flammable components
Mainly hydrocarbons such as acetylene, acetylene is the most dangerous, its solubility in liquid oxygen is very low (5.6×10-6mg/L), and it is easy to precipitate in the solid state and cause an explosion.
clogging component
Mainly carbon dioxide, water and nitrous oxide, especially nitrous oxide, have attracted increasing attention. After they crystallize and separate, they will block the main cold channel, causing "dry evaporation" and "dead-end boiling" of the main cold, resulting in the concentration of hydrocarbons. , accumulation and precipitation, causing a main cold explosion.
Strong oxidants
Liquid chlorine is a strong oxidant.
detonating factor
a. Mechanical impact detonation of solid impurity particles (friction of acetylene particles, liquid oxygen impact).
b. Static electricity. For example, when carbon dioxide particles reach (200~300)×104ppm, static electricity can be generated with a voltage of 3kV.
c. Chemically sensitive substances (such as ozone and nitrogen oxides).
d. Pressure pulses caused by air flow impact, pressure impact, and cavitation phenomena can cause temperature rise and cause explosions.
QC
The oxygen production area should be in the upwind direction all year round, more than 300m away from the acetylene generation station, away from sources of harmful gases, and the air quality control of raw materials should be strengthened. If the pollution is serious, corresponding measures should be taken.
The main factors of accumulation are as follows:
a. Give full play to the role of the liquid air and liquid oxygen adsorber in removing acetylene and other hydrocarbons, strictly replace the adsorber on schedule and control the heating and regeneration temperature to improve the adsorption efficiency.
b. Discharge 1% of the product liquid oxygen from the main cooling to remove hydrocarbons.
c. Regularly heat the air separation to remove residual carbon dioxide and hydrocarbon impurities accumulated in the heat exchanger and distillation tower.
d. The liquid oxygen pump has been put into operation for a long time and uses molecular sieve for adsorption. If the nitrous oxide adsorption effect is not good, a layer of 5A molecular sieve can be added to the molecular sieve adsorber.
This work must be normalized, institutionalized, and carried out regularly. If the environment deteriorates, effective measures must be taken at any time to control harmful substances within the standards. Acetylene should be within 0.5, methane 120, total carbon 155, carbon dioxide 4, and nitrous oxide 100 ( Order of magnitude 10-6).
The liquid level is high and the circulation ratio is large, so carbon dioxide and hydrocarbon compounds are not easy to accumulate and concentrate. The Wuhan Iron and Steel Gas Plant adopts full immersion operation. After many years of safe operation, all process parameters are the same as before without immersion, and there is still enough separation space, the heat exchange area also meets the requirements, and there is no gas-liquid entrainment in the oxygen taken out, so the main cooling Total immersion operation is beneficial and harmless.
During temporary shutdown and restart, there will inevitably be a certain period of low liquid level operation. At this stage, local concentration of hydrocarbons is prone to occur. At the same time, when restarting, the plate heat exchanger will not work normally for a period of time, and the self-cleaning effect is not good. , causing carbon dioxide blockage, coupled with air flow impact, it is possible for micro-explosion to occur in the main cooling, so the number of temporary stops should be minimized, or full draining should be avoided, and the main cooling should be heated separately. If possible, the main cooling should be fully Warm.
When operating for 2 years or more, the distillation tower and liquid oxygen circulation system should be cleaned and degreased. The main cooling unit should be soaked for 8 hours. After cleaning, it should be completely blown with air of sufficient pressure, and then fully heated and dried.
1. Always check whether the compressor belt is in good condition. If there is a "squeaking" noise when starting the air conditioner, it means that the belt is slipping seriously, and the belt and pulley should be replaced in time; if the belt is too loose, it will affect the air conditioner refrigeration.
2. Clean the condenser frequently. Some car owners often flush the condenser with a water pipe when using the air conditioner in the summer. This method is good and can prevent dust, mud and other things from being deposited and affecting heat dissipation.
3． The filter of the air conditioner should be replaced every year. The filter is often stained with various dust and impurities, which not only affects the air flow, but may also create odor.
4． If the car has been used for more than two years, the evaporator box needs to be cleaned. The evaporator box is located under the wiper. Every time the air conditioner is turned on, dust and bacteria are easily contaminated on the evaporator box, so it is best to clean it with a foam agent with cleaning function.
