A method for large-scale remediation of contaminated soil using a rotary kiln

Abstract

This invention discloses a method for large-scale remediation of contaminated soil using a rotary kiln, relating to the field of contaminated soil remediation. The method involves the contaminated soil entering the remediation system via two pathways, thermal desorption within the rotary kiln, and incineration decomposition in a suspension combustion furnace. This remediation method features high temperature, long residence time of contaminated soil, and large volume. Organic matter in the contaminated soil can be completely decomposed, and heavy metal elements can be solidified within the contaminated soil. Simultaneously, it enables large-scale disposal of contaminated soil, further reducing disposal costs. The remediation method of this invention is highly adaptable to contaminated soil; different input paths are used for contaminated soil with large or small particle sizes, fully demonstrating the system's strong adaptability to contaminated soil, eliminating the need for extensive pretreatment of the contaminated soil at the front end.

Description

Technical Field

[0001] This invention relates to the field of environmental solid waste disposal technology, and further to the field of contaminated soil remediation, specifically to a method for large-scale remediation of contaminated soil using a rotary kiln. Background Technology

[0002] The main technologies for remediating contaminated soil include the following:

[0003] Soil washing technology can be categorized into in-situ washing and ex-situ washing based on the site. Ex-situ washing can be further divided into off-site treatment and off-site treatment. Compared with other treatment methods, washing effectively limits the spread of pollutants, while ex-situ washing confines pollution to a certain area. In-situ washing can effectively control the spread of pollution using methods such as grid walls, significantly reducing soil pollutant removal. It also offers advantages such as lower investment, lower consumption, and no need for technicians to directly contact pollutants.

[0004] Electrokinetic remediation, a type of physical remediation technology, utilizes two electrodes inserted into the soil to apply a low-voltage direct current electric field to both ends of the contaminated soil. Under the influence of this low-intensity direct current, water-soluble or adsorbed pollutants move towards different electrodes according to their different charges. Through the combined effects of electrochemical and electrodynamic processes, soil pollutants are enriched or collected and recovered near the electrodes.

[0005] Bioremediation technology, a relatively recent development, primarily includes phytoremediation and microbial remediation. Phytoremediation utilizes the absorption, volatilization, transformation, and degradation mechanisms of plants and their rhizosphere microbial systems to remove pollutants from the environment. Microbial remediation addresses contaminated soil layers containing sulfate-producing bacteria or other organisms capable of breaking down chromium (Cr). 6+ The reduced bacteria are injected into the contaminated formation via injection wells, providing the necessary nutrients (culture medium) for their growth and reproduction. The bacteria then directly engulf chromate and excrete Cr. 3+ Or, reducing agents such as hydrogen and hydrogen sulfide produced by bacterial metabolism can reduce Cr. 6+ Reduced to Cr 3+ .

[0006] Chemical reduction technology is an in-situ remediation method that uses iron filings, ferrous sulfate, or other readily available chemical reducing agents (which may also be supplemented with certain adhesives) to remove Cr. 6+ Reduced to Cr 3+ This process forms insoluble compounds, thereby reducing the migration and bioavailability of chromium in the environment and mitigating the harm of chromium pollution. Depending on the reducing agent used, chemical reduction can be divided into iron-based reduction technology, SO2 reduction technology, and H2S reduction technology. Each technology has engineering examples in the United States with good results. Most remediation methods utilize redox reactions to reduce chromium... 6+ Transformed into Cr3+ .

[0007] Solidification / stabilization technology involves mixing soil with additives, transforming pollutants in the soil into insoluble substances and fixing them within the formed mineral lattice. This isolates the pollutants from the surrounding environment, reducing their mobility and bioavailability, thereby lowering the risk of pollution. Solidification / stabilization comprises two processes, solidification and stabilization, which are generally carried out simultaneously. This technology has both in-situ and ex-situ operation modes. Commonly used additives include fly ash, lime, asphalt, and silicate cement, with cement being the most widely used. This technology can be applied to the remediation of soils contaminated with heavy metals, radioactive materials, and other inorganic and non-volatile or semi-volatile organic compounds. Sealing technology uses physical barriers to separate contaminated soil from surrounding uncontaminated soil, preventing the spread of pollutants. It is suitable for the remediation of low-toxicity and low-migration pollutants.

