DE2536530A1 - Refuse incinerator pollution reduction system - recirculates washed gases through radiation heat exchanger at combustion chamber outlet - Google Patents

Abstract

The large refuse incinerator designed for reduced pollution, which also includes a gas washing system, also uses a radiation type heat recuperator, where the washed gases leave the chamber at a temp. between 55 and 75 deg.C and are returned to the heat exchanger which is positioned at a chimney located directly on the combustion chamber outlet, where the gas temp. is between 650 and 800 deg.C, so that the washed gases which include water vapour, are raised to a temperature of 650 to 800 deg.C.

Description

Method and device for reheating scrubbed flue gases.

The invention relates to a method for reheating washed items Flue gases, in particular from garbage and waste incineration plants, with the heating takes place recuperatively in heat exchange with the flue gases from the incinerator. the The invention also relates to a device for carrying out this method.

Regulations and requirements for keeping the air clean state that in the case of waste and waste incineration plants, in addition to dust, emission limit values for gaseous pollutants are set in the flue gas. This is necessary for the flue gas treatment In addition to dedusting, the use of smoke gas monitoring systems.

During the washing process, the flue gases are enriched with water vapor and completely saturated. You leave the car wash at a temperature of approx. 55 - 75 C C in the area of the respective dew point. This cold flue gas and water vapor mixture shows up in the discharge into the atmosphere, as in many similar processes known as visible Banner. This is visually a disadvantage, as water vapor in certain atmospheric conditions dark to black at some distance appears. It also occurs due to condensation with the cold outside air Falling below the dew point, d. H. to form water droplets that do not enter the Atmosphere rise, but fall to the ground and connect with the still residual pollutants (acids) contained in the flue gas lead to considerable disadvantages being able to lead.

In order to avoid these disadvantages, the washed flue gases reheated after the washing process, using different procedures served. Of these, only those methods are discussed below that on the reheating of the washed flue gases in heat exchange with the warmer ones Obtain flue gases.

Recuperative and regenerative heat exchangers are used for this known, which are usually connected downstream of the flue gas dedusting systems. They are therefore in the range of approx. 250 - 300 ° C, based on the heat emitting Flue gas. These heat exchangers must be connected downstream of the dedusting systems, as they are not suitable for exposure to dusty smoke gases. According to the specified temperature range for the heat exchangers taking into account economically justifiable construction sizes reheating temperature - Reach temperatures for the scrubbing gases of approx. 120 - 160 ° C. This thermal cant of the watered smoke gases is moderate, especially considering the fact that when the flue gases are discharged via high chimneys, temperature losses of 0.3 - 0.5 e C occur per meter of chimney height. At the chimney outlet This means that the reheated, washed flue gas enters the condensation area at an early stage, before it can mix with the outside air, which in turn results in a visible plume of smoke leads.

Another disadvantage of these heat exchangers is their design Structure and choice of material for the heating surfaces, especially with fluorine compounds in the flue gas, with their presence in addition to various other acidifiers Waste incineration plants must always be expected. The one coming out of the car wash Flue gas is saturated with water vapor. At least when starting up such systems as well at partial load, the housing and heating surface of the heat exchanger are below the dew point not to avoid the partial condensation and in connection with the proportions not acids that have been washed out or traces of residual acids lead to corrosion. This circumstance is taken into account through evasive action; selectability of parts, choice of material and corrosion protection, as far as possible according to the state of the art.

In the recuperative heat exchanger, for example as Tubular heat exchanger with hot flue gas through and with washed Flue gas formed around the tubes, the heating surface can be made of glass tubes or if present of hydrofluoric acid, due to the fluorine content in the gas, consist of graphite tubes that known to be elastically suspended and exchangeable. The housing must be on the endangered surfaces receive corrosion protection.

With regenerative heat exchangers, from boiler construction as Air preheater (Ljungström) known, with slowly rotating rotor with storage plates, each half-sided with hot flue gases resp.

washed flue gases is applied, the storage disks (Heating surface) can be provided with a ceramic coating, for example, so that in This area has been given good corrosion protection when the dew point is not reached is. The storage disks can also be exchanged. However, it is difficult Corrosion protection for the rotating housing, for the seals between the rotor and stator as well as the two half cylinders and the protection of the drive shaft with bearings.

