CN113088706B - Device and method for recovering valuable elements in fly ash of urban solid waste incinerator - Google Patents

Abstract

The invention discloses a device and a method for recovering valuable elements in fly ash of an urban solid waste incinerator, wherein the method comprises the following steps: pressing fly ash of the urban solid waste incinerator into porous blocks; heating the porous block in a reducing atmosphere to be lower than the target fly ash deformation temperature by 100-150 ℃ to gasify the metal in the porous block to obtain metal vapor; when the fly ash is heated, the heating rate is not higher than 25 ℃/min; recovering condensate obtained by fractional condensation of the metal vapor in a vacuum state, wherein the condensation temperature of the fractional condensation is determined according to the condensation temperature of the metal vapor; heating the fly ash in a gasification furnace, gasifying the metal phase change, and condensing the metal steam in a condenser; the invention utilizes the fly ash gasified in the reducing atmosphere and condenses the metal vapor in stages, can effectively recover partial heavy metal in the fly ash, and utilizes toxic substances such as dioxin and the like to decompose at high temperature, thereby realizing the resource utilization of the fly ash and protecting the environment.

Description

A device and method for recovering valuable elements in fly ash of urban solid waste incinerators

technical field

The invention belongs to the field of energy saving and emission reduction, and particularly designs a device and method for recovering valuable elements in fly ash of urban solid waste incinerators.

Background technique

With the development of the economy and the improvement of the living standards of the residents, the living habits of the residents have changed greatly, and the pollution of urban solid waste is very serious; it has brought great harm to people's health and affected the industry and agriculture The development of urban solid waste has become a major problem to be solved urgently in the current environmental field.

At present, the technologies used to treat urban solid waste include landfill method, aerobic composting method, anaerobic digestion method and incineration method. Among them, the incineration method has the advantages of large capacity reduction, thorough innocence, and resource utilization of solid waste, etc. Advantages, it has become the main way of urban solid waste treatment. Although the waste incineration method has many advantages mentioned above, a large amount of fly ash will be produced during the incineration process. The fly ash contains heavy metals such as Pb, Cd, Cu, Zn and other heavy metals with high leaching concentration, which have been classified as hazardous waste. Most of these heavy metals are deposited in the fly ash. The surface of the particles will be dissolved at any time. If not disposed of properly, the heavy metals in the fly ash will leach out and pollute the groundwater and soil. At present, the commonly used methods for treating fly ash mainly include safe landfill method, solidification and stabilization technologies such as cement solidification, and high-temperature sintering, melting and other technologies. These treatment methods can effectively reduce the leaching of heavy metals, but considering the long-term safety of the environment, the heavy metals solidified in fly ash cannot be utilized as resources, which is not only a waste of resources, but also a potential threat to the environment.

SUMMARY OF THE INVENTION

In order to solve the problems existing in the prior art, the present invention provides a device and method capable of effectively recovering valuable metal elements in fly ash of urban solid waste incineration, and recovering heavy metals in fly ash by gasification and condensation, which can effectively destroy Dioxins and other toxic organic compounds in fly ash can also effectively recover some valuable metals, which not only protects the environment but also improves economic benefits.

In order to achieve the above object, the technical scheme adopted in the present invention is: a method for recycling valuable elements in the fly ash of urban solid waste incinerators, specifically as follows:

Pressing fly ash from urban solid waste incinerators into porous blocks;

The porous block is placed in a reducing atmosphere and heated to a temperature of 100-150°C lower than the target fly ash deformation temperature to gasify the metal therein to obtain metal vapor; when the fly ash is heated, the heating rate is not higher than 25°C /min;

The condensate obtained by the fractional condensation of the metal vapor in a vacuum state is recovered, and the condensation temperature of the fractional condensation is determined according to the condensation temperature of the metal vapor.

The 30-100 μm municipal solid waste incinerator is sieved and pressed into a porous block, wherein the holes are variable-diameter holes with a diameter of 8mm-15mm, and the holes are randomly or regularly arranged on the block, The volume of the pores is 35% ± 5% of the bulk volume.

