A roasting device and a roasting method for roasting industrial waste salt

Abstract

The invention discloses a roasting device and a roasting method for roasting industrial waste salts. The device comprises a lower hopper and a vertical furnace barrel. The inner cavity of the vertical furnace barrel is provided with a rotating cone, a collecting hopper and a distribution cone arranged from top to bottom to achieve material dispersion and collection, and form multiple temperature intervals for oxygen-deficient or oxygen-enriched roasting of waste salts. The vertical roasting device of the invention has a unique structure, ensures efficient heat and mass transfer in the furnace, improves the thermal decomposition efficiency of organic matter and the thermal energy utilization efficiency, and solves the problems of equipment corrosion and secondary pollution during the roasting process.

Description

Technical Field

[0001] The invention relates to a method for treating solid waste and hazardous waste, and in particular to equipment and a method for roasting industrial waste salts. Background Art

[0002] At present, there are four methods for treating chemical by-product salt slag: ① Extraction of organic matter: Use solvent to extract organic matter from waste salt slag to remove toxic and harmful chemicals in the salt slag as much as possible. This method has a small scope of application, the extractant will cause secondary pollution, and the organic matter is not completely removed; ② High-temperature oxidation method: Use thermal equipment such as rotary kilns and boiling furnaces to calcine waste salt at a high temperature of more than 800°C, so that the organic matter in the waste salt is decomposed and oxidized into gaseous components at high temperature. However, some impure salts have low melting points, and phenomena such as melting, ringing, and agglomeration occur, which affects the rotary kiln or boiling furnace. The equipment is operating normally; ③ Molten state treatment method: The salt slag is heated to above the melting point through thermal equipment, and the organic harmful impurities are thermally decomposed and oxidized. This method has the disadvantages of high equipment investment, complex process, and high energy consumption; ④ Medium and low temperature pyrolysis method: This method treats the salt slag through a pyrolysis furnace below 600°C. Generally, the residence time is long, and the organic matter is thermally decomposed into volatile tail gas and separated from the solid salt, while the decomposed solid components remain on the surface of the solid salt. The disadvantages are insufficient oxygen supply, incomplete combustion, release of volatile organic matter, and difficulty in producing pure white salt. Equipment corrosion protection and secondary pollution prevention and control during the high-temperature roasting of industrial waste salt are also a big problem. Summary of the invention

[0003] Based on the shortcomings of the above-mentioned prior art, the present invention provides a roasting equipment and a roasting method for roasting industrial waste salts, aiming to ensure efficient heat and mass transfer in the furnace, improve the thermal decomposition efficiency of organic matter and the thermal energy utilization efficiency, and solve the problems of equipment corrosion and secondary pollution during the roasting process.

[0004] In order to achieve the purpose of the invention, the present invention adopts the following technical solution:

[0005] The invention discloses a roasting device for roasting industrial waste salts, which is characterized in that: the roasting device comprises a vertical furnace barrel, and a lower hopper with a top seal is fixed above the vertical furnace barrel;

[0006] The top of the lower hopper is connected with a feeding pipe, and a lower hopper is provided with a lowering screw driven by a lowering driving motor; a lower hopper inner feeding cone or a lower hopper inner scraper is provided in the lower hopper and below the outlet of the feeding pipe, and the lower hopper inner feeding cone or the lower hopper inner scraper is fixed on the lowering screw; the bottom of the lower hopper is a vent plate; a discharge port is provided at the center of the bottom of the lower hopper, and the lower hopper screw passes through the discharge port and extends into the inner cavity of the vertical furnace barrel, and a rotating cone is connected to the front end of the lowering screw;

[0007] A collecting hopper is provided in the inner cavity of the vertical furnace barrel and below the rotating cone, and the bottom end of the collecting hopper is open; a lower distribution cone is provided below the collecting hopper; a hot air flow inlet of a burner is provided on the side wall of the vertical furnace barrel, a hot air flow conduit is inserted into the hot air flow inlet of the burner, one end of the hot air flow conduit is used to connect to the hot air flow outlet of the burner, and the other end extends into the inner cavity of the vertical furnace barrel and is provided with a radial nozzle; the lower distribution cone is fixed above the hot air flow conduit, or fixed on the inner wall of the vertical furnace barrel;

[0008] The bottom of the vertical furnace barrel is bucket-shaped and is provided with a discharge port;

[0009] A waste gas outlet is arranged on the top of the lower hopper.

