Flue gas circulation waste heat utilization type steel mill solid waste treatment process

Abstract

The invention relates to a flue gas circulation waste heat utilization type steel mill solid waste treatment process, which specifically comprises the following steps: mixing a solid waste raw material with fuel, pretreating, feeding into a rotary kiln, reacting in the rotary kiln to generate first flue gas, cooling the first flue gas, and purifying in a desulfurization process to form second flue gas, the third flue gas enters a cooling section of the rotary kiln, and iron-containing materials in the rotary kiln are cooled to form fourth flue gas; the fourth flue gas and the first air enter the second waste heat utilization device and then are subjected to non-contact heat exchange to form fifth flue gas, the first air is subjected to heat exchange through the second waste heat utilization device to form second air, the second air and the gas fuel enter the high-temperature calcination section of the rotary kiln to be combusted to form the first flue gas, and therefore cyclic utilization is achieved. And the third flue gas is adopted as the cooling flue gas to cool the high-temperature iron-containing material in the cooling section of the rotary kiln, so that the problem that the zero-valent iron reduced by the rotary kiln is easily oxidized into iron oxide again is solved.

Description

Technical Field

[0001] The invention relates to a solid waste treatment process for a steel plant utilizing waste heat from flue gas circulation, and belongs to the technical field of solid waste treatment. Background Art

[0002] Solid waste generated by steel enterprises has the characteristics of many types, large output and complex composition. Its main elements are Zn and iron, and it also contains other harmful elements such as K, Na, Cl, S, etc. High-temperature calcination in a rotary kiln is a widely used process technology for extracting iron and zinc. Solid waste and fuel in the steel plant are reduced in the high-temperature atmosphere of the rotary kiln. Zinc volatilizes into the gas phase in the form of steam along with the flow of flue gas and is discharged. Iron is discharged from the discharge section of the rotary kiln with the solid phase, and then after subsequent treatment, the purpose of extracting iron and zinc from solid waste in the steel plant is achieved.

[0003] In the prior art, during the process of treating solid waste from steel mills in a rotary kiln, the solid waste passes through the feeding section, preheating section, high-temperature calcination section, and discharge section in the rotary kiln in sequence, and the iron element is discharged from the rotary kiln in the form of a solid phase in the discharge section. In the high-temperature section, the iron element is reduced to elemental iron, and in the discharge section, the elemental iron reacts with the oxygen in the combustion-supporting air and is oxidized to iron oxide again, resulting in a decrease in the metallization rate in the solid waste treatment process. To solve this problem, my country's invention patent publication number: CN115161493 A, uses nitrogen to cool the reduced solid iron, uses an air separation process, passes the air through the air separation process, obtains oxygen and nitrogen, transports the nitrogen to the cooling process, and then transports the nitrogen after heat exchange and temperature increase in the cooling process to the rotary kiln.

[0004] In the prior art, the middle section of the rotary kiln is a high-temperature zone with a temperature of 1100-1300°C. In order to maintain a high-temperature atmosphere and flue gas flow, it is necessary to continuously supplement the high-temperature flue gas into the rotary kiln system. The high-temperature flue gas consumes air or oxygen. In the prior art, ambient air is used as a supplement to the high-temperature flue gas. Heating the ambient air to 1100-1300°C requires a large amount of fuel.

[0005] In the prior art, harmful element sulfur contained in solid waste enters into flue gas in the form of sulfur dioxide after high-temperature calcination and oxidation in a rotary kiln, and is removed by a wet desulfurization process in the subsequent treatment process. During the removal process by the wet desulfurization process, on the one hand, new solid waste gypsum will be generated. The quality of the desulfurized gypsum is not high and it is difficult to reuse; on the other hand, the water content in the flue gas increases after desulfurization, and the difficulty of reusing the flue gas after wet desulfurization increases. Summary of the invention

[0006] In order to solve the above technical problems, the present invention adopts the third flue gas as the cooling flue gas to cool the high-temperature iron-containing material in the cooling section of the rotary kiln, thereby solving the problem that the elemental iron reduced by the rotary kiln is easily oxidized into iron oxide again; a second waste heat utilization device is used to preheat the first air, so that the first air is heated to the second air with a higher temperature, and the second air is mixed with the fuel gas and burned before entering the high-temperature heating section of the rotary kiln, effectively utilizing the waste heat discharged by the rotary kiln and saving the system fuel usage; a fixed bed dry desulfurization process is adopted, so that no new solid waste is generated in the steel plant during the flue gas treatment process, and the moisture content of the flue gas is not increased during the treatment process, so that the flue gas can be recycled.

