Description of dangerous factors and preventive me

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Polyester plant description, risk factors and preventive measures

polyester process was produced in the 1940s and industrialized in the 1950s. It is a process technology for producing synthetic fibers using basic chemical raw materials. Since the 1970s, many countries have carried out modification research on the shortcomings of polyester, such as low water absorption, not easy to dye, easy to generate static electricity and so on, and achieved many results, which has led to the rapid development of polyester industry. At the end of 1970s, China introduced the first set of industrial production device for direct esterification and continuous polycondensation to produce polyester resin from former West Germany. After decades of development, polyester has played a decisive role in the three major synthetic fiber industries in China. By the end of 2003, the production capacity of polyester plants in China had reached 1115 × 104t/A, accounting for about one third of the world's total output. In the 21st century, with the continuous development of process technology, China's polyester plant is developing towards the square foam granulator with more advanced process technology and better economic benefits

2. production process route

polyester is usually a high molecular polycondensate made by esterification and polycondensation of the Audi A8 (Audi A8) body inner frame (ASF) and covering parts produced by German Audi automobile company in 1994, all of which are made of meta acid and binary alcohol made of extruded aluminum and sheet of Alcoa. At present, the most widely used polyester is polyethylene terephthalate produced by esterification and polycondensation of terephthalic acid and ethylene glycol. The production technology of polyester mainly depends on the production development of purified terephthalic acid, dimethyl terephthalate and ethylene glycol. The main raw material routes for the synthesis of polyethylene terephthalate intermediates are as follows: one is ester exchange method (DMT method for short); The other is direct esterification (PTA for short); The third is ethylene oxide esterification polycondensation route (ethylene oxide method for short)

transesterification method (DMT method): it is to react terephthalic acid with methanol to produce dimethyl terephthalate, which is easy to refine and purify, or combine oxidation and esterification of paraxylene to produce dimethyl terephthalate, and then transesterify the purified dimethyl terephthalate with ethylene glycol to produce polyester. This method was widely used in the early stage of polyester industrialization when no effective method for purifying p-xylene was found

direct esterification method (PTA method): polyester is prepared by direct esterification and continuous polycondensation with purified terephthalic acid and ethylene glycol as raw materials. By the early 1990s, the output of PTA method had exceeded that of DMT method and became the mainstream production process of polyester industry

ethylene oxide method because ethylene oxide is used instead of ethylene glycol (eg), the hydrolysis process of ethylene oxide can be omitted, and the synthetic reaction product is a single terephthalic acid β— Hydroxyethyl ester (BHET), which does not need recovery equipment, has short process flow and low cost, so it is a promising production method

from the perspective of process flow, PTA continuous production used to be dominated by six kettle process, namely three-stage esterification, two-stage pre shrinkage and one-stage post shrinkage. This process technology is relatively backward, with high material and energy consumption, and has been basically eliminated. The current production process is the five kettle process represented by Gemma company, Zhongfang company and evanda company, or the three kettle process represented by DuPont company and Rhine company, which has enhanced its ability to deal with trade protectionism. The five kettle process is two-stage esterification, two-stage pre shrinking, one-stage post shrinking, and the three kettle process is one-stage esterification, one-stage pre shrinking, and one-stage post shrinking. Their common characteristics are advanced technology, simplified process flow, advanced production control, and flexible device operation

II. Key parts and equipment

(I) hazard analysis of main raw materials of polyester plant

1 Safety characteristics of main raw materials of polyester plant

in the whole process of polyester production, there are many flammable and explosive media, such as PIA, ethylene glycol (EC), titanium dioxide (TiO2), antimony triacetate or antimony trioxide (Sb2O3), heat medium (HTM), diethylene glycol (DEG), triethylene glycol (TEG), etc. see table 3-64 and table 3-65 for toxic and harmful media. When production is unstable or leakage occurs, it is easy to cause major accidents, endangering production and personal safety

2. Hazard analysis of main raw materials in polyester plant

polyester plant is a key production plant and key production part, which is characterized by continuous production, complex process and high medium hazard. These characteristics determine that the management of the device should be refined and the operators should have high technical quality

(1) polyester device is a device produced under negative pressure. The main materials are purified terephthalic acid and ethylene glycol, which are flammable and explosive. The carrier of heating materials is heat medium, which is toxic

(2) the main toxic materials are eg and antimony trioxide. Long term exposure to eg will cause chronic poisoning. Antimony trioxide heating can release antimony oxide toxic smoke

(3) the temperature of heat medium and heat carrier is very high, generally around 330, so you must wear heat proof clothes, gloves and masks during operation

(4) PTA powder is conveyed by PTA device and PTA powder is conveyed by PTA intermediate silo to polyester device with nitrogen. Prevent dust explosion. And analyze the oxygen content of nitrogen transporting PTA

3. The main hazardous substances in the polyester plant are restricted by the material division

according to the characteristics of the process flow of the polyester plant and the actual layout of the equipment and pipelines of the plant, the actual distribution of toxic, harmful and dangerous chemical crystals used in the plant is investigated, as shown in table 3-66 and table 3-67

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