Circulating fluidized bed boiler for effectively reducing oxycarbide emission

Abstract

The invention discloses a circulating fluidized bed boiler for effectively reducing oxycarbide emission. The circulating fluidized bed boiler for effectively reducing oxycarbide emission comprises a combustion furnace, a cyclone separator connected with the combustion furnace, and a secondary air system for arranging secondary air. An outlet of the combustion furnace is connected with an inlet of the cyclone separator, a burn-out chamber is arranged at an outlet of the cyclone separator, and overfire air is introduced into the burn-out chamber. The secondary air system comprises a secondary air pipe, a plurality of secondary air vertical pipes arranged on the outer sides of a front wall and a back wall of the combustion furnace, and secondary air nozzles arranged on a water-cooled wall and connected with the secondary air vertical pipes. According to the circulating fluidized bed boiler for effectively reducing oxycarbide emission, part of flue gas is mixed with primary air and secondary air, so that NOx emission is reduced; secondary air classification in the height direction and the horizontal direction is achieved through a secondary air arrangement mode; the burn-out chamber is arranged at the outlet of the separator, carbon in fine flying ash at the outlet of the separator is burned again in the burn-out chamber, the carbon content of the flying ash is reduced, and thus the contradiction caused by reduction of the oxygen content of the combustion furnace between NOx emission reduction and the high carbon content of the flying ash can be overcome effectively.

Description

technical field [0001] The invention belongs to the technical field of boiler combustion, in particular to a circulating fluidized bed boiler that can effectively reduce carbon oxide emissions. Background technique [0002] In the nitrogen oxides produced during boiler combustion, NO accounts for more than 90%, and nitrogen dioxide accounts for 5%-10%. The production mechanism is generally divided into the following three types: (1) Thermal type: During combustion, nitrogen in the air is Oxidation, with the increase of the reaction temperature T, the reaction rate follows an exponential law. When T<1500°C, the amount of NO produced is very small, and when T>1500°C, the reaction rate increases for every 100°C increase in T. 6-7 times larger; (2) Instantaneous reaction type: CH free radicals generated by pyrolysis of hydrocarbons in fuel volatiles can react with nitrogen in the air to form HCN and N, and then react with oxygen to form at an extremely fast speed. Its for...

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Problems solved by technology

However, circulating fluidized bed boilers still have room for low-nitrogen combustion transformation

[0005] The invention patent with application number 201310351741X discloses a horizontal circulating fluidized bed heat transfer oil furnace, which includes a feeding device, a main combustion chamber, a secondary combustion chamber, a burnout chamber, a cyclone separator, a separator outlet flue and The induced draft fan, the secondary air device is arranged at the junction of the dense-phase area and the dilute-phase area of ​​the main combustion chamber, below the auxiliary combustion chamber and the burnout chamber, and the nitrogen oxides are effectively controlled through the ratio of the primary air to the secondary air. However, after two combustions in the boiler-burnout chamber, the air volume is particularly large when entering the separator, which will affect the effect of the cyclone separator, so that some large particles are not separated, and are directly discharged with the flue gas, and the fly ash High carbon content

[0006] Studies have shown that reducing the primary air volume and total air volume, reducing the oxygen content of the furnace is the key to reducing NO x It is an effective means of emission, but the reduction of oxygen at the furnace outlet will inevitably increase the carbon content of fly ash and the CO content of exhaust smoke, which will reduce the combustion efficiency of the boiler.

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