Chemical water process scheme for low-pressure waste heat boilers

For ordinary groundwater, if this process includes a mixed-bed filter after the RO stage, it should be sufficient to meet the requirements for water supply to high-pressure boilers. I also want to ask whether it is appropriate to place the sodium ion softening device before the mechanical filtration stage

Regarding the project mentioned by the original poster, I mainly work in boiler water treatment; if you’re interested, you can add me to discuss it further

I think the original poster has gotten the process wrong; the correct sequence should be: industrial water pipeline in the plant – raw water tank – raw water pump – mechanical filtration – activated carbon filtration – reverse osmosis unit – demineralized water tank. This is a more logical arrangement. Also, the original poster should mention what the rated steam pressure of the low-pressure waste heat boiler is If the pressure is below 2.5 MPa, softened water can be considered; there is no need to use deionized water, which makes the process simpler and cheaper.

I think by adopting the following process – plant water network – raw water tank – raw water pump – mechanical filtration – activated carbon filtration – reverse osmosis unit – decarburization unit – mixed-bed reactor – demineralized water tank – the quality of the output water will be more reliable

Thank you all. The current situation is that the waste heat boiler is a new addition, while the water softening unit is already existing in the plant. The hardness of the raw water supplied by the client is 798 mg/L; taking this into account, I have adopted the following scheme: the concentrate water from the reverse osmosis process can be reused for the regeneration of the water softening unit. The water flow path in the plant is as follows: water softening network – raw water tank – raw water pump – mechanical filtration – activated carbon filtration – reverse osmosis unit – demineralized water tank. The steam pressure of the boiler is 1.25–1.3 MPa

Hehe, if the steam pressure of the boiler is 1.25–1.3 MPa, then softened water is sufficient. What range does the hardness of the water output by the softening system currently in use fall within? I took a close look at the process described by the original poster, and I think there might be a mistake – why would a water softener be followed by a mechanical filter and an activated carbon filter? In confusion. . . . . This post was last edited by Tan Zhaofeng on 2008-2-25 11:34.]

:Handshake is completely feasible! Don’t worry about water quality!

Tan Zhaofeng: The actual situation is as follows – the softening unit used by the client right now is just a sodium bed, and no filtering device is installed in front of it. (The soft water treatment scheme wasn’t designed by me.) I was concerned that this might cause blockages in the reverse osmosis membranes, leading to membrane contamination; that’s why I added a filtering device in front of them. I think this approach is safer.

Reply (Floor 10): OP, if no filtering device is installed in front of the sodium bed, then the quality of the water coming out will not be much better; problems should have arisen already early in the morning! Therefore, the mechanical filter and the activated carbon filter should be placed in front of the sodium bed, rather than behind it. On the other hand, if the water entering the sodium bed meets the following requirements, there will be no problem: pH value: 6.5–8.5, turbidity ≤ 5 mg/l, colority ≤ 15, hardness ≤ 2.5 mmol/L.

There are a few issues: 1: If it is a low-pressure boiler, desalination may not be necessary depending on the water quality. Cationic and anionic resins will suffice. 2: If demineralized water is used, an deoxidation device is necessary, as demineralized water actually has a higher corrosion rate than non-demineralized water. 3: If chemical deoxygenation is used, then it’s better not to use deionized water at all.

Water that has passed through cation-anion resins can meet the standards of demineralized water. The claim that \"demmineralized water has a higher corrosion rate than non-demmineralized water\" is unfounded; demineralized water primarily serves to reduce the solid content and scaling in boiler water, while deoxygenated water is mainly used to prevent corrosion.

The so-called ion exchange resins generally refer to cationic resins, which are mainly sodium-based and used to exchange ions such as Ca and Mg; when combined with anionic resins in a mixed-bed system, the concentration of Na ions can be reduced, but this seems to be only a first-stage desalination system. Additionally: Desalinated water does indeed have a higher corrosion rate than non-desalinated water (of course, when no corrosion inhibitors are used), as the Ca and Mg ions in water actually possess a certain corrosion-inhibiting effect, which can be found in textbooks

  Hehe, to clarify: the anion exchange bed plus cation exchange bed produce first-grade deionized water, while adding a mixed-bed results in second-grade deionized water.     This post was last edited by Tan Zhaofeng on 2008-2-27 21:07.]

Thank you all! Now a problem has arisen: the client has decided to renovate the soft water treatment system in the existing facility. They provided a water quality report showing that the turbidity is 0.2; hardness is 789.9 mg/L; dissolved solids are 908.6 mg/L; calcium ions are 207.41 mg/L; magnesium ions are 25.52 mg/L; iron ions are 0.15 mg/L; and the pH value is 7.19 (these are the main values). I have drafted two possible processes – I’m not sure which one would work. Option 1: Raw water → pipeline filter → first-stage sodium exchange resin bed → treated water (using the existing factory building). Option 2: Raw water → mechanical filter → activated carbon filter → first-stage sodium exchange resin bed → treated water (requires construction of a new factory building). The required soft water treatment capacity is 160 t/h. Another issue is that the hardness of the raw water is 789.9 mg/L, while the required hardness of the treated water is less than or equal to 3 mg/L. Will using a first-stage sodium exchange resin bed be sufficient?

  Right! Use it if you want the device to get scrapped quickly! Such a high salt content, such high hardness! Desalination is necessary!  

Reply to the person on floor 17: Could you please help me come up with a good solution?