System for deeply recovering low-temperature waste heat and water resources in sulfuric acid production flue gas

Abstract

The invention discloses a system for deeply recovering low-temperature waste heat and water resources in sulfuric acid production flue gas, and belongs to the field of waste heat and water resource recovery. According to the system for deeply recovering the low-temperature waste heat and the water resources in the sulfuric acid production flue gas, a steam pocket, a low-temperature waste heat boiler, a deoxygenated water tank, a boiler water feeding pump, a water diversion header, a water return pump, an acid-resistant pump, a ceramic filter, a liquid storage well, a plurality of connecting pipelines, necessary valves and control elements are additionally arranged on an original system; sulfuric acid production flue gas at 350 DEG C from a high-temperature waste heat boiler in an original system enters a low-temperature waste heat boiler after passing through an electric dust remover, the low-temperature waste heat boiler is a three-section vertical waste heat boiler from top to bottom, and the three-section vertical waste heat boiler from top to bottom is of a three-section heat absorption type structure of an evaporation section, a preheating section and a low-temperature heating section. The sulfuric acid production flue gas with the temperature of 350 DEG C sequentially passes through an evaporation section, a preheating section and a low-temperature heating section of the low-temperature waste heat boiler from top to bottom, and then the sulfuric acid production flue gas is cooled to 50 DEG C and discharged from a flue outlet of the low-temperature waste heat boiler; a liquid storage well is arranged at the bottom of the low-temperature waste heat boiler. According to the invention, the recovery efficiency of waste heat and water resources is obviously improved, and the system has the characteristics of high efficiency, low carbon emission and high economic benefit, and shows huge potential in the field of industrial energy conservation and emission reduction.

Description

Technical Field

[0001] The invention discloses a system for deeply recovering low-temperature waste heat and water resources in sulfuric acid production flue gas, belonging to the field of waste heat and water resource recovery. Background Art

[0002] Sulfuric acid is known as the "mother of industry" and is an important chemical raw material. The development of the sulfuric acid industry has always received great attention from countries around the world.

[0003] In China, pyrometallurgy is one of the main copper smelting processes. After preliminary processing, copper ore enters the refined copper smelting stage, which can be divided into two categories: pyrometallurgy and hydrometallurgy. Pyrometallurgy converts copper concentrate into crude copper through flash blowing or converter treatment, and then makes anode copper through pyrometallurgy, and finally obtains electrolytic copper with a copper content of more than 99.99% through electrolytic refining. In this process, SO2 is an important by-product. It is released from sulfur-containing ores during the smelting process. These sulfur dioxide gases can be collected and used for acid production, that is, the production of sulfuric acid (H2SO4). The sulfuric acid preparation process covers a series of exothermic reactions from the pyrolysis of sulfur-containing raw materials to the oxidation of SO2 and the absorption of SO3. These links constitute the energy-intensive process of sulfuric acid production and are also the key nodes for waste heat recovery. Today, many sulfuric acid production plants are committed to maximizing the recovery of high-temperature and medium-temperature potential heat energy generated by the combustion of sulfur-containing raw materials and the oxidation of sulfur dioxide. At present, the temperature of acid-making flue gas after passing through the electrostatic precipitator and entering the purification equipment (power wave) is generally above 300°C, resulting in a large waste of waste heat. It also causes a large amount of circulating cooling water required during the flue gas purification process, and at the same time leads to high energy and water consumption in the cooling water system. These have led to a considerable gap between the energy efficiency and water efficiency of acid-making in metallurgical enterprises and the advanced level of the industry. In order to narrow this gap, the sulfuric acid production industry needs to adopt innovative technologies and strategies to improve the utilization efficiency of energy and water resources. Summary of the invention

[0004] In view of the inventions and deficiencies of the above-mentioned prior art, the present invention provides a system for deep recovery of low-temperature waste heat and water resources in sulfuric acid flue gas. The present invention adds a low-temperature waste heat boiler to the existing pyrometallurgical copper (or zinc) smelting acid flue gas system to further recover 350°C low-temperature waste heat in the flue gas. The present invention not only significantly improves the recovery efficiency of waste heat and water resources, but also has the characteristics of high efficiency, low carbon emissions and high economic benefits, showing its great potential in the field of industrial energy conservation and emission reduction.

