What should be done if the parameters of boiler feedwater and boiler water exceed the specified limits?
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RT, 1. Our facility uses thermal deaerators for deoxygenation; chemical deoxygenation is not employed. The temperature of the deaerator is kept around 110 degrees. Demineralized water is used, and the dissolved oxygen level measured by the laboratory remains around 10 Mg/L, with a pH value of 7–8. These values differ significantly from the standard specifications. When asked, the laboratory staff said that the sample water is allowed to reach room temperature before measurement, and electronic dissolved oxygen meters and pH meters are used for testing. My question is: at what temperature should dissolved oxygen be measured? Will there be differences in the readings, and which method provides a more accurate reflection of the actual operating conditions? 2. The alkalinity of the water in the pot is only around 0.7 mmol/L, and the pH value is also between 8 and 9 – this is a significant deviation from the **standards. Is it necessary to add chemicals? How should this be addressed?
A decrease in alkalinity leads to a drop in pH, which can cause acidic corrosion of the water wall tubes. Solution: If phosphate treatment in the furnace or sodium hydroxide addition is carried out, the amount of chemical added should be reduced, as the alkalinity drops rapidly, especially when phosphates are used. This is control at the source. Emergency solution: Immediately carry out boiler blowdown. If a continuous blowdown system is available, the amount of continuous blowdown can be increased; at the same time, attention should be paid to analyzing the alkalinity of the boiler water to prevent it from dropping too rapidly. Although regular discharge of waste can also reduce acidity, its effect is still inferior to that of continuous discharge.
Is the dissolved oxygen concentration of 10 mg/L mentioned by the poster before deoxygenation or after it? But whether it is on the front or the back, such a level of dissolved oxygen is too high for boiler feedwater. Furthermore, for the testing of pure water’s pH, conductivity, and dissolved oxygen, online analysis should be preferred. If offline analysis is used, an appropriate laboratory sampling system must be designed; before sampling, the samples should be cooled and depressurized to minimize the impact of the environment, as well as the sampling containers and process, on the representativeness of the samples.
Dissolved oxygen is a parameter that is measured after passing through the deaerator; it is analyzed by taking samples in the laboratory. The laboratory stated that the samples are allowed to reach room temperature before testing. Now the company wants to add chemicals to the boiler in order to adjust its pH value. What chemicals should be used? Should hydrazine be added to the feed water, or trisodium phosphate to the boiler water? Are there any other things to keep in mind? The requirement for feed water is 8-9.5, and that for boiler water is 10-12. What measures should be taken?
Don’t you have any inspection and control parameters for your boiler feedwater? There must always be operating procedures. These details should all be specified in the operating procedures. Additionally, the details of your boiler feedwater sampling and testing procedures should be discussed in detail. Such situations where the test results differ significantly from the actual values are entirely due to issues with corporate management and the implementation of procedures, rather than any technical problems.
The operating procedures specify control parameters for feed water and boiler water; this aspect was not controlled before. Now, the boiler inspection agency requires that water quality parameters be monitored, and that’s why such problems have arisen. For specific details regarding testing, we will need to consult our laboratory staff.
Treat the feedwater and boiler water in accordance with the standards, boiler operation procedures, or the requirements of the installation and use instructions.