The metals include Zn, Pb, Cu and Cd.

The reducing atmosphere is created by hydrogen and nitrogen, and the flow ratio of hydrogen and nitrogen is 1:9.

The condensate is recovered while the uncondensed gas is recovered.

The degree of vacuum in the vacuum state is Pa.

A device for recovering valuable elements in the fly ash of an urban solid waste incinerator, comprising a gasifier and a condenser, the gasifier is provided with an air inlet, the air inlet is respectively connected to hydrogen and nitrogen gas sources through pipes, and the gasification A reducing atmosphere is maintained in the furnace, the gas outlet of the gasification furnace is connected to the gas inlet of the condenser, a first electric heater is arranged at the lower part of the gasification furnace, a second electric heater is arranged at the lower part of the condenser, and several stages of condenser pipes are arranged in the condenser to condense the gas. The tube is graded according to the condensation temperature of the metal vapor, and the condenser is provided with a suction port for vacuuming and an outlet for discharging uncondensed gas; the first electric heater and the second electric heater are electric heaters controlled by self-tuning PID, gasification A thermocouple is set in the furnace, a feeding port is set on the gasifier, and an exhaust valve is set on the top of the gasifier; a thermocouple is arranged at each stage of the condenser pipe, and the condenser pipe is connected to the circulating cooling water system.

The gas inlet of the gasifier is connected to the hydrogen gas storage cylinder and the nitrogen gas storage cylinder through a pipeline. The outlet of the hydrogen gas storage cylinder and the nitrogen gas storage cylinder are equipped with flow control valves. The outlet of the hydrogen gas storage cylinder and the nitrogen gas storage cylinder is connected to the gas cylinder. A mixer is arranged on the pipeline of the gas inlet of the furnace; the condenser is connected with a vacuum pump and an unreacted gas recovery bottle.

Condenser fins are arranged on the surface of the condenser tube. The condenser fins are made of triangular fins made of alloy steel. The condenser fins are distributed on the ceramic tube at intervals of 55-90°.

In the condenser, the temperature gradually decreases along the gas flow toward the condenser tube.

Compared with the prior art, the present invention at least has the following beneficial effects:

The invention utilizes the reducing atmosphere to gasify the fly ash processed into blocks, and condenses the metal vapor in stages, so that part of the heavy metals in the fly ash can be effectively recovered. At the same time, it helps to protect the environment; the heating rate is not higher than 25°C/min, and the maximum temperature is 100-150°C lower than the target fly ash deformation temperature to prevent the fly ash from being partially or completely melted and hinder the dissociation of heavy metal vapors in the ash particles. And diffusion, the metal is staged and condensed to realize the simultaneous recovery of more kinds of metals.

The invention can realize the recovery and utilization of some valuable metals in the solid waste incineration fly ash. By creating a reducing atmosphere in the gasifier, the gasification temperature of zinc and cadmium metals can be reduced, and a small electric power generator controlled by self-tuning PID is adopted. Heater heating can overcome the influence of complex characteristics such as pure lag, inertial lag, nonlinearity and time-varying in the traditional electric heating control process, and the generated metal vapors are condensed in the corresponding condenser tubes, which can realize staged condensation and recovery, and finally the unused The condensed metal gas and harmful gas are passed into the recovery bottle, and the toxic substances such as dioxins in the fly ash can be decomposed by high temperature, so as to realize the resource utilization of fly ash and reduce the pollution to the environment.

Description of drawings

Figure 1 is a schematic diagram of the overall structure of the present invention.

In the picture: 1-Hydrogen gas storage cylinder, 2-Nitrogen gas storage cylinder, 3-Flow control valve, 4-Mixer, 5-Exhaust valve, 6-Gasifier, 7-Temperature measuring thermocouple, 9-Part One electric heater, 13—second electric heater, 8—feeding port, 10—vacuum pump, 11—condensing pipe, 12—condenser, 14—unreacted gas recovery bottle.

Detailed ways

The present invention will be further described in detail below in conjunction with specific implementation cases.

