Main technical features of W-type boilers by the three major boiler manufacturers

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Main technical features of W-type boilers from the three major boiler manufacturing companies I. Main technical features of FW Company: FW Company has been developing and researching technologies for low-volatility coal-fired boilers for over 50 years. The key to its success lies in the combination of Foster Wheeler’s vertically burning burner equipped with a cyclone separator and a double-inlet, double-outlet ball mill for coal grinding. The XiniV 1 dual-cyclone concentration-separation burner is a Foster Wheeler dual-cyclone concentration-separation burner that is installed vertically on the furnace arch. The primary air-coal powder mixture stream is divided into two streams by a one-to-two distributor, and these streams enter two parallel cyclone-type burners tangentially; one rotates clockwise while the other rotates counterclockwise. Under the effect of centrifugal force, a large amount of coal powder is flung to the outer wall of the separator (the powder-rich gas stream), while the central part contains a mixture with a very low concentration of coal powder (the lean gas). The lean gas is drawn out from the center of the separator and enters the furnace through the lean gas duct. The outlet of the exhaust gas duct is located in the high-temperature zone between the burner nozzle and the upward airflow in the combustion area, allowing the exhaust gas to ignite rapidly. The main stream of coal powder is ejected vertically downward from the burner nozzle almost parallel to the front and rear furnace walls; this concentrated stream of coal powder is quickly ignited as soon as it enters the furnace chamber. By adjusting the opening of the exhaust damper, it is possible to control the coal powder concentration and the primary air velocity, thereby enabling adaptation to changes in the type of coal used. ` 2 Double-Feed Double-Discharge Ball Mills. The double-feed double-discharge ball roller coal mills designed and manufactured by FW Company are specifically intended for grinding fuels with low grindability and high ash content. They feature the following advantages: a. High continuous operation rate; b. Low maintenance requirements; c. Efficient grinding of hard and highly abrasive coal types; d. Large coal powder storage capacity; e. Fast response to changes in boiler load; f. Increased coal powder fineness at low load operations; g. Low air-to-coal powder ratio during operation; h. Feeding at both ends, with the feeders able to operate on one side for short periods while still maintaining full capacity; i. Higher requirements regarding coal particle size and the presence of large particles in the coal compared to single-feed single-discharge ball mills, but lower requirements than those of MPS mills. qb-/ The main technical features of GEC-A: When designing new power units, GEC-A pays special attention to the analysis of the quality of coal used for combustion. In addition to conducting standard analyses on the \"new\" fuel as a form of verification, special experimental studies are also carried out on representative samples of such coal. It is believed that the adiabatic combustion temperature is an important indicator for assessing the ignitability of coal. The concept of an adiabatic combustion temperature curve is proposed, with the primary air-to-powder ratio as the abscissa and the ignition temperature as the ordinate. Two practical limits are used to define the flame stability zone: the minimum air-to-powder ratio for the coal powder stream serves as the \"vertical\" limit, while the lowest ignition temperature acts as the horizontal limit; these values are used as a basis for selecting the pulverization system and boiler type. >For the 5EU 1 grinding system, a N\o double-inlet double-outlet direct-blowing system is selected. When a direct-fired system is used, a coal-enrichment system is generally installed between the coal grinder and the burner. The main difference between the 67% GEC-A and FW company’s dual-inlet/dual-outlet grinding systems lies in the separator: GEC-A uses a cyclone separator, while FW company employs a separator with a simpler structure consisting of two vortex channels; in terms of separation efficiency, the latter is slightly inferior. 