The production of toluene diisocyanate (TDI) equipment involves phosgene synthesis and phosgenation reactions, and there are many dangerous and harmful factors. Through the risk assessment and labor safety and hygiene pre-evaluation of new TDI devices in China, the dangerous and harmful factors that may exist in the production process of TDI devices are identified, and corresponding safety control measures are proposed.
Toluene diisocyanate (TDI) is one of the main raw materials for polyurethane plastics. Polyurethane is an important synthetic material and has a wide range of applications. The production capacity of existing TDI devices in China is far from meeting market demand, and more and more TDI devices are being built and expanded. However, due to the phosgene and phosgenation products in the production of TDI, most of the raw materials, intermediate products, by-products and products processed in the production process are highly toxic, flammable and explosive. It is therefore important to ensure the safe production of TDI devices.
China has always attached importance to the safe production of phosgene and phosgenation products. Since the Bhopal accident in India, the state has strengthened safety precautions against phosgene production and formulated the Safety Regulations for the Production of Phosgene and Gaseous Products (GB19041). -2003), "General rules for the safety evaluation of production equipment for phosgene and phosgenation products" GB13548-92 and other standard standards.
1 TDI device technology <br> Take a domestic TDI device as an example, briefly introduce the process technology of using the Swedish International Chemical Company (CEAB).
(1) Production of m-toluenediamine (MTD) Under a certain temperature and pressure, dinitrotoluene (DNT) is continuously hydrogenated to form toluenediamine (TDA) in the presence of a palladium metal slurry catalyst. The reaction mixture sequentially removes the catalyst, hydrogenated water, and o-toluenediamine (OTD) and other impurities to produce the m-toluenediamine (MTD) required for TDI production.
(2) Production of TDI The apparatus includes carbon monoxide preparation, phosgene synthesis, reaction of dioxytoluene with phosgene to produce TDI, and alkali destruction of phosgene tail gas.
a) Carbon monoxide production mainly includes natural gas compression, natural gas desulfurization and conversion, pressure swing adsorption purification of CO, hydrogen production feed gas compression, pressure swing adsorption purification of hydrogen, hydrogen purification and deoxidation.
b) Phosgene synthesis uses dry chlorine and carbon monoxide in a certain ratio to react in the presence of a catalyst to form phosgene. The phosgene synthesizers are all shell-and-tube fixed bed reactors, and activated carbon is used as a catalyst in the shell. The mixed gas undergoes a synthesis reaction in the fixed bed layer, and the reaction heat is released, and the reaction heat is removed by the shell-side cooling water or the heat-conducting oil.
c) TDI is produced by phosgenation reaction of MTD and phosgene (o-dichlorobenzene (ODCB) as solvent). TDI production includes main processes such as solution drying, phosgenation, degassing, HCI stripping, phosgene recovery, first deODC, decoking, second deODC, TDI refining and venting systems. The tail gas of the phosgenation reaction is absorbed by the cold solvent to separate the phosgene and HCI, and the phosgene absorbed by the cold solvent can be recycled, and HCI is used as a by-product. A small amount of phosgene that is not absorbed by the solvent enters the phosgene tail gas alkali destruction tower, and after being decomposed, the atmosphere is discharged at a high altitude.
2 Analysis of major hazard and harmful factors in the production process The dangers and hazards of TDI devices are mainly poisoning, fire, explosion, high temperature burning, mechanical damage, electric shock, falling from high places, noise hazard, dust hazard and so on. Due to space limitations, this article only analyzes poisoning, fire and explosion.
(1) Poisoning a) The toxic and harmful substances in the MTD device mainly include dinitrotoluene, toluenediamine, and catalyst. Direct contact should be avoided during the production process.
b) The toxic and harmful substances in the TDI device are mainly carbon monoxide, chlorine, phosgene, toluene diamine, o-dichlorobenzene, sodium hydroxide solution, toluene diisocyanate (TDI) and the like. There have been too many phosgene leaks at home and abroad to cause fatal accidents. In the event of leakage of phosgene, chlorine, and carbon monoxide, it can lead to the occurrence of human poisoning and casualties. The causes of these accidents are mainly due to the high moisture content of chlorine gas and the high moisture content of CO, which cause corrosion of equipment and pipelines. The equipment materials are improperly selected, the monitoring and control system is out of control, the sealing of dynamic sealing equipment is not strict or the operation is wrong, and the maintenance is not timely. Water supply system accidents and cooling system failures. Liquid phosgene intermediate tanks are a potential hazard and should have comprehensive protective measures, drainage systems and accident blowout tanks.