[0005] The present invention is achieved through the following solutions.

[0006] A system for deep recovery of low-temperature waste heat and water resources in sulfuric acid flue gas, comprising adding a steam drum 2, a low-temperature waste heat boiler 3, a deaerator water tank 4, a boiler feed water pump 5, a water distribution header 6, a return water pump 7, an acid-resistant pump 8, a ceramic filter 9, a liquid storage well 10 and a number of connecting pipes, necessary valves and control components to the original system;

[0007] The sulfuric acid production flue gas at 350°C from the high-temperature waste heat boiler in the original system passes through the electrostatic precipitator 1 and enters the low-temperature waste heat boiler 3. The low-temperature waste heat boiler 3 is a three-stage vertical waste heat boiler from top to bottom. The three-stage vertical waste heat boiler from top to bottom is a three-stage endothermic structure of an evaporation section, a preheating section, and a low-temperature heating section. The sulfuric acid production flue gas at 350°C passes through the evaporation section, preheating section, and low-temperature heating section of the low-temperature waste heat boiler 3 from top to bottom in sequence, and then the sulfuric acid production flue gas is cooled to 50°C and discharged from the flue outlet of the low-temperature waste heat boiler 3; a liquid storage well 10 is arranged at the bottom of the low-temperature waste heat boiler 3;

[0008] The gas-liquid mixture in the drum 2 is heated to the flue gas acid dew point of 10-15°C by a pressure deaerator, and then introduced into the gas-liquid mixture inlet at the bottom of the pipeline of the evaporation section of the low-temperature waste heat boiler 3. The saturated steam outlet at the top of the pipeline of the evaporation section of the low-temperature waste heat boiler 3 is connected to the drum 2. The saturated steam outlet at the top of the drum 2 is transported to the steam network of the plant through a pipeline.

[0009] The condensate or desalted water is introduced into the water inlet at the bottom of the low-temperature heating section pipeline of the low-temperature waste heat boiler 3 through the condensate or desalted water pump, and the hot water outlet at the upper part of the low-temperature heating section pipeline of the low-temperature waste heat boiler 3 is transported to the water distribution header 6. Part of the water in the water distribution header 6 provides 50-60°C hot water for users, and the return water after use is returned to the bottom of the low-temperature heating section pipeline of the low-temperature waste heat boiler 3 through the return water pump 7;

[0010] Another part of the water in the water-dividing manifold 6 is mixed with the deoxygenated steam and passed through the deoxygenating water tank 4 (a pressure deaerator is provided in the deoxygenating water tank 4) to raise the water-steam mixture to the flue gas acid dew point of 10-15°C, and then transported to the water-steam mixture inlet at the bottom of the preheating section pipeline in the low-temperature waste heat boiler 3 through the boiler feed water pump 5, and the gas-liquid mixture outlet at the upper part of the preheating section pipeline in the low-temperature waste heat boiler 3 is connected to the steam drum 2.

[0011] The evaporation section and preheating section pipelines of the low-temperature waste heat boiler 3 are both ordinary carbon boiler steel pipes with high-frequency welded spiral fins; the low-temperature heating section of the low-temperature waste heat boiler 3 is a fluoroplastic steel pipe.

[0012] The height of the evaporation section of the low-temperature waste heat boiler 3 is 2000-4000 mm.

[0013] The height of the preheating section of the low-temperature waste heat boiler 3 is 1500-3000 mm.

[0014] The height of the low temperature heating section of the low temperature waste heat boiler 3 is 1000-2500 mm.

[0015] The present invention realizes efficient utilization of flue gas through specific dimensions of the evaporation section, preheating section, and low-temperature heating section of the low-temperature waste heat boiler 3 .

[0016] After the sulfuric acid production flue gas is cooled to 50°C and discharged from the flue outlet of the low-temperature waste heat boiler 3, it is sequentially connected to a first-stage dynamic wave scrubber 11, a gas cooling tower 12, a second-stage dynamic wave scrubber 13, an electric precipitator 14, and a flue gas drying tower 15, and finally discharged through a SO2 blower 16 to enter the subsequent conversion and absorption process.

