Chromium is one of modern industry's most essential and versatile elements. In addition, it is one of the most important strategic and critical minerals. Of the many minerals that contain chromium, chromite is the only ore of commerce. It has a wide range of usage in three types of industries, namely the metallurgical, chemical and refractory. Chromium's use in iron, steel and nonferrous alloys enhance hardness and resistance to corrosion and oxidation. The use of chromium to produce stainless steels and nonferrous alloys are two of its more important applications. Other applications are in alloy steel, plating of metals, pigments, leather processing, catalysts, and refractories.
II. Product Description
Chromium is a steel-gray metal similar to platinum on luster. Some chemical constant of chromium include atomic number, 24; atomic weight, 51.996; density, 7.19 grams per cubic centimeter; melting point, 1,857 degrees Celsius (plus or minus 20 degree Celsius); and boiling point, 2,672 degrees Celsius.
Chromium metal in its purest form (99.96% chromium) is produced in limited quantities by vapor deposition from anhydrous chromium iodide. Commercial chromium metal is produced either by electrolysis of a chromium-containing electrolyte or by aluminothermic reduction of pure chromic oxide.
For most metallurgical applications, chromium is primarily used as additive in the form of alloys with iron and carbon as ferrochromium, or silicon as ferrochromium-silicon. Charge chromium is essentially a high-carbon ferrochromium with high silicon content. Chromium alloys, as well as chromium metal, are made in a number of commercial grades.
The mineral chromite consists of varying percentages of chromium, iron aluminum, and magnesium oxides. Historically, chromite has been classified into general grades associated with end use: metallurgical, chemical and refractory. During the past decade, technological advances have allowed considerable interchangeability among the various grades, particularly chemical grade, which can be used in all three industries.
Chromite ore and concentrates derived from chromite ore are further classified into three categories. These are ore and concentrate containing not more than 40% Cr2O3 (refractory industry), containing more than 40% Cr2O3 but less than 46% Cr2O3 (refractory, chemical and metallurgical industry), and 46% or more Cr2O3 (metallurgical and chemical industries).
III. Mining and Processing Method
Both surface and underground methods were used to mine chromite. It undergoes hand sorting, washing and screening, or gravity concentration. Concentrates are prepared from fines or crushed lower grade ore using such concentrating equipment as jigs, tables, spirals, or magnetic separators. Although flotation separation has been used, gravity separation methods predominate.
In the metallurgical industry, chromite is converted to chromium alloys or chromium additives by pyrometallurgical techniques. Chromite, fluxes, and reducing agents are smelted in a three-phase submerged electric arc furnace. By adjusting charge mixes and process variables, various types of ferrochromium products such as chromium metals are produced.
Either electrochemical or pyrometallurgical process produces chromium metals. The electrochemical process involves deposition of chromium metal by the electrolycic of a purified chromium alum solution prepared by a complex process that begins with dissolution of ferrochromium in sulfuric acid. The pyrometallurgical process is an aluminothermic reduction, which involves the reduction of pure chromic oxide by finely divided aluminum metal.
The chemical industry treats chromite by a hydrometallurgical process involving roasting ground chromite mixed with soda ash and lime followed by leaching with a weak chromate liquor or water. After neutralization with sulfuric acid to convert chromate to dichromate, the pregnant solution is filtered to remove alumina hydrate. The filtrate is further treated with sulfuric acid and concentrated by evaporation prior to removal of by-product sodium sulfate. The final purified sodium dichromate solution is marketed directly or as crystals after a crystallization step.
Chromite in the refractory industry is either purchased to size specifications or is size reduced in conventional crushing equipment, and the crushed product is screened into various particle size ranges. Specific quantities of variously sized particles together with magnesite are blended prior to pressing into refractory shapes to meet application requirements. These refractory shapes may be bonded chemically (unburned), burned, or fusion cast.
IV. Uses and Benefits
Chromium is seldom used alone. It is the supreme additive, endowing alloys or materials with economical new properties - strength, hardenability, permanence, hygiene, color and resistance to temperature, wear and corrosion. This versatility has established chromium in countless everyday applications.
Primary commercial supply is as chromite ore or as ferrochromium - the small requirement for metallic chromium is derived through secondary chemical routes. The primary supply feeds the ferrous and non-ferrous metals industries, the chemical industry and the refractories industry, which has an associated direct application of ore as conductive foundry moulding sand.
A. Metallurgical Uses
The major use of chromium is in the rapidly growing production of stainless steels. They accounted for almost the total increase in chromium demand through the 1980's.
