Common material requirements for grate bars of waste incineration grate
Application of grate bar material of waste incineration grate
(1) Material requirements. The grate piece mainly works in a high temperature and corrosive atmosphere. It is necessary to maintain a certain structural strength during the reciprocating motion. Between the garbage and the grate piece, the movable grate piece and the fixed grate piece wear each other. Therefore, the material of the grate piece is proposed as follows Require:
①High temperature resistance: The grate in the combustion section is required to have excellent high temperature strength and microstructure stability at 650-950℃; ②Wear resistance: It has good high temperature wear resistance; ③Antioxidation: It is required that after the grate is oxidized, its surface will form The oxide film is continuous and dense and not easy to fall off, so as to ensure that the grate does not fail due to changes in its dimensional properties due to corrosion loss; ④ The thermal expansion coefficient is appropriate, that is, the thermal expansion of the grate material does not affect the normal operation of the grate.
Common grate pieces are made of heat-resistant, corrosion-resistant and wear-resistant castings containing Cr, Ni, Mo and other alloying elements, with long service life. If the material selection and structural design of the grate sheet are reasonable, the overall service life can reach 80,000 hours.
(2) Development of material application. In foreign countries, the incineration technology of municipal solid waste in developed countries such as Germany, Denmark and Japan developed earlier, and there are many researches on the material of the grate. The grate pieces of the grate furnace imported by NOELL Company in Germany are heat-resistant dual-phase cast steel, a high-performance nickel-based alloy material specially developed for the high-temperature corrosive environment developed for the incineration of municipal solid waste, and is suitable for waste with a combustion temperature below 1000 ℃ The grate of an incinerator. Grate manufacturers such as Denmark's Bavi-Willon Company and Japan's Mitsubishi Heavy Industries Co., Ltd. Mitsubishi-Martin reverse thrust grate also use nickel-based heat-resistant materials, which have good performance and toughness, and are expensive.
In my country, the research on grate-related fields started late, and Cr-based heat-resistant materials are often used, such as 3Cr18Mn12Si2N, 2Cr20Mn9Ni, etc. The tensile strength of these materials can reach 490MPa after heat treatment, and the process is simple and easy to implement, which has certain advantages. Si-based heat-resistant castings such as RTSi5, RQTSi4, RQTSi5, RQT2Si4Mo, etc. belong to medium-silicon ductile iron. Because of their good casting processability, excellent oxidation resistance, relatively low price, and heat-resistant temperature around 800 °C, they are widely used as Grate material.
At present, a new type of welding grate sheet technology has begun to be applied in waste incinerators. The grate sheet is made of composite materials, and the high temperature layer in the combustion furnace is made of metal with high wear resistance, high temperature resistance and wear resistance, and the thickness is generally not more than 8mm. The air low temperature layer is made of conventional carbon steel, and the composite requirements are completed by surfacing. The rib is made of conventional carbon steel, and the grate sheet is welded as a whole, which not only reduces the weight of the product, but also improves the service life of the product.
(3) Material selection. In terms of material application, domestic waste incineration design units usually carry out localized production and manufacturing based on technology introduction technology to adapt to the domestic waste combustion characteristics. At present, most waste incineration plants use castings, and some incineration plants use welded grate. At present, high-nickel and high-chromium castings are commonly used for heat-resistant grate pieces at 950 to 1200 °C, which are mainly used in high temperature areas such as the combustion section, and cast iron is used in the drying section and the burning section. material, so as to ensure the overall cost-effectiveness of the grate.
In the selection of the material of the grate sheet, some research units have optimized the design of the component distribution ratio, and distributed a hardness phase with good high temperature stability and high hardness on the matrix with good oxidation resistance and high temperature strength, so as to obtain wear, hardness, resistance to wear and tear. It has excellent properties in terms of oxidation, tensile and toughness, and meets the requirements of chemical composition and mechanical properties of foreign products.
The overall performance of the grate
At present, the grate sheet is the core component of waste incineration, and the high-temperature part is mostly made of alloy cast steel material, which not only withstands thermal deformation and mechanical wear, but also withstands the corrosion of the garbage atmosphere. Although there are currently many grate furnaces in operation in my country, most of the grate pieces in the early stage were imported. Therefore, whether the domestically purchased alloy steel castings can meet the design requirements and meet the operation and maintenance requirements of the waste incineration plant is to ensure the incineration plant. necessary for stable operation. The grate sheet should not only meet the temperature resistance and wear resistance requirements of the grate furnace, but also ensure that the structure of the grate sheet is reasonable, ensure its reasonable temperature distribution, and prevent excessive local thermal stress.
To sum up, the reasonable structure and durable material of the grate pieces for waste incinerators play a crucial role in the stable operation of the incinerator. In terms of structural design, it is necessary to ensure reliable installation and fixation, as well as reasonable ventilation performance, so as to avoid inclusion of foreign objects, abnormal warping, and offset wear.
In terms of material application, distinguish between high temperature area and low position area. High temperature area adopts alloy metal material with high temperature stability, corrosion resistance, wear resistance and high temperature oxidation, and low temperature adopts cast iron material, so as to ensure that the grate system is not only cost-effective , and excellent performance, suitable for domestic garbage characteristics of grate products.
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