Solid waste pyrolysis system and pyrolysis method

Abstract

The invention relates to a solid waste pyrolysis system and a pyrolysis method. The solid waste pyrolysis system comprises a pyrolysis reactor, a fluidized bed and a hot blast stove. The solid waste pyrolysis method comprises the following steps that S1, in the pyrolysis reactor, solid waste is pyrolyzed, and crude pyrolysis solid waste and pyrolysis flue gas are generated; s2, in the fluidized bed, fluidizing the crude pyrolysis solid waste to generate pyrolysis solid waste and fluidizing gas; s3, combustion is conducted in the hot blast stove, and combustion flue gas is generated; and S4, after the combustion flue gas heats the pyrolysis reactor in the mixed gas heating jacket, the obtained mixed flue gas is partially recovered into the pyrolysis reactor and the hot blast stove. According to the solid waste pyrolysis system, the energy consumption of the system is reduced by 15% or above, the content of TOC in the raw material is greatly reduced, and deep removal of organic pollutants is achieved.

Description

Technical Field

[0001] The invention relates to a solid waste pyrolysis system and a pyrolysis method. Background Art

[0002] Waste salt is a crystalline salt byproduct of industrial production. Its primary sources include chemical production byproducts and water treatment processes such as pure water preparation, chemical preparation, and high-salt wastewater treatment. According to statistics, China produces over 20 million tons of waste salt annually. This solid waste contains both organic and inorganic pollutants. Removal of organic pollutants is essential for its resource recovery and harmless utilization.

[0003] To remove organic impurities, methods such as wet oxidation, anaerobic pyrolysis, and high-temperature melting are generally used to remove organic matter from waste salt. Pyrolysis has been widely used due to its fast reaction speed, mild reaction conditions, ease of operation, and high removal efficiency. However, pyrolysis reactions are typically carried out in an anaerobic environment, using indirect heat exchange via a jacket structure. This results in low system thermal efficiency, high energy consumption, and poor removal of organic pollutants, seriously hindering the harmless and resource-based disposal of waste salt.

[0004] CN 113562745 A discloses a system and method for treating waste salt using a two-stage pyrolysis technology. This technology uses flue gas as a heat source and a two-stage internally heated rotary kiln as a reactor. Direct contact between flue gas and waste salt heats the waste salt to remove organic matter. Problems with this technology include: (1) the flue gas waste heat and the sensible heat of the pyrolyzed salt are not recovered, resulting in high system energy consumption; (2) the use of a completely internal heating method results in a large amount of oxygen in the flue gas, which can easily lead to localized high temperatures in the kiln, resulting in insufficient pyrolysis of the waste salt and coking and agglomeration; and (3) the amount of flue gas required for complete internal heating is enormous, resulting in a large amount of particles carried. Furthermore, due to the oxidizing atmosphere in the internally heated rotary kiln, dioxins are easily generated, resulting in high subsequent flue gas disposal costs.

[0005] CN117920723A discloses a stepwise thermal removal method for organic matter in industrial waste salt. This technology involves subjecting industrial waste salt to anaerobic, medium-low temperature pyrolysis (200-600°C) in a pyrolysis reactor, followed by a rapid, high-temperature oxidation reaction (600-800°C) in an oxidation reactor, to effectively remove the organic matter. Problems with this technology include: (1) the sensible heat of the pyrolysis salt is not recovered, and the pyrolysis and oxidation flue gases after high-temperature treatment are not utilized in the waste salt disposal process, resulting in high system energy consumption; and (2) the high-temperature oxidation reaction (600-800°C) is prone to localized high temperatures, resulting in insufficient pyrolysis of the waste salt and coking and agglomeration.

[0006] CN 114811591 A discloses a hazardous waste salt pyrolysis system and pyrolysis process. High-temperature flue gas first enters the jacket of an externally heated rotary kiln to provide the heat required for pyrolysis. It then enters a drying reactor, where the low-temperature flue gas after heat exchange is used to dry the waste salt, achieving a cascaded utilization of flue gas energy. Problems with this technology include: (1) the sensible heat of the pyrolyzed salt is not recovered, resulting in high system energy consumption; and (2) strict oxygen control within the pyrolysis rotary kiln results in poor organic matter removal. Summary of the Invention

[0007] The present invention addresses the deficiencies in the prior art and provides a solid waste pyrolysis system and method. The solid waste pyrolysis system of the present invention reduces system energy consumption by more than 15%, significantly reduces the TOC content of the raw materials, and achieves deep removal of organic pollutants.

[0008] In a first aspect, the present invention provides a solid waste pyrolysis system comprising a pyrolysis reactor, a fluidized bed, and a hot air furnace;

[0009] The pyrolysis reactor is provided with a solid waste feed port, a first mixed flue gas recovery port, a pyrolysis flue gas discharge port and a coarse pyrolysis solid waste discharge port; the pyrolysis reactor is provided with a mixed gas heating jacket, and the mixed gas heating jacket is provided with a combustion flue gas inlet and a mixed flue gas outlet;

[0010] The fluidized bed is provided with a crude pyrolysis solid waste inlet, a fluidizing gas inlet, a fluidizing gas outlet and a pyrolysis solid waste outlet; the hot blast furnace is provided with a hot blast furnace burner, a pyrolysis flue gas inlet, a second mixed flue gas recovery port and a combustion flue gas outlet;

[0011] The pyrolysis flue gas outlet of the pyrolysis reactor is connected to the pyrolysis flue gas inlet of the hot blast furnace, the crude pyrolysis solid waste outlet of the pyrolysis reactor is connected to the crude pyrolysis solid waste inlet of the fluidized bed; the fluidizing gas outlet of the fluidized bed is connected to the supporting gas inlet of the hot blast furnace burner;

[0012] The combustion flue gas discharge port of the hot blast furnace is connected to the combustion flue gas inlet of the mixed gas heating jacket, and the mixed flue gas outlet of the mixed gas heating jacket is connected to the first mixed flue gas recovery port of the pyrolysis reactor through a first flue gas pipeline; a first flue gas branch pipe is provided on the first flue gas pipeline, and the first flue gas branch pipe is connected to the second mixed flue gas recovery port of the hot blast furnace.

