DE3512810A1 - METHOD AND INSTALLATION FOR THE COMBUSTION OF WASTE - Google Patents

Abstract

In a process to burn refuse materials, in particular relatively moist and/or low caloric value refuse materials from households, municipalities and industry, commonly referred to as ''garbage'', combustion air is added in staggered amounts to the firing during the refuse burning process depending on the progressive burning down or burning out of the refuse as it undergoes its combustion in the furnace. In order to prevent the formation of toxic organic compounds and, as applicable, to decompose them thermically and to reduce the nitrogen oxide content of the fumes, it is proposed that instead of at least part of the combustion air, oxygen be blown into the furnace. Preferably, oxygen should be added to the burning refuse at an advanced stage of burning out during the second half of the combustion process.

Description

Process and installation for the incineration of waste materials

The invention relates to a method for incinerating waste materials, in particular of relatively moist and / or low-calorific waste materials from households, Municipalities and economy, referred to as garbage for short, with the firing in the garbage incineration process according to the progressive burnout or burnout of the garbage in the course of the combustion path through the combustion chamber, graded amounts of combustion air are added.

The economical and at the same time harmless to the environment disposal waste of the type mentioned at the beginning poses a difficult problem. This is especially true when such waste materials are in conventional waste incineration plants be eliminated.

Most of the waste incineration plants currently in operation is equipped with grate furnaces, which require large excesses of air for operation, in order to guarantee an almost complete recognition. For example are for waste incineration in grate furnaces, excess air numbers of 1.8 to 2.2 and above common. This results in considerable disadvantages, including the fact that Furnaces operated in this way large quantities of flue gas at a relatively low temperature, for example between 800 and 900 OC, produce. Consequently is the efficiency of a device connected to the flue gas flow Energy generation, for example for steam or electricity generation, is relatively low. Furthermore, large amounts of flue gas require large and therefore costly exhaust gas cleaning systems.

As a result of material inhomogeneity and different calorific values the waste and the difficulty of getting them fairly evenly in the grate oven To supply combustion air and bring it into contact, there are zones in the furnace imperfect combustion, in which, for example, burning temperatures of less than 800 ° C and there is a lack of oxygen. This condition is special critical during those periods when they are relatively humid and / or have a lower calorific value Waste is used. The areas that arise in this way are uncontrollably incomplete Combustion in the furnace occurs preferentially in the presence of chlorine and / or other aromatic base bodies (e.g. made of chlorine-containing plastics, Lignosulfonic acids, pentachlorophenol, polychlorinated biphenyls, etc.), which are im Waste is present, polychlorinated dibenzodioxins and / or dibenzofurans, in particular TCDD and TCDF. Dioxins in particular are still stable at temperatures of up to 1000 OC, so that they do not disintegrate in a grate incinerator and thus not thermally be rendered harmless. There were already dioxin levels in the fly ash and detected in the clean gas dust of various waste incineration plants (Die Zeit ", 02.03.1984, Dioxin, the avenger from the retort ").

The extreme toxicity of dioxins is known (ila der Wissenschaft ", November 1984, pp. 64 to 76).

Conventional waste incineration is therefore generally called into question (Chemical Engineering, June, 6, 1983, pp. 20 to 64).

Theoretically, dioxins that are produced during combustion could be Bring it back to disintegration by adding an afterburning stage to conventional waste incineration downstream with a furnace temperature of at least i200 ° C. This would however, require increased investment and the use of conventional fuels and would consequently have an economically unacceptable high cost tied together.

Another possibility, namely waste incineration through application carry out high-temperature combustion air at higher combustion temperatures, fails with a grate firing because the combustion air is 70 to 80% as Primary air is supplied under the grate and at the same time for cooling the grate plates serves, which is why this major part of the Combustion air are relatively narrow limits.

The heating of the secondary air would also only be relatively minor Bring temperature increase of the flue gases, especially since the combustion temperature is below the secondary air inlet is not increased as a result.

And finally there is a substantial increase in the combustion temperature Not possible in the grate furnace because it would melt the slag and thus the grate plates would clog.

