Conjoint analysis device and method for acid mist and sulfur dioxide in industrial tail gas

Abstract

The invention discloses a combined analysis device and method for acid mist and sulfur dioxide in industrial tail gas, in the analysis device, an acid mist catcher is used for catching the acid mist in the tail gas, a sulfur dioxide reactor is used for sulfur dioxide reaction to detect the concentration of sulfur dioxide, and the sulfur dioxide reactor is connected with gas metering equipment through an exhaust pipe; the gas metering equipment is used for metering the volume of residual gas which does not participate in the reaction; the gas buffer is connected with the movable negative pressure system and is used for buffering negative pressure generated by the movable negative pressure system; the movable negative pressure system comprises an adjusting device installed on the breather pipe, and the proportion of the desulfurized tail gas sucked by the vacuum pump to the air is adjusted through the adjusting device. According to physicochemical properties of sulfur dioxide and sulfuric acid mist, two sections of glass fiber filter columns are creatively adopted to separate sulfuric acid mist and sulfur dioxide, sulfur dioxide is titrated on site by adopting an iodometric method, sulfuric acid mist is analyzed by adopting a neutralization method, and joint detection of sulfur dioxide and sulfuric acid mist is realized.

Description

Technical Field

[0001] The invention relates to the technical field of tail gas treatment in acid plants, and in particular to a device and method for jointly analyzing acid mist and sulfur dioxide in industrial tail gas. Background Art

[0002] Sulfur dioxide and sulfuric acid mist in the tail gas of acid plants are one of the main sources of air pollution. These substances are easily oxidized into sulfur trioxide in the atmosphere, and sulfur trioxide has strong hygroscopicity and combines with water vapor in the air to form sulfuric acid mist. Sulfuric acid mist is an atmospheric pollution phenomenon, which is about 10 times more toxic than sulfur dioxide and has great harm to the ecological environment, human health, metals, building materials, etc. According to the "Comprehensive Emission Standard of Air Pollutants GB16297-1996", the emission standard of sulfur dioxide (SO2) shall not exceed 100 micrograms / cubic meter, and the maximum allowable emission concentration of sulfuric acid mist (SO3) from new pollution sources is 45 micrograms / cubic meter. The monitoring methods of sulfur dioxide and sulfuric acid mist mainly adopt online monitoring and chemical detection and analysis. In order to ensure the accuracy and reliability of the data, the calibration of online monitoring equipment for sulfur dioxide and sulfuric acid mist is crucial. During the long-term use of these devices, due to environmental factors, sensor aging and other reasons, the measurement accuracy may gradually decrease. Through regular chemical calibration, errors can be discovered and corrected in a timely manner to ensure the accuracy and reliability of the test results. Currently, chemical analysis of sulfur dioxide and sulfuric acid mist mainly adopts independent analysis.

[0003] Sulfuric acid mist detection includes ion chromatography, spectrophotometry and acid-base titration. Ion chromatography comes from "Ion chromatography for determination of sulfuric acid mist in waste gas from stationary pollution sources (HJ 544-2016)". Barium chromate spectrophotometry for determination of sulfuric acid mist in stationary pollution sources comes from the paper (Liu Shuanli. Barium chromate spectrophotometry for determination of sulfuric acid mist in stationary pollution sources [J]. China Environmental Monitoring, 1997, 5). Acid-base titration comes from "Determination of sulfuric acid mist in tail gas from sulfuric acid industry GB / T38685-2020", which stipulates that glass fiber filter cartridges or quartz fiber filter cartridges are connected in series with an absorption bottle filled with isopropanol solution to collect sulfuric acid mist, and the acid-base titration method is used to titrate and calculate the content of sulfuric acid mist.

[0004] Sulfur dioxide detection includes spectrophotometry, iodine titration and ion chromatography. The spectrophotometry method is from the "Determination of Sulfur Dioxide in Ambient Air - Formaldehyde Absorption Pararosaniline Spectrophotometry (HJ 482-2009)". The operating conditions of this method are relatively strict and the determination process is relatively cumbersome. This method is prone to affect the accuracy of the determination results due to improper operation. Ion chromatography is from the "Water Quality Inorganic Anion (F - , Cl - 、NO 2- Br - 、NO3- PO4 3- 、SO3 2- 、SO4 2- The iodine titration method is derived from the Iodine titration method for determination of sulfur dioxide in exhaust gas from stationary pollution sources (HJT56-2000). It is a classic analytical method with high accuracy and reliability, and can accurately determine the sulfur dioxide content in exhaust gas from stationary pollution sources.

[0005] Traditional analysis methods have the following problems:

[0006] 1. Sulfur dioxide and sulfuric acid mist are analyzed independently, and the analysis process takes a long time;

[0007] 2. In traditional sulfuric acid mist analysis, acid mist is captured by using a glass fiber filter column plus isopropanol solution. This method requires the sulfuric acid in the glass fiber and isopropanol to be titrated separately during sulfuric acid mist analysis, which is a cumbersome process.