[0008] Cement kiln co-processing technology generally employs two methods for treating ordinary waste in cement kilns: First, adding it from the raw meal mill. This method is commonly used for inorganic wastes such as fly ash and slag. Its advantage is that the raw meal homogenization process allows for controllable composition and minimizes impact on the clinker calcination system. However, due to the high temperature inside the raw meal mill (around 200℃), it may cause the volatilization of organic pollutants in contaminated soil, thus posing a certain risk. Second, adding it from the preheater decomposition furnace. This method is suitable for treating contaminated soil containing organic pollutants (especially volatile organic pollutants), but existing methods often suffer from incomplete treatment.

[0009] In the solid waste disposal industry, especially in the field of contaminated soil remediation, my country's soil remediation technology application and green remediation industrialization are developing in depth, and the gap with advanced countries in remediation technology, equipment, and large-scale application is rapidly narrowing. However, although contaminated soil remediation has been carried out for several years, the scale of treatment is still relatively low, and ex-situ remediation technologies are relatively simple. Among them, the cement kiln co-processing technology for contaminated soil remediation is limited by the impact of cement production, and its treatment capacity and efficiency have reached their limit. There is an urgent need for a new process and technology to meet the requirements of large-scale treatment, fewer interfering factors, and environmentally friendly contaminated soil treatment technology. Summary of the Invention

[0010] Therefore, this invention provides a method for large-scale remediation of contaminated soil using a rotary kiln, addressing issues such as incomplete treatment, dangerous additives, and incomplete treatment in cement kiln co-processing technologies. This invention, fully adhering to the theory of ex-situ thermal desorption remediation technology for contaminated soil, forms a novel ex-situ remediation technology that effectively supplements the current contaminated soil remediation technology system and significantly improves labor productivity in ex-situ remediation.

[0011] This invention is developed from the cement kiln co-processing technology for contaminated soil, but it is fundamentally different from the cement kiln co-processing technology. It focuses on solving the bottleneck of contaminated soil remediation technology, enabling large-scale off-site treatment of contaminated soil, promoting the development and industrialization of off-site contaminated soil remediation technology, further reducing remediation costs, further reducing environmental impact, and promoting the healthy development of the contaminated soil remediation industry.

[0012] Thermal desorption technology is a highly effective and efficient remediation technique for treating organically contaminated soil. It boasts advantages such as strong adaptability, mobile equipment, short processing time, high removal efficiency, reusable remediated soil, no secondary pollution, and high public acceptance. Thermal desorption involves heating the contaminated soil and its contaminants to a sufficient temperature through direct or indirect heat exchange. This causes moisture and contaminants to evaporate or separate from the soil, and the contaminants are then transferred to the gas phase using air, fuel gas, or inert gas as a transport medium for collection and treatment. Due to the presence of oxygen in the air and the relatively high desorption temperature, the actual thermal desorption process involves reactions such as oxidation, degradation, and pyrolysis of contaminants, with the reaction intensity increasing with higher oxygen content and desorption temperature. Thermal desorption technology is widely used to remediate soils contaminated with volatile / semi-volatile organic compounds, pesticides, and high-boiling-point chlorinated compounds. Ex-situ thermal desorption involves excavating the contaminated soil from its original location, transporting or transferring it to another site, and then using thermal treatment to remove the contaminants through volatilization.

[0013] This invention is a type of ex-situ thermal desorption technology, belonging to the category of direct thermal desorption technology. It utilizes a circulating suspension combustion furnace and a rotary kiln as key equipment. The heat source directly contacts the contaminated soil in both the suspension fuel furnace and the rotary kiln. The suspension combustion furnace can perform secondary combustion of harmful substances in the flue gas, with temperatures reaching over 1100℃ and flue gas residence time exceeding 2 seconds. The temperature inside the rotary kiln can be adjusted according to the composition of the contaminated soil, with an adjustment range of 600℃-1100℃ for the flue gas and a contaminated soil residence time exceeding 20 minutes.

