Abnormal conditions, how to handle them? The guidelines are here!

Release Date:

2024-05-07 15:05

Source:

Ministry of Emergency Management of the People's Republic of China

Abnormal conditions, how to handle them? The guidelines are here!

General Office of the Ministry of Emergency Management on Issuing

Notice on the "Guidelines for Safe Handling of Abnormal Conditions in Chemical Enterprise Production Processes (Trial)"

Emergency Management Office [2024] No. 17

Emergency Management Departments (Bureaus) of all provinces, autonomous regions, and municipalities directly under the Central Government, Emergency Management Bureau of Xinjiang Production and Construction Corps, relevant central enterprises:

To thoroughly implement General Secretary Xi Jinping's important instructions and directives on work safety, conscientiously implement the decisions and deployments of the Party Central Committee and the State Council on chemical and hazardous chemical safety production, deeply learn from typical accident lessons, effectively prevent and resolve major safety risks, and after review and approval by the Ministry of Emergency Management's executive meeting, the "Guidelines for Safe Handling of Abnormal Conditions in Chemical Enterprise Production Processes (Trial)" (hereinafter referred to as the "Guidelines") are hereby issued to you. Please conscientiously implement them and the following requirements are proposed:

1. Emergency management departments in all regions and headquarters of relevant central enterprises shall earnestly implement the three-year action plan for fundamental safety production governance of chemical and hazardous chemicals, strengthen publicity and training of the "Guidelines", guide enterprises to raise awareness, deeply understand and fully grasp the requirements of the "Guidelines", and improve the safety risk control level of abnormal conditions in production processes.

2. Emergency management departments in all regions and headquarters of relevant central enterprises shall organize enterprises to carefully compare with the "Guidelines", establish and improve abnormal condition handling systems, standardize abnormal condition handling procedures, and improve the ability to safely handle abnormal conditions in production processes.

3. Emergency management departments in all regions shall combine daily supervision work to strengthen supervision and guidance on the safe handling of abnormal conditions in chemical enterprise production processes, ensure the implementation of relevant requirements for abnormal condition safety handling, and strictly investigate and deal with illegal and irregular acts according to law to prevent and reduce production safety accidents.

General Office of the Ministry of Emergency Management

April 25, 2024

Guidelines for Safe Handling of Abnormal Conditions in Chemical Enterprise Production Processes

(Trial)

1 Purpose

To further standardize and strengthen the safety risk control of abnormal conditions in chemical enterprise production processes, improve awareness and capability of safe handling of abnormal conditions, guide enterprises to respond scientifically and prudently, and prevent and reduce production safety accidents, these guidelines are formulated.

2 Scope of Application

These guidelines apply to situations during the production operation phase of chemical enterprises including unit start-up and shutdown, unplanned maintenance, abnormal operating parameters, abnormal operations or equipment and facility failures, and other situations with potential risk of unexpected energy release.

3 Basic Requirements

3.1 Enterprises should conduct risk assessments against abnormal condition scenarios in daily work, establish or clarify emergency handling procedures, and carry out training and drills.

3.2 Emergency handling procedures should at least include: handling steps, safety measures, and shutdown conditions.

3.3 During emergency handling, enterprises shall not remove or bypass interlocks to forcibly maintain equipment or unit operation without conducting assessments and obtaining approvals.

3.4 Enterprises should establish and improve authorization mechanisms for personnel to perform emergency shutdowns and evacuations.

3.5 After unit interlocks are triggered, the cause should be promptly identified and interlock trigger conditions eliminated one by one; forcible reset is strictly prohibited.

3.6 All unit alarms must be responded to promptly. After combustible gas and toxic gas detection or fire alarm system alarms, it is strictly forbidden to cancel alarms arbitrarily without analyzing the cause and confirming on site.

3.7 For hot work, confined space, equipment or pipeline opening operations, enterprises shall handle work approvals according to regulations.

