1. What is the reflux ratio? What effect does it have on rectification?
Answer: The reflux ratio refers to the ratio of the amount of downstream liquid in the rectification column to the amount of rising vapor. The purity of the rectified product depends on the reflux ratio under certain conditions of the number of plates. When the reflux ratio is large, the purity of nitrogen in the obtained gas phase is high, and the purity of oxygen in the liquid phase is low. When the reflux ratio is small, the purity of nitrogen in the obtained gas phase is low, and the purity of oxygen in the liquid phase is high.
2. What are the causes of the molecular sieve water ingress accident?
Answer: 1. When the liquid cooling tower liquid level is higher than 3500mm, the water exceeds the air inlet pipe height, and a large amount of water enters the molecular sieve adsorber with the air;
2. When the resistance of the air cooling tower rises above 7kPa, liquid suspension will form in the air cooling tower, causing the bottom water level to fluctuate, the air cooling tower resistance fluctuates, and the water enters the molecular sieve adsorber with the air;
3. The molecular sieve switching procedure is disordered, causing the air to suddenly pass through the molecular sieve adsorber for air defense, and the airflow speed in the air cooling tower is rapidly increased, and the water enters the molecular sieve adsorber with the air;
4. The air pressure of the instrument is reduced, and the pneumatic valve is out of control, causing the water level to rise;
5. The flow of cooling water and chilled water is too large, so that the air cooling tower is suspended at night.
3. What are the preventive measures for the expansion machine accident?
Answer: 1. The front bearing temperature alarm value of the expander is 70 °C, and the interlock value is 75 °C;
2. When the speed of the expander exceeds the alarm value, the return valve is gradually opened. When the interlock value is exceeded, the expander stops.
3. The flow rate of the booster is lower than the minimum alarm value. The expander return valve is fully open;
4. The inlet valve is closed when the inlet temperature of the expander is less than -180 °C.
4. What are the precautions for the operation of the turbocharger?
Answer: 1. In any case, it is not allowed to remove the interlock to start the expander;
2. Control the inlet temperature of the expander to not lower than -118 °C;
3. It is not allowed to start the expander when the booster bypass valve FCV401 is closed. The first use of the expander or the use of the expander in the hot state should be pre-cooled first.
5. What are the impurities in the air?
Answer: In addition to oxygen and nitrogen in the air, there are a small amount of solid impurities such as water vapor, carbon dioxide, acetylene and other hydrocarbons and a small amount of dust.
6. Why should I remove impurities during the air separation process?
A: As the air cools, the frozen water and carbon dioxide deposit in the low temperature heat exchanger, turboexpander or rectification tower, which will block the passages, pipelines and valves; the accumulation of acetylene in the liquid oxygen has an explosion. Danger; dust can wear and run machinery. In order to ensure the long-term stable and reliable operation of the air separation plant, special purification equipment must be set up to remove these impurities.
7. How to judge whether the heating regeneration of molecular sieve is thorough?
Answer: First, the gas pressure and flow rate required for heating the molecular sieve are required to meet the requirements of the process. The heating regeneration process can be judged by the regeneration curve. The "cold blow peak" temperature is a sign of whether the entire bed regeneration is complete.
8. What is the oxygen release rate?
Answer: Refers to the proportion of oxygen (gaseous and liquid) products produced by oxygen generators that are not used and emptied. Oxygen emission rate is an important indicator of the adaptability of the reaction equipment and the level of production organization. The more oxygen is released, the more energy is wasted, and the overall economic benefits are worse. Therefore, the oxygen release rate must be reduced by various means.
9. What are the types of air precooling systems?
Answer: 1. Air cooling tower with low temperature water;
2. Low temperature water indirect cooling system
3. A system for direct heat exchange between air and a freezer;
4. Sewage nitrogen evaporation cooling system;
5, directly with the machine after the cooler to cool.
