Method and system for purifying sulfur-containing flue gas and recovering sulfur resource

Abstract

The invention discloses a method and a system for purifying sulfur-containing flue gas and recovering sulfur resources. The system comprises an activated carbon adsorption tower, an activated carbon desorption tower, a hot blast stove, a washing and purifying device, a condensing device, an indirect heat exchange device, a multi-stage countercurrent absorption reaction device, an air mixing chamber, a wastewater treatment unit and the like. The washed and purified SRG is cooled and dewatered in advance before being pressurized, a large amount of water carried in the SRG is removed, precipitation of condensed acid water in the follow-up pressurization process is avoided, corrosion loss of pressurization equipment and follow-up equipment is prevented, safe and stable operation of a system is guaranteed, and the purpose of continuous non-stop production is achieved; and the production efficiency can be remarkably improved while the input cost is reduced. Meanwhile, waste heat of the system can be fully utilized, extra energy consumption is reduced, and then carbon emission is remarkably reduced.

Description

Technical Field

[0001] The invention relates to a steel plant flue gas treatment technology, and in particular to a method and a system for purifying sulfur-containing flue gas and recovering sulfur resources, belonging to the technical field of flue gas treatment. Background Art

[0002] The sintering pelletizing process is the basic link in the steel industry, and the amount of waste gas discharged is large (about 2000-3000Nm 3 / t (sintered ore), high temperature (160-180℃), complex pollutant composition, including SO2, NOx, dioxin, dust, etc., among which SO2, NOx, dioxin, and dust account for about 70%, 48%, 90%, and 40% of the total emissions of each pollutant in the steel industry, respectively, and are the focus and difficulty of air pollution control. Activated carbon flue gas purification has been widely promoted in the steel pelletizing process. Activated carbon flue gas purification can make use of sulfur dioxide in flue gas as a resource, and the general by-product is concentrated sulfuric acid or sodium pyrosulfite.

[0003] In the prior art, the upper part of the decomposition tower is a heating section, and the hot flue gas generated by the hot blast furnace is used to indirectly decompose the activated carbon, so that pollutants such as sulfur dioxide adsorbed in the activated carbon are released, and the activated carbon is simultaneously decomposed and regenerated and enters the cooling section; in the cooling section, it is indirectly cooled by air to a safe temperature and discharged from the decomposition tower. Nitrogen is passed through the upper and lower parts of the decomposition tower, and the decomposed SO2 gas and other impurities are taken out from the transition section and sent to the by-product treatment system (such as the sodium pyrosulfite production process). This mixed gas containing SO2 is called SRG gas. Chinese patent document CN111153418A discloses a system and method for the resource recovery of activated coke regeneration gas to produce polysalts. The SRG gas is first washed and purified, and then the dust and other gaseous impurities are removed and sent to a three-stage absorption reactor after pressurization to generate a supersaturated solution of sodium pyrosulfite. The supersaturated solution is separated by a centrifuge and dried by a dryer to obtain a finished product of sodium tar sulfate. However, in actual operation, due to the high water content of SRG gas after washing and purification, condensed acid water will precipitate after pressurization, which will seriously affect the completely stable operation of the booster fan. Therefore, it is necessary to frequently shut down for maintenance and replace new fans, which will seriously affect the continuous production and significantly increase production costs. Summary of the invention

[0004] In view of the problems in the prior art that the existing process of producing sodium metabisulfite using SRG gas has serious equipment corrosion, which affects the safe operation of the system, is unable to achieve continuous production, and has high cost investment, the present invention provides a method and system for purifying sulfur-containing flue gas and recovering sulfur resources. The method cools and removes water in advance the washed and purified SRG gas before the pressurization treatment, thereby removing a large amount of water entrained in the SRG gas, avoiding the precipitation of condensed acid water in the subsequent pressurization process, preventing corrosion loss of the pressurization equipment and its subsequent equipment, ensuring the safe and stable operation of the system, achieving the purpose of continuous production without stopping, and significantly improving production efficiency while reducing investment costs.

[0005] In order to achieve the above technical objectives, the technical solutions adopted by the present invention are as follows: According to a first embodiment of the present invention, a method for purifying sulfur-containing flue gas and recovering sulfur resources is provided: A method for purifying sulfur-containing flue gas and recovering sulfur resources, the method comprising: 1) The sulfur-containing flue gas is adsorbed by activated carbon (desulfurization and denitrification). After the adsorption treatment is completed, the clean flue gas is discharged and the activated carbon that adsorbs the pollutants is processed in the next step.

[0006] 2) The activated carbon adsorbed with pollutants is subjected to analytical regeneration treatment. After the analytical regeneration treatment is completed, the regenerated activated carbon obtained is returned to step 1) for recycling, and the analyzed sulfur-rich gas is subjected to the next step of treatment.

[0007] 3) The sulfur-rich gas is washed to obtain high-sulfur gas and washing wastewater, the washing wastewater is treated separately and discharged in compliance with the standards, and the high-sulfur gas is treated in the next step.

[0008] 4) The high-sulfur gas is sequentially subjected to condensation dehumidification and pressurization treatment, and then subjected to multi-stage countercurrent absorption reaction with alkali solution, and after the reaction is completed, reaction waste liquid, sodium pyrosulfite crystals and reaction tail gas are obtained respectively. The reaction waste liquid is used as alkali solution after alkali preparation, and the sodium pyrosulfite crystals are dried to obtain sodium pyrosulfite finished product and dry tail gas, and the reaction tail gas and dry tail gas are both introduced into the sulfur-containing flue gas of step 1) to participate in adsorption treatment.

[0009] Preferably, in step 4), the high-sulfur gas is first subjected to condensation and dehumidification treatment and temperature increase treatment in sequence and then to pressurization treatment.

[0010] Preferably, the condensation dehumidification treatment is to cool the high-sulfur gas to below 10°C, preferably 1-8°C.

[0011] Preferably, the temperature raising treatment is to perform indirect heat exchange between the high-sulfur gas and the sulfur-rich gas and make the temperature of the high-sulfur gas be 30-60°C, preferably 35-50°C.

[0012] Preferably, in step 4), the reaction tail gas and the drying tail gas are discharged after being subjected to spray absorption treatment with alkali solution. Preferably, the alkali solution after spray absorption treatment is subjected to multi-stage countercurrent absorption reaction with high-sulfur gas. Preferably, the alkali solution is a sodium carbonate solution.

[0013] As a preferred method, during the spray absorption process, the target flow rate of the spray liquid during the spray absorption is set as q2, Nm 3 / h. Then we have: q2=a×(L1+1.07q1×(1-c1)+4000) (1) In formula (1), q1 is the flow rate of high-sulfur gas after supercharging, Nm 3 / h. c1 is the volume concentration of SO2 in the high-sulfur gas after pressurization. a is the system empirical constant, with a value of 0.0015~0.004. L1 is the input amount of hot air during drying, Nm 3 / h.

[0014] The actual flow rate of the spray liquid during real-time detection of spray absorption is recorded as q3, Nm 3 / h. Real-time detection of the frequency of the spray liquid circulation pump is recorded as f, Hz. Then: (I) When (q3-q2) / q2≥2%, reduce the frequency of the spray liquid circulation pump by f×[(q3-q2) / q2] 1 / 2 .

[0015] (II) When (q3-q2) / q2≤-2%, increase the frequency of the spray liquid circulation pump by f×[(q3-q2) / q2] 1 / 2 .

[0016] (III) When -2%<(q3-q2) / q2<2%, steps (I)-(III) are repeated periodically.

[0017] Preferably, in step 4), the drying is hot air drying. During the drying process, the corresponding amount of hot air is delivered according to the mass of the sodium pyrosulfite crystals and the moisture content of the finished sodium pyrosulfite reaches the target value. The mass of the sodium pyrosulfite before drying is recorded as m1, kg. The input amount of hot air during drying is recorded as L1, Nm 3 / h. Then we have: m1=q1×c1×(190 / 22.4)×η / (1-r1) (2) L1=[m1×(r1-r2)×(Cp3×(t3-t2)+γ)+m2×Cp2×t4-m1×Cp2×t2] / [Cp1×ρ1×(t1-t3-(k×t1)] (3) In equations (2)-(3), q1 is the flow rate of high-sulfur gas after supercharging, Nm 3 / h. c1 is the volume concentration of SO2 in the high-sulfur gas after pressurization. η is the conversion efficiency, with a value ranging from 0.9 to 1. r1 is the moisture content of sodium metabisulfite before drying, %. r2 is the moisture content of sodium metabisulfite after drying, %. Cp1 is the specific heat capacity at constant pressure of the hot air, with a value of 0.245 kcal / (kg·°C). Cp2 is the specific heat capacity of sodium metabisulfite, with a value of 0.41 kcal / (kg·°C). Cp3 is the specific heat capacity of water, with a value of 1.0 kcal / (kg·°C). ρ1 is the density of the hot air under standard conditions, with a value of 1.252 kg / Nm 3 . t1 is the temperature of the hot air before drying, °C. t2 is the temperature of sodium metabisulfite before drying, °C. t3 is the temperature of the hot air after drying, °C. γ is the heat of vaporization of water at temperature t3, with a value of 535.8 kcal / kg. t4 is the temperature of sodium metabisulfite after drying, °C. m2 is the mass of sodium metabisulfite after drying, kg. k is the heat loss coefficient of the system before and after drying, with a value ranging from 0.5 to 5%. Both r1 and r2 are mass moisture contents.

