System and method for recycling waste heat of non-ferrous smelting waste gas with preposed dust removal device

Abstract

The invention discloses a non-ferrous smelting waste gas waste heat recycling system and method with a preposed dust removal device, hot flue gas at an outlet of a medium-temperature medium-pressure waste heat boiler is directly introduced into a high-temperature-resistant bag type dust removal device for dust removal treatment, and an outlet of the dust removal device is connected with a shell pass of a two-section type flue gas heat exchanger; the two-section type flue gas heat exchanger comprises an evaporation section and a heating section, hot flue gas and circulating water in a tube pass of the heat exchanger flow reversely, the hot flue gas firstly enters the evaporation section to heat hot water in a tube into saturated steam, then enters the heating section to heat the hot water in the tube pass to a phase change critical point, and finally enters the evaporation section to heat the saturated steam. Saturated steam enters a steam pocket arranged at the top of the heat exchanger through a steam end outlet of the tube pass, and low-pressure steam in the steam pocket can be supplied to a steam user or used for organic Rankine cycle power generation. The problems of dust deposition, hardening and corrosion of a traditional technical route are effectively solved, efficient recovery and utilization of flue gas waste heat are achieved, and remarkable economic and social benefits are brought.

Description

Technical Field

[0001] This invention belongs to the field of waste heat recovery technology of smelting waste gas, and particularly relates to a system and method for waste heat recovery of non-ferrous smelting waste gas with a dust removal device in place. Background Technology

[0002] In recent years, my country's lead and zinc smelting industry has achieved large-scale development. After years of exploration and progress, lead and zinc smelting technology has reached an advanced level. However, the high energy consumption problem that has long existed in my country's non-ferrous metals industry remains very prominent. Data shows that the energy consumption per unit of product in my country's non-ferrous metals industry is about ten percentage points higher than the international advanced level. In the energy consumption composition of non-ferrous metallurgy, effective heat accounts for only 32%, another 8% of the heat is lost through furnace walls, etc., and the remaining 60% is the waste heat in the non-ferrous metal smelting process. Among these waste heat, the proportion of flue gas waste heat is as high as about 80%. It can be seen that recovering the waste heat of flue gas in the non-ferrous metallurgical industry is of great significance for reducing the energy consumption of the non-ferrous metallurgical industry. At present, the more common methods for recovering and utilizing the waste heat of flue gas from non-ferrous furnaces and kilns include: installing waste heat boilers in the flue to produce steam, using waste heat to generate electricity, using waste heat to preheat air or materials, installing vaporization water jackets to produce low-pressure steam, or installing cooling water jackets to produce hot water, etc. Moreover, the recovery of waste heat from flue gas in non-ferrous furnaces and kilns mainly targets high-temperature flue gas.

[0003] In the smelting process, the product enters the cooling line for cooling, generating a large amount of medium- and low-temperature waste heat gas emissions. After passing through the waste heat boiler, the emission temperature of this waste gas remains above 300℃ for most of the year. This portion of medium- and low-temperature flue gas waste heat accounts for about half of the total flue gas waste heat, and the particulate matter concentration is very high, generally above 40g / m³. The existing technical route first requires passing the product through a surface cooler, where it is cooled by air before entering the bag filter for treatment. Not only is this heat not fully utilized and is wasted, but the surface cooler also suffers from severe ash accumulation, caking, and corrosion during operation, leading to serious equipment damage in this process and high operating, maintenance, and repair costs. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a system and method for reusing waste heat from non-ferrous smelting waste gas. The aim is to solve the problems in existing technologies where the utilization of low-temperature flue gas waste heat is insufficient and wasted, and where severe ash accumulation and caking occur on the surface coolers of system equipment during operation, leading to serious equipment damage in this process and high operating, maintenance, and repair costs.

[0005] This invention is implemented as follows: A waste heat recovery system for non-ferrous smelting waste gas, with a dust removal device preceding it, is disclosed. Hot flue gas from a medium-temperature, medium-pressure waste heat boiler is directly introduced into a high-temperature resistant bag filter for dust removal. The flue gas outlet of the dust collector is connected to the shell side of a two-stage flue gas heat exchanger, which includes an evaporation section and a heating section. The hot flue gas flows counter-currently to the circulating water in the tube side of the heat exchanger. The hot flue gas first enters the evaporation section, heating the hot water in the tube side into saturated steam. Then, the cooled flue gas enters the heating section, heating the hot water in the tube side to the phase change critical point. The tube side is connected to a circulating water system, which includes a soft water tank. The inlet of the heating section is connected to the soft water tank, and the outlet of the evaporation section is connected to the circulating water system via an ash conveying device located below the dust collector. The saturated steam generated in the heat exchanger can be supplied to steam users or used for organic Rankine cycle power generation.