10. What is molecular sieve? What kinds? What are its characteristics?
A: Molecular sieves are synthetic crystalline aluminosilicates, which are also natural, commonly known as zeolites. At present, there are mainly A type, X type and Y type. The main characteristics of molecular sieves:
1. Strong adsorption and good selective adsorption performance;
2, the dryness is extremely high, and has good drying ability for high temperature gas;
3, good stability, can maintain normal adsorption capacity below 200 °C. Molecular sieves also have a long service life.
4. Molecular sieves have strong adsorption capacity for water, followed by acetylene and carbon dioxide.
11. What are the characteristics of the air separation equipment for the molecular sieve adsorption purification process? What should I pay attention to when operating?
Answer: The air separation equipment of the molecular sieve purification process is mainly focused on giving full play to the cooling capacity of the expander, rationally distributing the cooling capacity, and comprehensively cooling the equipment during the startup process. It can be divided into three stages: cooling, accumulating liquid, and adjusting working conditions.
Precautions:
1. The first used molecular sieve is subjected to an activation regeneration to remove moisture and carbon dioxide adsorbed during transportation and filling. The activation temperature is generally above 200 ° C and below 250 ° C. When the outlet temperature reaches 80 ° C, it can be cold blown. The activation time is not less than two cycles;
2. When the molecular sieve is started, the gas supply process should be slow, and the venting valve should be kept small to prevent the molecular sieve in the bed from being damaged due to pressure fluctuation;
3. When two expanders need to be started, fully open the booster return valve, reduce the pressure of the first operating expander, and then load the two expanders at the same time to prevent the surger from starting up to surge;
4. Pay attention to the control of the temperature in the middle of the heat exchanger;
5. Pay attention to the work of the air cooling tower to ensure that the air after pre-cooling meets the design requirements.
12. What problems should be paid attention to when the molecular sieve purification system is operated?
Answer: 1. Installation requirements for molecular sieve adsorber: It is necessary to carefully check whether the upper and lower screens are damaged; whether the molecular sieves are filled and flattened; carefully seal the inner and outer manholes to prevent mutual gas from colliding;
2. When the molecular sieve adsorber is in operation, it is necessary to regularly monitor the molecular sieve temperature curve and the output carbon dioxide content to determine whether the adsorber works normally;
3. It is necessary to closely monitor whether the pressure difference of the switching procedure of the adsorber is normal;
4. Pay close attention to whether the operation of the freezer is normal. In case of short-term failure, causing the air outlet temperature to rise, the switching period of the adsorber should be shortened in time, and the fault should be eliminated in time; ECT
5. When the air compressor starts to boost, it should be carried out slowly, and the air flow rate is too large;
6. When the air separation equipment is parked, the air main valve after the adsorber should be closed immediately, so as to avoid the air flow speed too fast and impact the molecular sieve bed.
13. What should be done when the air separation unit of the molecular sieve purification process suddenly loses power?
Answer: 1. First open the vent valve of the air compressor (anti-surge valve) to prevent the air compressor from surge, and the air backflow causes the air compressor to reverse;
2. The switching of the molecular sieve adsorber should be closed by interlocking. If it is not closed, it should be closed manually. The program state of the molecular sieve adsorber operation before the power failure was recorded. The expander, freezer, air pre-cooling system, and argon purification system shall be interlocked and stopped, otherwise manual shutdown;
3. Stop the sending of oxygen and nitrogen products, and stop the output of liquid oxygen and liquid nitrogen liquid argon;
4. Close the water valve connected to the air pre-cooling system.
14. Why does the molecular sieve purification system sometimes have a water accident? What is the phenomenon?
A: In order to reduce the temperature of the process air before the molecular sieve purifier, first enter the air cooling tower to cool. In the air cooling tower, the air enters from the bottom, exits from the top of the tower, enters the molecular sieve purifier, and the water is sprayed from the top of the tower to contact with the air to mix and cool the air. The air cooling tower is provided with a plurality of flow-through trays or fillers. To increase the contact area. In order to separate the water, there is a water trap at the top of the tower. When the air flow rate in the air cooling tower is too fast, the water in the air belt is too much or the amount of spray water is too large, and the water level automatic adjustment fails, the water inflow into the molecular sieve purifier will occur. Phenomenon: The molecular sieve pressure fluctuates wildly and fluctuates, the resistance of the adsorber increases, and the temperature curve after heating and cold blowing changes. The most obvious is the temperature drop after cold blowing, and a flat peak appears. The longer the curve distance of the flat wind, the more water the molecular sieve enters.