[0013] As used herein, a pyrolysis reactor refers to equipment used for the high-temperature thermochemical decomposition of organic materials under oxygen-free (or oxygen-depleted) conditions, typically producing gaseous and / or liquid and / or solid byproducts. A pyrolysis reactor typically consists of multiple components, including a feed system, a heating device, a reactor body, a gas collection device, and a discharge system.

[0014] In the present invention, the core principle of the fluidized bed is to suspend solid particles through gas or liquid and make them present a fluid-like flow state, which is called "fluidization". The solid particles are suspended, moved and accumulated under the action of the fluid.

[0015] In this invention, a hot air furnace generates high-temperature gas by burning fuel and transfers heat to air or other media using heat exchange technology, thereby achieving processes such as heating, drying, baking, and heat treatment. The operating principle of a hot air furnace involves combustion and heat exchange. Fuel burns in a combustion chamber, generating high-temperature flue gas. This heat is transferred to air or water through a heat exchanger, raising the air temperature before being output for use.

[0016] In the present invention, the solid waste pyrolysis system may further include a cyclone cooler, which is provided with a pyrolysis flue gas inlet, a pyrolysis flue gas outlet, and a first solid recovery outlet. The cyclone cooler is preferably provided with a cooling jacket. The pyrolysis flue gas outlet of the pyrolysis reactor is connected to the pyrolysis flue gas inlet of the cyclone cooler, and the pyrolysis flue gas outlet of the cyclone cooler is connected to the pyrolysis flue gas feed inlet of the hot blast furnace via a second flue gas pipeline. The first solid recovery outlet of the cyclone cooler is connected to the crude pyrolysis solid waste inlet of the fluidized bed. Preferably, a second flue gas fan is provided on the second flue gas pipeline.

[0017] In the present invention, the cyclone cooler is a device that uses the cyclone separation principle for cooling. Its core working principle is to achieve heat exchange through high-speed rotating airflow, thereby achieving the purpose of cooling.

[0018] In the present invention, the solid waste pyrolysis system may further include a cyclone separator, which is provided with a mixed gas inlet, a mixed gas outlet and a second solid recovery outlet; the fluidized bed is also provided with a solid recovery port; the fluidizing gas outlet of the fluidized bed is connected to the mixed gas inlet of the cyclone separator, the mixed gas outlet of the cyclone separator is connected to the combustion gas feed port of the hot blast furnace burner, and the second solid recovery outlet of the cyclone separator is connected to the solid recovery port of the fluidized bed.

[0019] The cyclone separator in this invention is a highly efficient dust removal device designed based on the principle of centrifugal force, primarily used for separating gas-solid or gas-liquid systems. Its operating principle is to utilize the centrifugal force generated by a rotating airflow to separate solid particles or liquid droplets from the gas or liquid, thereby achieving gas-solid or gas-liquid separation. When dust-laden gas enters tangentially at a certain speed, the airflow forms a rotating motion within the cylinder. Solid particles in the rotating airflow are flung toward the wall due to inertia and centrifugal force, falling along the wall to be discharged through the ash outlet at the bottom, while the purified gas is discharged through the exhaust pipe at the top.

[0020] In the present invention, the fluidizing gas inlet of the fluidized bed is connected to a fluidizing gas blower; the pyrolysis solid waste outlet of the fluidized bed is connected to the feed port of a discharge conveyor. The discharge conveyor is preferably a screw discharger. The discharge conveyor is preferably provided with a water-cooling jacket. The discharge port of the discharge conveyor is preferably connected to an inorganic impurity removal system. The combustion-supporting gas feed port of the hot blast furnace burner is also preferably connected to a second blower.

[0021] In the present invention, a pyrolysis heating jacket may be further provided outside the pyrolysis reactor, and the pyrolysis heating jacket is located downstream of the material flow of the mixed gas heating jacket, and the pyrolysis heating jacket is provided with a rotary kiln burner and a heating flue gas discharge port; the mixed gas heating jacket is also provided with a heating flue gas inlet; the heating flue gas discharge port of the pyrolysis heating jacket is connected to the heating flue gas inlet of the mixed gas heating jacket, and the combustion-supporting gas feed port of the rotary kiln burner is connected to the first fan through the first combustion-supporting gas pipeline.

[0022] Wherein, a heat exchanger may be provided on the first combustion-supporting gas pipeline; the tube-side inlet and outlet of the heat exchanger are arranged on the first combustion-supporting gas pipeline, and the shell-side inlet and outlet of the heat exchanger are arranged on the first flue gas pipeline.

[0023] In the present invention, the first flue gas pipeline may also be provided with a heat recovery device and a first flue gas fan. A second flue gas branch pipe is preferably provided between the heat recovery device and the first flue gas fan. An exhaust flue gas fan is preferably provided on the second flue gas branch pipe. A back-mixing flue gas fan is preferably provided on the first flue gas branch pipe.

