Agents and methods and systems for treating odors of oil and gas field acidizing wastewater

Abstract

The application discloses a medicament and a method and system for treating the odor of oil and gas field acidification wastewater, and the medicament for treating the odor of oil and gas field acidification wastewater comprises sodium persulfate, hydrogen peroxide and ferrous sulfate, wherein the molar ratio of the sodium persulfate to the hydrogen peroxide is greater than or equal to 10:1, and the molar ratio of the sodium persulfate to the ferrous sulfate is greater than or equal to 2:1. The application adds two closed tank bodies as oxidation reaction kettles between a gas-liquid separator and a waste liquid pool, the two closed tank bodies are respectively used for adding Fenton reagent for primary oxidation treatment and adding the medicament for secondary oxidation treatment, different oxidation processes are selected according to the detection result of the odor concentration of the oil and gas field acidification wastewater, the odor content in the oil and gas field acidification wastewater is reduced, the application can not only effectively reduce the odor concentration in the oil and gas field acidification wastewater, but also can avoid odor overflow in the conveying process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oilfield acidification wastewater treatment, in particular to a medicament and method and system for treating the odor of oil and gas field acidification wastewater. BACKGROUND

[0002] The acidification wastewater of the oilfield construction site is divided into two stages of continuous flowback and waste liquid storage, wherein the continuous flowback is to discharge the acidification wastewater after the gas-liquid separator to the waste liquid pool, and then store it in the waste liquid pool; in the case of not supporting capping on site, the acidification wastewater will continuously emit and overflow the odor gas during the flowback, storage and transportation. Therefore, the acidification wastewater of the oilfield is treated to reduce the content of odor gas.

[0003] In the oilfield construction site, the existing technology for treating the oilfield acidification wastewater is alkali absorption method, spraying method and biological method. The alkali absorption method is to directly add sodium hydroxide to the waste liquid pool filled with flowback liquid, which can remove the main pollutant H2S in the wastewater, but the removal effect of volatile organic compounds is poor. The spraying method is to use absorption liquid to intermittently spray on the top of the waste liquid pool to absorb the volatilized gas, thereby reducing the odor concentration, but the effect of the method is not good in the field application. The biological method has high dependence on the pH of the wastewater and slow effect, so the application is also relatively less. SUMMARY

[0004] The purpose of the present application is to provide a medicament for treating the odor of oil and gas field acidification wastewater, which can effectively reduce the content of odor gas in the oil and gas field acidification wastewater.

[0005] In addition, the present application also includes a treatment method based on the above-mentioned medicament and a system for realizing the treatment method, which can reduce the content of odor gas in the acidification wastewater before it enters the waste liquid pool.

[0006] The present application is realized by the following technical solutions:

[0007] The medicament for treating the odor of oil and gas field acidification wastewater comprises sodium persulfate, hydrogen peroxide and ferrous sulfate, wherein the molar ratio of sodium persulfate to hydrogen peroxide is greater than or equal to 10:1, and the molar ratio of sodium persulfate to ferrous sulfate is greater than or equal to 2:1.

[0008] The present application determines the above-mentioned medicament formula through a large number of tests, which can effectively reduce the content of odor gas in the oil and gas field acidification wastewater, not only has good deodorizing effect for the oil and gas field acidification wastewater, but also has relatively high economic benefit.

[0009] The screening process of the present application is as follows:

[0010] The wastewater containing various odor sources was studied, and the five selected oxidants, potassium ferrate, sodium persulfate, hydrogen peroxide, sodium iodate and sodium hypochlorite, were used for wastewater oxidation and deodorization, and the conclusions were as follows:

[0011] Oxidant screening: The wastewater containing various odor sources was studied, and the five selected oxidants, potassium ferrate, sodium persulfate, hydrogen peroxide, sodium iodate and sodium hypochlorite, were used for wastewater oxidation and deodorization, and the conclusions were as follows:

[0012] (1) For the first sampling of wastewater, the five oxidants had certain effect on the elimination of odor substances in wastewater, among which the deodorization effect of hydrogen peroxide was general, sodium hypochlorite had certain oxidation effect on odor substances, but it itself had chlorine odor.

