System and method for coordinated disposal of sludge and hazardous waste

Abstract

The invention discloses a system and method for the coordinated disposal of sludge and hazardous wastes. The system comprises: a sludge drying device, a rotary kiln incinerator, a secondary combustion chamber and a waste heat recovery device. The sludge drying device has a wet sludge inlet and a dry sludge outlet. The rotary kiln incinerator has a dry sludge inlet, a hazardous waste inlet, a primary air inlet, an incineration slag outlet and an incineration flue gas outlet. The secondary combustion chamber has an incineration flue gas inlet, a secondary air inlet and a combustion flue gas outlet. The incineration flue gas inlet of the secondary combustion chamber is connected to the incineration flue gas outlet of the rotary kiln. The waste heat recovery device has a boiler feed water inlet, a combustion flue gas inlet, a low-pressure steam outlet and a heat exchange flue gas outlet. The boiler combustion flue gas inlet is connected to the combustion flue gas outlet of the secondary combustion chamber, and the low-pressure steam outlet is connected to the drying device. The system can be used to simultaneously treat sludge and hazardous wastes, and the calorific value of the rotary kiln incinerator is reduced, overheating in the furnace is avoided, and the purpose of treating waste with waste is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid waste resource utilization, and specifically relates to a system and method for the coordinated disposal of sludge and hazardous waste. Background Art

[0002] With the rapid development of social economy and urbanization, the discharge and treatment volume of municipal sewage in cities are constantly increasing. The large amount of sludge generated by municipal sewage treatment has brought new challenges to the city's environmental management. Municipal sludge contains a large number of impurities such as bacteria, viruses, insect eggs, heavy metals, etc., which need to be treated to meet the standards before they can be discharged. The commonly used harmless treatment technologies in the prior art include thermal hydrolysis-anaerobic digestion treatment technology, drying-direct incineration technology, drying-garbage incinerator blending technology, etc. Among them, thermal hydrolysis-anaerobic digestion treatment technology has extremely high energy consumption, large investment, and requires additional fuel. The disposal cost is high, and the product destination is also a problem; drying-direct incineration technology has high energy consumption and high disposal cost; although the drying-garbage incinerator blending technology can utilize the excess heat energy of the garbage power plant, the blending of sludge brings many unfavorable factors to the incineration system, such as increased fly ash volume, boiler superheater blockage and other problems, which reduces the domestic garbage treatment capacity of the incineration system.

[0003] Hazardous waste refers to waste that is toxic, flammable, explosive, corrosive, chemically reactive and / or infectious, and poses a serious threat to the ecological environment and human health. It is currently mainly disposed of through landfill or incineration. With the development of domestic technology and economy, the calorific value of incineration raw materials is currently on the rise, with the average calorific value rising from 3000kcal / kg to 4000-4500kcal / kg, and even the calorific value of some raw materials exceeds 5000kcal / kg. Most of the domestic hazardous waste incineration adopts rotary kiln downstream technology, and the calorific value range that this technology can adapt to is about 3500kcal / kg. If it exceeds this range, it will cause the incineration system to overheat severely, and the incineration slag will melt and stick together, affecting normal production. The newly designed incineration system prevents the system from overheating by blowing in excess air. On the one hand, this will lead to an increase in the overall flue gas volume, investment and treatment costs, and on the other hand, due to the high oxygen content in the flue gas, the dioxins and nitrogen oxides in the flue gas will also increase accordingly, increasing the difficulty of disposal.

[0004] Therefore, how to effectively treat sludge and hazardous waste needs to be solved urgently. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. To this end, one purpose of the present invention is to propose a system and method for the coordinated disposal of sludge and hazardous waste, which can simultaneously treat sludge and hazardous waste, and reduce the calorific value of the rotary kiln incinerator, avoid overheating in the furnace, achieve the purpose of treating waste with waste, conform to the national environmental protection technology research and development direction, and have good market application prospects.