As a result, conventional garbage incineration plants are more modern today Knowledge on the one hand uneconomical and on the other hand toxic as a result of emissions organic compounds are no longer operationally due to environmental pollution to answer for.

The invention is based on the problem of burning methods of waste of the types mentioned above in an economically justifiable manner so to improve that flue gas temperatures of at least 1200 ° C at the lowest possible Exhaust gas quantities reached and organic compounds, such as dioxins in particular, completely be dismantled.

In addition, economically more favorable conditions for the necessary exhaust gas cleaning can be created.

The problem is solved with a method for incineration of waste materials of the type mentioned, the firing in the waste incineration process according to the progressive burnout or burnout of the garbage in the course Graded amounts of combustion air are added to the combustion path through the combustion chamber, with the invention in that, instead of at least part of the combustion air, oxygen is blown into the combustion chamber.

It is advantageous by reducing the air supply at the same time targeted injection of oxygen into the combustion chamber locally a significant increase the combustion temperatures reached such a level that the formation of Dioxins are avoided, or a complete breakdown of existing ones Dioxins takes place.

By using oxygen instead of at least part of it the combustion air is reduced on the one hand according to the oxygen enrichment the amount of exhaust gas and, on the other hand, a significant increase in exhaust gas temperature achieved. In addition, the combustion air is enriched with oxygen or respectively their replacement by oxygen a qualitative improvement of the combustion reaction, whereby the firing is advantageous overall with a reduced excess of oxygen can be operated.

Because thus in the furnace exhaust gas in a reduced amount at increased Temperatures, on the one hand, is a more economical generation of useful energy from flue gas heat, and on the other hand, there are the costs for exhaust gas final cleaning in some cases considerably reduced.

The method has the further advantage that it is uncomplicated and in particular is easily adjustable.

As a result, the method can be flexibly adapted to different ones Calorific values of the waste materials as well as different water contents are possible without any problems.

Another advantage arises with the method according to the invention in that with this process existing uneconomical or environmentally hazardous Waste incineration plants improved, retrofitted and with regard to any dioxin emissions can be detoxified.

Due to lower exhaust gas quantities when using oxygen-enriched Combustion air in such existing systems is also the efficiency of dedusting and neutralization systems improved.

The use of oxygen in industrial furnaces is on the one hand known in principle (for example: "Technical reports on metalworking practice in metal processing", P. 890 Use of oxygen in industrial furnaces "by Ing. (Grad.) Helmut Peiler, Krefeld).

On the other hand, the technical report shows that the same procedural aspects Consequences of adding oxygen various thermal Processes can be very different. If, for example, in one of the furnace downstream convection zone, a material flow is thermally treated with exhaust gas heat Must be, the shift in heat distribution in the system of the plant, for example in the oven on the one hand to overburn the goods and / or to overuse the Lead refractory lining of the furnace, and on the other hand, too little heating of the goods carried in countercurrent to the exhaust gases have a disadvantageous consequence.

For example, U.S. Patent No. 3,074,707 describes the burning of cement clinker using oxygen-enriched combustion air in the rotary kiln, the teaching (column 3, Lines 58 to 67) that the addition of oxygen is limited because in the system of Cement burning plant with increasing oxygen content in the combustion air the temperature of the exhaust gas flow decreases so that the exhaust gas may even fall below the dew point will.

The improvement of the efficiency of a thermal process by adding oxygen to the combustion air or replacing it with oxygen therefore largely depends on the manner in which this addition is carried out will. The same applies at least to the economic viability of adding oxygen to a thermal or chemothermal process.

It is certainly no coincidence that from this point of view on the one hand For example, the use of oxygen when performing metallurgical processes The prior art is while on the addition of oxygen to a waste incineration process so far nothing has become known in the prior art.

Decisive for the expediency and economic efficiency of the exchange of oxygen against combustion air is the operating mode, i.e. with which operational Parameters, in particular the excess air with which a furnace is usually operated will. For example, one with 10% excess air and with high quality Fuel-powered industrial combustion system based on oxygen exchange The effect of reducing exhaust gas that can be achieved against combustion air is significantly less than o in a waste incineration plant operated with 80 to 120% excess air.