[0008] 3. Since the tail gas desulfurization tower is under negative pressure, sample collection usually requires the installation of fixed samplers and vacuum pumps. Most of the vacuum vacuum pumps currently sold on the market cannot be frequency-converted, and cannot meet the conditions for the iodine titration method to detect the sulfur dioxide bubbles overflowing evenly one by one. In addition, most sulfuric acid plants are in an acidic environment, and fixed samplers and vacuum pumps are prone to corrosion and damage.

[0009] 4. The iodine titration method is used to analyze sulfur dioxide in tail gas, which is a gas-liquid reaction. At present, there is no dedicated reaction device for sulfur dioxide and iodine liquid, and most conventional reactors have a relatively small length-to-diameter ratio, and the gas-liquid contact is not sufficient, causing sulfur dioxide gas to escape, affecting the accuracy of the analysis results. Sulfuric acid mist (sulfur trioxide) in tail gas can react with iodine liquid, so when using the iodine titration method to analyze sulfur dioxide, sulfur trioxide needs to be separated in advance. Summary of the invention

[0010] The invention provides a device and method for jointly analyzing acid mist and sulfur dioxide in industrial tail gas, so as to solve the technical problem that sulfur dioxide and sulfuric acid mist are analyzed independently in the prior art, and the analysis process is time-consuming.

[0011] According to one aspect of the present invention, there is provided a combined analysis device for acid mist and sulfur dioxide in industrial tail gas, comprising an acid mist collector, a sulfur dioxide reactor, a gas metering device, a gas buffer, and a mobile negative pressure system, wherein:

[0012] The acid mist collector is used to capture the acid mist in the tail gas and pass the sulfur dioxide in the tail gas into the sulfur dioxide reactor;

[0013] The sulfur dioxide reactor is used for sulfur dioxide reaction to detect sulfur dioxide concentration. The first end of the sulfur dioxide reactor is connected to the acid mist collector through an air inlet pipe, and the second end is connected to a gas metering device through an exhaust pipe; the gas metering device is used to measure the volume of residual gas that does not participate in the reaction;

[0014] The gas buffer comprises a vent pipe, one end of which is connected to the gas metering device and the other end is connected to the mobile negative pressure system, and is used to buffer the negative pressure generated by the mobile negative pressure system;

[0015] The mobile negative pressure system comprises a vacuum pump and a regulating device installed on the ventilation pipe. The vacuum pump overcomes the negative pressure of the flue to introduce the flue gas into the detection device, and the regulating device adjusts the ratio of the desulfurized tail gas and air sucked by the vacuum pump.

[0016] Furthermore, the acid mist collector comprises a first glass fiber filter column and a second glass fiber filter column connected to each other, wherein the first glass fiber filter column is used to capture sulfuric acid mist, and the second glass fiber filter column performs secondary capture on sulfuric acid mist escaping from the first glass fiber filter column.

[0017] Furthermore, the sulfur dioxide reactor also includes a reaction tube, and the length-to-diameter ratio of the reaction tube is greater than 10:1.

[0018] Furthermore, the sulfur dioxide reactor also includes a porous coil, the air inlet pipe is connected to the porous coil, the porous coil is provided with a plurality of small holes for increasing the gas-liquid contact area, and the porous coil is arranged 1-2 cm away from the bottom of the reaction tube.

[0019] Furthermore, the gas metering equipment uses a wet gas flow meter and a thermometer for simultaneous measurement of gas volume and temperature.

[0020] Furthermore, the volume of the gas buffer is not less than 2500 ml.

[0021] Furthermore, the mobile negative pressure system is a circulating water vacuum pump, and the regulating device includes a T-type tee and an air-controlled valve. The T-type tee is installed on the air inlet, one end of the T-type tee is connected to the desulfurization tail gas, and the other end is connected to the air, and the air-controlled valve is installed at the port connected to the air.

[0022] According to another aspect of the present invention, a method for the combined analysis of acid mist and sulfur dioxide in industrial tail gas is provided. Using the device for the combined analysis of acid mist and sulfur dioxide in industrial tail gas, the method comprises the following steps:

[0023] (1) The acid mist collector is connected to the tail gas tower, the sulfur dioxide reactor is filled with deionized water, the iodine standard solution is injected into the sulfur dioxide reactor using a pipette, and the starch indicator solution is added;

[0024] (2) Start the mobile negative pressure system and observe the color change in the sulfur dioxide reactor. When the reaction reaches the stoichiometric point and the liquid in the reactor changes from blue to colorless, stop sampling;

[0025] (3) Read the readings of the gas metering equipment and the thermometer, and calculate the sulfur dioxide content;

[0026] The sulfur dioxide content is calculated as follows:

[0027]

[0028] Where: C1 is the molar concentration of the iodine standard solution (mol / L); V1 is the volume of the iodine solution removed (ml); V0 is the residual gas volume (ml); P is the atmospheric pressure value when sampling (Pa); P0 is the reading of the negative pressure gauge (Pa); P1 is the saturated vapor pressure of water vapor when the gas temperature is T (Pa); T is the temperature of the gas (℃);

[0029] (4) taking out the glass fiber from the acid mist collector into a reaction container, rinsing it with deionized water, and titrating it with a sodium hydroxide standard solution using methyl orange as an indicator to calculate the content of sulfuric acid mist;

[0030] The calculation formula of sulfuric acid mist content is as follows:

[0031]

[0032] Where: C2 is the molar concentration of sodium hydroxide standard solution (mol / L); V2 is the volume of sodium hydroxide consumed (ml).