[0013] (2) For the second sampling of wastewater, potassium ferrate, sodium persulfate and sodium iodate were selected as deodorants, and the results showed that potassium ferrate had the best oxidation effect, but it produced a weak iron rust smell, sodium iodate had general deodorization effect in a short time, and sodium persulfate showed good performance in oxidation and deodorization experiment.

[0014] (3) For the fourth sampling of wastewater, two batches of potassium ferrate, sodium persulfate and sodium iodate with different mass ratios were selected as deodorants, and the results showed that the oxidants had certain effect on the removal of odor substances in wastewater, but the wastewater odor intensity needed to be further reduced by activating the oxidants.

[0015] Considering the economic benefits and deodorization effect, sodium persulfate was the most suitable deodorant for wastewater containing various odor sources.

[0016] Ferrous sulfate / hydrogen peroxide / sodium persulfate combination single factor screening: The analysis of different well stations' flowback fluid in Sichuan oil and gas field and the on-site air detection showed that the flowback fluid contained various odor sources with complex components, including a large amount of hydrogen sulfide, sulfide, mercaptan, short-chain aliphatic hydrocarbons, aromatic hydrocarbons, oxygen-containing organic compounds, etc. The deodorization mechanism was that the persulfate radical produced by the activation of sodium persulfate by ferrous sulfate had selectivity, which could selectively oxidize short-chain and branched-chain aliphatic hydrocarbons, short-chain sulfides and mercaptans, monocyclic and low-ring aromatic hydrocarbons, etc. The hydroxyl radical produced by the activation of sodium persulfate by alkali and the hydroxyl radical produced by the activation of hydrogen peroxide by ferrous sulfate had no selectivity, which could make up for the deficiency of selective oxidation of persulfate radical to some extent. The hydroxyl radical could oxidize and degrade the remaining n-alkanes and polycyclic aromatic hydrocarbons. The addition of sodium hydroxide to adjust the solution to alkaline not only activated sodium persulfate by alkali, but also quickly absorbed and fixed hydrogen sulfide and sulfur dioxide in the wastewater. The synergistic effect of the combination of the reagents reduced the odor intensity of the odor substances in the wastewater containing various odor sources to the greatest extent.

[0017] The present application is proved by a large number of repeated experiments. When the dosage is large, the combination of hydrogen peroxide and ferrous sulfate (Fenton reagent) has a better oxidation effect on the odor substances in the wastewater, but the volume of the water body will increase significantly. When the dosage is small, the removal ability of the wastewater odor is weak. The combination of sodium persulfate, hydrogen peroxide and ferrous sulfate has better stability and strong removal ability for odor substances in wastewater, that is, the reagent of the present application has better stability and stronger deodorization ability than the existing Fenton reagent.

[0018] Further, the molar ratio of the sum of sodium persulfate and hydrogen peroxide to ferrous sulfate is greater than or equal to 4:1.

[0019] Further, the dosage of the reagent is 3000-3300 mg / L, and the reaction environment is alkaline.

[0020] The system for treating the odor of acidification wastewater in oil and gas fields comprises a first closed tank and a second closed tank, which are sequentially arranged between a gas-liquid separator and a waste liquid pool. The first closed tank and the second closed tank respectively perform primary oxidation treatment and secondary oxidation treatment on the acidification wastewater treated by the gas-liquid separator. Fenton reagent is added to the first closed tank during the primary oxidation treatment, and the above-mentioned reagent is added to the second closed tank during the secondary oxidation treatment.

[0021] Preferably, a filter screen is arranged in the first closed tank to preliminarily filter the suspended matter in the wastewater, and the filtered liquid enters the second closed tank.

[0022] Further, the first closed tank and the second closed tank are both communicated with a gas treatment system through exhaust pipes, and the second closed tank is communicated with a residue treatment system through a pipeline.