[0007] To achieve the above object, the present invention provides a flue gas recycling waste heat utilization steel plant solid waste treatment process, comprising:

[0008] Step 1: After mixing the solid waste raw materials with the fuel, they are pre-treated by cold briquetting or disc pelletizing, and then sent to a rotary kiln. After the reaction in the rotary kiln, the iron-containing materials in the solid waste are discharged from the discharge section of the rotary kiln, and the zinc-containing and sulfur dioxide-containing gases in the solid waste are discharged as the first flue gas after heat exchange by the first waste heat utilization device. The first flue gas is low-temperature, low-oxygen flue gas;

[0009] Step 2: After the temperature of the first flue gas is reduced to a set temperature after passing through a surface cooler, the first flue gas enters a bag filter after the temperature of the first flue gas is reduced by the bag filter, and enters a first induced draft fan, wherein zinc-containing gas is recovered in the bag filter, and after being pressurized by the first induced draft fan, enters a desulfurization process, and after the first flue gas is purified in the desulfurization process, a second flue gas is formed, and the second flue gas is low-oxygen, low-sulfur, and low-temperature flue gas;

[0010] Step 3, a part of the second flue gas is discharged from the chimney, and another part of the second flue gas becomes the third flue gas, and the third flue gas enters the cooling section of the rotary kiln to cool the iron-containing material in the rotary kiln to form the fourth flue gas;

[0011] Step 4: the fourth flue gas and the first air enter the second waste heat utilization device and undergo non-contact heat exchange to form the fifth flue gas, which is discharged from the chimney;

[0012] Step 5: The first air is heat exchanged in the second waste heat utilization device to form the second air. The second air and the gas fuel enter the high-temperature calcination section of the rotary kiln and burn to form the first flue gas, which is then recycled.

[0013] Furthermore, the step one specifically comprises mixing the solid waste raw materials evenly with fuels such as anthracite and coke, preparing the powdered solid waste raw materials into blocks or balls by briquetting or pelletizing, feeding the blocks or balls of solid waste raw materials into the feeding section of the rotary kiln, cooling through the preheating section, high-temperature heating section and cooling section of the rotary kiln, and discharging the iron-containing materials in the solid waste from the discharging section of the rotary kiln. After the zinc-containing and sulfur dioxide-containing gases in the solid waste pass through the first waste heat utilization device, the first flue gas is discharged from the tail of the kiln.

[0014] Furthermore, in the step 1, the first flue gas is low-temperature, low-oxygen flue gas, which is specifically achieved by controlling the air intake of the rotary kiln combustion air to control the oxygen content in the first flue gas, so that the oxygen content in the first flue gas is ≤16%; the temperature of the first flue gas is controlled by the low-temperature medium working condition of the first waste heat utilization device, so that the temperature of the first flue gas is in the range of 300-350°C and the moisture content is 8%-12%.

[0015] Furthermore, in the step 2, the moisture content of the second flue gas is 8% to 12%, the oxygen content is ≤16%, and the temperature of the second flue gas is 130 to 160°C.

[0016] Furthermore, in the step three, the moisture content of the third flue gas is 8% to 12%, the oxygen content is ≤16%, and the temperature of the third flue gas is 130 to 160°C.

[0017] Furthermore, in the step 4, the moisture content of the fourth flue gas is 8% to 12%, the oxygen content is ≤16%, and the temperature of the fourth flue gas is 300 to 350°C.

[0018] Furthermore, in the step 5, the moisture content of the fifth flue gas is 8% to 12%, the oxygen content is ≤16%, and the temperature of the fifth flue gas is 130 to 160°C.

[0019] Furthermore, the oxygen content of the first air is 22%; the oxygen content of the second air is 22%, and the temperature is 200-400°C.

[0020] The present invention discloses a flue gas circulation waste heat utilization steel plant solid waste treatment process, which has the beneficial effects of ensuring the metallization rate of the iron element in the system, reducing the fuel usage of the system, and not generating new solid waste during the desulfurization process through the flue gas circulation technology and the waste heat utilization technology.

