DD280816A1 - METHOD AND ARRANGEMENT FOR OPERATING A STEAM BOILER - Google Patents

Abstract

The invention relates to a method and an arrangement for operating a pulverized coal-fired steam boiler, wherein the temperature of the exhaust gases is lowered in the exhaust stream before induced draft with a cooling medium. The cooling medium is diverted as a flue gas partial flow from the sucked back flue gas for the Mahltrocknung the pulverized coal firing, opposite the Rohbraunkohlestrom before flue gas return suction channel gefoerdert and cooled introduced into the exhaust stream. For the realization of the cooling medium channel is integrated in front of flue gas back suction duct for the grinding drying of the coal dust firing. figure

Description

For this 1 page drawing

Field of application of the guideline

The invention relates to a method and an arrangement for operating a steam boiler, wherein the temperature of the exhaust gases is lowered in the exhaust stream before induced draft with a cooling medium.

Characteristic of the known state of the art

This temperature reduction is required when an increase in the exhaust gas volume occurs due to technical or technological temperature increase of the exhaust gases after Nacnschaltheizflächen. Such an exhaust gas volume increase exceeds the delivery rate of the induced draft or the induced draft is extended to the power limit. As a result, the required negative pressure in the combustion chamber is no longer achieved and adversely affects the separation efficiency of the electrostatic filter or the controllability of the induced draft is no longer guaranteed.

In many cases, therefore, the induced draft was retrofitted or a Saugzug greater power installed, so that it considerable material expenses are required.

The introduction of additional heating surfaces in the flue gas tract zui further cooling of the flue gases is due to no longer existing spaces and only with considerable effort feasible (DD-PS 131 786). In addition, there is the defect that the heating surfaces aufgrünt! The high ballast content in the raw lignite coal quickly reinstate and a renewed exhaust gas temperature increase is the result. Due to the high water content of the raw lignite a further increase in the flue gas volume is given.

For controlled exhaust gas temperature reduction has therefore become known to spray before electrostatic precipitator water (DD-PS 91873), the water must be provided by separate systems. Although mi *, this measure the desired goal is partially achievable, however, the sprayed water also leads to the increase in volume of the exhaust gases and thus to the additional burden of the induced draft and unwanted influence on the electrostatic precipitator. In addition, a high material cost is required because equipment and cooling medium must be provided.

Object of the invention

The aim of the invention is to achieve with simple means eino effective cooling of the exhaust gases.

Explanation of the essence of the invention

The invention has for its object to produce for cooling sin process-related cooling medium.

This is achieved in that according to the invention, the cooling medium as a flue gas partial stream from the sucked flue gas for the time drying of the pulverized coal firing diverted, opposite to the Rohbraunkohlestrom promoted before flue gas Rücksaug channel and cooled in the Abga jstrom is initiated.

To realize the cooling medium channel is integrated before flue gas Rücksaug-channel for Mahltrccknunp the coal dust firing.

By the invention it is achieved that takes place by the branched Rauchgastoilstrom a much improved drying dei Rohbraunkchle. By the thus cooled flue gas partial flow, a process-dependent cooling medium for the controlled exhaust gas temperature reduction is generated, which is subtracted from the own combustion system. In addition, this flue gas partial stream (vapors) does not lead to ignition problems at the pulverized coal burner.

embodiment

In one embodiment, the invention is explained in detail. The drawing shows the system diagram for the recovery of d6s cooling medium and its introduction into the exhaust gas tract

In the combustion chamber 1 of the flue gas suction channel 2 and the subsequent Mahltrocknungsschacht 3 is involved. The Mahltrocknungsschacht 3 is connected via the chute 4 with the allocation device 5. The metering device 5 is connected via lock 6 with the crusher 7. In the head part 8 of the F. jllschachtos 4 is the cooling medium channel 9.1 or 10 in the task of the allocation device 5 Kühlmediumükaoal 9.2 or in the hood 23 of the crusher 7, the cooling medium channel 9.3 with the corresponding actuators 11; 12; 13 involved.