0/]-J Indirect combustion system with stored heat. The storage-type coal grinding system in ball mill coal crushers has the following advantages, aside from the drawback that its structure is slightly more complex than that of the direct-injection system: a. It enables a higher temperature of the primary air (the temperature of the air-coal mixture before the burner); in a direct-injection system, this temperature is approximately 100°C, which is the outlet temperature of the mill, while in a storage-type system this temperature can exceed 250°C; b. It allows for an optimal concentration of coal particles in the primary air; c. The mill has better adaptability to different types of coal; d. The load is not affected by blockages in the coal hopper. As can be seen from LyX^9, the storage-type coal grinding system has certain advantages over bituminous coals with low activity, as it is able to achieve the optimal temperature and coal powder concentration, without being constrained by the operating conditions of the coal grinder. Since this system is equipped with many feeders that can be started and stopped easily, it possesses high operational flexibility. k5nKG” 2 Slit-type DC burner. The selection of the shape of the coal powder nozzle in GEC-A company’s slit-type DC burners is aimed at rapidly heating the coal particles: a narrow, elongated nozzle sprays a rectangular-shaped stream of coal powder into the furnace; its radiation surface area is twice that of a circular coal powder stream, allowing it to absorb twice as much energy, which facilitates timely ignition of the coal powder. {bp_ Three key technical features of B&W Company 6 1 Primary air exchange PAX burner iRjSk. Currently, the burners used for burning low-volatility, low-quality coal that are practical in use are all primary air exchange (concentration) burners, namely AAX burners, which can be divided into two categories: burners with external separators and burners with internal separators.} External coal powder nozzles are further divided into slit-type and concentrated-type depending on their design. The separator is usually placed on top of the blower box and constitutes a separate component independent of the burner itself. Compared to internal ventilation units, external ventilators have a more complex structure and higher flow resistance. The most distinctive feature of the PAX (Primary Air Exchange) burner is its simply structured, built-in primary air exchange device (separator). B&W’s built-in air exchange device makes clever use of the centrifugal force generated by the flow of pulverized coal gas through the elbow connecting the primary air duct and the burner to achieve separation. After the primary air-powder stream enters the eccentric elbow duct before the burner, 90% of the coal powder is separated and flows forward with the rich-powder stream, while the remaining 10% of the fine powder and 50% of the original primary air are drawn out through the inner exhaust duct and sent into the furnace via the exhaust nozzle. At the same 2fO' condition, a stream of hot air is introduced into the separator, where it mixes with the coal powder airflow before entering the burner nozzle directly. The result of mixing raises the temperature of the gas and powder before entering the furnace to 175°C–200°C, and the air-to-powder ratio can also be adjusted depending on the amount of hot air introduced. Another feature of the PAX burner is the use of a dual swirl air regulator to control the swirl intensity of the secondary air, thereby regulating backflow and mixing. Both the inner and outer sections of the dual \A regulator are equipped with a set of axially adjustable vanes to regulate their respective swirl intensities. To ensure that the coal powder torch has sufficient stiffness to descend to an appropriate depth in the lower furnace chamber, the swirl intensity in the outer zone is generally set to a low level; whereas to maintain sufficient high-temperature flue gas flowing back to the ignition zone in front of the burner to enhance ignition, the swirl intensity in the inner zone is set to a moderately high level. An appropriate combination of swirl rates in the inner and outer zones allows the PAX burner to operate at its optimal condition. _The 2-direct blowing system and the MPS medium-speed coal grinder feature low noise, low power consumption for coal grinding, and good uniformity of coal powder. However, they require high-quality coal, are prone to damage from foreign objects, have lower reliability compared to ball mills, and blockages in the raw coal system are detrimental to combustion. The tubular ball mill has certain advantages over the medium-speed MPS mill in terms of fineness and low gas-to-powder ratio. The overall fineness of the material produced by ball mills is higher, especially in terms of the percentage passing through 200-mesh screens, compared to medium-speed mills; however, the amount of residue on the 50-mesh screen for ball mills is higher than that for medium-speed mills. The former is highly beneficial for combustion, while the latter has a significant impact on burnout. Additionally, the air-to-powder ratio in ball mill grinding can be kept lower, but its power consumption and cost are **higher than those of MPS mills. o Comparison of the main technical features of W-type boilers by the 3 major boiler manufacturers}` The W-type boiler features rapid ignition, stable combustion, and wide adaptability to different types of coal; it has a low load at which oil injection is not required for stable combustion, the carbon content in the fly ash remains at a low level, the boiler is efficient, and it operates well. .f<