Regarding high-pressure water injection

Prevent heat exchangers. Crystallization occurs in the air-cooled tube bundles; continuous water injection in certain areas can affect the heat exchange efficiency or the separation performance.

Prevent pipeline erosion and corrosion； At the same time, the temperature is low after heat exchange, resulting in high gas consumption by the heating furnace and increased energy consumption

Generally, water is injected to prevent the crystallization of ammonium salts, which could cause corrosion. What does the original poster mean by injecting water directly in front?

Regular water injection is intended to remove ammonium salts from within the heat exchanger tubes. If water is injected on a continuous basis through this regular injection process, it causes corrosion and erosion of the heat exchanger tubes, leading to internal leaks in the heat exchanger; as a result, the feed mixture mixes with the output stream, causing the product to be of substandard quality

Based on the crystallization temperature of ammonium salts, lower high-pressure air cooling temperatures facilitate crystallization the most; prolonged boiling in water also contributes to this； The temperature in the upstream heat exchanger is high, resulting in less crystallization; therefore, water is injected periodically to flush the tube side

The water injection before high-pressure air cooling is used to flush out ammonium sulfide salts, while the water injection mentioned earlier refers to the intermittent high-pressure water injection before the thermal high-pressure gas-liquid heat exchanger, which is used to flush out ammonium chloride salts. These two types of ammonium salts have different crystallization temperatures at the same pressure; the crystallization temperature of ammonium sulfide salts during high-pressure hydrogenation is around 170°C, whereas that of ammonium chloride salts is around 210°C. Since ammonium salts can only be dissolved in liquid water, as water vapor cannot dissolve them, the location of the water injection points must be determined by measuring the temperature – water should be injected at a temperature higher than that at which the ammonium salts start to crystallize. Additionally, it is necessary to calculate the rate of vaporization of water under certain pressure and temperature conditions, in order to determine where the water injection points should be located. Therefore, two water injection points are required. Moreover, the chloride ions in the feedstock can be controlled through upstream equipment and temperature regulation – by increasing the efficiency of electrical desalination in the atmospheric and vacuum distillation units or by adjusting the proportion of crude oil processed, it is possible to control the chlorine content in the feed to the hydrocracking unit (although the sulfur content in the crude oil processed remains far higher than the chlorine content regardless of any adjustments). It is also possible to prevent blockages in the heat exchangers by raising the inlet temperature of these exchangers, thereby shifting the crystallization point of ammonium chloride; hence, intermittent water injection is used at the early stages of the process. If the intermittent water injection at the front end is replaced with continuous injection, it will increase the load on the high-pressure heat exchanger, leading to higher initial investment costs during the design phase. As for ammonium sulfide salts, the extended distance of the demineralized water injection point results in a longer residence time of water within the oil, which increases the vaporization rate; as a consequence, the cleaning effect on ammonium sulfide salts is reduced, and the high-pressure air coolers can become clogged.

Regular water injection is primarily considered in terms of the production cost of the device; since water needs to be injected, it means that certain costs are incurred during the production of the device； Ammonium salts, ammonium chloride salts – salts of this kind tend to crystallize and adhere to the inner walls of equipment at temperatures below 175 degrees; adding water helps to dissolve them in water

I would like to ask: have you encountered any cases of internal leakage caused by continuous water injection for a long period of time before high pressure switching?