Composite additive and its preparation and application in crude coal gas absorption and oil-water separation

Abstract

The application discloses a composite auxiliary agent and a preparation and application thereof in crude coal gas absorption and oil-water separation. The application uses dimethylaminopropanol as a starting agent, and carries out polymerization reaction with propylene oxide and ethylene oxide as monomers to prepare a block polyether; then, the block polyether is used as a functional main body, is responsible for efficient wetting, cleaning and oil-water separation, and a small amount of hyperbranched polyethylene imine is compounded as a demulsification enhancer, is responsible for electric neutralization and flocculation, so that an alkali-resistant and high-temperature-resistant composite auxiliary agent is obtained, the problems of incomplete crude coal gas absorption and difficult oil-water separation are solved, the crude coal gas-ammonia water system is used, the "secondary emulsification" is avoided from the source, and the absorption effect of the crude coal gas and the oil-water separation efficiency are far higher than those of a traditional auxiliary agent.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of block polyether preparation and oil-water separation, and particularly relates to a chemical additive applied to the purification process of raw coal gas in the coal chemical industry and coking industry, and especially to a composite additive with the dual functions of efficient absorption and rapid oil-water separation in a high-temperature and alkaline ammonia water environment and a preparation method and application thereof. BACKGROUND

[0002] In the field of modern energy and chemical industry, the Lurgi gasification process occupies an important position in coal gasification production due to its advantages of using low-quality coal, high production capacity of pressurized gasification, and low oxygen consumption. With coal as the raw material, steam and oxygen as the gasifying agent, the Lurgi furnace can produce raw coal gas containing carbon monoxide, hydrogen, methane, heavy tar and other components. However, this process also brings about a thorny problem, i.e., the light tar (such as phenol, cresol), asphaltene, polycyclic aromatic hydrocarbons (such as naphthalene, anthracene), single-ring aromatic hydrocarbons and crude benzene in the raw coal gas, which, at high temperatures, are mixed with dust (coal powder, carbon black) and adhere to the surface of the scrubbing tower, pipeline and heat exchanger, forming a tough composite fouling. These fouling layers have low thermal conductivity and poor flowability, greatly reducing the heat exchange efficiency, increasing the system pressure drop, and even causing equipment blockage, which requires frequent shutdown for cleaning, resulting in huge economic losses.

[0003] To solve the problem of impurities in raw coal gas, the ammonia water cleaning process is generally used in the industry. Ammonia water can absorb acidic gases such as hydrogen sulfide and carbon dioxide in raw coal gas, reducing the content of acidic substances in coal gas and reducing the corrosion of equipment. Moreover, the absorption of hydrogen sulfide by ammonia water solution is selective, and in the case of very short gas-liquid contact time, it can quickly absorb hydrogen sulfide from coal gas. However, ammonia water cleaning also has limitations. During the washing process, due to the presence of coal tar, liquid hydrocarbons and other substances in the raw coal gas, the polar compounds therein are prone to form oil-in-water (O / W) emulsions with water, making it difficult to separate ammonia water, tar and oil residue. Tar has high viscosity and is difficult to precipitate and separate, and the density of tar residue is similar to that of tar, further increasing the difficulty of separation. Micron-sized dust particles are negatively charged on their surfaces and are adsorbed at the oil-water interface, making the emulsion abnormally stable, and traditional demulsifiers are difficult to break, resulting in difficulty in oil-water separation, high oil content in waste water, and increased subsequent treatment costs.

[0004] Common alkaline cleaning agents have poor penetration and low absorption efficiency for organic fouling layers; conventional demulsifiers are easily hydrolyzed and lose effectiveness in high-temperature alkaline environments, resulting in low oil-water separation efficiency; and the addition of cleaning agents and demulsifiers separately not only increases the cost, but also may cause the oil stains washed out to be re-emulsified, forming "secondary emulsification" and exacerbating system deterioration.

[0005] Therefore, developing a multifunctional additive that can withstand extreme working conditions, has efficient absorption and oil-water separation capacity, and can specifically treat stable emulsions of solid particles, is a technical problem that needs to be solved in this field. SUMMARY

[0006] To solve the shortcomings and deficiencies of the prior art, the primary purpose of the present application is to provide a preparation method of a composite additive for crude gas absorption and oil-water separation. The present application designs to synthesize a block polyether with dimethylaminopropanol (DMAPA) as a starter, EO and PO as a functional main body, responsible for efficient wetting, cleaning and oil-water separation, and a small amount of hyperbranched polyethyleneimine (HPEI) as a demulsification enhancer, responsible for electric neutralization and flocculation.