15. How to prevent the water in the molecular sieve purifier from entering the water accident?
Answer: 1. The air-cooled tower should be operated according to the regulations. First, the air is introduced, and the pressure is increased after the pressure is stabilized. 2. The air volume cannot be suddenly increased or decreased.
3. Maintain the water level of the air cooling tower;
4, the amount of water spray can not be too large
5, the water quality should meet the requirements, reduce the inlet water temperature, and reduce scale.
16. What should I do if the molecular sieve purifier has a water intrusion accident?
Answer: After the water inlet occurs, the air cooling tower working condition should be dealt with first, the water pump water supply should be stopped, the air cooling tower liquid level should be lowered, and the normal working condition should be restored. At the same time, the air separation equipment is reduced to reduce the molecular sieve load, and the water inlet condition is judged by the pressure, resistance, regeneration temperature curve and carbon dioxide content of the purifier. If the water intake is small, the remedial adjustment is taken immediately. Working conditions (such as: increase heating temperature, increase heating and cold blowing flow, extend heating time and switch programs to switch ahead). Nowadays, if the amount of water is too large, it is necessary to activate the molecular sieve purifier. When activating, pay attention to cold blowing with a large airflow and heating when the free water is blown. If the activation operation is unsuccessful, only the molecular sieve can be replaced.
17. What problems should be paid attention to when the air separation equipment of the molecular sieve purification process is restarted after a short-term parking?
Answer: 1. The air compressor should be slowly boosted to prevent the impact of the sudden increase of pressure on the air cooling tower. The pump should be boosted first;
2, pay attention to the water level of the air cooling tower to prevent the molecular sieve adsorber from entering the water due to the high water level; 3. If the molecular sieve adsorber is regenerated just after the short-term parking, the regenerated molecular sieve adsorber can be manually switched;
4. The air is slowly introduced into the air cooling tower when the molecular sieve adsorber regeneration system is adjusted to the normal process conditions, and the carbon dioxide content of the analysis point after the molecular sieve is less than 1×10-6;
5. Slowly switch the molecular sieve regeneration gas while adjusting the air separation working condition, and switch to the nitrogen to ensure the regeneration gas flow.
18. Why does the air cooling tower need to be ventilated before starting the pump?
A: This is a measure to prevent air from carrying water. The pressure of the air in the tower before inflation is atmospheric pressure. When the air with a pressure of 0.5 MPa is introduced into the tower, the pressure will suddenly decrease due to the expansion of the volume, and the airflow speed will increase sharply, and its impact enthalpy effect is strong. At this time, if the cooling water has been sprayed, the air is very easy to bring water when it is emptied into the cold tower. Therefore, the inside of the tower is required to be inflated first, and the water supply is sprayed after the airflow is stabilized. Secondly, if the water pump is opened first, the water level in the air cooling tower is too high, and even exceeds the elevation of the air inlet pipe, so that the resistance of the air compressor outlet pipe increases, causing the turbo air compressor to surge. Our factory can only start the circulating water pump after the pressure in the air cooling tower is higher than 0.4MPa. The pump should stop automatically when the pressure is lower than this value during operation.