[0024] In a second aspect, the present invention provides a solid waste pyrolysis method, which uses the solid waste pyrolysis system as described above, comprising the following steps:

[0025] S1. Pyrolyzing solid waste in the pyrolysis reactor to produce crude pyrolysis solid waste and pyrolysis flue gas;

[0026] S2. Fluidizing the crude pyrolysis solid waste in the fluidized bed to generate pyrolysis solid waste and fluidizing gas;

[0027] S3, burning in the hot blast furnace to generate combustion flue gas;

[0028] S4. After the combustion flue gas is heated by the mixed gas heating jacket on the pyrolysis reactor, the obtained mixed flue gas is partially recovered into the pyrolysis reactor and the hot blast furnace.

[0029] In the present invention, in step S1, the solid waste is generally waste salt. Waste salt refers to solid inorganic salts containing certain pollutants generated during industrial production processes. These waste salts mainly come from industries such as chemical, pharmaceutical, pesticide, coal chemical, and printing and dyeing, and may contain organic pollutants and inorganic salts.

[0030] In the present invention, conventionally, in step S1, the solid waste may include salt, and the salt is preferably NaCl.

[0031] In the present invention, conventionally, in step S1, the solid waste may include organic matter, and the mass content of the organic matter is preferably 1-1.5%.

[0032] In the present invention, conventionally, in step S1, the solid waste may include water, and the mass content of the water is preferably 4-5%.

[0033] In the present invention, according to the processing requirements, in step S1, the flow rate of the solid waste can be 2.5-2.8 t / h;

[0034] In the present invention, in step S1, the pyrolysis temperature is based on achieving the pyrolysis purpose, for example, 500-700° C. The pyrolysis temperature is based on the material temperature at the discharge port of the crude pyrolysis solid waste.

[0035] In the present invention, in step S1, the residence time of the pyrolysis reactor is based on achieving the purpose of pyrolysis, preferably 1-3 hours, for example 1.5 hours.

[0036] In the present invention, in step S1, the pressure in the pyrolysis reactor is a slightly positive pressure or slightly negative pressure conventional in the art, for example, -300 to 300 Pa.

[0037] In the present invention, in step S1, the flow rate of the pyrolysis flue gas can be 220-250Nm 3 / h.

[0038] In the present invention, in step S1, the components of the pyrolysis flue gas generally include CO, H2, CO2, condensable organic matter and pyrolysis carbon.

[0039] In the present invention, in step S2, the pressure in the fluidized bed is a slightly negative pressure conventional in the art, for example, -300 to -50 Pa.

[0040] In the present invention, in step S2, the fluidization number of the fluidized bed is selected conventionally in the art, such as 1-4, for example 3. The fluidization number of the fluidized bed refers to the ratio of the actual operating velocity (carry-out velocity) of the fluidized bed to the critical fluidization velocity (initial fluidization velocity).

[0041] In the present invention, in step S2, the temperature of the pyrolysis solid waste may be 150-350°C, for example, 200°C.

[0042] In the present invention, in step S2, the temperature of the fluidizing gas may be 300-500°C, for example, 470°C.

[0043] In the present invention, conventionally, in step S3, the temperature of the combustion flue gas may be 800-1000°C, for example, 950°C.

[0044] In the present invention, according to the actual operation situation, in step S3, the flow rate of the combustion flue gas can be 2700-2800Nm 3 / h;

[0045] In the present invention, according to actual operation conditions, in step S3, the oxygen content of the combustion flue gas may be 8-15 vol%, for example, 13 vol%.

[0046] In the present invention, according to the actual operation situation, in step S4, the flow rate of the mixed flue gas can be 4800-4900Nm 3 / h;

[0047] In the present invention, according to actual operation conditions, in step S4, the temperature of the mixed flue gas may be 520-525°C;

[0048] In the present invention, according to the processing requirements, in step S4, the mixed flue gas recovered into the pyrolysis reactor accounts for 0.5%-3%, for example, 2.08%, of the total mixed flue gas.

[0049] In the present invention, according to the processing requirements, in step S4, the mixed flue gas recovered into the hot blast furnace accounts for 5%-35% of the total mixed flue gas, for example, 20.8%.

[0050] In certain specific embodiments of the present invention, when a pyrolysis heating jacket is provided outside the pyrolysis reactor, the temperature of the heated flue gas generated by the pyrolysis heating jacket is 700-900°C. Furthermore, when the solid waste pyrolysis system further includes a heat exchanger, the temperature of the combustion gas required by the pyrolysis heating jacket can be heated to 200-450°C, for example, 420°C, via the heat exchanger.

[0051] In certain specific embodiments of the present invention, when a pyrolysis heating jacket is provided outside the pyrolysis reactor, the flow rate of the heating flue gas generated by the pyrolysis heating jacket is 2000-2100 Nm 3 / h.

[0052] In certain specific embodiments of the present invention, when the solid waste pyrolysis system further comprises a cyclone cooler, the temperature of the pyrolysis flue gas is cooled to 200-300°C, for example, 250°C, by the cyclone cooler.

[0053] In certain specific embodiments of the present invention, when the solid waste pyrolysis system further comprises a discharge conveying device, the temperature of the pyrolyzed solid waste is cooled to 40-80° C., for example, 60° C., by the discharge conveying device.

[0054] In certain embodiments of the present invention, when the solid waste pyrolysis system further includes a heat recovery device, the temperature of the mixed flue gas is cooled to 150-250° C. by the heat recovery device. On this basis, the temperature of the medium in the heat recovery device can be raised to 50-80° C., for example, 65° C.