Thus, there is a difference in a waste incineration plant to an industrial combustion system surprising advantages as a result of a positive one Chain of effects: - a relatively much more extensive reduction in the nitrogen content in the exhaust gas, - a reduction in the required excess oxygen as a result significantly more extensive relative improvement in the quality of the combustion reaction, - as a result of greatly increased flame radiation, an earlier onset of uno overall more intensive gasification of the waste layer, as a result, improved and in particular intensified ignition and burnout readiness of the waste - a relatively essential intensified combustion process with higher flue gas temperatures, - a relatively substantial reduction in the amount of smoke gas.

The process produces these very positive individual results according to the invention in a waste incineration process by exchanging oxygen far more extensive advantages against combustion air than with industrial furnaces.

An expedient embodiment of the method provides that the exchange of oxygen for combustion air in the case of advanced burnout and preferably carried out in the area of the second half of the focal path and thereby Oxygen is added to the burning garbage, or that in one with Primary air and secondary air carried out waste incineration process instead of at least part of the secondary air oxygen is blown into the combustion chamber.

An embodiment further advantageously provides that the waste incineration process with one that is essentially stoichiometrically balanced in relation to the fuel Proportion of combustion air in the first part of the combustion section started and partially carried out and the resulting, still flammable intermediate products such as carbonization gas and / or Partly burned, through the use of oxygen in the remaining part of the burn line be brought to complete burnout by increasing the firing temperature.

While, for example, according to the aforementioned US Pat. No. 3,074,707 a increased addition of oxygen to the combustion air to a local temperature increase, in particular in the radiation zone of the flame and at the same time to one essential Reduction in the amount of flue gas leads, with the disposable contained in the flue gas Amount of heat for heat exchange in the preheating or calcination zone the cement burning plant is no longer available to a sufficient extent these negative effects do not exist in the waste incineration process.

On the contrary: The local achievement of high temperatures, preferably towards the end of the burning distance on the one hand, and the reaction of the amount of exhaust gas at a higher level Exhaust gas temperature on the other hand, have a positive effect on economy and Environmental friendliness of a waste incineration plant because it is the creation and / or Emission of dioxins prevents the production of useful energy from the exhaust gas as a result the higher temperature level enables more economical and ultimately also the Costs for the final cleaning of the exhaust gas reduced.

An embodiment advantageously provides that in the case of one in the grate furnace carried out waste incineration process oxygen above the grate and preferably is blown in near the combustion chamber outlet.

In such a grate furnace, instead of part of the Under the grate, oxygen is specifically used in the vicinity of the combustion chamber outlet will.

This advantageously results in the possibility, for example, of so-called old systems, which are equipped with grate furnaces, with relative to convert to a more economical and environmentally friendly operation at low cost.

An embodiment of the method advantageously further provides that in a waste incineration process in a rotary kiln the introduction is made of oxygen in the depth of the rotary kiln, preferably in the second half of the combustion path in a furnace zone, in which the waste incineration process reached the highest temperatures.

A major advantage of this process is, among other things, that the introduction of oxygen at a point in the furnace where the temperatures are already high and NO would form preferentially, which leads to the formation of nitric oxide leading reaction is partially throttled because of less excess air and partial replacement of the combustion air, a reduction in the nitrogen content in the flue gas he follows. As a result, less free nitrogen is available for the nitric oxide reaction.

For problem-free implementation of the method, an advantageous one provides The embodiment further provides that the addition of oxygen through targeted injection into a zone of the combustion chamber with the help of a high-energy accelerated gas jet is made.

The addition of oxygen by means of a gas jet can advantageously be used here be carried out in countercurrent to the flue gas, for example in a rotary kiln.

The setting of the intended temperature, respectively, is advantageous Composition of the flue gas achieved by the amount of exchanged Oxygen adjusted in accordance with the corresponding reference variables of these states will.