[0006] Furthermore, the heat exchange area of ​​the evaporation section of the heat exchanger is 1.2 to 1.4 times that of the heating section.

[0007] 3. The waste heat recovery system for non-ferrous smelting waste gas before the dust removal device according to claim 1, characterized in that the shell length of the heat exchanger is 5 to 6 meters.

[0008] Furthermore, the high-temperature bag filter is designed with a preheating jet cleaning device at the top, and the compressed air for cleaning is connected to the jet valve after passing through the preheater.

[0009] Furthermore, the ash conveying device is equipped with a fluidized bed heat exchanger, which has a heat recovery function, and the outlet of the evaporation section is connected to the fluidized bed heat exchanger.

[0010] Furthermore, the tubes are arranged in staggered or sequential rows inside the heat exchanger.

[0011] Furthermore, the filter bags of the high-temperature bag filter are made of high-temperature resistant metal or ceramic filter bags, with a length of 4 meters or 6 meters, and are suspended at the top of the tube sheet inside the dust collector shell.

[0012] Furthermore, a steam drum is provided at the top of the heat exchanger, and the generated saturated steam enters the steam drum. The steam drum is connected to the user end through a pipeline, and the condensate generated by the steam drum flows back to the tube side of the heating section through a pipeline.

[0013] A method for reusing waste heat from non-ferrous smelting waste gas before a dust removal device, based on the aforementioned system for reusing waste heat from non-ferrous smelting waste gas before a dust removal device, is characterized by the following process steps: S1, the flue gas with a temperature between 320 and 400°C drawn from the end of the flue gas outlet of the medium-temperature and medium-pressure waste heat boiler is introduced into the high-temperature dust collector through the heat-insulated pipe for high-temperature dust removal. S2, the flue gas after dust removal in step S1 is introduced into the shell side of the evaporation section of the two-stage flue gas heat exchanger through an insulated pipe, where it exchanges heat with hot water at 90-99°C inside the pipe. After heat exchange, the temperature of the flue gas is reduced to 220-180°C, and saturated low-pressure steam at 0.4-0.5MPa is obtained on the water side inside the pipe. S3, the flue gas cooled to 220-180°C in step S2 is introduced into the shell side of the heating section of the flue gas heat exchanger to exchange heat with the hot water at 70-90°C in the tube, so that the flue gas is further cooled to about 140°C. The hot water in the tube is heated to the phase change critical point before entering the evaporation section. S4. After dust removal and cooling in the two-stage heat exchanger, the flue gas enters the next process through the insulated flue pipe. The saturated low-pressure steam is introduced into the steam drum at the top of the heat exchanger through the steam end outlet of the tube side. S5, the high-temperature dust obtained in step S1 is introduced into the ash conveying device, and the high-temperature dust exchanges heat with the water in the fluidized heat exchanger of the ash conveying device. The cooled heavy metal dust enters the metal recovery system for reuse, and the heated water enters the circulating water system and returns to the tube side of the heat exchanger through the inlet for continued recycling.

[0014] Furthermore, the low-pressure saturated steam in the steam drum can be used for low-pressure steam user terminals or for organic Rankine cycle power generation.

[0015] The beneficial effects of this invention are: This innovative approach places the high-temperature dust collector before the heat exchanger, changing the traditional process of cooling before dust removal. This reduces particulate matter in the flue gas, preventing blockage and caking in subsequent equipment, especially addressing the severe dust accumulation and caking issues that plague the surface coolers during system operation, leading to significant equipment damage in this stage. By placing the dust collector before the heat exchanger, maintenance costs for this stage can be reduced by at least 30%, improving system stability and reducing environmental pollution. Simultaneously, in conjunction with a two-stage heat exchanger, the flue gas in the shell side and the circulating water in the tube side undergo counter-current heat exchange in an evaporation and heating section. This gradually transfers the heat from the smelting waste gas to the hot water, ultimately producing steam. This improves the efficiency of heat recovery from the smelting waste gas, maximizing the utilization of waste heat and minimizing heat waste. The low-pressure steam obtained by this invention can not only be supplied to industrial users but also used for power generation, achieving multi-functional utilization of waste heat. In addition to the waste heat of hot flue gas, this invention also makes full use of the waste heat of high-temperature ash, maximizing the utilization of waste heat energy. The generated saturated steam enhances the full utilization of thermal energy, reduces additional energy consumption, lowers production costs, further improves the overall economic efficiency and resource utilization of the system, and further reduces the production cost of non-ferrous metal smelting.

