-able. The influence on recovery for systems including organic solvents is assessed for a variety of situations.

Jan 1, 1971

By C. F. Johnson

Nearly all of the sulphur produced in the world today is converted to sulphuric acid and 49 % is used in the manufacture of fertilizers. In the last few years we have seen the beginning of another chapter in the volatile history of sulphur as the severe shortage of 1963:-67 has been transformed into present-day surplus. Prospects for further aggravation of this situation in the years ahead seem assured. In 1970, western world production showed a rate of increase of 4 -5%, which 1S somewhat less than that of 8% for the period 1963-1967. The rate of growth of consumption dropped considerably in 1968 when the demands of the fertilizer industry fell. During the same period of time, wide-spread demands have been set in motion for a clean environment which indicates that a fundamental change in sulphur supply, demand, and even sources, is likely to result from this upheaval. The sale of sulphur by Poland to the western world has increased and for 1970 was estimated at over one million metric tons. In the next few years, increase in Canadian sulphur supply will stern from two sources;

Jan 1, 1972