Sulfuric acid mist tail gas analysis method

Abstract

The invention discloses a sulfuric acid mist tail gas analysis method which comprises the following steps: in an HJ 544-2016 sampling process, taking an isopropanol solution with the volume concentration of 80% as an absorption liquid; the solvent of the isopropanol solution is water; the adding amount of the isopropanol solution in the absorption bottle is 50ml. The method can effectively prevent sulfate radicals generated by absorption of sulfur dioxide in the tail gas from being merged into a sulfuric acid mist result, the detection accuracy of the result of the acid mist part in the tail gas is improved, and the acid mist content is reduced by 89% compared with an existing method. The average recovery rate of sulfur dioxide is 98.87% and 99.94% respectively.

Description

Technical Field

[0001] The present application relates to the field of petrochemical detection technology, and in particular to a method for analyzing sulfuric acid mist tail gas. Background Art

[0002] Sulfur-based acid production is an important sulfuric acid production process, primarily involving sulfur combustion, oxidation reaction, condensation, and concentration. The primary raw material is sulfur. Combustion of sulfur produces gases such as sulfur dioxide and sulfur trioxide, which are continuously oxidized, absorbed, and concentrated in a sulfuric acid production unit to produce high-concentration sulfuric acid. This production process generates exhaust gas, which includes sulfuric acid mist and sulfur dioxide gas. Because sulfuric acid mist is highly corrosive, accurate measurement of the sulfuric acid mist content in the treated exhaust gas is essential to ensure environmental safety. Existing methods for measuring sulfuric acid mist in this exhaust gas include those from USEPA, ASTM, OSHA, and ISO. my country's national standards for measuring sulfuric acid mist in this exhaust gas include the barium chromate colorimetric method (GB4920-1985) and the ion chromatography method (HJ 544-2016).

[0003] However, during the sampling process of the existing national standard detection method, the filter cartridge used can only retain 10% of the sulfuric acid mist in the exhaust gas. An absorption liquid is required to absorb the remaining 90% of the sulfuric acid mist in the exhaust gas before entering the detection. However, this absorption liquid also absorbs sulfur dioxide in the exhaust gas while absorbing the sulfuric acid mist, generating sodium sulfite, sodium bisulfite, and sodium sulfate in the absorption liquid. These substances all contain sulfate ions. When measured by ion chromatography, these sulfate ions will also be included in the sulfuric acid mist detection results and be measured, resulting in an overestimate of the sulfuric acid mist result. This makes the results measured by this method very likely to exceed the standard.

[0004] The information disclosed in the background section is only intended to enhance understanding of the overall background of the invention and should not be considered as an admission or any form of suggestion that the information constitutes the prior art already known to a person of ordinary skill in the art. Summary of the Invention

[0005] The present application provides a sulfuric acid mist tail gas analysis method to solve the above technical problems. The method can avoid the absorption of SO2 in the tail gas generated in the sulfur-sulfur production method into the detection sample, and can improve the accuracy of the acid mist detection results of the sulfur-sulfur production tail gas.

[0006] The present application provides a sulfuric acid mist tail gas analysis method, comprising the following steps: in the GB / T16157 sampling process, using an isopropyl alcohol solution with a volume concentration of 80% as the absorption liquid; the solvent of the isopropyl alcohol solution is water; and the amount of the isopropyl alcohol solution added to the absorption bottle is 50 ml.

[0007] Preferably, the sulfuric acid mist content calculated as sulfuric acid is reduced by 68.48% to 89.92% relative to that using sodium hydroxide solution as the absorption liquid.

[0008] Preferably, the adoption process includes the following steps:

[0009] A pipeline connected to the air inlet of the smoke sampler is set at the measuring point, and two absorption bottles are set in series on the air outlet of the smoke sampler, and the absorption bottles are respectively filled with isopropyl alcohol absorption liquid;

[0010] Insert the smoke gun equipped with a filter cartridge into the sampling point in the chimney for constant speed sampling for 30 to 60 minutes. The heating temperature of the smoke gun is 120℃ to 130℃. The sampling flow rate is determined according to the constant speed sampling principle, and the flow rate range is 5L / min to 15L / min.