[0016] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0017] Figure 1 Schematic diagram of the process flow of this invention; Figure 2 A schematic diagram of the system connection relationship of this invention.

[0018] In the picture, 11 is a high-temperature dust collector; 12 Heat exchanger, 121 Shell side, 122 Tube side, 123 Evaporation section, 124 Heating section, 125 Steam outlet, 126 Water inlet, 127 Water outlet; 13 Circulating water pump, 14 Soft water tank, 15 Steam drum, 16 Ash conveying device, 17 Pulse jet cleaning device, 18 Air supply end, 19 Flue gas temperature and flow meter, 20 Water temperature and flow sensor. Detailed Implementation

[0019] Example 1: This embodiment is a waste heat recovery system for non-ferrous smelting waste gas, located before a dust removal device. The system includes a high-temperature dust collector 11, a flue gas heat exchanger 12, a circulating water pump 13, a soft water tank 14, a steam drum 15, an ash conveying device 16, a pulse-jet cleaning device 17, and a gas-using end 18, all connected by pipelines. Figure 1 , Figure 2 As shown.

[0020] Hot flue gas from the outlet of the medium-temperature and medium-pressure waste heat boiler is directly introduced into a high-temperature resistant bag filter 11 for dust removal. The outlet of the dust collector 11 is connected to the shell side 121 of a two-stage flue gas heat exchanger 12. The hot flue gas from the dust collector 11 exchanges heat with the circulating water flowing counter-currently in the tube side 122 of the flue gas heat exchanger 12. The two-stage flue gas heat exchanger 12 includes an evaporation section 123 and a heating section 124. The hot flue gas first enters the evaporation section 123 of the heat exchanger 12, heating the hot water in the tube side 122 into saturated steam. Then it enters the heating section 124, heating the hot water in the tube side to the phase change critical point. The tube side 122 is arranged in staggered or parallel rows inside the heat exchanger 12. The tube side 122 is connected to a circulating water system, which includes a soft water tank 14 and a circulating water pump 13, forming a closed-loop circulating water system through pipeline connections. The inlet 126 of the heating section 124 is connected to the soft water tank 14, and the outlet 127 of the evaporation section 123 is connected to the circulating water system through the ash conveying device 16 located below the dust collector 11. The steam generated in the heat exchanger 12 is connected to the steam drum 15 located at the top of the heat exchanger 12 through the steam outlet 125. The low-pressure steam in the steam drum 15 can be supplied to the steam user at the gas consumption end 18 or used for organic Rankine cycle power generation. The cooled flue gas then enters the next process.

[0021] The specific dimensions of the shell side 121 of the heat exchanger 12 can be calculated and customized according to the flue gas velocity and site conditions. The tube side 122 is arranged in staggered or sequential rows inside the heat exchanger 12 so that the softened water can flow in the pipe and fully contact the waste heat flue gas. It is made of acid-resistant and wear-resistant material.

[0022] In this preferred embodiment, the total length of the shell side 121 of the heat exchanger 12 is 5 to 6 meters, the heat exchange area of ​​the evaporation section 123 is 1.2 to 1.4 times that of the heat exchange area of ​​the heating section 124, and the flue gas velocity is 2 to 4 m / s.

