Reasons for wall sticking in hydrothermal synthesis of reaction kettle

Release time:

2023-09-05

Once wall sticking occurs during the use of reactor equipment, it will seriously affect the operation of the reactor. So what is the reason for this?

Reasons for wall sticking in hydrothermal synthesis of reaction kettle

Once wall sticking occurs during the use of reactor equipment, it will seriously affect the operation of the reactor. So what is the reason for this?
1. Sulfate content
Due to the high sulfate content in urea, when urea is added in the later stage of resin condensation reaction, it is equivalent to adding a curing agent, which promotes the resin to quickly crosslink into a network structure. If not treated in time, the resin will solidify in the reaction vessel. Therefore, standard industrial urea raw materials should be selected in production to limit the sulfate content in urea to below 0.01%.
2. Degree of operational balance
When the control of temperature, pressure and other adhesive process indicators is unstable or fluctuates too much, the resin polymerization reaction process is uneven, which can easily cause wall adhesion. So in the production operation, the reactor should be slowly pressurized and heated. Generally, about 0.15Mpa of steam is introduced and kept for 2-3 minutes before slowly increasing pressure and temperature. The recommended speed for improvement is 0.1-0.15Mpa per minute.
3. Temperature difference of kettle wall
If the temperature of the cooling medium is too low or suddenly drops, the temperature difference between the reactor wall and the material is too large, causing the adhesive liquid in contact with the reactor wall to stick to the wall. Therefore, both heating and cooling should be carried out within a reasonable temperature difference range. Generally, the steam usage temperature should be less than 180 ℃, the temperature difference thermal shock should be less than 120 ℃, and the cooling shock should be less than 90 ℃. At the same time, attention should be paid to determining the appropriate inlet and outlet temperatures of the cooling medium and maintaining balanced operation.
4. Reaction temperature and time
When the temperature of the reaction liquid in the hydrothermal synthesis reactor is lower than 80 ℃, if ammonia chloride is used as the catalyst, the PH value cannot be displayed because of the fast reaction speed of ammonia chloride. When the temperature rises, the PH value drops rapidly, the reaction speed is accelerated, and the condensation reaction is too intense, resulting in gel sticking. In addition, if the condensation reaction time is too long, the molecular weight of the resin is large, and the viscosity is too high, it is also easy to cause wall sticking phenomenon.