What is Chromium? Chromium slag, the production of industrial waste chromium metal and chromium salts generated in the process. It has certain harm to human beings. Chromium slag is an industrial waste produced during the production of metallic chromium and chromium salts. China currently has more than 20 provinces and cities emitting chromium slag. Chromium slag chemical composition components are: being 4 to 30% silica, aluminum trioxide slag accounts for 5 to 10% of calcium oxide accounts for 26 to 44% of magnesium oxide accounting for 8 to 36% ferric oxide accounted 2 to 11%, chromium oxide (Cr2O6) accounts for 0.6 to 0.8%, and sodium dichromate (Na2Cr2O7) accounts for about 1%. The main minerals contained in the chromium slag include periclase (MgO), calcium silicate (2CaO·SiO2), Brinellite (4CaO·Al2O3·Fe2O3), and 1 to 10% of residual chromite.
What are the main hazards of chromium slag?
In the absence of a reducing agent, the aqueous solution of sodium dichromate contains highly toxic hexavalent chromium ions.
The chromium slag is stacked in the open air and immersed in rain and snow. The hexavalent chromium contained in it is dissolved and infiltrated into the groundwater or into rivers and lakes, polluting the environment. The content of hexavalent chromium in water in a heavily polluted zone can be as high as tens of milligrams per liter, several times higher than the drinking water standard. Hexavalent chromium, chromium compounds, and chromium compound aerosols can harm human and animal health in many forms (see the health effects of chromium pollution). Therefore, the storage yard of the chromium slag must adopt the paving anti-seepage and the installation of a hood.
The way to prevent the damage of chromium slag is to carry out high temperature treatment to eliminate its toxicity. Hexavalent chromium can be reduced under acidic conditions with a reducing agent, or under alkaline conditions with alkali metal sulfides or hydrosulfides, or at high temperatures and anoxic conditions in the presence of sulfur, carbon and carbide. It is a less toxic trivalent chromium. The use of chromium slag mainly has the following aspects:
1 made of sintered brick: the chromium residue is dried and pulverized, and the mixture is mixed according to the ratio of 40% of chromium slag powder and 60% of clay to make a brick blank and fired in a kiln. In high temperature and strong reducing environment, hexavalent chromium is reduced to water-insoluble chromium oxide, eliminating highly toxic. Bricks can meet architectural requirements.
2 high-strength chrome-tanned bricks: Mix 5 parts of chromium slag and 3 parts of lanthanum carbonate residue with 40% water and wet- mill in a ball mill . The hexavalent chromium in the chromium slag becomes water-insoluble strontium chromate, and a part is converted into trivalent chromium. 3 parts by chromium, barium and 2 parts of coal slurry Slag, simmer after rolling and material, made of brick. Then, the temperature was raised, the temperature was kept constant, and the temperature was lowered for 2 hours, and steam curing was carried out at 8 atmospheres to prepare a chrome-tanned brick. The chromium slag contains more magnesium oxide, the volume will expand, it needs to be stored for a period of time, and the volume is stable and used.
3 chromium slag cast stone: 30% chromium slag, 25% silicate and 45% coal slag, and then mixed with 3 ~ 5% iron oxide, melt casting, crystal annealing, to obtain compressive strength of 4800 ~ 5500 Kilogram force/cm high strength, wear resistant, corrosion resistant cast stone.
4 cement: using chromium slag, limestone , clay and other raw materials according to ordinary Portland cement, can burn cement clinker, used to make cement. The chromium residue after carbon reduction is combined with blast furnace granulated slag, converter steel slag and Portland cement clinker, and about 5% of gypsum is added to make less clinker steel slag cement.
In addition, chromium slag can also replace chrome ore powder as an emerald coloring agent for glass. The water-quenched chromium residue can also be used as a cement mixed material, a mineral wool raw material, a heat-resistant cementing material, a molten cement raw material, and the like. In Japan, in the chromium residue after detoxification, a reducing agent such as ferrous sulfate or ferrous oxide is added to prepare a plastically solidified material or a gypsum board filler.
Chromium slag is toxic and difficult to transport, and its use has not yet opened.
Historical chromium slag pollution incident
Chromium pollution incidents are not uncommon worldwide, especially in the 1970s, when there were serious chromium pollution incidents in Japan and the United States. Occurred in 1993 in California after the chromium pollution case caused a sensation onto the silver screen, the title is "Erin Brockovich." The film tells a female lawyer who accidentally discovered that the largest hydroelectric gas company in the United States illegally emits toxic sewage containing hexavalent chromium. She believes that this is probably the root cause of the deadly disease of the local residents. She is an unimaginable willpower for the local residents. Won a huge amount of compensation of 333 million US dollars. In fact, the plot in the movie is not far from us. Just around our city, the “ownerless†chromium slag heap left behind by some companies has been quietly hidden for decades.
Along the Zhengxi high-speed railway Gongyi section, you don't have to go too far to reach the Wogou, Beisi Village, Huiguo Town, Gongyi City. There is a huge “fortress†with a volume of 31,647 cubic meters. Looking up from the side of the "fortress", the dam that is made of hard stone is 10 meters high.