19. What are the factors related to the cooling capacity of the expander?
Answer: The total cooling capacity of the expander is related to the expansion amount and the unit cooling capacity, and the unit theoretical cooling capacity depends on the pressure before expansion, the temperature and the pressure after expansion. Therefore, the relationship between the cooling capacity of the expander and the various elements is:
1. The larger the amount of expansion, the greater the total cooling capacity;
2. When the inlet and outlet pressures are constant, the higher the temperature before the machine, the larger the unit cooling capacity;
3. When the temperature before the machine and the pressure behind the machine are fixed, the higher the pressure before the machine, the larger the unit cooling capacity; 4. The lower the pressure after the expander, the larger the pressure drop in the expander is, the larger the unit cooling capacity is;
5. The higher the adiabatic efficiency of the expander, the larger the cooling capacity.
20. What is the cold loss? What kind of it is it divided into?
A: The cooling capacity obtained by compressing the gas and then expanding it at a certain cost cannot be recovered and used as cooling loss. Including the following aspects:
1. Incomplete loss of heat exchange;
2, run cold loss;
3. Other cold losses.
21. What are the common methods for removing moisture, carbon dioxide and acetylene from the air? How to remove?
A: Removal of moisture, carbon dioxide and acetylene in the air is commonly used in adsorption and freezing methods. The adsorption method uses silica gel or molecular sieve as the adsorbent to separate the water, carbon dioxide and acetylene contained in the air, and the acetylene in the night sky and liquid oxygen, and concentrate on the surface of the adsorbent, and then heat and regenerate. Drive them off. The freezing method is to freeze the water and carbon dioxide contained in the air through the regenerator or the switching heat exchanger (the acetylene cannot be frozen), and then the gas is taken out of the device by the drying gas.
22. Why do some molecular sieves use bunk beds?
Answer: Because activated alumina has a relatively large air adsorption capacity for higher water content, the adsorption capacity decreases rapidly as the water content of the air decreases. Molecular sieves also have strong water absorption even in the case of very low water content. Moreover, the aluminum gelation is easy to absorb water, and the regeneration temperature can be lowered; the heat of adsorption to moisture is also smaller than that of the molecular sieve, so that the temperature rise of the air is small, which is favorable for the adsorption of carbon dioxide by the latter part of the sieve; the bark also has acid resistance and acts on the molecular sieve. Protective effects. Based on the above characteristics, some molecular sieves adopt a bunk bed, that is, air is introduced into the inlet side of the purifier, and some activated alumina is charged. It clears out most of the water contained in the air, while molecular sieves are mainly used to remove carbon dioxide, acetylene and other hydrocarbons. The use of a two-layer adsorption bed extends the life of the purifier.
23. What is self-clearing?
Answer: The air passes through the regenerator or the switched heat exchanger. As the temperature decreases, the water and carbon dioxide are continuously precipitated, frozen on the packing of the regenerator or on the fins of the switching heat exchanger. Take away the deposited water and carbon dioxide.
24. Why does the returning sewage nitrogen carry away the frozen water and carbon dioxide?
A: Because the nitrogen from the tower on the rectification tower is basically an unsaturated gas of water and carbon dioxide. Therefore, moisture and carbon dioxide can undergo evaporation and sublimation processes and enter the contaminated nitrogen. Although the temperature of the nitrogen is lower than that of the positive air, the saturated water content of the nitrogen and the carbon dioxide contained in the 1 m2 of the nitrogen is lower than that of the positive air, but the pressure of the nitrogen is lower than that of the positive air. Many, the actual volume is 3-4 times larger than the positive air, so the actual capacity of water and carbon dioxide can be larger than that of the positive flow, which can completely remove the silent water and carbon dioxide, and achieve the purpose of self-cleaning.
25. What are the factors that affect the purity of oxygen?
Answer: The oxygen extraction amount is too large; the oxygen purity in the liquid air is too low; the expansion amount into the upper tower is too large; the liquid level of the condensing evaporator is too high; the efficiency of the tray is low; the rectification working condition is abnormal; the main cold leakage.
26. Why is it generally necessary to pump liquid nitrogen to the lower column of the rectification tower of the oxygen generator of the switched heat exchanger process?
