Q&A on Ammonia Synthesis Plants

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I. True or False Questions 1. Since there have been no significant changes in the ammonia synthesis plants over the past three years, it is not necessary to revise the operating procedures. ( ) Answer: × Explanation: According to the \"Guiding Opinions of the State Administration of Work Safety on Strengthening the Safety Management of Chemical Processes\" (An Jian Zong Guan San [2013] No. 88), enterprises shall verify the suitability and effectiveness of their operating procedures and process cards on an annual basis. The operating procedures should be reviewed and revised at least every three years. When there are significant changes in process technology or equipment, the operating procedures should be reviewed and revised promptly. 2. The ammonia and methanol production plant has developed job operation procedures, so it is not necessary to create process cards. ( ) Answer: × Explanation: The Appendix to the \"Guidelines for the Identification and Rectification of Safety Risks and Hazards in Hazardous Chemical Enterprises\" (2019), namely the Table for Identifying Safety Risks and Hazards During Plant Operation, requires that the values indicated on the field instruments, as well as the DCS control values, should be consistent with the control values specified in the process cards. 3. At a certain pressure point in the ammonia synthesis plant, an alarm is triggered when the gas flow rate fluctuates; once the gas flow rate stabilizes, the alarm stops, and no inspection or recording is required. ( ) Answer: × Explanation: The Appendix to the \"Guidelines for Identifying and Addressing Safety Risks and Hazards in Hazardous Chemical Enterprises\" (2019), namely the Table for Identifying Safety Risks and Hazards During Plant Operation, requires enterprises to maintain records of operational activities, to monitor and inspect operating conditions on a regular basis, to address process alarms promptly, and to keep records of such actions. 4. Short-term overheating in the ammonia synthesis tower has no impact on production; no action is required as long as it is not a prolonged overheating situation. ( ) Answer: × Explanation: The Appendix to the \"Guidelines for Identifying and Addressing Safety Risks and Hazards in Hazardous Chemical Enterprises\" (2019), namely the Table for Identifying Safety Risks and Hazards During Plant Operation, requires that conditions such as overheating, overpressure, and excessive liquid levels must not occur during production ； The handling of abnormal operating conditions shall comply with the requirements of the operating procedures. II. Multiple-choice Questions 1. The carbon monoxide shift reaction is ( ). A. Reversible reaction B. Irreversible reaction C. Decomposition reaction D. Displacement reaction Answer: A Explanation: According to the \"Operating Procedures for the Shift Process in Ammonia Synthesis Plants\", 3.1 H2O + CO ⇌ CO2 + H2 + ΔH; under standard conditions, ΔH = -41.16 kJ/mol. The characteristics of this reaction are: high temperature and pressure, reversibility, exothermic nature, and the use of a catalyst. 2. The cobalt-molybdenum catalyst for the carbon monoxide conversion reaction needs to be sulfided before use, and the purpose is ( ). A. Improve the high-temperature resistance of the catalyst. B. Increase its selectivity during use. C. Endow it with activity. D. Give it toxicity resistance. Answer: C. Explanation: According to the \"Operating Procedures for the Shifts in the Ammonia Synthesis Plant – Section 6.2.2 Catalyst Sulfidation\", sulfur-resistant shift catalysts are in an oxidized state before use; they need to be sulfided in order to exhibit good catalytic activity. Generally, CS2 or H2S is used for sulfidation, in combination with hydrogen and nitrogen. 3. To extend the service life of the conversion catalyst, the inlet temperature should be maintained above the water vapor dew point by more than () °C during normal operation. A、10 B、15 C、20 D、25 Answer: D Explanation: According to the \"Operating Procedures for the Shifts in the Ammonia Synthesis Plant – Conversion Process\", 6.3.1 Normal operation of the catalyst: To extend the catalyst’s service life, it is necessary to maintain a low inlet temperature during normal operation (at least 25°C above the water vapor dew point), and to keep various operational parameters such as temperature, pressure, water/gas ratio, and hydrogen sulfide concentration stable. This helps to reduce the number of startups and shutdowns, and to avoid operating under conditions with no sulfur or too low sulfur content. 4. Which of the following pumps has the highest rated power? ( ) A、P04201 B、P04202 C、P04204 D、P04205 Answer: D Explanation: According to the \"Operating Procedures for Acid Gas Removal in Ammonia Synthesis Plants\", the rated power of P04201 is 110 Kw, that of P04202 is 132 Kw, that of P04204 is 400 Kw, and that of P04205 is 1600 Kw. III. Multiple-choice Questions 1. The characteristics of the carbon monoxide shift reaction are ( ). A. High temperature and high pressure B. Catalyst C. Reversible D. Exothermic Answer: ABCD Explanation: According to the \"Operating Procedures for the Shift Process in Ammonia Synthesis Plants\", 3.1 H2O+CO⇋CO2+H2+△H; the characteristics of this reaction are high temperature and high pressure, reversibility, exothermic nature, and the use of a catalyst. 2. The gas to be removed by liquid nitrogen washing is ( ). A. CO2 B. H2S C. CH4 D. CO Answer: CD Explanation: According to the \"Operating Procedures for the Gas Purification Process in Ammonia Synthesis Plants\", 1.1 The purpose of this process is to remove toxic substances such as carbon monoxide and methane, which are harmful to ammonia synthesis, as well as inert gases, from the purified gas obtained through low-temperature methanol washing. This enables the production of pure synthesis gas, with the hydrogen-to-nitrogen ratio in the final synthesis gas being adjusted to 3:1. Common Knowledge Q&A on Ammonia Synthesis Plants 2 I. True or False Questions 1. To avoid production fluctuations that lead to shutdowns and reduced output, process engineers determine that interlocks with minimal impact on safety can be temporarily disabled without the need for documentation. ( ) Answer: × Explanation: The Appendix to the \"Guidelines for Identifying and Addressing Safety Risks and Hazards in Hazardous Chemical Enterprises\" (2019), namely the Table for Identifying Safety Risks and Hazards Related to Plant Operation, requires that enterprises strictly implement interlock management systems and meet the following requirements: 1. The on-site interlock devices must be in use and in good condition ； 2. Removing interlocks requires approval procedures and safety measures ； Restoring interlocking is carried out in accordance with the prescribed procedures. 