[0010] Furthermore, observation windows are provided on the side walls of the vertical furnace barrel and on the top of the lower hopper.

[0011] Furthermore, the collecting hopper is provided with a plurality of through holes.

[0012] Furthermore, the vertical furnace barrel is made of high-temperature resistant stainless steel, and the inner surface is provided with a protective layer solidified from high-aluminum refractory material.

[0013] Furthermore, the lower hopper is made of carbon steel or stainless steel with an anti-corrosion treatment on the surface, and the anti-corrosion treatment is enamel treatment, refractory mud coating treatment or high-temperature resistant plastic coating treatment, and the withstanding temperature is 250-350°C.

[0014] Furthermore, the feeding screw, rotating cone, collecting hopper, lower distribution cone, hot air flow duct, nozzle, distribution cone in the feeding hopper or scraper in the feeding hopper, discharge port and exhaust gas outlet are all made of materials resistant to high temperature salt corrosion; the materials resistant to high temperature salt corrosion are refractory cement, mullite felt, ordinary ceramics, alumina ceramics, silicon carbide ceramics, carbon steel with enameled surface or plasma sprayed ceramic film, or 310S stainless steel with silicon-aluminum refractory material coated on the surface or provided with a silicon carbide ceramic protective sleeve. The most preferred method is to form silicon carbide ceramics by molding and firing silicon carbide powder.

[0015] Furthermore, a thermocouple is arranged on the side wall of the vertical furnace barrel, and the thermocouple is provided with a protective sleeve of silicon carbide ceramic.

[0016] The method of roasting industrial waste salts by using the roasting equipment is as follows: it can be used for the oxygen-deficient roasting of industrial waste salts, and can also be used for the oxygen-enriched roasting of industrial waste salts;

[0017] The waste salt is transported to the sealed hopper through the Jiaolong elevator outside the furnace through the feeding pipe. The feeding drive motor drives the feeding screw to discharge the material. The material distribution cone or scraper in the hopper makes the material in the hopper evenly distributed. The rotating cone at the front end of the feeding screw makes the material scattered around the inner cavity of the vertical furnace barrel in a dispersed state, thereby improving the heat exchange efficiency.

[0018] The freely falling materials are collected in the center through the collecting hopper, and the heat exchange with the rising hot air flow is enhanced, and the upper and lower spaces in the furnace are isolated to form temperature zones;

[0019] The material passing through the center of the collecting hopper falls onto the lower distribution cone again and slides down to all sides to achieve uniform distribution and exchange heat with the hot air flow again;

[0020] When it is oxygen-deficient roasting: the burner uses natural gas or fuel oil as fuel, burns in air or pure oxygen, and maintains the residual oxygen content in the generated hot air flow to be no more than 1%; the waste salt is thermally decomposed in the vertical furnace barrel at 600-800℃ in the absence of oxygen, and the exhaust gas after roasting is drawn out from the exhaust gas outlet, purified by a bag filter, and catalytically burned at 250-400℃ before meeting the emission standards, or discharged as flue gas after secondary high-temperature combustion and heat exchange in a waste heat boiler;

[0021] When it is oxygen-enriched roasting: the burner uses natural gas as fuel and burns in pure oxygen, and the oxygen volume concentration in the tail gas after roasting is controlled to be 3-10%; the waste salt is thermally decomposed in an oxygen-enriched furnace at 600-750°C in a vertical furnace barrel; the tail gas after roasting is drawn out from the exhaust gas outlet, and is washed and purified to remove ammonia, carbon dioxide, nitrogen oxides, and sulfur dioxide. Part of the remaining oxygen-enriched gas returns to the oxygen supply pipeline for combustion, and part of it is discharged as flue gas after secondary high-temperature combustion and heat exchange; or, the tail gas after roasting is drawn out from the exhaust gas outlet, and is dry-purified in a filter bag to remove ammonia, nitrogen oxides, sulfur dioxide, and salt particles, and the tail gas is catalytically burned at 250-400°C before meeting the emission standards.

