physicochemical property
This substance consists of three elements: carbon, hydrogen and oxygen.
Colorless liquid, smells like chloroform. The molecular formula is C2-H-Cl3. The molecular weight is 13 1.39. The relative density is 1.4649(20/4℃). Melting point -73℃. The boiling point is 86.7℃. The flash point is 32.22℃ (closed cup). The autoignition point is 420℃. The steam density is 4.53. The vapor pressure is 13.33 kpa (100 mm Hg at 32℃). The flammable limit of the mixture of steam and air is 8.0% ~ 10.5%. Almost insoluble in water; Soluble with ethanol, ether and chloroform; Soluble in all kinds of volatile oils and volatile oils. When wet, hydrochloric acid is generated when exposed to light. High concentration steam will burn at high temperature. Decompose by heating, releasing toxic chloride. Heating to 250 ~ 600℃ and contacting with iron, copper, zinc and aluminum to generate phosgene. It can react violently with barium, nitrogen tetroxide, lithium, magnesium, liquid oxygen, ozone, potassium hydroxide, potassium nitrate, sodium, sodium hydroxide and titanium.
Main uses: used as solvent.
Health hazard: This product has stimulating and anesthetic effects. Patients with acute inhalation poisoning have symptoms such as upper respiratory tract irritation, tears and salivation. Then dizziness, headache, nausea, dyskinesia and symptoms similar to drunkenness appear. Dizziness, headache, lethargy, nausea, vomiting, abdominal pain, blurred vision, numbness of limbs, even excitement, convulsions and even coma can be fatal. Chronic effects: fatigue, dizziness, nausea and drunkenness. There may be liver damage. Repeated skin contact can cause dermatitis and eczema.
Explosion hazard: this product is flammable, toxic and irritating.
Hazard characteristics: generally, it will not burn, but it can still burn after being exposed to open fire and high temperature for a long time. Pyrolysis will produce toxic and corrosive smoke.
Correct understanding of dry cleaning solvent tetrachloroethylene
As a dry cleaning solvent, tetrachloroethylene has been successfully applied to dry cleaning for more than 60 years because of its remarkable characteristics such as low relative toxicity, good thermal stability, strong degreasing ability and recycling, and it is recognized as a good dry cleaning solvent in laundry industry. However, with the improvement of people's quality of life, people pay more and more attention to the impact and side effects of various daily necessities on the environment, so people naturally begin to pay attention to the low toxicity of tetrachloroethylene. At 1997 las Vegas washing Expo, oil dry cleaning machines and solvents (such as DF2000) became hot spots for a while. In the washing publications during the Expo, there is also a message that the Massachusetts government will ban tetrachloroethylene in 2002. This message arrived in China on 1998 one year later, so there was a strong wind of using petroleum solvents as "green laundry" in China, and tetrachloroethylene was strongly criticized. However, after several years of practice, this trend has gradually weakened and become more realistic in the United States and Western Europe. But in China, this trend has been blowing for a long time, even worse. Therefore, it is necessary to put tetrachloroethylene as a dry cleaning solvent on the agenda of research and discussion.
Second, the development of dry cleaning industry and the adoption of tetrachloroethylene
The so-called dry cleaning refers to a dry-in and dry-out washing method of washing clothes with chemical solvents to remove stains. Organic solvents such as tetrachloroethylene and petroleum solvents are usually used. At the same time, auxiliary additives (such as oil) rub, roll and wash the water-solvent dirt through mechanical force. As everyone in the industry knows, dry cleaning originated in Paris, France at the beginning of the19th century. There are two kinds of legends. One is that the lamp oil was accidentally spilled on the dirty tablecloth, and it was found that the stain on the dirty tablecloth was removed. Secondly, oil stains on clothes soaked in benzene (C6H6) have been eliminated. Therefore, the role of hydrocarbons in removing oil stains was discovered, and its cleaning ability was recognized. JOLLY—BELIN Paris began to use dry cleaning in the factory opened in 1840, which avoided the shrinkage and decoloration problems of traditional water washing. Dry cleaning began to use petroleum solvents.