[0011] Preferably, the method further comprises: setting a blank sample, measuring the acid mist content in the filter cartridge, and measuring the acid mist content in the absorption liquid.

[0012] Preferably, setting up a blank sample comprises the following steps: cutting a blank filter cartridge from the same batch as the sample into pieces, placing the pieces in a 250 mL conical flask, and adding water to approximately 100 mL. Adding 2 to 3 drops of a mixed indicator solution of methyl red and methylene blue to the test solution, and titrating with a 0.05 mol / L hydrochloric acid standard titrant until the solution changes from gray-green to purple-red, which is the endpoint;

[0013] Record the volume V of the hydrochloric acid standard titration solution consumed by the blank filter cartridge.

[0014] Preferably, determining the acid mist content in the filter cartridge comprises the following steps:

[0015] Cut the filter cartridge with the collected sample into pieces, place them in a 250mL conical flask, and add water to 100mL to obtain a test solution. Add 2 to 3 drops of methyl red-methylene blue mixed indicator solution to the test solution and perform the following operations according to the color of the solution:

[0016] a) If the solution is purple-red, titrate with 0.05 mol / L sodium hydroxide standard titrant until the solution turns gray-green. Record the volume V2 of sodium hydroxide standard titrant consumed by the sample.

[0017] b) If the solution is gray-green, titrate with 0.05 mol / L hydrochloric acid standard titrant until the solution turns purple-red. Record the volume V3 of hydrochloric acid standard titrant consumed by the sample.

[0018] Preferably, determining the acid mist content in the absorption liquid comprises the following steps: after sampling, transferring the solution in each absorption bottle to a 250 mL conical flask, adjusting the acidity of the solution with hydrochloric acid solution or sodium hydroxide solution so that the pH of the solution to be measured during titration is maintained at 3.2 to 4.0;

[0019] Add 2 to 3 drops of thorium indicator and titrate with barium perchlorate standard solution until the solution changes from khaki to pink.

[0020] At the same time, a blank test was performed using unabsorbed isopropyl alcohol.

[0021] Preferably, the sulfuric acid mist tail gas comes from the sulfuric acid production process of sulfur.

[0022] The beneficial effects of this application include:

[0023] 1) The sulfuric acid mist exhaust gas analysis method provided in this application can effectively prevent the sulfate ions generated by the absorption of sulfur dioxide in the exhaust gas from being incorporated into the sulfuric acid mist results, thereby improving the detection accuracy of the acid mist part results in the exhaust gas.

[0024] 2) The sulfuric acid mist tail gas analysis method provided in this application uses isopropyl alcohol as an absorption liquid to absorb the tail gas of a sulfuric acid production device and adopts the "Ion Chromatography" (HJ 544-2016) method for measurement. This method has good selectivity for SO2 and can selectively absorb SO3 in the tail gas. It is a good polarity selective absorption liquid for sulfuric acid mist; laboratory and field test results using isopropyl alcohol absorption liquid show that the average recovery rates of sulfur dioxide are 98.87% and 99.94%, respectively, and the accuracy of sulfuric acid mist measurement results is improved by 79.18%.

[0025] 3) The sulfuric acid mist exhaust gas analysis method provided in this application, as a sampling method of the standard GB / T38685-2020, has been widely promoted and used. It is suitable for accurately measuring the sulfuric acid mist content in waste gases containing SO2 and SO3 at the same time from sulfur-based sulfuric acid and mineral-based acid production, avoiding misjudgments in environmental law enforcement, and contributing to the protection of the atmospheric environment and green production of enterprises. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the sampling device used in Example 1 of the present application;

[0027] Figure 2 Schematic diagram of the sampling device used in Example 5 of the present application;

[0028] Figure 3 This is a flow chart of the method in Example 5 of the present application; DETAILED DESCRIPTION

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the present invention is not limited in any way. Any changes or improvements made based on the teachings of the present invention fall within the scope of protection of the present invention.

[0030] Unless otherwise specified, the materials and instruments used in the following examples were obtained from commercial channels; the detection methods used were all existing methods unless otherwise specified.

