FI74795C - EFFECTIVE EFFECTIVE AV AVGASER FRAON FOERBRAENNINGSANLAEGGNINGAR. - Google Patents

Description

1 74795

Apparatus for afterburning the exhaust gases from combustion plants

The invention relates to an apparatus for afterburning the exhaust gases of combustion plants, the apparatus comprising 5 afterburning chambers into which a burner is inserted, opposite which a cup is located for capturing and turning the burner flame, a height-adjustable for the exhaust gases, and that an outlet to the atmosphere leaves the afterburner.

In modern society, a series of burns are carried out, involving both the intended fuels and the pollutants, and which to some extent burn. Post-combustion chambers have long been used in connection with military aircraft-15 reaction engines. However, for environmental reasons, the intention was not to carry out the complete combustion of kerosene, but rather to achieve higher performance. Exhaust gas purifiers for car engines are not really afterburners, but rather organs for exhaust gas recirculation.

In the case of waste incinerators, destruction furnaces and industrial process furnaces, as well as boilers, incineration is carried out up to a stage 25 that is balanced in terms of the economic benefits of the process and the environmental requirements imposed by the authorities. The most commonly used means of reducing the level of pollutants in an emission is an exhaust gas filter or an exhaust gas scrubber. The problem, however, is that it is necessary to get rid of what has been collected by the filters or washing liquids. One traditional method of reducing the degree of contamination in the immediate environment is to send contaminants through long chimneys to dilute to higher atmospheric layers. The impact of such a procedure is becoming increasingly apparent in the forested areas of the Skan-35 dynamics, where sulfuric acid descends from high 2,74795 chimneys in mainland combustion plants. The idea behind the use of destruction furnaces and waste incineration plants has been, above all, to reduce the content of bad odors in the exhaust gases. When the high chimneys have not been sufficient, the burning has therefore been carried out at night, because then few people are outside. For ethical reasons, the same work design has long been used for crematorium furnaces.

It can be seen from the above that there are a number of burner installations where it is desirable to reduce the concentrations of pollutants in the exhaust gases. Fifty substances from different plastic materials can already be found in the exhaust gases when household waste is incinerated. Most of these can be burned into water vapor and carbon dioxide by the invented method.

It is an object of the invention to provide an apparatus for converting non-combustible components contained in the exhaust gases of combustion plants into non-hazardous substances by post-combustion.

In order to illustrate the invention, it may be appropriate to consider a method for post-combustion of household waste gases.

For the construction and sizing of the afterburner for this use, it is necessary to know what decomposition products are formed and how large amounts of these will be burned per unit time. Using the formula below, a calculation is made based on the fact that 1 kg of ethylene plastic decomposes in the incinerator and is largely converted to 1-hexene, 1-pentene, propane and propylene. Accordingly, the rate of thermal decomposition of the polyethylene polymers 30 in a vacuum is determined, and a rough estimate is made of the decomposition of the polyethylene plastic under the conditions prevailing in the incinerator.

K = A. e

K = velocity constant (S j 35 A = Arrhenius factor (S

E = activation energy (kJ. Mol R = gas constant (8.314 J. ° K. Mol I! 3 74795 By calculation and experimentally, it has been found that polyethylene plastic decomposes in vacuo at a rate of about 1% per minute at 415 ° C. lasts about one and a half hours at a temperature of 415 [deg.] C. Under actual conditions, the process would decompose 10-15 g of polyethylene per minute in an incinerator, corresponding to a gas volume of 6-9 l / min, to afterburn this gas and maintain a temperature of 1500-2000 [deg. in order to maintain a closed flame volume at the same time, from which the amount of gas delivered by the waste portion cannot penetrate completely without burning, the following amounts of gas are required for the afterburner burner: gas oil 0.2 = 0.3 m ^ / h (NTP) 15 air 5-8 m ^ / h (NTP)

The design of the burner to ensure said closed flame, in which complete mixing between the exhaust gases and the combustion gases is achieved, is described below.

20 It is not possible to increase the size of the afterburner to any extent, but if very large capacity is required, several afterburners must be connected in parallel.

The afterburner burner can be controlled by ion analyzing sensors located at the afterburner outlet that control the selection of any combustion gas addition when the temperature needs to be raised to achieve complete combustion, such as adding gas oil to air or alternatively adding hydrogen to air. 30 The temperature range of the afterburner is usually set on the basis of empirical information on the composition of the exhaust gases from the fuel and, depending on this, for example the mixing or excess of oxygen with the exhaust gases introduced through the burner.

In order to achieve the objects of the invention, it is given special features, which will become apparent from the following claims.

4,74795

The device according to the invention will now be described with reference to the accompanying drawing, in which Figure 1 shows an embodiment of an afterburning chamber in longitudinal section.

The afterburning chamber 1, which may be provided with cooling flanges 2, or which may be surrounded by a cooling jacket, contains a flame plate 3 of highly refractory material. The flame plate 3 has a nearly hemispherical end 4 which coincides with a cylindrical jacket surface 5. 5, a certain distance 10 from the end 4, a number of holes 6 are made to make a connection between the interior of the flame bowl 3 and the part of the afterburner outside it. The flame cup 3 is sealed outwards around its cylindrical jacket surface 5 at its edge 7 away from the end 4 against the wall of the afterburning chamber 15 1 by means of one or more seals 8 made of ceramic or centrifugal sealing material. The inner side of these seals presses against the fire tube 9 connected to the nozzle 11 of the burner 10.

