On December 26, 1996, Shanghai Baosteel signed a contract with LINDE of Germany to purchase a 60000m 3 / h oxygen generator (No. 6), in which key equipment was imported from Germany; the rest was produced and purchased by Baosteel. LINDE is part of a joint venture company (LPP) manufacturing in Dalian, China. The Joint Venture Company (LPP) is also responsible for the production and inspection of equipment and equipment manufactured and purchased in China. Thereby, the total cost of the equipment is reduced, and the project investment is saved. On June 9, 1999, Baosteel's No. 6 “60000†oxygen generator was put into full production. On September 13, Baosteel Group Corporation and LINDE Company held a grand ceremony for the completion of No. 6 oxygen generator in Baoshan.
1 Baosteel No. 6 Oxygen Generator Features Baosteel No. 6 60000m 3 / h Oxygen Generator Process.
(1) In the air pre-cooling system, the refrigeration unit that eliminates the chilled water multiplies the filling amount of the adsorbent, and the switching time of the adsorber A2626A, B is extended to 4 hours, which will undoubtedly increase the long-term operation of the equipment. reliability.
(2) Each unit in the main heat exchanger is designed and manufactured according to different working pressures and process requirements. One group (E3116A, B, C, D) is specially used for three units of high pressure liquid oxygen, liquid nitrogen, liquid argon vaporization and reheating to normal temperature after being pressurized by each liquid pump. The plate-fin heat exchange passage of this group has a pressure resistance of 810 MPa, which is required for the internal compression process.
(3) Eight centrifugal cryogenic liquid pumps are installed around the cold box, which meets the needs of the internal compression process on the one hand; on the other hand, the original upper and lower secondary distillation columns are placed, and the main cold steaming evaporation is placed in the middle. The arrangement of the connected devices is completely changed, and the upper and lower towers are arranged on the same horizontal elevation DDD cold box, and the main cold subunit is mounted in the middle of the main tower. This arrangement is simple and convenient, reducing the height of the cold box, saving installation costs and shortening the installation time. In normal operation, it is possible to further reduce the working pressure of the pressure tower, and the technical and economic benefits are very significant. The total height of the air separation cold box of Linde "30000" is 42 meters, and the total height of the air separation cold box of "60000" is 59 meters.
(4) The internal compression of oxygen and nitrogen of the product forces the liquid oxygen to rapidly vaporize in the main heat exchanger, and then flows out of the cold phase and enters the pipe network. At the same time, the hydrocarbons such as methane originally present in the liquid oxygen will be cleanly and thoroughly removed from the cold box, thereby avoiding the risk of explosion caused by the sudden accumulation of hydrocarbons in the liquid oxygen; Long-term low temperature, extended operating cycle, can no longer provide the preconditions for the conventional two-year cold box thawing heating.
(5) Replace the oxygen compressor and the high-pressure nitrogen compressor with an air booster. First, the site occupation is reduced; second, the equipment cost is reduced; third, it facilitates daily operation and maintenance; fourth, the requirements for spare parts and spare parts inventory are reduced, and capital occupation is reduced; In the above, the consumption of reactive power is reduced; sixthly, the manpower input for operation and maintenance can be reduced.
(6) The pressurized liquid argon product is returned to the cold box and reheated in the main heat exchangers E3116A, B, C, and D, and all of the cooling capacity is recovered. This energy saving measure provides conditions for increasing the production of liquid oxygen or liquid nitrogen, which is simple and practical. However, if the liquefaction unit of liquid oxygen or liquid nitrogen with a production capacity of about 2380 m 3 / h is separately increased, according to the current market price estimate, an investment of nearly 20 million yuan is required.
(7) The air booster and medium-pressure nitrogen press are all selected by Demark's “H†type compressor. Each stage has an adjustable vane at each inlet to smoothly load the extra large oxygen generator. Operation, which reduces product emissions, saves energy and reduces consumption provides convenient measures.
(8) Next to the manual operation valve on the high-pressure oxygen pipeline, a firewall constructed of high-strength asbestos board, steel plate and steel structure frame is arranged, and connecting pipes, bypass valves and corresponding ones are designed on the pipes at both ends of the valve. The relief valve reduces the possibility of operator injury.