[0014] To achieve the above objectives, the present invention provides the following technical solution:

[0015] According to the present invention, a method for large-scale remediation of contaminated soil using a rotary kiln is provided, the method comprising:

[0016] Step one: The contaminated soil enters the remediation system in two streams:

[0017] One path is for contaminated soil to enter the rotary kiln from one end of the static smoke chamber, and the other path is for dust in the contaminated soil to enter the suspension combustion furnace through the other end of the static smoke chamber;

[0018] Contaminated soil with a moisture content greater than 30% or particles larger than 25mm enters the rotary kiln; dust with a moisture content less than 30% and particles smaller than 25mm enters the suspension combustion furnace.

[0019] Step two: The contaminated soil undergoes thermal desorption in the rotary kiln, with the temperature range adjusted to 600-1000℃. After thermal desorption, the contaminated soil enters a vertical cooler for cooling. The cooled contaminated soil is then conveyed to a treated contaminated soil storage silo for storage. Ambient air is blown into the vertical cooler, and after heat exchange, the air enters the rotary kiln as combustion air for fuel combustion.

[0020] Step three: The dust entering the suspension combustion furnace is suspended by the upward airflow. While suspended, it burns and rises simultaneously. As the dust rises with the air, gas-solid heat exchange occurs, rapidly increasing the temperature of the contaminated soil. Simultaneously, under the influence of the fuel in the suspension combustion furnace, harmful substances in the dust are thoroughly desorbed and removed. These removed harmful substances are then oxidized and burned in the flue gas at high temperatures. At the same time, some inorganic matter in the dust partially melts, forming a small amount of glass, until it enters the mixing cyclone separator for further gas-solid separation. Larger contaminated soil particles re-enter the rotary kiln through the static flue for further desorption and desorption. The flue gas undergoes further treatment.

[0021] Furthermore, the method also includes pretreatment of contaminated soil, including crushing the contaminated soil using an impact crusher.

[0022] Furthermore, the pretreatment also includes the crushed contaminated soil being preheated and homogenized by a mixing, preheating and homogenizing device before entering a static smoke chamber. The contaminated soil with different requirements is then sent to a rotary kiln and a suspension combustion furnace for remediation treatment through the static smoke chamber.

[0023] Furthermore, in step two, the vertical cooler is used to cool the contaminated soil on the one hand, and to recover the heat from the contaminated soil on the other hand, for combustion of the contaminated soil in the rotary kiln.

[0024] Furthermore, in step three, the mixing cyclone separator is divided into a first mixing cyclone separator and a second mixing cyclone separator, and the high-temperature flue gas from the suspension combustion furnace enters the first mixing cyclone separator and the second mixing cyclone separator in sequence;

[0025] The contaminated soil pipeline of the first mixing cyclone separator is divided into two paths: one path enters the static smoke chamber, and the other path enters the suspension combustion furnace for re-combustion. After the flue gas exits, it undergoes denitrification treatment.

[0026] The contaminated soil from the second mixed cyclone separator directly enters the suspension combustion furnace, and the flue gas undergoes desulfurization treatment after exiting the furnace.

[0027] Furthermore, the denitrification treatment method includes: installing a denitrification nozzle in the outlet pipe of the first mixing cyclone separator and introducing ammonia water for denitrification treatment;

[0028] The desulfurization process includes: a second mixed cyclone separator being connected to the desulfurization device, and sulfur-fixing agents being added to the desulfurization device for desulfurization treatment.

[0029] Furthermore, the method also includes heat exchange treatment, specifically including: after the second mixing cyclone separator, the flue gas passes through a flue gas duct, and a heat exchange device is installed on the flue gas duct to collect part of the heat to provide hot water for production and domestic use; a water spray quenching device cools the gas by spraying water, reducing the outlet gas temperature from 600°C to 200°C, and the cooling process is completed within 1 second.