[0033] Furthermore, the analysis method also includes adding clean water to the acid mist collector and the sulfur dioxide reactor before the formal analysis, adjusting the gas flow rate of the acid mist and sulfur dioxide joint analysis device in the industrial exhaust gas, ensuring that the bubbles in the sulfur dioxide reactor overflow evenly one by one, and checking whether the gas metering equipment is operating normally.

[0034] Furthermore, the analysis method also includes short-circuiting the acid mist collector and the sulfur dioxide reactor, and starting the mobile negative pressure system to inhale for 5 minutes to replace the air in the pipeline.

[0035] The present invention has the following beneficial effects:

[0036] 1. According to the physicochemical properties of sulfur dioxide and sulfuric acid mist, the present invention creatively adopts two sections of glass fiber filter columns to separate sulfuric acid mist and sulfur dioxide, simultaneously adopts iodine titration method to titrate sulfur dioxide on site, and adopts neutralization method to analyze sulfuric acid mist, thereby realizing the joint detection of sulfur dioxide and sulfuric acid mist.

[0037] 2. In terms of the detection device, the acid mist collector of the present invention adopts a two-stage capture method. The first stage adopts a glass fiber filter column to mainly capture sulfuric acid mist, and the second stage glass fiber filter column captures the sulfuric acid mist after escape; the sulfur dioxide reactor adopts a porous coil design to increase the area of ​​contact with the gas liquid; the gas metering equipment adopts a wet gas flowmeter to measure the volume and temperature of the gas at the same time; a large-capacity gas buffer is set to stabilize the sampled gas flow and prevent the air pump from instantaneously rotating too fast to cause equipment damage; the mobile negative pressure system adopts a circulating water vacuum pump to overcome the negative pressure of the flue. In order to achieve the purpose of freely adjusting the vacuum pump pressure according to demand, an adjusting device is installed at the air inlet of the circulating water vacuum pump. The opening is adjusted by the adjusting device to ensure that the sampling system is stable and the reaction is sufficient, so as to achieve uniform overflow of bubbles in the sulfur dioxide reactor.

[0038] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0040] Figure 1 This is a schematic diagram of a combined analysis device for acid mist and sulfur dioxide in industrial tail gas;

[0041] Figure 2 It is a structural schematic diagram of the acid mist collector;

[0042] Figure 3 is a schematic structural diagram of a sulfur dioxide reactor;

[0043] Figure 4 It is a structural schematic diagram of a mobile negative pressure system;

[0044] Figure 5 It is a schematic diagram of the structure of the gas buffer bottle;

[0045] In the figure: 1- tail gas tower, 2- acid mist collector, 3- sulfur dioxide reactor, 4- gas metering equipment, 5- thermometer, 6- gas buffer, 7- gas control valve, 8- vacuum pump, 9- air inlet pipe, 10- porous coil, 11- reaction tube, 12- exhaust pipe, 13- T-type tee. DETAILED DESCRIPTION

[0046] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0047] See also Figures 1 to 5The embodiment of the first aspect of the present invention provides a combined analysis device for acid mist and sulfur dioxide in industrial tail gas, comprising an acid mist collector 2, a sulfur dioxide reactor 3, a gas metering device 4, a gas buffer 6, and a mobile negative pressure system, wherein: the acid mist collector 2 is used to capture acid mist in the tail gas, and at the same time, the sulfur dioxide in the tail gas is passed into the sulfur dioxide reactor 3; the sulfur dioxide reactor 3 is used for sulfur dioxide reaction to detect sulfur dioxide concentration, the first end of the sulfur dioxide reactor 3 is connected to the acid mist collector 2 through an air inlet pipe 9, and the second end is connected to the acid mist collector 2 through an air inlet pipe 9. The exhaust pipe 12 is connected to the gas metering device 4; the gas metering device 4 is used to measure the volume of residual gas that has not participated in the reaction; the gas buffer 6 includes a ventilation pipe, one end of which is connected to the gas metering device 4, and the other end is connected to the mobile negative pressure system, and is used to buffer the negative pressure generated by the mobile negative pressure system; the mobile negative pressure system includes a vacuum pump 8 and a regulating device installed on the ventilation pipe, and the vacuum pump 8 overcomes the negative pressure of the flue to introduce the flue gas into the detection device, and at the same time, the regulating device adjusts the ratio of the desulfurized tail gas and air sucked by the vacuum pump 8.

