It should be that certain cities in our country and Japan have high garbage recycling efficiency
Our country has a large population and a lot of garbage. There are two major methods of garbage disposal: burial and incineration
Incineration of garbage can The disadvantage of generating electricity is that it pollutes the atmosphere.
After 11 years of independent research and development by Fujian private enterprise Fengquan Environmental Protection Equipment Co., Ltd., an internationally leading domestic waste incineration technology - "double-loop pyrolysis incineration" technology was recently born, and was first used in Zhuji, Zhejiang The city's Fengquanlipu Domestic Waste Harmless Treatment Center has been successfully applied. This technology does not require the addition of auxiliary fuels such as coal and oil, and the raw waste does not need to be sorted. It is directly burned to produce efficient heat energy and clean emissions.
Waste incineration technology has been applied and developed abroad for decades. The more mature furnace types include pulse thrown grate incinerators, mechanical grate incinerators, fluidized bed incinerators, Rotary incinerator and CAO incinerator, the following is a brief introduction to these types of furnaces.
Mechanical grate incinerator
Working principle: The garbage enters the downward sloping grate through the feed hopper (the grate is divided into drying area, burning area and burnout area). Due to the staggered movement between the grates, the garbage is pushed downward, so that the garbage passes through each area on the grate in turn (when the garbage enters from one area to another, it plays a big turning role) until it is burned out and discharged. hearth. The combustion air enters from the lower part of the grate and mixes with the garbage; the high-temperature flue gas passes through the heating surface of the boiler to generate hot steam, and the flue gas is also cooled. Finally, the flue gas is processed by the flue gas treatment device and discharged.
Features: The material requirements and processing accuracy of the grate are high, which requires the contact surface between the grate to be quite smooth and the gap between the grates to be quite small. In addition, the mechanical structure is complex, the damage rate is high, and the amount of maintenance is large. The high cost of construction and maintenance of grate furnaces makes its promotion and application in China difficult.
Fluidized bed incinerator
Working principle: The furnace body is composed of porous distribution plates. A large amount of quartz sand is added into the furnace, and the quartz sand is heated to above 600°C. Hot air above 200℃ is blown into the bottom of the furnace to boil the hot sand, and then the garbage is thrown in. The garbage boils with the hot sand, and the garbage is quickly dried, set on fire, and burned. The unburned garbage has a lighter specific gravity and continues to boil and burn. The burned garbage has a larger specific gravity and falls to the bottom of the furnace. After being cooled by water, coarse slag and fine slag are sent to the outside of the factory using sorting equipment. A small amount of medium slag and The quartz sand is returned to the furnace through lifting equipment for further use.
Features: Fluidized bed combustion is sufficient and combustion control in the furnace is good, but there is a large amount of dust in the flue gas, the operation is complex, the operating cost is high, the requirements for fuel particle size uniformity are high, and high power is required The crushing device, quartz sand causes serious wear and tear on the equipment, and the maintenance of the equipment is heavy.
Rotary incinerator
Working principle: The rotary incinerator uses cooling water pipes or refractory materials arranged along the furnace body. The furnace body is placed horizontally and slightly inclined. Through the continuous operation of the furnace body, the garbage in the furnace body is fully burned, and at the same time, it moves in the direction of the furnace body tilt until it is burned out and discharged from the furnace body.
Features: high equipment utilization, low carbon content in ash, low excess air, and low harmful gas emissions. However, combustion is difficult to control, and it is difficult to burn when the calorific value of garbage is low.
CAO incinerator
Working principle: The garbage is transported to the storage pit, enters the biochemical treatment tank, and is dehydrated under the action of microorganisms to decompose natural organic matter (food waste, leaves, grass, etc.) Other solids, including synthetic organic matter such as plastics and rubber, and inorganic matter in garbage cannot be decomposed into powder. After screening, the waste that cannot be pulverized enters the first combustion chamber (temperature is 600°C) when entering the incinerator. The combustible gas generated then enters the second combustion chamber. The non-combustible and non-pyrolyzable components become ash. is discharged from the first combustion chamber. The temperature of the second chamber is controlled at 860°C for combustion, and the high-temperature flue gas heats the boiler to generate steam. The flue gas is discharged from the chimney to the atmosphere after treatment. The metallic glass will not be oxidized or melted in the first combustion chamber, and can be sorted and recycled in the ash.
Features: Recyclable useful substances in garbage; however, the processing capacity of a single incinerator is small and the processing time is long. Currently, the daily processing capacity of a single incinerator reaches a maximum of 150 tons. Since the flue gas is at 850℃ The above residence time is difficult to be shorter than 1 second, and the dioxin content in the flue gas is high, making it difficult to meet environmental protection standards.
Pulse thrown grate incinerator
Working principle: The garbage is fed into the drying bed of the incinerator through the automatic feeding unit for drying, and then fed into the first-stage grate. After high-temperature volatilization and cracking, the grate is thrown by the pulse aerodynamic device, and the garbage is thrown step by step into the next grate. At this time, the polymer substances are cracked and other substances are burned. This continues until it is finally burned out and enters the ash pit, where it is discharged by the automatic slag removal device. Combustion air is injected through the air holes on the grate and mixed with the garbage to burn, while the garbage is suspended in the air. The volatile and cracked substances enter the second-stage combustion chamber for further cracking and combustion, and the unburned flue gas enters the third-stage combustion chamber for complete combustion; the high-temperature flue gas heats the steam through the heating surface of the boiler, and at the same time the flue gas passes through Cool and then drain.
Its advantages are:
(1) It has a wide range of waste processing and can process industrial waste, domestic waste, hospital waste, waste rubber tires, etc.
(2) High combustion thermal efficiency. The normal combustion thermal efficiency is above 80. Even for domestic waste with high water content, the combustion thermal efficiency is above 70.
(3) Low operation and maintenance costs. Due to the adoption of many special designs and a high level of automation control, there are few operating personnel (only two people are needed for one furnace including ash and slag removal personnel). There is also less maintenance required.
(4) High reliability. After nearly 20 years of operation, it has been shown that the failure rate of this incinerator is very low, with an annual operation of more than 8,000 hours, and a general utilization rate of more than 95%.
(5) High level of emission control. Due to the use of secondary flue gas re-burning and advanced flue gas treatment equipment, the flue gas has been fully treated. After long-term testing, the CO content in flue gas emissions is 1-10 PPM, HC content is 2-3 PPM, and NOx content is 35 PPM, fully complying with European and American emission standards. When the flue gas burns in the second and third stage combustion chambers, the temperature reaches 1000°C and the residence time is more than 2 seconds, which can basically decompose the dioxin. The dioxin content in the flue gas is 0.04 ng/m3, which is much lower than that in Europe and the United States. Standard 0.1 ng/m3.
(6) The grate has a self-cleaning function under the purge of compressed air.