[0017] The working principle of the present invention is:

[0018] The flue gas discharged from the smelting furnace / converter in the original system has an initial temperature of about 800-900℃. It first recovers the waste heat in the high-temperature section through the waste heat boiler. When its temperature drops to about 350℃, it enters the electrostatic precipitator 1 for treatment. During the dust removal process, the dust and particulate matter in the flue gas will be effectively adsorbed and removed. After being treated by the electrostatic precipitator 1, the flue gas enters the newly added low-temperature waste heat boiler 3 to further recover the low-temperature waste heat in the flue gas.

[0019] Inside the low-temperature waste heat boiler 3, the flue gas passes through the evaporation section, preheating section and low-temperature heating section in sequence, and performs deep heat exchange with the gas-liquid mixture and condensed water or desalted water in the pipeline. In this process, the sulfuric acid flue gas in the low-temperature heating section drops below the flue gas acid dew point to form dilute sulfuric acid condensate, which then flows into the liquid storage well 10. The dilute sulfuric acid condensate is sent to the enterprise waste acid (water) treatment and recovery system by the acid-resistant pump 8 to recover water resources and sulfuric acid.

[0020] After the sulfuric acid flue gas is cooled to 50°C and discharged from the flue outlet of the low-temperature waste heat boiler 3, it is sequentially connected to the first-stage dynamic wave scrubber 11, the gas cooling tower 12, the second-stage dynamic wave scrubber 13, the electrostatic precipitator 14, the flue gas drying tower 15, and finally discharged through the SO2 fan 16 to enter the subsequent conversion and absorption process.

[0021] Condensate or treated desalted water is injected into the low-temperature heating section of the low-temperature waste heat boiler 3 by the pump system to absorb the heat of the flue gas, forming 50-60°C hot water, which is transported to the water distribution manifold 6. Part of the water in the water distribution manifold 6 provides 50-60°C hot water for users, and the return water after use is returned to the bottom of the low-temperature heating section pipeline of the low-temperature waste heat boiler 3 through the return pump 7 to complete the cycle.

[0022] Another part of the water in the water-dividing manifold 6 is mixed with the deoxygenated steam and passed through the deoxygenating water tank 4 (a pressure deaerator is provided in the deoxygenating water tank 4) to raise the water-vapor mixture to the flue gas acid dew point of 10-15°C, and then is transported to the water-vapor mixture inlet at the bottom of the preheating section pipeline in the low-temperature waste heat boiler 3 through the boiler feed water pump 5, where the water-vapor mixture is preheated after absorbing the flue gas heat and then is transported to the steam drum 2.

[0023] The water vapor mixture preheated in drum 2 is raised to the flue gas acid dew point of 10-15°C by a pressure deaerator, and then introduced into the evaporation section of low-temperature waste heat boiler 3, absorbing the flue gas heat to form saturated steam, and then enters drum 2. The saturated steam outlet at the top of drum 2 is transported to the steam network of the plant through a pipeline. Raising the water vapor mixture to the flue gas acid dew point prevents corrosion of the evaporation section and preheating section pipelines in the low-temperature waste heat boiler 3.

[0024] The beneficial effects of the present invention are:

[0025] (1) The present invention adds a low-temperature waste heat boiler to the current pyrometallurgical copper (or zinc) smelting acid production flue gas system. Compared with the prior art, the present invention can maximize the recovery of 350°C low-temperature waste heat in the flue gas to generate medium- and low-pressure steam for power generation or other steam-using processes, greatly reducing the comprehensive energy consumption per unit of sulfuric acid product.

[0026] (2) The present invention greatly reduces the SO3 content in the flue gas entering the power wave through the low-temperature waste heat recovery system, reduces the heat load of the power wave, and reduces the power consumption of the heat exhaust circulating water system and the cooling tower. At the same time, it can also recover the sulfuric acid generated by the reaction of SO3 in the flue gas with water vapor, thereby increasing the sulfuric acid output and saving production costs.

[0027] (3) The present invention optimizes the recycling of water and steam, reduces dependence on external water sources, saves water resources, and reduces the water consumption and water purchase costs of enterprises. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural diagram of a system for deeply recovering low-temperature waste heat and water resources from sulfuric acid production flue gas.