[0006] In one aspect of the present invention, the present invention provides a system for the coordinated disposal of sludge and hazardous waste. According to an embodiment of the present invention, the system comprises:

[0007] A drying device having a wet sludge inlet and a dry sludge outlet;

[0008] A rotary kiln incinerator, wherein the rotary kiln incinerator has a dry sludge inlet, a hazardous waste inlet, a primary air inlet, an incineration slag outlet and an incineration flue gas outlet, and the dry sludge inlet is connected to the dry sludge outlet;

[0009] A secondary combustion chamber, wherein the secondary combustion chamber has a combustion smoke inlet, a secondary air inlet and a combustion smoke outlet, and the combustion smoke inlet is connected to the combustion smoke outlet;

[0010] A waste heat recovery device, wherein the waste heat recovery device has a condensed water inlet, a combustion flue gas inlet, a low-pressure steam outlet and a heat exchange flue gas outlet, the combustion flue gas inlet is connected to the combustion flue gas outlet, and the low-pressure steam outlet is connected to the drying device.

[0011] According to the system for the coordinated disposal of sludge and hazardous wastes of the embodiment of the present invention, after drying the sludge, it is supplied to the rotary kiln incinerator together with the hazardous wastes with high calorific value for incineration. On the one hand, it can significantly reduce the calorific value of the incinerator, avoid overheating in the furnace, and thus effectively treat the hazardous wastes without replacing the equipment. On the other hand, it effectively treats the sludge and hazardous wastes at the same time, achieving the purpose of treating wastes with wastes, conforming to the development direction of national environmental protection technology, and having good market application prospects. Then, the combustion flue gas generated in the incineration process is supplied to the secondary combustion chamber for secondary combustion, so that the dioxins and organic matter in the flue gas are further burned and decomposed, and the combustion flue gas is supplied to the waste heat recovery device for heat exchange, and the low-pressure steam obtained after the heat exchange is returned to the drying medium of the sludge drying process, thereby reducing the water content in the sludge and increasing the calorific value of the sludge. Therefore, the system can simultaneously treat sludge and hazardous wastes, and achieve waste reduction and harmless treatment.

[0012] In addition, the system for coordinated disposal of sludge and hazardous waste according to the above embodiment of the present invention may also have the following additional technical features:

[0013] In some embodiments of the present invention, the above-mentioned system for the coordinated disposal of sludge and hazardous waste further comprises: a melting device, the melting device having an inlet for incineration slag, an inlet for calcium-based additives and an outlet for harmless slag, the inlet for incineration slag being connected to the outlet for incineration slag via a scraper, thereby achieving harmless treatment of the waste.

[0014] In some embodiments of the present invention, the above-mentioned system for the coordinated disposal of sludge and hazardous waste further comprises: a purification device, wherein the purification device has a heat exchange flue gas inlet and a purified flue gas outlet, wherein the heat exchange flue gas inlet is connected to the heat exchange flue gas outlet, thereby achieving standard flue gas emission.

[0015] In some embodiments of the present invention, the purification device includes a deacidification device, an activated carbon adsorption device and a denitration device connected in sequence, thereby achieving emission of flue gas in compliance with standards.

[0016] In some embodiments of the present invention, the drying device is a horizontal disc dryer, a paddle dryer or a belt dryer, thereby improving the drying efficiency of the sludge.

[0017] In another aspect of the present invention, the present invention provides a method for the coordinated disposal of sludge and hazardous waste. According to an embodiment of the present invention, the method comprises:

[0018] (1) supplying wet sludge to the drying device for drying to obtain dry sludge;

[0019] (2) supplying the dry sludge and hazardous waste to the rotary kiln incinerator and mixing with primary air for incineration to obtain incineration slag and incineration flue gas;

[0020] (3) supplying the combustion flue gas to the secondary combustion chamber for secondary combustion with secondary air to obtain combustion flue gas;

[0021] (4) The combustion flue gas is supplied to the waste heat recovery device to exchange heat with condensed water to obtain low-pressure steam and heat exchange flue gas, and the low-pressure steam is returned to step (1) as a drying medium to dry the sludge.