[0055] In the present invention, TOC in solid waste refers to the total carbon content of all organic matter in the solid waste, reflecting the total amount of organic matter in the solid waste and the degree of pollution. The TOC test method refers to HJ 501-2009 "Water quality - Determination of total organic carbon - Combustion oxidation - non-dispersive infrared absorption method" (solid waste is dissolved in 305g / L aqueous solution).

[0056] Without violating the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain preferred embodiments of the present invention.

[0057] The reagents and raw materials used in the present invention are commercially available.

[0058] The positive progress effect of the present invention is:

[0059] (1) The solid waste pyrolysis system of the present invention uses flue gas as a protective gas, combines flue gas waste heat with sensible heat recovery of pyrolysis salts, reduces system energy consumption by more than 15%, and can achieve deep removal of organic pollutants;

[0060] (2) The solid waste pyrolysis system of the present invention can be combined with the further oxidation of the solid waste raw materials after pyrolysis in a fluidized bed to further achieve deep removal of organic pollutants, so that the TOC content of the raw materials can be reduced to below 10 ppm;

[0061] (3) The solid waste pyrolysis system of the present invention can improve its adaptability to the moisture content of raw materials by means of zoned external heating combined with multi-channel heat exchange of internal heat of flue gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 This is a schematic structural diagram of the solid waste pyrolysis system in Example 1;

[0063] Figure 2 Schematic diagram of the solid waste pyrolysis system structure in Comparative Example 1;

[0064] As shown in the figure, the symbols are: rotary kiln pyrolysis reactor 1, mixed gas heating jacket 1a, pyrolysis heating jacket 1b, rotary kiln burner 1c, cyclone cooler 2, fluidized bed 3, cyclone separator 4, fluidizing air fan 5, discharge conveying device 6, second flue gas fan 7, second air fan 8, hot blast furnace 9, hot blast furnace burner 9a, heat exchanger 10, exhaust flue gas fan 11, first air fan 12, first flue gas fan 13, back-mixing flue gas fan 14, and heat recovery device 15. DETAILED DESCRIPTION

[0065] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples where specific conditions are not specified were performed according to conventional methods and conditions, or selected according to the product specifications.

[0066] Example 1

[0067] A solid waste pyrolysis system, such as Figure 1 The invention comprises a rotary kiln pyrolysis reactor 1, a cyclone cooler 2, a fluidized bed 3, a cyclone separator 4 and a hot air furnace 9, etc.

[0068] In this embodiment, the rotary kiln pyrolysis reactor 1 is provided with a mixed gas heating jacket 1a and a pyrolysis heating jacket 1b, and the pyrolysis heating jacket 1b is located downstream of the mixed gas heating jacket 1a in the material flow direction. The rotary kiln pyrolysis reactor 1 is provided with a solid waste feed port, a first mixed flue gas recovery port, a pyrolysis flue gas discharge port, and a coarse pyrolysis solid waste discharge port; the mixed gas heating jacket 1a is provided with a combustion flue gas inlet, a mixed flue gas outlet, and a heating flue gas inlet; the pyrolysis heating jacket 1b is provided with a rotary kiln burner 1c and a heating flue gas discharge port, the heating flue gas discharge port is connected to the heating flue gas inlet, the rotary kiln burner 1c is provided with a combustion gas feed port and a fuel feed port, the combustion gas feed port of the rotary kiln burner 1c is connected to the first air blower 12 via a first combustion gas pipeline, the first combustion gas pipeline is provided with a heat exchanger 10, and the pipe inlet and outlet of the heat exchanger 10 are provided on the first combustion gas pipeline.

[0069] In this embodiment, the fuel entering the fuel feed port of the rotary kiln burner 1c is natural gas; in other embodiments, the fuel may be heavy oil. In this embodiment, the number of rotary kiln burners 1c is two; in other embodiments, the number of rotary kiln burners 1c may be one to four. In this embodiment, the effective heat exchange area ratio of the mixed gas heating jacket 1a to the pyrolysis heating jacket 1b is 2:1; in other embodiments, it may be any value between (1-3):1. In this embodiment, the cyclone cooler 2 is provided with a pyrolysis flue gas inlet, a pyrolysis flue gas outlet, and a first solids recovery outlet, and a cooling jacket is provided externally to the cyclone cooler 2. In this embodiment, the fluidized bed 3 is provided with a crude pyrolysis solid waste inlet, a fluidizing gas inlet, a solids recovery outlet, a fluidizing gas outlet, and a pyrolysis solid waste outlet; the fluidizing gas inlet is connected to the fluidizing air blower 5, and the pyrolysis solid waste outlet is connected to the discharge conveyor 6. In this embodiment, the discharge conveyor 6 is a screw discharger. In this embodiment, the cyclone separator 4 is provided with a mixed gas inlet, a mixed gas outlet, and a second solids recovery outlet.