[0029] The numbers in the figure are: 1-electrostatic precipitator, 2-steam drum, 3-low-temperature waste heat boiler, 4-deaerator water tank, 5-boiler feed water pump, 6-water distribution header, 7-return water pump, 8-acid-resistant pump, 9-ceramic filter, 10-liquid storage well, 11-first-stage dynamic wave scrubber, 12-gas cooling tower, 13-second-stage dynamic wave scrubber, 14-electrostatic demister, 15-flue gas drying tower, 16-SO2 fan. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. It should be noted that the embodiments in this application and the features in the embodiments can be combined with each other arbitrarily without conflict.

[0031] Example 1: Figure 1 As shown, the system for deep recovery of low-temperature waste heat and water resources in sulfuric acid flue gas includes a steam drum 2, a low-temperature waste heat boiler 3, a deaerator water tank 4, a boiler feed water pump 5, a water distribution header 6, a return water pump 7, an acid-resistant pump 8, a ceramic filter 9, a liquid storage well 10 and a number of connecting pipes, necessary valves and control components added to the original system;

[0032] The sulfuric acid production flue gas at 350°C from the high-temperature waste heat boiler in the original system passes through the electrostatic precipitator 1 and enters the low-temperature waste heat boiler 3. The low-temperature waste heat boiler 3 is a three-stage vertical waste heat boiler from top to bottom. The three-stage vertical waste heat boiler from top to bottom is a three-stage endothermic structure of an evaporation section, a preheating section, and a low-temperature heating section. The sulfuric acid production flue gas at 350°C passes through the evaporation section, preheating section, and low-temperature heating section of the low-temperature waste heat boiler 3 from top to bottom in sequence, and then the sulfuric acid production flue gas is cooled to 50°C and discharged from the flue outlet of the low-temperature waste heat boiler 3; a liquid storage well 10 is arranged at the bottom of the low-temperature waste heat boiler 3;

[0033] The gas-liquid mixture in the drum 2 is heated to the flue gas acid dew point of 10-15°C by a pressure deaerator, and then introduced into the gas-liquid mixture inlet at the bottom of the pipeline of the evaporation section of the low-temperature waste heat boiler 3. The saturated steam outlet at the top of the pipeline of the evaporation section of the low-temperature waste heat boiler 3 is connected to the drum 2. The saturated steam outlet at the top of the drum 2 is transported to the steam network of the plant through a pipeline.

[0034] The condensate or desalted water is introduced into the water inlet at the bottom of the low-temperature heating section pipeline of the low-temperature waste heat boiler 3 through the condensate or desalted water pump, and the hot water outlet at the upper part of the low-temperature heating section pipeline of the low-temperature waste heat boiler 3 is transported to the water distribution header 6. Part of the water in the water distribution header 6 provides 50-60°C hot water for users, and the return water after use is returned to the bottom of the low-temperature heating section pipeline of the low-temperature waste heat boiler 3 through the return water pump 7;

[0035] Another part of the water in the water-dividing manifold 6 is mixed with the deoxygenated steam and passed through the deoxygenating water tank 4 (a pressure deaerator is provided in the deoxygenating water tank 4) to raise the water-steam mixture to the flue gas acid dew point of 10-15°C, and then transported to the water-steam mixture inlet at the bottom of the preheating section pipeline in the low-temperature waste heat boiler 3 through the boiler feed water pump 5, and the gas-liquid mixture outlet at the upper part of the preheating section pipeline in the low-temperature waste heat boiler 3 is connected to the steam drum 2.

[0036] The evaporation section and preheating section pipelines of the low-temperature waste heat boiler 3 are both ordinary carbon boiler steel pipes with high-frequency welded spiral fins; the low-temperature heating section of the low-temperature waste heat boiler 3 is a fluoroplastic steel pipe.

[0037] The height of the evaporation section of the low-temperature waste heat boiler 3 is 3000 mm; the height of the preheating section of the low-temperature waste heat boiler 3 is 2000 mm; and the height of the low-temperature heating section of the low-temperature waste heat boiler 3 is 1000 mm.

