CN104438313A - Contaminated soil thermal desorption system capable of efficiently recycling waste heat and method adopting contaminated soil thermal desorption system - Google Patents

Abstract

The invention discloses a thermal desorption system for polluted soil with high-efficiency reuse of waste heat, which includes a soil thermal desorption system and a tail gas incineration system. A part of the high-temperature flue gas generated by the tail gas incineration system is discharged through one of the flue gas outlets. The other part is mixed with air and enters the soil thermal desorption system as heat source gas. The invention takes full advantage of the advantages of thermal desorption technology in the process of repairing organic matter-contaminated soil, combines the structure of the flue gas furnace, fully utilizes the heat in the high-temperature flue gas after thermal desorption tail gas is incinerated, shunts out a part of the high-temperature flue gas and mixes it with fresh cold The mixed air is passed into the rotary kiln reactor as the heat source gas, and is used as the heat source gas for heating the soil, so the setting of the separate burner of the rotary kiln is reduced structurally.

Description

A polluted soil heat desorption system and method for efficient waste heat recovery

technical field

The invention relates to the field of soil remediation, in particular to a thermal desorption system for polluted soil with high-efficiency reuse of waste heat.

Background technique

Thermal desorption technology is an important contaminated soil remediation technology, which can remediate the soil that has been polluted by organic matter, and can achieve good remediation effect. It uses heating to heat the soil polluted by organic matter to above the boiling point of the organic matter, so that the organic matter adsorbed in the soil is volatilized into a gaseous state and then separated. Thermal desorption technology can effectively remove volatile organic compounds, such as aromatic hydrocarbons, etc., and can also effectively remove non-volatile and refractory organic pollutants such as PCBs, DDT, dioxins, and chlorine-containing pesticides. Organic substances with different boiling points can be heated at one time to achieve the restoration goal.

In the existing thermal desorption technology, the tail gas containing organic pollutants is usually incinerated for harmless disposal. Fuels such as pulverized coal or natural gas are used in the incineration process. The flue gas after incineration has a temperature of nearly 1,000 degrees Celsius. High temperature, with a lot of heat, must be equipped with waste heat utilization equipment before discharge. The commonly used waste heat utilization system is an air-air heat exchanger or an air-water heat exchanger followed by a waste heat boiler. Not only is the equipment complex, but the heat loss during the heat exchange is also a great waste, and it is not easy to control. The hot air after heat exchange is very expensive. It is difficult to meet the temperature and air volume required for soil thermal desorption.

Contents of the invention

In view of this, one of the purposes of the present invention is to provide a thermal desorption system for polluted soil with high-efficiency reuse of waste heat. , making full use of the heat in the high-temperature flue gas after thermal desorption tail gas incineration, diverting a part of the high-temperature flue gas and mixing it with fresh cold air as the heat source gas into the rotary kiln reactor as the heat source gas for heating the soil, so structurally The arrangement of separate burners in the rotary kiln is reduced; at the same time, the invention also provides a method for soil thermal desorption using the aforementioned desorption system.

One of the objectives of the present invention is achieved through the following technical solutions, a polluted soil thermal desorption system for efficient waste heat recovery, including a soil thermal desorption system and a tail gas incineration system, the high temperature flue gas produced by the tail gas incineration system Part of it is discharged through one of the flue gas outlets, and the other part is mixed with air and enters the soil thermal desorption system as heat source gas.

Further, the soil thermal desorption system includes a soil feeding device, a soil thermal desorption device, and a soil discharge device, the three are connected in sequence, and the soil thermal desorption device is connected to the tail gas incineration system.

Further, the soil thermal desorption device is an internal heating thermal desorption rotary kiln reactor, the soil feeding device is connected to the feed port of the internal thermal thermal desorption rotary kiln reactor, and the internal heating thermal desorption rotary kiln reacts The discharge port of the device is connected with the soil discharge device.

Furthermore, the internal heating type thermal desorption rotary kiln reactor is placed with an inclination of 0.01-0.03.