[0048] See also Figure 1 The acid mist collector 2 of the present invention is connected to the tail gas tower 1, and is used to capture the acid mist in the tail gas; the sulfur dioxide reactor 3 is connected to the acid mist collector 2, and the tail gas filtered by the acid mist collector 2 enters the sulfur dioxide reactor 3, and the sulfur dioxide reactor 3 is used to detect the sulfur dioxide concentration using the iodine titration method, and the unreacted tail gas enters the gas metering device 4 through the exhaust pipe 12; the gas metering device 4 uses a wet gas flow meter, and the wet gas flow meter measures the volume of the unreacted tail gas, and the gas metering device 4 is also provided with a thermometer 5, which can measure the volume and temperature of the gas at the same time. The present invention is provided with a large-capacity gas buffer 6 to stabilize the sampled gas flow rate and prevent the mobile negative pressure system from being damaged by the instantaneous flow meter speed of the air pump being too fast. The mobile negative pressure system adopts a vacuum pump 8 to overcome the negative pressure of the flue. The vacuum pump 8 is a circulating water vacuum pump. In order to achieve the purpose that the pressure of the vacuum pump 8 can be arbitrarily adjusted according to demand, an adjusting device is installed at the air inlet of the vacuum pump 8. The opening is adjusted by the adjusting device to ensure that the sampling system is stable and the reaction is sufficient, so that the bubbles in the sulfur dioxide reactor 3 can overflow evenly.

[0049] This method makes full use of the need to separate sulfur trioxide in advance when analyzing sulfur dioxide by iodine titration, adopts a two-stage capture method of glass fiber acid mist collector 2, completely adsorbs acid mist on the glass fiber filter column, and the filtered sulfur dioxide gas enters the sulfur dioxide reactor 3, adopts neutralization method to titrate sulfuric acid mist, and iodine titration to titrate sulfur dioxide, so as to realize the joint detection of sulfur dioxide and acid mist, shorten the detection time of sulfur dioxide and sulfuric acid mist to half of the original, and improve the accuracy of sulfur dioxide and acid mist analysis. In this scheme, iodine titration is selected for sulfur dioxide analysis, which can achieve rapid results of on-site titration, and iodine titration is a classic analysis method. This method has high accuracy and reliability and can accurately determine the sulfur dioxide content in the exhaust gas of fixed pollution sources. In sulfuric acid mist analysis, glass fiber filter column is selected for two-stage capture. Compared with the traditional method of glass fiber filter column and isopropanol to capture sulfuric acid mist and then titrate its sulfuric acid content separately, this method can achieve better acid mist capture effect, and can calculate its content by titrating sulfuric acid mist in glass fiber once, optimizes the analysis process of acid mist, and improves the detection efficiency of acid mist.

[0050] See also Figure 2 In an embodiment of the present invention, the acid mist collector 2 includes a first section of glass fiber filter column and a second section of glass fiber filter column connected to each other. The first section of glass fiber filter column is used to capture sulfuric acid mist, and the second section of glass fiber filter column performs secondary capture of sulfuric acid mist after escaping from the first section of glass fiber filter column. The particle size of sulfuric acid mist is usually between 0.1 and 10 μm. This particle size range indicates that sulfuric acid mist is a substance between flue gas and water mist, with a smaller particle size and higher humidity. When a section of glass fiber filter column is used to capture sulfuric acid mist, there is a problem of a small amount of acid mist escaping and incomplete capture. The second section of glass fiber filter column is added to perform secondary capture of sulfuric acid mist after a section of escape, which greatly improves the capture rate of acid mist.

[0051] See also Figure 3 In an embodiment of the present invention, the sulfur dioxide reactor 3 further includes a reaction tube 11, and the length-to-diameter ratio of the reaction tube 11 is greater than 10:1. In a gas-liquid reaction, the size of the length-to-diameter ratio directly affects the mass transfer efficiency of the reactor, and thus affects the reaction rate. When the length-to-diameter ratio is greater than 10:1, the mass transfer effect is relatively good, because a larger length-to-diameter ratio means that the reactants have a longer residence time and a larger space in the reactor for sufficient mixing and reaction, thereby improving the reaction efficiency. When the length-to-diameter ratio is less than 10:1, the residence time and space of the reactants in the reactor will become smaller, and the reaction of sulfur dioxide and the iodine standard solution will not be complete, which can easily cause the analysis result to be low.

