Microwave treatment and utilization method for cold rolling acid regeneration impurity removal sludge

Abstract

The invention discloses a microwave treatment and utilization method of cold-rolled acid regenerated impurity-removed sludge, which comprises the following steps: crushing the cold-rolled acid regenerated impurity-removed sludge, roasting the crushed cold-rolled acid regenerated impurity-removed sludge in a microwave kiln, and further sintering and utilizing the roasted iron-containing material; corrosive chlorine-containing gas generated by roasting is conveyed to the acid regeneration chlorine-containing gas treatment and utilization system to obtain hydrochloric acid, and tail gas generated by the acid regeneration chlorine-containing gas treatment and utilization system is discharged after reaching the standard. According to the invention, green electricity microwave roasting cold rolling acid regeneration impurity removal sludge is adopted, washing is not needed, the waste disposal amount is not increased, fuel gas is not used, extra waste is not added in the disposal process, pollutant discharge is reduced, and green electricity driving equipment does not occupy the carbon emission limit; microwave heating is uniform, the dechlorination effect is better under the same temperature roasting condition, the roasting temperature is lower under the same dechlorination effect condition, and energy consumption and carbon emission are reduced; the amount of flue gas generated by heating is small, the proportion of chlorine-containing gas is high, the concentration of hydrochloric acid obtained at a time is high, and energy consumption in the acid making process is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of waste utilization, and in particular relates to a microwave treatment and utilization method of cold rolling acid regeneration impurity removal sludge. Background Art

[0002] The waste liquid produced by the cold rolling mill of steel enterprises using hydrochloric acid to pickle strip steel has a pH of ﹤3, and its main component is FeCl 2 , and contains a small amount of FeCl 3 , HCl and trace amounts of SiO 2 The waste liquid needs to be reclaimed by spray roasting process. Impurity removal is to form Fe(OH) 3 After the impurities are adsorbed, the solid and liquid are separated by filter pressing. The pure liquid produced by separation is roasted to obtain high-purity Fe 2 O 3 The chlorine-containing gas produced by roasting is sold at a high price. After being treated by pre-concentrators, absorption towers, washing towers and other process equipment, it becomes HCl concentrate and is returned to the steel strip for pickling and reuse. The tail gas is discharged in compliance with the standards. The sludge produced by separation has high water content, high chlorine content and strong corrosiveness, and requires special treatment. The main treatment method at present is landfill. The main component of sludge is Fe(OH) 3 , FeO(OH) and a small amount of FeCl 3 and trace amounts of FeCl 2 、SiO 2 Landfill disposal not only wastes iron resources, the main component of sludge, but also occupies limited land resources.

[0003] Most of the iron-making raw materials of steel enterprises contain chlorine. The highest temperature of the sintering process of smelting reaches about 1350℃, which has excellent dechlorination effect and can remove about 90% of the chlorine in the raw materials. Therefore, some enterprises use the high-temperature dechlorination effect of sintering and perfect environmental protection facilities to directly return the acid regeneration and impurity removal sludge to sintering for disposal. However, the acid regeneration and impurity removal sludge is highly corrosive, and directly returning it to sintering will cause serious corrosion to the equipment entering the sintering process. At the same time, the acid regeneration and impurity removal sludge cannot be dried at a low temperature of ≤315℃ like ordinary sludge, because it contains FeCl which has strong water absorption. 3 After drying, it is easy to absorb water and deliquesce when exposed to air, causing blockage of equipment and affecting its application in sintering.

[0004] Application No. 200810024330.9 Acid-washed iron red desiliconized filter cake processing device and processing method invents a device and method in which a filter cake is fed into a burner on a roasting tower through a feeder, the filter cake is roasted, heated, dried and decomposed to generate iron oxide powder during the process of falling from the top of the tower, and the gas is absorbed by pure water spray and returned to the acid washing process. This invention only describes the functions of each device in the acid-washed iron red desiliconized filter cake processing device and processing method, lacks specific operating parameters for realizing the functions, and cannot guarantee the harmless disposal effect.