[0038] The sulfuric acid production flue gas is cooled to 50°C and discharged from the flue outlet of the low-temperature waste heat boiler 3, and is sequentially connected to a first-stage dynamic wave scrubber 11, a gas cooling tower 12, a second-stage dynamic wave scrubber 13, an electrostatic precipitator 14, and a flue gas drying tower 15, and is finally discharged through a SO2 blower 16 to enter the subsequent conversion and absorption process.

[0039] Taking a pyrometallurgical copper smelting furnace as an example, the design parameters of the waste heat boiler of the smelting furnace are steam temperature: 254℃; rated evaporation capacity: 12t / h (saturated steam); actual evaporation capacity: 16-19t / h; smoke volume: 75000Nm 3 / h; inlet flue gas temperature: 900℃, outlet temperature: 350℃. Before the technical transformation, the upper limit of the available temperature of the system was 550℃ (900℃-350℃=550℃). By adopting the technology of the present invention, the low-temperature waste heat boiler 3 of the present invention and other components are arranged behind the high-temperature boiler, and the outlet flue gas temperature of the low-temperature waste heat boiler 3 will be reduced to about 50℃, so that the available temperature range is greatly increased to 850℃ (900℃-50℃=850℃). This improvement greatly improves the efficiency of energy utilization and may provide the factory with more energy recovery opportunities, such as power generation, heating or other process requirements. In addition, in order to prevent low-temperature corrosion in the preheating section and evaporation section of the boiler, a pressure deaerator is used. By maintaining the absolute pressure of the pressure deaerator not less than 0.2MPa, it can be ensured that the boiler feed water temperature is 10 to 15℃ higher than the acid dew point.

[0040] The waste heat recovery rate is calculated as follows:

[0041] Specific heat capacity of flue gas at 900℃~350℃ is 1.10kJ / m 3 Calculation, 0.96 is the proportion after considering various heat losses.

[0042] Before improvement (usable temperature is 550℃):

[0043] Waste heat utilization rate = [m 烟气流量 ×c pg1 ×(T 烟气进口温度1 -T 烟气出口温度1 )] / [m 烟气流量 ×c pg1 ×(T烟气进口温度1 -T 环境温度] )×0.96=60.4%

[0044] After adopting the present invention (the applicable temperature is 850°C):

[0045] Specific heat capacity of flue gas at 900℃~50℃ is 1.20kJ / m 3 The calculation takes into account the heat release due to condensation, and 0.96 is the percentage after taking into account various heat losses.

[0046] Waste heat utilization rate = [m 烟气流量 ×c pg2 ×(T 烟气进口温度1 -T 烟气出口温度2 )] / [m 烟气流量 ×c pg2 ×((T 烟气进口温度1 -T 环境温度 )]×0.96=93.2%

[0047] Obviously, the waste heat utilization rate of the unmodified system is only 60.4%. However, after the improvement, the waste heat utilization rate of the system reached 93.2%. The improved system optimizes the recovery process of flue gas heat energy through advanced waste heat recovery technology, and realizes a more efficient conversion of the heat energy contained in the flue gas. The system upgrade effectively reduces the energy loss caused by flue gas emissions and reduces the dependence on the original energy, thereby optimizing the overall utilization efficiency of resources. The effective utilization of waste heat directly reduces the cost of energy procurement and enhances the profitability of enterprises by improving the efficiency of production processes. The system reduces overall energy consumption by improving energy conversion efficiency, supporting the environmental protection policy of energy conservation and emission reduction. In the process of waste heat recovery, the system optimizes the recycling of water and steam, reduces dependence on external water sources, and realizes water resource conservation. The improved system indirectly reduces greenhouse gas emissions by reducing energy consumption, helping enterprises to achieve low-carbon development while improving energy efficiency. Overall, the technical improvement of the system not only improves the efficiency of energy utilization, but also achieves a comprehensive improvement in the economic and environmental responsibilities of enterprises by reducing resource consumption and environmental impact.