4 Handling Principles

4.1 Timely retreat to a safe state

4.1.1 In the following situations, timely retreat to a safe state according to emergency handling procedures is required:

(1) Abnormal conditions such as sudden temperature or pressure changes, runaway polymerization, boiling overflow, pipeline blockage, medium cross-contamination, stirring failure, severe equipment vibration in the operating unit.

(2) Emergency pressure relief devices such as safety valves or rupture discs activate abnormally with unknown causes and cannot be restored to normal.

(3) Key equipment failures, interruption of important utilities (water, electricity, steam, air), instrument control system failures with unknown causes and cannot be restored to normal.

(4) Obvious leakage of flammable, explosive, highly toxic, or extremely toxic media with risk of loss of control.

(5) Natural disasters such as earthquakes, typhoons, heavy rainfall occur, making normal production impossible.

Safe retreat methods include but are not limited to: full unit shutdown, partial shutdown, stopping heating, emergency cooling, stopping feed, terminating reactions, unloading and depressurizing, unit isolation, etc.

4.1.2 If abnormal conditions occur that were not previously assessed and have no emergency handling procedures, the unit should be shut down immediately.

4.2 Minimize on-site handling personnel

4.2.1 When the on-site situation is unclear, no one shall enter the site without safety risk assessment and protective measures. After preliminary confirmation that the site is accessible, up to 2 persons wearing necessary protective equipment, alarm devices, and related safety tools may enter to further investigate.

4.2.2 During handling, on-site personnel should be strictly controlled, responsibilities clearly divided, and the number of personnel controlled to a minimum. Personnel unrelated to handling are strictly prohibited from entering the work area.

4.2.3 During on-site handling, cross operations at the same location are generally not allowed; usually 2 persons in the same unit area, with a maximum of no more than 6 persons.

4.2.4 Command personnel should use video, radio communication, and other equipment for remote dispatch and command as much as possible.

4.2.5 Video monitoring, electronic fences, personnel positioning system-based crowd risk monitoring and early warning, and other information digital technologies should be used to strengthen risk control of personnel gathering at the handling site.

4.3 Comprehensive risk identification, analysis, and prudent handling

4.3.1 Before handling, a comprehensive analysis and judgment of safety risks during the handling process should be conducted, effective control measures formulated and implemented, and blind handling under unknown or uncontrollable risks is strictly prohibited.

4.3.2 When dealing with blockages in pipelines, valves, etc., the method of clearing should be comprehensively considered based on the characteristics of the blockage, the design conditions of the equipment pipeline, and the properties of the clearing medium. Reckless actions are prohibited. When handling blockages sensitive to impact, external force striking is strictly forbidden.

4.3.3 Strictly confirm safe working conditions; it is forbidden to rely solely on "visual inspection, smelling, listening, touching" as the final means of safety confirmation. Confirmation methods include but are not limited to:

(1) Confirmation of the end of pressure relief, such as observing the pointer movement on the on-site pressure gauge or the pressure change curve on the DCS, verifying through comparison of two or more different types of pressure monitoring systems, or confirming by slightly opening the quench or vent valve based on the hazardous characteristics of the material.

(2) Confirmation of the effectiveness of energy isolation for containers and pipelines, such as whether blind flanges are installed as required, whether vent quench valves are fully opened, and whether connecting pipelines have been disconnected.

(3) Confirmation of electrical equipment power-off, such as locking and tagging the switchgear after power-off, conducting on-site testing, using instruments for live detection, pulling the circuit breaker (drawer) to the maintenance (test) position, opening isolation switches, and removing fuses.

(4) Before entering confined spaces, use detection instruments that meet relevant standards to conduct representative and comprehensive gas detection. If conditions permit, portable detectors and laboratory sampling analysis can be used for comparison and confirmation.

4.3.4 Personnel handling the situation should wear complete and effective personal protective equipment according to the characteristics and potential risks of the on-site materials.