The burner 10 consists, except for the fire tube 9 and the nozzle 20, of the inner burner tube 12 and the outer burner tube 13. The outer burner tube 13 is surrounded by a heat-insulating material 14 having the required heat resistance and secured by the jacket 15.

Between the outer and inner burner tube runs a heating element 16, which is preferably made as at least one electrical resistance element. Axially through the inner burner tube 12, the burner feed tube 17 protrudes to introduce combustion gas, e.g., air, oxygen, or alternatively mixed with either gas oil, into the nozzle 11. The jacket 15 of the burner 10 is connected to the jacket of the afterburning chamber 1 by a screw connection 19. Similarly, by means of the screw connection 20 35, the rear end 21 is arranged on the jacket 15. The rear end 21 has through-openings 22 for the heating element 16. The rear end 5 74795 inside the dyn 21 and between the outer and inner burner tubes and around the inlet portions of the heating member 16 has a heat-resistant seal 23. A seal 23 'is also made between the burner supply tube 17 and the inner burner tube 12 5 against the rear end 21.

When the apparatus is used, gases which are to be "afterburned" or oxidized, in particular to water vapor and carbon dioxide, are introduced into the afterburning chamber 1 via an inlet pipe 24 which communicates with the space 25 between the outer 13 and inner 12burner burners. with transverse members 16, which are preferably adapted to form a zigzag-shaped flow channel. In this case, if the length of the burner has been adapted for this purpose and a heating coil covered with a high-temperature resistant material, for example silicon oxynitrile, has been chosen as the heating element, the exhaust gases can be heated to a temperature substantially higher than 1000 ° C.

The exhaust gases thus heated exit the space 25 20 through one or more holes 26 in the inner burner tube 12. The edges of these holes are arranged to guide the exhaust gases towards the burner supply pipe 17, and then preferably so as to cause the exhaust gases to rotate around the burner supply pipe nozzle 18. This rotational movement is intensified because the combustion gases flow out through the tangential outlets in the mouthpiece 18. Thus, very good gas mixing is achieved.

The combustion gases introduced through the burner supply pipes 30 have a composition selected with regard to the composition of the exhaust gases to be afterburned. Thus, in some cases air may come into question, in others pure oxygen. If the substances contained in the flue gases could only be burned endothermically, for example, gas oil is mixed with the flue gases in the required amount.

6 74795

Since the exhaust gases and the combustion gases, when vigorously mixed, react as the temperature rises to a flame temperature of 1500-2000 ° C, their volume increases due to the fact that the nozzle 11 is made conical. From this, the gas continues as a homogeneous flame, preferably through a fire pipe 9 made of a highly refractory material. This opens into the flame bowl 3 and the gas flame pushes towards its end 4, whereby it turns 180 ° and penetrates at an increased speed into the annular gap formed between the outer 10 of the fire tube 9 and the cylindrical part 5 of the flame bowl 3. In the ring gap, the flame has burned out and the remaining gases penetrate through the holes 6 into the afterburner itself. As the volume of the gases then increases, the temperature drops sharply, however, considerable amounts of heat remain which can be released to the environment via the cooling flanges 2 shown, alternatively to the medium in the surrounding cooling jacket. Heat transfer back to the previous stage of the process is also possible.

20 Finally, the combusted gases are led out through the outlet line 27. This may, as schematically indicated at 28 (Figure 1), be surrounded by means for heat recovery or cooling. Should it be considered advantageous for safety reasons, the discharge line 27 can be routed to a scrubber or other device for the final treatment of the burned gases. This may be desirable if there is a risk of nitrous gases.

To ensure a certain gas flow through the device, a vacuum sensor can be connected to the outlet line 27. By this stepless speed control, a gas velocity adapted to the different gas flows from the combustion plant before the afterburner can be obtained. The speed of the fan can be adjusted manually or can be controlled by any of the advanced control devices by means of sensors located at useful points in or in connection with the afterburning chamber.

Il 7 74795

An embodiment of the invention has been described above, but of course other variations which fall within the scope of the following claims are also protected.

Claims (2)

8 74795 An apparatus for post-combustion of exhaust gases from combustion plants, the apparatus comprising an afterburner chamber 5 (1) into which a burner (10) is inserted, opposite which a cup (3) is arranged to capture and turn the burner flame, the height-adjustable burner (10) passes through passages (17,25) for the combustion gases and exhaust gases 10 to be fed to the afterburner, and that an outlet (27) exits the afterburner (1) into the atmosphere, characterized in that the inlet duct (25) has a heating (16) that the inlet duct (25) surrounds the duct for introducing fuel gases 15 formed as a supply pipe (17), and that holes (26) are formed in the inner pipe (12) of the inlet duct (25), the edges of which are adapted to conduct the exhaust gas flow. tangentially towards the nozzle (18) of the supply pipe (17), which nozzle also has a tangentially directed outlet. o for forced mixing of both gas streams. Device according to Claim 1, characterized in that the afterburning chamber is surrounded, at least in part, by means (2) for dissipating excess heat. li