Petroleum solvents, such as benzene, kerosene and gasoline, are flammable solvents, and the dry cleaning industry has become a dangerous industry. The most primitive dry cleaning method is to soak clothes by hand with gasoline solvent, brush them, wring them out to dry, and naturally volatilize, which not only wastes solvent, but also is unsafe.
1926, a kind of petroleum solvent "Stoddard" specially used for dry cleaning was trial-produced. The liquid in the machine was removed by dry cleaning machine, with little waste, but the flammable and explosive safety hazard was still serious.
In 1930s, developed countries also began to use trichloroethylene as a dry cleaning solvent. It is said that in 1960s, China also introduced a dry cleaning machine using this solvent. However, trichloroethylene has strong degreasing ability, which damages the physical and chemical properties of fiber, corrodes equipment and is highly toxic, and is also harmful to operators. During this period, carbon tetrachloride, trichlorotrifluoroethane, etc. It is also used for dry cleaning, but these solvents are not used any more because some are highly toxic, some are banned, and some are faded dyes.
Developed countries abroad began to use tetrachloroethylene in the 1940s, which overcame the shortcomings of trichloroethylene, and its performance was relatively stable. The KB value is relatively high, and its toxicity is relatively low compared with trichloroethylene. It is recognized by the laundry industry as a good dry cleaning solvent and has been used ever since.
Tetrachloroethylene (also known as perchloroethylene) is a colorless and transparent liquid, which is not easy to burn and has an odor similar to ether. Insoluble in water, soluble in ethanol, ether and benzene. In fact, it is related to hydrocarbons, that is, hydrocarbons. One of the preparation methods of tetrachloroethylene is the high-temperature chlorination of hydrocarbons, which is formed by chlorination and pyrolysis of hydrocarbons such as methane, ethane, propane and propylene at 50-500℃. Mainly used as solvent, dry cleaning agent, fire extinguishing agent, fuming agent, animal and vegetable oil extractant, etc. It is even used as a drug to repel human intestinal worms.
Since the advent of tetrachloroethylene, it has been used as the main cleaning agent for removing grease in machinery manufacturing industry for more than 70 years, and it has also been used safely in laundry industry for more than 60 years. As a chemical solvent, it has its advantages and disadvantages. It has strong degreasing ability and plays an extremely important role in machinery manufacturing and laundry industry, especially its distillability and safety and reliability. By the early 1960s, as a flammable petroleum solvent substitute, it developed rapidly in the laundry industry and was widely used in China.
At present, tetrachloroethylene solvent dry cleaning machine is still dominant in the world. According to the survey of equipment in American laundry industry conducted by International Fabric Maintenance Institute (IFI) in 1998, 932 of the 80 laundry factories surveyed1/kloc-0 used tetrachloroethylene, accounting for 79%; 12 1 family used petroleum solvents, accounting for10.2%; There are 16 companies using fluorocarbon solvents, accounting for1.4%; There are 1 companies that use tetrachloroethylene solvent, petroleum solvent or fluorocarbon solvent at the same time, accounting for 0. 1%. Among 1 180 laundry plants, * * has 1297 dry cleaners, of which 1042 is a tetrachloroethylene solvent dry cleaner, accounting for more than 80%.
Third, the low toxic and side effects of tetrachloroethylene can be controlled.