[0023] Further, the gas treatment system comprises a combustion chamber for burning the volatile gas in the first closed tank and the second closed tank, and the residue treatment system comprises a treatment pit for receiving and collecting the precipitate in the second closed tank.

[0024] Since the deodorant (Fenton reagent, reagent of the present application) added to the first closed tank and the second closed tank does not immediately produce an effect, and the volatile organic matter in the liquid will continue to volatilize under the stirring of the reactor, the volatile gas can be collected to the treatment system by using a fan or the like for combustion treatment. After adding an alkali solution into the second closed tank, a large amount of precipitate will be generated in the lower layer, which can be transferred to the treatment pit by pumping and still treated by adding the ferrous sulfate / sodium persulfate reagent combination. After treatment, it can be directly solidified and landfilled.

[0025] The method for treating the odor of oil and gas field acidification wastewater, if the oil and gas field acidification wastewater is acidic, first, the oil and gas field acidification wastewater is subjected to primary oxidation treatment by using Fenton reagent, and then is subjected to secondary oxidation treatment by using the above-mentioned reagent, if the oil and gas field acidification wastewater is alkaline, is directly subjected to oxidation treatment by using the above-mentioned reagent.

[0026] The oxidation principle of the present application is as follows:

[0027] First, the oil and gas field acidification wastewater is subjected to oxidation by using hydrogen peroxide / ferrous sulfate reagent combination (Fenton reagent), the original solution (the oil and gas field acidification wastewater) is acidic and contains a small amount of Fe 2+ , under the activation of Fe 2+ , the Fenton reagent can remove part of the odor substances contained in the liquid. By controlling the flow rate of wastewater input and output, the wastewater is subjected to primary oxidation reaction for about 10 minutes, the hydrogen peroxide in the Fenton reagent has a short half-life and can quickly perform oxidation reaction, and the remaining unreacted hydrogen peroxide will continue to play a role in the secondary oxidation reaction. In the secondary oxidation reaction, the liquid is adjusted to weak alkaline, H2S and the like can be absorbed by the alkaline solution, and Fe 2+ oxidized to produce Fe 3+ has a certain flocculation effect under alkaline conditions, and the suspended solids can be precipitated by using the net trapping ability of Fe(OH)3; at the same time, sodium persulfate / hydrogen peroxide / ferrous sulfate reagent combination is added, at this time, the liquid has very favorable conditions for the activation of sodium persulfate, and the generated persulfate free radicals have strong oxidation effect, and the residual odor substances in the water will be completely removed. The oxidation reaction temperature is the temperature of the flowback liquid itself, and the pressure is normal pressure, without adjustment.

[0028] Further, due to the differences of working fluid of each well station and formation conditions, and the differences of multi-section flowback liquid itself, the odor concentration in the wastewater is different, and accordingly, the dosing sequence under different conditions is designed, and the process flow of the odor removal system is as follows:

[0029] The odor concentration of the oil and gas field acidification wastewater is detected, if it is less than or equal to 30, no oxidation treatment is performed, and if it is greater than 30, the acid-base degree of the oil and gas field acidification wastewater is detected:

[0030] If the detection result is that the pH value is less than 7, the Fenton reagent is added for primary oxidation treatment, after the primary oxidation treatment is completed, the odor concentration is detected, if it is less than or equal to 30, no secondary oxidation treatment is performed, if it is greater than 30, the solution is adjusted to alkaline, and the above-mentioned reagent is added for secondary oxidation treatment, the odor concentration is detected, if it is less than or equal to 30, the oxidation treatment is completed, and if it is greater than 30, the above-mentioned reagent is continuously added for secondary oxidation treatment, until the odor concentration detection result is less than 30.

[0031] If the detection result is pH value greater than or equal to 7, directly add the agent as claimed in any one of claims 1-3 for oxidation treatment, detect the odor concentration, if less than or equal to 30, the oxidation treatment is completed, if greater than 30, continue to add the agent for secondary oxidation treatment until the odor concentration detection result is less than 30 (dimensionless).