The unit resistance of liquid oxygen is large and it is easy to generate static electricity. It can generate thousands of volts of static electricity when not grounded. Therefore, the grounding of the air separation unit must be checked regularly.
If oil is brought into the air separation unit, it will contaminate the adsorbent and affect the adsorption of acetylene. Therefore, the Roots blower that easily makes the air contaminated with oil should be cancelled, and the inspection and maintenance of the expander should be strengthened.
The remaining acetylene in carbide slag causes great air pollution, especially on rainy days. It should be strictly managed and it is best to bury it far underground.
In terms of operation, we must be careful about removing harmful impurities, such as temperature control of plate heat exchangers, main cooling stability control, monitoring of harmful substances, etc. In terms of maintenance, the instruments and meters used for monitoring must be calibrated regularly to ensure the accuracy of the test results; super-cycle operation must be performed with caution and the equipment must be stopped for heating and purging in a timely manner. In terms of management, we must strictly abide by process disciplines, strengthen equipment management, eliminate illegal operations, maintain the integrity of equipment, and strictly implement the "four no-misses".
Regular and irregular training is provided every year to enhance explosion-proof awareness and improve operating skills.
Because most cooling water contains calcium, magnesium ions and acid carbonate. When cooling water flows over the metal surface, carbonate is formed. In addition, oxygen dissolved in cooling water can also cause metal corrosion and form rust. Due to the generation of rust, the heat exchange efficiency of the condenser decreases. In severe cases, cooling water has to be sprayed outside the shell. In severe cases, the pipes will be blocked and the heat exchange effect will be lost. The study's data shows that scale deposits have a significant impact on heat transfer losses and that as deposits increase, energy bills increase. Even a thin layer of scale will increase the operating costs of the scaled part of the equipment by more than 40%. Keeping cooling channels free of mineral deposits can greatly improve efficiency, save energy, extend the service life of equipment, and save production time and costs.
For a long time, traditional cleaning methods such as mechanical methods (scraping, brushing), high-pressure water, chemical cleaning (pickling), etc. have caused many problems when cleaning equipment: scale and other sediments cannot be completely removed, and the acid causes corrosion to the equipment and forms loopholes. , the residual acid will cause secondary corrosion or subscale corrosion on the material, eventually leading to the replacement of equipment. In addition, the cleaning waste liquid is toxic and requires a lot of money for wastewater treatment.
In response to the above situation, efforts have been made at home and abroad to develop cleaning agents that are less corrosive to metals. Among them, the Fushitaike cleaning agent has been successfully developed. It has the characteristics of high efficiency, environmental protection, safety and non-corrosion. It not only has good cleaning effect but also has no corrosion to the equipment, ensuring the long-term use of the condenser. Fostech cleaning agent (unique added wetting agent and penetrating agent) can effectively remove the most stubborn scale (calcium carbonate), rust, oil, mud and other sediments produced in water-using equipment, while not harmful to the human body. It will not cause damage and will not cause corrosion, pitting, oxidation and other harmful reactions to steel, copper, nickel, titanium, rubber, plastic, fiber, glass, ceramics and other materials, which can greatly extend the service life of the equipment.
The condenser materials are generally made of carbon steel, stainless steel and copper. When the carbon steel tube plate is used as a cooler, the welds between the tube plate and the tubes often corrode and leak. The leakage will enter the cooling water system. Causes environmental pollution and waste of materials.
When the condenser is manufactured, manual arc welding is generally used to weld the tube sheets and tubes. The shape of the weld has varying degrees of defects, such as depressions, pores, slag inclusions, etc., and the stress distribution of the weld is also uneven. During use, the tube sheet part is in contact with industrial cooling water, and impurities, salts, gases, and microorganisms in the industrial cooling water will cause corrosion to the tube sheet and welds. Research shows that industrial water, whether fresh water or seawater, will contain various ions and dissolved oxygen. The concentration changes of chloride ions and oxygen play an important role in the corrosion shape of metals. In addition, the complexity of the metal structure will also affect the corrosion pattern. Therefore, the corrosion of the welds between the tube sheet and the tubes is mainly pitting corrosion and crevice corrosion. From the appearance, there will be many corrosion products and sediments on the surface of the tube sheet, and bubbles of varying sizes are distributed. When seawater is used as the medium, galvanic corrosion will also occur. Bimetallic corrosion is also a common phenomenon of tube sheet corrosion.
In view of the problem of condenser anti-corrosion