According to relevant data, tetrachloroethylene does have low toxic and side effects. When people inhale 96 ppm/7h, it will cause local anesthesia, conjunctivitis and hallucinations. When people inhale 280 ppm/2h, they will have conjunctivitis and general anesthesia. In the mouse experiment, according to the RTECS standard, 240g/kg/kg mice are carcinogens. Environmental data show that the olfactory threshold concentration of tetrachloroethylene in the air is 50PPM, which means that the concentration that people can smell by smell is 50PPM. Therefore, people will definitely feel uncomfortable working in a high-concentration air environment where they can smell tetrachloroethylene for a long time. Therefore, we advocate the use of fully enclosed environmental protection dry cleaning machines, rather than open dry cleaning machines. As long as restrictions are made in this respect, there will be no harm to the human body. The use of open dry cleaning machines has been banned in developed countries and China and Hongkong. According to the regulations of Hong Kong Environmental Protection Bureau, a fully enclosed tetrachloroethylene dry cleaning machine must be used, and the concentration of tetrachloroethylene in the drum should be reduced to below 300PPM before the drying process is completed and the door of the machine is opened. For dry cleaning machines that do not meet the standards, the deadline is 5-7 years, and the maximum fine is 6,543,800 yuan, and the daily fine is 20,000 yuan. Violation of the regulations prohibiting the sale of dry cleaning machines, the maximum fine is 6,543,800 yuan. The State Bureau of Technical Supervision of the People's Republic of China and the Ministry of Health 1996 issued the hygienic standard for tetrachloroethylene in the air of workplace. Namely: GBL 6204- 1996, which specifies the maximum allowable concentration of tetrachloroethylene in workplace air and its monitoring and inspection methods, and is applicable to all kinds of enterprises that produce and use tetrachloroethylene. The hygienic requirement of this standard is that the maximum allowable concentration of tetrachloroethylene in the air of workplace is 200 mg/m (27 ppm). Health supervision institutions at all levels are responsible for the implementation of this standard. According to this standard, there should be no smell of tetrachloroethylene in the workshop. The threshold value in occupational air recommended by the United States in 1982 is 335 mg/m (45.8 ppm), and the maximum allowable concentration in occupational air recommended by Germany in 198 1 is 345 mg/m (50 ppm). The maximum allowable concentration in the air of occupational environment is relatively late, and developed countries such as the United States, Germany and Italy have stipulated the environmental protection standard of tetrachloroethylene dry cleaning machine, that is, the working environment of dry cleaning machine is ≤25ppm and the simplified body is ≤300ppm. Although there is no environmental protection standard of tetrachloroethylene for dry cleaning machines in China, the hygienic standard of GBL 6204- 1996 is completely consistent with the international standard. Therefore, the workshop using tetrachloroethylene dry cleaning machine can reduce the toxic and side effects of tetrachloroethylene to zero as long as this standard is implemented.
It is unfair to determine that tetrachloroethylene is a carcinogen by drinking 240g per kilogram of mice, because the metabolism of rodents is completely different from that of humans. The conclusion of animal experiments should arouse people's attention to chemical solvents and take corresponding measures to prevent tragedies. Many chemicals are toxic, but they should not be discarded just because they are toxic. Even if excessive intake of tetrachloroethylene from the mouth can cause cancer, people will not drink tetrachloroethylene. The American Occupational Safety and Health Association (NIOSH) conducted a spot check on the health status of 600 laundry workers who have been engaged for many years, and there was no indication that cancer had increased. After 20 years of medical follow-up records of 2,600 workers in Lockheed Aircraft Factory, a machinery manufacturing industry, the statistical data did not clearly show the increase of special cancer spots. The incidence of leukemia, esophageal cancer, cervical cancer, paraluminol cancer and liver cancer is only close to or lower than expected. Most importantly, it was not found that workers exposed to tetrachloroethylene the most increased the risk of cancer. At the suggestion of the International Fabric Maintenance Association, the Environmental Protection Agency (FPA) of the United States deleted tetrachloroethylene from the list of carcinogens A and B when it revised the wooden furniture manufacturing regulations.