[0070] In this embodiment, the pyrolysis flue gas outlet of the rotary kiln pyrolysis reactor 1 is connected to the pyrolysis flue gas inlet of the cyclone cooler 2; the crude pyrolysis solid waste outlet of the rotary kiln pyrolysis reactor 1 is connected to the crude pyrolysis solid waste inlet of the fluidized bed 3; the first solid recovery outlet of the cyclone cooler 2 is connected to the crude pyrolysis solid waste inlet of the fluidized bed 3; the fluidizing gas outlet of the fluidized bed 3 is connected to the mixed gas inlet of the cyclone separator 4; and the second solid recovery outlet of the cyclone separator 4 is connected to the solid recovery inlet of the fluidized bed 3. The mixed flue gas outlet of the mixed gas heating jacket 1a is connected to the first mixed flue gas recovery inlet via a first flue gas pipeline. The shell-side inlet and outlet of the heat exchanger 10 are located on the first flue gas pipeline. A heat recovery unit 15 and a first flue gas fan 13 are also provided on the first flue gas pipeline, downstream of the heat exchanger 10 in the material flow direction. A second flue gas branch pipe is provided between the heat recovery unit 15 and the first flue gas fan 13, and an exhaust flue gas fan 11 is provided on the second flue gas branch pipe.

[0071] In this embodiment, the raw waste salt is pretreated (drying, screening, crushing, etc.) and then fed into the rotary kiln pyrolysis reactor 1 for pyrolysis. The pyrolysis reaction temperature is 500-700°C, the residence time is 1-3h, and the operating pressure is -300-300Pa (slightly positive pressure or slightly negative pressure). The pyrolysis salt obtained after pyrolysis is fed into the fluidized bed 3. In this embodiment, external air is fed into the fluidized bed 3 by the fluidizing air blower 5, and directly contacts and exchanges heat with the pyrolysis salt. The operating pressure of the fluidized bed 3 is -300--50Pa (slightly negative pressure operation), and the fluidization number of the fluidized bed 3 is 1-4. After heat exchange, the pyrolysis salt is cooled to 150-350°C, and the fluidizing air is heated to 300-500°C. At the same time, under the action of the fluidizing air, the pyrolysis carbon and organic matter in the pyrolysis salt are further oxidized, thereby achieving deep removal of organic matter. In this embodiment, the cooled pyrolysis salt is cooled to 40-80°C through the water-cooled discharge spiral jacket of the discharge conveyor 6 and sent to the downstream inorganic impurity removal system. The water-cooled discharge spiral jacket and the central axis of the discharge conveyor 6 are cooled by cooling water to increase the heat exchange area. The water-cooled discharge spiral can be single, two or three. In this embodiment, the preheated fluidized air is sent to the hot blast furnace 9 to be used as part of the combustion air after removing salt particles through the cyclone separator 4. In this embodiment, the pyrolysis flue gas containing some salt particles generated by the rotary kiln pyrolysis reactor 1 enters the cyclone cooler 2 to remove salt particles. The outer jacket of the cyclone cooler 2 is cooled by cooling water to cool the pyrolysis flue gas to 200-300°C. After cooling and dust removal, the pyrolysis flue gas is sent to the hot blast furnace 9 by the second flue gas fan 7.

[0072] In this embodiment, the rotary kiln pyrolysis reactor 1 uses a mixed flue gas as a protective gas, and the oxygen content of the mixed flue gas is 8-15 vol%. The pyrolysis flue gas (including CO, H2, CO2, condensable organic matter, etc.) and a small amount of pyrolytic carbon produced by pyrolysis will react with some of the oxygen present in the mixed flue gas, providing some of the heat required for pyrolysis and improving the removal efficiency of organic matter. In this embodiment, the pyrolysis heating jacket 1b is directly heated by the high-temperature flue gas generated by the fuel combustion of the rotary kiln burner 1c to increase the residence time of the raw waste salt in the high-temperature section and enhance the removal of organic pollutants. In this embodiment, the combustion air required by the rotary kiln burner 1c is preheated to 200-450°C via the heat exchanger 10. The heated flue gas generated by the combustion has a temperature of 700-900°C. This heated flue gas enters the mixed gas heating jacket 1a after heat exchange, and after mixing with the combustion flue gas from the hot blast furnace 9, it provides the additional heat required for pyrolysis in the rotary kiln pyrolysis reactor 1. By adjusting the temperature and volume of the combustion flue gas, the raw material waste salt can be dehydrated and preheated, improving its adaptability to the water content of the raw material waste salt. In this embodiment, the raw material temperature is raised to 300-600°C after passing through the mixed gas heating jacket 1a.

[0073] In this embodiment, the hot blast furnace 9 is provided with a hot blast furnace burner 9a, a pyrolysis flue gas feed port, a second mixed flue gas recovery port, and a combustion flue gas discharge port. The hot blast furnace burner 9a is provided with a fuel feed port and a combustion-supporting gas feed port. The combustion-supporting gas feed port of the hot blast furnace burner 9a is connected to the second air blower 8 via a second combustion-supporting gas pipeline. In this embodiment, the pyrolysis flue gas outlet of the cyclone cooler 2 is connected to the pyrolysis flue gas feed port of the hot blast furnace 9 via a second flue gas pipeline, and a second flue gas blower 7 is provided on the second flue gas pipeline; the mixed gas outlet of the cyclone separator 4 is connected to the combustion-supporting gas feed port of the hot blast furnace burner 9a; the first flue gas pipeline is provided with a first flue gas branch pipe between the heat recovery device 15 and the first flue gas blower 13, and a back-mixed flue gas blower 14 is provided on the first flue gas branch pipe. The first flue gas branch pipe is connected to the second mixed flue gas recovery port of the hot blast furnace 9.

