Method for resourceful treatment of solid hazardous waste

Abstract

The invention relates to the technical field of hazardous waste treatment and comprehensive utilization, in particular to a solid hazardous waste resource treatment method which comprises the following steps: feeding hazardous waste sludge, clay and fly ash into a stirring tank for mixing and stirring to obtain a mixed dry material; stacking and aging the mixed dry material in a stirring pool to obtain mixed pug; measuring the water content of the mixed pug; according to the water content of the mixed pug, adding the fly ash and the blending water again, and mixing and stirring to obtain a blank; feeding the blank into a double-roller granulator through a belt conveyor, and extruding and granulating to form a granular blank; feeding the granular blank into a first rotary kiln for pre-firing, and then transferring into a second rotary kiln for firing and forming to obtain ceramsite; and feeding the fired ceramsite into a single-cylinder cooling machine for cooling and grading to obtain finished ceramsite with corresponding specifications. According to the method, the hazardous waste sludge is turned into wealth, harmless resource reutilization is achieved, and the environmental benefit and the economic benefit are remarkable.

Description

Technical Field

[0001] The present invention relates to the technical field of hazardous waste disposal and comprehensive utilization, and in particular to a method for resource-based disposal of solid hazardous waste. Background Art

[0002] Hazardous solid waste refers to solid waste with one or more hazardous characteristics such as toxicity, corrosiveness, flammability, reactivity and infectivity. The storage of hazardous solid waste requires a large amount of land and is likely to pollute the soil, water and atmosphere through leachate, dust and other means. In addition, harmful substances in hazardous solid waste may enter organisms through the food chain, causing long-term impacts on the ecosystem.

[0003] The existing methods for treating solid hazardous waste are mainly physical and chemical methods. Physical methods include safe landfill (the disadvantage is that the landfill must be far away from residential areas, and sedimentation and gas pollution must be prevented, and the occupation and waste of land resources are serious), incineration (the disadvantage is that incineration will produce a large amount of acidic gas and incompletely burned slag, there is secondary pollution, and the investment and operation costs are high) and solidification (using coagulants to seal harmful substances, the disadvantage is that there is a risk of secondary pollution, the occupation and waste of land, and the cost is high). The chemical method uses the chemical properties of hazardous waste sludge to convert it into harmless substances through neutralization, oxidation-reduction, precipitation, etc., but lacks resource utilization and still has secondary land occupation and pollution problems. Summary of the invention

[0004] In view of the defects mentioned in the background technology, the present invention provides a method for resource-based disposal of solid hazardous waste, aiming to achieve harmless treatment and resource utilization of hazardous waste sludge.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: A method for resource disposal of hazardous solid waste comprises the following steps: S1. Add hazardous waste sludge, clay and fly ash into a mixing tank in a weight ratio of 4:3:1 and mix and stir to obtain a mixed dry material; S2. The mixed dry materials are piled in a mixing tank and aged for 25 to 40 hours to obtain a mixed mud material; S3, sampling the mixed mud at multiple points to measure the moisture content of the mixed mud; S4, preparing blending water by mixing ammonium bicarbonate and water in a weight ratio of (0.2-1):4, adding fly ash accounting for 10-22% of the total weight of the mixed dry materials and blending water accounting for 3-15% of the total weight of the mixed dry materials according to the moisture content of the mixed mud, mixing and stirring to obtain a blank with a moisture content of 25-28%; S5, sending the blank material to the roller granulator via a belt conveyor for extrusion granulation to form blanks with a particle size of 10 to 15 mm; S6, sending the embryonic grains into the first rotary kiln for pre-firing, the first rotary kiln is heated to 800-850°C, and then transferred to the second rotary kiln, the second rotary kiln is heated to 1000-1100°C, the smoke generated in the first rotary kiln is sent to the second rotary kiln, and the embryonic grains are fired and formed in the second rotary kiln to become ceramsite; S7, the fired ceramsite is sent to a single-drum cooler for cooling, and the cooled ceramsite is screened and classified by a grading device to obtain finished ceramsite of corresponding specifications.

[0006] Preferably, when the moisture content of the mixed mud is ≥80%, 3-4.5% of the mixed dry material mass of water and 20-22% of the mixed dry material mass of fly ash are added, and the weight ratio of ammonium bicarbonate to water is (0.2-0.3):4.