Chromium is the unique ingredient responsible for the remarkable corrosion and oxidation resistance of stainless steels. They normally contain between 10 to 30 percent chromium. Other elements, such as molybdenum and nickel, may be added to stainless steels to further enhance particular properties, but there is no substitute for essential chromium. Heat resisting steels are classified as a minor group of the stainless steels in which the same essential function of chromium is applied.
Fundamental forces in society are driving the increasing desirability of stainless steels - their provision for health and hygiene, safety, optimum working life, appearance and their contribution to equipment, structures and services to improve and maintain the environment and our lifestyle. Chromium's ready availability, high recyclability and energy efficiency result in cost-effective satisfaction of society's needs through stainless steels. Steel performance is enhanced with the incremental cost of adding chromium.
Chromium additions in low alloy steels contribute towards a range of improved properties, but especially hardenability - an ability to achieve a balance between hardness and toughness in engineering steels. Bearing steel tools, high speed steels and high-strength-low-alloy (HSLA) steels are specific sub-sectors that use chromium.
Alloy cast irons are a particular portion of the cast product uses for chromium which are applied in pumps, valves, pipes, rolls and wear plates to achieve hardness with toughness, dimensional stability and resistance to corrosion, abrasion, impact and wear.
In nickel alloys, cobalt alloys, electrical resistance alloys and superalloys, chromium is almost invariably an essential addition to assist in performance at high temperatures and under extremely corrosive conditions.
Small additions of chromium are made for important reasons to several aluminum, copper and titanium alloys.
B. Refractory Uses
The high melting point of chromium ore has encouraged its use in refractory compositions for more than 100 years. It is applied in various refractory bricks and mortars, ramming and gunning mixes and castables. Most compositions are blends of magnesia - chromite. These are used in the steel industry for lining AOD vessels, in the copper industry for lining coal-fired reverberatory furnaces and converters, and in the cement industry for lining the burning zones of rotary kilns. Changing technology in pyrometallurgical production has led to substitution due to more stringent performance requirements from refractories, and some elimination in favor of water-cooled roofs and side-walls. The rate of decline has only been slowed by the introduction of specialized, reconstituted, fused-grain magnesia-chromite refractories.
Highly specialized chrome oxide refractories derived from chemical production are used in glassmaking furnaces.
Chromite foundry moulding sands are used because of their increased heat conductivity, which alloys utilized, or the general chilling of castings to improve their integrity.
C. Chemical Uses
Chemical applications are served by the production of bulk chemical, normally sodium dichromate, from chromite ore following a kiln roasting process with soda ash. Derivative chemicals are then produced from the bulk chemical.
Chromium chemicals offer two distinctive features that govern several main applications, namely; permanence and color stability. Natural materials such as leather, wool and timber are stabilized for durability and long service by chromium salts, which also allow permanent fixing of other compounds (mordant behavior) such as colorful dyes, fungicides and insecticides. Leather tanning is the largest chemical use and timber preservation with the well known CCA product has been the fastest growing in recent years.
Chromium pigments, which are used in paints, inks and plastics coloring, are the second largest use. Feature colors are chrome green, chrome oxide green, chrome yellow. Zinc and strontium chromates are used in corrosion resistant priming paints.
Other uses include chromium metal production, chromium electroplating, other surface coatings, and catalysts, drilling muds, water treatment, textile dyes and refractories.
Chromium is introduced into irons, steels and many super alloys, through alloying additions with the intermediate product - ferrochromium. This is produced by the pyrometallurgical reduction of chromite ore with carbon and/or silicon in high temperature electric arc furnaces. Ferrochromium is essentially an alloy of iron and surface coatings, catalysts, drilling muds, water treatment, textile dyes and refractories. A common method of production is to melt carbon steel and stainless scrap in an electric arc furnace, to which controlled quantities of other ingredients including ferrochromium are added. Some further refining is undertaken in a second vessel where high temperature gas and/or vacuum technology is applied. The liquid stainless steel is cast into ingots, billets, or slabs for hot and cold working. A host of convertors, fabricators and manufacturers transform these mill products to meet the functional needs of society for chromium in stainless steels.
V. World Market Situation
A. World Production of Chromium
Chromite ore is considered abundant and geographically widely distributed. Deposits are mostly concentrated in South Africa and Russia. Both countries more or less generated about 55% of the total production of chromium ores and concentrates from 1983-1992, with annual average outputs of 56.2 million tonnes and 33 million tonnes, respectively. This period saw the general rise in the world production. In 1987, 1990, 1992, 1993 and 1996, production slumped by some 1.6%, 8.8%, 19.8%, 15.2 and 16.4%, respectively.