[0030] Furthermore, the method also includes flue gas adsorption and post-treatment, specifically including: the cooled flue gas from the water spray quenching device enters the kiln tail dust collector via a relay fan; an activated carbon injection device is installed before the kiln tail dust collector to adsorb heavy metals in the flue gas; the dust collected by the kiln tail dust collector enters the dust collection ash silo; the dust in the dust collection ash silo is then passed through a mixing, preheating, and homogenizing device and enters a rotary kiln or suspension combustion furnace for secondary incineration; the flue gas after dust removal is discharged through a chimney.

[0031] The present invention has the following advantages:

[0032] 1. The remediation method of the present invention has the characteristics of high temperature, long residence time of contaminated soil and large volume. Organic matter in contaminated soil can be completely decomposed, heavy metal elements in contaminated soil can be solidified in contaminated soil, and large-scale treatment of contaminated soil can be achieved, further reducing the cost of contaminated soil treatment.

[0033] 2. The remediation method of the present invention has a wide temperature adjustment range, which can reach 600-1000℃ in the rotary kiln and 900-1100℃ in the suspension combustion furnace. This makes it more adaptable to contaminated soil, with lower heat consumption and lower exhaust emissions.

[0034] 3. The remediation method of this invention is environmentally friendly, and pollutant emissions are controllable. The remediation method of this invention uses minimal air consumption; and this invention includes denitrification and desulfurization facilities, heavy metal and dioxin removal facilities, dust removal facilities, etc., capable of simultaneously desulfurizing, denitrifying, adsorbing heavy metals, and adsorbing organic pollutants. Furthermore, this invention employs a rotary kiln plus a suspension combustion furnace, resulting in a long high-temperature residence time of flue gas, exceeding 2 seconds, while simultaneously rapidly cooling from 600℃ to below 200℃ within 1 second, which can fully oxidize and decompose dioxins and prevent the continued synthesis of dioxins at low temperatures.

[0035] 4. The remediation method of the present invention has a high level of automation, high equipment reliability, high efficiency in remediating contaminated soil, high secondary utilization rate, and strong scalability.

[0036] 5. The remediation method of the present invention has strong adaptability to contaminated soil. Different input paths are adopted for contaminated soil with large or small particle size, which fully demonstrates the advantage of the system's strong adaptability to contaminated soil. There is no need for excessive pretreatment of contaminated soil at the front end.

[0037] 6. The repair process of the present invention is simple and the cost is low; the repair method of the present invention can be used for technical modification of the calcination system of a waste cement plant, with low investment, low cost and high secondary utilization rate. Attached Figure Description

[0038] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0039] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0040] Figure 1 A flowchart for large-scale remediation of contaminated soil using a rotary kiln is provided by the present invention;

[0041] Figure 2 This is a diagram of a vent cap connected to a vertical cooler, provided in Embodiment 1 of the present invention;

[0042] In the diagram: 1-Contaminated soil storage shed; 2-Shovel loader; 3-Medium-sized plate feeder; 4-Impact crusher; 5-Contaminated soil conveyor; 6-Mixing preheating and homogenization device; 7-Suspension combustion furnace; 8-Cyclone separator; 9-Rotary kiln; 10-Vertical cooler; 11-Conveyor; 12-Treatment contaminated soil storage silo; 13-Water spray quenching device; 14-Activated carbon injection device; 15-Kiln tail dust collector; 16-Chimney; 17-Dust collection silo; 18-Dust collector; 19-Static smoke chamber; 20-Desulfurization device; 21-Denitrification nozzle; 22-Heat exchange device; 23-Relay fan; 24-Central cooling hood; 25-Compartment cooling hood.

