Composite complex iron salt desulfurizer and preparation method thereof

Abstract

The application discloses a composite complex iron salt desulfurizer and a preparation method thereof, and relates to the technical field of gas purification. The composite complex iron salt desulfurizer comprises soluble iron salt, a composite complexing agent, a pH regulator, a crystal inhibitor and deionized water, and the mass content of the crystal inhibitor is 0.2-3.5%. The prepared composite complex iron salt desulfurizer has high saturated sulfur capacity, is not easy to crystallize at low temperature, has a wide pH application window, and has high desulfurization efficiency.

Description

Technical Field

[0001] This invention belongs to the field of gas purification technology, specifically relating to a composite complex iron salt desulfurizing agent and its preparation method. Background Technology

[0002] The LO-CAT process desulfurization liquid developed by Wheelabrator Clean Air Systems in the United States uses ethylenediaminetetraacetic acid (EDTA) and N-hydroxyethyl ethylenediaminetriacetic acid (NHETA) as iron complexing agents. These have excellent complexing ability for iron and high desulfurization efficiency, but the desulfurization operation cost is high and the sulfur capacity is low.

[0003] The DDS desulfurization process developed by the College of Chemistry and Molecular Engineering at Peking University uses porphyrin, heme, and other iron complexing agents in the desulfurization liquid. This method has high desulfurization efficiency and is environmentally friendly and pollution-free, but the stability of the desulfurization liquid is poor.

[0004] Chinese invention patent CN101874968B discloses a complexed iron desulfurizer suitable for centrifugal desulfurization. Its effective components consist of: soluble iron salts; iron salt complexing agents; sulfide absorbents, including alkaline substances and alkanolamines; and additives, including stabilizers, synergists, sulfur particle setters, and corrosion inhibitors. This complexed iron desulfurizer has an operating pH range of 8-9. By employing a centrifugal device, the desulfurizer is countercurrently contacted with sulfide-containing gas in the centrifugal machine, allowing the alkaline desulfurizer to absorb the sulfides in the gas phase, thereby improving its absorption rate and sulfur recovery efficiency. However, this complexed iron desulfurizer has a low saturated sulfur capacity and a narrow operating pH range, resulting in rapid circulation and the need for large-scale recycling of the desulfurizer when used for H2S removal, leading to high desulfurization costs. High-concentration desulfurizing agents are prone to recrystallization during storage and use, resulting in crystal precipitation, which reduces the complexing ability of the complexing agent. During use, there is also a significant loss of iron ions, further increasing operating costs. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a composite complex iron salt desulfurizer and its preparation method. The prepared composite complex iron salt desulfurizer has high saturated sulfur capacity, is not easy to crystallize at low temperature, has a wide pH application window, and has high desulfurization efficiency.

[0006] This invention provides the following technical solution:

[0007] In a first aspect, a composite complexed iron salt desulfurizer is provided, comprising a soluble iron salt, a composite complexing agent, a pH adjuster, a crystal inhibitor, and deionized water, wherein the mass content of the crystal inhibitor is 0.2% to 3.5%.

[0008] Furthermore, the soluble iron salt is one or more of ferric sulfate, ferrous sulfate, ferric chloride, ferrous chloride, ferric nitrate, and ferrous nitrate.

[0009] Furthermore, the complexing agent is one or more of HEDTA, EDTA-2Na, EDTA-4Na, 2-oxyacetic acid malonic acid, hypozonotriacetic acid and its sodium salt, sodium citrate, sulfosalicylic acid, and 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0010] Furthermore, the pH adjuster is one or more of NaOH, Na2CO3, NaHCO3, KOH, K2CO3, and KHCO3.

[0011] Furthermore, the crystal inhibiting agent is one or more of the following: oxidized stearin, sodium dodecyl sulfate, povidone K30, and dodecyl dimethyl benzyl ammonium chloride.

[0012] Furthermore, the molar ratio of the composite complexing agent to the soluble iron salt is (1.05-3):1, and the molar ratio of the pH adjuster to the soluble iron salt is (2-6):1.

[0013] Furthermore, the iron content in the composite complex iron salt desulfurizer is 2% to 8.5% by mass.

[0014] Furthermore, the pH value of the composite complex iron salt desulfurizer is 8.0 to 10.5.

