Question of the Day: Reducing Boiler Blowdown

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Question of the Day: Reducing Boiler Blowdown

How can one reduce blowdown for a low-pressure boiler?

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14 Answers

  2. First thing would be to see if addition of an anti-foam to the boiler treatment would allow higher cycles. Second convert from sulfite as the oxygen scavenger to DEHA or erythorate, lower resultant TDS, higher cycles. Finally, pretreat the makeup with an RO, lower TDS going in, much higher cycles. Higher cycles = lower blowdown. 

  3. Purpose for blowdown  ; Under  normal operating condition the only reason for blowdown is to lower the suspended and dissolved solids content of the boiler water. These solids   are brought in by the and since the steam leaving the boiler is relatively    pure concentration of solids    will develop in the boiler water. Excessive amount of  suspended solids will cause deposition of sludge .Excessive amount of dissolved solids have the same deleterious effect as suspended solid.                                   In fact , in many cases the effect of boiler water solids on steam purity needed no longer be considered of in controlling  boiler water balance.                                                                                                                                     BLOWDOWN CONTROL:  It is important that blowdown is such that the boiler water concentration . At the same time it is equally important that excessive blow down  to be avoided because of the related heat loss. Regardless of the factor limiting the boiler water blowdown is usually based  on the determination of total solids content of the boiler water. especially a boiler operating  pressure above 600 psig blow down is based on the limiting value of silica contents and for boiler operating  pressure 400 psig silica con. is not a problem. (for further details BETZ HAND BOOK OF INDUSTRIAL WATER CONDIIONING (sixth edition)

  4. Use ultra pure water (Mix bed water), all organic treatment for feed water treatment, Return condensate management can help you to achieve your goals.

  5. % Blow down = quantity of blowdown water / quantity of feed water x 100. Blowdown rate varies widely with feed water quality. It can be as low as 1% going upto 20% of feed water. I am assuming that all good practices for pre-treatment of feed water are in place, and still you want to reduce blowdown. Poor control or judgement can further add extra blowdowns. From operating economy point, frequent short blowdowns are preferred to infrequent lengthy blows. Generally, in low pressure boilers, bowdown controls are manual and poor with wide range of conductivity. Changing from a manually adjusted continuous blowdown to automatically controlled continuous blowdown  can save about 20% blowdown.

     

  6. A lot of good answers and suggestions. But more details are necessary for developing a sustainable solution, e. g. volumes of the actual flows at the process limits, feed water analysis, analysis of actual blowdown, local legal frame work addressing wastewater discharge.

    Reverse osmosis or  -  depending on the frame parameter  -  nanofiltration could be used for treatment of the feed water, and reverse osmosis for the treatment of the blowdown. But open channel module technology should be used, not conventional spiral wound membrane elements in order to reduce the usual problems concerning pretreatment.

    There exist approved sustainable solutions. You could contact us at dr.peters.consulting@t-online.de.     

  8. Installing a Softerwater catalytic water conditioner in the recircualting loop will keep minerals in suspension and reduce build up in associated pipework and equipment in the system.  Contact me for further information.

  9. Your answer is an absolute "Yes". Your motivation to do so is 100% directed by finances. If it costs you $2.00 to save $1.00, there is very little reason. However, if there are safety benefits or reliability benefits, those need to get added to the mix. Increasing the cycles (reducing blowdown) is not a technical issue, it is a business/cost issue.

  10. You reduce blowdown by improving feedwater quality and reducing condensate losses

     

  12. The answer is to reduce the level of dissolved solids in the make-up water to the boiler.  Plain and simple this is a direct, reliable path to achieving your goal.  One could make use of some new water purification equipment:  membrane capacitive deionization, for example, will very efficiently remove hardness from raw water, but further it will reduce other conductive ions to a low level, depending on operating parameters.  Additionally, recovery of water can easily be over 90%, rivaling that of traditional ion-exchange water softening.  No reverse osmosis or other pretreatment is needed, as the membrane CAP DI is very robust, tolerant of all chlorine species to levels not typically found in water supplies.

    One can also choose high-efficiency reverse osmosis (HERO), and nearly achieve the same results, but with additional required pretreatment necessary to protect the membranes.

  14. The limiting species must first be determined based upon maximum species limits in the boiler water.  Is it alkalinity, conductivity, silica, other.....once determined, appropriate treatment may be prescribed to remove the limiting species, or at least reduce it to a manageable level - thus allowing higher cycles of concentration and less boiler blowdown.,

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