[0005] Application No. 202010568356.0 A method for treating desiliconized sludge from cold-rolled acid regeneration has been invented. The desiliconized sludge is washed with water and high pressure dehydrated at a water-solid ratio of 5 to 12:1 for 30 to 60 minutes, and then dechlorinated by gas roasting at 300 to 450°C for 30 to 60 minutes. The residue after roasting is used in metallurgical processes, and the flue gas is discharged through cooling, deacidification, and purification, and the generated dilute acid liquid is reused. First, the filtrate increases by about 5-12 times after water washing in this method. The filtrate is acidic and belongs to hazardous waste, which greatly increases the amount of hazardous waste generated. Secondly, in order to ensure the dechlorination effect, this method relies on long-term high-temperature roasting with gas, which consumes energy and increases pollutant emissions.

[0006] The acid regeneration impurity removal sludge has high viscosity and is dense after filtration. The roasting heating relies on heat conduction from the sludge surface to the inside, which can easily cause the "cold core" phenomenon where the outside of the sludge has reached the heating temperature but the inside has not. In the current research on roasting dechlorination and corrosion removal technology, gas roasting or electric heating, affected by the decreasing heat conduction, will gradually reduce the temperature and reaction rate during the process of entering the sludge, causing uneven heating inside and outside the sludge, affecting the effect. In order to improve the effect, gas roasting or electric heating will inevitably increase the temperature or extend the roasting time, increasing energy consumption and pollutant emissions. At the same time, a large amount of CO2-containing 2 Gas flue gas, flue gas emissions occupy the limited corporate carbon emission quota, limiting the application of gas roasting dechlorination technology in the disposal and utilization of acid regeneration and impurity removal sludge. Summary of the invention

[0007] The purpose of the present invention is to solve the above-mentioned technical problems and provide a microwave treatment and utilization method for cold-rolled acid regeneration and impurity removal sludge that can reduce pollution and carbon, thereby solving the technical defects of traditional heating methods that rely on increasing temperature or extending roasting time to remove the corrosiveness of sludge and increase energy consumption and pollutant emissions.

[0008] To achieve the above-mentioned purpose, the present invention provides a microwave treatment and utilization method for cold-rolled acid regeneration and impurity removal sludge. After the cold-rolled acid regeneration and impurity removal sludge is crushed, it enters a microwave kiln for roasting, and the iron-containing material after roasting is further sintered and utilized; the corrosive chlorine-containing gas generated by the roasting is transported to the acid regeneration and chlorine-containing gas treatment and utilization system to obtain hydrochloric acid, and the tail gas generated by the acid regeneration and chlorine-containing gas treatment and utilization system meets the emission standards. The acid regeneration and chlorine-containing gas treatment and utilization system is an existing process at the source of acid regeneration and impurity removal sludge generation. The main equipment includes a pre-concentration tower, an absorption tower, a washing tower, etc. The main purpose is to absorb the chlorine-containing gas in the gas through liquid and concentrate the liquid to increase the HCl content in the liquid, so that the liquid can be directly used for acid washing, and at the same time, the tail gas meets the emission standards.

[0009] The main reaction principle of the roasting process:

[0010] 2Fe(OH) 3 (s)=Fe 2 O 3 (s)+3H 2 O (g)

[0011] 2FeOOH(s)=Fe 2 O 3 (s)+H 2 O(g)

[0012] FeCl 3 6H 2 O(s)=FeCl 3 (s)+6H 2 O(g)

[0013] 2FeCl 3 (s)+3H 2 O(g)=Fe 2 O 3 (s)+6HCl(g)

[0014] Furthermore, the hydrochloric acid obtained by the acid regeneration chlorine-containing gas treatment and utilization system is transported to the steel pickling process; the waste liquid obtained in the pickling process is crushed after the cold rolling acid regeneration impurity removal sludge produced by impurity removal and separation enters the microwave kiln, and the pure liquid produced by the waste liquid after impurity removal and separation is roasted in the roasting furnace to obtain high-purity Fe 2 O 3 The chlorine-containing gas generated after roasting is transported to the acid regeneration chlorine-containing gas disposal and utilization system.

[0015] Furthermore, the water content of the cold rolling acid regeneration impurity removal sludge is 40-60%, the iron content of the dry sludge is 42-50%, and the chlorine content is 7-31%.

[0016] Furthermore, the particle size of the cold-rolled acid regeneration impurity removal sludge after crushing is less than 25 mm.

[0017] Furthermore, the width of the microwave kiln tube is 50 to 100 cm.

[0018] Furthermore, the microwave heating temperature of the microwave kiln is 315-400°C and the heating time is 6-10 minutes. 3 The decomposition temperature is 315℃, and the low temperature drying below 315℃ is because it contains FeCl3 which is highly hygroscopic. After drying, it is easy to absorb water and deliquesce in the air, which will block the equipment and affect the application in sintering. Therefore, the microwave heating temperature cannot be lower than 315℃.

