Afterheat recovering device and dry slag-discharging boiler with same

Abstract

The invention relates to an afterheat recovering device for a boiler and in particular provides the afterheat recovering device for a dry slag-discharging boiler. The afterheat recovering device substitutes a transition slag hopper (slag well) of the boiler or is arranged in the transition slag hopper (slag well) for absorbing the radiant heat from the bottom of the boiler in a running process of the boiler and the heat of high-temperature ash slag, is connected to a condensate pump of a steam turbine or an outlet of a first-stage low-pressure regenerative heater and transfers the absorber heat to an inlet of a second-stage regenerative heater. The afterheat recovering device can further absorb the heat of the high-temperature ash slag and the radiant heat from the bottom of the boiler on the basis of a dry slag-discharging system of the boiler so as to improve the thermal efficiency of the boiler and improve the adaptability of the traditional air-cooled dry slag-discharging system to the changes of the coal quality and slag-discharging amount of the boiler.

Description

technical field [0001] The invention relates to a boiler waste heat recovery device, more particularly to a waste heat recovery device for a coal-fired dry slag discharge boiler. Background technique [0002] The thermal efficiency formula of a coal-fired boiler is: η2=100-∑q=[q2+q3+q4+q5+q6], where: η2 is the reverse equilibrium thermal efficiency of the boiler (%); q2 is the exhaust heat loss (%); q3 Incomplete combustion heat loss of gas (%); q4 is incomplete combustion heat loss of solid (%); q5 is heat loss (%); q6 is ash physical heat loss (%). The ash discharged from the coal-fired boiler also has a relatively high temperature, and the physical sensible heat it carries is called the ash physical heat loss q6. The main factors affecting the physical heat loss of ash and slag are the amount of slag discharged and the temperature of ash and slag. [0003] For low-to-medium calorific value fuels with an ash content higher than 30%, if the ash is not cooled, the physical...

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Problems solved by technology

However, in actual operation, the quality of coal source coal in coal-fired thermal power plants is relatively miscellaneous and varies greatly. The quality of coal actually burned often deviates from the design and verification of coal quality, and the amount of slag and ash discharged by boilers varies greatly ( These mainly depend on coal supply and changes in the coal market), resulting in the change of boiler slag discharge is passive and difficult to control (it is difficult to quantitatively evaluate in the design and selection stage), resulting in the cooling of steel belt slag discharger The air volume, cooling air temperature and processing capacity will also change accordingly, which will have a negative impact on the stability and thermal efficiency of boiler combustion conditions, thereby affecting the safety, reliability and economy of unit operation

For example, when the quality of the coal burned by the boiler deteriorates, the slag discharge volume of the boiler will be greater than the initially checked slag discharge volume, resulting in an increase in the air volume sent into the furnace through the air-cooled dry slag discharge machine; as mentioned above, When the total amount of combustion air into the furnace remains unchanged, this will reduce the amount of cold air passing through the air preheater, which will lead to an increase in the exhaust gas temperature of the boiler, thereby reducing the thermal efficiency of the boiler

[0008] In addition, although the above-mentioned air-cooled dry slag discharge system can recover and utilize the waste heat of high-temperature ash while cooling the high-temperature ash, the system is sensitive to changes in boiler coal quality and slag discharge, and cannot be well Absorbs radiant heat from the bottom of the boiler

It can be seen that there is still room for improvement in the existing coal-fired dry slagging boilers in terms of absorbing radiant heat at the bottom of the boiler and aspects related to the slagging system

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