[0018] Preferably, the hot air is the waste hot air discharged from the desorption heating section and / or the desorption cooling section during the desorption and regeneration process of the activated carbon. Preferably, the waste hot air is a mixed hot air composed of the waste hot air discharged from the desorption heating section and the waste hot air discharged from the desorption cooling section. The temperature of this mixed hot air is 130 - 160 °C, preferably 140 - 155 °C.

[0019] Preferably, during the drying process, the actual temperature of the waste hot air discharged from the desorption heating section is detected in real time and denoted as T1, °C. The actual temperature of the waste hot air discharged from the desorption cooling section is detected in real time and denoted as T2, °C. The actual temperature of the mixed hot air is detected in real time and denoted as T3, °C. The target temperature of the mixed hot air is set and denoted as T0, °C. Then: (i) When T3 - T0 ≥ 2, reduce the mixing amount of the waste hot air discharged from the desorption heating section and increase the mixing amount of the waste hot air discharged from the desorption cooling section. The reduction amount of the waste hot air discharged from the desorption heating section is 0.5×(T3 - T0) / T1, and the increase amount of the waste hot air discharged from the desorption cooling section is 0.5×(T3 - T0) / T2.

[0020] (ii) When T3 - T0 ≤ -2, increase the mixing amount of the waste hot air discharged from the desorption heating section and reduce the mixing amount of the waste hot air discharged from the desorption cooling section. The increase amount of the waste hot air discharged from the desorption heating section is 丨0.5×(T3 - T0) / T1丨, and the reduction amount of the waste hot air discharged from the desorption cooling section is 丨0.5×(T3 - T0) / T2丨.

[0021] (iii) When -2 < T3 - T0 < 2, the actual flow rate of the mixed hot air is detected in real time and denoted as L2, Nm 3 / h. The target flow rate of the mixed hot air is L1, Nm3 / h. Then there is: When (L2 - L1) / L1 ≥ 2%, simultaneously reduce the mixing amount of the waste hot air discharged from the analytical heating section and the analytical cold section. The reduction amount of both is (L2 - L1) / 2L1.

[0022] When (L2 - L1) / L1 ≤ -2%, simultaneously increase the mixing amount of the waste hot air discharged from the analytical heating section and the analytical cold section. The increase amount of both is 丨(L2 - L1) / 2L1丨.

[0023] When -2% < (L2 - L1) / L1 < 2%, periodically repeat steps (i)-(iii).

[0024] According to the second embodiment of the present invention, a system for purifying and recovering sulfur resources from sulfur-containing flue gas is provided: A system for purifying and recovering sulfur resources from sulfur-containing flue gas or a system for the method as described in the first embodiment. The system includes an activated carbon adsorption tower (including a desulfurization tower and a denitration tower), an activated carbon regeneration tower, a hot blast stove, a washing and purification device, a condensation device, a multi-stage countercurrent absorption reaction device, and a wastewater treatment unit. The raw flue gas inlet pipe is connected to the inlet of the activated carbon adsorption tower, and the outlet of the activated carbon adsorption tower is connected to the clean flue gas discharge pipe. The discharge port of the activated carbon adsorption tower is connected to the feed port of the activated carbon regeneration tower through a first activated carbon conveying mechanism, and the discharge port of the activated carbon regeneration tower is connected to the feed port of the activated carbon adsorption tower through a second activated carbon conveying mechanism.

[0025] The hot air outlet of the hot blast stove is connected to the air inlet of the heating section of the activated carbon regeneration tower through a first hot air pipe, and the air outlet of the heating section of the activated carbon regeneration tower is connected to the hot air inlet of the hot blast stove through a second hot air pipe. A fuel conveying pipe and an auxiliary gas conveying pipe are also connected to the hot blast stove. The air inlet of the cooling section of the activated carbon regeneration tower is connected to a cooling air inlet pipe, and the air outlet of the cooling section of the activated carbon regeneration tower is connected to a cooling exhaust pipe. The gas outlet of the SRG section of the activated carbon regeneration tower is connected to the air inlet of the washing and purification device through a rich sulfur gas conveying pipe. The air outlet of the washing and purification device is connected to the air inlet of the condensation device through a high-sulfur gas conveying pipe, and the air outlet of the condensation device is connected to the air inlet of the multi-stage countercurrent absorption reaction device through a high-sulfur dehumidified gas conveying pipe. A booster fan is also provided on the high-sulfur dehumidified gas conveying pipe. The water outlet of the washing and purification device is connected to the water inlet of the wastewater treatment unit through an acidic wastewater conveying pipe.

[0026] The liquid inlet of the multi-stage countercurrent absorption reaction device is connected to the liquid outlet of the alkali preparation tank through the alkali solution input pipeline. The material outlet of the multi-stage countercurrent absorption reaction device is connected to the material inlet of the centrifugal separation device through the solid-liquid mixture conveying mechanism. The liquid outlet of the centrifugal separation device is connected to the liquid inlet of the alkali preparation tank through the alkali solution circulation pipeline. The material outlet of the centrifugal separation device is connected to the material inlet of the drying device through the material conveying mechanism. The air inlet of the drying device is connected to a drying air inlet pipeline. The tail gas outlet of the multi-stage countercurrent absorption reaction device is connected to the air inlet of the activated carbon adsorption tower through the first tail gas conveying pipeline. The tail gas outlet of the drying device is connected to the air inlet of the activated carbon adsorption tower through the second tail gas conveying pipeline. Preferably, a dust collector is also provided on the second tail gas conveying pipeline.

[0027] Preferably, the system further comprises an indirect heat exchange device. The indirect heat exchange device is arranged between the sulfur-rich gas delivery pipeline and the high-sulfur dehumidification gas delivery pipeline. The hot mass end of the indirect heat exchange device is connected to the sulfur-rich gas delivery pipeline, and the cold mass end is connected to the high-sulfur dehumidification gas delivery pipeline.

[0028] Preferably, the system also includes a spray device. The tail gas outlet of the multi-stage countercurrent absorption reaction device is connected to the air inlet of the spray device through the first tail gas delivery pipeline. The tail gas outlet of the drying device is connected to the air inlet of the spray device through the second tail gas delivery pipeline. The air outlet of the spray device is connected to the clean flue gas emission pipeline through the clean tail gas delivery pipeline. The liquid outlet of the alkali preparation tank is connected to the liquid inlet of the spray device through the first alkali solution input pipeline, and the liquid outlet of the spray device is connected to the liquid inlet of the multi-stage countercurrent absorption reaction device through the second alkali solution input pipeline.

[0029] Preferably, the system further comprises an air distribution chamber. A first hot air branch pipe is led out from the second hot air duct and connected to the hot air inlet of the air distribution chamber. A second hot air branch pipe is led out from the cooling exhaust duct and connected to the hot air inlet of the air distribution chamber. A throttle valve is independently provided on the first hot air branch pipe and the second hot air branch pipe. The hot air outlet of the air distribution chamber is connected to the air inlet of the drying device through the drying air inlet pipe.

[0030] In the prior art, since SRG gas contains impurities such as dust, SO3, HCl, and HF in addition to a large amount of SO2, water washing is generally used for pretreatment to remove the above impurities and ensure the purity of subsequent by-products. However, due to the relatively high temperature of SRG gas (above 350°C), a large amount of acidic water vapor (generally not less than 5% by volume) will be generated during the washing and purification process. These acidic water vapors will enter the subsequent process with the purified high-sulfur gas, especially in the subsequent supercharging process, they will precipitate in the form of condensed acid water, which will damage the supercharging equipment and subsequent production facilities, increase production costs, and seriously affect the continuity of production. Therefore, the present invention provides a method and system for purifying sulfur-containing flue gas and recovering sulfur resources. The high-sulfur gas containing a large amount of acidic water vapor after washing and purification is first condensed and dehumidified to remove the acidic water vapor it carries. The dehumidified high-sulfur gas then enters the subsequent pressurization and absorption reaction process. This can prevent the precipitation of acidic water vapor in the pressurizing equipment and its subsequent equipment, which may cause corrosion and loss of the equipment, thereby increasing the service life of the equipment, reducing production costs, and ensuring the safe and stable operation of the system. At the same time, it achieves the purpose of long-term continuous production of the system without stopping, thereby significantly improving production efficiency.