2. To recover the exhaust gas from the process, an additional pipeline was added to the liquid nitrogen washing step for ammonia synthesis. After analyzing the risks associated with its use, the technical staff concluded that it would not affect the safe operation of the existing plant, so it was not necessary to go through the procedures for process modification. ( ) Answer: × Explanation: The Appendix to the \"Guidelines for Identifying and Addressing Safety Risks and Hazards in Hazardous Chemical Enterprises\" (2019), namely the Table for Identifying Safety Risks and Hazards Associated with Plant Operation, requires that when there are changes in the process route, control parameters, raw materials, etc., a change management system must be strictly followed, and a safety risk analysis of such changes must be conducted ； After the change, the relevant operating procedures should be revised, and the relevant personnel should be trained. 3. An operator involved in ammonia synthesis, drawing on years of experience, believes that the range of process parameters specified in the newly revised operating procedures is too strict; it is possible to operate within a broader range based on one’s own experience. ( ) Answer: × Explanation: The Appendix to the \"Guidelines for Identifying and Addressing Safety Risks and Hazards in Hazardous Chemical Enterprises\" (2019), namely the Table for Identifying Safety Risks and Hazards During Plant Operation, requires enterprises to establish operation records and shift handover management systems, and to meet the following requirements: 1. Strictly adhere to operating procedures and carry out operations in accordance with the specified process parameters ； 2. Conduct routine inspections as required, with operation records kept ； 3. Strictly implement the shift handover system. 4. During the commissioning of the ammonia synthesis plant, operations are intense; documents such as purging procedures, airtightness checks, and operation tickets can be completed after the plant has stabilized in operation. ( ) Answer: × Explanation: The Annex to the \"Guidelines for Identifying and Addressing Safety Risks and Hazards in Hazardous Chemical Enterprises\" (2019), namely the Table for Identifying Safety Risks and Hazards During Plant Operation, requires that enterprises sign off on the following key steps prior to starting up the plant: 1. When carrying out flushing, purging, and airtightness tests, it is necessary to confirm that effective safety measures have been put in place ； 2. Before introducing steam, nitrogen, or flammable and explosive substances, experienced professionals must be assigned to verify the process ； 3. When introducing materials, it is necessary to continuously monitor changes in parameters such as material flow rate, temperature, pressure, and liquid level to ensure that the process is operating correctly. II. Multiple-choice Questions 1. What temperature should be maintained above for the wastewater from Tower 5 of acid dehydration? A、135 B、136 C、138 D、140 Answer: C Explanation: According to the \"Operating Procedures for Acid Gas Removal in Ammonia Synthesis Plants\", the control range for the outlet temperature TI042098 at the bottom of tower C04205 is 138–143°C. 2. The control range for the inlet temperature TIC04106 of the first converter in ammonia synthesis is ( ) °C. A、120～200 B、245～310 C、320～350 D、365～400 Answer: B Explanation: According to Section 6.3 of the \"Technical Specifications for Ammonia Synthesis Production Processes\", these are the process control parameters for various stages of the production process. 3. The hydrogen-to-nitrogen ratio of the syngas leaving the liquid nitrogen washing unit should be ( ). A、3:2 B、3:1 C、1:3 D、2.5:1 Answer: B Explanation: According to the \"Operating Procedures for the Ammonia Synthesis Process in Ammonia Production Plants\", 3.1 states that the ammonia synthesis reaction is 3H2 + N2 ⇋ 2NH3 + ΔH. 4. The correct sequence for washing the molecular sieve with liquid nitrogen is (). A. Adsorption, pressure relief, purging, heating, cooling, pressing, parallel operation, adsorption B. Adsorption, purging, pressure relief, heating, cooling, pressing, parallel operation, adsorption C. Adsorption, pressure relief, purging, cooling, heating, pressing, parallel operation, adsorption D. Adsorption, pressure relief, heating, purging, cooling, pressing, parallel operation, adsorption Answer: D Explanation: According to the \"Operating Procedures for the Gas Purification Process in Ammonia Synthesis Plants\" 5.3.1.1, the sequential steps for treating molecular sieves with liquid nitrogen are adsorption, pressure relief, purging, heating, cooling, pressing, parallel operation, adsorption. The molecular sieve adsorbers Z04301 A and Z04301 B are used alternately; when one adsorber is in the adsorption mode, the other is in the regeneration mode. III. Multiple-choice Questions 1. The possible causes of surge in ammonia synthesis compressors are ( ). A. The compressor inlet filter is clogged. B. The volume of air entering the compressor is too low. C. The inlet temperature is too high. D. The anti-surge valve is malfunctioning. Answer: ABCD. Explanation: According to the \"Operating Procedures for the Syngas Compression Unit in Ammonia Synthesis Plants\", 5.5.7, the causes of compressor surge can be a clogged compressor inlet filter, too low an air flow rate into the compressor, or too high an inlet temperature. The unit speed indication is low, and the anti-stall controller cannot function properly. Stall prevention valve failure. Large fluctuations in the air volume or pressure of the refrigeration system, overpressure, etc. Inter-stage cooler efficiency drops or water supply is interrupted. The unit’s speed is unstable: the voltage rises too quickly when starting up, and the speed drops too rapidly when shutting down or reducing load. 2. The phenomena of high-pressure steam interruption in