[0015] In a second aspect, a method for preparing the composite complex iron salt desulfurizer described in any one of the first aspects is provided, comprising the following steps:

[0016] Dissolve the pH adjuster in deionized water to obtain a pH adjuster solution;

[0017] The complexing agent is added to the pH adjuster solution and dissolved to obtain a mixed solution;

[0018] A soluble iron salt is added to the mixed solution, and after dissolution, a crystal inhibitor is added and stirred to dissolve, thus obtaining a composite complex iron salt desulfurizer.

[0019] Furthermore, the pH adjuster is dissolved in deionized water at a temperature maintained at 45°C.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] (1) In the composite complex iron salt desulfurizing agent provided by the present invention, Fe ions exist in the form of a complex, which can be represented here as Fe 3+ L and Fe 2+L represents the complexation state; during the absorption of sulfur-containing gases, H2S gas is absorbed and converted into HS under alkaline solution conditions. - Then through Fe 3+ L will HS - Oxidized to elemental sulfur, while Fe 3+ L is reduced to Fe 2+ L; During regeneration, Fe 2+ L is re-oxidized from oxygen in the air to Fe. 3+ L, the desulfurizing agent is regenerated and circulates to absorb H2S gas, and the operation process is not affected by temperature, with a desulfurization efficiency of up to 99%;

[0022] (2) The composite complex iron salt desulfurizer provided by the present invention specifically limits the mass content of the crystal inhibitor to 0.2% to 3.5%. Below this range, the crystallization efficiency and crystallization of the desulfurizer at low temperature are significantly increased; above this range, the effect of inhibiting crystallization at low temperature tends to saturate and there is no longer a significant inhibitory effect.

[0023] (3) The composite complex iron salt desulfurizer provided by the present invention has a saturated sulfur capacity of 7-9 g / L. During use, it can directly treat high concentrations of H2S gas. It is not easy to recrystallize at low temperatures. It has a wide pH application window and can reduce the loss of iron elements during operation.

[0024] (4) When using the composite complex iron salt desulfurizing agent provided by the present invention for wet complex iron desulfurization, the process is simple, the gas-liquid mass transfer efficiency is high, the equipment is small in size and easy to skid-mount, and it is expected to be widely used in the removal of H2S from natural gas or associated gas on offshore oil and gas platforms. Attached Figure Description

[0025] Figure 1 This is a graph showing the growth trend of crystallization quality at low temperature for Examples 1-4 and Comparative Examples 1-2 of the present invention;

[0026] Figure 2 These are schematic diagrams of the operating devices for continuous H2S removal in Embodiments 1-4 of the present invention;

[0027] Figure 3 This is a graph showing the trend of iron ion loss during the continuous H2S removal process in Examples 1-4 of the present invention. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0029] Example 1

[0030] This embodiment provides a composite complex iron salt desulfurizing agent and its preparation method, wherein the specific preparation method is as follows:

[0031] Step 1: Dissolve 1.4 mol sodium hydroxide and 0.6 mol potassium hydroxide in 4480 mL of deionized water, stir to dissolve, and maintain the temperature at 45℃ to obtain a pH adjusting solution;

[0032] Step 2: Add 0.5 mol EDTA-2Na, 0.4 mol HEDTA, 0.1 mol sulfosalicylic acid, and 0.1 mol 2-oxyacetic acid malonic acid to the pH adjuster solution in step 1 in sequence, and stir for 15-30 minutes until fully dissolved;

[0033] Step 3: Add 0.4 mol ferric chloride, 0.4 mol ferric sulfate, and 0.2 mol ferrous sulfate to the solution obtained in Step 2, and stir for 10-20 minutes until fully dissolved;

[0034] Step 4: Add 1g of povidone K30 and 0.9g of oxidized stearin to the solution obtained in Step 3, and stir at a constant temperature for 1-2 hours to obtain a composite complex iron salt desulfurizer, wherein the mass content of iron is 7.96% and the mass content of the crystal inhibitor is 0.2%.