[0022] According to the method for co-disposal of sludge and hazardous wastes of the embodiment of the present invention, after drying the sludge, it is supplied to the rotary kiln incinerator together with the hazardous wastes with high calorific value for incineration. On the one hand, the calorific value of the incinerator can be significantly reduced, and the overheating phenomenon in the furnace can be avoided, so that the effective treatment of hazardous wastes can be achieved without replacing the equipment. On the other hand, the sludge and hazardous wastes are effectively treated at the same time, and the purpose of treating wastes with wastes is achieved, which is in line with the development direction of national environmental protection technology and has good market application prospects. Then, the combustion flue gas generated in the incineration process is supplied to the secondary combustion chamber for secondary combustion, so that the dioxins and organic matter in the flue gas are further burned and decomposed, and the combustion flue gas is supplied to the waste heat recovery device for heat exchange, and the low-pressure steam obtained after the heat exchange is returned to the drying medium of the sludge drying process, so as to reduce the water content in the sludge and increase the calorific value of the sludge. Therefore, the method can simultaneously treat sludge and hazardous wastes, and achieve waste reduction and harmless treatment.

[0023] In addition, the method for co-disposal of sludge and hazardous waste according to the above embodiment of the present invention may also have the following additional technical features:

[0024] In some embodiments of the present invention, in step (1), the moisture content of the dry sludge is not higher than 45 wt %.

[0025] In some embodiments of the present invention, in step (2), the average calorific value of the hazardous waste is not less than 4000 kcal / kg.

[0026] In some embodiments of the present invention, in step (2), the mass ratio of the dry sludge to the hazardous waste is 0.05 to 0.3. Thus, the calorific value of the incinerator is reduced, overheating in the furnace is avoided, and the hazardous waste can be effectively treated without replacing equipment.

[0027] In some embodiments of the present invention, in step (2), the incineration temperature is 850-1000°C.

[0028] In some embodiments of the present invention, in step (3), the temperature of the secondary combustion is 1100-1200° C. Thus, the dioxins and organic matter in the flue gas are further burned and decomposed.

[0029] In some embodiments of the present invention, the method for the coordinated disposal of sludge and hazardous waste further comprises: (5) supplying the incineration slag obtained in step (2) to the melting device for melting with a calcium additive to obtain harmless slag, thereby achieving harmless treatment of the waste.

[0030] In some embodiments of the present invention, the method for the coordinated disposal of sludge and hazardous waste further comprises: (6) supplying the heat exchange flue gas obtained in step (4) to the purification device for purification treatment to obtain purified flue gas, thereby achieving standard flue gas emission.

[0031] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0033] Figure 1 is a schematic diagram of the system structure for the coordinated disposal of sludge and hazardous waste according to an embodiment of the present invention;

[0034] Figure 2 is a schematic diagram of the structure of a system for coordinated disposal of sludge and hazardous waste according to another embodiment of the present invention;

[0035] Figure 3 is a schematic flow chart of a method for co-disposal of sludge and hazardous waste according to an embodiment of the present invention;

[0036] Figure 4 It is a flow chart of a method for coordinated disposal of sludge and hazardous waste according to another embodiment of the present invention. DETAILED DESCRIPTION

[0037] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0038] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0039] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0041] In one aspect of the present invention, the present invention provides a system for the coordinated disposal of sludge and hazardous waste. Figure 1-2 The system includes: a drying device 100, a rotary kiln incinerator 200, a secondary combustion chamber 300 and a waste heat recovery device 400.