the ammonia synthesis compressor include ( ). A. The high-pressure steam pressure PT04487 drops rapidly. B. The steam pressure alarm on the auxiliary control panel sounds. C. The position of the steam throttle valve in the turbine rises quickly. D. The speed of the compressor drops rapidly. Answer: ABCD. Explanation: According to the \"Operating Procedures for the Syngas Compression Unit in Ammonia Synthesis Plants\", 5.5.9 states that the symptoms of a disruption in high-pressure steam supply to the ammonia synthesis compressor include a rapid drop in the high-pressure steam pressure PT04487, as well as the activation of the steam pressure alarm on the auxiliary control panel. The steam throttle valve position of the turbine rises rapidly. The compressor speed drops rapidly. Common Knowledge Q&A on Ammonia Synthesis Plants 3 I. True or False Questions 1. The blind flanges on site have been numbered and labeled; therefore, when performing operations related to removing or installing these blind flanges, process engineers or operators do not need to conduct on-site verification. ( ) Answer: × Explanation: According to the Annex of the “Guidelines for Identifying and Rectifying Safety Hazards in Hazardous Chemicals Enterprises” (2019), namely the Checklist for Identifying Safety Hazards in Plant Operations, blind flange removal and installation operations must be carried out in a specified order following proper numbering, labeling, and registration procedures; furthermore, designated personnel must conduct on-site verification for each operation. 2. At the beginning of use, the ammonia synthesis shift catalyst should be operated at as low an activity temperature as possible. ( ) Answer: √ Explanation: According to the \"Operating Procedures for the Shift Process in Ammonia Synthesis Plants\", 5.3.1 states that at the beginning of use, the conversion catalyst should be operated at temperatures corresponding to its low activity level. If the catalyst is operated at high-activity temperatures from the start, it is as if the low-activity phase is skipped, which shortens the catalyst’s service life. 3. Under normal operation, the hotspot temperature in the shift converter is generally controlled by regulating the volume of inlet gas. In cases where the CO content is high, excessive reaction heat requires adjustment of the gas-to-vapor ratio in the shift converter in order to control the hotspot temperature of the bed. ( ) Answer: × Explanation: According to the \"Operating Procedures for the Shift Operation in the Ammonia Synthesis Plant – Section 5.3.1.1b\", under normal operation, the hot spot temperature of the converter is controlled by regulating the inlet temperature. In cases where the CO content is high, the excessive reaction heat requires adjustment of the steam-to-gas ratio fed into the converter in order to control the hot spot temperature of the catalyst bed. 4. Adjusting the load by adding or removing it is achieved by controlling the temperature of the corresponding converter and the H2 output value. ( ) Answer: × Explanation: According to the \"Operating Procedures for the Shifts in the Ammonia Synthesis Plant’s Shift Process\" section 5.3.2, adjusting the load on the shift unit is achieved by controlling the temperature of the corresponding shift furnace as well as the CO level at its outlet. II. Single-choice Questions 1. The control range of the hot spot temperature TI04105C in the first ammonia synthesis converter is ( ) °C. A、245～310 B、320～375 C、380～405 D、410～475 Answer: D Explanation: According to the \"Operating Procedures for the Shifts in the Ammonia Synthesis Plant’s Shift Process\" section 5.4.1 – Process Parameters, the control range for the temperature of the purified gas at the top of tower C04211, indicated by TI042010, is ( ) °C. A、-45～-38 B、-50～-40 C、-54～-45 D、-60～-54 Answer: C Explanation: According to Section 6.3 of the \"Technical Regulations for Ammonia Synthesis Production Processes\", these are the process control parameters for various stages of the production process. 3. In the ammonia synthesis reaction, as the temperature increases, the equilibrium ammonia concentration ( ). A. Increase B. Decrease C. Remain unchanged D. Unaffected Answer: B Explanation: According to the \"Operating Procedures for the Ammonia Synthesis Process in Ammonia Production Plants\", 3.1 The ammonia synthesis reaction is an exothermic, reversible chemical reaction that results in a decrease in volume, and it takes place under specific conditions of pressure, temperature, and catalyst presence. When the gas passes through the catalyst layer, only a portion of the hydrogen and nitrogen is converted into ammonia; high pressure and low temperature help to increase the equilibrium concentration of ammonia. 4. The cooling principle of the ammonia cooler relies on the () stage of the refrigeration cycle. A. Compression B. Condensation C. Expansion D. Evaporation Answer: D Explanation: According to the \"Operating Procedures for the Refrigeration Unit in Ammonia Synthesis Plants\", 3.1.1 Liquid ammonia is sent to the refrigeration points of various ammonia coolers in the butyl octanol plant, acetic acid plant, air separation plant, methanol washing plant, and ammonia synthesis plant. There, it evaporates at low pressure; by absorbing heat, liquid ammonia transforms into gaseous ammonia, which then absorbs a large amount of heat from the process fluids that require cooling, thereby lowering their temperature and achieving the purpose of cooling. The gaseous ammonia then returns to the compressor for compression, condensation, and reuse. III. Multiple-choice Questions 1. The startup heater (F04501) provides energy for the catalyst ( ) during startup. A. Heating up B. Reduction C. Oxidation D. Sulfurization Answer: AB Explanation: According to the \"Operating Procedures for the Ammonia Synthesis Unit in Ammonia Synthesis Plants\", section 3.2, there is also a startup heating furnace (F04501) in such plants. The fuel gas derived from gasification, after gas-liquid separation, is used to provide the energy needed to heat up and reduce the catalyst during startup. 