The invention provides a method for recovering valuable elements in the fly ash of urban solid waste incinerators, the details are as follows:

Pressing fly ash from urban solid waste incinerators into porous blocks;

The porous block is placed in a reducing atmosphere and heated to a temperature of 100-150°C lower than the target fly ash deformation temperature to gasify the metal therein to obtain metal vapor; when the fly ash is heated, the heating rate is not higher than 25°C /min;

recovering the condensate obtained by conducting the staged condensation of the metal vapor in a vacuum state, and the condensation temperature of the staged condensation is determined according to the condensation temperature of the metal vapor;

The 30-100 μm municipal solid waste incinerator is sieved and pressed into a porous block, wherein the holes are variable-diameter holes with a diameter of 8mm-15mm, and the holes are randomly or regularly arranged on the block, The volume of the pores is 35% ± 5% of the bulk volume.

Referring to Figure 1, a device for recovering valuable elements in urban solid waste incineration fly ash, including hydrogen gas storage cylinder 1, nitrogen gas storage cylinder 2, flow control valve 3, mixer 4, exhaust valve 5, gasifier 6. Temperature measuring thermocouple 7, first electric heater 9, second electric heater 13, feed port 8, vacuum pump 10, condenser pipe 11, condenser 12 and unreacted gas recovery bottle 14; along the flow direction of the medium, Two hydrogen gas storage cylinders 1 and nitrogen gas storage cylinders 2 are arranged upstream of the mixer 4, and a flow control valve 3 is arranged on both the hydrogen gas storage cylinder 1 and the nitrogen gas storage cylinder 2, and a gas storage cylinder 3 is arranged downstream of the mixer 4. The furnace 6 is connected in two phases through gas pipelines. The gasifier 6 is connected with the condenser 12 through pipes, and the gasifier 6 is provided with a feed port 8 and an exhaust valve 5, and the exhaust valve 5 is arranged on the top of the gasifier 6. As an optional embodiment, The feeding port 8 is opened in the middle of the gasification furnace 6, and a rotating device for storing the blocks pressed by the fly ash is arranged inside the gasification furnace 6, and the first electric heater 9 controlled by the self-tuning PID is used to heat the fly ash. The top of the condenser 12 is provided with a vacuum pump 10, the middle of the condenser 12 is provided with four condensation pipes 11 covered with condensing sheets, the bottom end is provided with a second electric heater 13, and the outlet is connected with an uncondensed gas recovery bottle 14.

Referring to Fig. 1, the thermocouple of the present invention feeds back the temperature of the gasifier and the condensing tube to the temperature controller in real time, and the temperature controller controls the start and stop of the heater in real time according to the temperature difference, and a controller can also be added to convert the temperature of the thermocouple. The temperature data is fed back to the controller in real time, and the controller controls the input of circulating cooling water according to the actual temperature.

The fly ash collection tank is connected to the ash discharge outlet of the dust collector, and the ash discharge outlet of the dust collector is connected to the incinerator. The fly ash collection tank is used to collect the fly ash produced by the urban solid waste incineration, and then the fly ash in the collection tank is collected. It is transported to the screening system, and the fly ash with a particle size of 30-100 μm is screened out, and then the screened fly ash is quantitatively sent to the molding die by an automatic feeder to be extruded into a porous hexahedron or other polyhedron shape. The holes are arranged in a certain combination of blind holes and through holes, and the size is designed to be variable diameter, ranging from 8mm to 15mm. The holes are distributed evenly or staggered or in any form on the surface of the hexahedron, and their volume accounts for about 35% of the volume of the hexahedron. The hexahedral-shaped fly ash is transported to the rotating device of the gasifier through the feed port, and the fly ash is evenly distributed in the rotating device. The metal is condensed on different condensation pipes 11 in the condenser through the gas pipeline, and finally the uncondensed gas enters the uncondensed gas recovery bottle 14 through the gas outlet at the bottom of the condenser.

Of course, the block in the present invention can be a cylinder, a sphere, or a polyhedron, and the specific shape is not limited. The block is provided with a plurality of variable diameter holes, and the holes can be blind holes. It can also be a through hole.