(2) Fire and explosion hazard a) According to the characteristics of the process equipment and the characteristics of the raw materials, the fire hazard of hydrogen and dinitrotoluene in the MTD device is Class A. Therefore, the biggest risk factor in the production process is the explosion hazard caused by collision or impact of dinitrotoluene during the batching process. Another dangerous substance is hydrogen. The explosion limit of hydrogen in air is 4.1%-74.1% (V), and the ignition temperature is about 450 °C. Therefore, the abnormal operation of hydrogen compression and the failure of the cooling water circulation system may cause potential dangers of fire and explosion.
b) The fire hazard of carbon monoxide in the TDI device is Class B. The explosion limit in air is 12.5%~~74.2%(V). In the carbon monoxide gas production process, once the carbon monoxide leaks, there may be a fire or explosion in the event of fire. accident.
c) If there is NCl 3 enrichment in the liquid chlorine tank, it may cause an explosion hazard.
Due to the long process flow and many equipments, the device has many pumps for conveying materials. The structure and material of the equipment are different due to different material properties. It is necessary to prevent the production system from being mistaken due to improper design selection and the out of control of the power supply and water supply system. Loss of control, operational errors, and accidents in the power supply and water supply system of any monitoring system can lead to fire and explosion accidents.
3 Safety Control Measures and Suggestions <br> According to the above analysis, the main dangers in the production process of TDI are poisoning, fire, explosion hazard and so on. The following are only the main measures and recommendations to prevent poisoning:
(1) The safety protection distance between the site selection, phosgene and phosgenation production facilities and surrounding residents, factories and public facilities must meet the requirements of the “Safety Regulations for the Production of Phosgene and Phosphorus Productsâ€.
(2) According to the process requirements, the main production equipment must ensure the safety of the production equipment and the concentration of harmful substances in the workplace, regardless of whether the open or semi-open building (structure) or closed structure (structure) is used. Safety and hygiene standards. The enclosed building (structure) adopts forced exhaust; the open or semi-open structure (structure) adopts a hose type local exhaust system.
(3) Using advanced technology, the design of phosgene system should follow the principle of intrinsic safety, minimize the storage and retention of phosgene in the system; optimize pipeline configuration and reduce the length of connection of phosgene pipelines. As far as possible, the relatively safe gaseous phosgene method is used for the phosgenation reaction process, and the phosgene production amount is determined at the rate required for downstream production. The phosgene is not liquefied and no other buffering equipment is provided. When the phosgenation, phosgene recovery or accidental spray system fails, the safety interlock system automatically stops the feeding of chlorine and CO.
(4) Equipment should be designed to ensure high airtightness.
(5) All pressure vessels containing phosgene materials shall be designed, manufactured and accepted in accordance with the requirements of Class III pressure vessels.
(6) The phosgene and phosgenation unit is provided with an isolation operation room. The control room of the device should be designed with concentrated positive pressure ventilation. The ventilation air must be kept free of pollution. The air suction port is designed with filter with activated carbon or other adsorbent as the filter medium.
(7) In an emergency, the system can realize automatic segmentation isolation and drainage to achieve system pressure relief in a short period of time, and the discharged gas directly enters the emergency decomposition system.
(8) Exhaust gas treatment facilities, hose ventilation facilities and emergency accident damage systems in emergency situations shall be provided. The lye circulation system of the emergency accident destruction system shall maintain uninterrupted operation, and the exhaust gas shall be discharged into the atmosphere after being decomposed by alkali washing.
(9) For materials with high toxicity such as phosgene, spare storage tanks of corresponding capacity and accident storage tanks with sufficient capacity shall be designed; the production system shall not store or minimize the storage of harmful and dangerous materials.
(10) Power supply with dual loops.
(11) Set up a flammable and toxic gas alarm system, and set up a detector in a workplace where chlorine, phosgene, carbon monoxide and other gases may escape, and the controller is located in the control room.
(12) In the dangerous areas such as phosgene synthesis, phosgenation reaction and tail gas treatment, it is necessary to make obvious marks, and set wind vane and wind direction monitors at high places that are easy to see, so as to facilitate the accidents of workers and other personnel in the event of poison leakage. Identify the wind direction and dispose of it correctly.