Further, the tail gas incineration system includes cyclone dust collector, flue gas incinerator, spray cooling tower and activated carbon adsorption tower; the gas outlet of the internal heating type thermal desorption rotary kiln reactor, cyclone dust collector, flue gas incinerator, spray cooling tower It is sequentially connected with the activated carbon adsorption tower; the dust outlet at the bottom of the cyclone dust collector is connected with the soil discharge device.

Further, the flue gas incinerator includes a combustion chamber and a gas distribution chamber, the combustion chamber communicates with the gas distribution chamber, the combustion chamber is equipped with a fuel ignition device and an air compensation nozzle, and part of the high-temperature flue gas generated in the combustion chamber enters the The rest of the gas distribution chamber enters the spray cooling tower; the gas distribution chamber is used for mixing air and high-temperature flue gas and the mixed gas is used as the heat source gas of the internal heating type thermal desorption rotary kiln reactor. The gas outlet of the gas distribution chamber is connected to the The air inlets of the internal heating type thermal desorption rotary kiln reactors are connected to each other.

Further, the discharge port of the soil discharge device is a screw discharge port.

The second object of the present invention is achieved through the following technical solutions, a method for desorption of polluted soil, comprising the following steps:

Step 1: After the contaminated soil is pretreated by screening and crushing, remove stones or metals and crush the soil to below 5cm;

Step 2: The pretreated soil is fed from the feed port of the rotary kiln reactor, and the polluted soil is continuously rolled along the cylinder of the rotary kiln reactor for thermal desorption;

Step 3: The organic matter-contaminated soil after thermal desorption is discharged from the discharge port of the rotary kiln reactor into the soil discharge device, and discharged after cooling and humidity control;

Step 4: The organic waste gas generated by the rotary kiln reactor is transported to the cyclone dust collector through the outlet of the rotary kiln reactor for dust removal, and the flue gas after dust removal is passed into the combustion chamber of the flue gas incinerator for secondary combustion, and the dust collected by the dust collector Enter the soil conditioner to cool down the discharge;

Step 5: Part of the organic waste gas after secondary combustion is mixed with a certain proportion of fresh air in the gas distribution chamber to form a high-temperature gas with a certain temperature and a certain volume, and enters the rotary kiln reactor as heat source gas through the air inlet of the rotary kiln reactor for heating Soil; another part of the high-temperature flue gas is discharged into the atmosphere through the exhaust pipe of the combustion chamber through the spray cooling tower and the activated carbon adsorption tower in turn.

Owing to adopting above-mentioned technical scheme, the present invention has following advantage:

1. The high-temperature flue gas after incineration is split, and a part of it is mixed with fresh cold air to generate the heat source gas required for the thermal desorption process. The temperature and volume of this part of the gas can be controlled simultaneously, and its low-oxygen atmosphere can be controlled to a certain extent. On the one hand, it suppresses the risk of producing toxic substances such as dioxins during the thermal desorption process;

2. After the thermal desorption tail gas enters the flue gas incinerator, the production of harmful gases such as NOx can be suppressed by controlling the supplementary amount of oxygen;

3. Combine the thermal desorption heat source system with the thermal desorption tail gas incineration disposal system to save fuel and reduce energy consumption;

4. The high-temperature soil desorbed by heat will be discharged after being cooled and adjusted to humidity through the soil spiral outlet, which will not cause dust pollution.

Description of drawings

In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with the accompanying drawings, wherein:

Fig. 1 is a block diagram of the present invention;

Figure 2 is a process flow diagram of the thermal desorption method.

Detailed ways

The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings; it should be understood that the preferred embodiments are only for illustrating the present invention, rather than limiting the protection scope of the present invention.

As shown in Figure 1, a thermal desorption system for polluted soil with high-efficiency reuse of waste heat includes a soil thermal desorption system and a tail gas incineration system, and part of the high-temperature flue gas generated by the tail gas incineration system passes through one of the flue gas outlets The other part is mixed with air and enters the soil thermal desorption system as heat source gas.

This new type divides the high-temperature flue gas after incineration, and a part of it is mixed with fresh cold air to generate heat source gas for thermal desorption. The temperature and volume of this part of gas are easy to control, and at the same time, its low oxygen atmosphere can suppress The risk of toxic substances such as dioxins in the thermal desorption process is eliminated.