[0042] According to an embodiment of the present invention, the drying device 100 has a wet sludge inlet 101 and a dry sludge outlet 102, and is suitable for drying wet sludge to obtain dry sludge. Specifically, the wet sludge is municipal sludge and / or low calorific value oil sludge and / or chemical sludge and / or sludge after sewage treatment, etc., and its wet basis has basically no calorific value due to its high water content. After drying, its water content is reduced to no more than 45%. The calorific value of the dry sludge can reach 1350Kcal / kg, but it still cannot be incinerated by self-heating. Preferably, the drying device can be a horizontal disc dryer, a paddle dryer or a belt dryer, and the drying medium is low-pressure steam, with a temperature of 150 to 200°C and a pressure of 0.4Mpa to 0.8Mpa, thereby improving the drying efficiency of the sludge.

[0043] According to an embodiment of the present invention, the rotary kiln incinerator 200 has a dry sludge inlet 201, a hazardous waste inlet 202, a primary air inlet 203, an incineration slag outlet 204 and an incineration flue gas outlet 205. The dry sludge inlet 201 is connected to the dry sludge outlet 102 and is suitable for supplying the above-obtained dry sludge to the rotary kiln incinerator for mixed incineration with hazardous waste. The sludge and hazardous waste undergo drying, dehydration, pyrolysis and combustion stages in the rotary kiln, wherein most of the organic matter in the sludge and hazardous waste is converted into CO2 and H2O, and a small part is decomposed into small molecules of CO, CH4, etc., and some organic matter is not fully burned to produce dioxins, while the inorganic matter in the sludge and hazardous waste is converted into kiln slag, obtaining incineration slag containing heavy metals and incineration flue gas containing dioxins and small molecular organic matter as well as carbon dioxide, carbon monoxide, methane and water. The inventor found that by drying the sludge and supplying it to the rotary kiln incinerator together with the hazardous waste with high calorific value for incineration, on the one hand, the calorific value of the incinerator can be significantly reduced, and the overheating phenomenon in the furnace can be avoided, so that the effective treatment of hazardous waste can be achieved without replacing the equipment. On the other hand, the sludge and hazardous waste are effectively treated at the same time, and the purpose of treating waste with waste is achieved, which is in line with the development direction of national environmental protection technology and has good market application prospects. Specifically, the rotary kiln incinerator of the present application can be downstream incineration or upstream incineration, and the average calorific value of the hazardous waste treated is not less than 4000kcal / kg, for example, it can be HW02 (medical waste), HW04 (pesticide waste), HW08 (waste mineral oil), HW11 (refining (steaming) distillation residue), HW13 (organic resin waste), etc., so as to mix it with the dry sludge, not only to achieve the incineration of the sludge, but also to make the calorific value of the mixed waste not higher than the calorific value range in the rotary kiln incinerator, and avoid the melting and adhesion of the incineration slag in the furnace.

[0044] Furthermore, the mass ratio of dry sludge to hazardous waste is 0.05 to 0.3. The inventors found that if the ratio of dry sludge to hazardous waste is too low, the effect of reducing the incineration temperature is not obvious; and if the ratio of dry sludge to hazardous waste is too high, it will significantly affect the incineration conditions. Therefore, within the mixing ratio range of the present application, the incineration temperature can be maintained between 850 and 1000°C, which can avoid incomplete incineration and prevent the temperature in the furnace from being too high to cause adhesion.

[0045] According to an embodiment of the present invention, the secondary combustion chamber 300 has a combustion flue gas inlet 301, a secondary air inlet 302 and a combustion flue gas outlet 303. The combustion flue gas inlet 301 is connected to the combustion flue gas outlet 205 and is suitable for secondary combustion of the combustion flue gas containing dioxins and small molecular organic matter as well as carbon dioxide, carbon monoxide, methane and water, etc., so that the dioxins and small molecular organic matter are further burned and decomposed to obtain combustion flue gas. Specifically, the temperature of the secondary combustion is 1100-1200°C.