[0052] In an embodiment of the present invention, the sulfur dioxide reactor 3 further includes a porous coil 10, the air inlet pipe 9 is connected to the porous coil 10, and the porous coil 10 is provided with a plurality of small holes for increasing the gas-liquid contact area, and the porous coil 10 is arranged at a distance of 1-2 cm from the bottom of the reaction tube 11, preferably 1 cm. The porous coil 10 at the bottom of the air inlet pipe 9 is designed at 1-2 cm from the bottom, preferably 1 cm, instead of lower or contacting the bottom surface. First, during the long-term use of the reactor, the reaction bottle and the bottle mouth plug rub against each other, and the bottle mouth becomes larger. If the design is less than 1 cm or contacts the bottom surface, it is easy to cause the air guide tube to break. Second, the bottom 1 cm is at a distance close to the bottom of the reactor, which can ensure that sulfur dioxide has a longer residence time and a larger space in the reactor, so it is designed to be 1 cm away from the bottom of the porous coil 10. At 1 cm from the bottom, sulfur dioxide has a longer residence time and a larger space in the reactor, and the reaction is more complete. The gas-liquid reaction can drive the liquid flow to achieve the effect of liquid mixing. The lower gas outlet at the bottom of the inlet pipe 9 can make the liquid in the entire reactor mix while reacting, thereby improving the efficiency of the reaction. The multi-porous coil design at the end of the inlet pipe 9 can significantly increase the contact area and disturbance between the gas and the solution, thereby improving the reaction efficiency and the utilization rate of the reactants. This design is not only conducive to the full contact between sulfur dioxide and the absorbent in the solution to carry out gas-liquid reaction, but also can improve the accuracy of the experiment and ensure the reliability of the measurement results.

[0053] In the embodiment of the present invention, the gas metering device 4 adopts a wet gas flow meter and a thermometer 5 for simultaneous measurement of gas volume and temperature.

[0054] See also Figure 5 In the embodiment of the present invention, the volume of the gas buffer 6 is not less than 2500ml. The gas buffer 6 uses a larger gas cylinder as a buffer chamber to achieve the purpose of buffering. The first function is to reduce the impact force caused by the rapid flow of gas at the moment of starting the vacuum pump 8, which causes the flow meter to rotate too fast and be damaged; the second function is to avoid the reaction liquid in the sulfur dioxide reactor 3 from rushing out due to the rapid flow of gas, affecting the accuracy of the analysis result.

[0055] See also Figure 4In the embodiment of the present invention, the vacuum pump 8 is a circulating water vacuum pump, and the regulating device includes a T-type three-way 13 and an air control valve 7. The T-type three-way 13 is installed on the air inlet, one end of the T-type three-way 13 is connected to the desulfurized tail gas, and the other end is connected to the air. The air control valve 7 is installed on the port connected to the air. The ratio of the desulfurized tail gas and air sucked by the vacuum pump 8 is changed by adjusting the size of the air control valve 7. The first function is to achieve the effect of uniform overflow of the bubbles in the sulfur dioxide reactor 3 one by one, so that the sulfur dioxide reaction is more sufficient and the reaction result is accurate; the second is that the flue of the desulfurization tower is under negative pressure, and the gas cannot be normally exported through the sampling interface. It is necessary to use a negative pressure system to overcome the negative pressure of the flue and export the gas normally. The third is that most sulfuric acid plants belong to an acidic environment. The fixed sampler and vacuum pump 8 are prone to corrosion and damage. The use of a mobile negative pressure system can avoid corrosion damage caused by long-term contact with the acidic environment.

[0056] According to an embodiment of the second aspect of the present invention, a method for jointly analyzing acid mist and sulfur dioxide in industrial tail gas is also provided. Using the device for jointly analyzing acid mist and sulfur dioxide in industrial tail gas, the method comprises the following steps:

[0057] (1) The acid mist collector is connected to the tail gas tower, the sulfur dioxide reactor is filled with deionized water, the iodine standard solution is injected into the sulfur dioxide reactor using a pipette, and the starch solution is added;

[0058] (2) Start the mobile negative pressure system and observe the color change in the sulfur dioxide reactor. When the reaction reaches the stoichiometric point and the liquid in the reactor changes from blue to colorless, stop sampling;

[0059] (3) Read the readings of the gas metering equipment and the thermometer, and calculate the sulfur dioxide content;

[0060] The sulfur dioxide content is calculated as follows:

[0061]

[0062] Where: C1 is the molar concentration of the iodine standard solution (mol / L); V1 is the volume of the iodine solution removed (ml); V0 is the residual gas volume (ml); P is the atmospheric pressure value when sampling (Pa); P0 is the reading of the negative pressure gauge (Pa); P1 is the saturated vapor pressure of water vapor when the gas temperature is T (Pa); T is the temperature of the gas (℃);

[0063] (4) taking out the glass fiber from the acid mist collector into a reaction container, rinsing it with deionized water, and titrating it with a sodium hydroxide standard solution using methyl orange as an indicator to calculate the content of sulfuric acid mist;

[0064] The calculation formula of sulfuric acid mist content is as follows:

[0065]

[0066] Where: C2 is the molar concentration of sodium hydroxide standard solution (mol / L); V2 is the volume of sodium hydroxide consumed (ml).

[0067] In an embodiment of the present invention, the analysis method also includes adding clean water to the acid mist collector and the sulfur dioxide reactor before the formal analysis, adjusting the gas flow rate of the acid mist and sulfur dioxide joint analysis device in the industrial exhaust gas, ensuring that the bubbles in the sulfur dioxide reactor overflow evenly one by one, and checking whether the gas metering equipment is operating normally.