[0007] Preferably, when the moisture content of the mixed mud is 60-80%, 4.5-7% of the mixed dry material mass of water and 16-20% of the mixed dry material mass of fly ash are added, and the weight ratio of ammonium bicarbonate to water is (0.3-0.7):4.

[0008] Preferably, when the moisture content of the mixed mud is 40-60%, 7-10% of the mixed dry material mass of water and 12-16% of the mixed dry material mass of fly ash are added, and the weight ratio of ammonium bicarbonate to water is (0.7-0.9):4.

[0009] Preferably, when the moisture content of the mixed mud is ≤40%, 10-12% of the mixed dry material mass of water and 10-12% of the mixed dry material mass of fly ash are added, and the weight ratio of ammonium bicarbonate to water is (0.9-1):4.

[0010] Preferably, the air cooled by the single-drum cooler after the ceramsite is cooled is sent into the second rotary kiln.

[0011] Preferably, the flue gas generated in the second rotary kiln is sent to the steam boiler for waste heat utilization after purification, and the high-temperature flue gas exchanges heat with the water in the boiler to generate high-temperature steam, which drives the turbine blades to rotate, thereby driving the generator to generate electricity.

[0012] Preferably, the flue gas from the steam boiler is passed through a ceramic multi-tube dust collector to collect large particles, and then enters a bag dust collector for dust removal, and then the dust-removed exhaust gas is sent to a water washing tower for water washing through a fan, and then passed through an alkali washing tower for alkali washing, and the flue gas after alkali washing enters a deodorization device for deodorization and is then discharged from the chimney.

[0013] After adopting the above technical solution, the beneficial effects of the present invention are: The invention avoids the problem of wasting a large amount of national soil resources in traditional landfill methods for treating hazardous waste sludge and the problem of resources such as cement, asphalt, additives, etc. required by the solidification method, solves the problem of secondary pollution of hazardous waste sludge, turns hazardous waste sludge into treasure, realizes harmless resource recycling, and has significant environmental and economic benefits. DETAILED DESCRIPTION

[0014] The features and exemplary embodiments of various aspects of the present invention will be described in detail below. In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are not configured to limit the present invention. For those skilled in the art, the present invention can be implemented without the need for some of these specific details. The following description of the embodiments is only to provide a better understanding of the present invention by illustrating examples of the present invention.

[0015] The embodiment of the present invention provides a method for resource-based disposal of hazardous solid waste, the process of which includes raw material mixing and stirring, aging, moisture content determination, water and fly ash addition, extrusion granulation, rotary kiln firing, and ceramsite cooling and classification. This method not only successfully overcomes the difficulties in the treatment of hazardous solid waste, but also creates a new economic value growth point through resource recycling, realizes the harmonious coexistence of environmental protection and economic benefits, and achieves a significant win-win effect.

[0016] The hazardous waste sludge, clay and fly ash after screening to remove impurities are sent into the mixing tank in a weight ratio of 4:3:1. The three raw materials are fully mixed and stirred by the mixing equipment for 1 to 2 hours to ensure uniform mixing between the raw materials to obtain mixed dry materials.

[0017] The mixed dry material obtained by mixing the raw materials is placed in a mixing tank and aged for 25 to 40 hours to obtain a mixed mud material. During the aging process, the liquid components in the dry material will gradually penetrate and diffuse, so that the uniformity of the entire mixture is improved, and its plasticity is improved, the viscosity of the mixed mud material is improved, and the molding performance is improved.

[0018] The mixed mud is sampled at multiple points, and the mud samples are quickly heated using a halogen moisture meter to measure their mass changes to obtain the moisture content of the mud samples. The moisture content of the mud samples is averaged to obtain the moisture content of the mixed mud.

[0019] The mixing water is prepared by mixing ammonium bicarbonate and water in a weight ratio of (0.2-1):4. According to the moisture content of the mixed mud, fly ash accounting for 10-22% of the total weight of the mixed dry materials and mixing water accounting for 3-15% of the total weight of the mixed dry materials are added, and the mixture is mixed and stirred to obtain a blank with a moisture content of 25-28%.

[0020] The hazardous waste sludge used in this method is in the form of mud cake (filter press dehydration product), and its moisture content is generally between 60% and 80%. The moisture content of clay depends on factors such as type, state and treatment process, and its moisture content is generally between 25% and 55%. Fly ash refers to the solid waste produced during the combustion of coal, also known as fly ash, and its moisture content is generally between 5% and 20%. It can be seen that before adding the blending water and the second addition of fly ash, the mixed mud already has a certain initial moisture content.