4.4 Effectively prevent accidental energy release

4.4.1 When opening pipelines or equipment during handling operations, the front and rear ends of the disassembled parts should be depressurized, purged, and replaced, and effectively physically isolated from the operating system. Using water seals or closed valves instead of installing blind flanges is strictly prohibited.

4.4.2 During handling operations, pressurized sealing and pressurized hole opening operations should not be performed unless necessary. If emergency handling requires it, the enterprise should conduct a feasibility assessment of the operation, survey the site environment and equipment status, and develop a special operation plan.

4.4.3 Pressurized operations are strictly prohibited on equipment and pipelines containing extremely hazardous toxic media; pressurized operations are also forbidden if thickness measurement has not been performed, if material cracks cannot be effectively prevented from further expansion, if the stiffness and strength of the structure and materials do not meet safety requirements, or if protective measures have not been effectively implemented.

4.5 Consider unified command globally

4.5.1 Handling of abnormal conditions should comprehensively consider the stability of internal and external utilities of the unit and the material balance upstream and downstream. Multi-headed command and disorderly handling are strictly prohibited.

4.5.2 A dedicated person should be clearly assigned in the control room to monitor the DCS and other means to promptly check the upstream and downstream units and on-site safety risk control during abnormal condition handling.

4.5.3 After handling abnormal conditions, the causes should be promptly analyzed, improvements made from management and technical aspects, operating procedures and emergency plans perfected, and regular training and drills organized for relevant personnel to enhance abnormal condition handling capabilities.

4.5.4 If abnormal conditions meet the criteria for activating emergency plans, respond according to the response procedures and handling measures of the plan.

Appendix:

1. Key safety handling points for typical abnormal conditions in fine chemical enterprises

2. Key safety handling points for typical abnormal conditions in ammonium nitrate production and usage enterprises

3. Key safety handling points for typical abnormal conditions in synthetic ammonia production enterprises

4. Key safety handling points for typical abnormal conditions in hydrogen peroxide production enterprises

Appendix 1

Typical abnormal conditions in fine chemical enterprises

Key safety handling points

1. After a reactor failure shutdown, the feed valve should be closed and heating stopped. For exothermic reactions, the cooling system should be immediately started. If the cooling system or stirring fails, the material should be dispersed and transferred to other reactors operating normally.

2. If a reaction runaway is judged by a sudden rise in temperature or pressure, material boiling over, or surging, handle according to the previous point first; if still uncontrollable and release is necessary, the material should be released into a discharge facility pre-charged with quenching agents. Unauthorized on-site discharge is strictly prohibited.

3. When the oxygen content abnormally rises in the hydrogenation reaction unit, hydrogen supply should be immediately stopped.

4. If the Grignard reagent preparation does not initiate after adding the initiator, the cause should be immediately investigated. Direct heating or further addition of initiator is strictly prohibited. The material should be placed in a quenching reactor and quenched by adding quenching agents. After pressure and temperature stabilize, post-treatment can proceed.

5. Before starting a reactor with material, risk assessment should be conducted, and reaction control operation plans and emergency handling measures formulated. For risks of reaction runaway, material should be withdrawn before startup.

6. When distillation, rectification, and other processes do not discharge material, the cause should be analyzed. Continuing heating or dry distillation is strictly prohibited.

7. When exhaust systems involving highly toxic gases such as chlorine, hydrogen fluoride, and ammonia fail, the backup system should be able to start interlock promptly or be remotely started immediately.

Appendix 2

Typical abnormal conditions in ammonium nitrate production and usage enterprises

Key safety handling points

1. During ammonium nitrate production or usage, if the following occur, immediate shutdown and emergency dilution or cooling measures should be initiated, and personnel evacuated:

(1) Abnormal temperature rise of ammonium nitrate solution or signs of decomposition;

(2) Thick smoke, blue smoke, or yellow smoke from ammonium nitrate solution storage tanks or warehouses.