[0007] 1. Functional main body: block polyether with DMAPA as a starter

[0008] With dimethylaminopropanol (DMAPA) as a starter, the tertiary amine group at the molecular end has weak cationic property and certain steric hindrance, which helps to control the initial reaction and the directional anchoring of the final product on the interface. The strict sequence of polymerizing PO (hydrophobic block) first and then polymerizing EO (hydrophilic block) is adopted to form the block structure of polypropylene oxide segment and polyethylene oxide segment. The PO block constitutes the strong hydrophobic tail of the molecule, and its propyl group can strongly penetrate and insert into the complex heavy tar and hydrocarbon droplets in the crude gas, effectively destroying the stability of the original interface film, and reducing the interface strength through the lateral spread of the molecule. Multiple PO blocks provide excellent oil solubility, ensuring that the molecule can quickly migrate to the oil-water interface. The EO block constitutes the hydrophilic head of the molecule, and its ether bond forms hydrogen bonds with water molecules in ammonia water, giving the molecule the necessary water solubility and dispersibility, preventing it from being completely dissolved in the oil phase and losing effectiveness. The polyethylene oxide segment provides a moderate steric hindrance effect to prevent the re-emulsification of oil droplets after demulsification. At the same time, the molecular weight of the polyether is controlled at 2000-6000, and the mass ratio of PO to EO is adjusted to 1.1-1.5:1. This design ensures that the molecule has sufficient hydrophobic power and molecular weight, can effectively bridge multiple oil droplets, and balances the hydrophilicity, making it easy to disperse in alkaline ammonia water and the HLB value is in the optimal interval for demulsification (about 7-12).

[0009] 2. Functional auxiliary component: hyperbranched polyethyleneimine (HPEI)

[0010] The large amount of primary amine, secondary amine and tertiary amine groups on the molecular chain of HPEI can be partially protonated in an ammonia alkaline medium, and have positive electricity. It can effectively neutralize the negative charge usually carried on the surface of oil droplets and dispersed solid particles, compress the double electric layer, eliminate the electrostatic repulsion, and greatly promote the coalescence of oil droplets and particles. HPEI has a highly branched three-dimensional spherical structure and a large specific surface area, and its molecular chain can simultaneously adsorb multiple oil droplets and particles, and through the strong bridging action, multiple small droplets are pulled together and gathered to form larger flocs, thereby accelerating phase separation. The branched segments of HPEI can intermolecularly entangle and spatially interlock with the PO / EO blocks of the block polyether at the oil-water interface to form a more dense and firm composite interface film. This film can more effectively replace the original emulsifier and prevent the reformation of the original interface film, thereby locking the demulsification effect.

[0011] The polyether block copolymer is compounded with HPEI at a mass ratio of 8:1 to 15:1. This ratio ensures the dominant position of the polyether, and the HPEI is added in a small amount as a functional substance, avoiding the influence of excessive cationicity on the cleaning and penetration functions of the polyether.

[0012] To achieve the object of the present application, the following technical solutions are adopted:

[0013] In a first aspect, the present application provides a preparation method of a composite additive for crude coal gas absorption and oil-water separation, comprising the following steps:

[0014] (1) A starting agent dimethylaminopropanol and a catalyst are added to a pressure reactor, inert gas is introduced, and the temperature is raised to the polymerization reaction temperature. Propylene oxide is added three times for polymerization reaction, and the feeding rate is controlled to maintain the pressure in the reactor below 0.4 MPa during the addition of propylene oxide each time. The polymerization reaction is continued until the pressure in the reactor no longer continues to drop. After cooling, a polypropylene oxide segment is obtained.

[0015] (2) The pressure reactor containing the polypropylene oxide segment obtained in step (1) is heated to the polymerization reaction temperature, and ethylene oxide is added three times for polymerization reaction. The feeding rate is controlled to maintain the pressure in the reactor below 0.4 MPa during the addition of ethylene oxide each time. The polymerization reaction is continued until the pressure in the reactor no longer continues to drop. After cooling, a block polyether is obtained.