[0023] The filter bags of the high-temperature dust collector 11 described in this embodiment are made of either high-temperature resistant metal or ceramic materials, with a length of 4 meters or 6 meters. They are suspended at the top of the tube sheet inside the dust collector 11 shell for easy installation and maintenance. Hot flue gas enters the dust collector 11 directly from the outlet of the medium-temperature, medium-pressure waste heat boiler. The top of the high-temperature dust collector 11 is designed with a preheating jet cleaning device 17. This device is equipped with a preheater; the compressed air used for cleaning is preheated by the preheater and then jetted into the dust collector 11 through a jet valve, blowing off the dust adhering to the inner wall of the dust collector 11. The blown-off dust falls into the ash conveying device 16 below. The ash conveying device 16 is equipped with a fluidized heat exchanger, which has a heat recovery function and can recover the heat of the high-temperature dust. The outlet 127 of the evaporation section 123 is connected to the fluidized heat exchanger. The recovered heat energy is used to exchange heat with the water in the circulating water system, increasing the water temperature entering the heating section 124, making full use of the heat energy of the high-temperature ash, and further saving energy.

[0024] The softened water tank 14 of the system of the present invention is used to replenish the water volume reduced in the system by the discharged steam, or to provide all the water volume required for startup. All connecting pipes between system equipment are insulated pipes to reduce heat loss.

[0025] This system is further equipped with an automatic control system connected to a terminal console for real-time monitoring of equipment operation. A flue gas temperature and flow meter 19 is installed at the inlet of the heat exchanger 12, and the heat exchanger itself is equipped with a water temperature and flow sensor 20. The control system can adjust the system operation based on factors such as the flow rate and temperature of the flue gas entering the shell side 121 and the circulating water in the tube side 122 of the heat exchanger, to meet the requirements of generating saturated low-pressure steam and cooling the flue gas to the desired temperature.

[0026] Example 2: This embodiment describes a process for reusing waste heat from non-ferrous smelting waste gas. It utilizes a waste heat recovery system for non-ferrous smelting waste gas pre-installed with the aforementioned dust removal device. The process steps are as follows: S1, the flue gas with a temperature between 320 and 400°C, drawn from the end of the flue gas outlet of the medium-temperature and medium-pressure waste heat boiler, is introduced into the high-temperature dust collector 11 through an insulated pipe for high-temperature dust removal.

[0027] S2, the flue gas after dust removal in step S1 is introduced into the shell side 121 of the two-stage flue gas heat exchanger 12 through an insulated pipe, and then enters the shell side 121 of the evaporation section 123 of the heat exchanger 12. The flue gas in the shell side 121 exchanges heat with the 90-99°C hot water flowing counterclockwise in the tube side 122. After heat exchange, the temperature of the flue gas drops to 220-180°C, and the water inside the tube side 122 obtains low-pressure saturated steam of 0.4-0.5 MPa. The saturated steam enters the steam drum 15 located at the top of the heat exchanger 12. The low-pressure saturated steam in the steam drum 15 can be used for low-pressure steam supply 18 or for organic Rankine cycle power generation.

[0028] S3, the flue gas from the evaporation section 123 is introduced into the shell side 121 of the heating section 124 to exchange heat with the water at 70-90°C flowing counter-currently in the tube side 122, which further reduces the flue gas temperature to about 140°C. The hot water in the tube is heated to the phase change critical point before entering the evaporation section and then enters the evaporation section 123.

[0029] S4, the flue gas that has been cooled in the two-stage heat exchanger 12 enters the next process through the insulated flue pipe, and the saturated low-pressure steam obtained by the evaporation section 123 is introduced from the steam outlet 125 of the heater 2 into the steam drum 15 located at the top of the heat exchanger 12.

[0030] S5, the high-temperature dust obtained in step S1 is introduced into the ash conveying device 16, and the high-temperature dust exchanges heat with the water in the fluidized heat exchanger of the ash conveying device 16. The cooled heavy metal dust will enter the metal recovery system for reuse, and the heated water will enter the circulating water system and return to the tube side 122 of the evaporator 2 through the water inlet 126 for continued recycling.

[0031] Finally, it should be noted that the above description is only used to illustrate the technical solutions of the present invention and is not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention.

Claims

1. A non-ferrous smelting waste gas waste heat recycling system with a dust removal device in front, characterized in that: The hot flue gas at the outlet of the medium-temperature and medium-pressure waste heat boiler is directly introduced into a high-temperature resistant bag dust collector for dust removal. The flue gas outlet of the dust collector is connected to the shell side of a two-stage flue gas heat exchanger. The two-stage flue gas heat exchanger includes an evaporation section and a heating section. The hot flue gas and the circulating water in the tube side of the heat exchanger flow in the opposite direction. The hot flue gas first enters the evaporation section to heat the hot water in the tube side to become saturated steam. Then the cooled flue gas enters the heating section to heat the hot water in the tube side to the critical point of phase change. The tube side is connected to a circulating water system, which includes a soft water tank. The water inlet of the heating section is connected to the soft water tank. The water outlet of the evaporation section is connected to the circulating water system through an ash conveying device arranged below the dust collector. The saturated steam generated in the heat exchanger can be supplied to steam users or used for organic Rankine cycle power generation.