The villagers near Huiguo Town, especially in Beiluo and Qingxi, know that this “fortressâ€, which is only 3 kilometers away from the Yiluo River, stores more than 50,000 tons of chromium slag. Since 1990, the "Chromium Slag Fortress" has existed here for 20 years.
The chromium slag heap was not originally here. It has been piled up in a local chemical factory in the open air. It was relocated in 1990 due to repeated mass dissatisfaction.
On October 12, 2010, Wu Jiwei, director of the disposal department of Gongyi City Environmental Protection Bureau and director of the Center for Dangerous Waste Radiation, said: The chromium slag piled up in Guozhen Town is the former Guo County of Gong County, which was called “the second generation†by the locals. Chromium waste generated in the production process of the chemical plant.
"Elderly" was founded in April 1976 and mainly produces chromic anhydride. "The business was very prosperous in the past, it was the backbone of Guozhen and even the entire Gongyi City, a large tax source."
However, the process of producing chromic anhydride produces a large amount of chromium residue. “At that time, the awareness of environmental protection was weak, and the hazard of chromium slag was insufficient. It was piled up without treatment and the groundwater in the villages of Beiluo and Qingxi was polluted. When the rainy season came, the leaching liquid of chromium slag entered the Yiluo River with rainwater. And the surface water is seriously polluted..."
In the early years, the vegetables and food grown by the farmers in Guo Town were not eaten by themselves, but they were sold to other places. Sometimes the land is almost empty, the fish in the water is difficult to live, and some of the inexplicable diseases of the surrounding villagers are hard to find. The villagers blamed it on the chromium slag pollution, and the factory disputes continued.
In 1990, the “secondaryization†was under pressure, and a chromium slag dump was built on 6 mu of land in the Beigou Village of Beisi Village in the south of Guozhen Town. Although the bottom of the dumping site was hardened, a slag dam was built and covered with a 50 cm thick limestone cushion, but the new chromium slag continuously produced by the plant was still threatening the surrounding environment.
In 1992, "the second child" was forced to shut down. The chromium slag is sealed from the pits. According to a survey conducted by the Provincial Environmental Protection Agency, there are five chromium slag piles in Huiguo Town, which are hidden in Sifangfang Township, Anyang County, Xinfeng Town, Fengquan District, Kaifeng Longting District, Sanmenxia. Yima City and Daxie Town, Xinmi City, Zhengzhou.
The six chromium slag piles totaled 520,000 tons, of which the smallest was in Xinxiang, 28,400 tons, the largest in Yima City, 325,000 tons, and Yima's chromium slag accounted for 67% of the province.
Poison treatment
["These pollutants are difficult to remove once they enter the water or soil, and may affect generations."]
What is chromium slag? What harm is there?
Shao Feng, director of the Solid Waste Management Center of the Henan Provincial Environmental Protection Agency, told reporters that chromium is a silver-white hard metal that is slightly lighter than iron and has trivalent and hexavalent compounds. Chromium-containing compounds are toxic, with hexavalent chromium being the most toxic. Chromium slag is an industrial waste generated in the process of producing metal chromium and chromium salts, and is a highly hazardous hazardous waste.
Due to the specific needs of the production process, as long as the chromium is not converted into a product that is fixed and becomes insoluble, the chromium becomes ionic chromium, which dissolves in water and quickly becomes highly toxic hexavalent chromium.
“If the soil and water are rich in hexavalent chromium, it is easily absorbed by the organism. If the chromium residue left over from history is not effectively disposed, it is a serious safety hazard for the entire ecosystem.†Shao Feng said.
On October 18, the relevant personnel of the Henan Provincial Occupational Disease Prevention and Treatment Institute introduced that chromium poisoning refers to the content of chromium in the blood and urine of the human body exceeding the normal standard. Workers engaged in chemical and electroplating work are prone to chrome poisoning, and hexavalent chromium is easily absorbed by the body and accumulates in the body.
A doctor working on toxicity studies said that industrial exposure to chromium and its compounds is mainly the dust and fumes of chrome ore and chromium smelting. Clinically, chromium and its compounds mainly invade the skin and respiratory tract, and dermatitis, ulcers, rhinitis, perforation of the nasal septum, and pharyngitis occur. Long-term exposure is also very harmful to the digestive system, gastrointestinal ulcers may occur, and taste and smell may decrease or even disappear. "But clinically, there is no specific treatment for acute and chronic chromium poisoning. It is usually treated with metal poisoning. Chromium has carcinogenic effects. The site of chromium carcinogenesis is mainly lung, followed by liver and kidney."
A researcher at the Occupational Health and Poison Control Institute of the Chinese Center for Disease Control and Prevention said that hexavalent chromium is mainly chronic poisoning, and it mainly accumulates in the liver, kidney and endocrine glands after invading the human body through the digestive tract, respiratory tract, skin and mucous membranes. After humans and animals drink water containing hexavalent chromium, hexavalent chromium is absorbed by cells in many tissues and organs in the body. The human lethal dose is 5 grams. But at the same time, the researcher also said: Chromium is also a necessary trace element in the human body, and the normal range of daily intake of chromium is 0.05 micrograms. Myopia and diabetes in the eye are associated with a lack of chromium.
