Explanations of boiler-related terms (partial)

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I. Term Explanations (related to boilers) 1. Boiler rated evaporation capacity: The amount of steam produced by a steam boiler under rated steam parameters, rated feedwater temperature, using the designed fuel, and while maintaining efficiency. 2. Maximum continuous evaporation capacity of the boiler: The maximum amount of vapor that a steam boiler can produce when it operates continuously under rated steam parameters, rated feedwater temperature, and using the designed fuel. 3. Rated steam parameters of the boiler: the rated steam pressure and rated steam temperature at the superheater outlet. 4. Boiler accident rate: Boiler accident rate = ×100%
5. Boiler availability rate: Boiler availability rate = ×100%
6. Boiler thermal efficiency: It is the percentage of the effective heat utilized per hour by the boiler relative to the total amount of heat input into the boiler. 7. Boiler steel consumption rate: The tons of steel used per unit of evaporation capacity of the boiler. 8. Continuous operating hours: The number of hours the system operates between two maintenance sessions. II. Term Explanations (related to fuel) 1. Calorific value: The heat released when a unit mass or volume of fuel burns completely. 2. Higher heating value: The total amount of heat released when a unit amount of fuel is completely burned, and all the water vapor in the combustion products condenses into water, is referred to as the higher heating value of the fuel. 3. Lower heating value: the total heat released when a unit amount of fuel is completely burned, with all water vapor in the combustion products remaining in gaseous form. 4. Conversion component: refers to the component of the fuel corresponding to its lower heating value on a received basis of 4190 kJ/kg. 5. Standard coal: Coal with a specified lower heating value on a received basis of Qarnet=29270 kJ/kg. 6. Volatile matter in coal: The gases that are released as a result of the decomposition of the organic substances in coal when the coal sample, after having had its moisture removed, is heated under specified conditions. 7. Flash point of oil: The lowest temperature at which, when a liquid fuel is heated under certain conditions, the mixture of vapor on the surface of the liquid and air undergoes a brief ignition upon contact with an open flame before going out again. 8. Ash fusion behavior: The characteristic changes in the physical states of ash such as deformation, softening, and flowage as the heating temperature changes under specified conditions. III. Definitions of Terms (related to combustion)
1. Combustion: A chemical reaction process in which combustible substances in a fuel react with oxygen under high temperatures, resulting in intense light emission and heat release. 2. Complete combustion: Combustion in which the combustion products no longer contain any combustible materials. 3. Incomplete combustion: Combustion in which combustible substances still remain in the combustion products. 4. Theoretical air volume: The amount of air required for complete combustion of 1 kg of fuel on a received basis, with no residual oxygen present. 5. Excess air factor: The ratio of the actual amount of air supplied during fuel combustion to the theoretical amount of air. That is, α=VK/V0. 6. Air leakage coefficient: the ratio of the amount of air ΔVK that leaks in per 1 kg of fuel on a basis weight to the theoretical amount of air V0. 7. Theoretical flue gas volume: The amount of flue gas generated when air is supplied based on the theoretical air volume, for the complete combustion of 1 kg of fuel. 8. Flue gas enthalpy: The heat required to heat the flue gas generated by 1 kg of solid or liquid fuel from 0°C to θ°C at constant pressure. 9. Flue gas composition: The percentage of the volume of a certain gas in the flue gas relative to the volume of the dry flue gas. IV. Term Explanations (related to thermal efficiency and heat loss) 1. Boiler thermal balance: The state of equilibrium between the heat input to the boiler and the heat output by the boiler under stable operating conditions.   2. Optimal excess air coefficient: The excess air coefficient at which the sum of (q2+q3+q4) is minimized. 3. Heat loss due to flue gas, q2: The heat loss caused by the sensible heat of the flue gases expelled from the boiler.   4. Mechanical incomplete combustion loss q4: The loss resulting from the failure of solid combustibles in fly ash, slag, and spilled coal to release their heat of combustion.   5. Chemical incomplete combustion loss q3: The loss resulting from residual combustible gases in the boiler exhaust failing to release their heat of combustion.   6. Positive balance thermal efficiency: The percentage of the heat effectively utilized by the boiler, relative to the heat input from the fuel consumed per unit of time.   7. Reverse balance thermal efficiency: It is the efficiency calculated by taking the input heat as 100% and then subtracting various heat losses from this value.   