HZAOP analysis data

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This post was last edited by leo_0088 on August 9, 2015, at 10:17. Category: Risk Analysis. Number: HAZOP2013.01.01. Jiangsu XX Biochemical Products Co., Ltd.: A technical renovation project involving the production of 40,000 tons/year of divinyl ether (with an additional 8,000 tons/year capacity), 6,000 tons/year of diacetylated products, 2,000 tons/year of ethyl acetoacetate, and 18,000 tons/year of sorbic acid (potassium). This project includes the cracking unit in the divinyl ether production process, as well as the cracking and polymerization units in the sorbic acid production process. HAZOP analysis was conducted by XX City Chemical Engineering Design Institute Co., Ltd. in January 2013. I. Introduction to the HAZOP method: The HAZOP analytical method, or Hazard and Operability Study, is a structured analytical technique used to identify design flaws, potential hazards in the manufacturing processes, and operational issues. The essence of this method is to analyze process drawings and operating procedures through a series of meetings, with the focus on various specific values related to the process aspects or operational steps. The basic process involves using guiding words to analyze possible changes (deviations) in the process conditions (parameters) throughout the process, in order to identify the potential dangers that may arise from such changes. One of the main purposes of guide words is to enable the evaluation of all relevant process parameters related to deviations. The HAZOP method can be applied to both construction projects and existing installations. The usual form of a deviation is “guide word + process parameter”. 1. Main materials required for HAZOP analysis: (1) Process flow diagram with control points (PIDS); (2) Plant layout diagram; (3) Process technical specifications; (4) Instrument control diagram; (5) Equipment operating conditions; (6) Configuration of safety facilities. 2. Analysis steps: (1) Form a HAZOP analysis team and determine the object of analysis ； (2) Preparation for analysis: collect relevant drawings, documents, and regulations ； (3) Divide it into several process units or operational steps, and use guiding words to analyze each analysis node in sequence to obtain a series of analysis results ； (4) Hold meetings for discussion and analysis, make additions and corrections, and prepare a report. II. Determination of the analysis objects According to the “Notice on Publishing the List of Key Hazardous Chemical Processes Subject to Strict Supervision” (An Jian Zong Guan San (2009) No. 116), the pyrolysis unit of Jiangsu xx Biochemical Products Co., Ltd., with a capacity of 40,000 t/a (plus an additional 8,000 t/a), as well as the polymerization and pyrolysis units of its project for producing sorbic acid (potassium) at a capacity of 18,000 t/a, are relatively hazardous operation units. In the event that the process gets out of control, there is a risk of explosions, fires, and poisoning. Therefore, the pyrolysis and polymerization units were chosen as the objects for this HAZOP analysis. III. Analysis: A HAZOP analysis team is to be established, consisting of technical personnel from Jiangsu Tiancheng Biochemical Products Co., Ltd., safety assessment experts from Jiangsu Antai Safety Technology Co., Ltd., and staff from Dalian Chemical Engineering Design Institute Co., Ltd. The specific division of tasks is as follows: the technical staff from Jiangsu XX Co., Ltd. are responsible for gathering team members and presiding over regular analysis meetings. The business focuses on participating in process hazard analysis. The technical staff of Jiangsu XX Co., Ltd. are responsible for collecting the process procedures and technical documents related to the units under analysis. A safety assessment specialist at Jiangsu XX Safety Technology Co., Ltd., focusing on analysis from the perspectives of safety controls, protection, and preventive measures. An engineer at the design institute, responsible for collecting operating procedures and analyzing the causes of deviations. All analytical records are compiled to ultimately produce an analysis report. IV. HAZOP Analysis of Polymerization and Cracking Units 1. Process and safety control measures for the cracking unit in the divinylbenzene production process and the sorbic acid production process (1) Reaction mechanism: file:///C:/DOCUME~1/ADMINI~1/LOCALS~1/Temp/msohtml1/01/clip_image002.gif Side reactions: file:///C:/DOCUME~1/ADMINI~1/LOCALS~1/Temp/msohtml1/01/clip_image004.gif (2) Description of the cracking process: Acetic acid is added to an acetic acid evaporator heated by steam, where it is vaporized at 120°C and 0.01–0.03 Mpa. It then enters a preheating section where it is preheated to 500°C before going into an auxiliary mixer. There, it mixes with an aqueous