【Abstract】 The waste incinerator reduces the nitrogen oxide emission system and is a technical method to solve the waste incinerator to reduce the generation of nitrogen oxides. The flue gas is divided into two paths after the bag filter, all the way using the induced draft fan to pass the flue gas through the chimney row Into the atmosphere, all the way to use flue gas recirculation fan into the furnace.

At present, the promotion of garbage disposal in our country gradually turns to incineration. If we do not take measures, it will release a large amount of nitrogen oxides to the atmosphere and cause serious pollution to the atmosphere, which is not conducive to the decontamination and reduction of urban waste in the end. The resources Processing. In the process of MSW incineration, there are mainly three sources of NOx: one is that the organic and inorganic nitrogen compounds in the refuse itself react with O2 during the incineration process to generate NOx; and the other is that N2 in the combustion air is oxidized under high temperature NOx; Third, combustion-supporting fuel (such as coal, natural gas, oil, etc.) combustion to generate NOx. It is the most effective way to reduce the NOx emissions from incinerator exhaust by strengthening the control measures to suppress the formation of NOx or to reduce the already formed NOx to N2 molecules. To control the NOx emissions, it is usually necessary to introduce secondary air at the exit of the afterheat furnace in the incinerator system, In the secondary air continuous injection of urea water or ammonia to control the production of NOx; Although this structure can inhibit the production of NOx, but the use of large amounts of urea or ammonia also brought urea water or ammonia transport storage, and Deal with the high cost of the problem.

The method is a waste incinerator to reduce nitrogen oxide emissions system is a solution to the waste incinerator to reduce the formation of nitrogen oxides from the bag filter after the flue gas is divided into two, The gas is discharged into the atmosphere through the chimney, and the flue gas before it is discharged into the atmosphere is used to monitor the NOx content online through the flue gas. On the other hand, the flue gas is introduced into the waste incinerator through the flue gas preheater to replace the original Some secondary fans function to suppress the normal agitation required to produce CO and VA.

In order to achieve the above object, the waste incinerator reduces the nitrogen oxide emission system including an incinerator, a waste heat boiler, a boiler economizer, a reaction tower, and a dust collector connected in series. A primary air inlet is provided in the incinerator, A secondary air inlet and a dust collector outlet are connected with the smoke exhaust pipe through a connecting passage, a first smoke exhausting machine is arranged in the connecting passage, wherein a connecting passage between the outlet of the dust precipitator and the first smoke exhausting machine is communicated with a smoke exhaust A bypass pipe connected to the waste heat boiler, a second smoke exhaust machine being provided in the smoke exhaust bypass pipe, and a recirculation flue gas preheater being provided on the smoke exhaust bypass pipe.

In the process of refuse combustion, the amount and emissions of nitrogen oxides are closely related to the combustion modes of refuse, especially the excess air ratio and combustion temperature. The NOX produced by the garbage in the combustion equipment mainly includes NO and NO2, wherein NO accounts for 90% -95%, and NO2 is generated by NO being oxidized by O2 at low temperature. The heat-type NOX is generated by the reaction of nitrogen in the air with oxygen at high temperatures. The mechanism by which nitrogen in air is oxidized to NO at high temperatures is rather complicated and its formation mechanism follows the Zeldovich mechanism, which is a free radical chain reaction initiated by oxygen atoms: O2 → 2 O ⑴ N2 + O → NO + N (2) N + O2 → NO + O⑶

Reaction â‘´ is in the boiler hearth under high temperature oxygen molecules in the air is dissociated into free oxygen atoms of the process. The generated oxygen atoms react with the nitrogen molecules in the air at high temperature to generate NO and release nitrogen atoms, and the nitrogen atoms can only be generated through the reaction (2) but not by the decomposition of nitrogen molecules. The nitrogen atoms released by the reaction (2) reacts with the oxygen molecules in the air to generate NO. The NO generated by the above reaction is only related to the concentration of nitrogen and oxygen in the air but not the fuel component.

