How should the urea unit be operated during an emergency shutdown caused by a stoppage of steam supply?

For different situations of power outage, water outage, steam outage, and instrument air outage, we should focus on corresponding processing. 1. Power outage 1.1 During a power outage, since the high-pressure operation equipment has stopped, the flow of the three materials into the synthesis tower should be cut off in time to prevent the materials in the tower from flowing back and clogging the pipe valve. The regulating valve controls the µXL backup power supply (UPS) to last for 30 minutes. 1.2 When there is no backup power supply for the high-pressure flushing water pump, the pipes that can be blown should be fully blown with steam, and attention should be paid to insulation. After power is available, immediately start the steam condensate pump, high-pressure flushing pump, evaporation condensate pump, ammonia water pump, and dimethyl pump. Flush the dilution equipment as soon as possible. If the residual materials in the pipeline cannot be restored for a while, the materials that are easy to block should be discharged in time. 1.3 The rest should be treated as short-stop. (If the water is cut off due to power outage, the PRCA-302 and PRCA-303 regulating valves can be left on line to control the pressure to prevent overpressure. 2. Cut off the circulating water 2.1 After the three materials stop entering the tower, close the front and rear shut-off valves of PRCA-301, LICA-301, LRCA-303 and LRCA-304. 2.2 Pay attention to PRCA-302 and PRCA-303, use the auxiliary line to control the overpressure, open the drain valve at the bottom of the ammonia cooler, and drain away the accumulated water. 2.3 The rest will be handled as short stops. 3. Steam cutoff 3.1 Use residual steam to quickly handle the shutdown of the evaporation system. 3.2 Flush the system promptly and according to the steps. 3.3 Dilute the solution in the suction tower and discharge it while diluting. 3.4 The rest will be handled as short stops. 4. Cut off the instrument air 4.1 After the three materials stop entering the tower, close the cut-off valves of the PRCA-301, PRCA-302, PRCA-303, LICA-301, LRCA-303, LRCA-304, and TRCA-310 regulating valves. 4.2 Open and close the regulating valve according to the air, and use the auxiliary line or the regulating valve to control the stop.