[0046] According to an embodiment of the present invention, the waste heat recovery device 400 has a condensed water inlet 401, a combustion flue gas inlet 402, a low-pressure steam outlet 403 and a heat exchange flue gas outlet 404. The combustion flue gas inlet 402 is connected to the combustion flue gas outlet 303, and the low-pressure steam outlet 403 is connected to the drying device 100, and is suitable for exchanging heat between the combustion flue gas obtained above and the condensed water to obtain low-pressure steam and heat exchange flue gas, and returning the low-pressure steam to the drying device 100 for use as a drying medium. In this way, not only the waste heat of the combustion flue gas is fully utilized, but also the low-pressure steam obtained after the heat exchange is supplied to the drying device to dry the sludge, reducing the dependence of the drying device on the outside world. Specifically, the temperature of the low-pressure steam is 150-200°C and the pressure is 0.4Mpa-0.8Mpa.

[0047] According to the system for the coordinated disposal of sludge and hazardous wastes of the embodiment of the present invention, after drying the sludge, it is supplied to the rotary kiln incinerator together with the hazardous wastes with high calorific value for incineration. On the one hand, it can significantly reduce the calorific value of the incinerator, avoid overheating in the furnace, and thus effectively treat the hazardous wastes without replacing the equipment. On the other hand, it effectively treats the sludge and hazardous wastes at the same time, achieving the purpose of treating wastes with wastes, conforming to the development direction of national environmental protection technology, and having good market application prospects. Then, the combustion flue gas generated in the incineration process is supplied to the secondary combustion chamber for secondary combustion, so that the dioxins and organic matter in the flue gas are further burned and decomposed, and the combustion flue gas is supplied to the waste heat recovery device for heat exchange, and the low-pressure steam obtained after the heat exchange is returned to the drying medium of the sludge drying process, thereby reducing the water content in the sludge and increasing the calorific value of the sludge. Therefore, the system can simultaneously treat sludge and hazardous wastes, and achieve waste reduction and harmless treatment.

[0048] For further reference, Figure 2 The above-mentioned system for coordinated disposal of sludge and hazardous waste further includes: a melting device 500 and a purification device 600.

[0049] According to an embodiment of the present invention, the melting device 500 has an incineration slag inlet 501, a calcium additive inlet 502 and a harmless slag outlet 503, and the incineration slag inlet 501 is connected to the incineration slag outlet 204 through a scraper (not shown), and is suitable for mixing the incineration slag obtained above with the calcium additive for melting treatment, wherein the calcium additive is heated to above 1150°C under electric heating conditions, and the alkaline metal oxides such as Ca, Mg, and Na in the calcium additive react with the acidic oxides such as Si and Al in the incineration slag to form a low-melting-point liquid slag, and the heavy metal elements are solidified in the Si-O tetrahedral structure in the slag, thereby realizing the harmless treatment of the slag. Specifically, the calcium additive is steelmaking converter slag, limestone, etc. The melting treatment temperature is 1120±50℃, and the amount of incineration slag and calcium additives is based on controlling the alkalinity in the harmless slag to 0.6-0.8 (i.e., the sum of the mass of alkaline oxides divided by the sum of the mass of acidic oxides). The inventors found that if the alkalinity is too high, the viscosity of the harmless slag is low, and crystals are easily precipitated during the water crushing process, which may cause the leaching toxicity to exceed the standard; if the alkalinity is too low, the viscosity of the harmless slag is too high, which is not conducive to discharge, and glass fibers will come out during the water crushing process, reducing its subsequent resource utilization effect. Therefore, controlling the alkalinity in the harmless slag to 0.6-0.8 can achieve the resource utilization of waste while avoiding the toxicity of the harmless slag exceeding the standard during the water quenching process.