[0074] In this embodiment, the hot blast furnace burner 9a uses natural gas as fuel and is equipped with a second air blower 8 for adjusting the combustion air volume. In this embodiment, the second recovery port of the mixed flue gas of the hot blast furnace 9 introduces a path of mixed flue gas to reduce NO by recycling the flue gas. xGeneration. In this embodiment, the temperature of the combustion flue gas at the combustion flue gas outlet of the hot blast furnace 9 is 800-1000°C, and the combustion flue gas enters the combustion flue gas inlet of the mixed gas heating jacket 1a, mixes with the heating flue gas generated by the rotary kiln burner 1c, and provides part of the heat required for pyrolysis. In this embodiment, after the mixed flue gas in the mixed gas heating jacket 1a exchanges heat, it leaves the mixed gas heating jacket 1a and enters the heat exchanger 10 to exchange heat with the combustion air required by the rotary kiln burner 1c. In this embodiment, the temperature of the mixed flue gas after heat exchange in the heat exchanger 10 is 200-450°C. The mixed flue gas leaving the heat exchanger 10 enters the downstream heat recovery device 15, exchanges heat with the cooling water to recover waste heat. After heat exchange, the cooling water temperature rises to 50-80°C, which is used for inorganic impurity removal system salt. In this embodiment, after two heat exchanges, the temperature of the mixed flue gas drops to 120-250°C. After leaving the heat recovery unit 15, a portion of the mixed flue gas is delivered to the rotary kiln pyrolysis reactor 1 via the first flue gas blower 13 as a shielding gas, a portion is delivered to the hot blast furnace 9 via the back-mixed flue gas blower 14, and the remainder is delivered to the downstream flue gas purification system via the exhaust flue gas blower 11. In this embodiment, the flue gas back-mixed into the hot blast furnace accounts for 5%-35% of the total flue gas flowing out of the heat recovery unit 15, and the flue gas entering the rotary kiln pyrolysis reactor 1 as a shielding gas accounts for 0.5%-3% of the total flue gas flowing out of the heat recovery unit 15.

[0075] Example 2

[0076] A solid waste pyrolysis method, which uses the solid waste pyrolysis system in Example 1, comprises the following steps:

[0077] S1. After pretreatment (drying, screening, crushing, etc.), the waste salt is sent to the rotary kiln pyrolysis reactor 1 for pyrolysis to produce crude pyrolysis salt and pyrolysis flue gas; the waste salt is mainly composed of NaCl, with a water content of 4wt% and an organic matter content of 1.5wt%, and a processing capacity of 2.8t / h; the pyrolysis temperature is 700°C (based on the material temperature at the crude pyrolysis solid waste discharge port), the residence time is 1.5h, the operating pressure is -300~300Pa, and the pyrolysis flue gas flow rate generated by pyrolysis is 220Nm 3 / h, the pyrolysis flue gas is cooled to 250℃ by cyclone cooler 2. Among them, the total natural gas consumption of rotary kiln burner 1c is 47.6Nm 3 / h, the temperature of the heated flue gas produced by combustion is 900℃, and the amount of heated flue gas produced is 2100Nm 3 / h.

[0078] S2. In the fluidized bed 3, the crude pyrolysis solid waste is fluidized to produce pyrolysis solid waste and fluidizing gas; the operating pressure of the fluidized bed 3 is -300 to -50 Pa, the fluidization number of the fluidized bed 3 is 3, the temperature of the combustion-supporting gas generated by the fluidizing gas through the mixed gas outlet of the cyclone separator 4 is 470°C, the temperature of the pyrolysis salt generated at the pyrolysis solid waste outlet of the fluidized bed 3 is 200°C, and it is further cooled to 60°C through the discharge conveying device 6 and enters the downstream inorganic impurity removal system.

[0079] S3, the combustion-supporting gas and pyrolysis flue gas are sent to the hot blast furnace 9 for combustion, and the generated combustion flue gas is used to heat the rotary kiln pyrolysis reactor 1; wherein, the natural gas consumption of the hot blast furnace burner 9a is 61.6Nm 3 / h, the temperature of the combustion flue gas generated by the combustion flue gas outlet of the hot blast furnace 9 is 950℃, and the flow rate is 2700Nm 3 / h;

[0080] S4, after the combustion flue gas is heated in the mixed gas heating jacket 1a to heat the pyrolysis reactor 1, the total amount of mixed flue gas is 4800Nm 3 / h, containing 13 vol% oxygen, with a temperature of 520°C. The mixed flue gas passes through the heat exchanger 10 to preheat the combustion air required by the rotary kiln burner 1c to 420°C. The mixed flue gas is then cooled to 250°C by the heat recovery device 15. The cooling water medium temperature of the heat recovery device 15 is raised to 65°C and used for inorganic impurity removal system salt. Among them, 100Nm 3 / h mixed flue gas is recycled to the pyrolysis reactor 1 as protective gas, 1000Nm 3 / h of mixed flue gas is recovered to the hot blast furnace 9, and the rest enters the downstream flue gas purification system.

[0081] The natural gas consumption of this system per ton of waste salt treated is 39Nm 3 After the waste salt is treated by this system (before inorganic impurities are removed), the TOC content is 5.9ppm.