[0021] (1) The flue gas circulation form is adopted, and the third flue gas is used as the cooling flue gas to cool the high-temperature iron-containing materials in the cooling section of the rotary kiln, avoiding the use of fresh air as the cooling medium, causing the elemental iron reduced by the rotary kiln to be oxidized into iron oxide again, thereby improving the metallization rate of the iron element in the system;

[0022] (2) A second waste heat utilization device is used to preheat the first air with the fourth flue gas, so that the first air is heated to the second air with a higher temperature. The second air is mixed with the gas and then burned to enter the high-temperature heating section of the rotary kiln, thereby saving the amount of fuel used in the system;

[0023] (3) The desulfurization process is used to ensure that the moisture and oxygen content in the flue gas after desulfurization meet the conditions of flue gas circulation cooling air, and no new solid waste is generated during the desulfurization process. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0025] Figure 1 This is a schematic diagram of a process flow for treating solid waste in a steel plant by utilizing waste heat from flue gas circulation according to Example 1 of the present invention;

[0026] Figure 2 This is a schematic diagram of a process flow for treating solid waste in a steel plant by utilizing waste heat from flue gas circulation according to Example 2 of the present invention.

[0027] As shown in the figure: 1. first flue gas; 2. second flue gas; 3. third flue gas; 4. fourth flue gas; 5. fifth flue gas; 6. first air; 7. second air; 8. rotary kiln; 9. first waste heat utilization device; 10. second waste heat utilization device; 11. flue gas cooling and desalination process system; 12. flue gas zinc oxide recovery process system; 13. first induced draft fan; 14. desulfurization device; 15. chimney; 16. second induced draft fan; 17. combustion-supporting fan; 18. gas fuel fan; 19. regulating valve. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In order to further understand the content of the invention, this technical solution is further described below in conjunction with specific implementation methods.

[0030] Example 1: Figure 1 As shown, this embodiment provides a flue gas recycling waste heat utilization steel plant solid waste treatment process, the sulfur content in the solid waste is low and the iron content is high. Specifically including:

[0031] Step 1: After mixing the solid waste raw materials with fuels such as anthracite and coke, the powdered solid waste raw materials are prepared into blocks or balls by briquetting or pelletizing, and the blocks or balls of solid waste raw materials are fed into the feeding section of the rotary kiln 8. After being cooled by the preheating section, high-temperature heating section and cooling section of the rotary kiln 8, the iron-containing materials in the solid waste are discharged from the discharging section of the rotary kiln 8, and the zinc-containing and sulfur dioxide-containing gases in the solid waste are discharged from the kiln tail of the rotary kiln 8 and are discharged as the first flue gas 1 after heat exchange by the first waste heat utilization device 9; in this embodiment, the flue gas volume of the first flue gas 1 is 100000Nm 3 / h, the oxygen content of the first flue gas 1 is 15%, the temperature is 330℃, the moisture content is 10%, and the sulfur dioxide concentration is 300mg / Nm 3 .

[0032] Step 2: After the temperature of the first flue gas 1 is reduced to 160°C after passing through the surface cooler, the first flue gas 1 enters the bag filter after the temperature is reduced by the bag filter. The first flue gas 1 enters the first induced draft fan 13, wherein the zinc-containing gas is recovered in the bag filter. After being pressurized by the first induced draft fan 13, the first flue gas 1 enters the desulfurization process. After the first flue gas 1 is purified in the desulfurization process, the second flue gas 2 is formed. The second flue gas 2 is low-oxygen, low-sulfur, and low-temperature flue gas; the oxygen content of the second flue gas 2 is 15%, the moisture content is 10%, the temperature is 160°C, and the sulfur dioxide content is 30mg / Nm 3 , meeting national ultra-low emission requirements.

[0033] Step 3: The second flue gas 2 is divided into two parts. One part of the second flue gas 2 is discharged from the chimney 15 along the main pipe, and the other part of the second flue gas 2 enters the branch pipe to become the third flue gas 3. The third flue gas 3 enters the cooling section of the rotary kiln 8 to cool the iron-containing materials in the rotary kiln 8 to form the fourth flue gas 4. The flue gas volume of the third flue gas 3 is 30000Nm 3 / h, oxygen content is 15%, moisture content is 10%, temperature is 160℃, sulfur dioxide content is 30mg / Nm 3 The temperature of the iron-containing material in the cooling section of the rotary kiln 8 is higher than that of the third flue gas 3. The fourth flue gas 4 absorbs the heat in the iron-containing material and the temperature increases. The flue gas volume of the fourth flue gas 4 is 30000Nm 3 / h, oxygen content is 15%, moisture content is 10%, temperature is 330℃, sulfur dioxide content is 30mg / Nm 3 .

