Calculation of savings from recovering condensate.
- Calculate the current annual cost of fuel used to produce steam.
- Decide whether an open or a closed condensate return system will be used.
- Estimate how hot the condensate will be when it reaches the boiler system.
- Use the tables on the following pages to determine the maximum percentage of energy that can be saved by returning all condensate.
- Estimate the fraction of condensate that can actually be recovered when reduced by unavoidable losses such as boiler blowdown, leaks, flash steam loss or evaporation from open tanks.
- Multiply the maximum energy savng percentage by the fractional amount of condensate that can actually be recovered.
- Calculate the actual fuel saving.
Water treatment savings:
- Calculate the total current cost of treating feed water.
- Estimate what fraction of condensate will be returned to the boiler system. Reduce this figure a little to account for unavoidable losses such as boiler blowdown.
- Calculate the maximum cost saving of recovering condensate by multiplying the current cost of water treatment by the fractional amount of water recovered as this theoretically will not require treatment. The figure will actually be less as some water treatment may sill be required.
Example Fuel cost savings
- Steam is produced at a fuel cost of $10 per ton, and the boiler operates at 10 tons per hour. The factory operates 5 days per week for 8 hours per day 50 weeks per year.
- The cost of steam per year is $10 x 10 x 8 x 5 x 50 =$200,000 per year.
- An open condensate return system is being considered.
- The boiler operates at 21 bar. Condensate can be returned to the boiler house at a temperature of 70˚C using an open return system. Raw water is supplied at a temperature of 10˚C. The following table gives a maximum energy saving percentage of 9.1%.
- It is estimated that after losses and blowdown only ¾ of the condensate can be returned.
- The amount of energy that can be saved is then 9.1% x ¾ = 6.825%.
- The actual energy saving is thus $200,000 x 6.825/100 = $13,650.