High-temperature bottom slag cooling and afterheat recycling device of circulating fluidized bed boiler

Abstract

The invention provides a high-temperature bottom slag cooling and afterheat recycling device of a circulating fluidized bed boiler. The device comprises the circulating fluidized bed boiler, a recirculation smoke fan, a cross flow moving bed heat exchanger and a rotary jet nozzle; a boiler slag discharge port is formed in the lower end of the circulating fluidized bed boiler; the cross flow movingbed heat exchanger comprises a bottom slag inlet and boiler walls; the bottom slag inlet communicates with the boiler slag discharge port through a slag inlet pipe; the recirculation smoke fan communicates with the slag inlet pipe through the rotary jet nozzle; the boiler walls are arranged in the cross flow moving bed heat exchanger side by side; bottom slag runners are formed between two adjacent boiler walls; each boiler wall is provided with a gradual increasing channel communicating with two adjacent bottom slag runners; smoke inlets and smoke outlets are staggered between the boiler walls; spiral slag discharge devices are arranged at the bottoms of the boiler walls; and bottom slag flow homogenizing devices are arranged at the tops of the boiler walls. The device can efficiently recover physical sensible heat of thick and fine particles in bottom slag, reduces the system energy consumption, and recovers part of fine particle bottom slag.

Description

technical field [0001] The invention belongs to the technical field of circulating fluidized bed boilers, and more specifically relates to a high temperature bottom slag cooling and waste heat recovery and utilization device for circulating fluidized bed boilers. Background technique [0002] When a circulating fluidized bed boiler is used to burn fuels with high ash and low calorific value (such as coal gangue, oil shale and oil shale semi-coke, etc.), a large amount of high-temperature bottom slag will be discharged from the bottom of the furnace. The slag physical heat loss may be as high as 10%, which greatly reduces the boiler efficiency. At the same time, the upper limit of temperature that conventional ash and slag conveying machinery can withstand is mostly only between 150-300°C, which also increases the difficulty of mechanized transportation of high-temperature bottom slag. Therefore, it is necessary to use a suitable bottom slag cooling device for bottom slag co...

AI Technical Summary

Problems solved by technology

However, due to the good gas-solid mixing characteristics and high heat transfer coefficient in the fluidized bed slag cooler, the air temperature after heat exchange usually does not exceed 400°C, and the energy quality is low, resulting in low utilization rate of bottom slag waste heat , and the gas-solid concentration is high, and the return air duct is seriously worn

In addition, as the amount of bottom slag increases, the fluidization air volume required by the fluidized bed slag cooler also increases accordingly, and the influence on gas-solid flow and combustion heat transfer in the furnace also increases, and there are still all secondary The air volume is not enough to meet the possibility of cooling the bottom slag

Using a moving bed heat exchanger (application number 201710238950.1) solves the above problems to a certain extent, but when dealing with bottom slag with a small average particle size, the bed resistance is large and the system energy consumption increases

However, although the cross-flow moving bed heat exchanger (application number 201810711431.7) separates the bottom slag particles, it does not fully and effectively recover the waste heat of the fine-grained bottom slag, and cannot recover the fine particles in the bottom slag.

[0003] In general, the existing bottom slag cooling and waste heat recovery devices can only obtain hot water below 100°C and hot air at 300-400°C, and the cooling medium with a lower final temperature limits the efficiency of waste heat recovery and utilization

Images