Circulating fluidized bed boiler for burning low-heat-value high-ash fuel

Abstract

The invention relates to a circulating fluidized bed boiler for burning low-heat-value high-ash fuel. The circulating fluidized bed boiler comprises a hearth, a primary air chamber, a cyclone separator, a dipleg, a material returning valve, a slag discharging pipe, a gas-solid heat exchanging bed and a tail flue. The tail flue is internally provided with a superheater, an economizer and an air preheater. The gas-solid heat exchanging bed is connected with the dipleg through an ash discharging pipe. A part of high-temperature returning ash in the dipleg enters into the gas-solid heat exchangingbed. The gas-solid heat exchanging bed comprises a heat exchanging bed air chamber, a heat exchanging bed air cap, a heat exchanging bed heat exchanging chamber, a heat exchanging bed gas-solid separation device and a heat exchanging bed slag discharging pipe. A gas outlet in the top of the heat exchanging bed gas-solid separation device is connected with the primary air chamber of the boiler through a gas pipeline. The heat exchanging bed air chamber is connected with the air preheater through the gas pipeline. According to the circulating fluidized bed boiler, on the one hand, partial ash cooling and slag discharging are realized by utilizing the gas-solid heat exchanging bed, the ash slag heat is fully recovered, the heat loss of slag discharging is reduced, and the heat efficiency ofthe boiler is improved; and on the other hand, primary air temperature can be greatly improved, and stable burning of the low-heat-value high-ash fuel is facilitated.

Description

technical field [0001] The invention belongs to the field of combustion application of circulating fluidized bed boilers, and discloses a circulating fluidized bed boiler which includes a gas-solid heat exchange bed and is suitable for burning low calorific value and high ash fuels such as oil shale, oil shale semi-coke and gangue. Background technique [0002] my country has huge reserves of fuels with low calorific value and high ash content, such as oil shale, which has proven reserves of 700 billion tons and has great application potential. -70%, it is difficult to achieve stable combustion in general combustion equipment, so its efficient use of energy has been widely concerned. [0003] Circulating fluidized bed boiler has the advantages of good fuel adaptability and low pollutant emission level. Because its dense phase zone contains a large number of high-temperature solid particles and has strong heat storage capacity, it has the potential to burn fuels with high ash ...

AI Technical Summary

Problems solved by technology

However, due to the low calorific value of the fuel itself, its stable combustion is relatively difficult. Generally, it is necessary to use a higher primary air temperature or blend fuel with high calorific value, and the fuel has a high ash content and a large amount of slag discharge, which not only requires multiple slag coolers, but also affects The overall layout of the boiler also has a huge slagging heat loss, which greatly reduces the thermal efficiency of the boiler

Therefore, circulating fluidized bed boilers burning fuels with low calorific value and high ash content generally have the problems of difficult stable combustion and low thermal efficiency.

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