[0031] In the present invention, in order to remove as much water as possible (the volume content of water is less than 1% or less) in the high-sulfur gas after washing and purification, the high-sulfur gas needs to be cooled to below 10°C during the condensation and dehumidification process. In actual production, it is found that if the high-sulfur gas with a lower temperature after condensation and dehumidification is directly pressurized and enters the subsequent countercurrent absorption reaction process, it will cause the fan and pipeline to be easily corroded, causing sulfur dioxide gas leakage, posing a safety hazard. Therefore, based on the characteristics of the analyzed sulfur-rich gas with a higher calorific value, the present invention designs a heat exchanger (a dust-resistant and corrosion-resistant heat pipe heat exchanger: such as Figure 5As shown, the heat exchanger has two upper and lower chambers. The lower chamber carries high-temperature sulfur-rich gas, and the upper chamber carries low-temperature high-sulfur gas or high-sulfur dehumidified gas. Multiple heat pipes are arranged between the two chambers. The heat pipes pass through the upper and lower cavities, are fixed on the upper cavity, and the lower part expands freely. To avoid dust accumulation and blockage, the heat pipes are both bare pipes inside and outside, and no fins are set. The inside of the heat pipe is rust-proofed. Each heat pipe has an openable lid at the top, into which a certain amount of heat medium is injected, and the lid is closed and sealed after the pressure is controlled. The boiling point of the heat medium in the heat pipe is 280°C. The purpose is to control the temperature of the heat pipe on the lower cavity side not to be lower than 280°C, so that there will be no condensate in the lower cavity and no scaling. The heat exchanger and heat pipe are made of metal. To resist the corrosion of the upper low-temperature high-sulfur gas, the upper cavity and the upper heat pipe are lined with plastic for corrosion protection. The size of the upper and lower cavities, the number of heat pipes, etc. are designed according to the heat balance of the specific project. Part of the heat of the sulfur-rich gas is used to heat the high-sulfur gas before supercharging through the heat medium, and the high-sulfur gas after condensation and dehumidification is heated. After heat exchange, the sulfur-rich gas can be reduced to about 300°C, the temperature of the high-sulfur gas is increased from less than 10°C to about 40°C, and the water saturation is reduced from 100% to less than 20%, ensuring the safe operation of the booster fan. The heat exchanger for heat exchange is composed of heat pipes. At the same time, through refined design, the surface temperature of the heat exchanger at its heat and mass end (i.e., the sulfur-rich gas section) is ensured to be not lower than 280°C. The heat exchanger is designed to be difficult to accumulate dust. The heat exchanger can save heat energy, and at the same time, it can appropriately reduce the temperature of the original sulfur-rich gas, reduce the water consumption of the purification system, and reduce the water content of the purified high-sulfur gas, and does not require additional power.

[0032] In the present invention, it is found in actual production that the tail gas generated by the production process of the present invention mainly comes from the absorption tail gas after the high-sulfur gas absorption reaction and the dry tail gas of sodium pyrosulfite. The main pollutants of these two tail gases, SO2, NOx and dust, are very low, but the gas volume is relatively large. Although recycling the tail gas to the flue gas adsorption process for adsorption treatment can achieve standard tail gas emissions, in fact, this part of the tail gas only needs desulfurization, and does not need dust removal and denitrification. Therefore, it is unreasonable to recycle it into the flue gas adsorption process for desulfurization and denitrification, which will significantly increase the load of the activated carbon adsorption device, thereby greatly increasing the operating costs; with 280m 2Taking the sintering machine as an example, the tail gas volume is generally about 3% of the sintering flue gas volume, which increases the load of the activated carbon flue gas purification device, so that the annual operating cost of the activated carbon flue gas purification device will increase by about 1.2 million yuan. Therefore, the present invention further utilizes the raw material (alkali solution) produced by sodium pyrosulfite to absorb and purify the tail gas, which can not only save operating costs, but also recover SO2 in the tail gas. That is, the present invention treats the tail gas separately by setting an alkali solution spraying process. Before the alkali solution enters the multi-stage countercurrent absorption reaction process, the tail gas is first washed and absorbed in the absorption tower to recover SO2 in the tail gas. The purified tail gas can meet the emission standards. In the tail gas absorption tower, because the alkali solution is greatly excessive, it is easy to capture SO2 in the tail gas, so that the tail gas meets the emission standards. The alkali solution only absorbs a small amount of SO2, which can still meet the requirements of the multi-stage countercurrent absorption reaction process. In this way, not only does it not require additional consumption of alkali solution and increase the load of the activated carbon adsorption device, but it also further realizes the enrichment of sulfur elements, increases the output of by-products and greatly reduces production costs.

[0033] In the present invention, due to the fluctuations in the flue gas volume and sulfur dioxide concentration of sintering (pelletizing), the air intake volume of the tail gas circulation spray absorption tower also fluctuates greatly, and the tail gas circulation spray absorption tower can only be designed according to the maximum working condition, but the operating parameters can be operated according to the most economical working condition. For this system, the tail gas circulation spray absorption tower is a fixed equipment. The present invention adjusts the flow rate of the circulating liquid by adjusting the frequency of the spray liquid circulation pump in the tail gas circulation spray absorption tower. Specifically: the spray liquid circulation pump adopts a variable frequency centrifugal pump, and a flowmeter is set at the outlet of the pump to measure the actual flow rate at the pump outlet, which is recorded as q3. The target flow rate of the spray liquid circulation pump is set by the gas volume q1 of the pressurized high-sulfur gas at the outlet of the booster fan and the volume concentration c1 of SO2 in the pressurized high-sulfur gas, which is recorded as q2: q2=a×(L1+1.07q1×(1-c1)+4000) (1) In formula (1), q1 is the flow rate of high-sulfur gas after supercharging, Nm 3 / h. c1 is the volume concentration of SO2 in the high-sulfur gas after pressurization. a is the system empirical constant, with a value of 0.0015~0.004, preferably 0.0025~0.003. L1 is the input amount of hot air during drying, Nm 3 / h. According to the calculation result of formula (1), the frequency of the spray liquid circulation pump is adjusted to make the actual flow rate q3 at the pump outlet approach the target flow rate q2. The specific method is as follows: read the existing frequency of the pump, recorded as f; read the actual flow rate at the pump outlet, recorded as q3, calculate △q (△q=q3-q2); judge △q / q2: (I) When (q3-q2) / q2≥2%, reduce the frequency of the spray liquid circulation pump by f×[(q3-q2) / q2] 1 / 2 .

[0034] (II) When (q3-q2) / q2≤-2%, increase the frequency of the spray liquid circulation pump by f×[(q3-q2) / q2] 1 / 2 .

[0035] (III) When -2%<△q / q2<2%, repeat steps (I)-(III) periodically (e.g., at intervals of 1 to 10 minutes).

[0036] In the present invention, the temperature of the tail gas after being treated by the tail gas circulation spray absorption tower is about 50-60°C, and the volumetric moisture content is about 12-20%. Although it can meet the ultra-low emission requirements of sintering pellets, the water content of the purified tail gas is high, and there will be a white mist tailing phenomenon after being discharged alone, which is not good for the senses. Under normal circumstances, the amount of tail gas is about 3-8% of the sintering (pellet) flue gas, the temperature of the sintering net flue gas is about 120-140°C, and the volumetric moisture content is about 8-14%. The purified tail gas is mixed with the purified sintering flue gas and discharged, the temperature is about 115-130°C, and the volumetric moisture content is about 7-15%. After the flue gas is mixed and discharged, the white mist tailing phenomenon can be avoided, which is more conducive to the diffusion of pollutants and reduces the difficulty of pollutant emission management.

[0037] In the present invention, in the multi-stage (three-stage or four-stage) countercurrent absorption reaction process, an alkali solution (such as sodium carbonate solution) is used to absorb and react the high-sulfur gas to generate sodium pyrosulfite. Since the absorption of sulfur dioxide by the alkali solution to generate sodium pyrosulfite is an exothermic reaction, the present invention sets a cooler in the absorption reactor to reduce the reaction temperature. Low temperature is conducive to the crystal growth of sodium pyrosulfite, the crystal growth quality is better, it is more conducive to centrifugal dehydration, and it can also save energy consumption in the drying process. Generally, the optimal control temperature in the absorption reactor is controlled by the cooler to be 28~50℃, preferably 35~45℃.