2. Which of the following changes in conditions will cause an increase in pressure in the ammonia synthesis system? ( ) A. Increase in the amount of fresh gas B. Increase in the circulation volume C. Increase in the content of inert gases D. Increase in the ammonia content at the inlet of the synthesis tower. Answer: ABCD. Explanation: According to Section 5.3.2.3(6) of the \"Operating Procedures for the Ammonia Synthesis Unit,\" changes in the following conditions will lead to an increase in system pressure, while the opposite will result in a decrease in pressure: a. Increase in the amount of fresh gas ； b. Increased circulation volume ； c. Increase in inert gas content ； d. Increase in ammonia content at the inlet of the synthesis tower ； e. When the inlet temperature of the bed layer increases or decreases by a few degrees, it changes the currently optimal temperature ； f. When the hydrogen-to-nitrogen ratio is adjusted to below 2.5 or above 3.0 ； g. Decreased catalyst activity. Common Q&A on ammonia synthesis plants 4. I. True or False questions. 1. When the load of the shifted gas is too high, it is necessary to contact the central control room to reduce the load on the post-shift system or open the unshifted gas vent valve. ( ) Answer: √ Explanation: According to the \"Operating Procedures for the Shifts in the Ammonia Synthesis Plant’s Shift Reaction Unit\", 5.5.1 states that when the load on the shift reaction gas is too high, it is necessary to contact the control room in order to reduce the load on the system after the shift reaction, or to open PV04109 to allow unprocessed gas to be vented. 2. Once the methanol cycle in the low-temperature methanol washing process is established, the system temperature must not exceed 50°C; the ammonia cooler must be put into operation before the temperature reaches 45°C. ( ) Answer: √ Explanation: According to the \"Operating Procedures for Acid Gas Removal in Ammonia Synthesis Plants\", 5.1.1.6 states that once the methanol cycle is established, the system temperature must not exceed 50°C. The ammonia cooler must be activated before the temperature reaches 45°C, in order to prevent cavitation in the pumps and damage to the insulation materials. 3. When removing methanol from the low-temperature methanol washing shutdown system, the system should be depressurized in the order of low pressure first, followed by high pressure. ( ) Answer: × Explanation: According to the \"Operating Procedures for Acid Gas Removal in Ammonia Synthesis Plants\", section 5.2.1 on precautions for depressuring the system, the depressurization process must be carried out in order, starting with high-pressure areas before moving on to low-pressure areas. When draining liquid, only 1–2 drain valves should be opened at a time. Meanwhile, when draining liquid from the lowest points of the pipes, the relevant manual valves and control valves must be opened as appropriate, in order to ensure that as much methanol as possible is removed from the pipes. 4. When faults occur in the butanol and octanol plant, the acetic acid plant, and the CO cryogenic tank unit downstream of the untreated gas, the purified untreated gas can be sent to the flare via the pressure control valve PV042014.B. ( ) Answer: √ Explanation: According to the \"Operating Procedures for Acid Gas Removal in Ammonia Synthesis Plants\", section 5.2.3(10), when there are faults in the butanol and octanol production units, the acetic acid production unit, and the CO cooling unit located downstream of the untransformed gas stream, the purified untransformed gas can be sent to the flare via the pressure control valve PV042014.B. II. Multiple-choice Questions 1. The control range for the CO2 content in syngas purified by low-temperature methanol washing is ( ) ppm. A、<10 B、<18 C、<20 D、<25 Answer: A Explanation: \"Operating Procedures for Acid Gas Removal in Ammonia Synthesis Plants\" 1.2 Raw Materials and Product Specifications (2) Main Products. 2. The control range for the nitrogen temperature TI043060 during liquid nitrogen washing is ( ) °C. A、-180～-186 B、-186～-195 C、-166～-175 D、-176～-180 Answer: B Explanation: Table of alarm interlocks in 5.4.2 of the \"Operating Procedures for the Gas Purification Process in Ammonia Synthesis Plants\". 3. The purified gas first passes through a molecular sieve to remove small amounts of CO2 and methanol before entering the CO cryogenic box. There, deep cryogenic separation is employed, taking advantage of the differences in ( ) among various gas components, to achieve the separation of the gas mixture through low-temperature distillation. A. Ignition point B. Boiling point C. Molecular weight D. Solubility Answer: B Explanation: According to the \"Operating Procedures for the Carbon Monoxide Cooling Unit in Ammonia Synthesis Plants\", 3.1 The purified gas first passes through a molecular sieve to remove small amounts of CO2 and methanol before entering the CO cooling unit. There, deep cooling separation is employed, taking advantage of the differences in boiling points among various gas components, so as to achieve the separation of the gas mixture through low-temperature distillation. The resulting CO product is then pressurized using a CO compressor and sent to the acetic acid production plant. 4. The basic principle of pressure swing adsorption is to utilize the fact that adsorbents have different adsorption capacities for adsorbates at various partial pressures, and also possess the ability to selectively adsorb various components of a gas mixture to be separated under certain pressures. By applying pressure, impurity components in the feed gas are removed, thereby regenerating the adsorbent. A. Temperature increase for desorption B. Temperature decrease for desorption C. Pressure increase for desorption D. Pressure decrease for desorption Answer: D Explanation: According to the \"Operating Procedures for PSA Units in Ammonia Synthesis Plants\", 3.1 The basic principle of pressure swing adsorption is based on the fact that adsorbents have different adsorption capacities for adsorbates at various partial pressures, and they also possess the ability to selectively adsorb various components of a gas mixture to be separated under certain pressures. Pressure increase is used to remove impurity components from the feed gas, while pressure decrease is used to desorb these impurities, thereby regenerating the adsorbent. III. Multiple-choice questions 1. Possible reasons for a decrease in the temperature of the ammonia synthesis catalyst layer and an increase in system pressure are ( ). A. High levels of CO+CO2 can cause the catalyst to become poisoned and inactive. B. High ammonia content in the material entering the synthesis tower. C. Low ammonia content in the material entering the synthesis tower. D. An imbalance in the hydrogen-to-nitrogen ratio. Answer: ABD. Explanation: According to the \"Operating Procedures for the Ammonia Synthesis Unit,\" 5.5.1 A drop in the temperature of the catalyst layer and an increase in system pressure may be caused by high levels of CO+CO2, which lead to catalyst poisoning and inactivity. The ammonia content in the synthesis tower is high. Imbalance in the hydrogen-to-nitrogen ratio. 