[0022] The vertical roasting equipment of the present invention has a unique structure, which ensures efficient heat and mass transfer in the furnace, improves the thermal decomposition efficiency of organic matter and the efficiency of thermal energy utilization, and solves the problems of equipment corrosion and secondary pollution during the roasting process. The beneficial effects of the present invention are specifically embodied in:

[0023] 1. Waste salt is transported to the sealed hopper through the Jiaolong elevator outside the furnace. The feeding drive motor drives the feeding screw to discharge the material. The motor speed adjusts the feeding speed. The material distribution cone or scraper in the hopper makes the material in the hopper evenly distributed. The rotating cone at the front end of the feeding screw makes the material scattered around the inner cavity of the vertical furnace barrel in a dispersed state, which improves the heat exchange efficiency, is conducive to improving the utilization rate of thermal energy, and reducing the upper gas temperature;

[0024] 2. The freely falling materials are collected in the center through the collecting hopper, and the heat exchange with the rising hot air flow is enhanced, and the upper and lower spaces in the furnace are isolated to form temperature zones;

[0025] 3. The material passing through the center of the collecting hopper falls onto the lower distribution cone again and slides to the surroundings to achieve uniform distribution, exchange heat with the hot air flow again, and quickly decompose organic matter;

[0026] 4. The high-temperature hot air flow generated by the burner is ejected through the hot air flow duct and radial nozzles. The materials accumulated at the bottom of the furnace are directly baked by the high-temperature gas to decompose the organic matter. The hot air flow continuously exchanges heat with the materials, and the air flow rises and falls in temperature. Finally, it is further cooled in the process of penetrating through the gaps at the bottom of the lower hopper and the pores of the material particles. The chlorides volatile at high temperature are completely condensed, and the exhaust gas is discharged from the exhaust gas outlet at the top of the lower hopper. Since the air flow has been filtered and humidified by the waste salt material, the particulate matter in the exhaust gas is basically removed, and then it is washed with acid to remove ammonia, washed with alkali to remove sulfur and nitrogen, and catalytically burned by pyrolysis gas, and finally the exhaust gas is purified to meet the emission standards.

[0027] 5. All parts of the equipment located in the high temperature zone above 300℃ are made of fire-resistant and high-temperature chloride salt corrosion-resistant materials, or are provided with fire-resistant and high-temperature chloride salt corrosion-resistant protective layers, which solves the problem of equipment corrosion; in the entire roasting equipment, the waste salt is completely isolated from the metal to avoid the reaction of metal oxides and chlorides to generate chlorine gas, and completely eliminate the risk of further generation of toxic and harmful halogenated compounds. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of the structure of a roasting device for roasting industrial waste salts according to the present invention;

[0029] Figure 2 Another schematic diagram of the structure of the roasting equipment for roasting industrial waste salts of the present invention;

[0030] Numbers in the figure: 1-vertical furnace barrel, 2-feed pipe, 3-discharging drive motor, 4-discharging screw, 5-rotating cone, 6-collecting hopper, 7-lower distribution cone, 8-nozzle, 9-hot air flow duct, 10-thermocouple, 11-discharge port, 12-waste gas outlet, 13A-discharging cone of the lower hopper, 13B-scraper inside the lower hopper, 14-air perforated plate, 15-observation window. DETAILED DESCRIPTION

[0031] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0032] like Figure 1 or Figure 2 As shown, the roasting equipment of the following embodiment includes a vertical furnace barrel 1, and a lower hopper with a top seal is fixed above the vertical furnace barrel 1;

[0033] The top of the lower hopper is connected to a feed pipe 2, and a feed screw 4 driven by a feed drive motor 3 is arranged in the lower hopper; a feed cone 13A (such as Figure 1 as shown) or scraper 13B in the lower hopper (as shown Figure 2 As shown in the figure, a feeding cone 13A or a scraper 13B in the lower hopper is fixed on the lowering screw 4; the bottom of the lower hopper is a vent plate 14; a discharge port is arranged at the center of the bottom of the lower hopper, the lowering screw 4 passes through the discharge port and extends into the inner cavity of the vertical furnace barrel 1, and a rotating cone 5 is connected to the front end of the lowering screw 4;

