DE3420408C2 - Burners for burning exhaust gases - Google Patents

Abstract

A burner for burning exhaust gases, in particular from nuclear facilities, with the aid of oxidizing agents is described, which is space-saving, easy to handle and reliable and also provides little secondary exhaust gas. For this purpose, mixing chambers are arranged one behind the other in a high-temperature part, with feeds for the oxidizing agent attached tangentially. In addition, the high-temperature part is heated by two or more separately controlled heating coils.

Description

The invention relates to a burner for burning exhaust gases with the aid of an oxidizing agent, in particular of exhaust gases from nuclear processes, consisting of a high-temperature part with two or several electrical heating coils and a post-reaction part.

The increased environmental awareness and the stricter emission laws have the application of the thermal Post-combustion has been strongly promoted in recent years.

A generic burner is known from DE-OS 22 27 389. With this are in a single Mixing and combustion chamber as a high-temperature part, several electrical heating coils connected in series. In the event of failure one heating coil, the entire heating effect and thus the ignition reliability falls in the case of unfavorable Fuel / air ratios, d. H. with a very large excess of air, and the exhaust gas leaves incompletely burned the burner. In the event of strong fluctuations in the fuel content in the exhaust gas, it can be due to the feed the air via a single line in the entire combustion chamber also leads to unfavorable fuel / air ratios come, so that a complete burnout is no longer guaranteed.

It is therefore the object of the present invention to develop a burner of the generic type, thanks to a high level of ignition reliability and good burnout over a wide range of the exhaust gas / air ratio is operationally safe.

According to the invention, this object is achieved in that the heating windings are independent of one another Heating circuits are controlled that several mixing chambers and assigned to the heating circuits in the high-temperature part High-temperature zones are arranged alternately one behind the other, and that in the first mixing chamber tangential four feeds for the oxidizing agent and tangential in the further mixing chambers two feeds for the oxidizing agent are attached.

Appropriate further developments of the burner emerge from the subclaims.

The division of the combustion of the pollutant, flammable exhaust gases into several sections with separate ones Mixing chambers and separately controlled heating windings produce in cooperation with the tangential supply of the oxidizing agent, normally air, an optimal, practically quantitative conversion the pollutants.

Figures I and II show schematically an exemplary embodiment of the burner according to the invention, where FIG. I shows a longitudinal section and FIG. II shows a cross section corresponding to the line A-B in FIG reproduces

The exhaust gases flow to the burner in the high-temperature part (18) through the connection (1) in the middle of the first mixing chamber (3). In the conical mixing chamber (3) there are tangentially arranged feeds (2) for the oxidizing agent at four points over the circumference. The conicity favors the mixing of the exhaust gas with the oxidizing agent. For this purpose z. B. air or an air-oxygen mixture is used. It has been found to be favorable if the opening ratio of the first mixing chamber (3), outlet diameter (D) to inlet diameter (d), is in the range from 1.2 to 1.5 The exhaust gas-air mixture flows to the first mixing chamber (3) into the first high-temperature zone (19) and ignites at the heating coil (6) of the first electrical heating circuit. Slightly substoichiometric combustion takes place in this first high-temperature zone (19) (lack of air).

In the next mixing chamber (5), oxidizing agent is also tangential via two inlets (8) (Air, oxygen or air-oxygen mixture) overstoichiometric blown in and in the second high temperature zone (20) with the help of the second heating coil (9) the mixture continued to burn. The way, several mixing chambers (3.5) and high-temperature zones (19, 20) in a row prevents overheating at one point on the burner. Likewise, the formation of Nitrogen oxides severely restricted. After the reaction in the last high-temperature zone (20), the gas flows through the end ring (10) and the flange connection (11) in the post-reaction part (17) of the burner. The end ring (10) is primarily used to dissipate heat and is preferably made of aluminum oxide.

The post-reaction part (17) consists of an externally heated tube (14) with an internal displacement body (13). The thus formed annular space with, for example, a maximum of 100 mm annular gap width, depending on the gap in a concentration derived from nuclear facilities exhaust gas is used for the subsequent reaction at temperatures of about 800 ⁰ C. To protect the displacement body (13), a ceramic tip (12) is attached to its front side facing the high-temperature part (18). There are cooling connections (16) on the opposite side of the displacement body (13).

The flue gases escape through the nozzle (22) which is attached radially to the end of the post-reaction part (17) is.

The possibility of adjusting the free diameter of the high-temperature part (18) through tube inserts (7) to vary the different fissile material contents,

makes the burner especially for nuclear applications useful. In addition, the pipe inserts (7) serve to protect the heating coil (6, 9) from corrosion and Overtemperature.

For the nuclear pit operation it turns out to be particularly favorable that the individual parts (5,6,7,8,9,10) of the high-temperature part (18) after removing the cover (4) are removable.

The simplicity of the regulation, only electrical heaters are regulated with the help of thermocouples, make the burner very reliable. Particularly noteworthy are the absolute ignition reliability and the good burnout in large areas of the exhaust-air ratio. Important measuring points, especially for regulation the heaters are monitored twice. At the end of the high-temperature part (18) there is a measuring point (21) for the combustion chamber outlet temperature. The burner can also be equipped with a feed lock ^ n will.

In the event of a power failure, the exhaust gas that is still supplied remains on the hot mixing chamber walls for a certain period of time ignited and safely burned The system can then be used without soot formation or release of unburned Harmful gases are slowly removed.

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Claims (4)

Patent claims: 1. Burner for burning exhaust gases with the aid of an oxidizing agent, in particular exhaust gases from nuclear processes, consisting of a high-temperature part with two or more electrical heating coils and a post-reaction part, characterized in that the heating coils (6,9) are controlled by independent heating circuits that in the high temperature part (18) several mixing chambers (3, 5) and high-temperature zones assigned to the heating circuits (19, 20) are arranged alternately one behind the other, and that in the first mixing chamber (3) tangentially four feeds (2) for the oxidizing agent and in the further mixing chambers (5) tangentially two feeds (8) for the oxidizing agent are attached. 2. Burner according to claim 1, characterized in that the first mixing chamber (3) to the first High-temperature zone (19) is widened conically 3. Burner according to Claim 2, characterized in that the ratio of the mixing chamber outlet diameter (D) to the mixing chamber inlet diameter (d) of the first mixing chamber (3) is between 1.2 and 1.5. 4. Burner according to claim 1, characterized in that the free diameter of the high-temperature part (18) is variable by tube inserts (7)