According to data from the Ministry of Environmental Protection, the main heavy metal pollution in surface water in China is mercury , followed by cadmium , chromium and lead . At present, China's cultivated land contaminated by heavy metals such as cadmium, arsenic , chromium and lead is nearly 20 million hectares, accounting for about one-fifth of the total cultivated land. The country produces more than 10 million tons of grain per year due to heavy metal pollution.
Zhao Qiguo, an academician of the Chinese Academy of Sciences who has been dealing with the soil for a lifetime, said: "The metallurgical and chemical industries have been infiltrated into the soil for many years. Some chemical substances have infiltrated into the soil, and some even exist for 30 years. These pollutions still exist. Once the matter enters the water or the soil, it is difficult to remove, which may affect generations. After the chemicals in the soil enter the food chain, they are still eaten by humans themselves."
During the interview, the reporter learned that in 2005, the State Council issued a notice to the whole country requesting that all historically stored chromium slag should be disposed of harmlessly at the end of the “Eleventh Five-Year Planâ€, that is, the end of this year is the time limit for disposal.
Anti-seepage facilities [extra-extension phenomenon still exists under continuous repair]
So, why are these “drug castles†that threaten people’s safety for decades? Since the 1950s, more than 70 sodium dichromate chemical companies have been built in the country, also known as chromium salt enterprises. Sodium is the parent product of the chromium salt series products. It has a wide range of uses, and the company has good benefits but serious pollution.
Han Chongting, the director of the security department of Yima Zhenxing Chemical Group Co., Ltd., is a Kaifeng person who has worked in the chromium salt industry for nearly 30 years. He blamed the formation of chromium slag heaps on technical processes. However, the demand for chromium-containing products is high. “Stainless steel faucets, soup spoons, chrome handlebars and steel rings on bicycles, jewellery, tapes, straps and even coins contain chromium. Ordinary metals can be rust-proof after chrome plating. The low-cost metal is durable and beautiful after being covered with a thin chrome coat.
Chromium salt enterprises mainly extract metal chromium and chromium compounds from chromite ore, and a large amount of chromium residue is produced in the production process. According to the data, due to the backward production process, the extraction rate of chromium salt is only 75%, and 2.5 to even 3 tons of highly toxic chromium residue per ton of chromium salt produced. Most of these chromium slags are piled up around the plant site, and only a few are protected by damming and sealing. In the 1980s and 1990s, the international community generally recognized the hazards of chromium slag. The Chinese government began to pay attention to the control of chromium slag pollution, comprehensively rectified the chromium salt industry, and gradually shut down and transferred more than 40 chromium salt enterprises.
The company closed, but left a lot of "no master" chromium slag heap. More than 6 million tons of chromium slag have been left in more than 20 cities including Shanghai, Tianjin, Suzhou, Jinzhou, Baotou, Wuhan, Qingdao, Hangzhou, Shenyang, Jiangmen, Changsha, Guangzhou, Shaoguan and Zhengzhou. Due to technical and financial constraints, there was no ability to detoxify these chromium slags in the past, thus forming a slag "fortress".
On the 20th of October, the highly toxic substance produced by the chromium slag in contact with water, the reporter saw a larger "chrome slag fortress" in Lianggou, 4 kilometers away from the city of Yima, and the volume was enough to cover Guo. Four times as many as Zhenwogou, the sporadic chromium slag scattered under the dam has a yellowish eye under the drizzle of the day, and there is a striking danger sign on the outer wall.
Zhang Weidong, head of pollution control at Yima Environmental Protection Bureau, said that hundreds of thousands of tons of chromium slag has been sealed for 26 years and is the "heritage" after the booming of Yima Zhenxing Chemical Factory.
According to a source from the Ministry of Environmental Protection, companies producing chromium slag were built in densely populated areas, scenic areas, and water sources. For the chromium slag piles produced, only some enterprises have anti-leakage facilities, and most of them are simply stacked. After being continuously washed by rain, the hexavalent chromium in the chromium slag is transferred into the nearby surface water or infiltrated into the groundwater, causing serious pollution to surface water, groundwater and soil.
The chromium slag piles in Anyang Huaxian County, Xinxiang Fengquan District and Kaifeng Longting District did not have any protective measures from beginning to end. The landfill of Wulibao Village, Datun Town, Xinmi City is located in the slag yard of the low-lying tunnel opposite the Wulibao Chemical General Plant in Zhengzhou. The 3,000-square-meter chromium slag yard has no protective facilities on the ground floor and the surface is It is completely covered by construction waste and domestic garbage of nearby businesses and residents. On October 12, Wu Jiwei, director of the Center for Dangerous and Waste Radiation of the Environmental Protection Bureau of Gongyi City, sent a message: “Even if the 50,000 tons of chromium slag (returned to Guozhen) is all harmlessly disposed, the ecological water system and soil in this area will be restored. In the past, I am afraid I have to be 40 years..."
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