In this embodiment, the temperature and gas volume of the mixed gas used as the heat source gas are controlled by adjusting the position of the splitter plate at the outlet of the flue gas incinerator to control the split ratio of the high-temperature flue gas. At the same time, the air volume introduced into the gas distribution chamber can be adjusted to of. Since the thermal desorption operating parameters (mainly desorption temperature and residence time) required by different kinds of organic matter-contaminated soils are different, the precise control of the heat source gas is necessary to control the thermal desorption process.

The soil thermal desorption system includes a soil feeding device, a soil thermal desorption device, and a soil discharge device, and the three are connected in sequence, and the soil thermal desorption device is connected with a tail gas incineration system. The soil thermal desorption device is an internal heating type thermal desorption rotary kiln reactor, the soil feeding device is connected to the feed port of the internal heating type thermal desorption rotary kiln reactor, and the internal heating type thermal desorption rotary kiln reactor The discharge port is connected with the soil discharge device. The tail gas incineration system includes cyclone dust collector, flue gas incinerator, spray cooling tower and activated carbon adsorption tower; the gas outlet of internal heat type thermal desorption rotary kiln reactor, cyclone dust collector, flue gas incinerator, spray cooling tower and activated carbon The adsorption towers are connected in sequence; the dust outlet at the bottom of the cyclone dust collector is connected with the soil discharge device. The flue gas incinerator includes a combustion chamber and a gas distribution chamber. chamber, and the rest enters the spray cooling tower; the gas distribution chamber is used for mixing air and high-temperature flue gas and the mixed gas is used as the heat source gas of the internal heating type thermal desorption rotary kiln reactor, and the gas outlet of the gas distribution chamber is connected to the The air inlet of the internal heating type thermal desorption rotary kiln reactor is connected.

As shown in Figure 2, the soil is screened by the soil feeding device, crushed and pretreated, and then enters the rotary kiln reactor for thermal desorption process. After thermal desorption, the clean soil is discharged through the soil screw discharge machine with cooling and humidity control. Part of the thermal desorption tail gas is discharged through the cyclone dust collector, flue gas incinerator, spray cooling tower and activated carbon adsorption tower in sequence, and the other part of the tail gas is mixed with air in the gas distribution chamber to produce high-temperature flue gas at a certain flow rate and temperature. Gas can be used as heat source gas for soil thermal desorption rotary kiln reactor.

In this embodiment, the discharge port of the soil discharge device is a spiral discharge port, and the thermally desorbed high-temperature soil is discharged through the soil spiral discharge port after cooling and humidity adjustment, without causing dust pollution.

In this embodiment, the internal heating type thermal desorption rotary kiln reactor is placed with an inclination of 0.01-0.03.

According to the above-mentioned thermal desorption device, the present invention also provides a method for thermal desorption of polluted soil, comprising the following steps:

Step 1: After the contaminated soil is pretreated by screening and crushing, remove stones or metals and crush the soil to below 5cm;

Step 2: The pretreated soil is fed from the feed port of the rotary kiln reactor, and the polluted soil is continuously rolled along the cylinder of the rotary kiln reactor for thermal desorption;

Step 3: The organic matter-contaminated soil after thermal desorption is discharged from the discharge port of the rotary kiln reactor into the soil discharge device, and discharged after cooling and humidity control;

Step 4: The organic waste gas generated by the rotary kiln reactor is transported to the cyclone dust collector through the outlet of the rotary kiln reactor for dust removal, and the flue gas after dust removal is passed into the combustion chamber of the flue gas incinerator for secondary combustion, and the dust collected by the dust collector Enter the soil conditioner to cool down the discharge;

Step 5: Part of the organic waste gas after secondary combustion is mixed with a certain proportion of fresh air in the gas distribution chamber to form a high-temperature gas with a certain temperature and a certain volume, and enters the rotary kiln reactor as heat source gas through the air inlet of the rotary kiln reactor for heating Soil; another part of the high-temperature flue gas is discharged into the atmosphere through the exhaust pipe of the combustion chamber through the spray cooling tower and the activated carbon adsorption tower in turn.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and equivalent technologies thereof, the present invention also intends to include these modifications and variations.