[0032] The application first detects whether the odor concentration exceeds the secondary plant boundary allowable emission value according to the national standard, and if greater than 30, the wastewater is treated, the pH value of the wastewater is measured, if acidic, the pH value can be adjusted to about 4, and a proper amount of Fenton reagent is added for preliminary oxidation treatment of the malodorous substances, if the effect is not achieved, the wastewater is alkalized, the alkali not only can neutralize part of the acidic gas, but also can react with the ferric ion in the wastewater to precipitate suspended solids in the wastewater, if the effect is still not achieved, sodium persulfate is added, at this time, the alkalinity and high temperature of the wastewater can activate the sodium persulfate, the residual hydrogen peroxide can form a double oxidation system with the sodium persulfate to oxidize the reducing substances without distinction, and finally the deodorization effect is achieved.

[0033] Further, the pH value of the secondary oxidation treatment is 8-10.

[0034] Further, the temperature of the secondary oxidation treatment is 40-60 DEG C.

[0035] Compared with the prior art, the application has the following advantages and beneficial effects:

[0036] 1. The agent has the advantages of strong deodorization ability and good stability, and can effectively reduce the content of malodorous gas in the oil and gas field acidification wastewater.

[0037] 2. Compared with the prior art, the application selects a new agent combination (Fenton reagent combined with the agent) and designs a new treatment process; on the basis of ensuring the treatment effect, the agent cost is saved, and the wastewater containing multiple odor sources is comprehensively treated.

[0038] 3. The oxidation reaction is carried out in a closed tank, which avoids the odor overflow caused by the direct addition method in the traditional method.

[0039] 4. After the treatment method, the odor intensity grade of the oil and gas field acidification wastewater is reduced from 5 to 2, which reaches the plant boundary emission standard of the related pollutants in the national standard. DETAILED DESCRIPTION

[0040] The accompanying drawings, which are included to provide a further understanding of the embodiments of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the principles of the application. In the drawings:

[0041] Figure 1The structural schematic diagram of the treatment system of the present application;

[0042] Figure 2 The logic diagram of the treatment method of the present application;

[0043] Figure 3 The reaction mechanism schematic diagram of the medicament of the present application;

[0044] Figure 4 COD residual amount schematic diagram of water samples treated by different proportions of hydrogen peroxide and sodium persulfate Cr COD residual amount schematic diagram of water samples treated by different proportions of hydrogen peroxide and sodium persulfate

[0045] Figure 5 COD residual amount schematic diagram of water samples treated by different proportions of hydrogen peroxide and sodium persulfate Cr COD residual amount schematic diagram of water samples treated by different proportions of hydrogen peroxide and sodium persulfate

[0046] Figure 6 COD removal effect schematic diagram of different medicament addition amounts Cr COD removal effect schematic diagram of different medicament addition amounts DETAILED DESCRIPTION

[0047] In order to make the purpose, technical scheme and advantages of the present application clearer and more apparent, the present application will be further described in detail below with reference to the embodiments and drawings, and the schematic embodiments of the present application and the description thereof are only used to explain the present application, and do not limit the present application.

[0048] Example 1

[0049] The medicament for treating the odor of acidizing wastewater in oil and gas fields comprises sodium persulfate, hydrogen peroxide and ferrous sulfate,

[0050] In this example, the molar ratio of ferrous sulfate to hydrogen peroxide is 1:8, and the molar ratio of hydrogen peroxide to sodium persulfate is 1:10.

[0051] Comparative Example 1

[0052] This comparative example is based on Example 1, and the difference between Example 1 and this comparative example is that:

[0053] The molar ratio of hydrogen peroxide to sodium persulfate is 1:7.

[0054] Comparative Example 2

[0055] This comparative example is based on Example 1, and the difference between Example 1 and this comparative example is that:

[0056] The molar ratio of hydrogen peroxide to sodium persulfate is 1:4.

[0057] Comparative Example 3

[0058] This comparative example is based on Example 1, and the difference between Example 1 and this comparative example is that:

[0059] The molar ratio of hydrogen peroxide to sodium persulfate is 1:1.