[0031] Example 1 Determination of the Absorption of SO2 Standard Gas by Sodium Hydroxide Absorption Liquid in Laboratory Environment The absorption of SO2 standard gas by sodium hydroxide absorption liquid was verified by the following experiment.

[0032] 1. Experimental setup Figure 1 As shown, the experimental device includes: a water bath 1, a first absorption tube 21, a second absorption tube 22, and a wet gas flowmeter 23; after the water bath liquid that needs to be temperature-controlled is added to the water bath 1, the first absorption tube 21 and the second absorption tube 22 are inserted into the water bath 1 at intervals; the SO2 standard gas delivery pipe 213 is inserted into the first absorption tube 21 and arranged below the liquid surface of the absorption liquid; the first absorption tube 21 and the second absorption tube 22 are connected by a connecting pipe 211; one end of the connecting pipe 211 is inserted into the first absorption tube 21 and arranged, and is suspended in the space above the liquid surface, and the other end is inserted into the second absorption tube 22 below the liquid surface, and one end of the exhaust pipe 212 is inserted into the second absorption tube 22 and suspended above the liquid surface of the absorption liquid; the wet gas flowmeter 23 is respectively arranged on the SO2 standard gas delivery pipe 213 and the exhaust pipe 212.

[0033] 2. Operation steps: In a laboratory environment, the sampling device is placed in an ice water bath 1 with the ice water temperature at -4° to conduct the experiment.

[0034] In an ice-water bath, SO2 standard gas delivery pipe 213 was opened to introduce SO2 standard gas of varying concentrations (see Table 1 for standard gas concentrations). The wet gas flowmeter 23 controlled the total ventilation volume (see Table 1 for standard gas ventilation volume). 50 ml of sodium hydroxide absorption solution with a sodium hydroxide concentration of 30 mmol / L was added to the first absorption tube 21 and the second absorption tube 22, respectively. After ventilation, the absorption solution in the first absorption tube 21 and the second absorption tube 22 was taken and the following operations were performed: the volume was fixed to 100 ml with sodium hydroxide absorption solution, and then sulfate and sulfite were determined by ion chromatography. The ion chromatography test conditions were: sulfuric acid solution with a volume concentration of 5‰ as the regeneration solution; a flow rate of 1.00 ml / min, a suppressor current of 75 mA, a detector temperature of 30°C, a column temperature of 20°C, and an injection volume of 10 μL.

[0035] In the above experiments, sulfur dioxide standard gas with different concentrations was used to simulate exhaust gas for detection.

[0036] 3. Under ice water bath conditions, the absorption results of sodium hydroxide absorption liquid for sulfur dioxide standard gas with different flow rates and concentrations are as follows:

[0037] Table 1 Sodium hydroxide absorption liquid determination of sulfur dioxide standard gas test results

[0038]

[0039]

[0040]

[0041]

[0042] 4. Result Analysis The above experiment was carried out according to the parameters in Table 1, and 58 sets of data were measured, which are listed in Table 1. It can be seen that the sulfur content in sulfate + the sulfur content in sulfite is basically equal to the theoretical sulfur content; the SO2 oxidation recovery rate is as high as 97.29%, indicating that the secondary sodium hydroxide absorption liquid method of the above device can basically completely absorb the sulfur dioxide in the sulfur dioxide standard gas;

[0043] Ion chromatography was used to determine the sulfite and sulfate content in the resulting sodium hydroxide absorption solution, and the sulfur dioxide conversion rate was calculated. The results ranged from 24.06% to 66.62%, with an average of 39.5%. The contribution of sulfur dioxide to sulfuric acid mist ranged from 24% to 67%, with an average contribution of 40% in the sodium hydroxide absorption solution. This indicates that sulfur dioxide significantly affects the measurement results when sodium hydroxide is used as the absorption solution.

[0044] Through the above experiments, it can be seen that sodium hydroxide absorption liquid will absorb SO2, causing the sulfuric acid mist test results to increase by 40% relative to the true value. Therefore, choosing an appropriate absorbent is very important for the experimental results.