[0019] Furthermore, the microwave heating system of the microwave kiln is vertically distributed to the kiln tube, and the microwaves generated by heating pass vertically through the kiln tube.

[0020] Furthermore, the microwave kiln body is made of 316L stainless steel, and the inner wall is sprayed with polytetrafluoroethylene; the microwave kiln tube is made of microwave-specific silicon carbide ceramic material, and the insulation system is made of ceramic fiber material; the main shaft and blades of the transmission system are made of stainless steel with glaze sprayed on the surface.

[0021] Furthermore, the cold-rolled acid regeneration and impurity removal sludge enters the crushing conveyor through a hopper, and the surface of the steel in contact with the hopper and the cold-rolled acid regeneration and impurity removal sludge is covered with a fiberglass layer; the crushing conveyor adopts a double-roller double-screw conveyor made of 316L grade or above corrosion-resistant stainless steel, and polytetrafluoroethylene is sprayed on the surface of the material in contact with the cold-rolled acid regeneration and impurity removal sludge.

[0022] Furthermore, the iron-containing material is cooled to ≤30°C and then transported to a raw material plant, mixed with other raw materials and sintered into a blast furnace for ironmaking, and the iron-containing material TFe after roasting is ≥55%.

[0023] Compared with the prior art, the present invention has the following beneficial effects: the present invention adopts green electricity microwave roasting to remove impurities from cold-rolled acid regeneration sludge, does not undergo water washing, does not increase the amount of waste to be disposed of, does not use gas, does not add extra waste during the disposal process, reduces pollutant emissions, and green electricity-driven equipment does not occupy carbon emission limits; microwave heating is uniform, and under the same temperature roasting conditions, the dechlorination effect is better, and under the same dechlorination effect conditions, the roasting temperature is lower, reducing energy consumption and carbon emissions; the amount of flue gas generated by heating is small, the proportion of chlorine-containing gas is high, and the concentration of hydrochloric acid obtained at one time is high, reducing the energy consumption of the acid-making process; the iron-containing material produced by roasting is sintered and utilized, reducing the amount of sintered iron ore used, and the utilization process does not cause corrosion to the equipment; the technical defects of traditional heating methods that rely on increasing the temperature or extending the roasting time to remove the corrosiveness of the sludge and increase energy consumption and pollutant emissions are solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a flowchart of the method for treating and utilizing cold rolling acid regeneration and impurity removal sludge by microwave method. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0026] Example 1

[0027] Start the microwave kiln, hopper, crushing conveyor, etc. The microwave kiln temperature is set to 330℃ and the insulation time is 10min. The dry sludge iron content in the cold rolling acid regeneration and impurity removal sludge is 42.3% and the Cl content is 23.8%. The cold rolling acid regeneration and impurity removal sludge is fed into the running crushing conveyor through the hopper and crushed to a particle size of less than 25mm, and then transported into the microwave kiln. The distributor in the microwave kiln evenly distributes the cold rolling acid regeneration and impurity removal sludge, and the material layer thickness is 40cm. Heating produces flue gas 98Nm 3 / h, and then discharged to the acid regeneration chlorine-containing gas disposal and utilization system for disposal and utilization. After the heating reaches the set conditions, the heating is automatically stopped and the discharging system is started. The iron content of the obtained material is 56.6%, and the Cl content is 0.8%. After the iron-containing material is cooled to 28°C, it is transported to the raw material plant and evenly mixed with other sintering raw materials for sintering utilization.

[0028] The hydrochloric acid obtained by the acid regeneration chlorine-containing gas treatment system is transported to the steel pickling process; the waste liquid obtained in the pickling process is separated by impurities to produce cold-rolled acid regeneration impurity sludge, which is crushed and enters the microwave kiln. The pure liquid produced by the waste liquid after impurity separation is roasted in the roasting furnace to obtain high-purity Fe 2 O 3 The chlorine-containing gas generated after roasting is transported to the acid regeneration chlorine-containing gas disposal and utilization system.

