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Multi-stage step furnace
The multi-step ladder grate is composed of reciprocating moving parts, and the garbage is pushed to the inclined grate through the feeding device, and the high temperature is heated in the furnace to make part of the garbage dry, and the movement of the grate is pushed forward. In addition, the waste layer is loosened and can be subjected to various stages such as drying, fuel and afterburning to achieve complete combustion. At present, there are many kinds of multi-step ladders in the application. Most of the grate design belongs to the patent of the design manufacturer. For example, the new grate imported from Shenzhen in China is a German patent.
However, the rotary grate is easy to block the vaporization of the grate, the maintenance workload is large, the possibility of large items being clamped is large, the mobile grate is large, the air duct system is complex, and the high-moisture, low-value garbage Incineration is not complete, fire is more difficult and less used. The fan-shaped inverted grate is difficult to control due to combustion, and the furnace temperature is high, and it is still in the stage of continuous improvement.
Because the Martin grate has not been manufactured by itself, it must import foreign equipment and it is expensive. Generally, small and medium-sized towns cannot afford their investment costs. In China, only three Martin furnaces imported from Japan have been used in Shenzhen, but the combustion conditions of the Martin grate are more susceptible to fluctuations in garbage grade.
The advantage of the grate furnace is that it does not require pre-treatment of the waste. The technology is relatively mature, and the foreign application is more extensive. The shortcomings are as follows:
1. The grate must be heat-resistant. During long-term continuous operation, the thermal stress must be constant, so that the grate has high material requirements and the grate processing is complicated. Because the grate needs to rotate, the reliability is low and the energy consumption is high. .
2. Due to the complexity of the garbage composition, it is difficult to maintain the uniform grate in the entire grate and to burn evenly and completely.
3. The grate is difficult to adapt to the waste incineration with a wide range of water fluctuations, because the higher moisture waste requires a wider drying zone, which makes it difficult to completely burn the high water waste.
4. The furnace temperature is difficult to control. The slag of the garbage is softened and viscous at 1000 ° C and above and 1050--1100 ° C. It becomes a special corrosive substance, which may corrode the furnace wall and increase the Nox concentration at high temperature.
5. It is difficult to achieve large-scale grate furnace, it is difficult to remove HCI gas in the furnace, and special and HCI removal equipment needs to be installed at the tail to increase the investment cost.
6. Difficult to handle landfill leachate requires special sewage treatment facilities.
7. The grate of the grate furnace is not only complicated to manufacture, high in cost, but also bulky and large in area, so it is not suitable for occasions where the amount of garbage disposal in small and medium-sized cities is not very large.
Rotary furnace
The rotary furnace incineration system is derived from the design of refractory brick lining rotary forging kiln which has been widely used in the cement industry. The garbage is fed from the front end of the inclined and slowly rotating rotary kiln, and the speed of the garbage is controlled by the rotation speed to complete the process of drying, incineration and ash cooling in the forward transportation of the garbage in the kiln, and the cooled ash is The bottom end of the kiln is discharged. The whole furnace body of the rotary kiln can be formed by the cooling water pipe and the perforated steel plate to form a barrel shape. The steel drum can also be equipped with a fireproof lining. The furnace body is inclined downwards and divided into three sections: dry combustion and post-combustion. Special wheel support. The special wheel is supported by four rollers. The sprocket drive rotates the wheel to rotate the furnace body. The garbage is on the furnace body. It is rotated and transferred to the front. The preheated air passes through the perforated steel plate from the bottom. Into the kiln, the garbage can be completely burned.
The rotary kiln has wide adaptability for combustion and can incinerate waste of different performances. This type of furnace has fewer mechanical parts and fewer faults, and can be continuously operated for a long time. However, the rotary kiln has low thermal efficiency, consumes more fuel when auxiliary fuel is needed, has low exhaust gas temperature, has foul odor, needs deodorization device or introduces high temperature after combustion chamber incineration, because the kiln body is long, the floor space is large, and afterburning The grate structure of the room is relatively strict, so its cost is high and the price is relatively expensive.