Heavy metals in urban solid waste incineration fly ash mainly include Al, Fe, Zn, Pb, Cu, Cd, Cr, etc. The target metals recovered by this device are Zn, Pb, Cu, and Cd.

The first electric heater and the second electric heater of the present invention are electric heaters controlled by self-tuning PID. /min.

The reducing atmosphere in the gasifier is jointly created by hydrogen and nitrogen, and the flow ratio of hydrogen and nitrogen is 10:90.

A second electric heater 13 is arranged at the bottom of the condenser 12 to heat the condenser. By controlling the flow rate and flow rate of the cooling water, each condenser tube is placed in a different temperature range, and the metal vapor with a high boiling point is on the condenser sheet with a higher temperature. Condensation, the metal vapor with a lower boiling point condenses on the cooler fins.

A thermocouple is placed at each condensing tube to monitor the temperature at the condensing pan in real time, so as to adjust the heating temperature of the second electric heater and the flow and flow rate of the condensed water in time.

The condensing fins are made of triangular fins made of alloy steel. In order to facilitate the recovery of the condensing fins and the condensate on the condensing tube, the condensing fins are evenly distributed on the ceramic condensing tube at 60° intervals. Take it out and replace it, clean and recover the condensate on the condensing sheet, and then put it into the condenser to continue condensing.

As an option, the condenser fins can be straight fins parallel to the axial direction of the condenser tube.

Of course, the condensing fins can also be randomly distributed on the surface of the condensing tube, and the surface of the condensing fins can also be further provided with concave-convex lines to increase the surface area of the condensing fins, and the concave-convex lines make smooth transitions.

As an optional embodiment of the present invention, the condenser tube is in the form of a coil tube, and a gap for gas to pass through is set between each circle of the coil tube.

The used incineration fly ash samples were taken from a waste incinerator of a solid waste incineration center. The main metal elements in the incineration fly ash were iron, aluminum, chromium, cadmium, copper, zinc and lead. First, the pretreated porous hexahedral shape (can be made into other shapes as required) fly ash is put into the rotary device through the feed port 8 of the gasifier 6, the flow control valve 3 is opened, and the hydrogen and nitrogen flow out from the bottle, The flow ratio of hydrogen and nitrogen is 10:90. After mixing in the mixer 4, it is passed into the gasifier 6 through the air inlet, and the gas outlet of the gasifier 6 is closed. Then the vacuum pump 10 is turned on to maintain the The vacuum degree is 10 Pa, then the first electric heater 9 and the second electric heater 13 are turned on, heated to a set temperature of 1000 °C at a temperature rise rate of 20 °C/min, and then maintained at a constant temperature, and the gasification is turned on every two hours. The air outlet on the furnace 6 and the condenser 12 and the air inlet on the condenser 12, by controlling the flow rate and flow rate of the cooling water, make the condensing pipe in different condensing temperature ranges, and the condensation in the recovery device is recovered every minute. Take out the tube, clean and recover the condensate and then put the condensation tube back into the condenser to continue to condense the unreacted gas and pass it into the uncondensed gas recovery bottle 14. After the reaction is completed, turn off the vacuum pump and the electric heater.

As another example, a second electric heater 13 is provided at the bottom end of the condenser 12 to heat the condenser 12, so that the temperature of the condenser 12 reaches 1000°C, and the cooling water flow rate is controlled so that the condenser pipes are in different temperature ranges ; The condensation pipe 11 for condensing and recovering Cu vapor is located in the upper part of the condenser 12, and the corresponding condensation temperature interval is 800-1000 ° C, and the condensation pipe 11 for recovering Zn and Pb vapor is located in the middle of the condenser 12, and the corresponding condensation The temperature ranges are 300-400°C and 200-300°C respectively. The condensation pipe 11 for recovering Cd metal is located below the condenser 12, and the corresponding condensation temperature range is 100-200°C. The condensed gas is recovered in the bottle 14 .