[0021] According to the moisture content of the mixed mud, water and fly ash are added to adjust the moisture content of the blank: 1. If the moisture content of the mixed mud is ≥80%, add 3-4.5% of the mixed dry material mass of water and 20-22% of the mixed dry material mass of fly ash, and the weight ratio of ammonium bicarbonate to water is (0.2-0.3):4; 2. If the moisture content of the mixed mud is 60-80%, add 4.5-7% of the mixed dry material mass of water and 16-20% of the mixed dry material mass of fly ash, and the weight ratio of ammonium bicarbonate to water is (0.3-0.7):4; 3. The moisture content of the mixed mud is 40-60%, and 7-10% of the mixed dry material weight of water and 12-16% of the mixed dry material weight of fly ash are added. The weight ratio of ammonium bicarbonate to water is (0.7-0.9):4; 4. The moisture content of the mixed mud is ≤40%. Add 10-12% of the mixed dry material mass of water and 10-12% of the mixed dry material mass of fly ash. The weight ratio of ammonium bicarbonate to water is (0.9-1):4.

[0022] The blank is sent to the roller granulator via a belt conveyor for extrusion granulation, and finally forms blanks with a particle size ranging from 10 to 15 mm.

[0023] Two rotary kilns are prepared, the first rotary kiln is heated to 800-850°C, and the second rotary kiln is heated to 1000-1100°C.

[0024] The pellets are first sent to the first rotary kiln for pre-firing. At this time, the moisture and volatiles in the pellets begin to be discharged in large quantities and enter the flue gas. As the gas is generated and accumulated, a large number of pores are formed inside the ceramsite, and these pores gradually expand under the action of gas pressure, thereby increasing the volume of the ceramsite. The ammonium bicarbonate contained in the ceramsite is decomposed by heat to produce carbon dioxide, ammonia and water vapor. These gas products will be released simultaneously during the reaction process, further increasing the number of pores and channels, increasing the porosity of the ceramsite, and making the ceramsite lighter, more heat-insulating, heat-insulating, and sound-absorbing.

[0025] After the pre-firing stage, the embryos are transferred to the second rotary kiln for further firing and shaping. The flue gas generated during the firing process in the first rotary kiln is sent to the second rotary kiln. The embryos are fired and shaped at high temperature to become ceramsite products. The flue gas from the first rotary kiln is burned and decomposed at high temperature, completely eliminating harmful components such as dioxins, and the heat in the flue gas can be absorbed by the embryos in the second rotary kiln, improving energy utilization efficiency. The ammonia in the flue gas is decomposed by heat at high temperature to generate nitrogen and hydrogen. The hydrogen reacts with the air in the second rotary kiln, further increasing the heat and combustion efficiency in the kiln.

[0026] In order to improve the yield rate of the embryonic grains, the embryonic grains can be preheated by the preheating equipment before entering the first rotary kiln. Part of the flue gas from the first rotary kiln is sent to the preheating equipment as a heat source to preliminarily heat the embryonic grains, and the flue gas discharged from the preheating equipment is then sent to the second rotary kiln. Directly putting the cold embryonic grains into the high-temperature first rotary kiln may cause the surface of the embryonic grains to heat up rapidly while the internal temperature rises slowly, generating thermal stress, which may cause the embryonic grains to crack or deform. The preheating equipment gradually increases the temperature of the embryonic grains to reduce the temperature difference between the inside and outside, thereby avoiding the damage to the embryonic grains caused by this thermal shock.

[0027] The fired high-temperature ceramsite is first sent to a single-drum cooler for cooling. The fan in the cooler will continuously blow cold air to quickly dissipate the heat on the surface of the ceramsite. The cooled ceramsite will then be screened and graded by a grading device.

[0028] The flue gas generated in the second rotary kiln first needs to be purified to remove particulate matter in the flue gas. After preliminary purification, the flue gas is sent to the steam boiler for waste heat utilization. In the boiler, the high-temperature flue gas exchanges heat with the water in the boiler, heating the water and evaporating it into high-temperature steam. In this process, the waste heat of the flue gas is effectively utilized and converted into the thermal energy of steam. The high-temperature steam is then used to drive the turbine blades to rotate, which in turn drives the generator to generate electricity, realizing the cascade utilization and efficient conversion of energy.