Claims (8)

1. A thermal desorption system for polluted soil with efficient reuse of waste heat, comprising a soil thermal desorption system and a tail gas incineration system, characterized in that a part of the high-temperature flue gas generated by the tail gas incineration system passes through one of the flue gas outlets The other part is mixed with air and enters the soil thermal desorption system as heat source gas. 2. The thermal desorption system for polluted soil with efficient reuse of waste heat according to claim 1, characterized in that: the soil thermal desorption system comprises a soil feeding device, a soil thermal desorption device, and a soil discharge device, three The ones are connected sequentially, and the soil thermal desorption device is connected with the tail gas incineration system. 3. The thermal desorption system for polluted soil with high efficiency reuse of waste heat according to claim 2, characterized in that: the soil thermal desorption device is an internal heating type thermal desorption rotary kiln reactor, and the soil feeding device and The feed port of the internal heating type thermal desorption rotary kiln reactor is connected, and the discharge port of the internal heating type thermal desorption rotary kiln reactor is connected with the soil discharge device. 4. The thermal desorption system for polluted soil with high efficiency reuse of waste heat according to claim 3, characterized in that: the internal heating type thermal desorption rotary kiln reactor is placed with an inclination of 0.01-0.03. 5. The thermal desorption system for polluted soil with efficient reuse of waste heat according to claim 3, characterized in that: the tail gas incineration system includes a cyclone dust collector, a flue gas incinerator, a spray cooling tower and an activated carbon adsorption tower; The gas outlet of the thermal desorption rotary kiln reactor, the cyclone dust collector, the flue gas incinerator, the spray cooling tower and the activated carbon adsorption tower are sequentially connected; the dust outlet of the cyclone dust collector is connected with the soil discharge device. 6. The thermal desorption system for polluted soil with efficient reuse of waste heat according to claim 5, characterized in that: the flue gas incinerator includes a combustion chamber and an air distribution chamber, and the combustion chamber is connected to the air distribution chamber, The combustion chamber is equipped with a fuel ignition device and an air compensation nozzle. Part of the high-temperature flue gas generated by the combustion chamber enters the air distribution chamber, and the rest enters the spray cooling tower; the air distribution chamber is used for mixing air and high-temperature flue gas and mixing gas As the heat source gas of the internal heating type thermal desorption rotary kiln reactor, the gas outlet of the gas distribution chamber is connected with the air inlet of the internal heating type thermal desorption rotary kiln reactor. 7. The thermal desorption system for polluted soil with high efficiency reuse of waste heat according to claim 2, characterized in that: the discharge port of the soil discharge device is a spiral discharge port. 8. The method for performing thermal desorption using the polluted soil thermal desorption system for waste heat efficient reuse according to claim 6, characterized in that it comprises the following steps: Step 1: After the contaminated soil is pretreated by screening and crushing, remove stones or metals and crush the soil to below 5cm; Step 2: The pretreated soil is fed from the feed port of the rotary kiln reactor, and the polluted soil is continuously rolled along the cylinder of the rotary kiln reactor for thermal desorption; Step 3: The clean soil after thermal desorption is discharged from the discharge port of the rotary kiln reactor into the soil discharge device, and discharged after cooling and humidity control; Step 4: The organic waste gas generated by the rotary kiln reactor is transported to the cyclone dust collector through the outlet of the rotary kiln reactor for dust removal, and the flue gas after dust removal is passed into the combustion chamber of the flue gas incinerator for secondary combustion, and the dust collected by the dust collector Enter the soil conditioner to cool down the discharge; Step 5: Part of the organic waste gas after secondary combustion is mixed with a certain proportion of fresh air in the gas distribution chamber to form a high-temperature gas with a certain temperature and a certain volume, and enters the rotary kiln reactor as heat source gas through the air inlet of the rotary kiln reactor for heating Soil; another part of the high-temperature flue gas is discharged into the atmosphere through the exhaust pipe of the combustion chamber through the spray cooling tower and the activated carbon adsorption tower in turn.