[0050] According to an embodiment of the present invention, the purification device 600 has a heat exchange flue gas inlet 601 and a purified flue gas outlet 602, and the heat exchange flue gas inlet 601 is connected to the heat exchange flue gas outlet 404, and is suitable for purifying the heat exchange flue gas obtained above, so that the purified flue gas meets the emission standards. Specifically, the purification device includes a deacidification device, an activated carbon adsorption device and a denitration device connected in sequence. It should be noted that the deacidification device, the activated carbon adsorption device and the denitration device are conventional operations in the field, and those skilled in the art can select them according to actual needs, which will not be repeated here.

[0051] In another aspect of the present invention, the present invention provides a method for co-disposal of sludge and hazardous waste using the above system. Figure 3-4 , the method comprising:

[0052] S100: The wet sludge is supplied to the drying device for drying

[0053] In this step, the wet sludge is supplied to a drying device for drying to obtain dry sludge. Specifically, the wet sludge is municipal sludge and / or low calorific value oil sludge and / or chemical sludge and / or sludge after sewage treatment, etc., and its wet basis has basically no calorific value due to its high water content. After drying, its water content is reduced to no more than 45%. The calorific value of the dry sludge can reach 1350Kcal / kg, but it still cannot be incinerated by self-heating. Preferably, the drying device can be a horizontal disc dryer, a paddle dryer or a belt dryer, and the drying medium is low-pressure steam with a temperature of 150 to 200°C and a pressure of 0.4Mpa to 0.8Mpa, thereby improving the drying efficiency of the sludge.

[0054] S200: Dry sludge and hazardous waste are fed to the rotary kiln incinerator and mixed with primary air for incineration

[0055] In this step, the dry sludge obtained above is supplied to the rotary kiln incinerator for incineration with hazardous waste and primary air. The sludge and hazardous waste undergo drying, dehydration, pyrolysis and combustion stages in the rotary kiln, wherein most of the organic matter in the sludge and hazardous waste is converted into CO2 and H2O, a small part is decomposed into small molecules of CO, CH4, etc., and some organic matter is not fully burned to produce dioxins, while the inorganic matter in the sludge and hazardous waste is converted into kiln slag, and incineration slag containing heavy metals and incineration flue gas containing dioxins and small molecules of organic matter as well as carbon dioxide, carbon monoxide, methane and water are obtained. The inventors have found that by drying the sludge and supplying it to the rotary kiln incinerator together with high calorific value hazardous waste for incineration, on the one hand, the calorific value of the incinerator can be significantly reduced, and overheating in the furnace can be avoided, thereby achieving effective treatment of hazardous waste without the need to replace equipment. On the other hand, the sludge and hazardous waste are effectively treated at the same time, achieving the purpose of treating waste with waste, which is in line with the development direction of national environmental protection technology and has good market application prospects. Specifically, the rotary kiln incinerator of the present application can be used for co-current incineration or counter-current incineration, and the average calorific value of the hazardous waste treated is not less than 4000Kcal / kg, for example, it can be HW02 (medical waste), HW04 (pesticide waste), HW08 (waste mineral oil), HW11 (distillation residue), HW13 (organic resin waste), etc., so as to mix them with dry sludge, which not only realizes the incineration of sludge, but also makes the calorific value of the mixed waste not higher than the calorific value range within the rotary kiln incinerator, thereby avoiding melting and sticking of the incineration slag in the furnace.

[0056] Furthermore, the mass ratio of dry sludge to hazardous waste is 0.05 to 0.3. The inventors found that if the ratio of dry sludge to hazardous waste is too low, the effect of reducing the incineration temperature is not obvious; and if the ratio of dry sludge to hazardous waste is too high, it will significantly affect the incineration conditions. Therefore, within the mixing ratio range of the present application, the incineration temperature can be maintained between 850 and 1000°C, which can avoid incomplete incineration and prevent the temperature in the furnace from being too high to cause adhesion.

