Briefly describe the normal startup steps for double-column distillation?

1. The first start-up of the distillation tower after maintenance requires nitrogen purging and deionized water cleaning. 2. Check and close all the small valves in the vent valve and drain valve systems, close the sampling valve, and close the bottom level control valve. 3. Supply cooling water to the top condenser, direct steam to before the reboiler, and keep the drain valve ready for use. 4. Feeding. 5. Increase temperature. 6. Raise the temperature to the boiling point as required by each distillation column’s temperature rise rate, via control operations. 7. Establish a return flow. 8. Adjust the load.

Normal startup procedure for double-column distillation: In principle, the pre-distillation column is started first, followed by the main distillation column; feed is introduced to the main distillation column only after the temperature inside the pre-distillation column, the reflux rate, and all other process parameters are within normal ranges. 1) Inform the dispatch room and relevant stations before driving. 2) Open the outlet valve of the crude methanol storage tank and the inlet and outlet valves of the crude methanol pump in the warehouse, and perform pump rotation. 3) Open the inlet valves for the full condenser of the distillation tower, the pre-tower condenser, the pure methanol cooler, and the fusel oil cooler. 4) Turn on the power and gas supply for the instruments, and open the inlet and outlet valves of the condensate tank. 5) Drain the steam system, open the steam inlet valves of each circulating evaporator, as well as the condensate regulation system and the main condensate discharge valves; activate the steam regulation system to maintain a steam pressure of 0.3~0.35 Mpa (auto-regulation). 6) Start the crude methanol pump to supply material, and at the same time add alkaline solution along with extraction condensate to the pre-tower. 7) Operate the remote control panel for adjusting the condensate water in the pre-tower cyclic evaporator, in order to regulate the steam supply to the pre-tower. Set the pre-tower startup temperature; once 4/5 of the pre-tower collection tank is filled, start the pre-tower reflux pump. Adjust the return flow rate according to the load; perform this operation on the main tower as well. 8) Adjust the temperatures at various points in the two towers to normal levels; once the temperature at layer 26 of the main tower is within the normal range, open the purified methanol outlet valve to begin extraction. Before the quality parameters are met, it is extracted and returned to the crude alcohol tank. 9) When the temperature at the base of the main tower exceeds 140°C, open the residual liquid control valve; the residual liquid is discharged into the residual liquid tank, and the dispatch team is contacted to arrange biochemical treatment, At the same time starting the residual liquid pump. 10) When the temperature of the fusel oil in the main tower reaches the extraction temperature, fusel oil extraction begins. Adjust the production well and production volume based on the analysis of the oil layer. 11) After the quality of the finished products meets the standards, switch to using the inlet channel to feed them into the finished product tank. 12) Once production becomes stable, activate the automatic control system using the instruments.