2. If the ammonia evaporation process shows ammonia gas carrying liquid or the ammonia preheater temperature continuously drops rapidly, ammonia evaporation should be immediately stopped, the cause investigated, and continuous ammonia evaporation treatment strictly prohibited.

3. When the flow rates of ammonia and nitric acid entering the neutralization reactor fluctuate significantly, causing unstable neutralization reaction, feeding of ammonia and nitric acid should be stopped, the cause investigated, and feeding strictly prohibited until flow stabilizes.

4. When the ammonium nitrate neutralization reactor or flash tank exhibits the following conditions, feeding should be stopped immediately:

(1) Solution pH value is below 1;

(2) Process steam on site emits blue smoke;

(3) Ammonium nitrate solution appears green or red in color.

5. In case of leakage in the neutralization reactor, the neutralization reaction should be stopped immediately, the cause investigated, the leakage properly handled, and the leakage source eliminated; no more than two operators are allowed, and hot work is strictly prohibited.

6. When the discharge pipe of the ammonium nitrate solution evaporator (primary and secondary evaporation) is blocked or material does not discharge, continuous heating and feeding of the evaporator flash tank is strictly prohibited; feeding should be stopped immediately, heating steam valve closed, vacuum system and evaporation temperature checked, and condensate (or hot water) added to the evaporator for clearing.

7. When the ammonium nitrate granulation process stops due to malfunction, steam-heated storage tanks should have steam supply cut off immediately; the residence and circulation times of material in the liquid seal tank and mixing tank should be strictly controlled, with residence time in the liquid seal tank less than 20 minutes and in the intermediate tank less than 30 minutes; if temperature rises abnormally or during shutdown maintenance, material should be unloaded immediately.

8. When blockage or abnormal temperature rise occurs in the inlet or outlet pipelines of the ammonium nitrate solution transfer pump, the pump should be stopped immediately, heating steam cut off, and cleaning performed by steam or deionized water flushing; cleaning by striking or scraping with metal objects is strictly prohibited.

9. During short-term shutdowns in the production of nitrate-sulfur compound fertilizer, the solution temperature in the mixing tank should be lowered to 130-140°C, with insulation time less than 4 hours; if temperature exceeds 160°C, water should be added immediately for cooling and the tank emptied.

10. During short-term shutdowns in the production of nitrate-chloride compound fertilizer, the solution temperature in the mixing tank should be lowered to 130-140°C, with insulation time less than 1 hour; the material temperature in the tank should be monitored continuously, and if abnormal temperature rise occurs, the tank should be emptied immediately.

11. During the production of tower-type nitrate compound fertilizer, if the ammonium nitrate solution temperature exceeds 185°C, accompanied by the generation of irritating gases and dense smoke, blue smoke, or yellow smoke emissions, or material overflow, feeding should be stopped immediately and water added remotely for cooling; the main steam valve should be closed, personnel organized to evacuate via stairs immediately, elevator evacuation or moving to upper tower levels to avoid smoke is strictly prohibited, and power to the tower should be cut off as appropriate.

Appendix 3

Typical Abnormal Conditions in Ammonia Synthesis Enterprises

Key safety handling points

1. When any of the following abnormal conditions occur, system or partial shutdown measures should be taken:

(1) Large leaks of ammonia, coal gas, or synthesis gas occur;

(2) Corrosion thinning of pipelines involving synthesis gas or other flammable, explosive, or toxic materials falls below design requirements;

(3) Abnormalities or faults occur in equipment or instruments that may cause high pressure to connect to low pressure, such as from high-pressure separator to low-pressure flash tank;

(4) Power, water, or gas outages occur during temperature rise and reduction in the converter or ammonia synthesis tower;

(5) Rupture, severe deformation, or displacement occurs in the flare pipeline;

(6) Nitrogen-hydrogen compressor experiences over-temperature, over-pressure, leakage, water carryover, liquid carryover, or sudden current increase (except for standby machines);

(7) Leakage in the tubes of synthesis waste heat boiler or ammonia cooler coils causes sudden pressure rise in the low-pressure system, and the cause of leakage is unknown;

(8) Overpressure or frequent oxygen-coal ratio fluctuations occur in the gasifier;

(9) Large fluctuations occur in air-to-carbon or water-to-carbon ratios in the conversion system.

