DE19606640A1 - Burning sewage sludge as fuel in a fluidised slag tap furnace - Google Patents

Abstract

Sewage sludge after treatment in a fuel processor is burnt as fuel in a fluidised slag tap furnace. The device used includes a flue gas cleaning apparatus. Also claimed is a process for disposing of sewage sludge by simultaneous drying and comminution to a desired grading, separation of solid and gas phases in a cyclone collector and introduction of the milled and dried sludge into a fluidised slag tap furnace. Flue gases are led off at a temp. suitable for the reduction of NOx and SOx and any slag produced is carried off.

Description

The invention relates to a device for sewage sludge combustion tion with the features of the preamble of claim 1 and a method with the features of claim 13.

In the municipal and industrial wastewater sector fall into the Sewage treatment plants in the treatment of domestic and commercial waste water thin liquid sewage sludge, their recycling and ent supply especially with regard to the expected strong growth sludge generation in the coming years must be secured in time.

The scope for disposal is on the one hand by the Be limitation of the landfill capacity and on the other hand by the of Legislators additionally tightened tightening requirements. As As a result, agricultural use is also reduced least slowed down, so that the sewage sludge incineration as disposal possibility is becoming increasingly important.

Sewage sludge incineration has so far been an admixture of sewage sludge to other fuels, e.g. B. in waste incineration he follows.

It is therefore an object of the present invention to provide a front direction and to create a process with which more typical sewage sludge with water contents between about 70%  and disposed of about 30% easily and environmentally friendly thermally can be.

This task is performed by a device with the features of Claim 1 and a method with the features of the An Proof 13 solved.

Because the device for burning sewage sludge as a fire sewage sludge firing, sewage sludge Roughly ground with a suitable residual water content be, which on the one hand the necessary for grinding Energy consumption is relatively low and on the other hand the burning a good primary incorporation in the vortex melting furnace degree of expansion. The vortex melt firing enables at a good level of primary integration is also a relative low-dust flue gas' which has been used in sewage sludge incineration so far was not available. Eventually, the combustion back drop would be from the vortex melt firing as slag, the lukewarm is genresistant and can therefore be used as a building material can or can be deposited uncritically.

It is advantageous if the fuel processing device has a fan beater mill, because in this mill the Drying and grinding the fuel simultaneously and with high efficiency until the required parameters are reached can be done. Equivalent mills with assigned Drying is advantageous. The fuel processing processing device advantageously comprises a separating cyclone, in which the ground sewage sludge as a solid phase of the Drying air and the water generated by the drying steam and gaseous residual components are separated.

The flue gas cleaning device has on the flue gas side advantageous means for injecting NH₃ or urea, the in a reaction path set up for this purpose with the in the nitrogen oxides produced by the vortex melting firing react and can reduce it there. The reaction path should be there  at the tempera required for the desired reaction doors and dwell times must be adapted. A particularly good fil The flue gas is used to remove pollutants is sufficient if the flue gas cleaning device is an active sensor bensfilter includes. This filter can be used, for example, with Her oven coke, lignite activated coke, dried sewage sludge in In the form of granules or pellets or the like the. The flue gas passing through the filter is in this Filter with suitable dwell times of remaining sweat feloxides, hydrocarbons, dusts, dioxins, furans, Heavy metals and similar pollutants and in part from Free nitrogen oxides. A particularly good implementation of Nitrogen oxides to nitrogen and water can be obtained if the Flue gas cleaning device catalysts are assigned which is the conversion of nitrogen oxides with ammonia or urea promote.

Sulfur oxides can be converted into harmless substances in the flue gas be set when the flue gas cleaning device Assigned feed of calcium hydroxide or calcium carbonate are. The fuel processing device can also have means added to feed calcium hydroxide or calcium carbonate be classified as additives in the vortex melting furnace the flowability of the resulting combustion residues, al so the slag can positively influence.

For the disposal of the flue gas cleaning pollutant-laden adsorbents, it is advantageous if the Fuel processing device also means for supply tion of pollutant-laden adsorbents. Especially the dust filtered out of the flue gas can be in this way se into the slag produced in the vortex melting furnace be bound and thus returned to the solid phase will.

The thermal generated when sewage sludge is burned Energy is advantageously used in that at least one  Partial flow of the warm flue gas for drying the fuel is being used. The energy available in the essentially in the evaporation of the sewage sludge Water content. It is also energetically favorable, the distillate stock preparation device an air preheater for the led to assign fresh air as combustion air, in the just if thermal energy of the flue gas directly or indirectly the combustion air and thus the combustion process again is fed.