[0029] In this embodiment, the width of the microwave kiln tube is 50-100cm, and the microwave heating system of the microwave kiln is vertically distributed with the kiln tube; the microwave kiln body is made of 316L stainless steel, and the inner wall is sprayed with polytetrafluoroethylene; the microwave kiln tube is made of silicon carbide ceramic material for microwave, and the insulation system is made of ceramic fiber material; the main shaft and blades of the transmission system are made of stainless steel with glaze sprayed on the surface. The steel surface of the hopper in contact with the cold-rolled acid regeneration impurity removal sludge is covered with a glass fiber reinforced plastic layer; the crushing conveyor adopts a double-roller double-screw conveyor made of 316L grade or above corrosion-resistant stainless steel, and polytetrafluoroethylene is sprayed on the surface of the material in contact with the cold-rolled acid regeneration impurity removal sludge.

[0030] Example 2

[0031] The difference between Example 2 and Example 1 is that:

[0032] Start the microwave kiln, hopper, crushing conveyor, etc. The microwave kiln temperature is set to 360℃ and the insulation time is 8min. The dry sludge iron content in the cold rolling acid regeneration and impurity removal sludge is 43.5% and the Cl content is 22.6%. The cold rolling acid regeneration and impurity removal sludge is fed into the running crushing conveyor through the hopper and crushed to a particle size of less than 25mm, and then transported into the microwave kiln. The distributor in the microwave kiln evenly distributes the cold rolling acid regeneration and impurity removal sludge, and the material layer thickness is 60cm. Heating produces flue gas 99Nm 3 / h, and then discharged to the acid regeneration chlorine-containing gas disposal and utilization system for disposal and utilization. After the heating reaches the set conditions, the heating is automatically stopped and the discharging system is started. The iron content of the obtained material is 59.4%, and the Cl content is 0.4%. After the iron-containing material is cooled to 28°C, it is transported to the raw material plant and evenly mixed with other sintering raw materials for sintering and utilization.

[0033] Example 3

[0034] The difference between Example 3 and Example 1 is that:

[0035] Start the microwave kiln, hopper, crushing conveyor, etc. The temperature of the microwave kiln is set to 400℃ and the insulation time is 8 minutes. The dry sludge iron content in the cold rolling acid regeneration and impurity removal sludge is 46.3% and the Cl content is 26.5%. The cold rolling acid regeneration and impurity removal sludge is fed into the running crushing conveyor through the hopper and crushed to a particle size of less than 25mm, and then transported into the microwave kiln. The distributor in the microwave kiln evenly distributes the cold rolling acid regeneration and impurity removal sludge, and the material layer thickness is 40cm. Heating produces flue gas of 100Nm 3 / h, and then discharged to the acid regeneration chlorine-containing gas disposal and utilization system for disposal and utilization. After the heating reaches the set conditions, the heating is automatically stopped and the discharging system is started. The iron content of the obtained material is 63.2%, and the Cl content is 0.1%. After the iron-containing material is cooled to 30°C, it is transported to the raw material plant and evenly mixed with other sintering raw materials for sintering utilization.

[0036] Comparative Example 1

[0037] 1) Start the gas roasting furnace, feeding system, crushing system and supporting equipment, set the temperature to 330℃ and the insulation time to 20min;

[0038] 2) The TFe content in the acid regeneration impurity removal sludge is 42.3% and the Cl content is 23.8%. The special hopper for the acid regeneration impurity removal sludge is placed in the turning machine, and the turning machine is started to turn the sludge into the running double screw conveyor and transport it into the roasting furnace;

[0039] 3) Evenly distribute the material in the roasting furnace until the material layer thickness is 40cm;

[0040] 4) Start the roasting furnace heating system and exhaust system. Heating produces flue gas 1426Nm 3 / h, and discharged to the acid regeneration chlorine-containing gas disposal and utilization system for disposal and utilization;

[0041] 5) After the heating reaches the set conditions, the heating stops automatically and the material is discharged. The iron-containing material with TFe content of 52.8% and Cl content of 6.1% is obtained. After cooling to 28°C, the material is discharged to the transport vehicle;

[0042] 6) Transport to the raw material plant and mix evenly with other raw materials for sintering.