Answer: For the oxygen generator of the switched heat exchanger process, in order to achieve the self-cleaning of water and carbon dioxide, the amount of sewage nitrogen is relatively large to ensure that the conditions are not frozen. Therefore, the amount of pure nitrogen nitrogen products is small, and the maximum is oxygen production. 1.3 times, so the amount of pure liquid nitrogen supplied to the upper tower of the lower tower is less, so that one liquid nitrogen can be extracted to the upper tower, so that the reflux ratio of the rectification section of the upper tower is increased, and the rectification capacity is larger, thereby Allow more expanded air to enter the upper tower, reduce the expansion of the expanding air, affecting the oxygen extraction rate.
27. Why is it generally not necessary to pump liquid nitrogen to the lower column of the rectification tower of the molecular sieve pressurization expansion process oxygen generator?
Answer: For the oxygen generator of the supercharging and expansion process, the amount of pure gas nitrogen product has been greatly improved due to the limitation of self-cleaning. In addition to the sewage nitrogen for the regeneration of the molecular sieve purifier, it can be used as a pure gas nitrogen product. The ratio of pure nitrogen production to oxygen production is 3 to 3.5 times. Thus, the lower column requires a larger reflux ratio to ensure the amount and purity of pure nitrogen, and then is sent to the upper column as a reflux. In addition, due to the use of supercharging expansion, the unit cooling capacity of the expanding working medium is relatively high. Under the premise of supplementing the same cold loss, the required amount of expansion is small, and generally does not exceed the amount of air allowed to enter the upper tower. Therefore, It is not necessary to pump liquid nitrogen to directly increase the reflux ratio of the rectifying section.
28. How is the resistance of the tray formed? What parts are included?
A: Plate resistance refers to the pressure drop that occurs when rising vapor passes through the tray screen and the liquid layer on the tray. The resistance of the tray includes: dry tray resistance; surface tension and liquid column static pressure.
29. What factors will cause liquids in the turboexpander?
Answer: 1. The bypass amount is too large;
2. The circulating or medium pumping temperature is too low;
3. With liquid air in front of the expander.
30, what is rectification?
Answer: It is the process of separating the partial condensation of the mixed vapor and the partial evaporation of the mixed liquid by using the boiling points of the two substances differently to achieve the purpose of separation.
31, what is throttling?
A: It is the process of encountering local resistance when the fluid flows, causing a large drop in pressure.
32. What are the methods of air separation?
Answer: 1. Low temperature method;
2. Adsorption method;
3. Membrane separation method.
33. What are the components of the cryogenic separation air equipment?
A: It consists of four parts: air compression, expansion refrigeration; air removal of moisture and impurities in the air; air cooling, liquefaction, rectification and separation through heat exchange; cold recovery and compression of low temperature products.
34. What is a solenoid valve?
A: The position of the spool is controlled by an electromagnetic coil to achieve the purpose of changing the direction of fluid flow, or to cut off and turn on the air supply.
35. What is a gas-opening membrane regulating valve?
Answer: When there is no pressure signal input, the valve is closed. When the pressure signal is input, the valve starts to open. The larger the pressure signal is, the larger the valve opening valve is.
36, what is naked cold?
Answer: After the air separation unit is installed or overhauled, after the full heating and blowing is performed, the driving in the cold box is not filled with the cold insulation material.
37. How is the switching time of the molecular sieve purifier selected?
A: In theory, the maximum switching time can only be equal to the conversion time of the molecular sieve adsorption process. The length of the conversion time is determined by the molecular sieve's dynamic adsorption capacity for water and carbon dioxide.
38. Which heat exchangers are in the air separation plant?
A: The equipment that transfers heat from the hot fluid to the cold fluid is called a heat exchanger or heat exchanger. The main heat exchangers in air separation are: nitrogen water precooler, switching heat exchanger, main heat exchanger, condensing evaporator, subcooler, liquefier, gasifier, heater and air compressor cooler. .
