Description of key parts of the hottest phenol ace

Description of risk factors and preventive measures for phenol and acetone devices and equipment in key parts

1. device development

the preparation of phenol and acetone by cumene method is the main technical route to obtain phenol and acetone in the world at present. Since the industrialization began in the 1950s, so far, about 90% of the world's phenol comes from this route, which plays a leading role in the world's phenol industry: the world's phenol production capacity was about 720 in 2002 × 104t/A, 91% of which adopts cumene method

the preparation of phenol and acetone by cumene method in China began in the mid-1960s, the first set of 10000 ton cumene in China; The phenol acetone plant was completed and put into operation in Yanhua company in 1970, and the first set of imported technology in China was 8 in 1986 × 104t/a cumene; The phenol acetone plant was completed and put into operation in Yanhua company, becoming the largest phenol acetone production plant in China at that time. At present, the main domestic benzene:

phenol acetone manufacturers include Yanshan Petrochemical, Gaoqiao Petrochemical, Huayu petrochemical, Jilin Petrochemical and Guangzhou Jiantao group. The process route adopted is cumene method to prepare phenol and acetone. With the continuous development and progress of technology, the production scale of phenol acetone plant continues to expand. At present, the maximum capacity of a single unit in China is 16% of that of Yanhua company × 04t/a phenol acetone unit, the maximum capacity of a single unit under construction in China is 20 × 104／a。 Germany Ineos phenol Co., Ltd. with a production capacity of 62.0 × 104t/a is the highest in the world

with the development of catalyst and production process, most production units have changed from the traditional A1C13 method to solid phosphoric acid or zeolite catalytic method. The latter is adopted by the four major manufacturers and production units under construction in China. At present, the more advanced process for preparing phenol from cumene is allied/UOP process, which is jointly developed by UOP company and United Chemical Company of the United States. 11 phenol manufacturers around the world have adopted this process

at present, many manufacturers around the world have improved the production technology of phenol and developed new production processes. Through the research on the catalyst, CHP decomposition and phenol refining in the mature process of preparing phenol from cumene, we are moving towards a shorter process route and better economic benefits

II. Key parts and equipment

(I. active zero adjustment of measurement system;) Key parts

1. Alkylation and transposition alkylation reaction system

it can be seen from figure 3-8 that the alkylation reaction system is mainly composed of benzene charging pump, circulating tower, dry benzene tank, feed heat exchanger, alkylation reactor, benzene ene mixer, propylene storage tank, propylene heater, propylene charging pump, external circulation heat exchanger, external circulation pump, transposition alkylation reactor, diisopropyl benzene storage tank, diisopropyl benzene pump, feed mixer Composition of feed preheater. The high reaction temperature is 160 ℃, and the high pressure is 3.1mh. Once the temperature flies, it is easy to cause overheating and overpressure, resulting in equipment leakage and fire and explosion

2. Oxidation reaction system

it can be seen from figure 3-9 that the oxidation reaction system is mainly composed of oxidizer feeding pump, oxidation inlet and outlet heat exchanger, compressor, air alkali washing tower, oxidation reactor, oxidizer circulating pump, circulating cooler, degassing tank, waste air cooler, waste air exchanger, waste air cryogenic cooler and activated carbon adsorber. Due to the thermal instability of the process product cumene hydroperoxide CHP, it is easy to decompose in case of heat, and the decomposition will release a lot of heat and accelerate the thermal decomposition reaction. Like alkali decomposition, it will not only cause the loss of CHP in the production process, but also increase the system temperature. At the same time, with the increase of system pressure, it will have a great impact on safety production. Moreover, thermal decomposition is more common and dangerous than alkali decomposition in the production process, which should be paid great attention to. At the same time, CHP will decompose with acid to produce phenol and acetone. Phenol is an inhibitor of cumene oxidation reaction. Too high content in the system will cause reaction termination, which has occurred in the production process. When CHP meets alkali, it will decompose into by-products acetophenone and dimethyl benzyl alcohol, causing the loss of CHP in the production process, and the heat released from decomposition will increase the system temperature; CHP can decompose into dimethyl benzyl alcohol and other by-products, such as divalent iron ions, initiated by variable valence metal ions. In the process of oxidation reaction, many side reactions produce organic acids, which will corrode the equipment and cause system leakage in serious cases, which should also be paid special attention

3. Concentration process

it can be seen from figure 3-10 that the concentration system consists of concentration feed pump, pre flash feed heater, pre flash separator, first cumene stripper reboiler, first cumene stripper bottom pump, second cumene stripper, first cumene stripper condenser, cumene stripper reflux trough, and second cumene stripper, which can be directly molded by thermoplastic processing The condenser and tower kettle of the second cumene stripper are composed of the reboiler of the second cumene stripper, the bottom cooler of the second cumene stripper, the bottom tank of the second cumene stripper, the reflux tank of the cumene stripper and the cumene pump. The main danger of the concentration process is the thermal decomposition of CHP, especially the two concentration reboilers are prone to local overheating of CHP, which intensifies the thermal decomposition. At the same time, special attention should be paid to the cooling of the thickener, that is, the effect of the bottom cooler of the second cumene stripper, to prevent the heat accumulation of CHP and malignant thermal decomposition accidents when the cooling water is not opened or the cooling effect is not good