In particular, this can advantageously improve the quality of the combustion reaction significantly improved in the case of waste through the quantity-controlled addition of oxygen to the combustion air and as a result, the flue gas temperature at least towards the end of the combustion path can be increased to 1200 ° C or higher.

Another advantage arises with the method according to the invention also due to the fact that the ash melts in the incineration in the rotary kiln is carried out and introduced into a water bath.

This means that the slag falls as granules in a leach-resistant form that can also be used, for example, as a building material or as a cement clinker additive no longer excludes.

And finally, provides an advantageous embodiment of the method before that the heat content of the flue gas of the waste incineration in preferably two Stages for the generation of useful energy are used, whereDei in a first stage, at a relatively high temperature level, for example steam or mechanical or electrical Energy gained, and in a second stage, at a relatively lower temperature level, Useful heat to a heat transfer medium, for example to the combustion air of the waste incineration furnace is delivered.

In this way, among other things, in the method according to the invention improves the profitability of the generation of useful energy from waste heat, because due to the higher temperature level of the flue gas in the first stage, a higher one Efficiency is achievable.

In addition, the reduction in the amount of combustion air is a consequence of the oxygen enrichment the further advantage that a correspondingly smaller amount of cold air at combustion air temperature must be heated. This reduction in the amount of combustion air results on the one hand from the lower excess air ratio when starting and igniting the waste incineration zuminuest in the first Half of the burning distance and the other from the at least partial replacement of combustion air, in particular secondary air, in the burnout zone of the furnace.

A plant for the incineration of waste, in particular for implementation the method according to the invention with a grate furnace is characterized in that this has means for blowing oxygen into the furnace. An embodiment provides that above the grate in the area of the furnace outlet at least an oxygen lance is arranged, the axis of which is approximately parallel at a distance from the grate runs with its slope.

Furthermore, it can be provided in the system that above the grate an oxygen lance is arranged in the area of the combustion chamber outlet, the axis of which runs obliquely downwards from above, essentially perpendicular to the inclination of the grate.

In another embodiment of a waste incineration plant with grate firing can be one from bottom to top underneath the grate in the area of its outlet Oxygen lance directed towards the grate and towards the area of the combustion chamber outlet be arranged, the axis of which with the grate an angle between 30 and 900, preferably between 45 and 600, includes.

A waste incineration plant for carrying out the invention Process with a rotary kiln is designed so that on the discharge side of the Rotary kiln a direction opposite to the flue gas flow, into the interior of the rotary kiln protruding oxygen lance is arranged.

The oxygen lance can be up to about a third of the length of the rotary kiln protrude into this.

Furthermore, an embodiment of the waste incineration plant provides both one device for grate firing as well as rotary kiln firing to regulate the amount of oxygen introduced in exchange for combustion air Provision of a reference variable such as the temperature and / or composition of exhaust gas before. This includes a measuring probe for the reference variable and an adjusting element for the oxygen, as well as one that controls the setting element in accordance with the reference variable Control unit. A logic unit compares a temperature setpoint with the measured one Actual temperature value and calculated from a deviation in the values in a downstream Controller or computer unit sends an actuating pulse that controls the oxygen setting element corrected according to the deviation.

The invention is shown in schematic implementation drawings in a Preferred embodiment shown, with further advantageous from the drawings Details of the invention can be found.

They show: FIG. 1 a waste incineration plant with a grate furnace Section, Fig. 2 a waste incineration plant with a rotary kiln in a purely schematic Representation as a flow diagram.

The waste incineration plant according to FIG. 1 has a feed bunker 1 for raw waste with a purely schematically indicated discharge device 2 in the form for example a plunger. The amount discharged by this in a timed amount Waste materials 3 reach the grate 5 via a chute 4. To maintain the combustion becomes adjustable through the primary air shaft 7 Amount of air under the grate as primary air 9 in the space 10 below the grate 5. Secondary air is above the grate 5 through openings 11 and 12 in the furnace 13 initiated.

