Secondary air distribution device used for circulating fluidized bed boiler

Abstract

The invention discloses a secondary air distribution device used for a circulating fluidized bed boiler. The secondary air distribution device comprises the boiler, water walls arranged on the four walls of the interior of the boiler and provided with receding pipes and a secondary air system. The lower portion of the boiler is a dense-phase zone, and the upper portion of the boiler is a lean-phase zone. The secondary air system comprises a secondary air branch pipe, a plurality of secondary air stand pipes arranged on the outer side of the front wall of the boiler and the outer side of the rear wall of the boiler, and secondary air nozzles arranged on the water walls and connected with the secondary air stand pipes. The secondary air nozzles comprise the double nozzles and the single nozzles and are arranged in the lean-phase zone of the boiler in a layered mode. The receding pipes comprise the double-hole receding pipes and the single hole receding pipes. The disturbing effect of smoke in a boiler hearth is added through the secondary air distribution modes, fuel can be completely burnt, generation of NOx is reduced, grading of secondary air in the height direction is achieved, and grading of the secondary air in the horizontal direction is achieved.

Description

technical field [0001] The invention belongs to the technical field of boiler combustion, and in particular relates to a secondary air distribution device for a circulating fluidized bed boiler. 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 fo...

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Problems solved by technology

The secondary air of existing circulating fluidized bed boilers is usually arranged in two stages, and the horizontal direction cannot achieve classification. Although it can meet the requirements of the boiler for the secondary air volume, the disturbance effect of the secondary air on the flue gas in the furnace is poor. Conducive to the full combustion of fuel in the furnace

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