[0060] The above Example 1 and Comparative Examples 1-3 are used to determine the optimal molar ratio of hydrogen peroxide to sodium persulfate when the molar ratio of ferrous sulfate to hydrogen peroxide is constant, and the specific test process is as follows:

[0061] Take 4 sample bottles, and the numbers (serial numbers) of the 4 sample bottles are No. 1, No. 2, No. 3 and No. 4 respectively. No. 1, No. 2, No. 3 and No. 4 correspond to Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 respectively. 40 mL of wastewater is added to each sample bottle. The wastewater is first treated with Fenton reagent, and then treated with the reagent (Example 1, Comparative Example 1, Comparative Example 2 or Comparative Example 3). The total molar number of oxidants in the wastewater is 0.02 mol, and the treatment results are shown in Table 1. Figure 4

[0062] Table 1: Odor grade and COD of water samples after treatment with different ratios of sodium persulfate / hydrogen peroxide Cr

[0063]

[0064] Note: The oxidant in Table 1 is sodium persulfate, and the activator is hydrogen peroxide.

[0065] From the data in Table 1 and Figure 4 it can be seen that:

[0066] When Fenton reagent and sodium persulfate are used together, the COD Cr is the lowest when the molar ratio of hydrogen peroxide to sodium persulfate is 1:10, and the odor grade of the four groups of water samples is 2-3. Therefore, when the reagent is used in practice, the molar ratio of sodium persulfate to hydrogen peroxide in the reagent can be set to be greater than or equal to 1:10.

[0067] Example 2:

[0068] The reagent for treating the odor of acidizing wastewater in oil and gas fields comprises sodium persulfate, hydrogen peroxide and ferrous sulfate,

[0069] In this example, the molar ratio of hydrogen peroxide to sodium persulfate is determined to be 1:10, and the molar ratio of sodium persulfate to ferrous sulfate is 8:1.

[0070] Example 3:

[0071] This example is based on Example 2, and the difference between this example and Example 2 is:

[0072] The molar ratio of sodium persulfate to ferrous sulfate is 6:1.

[0073] Example 4:

[0074] ​This embodiment is based on example 2, and the difference from example 2 is that:

[0075] The molar ratio of sodium persulfate to ferrous sulfate is 4:1.

[0076] Example 5:

[0077] This embodiment is based on example 2, and the difference from example 2 is that:

[0078] The molar ratio of sodium persulfate to ferrous sulfate is 2:1.

[0079] The above examples 2-5 are used to determine the optimal molar ratio of sodium persulfate to ferrous sulfate when the molar ratio of hydrogen peroxide to sodium persulfate is constant, and the specific test process is as follows:

[0080] Take 4 sample bottles, and the numbers (serial numbers) of the 4 sample bottles are 1, 2, 3 and 4 respectively, 1, 2, 3 and 4 correspond to examples 2-5 respectively, 40mL of wastewater is added respectively, first treated with Fenton reagent, and then treated with reagent (examples 2-5), the total molar number of oxidizing agent in the wastewater is 0.02mol, the pH measured by precision pH test paper is 2.7, and the oxidation is carried out in 45℃ constant temperature water bath for 10min, and the intensity of odor grade after treatment is shown in table 2:

[0081] Table 2

[0082] Table 2 intensity of odor grade after treatment with different molar ratio of sodium persulfate to ferrous sulfate

[0083]

[0084] Note: The oxidizing agent in table 2 is sodium persulfate, and the activator is ferrous sulfate.

[0085] From the data in table 2, we can know that:

[0086] When the molar ratio of hydrogen peroxide to sodium persulfate is constant, the molar ratio of sodium persulfate to ferrous sulfate is greater than or equal to 2:1, and the deodorization effect of the reagent is good.

[0087] Example 6:

[0088] The reagent for treating the odor of oil and gas field acidizing wastewater comprises sodium persulfate, hydrogen peroxide and ferrous sulfate,

[0089] In this embodiment, the molar ratio of sodium persulfate to ferrous sulfate is determined to be 8:1, and the molar ratio of ferrous sulfate to (sodium persulfate / hydrogen peroxide) is 1:4.