Both heat exchanger systems still have the disadvantage of the convective Heat transfer. As is known, convection heating surface is sensitive to contamination. Although the hot smoke gases are largely dedusted, it must be over time pollution are taken into account by existing residual dust to provide corresponding elaborate cleaning facilities.

To avoid the above-described disadvantages when reheating the washed To avoid smoke gases, it is proposed according to the invention that the heating carried out in the area of the hot flue gases emerging from the incinerator will. The temperature of the flue gases is around 800 - 1000 C.

One suitable for carrying out the method according to the invention The device is characterized in that a radiation recuperator for the heat exchange placed on the incinerator or immediately downstream of the incinerator is.

According to a further proposal of the invention, the flue gas chimney be placed directly on the radiation recuperator.

The radiation recuperator is known to be a cylindrical standing Double jacket construction with internal exposure to the hot smoke gases, whereby the heat is mainly caused by radiation to the inner jacket (heating surface) is specified, while in the outer annular gap the mediuni to be heated, in the present one Fall in direct current with the hot gases, is performed.

Tn Fig. E st an embodiment of an overall system with the according to the invention Flue gas reheating shown. For the purpose of better illustration a possible temperature profile within such an overall system is also specified. A radiation recuperator (2), which they are called, is placed on the incinerator (1) Flue gases flow through, whereby heat is transferred to the The flue gas to be heated is released from the flue gas scrubber in the outer annular gap will. Reduced by the heat capacity necessary for reheating the washed Flue gases has been produced, the hot flue gas enters the heat exchanger or Heat shredder (3), in which it is cooled to the dedusting temperature. To the dedusting (4) the flue gas is absorbed by the flue gas scrubber (5), saturated with water and washed.

An induced draft fan (6) takes over the washed flue gases and leads it through the annular gap of the radiation recuperator (2) and then through it Flue gas pipes in the chimney (7).

In Fig. 2, a radiation recuperator is shown in which the Chimney (7 ') is placed directly on the radiation recuperator (2). That is particularly advantageous because there are short flue gas paths and when there are several ovens or incineration plants, each incineration line is assigned a chimney, and thus the flue gas speed at the chimney inlet, regardless of this how many systems are in operation remains constant.

During the reheating of the washed flue gases according to the invention in the high temperature range by means of radiation recuperator (2) the following results essential advantages 1. The temperature increase is significantly higher (200 - 300 ° C), which has a positive effect on the smoke gas pattern at the chimney outlet.

2. Falling below the dew point and associated corrosion on the Heating surfaces cannot occur as the wall temperatures are above 400 ° C.

3. The ongoing cleaning required for convection heating surfaces the heating surface is omitted.

4 Despite the use of a greater temperature gradient due to higher rewarming, the heating surface is much smaller.

5.- By the fact that the high temperature area and a larger temperature gradient are used for heat exchange, there are savings in the heat exchanger or Warmeve rnichter.3, If the heat exchanger is designed, for example, as a boiler, so the expensive radiant heating surface is no longer necessary. On the other hand, if the heat dissipator is used as a Evaporation cooler (injection cooler) is formed, so there is an essential Water savings, a lower amount of flue gas and therefore smaller downstream Plant parts.

Claims (3)

Claims 1. Process for reheating scrubbed flue gases, in particular from garbage and waste incineration plants, the heating being recuperative in heat exchange takes place with the flue gases of the incinerator, characterized in that the Warming up in the area of the hot flue gases emerging from the incinerator is carried out. 2. Device for performing the method according to claim 1, characterized characterized in that a radiation recuperator (2j on the incinerator (1) is attached or immediately downstream of the incinerator. 3. Device according to claim 2, characterized in that the flue gas chimney (7 ') is placed directly on the Strahlungsrekupera tor (2). L e r s e i t e