[0016] (3) The block polyether obtained in step (2) is dissolved in water by heating, and after cooling, a hyperbranched polyethyleneimine solution is added dropwise under stirring, and mixed and aged sufficiently to obtain a composite additive.

[0017] Preferably, the starting agent dimethylaminopropanol (DMAPA) in step (1) accounts for 3-8% of the total moles of propylene oxide added three times, and more preferably 3.9-7.4%.

[0018] Preferably, the catalyst in step (1) comprises at least one of alkali metal hydroxide, double metal cyanide complex and alkali metal alkoxide, more preferably at least one of potassium hydroxide and sodium hydroxide among alkali metal hydroxide.

[0019] Preferably, the catalyst in step (1) accounts for 1-2‰ of the total mass of propylene oxide added in three times, further preferably 1-1.5‰.

[0020] Preferably, the inert gas in step (1) comprises at least one of nitrogen, helium and argon.

[0021] Preferably, the polymerization temperature in step (1) is 90-150 ℃, further preferably 110-140 ℃.

[0022] Preferably, the mass ratio of propylene oxide added in three times in step (1) is (2.5-4):(3-4.5):(2-4).

[0023] Preferably, the polymerization temperature in step (2) is 100-130 ℃.

[0024] Preferably, the mass ratio of ethylene oxide added in three times in step (2) is (2-4):(2.5-4.5):(2-5).

[0025] Preferably, the ratio of the total mass of propylene oxide (PO) in step (1) to the total mass of ethylene oxide (EO) in step (2) (i.e. the mass ratio of propylene oxide to ethylene oxide in the block polyether) is (1.1-1.5):1, further preferably 1.3:1.

[0026] Preferably, the number average molecular weight of the block polyether in step (2) is 2000-6000, further preferably 3000-4000; the weight average molecular weight is 3000-7000, further preferably 3300-4500; and the dispersity is 1.0-1.5, further preferably 1.1-1.3.

[0027] Preferably, the mass ratio of the block polyether to water in step (3) is 1:(6-10), further preferably 1:8.8.

[0028] Preferably, the temperature of heating in step (3) is 60-70 ℃.

[0029] Preferably, the mass ratio of the block polyether to hyperbranched polyethyleneimine in step (3) is (8-15):1, further preferably 10:1.

[0030] Preferably, the mass concentration of the hyperbranched polyethyleneimine solution in step (3) is 30-60 wt.%, further preferably 50 wt.%.

[0031] Preferably, in step (3), the number average molecular weight of the hyperbranched polyethyleneimine is 10000-20000; the degree of hyperbranching (DB) is 0.4-0.7, further preferably 0.55-0.65; the molar ratio of primary amine, secondary amine and tertiary amine groups in the hyperbranched polyethyleneimine is (1-2):(1-3):1.

[0032] Preferably, the stirring speed in step (3) is 150-250 r / min.

[0033] Preferably, the dropping time of the hyperbranched polyethyleneimine solution in step (3) is ≥15 min.

[0034] Preferably, after the dropping of the hyperbranched polyethyleneimine solution in step (3) is completed, the system is stirred at 60-90℃ for 45 min or more to ensure that the system is fully mixed and the reaction is matured.

[0035] In a second aspect, the application provides a composite additive for crude gas absorption and oil-water separation obtained by the above preparation method.

[0036] In a third aspect, the application provides the use of the above composite additive in crude gas absorption and oil-water separation.

[0037] Preferably, the above composite additive is used to remove the composite scale layer formed by tar, asphaltene, polycyclic aromatic hydrocarbons, monocyclic aromatic hydrocarbons and dust, etc. and to break the emulsion in the ammonia absorption of crude gas and oil-water separation.

[0038] Preferably, the application temperature of the composite additive is ≥50℃, and the application system is weakly alkaline, with a specific pH of 8.9-9.5.

[0039] The application takes a unique approach and proposes a solution to the problem of incomplete crude gas absorption and difficult oil-water separation. The main structure is a block polyether with DMAPA as a starter, which solves the problem of crude gas absorption and avoids "secondary emulsification" from the source. The specific block structure is suitable for the crude gas-ammonia water system, and after compounding with hyperbranched polyethyleneimine (HPEI), the absorption effect and oil-water separation efficiency far exceed that of traditional additives. In this composite system, the block structure of the block copolymer can precisely control the hydrophilic-lipophilic balance and adapt to the polarity of the complex oil phase in the crude gas, and the hyperbranched structure of HPEI can quickly bridge the interface particles and accelerate the coalescence of emulsion droplets.