[0043] Ⅰ-First mixing cyclone separator; Ⅱ-Second mixing cyclone separator. Detailed Implementation

[0044] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] like Figure 1 As shown, this invention employs a dual combustion method of a suspension combustion furnace 7 and a rotary kiln 9, further combined with a first mixing cyclone separator I and a second mixing cyclone separator II for cyclical and repeated combustion. The suspension combustion furnace 7 and the rotary kiln 9 are integrated. The fuel, suspended in the suspension combustion furnace 7 and propelled upwards by the air, undergoes upward gas-solid heat exchange as it rises. The temperature of the contaminated soil rises rapidly, and simultaneously, under the action of the fuel in the suspension furnace, harmful substances in the contaminated soil are thoroughly desorbed and removed. After being removed from the flue gas, the harmful substances undergo oxidative combustion under high temperature. At the same time, some inorganic matter in the contaminated soil partially melts, forming a small amount of glass, until it enters the first mixing cyclone separator I for gas-solid separation. Larger contaminated soil particles entering the suspension combustion furnace 7 are directly desorbed into the rotary kiln 9 through the static smoke chamber 19. After being preheated by the suspension fuel furnace 7, this part of the material greatly reduces the length of the preheating zone in the rotary kiln 9, improves the thermal efficiency of the rotary kiln 9, and can further release the spatial and temperature length distribution of the rotary kiln 9.

[0046] Large particles of contaminated soil in the mixing, preheating, and homogenizing device 6 enter the rotary kiln 9 through the static smoke chamber 19. After complete combustion and heat exchange in the flue gas, a portion of the contaminated soil entering the suspension combustion furnace 7 also enters the rotary kiln after passing through the mixing cyclone separator 1. In actual production, the amount of contaminated soil entering the suspension combustion furnace can be adjusted online. The contaminated soil tumbles within the rotary kiln, moving from the low-temperature end to the high-temperature end. In the rotary kiln, the contaminated soil undergoes thermal desorption at temperatures above 600°C. The desorbed harmful substances are then oxidized and detoxified, and some heavy metals can be fixed within the mineral contaminated soil. The contaminated soil ultimately completes thermal desorption within the rotary kiln 9, undergoes secondary preheating, further moisture removal, and organic matter volatilization and combustion, achieving a residence time of over 20 minutes.

[0047] The contaminated soil undergoes thermal desorption in the rotary kiln 9, with an adjustable temperature range of 600-1000℃. After thermal desorption, the hot contaminated soil enters the vertical cooler 10 for thorough gas-solid heat exchange. The vertical cooler 10 uses a blower to force in ambient air, cooling the contaminated soil before it enters the treated contaminated soil storage silo 12 for storage. The ambient air is heated to 600℃ and then enters the rotary kiln as combustion air.

[0048] Example 1

[0049] like Figure 1 As shown, this embodiment provides a method for large-scale remediation of contaminated soil using a rotary kiln:

[0050] Step one: The contaminated soil enters the remediation system in two streams:

[0051] One path is for contaminated soil to enter the rotary kiln 9 from one end of the static smoke chamber 19, and the other path is for dust in the contaminated soil to enter the suspension combustion furnace 7 through the other end of the static smoke chamber 19.

[0052] Contaminated soil with a moisture content greater than 30% or particles larger than 25mm enters the rotary kiln 9; dust with a moisture content less than 30% and particles smaller than 25mm enters the suspension combustion furnace 7.

[0053] The contaminated soil in the contaminated soil storage shed 1 is transported by a loader 2 to a medium-sized plate feeder 3 and fed into an impact crusher 4 for crushing. After crushing, the contaminated soil is dusted by a dust collector 18 and then transported by a contaminated soil conveyor 5 to a mixing, preheating and homogenizing device 6 for mixing, preheating and homogenizing. The treated contaminated soil enters a static smoke chamber 19 for branch processing and is then fed into a rotary kiln 9 and a suspension combustion furnace 7 for decomposition.

[0054] The mixing, preheating, and homogenizing device 6 is specially designed for material feeding into the kiln before it enters the kiln, thereby improving the rotary kiln's processing capacity. This device preheats the contaminated soil entering the kiln to above 400℃. It features counter-current feeding and convective heat exchange, enabling the contaminated soil to disperse, undergo gas-solid heat exchange, and separate. It can be divided into a conical core zone, a diffusion spray zone, a reflux vortex zone, and a constriction settling zone. Contaminated soil particles, in block or powder form, enter the mixing, preheating, and homogenizing device through chutes. Under gravity, they enter the constriction core zone and are dispersed by hot flue gas. The dispersed contaminated soil rises with the airflow into the vortex zone. Larger particles accumulate directly on the constriction slope and flow counter-currently back into the rotary kiln 9. In the vortex zone, the contaminated soil particles are pushed by the airflow to the device wall for gas-solid separation. The contaminated soil falls back onto the constriction slope and accumulates until it flows counter-currently back into the rotary kiln 9.