solution of ammonium dihydrogen phosphate, after which it enters the cracking furnace. Inside the furnace’s coils, the mixture undergoes cracking at 750°C and -0.075 Mpa. (3) The unit’s automatic control measures employ an automatic interlock control system. Pyrolysis control measures: The pyrolysis process is controlled through interlocked regulation of the gas flow rate and the temperature at the outlet of the cracking tubes, in order to prevent overheating and with an over-temperature alarm in place. Set up an interlock control system for the induced draft fan motor and gas shut-off valve (when the motor loses power, the gas supply is automatically cut off to halt the reaction). A temperature monitoring and over-temperature alarm system is also installed in the cracking section of the reactor. Thereby effectively preventing accidents and improving the intrinsic safety level of the entire system. 2. Polymerization unit processes and safety control measures in the sorbic acid production process (1) Polymerization reaction mechanism: file:///C:/DOCUME~1/ADMINI~1/LOCALS~1/Temp/msohtml1/01/clip_image006.gif Sorbic acid polyester: file:///C:/DOCUME~1/ADMINI~1/LOCALS~1/Temp/msohtml1/01/clip_image008.gif (2) Description of the polymerization process: Butyraldehyde, toluene, and the catalyst zinc acetylpropionate are added to the polymerization reactor; then ethylene gas is introduced. An absorption liquid is circulated in the absorber tower above the reactor to carry out a reverse absorption reaction. The reaction temperature is maintained at around 50–60°C (-0.094 MPa) using cooling water in the jacket, allowing the polymerization reaction to proceed; after 3 hours, a polyester that meets the required standards is produced. (3) The automatic control measures for the unit employ a DCS control system. Aggregation control measures: The aggregation process is controlled through interlocked regulation of the reaction temperature, the inlet valve for the jacket cooling water, and the ethylene feed, in order to control overheating and trigger alarms when such conditions occur. Install a rupture disc pressure relief system. 3. Selection of molecular units: The cracking unit consists of an acetic acid evaporator and a cracking reactor ； The cracking unit conducts a HAZOP analysis of the acetic acid cracking reaction process, taking into account the actual operating conditions of the production equipment; the polymerization unit carries out a HAZOP analysis of the polymerization reaction process, also based on the actual operating conditions of the production equipment. 4. The results of the HAZOP analysis were discussed and analyzed by the analysis team, resulting in the following analysis report. Pyrolysis reaction unit: Table 1-2 Records of Hazard and Operability Study Analysis for the Pyrolysis Unit HAZOP analysis; Operability study. Workshop/unit: 1# and 2# Cracking Workshops \ Diethylene Workshop \ Sorbic Acid Workshop. System: Pyrolysis reactor. Task: Pyrolysis production process. Date: 2012.12.25. Designer: Technical personnel from Tiancheng Company. Keywords, Possible causes of deviations, Consequences, Necessary countermeasures. A – Guiding words: Material: Acetic acid. None. There is no acetic acid material inside the reactor tubes. 1. Forgetting to add material; the acetic acid tank is empty. 2. The material transfer pump is malfunctioning. 3. The feed valve is not open. 4. There is a fault in the steam heating system of the acetic acid reboiler, or the valve is not open. 1. This can lead to excessively high temperatures in the preheater tubes, which may cause damage to those tubes, result in material leakage, and give rise to explosive gases. 1. Strict operational review. Set a low liquid level alarm for the acetic acid tank. 2. Install a backup pump for the transfer pump. 3. Conduct thorough operational checks. 4. Set up a bypass for the steam heating system and carry out strict operational checks. The acetic acid flow rate in the reactor is low. 1. The operational traffic is low. 2. The feed valve is not fully open. 4. The steam heating flow rate to the reboiler is too low. 1. This can lead to an excessively high reaction temperature, posing a risk of temperature loss of control. 1. Strictly follow the operating procedures and conduct thorough checks during operation. 2. Install a pressure stabilization interlock system and pressure alarms; install pressure gauges along the steam pipelines to monitor pressure levels. 3. Install a flow stabilization interlock system and temperature alarm. In multiple reactors, the acetic acid flow rate is too high: 1. The operating flow rate is too high; 2. The steam heating flow rate to the reboiler is too high, which results in a lower reaction temperature ； It affects the product yield. 1. Strictly follow the operating procedures and conduct thorough operational checks. 