Based on this philosophy, it is advisable to add gas perturbations at the exit of the incinerator, as well as the proper conditioning of the air instead of simply injecting urea or ammonia. Therefore, the waste incinerator reduces the nitrogen oxide emission system, as shown in FIG. 1, and includes an incinerator 1, a waste heat boiler 2, a boiler economizer 3, a reaction tower 4, and a precipitator 5 which are sequentially connected, A wind inlet 101, a secondary air inlet 201 is arranged in the waste heat boiler, the outlet of the precipitator is connected with the smoke exhausting pipe 7 through the connecting passage 6, a first smoke exhausting machine 8 is arranged in the connecting passage, wherein, The connecting passage between a row of smoke machines is connected to a smoke exhaust bypass pipe 9 which is connected to the waste heat boiler, a second smoke exhaust machine 10 is arranged in the smoke exhaust bypass pipe, The pipeline is provided with a recirculation flue gas preheater 11. A nitrogen oxide sensor 12 is arranged in the connecting channel, a signal receiving end of a microprocessor controller is connected with a nitrogen oxide sensor, and a control output of the microprocessor controller is respectively connected with a first smoke exhausting device and a second smoke exhausting device Machine's inverter motor. The primary air inlet communicates with the primary air blower 13, and a primary air bypass pipe 14 is connected to the primary air outlet. The primary air bypass pipe is connected to the secondary air inlet, and the primary air bypass pipe is provided with a control valve 15. The flue gas recirculation system composed of the exhaust bypass pipe, the second smoke exhaust machine and the recirculation flue gas preheater replaces the original secondary air system and also promotes the full combustion of the original secondary air through the flue gas turbulence Reduce the production of CO and two VA British at the same time, but also through the low-oxygen combustion, inhibiting the occurrence of NOx, reducing flue gas emissions and increase waste heat boiler efficiency.

Recirculation flue gas system uses flue gas recirculation instead of secondary air, normal operation does not require secondary air, the secondary air is only used as an auxiliary means of oxygen control from a fan outlet leads to low oxygen From the top of the case to supplement in order to reduce the production of CO. Recycled flue gas system refers to the combustion of flue gas incinerator back through the fan, and then sent to the incinerator outlet (secondary air outlet below) in order to achieve low-oxygen combustion, NOx emissions to reduce emissions and improve boiler efficiency purpose. The high-temperature flue gas generated in the incinerator is recovered by heat recovery devices such as waste heat boilers and economizers, and superheated steam generated by the waste heat boiler is sent to the turbine generator for power generation.

Waste heat boiler means a complete set of steam boiler equipment, consisting of pressure-bearing parts, frame structure and refractory lining, including the necessary valves, gauges and insulation materials, cleaning equipment, furnace safety monitoring system, drum level and furnace flame monitoring system. Waste heat boiler with horizontal layout. The primary air inlet is connected with the fan once through the air duct 18, the primary air fan passes through the air duct all the way through the secondary air regulating valve 15 into the waste heat boiler, all the way through the air duct through the air preheater into the ash hopper 102, Steam through the steam pipe through the primary air temperature control valve 19 into the air preheater steam side, the ash hopper (also Bellows) connected grate incinerator, garbage hopper 20 connected grate incinerator, waste heat boiler connected boiler drum 21 and boiler economizer 11, boiler economizer connected to the reaction tower, the reaction tower through the flue gas pipe connected to the precipitator, precipitator outlet flue gas in two ways, all the way through the boiler exhaust fan to the chimney through the pipeline, all the way The boiler flue gas recirculation fan and the recirculation air preheater are piped to the waste heat boiler (the interface location is located below the secondary tuyere outlet of the afterheat furnace outlet) and the steam is passed through the steam pipe through the recirculation air temperature control valve 22 into the recirculation air preheater Steam side of the boiler, in addition to the outlet of the boiler fan also has a flue gas online monitoring device.

The tail of the garbage incinerator into two outputs, one of the way to replace the original secondary air supply to the corresponding parts of the furnace, the advantage of doing so is to effectively reduce the oxygen concentration in the region, when the reasonable control of the return smoke Gas temperature can effectively inhibit the formation of NOx. Due to the effectiveness of the system, no urea or ammonia water is injected under rated conditions, which reduces the cost of MSW incineration and can meet the daily average of 200mg / Nm3 of environmental indicators.

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