[0068] In an embodiment of the present invention, the analysis method further comprises short-circuiting the acid mist collector and the sulfur dioxide reactor, and starting a mobile negative pressure system to inhale air for 5 minutes to replace the air in the pipeline.

[0069] The method uses a glass fiber filter column to separate sulfuric acid mist and sulfur dioxide. The sulfur dioxide gas passes through a reactor of an iodine standard solution. The sulfur dioxide content is calculated by the gas volume recorded by an iodine standard solution concentration meter flow meter. The acid mist captured by the glass fiber filter column is determined by an acid-base titration method.

[0070] 1. Detection mechanism

[0071] Sulfur dioxide detection: Utilize the strong reducing property of sulfur dioxide and use iodine titration.

[0072] SO2+2I+2H2O=H2SO4+2HI

[0073] The above reaction can use starch solution as an indicator to indicate the chemical stoichiometric point, use a flow meter to measure the residual gas that cannot react with the iodine solution, and calculate the volume concentration of sulfur dioxide in the gas using the amount of standard iodine solution and the volume of the collected residual gas.

[0074] Sulfuric acid mist detection: Based on the acid-base neutralization reaction, titrate with sodium hydroxide.

[0075] H + +OH - →H2O

[0076] Taking advantage of the adsorption capacity of glass fiber to sulfuric acid mist, the glass fiber adsorbing acid mist is titrated with sodium hydroxide to determine its sulfuric acid content, and the concentration of acid mist in the flue gas is calculated by a formula.

[0077] 2. Instruments and Reagents

[0078] About 0.01mol / LI standard solution (specific calibration value is used for calculation);

[0079] About 0.1mol / LI standard solution (specific calibration value is used for calculation);

[0080] 0.5% starch solution;

[0081] Methyl red-methylene blue mixed indicator (1 part methyl red + 1 part methylene blue);

[0082] Sodium hydroxide standard titration solution (about 0.01 mol / L);

[0083] Glass fiber filter column, sulfur dioxide reactor, wet gas flow meter, suction bottle, circulating water vacuum pump, T-type three-way, and gas control valve.

[0084] 3. Determination steps

[0085] Connect the detection device and check whether it is leaking;

[0086] Use a reaction tube with clean water and a blank acid mist trap to adjust the gas flow rate of the detection system to ensure that the bubbles in the reactor overflow evenly one by one, and check whether the wet gas flow meter is operating normally;

[0087] Short-circuit the reaction tube and the acid mist absorption tube, turn on the circulating water vacuum pump to absorb air for 5 minutes to replace the air in the pipeline;

[0088] Replace the acid mist collector and the reactor filled with deionized water used for detection;

[0089] Use a pipette or pipette gun to accurately transfer 0.01 mol / LI standard solution into the reaction tube, and add 2 ml of starch solution;

[0090] Start the mobile negative pressure system and observe the color change in the reactor. When the reaction reaches the stoichiometric point and the liquid in the reactor changes from blue to colorless, stop sampling.

[0091] Read the wet gas flow meter and the thermometer;

[0092] Calculate the sulfur dioxide content based on the above data;

[0093] Take out the glass fibers from the two acid mist collectors into a 400 ml beaker, rinse with deionized water, and titrate with a sodium hydroxide standard solution using methyl orange as an indicator.

[0094] 4. Preparation of standard solution

[0095] 4.1 Iodine standard solution

[0096] C(I)=0.1mol / L

[0097] 4.1.1 Preparation

[0098] Weigh 13g iodine and 35g potassium iodide, dissolve in 100ml water, dilute to 1000ml, shake well, and store in a brown stoppered bottle.

[0099] 4.1.2 Calibration method

[0100] Accurately measure 30.00-35.00 ml of the prepared iodine solution C(I)=0.1 mol / L, place it in an iodine volumetric flask, add 150 ml of water, and titrate with sodium thiosulfate standard solution C(Na2S203)=0.1 mol / L. When approaching the end point, add 3 ml of starch indicator solution (5 g / L) and continue titrating until the blue color of the solution disappears.

[0101] At the same time, a blank test of iodine consumption by water was performed: 250 ml of water was taken, 0.05 ml of the prepared iodine solution C (I) = 0.1 mol / L and 3 ml of starch indicator solution (5 g / L) were added, and then titrated with sodium thiosulfate standard solution C (Na2S203) = 0.1 mol / L until the blue color of the solution disappeared.

[0102] 2S2O3 2- +2I-S4O6 2- +2I -

[0103] 4.1.3 Calculation

[0104] The concentration of iodine standard solution is calculated as follows:

[0105] C(I)=(V-V2)*C1 / (V1-0.05)

[0106] Where:

[0107] C(I)——the molar concentration of iodine standard solution, mol / L;

[0108] V——the amount of sodium thiosulfate standard solution used (ml);

[0109] V2——the amount of sodium thiosulfate standard solution used in blank test (ml);

[0110] C1——the molar concentration of sodium thiosulfate standard solution, mol / L;

[0111] V1——the amount of iodine solution, ml;

[0112] 0.05——the amount of iodine solution added in the blank test, ml;

[0113] 4.2 Sodium thiosulfate standard solution

[0114] C(Na2S2O3)=0.1mol / L

[0115] 4.2.1 Preparation

[0116] Weigh 26g of sodium thiosulfate (Na2S2O3.5H2O), dissolve in 1000ml of water, boil slowly for 10min, cool, and filter after standing for two weeks.