2 Problems found during the test run and treatment (1) The main air compressor introduced from Sulzer Company during the load test process, when the opening of the rear vent valve is increased, the butterfly valve is under the action of a large amount of air flow. The position of the valve plate cannot be completely fixed, and the main machine cannot be operated smoothly under load. After analysis and research by experts at both the center and the outside of the field, it is found that the cause of the problem is that the selection of the drive device of the valve is not suitable. The torque generated by the cylinder meets the drive requirements of this type of valve, allowing the valve plate to open and close. However, when the valve plate is in the intermediate position, the torque of the cylinder in both directions and at the same time is too small, causing the valve plate to float under the impact of a high-speed air stream having a large kinetic energy. When the valve manufacturer timely feedbackd this situation, it was recognized that the valve manufacturer timely airlifted to a new large-sized two-way positioning drive device. After replacement, the air compressor was restarted for load test and successful.
(2) Vacuum inspection of five vacuum insulated tanks of domestic vacuum insulation was carried out, and it was found that the vacuum degree of one of the tanks was lower than the standard requirements, and the manufacturer transported special tools and equipment to the site for inspection and treatment. . After careful searching, the leak point was found on the interface of the measuring vacuum meter, the components were replaced, the vacuum was re-extracted, and the inspection was carried out again to meet the requirements.
(3) During the first no-load test of the medium pressure nitrogen compressor C1761, the motor has just reached the synchronous speed. Before the auxiliary oil pump stops automatically, the pipe behind the main oil pump suddenly rises through the wall panel of the sound insulation cover. A serious oil spill occurred and was forced to stop at the scene. After the analysis, the reason is very clear. After the oil pipeline is tested, the sound insulation wall installed and the oxygen lance are damaged, so that the oil pipeline can be damaged, so that it can not withstand the peak oil pressure generated by the simultaneous operation of the two oil pumps, resulting in leakage. oil. After the replacement of the pipe section, the re-testing was successful.
(4) After the turbine expander was rotated for a period of time, it was found that the load of the X3471A generator was slightly leaking. The motor manufacturer provided the shaft end seal ring, which was completely solved by the professional team of Baosteel.
(5) After the whole unit was put into normal production, before the performance appraisal, it was found that the discharge valve (PV3925) on the pipeline of the high-pressure oxygen product was not properly closed to zero in the normal adjustment, leaving a 25% opening. Fully open to 100% opening. After the temporary parking and after the parking inspection, it is found that when the pressure in the pipeline is low or there is no pressure, whether the signal is added locally or the opening degree is set on the DCS of the main control room, the movement can be freely performed, and Can be fully closed and fully open.
The driving device of the valve is air-opening, and the closing process of the valve is completed by the elastic force of the returning spring. Therefore, the main reason for the valve not being fully closed is that the spring specification is small, and the rebounding force cannot fully meet the requirements. After the cause analysis is clear, the unit is restarted for normal production. Because this phenomenon does not constitute a safety issue, it does not affect performance assessment. After the valve manufacturer re-provided a larger model of the drive to the site, according to Baosteel's overhaul and repair plan, temporary and short-term parking of the air separation equipment and replacement of the new drive, the problem was completely solved. .
3 Air separation equipment bare cold test, cold start, performance assessment Baosteel prepared the required external conditions for the No. 6 oxygen generator in advance, which is the successful completion of single machine test, bare cold test, air separation cold drive, performance evaluation, etc. A series of key measures for important work.
Water, electricity, steam, instrument gas source, high-flow nitrogen gas, etc. were delivered to the site in advance, which won time for the test operation. For example, the use of high-pressure steam to clean the pipes and tubes before assembly saves manpower and the cleaning effect is good; the high-pressure nitrogen is used for blasting of large-diameter pipes, the direct cleaning of small-diameter pipes, and the continuous strength of oxygen pipes. Purge. The purging operation avoids the danger of dust pollution caused by the poor environment and long construction period in the open-air construction of the plant, which is also an important measure to ensure a successful test run and long-term, trouble-free operation. For this reason, when all the pipelines were successfully tested, most of the pipelines inside and outside the cold box were partially and systematically purged.
