Environmental issues related to the shutdown and restart of major overhauls in the refining industry

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Key Points of Environmental Management for Major Equipment Overhaul I. General Environmental Requirements for Major Overhaul (1) Ensure that pollutants are discharged within specified limits; discharge beyond these limits is strictly prohibited, and no pollution incidents or other environmental problems shall occur throughout the overhaul process. 1. Wastewater discharge is prohibited when it exceeds standards, and only allowed within specified limits, thus avoiding strain on wastewater treatment plants ； 2. Exhaust emissions meet the requirements of exhaust pollutant emission standards ； 3. Proper disposal of solid waste, with hazardous waste being handled in a manner that ensures it is unloaded and loaded immediately without any accumulation ； (II) General requirements: Maintenance units shall strictly comply with pollutant emission standards (such as GB31570) and the requirements outlined in the \"Key Points for Environmental Protection Management during Major Equipment Overhauls in 2018\". They must develop and submit plans for environmental protection measures prior to the overhaul, conduct predictions and statistics regarding pollutant emissions, and establish control measures accordingly ； Formulate targeted safeguard measures for various stages such as parking, maintenance, and operation, as well as key maintenance tasks ； The maintenance plan for environmental protection facilities should be formulated following the principle of \"carrying out maintenance later than that of the production units, but earlier than the restart of those units.\" During maintenance periods, the branch company and workshops should strengthen environmental protection inspections to ensure that all environmental protection measures are implemented. At the same time, environmental monitoring should be strengthened, the frequency of air analysis at and around emission sources should be increased, and it is necessary to ensure that online monitoring instruments transmit accurate data that meets the specified standards. All units should strengthen communication with the control center and the wastewater treatment plant, so that emergency measures can be taken promptly in case of abnormalities, ensuring compliant discharge. II. Wastewater Discharge (I) Discharge Requirements 1. All units shall strictly control the amount of wastewater discharged; any significant fluctuations should be reported promptly to enable coordinated handling. During the major maintenance shutdown – inspection – restart process, the peak limit for wastewater discharge is 1,500 tons per hour. 2. It is strictly prohibited to discharge inspection wastewater in excess of the specified limits; the group company has set the following limits for wastewater quality: COD 700 mg/L, petroleum compounds 100 mg/L, ammonia nitrogen 50 mg/L, pH 6–9, and conductivity 2,000 uS/cm. (II) Management measures: 1. Process treatment: Each unit should plan to discharge wastewater in stages in advance, in order to avoid large-scale discharge at once ； On-site material returns must be collected in containers and must not be discharged into the drainage system ； It is prohibited to use fire-fighting water for flushing the discharge ； Discharge of wastewater exceeding standards is strictly prohibited ； Chemical cleaning wastewater must not be discharged directly into sewage treatment plants; each unit should establish specific wastewater treatment measures and submit them to the relevant authorities for approval. 2. Equipment cleaning: Cleaning operations for equipment in the plant area must be carried out in a dedicated cleaning area equipped with bunds, so as to collect cleaning wastewater, residual liquids, and sludge, ensuring that such wastewater is discharged into the sewage system. Mixing of rainwater and wastewater is strictly prohibited; in the event of contamination of the rainwater system during major repairs, it will be treated as a pollution incident. 3. Rainwater system: All units shall strictly protect the rainwater system; process discharge water, cleaning wastewater, and residual liquids must not be discharged into the rainwater system ； During maintenance, the cofferdam surrounding the equipment area must not be damaged arbitrarily; if it is necessary to remove it, temporary measures should be taken, including constructing a temporary dike and covering nearby rainwater drains ； The refining and chemical subsidiary should carefully inspect the drainage facilities in the plant area to ensure that the rainwater valves are properly closed, thereby preventing sewage from entering the rainwater drainage system. Each unit should also formulate emergency plans for flood control during maintenance periods to ensure that water quality meets standards during emergency drainage. 4. Tank cleaning: When cleaning the storage tank, it is necessary to close the sump drain valve and install a filter to prevent sludge and debris from entering the sewage system. 5. Wastewater monitoring: During the shutdown period for major maintenance, units should increase the frequency of water quality tests, and the testing center should also do so. Report in case of abnormal water quality. 6. Standardized discharge: Wastewater from maintenance activities must be treated in a wastewater treatment plant before being discharged through the designated wastewater outlet; it is prohibited to use the general rainwater discharge outlet for such purposes. III. Exhaust Gas Emissions (I) Emission Requirements 1. On-site emission of process exhaust gases is strictly prohibited. 2. Incomplete combustion resulting in black smoke during flare emissions is strictly prohibited. (II) Management Measures When formulating plans for starting up, shutting down operations, and handling processes, various units must, in accordance with pollutant emission standards such as GB31570, develop effective control measures to ensure that no flaring occurs during start-up or shutdown operations, and that there are no unpleasant odors at the site during thorough cleaning and steaming of the process systems. Each unit must designate a responsible person for emission management who is tasked with coordinating and overseeing activities related to flare emissions, control of process exhaust emissions, and exhaust gas monitoring during the startup, shutdown, and operational phases. IV. Noise Control: All relevant units should actively implement soundproofing and noise reduction measures to control the noise at the maintenance sites, especially exhaust noise, ensuring that the noise level at the factory boundaries remains within the specified limits during maintenance (65 dB during the day, 55 dB at night). V. For the disposal of solid waste, each unit responsible for maintenance work should prepare a plan in advance for dealing with the hazardous waste generated during such work. It is necessary to determine the quantity and type of this waste, and then contact waste disposal companies based on the category of the hazardous waste. A disposal contract should be established through bidding, and this contract must specify the deadline for disposal as well as penalties in case of delays, so as to ensure that the waste is disposed of promptly once it is collected. General solid waste generated during maintenance should be disposed of promptly; it must not be piled up or transported away for dumping arbitrarily ； The unauthorized dumping of industrial solid waste, construction debris, and household waste is prohibited. The company will conduct strict assessments of the disposal of solid waste resulting from major overhauls in various units. VI. Environmental protection facilities 1. The parking plan for environmental protection facilities must be submitted in advance; parking is allowed only after approval. Upon completion of maintenance, these facilities should be inspected to ensure they are in good condition. 2. Operate the accident tank empty to ensure an accurate tank level, so as to be prepared for emergencies. 3. Before maintenance, ensure that the water quality in the rainwater tank meets the standards and that the tank is operating at a low liquid level. Ensure that emergencies can be discharged directly. 4. The temporary storage facility for hazardous waste should maintain sufficient space before maintenance to accommodate emergency situations. Let’s discuss, what needs to be added?