[0117] 4.2.2 Calibration method

[0118] Weigh 0.15g of potassium dichromate dried at 120℃ to constant weight, accurate to 0.0001g. Place in an iodine bottle, dissolve in 25ml of water, add 2g of potassium iodide and 20ml of sulfuric acid solution (20%), shake well, and place in a dark place for 10min. Add 150ml of water, and titrate with the prepared sodium thiosulfate standard solution C (Na2S2O3) = 0.1mol / L. When near the end point, add 3ml of starch indicator solution (5g / L), and continue to titrate until the solution turns from blue to bright green. Perform a blank test at the same time.

[0119] 4.2.3 Calculation

[0120] The concentration of sodium thiosulfate standard solution is calculated as follows;

[0121]

[0122] Where:

[0123] C(Na2S2O3)——the molar concentration of sodium thiosulfate solution, mol / L;

[0124] m——the mass of the benchmark potassium dichromate;

[0125] V2——the amount of sodium thiosulfate standard solution used (ml);

[0126] V1——blank, ml;

[0127] 294.2 – the molar mass of potassium dichromate;

[0128] 4.3 Preparation of sodium hydroxide

[0129] 4.3.1 Configuration

[0130] Weigh 100g of sodium hydroxide, dissolve it in 100ml of water, pour it into a polyethylene container, seal it and leave it until the solution is clear. Siphon the specified volume of supernatant with a plastic tube, pour it into 1000ml of water without carbon dioxide, and shake it well.

[0131]

[0132]

[0133] 4.3.2 Calibration method

[0134] Weigh the following specified amount and the 105-110 degree oven-dried constant weight standard potassium hydrogen phthalate, accurate to 0.0001 g, dissolve in the following specified volume of carbon dioxide-free water, add 2 drops of phenolphthalein indicator solution (10 g / L), titrate with the prepared sodium hydroxide solution until the solution turns pink, and perform a blank test at the same time.

[0135]

[0136] 4.3.3 Calculation

[0137] The concentration of sodium hydroxide standard solution is calculated as follows:

[0138]

[0139] Where:

[0140] C(NaOH)-the molar concentration of sodium hydroxide standard solution, mol / l;

[0141] m-Mass of potassium hydrogen phthalate, g;

[0142] V1-the amount of sodium hydroxide solution, ml;

[0143] V2-the amount of sodium hydroxide solution used in the blank test, ml;

[0144] 0.2042 - The mass of potassium hydrogen phthalate expressed in grams equivalent to 1.00 ml of sodium hydroxide standard solution [C(NaOH) = 1.000 mol / L].

[0145] The following examples describe the present disclosure in more detail, and these examples are intended for illustrative purposes only.

[0146] The technical solution of the present invention has been put into practical application in the analysis of flue gas from the desulfurization tower of an acid plant, and good results have been achieved. In June, July and August 2023, the desulfurization tower flue gas was analyzed using this solution, and the analysis results are shown in Tables 1, 2 and 3.

[0147] Table 1 Combined analysis of sulfuric acid mist and sulfur dioxide in sulfuric acid industrial tail gas in June 2023

[0148]

[0149]

[0150] Table 2 Combined analysis of sulfuric acid mist and sulfur dioxide in sulfuric acid industrial tail gas in July 2023

[0151]

[0152] Table 3 Combined analysis of sulfuric acid mist and sulfur dioxide in sulfuric acid industry tail gas in August 2023

[0153]

[0154]

[0155] It can be seen from Table 1, Table 2 and Table 3 that the technical solution of the present invention has a good analysis effect and a fast analysis speed for the analysis of sulfuric acid mist and sulfur dioxide in the industrial tail gas of a sulfuric acid plant in the actual production process, and the combined detection equipment operates stably, indicating that the technical solution of the present invention has good adaptability to the analysis of sulfuric acid mist and sulfur dioxide in the tail gas of the sulfuric acid industry, and is conducive to rapid and accurate analysis.