[0034] A collecting hopper 6 is provided in the inner cavity of the vertical furnace barrel 1 and below the rotating cone 5, and the bottom end of the collecting hopper 6 is open; a lower distribution cone 7 is provided below the collecting hopper 6; a hot air flow inlet of a burner is provided on the side wall of the vertical furnace barrel 1, and a hot air flow conduit 9 is inserted into the hot air flow inlet of the burner, one end of the hot air flow conduit 9 is used to connect to the hot air flow outlet of the burner, and the other end extends into the inner cavity of the vertical furnace barrel 1 and is provided with a radial nozzle 8; the lower distribution cone 7 is fixed above the hot air flow conduit 9, or fixed on the inner wall of the vertical furnace barrel;

[0035] The bottom of the vertical furnace barrel 1 is bucket-shaped and is provided with a discharge port 11;

[0036] An exhaust gas outlet 12 is provided at the top of the lower hopper.

[0037] A thermocouple 10 is arranged on the side wall of the vertical furnace drum 1 .

[0038] In a specific implementation, observation windows 15 are provided on the side walls of the vertical furnace drum 1 and on the top of the lower hopper.

[0039] In a specific implementation, a plurality of through holes may be provided on the collecting hopper 6. The provision of the through holes allows part of the hot air flow to rise from the through holes, resulting in a better heat exchange effect and avoiding the hot air flow being concentrated in the center, resulting in a higher central air velocity.

[0040] In the specific implementation, the vertical furnace barrel 1 is made of high-temperature resistant stainless steel, and the inner surface is provided with a protective layer solidified by high-aluminum refractory material. Specifically, the vertical furnace barrel is made of high-temperature resistant stainless steel, 5 cm long claw nails are welded on the inner surface at 10 cm intervals, and then a 10 cm thick mud paste made of high-aluminum refractory material is coated, which serves as a fire-resistant and high-temperature salt corrosion-resistant protective layer after solidification.

[0041] In a specific implementation, the lower hopper is made of carbon steel or stainless steel with an anti-corrosion treatment on the surface, and the anti-corrosion treatment is enamel treatment, refractory mud coating treatment or high temperature resistant plastic coating treatment. Specifically, in the following embodiments, the lower hopper is made of stainless steel, and the surface of the air perforated plate 14 on the inner wall and the bottom is enameled and can withstand a temperature of 350°C.

[0042] In a specific implementation, the material feeding screw 4, the rotating cone 5, the collecting hopper 6, the lower material distribution cone 7, the hot air flow conduit 9, the nozzle 8, the material distribution cone 13A in the feeding hopper or the scraper 13B in the feeding hopper, the material outlet 11 and the exhaust gas outlet 12 are all made of materials resistant to high temperature salt corrosion. Specifically, silicon carbide ceramics are used as the material in the following embodiments.

[0043] Example 1

[0044] This example selects typical industrial waste salts and uses Figure 1 The roasting equipment shown was used for anoxic roasting experiments, and the results of the impurity salt analysis test were: sodium chloride 85.3%, potassium chloride 1.1%, organic matter 12.7%, and other impurities 0.9%.

[0045] The burner uses natural gas as fuel and burns in the air. The air-fuel ratio of the burner is close to the theoretical ratio, and the oxygen excess coefficient in the generated hot air flow is maintained at no more than 1%; the temperature of the roasting salt accumulation part at the bottom of the vertical furnace barrel is controlled to be 650-750°C, the temperature above the collecting hopper 6 is lower than 400°C, the temperature at the air perforated plate at the bottom of the lower hopper is less than 250°C, and the temperature at the exhaust gas outlet 12 is less than 150°C.

[0046] The organic matter in the waste salt is thermally decomposed in a high temperature and oxygen-deficient environment, and the inorganic impurities ammonium salts, nitrates, and sulfates are decomposed into ammonia, nitrogen oxides, and SO2;

[0047] Ultrafine sodium carbonate is sprayed into the tail gas after roasting discharged from the exhaust gas outlet 12, and dry desulfurization and denitrification are carried out in the bag filter; the organic matter in the gas is then catalytically burned at 280-350°C, and the gas is discharged in compliance with the emission standards after heat exchange.