[0038] In the prior art, the sodium metabisulfite crystals obtained by centrifugal separation need to be dried to remove the entrained water (the water content of sodium metabisulfite after centrifugal dehydration is generally about 3~8wt%) to obtain the finished sodium metabisulfite. The hot air (130~160℃) used in the drying process is generally provided by heat exchange between air and steam, which has high energy consumption and no problem of adjusting the load of hot air drying according to the change of product load. Based on the phenomenon that both the heating section and the cooling section of the analysis process have waste hot air discharged, there is heat waste, and the sodium metabisulfite drying process requires a large amount of heat source. The present invention is based on the premise that the waste hot air discharged from the heating section and the cooling section of the analysis process is used as the heat source of the drying process. On the one hand, it can realize the utilization of the waste heat of the system and reduce energy consumption. On the other hand, it can reduce the additional processing load of the hot air discharged from the heating section of the analysis tower (generally, it is recycled to the activated carbon adsorption process for purification).

[0039] In the present invention, for the drying heat source of sodium metabisulfite, the hot air in the cooling section of the desorption process and the waste hot gas discharged from the heating section are both excessive. The present invention uses the waste gas discharged from the desorption tower as the drying heat source, mixes the two waste gases discharged from the desorption process in a certain proportion to 140°C to 160°C, and then leads them to the drying process to directly dry sodium metabisulfite. The specific method is as follows: Lead a hot gas pipeline from the hot air pipeline discharged from the desorption heating section, set a control valve V1 and a thermometer, and measure the temperature as T1 (unit: °C); Lead a hot gas from the hot air pipeline discharged from the desorption cooling section, set a control valve V2 and a thermometer, and measure the temperature as T2 (unit: °C); After the two hot gas pipelines are mixed, set a flow regulator (adjust and control the flow rate to the target flow rate L1 of the drying hot air, unit: Nm 3 / h) and a thermometer (measure the temperature as T3). Adjust the gas volume and proportion of the two heat sources through two control valves to achieve the purpose of controlling the target temperature and target flow rate. Set the target temperature of the mixed hot air as T0, °C. Then: (i) When T3 - T0 ≥ 2, reduce the mixing amount of the waste hot air discharged from the desorption heating section and increase the mixing amount of the waste hot air discharged from the desorption cooling section at the same time. The reduction amount of the waste hot air discharged from the desorption heating section is 0.5×(T3 - T0) / T1, and the increase amount of the waste hot air discharged from the desorption cooling section is 0.5×(T3 - T0) / T2.

[0040] (ii) When T3 - T0 ≤ -2, increase the mixing amount of the waste hot air discharged from the desorption heating section and reduce the mixing amount of the waste hot air discharged from the desorption cooling section at the same time. The increase amount of the waste hot air discharged from the desorption heating section is 丨0.5×(T3 - T0) / T1丨, and the reduction amount of the waste hot air discharged from the desorption cooling section is 丨0.5×(T3 - T0) / T2丨.

[0041] (iii) When -2 < T3 - T0 < 2, the actual flow rate of the mixed hot air is measured in real time and recorded as L2, Nm 3 / h. The target flow rate of the mixed hot air is L1, Nm 3 / h. Then: When (L2 - L1) / L1 ≥ 2%, reduce the mixing amounts of the waste hot air discharged from the desorption heating section and the desorption cooling section at the same time. The reduction amounts of both are (L2 - L1) / 2L1.

[0042] When (L2 - L1) / L1 ≤ -2%, increase the mixing amounts of the waste hot air discharged from the desorption heating section and the desorption cooling section at the same time. The increase amounts of both are 丨(L2 - L1) / 2L1丨.

[0043] When -2% < (L2 - L1) / L1 < 2%, steps (i)-(iii) are periodically repeated. Here, "||" means taking the absolute value of the result.

[0044] In the present invention, during the drying process of sodium metabisulfite crystals (wet materials), it is necessary to reasonably control the input amount of drying hot air according to the production of sodium metabisulfite, so as to achieve the purpose of energy conservation and emission reduction on the premise of ensuring the drying effect. Since it is difficult to measure the wet sodium metabisulfite at the outlet of the centrifugal separation process, after the system is balanced, we can calculate the amount of wet sodium metabisulfite through the gas volume and sulfur dioxide concentration of the high-sulfur gas at the outlet of the booster fan. Specifically: Denote the mass of sodium metabisulfite before drying as m1, kg. Then there is: m1 = q1 × c1 × (190 / 22.4) × η / (1 - r1) (2) Denote the mass of sodium metabisulfite after drying as m2, kg. According to the material balance, there is: m2 = m1 × (1 - r1) / (1 - r2) (2 - 1) In formulas (2)-(2 - 1): q1 is the flow rate of the high-sulfur gas after boosting, Nm 3 / h. c1 is the volume concentration of SO2 in the high-sulfur gas after boosting. η is the conversion efficiency, with a value of 0.9 - 1. r1 is the moisture content of sodium metabisulfite before drying, generally with a value of 3 - 6%. r2 is the moisture content of sodium metabisulfite after drying, generally with a value of 0 - 0.3%. 190 is the molecular weight of Na2S2O5.

[0045] In the present invention, the heat balance of the wet sodium metabisulfite in the drying process is as follows: Denote the total heat brought in by the hot air before drying as Q1, the total heat brought in by the sodium metabisulfite before drying as Q2, the total heat taken away by the waste hot air after drying as Q3, the total heat taken away by the moisture after drying as Q4, the total heat taken away by the sodium metabisulfite after drying as Q5, and the total heat loss of the system after drying as Q6, with a value of approximately 0.5 - 5% of Q1. Then according to the heat balance theorem, there is: Q1 + Q2 = Q3 + Q4 + Q5 + Q6 (3 - 1) Among them: The total heat brought in by the hot air before drying: Q1 = L1 × Cp1 × ρ1 × t1 (3 - 2).

[0046] The total heat brought in by the sodium metabisulfite before drying: Q2 = m1 × Cp2 × t2 (3 - 3).

[0047] The total heat taken away by the waste hot air after drying: Q3 = L1 × Cp1 × ρ1 × t3 (3 - 4).

[0048] The total heat taken away by the moisture after drying: Q4 = m1 × △r × (Cp3 × (t3 - t2) + γ) (3 - 5).

[0049] The total heat taken away by sodium metabisulfite after drying: Q5 = m2 × Cp2 × t4 (3-6).

[0050] The total heat loss of the system after drying is completed: Q6 = k×L1×Cp1×ρ1×t1 (3-7).

[0051] In formulas (3-1)-(3-7): L1 is the input amount of hot air during drying (Nm 3 / h). Cp1 is the constant pressure specific heat capacity of hot air (generally 0.245 kcal / (kg·℃)). ρ1 is the density of hot air at standard state (generally 1.252 kg / Nm 3 ). t1 is the temperature of hot air before drying (℃). m1 is the mass of sodium metabisulfite before drying (kg). Cp2 is the specific heat of sodium metabisulfite (generally 0.41kcal / (kg·℃)). t2 is the temperature of sodium metabisulfite before drying (℃). t3 is the temperature of hot air after drying (℃). △r is the difference in moisture content of sodium metabisulfite before and after drying, that is, (r1-r2). Cp3 is the specific heat of water (generally 1.0kcal / (kg·℃)). γ is the heat of vaporization of water at t3 temperature (generally 535.8kcal / kg). m2 is the mass of sodium metabisulfite after drying (kg). t4 is the temperature of sodium metabisulfite after drying (℃). k is the heat loss coefficient of the system before and after drying (generally 0.5~5%).

[0052] Substituting equation (3-2)-(2-3) into equation (3-1), we get: L1×Cp1×ρ1×(t1-t3-(k×t1)=m1×△r×(Cp3×(t3-t2)+γ)+m2×Cp2×t4-m1×Cp2×t2 (3-8).

[0053] After converting (3-8), we get: L1=[m1×△r×(Cp3×(t3-t2)+γ)+m2×Cp2×t4-m1×Cp2×t2] / [Cp1×ρ1×(t1-t3-(k×t1)] (3).

[0054] In the present invention, all formulas in the present invention are fitted by the inventors based on experiments and engineering applications, and all calculations are numerical values ​​converted according to prescribed units, which are obtained by substituting the numerical values ​​after the conversion into the formulas (after the conversion of the units, only the numerical values ​​are substituted into the formulas for calculation, without substituting the units, and the units are only used to adjust the size of the numerical values).