[0034] Step 4: The fourth flue gas 4 is transported to the second waste heat utilization device 10 through the second induced draft fan 16, and the first air 6 is transported to the second waste heat utilization device 10 through the combustion-supporting fan 17. The fourth flue gas 4 and the first air 6 are subjected to non-contact heat exchange in the second waste heat utilization device 10 to form the fifth flue gas 5, which is discharged from the chimney 15; the flue gas volume of the fifth flue gas 5 is 30000Nm 3 / h, oxygen content is 15%, moisture content is 10%, temperature is 130℃, sulfur dioxide content is 30mg / Nm 3 .

[0035] Step 5: The oxygen content of the first air 6 is 22% and the temperature is 25°C. The first air 6 is heat exchanged by the second waste heat utilization device 10 to form the second air 7, which is oxygen-enriched and high-temperature air with an oxygen content of 22% and a temperature of 250°C. The gaseous fuels such as blast furnace gas and coke oven gas are transported to the rotary kiln 8 through the gas fuel blower 18. The second air 7 and the gaseous fuels such as blast furnace gas and coke oven gas enter the high-temperature calcining section of the rotary kiln 8 and are burned to form the first flue gas 1, which is then recycled.

[0036] The process system includes: a solid waste raw material and fuel forced mixing process system, a material pelletizing process system, a rotary kiln 8 solid waste reduction process system, a desulfurization process and a flue gas circulation process system. The solid waste raw material and fuel forced mixing process system is used to evenly mix the solid waste raw material with anthracite, coke and other fuels; the material pelletizing process system is used to prepare the powdered solid waste raw material into blocks or balls; the rotary kiln 8 solid waste reduction process system includes a feeding section, a preheating section, a high-temperature heating section, a cooling section, and a discharge section, wherein the cooling section includes an air inlet and an air outlet. The desulfurization process includes a flue gas cooling and desalination process system 11, a flue gas zinc oxide recovery process system 12, and a desulfurization device 14 connected in sequence.

[0037] The process uses the fourth flue gas 4 to preheat the first air 6, so that the first air 6 is heated to the second air 7 with a higher temperature. The temperature of the second air 7 reaches above 250°C, and then it is mixed with gas fuels such as blast furnace gas and coke oven gas and burned to enter the cooling section of the rotary kiln 8. After passing through the high-temperature heating section and preheating section, it is discharged from the rotary kiln 8 system from the feed end, saving the use of system fuel.

[0038] The process adopts a flue gas circulation form, and uses the second flue gas 2 as the cooling flue gas. The second flue gas 2 is introduced into the cooling section of the rotary kiln 8 through a branch pipe, enters from the air inlet of the cooling section, cools the high-temperature solid iron-containing material in the cooling section, and is discharged from the air outlet of the cooling section. This process is used to cool the iron-containing material in the cooling section of the rotary kiln 8, avoiding the use of fresh air as a cooling medium, which causes the reduction product elemental iron to be oxidized into iron oxide again.

[0039] The desulfurization device 14 uses a set of desulfurization towers containing desulfurizers. Since the solid waste is low-sulfur material and the concentration of sulfur dioxide in the flue gas is low, the desulfurizer in the desulfurization tower reacts with the sulfur dioxide in the flue gas by adsorption. When the desulfurizer is saturated with adsorption, the desulfurizer is replaced. No new solid waste is generated during the whole desulfurization process. The normal operating temperature of the desulfurization tower is 150°C, and the flue gas temperature at the outlet of the desulfurization tower is 150-155°C.

[0040] The process system is provided with regulating valves 19 on both the main pipe and the branch pipe. Since the process system requires a relatively high amount of heat, under normal operating conditions, it is necessary to close the regulating valve 19 on the main pipe and open the regulating valve 19 on the branch pipe to adjust the flue gas circulation volume according to the thermometer provided on the cooling section.

[0041] The second induced draft fan 16 is disposed between the second waste heat utilization device 10 and the cooling section of the rotary kiln 8, so that the suction force of the cooling section is greater, which is beneficial to the cooling effect of the cooling section.

[0042] The first waste heat utilization device 9 is used to cool the first flue gas 1 , and the first waste heat utilization device 9 uses a waste heat boiler to produce high-pressure steam; the second waste heat utilization device 10 uses a plate heat exchanger to perform non-contact heating on the first air 6 .

