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

Abstract

The application discloses a system for deeply recycling low-temperature waste heat and water resources in sulfuric acid production flue gas, and belongs to the field of waste heat and water resource recycling. The system for deeply recycling low-temperature waste heat and water resources in sulfuric acid production flue gas comprises a newly-added steam drum, a low-temperature waste heat boiler, an oxygen-removed water tank, a boiler feed water pump, a water distribution header, a backwater pump, an acid-resistant pump, a ceramic filter, a liquid storage well and a plurality of connecting pipelines, necessary valves and control elements on an original system. 350 DEG C sulfuric acid production flue gas from the high-temperature waste heat boiler of the original system enters the low-temperature waste heat boiler after passing through an electric dust collector. The low-temperature waste heat boiler is a three-section vertical waste heat boiler from top to bottom. The three-section vertical waste heat boiler is a three-section heat absorption type structure including an evaporation section, a preheating section and a low-temperature heating section from top to bottom. The 350 DEG C sulfuric acid production flue gas passes through the evaporation section, the preheating section and the low-temperature heating section of the low-temperature waste heat boiler from top to bottom in sequence, 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. The liquid storage well is arranged at the bottom of the low-temperature waste heat boiler. The application not only significantly improves the recycling efficiency of waste heat and water resources, but also has the characteristics of high efficiency, low carbon emission and high economic benefit, and shows great potential in the field of industrial energy saving and emission reduction.

Description

TECHNICAL FIELD

[0001] The application 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. BACKGROUND

[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 been highly concerned by countries around the world.

[0003] In China, pyrometallurgical process is one of the main copper smelting processes at present. After preliminary processing, copper ore enters the refined copper smelting link, which can be divided into pyrometallurgical process and hydrometallurgical process. Pyrometallurgical process converts copper concentrate into blister copper through flash smelting or converter treatment, and then produces anode copper through pyrometallurgical refining, and finally produces electrolytic copper with a copper content of more than 99.99% through electrolytic refining. In this process, SO2 is an important by-product, which is released from sulfur-containing ores during the smelting process. These sulfur dioxide gases can be collected and used for acid production, i.e. the production of sulfuric acid (H2SO4). The sulfuric acid production 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 an energy-intensive process of sulfuric acid production, and are also key nodes for waste heat recovery. Today, many sulfuric acid production devices strive to maximize the recovery of high-temperature and medium-temperature heat energy generated by the combustion of sulfur-containing raw materials and the oxidation of sulfur dioxide. At present, the temperature of the acid-making flue gas after passing through the electrostatic precipitator and entering the purification equipment (dynamic wave) is generally above 300 DEG C, resulting in a large waste of waste heat, and also causing a large amount of circulating cooling water required in the flue gas purification process. At the same time, it leads to high energy consumption and water consumption of the cooling water system. These result in a not small gap between the energy efficiency and water efficiency of the sulfuric acid production of 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 efficiency of energy and water resources. SUMMARY

[0004] In view of the above-mentioned problems and deficiencies of the prior art, the present application provides a system for deeply recovering low-temperature waste heat and water resources in sulfuric acid production flue gas. The present application adds a low-temperature waste heat boiler to the existing pyrometallurgical copper (or zinc) smelting acid-making flue gas system to further recover the low-temperature waste heat of 350 DEG C in the flue gas. The present application not only significantly improves the recovery efficiency of waste heat and water resources, but also has the characteristics of high efficiency, low carbon emission and high economic benefit, and shows great potential in the field of industrial energy saving and emission reduction.

[0005] The present application is realized by the following scheme.

[0006] A system for deeply recovering low-temperature waste heat and water resources in sulfuric acid production flue gas, comprising a newly added system on the original system, including a steam drum 2, a low-temperature waste heat boiler 3, an oxygen removal water tank 4, a boiler feed water pump 5, a water distribution header 6, a backwater pump 7, an acid-resistant pump 8, a ceramic filter 9, a liquid storage well 10 and several connecting pipelines, necessary valves and control elements;

[0007] The 350℃ sulfuric acid production flue gas from the high-temperature waste heat boiler in the original system passes through the electric precipitator 1 and enters the low-temperature waste heat boiler 3. The low-temperature waste heat boiler 3 is a three-section vertical waste heat boiler from top to bottom. The three-section vertical waste heat boiler is a three-section heat absorption structure from top to bottom, including evaporation section, preheating section and low-temperature heating section. The 350℃ sulfuric acid production flue gas 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 turn, and then the sulfuric acid production flue gas is cooled to 50℃ and discharged from the flue outlet of the low-temperature waste heat boiler 3. The bottom of the low-temperature waste heat boiler 3 is provided with a liquid storage well 10.