[0055] Compared with the prior art, the beneficial technical effects of the present invention are as follows: 1: The method and system of the present invention further reduce the water content in the high-sulfur gas by pre-condensing and dehumidifying the high-sulfur gas before pressurization, thereby ensuring the safe, stable and sustainable operation of the system; at the same time, the waste heat of the sulfur-rich gas is further utilized to reduce the water saturation of the high-sulfur gas, further extending the life of the booster fan and related pipeline valves, and improving the stability of the system.

[0056] 2: The method and system of the present invention utilize the waste heat of the analytical regeneration process, thereby reducing the steam consumption of the sodium pyrosulfite drying process and reducing the amount of waste heat gas to be processed.

[0057] 3: The method and system of the present invention uses the alkaline solution required by the system itself to purify the tail gas, and then directly transports it to the chimney for discharge, avoiding the return to the activated carbon device for circulation purification, reducing the disposal cost of the activated carbon flue gas purification device, and reducing the pollutant discharge port. The tail gas and sintering flue gas are discharged from one chimney, which is easy to manage, conducive to the diffusion of pollutants, and improves the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 The process flow chart of the method of the present invention is shown in FIG.

[0059] Figure 2 This is a process flow chart of the method of the present invention having dehumidification heat exchange and waste heat utilization mechanisms.

[0060] Figure 3 It is a schematic diagram of the structure of the system of the present invention.

[0061] Figure 4 It is a structural schematic diagram of the system of the present invention having dehumidification heat exchange and waste heat utilization mechanisms.

[0062] Figure 5 It is a schematic structural diagram of the indirect heat exchange device of the system of the present invention.

[0063] Figure numerals: 1: activated carbon adsorption tower; 101: raw flue gas intake pipe; 102: clean flue gas discharge pipe; 2: activated carbon analysis tower; 201: first activated carbon conveying mechanism; 202: second activated carbon conveying mechanism; 203: cooling air intake pipe; 204: cooling exhaust pipe; 205: sulfur-rich gas conveying pipe; 3: hot air furnace; 301: first hot air pipe; 302: second hot air pipe; 303: fuel conveying pipe; 304: combustion-aiding gas conveying pipe; 4: washing and purification device; 401: high-sulfur gas conveying pipe; 402: acid wastewater conveying pipe; 5: condensing device; 501: high-sulfur dehumidification gas conveying pipe; 502: booster fan; 6 : Multi-stage countercurrent absorption reaction device; 601: alkali solution input pipeline; 601a: first alkali solution input pipeline; 601b: second alkali solution input pipeline; 602: alkali preparation tank; 603: solid-liquid mixture conveying mechanism; 604: centrifugal separation device; 605: alkali solution circulation pipeline; 606: material conveying mechanism; 607: drying device; 608: drying air inlet pipeline; 609: first tail gas conveying pipeline; 610: second tail gas conveying pipeline; 611: dust collector; 7: wastewater treatment unit; 8: indirect heat exchange device; 9: spray device; 901: clean tail gas conveying pipeline; 10: air distribution chamber; 1001: first hot air branch pipe; 1002: second hot air branch pipe. DETAILED DESCRIPTION

[0064] The technical solution of the present invention is illustrated below by way of example, and the scope of protection requested by the present invention includes but is not limited to the following embodiments.

[0065] A system for purifying sulfur-containing flue gas and recovering sulfur resources, the system comprises an activated carbon adsorption tower 1, an activated carbon analysis tower 2, a hot air furnace 3, a washing and purification device 4, a condensing device 5, a multi-stage countercurrent absorption reaction device 6 and a wastewater treatment unit 7. The original flue gas inlet pipe 101 is connected to the air inlet of the activated carbon adsorption tower 1, and the air outlet of the activated carbon adsorption tower 1 is connected to the clean flue gas discharge pipe 102. The discharge port of the activated carbon adsorption tower 1 is connected to the feed port of the activated carbon analysis tower 2 through the first activated carbon conveying mechanism 201, and the discharge port of the activated carbon analysis tower 2 is connected to the feed port of the activated carbon adsorption tower 1 through the second activated carbon conveying mechanism 202.

[0066] The hot air outlet of the hot blast furnace 3 is connected to the air inlet of the heating section of the activated carbon analysis tower 2 through the first hot air duct 301, and the air outlet of the heating section of the activated carbon analysis tower 2 is connected to the hot air inlet of the hot blast furnace 3 through the second hot air duct 302. The hot blast furnace 3 is also connected with a fuel delivery pipeline 303 and a combustion gas delivery pipeline 304. The air inlet of the cooling section of the activated carbon analysis tower 2 is connected to a cooling air inlet pipeline 203, and the air outlet of the cooling section of the activated carbon analysis tower 2 is connected to a cooling exhaust air pipeline 204. The air outlet of the SRG section of the activated carbon analysis tower 2 is connected to the air inlet of the washing and purification device 4 through the sulfur-rich gas delivery pipeline 205. The air outlet of the washing and purification device 4 is connected to the air inlet of the condensing device 5 through the high-sulfur gas delivery pipeline 401, and the air outlet of the condensing device 5 is connected to the air inlet of the multi-stage countercurrent absorption reaction device 6 through the high-sulfur dehumidification gas delivery pipeline 501. A booster fan 502 is also provided on the high-sulfur dehumidified gas delivery pipeline 501. The water outlet of the washing and purification device 4 is connected to the water inlet of the wastewater treatment unit 7 through the acid wastewater delivery pipeline 402.

[0067] The liquid inlet of the multi-stage countercurrent absorption reaction device 6 is connected to the liquid outlet of the alkali preparation tank 602 through the alkali solution input pipeline 601. The material outlet of the multi-stage countercurrent absorption reaction device 6 is connected to the material inlet of the centrifugal separation device 604 through the solid-liquid mixture conveying mechanism 603. The liquid outlet of the centrifugal separation device 604 is connected to the liquid inlet of the alkali preparation tank 602 through the alkali solution circulation pipeline 605. The material outlet of the centrifugal separation device 604 is connected to the material inlet of the drying device 607 through the material conveying mechanism 606. The air inlet of the drying device 607 is connected to the drying air inlet pipeline 608. The tail gas outlet of the multi-stage countercurrent absorption reaction device 6 is connected to the air inlet of the activated carbon adsorption tower 1 through the first tail gas conveying pipeline 609. The tail gas outlet of the drying device 607 is connected to the air inlet of the activated carbon adsorption tower 1 through the second tail gas conveying pipeline 610. A dust collector 611 is also provided on the second tail gas conveying pipeline 610.

[0068] Preferably, the system further comprises an indirect heat exchange device 8. The indirect heat exchange device 8 is arranged between the sulfur-rich gas delivery pipeline 205 and the high-sulfur dehumidification gas delivery pipeline 501. The hot mass end of the indirect heat exchange device 8 is connected to the sulfur-rich gas delivery pipeline 205, and the cold mass end thereof is connected to the high-sulfur dehumidification gas delivery pipeline 501.

[0069] Preferably, the system further includes a spray device 9. The tail gas outlet of the multi-stage countercurrent absorption reaction device 6 is connected to the air inlet of the spray device 9 through the first tail gas delivery pipeline 609. The tail gas outlet of the drying device 607 is connected to the air inlet of the spray device 9 through the second tail gas delivery pipeline 610. The air outlet of the spray device 9 is connected to the clean flue gas emission pipeline 102 through the clean tail gas delivery pipeline 901. The liquid outlet of the alkali preparation tank 602 is connected to the liquid inlet of the spray device 9 through the first alkali liquid input pipeline 601a, and the liquid outlet of the spray device 9 is connected to the liquid inlet of the multi-stage countercurrent absorption reaction device 6 through the second alkali liquid input pipeline 601b.

[0070] Preferably, the system further includes an air distribution chamber 10. A first hot air branch pipe 1001 is led out from the second hot air duct 302 and connected to the hot air inlet of the air distribution chamber 10. A second hot air branch pipe 1002 is led out from the cooling exhaust air duct 204 and connected to the hot air inlet of the air distribution chamber 10. A throttle valve is independently provided on the first hot air branch pipe 1001 and the second hot air branch pipe 1002. Example 1

[0071] like Figure 3-5 As shown, a system for purifying sulfur-containing flue gas and recovering sulfur resources includes an activated carbon adsorption tower 1, an activated carbon analysis tower 2, a hot air furnace 3, a washing and purification device 4, a condensing device 5, a multi-stage countercurrent absorption reaction device 6 and a wastewater treatment unit 7. The original flue gas inlet pipe 101 is connected to the air inlet of the activated carbon adsorption tower 1, and the air outlet of the activated carbon adsorption tower 1 is connected to the clean flue gas discharge pipe 102. The discharge port of the activated carbon adsorption tower 1 is connected to the feed port of the activated carbon analysis tower 2 through the first activated carbon conveying mechanism 201, and the discharge port of the activated carbon analysis tower 2 is connected to the feed port of the activated carbon adsorption tower 1 through the second activated carbon conveying mechanism 202.