(13) Set up a gas protection station with a complete gas protection facility to be responsible for gas protection. Establish an ambulance organization, equipped with professional medical personnel, and regularly train operators on toxic substance poisoning and first-aid common sense. All production positions should be equipped with commonly used emergency medicines.
(14) In addition to protective glasses, gloves, protective shoes, overalls and other general protective equipment, phosgene or phosgenation production workshops should also be equipped with air breathing apparatus, operators equipped with gas masks, equipped with flushing spray facilities and first aid in production positions. box.
(15) Operators engaged in TDI production must be assessed and hired, and trained carefully. After passing the examination, they will be certified.
(16) Warning signs shall be provided in dangerous areas and key positions to indicate the risk factors and important precautions. The identification of equipment, conveying pipes and valve switches for storing toxic materials such as phosgene and flammable and explosive materials should be clear.
(17) According to the “Significant Hazard Source Identification†GB18218 standard, if it is a major source of danger, it must strengthen the management of major hazards.
Toluene diisocyanate (TDI) is one of the main raw materials for polyurethane plastics. Polyurethane is an important synthetic material and has a wide range of applications. The production capacity of existing TDI devices in China is far from meeting market demand, and more and more TDI devices are being built and expanded. However, due to the phosgene and phosgenation products in the production of TDI, most of the raw materials, intermediate products, by-products and products processed in the production process are highly toxic, flammable and explosive. It is therefore important to ensure the safe production of TDI devices.
China has always attached importance to the safe production of phosgene and phosgenation products. Since the Bhopal accident in India, the state has strengthened safety precautions against phosgene production and formulated the Safety Regulations for the Production of Phosgene and Gaseous Products (GB19041). -2003), "General rules for the safety evaluation of production equipment for phosgene and phosgenation products" GB13548-92 and other standard standards.
1 TDI device technology <br> Take a domestic TDI device as an example, briefly introduce the process technology of using the Swedish International Chemical Company (CEAB).
(1) Production of m-toluenediamine (MTD) Under a certain temperature and pressure, dinitrotoluene (DNT) is continuously hydrogenated to form toluenediamine (TDA) in the presence of a palladium metal slurry catalyst. The reaction mixture sequentially removes the catalyst, hydrogenated water, and o-toluenediamine (OTD) and other impurities to produce the m-toluenediamine (MTD) required for TDI production.
(2) Production of TDI The apparatus includes carbon monoxide preparation, phosgene synthesis, reaction of dioxytoluene with phosgene to produce TDI, and alkali destruction of phosgene tail gas.
a) Carbon monoxide production mainly includes natural gas compression, natural gas desulfurization and conversion, pressure swing adsorption purification of CO, hydrogen production feed gas compression, pressure swing adsorption purification of hydrogen, hydrogen purification and deoxidation.
b) Phosgene synthesis uses dry chlorine and carbon monoxide in a certain ratio to react in the presence of a catalyst to form phosgene. The phosgene synthesizers are all shell-and-tube fixed bed reactors, and activated carbon is used as a catalyst in the shell. The mixed gas undergoes a synthesis reaction in the fixed bed layer, and the reaction heat is released, and the reaction heat is removed by the shell-side cooling water or the heat-conducting oil.
c) TDI is produced by phosgenation reaction of MTD and phosgene (o-dichlorobenzene (ODCB) as solvent). TDI production includes main processes such as solution drying, phosgenation, degassing, HCI stripping, phosgene recovery, first deODC, decoking, second deODC, TDI refining and venting systems. The tail gas of the phosgenation reaction is absorbed by the cold solvent to separate the phosgene and HCI, and the phosgene absorbed by the cold solvent can be recycled, and HCI is used as a by-product. A small amount of phosgene that is not absorbed by the solvent enters the phosgene tail gas alkali destruction tower, and after being decomposed, the atmosphere is discharged at a high altitude.
2 Analysis of major hazard and harmful factors in the production process The dangers and hazards of TDI devices are mainly poisoning, fire, explosion, high temperature burning, mechanical damage, electric shock, falling from high places, noise hazard, dust hazard and so on. Due to space limitations, this article only analyzes poisoning, fire and explosion.