[0082] Comparative Example 1

[0083] Compared with Example 1, the main difference is that Figure 2 In this comparative example, the fluidized bed 3, the cyclone separator 4, and the fluidizing air blower 5 are not provided. The pyrolysis flue gas discharge port of the rotary kiln pyrolysis reactor 1 is directly connected to the discharge conveying device 6. The supporting combustion gas feed port of the hot blast furnace burner 9a is only connected to the second air blower 8 through the second supporting combustion gas pipeline. The solid waste pyrolysis method using the solid waste pyrolysis system in Comparative Example 1 includes the following steps:

[0084] S1. After pre-treatment (drying, screening, crushing, etc.), the waste salt is sent to the rotary kiln pyrolysis reactor 1 for pyrolysis to produce crude pyrolysis salt and pyrolysis flue gas; the waste salt is mainly composed of NaCl, with a water content of 4wt% and an organic matter content of 1.5wt%, and a processing capacity of 2.8t / h; the pyrolysis temperature is 700°C (based on the material temperature at the crude pyrolysis solid waste discharge port), the residence time is 1.5h, the operating pressure is -300~300Pa, and the flow rate is 100Nm 3 / h, the flue gas containing 13 vol% oxygen is used as the protective gas, and the flue gas flow rate generated by pyrolysis is 220 Nm 3 / h; of which the total natural gas consumption of rotary kiln burner 1c is 47.6Nm 3 / h, the temperature of the heated flue gas produced by combustion is 900℃, and the amount of heated flue gas produced is 2100Nm 3 / h, the total amount of mixed flue gas generated by the mixed flue gas outlet of the mixed gas heating jacket 1a is 4900Nm 3 / h, the temperature is 525℃, the combustion air required by the rotary kiln burner 1c is preheated to 420℃ through the heat exchanger 10, and the mixed flue gas is then cooled to 250℃ through the heat recovery device 15, and the latter part enters the downstream flue gas purification system.

[0085] S2, the pyrolysis flue gas generated in step S1 is sent to the hot blast furnace 9 for combustion, and the generated combustion flue gas is used to heat the rotary kiln pyrolysis reactor 1; the temperature of the mixed flue gas entering the second recovery port is 250 ° C, and the flow rate is 1090Nm 3 / h, natural gas consumption of hot blast stove burner 9a is 93.8Nm 3 / h, the temperature of the combustion flue gas generated by the combustion flue gas outlet of the hot blast furnace 9 is 950℃, and the flow rate is 2800Nm 3 / h; the crude pyrolysis salt is further cooled to 60°C through the discharge conveying device 6 and enters the downstream inorganic impurity removal system.

[0086] The natural gas consumption of this system per ton of waste salt treated is 50.5Nm 3 After the waste salt is treated by this system (before inorganic impurities are removed), the TOC content is 21ppm.

Claims

1. A solid waste pyrolysis system, characterized in that: It includes a pyrolysis reactor, a fluidized bed and a hot air furnace; The pyrolysis reactor is provided with a solid waste feed port, a first mixed flue gas recovery port, a pyrolysis flue gas discharge port and a coarse pyrolysis solid waste discharge port; the pyrolysis reactor is provided with a mixed gas heating jacket, and the mixed gas heating jacket is provided with a combustion flue gas inlet and a mixed flue gas outlet; The fluidized bed is provided with a crude pyrolysis solid waste inlet, a fluidizing gas inlet, a fluidizing gas outlet and a pyrolysis solid waste outlet; the hot blast furnace is provided with a hot blast furnace burner, a pyrolysis flue gas inlet, a second mixed flue gas recovery port and a combustion flue gas outlet; The pyrolysis flue gas outlet of the pyrolysis reactor is connected to the pyrolysis flue gas inlet of the hot blast furnace, the crude pyrolysis solid waste outlet of the pyrolysis reactor is connected to the crude pyrolysis solid waste inlet of the fluidized bed; the fluidizing gas outlet of the fluidized bed is connected to the supporting gas inlet of the hot blast furnace burner; The combustion flue gas discharge port of the hot blast furnace is connected to the combustion flue gas inlet of the mixed gas heating jacket, and the mixed flue gas outlet of the mixed gas heating jacket is connected to the first mixed flue gas recovery port of the pyrolysis reactor through a first flue gas pipeline; a first flue gas branch pipe is provided on the first flue gas pipeline, and the first flue gas branch pipe is connected to the second mixed flue gas recovery port of the hot blast furnace.

2. The solid waste pyrolysis system according to claim 1, characterized in that: It also includes a cyclone cooler, which is provided with a pyrolysis flue gas inlet, a pyrolysis flue gas outlet and a first solid recovery outlet; the cyclone cooler is preferably provided with a cooling jacket; The pyrolysis flue gas outlet of the pyrolysis reactor is connected to the pyrolysis flue gas inlet of the cyclone cooler, the pyrolysis flue gas outlet of the cyclone cooler is connected to the pyrolysis flue gas feed inlet of the hot blast furnace through a second flue gas pipeline, and the first solid recovery outlet of the cyclone cooler is connected to the coarse pyrolysis solid waste inlet of the fluidized bed; The second flue gas pipeline is preferably provided with a second flue gas fan.

3. The solid waste pyrolysis system according to claim 1, characterized in that: It also includes a cyclone separator, the cyclone separator is provided with a mixed gas inlet, a mixed gas outlet and a second solid recovery outlet; the fluidized bed is also provided with a solid recovery outlet; The fluidizing gas outlet of the fluidized bed is connected to the mixed gas inlet of the cyclone separator, the mixed gas outlet of the cyclone separator is connected to the combustion gas feed port of the hot blast furnace burner, and the second solid recovery outlet of the cyclone separator is connected to the solid recovery port of the fluidized bed.

4. The solid waste pyrolysis system according to claim 1, characterized in that: The fluidizing gas inlet of the fluidized bed is connected to the fluidizing gas blower; The pyrolysis solid waste outlet of the fluidized bed is connected to the feed port of the discharge conveying device; the discharge conveying device is preferably a screw discharger; the discharge conveying device is preferably provided with a water-cooling jacket; the discharge port of the discharge conveying device is preferably connected to an inorganic impurity removal system; The combustion-supporting gas feed port of the hot blast stove burner is preferably also connected to a second blower.