Document number [1997]733 of the State Economic and Trade Commission and the State Administration for Industry and Commerce points out: "Ozone layer destruction is one of the global environmental problems today. In order to protect the ozone layer, the international community formulated the Montreal Protocol on Substances that Deplete the Ozone Layer in 1987. China acceded to the amended Montreal Protocol on Substances that Deplete the Ozone Layer 199 1 in June. According to relevant regulations, China should add CFC (including CFC-11CFC-12cfc-113cfc-14) to 199. Production and consumption are frozen at the average level of 65,438+0,995-65,438+0,997. By 2065,438+00, CFCs and halons (including halons 65,438+0,265,438+0 and halons 65,438+0) will be consumed. In the introduction of the first chapter of the Overall ODS Elimination Plan for Clean Industry in China, it is clearly pointed out that "the clean industry plan includes the elimination of CFC- 1 13, 1, 1-trichloroethane and carbon tetrachloride". It is not difficult to see that the purpose of the Montreal Protocol and OMELCO and OMELCO documents is to destroy the atmospheric ozone layer. The substances that destroy the ozone layer listed in the document are CFC- 1 13, namely trichlorotrifluoroethane and carbon tetrachloride. Carbon tetrachloride as a dry cleaning solvent has long been stopped, and CFC- 1 13 has also been banned in developed countries, but this really banned dry cleaning machine with CFC- 1 13 as a solvent has sneaked into China in recent years. It will not destroy the atmospheric ozone layer, but tetrachloroethylene has become a scapegoat and has been condemned, because tetrachloroethylene is not included in the Montreal Protocol and OMELCO documents. During the period of 1998, the environmental protection bureau of an urban area in Beijing refused to go through the examination and approval procedures for a self-employed person. The reason is that, according to the documents of the Municipal Bureau and the two committees, in fact, the self-employed person used the "Di Mei" fully enclosed dry cleaning machine. To this end, the author visited the Atmospheric Group of the State Environmental Protection Administration, which issued the document. The person in charge told the author that this was a misunderstanding of the document because it did not contain tetrachloroethylene, and immediately called the Beijing Environmental Protection Bureau to correct the misunderstanding of the next bureau.
In addition, according to the revised national plan for the elimination of ozone-depleting substances in China, by the end of 2005, five industries in China will eliminate ozone-depleting substances, including household appliances, industrial and commercial refrigeration, compressors, automobile air conditioners and tobacco, and halons and cleaning industries will adopt the elimination strategy. Phase out halon 12 1 1, CFC-13 and carbon tetrachloride cleaning agents by the end of 2005, and phase out halon 130 1 and TCA (trichloroethane) by the end of 2009.
Verb (abbreviation of verb) Introduction of the fifth generation tetrachloroethylene dry cleaning machine
There are two main ways to solve the environmental problems in dry cleaning industry. First, seek to use non-toxic, pollution-free, effective, economical, practical, safe and reliable washing solvent. In recent ten years, the laundry industry and researchers all over the world have made a lot of efforts in this regard, but so far they have not found this ideal solvent. The liquid carbon dioxide solvent discovered in recent years has a slightly lower KB value than tetrachloroethylene (the KB value of tetrachloroethylene is 9 0, the KB value of carbon dioxide is 65, and the KB value of petroleum solvent is only 34), which is non-toxic, pollution-free, non-flammable and low in solvent cost, and is a good dry cleaning solvent. However, carbon dioxide can only remain liquid when it exceeds 60 atmospheres. In this way, the liquid carbon dioxide dry cleaning machine becomes a high-pressure container, and the manufacturing cost is quite high, so it is difficult to popularize in the market in a short time.
The second way to solve the environmental protection problem of dry cleaning is to improve the technical level and function of dry cleaning machine to meet the increasing environmental protection requirements. In this regard, the dry cleaning machine manufacturing industry has made considerable achievements. After decades of efforts, the dry cleaning machine has developed to the fifth generation, and the emergence of each generation of new models is related to environmental protection.
The first generation was an independent washing machine and dryer. Washing and drying are carried out in two machines respectively. Without gas recovery device, clothes are completely exposed to the atmosphere when they are taken out of the washing machine and put into the dryer, which seriously pollutes the environment. This kind of tetrachloroethylene dry-cleaning machine no longer exists, but 99.99% of the dry-cleaning machines for petroleum solvents currently used in China are this kind of split machine.
The second generation open dry-cleaning machine, which combines washing and drying, adopts water-cooling recovery system, but the exhaust valve is communicated with the atmosphere during cooling. Before cylinder opening, tetrachloroethylene waste gas is deodorized by inhaling fresh air, which still pollutes the environment and has low solvent recovery rate, but it has made progress compared with the first generation machine. At present, a considerable number of small and medium-sized dry cleaners in China still use this kind of dry cleaning machine, but it has been banned in developed countries.
The third generation closed dry cleaning machine adopts refrigeration recovery system. In the process of deodorization, the gas in the machine does not exchange with the gas in the workplace, and no gas is discharged, thus reducing the pollution to the environment. However, after completing a cycle, the exhaust port communicating with the atmosphere is opened to discharge the odor, and the discharged odor will still pollute the atmosphere.