39. Which three types of heat exchangers in air separation equipment can be divided according to the heat transfer principle? What are the characteristics?
Answer: 1. The partition type: the hot and cold fluid is separated by the heat transfer wall (wall or wall), and does not touch each other during the heat transfer process. The heat is transferred from the hot fluid to the cold fluid through the wall surface;
2. Regenerative type: The characteristic is that the hot and cold fluid alternately passes through the solid heat storage body with sufficient heat capacity. When the hot fluid flows, the heat accumulator absorbs heat. When the cold fluid flows, the heat accumulator releases heat, thereby realizing heat exchange between the hot and cold fluids. ;
3. Hybrid: The heat transfer between the two fluids is realized in the process of direct mixing, accompanied by the exchange of substances in the heat exchange process.
40. What is a pneumatic diaphragm control valve?
A: The execution part of the pneumatic unit meter is used to change the flow of fluid on the conveying pipe to achieve the purpose of adjusting the liquid level, flow, pressure or temperature.
41. What is latent heat of condensation and latent heat of evaporation?
Answer: The saturated steam releases heat to condense into a saturated liquid, and the temperature remains unchanged. This part of the heat is called latent heat of condensation. The saturated liquid absorbs heat and evaporates into saturated steam, and the temperature remains unchanged. This part of the heat is called latent heat of evaporation.
42. Why does the top of the air separation tower have both liquid nitrogen and gas nitrogen?
Answer: Because gas nitrogen and liquid nitrogen are in a state of coexistence saturation, they have the same saturation temperature. However, saturated liquid and saturated steam at the same temperature belong to different states. The saturated steam releases heat to condense into a saturated liquid, the temperature remains unchanged, and the saturated liquid absorbs heat to evaporate into saturated steam, and the temperature remains unchanged. For the same substance, the latent heat of condensation and the latent heat of vaporization are numerically equal under the same pressure.
43. Why can I use gaseous nitrogen to cool liquid nitrogen in a liquid nitrogen subcooler?
Answer: The liquid nitrogen subcooler uses the low temperature gas nitrogen extracted from the upper tower to cool the liquid nitrogen extracted from the lower tower to reduce the vaporization rate of liquid nitrogen. The lower temperature of gaseous nitrogen than liquid nitrogen is due to the fact that the phase transition temperature (saturation temperature) is related to pressure for the same species. The lower the pressure, the lower the saturation temperature. Therefore, the liquid nitrogen extracted from the lower tower is about 16 °C higher than the temperature of the gas nitrogen in the upper tower. Therefore, when the two fluids flow through the liquid nitrogen subcooler, the heat is exchanged, and the liquid nitrogen releases heat and is cooled to be too cold. Liquid, gas nitrogen becomes superheated steam due to heat absorption.
44. According to different cooling methods, what kind of cooling capacity is it divided into?
Answer: 1. Throttle effect cooling capacity;
2. Expansion capacity of the expander;
3, the refrigeration capacity of the freezer.
45. What is a gas-closed membrane regulating valve?
Answer: When there is no pressure signal input, the valve is fully open, the valve starts to close when the pressure signal is input, and the membrane regulating valve is closed when the input signal is maximum.
46. ​​What is the expansion capacity of the expander?
Answer: It refers to the size of work done by the working medium during the expansion process, which is equal to the depreciation of the working medium during the expansion process.
47, what is the switching loss?
Answer: When the regenerator (switching heat exchanger) is equalized, a part of the air fails to enter the tower and participate in rectification.
48. Is the switching loss related to those factors?
Answer: Before the sewage nitrogen enters the original air passage, the air remaining after the pressure equalization must be emptied first. Therefore, the size of the switching loss is related to the size of the heat exchanger, the length of the switching cycle, and the pressure difference before and after switching.
49. What is the switching loss of the regenerator, switching heat exchanger and molecular sieve purifier?
Answer: The regenerator can reach 7-8%; the switching heat exchanger is about 4%; the switching loss of the molecular sieve occurs when switching the purifier. Because of its long switching period, the switching loss is much smaller, about 0.4%. .