[0043] Comparative Example 2

[0044] 1) Start the electric heating roasting furnace, feeding system, crushing system and supporting equipment, set the temperature to 330°C and the insulation time to 30 minutes;

[0045] 2) The TFe content in the acid regeneration impurity removal sludge is 42.3% and the Cl content is 23.8%. The special hopper for the acid regeneration impurity removal sludge is placed in the turning machine, and the turning machine is started to turn the sludge into the running double screw conveyor and transport it into the electric heating roasting furnace;

[0046] 3) Evenly distribute the material in the electric heating roasting furnace until the material layer thickness is 40cm;

[0047] 4) Start the heating system and exhaust system of the electric heating roasting furnace. Heating produces flue gas 216Nm 3 / h, and discharged to the acid regeneration chlorine-containing gas disposal and utilization system for disposal and utilization;

[0048] 5) After the heating reaches the set conditions, the heating stops automatically and the material is discharged. The iron-containing material with TFe content of 52.2% and Cl content of 6.8% is obtained. After cooling to 28°C, the material is discharged to the transport vehicle;

[0049] 6) Transport to the raw material plant and mix evenly with other raw materials for sintering.

[0050] Partial test data of pickling filter cake

[0051]

Claims

1. A method for treating and utilizing cold rolling acid regeneration impurity removal sludge by microwave method, characterized in that: The cold-rolled acid regeneration impurity removal sludge is crushed and then enters the microwave kiln for roasting. The iron-containing material after roasting is further sintered and utilized. The corrosive chlorine-containing gas generated by roasting is transported to the acid regeneration chlorine-containing gas treatment and utilization system to obtain hydrochloric acid. The exhaust gas generated by the acid regeneration chlorine-containing gas treatment and utilization system meets the emission standards.

2. The method for treating and utilizing cold rolling acid regeneration impurity removal sludge by microwave method according to claim 1, characterized in that: The hydrochloric acid obtained by the acid regeneration chlorine-containing gas treatment and utilization system is transported to the steel pickling process; the waste liquid obtained in the pickling process is subjected to impurity removal and separation to produce cold-rolled acid regeneration impurity removal sludge which is crushed and then enters the microwave kiln; the pure liquid produced by impurity removal and separation of the waste liquid is roasted in a roasting furnace to obtain high-purity Fe2O3, and the chlorine-containing gas produced after roasting is transported to the acid regeneration chlorine-containing gas treatment and utilization system.

3. The method for treating and utilizing cold rolling acid regeneration impurity removal sludge by microwave method according to claim 1, characterized in that: The cold rolling acid regeneration impurity removal sludge has a water content of 40-60%, an iron content of 42-50% and a chlorine content of 7-31% in the dry basis sludge.

4. The method for treating and utilizing cold rolling acid regeneration impurity removal sludge by microwave method according to claim 1, characterized in that: The particle size of the cold rolling acid regeneration impurity removal sludge after crushing is less than 25 mm.

5. The method for treating and utilizing cold rolling acid regeneration impurity removal sludge by microwave method according to claim 1, characterized in that: The width of the microwave kiln tube is 50 to 100 cm.

6. The method for treating and utilizing cold rolling acid regeneration impurity removal sludge by microwave method according to claim 1, characterized in that: The microwave heating temperature of the microwave kiln is 315-400° C., and the heating time is 6-10 minutes.

7. The method for treating and utilizing cold rolling acid regeneration impurity removal sludge by microwave method according to claim 1, characterized in that: The microwave heating system of the microwave kiln is vertically distributed with the kiln tube.

8. The method for treating and utilizing cold rolling acid regeneration impurity removal sludge by microwave method according to claim 1, characterized in that: The microwave kiln body is made of 316L stainless steel, and the inner wall is sprayed with polytetrafluoroethylene; the microwave kiln tube is made of microwave-specific silicon carbide ceramic material, and the insulation system is made of ceramic fiber material; the main shaft and blades of the transmission system are made of stainless steel with glaze sprayed on the surface.

9. The method for treating and utilizing cold rolling acid regeneration impurity removal sludge by microwave method according to claim 1, characterized in that: The cold-rolled acid regeneration impurity removal sludge enters the crushing conveyor through a hopper, and the steel surface where the hopper contacts the cold-rolled acid regeneration impurity removal sludge is covered with a fiberglass layer; the crushing conveyor adopts a roller double-screw conveyor made of 316L grade or above corrosion-resistant stainless steel, and polytetrafluoroethylene is sprayed on the surface of the material in contact with the cold-rolled acid regeneration impurity removal sludge.

10. The method for treating and utilizing cold rolling acid regeneration impurity removal sludge by microwave method according to claim 1, characterized in that: The iron-containing material is cooled to ≤30°C and then transported to a raw material plant, mixed with other raw materials and sintered into a blast furnace for ironmaking. The iron-containing material after roasting has a TFe of ≥55%.

Images