[0048] The specific implementation modes of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A system for deep recovery of low-temperature waste heat and water resources from sulfuric acid production flue gas, characterized in that: The original system is equipped with a steam drum (2), a low-temperature waste heat boiler (3), a deaerator water tank (4), a boiler feed water pump (5), a water distribution header (6), a return water pump (7), an acid-resistant pump (8), a ceramic filter (9), a liquid storage well (10), and a number of connecting pipes, necessary valves, and control components; The sulfuric acid production flue gas at 350°C from the high-temperature waste heat boiler in the original system passes through the electrostatic precipitator (1) and then enters the low-temperature waste heat boiler (3). The low-temperature waste heat boiler (3) is a three-stage vertical waste heat boiler from top to bottom. The three-stage vertical waste heat boiler from top to bottom is a three-stage heat absorption structure of an evaporation section, a preheating section, and a low-temperature heating section. After the sulfuric acid production flue gas at 350°C passes through the evaporation section, preheating section, and low-temperature heating section of the low-temperature waste heat boiler (3) from top to bottom in sequence, the sulfuric acid production flue gas is cooled to 50°C and discharged from the flue outlet of the low-temperature waste heat boiler (3); A liquid storage well (10) is provided at the bottom of the low-temperature waste heat boiler (3); The gas-liquid mixture in the drum (2) is heated to a flue gas acid dew point of 10-15° C. by a pressure deaerator, and then introduced into the gas-liquid mixture inlet at the bottom of the pipeline of the evaporation section in the low-temperature waste heat boiler (3). The saturated steam outlet at the top of the pipeline of the evaporation section in the low-temperature waste heat boiler (3) is connected to the drum (2). The saturated steam outlet at the top of the drum (2) is transported to the steam network in the plant through a pipeline. Condensate or desalted water is introduced into the water inlet at the bottom of the low-temperature heating section pipeline of the low-temperature waste heat boiler (3) through a condensation or desalted water pump, and the hot water outlet at the upper part of the low-temperature heating section pipeline of the low-temperature waste heat boiler (3) is transported to a water distribution header (6), and part of the water in the water distribution header (6) provides 50-60° C. hot water for users, and the return water after use is returned to the bottom of the low-temperature heating section pipeline of the low-temperature waste heat boiler (3) through a return water pump (7); Another part of the water in the water separation manifold (6) is mixed with the deoxygenated steam and passed through the deoxygenated water tank (4) to raise the water-steam mixture to the flue gas acid dew point of 10-15°C, and then is transported to the water-steam mixture inlet at the bottom of the preheating section pipeline in the low-temperature waste heat boiler (3) through the boiler feed water pump (5). The gas-liquid mixture outlet at the top of the preheating section pipeline in the low-temperature waste heat boiler (3) is connected to the steam drum (2).

2. The system for deep recovery of low-temperature waste heat and water resources from sulfuric acid production flue gas according to claim 1 is characterized in that: The evaporation section and preheating section pipelines of the low-temperature waste heat boiler (3) are both ordinary carbon boiler steel pipes with high-frequency welded spiral fins; the low-temperature heating section of the low-temperature waste heat boiler (3) is a fluoroplastic steel pipe.

3. The system for deep recovery of low-temperature waste heat and water resources from sulfuric acid production flue gas according to claim 1 is characterized in that: The height of the evaporation section of the low-temperature waste heat boiler (3) is 2000-4000 mm.

4. The system for deep recovery of low-temperature waste heat and water resources from sulfuric acid production flue gas according to claim 1, characterized in that: The height of the preheating section of the low-temperature waste heat boiler (3) is 1500-3000 mm.

5. The system for deep recovery of low-temperature waste heat and water resources from sulfuric acid production flue gas according to claim 1 is characterized in that: The height of the low-temperature heating section of the low-temperature waste heat boiler (3) is 1000-2500 mm.

6. The system for deep recovery of low-temperature waste heat and water resources from sulfuric acid production flue gas according to claim 1, characterized in that: After the sulfuric acid production flue gas is cooled to 50°C and discharged from the flue outlet of the low-temperature waste heat boiler (3), it is sequentially connected to a first-stage dynamic wave scrubber (11), a gas cooling tower (12), a second-stage dynamic wave scrubber (13), an electric precipitator (14), and a flue gas drying tower (15), and finally discharged through a SO2 blower (16) to enter a subsequent conversion and absorption process.

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