Posted by Paul K on June 02, 2001 at 12:36:30:
In Reply to: please answer these question posted by zaib on June 02, 2001 at 08:00:07:
Zaib
Unfortunately I cannot address all of your questions, but maybe I can shed some light on your # 3 question. From previous questions posted here in the forum, I will assume you are inquiring about the same system. You described a boiler that produces 40 tons of steam per day. This is equal to 80,000 pounds of steam, or 9604 gallons of water. What is your % of condensate return or % of make up? Blowdown is necessary for the removal of minerals and impurities that enter the system through makeup and the return process. Zeolite (cation exchange) alone may not reduce your need for continuous blowdown. If you have constituents in the makeup water that limit the maximum cycles of concentration and intermittent blowdown is inadequate to keep these under control, the easiest solution is continuous blowdown. You may consider R. O. or DI. for a higher quality make up to the feed water system. This will be costly, but may offer savings in wasted heat. I will further assume that your example boiler operates on low cycles and a low percentage of condensate return. This adds to the need for extra blowdown. If your makeup water quality is poor, coupled with little return you will need continuous blowdown. Remember, water softening only exchanges calcium and magnesium for sodium. Other impurities like alkalinity, chloride, tds, tss, silica, and copper will pass through the softener and concentrate in the boiler