2. Install a flow stability interlock system as well as temperature alarms. 3. Install an evaporation pressure stabilization interlock system and pressure alarms, and place pressure gauges at the steam pipeline inlet to monitor the pressure. Besides other acetic acids or ethylenes entering the cracking furnace through the tubes, tube failures in the furnace can lead to the formation of explosive gases, resulting in an explosion. Periodically conduct a tightness test on the vacuuming of the process systems, including the cracking furnace. B Guide Word: Reaction Temperature – Lower temperature. Reasons: 1. Faulty temperature indication; 2. Faulty inlet valve in the gas system. Consequences: 1. Decreased output; sudden temperature increases can lead to overflow or explosion accidents, posing risks. Actions: 1. Check the feeding situation; 2. Calibrate the thermometer; 3. Inspect the inlet valve of the gas system; 4. Install a gas-temperature interlock system. – Higher temperature. Reasons: 1. Faulty temperature indication; 2. Faulty inlet valve in the gas system. Consequences: 1. Faster reaction rate, increased intensity of the reaction, posing risks. Actions: 1. Check the feeding situation; 2. Calibrate the thermometer; 3. Inspect the inlet valve of the gas system; 4. Install a gas-temperature interlock system. Other than: Significant temperature fluctuations, same as above. Consequences: Unstable production, posing risks. Same as above. C Guide Word: Safety interlock devices, pressure relief facilities. – Opposite situation: Solenoid valve does not function. Reasons: 1. Electrical circuit faults or damaged coils; 2. Inensitive sensors; 3. Stuck solenoid valve. Consequences: Loss of safety interlock functionality, increased risk. Actions: 1. Check the electrical circuits; 2. Repair the solenoid valve; 3. Inspect the sensors and signal lines. Pressure relief device does not function during an accident. Reasons: 1. Excessively high burst pressure or corroded burst disc. Consequences: Loss of automatic pressure relief functionality, greatly increased risk. Actions: 4. Follow operating procedures; 5. Select an appropriate burst pressure based on production conditions; 6. Replace the burst disc. As well as: Alarms occur during normal operation. Reasons: 5. Faulty alarms or wiring; 6. DCS system faults, same as above. 3. False alarms may also occur, same as 1, 3, 4. Actions: 7. Check the alarms or wiring; 8. Check the DCS system. D Guide Word: Fuel: Water gas. – Lower water gas flow. Reason: Valve opening is too small, affecting output. A feed control valve should be installed in the water gas pipeline, linked to the outlet temperature. Additionally, there is a risk of excessively high water-gas temperature due to a relatively large valve opening. A feed regulating valve is installed in the water-gas pipeline and is interlocked with the outlet temperature. In addition to other gas-related issues with water-gas systems that can cause shutdowns, disrupt production, or even lead to explosions, emergency shut-off valves are installed on the water-gas pipelines. Pressure sensors are also placed at these shut-off valves; when the pressure drops below a set value, the emergency shut-off valve closes automatically. E guide word: Materials: Combustion air – Less: less; More: more; Other than: other. No fan failure related to combustion air. Water gas accumulates inside the cracking furnace, forming an explosive mixture with the air in the furnace, which may lead to an explosion. 1. Install interlock control between the fan motor and the water-gas feed; when no air enters the cracking furnace, the supply of water-gas should be cut off promptly ； Prepare emergency operation guidelines that outline the steps to take in case there is no water gas or no supply of combustion air in the cracking furnace. 2. Install a backup fan. FD keyword: Reaction conditions: Flame status – Less: Low; More: High; Other: Something else. The flame in the cracking furnace goes out due to 1) faults in the gas supply system or 2) fan failures. When the flame goes out, water gas and air mix inside the cracking furnace, forming an explosive mixture; if purging is not carried out before attempting to restart the furnace, this could lead to an explosion. Interlock the flame status with the water-gas supply. When a flame out is detected, the water-gas supply should be cut off urgently (two independent control circuits are provided, each of which cuts off the water-gas supply in case of a flame out to improve reliability), and the emergency purging procedure should be initiated promptly. G guide word: Water gas leakage. Less – Few; More – Many; Other than – Others. Causes of water gas leakage: 1. Accidents; 2. Fan failures. Leakage occurs from the air inlet of the cracker into the work area, leading to poisoning and even death of personnel. 