[0156] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A combined analysis device for acid mist and sulfur dioxide in industrial tail gas, characterized in that: It comprises an acid mist collector (2), a sulfur dioxide reactor (3), a gas metering device (4), a gas buffer (6), and a mobile negative pressure system, wherein: The acid mist collector (2) is used to capture the acid mist in the tail gas and simultaneously pass the sulfur dioxide in the tail gas into the sulfur dioxide reactor (3); The sulfur dioxide reactor (3) is used for sulfur dioxide reaction to detect sulfur dioxide concentration. The first end of the sulfur dioxide reactor (3) is connected to the acid mist collector (2) through an air inlet pipe (9), and the second end is connected to a gas metering device (4) through an exhaust pipe (12); the gas metering device (4) is used to measure the volume of residual gas that does not participate in the reaction; The gas buffer (6) comprises a vent pipe, one end of which is connected to the gas metering device (4) and the other end of which is connected to the mobile negative pressure system, and is used to buffer the negative pressure generated by the mobile negative pressure system; The mobile negative pressure system comprises a vacuum pump (8) and a regulating device installed on the ventilation pipe of the vacuum pump (8). The vacuum pump overcomes the negative pressure of the flue to guide the flue gas into the detection device, and the regulating device adjusts the ratio of the desulfurized tail gas and air sucked by the vacuum pump (8).

2. The combined analysis device for acid mist and sulfur dioxide in industrial tail gas according to claim 1, characterized in that: The acid mist collector (2) comprises a first section of glass fiber filter column and a second section of glass fiber filter column which are connected to each other, wherein the first section of glass fiber filter column is used to capture sulfuric acid mist, and the second section of glass fiber filter column performs secondary capture on the sulfuric acid mist escaping from the first section of glass fiber filter column.

3. The combined analysis device for acid mist and sulfur dioxide in industrial tail gas according to claim 1, characterized in that: The sulfur dioxide reactor (3) further comprises a reaction tube (11), and the length-to-diameter ratio of the reaction tube (11) is greater than 10:

1.

4. The combined analysis device for acid mist and sulfur dioxide in industrial tail gas according to claim 3, characterized in that: The sulfur dioxide reactor (3) further comprises a porous coil (10), the air inlet pipe (9) is connected to the porous coil (10), a plurality of small holes for increasing the gas-liquid contact area are provided on the porous coil (10), and the porous coil (10) is arranged at a distance of 1 to 2 cm from the bottom of the reaction tube (11).

5. The combined analysis device for acid mist and sulfur dioxide in industrial tail gas according to claim 1, characterized in that: The gas metering device (4) adopts a wet gas flow meter and a thermometer (5) for simultaneous measurement of gas volume and temperature.

6. The combined analysis device for acid mist and sulfur dioxide in industrial tail gas according to claim 1, characterized in that: The volume of the gas buffer (6) is not less than 2500 ml.

7. The combined analysis device for acid mist and sulfur dioxide in industrial tail gas according to claim 1, characterized in that: The regulating device comprises a T-shaped three-way valve (13) and a gas control valve (7). The T-shaped three-way valve (13) is installed on the air inlet. One end of the T-shaped three-way valve (13) is connected to the desulfurized tail gas, and the other end is connected to the air. The gas control valve (7) is installed on the port connected to the air.

8. A method for the combined analysis of acid mist and sulfur dioxide in industrial tail gas, characterized in that: Utilizing the combined analysis device for acid mist and sulfur dioxide in industrial tail gas according to any one of claims 1 to 7, the analysis method comprises the following steps: (1) The acid mist collector is connected to the tail gas tower, the sulfur dioxide reactor is filled with deionized water, the iodine standard solution is injected into the sulfur dioxide reactor using a pipette, and the starch solution is added; (2) Start the mobile negative pressure system and observe the color change in the sulfur dioxide reactor. When the reaction reaches the stoichiometric point and the liquid in the reactor changes from blue to colorless, stop sampling; (3) Read the readings of the gas metering equipment and the thermometer, and calculate the sulfur dioxide content; The sulfur dioxide content calculation formula is as follows: Where: C1 is the molar concentration of the iodine standard solution (mol / L); V1 is the volume of the iodine solution removed (ml); V0 is the residual gas volume (ml); P is the atmospheric pressure value when sampling (Pa); P0 is the reading of the negative pressure gauge (Pa); P1 is the saturated vapor pressure of water vapor when the gas temperature is T (Pa); T is the temperature of the gas (℃); (4) taking out the glass fiber from the acid mist collector into a reaction container, rinsing it with deionized water, and titrating it with a sodium hydroxide standard solution using methyl orange as an indicator to calculate the content of sulfuric acid mist; The calculation formula of sulfuric acid mist content is as follows: Where: C2 is the molar concentration of sodium hydroxide standard solution (mol / L); V2 is the volume of sodium hydroxide consumed (ml).

9. The combined analysis method of acid mist and sulfur dioxide in industrial tail gas according to claim 8, characterized in that: The analysis method also includes adding clean water to the acid mist collector and the sulfur dioxide reactor before formal analysis, adjusting the gas flow rate of the acid mist and sulfur dioxide joint analysis device in the industrial tail gas, ensuring that the bubbles in the sulfur dioxide reactor overflow evenly one by one, and checking whether the gas metering equipment is operating normally.

10. The method for combined analysis of acid mist and sulfur dioxide in industrial tail gas according to claim 9, characterized in that: The analysis method also includes short-circuiting the acid mist collector and the sulfur dioxide reactor, and starting a mobile negative pressure system to inhale air for 5 minutes to replace the air in the pipeline.

Images