[0045] Example 2 Study on the Absorption Performance of Isopropyl Alcohol Absorption Liquid for Sulfur Dioxide Standard Gas

[0046] 1. Operation steps: Using the experimental device in Example 1, experiments were conducted in a laboratory environment using isopropyl alcohol absorption liquid, sodium hydroxide absorption liquid, and hydrogen peroxide absorption liquid.

[0047] The isopropyl alcohol absorption liquid experiment differed from the procedure in Example 1 in that 50 ml of a 10% hydrogen peroxide absorption liquid (solvent in water) was added to each of the first absorption tube 21 and the second absorption tube 22. Sulfur dioxide standard gas was introduced at the concentrations shown in Table 2, and the total aeration volume was controlled by a wet gas flowmeter 23 according to the requirements in Table 2. After aeration, the absorption liquids were combined and fixed to volume, and then ion chromatography was performed to determine the sulfate and sulfite content.

[0048] The results are shown in Table 2:

[0049] Table 2 Test results of hydrogen peroxide absorption liquid for determination of sulfur dioxide standard gas (single)

[0050]

[0051] Example 3 Study on the Absorption Performance of Sodium Hydroxide Absorption Liquid for Sulfur Dioxide Standard Gas

[0052] The difference from Example 2 is that 50 ml of 30 mmol / L sodium hydroxide absorption solution is added to the first absorption tube 21 and the second absorption tube 22 respectively; sulfur dioxide standard gas is introduced according to the concentration shown in Table 3, and the total ventilation volume is controlled by the wet gas flowmeter 23 according to the requirements of Table 3.

[0053] The results are shown in Table 3:

[0054] Table 3 Sodium hydroxide absorption liquid determination of sulfur dioxide standard gas test results (single)

[0055]

[0056] Example 4 Study on the Absorption Performance of Hydrogen Peroxide Absorption Liquid for Sulfur Dioxide Standard Gas

[0057] The difference from Example 2 is:

[0058] Isopropyl alcohol absorption liquid (solvent is water) with a volume concentration of 80% isopropyl alcohol is added to the first absorption tube 21 and the second absorption tube 22. Sulfur dioxide standard gas is introduced according to the concentration shown in Table 4, and the total ventilation volume is controlled by the wet gas flow meter 23 according to the requirements of Table 4.

[0059] Table 4 Test results of isopropyl alcohol absorption liquid for determination of sulfur dioxide standard gas (single)

[0060]

[0061] The results in Tables 2-4 show that the recovery rates of the aforementioned isopropyl alcohol, sodium hydroxide, and hydrogen peroxide absorption solutions for various sulfur dioxide standard gas concentrations follow the order: hydrogen peroxide > sodium hydroxide > isopropyl alcohol. This indicates that the isopropyl alcohol absorption solution has a low absorption rate for sulfur dioxide, effectively preventing sulfur dioxide from entering the absorption solution and causing an increase in sulfate ions. This allows for accurate absorption measurement of sulfate ions in the sample, thereby improving the accuracy of the final test results.

[0062] Example 5: Using isopropyl alcohol as the absorption liquid, the acid mist content in the tail gas of sulfuric acid production from sulfur was tested on site according to GB / T 16157.

[0063] The following on-site production environment is the observation point of Sanhuan Zhonghua's sulfur-based sulfuric acid production phase I and phase II production systems and the 835 sulfuric acid exhaust stack (the 835 sulfur-based sulfuric acid production unit of the Phosphating Group).

[0064] See also Figure 3 1) Sample collection

[0065] The location and sampling of organized exhaust gas emissions shall comply with the relevant provisions of GB / T 16157. Exhaust gas sampling devices such as Figure 2 The following shows the equipment structure used in GB / T 16157 and will not be described in detail here.

[0066] The filter cartridge was installed into the filter cartridge clamp at the head of the sampler, and two impact absorption bottles containing 50 ml of 80% isopropyl alcohol absorption liquid were connected in series behind the smoke sampler as field test one. In addition, a "field test two" was set up, and the smoke gun equipped with the filter cartridge was extended into the sampling point in the chimney to conduct constant-speed sampling for 30 to 60 minutes.