[0035] Example 2

[0036] This embodiment provides a composite complex iron salt desulfurizing agent and its preparation method, wherein the specific preparation method is as follows:

[0037] Step 1: Dissolve 2 mol potassium hydroxide, 1.6 mol sodium bicarbonate, and 1.2 mol potassium carbonate in 4150 mL of deionized water, stir to dissolve, and maintain the temperature at 45℃ to obtain a pH adjusting solution;

[0038] Step 2: Add 1.2 mol EDTA-4Na, 0.4 mol 2-oxyacetic acid malonic acid, 0.4 mol sodium citrate, and 0.3 mol sodium hypotriacetate to the pH adjuster solution in step 1 in sequence, and stir for 20-45 minutes until fully dissolved;

[0039] Step 3: Add 0.6 mol ferric sulfate and 0.4 mol ferrous sulfate to the solution obtained in Step 2, and stir for 10-20 minutes until fully dissolved;

[0040] Step 4: Add 8.7g of povidone K30, 3.4g of oxidized stearin and 3.2g of sodium dodecyl sulfate to the solution obtained in Step 3, and stir at a constant temperature for 1-2 hours to obtain a composite complex iron salt desulfurizer, wherein the mass content of iron is 7.94% and the mass content of the crystal inhibitor is 2%.

[0041] Example 3

[0042] This embodiment provides a composite complex iron salt desulfurizing agent and its preparation method, wherein the specific preparation method is as follows:

[0043] Step 1: Dissolve 2 mol sodium carbonate and 0.8 mol potassium bicarbonate in 9300 mL deionized water, stir to dissolve, and maintain the temperature at 45℃ to obtain a pH adjusting solution;

[0044] Step 2: Add 1.2 mol EDTA-2Na and 0.6 mol 2-phosphonobutane-1,2,4-tricarboxylic acid to the pH adjuster solution in step 1 in sequence, and stir for 15-30 min until fully dissolved;

[0045] Step 3: Add 0.4 mol ferric nitrate, 0.4 mol ferrous nitrate, and 0.2 mol ferrous sulfate to the solution obtained in Step 2, and stir for 30–50 minutes until fully dissolved;

[0046] Step 4: Add 16.8g dodecyl dimethyl benzyl ammonium chloride, 5.4g oxidized stearin and 4.2g povidone K30 to the solution obtained in Step 3, and stir at a constant temperature for 1-2 hours to obtain a composite complex iron salt desulfurizer, wherein the mass content of iron is 3.99% and the mass content of the crystal inhibitor is 3.5%.

[0047] Example 4

[0048] This embodiment provides a composite complex iron salt desulfurizing agent and its preparation method, wherein the specific preparation method is as follows:

[0049] Step 1: Dissolve 1.8 mol sodium carbonate, 0.8 mol potassium carbonate, and 0.5 mol potassium bicarbonate in 8850 mL of deionized water, stir to dissolve, and maintain the temperature at 45℃ to obtain a pH adjusting solution;

[0050] Step 2: Add 1.2 mol HEDTA, 0.8 mol sulfosalicylic acid, 0.5 mol sodium citrate, and 0.5 mol EDTA-4Na to the pH adjuster solution in Step 1 in sequence, and stir for 30-40 minutes until fully dissolved;

[0051] Step 3: Add 0.6 mol ferric chloride and 0.4 mol ferrous sulfate to the solution obtained in Step 2, and stir for 10-20 minutes until fully dissolved;

[0052] Step 4: Add 15.8g sodium dodecyl sulfate, 13g povidone K30 and 8.4g oxidized stearin to the solution obtained in step 3, and stir at a constant temperature for 1-2 hours to obtain a composite complex iron salt desulfurizer, wherein the mass content of iron is 3.99% and the mass content of the crystal inhibitor is 3.5%.

[0053] Comparative Example 1

[0054] Step 1: Dissolve 1.8 mol sodium carbonate, 0.8 mol potassium carbonate, and 0.5 mol potassium bicarbonate in 8887.2 mL of deionized water, stir to dissolve, and maintain the temperature at 45℃ to obtain a pH adjusting solution;

[0055] Step 2: Add 1.2 mol HEDTA, 0.8 mol sulfosalicylic acid, 0.5 mol sodium citrate, and 0.5 mol EDTA-4Na to the pH adjuster solution in Step 1 in sequence, and stir for 30-40 minutes until fully dissolved;

[0056] Step 3: Add 0.6 mol ferric chloride and 0.4 mol ferrous sulfate to the solution obtained in Step 2, and stir for 10-20 minutes until fully dissolved;

[0057] Step 4: Without adding any crystal inhibitor, directly stir the solution obtained in Step 3 at a constant temperature for 1-2 hours to obtain the desulfurizer, wherein the mass content of iron is 3.99% and the mass content of crystal inhibitor is 0%.