In sewage treatment plants, in addition to sewage sludge, waste oil also falls and oil-contaminated soils, especially oil-contaminated sands. It is therefore advantageous if the fuel preparation direction by feeding in waste oil or oil-laden substances are classified, because on the one hand in the sewage sludge incinerator can be burned and the other de Ren combustion energy benefits the combustion process. There it is particularly advantageous when the means for on Feeding waste oil or oil-laden floors into a start-up or Include support burners for the vortex melting furnace.

Because in the method according to the invention, first the grinding of the sewage sludge until it reaches a predetermined grind of moisture while drying to a predetermined residue, then the separation of solid and gas phase in a separating cyclone, then the introduction of the ground and dried sewage sludge as fuel in a vortex melt, the removal and cooling of the resulting flue gas to a temperature suitable for NO _x and SO _x reduction and finally the removal of the slag resulting from the incineration, the sewage sludge incineration can be carried out in an energetically favorable manner, with the resulting pollutants be largely retained or eliminated. A residual moisture content of less than 15%, preferably about 5%, is to be aimed for as advantageous.

The thermal efficiency of the method according to the invention is positively influenced when the resulting process heat increases at least partially used to preheat the combustion air becomes. In addition, the resulting process heat can at least partly for thermal pretreatment of sewage sludge or to promote the biological treatment of waste water in one Sewage treatment plant (acceleration of digestion) can be used. The procedure Ren is particularly effective when grinding and drying the sewage sludge to be burned in a blower seschlägermühle takes place.

The procedure is simple to perform when Addi the fuel tive be added to the consistency of the combustion back affect stands. The pollutant emissions of the invention The process is particularly low if the flue gas contains substances be added to neutralize pollutants. About that In addition, the flue gas can be filled with an adsorbent Active sorbent filters are cleaned, giving him dust, coal Hydrogen, sulfur oxides, dioxins, furans, heavy metals and nitrogen oxides can be partially removed. The ge Entire pollutant balance and the energy balance of the invention according to the method improved in that the adsorbent after Use together with the fuel fed to the combustion becomes. Alternatively, the adsorbent can be used after use Process heat is cleaned by desorption and thus how be made usable.

The waste heat generated during the process can be used by those contained in the resulting superheated steam or in the flue gases thermal energy is coupled out. That way, at for example, electrical power can be obtained. The waste heat can also be used for heating buildings or for similar purposes will.

In the following an embodiment of the present Er Finding described with reference to the drawings.  

Show it:

Fig. 1 An inventive plant for sewage sludge combustion in a block diagram; such as

Fig. 2 is a flowchart of an embodiment of the inventive method.

In Fig. 1 an inventive device for sewage sludge combustion is illustrated in the form of a block diagram. Fig. 2 shows the corresponding flow chart.

The device comprises a fan beater mill 1 for drying and grinding the sewage sludge to be incinerated. The fan beater mill 1 is part of the fuel processing system, which also includes a separating cyclone 2 and an injector 3 . The actual firing comprises a vortex melt firing 4 , which is associated with a start-up and auxiliary burner 5 operated with gas or oil. On the output side of the vortex melting furnace, a wet deslagger 6 is provided, which absorbs the combustion residues in liquid or solid form. In addition, the vortex melting furnace 4 is followed by a second flue gas duct 7 . The flue gas system comprises, in addition to the second flue gas flue 7 , a mixer 8 , a device for lime injection 9 and a device for urea and NH 3 injection 10 . Furthermore, an air preheater 11 and a desorber 12 are assigned to the flue gas system before entering the blower beater mill 1 . The blower mill 1 is in turn penetrated by the flue gas, the clone Abscheidezy 2 and subsequently passes through a dust filter 15 . After the dust filter there is a blower 16 in the flue gas system, which is followed by an active sorbent filter 17 and a catalytic converter 18. Finally, a condenser 19 for process water and heat recovery is integrated into the flue gas system before the flue gas, which has been largely freed of pollutants and cooled, through a chimney 20 is released into the atmosphere. The fresh air or combustion air to be supplied to the combustion process is introduced into the device via a blower 30 . The combustion air is blown into the swirl melt furnace at 31 ; if necessary, preheated fresh air is also supplied to the start-up and auxiliary burner 5 at 32 .

Between the condenser 19 and the chimney 20 , cold gas cooled down can be removed from the flue gas, which is fed via a blower 33 into the mixer 8 of the second flue gas train and is used there for tempering the flue gas. On the other hand, the cooled flue gas is fed to the cold feed via a blower 34 and directly to the blower mill 1 . A storage template 35 is assigned to the separating cyclone for the solid phase, ie for the sewage sludge, and a storage template 36 is assigned to the dust filter 15 for the solid phase occurring there. A memory 37 for fresh active sorbent and a memory 38 for used sorbent are assigned to the active sorbent filter 17 . From the storage templates 35 , 36 and 38 , the solids held there can be feasible via suitable injectors of the vortex melting furnace.

