As steam is used in a process and gives up its heat energy, it becomes a liquid called condensate. This condensate is an exceptionally valuable resource that is typically designed to be recovered and used back into the boiler system.
Condensate’s value can be broken down into the following categories.
Condensate is hot and returning it back to the boiler system means less fuel is required to heat the cooler makeup water that would otherwise be required to replace the wasted condensate. Fuel savings can be significant and is commonly the highest component of condensate’s value. As shown in the example below, for every 1,000 gallons of condensate not returned to the boiler system, it costs an extra $14.60 in natural gas just to heat fresh makeup water to the same temperature as the condensate.
Temperature difference between makeup water and condensate
180°F - 60°F = 120°F
Heat required to heat makeup water to condensate temperature
1 BTU/lb. of heat energy is needed to raise 1 lb. of water by 1°F.
Therefore, it takes 120 BTU/lb. to raise 1 lb. of water by 120°F.
1,000 gals. of water weighs 8,340 lbs.
This 1,000 gals. of water requires 120 BTU/lb. * 8,340 lbs. = 1,000,800 BTU of heat.
For an 80% efficient boiler, it requires 1,167,600 BTU/0.80 = 1,251,000 BTU of heat.
Boiler fuel required = 1,251,000 BTU/(1,000 BTU/cu. ft.) = 1,251 cu. ft. of natural gas
Cost of boiler fuel required to heat 1,000 gals of makeup water = 1,251 cu. ft. * ($6/1,000 cu. ft.) = $7.51
Water Cost Value
Any condensate not returned to the boiler system must be replaced with fresh makeup water. Otherwise, the boilers would eventually run dry for lack of water. City water may cost $5, $10, $15, or higher per 1,000 gallons, including the sewer costs. This can add up quickly over the course of a year.
Returning more condensate back to the boiler system has the additional benefit of improving feedwater quality which can increase the number of boiler cycles of concentration and reduce the amount of blowdown required. Returning less condensate back to the boiler system will have the exact opposite effect. Depending upon the size of the boiler, current percent condensate return, fuel costs, etc., the impact upon blowdown costs can be significant and should be calculated.
It takes pretreated makeup water to replace any condensate that is not returned to the boiler system. This pretreatment may include softeners, dealkalizers, reverse osmosis, deionization, etc. Each of these has a cost for every gallon of water produced. Costs to consider include:
Chemical Cost Value
Neutralizing amines are widely used for condensate system corrosion control. Because a portion of the neutralizing amines recycle with the condensate, returning more condensate reduces neutralizing amine requirements. Returning more condensate also reduces the feedwater alkalinity which further reduces neutralizing amine requirements.
The total value of condensate can be substantial when all the costs of unrecovered condensate are taken into account. Depending upon system size, operating factors, costs, etc., the total value of condensate could easily be $15, $20, $30, or more per 1,000 gallons. Basically, for every gallon of condensate not returned, it may cost you 2 to 3 or more times more than what it originally cost to replace it.
For questions and help determining the value of condensate within your boiler system, contact the experts at Chem-Aqua today.