Why is the water quality in the low-pressure waste boiler always iron-red?
Thread Content
Our plant has a low-pressure waste boiler with a pressure of 0.2 MPa. The material used for the shell side is 16MnR, while the material for the tube side is 304 stainless steel. The fluids flowing through the tube side are mainly CO2, CO, H2, and water vapor. The pH value of the water in this boiler remains between 7 and 8. Water is supplied to it using the requirements applicable to high-pressure waste boilers, and the quality of the water has always been satisfactory. After being shut down for half a year and restarted, the water in the boiler has remained iron-red in color. It is suspected that this is caused by CO2 corrosion due to a leak in the tube side. If inspections after disassembly reveal no leak in the tube side, then could it be battery corrosion between the different materials (battery corrosion between the tube side and the shell side)? How should this issue be addressed?
Find a way to take a sample and see if there is process gas in the steam If there is, it proves that a leak has occurred; no other solutions are being considered. Should the boiler feed water also be analyzed to check if it is qualified? Did you bring anything? If the boiler feed water is of good quality, but it turns red after coming out of the waste heat exchanger, then you should analyze what might be wrong with that waste heat exchanger Analyze what the red thing is. If there’s something red, then there must be a reaction. This issue depends on analyzing the speech; it cannot be estimated. You can’t just guess either; how much money will you lose if you get it wrong? I’m just passing by as well, to learn from everyone*.
OP, is there still boiler water in the waste tank after you parked the vehicle? If so, then the waste tank has been corroded! Turn on the sewage discharge to see if it can make the color clearer! Phosphate in colored boiler water cannot be analyzed either; we need to find a solution quickly – let’s try turning on the waste discharge system! The pH of the boiler water is also a bit low.
The contents of the boiler water need to be identified through ion analysis before it is possible to further analyze the causes and determine appropriate measures.
Reply to 1# yxd808215: You can open the waste water discharge valve to check. If the water becomes clear after a short time, it’s due to rust that formed over an extended period of time with the boiler running; if there is no change even after a long time, then the issue lies in the quality of the water in the boiler itself. We have also encountered this phenomenon; we need to check the quality of the water at the source to see if any other acidic gases have leaked in.
Is it due to severe corrosion? Is it because the deionized water is of poor quality, with excessive oxygen corrosion or pitting corrosion occurring?
The first thing to consider is that you have been out of service for half a year; therefore, if you resume driving, the vehicle should be thoroughly washed and made ready before being put into use. Based on the current situation, a simple approach is to take samples from the boiler’s inlet and return water for comparative analysis, in order to determine whether the problem lies there; it is also necessary to check whether CO2 is leaking into the shell side. All these tasks require little effort and can be completed quickly. Only after considering all these aspects should one consider shutting down the equipment for maintenance. It is recommended that you discharge a large amount of waste first. .
What was said upstairs makes sense. Turn on the waste pot drain to see if the water becomes clear. If there is no change, analyze and check whether the furnace tube is corroded and leaking
Rust-colored; it can be basically concluded that oxygen corrosion is the main cause. If the steam system is shut down for an extended period of time, it is advisable to fill the steam piping system with nitrogen from a drain or another source, to keep the system under positive pressure; otherwise, oxygen corrosion can easily occur.