[0057] S300: Supply the incineration flue gas to the secondary combustion chamber for secondary combustion with the secondary air

[0058] In this step, the incineration flue gas containing dioxins and small organic molecules is subjected to secondary combustion, so that dioxins and small organic molecules as well as carbon dioxide, carbon monoxide, methane and water are further burned and decomposed to obtain combustion flue gas. Specifically, the temperature of the secondary combustion is 1100-1200°C.

[0059] S400: The combustion flue gas is supplied to the waste heat recovery device for heat exchange with condensed water, and the low-pressure steam is returned to step S100

[0060] In this step, the combustion flue gas obtained above is supplied to the waste heat recovery device for heat exchange with condensed water to obtain low-pressure steam and heat exchange flue gas, and the low-pressure steam is returned to the drying device 100 as a drying medium. In this way, not only the waste heat of the combustion flue gas is fully utilized, but also the low-pressure steam obtained after heat exchange is supplied to the drying device to dry the sludge, reducing the dependence of the drying device on the outside world. Specifically, the temperature of the low-pressure steam is 150-200°C and the pressure is 0.4Mpa-0.8Mpa.

[0061] According to the method for co-disposal of sludge and hazardous wastes of the embodiment of the present invention, after drying the sludge, it is supplied to the rotary kiln incinerator together with the hazardous wastes with high calorific value for incineration. On the one hand, the calorific value of the incinerator can be significantly reduced, and the overheating phenomenon in the furnace can be avoided, so that the effective treatment of hazardous wastes can be achieved without replacing the equipment. On the other hand, the sludge and hazardous wastes are effectively treated at the same time, and the purpose of treating wastes with wastes is achieved, which is in line with the development direction of national environmental protection technology and has good market application prospects. Then, the combustion flue gas generated in the incineration process is supplied to the secondary combustion chamber for secondary combustion, so that the dioxins and organic matter in the flue gas are further burned and decomposed, and the combustion flue gas is supplied to the waste heat recovery device for heat exchange, and the low-pressure steam obtained after the heat exchange is returned to the drying medium of the sludge drying process, so as to reduce the water content in the sludge and increase the calorific value of the sludge. Therefore, the method can simultaneously treat sludge and hazardous wastes, and achieve waste reduction and harmless treatment.

[0062] For further reference, Figure 4, the above-mentioned method for coordinated disposal of sludge and hazardous waste further comprises:

[0063] S500: The incineration slag obtained in step S200 is supplied to a melting device for melting with a calcium additive.

[0064] In this step, the incineration slag obtained in the above step S200 is supplied to a melting device and mixed with a calcium-based additive for melting treatment. The calcium-based additive is heated to above 1150°C under electric heating conditions, and alkaline metal oxides such as Ca, Mg, and Na in the calcium-based additive react with acidic oxides such as Si and Al in the incineration slag to produce a slag-forming reaction to form low-melting-point liquid slag. The heavy metal elements are solidified in the Si-O tetrahedral structure in the slag, thereby achieving harmless treatment of the slag. Specifically, the calcium additives are steelmaking converter slag, limestone, etc., the melting treatment temperature is 1120±50℃, and the amount of incineration slag and calcium additives is based on controlling the alkalinity in the harmless slag to 0.6-0.8 (i.e., the sum of the mass of alkaline oxides divided by the sum of the mass of acidic oxides). The inventors found that if the alkalinity is too high, the viscosity of the harmless slag is low, and crystals are easily precipitated during the water crushing process, which may cause the leaching toxicity to exceed the standard; if the alkalinity is too low, the viscosity of the harmless slag is too high, which is not conducive to discharge, and glass fibers will come out during the water crushing process, reducing its subsequent resource utilization effect. Therefore, controlling the alkalinity in the harmless slag to 0.6-0.8 can achieve the resource utilization of waste while avoiding the toxicity of the harmless slag exceeding the standard during the water quenching process.