[0008] The gas-liquid mixture in the steam drum 2 is heated to the acid dew point of the flue gas 10-15℃ by the pressure deaerator, and then enters the gas-liquid mixture inlet at the bottom of the evaporation section of the low-temperature waste heat boiler 3. The saturated steam outlet at the upper part of the evaporation section of the low-temperature waste heat boiler 3 is connected to the steam drum 2. The saturated steam outlet at the upper part of the steam drum 2 is connected to the steam pipe network in the plant area by a pipeline.

[0009] The condensed water or desalinated water is pumped into the water inlet at the bottom of the low-temperature heating section of the low-temperature waste heat boiler 3 by the condensed water or desalinated water pump. The hot water outlet at the upper part of the low-temperature heating section of the low-temperature waste heat boiler 3 is connected to the water distribution header 6. Part of the water in the water distribution header 6 provides 50-60℃ hot water for users. The backwater is pumped back to the bottom of the low-temperature heating section of the low-temperature waste heat boiler 3 by the backwater pump 7.

[0010] Another part of the water in the water distribution header 6 is mixed with deaerated steam, and then the water-steam mixture is heated to the acid dew point of the flue gas 10-15℃ by the deaerated water tank 4 (which is provided with a pressure deaerator). Then the water-steam mixture is pumped to the water-steam mixture inlet at the bottom of the preheating section of the low-temperature waste heat boiler 3 by the boiler feed water pump 5. The gas-liquid mixture outlet at the upper part of the preheating section of the low-temperature waste heat boiler 3 is connected to the steam drum 2.

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

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

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

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

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

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

[0017] The working principle of the present application is as follows:

[0018] The flue gas discharged from the smelting furnace / converter in the original system has an initial temperature of about 800-900 DEG C, is first subjected to high-temperature section waste heat recovery through the waste heat boiler, and when its temperature is reduced to about 350 DEG C, enters the treatment of the electrostatic precipitator 1. In the dust removal process, the dust and particulate matters in the flue gas are effectively adsorbed and removed. After the flue gas is treated by the electric precipitator 1, it enters the low-temperature waste heat boiler 3 which is additionally provided, to further recover the low-temperature waste heat in the flue gas.

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

[0020] After the sulfuric acid production flue gas is cooled to 50 DEG C and discharged from the flue discharge port of the low-temperature waste heat boiler 3, it is sequentially connected with the first power wave scrubber 11, the gas cooling tower 12, the second power wave scrubber 13, the electric 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] After the condensate water or the treated desalinated water is injected by the pump system into the low-temperature heating section of the low-temperature waste heat boiler 3 to absorb the heat of the flue gas, 50-60 DEG C hot water is formed and delivered to the water distribution header 6. Part of the water in the water distribution header 6 provides 50-60 DEG C hot water for users, and the used backwater is returned to the bottom of the low-temperature heating section pipeline of the low-temperature waste heat boiler 3 through the backwater pump 7 to complete the circulation.

[0022] Another part of water in the water distribution header 6 is mixed with deaerated steam, and then the water-steam mixture is increased to the acid dew point of flue gas 10-15℃ by the deaerated water tank 4 (a pressure deaerator is arranged in the deaerated water tank 4), and then the water-steam mixture is transported to the water-steam mixture inlet at the bottom of the preheating section pipeline in the low-temperature waste heat boiler 3 by the boiler feed water pump 5, the water-steam mixture is preheated by absorbing the heat of flue gas, and then the water-steam mixture is transported to the steam drum 2.

[0023] The preheated water-steam mixture in the steam drum 2 is increased to the acid dew point of flue gas 10-15℃ by the pressure deaerator, and then the water-steam mixture is introduced into the evaporation section of the low-temperature waste heat boiler 3, and then the water-steam mixture is formed into saturated steam by absorbing the heat of flue gas, and then the saturated steam is introduced into the steam drum 2, and then the saturated steam at the upper part of the steam drum 2 is transported to the steam pipe network in the plant area through a pipeline. The water-steam mixture is increased to the acid dew point of flue gas to prevent the corrosion of the pipeline in the evaporation section and the preheating section of the low-temperature waste heat boiler 3.