2. During gasifier startup or shutdown or when temperature or pressure parameters fluctuate, before taking energy isolation measures such as shutdown, pipeline switching, or pipeline depressurization and completing confirmation, personnel gathering on site is strictly prohibited.

3. When blockages or valve failures occur in pipelines between process units, shutdown or energy isolation measures should be taken; confirmation that each pipeline segment is at atmospheric pressure should be done by observing local or remote pressure gauges, switching pipelines, or venting; pressurized operations are strictly prohibited.

4. When pipelines or equipment involving flammable, explosive, toxic, or asphyxiating media such as synthesis gas, hydrogen, hydrogen sulfide, or nitrogen need to be opened, before operation, multiple methods such as local or remote instruments, venting, and on-site confirmation should be used to ensure internal pressure is atmospheric, energy isolation and personnel protection measures are in place, and pressurized operations are strictly prohibited.

5. Before depressurizing the oxygen pipeline system after gasifier shutdown, depressurization operations are strictly prohibited.

6. If the gasifier ignition fails initially or extinguishes midway, replacement should be performed again; re-ignition is strictly prohibited before sampling and analysis confirm qualification.

7. When hotspot temperatures in catalyst beds or outer wall temperatures in the converter, methanation furnace, or ammonia synthesis tower exceed the maximum allowable values without a downward trend, immediate shutdown and maintenance should be performed, maintaining system positive pressure.

Appendix 4

Typical Abnormal Conditions in Hydrogen Peroxide Production Enterprises

Key safety handling points

1. For all equipment and facilities involving hydrogen peroxide that may decompose, such as preparation kettles, hydrogenation towers, oxidation towers, extraction towers, alkali washing towers, purification towers, filters, concentration evaporators, resin towers, and hydrogen peroxide storage tanks, if temperature or pressure rises abnormally, operations should be stopped immediately, personnel evacuated promptly, and measures taken to prevent impact on surrounding production and storage facilities.

2. When any of the following abnormal conditions occur, the entire system interlock shutdown or manual one-button shutdown should be triggered for handling:

(1) Gas-liquid separator of the hydrogenation tower, gas-liquid separator of the oxidation tower deoxygenation liquid tank (or built-in gas-liquid separator), and continuous lowering of the liquid level at the bottom of the oxidation tower in the countercurrent oxidation process to the low-low limit alarm;

(2) Abnormal temperature rise of the oxidation tower, extraction tower, or purification tower to 60℃;

(3) In the parallel flow oxidation process, abnormal fluctuation of the liquid level in the gas-liquid separator at the top of the oxidation tower causes a high-high limit alarm; in the countercurrent oxidation process, abnormal fluctuation of the liquid level in the tail gas condensate receiving tank at the top outlet of the oxidation tower causes a high-high limit alarm;

(4) Continuous high-level operation of the liquid level (or interface) at the top of the extraction tower causes a high-high limit alarm;

(5) When the hydrogen peroxide content in the extraction residue exceeds 0.3g/L, a reanalysis should be immediately conducted, and after confirmation, the operation should be stopped immediately;

(6) Severe turbidity appears in the aqueous phase inside the sight glass of the extraction tower or severe emulsification occurs in the working liquid; the stability of hydrogen peroxide continues to decrease, and the water carryover phenomenon in the working liquid cannot be eliminated by adjusting process parameters;

(7) The oxygen concentration (volume percentage) at the top of the hydrogenation tower or in the hydrogenation tail gas exceeds 2%.