[0065] S600: The heat exchange flue gas obtained in step S400 is supplied to a purification device for purification treatment

[0066] In this step, the heat exchange flue gas obtained in the above step S400 is supplied to the purification device for purification treatment, so that the purified flue gas meets the emission standards. Specifically, the purification device includes a deacidification device, an activated carbon adsorption device and a denitration device connected in sequence. It should be noted that the deacidification device, the activated carbon adsorption device and the denitration device are conventional operations in the field, and those skilled in the art can select them according to actual needs, which will not be repeated here.

[0067] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0068] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A system for the coordinated disposal of sludge and hazardous waste, characterized in that: include: A drying device, wherein the drying device uses the incineration of low-pressure boiler steam as a heat source, has a wet sludge inlet and a dry sludge outlet, and is suitable for drying the wet sludge to obtain dry sludge; A rotary kiln incinerator, wherein the rotary kiln incinerator has a dry sludge inlet, a hazardous waste inlet, a primary air inlet, an incineration slag outlet and an incineration flue gas outlet, wherein the dry sludge inlet is connected to the dry sludge outlet, and is suitable for supplying the dry sludge to the rotary kiln incinerator for mixed incineration with hazardous waste, and the mass ratio of the dry sludge to the hazardous waste is 0.05-0.3; A secondary combustion chamber, wherein the secondary combustion chamber has a combustion smoke inlet, a secondary air inlet and a combustion smoke outlet, and the combustion smoke inlet is connected to the combustion smoke outlet; A waste heat recovery device, the waste heat recovery device having a condensed water inlet, a combustion flue gas inlet, a low-pressure steam outlet and a heat exchange flue gas outlet, the combustion flue gas inlet is connected to the combustion flue gas outlet, and the low-pressure steam outlet is connected to the drying device; The melting device comprises an incineration slag inlet, a calcium additive inlet and a harmless slag outlet, wherein the incineration slag inlet is connected to the incineration slag outlet via a scraper.

2. The system according to claim 1, characterized in that Further including: The purification device comprises a heat exchange flue gas inlet and a purified flue gas outlet, wherein the heat exchange flue gas inlet is connected to the heat exchange flue gas outlet.

3. The system according to claim 2, characterized in that The purification device comprises a deacidification device, an activated carbon adsorption device and a denitration device which are connected in sequence.

4. The system according to claim 1, characterized in that The drying device is a horizontal disc dryer, a paddle dryer or a belt dryer.

5. A method for co-disposal of sludge and hazardous waste using the system according to any one of claims 1 to 4, characterized in that: include: (1) supplying wet sludge to the drying device for drying to obtain dry sludge; (2) supplying the dry sludge and hazardous waste to the rotary kiln incinerator and mixing them with primary air for incineration to obtain incineration slag and incineration flue gas; (3) supplying the combustion flue gas to the secondary combustion chamber for secondary combustion with secondary air to obtain combustion flue gas; (4) The combustion flue gas is supplied to the waste heat recovery device to exchange heat with condensed water to obtain low-pressure steam and heat exchange flue gas, and the low-pressure steam is returned to step (1) as a drying medium to dry the sludge.

6. The method according to claim 5, characterized in that In step (1), the moisture content of the dry sludge is not higher than 45wt%; In step (2), the average calorific value of the hazardous waste is not less than 4000 kcal / kg; In step (2), the mass ratio of the dry sludge to the hazardous waste is 0.05-0.3; In step (2), the incineration temperature is 850-1000°C.

7. The method according to claim 5, characterized in that In step (3), the temperature of the secondary combustion is 1100-1200°C.

8. The method according to claim 5, characterized in that Further including: (5) The incineration slag obtained in step (2) is supplied to the melting device for melting treatment with a calcium-based additive to obtain harmless slag.

9. The method according to claim 5 or 8, characterized in that: Further including: (6) The heat exchange flue gas obtained in step (4) is supplied to a purification device for purification treatment to obtain purified flue gas.

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