How can we turn waste into energy

The main principle of domestic waste incineration power generation is to use domestic garbage as fuel, put it into the boiler for combustion, and input the superheated steam generated by it into the steam turbine to realize the process of converting thermal energy into electric energy. The whole process is mainly composed of garbage receiving and conveying system, garbage incinerator system, waste heat recovery system, steam turbine generator and thermal system, flue gas purification system, ash treatment system, landfill leachate treatment system, etc. Therefore, we follow This time, we will introduce the waste incineration power generation process.

Front-end reception - garbage receiving and conveying system
The garbage truck enters the factory from the logistics door of the factory. After weighing the weighbridge, the vehicle enters the garbage discharge hall according to the instructions and dumps the garbage into the garbage storage pit. The car will discharge garbage of several tons to more than 20 tons into the garbage storage pit through the rear body. According to the requirements, the garbage in the garbage storage pit will stay for 7-10 days. After the fermentation and dehydration, the heat value is significantly improved, which can meet the garbage furnace. The incineration requirements.
In the process of waste incineration and power generation, the escape of odorous gas has a certain impact on the surrounding environment and the health of the workers. Therefore, the deodorization of the waste incineration power generation process is a problem that plagues the operators. Usually, the staff will install a fan in the upper part of the garbage storage pit. The air in the garbage storage pit is pumped to the incinerator by the primary fan, so that the odor is also burned into the furnace and converted into odorless gas to control the odor and methane gas. Accumulation. In addition, the garbage storage pit is kept under negative pressure by means of suction or the like to prevent the odor in the pit from overflowing.
Mid-end processing - waste incineration system
Incinerator


At present, the reciprocating grate furnace waste incineration technology is basically adopted at home and abroad. The garbage grapple lifts the garbage in the bin to the feeding hopper, and continuously feeds the grate into the grate inlet through the feeding trough. Under the action of the pusher, the garbage first enters the drying zone of the exhaust furnace. Through the action of the grate, the garbage moves forward on the grate to the burning zone, and finally reaches the burning zone to ensure the garbage is at a temperature of 850 ° C ~ 1100 ° C. Get fully burned.

The domestic design institute will select the appropriate grate form for selection according to the local calorific value, moisture, composition and other basic data. The following pictures are a basic diagram of the garbage grate (the top two are the grate being installed, and the lower two are installed and ready to run).

Waste heat recovery system

The upper part of the incinerator is the boiler. The temperature of the flue gas from the incinerator is about 850 ° C. First, the water wall tube of the first passage in the upper part of the incinerator absorbs part of the heat, and then the flue gas continues to wash the screen heating surface and the superheater. Most of the heat in the flue gas is absorbed here. Finally, when the economizer passes through, the remaining heat is absorbed again, and the exhaust gas is discharged to the flue gas purification system. (The chart below shows the flow of flue gas in the boiler. All have a heat exchange tube screen, and the outlet at the right end is connected to the flue gas purification system).
While the flue gas flows, the soda is also flowing. Generally speaking, the flow of steam and water and the flow of flue gas are reversed, which facilitates heat exchange. Generally, the boiler feed water is sent by the feed water pump through the deaerator, is preheated by the economizer, and then sent to the drum, and then further heated by the water wall and the screen heating surface to generate the steam and water mixture into the drum. The saturated steam is separated in the drum, further heated by the superheater, and finally superheated steam is sent to the steam turbine.
After the superheated steam provided by the waste heat boiler enters the steam turbine to drive the generator to generate electricity, the steam enters the condenser to condense into condensed water, and the condensed water is pressurized by the condensate pump, and then passes through the two-stage extractor, the steam seal heater, the low-pressure heater and The deaerator is returned to the waste heat boiler by the boiler feed water pump after deoxidation. The steam used in the low-pressure heater and the deaerator is supplied by the steam turbine when the turbine is running. (The content of this part is not so well understood. I will not elaborate on it. After all, there are too many thermal energy objects involved, no design or People with operational experience can easily confuse things.)
Flue gas purification system

Flue gas purification systems mainly include: furnace denitration system, semi-dry integrated reaction tower, activated carbon adsorption system, bag filter system, flue gas emission system, flue gas online monitoring system and fly ash conveying system.
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