[0043] Example 2: Figure 2 As shown, this embodiment provides a flue gas recycling waste heat utilization steel plant solid waste treatment process, the solid waste has a high sulfur content and a low iron content. Specifically including:

[0044] Step 1: After mixing the solid waste raw materials with fuels such as anthracite and coke, the powdered solid waste raw materials are prepared into blocks or balls by briquetting or pelletizing, and the blocks or balls of solid waste raw materials are fed into the feeding section of the rotary kiln 8. After being cooled by the preheating section, high-temperature heating section and cooling section of the rotary kiln 8, the iron-containing materials in the solid waste are discharged from the discharging section of the rotary kiln 8, and the zinc-containing and sulfur dioxide-containing gases in the solid waste are discharged from the kiln tail of the rotary kiln 8 and are discharged as the first flue gas 1 after heat exchange by the first waste heat utilization device 9; in this embodiment, the flue gas volume of the first flue gas 1 is 100000Nm 3 / h, the oxygen content of the first flue gas 1 is 16%, the temperature is 330℃, the moisture content is 12%, and the sulfur dioxide concentration is 1500mg / Nm 3 .

[0045] Step 2: After the temperature of the first flue gas 1 is reduced to 130°C after passing through the surface cooler, the first flue gas 1 enters the bag filter after the temperature is reduced by the bag filter. The first flue gas 1 enters the first induced draft fan 13, wherein the zinc-containing gas is recovered in the bag filter. After being pressurized by the first induced draft fan 13, the first flue gas 1 enters the desulfurization process. After the first flue gas 1 is purified in the desulfurization process, the second flue gas 2 is formed. The second flue gas 2 is low-oxygen, low-sulfur, and low-temperature flue gas; the oxygen content of the second flue gas 2 is 16%, the moisture content is 12%, the temperature is 150°C, and the sulfur dioxide content is 30mg / Nm 3 , meeting national ultra-low emission requirements.

[0046] Step 3: The second flue gas 2 is divided into two parts. One part of the second flue gas 2 is discharged from the chimney 15 along the main pipe, and the other part of the second flue gas 2 enters the branch pipe to become the third flue gas 3. The third flue gas 3 enters the cooling section of the rotary kiln 8 to cool the iron-containing materials in the rotary kiln 8 to form the fourth flue gas 4. The flue gas volume of the third flue gas 3 is 20000Nm 3 / h, oxygen content is 16%, moisture content is 12%, temperature is 130℃, sulfur dioxide content is 30mg / Nm 3 The temperature of the iron-containing material in the cooling section of the rotary kiln 8 is higher than the temperature of the third flue gas 3. The fourth flue gas 4 absorbs the heat in the iron-containing material and the temperature increases. The flue gas volume of the fourth flue gas 4 is 20000Nm 3 / h, oxygen content is 16%, moisture content is 12%, temperature is 330℃, sulfur dioxide content is 30mg / Nm 3 .

[0047] Step 4: The fourth flue gas 4 is transported to the second waste heat utilization device 10 through the second induced draft fan 16, and the first air 6 is transported to the second waste heat utilization device 10 through the combustion-supporting fan 17. The fourth flue gas 4 and the first air 6 are subjected to non-contact heat exchange in the second waste heat utilization device 10 to form the fifth flue gas 5, which is discharged from the chimney 15; the flue gas volume of the fifth flue gas 5 is 20000Nm 3 / h, oxygen content is 16%, moisture content is 12%, temperature is 130℃, sulfur dioxide content is 30mg / Nm 3 .

[0048] Step 5: The oxygen content of the first air 6 is 22% and the temperature is 35°C. The first air 6 is heat exchanged by the second waste heat utilization device 10 to form the second air 7, which is oxygen-enriched and high-temperature air with an oxygen content of 22% and a temperature of 300°C. The gaseous fuels such as blast furnace gas and coke oven gas are transported to the rotary kiln 8 through the gas fuel blower 18. The second air 7 and the gaseous fuels such as blast furnace gas and coke oven gas enter the high-temperature calcining section of the rotary kiln 8 and are burned to form the first flue gas 1, which is then recycled.