A cooling water circuit is fed with cold water, for example from a sewage treatment plant 40 assigned to the sewage sludge incineration device. The cooling water is connected to the condenser 19 , a condensate storage 41 , a pump 42 and a cooling water storage 43 , from where it is fed to the wet slag remover 6 . A second pump 44 and a pump 45 coupled to a filter are in turn connected to the sewage treatment plant 40 .

Finally, the sewage treatment plant 40 is assigned a pump station 50 for sewage sludge and a collection station 51 for waste oils. Additives such as NH₃, urea, calcium hydroxide and calcium carbonate are respectively stored in stores 52 , 53 and 54 , in which they can be fed into the flue gas duct via the mixers 9 and 10 or 55 .

The process for the thermal disposal of sewage sludge proceeds in the present exemplary embodiment as follows: The sewage sludge to be disposed of is supplied from the sewage treatment plant 40 to the sewage sludge incineration plant via the pump station 50 , the sewage sludge water content being aimed at from about 30% to 70%. The sewage sludge is placed in the Gebläseschlägermüh le 1 , where it works together with the hot flue gas stream and is brought to the desired degree of grinding. The drying process, which is promoted by the temperature of the flue gas stream, allows the degree of drying to be set to less than 15% residual moisture. The target should be around 5%.

From the fan beater mill 1 , the stream of ground sewage sludge and gas phase enters the separating cyclone 2 , where it is separated into the solid phase and the gas phase. The solid phase enters the storage reservoir 35 , from where it is continuously introduced into the vortex melting furnace 4 in a suitable dosage by the injector 3 . The dried and ground sewage sludge is introduced into the furnace there, for example by means of a so-called secant injection, and burns there, with the remaining solids (ash) being deposited on the wall due to the rotation in the furnace and being melted there. The resulting liquid slag then flows into the wet slag 6 , from where it can be reused or disposed of after cooling. The resulting slag is alkali-resistant and can therefore be used in the building materials industry, in road construction or similar areas. In addition, due to the alkali resistance, the resulting slag can be easily disposed of. It is therefore an economic asset that cannot be eluted.

The resulting flue gas during combustion occurs in the so-called second train of the furnace and is there in the mixer 8 initially tempered with cold gas so that the subsequently injected additives, namely the calcium hydroxide or calcium supplied from the storage reservoir 53 through the mixer 9 carbonate and the injected from the supply 52 NH₃ or the urea, which is fed via the mixer 10 , find suitable reaction conditions. The temperature is set to parameters known per se from the flue gas treatment, which enables a NO _x reduction by reaction with NH₃ or urea and a SO _x reduction by reaction with calcium hydroxide and calcium carbonate. After the second train 7 , the still very hot flue gas first enters the air preheater 11 . There, part of the thermal energy contained in the flue gas is released to the fresh air conveyed by the blower 30 to the furnace 4 . This thermal energy is therefore immediately available to the furnace. Furthermore, the flue gas passes through a desorber 12 , in which the desorption of pollutants from flue gas filters can take place. The further path of the flue gas leads to the fan beater mill 1 , in which the thermal energy that continues to be used is used to reduce the water content of the sewage sludge, which is too high for combustion. Since a considerable part of the energy goes into the evaporation of the water portion. Together with the steam arising from the drying and the ground fuel, the flue gas then enters the separating cyclone 2 , where the gas phase, as already mentioned, is separated from the solid phase. The gas phase, that is to say steam and flue gas, then passes through the dust filter 15 , the solids discharge of which takes place in the storage reservoir 36 , while the gas phase largely freed from dust is conveyed on by the blower 16 to the active sorbent filter 17 . In the active sorbent filter 17 still existing pollutants such as SO _x , heavy metals, dusts, hydrocarbons as well as halogenated hydrocarbons and partly NO _{x are} adsorbed on a suitable active sorbent 37 . Suitable adsorbents here are, for example, hearth furnace coke, lignite coke or, with suitable preparation, sewage sludge granulate or sewage sludge pellets themselves. The pollutant-laden sorbent, also called Altsor bens, is either desorbed and reused or fed directly to the vortex melting furnace 4 as fuel or mill drying 1 as part of the fuel processing and burned there.