[0024] The beneficial effects of the present application are as follows:

[0025] (1) The present application adds a low-temperature waste heat boiler in the current pyrogenic copper (or zinc) smelting and acid-making flue gas system, compared with the prior art, the low-temperature waste heat boiler can maximize the recovery of the low-temperature waste heat in the flue gas at 350℃ to generate medium and low pressure steam, which is used for power generation or other steam-using processes, and greatly reduces the comprehensive energy consumption per unit product of sulfuric acid.

[0026] (2) The present application greatly reduces the SO3 content in the flue gas entering the dynamic wave through the low-temperature waste heat recovery system, reduces the heat load of the dynamic wave, reduces the power consumption of the heat removal circulating water system and the cooling tower, and at the same time, the sulfuric acid generated by the reaction of SO3 in the flue gas with water vapor can be recovered, the sulfuric acid production is increased, and the production cost is saved.

[0027] (3) The present application optimizes the recycling of water and steam, reduces the dependence on external water sources, realizes the saving of water resources, and reduces the water consumption and water purchase cost of enterprises. BRIEF DESCRIPTION OF DRAWINGS

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

[0029] In the figure, the numbers are as follows: 1-electric precipitator, 2-steam drum, 3-low-temperature waste heat boiler, 4-deaerated water tank, 5-boiler feed water pump, 6-water distribution header, 7-backwater 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-electric demister, 15-flue gas drying tower, and 16-SO2 fan. DETAILED DESCRIPTION

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0031] Example 1: As Figure 1 As shown, the system for deep recovery of low-temperature waste heat and water resources in sulfuric acid flue gas includes the addition of 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 manifold 6, a return water pump 7, an acid-resistant pump 8, a ceramic filter 9, a liquid storage well 10, and several connecting pipes, necessary valves, and control components to the original system.

[0032] The 350°C sulfuric acid flue gas from the high-temperature waste heat boiler in the original system enters the low-temperature waste heat boiler 3 after passing through the electrostatic precipitator 1. The low-temperature waste heat boiler 3 is a three-section vertical waste heat boiler from top to bottom, consisting of an evaporation section, a preheating section, and a low-temperature heating section. The 350°C sulfuric acid flue gas passes through the evaporation section, preheating section, and low-temperature heating section of the low-temperature waste heat boiler 3 from top to bottom, and then the sulfuric acid 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 set at the bottom of the low-temperature waste heat boiler 3.

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

[0034] Condensate or demineralized water is pumped into the water inlet at the bottom of the low-temperature heating section of the low-temperature waste heat boiler 3 via a condensate or demineralized water pump. The hot water outlet at the top of the low-temperature heating section of the low-temperature waste heat boiler 3 is transported to the water distribution manifold 6. Part of the water in the water distribution manifold 6 provides users with 50-60℃ hot water. The returned water after use is returned to the bottom of the low-temperature heating section of the low-temperature waste heat boiler 3 via a return water pump 7.

[0035] Another portion of the water in the water distribution manifold 6 is mixed with deoxygenated steam and then passed through the deoxygenated water tank 4 (which is equipped with a pressure deaerator) to raise the water-steam mixture to the flue gas acid dew point of 10-15℃. Then, it is transported by the boiler feed water pump 5 to the water-steam mixture inlet at the bottom of the preheating section pipe in the low-temperature waste heat boiler 3. The gas-liquid mixture outlet at the top of the preheating section pipe in the low-temperature waste heat boiler 3 is connected to the steam drum 2.

[0036] Wherein the evaporation section, preheating section pipe of low temperature waste heat boiler 3 are ordinary carbon boiler steel pipe, ordinary carbon boiler steel pipe outside with high frequency welding spiral fin; The low temperature heating section of low temperature waste heat boiler 3 is fluorine plastic steel pipe.

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

[0038] Wherein the flue gas of sulfuric acid production is cooled to 50 DEG C and discharged from the flue discharge port of low temperature waste heat boiler 3, then sequentially connected with first power wave scrubber 11, gas cooling tower 12, second power wave scrubber 13, electric precipitator 14, flue gas drying tower 15, and finally discharged through SO2 fan 16, and enters subsequent conversion and absorption process.

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

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

[0041] The specific heat capacity of flue gas from 900 DEG C to 350 DEG C is 1.10kJ / m 3 , and 0.96 is the proportion after considering various heat losses.

[0042] Before improvement (available temperature is 550 DEG C):

[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] ) x 0.96 = 60.4%

[0044] After the improvement of the present application (the temperature can be 850℃):

[0045] The specific heat capacity of flue gas at 900℃-50℃ is 1.20kJ / m 3 The calculation has considered the condensation heat release, and 0.96 is the proportion after considering various heat losses.