[0072] The hot air outlet of the hot blast furnace 3 is connected to the air inlet of the heating section of the activated carbon analysis tower 2 through the first hot air duct 301, and the air outlet of the heating section of the activated carbon analysis tower 2 is connected to the hot air inlet of the hot blast furnace 3 through the second hot air duct 302. The hot blast furnace 3 is also connected with a fuel delivery pipeline 303 and a combustion gas delivery pipeline 304. The air inlet of the cooling section of the activated carbon analysis tower 2 is connected to a cooling air inlet pipeline 203, and the air outlet of the cooling section of the activated carbon analysis tower 2 is connected to a cooling exhaust air pipeline 204. The air outlet of the SRG section of the activated carbon analysis tower 2 is connected to the air inlet of the washing and purification device 4 through the sulfur-rich gas delivery pipeline 205. The air outlet of the washing and purification device 4 is connected to the air inlet of the condensing device 5 through the high-sulfur gas delivery pipeline 401, and the air outlet of the condensing device 5 is connected to the air inlet of the multi-stage countercurrent absorption reaction device 6 through the high-sulfur dehumidification gas delivery pipeline 501. A booster fan 502 is also provided on the high-sulfur dehumidified gas delivery pipeline 501. The water outlet of the washing and purification device 4 is connected to the water inlet of the wastewater treatment unit 7 through the acid wastewater delivery pipeline 402.

[0073] The liquid inlet of the multi-stage countercurrent absorption reaction device 6 is connected to the liquid outlet of the alkali preparation tank 602 through the alkali solution input pipeline 601. The material outlet of the multi-stage countercurrent absorption reaction device 6 is connected to the material inlet of the centrifugal separation device 604 through the solid-liquid mixture conveying mechanism 603. The liquid outlet of the centrifugal separation device 604 is connected to the liquid inlet of the alkali preparation tank 602 through the alkali solution circulation pipeline 605. The material outlet of the centrifugal separation device 604 is connected to the material inlet of the drying device 607 through the material conveying mechanism 606. The air inlet of the drying device 607 is connected to the drying air inlet pipeline 608. The tail gas outlet of the multi-stage countercurrent absorption reaction device 6 is connected to the air inlet of the activated carbon adsorption tower 1 through the first tail gas conveying pipeline 609. The tail gas outlet of the drying device 607 is connected to the air inlet of the activated carbon adsorption tower 1 through the second tail gas conveying pipeline 610. A dust collector 611 is also provided on the second tail gas conveying pipeline 610.

[0074] The system also includes an indirect heat exchange device 8. The indirect heat exchange device 8 is arranged between the sulfur-rich gas delivery pipeline 205 and the high-sulfur dehumidification gas delivery pipeline 501. The hot mass end of the indirect heat exchange device 8 is connected to the sulfur-rich gas delivery pipeline 205, and the cold mass end is connected to the high-sulfur dehumidification gas delivery pipeline 501.

[0075] The heat exchanger is shown in the figure Example 2

[0076] Example 1 is repeated, except that the system further includes a spray device 9. The tail gas outlet of the multi-stage countercurrent absorption reaction device 6 is connected to the air inlet of the spray device 9 through the first tail gas delivery pipeline 609. The tail gas outlet of the drying device 607 is connected to the air inlet of the spray device 9 through the second tail gas delivery pipeline 610. The air outlet of the spray device 9 is connected to the clean flue gas emission pipeline 102 through the clean tail gas delivery pipeline 901. The liquid outlet of the alkali preparation tank 602 is connected to the liquid inlet of the spray device 9 through the first alkali solution input pipeline 601a, and the liquid outlet of the spray device 9 is connected to the liquid inlet of the multi-stage countercurrent absorption reaction device 6 through the second alkali solution input pipeline 601b. Example 3

[0077] Example 2 is repeated, except that the system further includes an air distribution chamber 10. A first hot air branch pipe 1001 is led out from the second hot air duct 302 and connected to the hot air inlet of the air distribution chamber 10. A second hot air branch pipe 1002 is led out from the cooling exhaust air duct 204 and connected to the hot air inlet of the air distribution chamber 10. A throttle valve is independently provided on the first hot air branch pipe 1001 and the second hot air branch pipe 1002. The hot air outlet of the air distribution chamber 10 is connected to the air inlet of the drying device 607 through the drying air inlet pipe 608. Example 4

[0078] Example 3 is repeated, except that one or more of a flow regulating valve, a temperature sensor, and a humidity sensor are independently and optionally provided on the first hot air duct 301, the second hot air duct 302, the fuel delivery pipeline 303, the combustion-supporting gas delivery pipeline 304, the cooling air inlet pipeline 203, the cooling exhaust air duct 204, the sulfur-rich gas delivery pipeline 205, the high-sulfur gas delivery pipeline 401, the high-sulfur dehumidification gas delivery pipeline 501, the alkali solution input pipeline 601, the solid-liquid mixture delivery mechanism 603, the drying air inlet pipeline 608, the first tail gas delivery pipeline 609, the second tail gas delivery pipeline 610, the first alkali solution input pipeline 601a, the second alkali solution input pipeline 601b, the air distribution chamber 10, the first hot air branch pipe 1001, and the second hot air branch pipe 1002.

[0079] Application Example 1 The system described in Example 1 is used to perform resource purification treatment on sulfur-containing flue gas: In unit time (1h), 280m 2 Sulfur-containing flue gas generated by the sintering machine (about 1 million Nm 3 , its sulfur dioxide concentration is about 2000mg / Nm 3 ) is transported to the activated carbon adsorption tower for adsorption treatment and then meets the emission standards. The activated carbon adsorbed with pollutants is further transported to the analytical tower for analytical treatment to obtain about 5000Nm 3, sulfur-rich gas with a temperature of about 403°C, the sulfur-rich gas is transported to a washing and purification device for washing to obtain about 3300Nm 3 , high-sulfur gas with a temperature of about 41°C (volume water content of about 7.3%, SO2 volume concentration of about 20.9%), and then the high-sulfur gas is sent to a condensing device to be cooled to 10°C for dehumidification treatment to obtain high-sulfur dehumidified gas with a volume water content of about 1.2%, and then the high-sulfur dehumidified gas is indirectly heat exchanged with the sulfur-rich gas and heated to about 40°C and then transported to a three-stage countercurrent absorption reactor through a booster fan for countercurrent reaction with a sodium carbonate solution to obtain a supersaturated sodium pyrosulfite solution. After centrifugal separation, sodium pyrosulfite crystals with a water content of about 6wt% and a mass of about 6064kg (sulfur conversion rate of about 96%, based on SO2 in the original flue gas) and about 3250Nm 3 The reaction tail gas; then the hot air obtained by heat exchange between air and steam (the steam consumption is estimated to be about 1350kg) at 150°C is used to dry the sodium pyrosulfite crystals to obtain a sodium pyrosulfite product with a moisture content of about 0.3wt%, a mass of about 5718kg and about 21000Nm 3 The reaction tail gas and dry tail gas as well as the acid-containing gas (about 28250Nm 3 ) is transported to the activated carbon adsorption tower for adsorption treatment and then meets the emission standards.

[0080] Application Example 2 Repeat Example 1 except that the 3250 Nm 3 The reaction exhaust gas and about 21000Nm 3 Dry exhaust gas and other processes about 4000Nm 3 After mixing with acidic gas, about 28250Nm 3 Mixed tail gas (SO2 concentration is about 1730mg / Nm 3 , the temperature is about 77℃) is sprayed and purified with sodium carbonate solution and then directly discharged. Then the sodium carbonate solution is sent to the three-stage countercurrent absorption reactor to react with the high-sulfur dehumidified gas to obtain a supersaturated sodium pyrosulfite solution. After centrifugal separation, sodium pyrosulfite crystals with a moisture content of about 6wt% and a mass of about 6218kg are obtained (sulfur conversion rate is about 98.4%, based on SO2 in the original flue gas). Then, the sodium pyrosulfite crystals are dried with hot air obtained from heat exchange between air and steam (the steam consumption is calculated to be about 1384kg) at 150℃ to obtain a finished sodium pyrosulfite product with a moisture content of about 0.3wt% and a mass of about 5862kg.