[0055] Step 2: The contaminated soil undergoes thermal desorption in the rotary kiln 9, with the temperature range adjusted to 600-1000℃. After thermal desorption, the contaminated soil enters the vertical cooler 10 for cooling. The cooled contaminated soil is then conveyed by the conveyor 11 into the treated contaminated soil storage silo 12 for storage. Ambient air is blown into the vertical cooler 10, and after heat exchange, the air enters the rotary kiln 9 as combustion air for fuel combustion within the rotary kiln 9.

[0056] The vertical cooler 10 is a device used to cool contaminated soil and also serves as a heat recovery unit. It seamlessly connects to the rotary kiln 9, fully utilizing its advantages of small footprint, low cooling air volume, and high flue gas temperature. The vertical cooler 10's structure is specifically designed for the morphology of the contaminated soil. After thermal desorption in the rotary kiln 9, the contaminated soil enters the vertical cooler 10. The vertical cooler 10 is lined with refractory bricks or cast with refractory refractory material on its sides and top. Figure 2 As shown, the vertical cooler 10 has a square cross-section, with a central cooling hood 24 and compartment cooling hoods 25 evenly distributed across the square cross-section. The hoods are connected to an external fan via pipes. A discharge chute is located at the bottom of the vertical cooler 10. Contaminated soil accumulates on the storage hoods inside the vertical cooler 10, forming a 200mm thick layer. Cooling air is blown in by an external fan, passes through the air chamber into the hoods, and exits from the hoods, contacting the high-temperature contaminated soil for gas-solid heat exchange. After cooling, the contaminated soil passes through a vibrating unloader into the treated contaminated soil storage silo 12 for temporary storage. The air that has undergone heat exchange can reach temperatures above 600℃ and enters the rotary kiln 9 through the kiln head hood, serving as high-temperature secondary air to aid fuel combustion.

[0057] Step 3: The dust entering the suspension combustion furnace 7 is suspended by the upward airflow. While suspended, it burns and rises simultaneously. As the dust rises with the air, gas-solid heat exchange occurs, causing the temperature of the contaminated soil to rise rapidly. Simultaneously, under the action of the fuel in the suspension combustion furnace 7, harmful substances in the dust are completely desorbed and removed. These removed harmful substances are then oxidized and burned in the flue gas at high temperatures. At the same time, some inorganic matter in the dust partially melts, forming a small amount of glass, until it enters the mixing cyclone separator 8 (using the mixing cyclone separator 8 ensures that the material can be repeatedly fed into the rotary kiln 9 and the suspension combustion furnace 7, guaranteeing secondary combustion). For subsequent gas-solid separation, larger contaminated soil particles re-enter the rotary kiln 9 through the static smoke chamber 19 for further desorption and desorption. The flue gas undergoes further treatment.

