Fine chemical production enterprises have several main production workshops and auxiliary workshops, and have several sets of reactors and distillation towers. On the whole, there are many equipments, many storage tanks, and vertical and horizontal pipe networks. From the structural point of view, the entire production system is a combination of several production units. Each production unit is a combination of one or more reaction vessels, condensers, and distillation columns. In the unit system, the safety technology measures of the reactor during the operation, an atmospheric reactor and a condenser using the liquid material transport and exothermic reaction as the simplest operating unit, analyze the possible dangerous and harmful factors, and formulate Corresponding safety precautions and contingency measures for emergencies.

Typical case analysis:

Gaomi Haishu Fine Chemical Technology Co., Ltd. 6.2 Fire Accident Cases

2012 at 16:45 on June 2, Gaomi City, Hai Yi Fine Chemical Technology Co., Ltd. 1000 tons of fire accidents in new technology experiments hydroquinone construction project, killing two people were killed and one seriously injured, one person With minor injuries, the direct economic loss was about 4 million yuan.

( I ) Direct Cause

The reactor is charged with methanol and phenol. After introducing oxygen, an explosive mixture of methanol and oxygen is formed in the reaction vessel. During the stirring process, the stirring rate of the reactor is increased, which accelerates the accumulation of static electricity in the reactor. The reactor has electrostatic discharge facilities, but it is difficult to remove the static electricity generated in the accelerated stirring process in time, and local static electricity accumulates to cause a reactor fire accident.

( b ) Indirect causes

First, the technical process does not have the conditions for conducting experiments in production facilities. No risk assessment was conducted prior to the experiment. This experiment did not establish specific experimental schemes, operating procedures, and corresponding accident emergency response plans ; Hu Yucai developed the technology only in laboratory experiments. After successful, without any department's authorization, there is no condition for conducting experiments in production facilities.

Second, in violation of the relevant provisions of the safety license for construction of dangerous chemicals, instead of adopting the mature technology provided by Beijing Tubin New Silicon Technology Co., Ltd., which was approved by the establishment of the report, the laboratory process was purchased and the new process experiment was performed on the production device .

Third, the equipment and facilities of the project have not been installed. The necessary remote control safety facilities such as pressure, temperature, liquid level, flow concentration detection, control, and alarm, chain control of the amount of reactor to be fed, pressure of the reaction kettle, etc. have not been used during the experiment. Temperature and oxygen are added to the valve chain, and the cooling water valve is linked to other automatic control facilities.

Main risk factors of reactors in fine chemicals

1 missed the material

If the feed rate is too fast, the feed ratio is out of control, or the feeding sequence is wrong, rapid exothermic reactions may occur. If the cooling cannot be synchronized, the heat builds up, causing the material to be partially decomposed by heat, forming a rapid reaction of materials and generating a large number of hazardous gases. Explosion accident

2 pipeline leakage

When feeding , for the normal pressure reaction, if the vent tube is not opened, when the pump is used to transport the liquid material into the kettle, a positive pressure is easily formed in the kettle, which may cause the connection of the material tube to crack, and the material leakage causes personal injury. Burn accident. When unloading , if the material in the kettle is not unloaded when it is not cooled to the specified temperature (general requirement is below 50 °C ), the material with higher temperature will easily degenerate and cause the material to splash down and burn the operator.

3 l warm too fast

The material in the kettle is too fast to be heated, the cooling rate is low, and the condensing effect is poor. This can cause the material to boil, form a vapor-liquid mixture, generate pressure, and leak from weak parts such as vent tubes and vapor tubes, and safety valves and blasting. The pressure relief system for the sheet is subjected to pressure relief. If the rushing cannot reach the rapid pressure relief of the suburban fruit, it may cause the explosion of the kettle body

4 maintenance of fire

During the material reaction in the kettle, if electric welding and gas cutting maintenance work is carried out without taking effective preventive measures, or bolts are tightened and sparks are hit by iron objects, once the flammable and explosive materials are encountered, it may cause fire explosion. ACCIDENT

Reactor safety technology in fine chemicals

1 heating control measures

2 For the material heating system with a reaction temperature of 100 °C or less, steam and hot water can be used for stepwise heating. In the case of ensuring that the material does not deteriorate due to local overheating, it is first heated to about 60 °C with medium steam to increase production. Efficiency, and then 100 °C boiling water circulation heat transfer, slowly warming to the temperature of the process and keep the reaction warm. In this way, staged heating can increase the production efficiency while at the same time preventing the material from being decomposed by high temperature or being strongly vaporized, thereby forming a vapor-liquid mixture and the material exploding. It can also balance the material to improve the yield and reduce the consumption cost.