(1) Poisoning a) The toxic and harmful substances in the MTD device mainly include dinitrotoluene, toluenediamine, and catalyst. Direct contact should be avoided during the production process.
b) The toxic and harmful substances in the TDI device are mainly carbon monoxide, chlorine, phosgene, toluene diamine, o-dichlorobenzene, sodium hydroxide solution, toluene diisocyanate (TDI) and the like. There have been too many phosgene leaks at home and abroad to cause fatal accidents. In the event of leakage of phosgene, chlorine, and carbon monoxide, it can lead to the occurrence of human poisoning and casualties. The causes of these accidents are mainly due to the high moisture content of chlorine gas and the high moisture content of CO, which cause corrosion of equipment and pipelines. The equipment materials are improperly selected, the monitoring and control system is out of control, the sealing of dynamic sealing equipment is not strict or the operation is wrong, and the maintenance is not timely. Water supply system accidents and cooling system failures. Liquid phosgene intermediate tanks are a potential hazard and should have comprehensive protective measures, drainage systems and accident blowout tanks.
(2) Fire and explosion hazard a) According to the characteristics of the process equipment and the characteristics of the raw materials, the fire hazard of hydrogen and dinitrotoluene in the MTD device is Class A. Therefore, the biggest risk factor in the production process is the explosion hazard caused by collision or impact of dinitrotoluene during the batching process. Another dangerous substance is hydrogen. The explosion limit of hydrogen in air is 4.1%-74.1% (V), and the ignition temperature is about 450 °C. Therefore, the abnormal operation of hydrogen compression and the failure of the cooling water circulation system may cause potential dangers of fire and explosion.
b) The fire hazard of carbon monoxide in the TDI device is Class B. The explosion limit in air is 12.5%~~74.2%(V). In the carbon monoxide gas production process, once the carbon monoxide leaks, there may be a fire or explosion in the event of fire. accident.
c) If there is NCl 3 enrichment in the liquid chlorine tank, it may cause an explosion hazard.
Due to the long process flow and many equipments, the device has many pumps for conveying materials. The structure and material of the equipment are different due to different material properties. It is necessary to prevent the production system from being mistaken due to improper design selection and the out of control of the power supply and water supply system. Loss of control, operational errors, and accidents in the power supply and water supply system of any monitoring system can lead to fire and explosion accidents.
3 Safety Control Measures and Suggestions <br> According to the above analysis, the main dangers in the production process of TDI are poisoning, fire, explosion hazard and so on. The following are only the main measures and recommendations to prevent poisoning:
(1) The safety protection distance between the site selection, phosgene and phosgenation production facilities and surrounding residents, factories and public facilities must meet the requirements of the “Safety Regulations for the Production of Phosgene and Phosphorus Productsâ€.
(2) According to the process requirements, the main production equipment must ensure the safety of the production equipment and the concentration of harmful substances in the workplace, regardless of whether the open or semi-open building (structure) or closed structure (structure) is used. Safety and hygiene standards. The enclosed building (structure) adopts forced exhaust; the open or semi-open structure (structure) adopts a hose type local exhaust system.
(3) Using advanced technology, the design of phosgene system should follow the principle of intrinsic safety, minimize the storage and retention of phosgene in the system; optimize pipeline configuration and reduce the length of connection of phosgene pipelines. As far as possible, the relatively safe gaseous phosgene method is used for the phosgenation reaction process, and the phosgene production amount is determined at the rate required for downstream production. The phosgene is not liquefied and no other buffering equipment is provided. When the phosgenation, phosgene recovery or accidental spray system fails, the safety interlock system automatically stops the feeding of chlorine and CO.
(4) Equipment should be designed to ensure high airtightness.
(5) All pressure vessels containing phosgene materials shall be designed, manufactured and accepted in accordance with the requirements of Class III pressure vessels.
(6) The phosgene and phosgenation unit is provided with an isolation operation room. The control room of the device should be designed with concentrated positive pressure ventilation. The ventilation air must be kept free of pollution. The air suction port is designed with filter with activated carbon or other adsorbent as the filter medium.
(7) In an emergency, the system can realize automatic segmentation isolation and drainage to achieve system pressure relief in a short period of time, and the discharged gas directly enters the emergency decomposition system.
(8) Exhaust gas treatment facilities, hose ventilation facilities and emergency accident damage systems in emergency situations shall be provided. The lye circulation system of the emergency accident destruction system shall maintain uninterrupted operation, and the exhaust gas shall be discharged into the atmosphere after being decomposed by alkali washing.