[0029] The flue gas from the steam boiler is collected by a ceramic multi-tube dust collector for large particles, and then enters a bag dust collector for dust removal. The exhaust gas after dust removal is then sent to a water washing tower for water washing through a fan. After water washing, it is washed with alkali in an alkali washing tower. The flue gas after alkali washing enters a deodorizing device for deodorization and is then discharged from the chimney.

[0030] Hazardous waste sludge is recycled into expanded clay through the method. In the expanded clay production process, the flue gas generated in the second rotary kiln is efficiently and environmentally friendly treated and the waste heat is utilized, which not only reduces environmental pollution but also realizes the recycling and efficient conversion of energy.

[0031] According to the embodiments of the present invention as described above, these embodiments do not describe all the details in detail, nor do they limit the invention to specific embodiments. Obviously, many modifications and changes can be made based on the above description. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and the modified use based on the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for resource disposal of hazardous solid waste, characterized in that: The steps include: S1. Add hazardous waste sludge, clay and fly ash into a mixing tank in a weight ratio of 4:3:1 and mix and stir to obtain a mixed dry material; S2. The mixed dry materials are piled in a mixing tank and aged for 25 to 40 hours to obtain a mixed mud material; S3, sampling the mixed mud at multiple points to measure the moisture content of the mixed mud; S4, preparing blending water by mixing ammonium bicarbonate and water in a weight ratio of (0.2-1):4, adding fly ash accounting for 10-22% of the total weight of the mixed dry materials and blending water accounting for 3-15% of the total weight of the mixed dry materials according to the moisture content of the mixed mud, mixing and stirring to obtain a blank with a moisture content of 25-28%; S5, sending the blank material to the roller granulator via a belt conveyor for extrusion granulation to form blanks with a particle size of 10 to 15 mm; S6, sending the embryonic grains into the first rotary kiln for pre-firing, the first rotary kiln is heated to 800-850°C, and then transferred to the second rotary kiln, the second rotary kiln is heated to 1000-1100°C, the smoke generated in the first rotary kiln is sent to the second rotary kiln, and the embryonic grains are fired and formed in the second rotary kiln to become ceramsite; S7, the fired ceramsite is sent to a single-drum cooler for cooling, and the cooled ceramsite is screened and classified by a grading device to obtain finished ceramsite of corresponding specifications.

2. The method for resource disposal of hazardous solid waste according to claim 1, characterized in that: When the moisture content of the mixed mud is ≥80%, 3-4.5% of the mixed dry material mass of water and 20-22% of the mixed dry material mass of fly ash are added, and the weight ratio of ammonium bicarbonate to water is (0.2-0.3):

4.

3. The method for resource disposal of hazardous solid waste according to claim 1, characterized in that: When the moisture content of the mixed mud is 60-80%, 4.5-7% of the mixed dry material mass of water and 16-20% of the mixed dry material mass of fly ash are added, and the weight ratio of ammonium bicarbonate to water is (0.3-0.7):

4.

4. The method for resource disposal of hazardous solid waste according to claim 1, characterized in that: When the moisture content of the mixed mud is 40-60%, 7-10% of the mixed dry material weight of water and 12-16% of the mixed dry material weight of fly ash are added, and the weight ratio of ammonium bicarbonate to water is (0.7-0.9):

4.

5. The method for resource disposal of hazardous solid waste according to claim 1, characterized in that: When the moisture content of the mixed mud is ≤40%, 10-12% of the mixed dry material mass of water and 10-12% of the mixed dry material mass of fly ash are added, and the weight ratio of the ammonium bicarbonate to water is (0.9-1):

4.

6. The method for resource disposal of hazardous solid waste according to claim 1, characterized in that: The air cooled by the single-drum cooler after the ceramsite is cooled is sent into the second rotary kiln.

7. The method for resource disposal of hazardous solid waste according to claim 1, characterized in that: The flue gas generated in the second rotary kiln is sent to the steam boiler for waste heat utilization after purification. The high-temperature flue gas exchanges heat with the water in the boiler to generate high-temperature steam. The high-temperature steam drives the turbine blades to rotate, thereby driving the generator to generate electricity.

8. The method for resource disposal of hazardous solid waste according to claim 7, characterized in that: The flue gas from the steam boiler is passed through a ceramic multi-tube dust collector to collect large particles, and then enters a bag dust collector for dust removal. The exhaust gas after dust removal is then sent to a water washing tower for water washing through a fan. After water washing, it is washed with alkali in an alkali washing tower. The flue gas after alkali washing enters a deodorizing device for deodorization and is then discharged from a chimney.