2. The purpose of installing an inter-stage cooler in an ice machine is ( ). A. Reduce the steam temperature. B. Reduce the temperature of the compressed gas. C. Minimize compression work as much as possible. D. Increase the pressure of ammonia gas. Answer: BC. Explanation: According to the operating procedures for ammonia synthesis refrigeration systems, section 3.1.2 states that inter-stage coolers are used in the unit to reduce the temperature of the compressed gas and thereby minimize compression work. Common Questions and Answers on Ammonia Synthesis Plants 5 I. True or False Questions 1. When adjusting the load in the ammonia synthesis process, it is necessary to do so slowly; while increasing the amount of air supplied, the circulation rate of methanol should be reduced gradually to ensure that the purity standards of the purified gas are met. ( ) Answer: × Explanation: According to the \"Operating Procedures for Acid Gas Removal in Ammonia Synthesis Plants\", section 5.3.1, the speed at which load is increased or decreased must be slow; when the amount of inlet gas is increased, the circulation rate of methanol must also be increased to ensure that the purity standards of the purified gas are met. 2. The heat balance of the acid stripping system is a key factor affecting the proper operation of the plant; in cases where there is insufficient cooling capacity, it is possible to appropriately lower the liquid level in each ammonia cooler in order to increase the amount of cooling provided. ( ) Answer: × Explanation: According to the \"Operating Procedures for Acid Gas Removal in Ammonia Synthesis Plants\", section 5.3.2, the heat balance of the acid gas removal system is a key factor that affects the proper operation of the plant. When there is insufficient cooling capacity, it is possible to increase the liquid level in the various ammonia coolers in order to provide more cooling capacity. 3. During load adjustment, it is necessary to promptly increase the low-pressure steam flow rates of C04204, C04205, and synthetic ammonia C04210 in order to ensure effective methanol regeneration and methanol-water separation. ( ) Answer: √ Explanation: According to the \"Operating Procedures for Acid Gas Removal in Ammonia Synthesis Plants\", 5.3.4.2.3, while adjusting the load, it is necessary to increase the flow rate of low-pressure steam in C04204, C04205, and C04210 related to ammonia synthesis, in order to ensure effective methanol regeneration and methanol-water separation. 4. During normal operation, if there are significant fluctuations in the temperature, pressure, level, and flow rates displayed on the DCS screen, and it is determined that these values are due to faulty instruments, the system should be stopped immediately. ( ) Answer: × Explanation: According to the \"Operating Procedures for Acid Gas Removal in Ammonia Synthesis Plants\" section 5.3.5.2, during normal operation, if there are significant fluctuations in the temperature, pressure, liquid level, and flow rates displayed on the DCS screen, and it is determined that these are false readings from the instruments, the corresponding control valves should be switched to manual mode immediately to restore stable operation of the plant. II. Single-choice questions
1. The control range of the shaft vibration VISA-04433/34 for the high-pressure cylinder of the synthetic ammonia compressor is ( ) μm. A. <11 B. <21 C. <31 D. <41 Answer: C Explanation: Section 6.3 of the “Technical Regulations for Ammonia Synthesis Production Process” regarding the process control indicators for each step. 2. The control range for the liquid level LIC-04531 in the high-pressure ammonia separator for ammonia synthesis is ( )%. A. 10–15 B. 20–30 C. 30–50 D. 50–70 Answer: C Explanation: Section 6.3 of the “Technical Regulations for Ammonia Synthesis Production Process” outlines the process control indicators for each step. 3. The smooth operation of the carbon monoxide compressor system is directly related to the proper functioning of the ( ) unit. A. Ammonia-soda process B. Butanol and octanol C. Acetic acid D. PDH unit Answer: C Explanation: According to the “Operating Procedures for the Carbon Monoxide Compressor in Ammonia Synthesis Plants”, the stable operation of the compressor system is directly related to the proper functioning of the acetic acid production plant. 4. The condensate from the torch separation tank is pressurized by a pump and sent to ( ). A. Sewage treatment system B. Rainwater well C. Emergency water well D. Methanol condensate tank Answer: A Explanation: According to the \"Operating Procedures for the Torch Unit in Ammonia Synthesis Plants\", the condensate from the separation tank is pressurized using a pump and then sent to the sewage treatment system. III. Multiple-choice Questions 1. In the event of any one of the following situations, the refrigeration system should be shut down urgently ( ). A. Failure of the ammonia compressor (K04701) B. Fluctuations in load C. Rupture or fire in the pipes and equipment of the refrigeration system D. Massive leakage of gaseous and liquid ammonia. Answer: ACD. Explanation: According to the \"Operating Procedures for Ammonia Synthesis Refrigeration Systems\" 5.2.2.3, the system should be shut down urgently in case of any of the following situations: a. Failure of the ammonia compressor (K04701) ； b. Bursting or fire in the pipes of the refrigeration system equipment ； c、Massive leakage of gaseous and liquid ammonia. 