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form or substance. Several improvements and supplements can also be made, and these improvements and supplements should also be considered within the protection scope of the claims of the present invention. All those skilled in the art, without departing from the spirit and scope of the present invention, can utilize the above-disclosed technical content to make some changes, modifications and equivalent changes of evolution, all belong to the present invention. Equivalent embodiments; at the same time, any modification, modification and evolution of any equivalent changes made to the above-mentioned embodiments according to the essential technology of the present invention still fall within the scope of the claims of the present invention.

Claims (5)

1. a method for recycling valuable elements in the fly ash of urban solid waste incinerators, is characterized in that, is specifically as follows: Pressing fly ash from urban solid waste incinerators into porous blocks; The porous block is placed in a reducing atmosphere and heated to a temperature of 100-150°C lower than the target fly ash deformation temperature to gasify the metal therein to obtain metal vapor; when the fly ash is heated, the heating rate is not higher than 25°C /min; The condensate obtained by the classified condensation of the metal vapor in a vacuum state is recovered, and the condensation temperature of the classified condensation is determined according to the condensation temperature of the metal vapor; the 30-100 μm urban solid waste incinerator is sieved out and pressed into Porous block, wherein the pores are variable diameter pores with a diameter of 8mm-15mm, the pores are randomly or regularly arranged on the block, and the volume of the pores accounts for 35%±5% of the block volume ; The reducing atmosphere is jointly created by hydrogen and nitrogen, and the flow ratio of hydrogen and nitrogen is 1:9; the vacuum degree in vacuum state is 10 Pa. 2 . The method for recovering valuable elements in fly ash from urban solid waste incinerators according to claim 1 , wherein the metals include Zn, Pb, Cu and Cd. 3 . 3. The method for recovering valuable elements in the fly ash of a municipal solid waste incinerator according to claim 1, wherein the condensate is recovered while the uncondensed gas is recovered. 4. A device for realizing the method for recovering valuable elements in the fly ash of urban solid waste incinerators according to any one of claims 1 to 3, characterized in that it comprises a gasifier (6) and a condenser (12), The gasification furnace (6) is provided with an air inlet, and the air inlet is respectively connected with hydrogen and nitrogen gas sources through pipelines, and a reducing atmosphere is maintained in the gasification furnace (6), and the gas outlet of the gasification furnace (6) is communicated with the condenser ( 12) gas inlet, the lower part of the gasifier (6) is provided with a first electric heater (9), the lower part of the condenser (12) is provided with a second electric heater (13), and several stages of condenser pipes are arranged in the condenser (12) (11), the condensation pipe (11) is graded according to the condensation temperature of the metal vapor, the condenser (12) is provided with a suction port for vacuuming and an outlet for discharging uncondensed gas; the first electric heater (9) and the second electric heater The heater (13) adopts an electric heater controlled by self-tuning PID, a thermocouple is arranged in the gasifier (6), a feeding port (8) is provided on the gasifier (6), and a top of the gasifier (6) is arranged Exhaust valve (5); a thermocouple is arranged at each stage of the condenser pipe (11), and the condenser pipe (11) is connected to the circulating cooling water system; in the condenser (12), the temperature along the gas flow to the condenser pipe (11) Gradually lower; condensing fins are arranged on the surface of the condensing pipe (11), the condensing fins are made of triangular fins made of alloy steel, and the condensing fins are distributed on the ceramic tube at intervals of 55-90°. 5. the device that reclaims valuable element in the fly ash of urban solid waste incinerator according to claim 4, is characterized in that, the air inlet of gasifier (6) communicates hydrogen gas cylinder (1) and nitrogen gas by pipeline The outlets of the gas storage cylinder (2), the hydrogen gas storage cylinder (1) and the nitrogen gas storage cylinder (2) are all provided with flow control valves (3), and the outlets of the hydrogen gas storage cylinder (1) and the nitrogen gas storage cylinder (2) are all provided with flow control valves (3). A mixer (4) is arranged on the pipeline to the gas inlet of the gasifier (6); the condenser (12) is connected with a vacuum pump (10) and an unreacted gas recovery bottle (14).

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