Catalytic fractionator top recycle water washing
Thread Content
The catalytic processing raw materials in our unit are quite diverse; salt accumulation at the top of the distillation tower causes pump cavitation, and washing treatment proves to be effective. Recently, the salt deposition has worsened, requiring water washing almost every month, which affects the stable operation of the equipment. Please help analyze the reasons. Raw material composition: vacuum wax oil 60%, normal residue 28%, coker wax oil 12%. Distillation column operating conditions: top temperature 125 degrees, top pressure 0.13 MPa, top recycle extraction temperature 127 degrees, refeed temperature 85 degrees
What’s the reason? I really want to share the burden with you; please let an expert handle it.
There are mainly three reasons for the failure of top circulation to deliver sufficient volume: 1. The oil collection tank at the bottom of the top circulation extraction port is cracked or corroded, resulting in no flow over an extended period of time； 2. Salt formation at the top of the tower; this condition improves after washing ； 3. If the top circulation tower or the temperature at the top of the tower is too low, increasing the outlet temperature will help improve the situation. With a maximum operating temperature of 125 degrees, the third cause can be ruled out ； Based on my experience, it could be the first reason.
Check whether the crude oil desalination rate of the atmospheric and vacuum distillation unit is satisfactory.
The salt accumulation mentioned by LZ is not due to an insufficient top circulation volume; water washing is currently the most effective method for addressing salt accumulation at the top of the distillation tower. Additionally, from a process perspective, increasing the temperature at the top of the distillation tower and improving the properties of the feed to the plant can also help reduce salt accumulation there.
If the salt content in the raw material cannot be reduced, regular washing is the only option. However, washing is not very troublesome; by using cold reflux to lower the top temperature, the steam in the tower condenses into water, and the top circulation pump is then used to remove this condensed water – there’s no need to reduce the flow rate.
Thank you all for your suggestions! There is no significant change in the salt content analyzed in the atmospheric and vacuum distillation units; could this be the result of coking wax oil? What should be considered when blending coking wax oil?
Reply to 3# maysee: Hello, could you explain the third issue related to the inability to achieve sufficient circulation volume? It is caused by too low temperature in the recirculation tower or at the top of the tower; increasing the outlet temperature can help resolve this problem
The issue with residue oil is the increase in salt content. I’m not sure if ammonia water is still added to the top of your distillation tower; ammonium salts and other salts can cause scaling at the tower top. Our plant has also carried out washing procedures, but the problem mainly lies with the crude oil itself