The filtered and cleaned flue gas then enters the Kata lyst 18 a, in which an amount of NH₃ is added by NH₃-spraying from the reservoir 54 via the mixer 55, the tralization to Neu of the remaining NO _x content is required. The catalyst 18 then causes in a known manner the reaction of NH₃ and NO _x to N₂ and water, which would not take place by itself without catalyst action at the temperatures prevailing in this part of the flue gas system. The condenser 19 , through which cooling water flows, extracts further thermal energy from the flue gas and condenses the vapor phase contained in the flue gas. The heat thus obtained and extracted from the flue gas can therefore be used further. From the condenser 19 , the cleaned and cooled flue gas is largely released into the atmosphere through the chimney 20 . A part of the flue gas, which still contains heat, is returned to the process by the blower 33 and used in the mixer 8 for tempering the flue gas. In addition, the tempera ture in the mill drying 1 and the separating cyclone 2 is set with mixed flue gas from the fan 33 .

Compared to conventional fuels such as B. Lignite contains sewage sludge relatively high ash content, which in addition to the water content lead to the fact that the combustion of sewage sludge does not work easily as a self-sustaining furnace without admixture of other fuels. In the present vorlie embodiment of a sewage sludge incineration device and a method for sewage sludge incineration is provided in numerous process steps that the resulting heat is returned to the process and the heat balance and thus the economy of the combustion process is particularly good. The cold combustion air entering the process is promoted by the fan 30 into the air preheater 11 ge, in which it is heated by the flue gas. The heated fresh air is then fed to the lines 31 and 32 of the vortex melting furnace 4 and the start-up and auxiliary burner 5 , so that there is already heated fresh air available for combustion. In addition, the injectors 3 are operated with heated fresh air, so that a high temperature level is already available at the inlet side of the furnace. The fuel coming from the storage reservoir 35 also already has an increased heat content which comes from the mill drying. Further process heat is generated in the condenser 19 when the steam content contained in the flue gas is condensed out and in the wet slag remover 6 , in which the liquid slag emerging from the vortex melting furnace 4 is cooled. The cooling water heated by the slag can, for example, be supplied to the sewage treatment plant to which the sewage sludge incineration device according to the invention is assigned and used there for the thermal pretreatment of the sewage sludge or for conditioning the biological clarification processes. For example, heat can be added to a digester to accelerate digestion. The process heat can also be used to generate electricity or to heat buildings.

In addition to sewage sludge, waste oils 51 in the form of waste oil or oil-contaminated sands or floors are produced in the sewage treatment plant 40 . These products of the sewage treatment plant can be easily burned in the sewage sludge combustion device, which may even be desirable if the furnace needs to be ignited or maintained using the start-up or auxiliary burner.

An important aspect in the design of the sewage sludge incineration plant according to the present exemplary embodiment is the treatment of the solids formed during the sewage sludge incineration. Already the combustion of the sewage sludge in the vortex melting furnace 4 leads to the fact that, due to the high degree of primary integration of a vortex melting furnace, essential parts are not obtained as ash in the gas phase, but as slag in the liquid phase of the furnace, which are then disposed of without problems via the wet slag remover 6 . But also the further flue gas treatment via dust filter and Aktivsor bensfilter leads to the fact that the dust still contained in the flue gas is filtered out and fed back to the combustion. This dust is then also integrated with high efficiency in the melt of the vortex melting furnace. In the exemplary embodiment described here, it is realistic to achieve a dust content in the flue gas that emerges through the chimney of around 10 mg / m³ or less. These dust contents are in the range of what can be expected as fine dust discharge from an active sorbent filter anyway and therefore represent the lower limit.

In the schematically shown in Figs. 1 and 2 Before direction for sewage sludge combustion approximately the following process parameters are set:

A thermal output of about 1 to 6 MW is aimed for in the vortex melting furnace. Such services can be handled with a relatively low expenditure on equipment. The resulting flue gas is set in the so-called second flue gas train 7 by the mixer 8 to a temperature of approximately 950 ° C to 1000 ° C. The preferred reaction temperature of denitrification and desulfurization devices lies in this temperature window.

There is a flue gas temperature in the mill dryer, which depends on the water content, more precisely on the degree of drying to be achieved. In the currently preferred embodiment of the process, the sewage sludge granulate will be dried to less than about 15% residual moisture. A residual moisture of 5% currently appears to be suitable for self-sustaining combustion with good efficiency. For this purpose, depending on the water content of the sewage sludge, an inlet temperature for grinding drying of about 700 ° C to 800 ° C (with a water content of 30% to 70%) should be aimed for. In the further course of the flue gas system, the flue gas cools down further and reaches the temperature of about 150 ° C. which is suitable for the catalytic reaction in the catalyst 18 . Further heat is removed in the area of the condenser, in which the vapor phase discharged from the sewage sludge is condensed. Here the flue gas temperature drops to around 110 ° C. With the described embodiment of a device according to the invention and a method according to the invention, it is thus possible for the first time to carry out thermal disposal of sewage sludge by sewage sludge combustion, in which, depending on the quality of the sewage sludge, no additional fuel supply is self-sustaining or energy can even be obtained. In addition, the measures described for flue gas cleaning are suitable to ensure extremely low emissions.