[0081] Compared with Application Example 1, Application Example 2 directly uses sodium carbonate solution to spray and purify the mixed exhaust gas, so that the sulfur recovery rate is significantly improved, and the operating load and operating cost of the activated carbon adsorption tower are also significantly reduced (according to calculations, the operating cost of the activated carbon adsorption tower in Application Example 2 is saved by approximately 1 million / a compared with that in Application Example 1), thereby improving its flue gas treatment efficiency.

[0082] Application Example 3 Example 1 was repeated, except that the waste hot gases discharged from the heating section and the cooling section of the analytical tower were mixed in proportion to obtain waste hot air with a temperature of about 150° C., and then the waste hot air was used as hot air for drying the sodium pyrosulfite crystals.

[0083] Compared with Application Example 1, Application Example 3 realizes the recycling of waste heat by combining the waste heat gases discharged from the heating section and the cooling section of the analysis tower to obtain hot air for drying the sodium metabisulfite crystals. At the same time, there is no need to produce additional steam, thus saving energy consumption. According to calculations, Application Example 1 requires about 11,000 tons of steam per year, and the annual steam cost is about 1.44 million yuan. The fossil energy consumed in producing this part of steam is calculated to release carbon dioxide emissions of about 2435 t / a.

[0084] Application Example 4 Example 2 was repeated, except that the waste hot gases discharged from the heating section and the cooling section of the desorption tower were mixed in proportion to obtain waste hot air with a temperature of about 150° C., and then the waste hot air was used as hot air for drying the sodium pyrosulfite crystals.

[0085] Comparative Example 1 In unit time (1h), 280m 2 Sintering machine produces flue gas (about 1 million Nm 3 , its sulfur dioxide concentration is about 2000mg / Nm 3 ) is transported to the activated carbon adsorption tower for adsorption treatment and then meets the emission standards. The activated carbon adsorbed with pollutants is further transported to the analytical tower for analytical treatment to obtain about 5000Nm 3 , sulfur-rich gas at a temperature of about 400°C, the sulfur-rich gas is transported to a washing and purification device for washing to obtain about 3300Nm 3 , high-sulfur gas with a temperature of about 40°C (volume water content of about 7.3%, SO2 volume concentration of about 20.9%), and then the high-sulfur gas is transported to the three-stage countercurrent absorption reactor through a booster fan for countercurrent reaction with a sodium carbonate solution to obtain a supersaturated sodium pyrosulfite solution. After centrifugal separation, sodium pyrosulfite crystals with a water content of about 6wt% and a mass of about 6052kg (sulfur conversion rate of about 95.8%, based on SO2 in the original flue gas) and about 3282Nm 3The reaction tail gas; then the hot air obtained by heat exchange between air and steam (the steam consumption is estimated to be about 1346kg) at 150°C is used to dry the sodium pyrosulfite crystals to obtain a sodium pyrosulfite product with a moisture content of about 0.3wt%, a mass of about 5706kg and about 21000Nm 3 of dry exhaust gas.

[0086] 3282Nm 3 The reaction exhaust gas and about 21000Nm 3 The dry exhaust gas and other processes in the above process are about 4000Nm 3 After mixing with acidic gas, about 28282Nm 3 Mixed exhaust gas (SO2 concentration is about 1729mg / Nm 3 , the temperature is about 77℃) and is transported to the activated carbon adsorption tower for adsorption treatment before meeting the emission standards.

[0087] In the above process, in Comparative Example 1, relative to Application Example 1, the high-sulfur gas has not been dehumidified, and acid water is precipitated during the supercharging process, which causes obvious corrosion to the supercharging fan. In Comparative Example 1, relative to Application Example 2, the tail gas of Comparative Example 1 is directly desulfurized and denitrated by an activated carbon adsorption tower. According to calculations, the operating cost of the activated carbon adsorption tower needs to be increased by about 1 million yuan / a relative to Application Example 2. In Comparative Example 1, relative to Application Example 3 and Application Example 4, Comparative Example 1 uses steam to heat air as a drying hot press, which increases the consumption of steam by about 1,346 kg. According to calculations, the annual steam requirement for Comparative Example 1 is about 11,000 tons, and the annual steam cost is about 1.44 million yuan, which greatly increases energy consumption and carbon emissions. According to calculations, the fossil energy consumed to produce this part of steam is calculated to release carbon dioxide emissions of about 2,435 t / a.

Claims

1. A method for purifying sulfur-containing flue gas and recovering sulfur resources, characterized in that: The method includes: 1) The sulfur-containing flue gas is subjected to adsorption treatment by activated carbon, and after the adsorption treatment is completed, the clean flue gas obtained is discharged, and the activated carbon adsorbed with pollutants is subjected to the next step of treatment; 2) performing analytical regeneration treatment on the activated carbon adsorbing the pollutants, and after the analytical regeneration treatment is completed, returning the obtained regenerated activated carbon to step 1) for recycling, and performing the analytical sulfur-rich gas to the next step of treatment; 3) washing the sulfur-rich gas to obtain high-sulfur gas and washing wastewater, treating the washing wastewater separately to meet the discharge standards, and subjecting the high-sulfur gas to the next step of treatment; 4) The high-sulfur gas is sequentially subjected to condensation, dehumidification and pressurization treatments, and then subjected to a multi-stage countercurrent absorption reaction with an alkali solution. After the reaction is completed, a reaction waste liquid, sodium metabisulfite crystals and a reaction tail gas are obtained respectively; the reaction waste liquid is used as an alkali solution after being prepared with alkali, and the sodium metabisulfite crystals are dried to obtain a sodium metabisulfite product and dry tail gas, and the reaction tail gas and the dry tail gas are both introduced into the sulfur-containing flue gas of step 1) to participate in the adsorption treatment.

2. The method according to claim 1, characterized in that: In step 4), the high-sulfur gas is first subjected to condensation and dehumidification treatment and temperature increase treatment in sequence and then to pressure increase treatment; Preferably, the condensation dehumidification treatment is to cool the high-sulfur gas to below 10°C, preferably 1-8°C; and / or The temperature raising treatment is specifically to perform indirect heat exchange between the high-sulfur gas and the sulfur-rich gas and make the temperature of the high-sulfur gas be 30-60°C, preferably 35-50°C.

3. The method according to claim 1 or 2, characterized in that: In step 4), the reaction tail gas and the dry tail gas are discharged after being subjected to spray absorption treatment with alkali solution; preferably, the alkali solution after the spray absorption treatment is subjected to a multi-stage countercurrent absorption reaction with the high-sulfur gas; preferably, the alkali solution is a sodium carbonate solution.

4. The method according to claim 3, characterized in that: During the spray absorption process, the target flow rate of the spray liquid before spray absorption is set as q2, Nm 3 / h; then: q2=a×(L1+1.07q1×(1-c1)+4000) (1) In formula (1), q1 is the flow rate of high-sulfur gas after supercharging, Nm 3 / h; c1 is the volume concentration of SO2 in the high-sulfur gas after pressurization; a is the system empirical constant, with a value of 0.0015~0.004; L1 is the input amount of hot air during drying, Nm 3 / h; The actual flow rate of the spray liquid during real-time detection of spray absorption is recorded as q3, Nm 3 / h; Real-time detection of the frequency of the spray liquid circulation pump, record it as f, Hz; then: (I) When (q3-q2) / q2≥2%, reduce the frequency of the spray liquid circulation pump by f×[(q3-q2) / q2] 1 / 2 ; (II) When (q3-q2) / q2≤-2%, increase the frequency of the spray liquid circulation pump by f×[(q3-q2) / q2] 1 / 2 ; (III) When -2%<(q3-q2) / q2<2%, steps (I)-(III) are repeated periodically.