[0067] The setting method of "Field Test 2" is: At the same sampling point in Field Test 2, connect the following Figure 2 The two sampling devices shown in the figure have valves installed on the branch pipes connected to the main pipes of the sampling points to control the sampling time. The first set of sampling devices has 50ml of 80% isopropyl alcohol absorption solution in the 1# and 2# absorption bottles.

[0068] In the second set of sampling devices, 50 ml of 30 mmol / L sodium hydroxide absorption solution was added to the absorption bottles #1 and #2. The sampling time of any set of sampling devices met the national standard requirements.

[0069] During the sampling process, the smoking gun is heated to a temperature of 120°C to 130°C. The sampling flow rate is determined according to the isokinetic sampling principle, and the flow rate range is 5L / min to 15L / min. The bubble size is required to be uniform during sampling.

[0070] The flow rate is stable and the liquid level does not exceed 1 / 2 of the height of the sampling bottle when the gas is flowing.

[0071] After sampling, carefully place the filter cartridge into a sealed polyethylene tube and record the standard sampling volume. To ensure the stability of the isopropyl alcohol absorption solution, complete subsequent measurements within 4 hours of sampling.

[0072] 2) Set up a blank sample

[0073] Cut a blank filter cartridge from the same batch as the sample into pieces and place them in a 250mL conical flask. Add water to approximately 100mL. Add 2-3 drops of a mixed indicator solution of methyl red and methylene blue to the test solution. Titrate with 0.05mol / L hydrochloric acid standard solution until the solution changes from gray-green to purple-red. Record the volume V of the hydrochloric acid standard solution consumed by the blank filter cartridge.

[0074] 3) Measurement of filter cartridge

[0075] Cut the filter cartridge with the sample into pieces, place it in a 250mL conical flask, and add water to about 100mL. Add 2 to 3 drops of methyl red-methylene blue mixed indicator solution to the test solution and measure according to the color of the solution:

[0076] a) If the solution is purple-red, titrate with 0.05 mol / L sodium hydroxide standard titrant until the solution turns gray-green. Record the volume V2 of sodium hydroxide standard titrant consumed by the sample.

[0077] b) If the solution is gray-green, titrate with 0.05 mol / L hydrochloric acid standard titrant until the solution turns purple-red. Record the volume V3 of hydrochloric acid standard titrant consumed by the sample.

[0078] 4) Determination of absorption liquid

[0079] After sampling, transfer the solution from each glass frit absorption bottle to a 250mL conical flask. Adjust the acidity of the solution with hydrochloric acid or sodium hydroxide solution, if necessary, to maintain a pH of 3.2-4.0 during titration. Add 2-3 drops of thorium indicator and titrate with standard barium perchlorate solution until the solution changes from khaki to pink. Simultaneously, perform a blank test with unabsorbed isopropyl alcohol.

[0080] 2. The test results of field test 1 are shown in the following table:

[0081] Table 5 Results of isopropyl alcohol absorption of sulfur dioxide (field test 1)

[0082]

[0083] As shown in Table 5, the average recovery rate of 15 test results at different sampling points when sulfuric acid tail gas was collected using isopropyl alcohol absorption liquid at a sulfur-sulfuric acid production site was 99.94%, indicating that the absorption of sulfur dioxide by the isopropyl alcohol absorption liquid is close to 0. The results obtained from the sulfuric acid mist measurement do not contain the sulfur dioxide content in the tail gas, and the results obtained are highly accurate.

[0084] 3. The test results of field test 2 are shown in the following table:

[0085] Table 6 Determination results after adding isopropyl alcohol to absorb sulfur trioxide

[0086]

[0087]

[0088] Table 6 shows that, under stable operating conditions and with varying sulfur dioxide concentrations at each sampling point, the sulfuric acid mist content measured with the isopropanol absorption solution can be reduced by up to 89.92% relative to that measured with the sodium hydroxide absorption solution. This indicates that sulfur dioxide significantly interferes with the true acid mist content in the sodium hydroxide absorption solution, resulting in an 89.92% higher relative deviation (δ = (value measured with the new absorption solution - value measured with the original absorption solution) / value measured with the original absorption solution * 100%) of the sulfuric acid mist measurement. Comparing the results obtained with the sodium hydroxide absorption solution and the isopropanol absorption solution at several measurement points, the relative deviation of the sulfuric acid mist measurement using the isopropanol absorption solution decreased by an average of 80.48%.