In order to start the combustion more strongly, according to the invention with one of the oxygen lances 14, 15 or 16 with gradual throttling preferably the secondary air is blown into the furnace 13 from the openings 11 or 12. The procedure here is that the main amount of oxygen with the to Step grate 5 is entered almost parallel arranged oxygen lance 15, while a small amount of oxygen is used for the afterburning of partially burned material is blown approximately vertically against the grate 5 with the lance 14. Can continue to support a complete burnout in the last area 17 of the grate 5 a possibly relatively small amount of oxygen from below through the grate plates be blown through.

The system according to FIG. 2 with a rotary kiln 18 also has a feed hopper 1 with a discharge device 2. The ones carried out with it Waste materials 3 pass through the feed hood 19 into the rotary kiln 18 and are aflame in it. Combustion air is entered via line 20. Using the The temperature equilibrium prevailing in the system can advantageously use cold intake air 21 heated in the recuperator 22 by residual heat from the flue gas and used as warm combustion air be entered into the rotary kiln 18. This results in an intensification the development of the flame as the temperature rises. To add oxygen is For example, one in the discharge housing on the discharge side 23 of the rotary kiln 18 24 permanently mounted oxygen lance 25 is provided. The oxygen supply 26 has a Adjusting member 27, which is controlled by a controller unit 28 with the help of Control line 35 adjustable volume is regulated. This includes the entire existing control device 29 a transmitter 30 for a command value of the flue gas, for example in the Flue gas line 31 is arranged and a corresponding value of a reference variable of the flue gas detected. A signal formed from this is transmitted to the signal line 32 connected to the logic unit 33 and therein with an adjustable actual value 34 compared. In the event of a discrepancy, a differential pulse is sent to the controller and Computing unit 28 forwarded, calculated therein a correction pulse and this with the control line 35 for setting the setting element 27 connected to this. In this way, for example, by increasing or decreasing the addition of Oxygen kept the temperature in the waste gas from the waste incineration plant constant will.

The control device 29 shown should only be understood as an example can of course also be used in the system according to FIG. 1, but this is not shown in it to avoid repetition.

In addition, each of the systems can, for example, be a two-stage device have to obtain useful energy from excess heat of the flue gas, wherein a hot gas turbine 37 is shown in a first stage 36 purely by way of example, which generates electricity with a generator 38 and supplies it to the grid, while in a second stage 39 exhaust gas heat, now at a lower temperature level, is used in the recuperator 22 to generate warm combustion air 20. Then is the exhaust gas after withdrawal of its usable heat with the exhaust pipe 40 in the Exhaust gas cleaning 41 initiated and from there according to arrow 42 via a (not shown) Exhaust gas chimney discharged into the open. Combustion residues be with the rotary kiln 18 from the discharge housing 24 in the form of molten slag 43 passed into a water bath 44 and discharged therefrom as granules 45. Further Combustion residues are separated from the flue gas with the exhaust gas cleaning system 41 and conveyed to the landfill 46, for example, with a transport device 47.

Claims (22)