2. The non-ferrous smelting waste gas waste heat recycling system with a pre-dust removal device according to claim 1 is characterized in that: The heat exchange area of ​​the evaporation section of the heat exchanger is 1.2 to 1.4 times that of the heating section.

3. The non-ferrous smelting waste gas waste heat recycling system with a pre-dust removal device according to claim 1 is characterized in that: The shell length of the heat exchanger is 5 to 6 meters.

4. The non-ferrous smelting waste gas waste heat recycling system with a pre-dust removal device according to claim 1 is characterized in that: The top of the high temperature resistant bag filter is designed with a spray cleaning device with a preheating function, and the cleaning compressed air is connected to the spray valve through the preheater.

5. The non-ferrous smelting waste gas waste heat recycling system with a pre-dust removal device according to claim 1 is characterized in that: The ash conveying device is provided with a fluidized heat exchanger with a heat recovery function, and the water outlet of the evaporation section is connected with the fluidized heat exchanger.

6. The non-ferrous smelting waste gas waste heat recycling system with a pre-dust removal device according to claim 1 is characterized in that: The tube paths are arranged in staggered or sequential tube rows inside the heat exchanger.

7. The non-ferrous smelting waste gas waste heat recycling system with a pre-dust removal device according to claim 1 is characterized in that: The filter bag of the high-temperature bag filter adopts a high-temperature resistant metal filter bag or a ceramic filter bag, has a length of 4 meters or 6 meters, and is hung on the upper end of the flower plate inside the dust collector shell.

8. The non-ferrous smelting waste gas waste heat recycling system with a pre-dust removal device according to claim 1 is characterized in that: A steam drum is provided on the top of the heat exchanger, and the generated saturated steam enters the steam drum. The steam drum is connected to the user end through a pipeline, and the condensed water generated by the steam drum flows back to the pipe side of the heating section through the pipeline.

9. A method for recycling waste heat from non-ferrous smelting waste gas with a pre-dust removal device, based on the system for recycling waste heat from non-ferrous smelting waste gas with a pre-dust removal device according to any one of claims 1 to 8, characterized in that: The process steps are as follows: S1, introducing the flue gas with a temperature between 320 and 400°C from the flue gas outlet of the medium-temperature and medium-pressure waste heat boiler into the high-temperature dust collector through an insulation pipe for high-temperature dust removal; S2, the flue gas after dust removal in step S1 is introduced into the shell side of the evaporation section of the two-stage flue gas heat exchanger through the insulation pipe, and heat exchange is carried out with the hot water at 90-99°C in the tube. The temperature of the flue gas after heat exchange is reduced to 220-180°C, and saturated low-pressure steam of 0.4-0.5MPa is obtained on the water side of the tube; S3, the flue gas cooled to 220-180°C in step S2 is further introduced into the shell side of the heating section of the flue gas heat exchanger to exchange heat with the hot water at 70-90°C in the tube, so that the flue gas is further cooled to about 140°C. The hot water in the tube is heated to the critical point of phase change before entering the evaporation section, and then enters the evaporation section; S4, the flue gas after dust removal and temperature reduction in the two-stage heat exchanger enters the next process through the heat-insulating smoke pipe, and the saturated low-pressure steam is introduced into the steam drum at the top of the heat exchanger through the steam end outlet of the tube pass; S5, introducing the high-temperature dust obtained in step S1 into the ash conveying device, and the high-temperature dust exchanges heat with water in the fluidized heat exchanger of the ash conveying device; The cooled heavy metal dust enters the metal recovery system for reuse, and the heated water enters the circulating water system and returns to the tube side of the heat exchanger through the water inlet for continued circulation.

10. The process for recycling waste heat from non-ferrous smelting waste gas according to claim 9, characterized in that: The low-pressure saturated steam in the steam drum can be used for low-pressure steam users or for organic Rankine cycle power generation.

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