50. What is the summary of the air separation process?
Raw material air is drawn in from the suction tower and removed by air filters to remove dust and other mechanical impurities.
After being filtered, the air is compressed to about 0.52Mpa in a centrifugal air compressor. After passing through the air cooling tower, the cooling water is divided into cooling towers. The lower section is circulating cooling water, the upper section is low temperature chilled water, and the air is worn from bottom to top. The air cooling tower is cleaned while being cooled.
After the air is cooled by the air cooling tower, the temperature drops to ~10 ° C, and then enters the molecular sieve adsorber for switching, and the carbon dioxide, hydrocarbons and residual water vapor in the air are adsorbed. The molecular sieve adsorber is used for two purposes, one of which is working and the other is regenerated.
The switching period of the purifier is 240 minutes, and the timing is automatically switched. After the air is purified, it is divided into two ways: most of the air directly enters the fractionation tower, and the other is pressurized by the turbocharger and then enters the fractionation tower. Most of the air in the main heat exchanger exchanges with the reflux gas (pure oxygen, pure nitrogen, nitrogen, etc.) to a temperature close to the air liquefaction temperature of about -173 ° C into the lower tower. The pressurized air is cooled by the returning cold gas in the main heat exchange to -105 °C, and is taken out into the expander for expansion and cooling. The expanded air passes through the thermosiphon evaporator and enters the upper tower to participate in the rectification.
In the lower column, the air is initially separated into nitrogen and oxygen-rich liquid, and the top nitrogen is condensed into a liquid in the condensing evaporator while the main cold low-pressure side liquid oxygen is vaporized. Part of the liquid nitrogen is used as the lower column reflux liquid, and another part of the liquid nitrogen is taken out from the top of the lower column, is subcooled by nitrogen and nitrogen gas through the cooler, and is throttled and sent to the top of the upper column and the condensation side of the condenser of the refined argon column. After the liquid air is supercooled in the subcooler, it is throttled into the middle of the upper column as a cold source for the reflux liquid and the condenser side of the crude argon column I. Oxygen is taken from the bottom of the upper tower and reheated in the main heat exchanger, and then exits the cold box and enters the oxygen compressor to pressurize it to 3.0Mpa (G) and send it to the user. The sewage nitrogen is taken out from the upper part of the upper tower, and is reheated in the subcooler and the main heat exchanger and sent out of the fractionation tower, and partially used as a regeneration gas of the molecular sieve adsorber.
Nitrogen is taken from the top of the upper tower, reheated in the subcooler and the main heat exchanger, and then out of the cold box. A part of the product is sent out as nitrogen gas. After being pressurized by the nitrogen compressor, it is sent to the user. The remaining nitrogen enters the water cooling tower as a cold source. Cool the outside water. The product liquid oxygen is discharged from the main cold and sent to the liquid oxygen storage tank for storage. The liquid oxygen is discharged from the liquid oxygen storage tank, and is pressurized to 15 MPa by the liquid oxygen pump. The pressurized liquid oxygen enters the vaporizer, evaporates into oxygen, and then is sent to the filling bottle, and the device is reserved for the liquid oxygen product outlet. .
51. What is the starting process of the air separation equipment?
Start the conditions that should be met:
1. The installation of pipelines, machinery and electrical appliances of the air separation equipment is completed and the test is qualified.
2. All operating machinery and equipment, such as air compressors, oxygen compressors, expanders, water pumps, liquid argon pumps, etc., have the conditions for starting, and some should first perform bicycle test.
3. All safety valves have been commissioned and put into use.
4, all manual, pneumatic valve switch flexible, each control valve needs to be debugged.
5. All mechanical and instrumentation performance is good and the conditions of use are available.
6. The molecular sieve adsorber program is controlled and debugged, and the operation is normal, with the use conditions.