[0049] The process system includes: a solid waste raw material and fuel forced mixing process system, a material pelletizing process system, a rotary kiln 8 solid waste reduction process system, a desulfurization process and a flue gas circulation process system. The solid waste raw material and fuel forced mixing process system is used to evenly mix the solid waste raw material with anthracite, coke and other fuels; the material pelletizing process system is used to prepare the powdered solid waste raw material into blocks or balls; the rotary kiln 8 solid waste reduction process system includes a feeding section, a preheating section, a high-temperature heating section, a cooling section, and a discharge section, wherein the cooling section includes an air inlet and an air outlet. The desulfurization process includes a flue gas cooling and desalination process system 11, a flue gas zinc oxide recovery process system 12, and a desulfurization device 14 connected in sequence.

[0050] The process uses the fourth flue gas 4 to preheat the first air 6, so that the first air 6 is heated to the second air 7 with a higher temperature. The temperature of the second air 7 reaches above 300°C, and then it is mixed with gas fuels such as blast furnace gas and coke oven gas and burned to enter the cooling section of the rotary kiln 8. After passing through the high-temperature heating section and preheating section, it is discharged from the rotary kiln 8 system from the feeding end, saving the use of system fuel.

[0051] The process adopts a flue gas circulation form, and uses a low-oxygen, low-temperature, and low-sulfur second flue gas 2 as a cooling flue gas. The second flue gas 2 is introduced into the cooling section of the rotary kiln 8 through a branch pipe, enters from the air inlet of the cooling section, cools the high-temperature solid-phase iron-containing material in the cooling section, and is discharged from the air outlet of the cooling section. This process is used to cool the iron-containing material in the cooling section of the rotary kiln 8, avoiding the use of fresh air as a cooling medium, which causes the reduction product elemental iron to be oxidized into iron oxide again.

[0052] The desulfurization device 14 uses two sets of desulfurization towers containing desulfurizers, and the two sets of desulfurization towers are used alternately; because the solid waste is low-sulfur material, the concentration of sulfur dioxide in the flue gas is relatively high, and the desulfurizer in the desulfurization tower reacts with the sulfur dioxide in the flue gas by adsorption. When the desulfurizer is saturated with adsorption, it switches to another set of desulfurization towers online, and the whole desulfurization process does not generate new solid waste. The normal operating temperature of the desulfurization tower is 130°C, and the flue gas temperature at the outlet of the desulfurization tower is 130-135°C.

[0053] The process system is provided with regulating valves 19 on both the main pipe and the branch pipe. Since the heat required by the process system is relatively low, under normal working conditions, it is necessary to open the regulating valve 19 on the main pipe and close the regulating valve 19 on the branch pipe. The flue gas circulation volume is adjusted according to the thermometer set on the cooling section to circulate as much flue gas as possible.

[0054] The second induced draft fan 16 is disposed between the second waste heat utilization device 10 and the chimney 15 .

[0055] The first waste heat utilization device 9 is used to cool the first flue gas 1 and produce high-temperature water using a flue heat exchange system; the second waste heat utilization device 10 uses a plate heat exchanger to perform non-contact heating on the first air 6.

[0056] As an improvement of the present invention, through the flue gas circulation process, the flue gas with an oxygen content of ≤16% generated by the solid waste reduction process system of the rotary kiln 8 is used as a cooling medium to cool the high-temperature iron-containing material in the cooling section of the rotary kiln 8. Under the condition of low oxygen content, the iron element is prevented from being oxidized again, thereby ensuring the metallization rate of the iron element in the system;

[0057] As another improvement of the present invention, the desulfurization device 14 used in the present invention is a fixed bed desulfurization tower containing a desulfurizer. No water or water-containing desulfurizer is required during the desulfurization process of the system. An adsorption reaction occurs in the desulfurization tower to remove sulfur dioxide in the flue gas, ensuring that the moisture content and oxygen content of the flue gas remain unchanged during the desulfurization process. The operating temperature of the desulfurization tower used in the present invention is 130-160°C, and the flue gas temperature at the outlet of the desulfurization tower is 130-160°C. On the one hand, it provides the system with circulating cooling flue gas with an oxygen content of ≤16%, and on the other hand, the desulfurization process does not generate new solid waste.