Method for incinerating waste materials, in particular of relatively moist and / or low-calorific waste materials from households, communities and economy, referred to as garbage for short, whereby the firing in the garbage disposal process according to the progressive burnout or burnout of the garbage in the course Graded amounts of combustion air are added to the raceway through the combustion chamber, characterized in that, instead of at least a portion of the combustion air, oxygen is blown into the furnace. 2. The method according to claim 1, characterized in that the oxygen aem burning garbage with advanced burnout, preferably in the area of the second half of the burning path, is added. 3. The method according to claim 1 and 2, characterized in that aass instead of a waste incineration process carried out with primary air and secondary air at least part of the secondary air is blown oxygen into the furnace. 4. The method according to any one of claims 1 to 3, characterized in that oass the waste incineration process with essentially one in relation to the fuel stoichiometrically balanced proportion of combustion air in the first part of the combustion section set in motion and partially carried out una resulting Intermediate products that are still flammable, such as low-temperature gas and / or partially burned material through use of oxygen gas in the remaining part of the aerating section with an increase in the firing temperature be brought to complete burnout. 5. The method according to claim 1 to 4, characterized in that at a waste incineration process carried out in a grate furnace oxygen above the grate is blown in. 6. The method according to claim 1 to 4, characterized in that at a waste incineration process carried out in a grate furnace instead of oxygen Part of the air under the grate is specifically used in the vicinity of a combustion chamber outlet will. 7. The method according to claim 1 to 4, characterized in that at a waste incineration process in the rotary kiln the ~ introduction of oxygen in zer Depth of the rotary kiln made w1ru. 8. The method according to any one of claims 1 ois 7, characterized in that that in the Müliver separation process in the rotary kiln the introduction of oxygen is preferred is carried out in the second half of the drennweg in a combustion chamber zone, in which the waste incineration process reaches the highest temperatures. 9. The method according to any one of claims 1 to 8, characterized in that that the addition of oxygen by targeted spraying in a zone of the furnace is carried out with the help of a high-energy accelerated gas jet. 10. The method according to one or more of claims 1 Dis 9, characterized characterized in that the addition of oxygen by a gas jet in countercurrent to the flue gas is made. 11. The method according to one or more of claims 1 to 10, characterized characterized in that the amount of introduced into the furnace in exchange for combustion air Oxygen is adjusted in accordance with the combustion temperature. 12. The method according to any one of claims 1 to 10, characterized in that that the amount of oxygen introduced into the furnace in exchange for combustion air is adjusted in accordance with the exhaust gas composition. 13. The method according to one or more of claims 1 to 12, characterized marked, oass aie discharge temperature of the garbage by quantity-controlled addition from oxygen to the combustion air, at least towards the end of the combustion path from the garbage in the combustion chamber, is increased to 1200 OC or higher. 14. The method according to one or more of claims 1 ois 13, characterized characterized in that the ash is molten during waste incineration in the rotary kiln discharged and introduced into a water bath. 15. The method according to one or more of claims 1 to 14, characterized characterized in that the heat content of the flue gas of the waste incineration in preferably two stages are used to generate useful energy, with a first Stage at a relatively high temperature level, for example steam or mechanical or electrical energy obtained and in a second stage at a relatively low level Temperature level of useful heat to a heat transfer medium, for example to the indoor air to waste incineration. 16. Plant for incineration of waste, in particular for implementation the method according to one or more of claims 1 to 15, with a grate furnace, characterized in that these means (14, 15, 16) for blowing in oxygen has in the furnace. 17. Plant according to claim 16, characterized in that above of the grate (5), in the area of the furnace outlet (30) at least one oxygen lance (15) is arranged, the axis of which in the Abstana from the grate (5) is approximately parallel with whose slope is. 18. Plant according to claim 16, characterized in that above of the grate (S) in the area of the combustion chamber outlet (50) an oxygen lance (14) is arranged, the axis of which is essentially perpendicular to the inclination of the grate (5) is directed obliquely downward from above. 19. Plant according to claim 16, characterized in that below of the grate (5) in the area of its outlet (10) one from bottom to top against the outlet area of the furnace (50) directed oxygen lance (16) arranged is whose axis with the grate (5) an angle between 30 and 900, preferably between 45 and 600, includes. 20. Plant for incineration of waste, in particular for implementation the method according to one or more of claims 1 to 15 with a rotary kiln furnace, characterized in that on the discharge side (23) of the rotary kiln (18) a opposing the flue gas flow, protruding into the interior of the rotary kiln (18) Oxygen lance (25) is arranged. 21. Plant according to claim 20, characterized in that the oxygen lance (25) protrudes into the rotary kiln (18) up to about a third of the length thereof. 22. Plant according to one of claims 16 to 21, characterized in that that this is a device for adjusting the molten in the furnace, against The amount of oxygen exchanged in the combustion air is based on a reference variable such as temperature or the composition of the flue gas, which has a transmitter (30) for the reference variable, an adjusting element (27) for the amount of oxygen and a regulator unit (29) with setpoint input (34) and a logic unit (33) for comparing the setpoint and actual value, as well as with a computer and control unit (28) with an integrated control pulse generator includes.