[0090] Example 7:

[0091] This embodiment is based on example 6, and the difference from example 6 is that:

[0092] Ferrous sulfate: (sodium persulfate / hydrogen peroxide) is 1:6 (molar ratio).

[0093] Example 8:

[0094] This example is based on Example 6, and the difference from Example 6 is that:

[0095] Ferrous sulfate: (sodium persulfate / hydrogen peroxide) is 1:8 (molar ratio).

[0096] Comparative Example 4:

[0097] This example is based on Example 6, and the difference from Example 6 is that:

[0098] Ferrous sulfate: (sodium persulfate / hydrogen peroxide) is 1:2 (molar ratio).

[0099] The above Examples 6-8 and Comparative Example 4 are used to determine the optimal molar ratio of ferrous sulfate: (sodium persulfate / hydrogen peroxide) when the molar ratio of sodium persulfate to ferrous sulfate is constant, and the specific test process is as follows:

[0100] Take 4 sample bottles, and the numbers (serial numbers) of the 4 sample bottles are No. 1, No. 2, No. 3 and No. 4, respectively. No. 1, No. 2, No. 3 and No. 4 correspond to Comparative Example 4, Examples 6-8, respectively, 40 mL of wastewater is added respectively, and the COD of the water sample is 16000 mg / L, 15023.16 mg / L, 16422.12 mg / L, 16401.24 mg / L, 17633.16 mg / L, respectively. First, the Fenton reagent is used for treatment, and then the reagent (Comparative Example 4, Examples 6-8) is used for treatment. The data after treatment are shown in Table 3 and Figure 5

[0101] From the data in Table 3, it can be seen that:

[0102] When the molar ratio of sodium persulfate to ferrous sulfate is constant, the molar ratio of the sum of sodium persulfate and hydrogen peroxide to ferrous sulfate is greater than or equal to 4:1, and the degradation rate of COD Cr in the waste liquid is greater than 60%.

[0103] Example 9:

[0104] As

[0105] Figure 1 ​As shown, a system for treating the odorous acidification wastewater from oil and gas fields includes a first sealed tank and a second sealed tank. The first and second sealed tanks are sequentially arranged between a gas-liquid separator and a waste liquid pool. The first and second sealed tanks are connected by a pipeline equipped with a pump. The first and second sealed tanks respectively perform primary oxidation treatment and secondary oxidation treatment on the acidification wastewater treated by the gas-liquid separator. During the primary oxidation treatment, Fenton's reagent is added to the first sealed tank, and during the secondary oxidation treatment, the reagent described in the above embodiment is added to the second sealed tank.

[0106] In this embodiment,

[0107] Both the first and second sealed tanks are connected to a gas treatment system via exhaust pipes, and the second sealed tank is connected to a residue treatment system via a pipeline. The gas treatment system includes a combustion chamber for burning the volatile gases in the first and second sealed tanks. The residue treatment system includes a treatment pit for receiving and collecting sediment in the second sealed tank. The exhaust pipe even has a fan that guides the volatile gases in the first and second sealed tanks into the combustion chamber.

[0108] Example 10:

[0109] like Figure 2 The method shown is for treating the malodorous wastewater from oil and gas field acidification processes.

[0110] The specific process is as follows:

[0111] The odor concentration of the oil and gas field acidification wastewater is tested. If it is less than or equal to 30, oxidation treatment is not performed. If it is greater than 30, the pH of the oil and gas field acidification wastewater is tested.

[0112] If the pH value is less than 7, add Fenton's reagent for primary oxidation treatment. After primary oxidation treatment, test the odor concentration. If it is less than or equal to 30, do not perform secondary oxidation treatment. If it is greater than 30, adjust the solution to alkaline, add reagent (ferrous sulfate / sodium persulfate / hydrogen peroxide reagent combination) for secondary oxidation treatment, and test the odor concentration. If it is less than or equal to 30, the oxidation treatment is complete. If it is greater than 30, continue to add reagent for secondary oxidation treatment until the odor concentration test result is less than 30.