The no-load test of the air booster and the medium-pressure nitrogen press was carried out in advance with nitrogen. The no-load test of the supercharger was completed before March 10, 1999, and the no-load test of the nitrogen press was completed before March 18. For the advancement of the bare cold test, we have won time.
311 bare cold test On March 19, 1999, the main air compressor was started and put into normal operation. After adjusting the water level at the bottom of the air pre-cooling tower (E2416), the adsorber A2626A, B was heated separately, and the valve HV2615 was opened on the 20th. The air is supplied in the box, and all the process pipelines are started to be blown off and dried. After thorough analysis on the 22nd, it is confirmed that the whole device has been dried and qualified, the booster is started to carry out the load test, and the test of two expanders is carried out at the same time. After successful trials, the test was transferred to normal bare cold operation. Both expanders were operated at a load of more than 80%. The temperature of the cryogenic vessels and pipelines in the cold box decreased continuously with time, and the temperature after the expander No longer falling, the lowest temperature is -105 ° C, the average temperature of the main hot cold end and the main tower is about - 90 ° C. The test achieved its intended purpose. On the 24th, the supercharger and two expanders were stopped. After the cold box was heated to normal temperature, the main air compressor was stopped.
On March 25, 1999, the position of the orifice plate on the liquid oxygen inlet pipe of the three main condensing evaporators was modified. The modification was completed in a few days, and then the partial system on the main cold liquid oxygen side was retested. After the pressure is passed, the construction personnel carefully inspect all the pipelines, pipeline supports, tower hangers and supports in the entire cold box from top to bottom, and no hard damage parts due to low temperature are found. Then all the welds were systematically checked for leaks, and several new leaks were detected and the bare cold test was completed.
The 312 air-freight cold drive started the main air compressor at 15 o'clock on the 28th and started the first air-freight cold drive. Firstly, the towers and pipelines in the cold box were dried for a long time, and after thorough sampling and analysis, the liquid storage tanks were thoroughly dried and blown through the liquid lines of each product, and the liquid was liquid until the analysis was qualified. The transportation and storage are ready. The turbocharger was started at 15:16 on May 2, and the two turboexpanders were started in turn at 15:46, and the official cold start was started. After comprehensive slow cooling equipment, starting from 9:20 on May 3, according to the normal gas path, slowly pre-cooling the process liquid oxygen pump P3366A, B, product oxygen pump P3568A, B; product nitrogen pump P3569A, B; Crude argon column reflux pump P4566A, B.
The function of the process liquid oxygen pump is to send the reflux liquid of the low pressure tower to the main cold (E3226A, B, C) to cool the rising steam of the pressure tower and become the reflux liquid of the pressure tower; on the contrary, the generated oxygen gas returns to the low pressure. The tower becomes the rising steam of the tower. Usually one pump runs another standby, and one spare one can be in a state of low temperature with low temperature, low speed rotation, and online standby. In normal operation, the exchange between the two pumps is started and stopped, which only affects the rise and decrease of the two liquid oxygen levels, and does not affect the production and operation conditions of the two-stage distillation column. The pump delivery amount is controlled by the opening degree of the return valve, and the opening degree of the valve is automatically controlled by the height of the liquid level LIC3212. The pump drive motor is a variable frequency control and explosion-proof type motor. The operator can set the load of the motor according to the overall production conditions. The two control methods combine to meet the requirements of process control.
The function of the product oxygen pump P3568 is to press the qualified liquid oxygen at the bottom of the low-pressure tower to the required pressure, and then reheat after the main heat exchanger E3116 to be sent to the oxygen product output pipe network. The operation mode is the same as the control and operation method, and the four groups (8 units) are the same.
The function of the product nitrogen pump P3569 is to pressurize the qualified liquid nitrogen at the top of the high pressure tower and then send it to the main heat. After gasification, it is reheated to normal temperature and then delivered to the end user.
The function of the crude argon column reflux pump P4566 is to transport the reflux of the lowest part of the second-stage crude argon column (T4111) back to the top of the first-stage crude argon column (T4110), and connect the two-stage crude argon column in series, so that The height of the filler layer of the crude argon column can be limited by factors such as operating pressure and high tower resistance, thereby ensuring a hard index of oxygen containing less than 1 × 10 -6 in the crude argon.