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

[0047] Obviously, the waste heat utilization rate of the unimproved system is only 60.4%. However, after the improvement, the waste heat utilization rate of the system reaches 93.2%. The improved system optimizes the flue gas heat recovery process through advanced waste heat recovery technology, realizing more efficient conversion of the heat energy contained in the flue gas. The system upgrade effectively reduces the energy loss caused by flue gas emission, reduces the dependence on primary energy, and optimizes the overall utilization efficiency of resources. The effective use of waste heat directly reduces the energy procurement cost, and through the improvement of the production process efficiency, the profitability of the enterprise is enhanced. The system improves the energy conversion efficiency, reduces the overall energy consumption, and supports the environmental protection policy of energy saving and emission reduction. In the waste heat recovery process, the system optimizes the recycling of water and steam, reduces the dependence on external water sources, and realizes the conservation of water resources. The improved system reduces the emission of greenhouse gases indirectly by reducing energy consumption, helping enterprises to improve energy efficiency while achieving low-carbon development. Overall, the technical improvement of the system not only improves the utilization efficiency of energy, but also reduces resource consumption and environmental impact, realizing the comprehensive improvement of enterprises in economic and environmental responsibility.

[0048] The specific embodiments of the present application are described in detail above in combination with the drawings, but the present application is not limited to the above-mentioned embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the purpose of the present application.

Claims

1. A system for deep recovery of low-temperature waste heat and water resources in sulfuric acid production flue gas, characterized in that, The new system includes a new steam drum (2), a low-temperature waste heat boiler (3), a deoxygenated water tank (4), a boiler feed water pump (5), a water distribution header (6), a backwater pump (7), an acid-resistant pump (8), a ceramic filter (9), a liquid storage well (10), and a plurality of connecting pipelines, necessary valves and control elements. The 350℃ sulfuric acid production flue gas from the high-temperature waste heat boiler in the original system passes through an electric dust collector (1) and then enters the low-temperature waste heat boiler (3). The low-temperature waste heat boiler (3) is a three-section vertical waste heat boiler from top to bottom. The three-section vertical waste heat boiler is a three-section heat absorption structure from top to bottom, including an evaporation section, a preheating section, and a low-temperature heating section. The 350℃ sulfuric acid production flue gas passes through the evaporation section, the preheating section, and the 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℃ and discharged from the flue outlet of the low-temperature waste heat boiler (3). The low-temperature waste heat boiler (3) is provided with a liquid storage well (10) at the bottom. The gas-liquid mixture in the steam drum (2) is heated by a pressure deaerator to a temperature 10-15℃ higher than the acid dew point of the flue gas, and then is introduced into the gas-liquid mixture inlet at the bottom of the evaporation section of the low-temperature waste heat boiler (3). The saturated steam outlet at the upper part of the evaporation section of the low-temperature waste heat boiler (3) is connected to the steam drum (2). The saturated steam outlet at the upper part of the steam drum (2) is connected to the steam pipeline network in the plant area through a pipeline. The condensed water or desalinated water is introduced into the water inlet at the bottom of the low-temperature heating section of the low-temperature waste heat boiler (3) through a condensed water pump or a desalinated water pump. The hot water outlet at the upper part of the low-temperature heating section of the low-temperature waste heat boiler (3) is connected to the water distribution header (6). Part of the water in the water distribution header (6) is used to provide 50-60℃ hot water. The backwater is pumped back to the low-temperature heating section of the low-temperature waste heat boiler (3) by a backwater pump (7). The other part of the water in the water distribution header (6) is mixed with deoxygenated steam, and the temperature of the water-steam mixture is increased to 10-15℃ higher than the acid dew point of the flue gas by the deoxygenated water tank (4). Then the water-steam mixture is pumped to the water-steam mixture inlet at the bottom of the preheating section of the low-temperature waste heat boiler (3) by a boiler feed water pump (5). The gas-liquid mixture outlet at the upper part of the preheating section of 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 in the process of sulfuric acid flue gas according to claim 1, characterized in that, The evaporation section and the preheating section of the low-temperature waste heat boiler (3) are made of ordinary carbon steel boiler pipes, and the outer surface of the ordinary carbon steel boiler pipes is provided with high-frequency welded spiral fins. The low-temperature heating section of the low-temperature waste heat boiler (3) is made of fluoroplastic steel pipes.

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

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

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

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

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