[0058] Comparative Example 2

[0059] Step 1: Dissolve 1.8 mol sodium carbonate, 0.8 mol potassium carbonate, and 0.5 mol potassium bicarbonate in 8843.8 mL of deionized water, stir to dissolve, and maintain the temperature at 45℃ to obtain a pH adjusting solution;

[0060] Step 2: Add 1.2 mol HEDTA, 0.8 mol sulfosalicylic acid, 0.5 mol sodium citrate, and 0.5 mol EDTA-4Na to the pH adjuster solution in Step 1 in sequence, and stir for 30-40 minutes until fully dissolved;

[0061] Step 3: Add 0.6 mol ferric chloride and 0.4 mol ferrous sulfate to the solution obtained in Step 2, and stir for 10-20 minutes until fully dissolved;

[0062] Step 4: Add 21.4g sodium dodecyl sulfate, 13.6g povidone K30 and 8.4g oxidized stearin to the solution obtained in Step 3, and stir at a constant temperature for 1-2 hours to obtain a desulfurizing agent, wherein the mass content of iron is 3.99% and the mass content of the crystal inhibitor is 4%.

[0063] Performance Comparison

[0064] 1. Crystallization test at low temperature.

[0065] Test method:

[0066] (1) Take 2400g of each of the composite complex iron salt desulfurizing agent obtained in Examples 1 to 4 and the desulfurizing agent obtained in Comparative Examples 1 to 2. Divide each solution into 24 portions, each portion weighing 100g, and label them as 1-1...6-24. Place them in an environment of -4℃.

[0067] (2) After standing for 2 hours, take one portion from each of Examples 1-4 and Comparative Examples 1-2, operate in a low-temperature oven, filter out crystals at 0°C, and dry the crystals by vacuum filtration. The weight is recorded as m. 1-1 ...m 6-1 ;

[0068] (3) Step (2) was repeated every 2 hours within 48 hours to obtain the crystal formation of Examples 1-4 and Comparative Examples 1-2 at different time durations. The results are as follows: Figure 1 As shown.

[0069] Depend on Figure 1 It can be seen that under low temperature conditions, as time goes on, the increase in crystal quality tends to level off and gradually stops, and not all crystals are precipitated. Moreover, the precipitated quality remains low, all below 7%. Specifically, Example 1 precipitated 6.9%, Example 2 precipitated 3.8%, Example 3 precipitated 3.7%, Example 4 precipitated 0.4%, Comparative Example 1 precipitated 10.1%, and Comparative Example 2 precipitated 0.42%.

[0070] In Example 1, the added inhibitor was 0.2%, which had a preliminary inhibitory effect and could control crystallization within a low range. In Example 2, the inhibitor was 2.0%, and in Example 3, the inhibitor was 3.5%. The inhibitory effects of these two were more obvious. The iron ion concentration in Example 2 was twice that in Example 3, and it also maintained a good inhibitory effect.

[0071] Compared to Example 3, Example 4 added more complexing agents at the same iron ion concentration, which further improved its crystal-inhibiting effect. At low temperatures, almost no crystals were precipitated, as low as 0.4%, which is negligible.

[0072] Compared to Examples 1-4, Comparative Example 1 had an addition ratio of 0% for the crystal inhibitor. It started crystallizing earliest and ultimately had the highest crystal mass, which was 10.1%. Compared to Examples 1-4, its crystal mass increased by 46%-75%. It can be seen that even with the addition of only the minimum proportion of the crystal inhibitor, a relatively significant crystal inhibition effect can still be achieved.

[0073] Compared to Examples 4 and 1, Comparative Example 2 added 4.0% of the crystal inhibitor, which is higher than the 3.5% limit of the crystal inhibitor's protective addition range. Compared to the crystal quality of Example 4, its crystal inhibition effect was almost unchanged, or even slightly reduced. After repeating multiple sets of tests, it was determined that this was not an isolated case. It should be because too much crystal inhibitor was added, which led to an increase in the conductivity of the solution, a decrease in pH, and a tendency for the crystal inhibition effect to saturate, thereby affecting the further inhibition effect of the crystal inhibitor on recrystallization.

