Regarding the gas generator grate

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Regarding the grates of gas generation furnaces 1, as well as their history of development and improvement, the early grates for such furnaces were pagoda-shaped and fan-shaped. These two types of grates did not have very good slag-breaking capabilities; when the quality of the raw materials used in the gas generation furnace declined or improper operation led to the formation of large slag masses inside the furnace, it became difficult to break apart and remove the slag. Operators have to frequently open the ash hopper gate and manually remove the lumps for treatment. In 1985, the Zijiang Fertilizer Factory in Hunan Province collaborated with East China University of Science and Technology to develop the evenly distributed grate for the first time, which was successfully tested in a Ф3000 mm gas generation furnace. In 1989, the former Ministry of Chemical Industry organized a special meeting on the promotion of evenly distributed grates in Zinan. The experts and representatives present agreed that the M-type evenly distributed grates ensured uniform gas distribution and strong slag breaking and removal capabilities; they enabled an increase in the gas production volume of the gas generation furnaces by over 20%, while also reducing carbon return ； The development of the M-type evenly distributed grating represented a qualitative leap for fixed-bed batch gas generators, and it was a major technological innovation in the fixed-bed batch gasification process. The M-type evenly distributed grating was listed as a key scientific and technological achievement promotion project during the \"Eighth Five-Year Plan\" and \"Ninth Five-Year Plan\" periods by the former Ministry of Chemical Industry, and it won awards for scientific and technological progress from both the former Ministry of Chemical Industry and Hunan Province. The evenly distributed nitrogen-supplying grates of Ф3000 and Ф3300 mm once accounted for over 80% of the market in medium-nitrogen plants, but they were not used in smaller gas generation furnaces with a diameter of less than Ф3000 mm. Since then, many fertilizer manufacturers and machinery producers have joined in the development and improvement of evenly distributed grates. Some have achieved success; for example, a factory in Pizhou, Jiangsu, developed evenly distributed grates for small gas generation furnaces and began to roll them out gradually. Later, some manufacturers began producing evenly distributed grates, and grates in quadrilateral, pentagonal, and hexagonal shapes started to appear ； Five-layer, six-layer, seven-layer grates. Now, some manufacturers have introduced eight-layer grates, as well as certain concepts related to specialized grates. 2. How to evaluate the quality of a furnace grate: Whether it is a uniformly distributed grate, a fan-shaped grate, or another type of grate, the criteria for assessing the quality of a furnace grate remain the same, namely: (1) high gasification intensity in the gas generator ； (2) Low residual carbon in ash ； (3) Stable operation. Of course, the gasification intensity of the gas generator and the residual carbon in the ash are also related to many factors such as the type of gas generator, the process flow, operating procedures, and raw materials; however, under identical conditions, they are still comparable. 3. Some misconceptions regarding the design of evenly distributed grates (1) The larger the ventilation area, the better. The ventilation area of a grate is not necessarily the larger it is, the better; the diameter of the primary air duct in a furnace generally does not exceed Ф770mm, resulting in a ventilation area of less than 0.45 m2. The diameter of the central pipe generally does not exceed Ф1200mm, giving a ventilation area of less than 1.245 m2. Designing an excessively large ventilation area for the grate can actually lead to uneven distribution of air. Taking a grate with a diameter of Ф3000mm as an example, it is ideal to have an appropriate ventilation area and a suitable central pipe (Ф1200mm), so that the air flow velocity within the grate and around the central pipe is around 7 m/s. When designing the ventilation area of a grate, it is necessary to consider not only even air distribution but also even steam distribution. Since the flow velocity of steam is lower than that of air, it tends to flow through the central area. An overly large ventilation area can result in uneven distribution of both air and steam. (2) The lower the total height of the grates, the better. There was a time when shorter grates were introduced; the theory behind this was that by reducing the height of the grates, it would be possible to increase the thickness of the fuel layer without increasing the height of the carbon layer, thereby increasing the thickness of the gasification zone. To maintain the overall angle of the grates, there are limits to how much the height of each layer of the grates can be reduced. In practice, reducing the total height of the grates means reducing the height of the base, and this reduction in base height decreases the space available for storing ash on the ash tray, resulting in uneven deposition of slag above the grates and ultimately leading to a deterioration in furnace performance. Taking the Ф3000mm grate as an example, the height of the grate base should not be less than 400mm, and the total height should not be less than 1600mm. (3) The grate base is designed with a polygonal structure. The purpose of designing the grate base as polygonal is to break down slag and push ash aside; in fact, only the layer with the largest diameter of the grate has the ability to break down slag, as large pieces of slag must be broken down in this layer before they can fall onto the ash tray. If the slag at the base is removed, it will inevitably wear out the furnace skirt base. The slag that falls on the ash tray is discharged through the rotation of the ash tray in combination with the ash plow; the grate base rotates synchronously with the ash tray, and there is no mechanism for pushing the ash away. (4) Design of multi-layer slag-breaking ribs. The purpose of designing multi-layer slag-breaking strips is to enhance slag breaking. From the perspective of the principle of slag breaking, large slag pieces can be broken only when the grates rotate, causing them to be squeezed between the grate slag-breaking ribs and the furnace wall slag-breaking strips. In other words, only the layer with the largest diameter, which is in contact with the furnace wall, can facilitate slag breaking; the layer or layers above this layer with the largest diameter, due to being too far away from the furnace wall, do not serve any role in slag breaking and can only function to push ash aside