(9) For materials with high toxicity such as phosgene, spare storage tanks of corresponding capacity and accident storage tanks with sufficient capacity shall be designed; the production system shall not store or minimize the storage of harmful and dangerous materials.
(10) Power supply with dual loops.
(11) Set up a flammable and toxic gas alarm system, and set up a detector in a workplace where chlorine, phosgene, carbon monoxide and other gases may escape, and the controller is located in the control room.
(12) In the dangerous areas such as phosgene synthesis, phosgenation reaction and tail gas treatment, it is necessary to make obvious marks, and set wind vane and wind direction monitors at high places that are easy to see, so as to facilitate the accidents of workers and other personnel in the event of poison leakage. Identify the wind direction and dispose of it correctly.
(13) Set up a gas protection station with a complete gas protection facility to be responsible for gas protection. Establish an ambulance organization, equipped with professional medical personnel, and regularly train operators on toxic substance poisoning and first-aid common sense. All production positions should be equipped with commonly used emergency medicines.
(14) In addition to protective glasses, gloves, protective shoes, overalls and other general protective equipment, phosgene or phosgenation production workshops should also be equipped with air breathing apparatus, operators equipped with gas masks, equipped with flushing spray facilities and first aid in production positions. box.
(15) Operators engaged in TDI production must be assessed and hired, and trained carefully. After passing the examination, they will be certified.
(16) Warning signs shall be provided in dangerous areas and key positions to indicate the risk factors and important precautions. The identification of equipment, conveying pipes and valve switches for storing toxic materials such as phosgene and flammable and explosive materials should be clear.
(17) According to the “Significant Hazard Source Identification†GB18218 standard, if it is a major source of danger, it must strengthen the management of major hazards.
(Responsible editor Guo Fengqin)
1. Product Informations of Aluminum Tube
Process of Aluminum Tube
Processing: hot extrusion, whole punching seamless, cold drawn etc.
Features of Aluminum Tube
The relative products: Aluminum Alloy Tube, Aluminum Tube Coil, Seamless Stainless Steel Pipe, Aluminium flat tube.
1. Tolerance of frame thickness: +/-0.1-0.25mm.
Round Aluminium Tube
1. Tolerance of frame thickness: +/-0.1~0.25mm.
5. Max. Length: 6.0m, export length for 20" Container: 5.8m.
Packing for Aluminum Tube/Pipe:
Standard export packing, PVC protective film, plastic bag, wooden case/crate
Surface Treatments of Aluminum Tube/Pipe:
1) Anodizing
1) Micro-motors
Square Aluminium Tube
2. Alloy & temper: Grade 6000 Series, T4-T6
3. Thickness: 1.0mm or according to customer`s requirements.
4. Max. Length: 6.0m, export length for 20" Container: 5.8m.
2. Alloy & temper: 6063-T5, Grade 6000 Series.
3. Thickness: 1.0mm , according to customer`s requirements.
4. Diameter: 2.5mm or according to customer`s requirements.
2) Polishing
3) Powder coated
4) Electrophoresis
5) Sand-blast
6) Coating film
Applications for Aluminum Alloy Tube/Pipe:
2) Cylinder machines without wearing sleeve
3) Pneumatic cylinder
4) Heat transfer equipment
5) Construction industry
6) Curtain track
7) Structure support
8) Irrigation pipes
9) Furniture
China factory 6061 aluminum pipe price per kg
Product Description
|
Material
|
1050 1060 1100 2014 3003 5052 6061 7075 etc |
| Temper | O-H112 T3-T8 |
| Surface treatment | Mill Finish,Anodized,Eletropharesis,Powder Coated,Wooden Finish,Polish |
| Length | as required |
| Shape | Round,Square,Rectangle,Triangle,Hexagon,Octagon,Oval,or as per the drawings and samples |
| Deep Process | cutting,drilling,punching,milling,deburring,clearing,etc |
| Wall thickness | > 0.3mm |
| Outer diameter | 2.5mm-250mm |
| Package | inner plastic paper interleaving each tube,outer fixed by plywood or pallets,or as required |
| Delivery time | 10-15 days after deposit |
| Certification |
ISO 9001:2008;ISO14001:2004;SGS |
Aluminium Pipe,Extruded Aluminium Pipe,Cold Drawn Aluminum Pipe,Aluminum Tube
Shijiazhuang Huize Pipe Fitting Co., Ltd. , http://www.huizegd.com