Reverse Osmosis for Boiler Makeup

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Reverse Osmosis for Boiler Makeup
What are advantages and disadvantages of using reverse osmosis permeate water for low-to-medium-pressure boiler makeup as compared to basic soft-water makeup?

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  1. Today there are zero honest disadvantages. RO units are far less expensive than ever. They are far easier to operate and maintain. The decrease in treatment chemicals and lost blowdown energy more than offset their initial cost.  In some parts of the world, you cannot discharge the softener salt brine to waste.  An RO solves that problem.  With an RO, you can also treat lesser quality waters and use them for boiler makeup.  When the carbon fiber ROs are commercialized, there will be a huge change in the technology.  Any disadvantages mentioned in the other answers will go away.  To be transparent, our company does not sell ROs nor do we sell RO membranes or parts. 

  2.           In my opinion, the main drawbacks of reverse osmosis are the high cost and complexity of maintenance. I think the high cost of the equipment pays off quickly enough by the absence of continuous boiler purging and more reliable working of the steam- condensate track equipment (by reducing the amount of carbon dioxide in steam and condensate). But the wrong organization of reverse osmosis in the boiler water treatment technology can lead to bad consequences.
             I think that for the preparation of water for low and medium pressure steam boilers in 90% of cases (depending on the composition of the source water) it is necessary to use a combined water treatment system, osmosis + softening. The boiler needs to feed with water containing sodium cation and bicarbonate ion. The Ca and Mg contained in the source water only reduce their salinity during osmosis. Even if the water hardness after osmosis can be obtained within the standard (which in practice is achieved very rarely), the lack of sodium will not allow to raise the pH of boiler water above 8.5. This will contribute to the strongest corrosion of the boiler and especially economizer. Of course, you can dose in osmotic water NaOH, but it is not a very good solution in the case of a steam boiler. It is better to organize the softening of osmotic water. At the same time, the filter cycle of such a softening system will be huge, the salt consumption for regeneration will be minimal, and the reliability and efficiency of the osmosis plant, deaerator, economizer, boiler and the steam- condensate track equipments will grow significantly.
               As having considerable production experience I can say that in practice it is more convenient to operate water treatment systems when softening is ahead of osmosis. Yes, this salt is consumed even more than just Na-cation of feed water, taking into account the consumption of the concentrate. But on softened water you can get a very high osmosis reсovery or even work in two stages of concentrate. In this case, the concentrate, depending on the composition of the source water, can be used, for example, in the reverse water supply system of the enterprise.
                It is obvious that the more condensate return to the deaerator, the less salt is contained in the feed water. With a large proportion of condensate return, the role of osmosis is not so significant. But even in this case, it can be quite significant. This is due to the working conditions of the steam and condensate line. This has already been said in the previous answers. 
                I apologize for such a long answer, but I would like to emphasize the prospects of osmosis is for water treatment of steam boilers as a powerful tool that can bring significant benefits or in case of improper operation to cause significant trouble. It is also necessary to develop competent guidance documents on the use of reverse osmosis in water treatment of steam boilers.

  3. Advantages:

    1-Operate at higher cycles of concentration.  The biggest savings are getting up to around 50 COC with diminishing returns to a practical max of around 75.

    2-Less scaling potential.  Your boiler should be much cleaner come inspection time.

    3-Boiler chemistry cost reduced up to 70%.

     

    Disadvantages:

    1-Greater operator attention than a water softener.

    2-Higher operating costs, especially in electricity.

    3-Capital cost.

    4-Make sure the metallurgy of your feed piping can handle the more corrosive feed water.

     

    Like everything else, it comes down to payback.  For most applications the payback is favorable over 2-3 years at most.  The cleaner the feed water and lower the pressure boiler, the longer the payback.

    1 Comment

  4. When treating steam boilers, the water quality of the make-up water needs to be taken into consideration and the steam usage as well as the condensate being returned as well as the type of boilers being used.  If the water has a low alkalinity and low dissolved solids, there is little point in using RO.  If the water has a moderate to high solids and alkalinity, then other forms such as de-alkalisation or reverse osmosis comes into its own.  The softening process removes the hardness but leaves dissolved solids and alkalinity.  This limits the concentration a boiler can run to without foaming because of high solids or high alkalinity.  The RO plant reduces the solids by 90% allowing the boiler to concentrate.  The second factor is the condensate corrosion.  If sodium bicarbonate enters a boiler, it breaks down and forms sodium hydroxide and carbon dioxide.  The latter flashes off in the steam and re-condenses with the water and forms carbonic acid.  This causes corrosion in the condensate and increases iron returning to the feed water.  It will even form grooving in stainless steel.  The use of the RO reduces the bicarbonate by 90 %, which in turn reduces the corrosion by reducing condensate pH.  In effect it should be close to neutral.

    1 Comment

  5. There is no advantage to using RO or softened water. Neither are balanced. Softened water just aids in scaling and RO water lacks content. 

    If your looking for water performance the answer is bonded pKw or neutral water electrolyzed in 10 amp AC/DC single flow chambers. 

    Structureless and neither alkaline or acidic, highly charged bonded pKw ionics is perfectly balanced for optimal water efficiency. Whether chillers, boilers, hydro coolers, hydroponics or just any commercial usage. 

    Safe, clean, sanitized Functional Electrolyzed Water, available in pure pKa, pure pKb and perfectly balanced pKw solutions and generators.

    Flows to 100 GPM - pH ranges from 2.4 ~ 11.8 and neutral from 5.5 ~ 9.5

    Stop fighting inhibitors, make them work for you. 

    2 Comments

  6. In general there are several pros and cons for using RO makeup in lower pressure boilers where traditionally softened water is adequate.  The RO water would necessarily allow for operation at much higher cycles of concentration thereby improving the energy efficiency of the boiler.  The purer nature of the water may mean that it could still have a lower tendency to scale further improving energy efficiency.  Obviously, the feed water system is more complex and more expensive from a capital perspective and likely carry higher on-going operational and maintenance expense.  Measures may need to be put in place to minimize corrosion potential on the front end of the boiler but that can be far off-set by far less corrosion potential in the condensate return.  In order to determine if the pros might outweigh the cons for a given application, one would have to look very closely at the quality of the makeup water to the pretreatment plant, as well as a detailed water and energy balance from the competing technologies.  Lower gas prices over the past few years have made the hurdle steeper but it's worth investigating.  Each application is unique and will stand on its own merits.

    1 Comment

    1. Optimal water performance comes from balancing the ions. The only way to balance is with applied power. 10,000 mA AC/DC generators. Bonding acidic and alkaline ions creating a neutral ion, then charging again creating the structureless ionic solution. 

      No scale, sanitized, structureless, redoux solutions for optimized performance. 

      ElectroLIFE for comercial utilities

  7. First in the industry there are high pressure boilers (pressure >1,000 psig) and low pressure boilers (

  10. Advantage,  the boiler could be operated on high cycle of concentration

    Disadvantage: as the RO permeate is of low pH , there might be a high risk of corrosion in the feed tank and piping if pH & Alkalinity is not maintained by proper chemical dosing

    2 Comments

    2. I agree with Khuram and will add: softeners have a lower initial capital cost versus RO, which should be compared to the energy/water/chemical savings of operating the boiler at higher cycles with an RO.  RO's membranes will need to be cleaned and/or have antiscalent fed to prevent fouling depending on makeup water quality.   Softeners will need a brine tank with salt added regularly unless a vessel exchange program is used, some plants don't want to deal with the salt/brine tank.  Lastly, if the boiler is operating at a high pressure, an RO is generally used/required due to the need for higher purity makeup water.