[0048] Example 2

[0049] This example selects typical industrial waste salts and uses Figure 2 The calcination equipment shown in the figure was used to carry out an oxygen-enriched calcination experiment, and the impurity salt composition was the same as that in Example 1:

[0050] The burner uses natural gas as fuel and burns in pure oxygen to control the oxygen volume concentration in the tail gas after roasting to 3-10%; the temperature of the roasting salt accumulation part at the bottom of the vertical furnace barrel is controlled to be 650-750°C, the temperature above the collecting hopper 6 is lower than 400°C, the temperature at the air perforated plate at the bottom of the lower hopper is less than 250°C, and the temperature at the exhaust gas outlet 12 is less than 150°C.

[0051] The organic and inorganic impurities in the waste salts are thermally decomposed in a high-temperature oxygen-rich environment. The tail gas after roasting is drawn out from the exhaust gas outlet 12, and is washed and purified to remove ammonia, carbon dioxide, nitrogen oxides, and sulfur dioxide. 90% of the remaining oxygen-rich gas is returned to the oxygen supply pipeline for combustion, and 10% is burned for secondary high-temperature heat exchange to meet emission standards.

[0052] Example 3

[0053] This example selects typical industrial waste salts and uses Figure 1 The calcination equipment shown in the figure was used to carry out an oxygen-enriched calcination experiment, and the impurity salt composition was the same as that in Example 1:

[0054] The burner uses natural gas as fuel and burns in pure oxygen to control the oxygen volume concentration in the tail gas after roasting to 3-10%; the temperature of the roasting salt accumulation part at the bottom of the vertical furnace barrel is controlled to be 650-750°C, the temperature above the collecting hopper 6 is lower than 400°C, the temperature at the air perforated plate at the bottom of the lower hopper is less than 250°C, and the temperature at the exhaust gas outlet 12 is less than 150°C.

[0055] The organic and inorganic impurities in the waste salt are thermally decomposed in a high-temperature oxygen-rich environment. The exhaust gas after roasting is drawn out from the exhaust gas outlet 12, and is dry-purified in the filter bag to remove ammonia, nitrogen oxides, sulfur dioxide, and salt particles. The exhaust gas is then catalytically burned and heat-exchanged at 250-350 degrees Celsius to meet emission standards.

Claims

1. A roasting device for roasting industrial waste salts, characterized in that: The roasting equipment comprises a vertical furnace barrel (1), and a lower hopper with a top seal is fixed above the vertical furnace barrel (1); The top of the lower hopper is connected to a feed pipe (2), and a lower hopper screw (4) driven by a lower hopper drive motor (3) is arranged in the lower hopper; a lower hopper inner material distribution cone (13A) or a lower hopper inner scraper (13B) is arranged in the lower hopper below the outlet of the feed pipe (2), and the lower hopper inner material distribution cone (13A) or the lower hopper inner scraper (13B) is fixed on the lower hopper screw (4); the bottom of the lower hopper is a vent plate (14); a discharge port is arranged at the center of the bottom of the lower hopper, the lower hopper screw (4) passes through the discharge port and extends into the inner cavity of the vertical furnace barrel (1), and a rotating cone (5) is connected to the front end of the lower hopper screw (4); A collecting hopper (6) is arranged in the inner cavity of the vertical furnace barrel (1) and below the rotating cone (5), the bottom end of the collecting hopper (6) is open, and a plurality of through holes are arranged on the collecting hopper (6); a lower distribution cone (7) is arranged below the collecting hopper (6); a hot air flow inlet of a burner is arranged on the side wall of the vertical furnace barrel (1), a hot air flow conduit (9) is inserted into the hot air flow inlet of the burner, one end of the hot air flow conduit (9) is used to connect to the hot air flow outlet of the burner, and the other end extends into the inner cavity of the vertical furnace barrel (1) and is provided with a radial nozzle (8); the lower distribution cone (7) is fixed above the hot air flow conduit (9), or fixed on the inner wall of the vertical furnace barrel; The bottom of the vertical furnace barrel (1) is bucket-shaped and is provided with a discharge port (11); An exhaust gas outlet (12) is provided at the top of the lower hopper; Observation windows (15) are provided on the side walls of the vertical furnace barrel (1) and on the top of the lower hopper.