The described device and the described method but are expressly intended only from the embodiment of the lying invention can be understood. Depending on the integration of the Sewage sludge incineration plant in a waste disposal concept can other components for fuel processing or Flue gas cleaning and energy recovery should be provided. It can, for example, with low pollutant content or high Calorific value of the fuel also on one or the other Component can be dispensed with.

Claims (23)

1. Device for the combustion of sewage sludge as fuel, with a fuel processing device, a furnace, and with a flue gas cleaning device, characterized in that the furnace is a vortex melting furnace ( 4 ). 2. Device according to claim 1, characterized in that the fuel processing device has a fan beater mill ( 1 ). 3. Apparatus according to claim 1 or 2, characterized in that the fuel processing device comprises a separating cyclone ( 2 ). 4. Device according to one of the preceding claims, characterized in that the flue gas cleaning device comprises means ( 10 , 52 ) for injecting NH₃ and / or urea. 5. Device according to one of the preceding claims, characterized in that the flue gas cleaning device comprises an active sorbent filter ( 17 ) which, for example, with hearth coke, lignite activated coke, ge dried sewage sludge in the form of granules or pellets. 6. Device according to one of the preceding claims, characterized in that the flue gas cleaning device comprises catalysts ( 18 ). 7. Device according to one of the preceding claims, characterized in that the fuel processing device and / or the Rauchgasreini supply device comprise means ( 9 ) for feeding Ca (OH) ₂ and / or CaCO₃. 8. Device according to one of the preceding claims, characterized in that the fuel preparation device comprises means ( 38 ) for supplying pollutant-laden adsorbents. 9. Device according to one of the preceding claims, there characterized in that the focal stock preparation device at least a partial flow of uses warm flue gas to dry the fuel. 10. Device according to one of the preceding claims, characterized in that the fuel preparation device is associated with air preheating ( 11 ) for the fresh air supplied as combustion air. 11. Device according to one of the preceding claims, there characterized in that the focal stock preparation device Means for feeding Al includes oil and / or oil-laden soils. 12. The apparatus according to claim 11, characterized in that the means for feeding waste oil and / or oil-laden floors comprise a start-up and support burner ( 15 ). 13. Process for the disposal of sewage sludge, with the following process steps:

• - Grinding the sewage sludge until reaching a predetermined degree of grinding while drying to a predetermined residual moisture;
• - Separation of solid and gas phase in a separating cyclone ( 2 );
• - Introducing the ground and dried sewage sludge as fuel into a vortex melting furnace ( 4 );
• - Removal and cooling of the resulting flue gas to a temperature suitable for NOX and SOX reduction; and
• - Removal of the slag produced.

14. The method according to claim 13, characterized records that the sewage sludge to a residual moisture less than 15%, preferably about 5%; is dried. 15. The method according to any one of the preceding claims 13 or 14, characterized in that the Process heat generated at least partially for preheating the combustion air is used. 16. The method according to any one of the preceding claims 13 to 15, characterized in that the ent standing process heat at least partially to the thermal front treatment of sewage sludge and / or to promote biolo wastewater treatment (acceleration of digestion) becomes. 17. The method according to any one of the preceding claims 13 to 16, characterized in that the pre-drying and grinding in a fan beater mill ( 1 ) it follows. 18. The method according to any one of the preceding claims 13 to 17, characterized in that the Fuel additives are added that increase the consistency of the Affect combustion residues. 19. The method according to any one of the preceding claims 13 to 18, characterized in that the  Flue gas substances to neutralize pollutants be. 20. The method according to any one of the preceding claims 13 to 19, characterized in that the flue gas is cleaned in an active sorbent filter filled with an adsorbent ( 17 ). 21. The method according to claim 20, characterized records that the adsorbent together after use with the fuel is supplied to the combustion. 22. The method according to claim 21, characterized records that the adsorbent after use under Ver process heat is cleaned by desorption. 23. The method according to any one of the preceding claims 13 to 22, characterized in that the in Superheated steam and / or flue gas contained thermal energy as Heating energy or to generate electricity.