On the basis of the third generation, the fourth generation closed dry cleaning machine adds a secondary recovery device-activated carbon filter at the exhaust port connected with the atmosphere to absorb the residual exhaust gas and further reduce pollution. At present, some large hotels, hotels and some large laundry enterprises in China use three or four generations of dry cleaning machines, which have been widely used in developed countries. The oil dry cleaning machines used in Europe and America are generally closed.
The fifth generation of activated carbon adsorption closed dry cleaning machine has activated carbon filtration, secondary recovery and automatic cleaning of distillation box. In the third and fourth generation closed dry cleaning machines, the minimum concentration of gaseous tetrachloroethylene in the drum is 1500-2000 ppm after the clothes are cooled and deodorized, while in the fifth generation machine, the concentration of gaseous tetrachloroethylene in the drum can be reduced to below 300PPM through the adsorption of carbon adsorption system. At this time, when you open the door to get clothes, the discharge of tetrachloroethylene can be minimized, reaching the international standard that the residual pollution in the cylinder is ≤300PPM and the surrounding environment is ≤. Some fifth-generation fully enclosed dry cleaning machines also have desorption function. When a certain amount of tetrachloroethylene is adsorbed, the internal activated carbon tends to be saturated. At this point, the desorption system can be started to regenerate activated carbon. And condensing the gaseous solvent into a liquid for recycling. The carbon adsorption system of the fifth generation dry cleaning machine was invented by Mr. HORST HAHN, the former president of MULTIMATIC Company in the United States. 1October, 1995, 165438 applied for a patent in the United States and obtained approval.
Ending of intransitive verbs
The laundry service industry in China, especially the dry cleaning service industry, can be said to be a sunrise industry, which started late and developed rapidly. At present, the competition in the whole industry is fierce, and the management of the industry is still chaotic. However, as a laundry service industry, it will continue to develop with the development of national economy, the improvement of people's living standards, the further socialization of housework and the change of people's consumption concept. The development direction of its store laundry service is the development of high-grade equipment, large-scale storefront and chain operation. The development direction of dry cleaning equipment should be the comprehensive development of environmental protection, energy saving, safety, washing effect and economic benefit. The tetrachloroethylene dry cleaning machine has not withdrawn from the historical stage. The fifth generation dry cleaning machine has been widely used in developed countries abroad. Through the carbon adsorption system, the secondary recovery is carried out in the machine, which makes the recovery of tetrachloroethylene more thorough and more conducive to environmental protection. Hydrocarbon solvent dry cleaning machine is developing to a fully enclosed machine integrating washing, drying, distillation and recovery of high flash point solvent. The liquid carbon dioxide dry cleaning machine needs to reduce the manufacturing cost to enter the market as soon as possible.
At present, tetrachloroethylene dry cleaning machine and hydrocarbon dry cleaning machine coexist at the same time, so it is necessary to strengthen industry management. Printing and dyeing industry associations and washing expert committees should assist relevant government departments to formulate regulations, emission standards and waste disposal regulations specifically for the use of dry cleaning machines. Before the introduction of new rules, regulations and standards, the applicability of existing standards in the washing and dyeing industry should be studied. For example, whether GBL 6024- 1996 Hygienic standard for tetrachloroethylene in workshop air is applicable to workshops using tetrachloroethylene dry cleaning machines, item 33 of GBL 6297- 1996 Comprehensive Emission Standard for Air Pollutants, and whether the specified standard for the maximum allowable emission concentration of total non-methane hydrocarbons can be used as a reference standard for workshops using hydrocarbon dry cleaning machines. How to restrict and update the continuous production and use of CFC- 1 13 dry cleaning equipment?
In a word, society is developing, technology is progressing and people's quality of life is improving. According to the thought of "Theory of Three Represents", high-grade products representing the development direction of advanced productive forces will inevitably replace backward products with backward technologies. Management, standards and regulations that are in line with the interests of consumers will certainly get the support and support of consumers. standard
Hygienic standard of workplace air: China MAC 30mg/m3；; The American TLV ACG ih-TWA is 269 mg/m3 (50 ppm ), STEL is 537 mg/m3 (100 ppm).