With rising cost of fuel prices, industries that use steam boilers for heating or power generation are hard pressed to operate at peak efficiencies.
While steam consumption, leakages, and other heat transmission losses can contribute to overall energy bill, this article focuses on heart of steam generator - boiler.
Controlling boiler is of utmost importance in any steam generation energy saving program. Below are some ways to improve boiler efficiencies:
1. Reducing excess air 2. Installing economizer 3. Reducing scale and deposits 4. Reducing blow down 5. Recovering waste heat from blow down 6. Stopping dynamic operation 7. Reducing boiler pressure 8. Operating at peak efficiency 9. Preheating combustion air 10.Switching from steam to air atomization 11.Switching to lower cost fuel
Reducing Excess Air
By far most common reason for energy inefficiencies in a boiler can be attributed to use of excess air during combustion at burners. When there is more air than is required for combustion, extra air becomes heated up and is finally discharged out to atmosphere. However, there are reasons for putting in some extra air for combustion - to compensate for imperfect burner fuel-air mixing conditions, air density changes, control system "slop", burner maintenance, fuel composition and viscosity variation, and imperfect atomizing steam or air controls for burners.
Adjusting fuel-air ratio for combustion can be quite tricky. If fuel is too much as compared to air, incomplete combustion occurs. This will give rise to carbon soot deposits inside combustion chamber or even over boiler tubes.
The consequences of having soot deposits over heat transfer surfaces and potential of having explosive flue gases inside boiler are much worst than losing a slight amount of energy through exhaust stack. Therefore, many boiler operators choose to adjust their burners to be slightly on excess air.
This is only appropriate if there are insufficient heat transfer surfaces in boiler. The economizer tubes may contain either circulating boiler water or circulating feed water. Because temperature of exhaust gases can be quite high, economizer tubes may be fitted with safety valves to avoid over-pressure damage. Also temperature control of feed water is required to prevent pump airlock. To avoid corrosion, careful design is needed to ensure that exhaust flue gas temperature does not drop below dew point.
Reducing Scale and Deposits
For any boiler operation, this is a must. The safety of boiler is at stake. Any scale or deposits will lead to reduced heat transfer that will eventually lead to overheating, reduction of mechanical strength of steel and finally to bursting.
This should already be in normal daily procedure of boiler operation.
Reducing Blow down
Blow down of boiler water is discharging hot water into drains. However, blow down is necessary to maintain boiler water concentration of dissolved solids that are necessary for conditioning boiler water. The dissolved solids are necessary for preventing boiler corrosion and scaling.