Introduction to the mixed combustion furnace for three types of waste
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I. Overview of the Fluidized Mixed Combustion Furnace for Treating Waste Streams The fluidized mixed combustion furnace (the third-generation gas generation blowair recovery device) is a system that mixes the blowair generated during the gas production process, gas generation slag, and fine ash from gas filtration devices with certain amounts of coal gangue, bituminous coal, and anthracite powder, and then burns them in a fluidized state within the furnace; this process generates high-temperature flue gases from which heat can be recovered. The first-generation gas generation blast air recovery device features an upper-combustion regenerative combustion mode; by utilizing the heat stored from the combustion of syngas with a high calorific value, it enables the combustion of blast air with a lower calorific value, thereby recovering heat and generating steam as a by-product to protect the environment. The second-generation gas generation blast air recovery device features an upper or middle combustion mode. Building on the first generation, it incorporates additional combustion nozzles, reduces the number of grid bricks inside the furnace, or uses a baffle-type flue gas arch channel for heat storage, thereby significantly reducing resistance within the furnace. This lowers the resistance during the blast air supply stage in the gas generation furnace, ensures more complete combustion of the flue gas, and enables the gas generation system to achieve self-sufficiency in steam production. The third-generation gas generation blast air recovery device, also known as the gas generation three-waste fluidized mixed-combustion furnace, operates on a mixed-combustion principle. It represents a breakthrough over the second generation, featuring a more rational design, more advanced technology, and greater reliability in operation. A patent was granted for it in 2001, with the patent number ZL 01215849.6. Its design takes advantage of the combustion characteristics of a bubbling bed, utilizes the return material recovery technology from circulating fluidized bed boilers, and adopts a blowair waste heat boiler configuration; this allows for the simultaneous combustion of the waste gases, residues, and ashes generated during gas production. Hence, it can also be referred to as a \"dual-energy blowair waste heat boiler\" or a third-generation blowair waste heat boiler. When burning purge gas, the three-waste fluidized mixed-combustion furnace functions as a purge gas waste-heat boiler; when burning coal, coal gangue, cinder, etc. separately, it acts as a circulating fluidized bed boiler; while burning slag, gas, and coal together, it functions as a gas-solid fluidized mixed-combustion furnace. The gas generation three-waste fluidized mixed-combustion furnace system boasts comprehensive performance that far exceeds that of the first and second generations of gas generation blast air recovery devices; it represents the current solution for converting synthetic ammonia, urea, and methanol production systems from using two types of coal to one type, as well as from using two furnaces to one. II. Combustion process, mechanism, and equipment composition of the flue gas fluidized mixed combustion furnace. The combustion section of the flue gas fluidized mixed combustion system consists of two devices: one is the flue gas fluidized mixed combustion furnace, and the other is a combined dust collector ； The heat recovery section consists of a steam superheater, a waste heat boiler, a economizer, an air preheater, and water-cooled components inside the furnace ； The flue gas washing and emission section consists of a water film dust collector and a chimney. The three-waste fluidized mixed combustion furnace features a steel casing; at its lower part there is a bubbling fluidized bed where the mixed slag and coal burn together. Its structure includes air distribution caps, air distribution plates, air chambers, viewing holes, coal feeding ports, return material ports, and an automatic oil-gas ignition system. In the middle are the air-blown premixed combustion inlet, high-temperature combustion nozzles for the synthetic exhaust gas, etc. The dust collector is a high-temperature cyclone dust collector with top feeding and bottom exhaust. The central cylinder in the cyclone section is either a swirl cylinder made of high-temperature resistant stainless steel 1Cr20Ni14Si2, or a water-cooled swirl cylinder composed of high-temperature resistant and wear-resistant cast materials as well as high-temperature resistant stainless steel plates 1Cr25Ni20; the bottom part of this cylinder features a sedimentation-type water seal. The three-waste fluidized mixed combustion furnace can be manufactured in various specifications to meet different requirements. In terms of steam production capacity, it is available in capacities of 10 tons per hour, 25 tons per hour, 35 tons per hour, 50 tons per hour, etc ； In terms of pressure: 1.27 MPa, 2.5 MPa, 3.82 MPa, 5.29 MPa, etc.
III. Characteristics of the flue gas mixing combustion furnace for treating three types of waste streams. Compared with the first-generation and second-generation waste gas heating boilers, the flue gas mixing combustion furnace for treating three types of waste streams has the following characteristics: high operational safety. Both the first-generation and second-generation waste gas combustion boilers require a fuel source for ignition; below 650°C, the waste gas cannot burn, and its introduction into the combustion chamber can lead to explosions. In addition, the valve used to control the flow of waste gas is opened and closed frequently, and if it isn’t sealed properly, gas can enter the combustion chamber, resulting in explosions when the air distribution valves cannot be adjusted in time. For example, a 30-ton blast furnace for burning blowing gas installed in a fertilizer factory in Shandong exploded due to improper operation during the ignition and heating process; the entire system was damaged except for the boiler itself. It took over two months and nearly 1 million yuan in additional investment to repair it. Explosions also occur frequently in other factories. The three-waste fluidized mixed-combustion furnace uses coal as the ignition source, maintaining a continuous flame with no risk of explosion ； In the fluidized mixed combustion furnace for the three types of waste, high temperatures and an excess of oxygen are present during coal combustion; if additional gas is fed in, it will simply continue to burn without any explosion occurring. The combustion system features low resistance, no ash accumulation, and improved efficiency in gas generation through blowing air. The first-generation blowing-air combustion furnace uses a large number of Siemens lattice bricks for heat storage; however, these bricks tend to get clogged, which reduces the efficiency of gas generation and forces the furnace to be shut down for cleaning. The second-generation air-blown combustion furnace also cannot completely solve the problem of ash accumulation inside the furnace; due to the low combustion temperature, it is unable to burn the coal powder brought in with the air flow, and as a result, it is necessary to add wastewater for washing after the induced draft fan in order to remove the coal powder. Some systems incorporate cyclone dust collectors in front of the combustion furnace; although this helps to prevent ash buildup and blockages inside the furnace, it also results in extremely fine combustion particles accumulating around the boiler’s heat exchange tubes. This reduces the boiler’s heat transfer efficiency, leading to a significant decrease in the amount of steam produced, far below the boiler’s rated capacity. The three-waste fluidized mixed combustion furnace completely eliminates the grid bricks inside the furnace, and no refractory materials are used to store heat in order to ensure the ignition of the blowing air; as a result, the combustion system has low resistance and does not accumulate ash.
I would like to ask how to ensure that the gas used for blowing is distributed evenly throughout the mixed-combustion furnace, so as to maintain stable pressure inside it. In our company’s mixed-combustion furnaces, the pressure fluctuates greatly; there is positive pressure when gas is supplied and negative pressure when it isn’t. Although these fluctuations last only a few seconds, they are significant and can be harmful to the furnace
Original poster, do you have a DCS solution for mixed combustion of waste materials? Could you send one to me for study*? hou*aoyao007@126.vom