[0058] As a further improvement of the present invention, the present invention heats the first air 6 through the second waste heat utilization device 10 before the first air 6 enters the rotary kiln 8 solid waste reduction process system, thereby reducing fuel consumption.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A flue gas recycling waste heat utilization steel plant solid waste treatment process, characterized in that: Step 1: After mixing the solid waste raw material with the fuel, the solid waste raw material is pre-treated by a cold briquetting process or a disc pelletizing process, and then sent to a rotary kiln (8). After the reaction in the rotary kiln (8), the iron-containing material in the solid waste is discharged from the discharge section of the rotary kiln (8). The zinc-containing and sulfur dioxide-containing gas in the solid waste is discharged as the first flue gas (1) after heat exchange in the first waste heat utilization device (9). The first flue gas (1) is a low-temperature, low-oxygen flue gas. Step 2: After the temperature of the first flue gas (1) is reduced to a set temperature through a surface cooler, the first flue gas (1) enters a bag filter, after the temperature of the first flue gas (1) is reduced through the bag filter, the first flue gas (1) enters a first induced draft fan (13), wherein zinc-containing gas is recovered in the bag filter, and after being pressurized by the first induced draft fan (13), the first flue gas (1) enters a desulfurization process, and after the first flue gas (1) is purified in the desulfurization process, a second flue gas (2) is formed; Step 3: a part of the second flue gas (2) is discharged from the chimney (15), and another part of the second flue gas (2) becomes the third flue gas (3). The third flue gas (3) enters the cooling section of the rotary kiln (8), cools the iron-containing material in the rotary kiln (8), and forms the fourth flue gas (4); Step 4: the fourth flue gas (4) and the first air (6) enter the second waste heat utilization device (10) and undergo non-contact heat exchange to form a fifth flue gas (5), and the fifth flue gas (5) is discharged from the chimney (15); Step 5: The first air (6) is heat exchanged in the second waste heat utilization device (10) to form the second air (7). The second air (7) and the gas fuel enter the high-temperature calcination section of the rotary kiln (8) and burn to form the first flue gas (1), which is then recycled.

2. The process for treating solid waste in a steel plant by utilizing flue gas recycling waste heat according to claim 1 is characterized in that: Step 1 specifically comprises the steps of uniformly mixing the solid waste raw material with anthracite and coke fuel, preparing the powdered solid waste raw material into blocks or balls by briquetting or pelletizing, feeding the blocks or balls of solid waste raw material into the feeding section of the rotary kiln (8), cooling through the preheating section, high-temperature heating section and cooling section of the rotary kiln (8), and then discharging the iron-containing material in the solid waste from the discharging section of the rotary kiln (8). After the zinc-containing and sulfur dioxide-containing gas in the solid waste passes through the first waste heat utilization device (9), the first flue gas (1) is discharged from the kiln tail.

3. The process for treating solid waste in a steel plant by utilizing flue gas recycling waste heat according to claim 2 is characterized in that: In step 1, the first flue gas (1) is a low-temperature, low-oxygen flue gas. Specifically, the oxygen content in the first flue gas (1) is controlled by controlling the intake amount of the combustion air of the rotary kiln (8), so that the oxygen content in the first flue gas (1) is ≤16%; the temperature of the first flue gas (1) is controlled by the low-temperature medium working condition of the first waste heat utilization device (9), so that the temperature of the first flue gas (1) is in the range of 300 to 350° C., and the moisture content is in the range of 8% to 12%.

4. The process for treating solid waste in a steel plant by utilizing flue gas recycling waste heat according to claim 3 is characterized in that: In step 2, the second flue gas (2) has a moisture content of 8% to 12%, an oxygen content of ≤16%, and a temperature of 130 to 160°C.

5. The process for treating solid waste in a steel plant by utilizing flue gas recycling waste heat according to claim 1 is characterized in that: In step 3, the moisture content of the third flue gas (3) is 8% to 12%, the oxygen content is ≤16%, and the temperature is 130 to 160°C.

6. The process for treating solid waste in a steel mill by utilizing flue gas recycling waste heat according to claim 1 is characterized in that: In step 4, the fourth flue gas (4) has a moisture content of 8% to 12%, an oxygen content of ≤16%, and a temperature of 300 to 350°C.

7. The process for treating solid waste in a steel plant by utilizing flue gas recycling waste heat according to claim 1, characterized in that: In step 5, the fifth flue gas (5) has a moisture content of 8% to 12%, an oxygen content of ≤16%, and a temperature of 130 to 160°C.

8. The process for treating solid waste in a steel plant by utilizing flue gas recycling waste heat according to claim 1, characterized in that: The oxygen content of the first air (6) is 22%; the oxygen content of the second air (7) is 22% and the temperature is 200-400°C.

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