2. A roasting equipment for roasting industrial waste salts according to claim 1, characterized in that: The vertical furnace barrel (1) is made of high-temperature resistant stainless steel, and the inner surface is provided with a protective layer formed by solidifying a high-aluminum refractory material.

3. A roasting equipment for roasting industrial waste salts according to claim 1, characterized in that: The lower hopper is made of carbon steel or stainless steel with an anti-corrosion treatment on the surface.

4. A roasting equipment for roasting industrial waste salts according to claim 3, characterized in that: The anti-corrosion treatment is enamel treatment, refractory mud coating treatment or high temperature resistant plastic coating treatment.

5. The roasting equipment for roasting industrial waste salts according to claim 1, characterized in that: The material discharging screw (4), the rotating cone (5), the collecting hopper (6), the lower material distributing cone (7), the hot air flow duct (9), the nozzle (8), the material distributing cone (13A) in the material discharging hopper or the scraper (13B) in the material discharging hopper, the material discharging port (11) and the waste gas outlet (12) are all made of materials resistant to high temperature salt corrosion.

6. A roasting equipment for roasting industrial waste salts according to claim 5, characterized in that: The material resistant to high temperature salt corrosion is refractory cement, mullite felt, ordinary ceramics, alumina ceramics, silicon carbide ceramics, carbon steel with enamel treatment or plasma sprayed ceramic film on the surface, or 310S stainless steel with silicon-aluminum refractory material coated on the surface or provided with a silicon carbide ceramic protective sleeve.

7. The roasting equipment for roasting industrial waste salts according to claim 1, characterized in that: A thermocouple (10) is arranged on the side wall of the vertical furnace barrel (1), and the thermocouple (10) is provided with a protective sleeve made of silicon carbide ceramic.

8. A method for roasting industrial waste salts using the roasting equipment according to any one of claims 1 to 7, characterized in that: It can be used for the oxygen-deficient roasting of industrial waste salts, and can also be used for the oxygen-enriched roasting of industrial waste salts; The waste salt is transported to the sealed discharge hopper through the Jiaolong elevator outside the furnace through the feeding pipe (2), and the discharge drive motor (3) drives the discharge screw (4) to discharge the material. The distribution cone (13A) or the scraper (13B) in the discharge hopper makes the material in the discharge hopper evenly distributed. The rotating cone (5) at the front end of the discharge screw (4) makes the material scattered around the inner cavity of the vertical furnace barrel (1) in a dispersed state, thereby improving the heat exchange efficiency. The freely falling materials are collected at the center through the collecting hopper (6), and the heat exchange with the rising hot air flow is enhanced, and the upper and lower spaces in the furnace are isolated to form temperature zones; The material passing through the center of the collecting hopper (6) falls again onto the lower distribution cone (7) and slides to the surroundings to achieve uniform distribution and exchange heat with the hot air flow again; When the anaerobic roasting is used: the burner uses natural gas or fuel oil as fuel, burns in air or pure oxygen, and maintains the residual oxygen content in the generated hot air flow to be no more than 1%; the waste salt is thermally decomposed in the vertical furnace barrel at 600-800°C in the absence of oxygen, and the exhaust gas after roasting is drawn out from the exhaust gas outlet (12), purified by a bag filter, catalytically burned at 250-400°C, and then discharged to meet the emission standards, or discharged as flue gas after secondary high-temperature combustion and heat exchange in a waste heat boiler; When the roasting is oxygen-enriched: the burner uses natural gas as fuel and burns in pure oxygen, and the oxygen volume concentration in the tail gas after roasting is controlled to be 3-10%; the waste salt is decomposed in oxygen-enriched heat at 600-750°C in a vertical furnace barrel; the tail gas after roasting is drawn out from the exhaust gas outlet (12), and is washed and purified to remove ammonia, carbon dioxide, nitrogen oxides, and sulfur dioxide. The remaining oxygen-enriched gas is partially returned to the oxygen supply pipeline for combustion, and partially combusted at a high temperature for secondary heat exchange and then discharged as flue gas; or, the tail gas after roasting is drawn out from the exhaust gas outlet (12), and is dry-purified in a filter bag to remove ammonia, nitrogen oxides, sulfur dioxide, and salt particles, and the tail gas is catalytically burned at 250-400°C before meeting the emission standards.

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