2. What measures can be taken if the high-pressure steam pressure of the turbine in the freezing process is low? ( ) A. Reduce the load; B. Adjust the steam parameters to normal levels; C. Shut down the system in case of liquid hammer; D. Increase the load. Answer: ABC. Explanation: According to Section 5.5.2 of the “Operating Procedures for the Ammonia Synthesis Refrigeration Unit”, when the main steam parameters are too low, measures include reducing the load and adjusting the steam parameters to normal levels. In the event of liquid hammer, the system must be shut down. Common Knowledge Q&A on Ammonia Synthesis Plants 6 I. True or False Questions 1. When it is necessary to shut down a heat exchanger after shutting down the plant, it is sufficient to close only the on-site valves for the cooling water and steam inlet of the heat exchanger. ( ) Answer: × Explanation: According to the \"Operating Procedures for Acid Gas Removal in Ammonia Synthesis Plants\", 5.3.5.4 states that after the heat exchanger is put into operation, it is necessary to monitor whether there is water hammer or pipeline vibration at the site; if such conditions occur, the inlet and outlet valves of the heat exchanger should be closed immediately, and water and air should be removed again. When it is necessary to shut down the heat exchanger after stopping production, the on-site valves for the cooling water and steam inlet and outlet of the heat exchanger must be closed. 2. All control valves for liquid level, flow rate, pressure, etc., in the acid removal system failed to operate; the cause of the incident was an interruption in instrument air supply. ( ) Answer: √ Explanation: Symptoms of an instrument air interruption accident as per the \"Operating Procedures for Acid Gas Removal in Ammonia Synthesis Plants\" 5.6.4 ； a. All control valves for liquid levels, flow rates, pressures, etc. have failed and cannot operate. b. Interruption of methanol circulation in the acid removal system. c. The pressure increases throughout the system, while the flow rate decreases. d. Fluctuations occur in the liquid levels of various towers and flash tanks. e. The indicators of the purified gas at the tops of towers C04201 and C04211 exceed the standards. f. The current readings of each pump decrease during operation. 3. There is no need to turn the acid regeneration cycle gas compressor before starting it up. ( ) Answer: × Explanation: According to Annex 1.1(7) of the \"Operating Procedures for Acid Gas Removal in Ammonia Synthesis Units\", turn the crank handle to the \"Cranking\" position, start the oil pump, and maintain the oil pressure PI042905 at 0.35–0.4 MPa (slightly higher during startup). After the pressure stabilizes, check whether the filter oil pressure difference PDI042908 is normal. Start the turning motor and rotate it a few times to check whether the moving mechanism is functioning properly, so that an oil film is formed on the friction surfaces. 4. A portion of the crude syngas obtained through acid stripping enters either molecular sieve adsorbers Z04301 A or Z04301 B to remove small amounts of methanol and CO2; these two adsorbers can be used alternately. This step is taken to prevent methanol and CO2 from forming solids at low temperatures in the cold box, thereby blocking the pipes. ( ) Answer: √ Explanation: According to the \"Operating Procedures for the Gas Purification Process in Ammonia Synthesis Plants\", 3.2.1 states that a portion of the crude synthesis gas coming from the acid removal unit enters either molecular sieve adsorbers Z04301 A or Z04301 B in order to remove small amounts of methanol and CO2; these two adsorbers can be used alternately. This step is taken to prevent methanol and CO2 from forming solids at low temperatures in the cold box, thereby blocking the pipes. II. Multiple-choice Questions 1. The control range for the shaft vibration VSA04720-21 at the drive end of the low-pressure cylinder of the compressor in the refrigeration unit is ( ) μm. A、<63.5 B、<68.5 C、<73.5 D、<78.5 Answer: A Explanation: According to the \"Technical Specifications for Ammonia Synthesis Production Process\", Section 6.3 outlines the process control parameters for various stages of the process. 2. The control range for the liquid level LIC142130 of C14201 in the CO cold box unit of the ammonia synthesis plant is ( )%. A、10～50 B、20～60 C、30～70 D、40～80 Answer: D Explanation: According to the \"Technical Specifications for Ammonia Synthesis Production Process\", section 6.3 outlines the process control parameters for various stages of the process. 3. The low-pressure flare gas flows sequentially into the low-pressure flare condensate tank, water seal tank, flare cylinder, molecular seal, and flare tip; () is continuously introduced at the bottom of the cylinder to prevent backflow. A. Oxygen B. Nitrogen C. Air D. Carbon dioxide Answer: B Explanation: According to the \"Operating Procedures for the Torch Unit in Ammonia Synthesis Plants\", 3.2.3 states that low-pressure torch gas flows sequentially into the low-pressure torch condensate tank, water seal tank, torch cylinder, molecular seal, and torch tip; nitrogen is continuously introduced at the bottom of the cylinder to prevent backflow. 4. The temperature of the wastewater from Tower 5 in the acid removal process should be maintained above ( ) degrees. A、135 B、136 C、138 D、140 Answer: C Explanation: According to the \"Operating Procedures for Acid Gas Removal in Ammonia Synthesis Plants\", the control range for the outlet temperature TI042098 at the bottom of tower C04205 is 138–143. III. Multiple-choice questions 1. The methods for acid demethanolization regeneration are ( ). A. Vacuum flash desorption B. Stripping regeneration C. Thermal regeneration D. Cold regeneration Answer: ABC Explanation: According to the \"Operating Procedures for Acid Gas Removal in Ammonia Synthesis Plants\", 3.1 The methods for regenerating methanol removed through acid treatment include vacuum flash desorption, stripping regeneration, and thermal regeneration. 