8. Effective heat utilization of the boiler: The total amount of heat absorbed by the working fluid in the boiler per unit time. 9. Boiler fuel consumption: The amount of fuel consumed by the boiler per unit of time.   10. Calculated fuel consumption of the boiler: The fuel consumption after deducting the heat loss due to incomplete combustion of solids. V. Term Explanations (related to coal powder) 1. Coal powder fineness: The percentage of the mass a of coal powder remaining on the sieve after it has been screened using a special sieve, relative to the total mass of the coal powder before screening. The definition formula is R = a/(a+b) × 100%. 2. Optimal fineness of coal powder: It refers to the fineness of coal powder that results in the minimum total value of the three types of losses, q4 + qn + qm, when considering both combustion and coal grinding aspects.   3. Coal grindability coefficient: The ratio of the energy consumed to grind standard coal and test coal of the same mass to the same fineness at the same particle size, under air-dried conditions. 4. Coal wear index: Under certain experimental conditions, it is the ratio of the amount of milligrams of pure iron worn per minute by a particular type of coal to the amount of pure iron worn per minute by standard coal under the same conditions.   5. Steel ball filling factor: The ratio of the volume occupied by the steel balls loaded in the ball mill to the volume of the mill cylinder.   6. Optimal coal grinding ventilation volume: Measured from the perspectives of coal grinding and ventilation, it is the ventilation volume at which the total of the power consumption for coal grinding, Em, and the power consumption for ventilation, Etf, is minimized, while keeping the load of steel balls constant.   7. Direct-blowing coal grinding system: A coal grinding system in which the coal powder ground by the coal grinder is directly blown entirely into the furnace for combustion; the amount of coal powder produced is equal to the amount required by the boiler, and it varies with the boiler load. 8. Silo-type coal grinding system: The coal powder ground by the coal grinder is first stored in a coal powder silo, and then, according to the requirements of the boiler’s load, it is sent from the silo to the furnace for combustion via a coal feeder – this is the coal grinding system. 9. Primary air: Hot air that carries coal powder into the furnace.   10. Secondary air: Pure hot air that enters the furnace through the burner to supply the oxygen required for fuel combustion. 11. Third air: In the hot air powder feeding system of intermediate storage-type coal grinding systems, the coal grinding exhaust gas carrying fine powder is fed into the furnace for combustion through specialized nozzles; this is known as third air.   12. Coal grinding output: The amount of raw coal that can be ground by the coal grinder per unit of time, under the condition that a certain particle size of the raw coal and a certain fineness of the coal powder are maintained.   13. Drying capacity: The amount of raw coal that can be dried by the coal grinding system per unit of time, from its initial moisture level Mar to the moisture level Mmf of the coal powder. VI. Term Explanations (Theoretical Knowledge of Combustion) 1. Power combustion zone: A combustion condition in which the combustion rate is primarily determined by the rate of chemical reactions (chemical conditions), with little relation to the diffusion rate.   2. Diffusion combustion zone: A combustion condition in which the combustion rate depends mainly on the oxygen diffusion conditions, with little relation to temperature.   3. Transitional combustion zone: A combustion condition in which the combustion rate depends both on the chemical reaction conditions and on the diffusion and mixing conditions. 4. Ignition heat: The heat absorbed to raise the temperature of the coal powder and primary air stream from their initial temperature before entering the furnace to the ignition temperature. 5. Jet stiffness: The ability of the jet to resist deflection.   6. Heat load per volume of the furnace chamber: The average amount of heat supplied per unit volume of the furnace chamber per hour.   7. Heat load per unit area of the furnace chamber: The average amount of heat supplied to each unit area of the furnace chamber per hour.   8. Heat load on the furnace wall in the burner area: The average heat input to the furnace per hour, calculated on a per unit area basis of the furnace wall in the burner area. 9. Slagging: The phenomenon in which sticky ash adheres to the furnace chamber or high-temperature heating surfaces. 10. Iron precipitation in the slag pool: In a liquid slag discharge furnace, the phenomenon in which coarse particles from the coal powder stream settle into the slag pool, thereby reducing iron oxide in the slag to pure iron. 11. High-temperature corrosion: refers to the corrosion that occurs on the outer surface of tubes in high-temperature heating surfaces such as water wall and superheaters, under the influence of high-temperature flue gas. 12. Low-temperature corrosion: Low-temperature corrosion is sulfuric acid corrosion that occurs in the heating surfaces at the rear of the boiler (economizer, air preheater). It is called low-temperature corrosion because the temperature of the flue gas and the tube walls in these rear heating surface areas is low. Low-temperature corrosion often occurs on air preheaters, but it can also occur in economizer tubes. 13. Oxygen diffusion rate: The amount of oxygen transported per unit time across the boundary layer to the surface of a single carbon particle.