7. The pipe of the low temperature equipment in the cold box is heated, the blowing is completed, and the inspection is qualified.
8. Except for the opening of v457 and v458 valves, all valves of air separation equipment should be in the closed state. In particular, check that the nozzle adjustment valve of the expander must be in the closed state.
9 power supply system works normally.
10 water supply system works normally.
Thoroughly warm and blow the pipes and containers in the cold box before starting the start-up.
There is no liquid or mechanical impurities present in all parts at low temperatures. Except for analytical instruments and measuring instruments, all valves leading to the indicating instrument must be turned on, turn on the temperature measuring instrument, and perform the following steps:
(1) Start the cooling water system
a, the notice is ready for the preparation of cooling water
b. Open the inlet and outlet valves of the cooling water
(2) Starting the switching system of the user instrument air system and the molecular sieve purifier system
a, open the air switching pipeline
b. Connect the standby instrument air (provided by the user)
c, switch on the program controller
d, switch on the switching valve, and check the switching procedure
e. According to the instructions of the instrument and the manufacturer of the instrument, all instruments except the analysis and measurement instruments will be put into operation.
(3) Start air compressor
(4) Start the air pre-cooling system
a, check all indicating instruments
b Check the instrumentation system of the air pre-cooling system
cCheck the condenser of the chiller
dOpen the cooling water inlet and outlet valves, and fill the air cooling tower through the normal temperature pump flow path.
e Slowly increase the air pressure at the outlet of the air compressor. And into the air cooling tower, when the pressure is stable and greater than 0.4Mpa, start the pump and chiller, WP1 (or WP2), pump WP3 (or WP4).
f adjust the pressure and flow of the cooling water pump
g switch liquid level controller
h slowly increase the air compressor discharge pressure
(5) Start air line
(6) Starting molecular sieve purification system
a, switch the operation of the program (manual)
b. Check, adjust and confirm the normal valve position of each control valve
c. Open V1253 and let the free water in the air drain through the V1257 trap.
d. Manually open V1203 (V1204) and V1254 (V1255). After slowly opening V1251 (V1252), slowly close V1254 (1255) and inflate the molecular sieve adsorber to balance the pressure and air cooling tower to keep the pressure stable. Manually turn on V1201 (V1202) and turn off V1251 (V1252).
e. Manually open the non-operating molecular sieve adsorber regeneration flow path valves V1208 (V1207), V1206 (V1205) and V1212.
f, slightly open V1239, strictly control PI-1205 pressure is less than 0.04Mpa, FIS-123 1 flow indication is greater than 20% of processing air.
Note that the heater can be switched on after the introduction of the regeneration gas, and the pressure equalization time and pressure relief time can be adjusted. The start of the molecular sieve adsorber (including adsorption and regeneration) can only be sent to the fractionation column after at least one cycle of normal operation. Note: When the electric heater is turned on, it must be supplied with gas and then energized. When it is turned off, it must be powered off before stopping the air supply.
(7) Blowing air line
The purpose of the blow is to remove magazines and dust, etc., and check for the presence of water droplets. The gas for blowing is the normal temperature dry air of the molecular sieve adsorber. Each blow-off valve is opened for blowing until there is no dust or moisture.
Precautions:
A. Check the water content of the outlet gas of each blow-off valve with a dew point meter. When the dew point of the outlet gas of each blow-off valve is ≤ -60 °C, the blow-off valve can be closed and other pipes can be purged.
B. In the process of blowing out, it is necessary to gradually open large v101, V102, V103, both to avoid pressure drop and to ensure a sufficient amount of blowing gas.
C. Strictly control the upper tower pressure PI-2<0.05MPa to avoid overpressure on the upper tower.
D. When connecting each system, the blow-off valve must be opened first, then the inlet valve should be opened. When stopping the blowing, the inlet valve should be closed first, then the inlet valve should be closed. E. During the blowing process, the air compressor should be in the main plant. The pressure holding operation cannot be automatically operated by the main control room.
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