In terms of regional turnout in 1996, Africa remained to be the world's number one producer that accounted for five million tonnes, a 53% of the world's total chromium production. South Africa as the major market producer of chromite posted a 46% share in the total production of Africa, followed by Zimbabwe, 6% and Madagascar, 1%.
Incidentally, South Africa's chrome industry is situated operationally in only two areas - the Northwest and Eastern Transvaal. But developments in the other two, PMV and Kwazulu/Natal ore, are expected to have a great impact in the country's industry taking into consideration the strategic location of the port area and transport facilities that lie in these area.
Most deposits are largely located in the South African region specifically in South Africa, Madagascar and Zimbabwe. Other reserve quantities are found in Kazakhstan, India, Finland, Brazil and countries in an alpine belt stretching from Albania through Greece, Turkey to Iran and Pakistan.
Active mining operations are well dispersed. South Africa and Kazakhstan each provide the largest supply of chromite for the world's total needs. Albania, Turkey, India, Zimbabwe, Finland, Brazil, the Philippines and other small countries collectively provide the rest.
VI. Philippine Chromite Industry
The discovery of chromite (FeO.Cr2O3) in the Philippines dates back to the early American occupation. Warren D. Smith, Chief of the Division of Mines, Bureau of Science from 1907-1914, recorded the discovery of chromium in three localities: Ilocos Norte; Ambil Island, Mindoro; and the province of Antique, Panay Island. He also reported chromium among the elements found in the laterites of Surigao, Mindanao Island. Later investigation of these laterite deposits revealed the presence of chromite in the laterite ore as well as in unaltered serpentine bedrock, occurring as grains, small masses, and lenticular bodies.
No new chromite discovery was made until 1922, when a prospector submitted to the Bureau of Science a chromite sample which was reported to be of little commercial value. In 1925, during a geological reconnaissance survey of the Zambales Range by the Bureau of Science, the largest Philippine chromite deposit was discovered along Lawis River, 24 km east of Masinloc, Zambales Province. The deposit was originally estimated at 10 to 15 million tons. The grade ranges from 30 to 37 percent CR2O3.
Chromite mining, however, did not start until 1934. The first shipment of ore was made a year later from Floraine Mines, a few kilometers northwest of Lagonoy, Camarines Sur.
Consolidated Mines inc. and Benguet Consolidated Inc. started to produce refractory chromite (>20% Al2O3.) from Masinloc, Zambales in 1938. Acoje Mining in Sta. Cruz, Zambales started shipment of metallurgical grade chromite (>46% Cr2O3; at 3:1 Cr to Fe ratio) also in 1938.
New chromite localities were reported in 1938. The Dinagat Chromite mines and the Tagobomar Development Company developed their respective properties in Dinagat Island, Surigao. The Mindanao Prospecting Association (Misamis Chromite) worked a property in Manticao; the Luzon Stevedoring Company developed a mine in Opol Misamis Oriental.
During World War II, the Japanese occupational forces exploited some 25 chromite lenses in Acoje Mine, Zambales, producing 80 to 120 tons per day. In 1944, around 70,000 MT of 48% chromite ore were shipped to Japan.
In 1942, chromite production was only 50,000 MT, or 1/6 of the prewar peak of 300,000 metric tons. The following year, production rose to 60,000 MT; in 1944 it was 70,000 metric tons.
The high post-war demand and consumption of chromite for industrial and civilian requirements, such as construction, railroad building, automobile industry, and the entire reconversion program and aid toward the rebuilding of war devastated countries, elevated chromite production to peace-time levels.
B. Ore Reserve
Chromite deposits in the Philippines are classified into two major groups: primary podiform deposits and residual/transported deposits. The first group includes these chromite bodies formed by primary igneous processes, such as, residual weathering and concentration by mechanical weathering and transport with alluvial or beach and sand placer deposits as examples.
Based on plots of chemical data of chromite ore samples mainly from Zambales and Palawan, and on the distinct association of their ultramafic-mafic host rocks, primary podiform chromite deposits are further subdivided into two types: refractory chromite and metallurgical chromite deposits. Philippine podiform chromite ores show a general bimodal variation between aluminum-rich refractory chromite and the chromium-rich metallurgical chromite (Bacuta, 1978; Evans and Hawkins, 1980). The Coto Mine of Benguet Corp. at Masinloc, Zambales is an example of a refractory type chromite deposit; the Acoje Mine operated by the Herdis Group at Sta. Cruz, Zambales, is representative of the metallurgical type.
Most chromite deposits in the Philippines occur at or near the surface where bulldozers and power shovels are employed to strip the overburden to mine the ore. Smaller companies use pick and shovel with low expenditures for explosives. This surface mining method is designed to keep initial or operating cost at a minimum. Big operations resort to bench mining (Consolidated Mines, Inc.) in addition to other surface activities. As the ore bodies go deeper, underground mining method is employed, including top-slicing and square setting. Otherwise, open pit method is employed.