Urban domestic waste incinerators are relatively mature technologies in developed countries. The calorific value of wastes burned in developed countries is mostly above 2000kcal/kg. The municipal solid waste incinerators developed and developed in China are mostly simple incinerators, and high-efficiency incineration and low-pollution emissions have not yet been achieved. The introduction of grate incinerators is expensive and economical, making it difficult to promote and apply.
Fluidized bed furnace
Fluidized bed furnace combustion technology is a new type of clean combustion technology that was rapidly developed in the early 1960s. The basic feature of the incinerator adopting the technology is that a temperature-resistant air distribution plate is arranged in the lower part of the furnace, and the plate is filled with heat-loading inert particles, and the inert particles are boiled under the bed to form a fluidized bed section. Above the fluidized bed section is a sufficiently high burning section (ie suspension section).
After the general material is put into the fluidized bed, the heat transfer and mass transfer rate between the particles and the gas is high, the material is almost completely mixed in the bed, and the waste thrown to the bed can be quickly dispersed evenly. Since the heat carrier stores a large amount of heat, the furnace temperature can be prevented from drastically changing when the material is fed, the temperature of the bed is kept uniform, and local overheating is avoided, so the bed temperature is easy to control. At the same time, it has high fuel efficiency, wide load regulation range, low pollutant emission, high heat intensity, and is suitable for burning low calorific value fuel. It can be said that the most dangerous waste incinerator in China's small and medium-sized towns is a fluidized bed furnace. In particular, China's waste heat value is relatively low, to achieve its efficient and stable combustion, fluidized bed incineration technology is undoubtedly the best choice.
The advantages of fluidized bed incinerators are mainly reflected in the following aspects:
1. Easy to operate and stable operation. After the garbage is crushed and mixed, the texture is relatively uniform, and the fluid bed bed material has a large heat storage capacity of the quartz sand, thereby avoiding the quenching and rapid heat of the bed and stabilizing the fuel. The drying, ignition, combustion and post-combustion of the garbage are carried out almost simultaneously, without complicated adjustments, easy to control the combustion, and easy to automate, and can be started or stopped in a very short time, so that continuous combustion can be achieved.
2. Good durability and long service life. There is no mechanical moving parts in the furnace, so the service life is long. Since the combustion is uniform, local overheating does not occur, and the furnace is a box structure, which is compatible with the thermal expansion of the refractory material, so that the damage of the refractory material is avoided to some extent.
3. A comprehensive anti-secondary pollution measure can be taken to treat the harmful substances generated during incineration. If no additional equipment is added, the Nox content can be reduced to below 100 ppm only by the combustion method peculiar to the fluidized bed. .
Fluidized bed incinerators, by their own characteristics, reduce the amount of wastewater produced. The slag is discharged in a dry state, there is no slag pit wastewater, and there is no need to deal with heavy metal sewage equipment. The waste water in the garbage tank can be sprayed into the incinerator for atomization and incineration.
4. Fluidized bed incinerator Due to the high combustion intensity and heat transfer intensity in the furnace, the volume of the fluidized bed furnace with the same waste treatment volume is smaller than that in the furnace, so the investment is saved and it is suitable for large-scale development.
5. Wide fuel adaptability, can burn high moisture, low calorific value, high ash waste, evenly mixed in the bed, high burning degree, greatly reducing the volume of garbage, especially suitable for the heat value of garbage varies greatly with seasonality. Features.
6. The furnace has a simple structure and there is no moving part in the furnace.
Based on the introduction of the above three types of waste incinerators, the advantages and disadvantages of various incineration methods are summarized. It can be seen that the comprehensive performance of fluidized bed waste incineration is superior, especially the low calorific value of waste in China, to achieve its efficient and stable combustion. The fluidized bed is undoubtedly the best choice. Therefore, the most inefficient waste incinerator in China's current towns should be a fluidized bed furnace.
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