5. The method according to any one of claims 1 to 4, characterized in that: In step 4), the drying is hot air drying; during the drying process, the corresponding amount of hot air is delivered according to the mass of the sodium metabisulfite crystals and the moisture content of the finished sodium metabisulfite reaches the target value; the mass of the sodium metabisulfite before drying is recorded as m1, kg; the input amount of hot air during drying is recorded as L1, Nm 3 / h; then: m1=q1×c1×(190 / 22.4)×η / (1-r1) (2) L1=[m1×(r1-r2)×(Cp3×(t3-t2)+γ)+m2×Cp2×t4-m1×Cp2×t2] / [Cp1×ρ1×(t1-t3-(k×t1)] (3) In equations (2)-(3), q1 is the flow rate of high-sulfur gas after supercharging, Nm 3 / h; c1 is the volume concentration of SO2 in the high-sulfur gas after pressurization; η is the conversion efficiency, which is 0.9~1; r1 is the moisture content of sodium metabisulfite before drying, %; r2 is the moisture content of sodium metabisulfite after drying, %; Cp1 is the constant pressure specific heat capacity of hot air, which is 0.245kcal / (kg·℃); Cp2 is the specific heat capacity of sodium metabisulfite, which is 0.41kcal / (kg·℃); Cp3 is the specific heat capacity of water, which is 1.0kcal / (kg·℃); ρ1 is the density of hot air at the standard state, which is 1.252kg / Nm 3 ; t1 is the temperature of hot air before drying, ℃; t2 is the temperature of sodium metabisulfite before drying, ℃; t3 is the temperature of hot air after drying, ℃; γ is the heat of vaporization of water at temperature t3, which is 535.8 kcal / kg; t4 is the temperature of sodium metabisulfite after drying, ℃; m2 is the mass of sodium metabisulfite after drying, kg; k is the heat loss coefficient of the system before and after drying, which is 0.5~5%.

6. The method according to claim 5, characterized in that: The hot air is waste hot air discharged from the analytical heating section and / or analytical cooling section during the analytical regeneration process of the activated carbon; preferably, the waste hot air is a mixed hot air composed of the waste hot air discharged from the analytical heating section and the waste hot air discharged from the analytical cooling section, and the temperature of the mixed hot air is 130~160℃, preferably 140~155℃.

7. The method according to claim 6, characterized in that: During the drying process, the actual temperature of the waste hot air discharged from the heating section is detected in real time and recorded as T1, °C; the actual temperature of the waste hot air discharged from the cooling section is detected in real time and recorded as T2, °C; the actual temperature of the mixed hot air is detected in real time and recorded as T3, °C; the target temperature of the mixed hot air is set as T0, °C; then: (i) When T3 - T0 ≥ 2, reduce the mixing amount of the waste hot air discharged from the analysis heating section and increase the mixing amount of the waste hot air discharged from the analysis cooling section at the same time. The reduction amount of the waste hot air discharged from the analysis heating section is 0.5×(T3 - T0) / T1, and the increase amount of the waste hot air discharged from the analysis cooling section is 0.5×(T3 - T0) / T2; (ii) When T3 - T0 ≤ -2, increase the mixing amount of the waste hot air discharged from the analysis heating section and reduce the mixing amount of the waste hot air discharged from the analysis cooling section at the same time. The increase amount of the waste hot air discharged from the analysis heating section is 丨0.5×(T3 - T0) / T1丨, and the reduction amount of the waste hot air discharged from the analysis cooling section is 丨0.5×(T3 - T0) / T2丨; (iii) When -2<T3-T0<2, the actual flow rate of the mixed hot air is detected in real time and recorded as L2, Nm 3 / h; the target flow rate of mixed hot air is L1, Nm 3 / h; then: When (L2 - L1) / L1 ≥ 2%, reduce the mixing amounts of the waste hot air discharged from the analysis heating section and the analysis cooling section at the same time. The reduction amount of both is (L2 - L1) / 2L1; When (L2 - L1) / L1 ≤ -2%, increase the mixing amounts of the waste hot air discharged from the analysis heating section and the analysis cooling section at the same time. The increase amount of both is 丨(L2 - L1) / 2L1丨; When -2% < (L2 - L1) / L1 < 2%, periodically repeat steps (i)-(iii).

8. A system for purifying sulfur-containing flue gas and recovering sulfur resources or a system for the method according to any one of claims 1 to 7, characterized in that: The system includes an activated carbon adsorption tower (1), an activated carbon desorption tower (2), a hot blast stove (3), a washing and purification device (4), a condensation device (5), a multi-stage countercurrent absorption reaction device (6), and a wastewater treatment unit (7); the raw flue gas inlet pipe (101) is connected to the inlet of the activated carbon adsorption tower (1), and the outlet of the activated carbon adsorption tower (1) is connected to the clean flue gas discharge pipe (102); the discharge port of the activated carbon adsorption tower (1) is connected to the feed port of the activated carbon desorption tower (2) through a first activated carbon conveying mechanism (201), and the discharge port of the activated carbon desorption tower (2) is connected to the feed port of the activated carbon adsorption tower (1) through a second activated carbon conveying mechanism (202); The hot air outlet of the hot air furnace (3) is connected to the air inlet of the heating section of the activated carbon analysis tower (2) through a first hot air duct (301), and the air outlet of the heating section of the activated carbon analysis tower (2) is connected to the hot air inlet of the hot air furnace (3) through a second hot air duct (302); a fuel delivery duct (303) and a combustion gas delivery duct (304) are also connected to the hot air furnace (3); the air inlet of the cooling section of the activated carbon analysis tower (2) is connected to a cooling air inlet duct (203), and the air outlet of the cooling section of the activated carbon analysis tower (2) is connected to a cooling exhaust duct (204); the air outlet of the SRG section of the activated carbon analysis tower (2) is connected to a cooling exhaust duct (204); The inlet of the washing and purifying device (4) is connected to the air inlet of the washing and purifying device (4) through the sulfur-rich gas delivery pipeline (205); the air outlet of the washing and purifying device (4) is connected to the air inlet of the condensing device (5) through the high-sulfur gas delivery pipeline (401); the air outlet of the condensing device (5) is connected to the air inlet of the multi-stage countercurrent absorption reaction device (6) through the high-sulfur dehumidification gas delivery pipeline (501); a booster fan (502) is also provided on the high-sulfur dehumidification gas delivery pipeline (501); the water outlet of the washing and purifying device (4) is connected to the water inlet of the wastewater treatment unit (7) through the acidic wastewater delivery pipeline (402); The liquid inlet of the multi-stage countercurrent absorption reaction device (6) is connected to the liquid outlet of the alkali preparation tank (602) through the alkali solution input pipeline (601); the material outlet of the multi-stage countercurrent absorption reaction device (6) is connected to the material inlet of the centrifugal separation device (604) through the solid-liquid mixture conveying mechanism (603); the liquid outlet of the centrifugal separation device (604) is connected to the liquid inlet of the alkali preparation tank (602) through the alkali solution circulation pipeline (605); the material outlet of the centrifugal separation device (604) is connected to the liquid inlet of the alkali preparation tank (602) through the material conveying mechanism (606). The drying device (607) is connected to the feed port of the drying device (607); the air inlet of the drying device (607) is connected to a drying air inlet duct (608); the tail gas outlet of the multi-stage countercurrent absorption reaction device (6) is connected to the air inlet of the activated carbon adsorption tower (1) via a first tail gas delivery duct (609); the tail gas outlet of the drying device (607) is connected to the air inlet of the activated carbon adsorption tower (1) via a second tail gas delivery duct (610); preferably, a dust collector (611) is also provided on the second tail gas delivery duct (610).

9. The system according to claim 8, characterized in that: The system further comprises an indirect heat exchange device (8); the indirect heat exchange device (8) is arranged between the sulfur-rich gas delivery pipeline (205) and the high-sulfur dehumidification gas delivery pipeline (501); the hot mass end of the indirect heat exchange device (8) is connected to the sulfur-rich gas delivery pipeline (205), and the cold mass end of the indirect heat exchange device (8) is connected to the high-sulfur dehumidification gas delivery pipeline (501).

10. The system according to claim 8 or 9, characterized in that: The system further comprises a spray device (9); the tail gas outlet of the multi-stage countercurrent absorption reaction device (6) is connected to the air inlet of the spray device (9) via a first tail gas delivery pipeline (609); the tail gas outlet of the drying device (607) is connected to the air inlet of the spray device (9) via a second tail gas delivery pipeline (610); the air outlet of the spray device (9) is connected to the clean flue gas discharge pipeline (102) via a clean tail gas delivery pipeline (901); the liquid outlet of the alkali preparation tank (602) is connected to the liquid inlet of the spray device (9) via a first alkali liquid input pipeline (601a), and the liquid outlet of the spray device (9) is connected to the liquid inlet of the multi-stage countercurrent absorption reaction device (6) via a second alkali liquid input pipeline (601b); Preferably, the system further comprises an air distribution chamber (10); a first hot air branch pipe (1001) is led out from the second hot air duct (302) and is connected to the hot air inlet of the air distribution chamber (10); a second hot air branch pipe (1002) is led out from the cooling exhaust duct (204) and is connected to the hot air inlet of the air distribution chamber (10); throttle valves are independently provided on the first hot air branch pipe (1001) and the second hot air branch pipe (1002); and the hot air outlet of the air distribution chamber (10) is connected to the air inlet of the drying device (607) via a drying air inlet pipe (608).

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