3. After normal shutdown of the hydrogen peroxide production unit, when the hydrogen efficiency of the hydrogenation tower and the oxygen efficiency of the oxidation tower have not dropped below 1g/L, it is strictly forbidden to discharge materials from the hydrogenation tower or oxidation tower; the working liquids of the hydrogenation system and post-treatment system and the oxidation system and extraction system should be discharged into separate storage tanks respectively.

4. When the hydrogen peroxide production unit requires full system inspection and maintenance after shutdown, the working liquid in the maintenance unit should be emptied, cleaned, and replaced. Only after taking material and energy isolation measures such as closing valves, installing blind plates, and switching equipment can work be carried out. When replacing the bleaching earth bed or filter, the number of operators must not exceed six.

5. During the operation of the preparation kettle, if temperature or pressure rises abnormally, the steam should be interlocked and cut off, heating stopped, and the jacket or coil cooling methods interlocked and started for indirect cooling. The emergency discharge valve at the bottom of the preparation kettle should be interlocked and opened to discharge the working liquid to a dedicated ground trough. It is strictly forbidden to close the vent line of the preparation kettle. When the preparation kettle temperature is excessively high, it is strictly forbidden to add water into the kettle for cooling to prevent sudden boiling.

6. After shutdown of the hydrogenation system, nitrogen should be used for purging until the hydrogen content in the hydrogenation system is below 0.5% (volume percentage), then nitrogen pressure should be maintained; before qualified purging, inspection, maintenance, and special operations are strictly prohibited; before startup, nitrogen purging should be used for pipelines and equipment involving hydrogen until the oxygen concentration in equipment and pipelines is less than 2% (volume percentage).

7. Phosphoric acid is added through the remote automatic acid addition system on the working liquid feed line before the oxidation tower to ensure that the acidity of the oxidation liquid at the oxidation tower outlet is maintained at 2-6mg/L (as phosphoric acid). When the acidity is below 1mg/L (as phosphoric acid), upstream and downstream feeding should be stopped. The automatic acid addition system should be used to urgently add acid or stabilizer automatically through fixed pipelines to the hydrogenation liquid storage tank and oxidation liquid storage tank. Manual acid or stabilizer addition is strictly prohibited.

8. When the temperature of the oxidation residue separator or oxidation residue storage tank rises abnormally, pure water should be interlocked and injected for dilution while withdrawing materials; it is strictly forbidden to close the manual valve of the vent line at the top of the oxidation residue separator and storage tank. When the residue in the oxidation tower is unstable and the bottom temperature is high, the frequency of residue discharge should be increased. If necessary, emergency shutdown should be performed and the cause of abnormal oxidation residue conditions investigated. After the cause is found and normal conditions restored, restart can proceed.

9. When the temperature of the catalyst bed or bleaching earth bed rises abnormally, steam heating should be stopped immediately and nitrogen or inert gas used to purge the catalyst bed and bleaching earth bed for cooling. Air purging for cooling is strictly prohibited.

10. After shutdown of the hydrogen peroxide purification unit resin tower, hydrogen peroxide should be discharged from the resin tower. After discharge is complete, pure water should be injected from the bottom of the resin tower to displace residual hydrogen peroxide in the resin bed. After the wash liquid passes inspection, the resin bed should be regenerated with methanol solution (or directly regenerated by washing with water). After successful regeneration, before reuse of the resin tower, the resin bed should be kept immersed in pure water. Free hydrogen peroxide residue in the resin tower is strictly prohibited, and hydrogen peroxide discharge by nitrogen pressurization alone is strictly prohibited.

11. When the temperature or pressure of the hydrogen peroxide storage tank rises abnormally, pure water and stabilizer should be interlocked and added to the tank respectively, and the tank spray system started. On-site manual operations are strictly prohibited.

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