For peculiar occurrence of chromite in the topsoil, either in sandy form or in coarser aggregates (Acoje Mining Co.) sluicing of sandy ore is done especially during rainy season. Most chromite deposits occur in periodite complexes of Zambales and Palawan.
During the first six years (1984-1989) under review, Philippine chromite reserves declined from 32.94 million metric tonnes in 1984 to 31.72 million metric tonnes in 1989. It registered an average negative growth rate of 0.42 percent. This is because the planned exploration/operation of several major projects were shelved in the eighties. Also, the negative growth can be attributed to high electricity and financing costs and inadequate infrastructure.
The early 90's posted growth rates, with 1992 registering the highest at 15.6%. In terms of volume, 1996 posted 45.68 million metric tons.
For the regional reserves, Region III posted the highest at 15.79 million MT, followed by Region X at 15.27 million MT.
C. Local Production
Chromite production in the Philippines can be traced back as early as 1935. Chromite deposits of various concentrations occur in periodite outcrops in the Philippines, an archipelagic group of islands in the southwestern margin of Circum-Pacific. Chromite is one of the ores whose production continued during the Japanese occupation. After the war, it experienced strong but erratic growth reaching a peak of 850,000 metric tonnes in 1955. However, during the latter years, production declined considerably to around 200,000 MT annually.
Chrome is classified into three types depending on the usage and market specifications: (1) metallurgical chromite, (2) chemical grade and (3) refractory chromite.
Historically, 85% of the country's chromite has been derived from the refractory ores of Zambales, which now contribute around 55.26% of total production. The four leading chromite producers for 1997 were Masinloc Chromite Operation (BC), Heritage Resources, Krominco Mining Corporation and Acoje Mining Corporation.
In terms of production, metallurgical chromite concentrate registered an average negative growth of 18.8% from 1983-1990. The decline during the eighties can be attributed to the failure of major chromite producers and some small-scale miners to produce. Likewise, during the nineties from 1990 to 1998, a positive average growth rate of 130.5% was registered
The metallurgical chromite concentrate on the other hand posted a positive average growth rate of 58.8% from 1983 to 1990 and a negative average growth of 13.6% from 1990 to 1998. The decline in the nineties can be attributed to the slow down in the production of Krominco Corporation located at Surigao del Norte, as the sole producer. The highest production increment of 95% was noted in 1996.
Refractory ore total production and production value posted negative growth rate in 1998 at 63.6% and 46.9% respectively. Masinloc Chromite Operation (BC) is the sole producer of refractory ore.
C. Local Price Situation
The price of chromite depends on the variations in its grade and presence of deleterious elements. Generally, however, prices are based on the world price quotations of chromite produced by Russia, South Africa, and Turkey.
Significant price increases of refractory ore, metallurgical ore, and metallurgical concentrates are due to increase in demand especially from the stainless steel industry.
The short and medium-term price projections fro chromite ore are strongly influenced by speculative and political aspects, though price increases will be influenced more by the rising cost of production. Producers will have to increase chromite prices to keep their operqtions profitable.
Export prices of Philippine chromite may increase following the trend of world prices, especially those countries supplying the United States.
The highest price for metallurgical chromite concentrate was registered in 1998 at P3,243 per DMT and lowest at P1,987 in 1991.
For metallurgical chromite ore the highest price was posted in 1997 at P2,704 per DMT and for refractory ore, in 1998 at P5,311 per DMT.
Local production of refractory chromite ore is mostly exported annually. The country's major markets in 1997 were Korea, Brazil, Japan and Canada. The movement of export earnings during these years (1983-1997) can be best described as erratic. Moreover, records showed that from 1989-1997 foreign receipts continued to go down from $10.62 million in 1989 to as low as $4.24 million in 1997, or a 60.1% decline. Export earnings for 1998 registered at $11.13 million or an increase of 162.8% from 1997.
The country's traditional export markets for both metallurgical chromite concentrate and metallurgical chromite ore were Japan. Inchrome and People's Republic of China (PROC). In 1997, Inchrome was the premier importer of metallurgical chromite concentrate, contributing as much as 49.5% of the country's total export receipts. No exports were recorded for 1998. China (PROC), on the other hand, was the sole importer of metallurgical chromite ore in 1998 at $6.262 million.
Among the three types of chromite, only the chemical grade ore followed the upbeat mood as exports both in quantity and value increased albeit gradually.
Source : 2000 Report, Mineral Economics Information and Publications Division - Mines and Geosciences Bureau.
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