1. Install carbon monoxide detectors at the site, set the alarm concentration according to the limits for carbon monoxide poisoning, and provide local alarms as well. 2. Installation of a backup fan: Major hazards identified through the HAZOP analysis of the pyrolysis unit and corresponding safety measures: · When there is no flow from the acetic acid evaporator, through the preheater, to the mixer, the tubes in the preheater may be damaged, which can severely affect production. The following safety measures are adopted: 1) Strict operational review. 2) Install a low liquid level alarm for the acetic acid tank ； 3) A standby pump is provided for the material transfer pump ； 4) A bypass is provided for the steam heating system. From the perspective of optimizing the process, in order to maintain a stable feed flow rate, an interlock system between the evaporation pressure and the heating steam is installed, along with pressure alarms; a pressure gauge is placed at the inlet of the steam pipeline to monitor the pressure ； Set up a traffic stabilization system. Periodically conduct a tightness test on the vacuuming of the process systems, including the cracking furnace. ·A rupture in the underground water-gas pipeline (due to external damage, for example) can lead to shutdown of the plant, disruption of production, and even explosions ； It is designed to install emergency shut-off valves on water-gas pipelines, with pressure monitoring points provided at these valves; the emergency shut-off valves will close when the pressure falls below a set value. ·3. If no combustion air enters the cracking furnace (for example, due to a fan failure), the furnace goes out. Water gas accumulates inside the cracking furnace, forming an explosive mixture with the air present there, which can lead to an explosion. Design (1): Implement interlock control between the fan motor and the water-gas feed; when no air enters the cracking furnace, the supply of water-gas should be cut off promptly ； (2) Prepare emergency operation guidelines that outline the steps to be taken in case there is no water gas or no supply of combustion air in the cracking furnace. (3) Install a backup fan. ·The flame in the 4th cracking furnace goes out; water gas and air mix inside the furnace to form an explosive mixture. If purging is not carried out before restarting the furnace, this can lead to an explosion. The design should include interlocking between the flame status and the water-gas supply. When a flame out is detected, the water-gas supply should be cut off urgently (it is advisable to have two separate control circuits, each capable of cutting off the water-gas supply in the event of a flame out, to enhance reliability), and an emergency purging procedure should be initiated promptly. ·5. Water gas contains carbon monoxide, which may leak from the air inlet of the cracking furnace into the work area, causing poisoning or even death in people. Carbon monoxide detectors should be installed on site, with their alarm thresholds set according to the limits for carbon monoxide poisoning, along with local alarms. Polymerization reaction unit: Table 1-2 Records of Hazard and Operability Study Analysis for Polymerization Units HAZOP analysis; Operability study. Workshop/unit: Sorbic acid workshop; System: Polymerization reactor; Task: Polymerization production process. Date: 2012.12.25; Designer: Technical personnel from Tiancheng Company. Keywords, Deviation, Possible causes, Consequences, Necessary countermeasures. Trigger word: Material; None. There is no polyester material inside the empty reactor. 1. Forgetting to add material; 1. It affects production; 2. Ethylene leaks out, posing a risk of fire and explosion. 1. Strictly follow the operating procedures and conduct thorough checks during operation. The liquid level in the reactor is too low. The operating liquid level is too low. 1. It affects production. 2. Ethylene leaks out, posing a risk of fire and explosion. 1. Strictly follow the operating procedures and conduct thorough checks during operation. 2. Open the feed valve, check the liquid level in the reactor, and add material for reaction once it is confirmed to be correct ； 3. The reaction vessel is equipped with a liquid level interlock and a low liquid level alarm. Too much material in the reactor: 1. Improper operation; 1. Excessive liquid material, which increases gas-phase resistance and affects production efficiency ； 1. Strictly follow operating procedures and conduct thorough operational checks. 