[0040] Compared with the prior art, the application has the following advantages and beneficial effects:

[0041] The composite adjuvant prepared by the application is suitable for complex oil-water systems, can well meet the needs of ammonia water absorbing crude coal gas and oil-water separation, is resistant to hydrolysis, resistant to high temperature, suitable for alkaline environment, and has long service life. The application amount is low, the efficiency is high, the demulsification is multifunctional, the process is simplified, the comprehensive cost is reduced, resource recovery and environmental protection are facilitated, and the application has excellent industrial application prospect. DETAILED DESCRIPTION

[0042] The application will be further described in detail below with reference to examples, but the embodiments of the application are not limited thereto.

[0043] In the embodiments of the application, specific conditions not specified are carried out according to conventional conditions or manufacturer's recommended conditions. The raw materials, reagents and the like used without specifying the manufacturer are all conventional products that can be purchased on the market.

[0044] Example 1

[0045] A dry high-pressure reaction kettle was added with DMAPA and KOH catalyst, and the specific amount was shown in Table 1. The reaction kettle was vacuumized (-0.095 MPa) and heated to 110 ℃ for 30 min to fully remove moisture. Nitrogen was used to replace to normal pressure, and the process was repeated for 3 times. The kettle temperature was increased to 135 ℃. Under continuous stirring (300 rpm), nitrogen was introduced, and propylene oxide was added into the kettle in three times, and the mass of propylene oxide added in each time was shown in Table 1. The feeding rate was controlled in each feeding process to maintain the pressure in the kettle below 0.4 MPa. After each feeding was completed, the kettle was kept at 135 ℃ until the pressure dropped to the lowest and stabilized, and the reaction was repeated until the three feeding reactions were completed, and the polymerization of three PO blocks was completed. The heating was stopped, and the material was cooled to room temperature (25-30 ℃) through the cooling coil in the reactor. This cooling step was crucial to ensure that the PO was completely reacted, to prevent violent series exothermic reaction when the EO was added subsequently, and to ensure safety. The kettle temperature was increased to 120 ℃. The ethylene oxide was added into the reaction kettle in three times by nitrogen pressure, and the mass of ethylene oxide added in each time was shown in Table 1. The feeding rate was controlled in each feeding process to maintain the pressure in the kettle below 0.4 MPa. The reaction was repeated until the three feeding reactions were completed until the pressure dropped to the lowest and stabilized. At this time, the block polyether was completely synthesized. The heating was stopped, and the reaction kettle was cooled to room temperature. The material was discharged to obtain the final product sample.

[0046] The formula of each product sample was shown in Table 1, and three block polyethers with different molecular weights were finally synthesized: sample A (molecular weight 2000-3000, PO:EO=1.3:1), sample B (molecular weight 3000-4000, PO:EO=1.3:1), and sample C (molecular weight 4000-5000, PO:EO=1.3:1).

[0047] Table 1 Feed amount of different molecular weight block polyether

[0048]

[0049] The molecular weight of the prepared block polyether samples A, B and C was determined by gel permeation chromatography (GPC), and the test results are shown in Table 2. The GPC curve of the sample shows a single and symmetrical peak shape, indicating that the molecular weight distribution is relatively concentrated.

[0050] Table 2 Molecular weight of sample

[0051]

[0052] The sample was characterized by Fourier transform infrared spectrometer (FTIR). The test result analysis shows that there is a very strong and broad C-O-C stretching vibration absorption peak at 1100 cm -1 , indicating that the PO / EO monomer has successfully ring-opening polymerization to form a polyether main chain; a wide O-H stretching vibration peak appears at 3450 cm -1 , proving that the polymer molecular chain end is active hydroxyl; and the most critical is the weak but clear C-H stretching vibration shoulder peak appearing near 2820 cm -1 and 2770 cm -1 , which is the characteristic signal of the methyl group on the tertiary amine group; and the C-N stretching vibration peak can be observed near 1200 cm -1 . These characteristic peaks show that the tertiary amine structure of the initiator dimethylaminopropanol (DMAPA) has been successfully retained at the starting end of the polymer, and the target product has been successfully prepared.