When the pumps and the pipelines before and after the pump are sufficiently cooled with a low temperature gas for a period of time, the gas flow of each pump is adjusted or the cooling is stopped for a period of time according to the cooling condition of the overall equipment. At 23 o'clock on May 3, when the liquid oxygen level of the low pressure tower reached 5618%, the P3366A and B pumps were slowly cooled by the liquid. When the P3366A and B pumps were found to be in liquid immersion, they passed through the return valves HIC3358 and HIC3368. Perform an actual test of the test run and control functions to confirm that there is no problem. However, it was found that the flanges on the front and rear of the pump body leaked. After stopping the pump treatment, wait for re-cooling and starting.
Obviously, in the latter stage of the first cold drive, the process of no-load test and load test of each pump must be carried out. The liquid cooling pump and the liquid leakage during the first boosting process are more likely. It is necessary to stop the pump, and each pump takes a while to reach normal operation. Therefore, after a series of operations in May 4th, the process oxygen pump P3366 and the product oxygen pump P3568 began to enter a stable rotation state at 17 o'clock, and the main cold average liquid oxygen level L13208, 9, 10 was stabilized at 30%. The gas oxygen flow rate is 15040m 3 / h, the oxygen pressure is 1833kPa; the low pressure tower liquid oxygen level LIC3212 is 6316%, the resistance PDI3211 is 11284kPa, PDI3212 is 31842kPa; the low pressure tower pressure PIC3271 is 3616kPa; the liquid nitrogen liquid at the top of the high pressure tower The LIC3211 is 1616%; the reflux volume FIC3206 of the high pressure column is 52312m 3 / h, the bottom pressure PI3201 is 38714kPa, and the tower resistance PDI3202 is 12145kPa. The key operating parameters of the above several main distillation columns indicate that the air separation system It has been converted to a stable production state under normal conditions (process air volume is 155000 m 3 / h), that is, under 50% of design capacity.
When the processing air volume FIC2615 is stably controlled below 179728m 3 / h at 10:00 on May 5, the oxygen flow rate is 34569m 3 / h, wherein the oxygen pressure of the outlet cold box is 2969kPa, the purity is 9918%; the low pressure product nitrogen outlet box The flow rate is 48912m 3 / h, the oxygen content is less than 1×10 - 6; the product nitrogen pump P3569A, B is in the test run; the expander X3471B is in normal operation, the expansion amount is 21404m 3 / h, X3471A is standby; the supercharger is four The discharge pressure is 5971 kPa, the flow rate is 70696 m 3 / h, the tertiary discharge pressure is 3305 kPa, the flow rate is 21311 m 3 / h, and the working load is 60% of the design capacity.
At 15 o'clock on the 5th, the product nitrogen pump P3569 was put into stable operation. The high-pressure nitrogen flow rate was 14609m 3 / h, the pressure was 2990kPa, and the oxygen content was less than 1×10 - 6. At this time, the important operating parameters of the main tower are as follows: LIC3201 is 5115%; PI3201 is 40516kPa; PDI3202 is 15126kPa; FIC3206 is 88746m 3 / h; LIC3211 is 4817%; LI3208, 9, 10 is 32%; LIC3212 is 5718%; PDI3211 is 11528kPa; PDI3212 is 41103kPa; LIC3208 is 2217%; PIC3271 is 2916kPa. Operation parameters of crude argon T4111: PIC4112 is 3212kPa; LIC4110 is 3212kPa; LIC4112 is 1618%; FIC4112 is 68812m 3 / h, other parameters are not large Variety. The above operating conditions indicate that the cold start process of the main system is basically completed, and it can be transferred to the pure operation of the crude argon system, and the pre-cooling and replacement of the liquid oxygen and nitrogen storage tanks.