5. The solid waste pyrolysis system according to claim 1, characterized in that: A pyrolysis heating jacket is further provided outside the pyrolysis reactor, and the pyrolysis heating jacket is located downstream of the material flow of the mixed gas heating jacket. The pyrolysis heating jacket is provided with a rotary kiln burner and a heating flue gas discharge port; the mixed gas heating jacket is also provided with a heating flue gas inlet; The heating flue gas outlet of the pyrolysis heating jacket is connected to the heating flue gas inlet of the mixed gas heating jacket, and the supporting gas feed port of the rotary kiln burner is connected to the first fan through a first supporting gas pipeline.

6. The solid waste pyrolysis system according to claim 5, characterized in that: A heat exchanger is provided on the first combustion-supporting gas pipeline; the tube-side inlet and outlet of the heat exchanger are arranged on the first combustion-supporting gas pipeline, and the shell-side inlet and outlet of the heat exchanger are arranged on the first flue gas pipeline.

7. The solid waste pyrolysis system according to claim 1, characterized in that: The first flue gas pipeline is also provided with a heat recovery device and a first flue gas fan; A second flue gas branch pipe is preferably provided between the heat recovery device and the first flue gas fan; and an exhaust flue gas fan is preferably provided on the second flue gas branch pipe; The first flue gas branch pipe is preferably provided with a back-mixing flue gas fan.

8. A solid waste pyrolysis method, characterized in that: The solid waste pyrolysis system according to any one of claims 1 to 7 is used, comprising the following steps: S1. Pyrolyzing solid waste in the pyrolysis reactor to produce crude pyrolysis solid waste and pyrolysis flue gas; S2. Fluidizing the crude pyrolysis solid waste in the fluidized bed to generate pyrolysis solid waste and fluidizing gas; S3, burning in the hot blast furnace to generate combustion flue gas; S4. After the combustion flue gas is heated by the mixed gas heating jacket on the pyrolysis reactor, the obtained mixed flue gas is partially recovered into the pyrolysis reactor and the hot blast furnace.

9. The solid waste pyrolysis method according to claim 8, characterized in that: It meets one or more of the following conditions: (1) In step S1, the solid waste includes salt; the salt is preferably NaCl; (2) In step S1, the solid waste includes organic matter; the mass content of the organic matter is preferably 1-1.5%; (3) In step S1, the solid waste includes water; the mass content of the water is preferably 4-5%; (4) In step S1, the flow rate of the solid waste is 2.5-2.8 t / h; (5) In step S1, the pyrolysis temperature is 500-700°C; (6) In step S1, the residence time of the pyrolysis reactor is 1-3 hours, for example, 1.5 hours; (7) In step S1, the pressure in the pyrolysis reactor is -300 to 300 Pa; (8) In step S1, the flow rate of the pyrolysis flue gas is 220-250 Nm 3 / h; (9) In step S1, the pyrolysis flue gas includes CO, H2, CO2, condensable organic matter and pyrolysis carbon; (10) In step S2, the pressure in the fluidized bed is -300 to -50 Pa; (11) In step S2, the fluidization number of the fluidized bed is 1-4, for example, 3; (12) In step S2, the temperature of the pyrolyzed solid waste is 150-350°C, for example, 200°C; (13) In step S2, the temperature of the fluidizing gas is 300-500°C, for example, 470°C; (14) In step S3, the temperature of the combustion flue gas is 800-1000°C, for example, 950°C; (15) In step S3, the flow rate of the combustion flue gas is 2700-2800 Nm 3 / h; (16) In step S3, the oxygen content of the combustion flue gas is 8-15 vol%, for example, 13 vol%; (17) In step S4, the flow rate of the mixed flue gas is 4800-4900 Nm 3 / h; (18) In step S4, the temperature of the mixed flue gas is 520-525°C; (19) In step S4, the mixed flue gas recovered into the pyrolysis reactor accounts for 0.5%-3% of the total mixed flue gas, for example, 2.08%; (20) In step S4, the mixed flue gas recovered into the hot blast furnace accounts for 5%-35% of the total mixed flue gas, for example, 20.8%.

10. The solid waste pyrolysis method according to claim 8 or 9, characterized in that: It meets one or more of the following conditions: (1) When a pyrolysis heating jacket is provided outside the pyrolysis reactor, the temperature of the heating flue gas generated by the pyrolysis heating jacket is 700-900°C; further, when the solid waste pyrolysis system further includes a heat exchanger, the temperature of the combustion gas required by the pyrolysis heating jacket is heated to 200-450°C, for example, 420°C, by the heat exchanger; (2) When a pyrolysis heating jacket is provided outside the pyrolysis reactor, the flow rate of the heating flue gas generated by the pyrolysis heating jacket is 2000-2100 Nm 3 / h; (3) When the solid waste pyrolysis system further includes a cyclone cooler, the temperature of the pyrolysis flue gas is cooled to 200-300° C., for example, 250° C., by the cyclone cooler; (4) When the solid waste pyrolysis system further includes a discharge conveying device, the temperature of the pyrolyzed solid waste is cooled to 40-80° C., for example, 60° C., by the discharge conveying device; (5) When the solid waste pyrolysis system further includes a heat recovery device, the temperature of the mixed flue gas is cooled to 150-250°C by the heat recovery device; further, the temperature of the medium in the heat recovery device is raised to 50-80°C, for example, 65°C.

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