2 chain cooling measures

For an exothermic reaction, heating is required at the initial stage of the reaction, but the reaction process is exothermic. Therefore, excess heat must be transferred quickly and efficiently. Normally used reactor cooling systems are jacket cooling and coil cooling. The cooling fluid used is mainly circulating water and cooling fluid. Cooling liquids cool fast but cost high. In the case of abnormal reactions during production, especially when the temperature and pressure rise sharply, the operator will quickly evacuate the operation site for personal safety. The heating source cannot be cut off effectively, and the cooling system cannot be activated effectively. For this purpose, an emergency opening and cooling chain system should be set up at a remote place outside the operating position. It is advisable to approach the steam valve in the workshop steam sub-cylinder. When the steam valve is closed and the stirring power is turned off, the cooling chain system is turned on. The measures of insulation, power failure, stop stirring, rapid cooling and cooling are implemented to control the accident in the initial stage. Prevent further accidents from expanding

3 chain explosion measures

In order to prevent the material in the kettle from being out of control and the pressure generated by the gas, the pressure can be relieved in time. For the atmospheric pressure reaction equipment, emergency pressure relief facilities should also be installed according to the specific conditions of the reaction. A safety valve should be installed at the top of the tank, and a bursting disc should be installed in a process that may have a relatively violent reaction. The connection of the bursting disc to the outlet must be extended to an outdoor safe place or an exhaust pipe, and it must not be directed to the road or operating platform to prevent materials from splashing. There should be strict control of the acceleration of the dropping reaction process

4 Custody transfer anti-static measures

For the material conveying pipe system, steel pipes or plastic pipes shall be selected according to the characteristics of the materials (in principle, plastic pipes shall not be used, except in special circumstances). Regardless of the type of pipe, flanges or bolts are firmly attached to prevent leakage of material. Do not use rubber sleeves to connect plastic tubes to deliver organic solvents. For the flange part of the steel pipe to be electrostatically bridged, if there are six bolts (including six) on a pair of flanges, do not electrostatically bridge, and four or less (including four) should be electrostatically bridged (for symmetry Normally, there are no five, and if there are five, they need to be bridged.) Electrostatic jumper wire to use 4 square mm copper wire. Plastic pipes should be electrostatically connected when transporting organic solvents or other materials that are prone to static electricity. The connection method is to set fine copper coins inside the pipes. The specific method is to weld a small steel nail at the outlet of the metal pipe and tilt it to the inside of the pipe. The thin copper coin must be wound on the small steel nail and fastened, pass through the plastic pipe, and the other port comes out and is fastened at the nozzle. . This is the only way to ensure that the electrostatic flow creates a loop and transfers static electricity to the grounding system in time.

5 Labor protection measures

The installation of a blower or extractor for the operation position can protect the operator's health and reduce the concentration of combustible gas in the operation position and prevent explosion limit. In order to prevent the leakage of the gas material from the pressure in the material in the kettle and spread to the operation room to injure the operator, a blower should be installed in the operation room. Introduce outdoor fresh air to the operating room to bring the operating room to a slight positive pressure. Equipment that emits toxic and harmful gases should be installed on the leeward side of the local dominant wind direction for easy diffusion or evacuation of gas, and it is also convenient for operators to operate to reduce the risk of gas pollution.