2. Open the feed valve and use a sight glass to verify that the liquid level inside the reactor is at the normal level ； 3. The reaction vessel is equipped with a liquid level interlock and a high liquid level alarm. Other than incorrect addition of materials in the reactor – B: Guide word; Temperature inside the reactor is too low. Reasons: 1. Insufficient amount of ethylene added; 2. Faulty temperature indicator; 3. Excessive flow rate of cooling water. Consequences: Decreased output. Solutions: 1. Check the feeding process; 2. Calibrate the temperature gauge; 3. Inspect the cooling water valves; 4. Implement interlock control between the polymerization temperature and the inlet valve for the jacket cooling water. More reasons for excessive temperature: 1. Excessive amount of ethylene added; 2. Faulty temperature monitoring; 3. Insufficient flow rate of cooling water. 2. The reaction accelerates, becoming more intense, which can lead to hazards related to points 1, 2, and 3. 4. Temperature data is sent to the DCS for interlock control, with settings for the polymerization temperature and the inlet valve for jacket cooling water being controlled via interlocks. Apart from other significant temperature fluctuations: 4. Fluctuations in the amount of ethylene added; 5. Fluctuations in cooling water flow rate; 3. Unstable production processes, which can easily lead to hazards; 5. Inspect the cooling water system; 6. Set up interlocked control between the polymerization temperature and the inlet valve for jacket cooling water. 7. Set interlock between ethylene addition amount and temperature control. C keywords: safety interlock device, pressure relief mechanism. Reverse – the control valve does not function. 1. Circuit failure or damaged coil; 2. Inensitive sensor; 3. Stuck solenoid valve. 1. Loss of safety interlock function, increased risk. 1. Check electrical circuits; 2. Repair the solenoid valve; 3. Inspect sensors and signal lines. The pressure relief mechanism does not function in case of an accident. 4. Excessively high bursting pressure of the rupture disc or it being rusted. 2. Loss of automatic pressure relief function, significantly increased risk. 4. Follow operating procedures; select an appropriate bursting pressure based on production conditions; replace the rupture disc. Also, alarms may sound during normal operation. 5. Faulty alarm or wiring; 6. DCS system failure (same as 1). 3. False alarms may also occur (same as 1, 3, 4). 7. Check the alarm or wiring; 8. Check the DCS system. Major hazards identified through HAZOP analysis for the polymerization unit and corresponding safety measures: · If the liquid level in the polymerization reactor is too low, it affects the absorption of ethylene and gases, posing a risk of explosion in subsequent processes. Therefore, a liquid level control system is installed in the reactor to stabilize the absorption process. ·2 If the feed flow rates of ethylene and gas are not controlled, it will result in significant heat absorption, causing the reaction to get out of control and leading to an explosion. Therefore, (1) ethylene and gas feed lines are equipped with control valves that are interlocked with the reaction temperature ； (2) Set interlock control between the polymerization temperature and the jacket cooling water inlet valve. (3) A burst disc is installed in the reactor to prevent accidental explosions. V. Some insights gained from HAZOP analysis Through a relatively systematic HAZOP analysis conducted on the ethylene dimer cracking section of Jiangsu XX Biochemical Products Co., Ltd., as well as the polymerization and cracking sections of the sorbic acid (potassium) technical improvement project, the following insights have been gained: 1. The occurrence of accidents is often unexpected; they are “accidental” in nature. Through HAZOP analysis, we have realized that the causes of most accidents can be identified, which indicates that accidents are inevitable to some extent; we should firmly believe that accidents can be prevented. 2. The depth and breadth of the HAZOP analysis depend on the professional competence of the members of the analysis team, as well as the communication, complementarity, and collaboration among specialists from various fields such as chemical engineering, mechanics, and safety. In future production processes, experience should be summarized to continuously improve the analysis content. 3. The analysis results provide valuable guidance for the design of project safety facilities; they help identify some overlooked aspects, thereby enabling more comprehensive and in-depth fault analysis and safety facility design. 4. Through analysis, we found that: (1) Some of the “deviations” can be addressed by ensuring that operators strictly adhere to safety procedures and by improving on-site management ； (2) The regular maintenance and inspection of electrical and mechanical equipment, control devices, and safety facilities are extremely important, and they represent the most fundamental steps in preventing accidents ； (3) Strengthen safety education and skill training for personnel working at the posts, enforce strict assessments, and foster a positive atmosphere of \"standardized operations and safe production\". HAZOP Analysis Team, April 2013