2. The CO cold box unit is responsible for removing ( ) from the purified, unconverted gas obtained through low-temperature methanol washing in the adsorption station, and then sending this gas to the cold box. The CO that is separated out is compressed using a CO compressor and sent to the acetic acid production facility, while the hydrogen-rich gas is sent to the PSA unit. A. Methanol B. Methane C. Carbon monoxide D. Carbon dioxide Answer: AD Explanation: According to the \"Operating Procedures for the Carbon Monoxide Cold Box\", 1.1 This position is responsible for sending the purified, unconverted gas obtained from low-temperature methanol washing to the adsorption unit, where methanol and CO2 are removed; thereafter, the gas is sent to the cold box to separate H2 from CO. The separated CO is compressed using a CO compressor and then sent to the acetic acid production facility, while the hydrogen-rich gas is sent to the PSA unit. Common Knowledge Q&A on Ammonia Synthesis Plants 7 I. True or False Questions 1. The purging procedure at the liquid nitrogen washing and adsorption station involves the purified gas coming from C04201 entering the adsorber from the top and exiting from the bottom; it then passes through filter JF04301 before entering the cold box. Removes CO2 and methanol from the purified gas. ( ) Answer: × Explanation: According to the \"Operating Procedures for the Gas Purification Process in Ammonia Synthesis Plants\", 5.3.1.1 – In the adsorption steps A1 to A9, the purified gas coming from C04201 enters the adsorber from the top and exits from the bottom; it then passes through filter JF04301 before entering the cold box. Removes CO2 and methanol from the purified gas. Purging P1 involves purging the adsorber with nitrogen (at 40°C at the inlet) before heating, after which this nitrogen is sent to C04203 of the low-temperature methanol wash unit. Purge P2 is the process by which the adsorber is purged with hot nitrogen (with the inlet temperature gradually increased from 40°C to 200°C) before heating; this nitrogen is sent to C04203 of the low-temperature methanol wash unit. 2. The cooling capacity required for the liquid nitrogen washing unit comes from: the flashing of the washing nitrogen in C04301, the throttling of the crude medium-pressure nitrogen gas, the throttling expansion at the bottom of S04301, and liquid nitrogen. ( ) Answer: √ Explanation: According to the \"Operating Procedures for the Gas Purification Process in Ammonia Synthesis Plants\", 5.3.2.5.1 Generation of cooling capacity: (1) The cooling capacity required by the liquid nitrogen washing unit comes from the flashing of the nitrogen being washed in C04301, the throttling of the crude medium-pressure nitrogen gas, the expansion due to pressure reduction at the bottom of S04301, and liquid nitrogen itself. (2) When the nitrogen being trapped generates an excess of cooling capacity, it will cause the liquid level in S04301 to rise; conversely, it will decrease. 3. High-pressure steam undergoes two main energy conversions within the turbine, enabling the turbine to perform work externally. The first energy conversion is the conversion of thermal energy into kinetic energy; this is achieved when high-pressure steam passes through nozzles (stator vanes), causing its pressure to drop and thus generating a high-speed airflow. The second energy conversion is the conversion of kinetic energy into mechanical energy; this is achieved by the impact force of high-speed steam acting on the moving blades, causing the rotor to rotate at high speed and thereby generating mechanical energy. ( ) Answer: √ Explanation: According to the \"Operating Procedures for the Syngas Compression Unit in Ammonia Synthesis Plants\", 3.1 Process Principle – High-pressure steam undergoes two energy conversions within the turbine, enabling the turbine to perform work externally. The first energy conversion is the conversion of thermal energy into kinetic energy; this is achieved when high-pressure steam passes through nozzles (stator vanes), causing its pressure to drop and thus generating a high-speed airflow. The second energy conversion is the conversion of kinetic energy into mechanical energy; this is achieved by the impact force of high-speed steam acting on the moving blades, causing the rotor to rotate at high speed and thereby generating mechanical energy. 4. Isolation gas must be supplied after the lubricating oil pump is started in the ammonia synthesis compressor. ( ) Answer: × Explanation: According to the \"Operating Procedures for the Syngas Compression Unit in Ammonia Synthesis Plants\", 5.1.1.2.1, isolation gas must be supplied before starting the lubricating oil pump. II. Multiple-choice Questions 1. The control range of the medium-pressure CO temperature TI142110 in vessel E14201, which is related to the CO cooling unit in the ammonia synthesis plant, is ( ) °C. A. -159 to -163 B. -153 to -159 C. -143 to -148 D. -137 to -142 Answer: B. Explanation: According to Section 6.3 “Process control indicators for each process step” in the “Technical Regulations for Ammonia Synthesis Production Process”, the controllable range of the shaft displacement ZI-142607 for the CO compressor in the ammonia synthesis unit is () mm. A、<0.25 B、<0.35 C、<0.45 D、<0.55 Answer: A Explanation: According to the \"Technical Specifications for Ammonia Synthesis Production Process\" section 6.3 on process control parameters for various stages, the ( ) streams of CO gas coming from the CO cooling box are sent to the CO compressors respectively. A. One B. Two C. Three D. Four Answer: B. Explanation: According to the \"Operating Procedures for Carbon Monoxide Compressors in Ammonia Synthesis Plants\", section 3.2, the two streams of carbon monoxide gas coming from the CO cooling tank are sent to the CO compressors respectively. The compressor has 3 stages of compression on each side; after each stage of compression, a cooler is used for cooling. Low-pressure CO is sent to the inlets of the first section (stages 1, 2, 3), while medium-pressure CO is sent to the inlets of the second section (stages 4, 5, 6). The carbon monoxide is compressed to the desired product pressure (around 3.4 MPa) and then sent to the boundary zone. 4. The PSA hydrogen production system utilizes fourteen adsorption towers, with () towers operating simultaneously, and employs a six-time pressure equalization purge process. . A、3 B、4 C、5 D、6 Answer: A Explanation: According to the \"Operating Procedures for PSA Units in Ammonia Synthesis Plants\", section 3.2, the hydrogen extraction system utilizes fourteen adsorption towers; three of these towers operate simultaneously for adsorption, with six pressure equalization and purge cycles being carried out. III. Multiple-choice questions 1. In the CO cold box operation, an emergency shutdown shall be initiated if one of the following ( ) situations occurs. A. Power outage B. Interruption of instrument air C. Explosion and fire D. Massive leakage of crude hydrogen. Answer: ABCD. Explanation: According to the \"Operating Procedures for Carbon Monoxide Cold Boxes\" 5.2.3.3, an emergency shutdown should be initiated in case of any of the following situations: (1) Power outage, (2) Interruption of instrument air, (3) Explosion and fire, (4) Massive leakage of crude hydrogen. 