[0053] Example 2

[0054] (1) Raw material preparation: The block polyether sample prepared in Example 1 was weighed and added to deionized water, the mass ratio of the block polyether sample to deionized water was 1:8.8, heated to 60°C and stirred to dissolve to obtain a uniform solution.

[0055] (2) Compound mixing: The uniform solution obtained in step (1) was cooled to room temperature, and a 50wt.% hyperbranched polyethyleneimine solution was added dropwise to the uniform solution under stirring at 200 r / min, the mass ratio of the block polyether sample to the hyperbranched polyethyleneimine is shown in Table 3, and the dropwise time is 15 min.

[0056] The specific type of hyperbranched polyethyleneimine is: the hyperbranched degree is 0.6, the molar ratio of primary amine, secondary amine and tertiary amine groups is 1.22:1.48:1, the number average molecular weight of HPEI-I is 12000; the number average molecular weight of HPEI-II is 16000.

[0057] (3) Maturation treatment: After the end of step (2) dropwise addition, 500 r / min stirring at 80 °C for 45 min to ensure that the system is fully mixed and the reaction is matured. Stop stirring, and stand for 5 min, no insoluble or precipitate, to obtain a well-mixed composite adjuvant.

[0058] Table 3 Adjuvant prepared in Example 2

[0059]

[0060] Example 3

[0061] Referring to the ratio of light hydrocarbons to heavy hydrocarbons in real raw coal gas, ethylbenzene (simulated light hydrocarbon) and asphalt (simulated heavy hydrocarbon) were mixed in a mass ratio of 4:1 to prepare 5 g of simulated oil; a glass sieve plate absorption bottle with a jacket was used as a washing bottle, 300 mL of 8 wt% ammonia solution was added, the jacket was connected to a circulating water bath to control the temperature during gasification (80 °C) and washing, then the composite adjuvant prepared in Example 2 was added (so that the concentration of the composite adjuvant in the ammonia solution was 100 mg / L). Turn on the device, set the gasification chamber temperature to 150 °C to fully gasify the simulated oil. Open the N2 steel cylinder, control the nitrogen flow to be 1.0 L / min through the mass flow controller, as a carrier gas to carry the gasified oil vapor into the washing bottle. In this process, the gaseous oil and the ammonia solution containing the composite adjuvant are fully contacted on the sieve plate and are washed and absorbed. After the gas washing is completed, turn off the heating and nitrogen. Transfer all the liquid in the washing bottle to a separatory funnel, stand for sedimentation, and record the time required from the addition of the adjuvant to the separation of 90% of the clear liquid from the emulsion as the oil-water separation time. The shorter the time, the better the demulsification effect. After standing, clear layering of the upper oil phase and the lower water phase is obtained. Carefully separate the lower water phase, collect the upper oil phase, and accurately weigh the mass of the recovered oil phase.

[0062] Comparative Example 1

[0063] Referring to the ratio of light hydrocarbon to heavy hydrocarbon in real crude coal gas, 5 g of simulated oil product was prepared by mixing ethylbenzene (simulated light hydrocarbon) and asphalt (simulated heavy hydrocarbon) at a mass ratio of 4:1; a glass sieve plate absorption bottle with a jacket was taken as a washing bottle, 300 mL of 8 wt% ammonia water solution was added, and the jacket was connected to a circulating water bath to control the temperature during gasification (80 ℃) and washing. Subsequently, 5 g of simulated oil product was completely gasified in a 150 ℃ gasification chamber, and 1.0 L / min of nitrogen was introduced as a carrier gas to carry the gasified oil vapor into the washing bottle. During this period, the gaseous oil product was fully contacted with the ammonia water solution on the sieve plate and was absorbed and emulsified. After the gas washing was completed, all the liquid in the washing bottle was transferred to a separatory funnel and allowed to stand and settle. The time required from the addition of the additive to the separation of 90% of the volume of the clear liquid was recorded as the oil-water separation time. The shorter the time, the better the demulsification effect. After standing, the separated oil phase was weighed, the oil yield was calculated, and the oil-water separation and the clarity of the water phase were observed and recorded. The oil yield was only 35.6%, and no obvious oil-water separation was observed after 2 h.