[0113] If the pH value is greater than or equal to 7, add the reagent directly for oxidation treatment and test the odor concentration. If it is less than or equal to 30, the oxidation treatment is complete. If it is greater than 30, continue adding reagent for secondary oxidation treatment until the odor concentration test result is less than 30 (dimensionless).

[0114] In this embodiment, the detection result of one wastewater odor concentration is greater than 30 as an example for illustration:

[0115] The wastewater (odor concentration is 43) delivered by the gas-liquid separator is input into the first closed tank body as a first-stage oxidation reaction kettle. Fenton reagent (hydrogen peroxide / ferrous sulfate (molar ratio 4:1)) is added first to oxidize the wastewater. The original solution is acidic (pH = 2.7). Under the activation of Fe 2+ , part of the odor substances contained in the liquid are removed, and long-chain molecules are oxidized into short-chain molecules. By controlling the flow rate of wastewater input and output, the wastewater stays in the first-stage oxidation reaction kettle for about 10 minutes. Hydrogen peroxide has a short half-life, so the oxidation reaction can be carried out quickly. The remaining unreacted hydrogen peroxide and ferrous sulfate enter the second-stage oxidation kettle (the second closed tank body) with the wastewater. After the first-stage oxidation treatment, the odor concentration is 32, and the pH is 5.6. In the second-stage oxidation reaction kettle, sodium hydroxide is used to adjust the liquid to weak alkaline. The specific pH value is adjusted to 8. H2S and other volatile substances reach the acid gas and are absorbed and fixed in water by the alkali solution; Fe 2+ is oxidized to Fe 3+ , which has a certain flocculation effect under alkaline conditions. The Fe(OH)3 has a net trapping ability, which can precipitate suspended solids. At the same time, the sodium persulfate / ferrous sulfate / hydrogen peroxide (molar ratio 10:1.25:1) reagent combination is added. At this time, the liquid has very favorable conditions for the activation of sodium persulfate. The generated persulfate radicals have strong oxidation effect, and the residual odor substances in the water are completely removed. The oxidation principle is shown in Figure 3 . The oxidation reaction temperature is the temperature of the produced fluid itself, and the pressure is normal pressure, which does not need to be adjusted. The dosage of the ferrous sulfate / sodium persulfate / hydrogen peroxide reagent combination is 3000 mg / L, the pH is 8, and the oxidation time is 40 minutes.

[0116] The embodiment of the present embodiment is based on the treatment system described in embodiment 9.

[0117] In order to verify the influence of the reagent addition amount on the deodorization effect, the following test is carried out:

[0118] Several 100 mL sample bottles are taken, and 40 mL of wastewater is added. The temperature is 45°C, the pH of the wastewater is 2.7, and the method described in embodiment 10 is used for treatment. The second-stage oxidation time is 30 minutes. The influence of different reagent dosages on the deodorization effect is explored at a concentration gradient of 300 mg / L. The results are shown in Table 4 and Figure 6 .

[0119] Table 4 Influence of reagent dosage on deodorization effect

[0120]

[0121] Note: The dosage combination addition amount refers to the dosage amount of the ferrous sulfate / sodium persulfate / hydrogen peroxide dosage combination, and the serial number is the sample bottle number.

[0122] From Table 4 and Figure 6 It can be seen that:

[0123] With the increase of the dosage combination amount, the treatment effect is more and more obvious. When the dosage combination amount is ≥3000 mg / L, the change range of the smell grade becomes smaller, and is stabilized at about 2, and the odor intensity is roughly equivalent to that when the oxidant combination is overdosed in the previous study. The activator (ferrous sulfate) in the dosage combination can react with sodium persulfate, hydrogen peroxide and the like to generate persulfate radicals and hydroxyl radicals which have stronger oxidation than persulfate radicals. When the dosage combination amount gradually increases from zero, the effective oxidizing components such as persulfate radicals are increased, the oxidation ability is continuously enhanced, and the treatment effect is obvious. However, due to the occurrence of some side reactions, when the dosage amount is increased to a certain extent, the increase of the dosage amount does not significantly increase the persulfate radicals and hydroxyl radicals which effectively participate in the reaction, resulting in no significant improvement in the sewage treatment effect. Therefore, the optimal dosage combination dosage is determined to be 3000-3300 mg / L.

