7. Automatic pressure relief control
Uncontrolled continuous discharge is very wasteful. Automatic blowdown control and sensing devices can be installed to monitor the conductivity and pH value of boiler water.
Reduce fouling and smoke loss
In oil-fired and coal-fired boilers, the accumulated soot on the pipeline plays an insulating role in preventing heat transfer. However, these soots must also be cleaned regularly. An elevated stack temperature may indicate excessive soot accumulation. It is also more likely to occur scale nodules. A high outlet gas temperature under normal excess air indicates poor heat transfer performance. This situation may be caused by the gradual accumulation of deposits on the gas or water side. It is estimated that for every 22°C increase in stack temperature, there will be a 1% loss in efficiency. The stack temperature should be regularly inspected and recorded as an indicator of soot thickness. When the flue gas temperature rises by about 20°C, it means it is time to remove the soot deposits. Therefore, it is recommended to install a dial thermometer at the bottom of the chimney to monitor the exhaust gas temperature. It is estimated that 3 mm of soot will lead to a 2.5% increase in fuel consumption.
9. The steam pressure of the boiler decreases
Reducing the boiler steam pressure is an effective way to reduce fuel waste by up to 1% to 2%. Lower steam pressure results in lower saturated steam temperatures, and without stack heat recovery, flue gas temperatures also have a similar reduction.
The pressure generated by steam is usually determined by the highest pressure/temperature required for a specific process. In some cases, this process is not always running, and the boiler pressure can sometimes be reduced.
10. Variable frequency speed control for fans, blowers and pumps
Variable speed control is an important means of achieving energy savings. Generally speaking, the control of combustion air is achieved by throttling dampers installed on forced and induced draft fans. Although dampers are simple control means, they lack accuracy and normally only have upper and lower limits. Generally speaking, if the load characteristics of the boiler are variable, the possibility of replacing dampers with VSDs should be evaluated.
11. Impact of boiler load on efficiency
The maximum efficiency of a boiler does not occur at full load, but at approximately two-thirds full load. If the load on the boiler is further reduced, the efficiency also tends to decrease. At zero output, the efficiency of the boiler is zero, and any fuel burned is only used to make up for losses. Factors that affect the efficiency of the boiler include: when the load decreases, the mass flow value of the flue gas passing through the pipeline also decreases. At the same heat transfer area, the decrease in flow rate causes the outlet flue gas temperature to slightly decrease, reducing heat loss. Below half load, most combustion appliances require more excess air to fully combust the fuel. Generally speaking, the efficiency of the boiler significantly decreases below 25% of rated load, so it should be avoided operating below this level.
12. Proper boiler dispatching
Since the optimal efficiency of boilers occurs at 65-85% of full load, running fewer boilers at higher loads is more efficient than running one at a lower load.
13. Substitution of boilers
The potential savings from replacing a boiler depend on the expected overall change in efficiency. If the existing boiler is old and inefficient, and cannot use cheaper alternative fuels, or is too large or too small based on current requirements, then a feasibility study designed for ideal load conditions should be reviewed and long-term fuel supply determined before replacing with a more suitable boiler based on the company's development plan. However, this should consider all financial and engineering factors.
