With the rapid development of the economy and the improvement of living standards of urban residents, the production of domestic garbage has been increasing rapidly. The landfill is the early and final disposal method of solid waste and its cost is relatively low. However, landfill takes up a lot of land resources, the waste degradation time is long, and the waste leachate pollutes the groundwater, so people must find a better way to dispose of the waste. In order to adapt to sustainable development and save land resources, the harmless and reductive incineration treatment of household garbage has attracted more and more attention. Waste heat generated by waste incineration can generate electricity and heat, which is one of the disposal methods to reuse waste as a renewable resource.
I. Structural analysis of domestic garbage incinerator
At present, the most typical type of incinerator is Martin mechanical grate incinerator, which can automate and continuously incinerate. The components mainly include: feeder, hopper, grate, furnace, and so on.
After being weighed, the garbage is unloaded from the unloading door in the waste storage pit, and the garbage crane will turn and mix the discharged garbage, and carry out the fermentation of the partition stack according to the procedure in the waste storage pit. Turning and mixing can make the garbage more even, avoid the high and low calorific value of garbage after entering the incinerator, and avoid the furnace temperature with large fluctuations. Stack fermentation is an important step in the incineration of low calorific value and high moisture garbage. The principle is to release some water and produce methane gas, which not only increases the calorific value of garbage but also makes it easier to burn garbage.
After three days or so of stack fermentation, it is put into the garbage hopper, which has the material door set and can be used to start the furnace and turn off the fire. There is no garbage in the hopper. After the material door is closed, the furnace can be separated from the outside, so as to maintain the negative pressure in the furnace. According to the heating curve, after putting garbage, open the feed door, and the garbage is transferred to the feeding platform along the feed trough. After the feed trough is full, the garbage is transported to the grate. In the process of furnace grate turning garbage, due to the thermal radiation effect generated by the burner and furnace wind, the water will be evaporated, so it is easier to ignite, and the temperature in the furnace will rise to a certain extent. When it reaches 600℃, the burner will exit, and the incineration of garbage is in a normal state. The furnace temperature continues to rise and can be maintained at 850℃. The garbage in the grate needs to pass through the dry area, the burning garbage area, and the burning-out area. Garbage flammability includes two kinds: one is complete combustion; The other is non-combustible ash. With the help of the slag drum, the slag will be fed out of the slag machine. There is a certain amount of water in the slag discharge machine, and the corresponding water level will have the function of water sealing, so the stability of negative pressure in the furnace is guaranteed. In the slag discharge machine, the ash is cooled and sent to the ash reservoir. After treatment, it becomes harmless ash.
II. Analysis of refractory materials for waste incinerators
Incinerators require refractories that not only exhibit ideal high-temperature resistance, but also exhibit corresponding high-temperature strength, volume stability, thermal insulation, and wear resistance.
The application of incinerators to refractory materials usually includes two categories: one is fixed refractory products; The other is amorphous refractory. The finished products are mainly silicon carbide brick, high alumina brick, and clay brick. Amorphous refractories include: high aluminum-plastic, clay, and silicon carbide castable. At present, due to the development of the research and further, to the quality of silicon carbide castable combination of phosphate build high aluminum pouring material, the wear resistance performance is very outstanding, so its usage also gradually improves, monolithic refractories, construction performance is very outstanding, combined with the different application conditions of the incinerator, the corresponding varieties can be selected.
For example, in mechanical grate incinerators, different parts of the application of amorphous refractories, there is a certain difference. For example, the temperature at the entrance to the garbage is about 550℃, because the garbage will have impact wear, and there is some moisture inside the garbage, so the probability of hot stripping is large. Therefore, the working layer needs to apply castable with higher strength and higher thermal shock resistance, while the non-directional fire surface needs to apply castable with excellent thermal insulation performance; The temperature of the walls on both sides of the grate area is usually higher than 800℃, and garbage will also wear it down. Therefore, on both sides, silicon carbide bricks with strong abrasion resistance and high-temperature smoke chemical erosion resistance should be used as the first layer of the fire-facing surface, and thermal insulation materials with low thermal conductivity should be used for the last several layers. In the furnace area, the front and rear arches and the front and rear walls, etc., need to use the rigid jade wear-resistant castable because the high-temperature flue gas will cause chemical erosion effect on them; At the ash hopper, the temperature is relatively low, only about 450℃, but there are still remnants causing wear to it, so the layer needs to use a higher strength castable.
Source : Greenergy Refractories