[0124] The above specific embodiments further specifically describe the purposes, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement and the like within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for treating the malodorous acidification wastewater from oil and gas fields, characterized in that, The specific process is as follows: The odor concentration of the oil and gas field acidification wastewater is tested. If it is less than or equal to 30, oxidation treatment is not performed. If it is greater than 30, the pH of the oil and gas field acidification wastewater is tested. If the pH value is less than 7, Fenton's reagent is added for primary oxidation treatment. After primary oxidation treatment, the odor concentration is measured. If it is less than or equal to 30, secondary oxidation treatment is not performed. If it is greater than 30, the solution is adjusted to alkalinity, and reagents are added for secondary oxidation treatment. The odor concentration is measured again. If it is less than or equal to 30, the oxidation treatment is complete. If it is greater than 30, the reagents are added again for secondary oxidation treatment until the odor concentration is less than 30. The reagents include sodium persulfate, hydrogen peroxide, and ferrous sulfate, wherein the molar ratio of sodium persulfate to hydrogen peroxide is greater than or equal to 10:1, and the molar ratio of sodium persulfate to ferrous sulfate is greater than or equal to 2:

1. If the pH value is greater than or equal to 7, add the reagent directly for oxidation treatment and test the odor concentration. If it is less than or equal to 30, the oxidation treatment is complete. If it is greater than 30, continue to add the reagent for secondary oxidation treatment until the odor concentration test result is less than 30.

2. The method for treating the malodorous wastewater from oil and gas field acidification as described in claim 1, characterized in that, The pH value for the secondary oxidation treatment is 8-10.

3. The method for treating the malodorous wastewater from oil and gas field acidification according to claim 1, characterized in that, The temperature for the secondary oxidation treatment is 40-60℃.

4. A system for treating the odorous acidification wastewater from oil and gas fields, used to implement the method described in any one of claims 1 to 3, characterized in that, The system includes a first sealed tank and a second sealed tank, which are sequentially arranged between a gas-liquid separator and a waste liquid pool. The first and second sealed tanks respectively perform primary oxidation treatment and secondary oxidation treatment on the acidified wastewater treated by the gas-liquid separator. During the primary oxidation treatment, Fenton's reagent is added to the first sealed tank, and during the secondary oxidation treatment, a reagent is added to the second sealed tank. The reagent includes sodium persulfate, hydrogen peroxide, and ferrous sulfate, wherein the molar ratio of sodium persulfate to hydrogen peroxide is greater than or equal to 10:1, and the molar ratio of sodium persulfate to ferrous sulfate is greater than or equal to 2:

1.

5. The system for treating the odorous wastewater from oil and gas field acidification as described in claim 4, characterized in that, The molar ratio of the sum of sodium persulfate and hydrogen peroxide to ferrous sulfate is greater than or equal to 4:

1.

6. The system for treating the odorous wastewater from acidification in oil and gas fields according to claim 4, characterized in that, The amount of the reagent added is 3000-3300 mg / L, and the reaction environment is alkaline.

7. The system for treating the odorous wastewater from acidification in oil and gas fields according to claim 4, characterized in that, Both the first and second sealed tanks are connected to the gas treatment system via exhaust pipes, and the second sealed tank is connected to the residue treatment system via a pipeline.

8. The system for treating the odorous wastewater from acidification in oil and gas fields according to claim 7, characterized in that, The gas processing system includes a combustion chamber for burning volatile gases in a first sealed tank and a second sealed tank; the residue processing system includes a processing pit for receiving and collecting sediment in the second sealed tank.

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