Boiler Terminology Explanation (Part 18)

Boiler Terminology Explanation (Part 18)

171.Soot Blower — A device that uses various media to remove ash and other deposits attached to the heating surfaces on the flue gas side of the boiler. It improves the heat transfer conditions of the boiler's heating surfaces, thereby enhancing boiler efficiency. It plays an important role in ensuring the boiler's output and controlling the superheated steam temperature. In this context, solutions provided by high pressure socket weld connection gate valve China manufacturer are often employed to guarantee reliable valve performance in such high-temperature, high-pressure environments.

172.Boiler Soot-Blowers Control — Soot blowers are installed on the boiler to regularly clean accumulated ash from the heating surfaces of different boiler parts. Soot blowers typically use low-pressure steam for blowing. In cases where heating surfaces operate at lower temperatures, water or compressed air may also be used as the cleaning medium. To prevent damage caused by the high temperature inside the furnace, soot blowers are withdrawn outside the furnace when not in operation and retracted into the furnace or flue during blowing. Soot blowers are usually equipped with motors to extend and retract the blower. For large-capacity boilers, programmable logic controllers (PLCs) are used to control the soot blowers, allowing the operation sequence and timing to be compiled and adjusted based on specific boiler operating experience, coal type, and boiler conditions. Operators can also select the operation mode.

173.Boiler Expansion Center — An artificially established zero-expansion point for medium and large suspension-type boilers. This position must not undergo any displacement in any direction. It is essential for both maintaining boiler sealing integrity and performing system stress analysis. Once the temperature distribution of various parts of the boiler is determined, the expansion displacement of each position under this condition can be calculated. The location of the expansion center depends on the boiler's arrangement type. For suspension boilers, it is always set at the fixed nut of the roof suspension device in the vertical direction; for boilers symmetrically arranged left and right, it is generally on the center symmetry line. Its position in the front-rear direction is largely related to the boiler layout — single-flue boilers typically have it on the furnace centerline. A guiding device is a dedicated limiting structure used to achieve the expansion center. Since the boiler is a fully suspended structure with substantial mass, the heating surface system and combustion equipment (fixed to the water-cooled walls) expand freely downward in the vertical direction, while in the front-rear and left-right directions, guiding devices are used for guidance.

174.Operating Regulations — Guidelines formulated to instruct operating personnel on correctly operating equipment to ensure safe and economical operation. Operating regulations are compiled based on the equipment’s structure, characteristics, manufacturer’s instructions and requirements, as well as accumulated experience in safe and economical operation. In thermal power plants, comprehensive operating regulations must be in place for boilers, steam turbines, and generators. Important auxiliary equipment, systems, and automatic control and protection facilities should also have corresponding operating regulations. There are two types of operating regulations: typical regulations and on-site regulations. Typical regulations are written by power management or research institutions for similar units and provided as a reference for power plants in formulating their on-site regulations. On-site regulations prioritize the manufacturer's requirements for equipment operation and maintenance, combined with operational experience, and are implemented after review and approval by the plant’s technical director. The contents of operating regulations should include technical specifications of the equipment, start-up procedures and operations, normal operational adjustments and operations, abnormal condition analysis and incident handling, as well as shutdown operations and standby maintenance.

175.Boiler Economic Operation — Refers to operating boiler units at the highest efficiency and with the lowest auxiliary power consumption under specified loads and parameters, also known as maintaining the highest net boiler efficiency. The performance of boiler units largely determines the overall safety and economic operation of a power plant. For modern thermal power units, every 1% increase in boiler efficiency improves the overall unit efficiency by approximately 0.3% to 0.4%, and reduces standard coal consumption by 3–4g/(kW·h). Depending on the load, the combustion condition, temperature level, fouling and heat exchange state of each heating surface, and auxiliary power consumption inside the furnace vary, leading to different levels of operational efficiency. The load point at which the boiler operates with the highest net efficiency within the entire load range is known as the economic load.

176.Techno-Economic Indexes of Power Plant Operation — Data reflecting the technical and economic performance of thermal power plant operations. These mainly relate to the overall plant or unit operating performance associated with the thermoelectric conversion efficiency. Typically calculated over a statistical period (such as one year), this involves collecting data on the total amount of fuel consumed, converting the fuel’s heat value into cumulative heat consumption, accounting for the power plant’s internal electricity consumption, and the power and heat output produced within the same period as the calculation basis.
Key indexes include:
Auxiliary Power Rate — the percentage of electricity consumed internally by the plant relative to its total generation.
Power Generation Heat Rate — the amount of heat consumed to generate 1 kWh of electricity.
Power Generation Efficiency — the ratio of power output converted to heat relative to heat input.
Power Supply Heat Rate — the amount of heat consumed to deliver 1 kWh of supplied power.
Power Supply Efficiency — the ratio of supplied power converted to heat relative to heat input.

177.Coal Consumption Rate of Power Sent-Out (Net Coal Consumption Rate) — The weight of standard coal consumed per 1 kWh of electricity sent out by a thermal power plant, usually abbreviated as the coal consumption rate, expressed in g/(kWh). It is determined by both the power generation coal consumption rate and the auxiliary power rate.

178.Power Generation Coal Consumption Rate — The amount of various fuels (coal, oil, gas) consumed per 1 kWh of electricity generated, converted to the weight of standard coal based on heat value. The heat content of standard coal is 29.3 kJ/g (7 kcal/g).

179.Boiler Efficiency — The percentage of heat released by each kilogram of fuel in the boiler that is effectively utilized. It is the most important metric for evaluating boiler economic performance. According to the heat balance equation, the heat released by the fuel input into the boiler (Q) equals the effectively utilized heat plus various heat losses.
That is:
Q = Q1 + Q2 + Q3 + Q4 + Q5 + Q6 (kJ/kg)
Where Q1 is the effective heat utilization, and the rest are heat losses.
Expressed in percentages:
η = 100 - (q2 + q3 + q4 + q5 + q6)%
Where:
q2 = Q2 / Q × 100% is the flue gas heat loss
q3, q4 are gas and solid incomplete combustion heat losses respectively
q5 is radiative heat loss
q6 is the physical heat loss of ash, usually the largest component.
Boiler efficiency is typically measured during operation through a heat balance test. For power plant boilers, the reverse balance method is commonly used — first measuring all heat losses, then calculating the efficiency. Generally, large-capacity high-parameter power station boilers have efficiencies η > 90% (based on lower heating value of fuel).

180.Constant Pressure Operation — A traditional operation method for power units, where the steam parameters at the turbine inlet are kept constant, and the steam flow is adjusted by changing the number and opening degree of the regulating valves to meet the grid’s load demands.
There are two main regulating modes for turbine steam admission: throttling regulation and nozzle regulation.
In throttling regulation, during constant pressure operation, the boiler maintains constant steam pressure and temperature. The load is controlled by adjusting the opening of the throttling regulating valves, thus changing the downstream pressure and steam flow into the turbine, which alters the available enthalpy drop and hence the unit load. At low loads, throttling losses are significant due to small valve openings, reducing the available enthalpy and decreasing operational efficiency. However, the throttling action provides good load adaptability, as volumetric flow rates and steam temperatures in the turbine remain relatively stable during load changes.
In nozzle regulation, the boiler still maintains constant steam parameters. Load is adjusted by sequentially opening or closing the regulating valves, thus varying the number of open valves and controlling the steam flow and unit load. Since fully open valves cause minimal throttling and throttling only occurs in partially opened valves, efficiency loss is less significant compared to throttling regulation under low-load conditions.