[0058] The suspension combustion furnace 7 is connected to the rotary kiln 9 via a specially designed static smoke chamber 19. A vertical cooler 10 is connected to the rotary kiln 9 at the discharge end to cool the contaminated soil and recover heat from it for fuel combustion within the rotary kiln 9. The upper part of the static smoke chamber 19 features a "throat" design (the throat design employs a special non-standard design mode to achieve flue gas jetting; the flue gas velocity is crucial, ensuring both flue gas jetting and material suspension, while also ensuring that some material enters the smoke chamber after passing through the throat), enhancing flue gas jetting and improving fuel combustion characteristics. The suspension combustion furnace 7 is connected upwards to the first mixing cyclone separator I and the second mixing cyclone separator II. The high-temperature flue gas from the suspension combustion furnace 7 sequentially enters the first mixing cyclone separator I and the second mixing cyclone separator II. The contaminated soil pipeline of the first mixing cyclone separator I is divided into two paths: one can enter the static smoke chamber, and the other can also enter the suspension combustion furnace 7; the contaminated soil pipeline of the second mixing cyclone separator II directly enters the suspension combustion furnace 7. The second mixed cyclone separator II is connected to the desulfurization unit 20, where a sulfur-fixing agent is added. A denitrification nozzle 21 is installed on the outlet pipe of the first mixed cyclone separator I, through which ammonia water is introduced for denitrification. After the second mixed cyclone separator II, the gas passes through a flue gas duct. A heat exchange device 22 is installed on the flue gas duct to collect some heat to provide hot water for production and domestic use. A water spray quenching device 13 cools the gas by spraying water, reducing the outlet gas temperature from 600℃ to 200℃ within 1 second. After cooling, the flue gas enters the relay fan 23 and then the kiln tail dust collector 15. An activated carbon injection device 14 is installed before the kiln tail dust collector 15 to adsorb heavy metals in the flue gas. The dust collected by the kiln tail dust collector 15 enters the dust collection ash silo 17. The dust in the dust collection ash silo 17 then re-enters the mixing preheating homogenization device 6 and the rotary kiln 9 for secondary incineration. After dust removal, the flue gas is discharged through the chimney 16. Before emissions, SO2, nitrogen oxides, and particulate matter in the flue gas are monitored online.

[0059] Water spray quenching device 13: Utilizing thermal insulation and refractory materials; a water spray quenching device 13 is installed on the pipeline connecting the second mixing cyclone separator II outlet to the relay fan. The effective inner diameter of this pipeline section is 1.7m, and the effective evaporation section length is approximately 15m. For the duct outlet of the second mixing cyclone separator II before water spray cooling (exhaust gas temperature around 600℃) and the duct within a 15m range after the spray gun, a 100mm thick layer of castable refractory is applied inside the duct. A 100mm thick layer of castable refractory is also applied inside the cyclone. Water consumption for a single pipeline water spraying system: not less than 10t / h (water quality: clean industrial water, temperature: <25℃, pressure: atmospheric pressure, approximately 0.1~0.3barg), compressed air consumption: not less than 10Nm3 / min (air pressure: >6barg, stable air source pressure).

[0060] Activated carbon injection device 14: An activated carbon injection device 14 is added to the air duct before the kiln tail dust collector 15. This device generally includes a ton bag unloading station, a loss-in-weight feeder, a Venturi injector, pipes and nozzles, and an electrical control system, which can realize remote control and accurate metering. Activated carbon can be in the form of ton bags and placed on the ton bag unloading station. The activated carbon is automatically unloaded into the loss-in-weight scale, which feeds the material into the Venturi injector according to the set output. The material is then transported into the flue gas duct by a positive pressure Roots blower to adsorb heavy metals and dioxins.

[0061] Flue gas desulfurization nozzle 20 and denitrification nozzle 21 are installed for desulfurization and denitrification; if necessary, an online flue gas emission monitoring device can be installed to monitor whether the emitted flue gas meets the standards. This invention, through the desulfurization and denitrification related devices, enables the flue gas emissions from the remediated contaminated soil to meet national and industry emission standards.