[0074] In summary, the anti-crystallization agent greatly enhances the anti-crystallization ability of the composite complex iron salt desulfurizer at low temperatures.

[0075] 2. Test on iron ion loss during continuous H2S removal operation.

[0076] Test method:

[0077] (1) Take 1600g of each of the composite complex iron salt desulfurizing agent solutions obtained in Examples 1-4, and in the following conditions... Figure 2 The four desulfurization units shown were tested in sequence for cyclic removal of H2S. Except for the desulfurization liquid, all other conditions were kept the same.

[0078] (2) The device operated continuously for 8 weeks. Each week, 2 mL samples were taken from each of the four regeneration tanks, and the iron ion concentration in the desulfurization solution was detected by ICP method to calculate the iron ion loss rate. The iron ion loss in Examples 1-4 under different operating cycles was obtained, and the results are as follows: Figure 3 As shown.

[0079] Depend on Figure 3 It can be seen that during continuous operation, as time goes on, the trend of iron ion loss tends to slow down and gradually stops, and all maintain a low loss rate, all below 5%. Example 1 precipitated 4.4%, Example 2 precipitated 1.26%, Example 3 precipitated 2.76%, and Example 4 precipitated 0.75%.

[0080] In Example 1, the amount of inhibitor added was 0.2%, and in Example 2, the amount of inhibitor added was 2%. Under the same or similar iron ion concentration, the higher the concentration of inhibitor, the less iron ion loss.

[0081] Examples 3 and 4 used 3.5% of a crystal inhibitor. At the same concentration, the more composite complexing agent added, the less iron ions were lost, which is in line with general rules.

[0082] In Example 4, the iron ion loss rate was 0.75% after 8 weeks, which is almost negligible. This indicates that under a suitable concentration of inhibitor, the increase in conductivity caused by other byproduct salts accumulated during long-term operation can be well suppressed, thereby ensuring a low iron ion loss rate.

[0083] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A composite complex iron salt desulfurizing agent, characterized in that, It includes soluble iron salts, complexing agents, pH adjusters, crystal inhibitors, and deionized water, wherein the mass content of the crystal inhibitor is 0.2% to 3.5%; The crystallization inhibitor is one or more of the following: oxidized stearin, sodium dodecyl sulfate, povidone K30, and dodecyl dimethyl benzyl ammonium chloride.

2. The composite complex iron salt desulfurizer according to claim 1, characterized in that, The soluble iron salt is one or more of ferric sulfate, ferrous sulfate, ferric chloride, ferrous chloride, ferric nitrate, and ferrous nitrate.

3. The composite complex iron salt desulfurizer according to claim 1, characterized in that, The complexing agent is one or more of HEDTA, EDTA-2Na, EDTA-4Na, 2-oxyacetic acid malonic acid, hypozonotriacetic acid and its sodium salt, sodium citrate, sulfosalicylic acid, and 2-phosphonobutane-1,2,4-tricarboxylic acid.

4. The composite complex iron salt desulfurizer according to claim 1, characterized in that, The pH adjuster is one or more of NaOH, Na2CO3, NaHCO3, KOH, K2CO3, and KHCO3.

5. The composite complex iron salt desulfurizer according to claim 1, characterized in that, The molar ratio of the complexing agent to the soluble iron salt is (1.05~3):1, and the molar ratio of the pH adjuster to the soluble iron salt is (2~6):

1.

6. The composite complex iron salt desulfurizer according to claim 1, characterized in that, The iron content in the composite complex iron salt desulfurizer is 2% to 8.5% by mass.

7. The composite complex iron salt desulfurizer according to claim 1, characterized in that, The pH value of the composite complex iron salt desulfurizer is 8.0~10.

5.

8. A method for preparing the composite complex iron salt desulfurizing agent according to any one of claims 1 to 7, characterized in that, Includes the following steps: Dissolve the pH adjuster in deionized water to obtain a pH adjuster solution; The complexing agent is added to the pH adjuster solution and dissolved to obtain a mixed solution; A soluble iron salt is added to the mixed solution, and after dissolution, a crystal inhibitor is added and stirred to dissolve, thus obtaining a composite complex iron salt desulfurizer.

9. The preparation method of the composite complex iron salt desulfurizer according to claim 8, characterized in that, When the pH adjuster is dissolved in deionized water, the temperature is maintained at 45°C.

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