Regarding the commissioning purging of the hydrogenation unit.

Apart from paying attention to the program-controlled valve during PSA purging, the purging process is similar to that of other devices in other aspects. The air supply point can be determined based on the actual situation. It can be blown out from the tower and the container. Blow from a higher place to a lower one. Unpurified air can be used as the purging medium. !

3.2. Purging of the plant’s pipelines 3.2.1. Purpose: Newly constructed plant pipelines usually contain welding slag, debris, and other impurities. After a thorough inspection and rectification, these pipelines need to be purged in order to remove dirt such as sediment, welding slag, and rust from within them； At the same time, another main purpose is to check whether the process pipelines are unobstructed and whether they have been installed correctly. 3.2.2. Requirements: (1) The principle for purging pipelines is to follow the flow direction, starting with the main lines before moving on to the branch lines, and to purge from higher to lower levels. (2) To prevent dirt from being blown into the equipment, the pipelines connected to it should be purged as much as possible from inside the equipment outward, and from high to low. (3) All clogged components such as control valves, flowmeter orifice plates, mass flowmeters, and sampling valves must be removed. The shut-off valves before and after the control valve should be opened and closed during the purging process. (4) The pump is not involved in the purging process; it can be connected via a bypass line, with its inlet and outlet opened for backflow to empty it. During the purging of the heat exchanger, the bypass line can be used first; once purging is complete, then the equipment can be accessed. (5) Connect to the instruments, remove the pressure gauge, and turn off all instrument leads. After it has been purged clean, contact the instrumentation team to purge the instrument lead wires. (6) Purging must be carried out system by system, and the pipelines and areas that have been purged can be isolated. (7) The purging process needs to be checked in advance; the check valve can be removed and a prefabricated short section added to ensure smooth flow. (8) The top vents in various locations, as well as the bottom drain outlets and drain vents, must be opened for drainage during purging. (9) Blind plates shall be installed at the boundary of the high and low pressure vent lines; discharge is carried out at this boundary before venting. The vent valves of the light and heavy contaminated oil tanks are opened, and any venting that occurs during the system purging is directed directly to the boundary for discharge. All venting from the light and heavy contaminated oil lines is sent directly to those tanks for discharge. (10) During the purging process, each subsystem shall be purged separately; the distillation, absorption and stabilization systems, as well as the liquid pipelines, can be purged using 1.0 MPa steam ； The hydrogen-handling system is purged with nitrogen. 3.2.3. Precautions: (1) If steam purging is used, first turn on the drain valve and then introduce the steam; ensure that the drainage path is unobstructed. The steam introduction process is carried out in stages, from small to large, to warm the pipelines, while taking strict precautions to prevent water hammer and damage to the pipelines. (2) When steam passes through the heat exchanger, the other side must be opened for venting first to prevent pressure buildup ； For water cooling, turn off the inlet and outlet valves and open the drain. (3) During the purging process, a dedicated person should be assigned to monitor the exhaust outlet to strengthen safety inspections. (4) After the purging is completed, the equipment’s vent valves and drain valves should be opened to prevent a negative pressure from forming inside the tower and containers. (5) During the purging process, try to use fixed points to introduce steam; if necessary due to actual circumstances, temporary fixed points can be used for this purpose. It is prohibited to use rubber belts to connect temporary lines for purging.

The hydrogenation system and the distillation system are isolated first; for gasoline and kerosene hydrogenation, water stripping is used first, while for diesel hydrogenation, direct steam purging is employed

May I ask, which source did you draw the content from?

In the initial stage, compressed air and steam are generally used; there are various options depending on the system and materials. You can take a look at a project startup plan, as all of this information is included there

For the reaction and distillation systems, high-pressure and low-pressure systems are purged separately, starting with the main lines before moving on to the branch lines

For a newly constructed plant, the hydrogen-handling system should first be purged using nitrogen blast cleaning; if it’s a plant that has just been overhauled, then such a question wouldn’t arise. The utility systems are first checked through using unpurified air, while the distillation and reaction systems must be isolated using blind flanges. Gas supply points and discharge points are established in accordance with the plant’s system layout. Once everything is in order, the hydrogen-handling system is purged with nitrogen, and the distillation system is purged with steam – the main pipelines are handled first in this process. Following the principle of the rear branch lines, purging is carried out one by one in a sequential front-to-back manner; once a branch line is completed, it is closed. After the common system is supplied with air, purging is done using the medium from that same line. It is important to pay attention to safety measures: a dedicated person should be responsible for each stage of purging, the process should be organized properly, and both the introduction of the medium and its discharge should be carried out slowly at first before increasing the rate