[0089] The above research results have been adopted and used as the sampling method of the national standard GB / T 38685-2020, and will be widely promoted and used in society in the future.

[0090] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for analyzing sulfuric acid mist tail gas, characterized in that: The following steps are involved: In the HJ 544-2016 sampling process, an isopropyl alcohol solution with a volume concentration of 80% was used as the absorption liquid; The solvent of the isopropyl alcohol solution is water; The amount of isopropyl alcohol solution added to the absorption bottle is 50 ml.

2. The sulfuric acid mist tail gas analysis method according to claim 1, characterized in that: The sulfuric acid mist content calculated as sulfuric acid is reduced by 68.48% to 89.92% compared with the case where sodium hydroxide solution is used as the absorption liquid.

3. The sulfuric acid mist tail gas analysis method according to claim 1, characterized in that: The adoption process includes the following steps: A pipeline connected to the air inlet of the smoke sampler is set at the measuring point, and two absorption bottles are set in series on the air outlet of the smoke sampler, and the absorption bottles are respectively filled with isopropyl alcohol absorption liquid; Insert the smoke gun equipped with a filter cartridge into the sampling point in the chimney for constant speed sampling for 30 to 60 minutes. The heating temperature of the smoke gun is 120℃ to 130℃. The sampling flow rate is determined according to the constant speed sampling principle, and the flow rate range is 5L / min to 15L / min.

4. The sulfuric acid mist tail gas analysis method according to claim 1, characterized in that: Also includes: Set up a blank sample, determine the acid mist content in the filter cartridge, and determine the acid mist content in the absorption liquid.

5. The sulfuric acid mist tail gas analysis method according to claim 4, characterized in that: Set up blank sample The method includes the following steps: Cut a blank filter cartridge from the same batch as the sample into pieces, place them in a 250mL conical flask, and add water to approximately 100mL. Add 2 to 3 drops of a methyl red-methylene blue mixed indicator solution to the test solution, and titrate with 0.05 mol / L hydrochloric acid standard titrant until the solution changes from gray-green to purple-red. Record the volume V of the hydrochloric acid standard titration solution consumed by the blank filter cartridge.

6. The sulfuric acid mist tail gas analysis method according to claim 1, characterized in that: Determination of acid mist content in filter cartridges The following steps are involved: Cut the filter cartridge with the collected sample into pieces, place them in a 250mL conical flask, and add water to 100mL to obtain a test solution. Add 2 to 3 drops of methyl red-methylene blue mixed indicator solution to the test solution and perform the following operations according to the color of the solution: a) If the solution is purple-red, titrate with 0.05 mol / L sodium hydroxide standard titrant until the solution turns gray-green. Record the volume V2 of sodium hydroxide standard titrant consumed by the sample. b) If the solution is gray-green, titrate with 0.05 mol / L hydrochloric acid standard titrant until the solution turns purple-red. Record the volume V3 of hydrochloric acid standard titrant consumed by the sample.

7. The sulfuric acid mist tail gas analysis method according to claim 1, characterized in that: Determination of the acid mist content in the absorption liquid includes the following steps: After sampling, transfer the solution in each absorption bottle to a 250 mL conical flask, and adjust the acidity of the solution with hydrochloric acid solution or sodium hydroxide solution to maintain the pH of the solution to be tested at 3.2-4.0 during titration. Add 2 to 3 drops of thorium indicator and titrate with barium perchlorate standard solution until the solution changes from khaki to pink. At the same time, a blank test was performed using unabsorbed isopropyl alcohol.

8. The sulfuric acid mist tail gas analysis method according to claim 1, characterized in that: Sulfuric acid mist tail gas comes from the production process of sulfuric acid from sulfur.

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