The cooling medium channel 9 is integrated via the vapor condenser 14 with turbid flow 19 and the fan 15 into the exhaust gas channel 16. The exhaust duct 16 leads via electrostatic precipitator 17 and induced draft 18 to the chimney (not shown). Optionally, the cooling medium channel 9 is also directly in front of fan 15 and before the intake 18 in 'Jon exhaust duct 16 einbindbar (dashed line).

The mode of action is the following:

The mill (not shown) draws flue gases 20 from the combustion chamber 1 via the flue gas return duct 2 in the Mahltrockni'ngsschacht 3 and the incident on the coal hopper 4 coal 21 is pre-dried. At the allocation device 5 with the lock 6, the suction of the flue gas partial stream 22 of the sucked-back flue gases 20 via the coal chute 4 in the cooling medium line 9.1; 9.2; 9.3 realized before and / or after the allocation device 5 and / or crusher 7. The actuators 11; 12; 13 in the cooling medium line 9.1; 9.2; 9.3 are used to adapt to the current state of the boiler. For the separation of occurring pulverized coal-water mixtures of the vapor condenser 14 is incorporated with a turbid flow 19 in the cooling medium line 9. The purified gas-water mixture is blown by means of the fan 15 in the exhaust duct 16 before or after electrostatic precipitator 17 or the promotion of the gas-Wassor mixture is bypassing the electrostatic precipitator 17 directly into the existing stronger negative pressure region before induced draft 16 using dei given pressure differences. The settled in the vapor condenser 14 sludge (not shown) is introduced via the turbidity process 19 in the ash removal. The extracted from the inner gas circulation of the boiler gas-water mixture has a high moisture content at a relatively low temperature level (<evaporation temperature), since the heat of evaporation from the lignite coal in the coal chute 4 is added. When blowing this mixture into the exhaust duct 16, a high heat energy is bound by the evaporation of the water. There is a decrease in the flue gas temperature before the induced draft 18. The temperature reduction results in a decrease in the flue gas volume flow, whereby the effective Saugzugförderleistung increases.

At the same time takes place in Kohlenfallschaci., *. in the metering device 5 and in the crusher 7, a further drying of the raw lignite 21, which leads to a stable combustion regime

 The invention achieves the following advantages:

1. Improved controllability of operated at the power limit induced draft.

2. By increasing dos Vortrocknungsgrades the Rohb ^r aunkohle increases the Dampikesselwirkungsgrad.

3. Coal burning with high ash content without reducing the output.

4. Low plant technician effort.

5. Existing systems easily retrofitted.

Claims (8)

1. A method for operating a pulverized coal-fired steam boiler, wherein the temperature of the exhaust gas is lowered in the exhaust stream before induced draft with a cooling medium, characterized in that the cooling medium as a flue gas substream from the sucked back flue gas for pulverizing the pulverized coal from lezweigt, opposite the Rohbraunkohlestrom conveyed before flue gas Rücksaug-Kc nal and cooled in the exhaust gas stream is introduced. 2. The method according to claim 1, characterized in that the flue gas partial stream is conveyed in the mill drying pit opposite the Rohbraunkohlestrom and introduced into the exhaust stream. 3. The method according to Ansp-uch 1 and 2, characterized in that the flue gas partial stream is conveyed in the mill drying shaft and the metering device opposite to the raw lignite coal stream and introduced into the Atgasstrom. 4. The method according to claim 1 to 3, characterized in that the flue gas partial stream in the mill drying shaft, the metering device and the crusher opposite to the raw lignite coal fed and introduced into the exhaust stream. 5. The method according to claim I to 4, characterized in that the cooled flue gas partial stream is introduced via a Brüd6nkondensator in the exhaust gas stream. 6. The method according to claim 1 to 4, characterized in that the flue gas partial stream is introduced before or after the electrostatic precipitator in the exhaust gas stream. 7. Arrangement for operating a pulverized coal-fired steam boiler, wherein a cooling medium channel is incorporated before the induced draft in the exhaust duct, characterized in that the cooling medium duct is integrated before flue gas suction channel for MahlVrocknung the pulverized coal firing. 8. Arrangement according to claim 7, characterized in that the cooling medium channel is integrated into the Mahltrocknungsschacht.