[0062] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for large-scale remediation of contaminated soil using a rotary kiln, characterized by, The method comprises: Step 1: The contaminated soil enters the remediation system in two ways: One way is that the contaminated soil enters the rotary kiln from one end of the static smoke chamber, and the other way is that the dust in the contaminated soil enters the suspended combustion furnace through the other end of the static smoke chamber; Among them, the contaminated soil with more than 30% moisture or more than 25mm particles enters the rotary kiln; the dust with less than 30% moisture and less than 25mm particles enters the suspended combustion furnace; Step 2: Pyrolysis in the rotary kiln The contaminated soil is pyrolyzed in the rotary kiln, and the temperature interval is adjusted to 600-1000℃ for pyrolysis. The pyrolyzed contaminated soil enters the vertical cooler for cooling, and the cooled contaminated soil enters the treated contaminated soil storage through the conveyor for storage; the vertical cooler blows in ambient air, which enters the rotary kiln after heat exchange as combustion air for fuel combustion in the rotary kiln; Step 3: Incineration and decomposition in the suspended combustion furnace The dust entering the suspended combustion furnace is carried by the upward air and suspended in the suspended state, and rises upward while burning; the dust rises with the air and exchanges heat with the gas, and the temperature of the contaminated soil rises rapidly, and the harmful substances in the dust are completely desorbed and removed under the action of the fuel in the suspended combustion furnace, and the removed harmful substances in the flue gas are oxidized and burned under the action of high temperature, and part of the inorganic matter in the dust is partially melted to form a small amount of glass, which is then separated from the gas in the mixed cyclone separator, and the contaminated soil with larger particles enters the rotary kiln again through the static smoke chamber for desorption and desorption again; In step 3, the mixed cyclone separator comprises a first mixed cyclone separator and a second mixed cyclone separator, and the high-temperature flue gas of the suspended combustion furnace enters the first mixed cyclone separator and the second mixed cyclone separator in sequence; Among them, the contaminated soil pipeline of the first mixed cyclone separator is divided into two ways, one of which enters the static smoke chamber, and the other of which enters the suspended combustion furnace for burning again, and the flue gas is treated by denitration after being discharged; The contaminated soil pipeline of the second mixed cyclone separator directly enters the suspended combustion furnace, and the flue gas is treated by desulfurization after being discharged.

2. The method for remediating large volumes of contaminated soil using a rotary kiln according to claim 1, wherein, The method further comprises pretreatment of the contaminated soil, which comprises crushing the contaminated soil by using an impact crusher.

3. The method for remediating large volumes of contaminated soil using a rotary kiln according to claim 2, wherein, The pretreatment further comprises that the crushed contaminated soil is preheated and homogenized by a mixed preheating and homogenizing device, and then enters the static smoke chamber, and the contaminated soil with different requirements is respectively sent to the rotary kiln and the suspended combustion furnace for remediation treatment.

4. The method for remediating large volumes of contaminated soil using a rotary kiln according to claim 3, wherein, In step 2, the vertical cooler is used for cooling the contaminated soil and recovering the heat in the contaminated soil for combustion of the contaminated soil in the rotary kiln.

5. The method for remediating large volumes of contaminated soil using a rotary kiln of claim 1, wherein, The denitration treatment method comprises that a denitration nozzle is arranged on the outlet pipeline of the first mixed cyclone separator, and ammonia water is introduced for denitration treatment; The desulfurization treatment comprises that the second mixed cyclone separator is connected to a desulfurization device, and a desulfurization agent is introduced into the desulfurization device for desulfurization treatment.

6. The method for remediating large volumes of contaminated soil using a rotary kiln according to claim 5, wherein, The method further comprises heat exchange treatment, specifically comprising: high-temperature flue gas enters the second hybrid cyclone separator and passes through a flue gas pipeline, a heat exchange device is arranged on the flue gas pipeline to collect part of heat to provide hot water for production and life, a water spraying quenching device is cooled by water spraying, the outlet gas temperature is reduced from 600 DEG C to 200 DEG C, and the cooling process is completed within 1s, wherein the water spraying quenching device is arranged on the second hybrid cyclone separator outlet connecting the induced draft fan pipeline.

7. The method for remediating large volumes of contaminated soil using a rotary kiln of claim 6, wherein, The method further comprises flue gas adsorption and post-treatment, specifically comprising: the cooled flue gas from the water spraying quenching device enters the kiln tail dust collector through the induced draft fan, an activated carbon spraying device is arranged in front of the kiln tail dust collector to adsorb heavy metals in the flue gas, the dust collected by the kiln tail dust collector enters the dust collection bin, and the dust in the dust collection bin is again introduced into the rotary kiln or the suspension combustion furnace through the mixing preheating homogenizing device to be incinerated for the second time, and the flue gas after dust removal is discharged through the chimney.

Images