4. Decomposition process

it can be seen from figure 3-11 that the decomposition system is composed of decomposition feed pump, decomposition reactor, sulfuric acid injection pump, decomposition discharge pump, mixer, decomposition reactor condenser, decomposition reactor tail gas cooler, secondary decomposition reactor and decomposition liquid cooler. The use of sulfuric acid as catalyst is the most widely used in industry. The advantage is that it decomposes rapidly and does not need to be recycled. The disadvantage is that CHP decomposes rapidly under the action of sulfuric acid and also releases a lot of heat. Once the process is out of control, it will explode and catch fire due to the sharp rise of temperature and pressure. Therefore, the stable operation of the decomposition process is also the core of the safety work of the whole device

(II) key equipment

air compressor is the key equipment of the whole device. Due to the factors such as large equipment, complex structure, high technical content and high price, most devices are generally equipped with only one, which is used to provide the air required for oxidation reaction. Once the outlet pipeline is blocked, it will not only stop the whole line, but also burst the pipeline and even directly damage the compressor. At the same time, the poor operation of the cooling system of the compressor can also cause damage to the compressor, leading to the shutdown of the whole line. When the air flow changes greatly, it may cause surge. Therefore, the air compressor should be taken as the key equipment of the whole device for special protection

III. risk factors and preventive measures

due to its process characteristics, the production process of phenol acetone production plant is carried out at a certain temperature and pressure. Some production units are always carried out under high temperature and high pressure. Most of the materials are flammable, explosive, toxic and harmful chemical dangerous goods, even class a chemical dangerous goods. Various accidents occur constantly in the production process, including human factors, equipment factors, technical factors and so on. Although many technical measures have been taken, some major and malignant accidents have also occurred, and the consequences are extremely serious. See table 3-84

(I) risk factors and preventive measures when starting and stopping

1 Hazard analysis and preventive measures during start-up

during start-up, a large number of materials, catalysts, water, electricity and steam are introduced into the device, the materials are heated from the original state, and the process parameters change greatly. With the progress of various chemical reactions, the composition of materials changes greatly, which is a time when accidents are more likely to occur. According to the accident statistics of a petrochemical company in Beijing from 1969 to 1994, 36 accidents occurred during the start-up phase, and two accidents occurred during the start-up phase of the phenol plant, especially the accident in 1974, resulting in 13 deaths, 5 serious injuries, 17 minor injuries, and serious consequences of damage to some plants and equipment

first of all, in the initial stage of start-up, during the process of removing the blind plate and restoring the process, it is easy to appear that the gasket is crooked, the bolts are not tight, the dump valve is not closed, and even the equipment and pipelines are not restored. It is easy to cause material running accident during driving. Secondly, it is easy to open and close valves by mistake, resulting in material channeling and accidents. During the material replacement phase of the system, it is easy to have material running and channeling accidents

all links in the start-up process are linked. It is necessary to establish not only the material balance, but also the heat balance. The process is complex, and the accident prone analysis of each stage is as follows:

(1) start up of alkylation and transposition reactor

the normal start-up steps of alkylation reactor are: use nitrogen for air tightness test; Remove the blind plate; Material preheating; The reactor is filled with benzene; Adjust the preheater and control the feeding temperature of the reactor; After the reactor is filled, fully open the outlet valve and close the bypass valve; Propylene is put into use; Adjustment operation. In the process of adjusting the preheater and controlling the feed temperature of the reactor, overheating and overpressure are easy to occur, which can cause damage to the catalyst in light cases and out of control in serious cases, leading to explosion and fire accidents. At the same time, improper benzene propylene ratio will also directly lead to temperature rise of the reaction, damage to the catalyst, and lead to fire and explosion accidents. Therefore, we should pay special attention to it

the normal start-up steps of the transposition alkylation reactor are generally similar to those of the alkylation reactor, and the degree of danger is slightly smaller

(2) start up of oxidation reactor

the normal start-up steps of oxidation reactor are: check the external circulation system; Inject nitrogen to maintain pressure; Put the adsorption bed into operation; Open the preheater; Cumene filling; Start the circulating pump; Pressure rise of oxidation tower; The external circulation heat exchanger is switched to the heating state, the steam is heated, and the oxidation tower is heated; Add compressed air; Adjust the operation according to the analysis results. Too fast pressure rise can cause the safety valve to jump, and materials to spill into the accident tank, causing losses and delaying the start-up process. If the temperature rises too fast, it can cause interlocking shutdown of the system and delay the start-up process. After starting the reaction, pay special attention to observe the changes of temperature and pressure and adjust them in time. After the temperature is normal, switch the external circulation and heat exchanger back to the cooling state in time; If the amount of air is raised too fast, it is easy to cause high oxygen content in the tail gas and form explosive gas, which is very dangerous

(3) normal start-up of concentration

normal start-up steps of concentration are: check air tightness; Open the upper and lower water valves of condenser and cooler; System vacuum pumping; Cumene filling; Put the preheater into operation; System temperature rise; Establish cumene reflux; CHP feed. It must be ensured that the upper and lower water valves of the condenser and cooler are in normal state, the valve opening is normal, and the water flow is normal, especially the CHP cooler. Establishing a good vacuum is a necessary guarantee to ensure that the system temperature is within the range of process requirements during startup. When the system heats up, the heating steam shall not be increased too fast to prevent CHP from local overheating, thermal decomposition, vacuum damage, sharp temperature rise, and even explosion and fire accidents

(4) disassemble the normal start-up

the steps of disassembling the normal start-up are: check the air tightness; Open the upper and lower water valves of condenser and cooler; The decomposition reactor is filled with circulating acetone; Establish a cycle; Add sulfuric acid to decomposition reactor; Sampling analysis; CHP feeding, with flow not exceeding 6m3/h; Sampling and analysis again; Break down the unit to neutralize the unit process; The lifting amount of decomposition feed reaches the normal value

decomposition and start-up principle: add sulfuric acid first and then CHP. Must be configured first