6 Maintenance Fire Safety Measures

The objectives of the fire safety management and safety technical measures are two guarantees: First, to ensure that there are no flammable materials inside the pipelines of the fire-fighting equipment, and second, to ensure that there is no flammable material around the pipelines of the fire-fighting equipment. To achieve two guarantees, we must correctly understand the importance of fire management, enhance safety awareness, and effectively implement safety technology measures such as cutting off, isolation, replacement, cleaning, and ventilation, and conduct preliminary inspections, review, approvals, monitoring, and cleanup according to procedures. , acceptance and other safety management measures

7 Other safety measures

The mechanical equipment must be effectively grounded, and the grounding resistance must not be greater than 10Ω ; the motor must have a zero-crossing measure; the gearbox must have a protective cover; the console must be stable and cannot be shaken, and there must be no openings; the guardrail must be higher than 1.05 meters , and The distance between the upper and lower railings shall not be greater than 0.35 meters ; it is advisable that the equipment is off the ground level so that it cannot hit the human head. For the batch operation in the middle of the operation, the valve and the funnel should be installed on the manhole cover; the vent tube of the condenser should be connected to the outside or the exhaust pipe through the connecting pipe, and the channel and the operator's place cannot be directly aligned; Conditions should also be set up emergency evacuation channel and the entire process of monitoring and alarming facilities; nitrogen protection measures should be done during parking. Equipment that may cause uncontrolled reactions to power outages should have dual-circuit dual-supply systems

Emergency Treatment Measures for Reaction Vessels in Fine Chemicals

1 The production temperature and pressure rise rapidly and cannot be controlled

When the production temperature and pressure rise rapidly, it is necessary to quickly close all material inlet valves; immediately stop the stirring; quickly close the steam (or hot water) heating valve, open the cooling water (or chilled water) cooling valve; quickly open the vent valve; When the vent valve and the temperature and pressure are still uncontrollable, the material discharge valve at the bottom of the equipment shall be quickly opened; if no effect is found in the above process, and the material at the bottom of the material discharge valve cannot be completed in a short time, the personnel shall be promptly notified to evacuate the site.

2 Poisonous and harmful substances leaked

When a large amount of toxic and hazardous substances leaks, immediately inform the surrounding personnel to quickly evacuate the site from the wind direction; quickly wear a positive pressure respirator to close (or close) poisonous and harmful leakage valves; and immediately notify the wind direction when the toxic and harmful substances cannot be closed. Or four weeks) units and personnel to disperse or do preventive work, and according to the material properties spray treatment agent for absorption, dilution and other treatment. Finally, contain the leaked material and handle it properly.

3 A large number of flammable and explosive leaks

When a large amount of flammable and explosive substances leak, quickly wear positive pressure respirator to close (or tightly) flammable and explosive leak valve; when it is impossible to close the flammable and explosive leak valve, notify the surrounding (especially downwind) personnel to stop immediately. Fire and spark-prone production and operations, and quickly stop other production or operations in the vicinity, and at the same time, move flammable and explosive substances to safe areas where possible. In the case of a gas leak that has already burned, the valve cannot be eagerly closed. Attention should be paid to the prevention of flashback and gas concentration reaching the explosion limit to cause an explosion.

4 To identify the cause of poisoning immediately after injury

In case of injury, the cause of poisoning should be immediately identified and treated effectively. When inhalation causes poisoning, the poisoned person is quickly moved to the fresh air in the upwind direction. In case of severe poisoning, it is quickly taken to the hospital for emergency treatment. When intoxication is caused by ingestion, drink plenty of warm water, induce vomiting, or detoxify milk or egg whites, or take other materials to induce leakage. When the skin causes poisoning, immediately take off the contaminated clothing. Rinse with plenty of clean water and seek medical advice. When the poisoning person stops breathing, he or she quickly takes artificial respiration. The poisoning person's heart stops beating, and he or she manually presses the heart to take a jump. When the person's body skin is burnt in a large area, immediately wash it with plenty of water. The net is burned and the flushing time is about fifteen minutes. Care must be taken not to cause cold frostbite. Replace the non-contaminated clothing and take it to the hospital immediately.

to sum up:

Reactor is the most common equipment for fine chemical production companies, and it is also the most typical equipment in the unit system. It is the focus of safety production supervision. Only by managing the safety of each reactor and each unit system, adopt appropriate safety chain protection measures and implement human error warning chain devices to reduce accidents.