More information is needed for the hot-state assessment!

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Hot-state testing of reactors and high-pressure systems I. Purpose of hot-state testing Hot-state testing is carried out on high-pressure hydrogen systems and high-temperature components in order to determine whether key equipment such as heaters, reactor internals, high-pressure heat exchangers, high-pressure separators, and high-pressure air coolers meet the requirements for operation. It also serves to check the sensitivity of instruments, as well as to remove any residual water from the reaction system. II. Heat test carrier gas: Nitrogen III. Working conditions required prior to the heat test 1. The reactor and high-pressure system must be airtight when filled with 8.0 MPa nitrogen ； 2. The nitrogen pressure in the reaction system was reduced to 3.0 MPa, and both the new hydrogen generator and the circulation pump were able to operate normally ； 3. The interlock verification of the reaction system has been completed and it is operating normally; the control valves of the high-pressure system have been adjusted properly ； 4. High-pressure air cooling unit A-101, new hydrogen return cooler E-104 – all are operating normally during trial operation, etc ； 5. The heating furnace F-101 has been completed drying, and it has been checked to be in good condition: the furnace chamber is clean with no debris, the burners are unobstructed, the thermocouples on the surface of the furnace tubes are properly insulated, the fire suppression steam system works normally, and it has been confirmed that the blind flanges in front of each burner’s manual valve are in place for isolation. IV. Steps for thermal performance testing 1. Igniting and heating furnace F-101 (1) Operate the circulator K-102 at its maximum speed, maintaining the system pressure at around 3.0 MPa. (2) Start the air-cooling fan A-101. (3) The flue gas from the F-101 convection chamber is directed to the atmosphere, breaking the connection with the fractional distillation reboiler F-201. (4) Verify that the oxygen content in the flue gas and gas from the analysis furnace is within acceptable limits, then ignite it in accordance with the operating procedures for heater F-101. Note: Turn on one burner and remove the blind flange of the burner manual valve. (5) After igniting the F-101, increase the furnace outlet temperature at a rate of 20°C/h until it reaches 200°C and remains constant. 2. Heating up of the reaction system and thermal performance testing: (1) When heating the cold reactor, it is necessary to comply with the temperature rise limitations for the reactor; that is, until the temperature at the lowest point of the reactor and its heat exchangers drops below 93°C, the heating rate must be kept below 30°C/h. The temperature at the reactor inlet shall not exceed the lowest surface temperature by more than 167°C. (2) During the process of raising the temperature at the outlet of the heating furnace to ≤200°C, it is necessary to strictly follow the temperature-raising constraints for the reactor; the wall temperature of the reactor should be increased gradually to above 93°C, while ensuring that the temperature at the inlet of the hot high-pressure stream reaches the specified value and remains there for a certain period of time. During the heating process, control the furnace outlet temperature as soon as possible by putting TIC8103/A and B into automatic mode. Refer to Figure 1 for the heating curve of the hot-state test. (3) During the heating process, start up high-pressure air coolers A-101/A to H in sequence, put the frequency converter controller and temperature controller TIC-8106 into operation, to control the outlet temperature of the air coolers at around 49°C. (4) Slowly increase the furnace outlet temperature to 250°C and maintain it at this level, while tightening the high-pressure flanges in the reaction system. Continue to raise the temperature to 300°C and 370°C respectively and maintain it at those levels, then thermally tighten each high-pressure flange in the reaction system. (5) The system pressure increases as the air flow temperature rises; control the emission to maintain the system pressure PIC-8106 at 3.0 MPa. (6) During the hot-state testing, strengthen the inspection of the pipelines for high-pressure equipment. When the reactor inlet temperature reaches four different constant temperatures of 200°C, 250°C, 300°C, and 370°C, personnel should be assigned to inspect the equipment pipelines after each temperature increase, and records should be kept regarding the condition of spring hangers, pipeline supports, and equipment displacement, with particular emphasis placed on the inspection of the pipelines for high-pressure equipment. Once severe thermal expansion is detected and it poses a threat to the safety of the equipment and pipelines, the load on the heating furnace should be reduced immediately, while the speed of the circulation pump should be increased; in severe cases, thermal testing should be stopped. (7) During the hot-state testing, it is still necessary to verify the airtightness of each sealing point in the reaction system under hot conditions, to ensure that all such points meet the sealing requirements when in operation at high temperatures. (8) During the system heating process, the condensed water formed as a result of drying collects in the cold high-pressure vessel D-105. The interface controller LIC-8103 is used to discharge this water into the drain (when the sulfur-containing wastewater system is not ready for use). In addition, all condensate discharge ports, sampling ports, instrument ducts, and dead-end pipelines are purged to remove the condensed water from the system. (9) The system is heated to 370°C at the reactor inlet and maintained at this temperature for 24 hours; once the water volume in the cold high-pressure section is less than 0.5 liters per hour, the thermal performance test of the reaction system is completed. 3. Cooling of the reaction system: The heating furnace F-101 is cooled at a rate of 20°C/h. During the cooling and depressurization process of the reactor, the following constraints must always be followed: (1) Before the temperature at the lowest point of the reactor and the heat exchanger drops to 93°C, the cooling rate must be kept below 30°C/h, and the temperature at the reactor inlet must not be lower than 167°C above the lowest surface temperature. (2) When the furnace temperature drops below 250°C, shut down the heating furnace, open all the ventilation doors in the furnace, and continue the cooling process through circulation. (3) Keep the new hydrogen compressor K-101 running, and supply nitrogen to the reaction system using low-pressure nitrogen from buffer tank D107 at the compressor inlet, via the return line at K101’s outlet, in order to maintain the system pressure at 3.0 MPa. (4) Keep the circulator running to continue the cooling process via circulation. 4. Perform a pressure test for hydrogen gas in the reaction system. (1) Keep the circulator operating until the temperature at the reactor inlet is below 50°C; isolate the nitrogen in D107 using a blind flange, then introduce hydrogen into the system to increase the pressure, and conduct pressure tests at 4.0 MPa, 6.0 MPa, and 8.0 MPa for the reaction system. (2) Keep the circulator running to continue cooling through circulation; once the reactor wall temperature drops below 60°C, stop the fresh hydrogen pump and the circulator, and verify that the system pressure drop is less than 0.01 MPa. (3) Release the system pressure using FV8108 or UV8110. ? (4) Perform nitrogen purging; once the hydrocarbon + hydrogen content in the system is below 0.5%, hand over the task to the maintenance team to carry out inspections following a hot-state test. 5. Inspection after hot-state testing: Before opening the reactor, heat exchangers, etc. for inspection, they should first be purged with industrial air. Sampling analysis must show that the oxygen content is at least 20%, and the system must be thoroughly isolated (see the reactor blind flange isolation procedure in the catalyst loading plan) before inspection can proceed. (1) Check whether the internal components are deformed and whether the gaps between the components meet the specified requirements. (2) Check whether there is any looseness among the fasteners and whether the blister pack is loose. (3) Check whether the support mesh is flat and free of deformation, and whether there are any gaps in its contact with the vessel wall. (4) Check whether the cold hydrogen tube is deformed. (5) Check whether each thermocouple is deformed and whether there are any abnormalities in its connection to the vessel wall. (6) After all the inspections are completed, make proper records and address each of the identified issues one by one. Appendix: Temperature curve for hot-state testing