2. The PSA adsorption bed can selectively adsorb (). A. Trace sulfides B. Methanol C. Carbon dioxide D. Carbon monoxide Answer: ABCD Explanation: According to Section 3.2.2 of the \"PSA Operation Procedures,\" under sequential adsorption using different types of adsorption beds, trace sulfides, methanol, carbon dioxide, carbon monoxide, methane, and nitrogen in the feed gas are adsorbed one after another. Common Knowledge Q&A on Ammonia Synthesis Plants 8 I. True or False Questions 1. At least ten minutes before the start of oil circulation in the ammonia synthesis plant, primary seal gas should be supplied. ( ) Answer: × Explanation: According to the \"Operating Procedures for the Syngas Compression Unit in Ammonia Synthesis Plants\", 5.1.1.2.3, the backflow isolation gas should be activated at least ten minutes before the compression unit starts operating. Before introducing the process gas, primary sealing gas must be introduced first to prevent the process gas inside the machine from contaminating the primary seal surface ； At the same time, it is necessary to ensure that the pressure in the primary sealing chamber is at least 0.15 MPa higher than the pressure in the flare line and balance pipe before the compression unit can be started. 2. The gaseous ammonia obtained through refrigeration and evaporation in the shell sides of the first and second ammonia coolers in ammonia synthesis is routed back to the ammonia freezing process, where it is compressed, cooled, and condensed into liquid ammonia for reuse. ( ) Answer: √ Explanation: According to the \"Operating Procedures for the Ammonia Synthesis Process in Ammonia Synthesis Units\", section 3.2 on the process flow, the gaseous ammonia obtained through refrigeration and evaporation in the shell sides of the first and second stage ammonia coolers is sent back to the ammonia freezing process, where it is compressed, cooled, and condensed into liquid ammonia for reuse. 3. During the process of reducing the load on the startup heater, it is possible to adjust the distribution of the syngas flow at various inlets of the synthesis tower; that is, reduce the syngas flow in the main path while increasing the syngas flow that enters the synthesis tower via the heater from the cold shock line. ( ) Answer: × Explanation: According to Section 5.1.1.2.6(12) of the \"Operating Procedures for the Ammonia Synthesis Unit in Ammonia Production Plants,\" when reducing the load on the start-up furnace, it is possible to adjust the distribution of the synthesis gas flow at various inlets of the synthesis tower; that is, the flow rate of synthesis gas in the main pathway can be increased, while the flow rate of synthesis gas that enters the synthesis tower via the heating furnace from the cold shock line can be reduced. 4. If the synthesis tower is not maintained after shutdown, it is not necessary to introduce nitrogen for cooling; natural cooling can be used instead. During this cooling period, attention should be paid to the temperature of the tower walls. ( ) Answer: √ Explanation: According to the \"Operating Procedures for the Ammonia Synthesis Process in Ammonia Synthesis Units\", 5.2.4 states that if the synthesis tower is not taken apart for maintenance after it is shut down, it is not necessary to introduce nitrogen gas to cool it; instead, natural cooling can be used, with attention paid to the temperature of the tower walls during this cooling process. II. Multiple-choice Questions 1. The control range of the oil pump pressure PIR14313/14 in the PSA unit of the ammonia synthesis plant is ( ) MPa. A、2.5～3.5 B、3.5～4.5 C、4.5～5.5 D、5.5～6.5 Answer: C Explanation: According to the \"Technical Specifications for Ammonia Synthesis Production Process\", section 6.3 on process control parameters for various stages, 2. The control range for the liquid level of the conventional flare water seal tank LIA1002 at the flare station of the first phase of the ammonia synthesis plant is ( ) mm. A、0～500 B、0～600 C、0～700 D、0～800 Answer: A Explanation: According to the \"Technical Specifications for Ammonia Synthesis Production Process\", section 6.3 on process control parameters for various stages, 3. The quality of operation at this position is related to the quality, yield, and consumption of acetic acid raw materials; it is a key factor in ensuring the long-term operational efficiency of the acetic acid production system. A. PSA B. Liquid nitrogen washing C. Carbon monoxide cold box D. Pressure compressor Answer: C Explanation: According to the \"Operating Procedures for the Carbon Monoxide Cold Box in Ammonia Synthesis Plants\", 1.1 The quality of operations at this position is related to the quality, yield, and consumption of acetic acid raw materials; it is a key component for ensuring the long-term operation of the acetic acid production system. III. Multiple-choice questions
1. The purpose of the PSA process is to supply ( ) to the two oxo-alcohol production units. A. Carbon dioxide B. Carbon monoxide C. Purified syngas D. Hydrogen Answer: CD Explanation: According to the ‘PSA Operation Procedures’, hydrogen with a purity of ≥99.9% – which is a qualified product – as well as syngas with the appropriate ratio of hydrogen to carbon monoxide, meeting the requirements for butyl octanol production, is sent to subsequent processing stages. 2. After entering the flare unit, the ammonia flare gas is directly burned and discharged through the flare tower; the main source of this flare gas is ( ). A. Exhaust gas from the synthetic ammonia chiller B. Exhaust gas from the ammonia synthesis tower C. Exhaust gas from the methanol chiller D. Exhaust gas from the Aojia ammonia tank area. Answer: ABCD. Explanation: According to the \"Operation Procedures for Torch Posts\" 3.2.7, the ammonia gas emitted through the torch is burned and discharged directly via the torch cylinder; the main sources of this gas are the exhaust gases from the synthetic ammonia chiller, the synthesis tower, the methanol chiller, and the Aojia ammonia tank area. 3. Which of the following pumps uses high-voltage electricity? ( ) A、P04202 B、P04203 C、P04204 D、P04205 Answer: BCD Explanation: According to the \"Operating Procedures for Acid Gas Removal in Ammonia Synthesis Plants\", the voltage for P04202 is 380V, while the voltage for P04203, P04204, and P04205 is 6000V.