In the early morning of May 6, after the crude liquid argon column reflux pump P4566A, B was successfully tested, just after the liquid was sent to the top of the T4110, the operator heard the crack of the cold box casing from the middle of the cold box, and then The cold air and pearl sand that was sprayed out were quickly confirmed, because the liquid pipe behind the pump might be damaged. The operation of the P4566A and B pumps was stopped immediately. To this end, stop the cold drive, re-discharge, and after heating the low-temperature system to normal temperature, a small amount of pearl sand was found, and the damaged place was found, confirming the initial judgment. The direct cause of the damage is that the edge of the pipe bracket passes through the lower part of the pipe. After modifying the elevation of the bracket and the pipeline, the replacement pipe section is tested and qualified, and after refilling the pearl sand, the site is cleaned.
At 10:15 on May 23, 1999, the main air compressor was started. At 11 o'clock, the molecular sieve adsorption device was put into operation, and the air separation system was started. At 12:48 on the 24th, the supercharger was started. At 13:30, two expansions were started. Start the cooling equipment; start P3366A, B at 3 o'clock on the 26th; start P3568A, B at 2 o'clock on the 27th; start P3369A, B at 7:55; start P4566A, B at 12 o'clock, then the unit is designed according to 100% Operation, ie the amount of processed air is
300000m 3 / h, oxygen production is 60,000m 3 / h, liquid oxygen, liquid nitrogen products have begun normal production, began to adjust the production conditions of the secondary crude argon column, reducing the control pressure of the tower, PIC4112 is 22kPa, PIC4111 It is about 30kPa to increase the rising steam and reflux liquid into the tower. At the same time, it pays great attention to the stability of the main tower system. Pay special attention to the stability of each flow and liquid level that is easy to fluctuate. The change of the valve opening cannot be done every time. Large; when the operating conditions fluctuate greatly, it can be changed to manual slow adjustment.
After a series of trial runs and exploring the optimal range of main control parameters, the purity, pressure and output of oxygen and nitrogen products are all within the required range. On June 3, high-pressure oxygen and nitrogen products were sent to users. Pipe network, on June 8th, the medium pressure nitrogen was sent to the user pipe network through a nitrogen press. Moreover, the operation of the refined argon column T4112 was started. On June 9th, the qualified liquid argon product was sent to the storage tank for replacement. After the analysis, the liquid argon was qualified, and the cold driving operation was completely completed.
313 performance assessment During the operation of the equipment, each analytical instrument was verified and the working status of each flowmeter was performed. The measurement accuracy was checked and confirmed, and the electrical inspection points related to the assessment were also confirmed to ensure the accuracy, authenticity and reliability of the performance assessment.
During the inspection, it was found that the data at the same time indicated by the main flow measurement point completely conformed to the calculation result of the material balance theory, and basically no correction was needed. See the results of the assessment. The group data of typical working conditions and variable load conditions are listed.
It can be seen from the variable load data that the oxygen extraction rate is basically unchanged, and each group basically conforms to the simple calculation formula that the amount of processed air is approximately equal to 5:1. When the load is small, the resistance of each distillation column is small, and the system pressure is low; when the load is 70%, the vent valve after the air compressor has a certain opening degree, indicating that the energy saving efficiency after the variable load is reduced.
However, in 70% of C operating conditions, argon production is stable and the product is qualified. From the temperature difference of the main hot and cold end, the minimum temperature difference is only 018 ° C, the maximum temperature difference is 318 ° C, less reheating, less cold damage, liquid production is guaranteed.
4Comprehensive comments The overall layout of the air separation cold box is simple and convenient, and the installation is convenient; the internal compression process overcomes the accumulation of dangerous impurities such as hydrocarbons that the original equipment has been unable to solve, which leads to the possibility of explosion and increases the bad atmosphere. The adaptability of conditions, especially for the air environment of chemical plants, is more suitable; automatic tracking of four variable load conditions, easy operation, low failure rate, reliable and stable operation for a long time; all economic and technical indicators are at The world's advanced level, oxygen extraction rate is 9912%, oxygen consumption unit consumption is 0138kWh / m 3 O 2, compressed product oxygen (nitrogen, argon) up to 310MPa sent to the user pipe network, its unit product compression power consumption 01169kWh / m 3; The extraction rate of argon is 8511%. The technical level of the two Linde 30,000m 3 / h oxygen generators introduced by WISCO has increased a big step.
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