[0064] Comparative Example 2

[0065] (1) Referring to the preparation process of Example 1, the difference lies in that the propylene oxide is added in two times, and the mass of the first and second additions is 86.6 g and 99.0 g, respectively, and the ethylene oxide is added in two times, and the mass of the first and second additions is 64.9 g and 75.9 g, respectively, to prepare a block polyether (molecular weight 3000-4000, PO:EO=1.3:1) with DMAPA as the starter.

[0066] (2) Referring to the preparation process of Example 2, the block polyether obtained in step (1) is mixed with hyperbranched polyethyleneimine (HPEI-II) at a mass ratio of 10:1 to prepare a composite additive CE2.

[0067] The gasification, gas washing (150 ℃ oil product, 1.0 L / min N2), standing and settling, and analysis and testing steps of oil-water separation were completely consistent with those of Examples 3 and 4, except that the composite additive was replaced by the composite additive CE2 prepared in this comparative example. The measured oil yield was 61.9%, and a certain oil-water separation was observed after 85 min.

[0068] Comparative Example 3

[0069] Referring to the preparation process of Example 2, the block polyether (sample B) described in Example 1 was mixed with hyperbranched polyethyleneimine (HPEI-II) at a mass ratio of 2:1 to prepare a composite additive CE3.

[0070] The analysis test procedures of vaporization, gas washing (150 °C oil, 1.0 L / min N2), standing and settling, and oil-water separation were completely consistent with those of Example 3, except that only the composite additive therein was replaced by the composite additive CE3 prepared in this comparative example. The measured oil yield was 54.1 %, and oil-water separation occurred after 60 min.

[0071] Comparative Example 4

[0072] Referring to the preparation process of Example 2, the composite additive CE4 was prepared using the block polyether (sample B) described in Example 1 and hyperbranched polyethyleneimine with a molecular weight of 800-1500 at a mass ratio of 10:1.

[0073] The analysis test procedures of vaporization, gas washing (150 °C, 1.0 L / min N2), standing and settling, and oil-water separation were completely consistent with those of Example 3, except that only the composite additive therein was replaced by the composite additive CE4 prepared in this comparative example. The measured oil yield was 72.3 %, and partial oil-water separation occurred after 70 min. The results of this comparative example show that the low molecular weight HPEI cannot produce effective synergy with polyether due to the lack of sufficient bridging ability and steric hindrance effect.

[0074] Comparative Example 5

[0075] Referring to Example 3, the difference is that only the composite additive therein is replaced by the block polyether (sample B) in Example 1. The measured oil yield was 83.6 %, and no significant effect of oil-water separation was observed after 110 min. This indicates that the addition of block polyether with DMAPA as a starter can promote the absorption of ammonia water by crude gas to some extent, but if not compounded with HPEI, it cannot effectively promote the oil-water separation of the subsequent emulsion.

[0076] Comparative Example 6

[0077] This comparative example used polyethyleneimine (Mw=600) as a starter to prepare an ethylene oxide and propylene oxide block polyether:

[0078] 10 g polyethyleneimine and 24 g potassium hydroxide were added to a high-temperature and high-pressure reaction kettle, and the reaction kettle was closed. Before heating, nitrogen was used for purging and replacement, and then vacuum was pumped by a vacuum pump, repeated twice, then the stirring was started and the temperature was raised, when the temperature was raised to 120℃, the heating was stopped, the feeding valve was opened, 800 g of propylene oxide was added dropwise, the reaction temperature was controlled to be not more than 140℃ and the pressure was controlled to be below 0.4 MPa, after the material was reacted, the pressure was reduced, and then reacted for 30 min, so that the pressure was reduced to 0 MPa; then, heated to 120℃, and then 800 g of ethylene oxide was added, the reaction temperature was controlled to be not more than 150℃ and the pressure was controlled to be below 0.4 MPa, after the material was reacted, the pressure was reduced, and then reacted for 30 min, so that the pressure was reduced to 0 MPa; finally, heated to 130℃, and then 6400 g of propylene oxide was added, the reaction temperature was controlled to be not more than 150℃ and the pressure was controlled to be below 0.4 MPa, after the material was reacted, the pressure was reduced, and then reacted for 30 min, so that the pressure was reduced to 0 MPa. The kettle was opened after cooling to discharge the material to obtain an ethylene oxide and propylene oxide block polyether demulsifier with polyethyleneimine as a starter, which is recorded as aid CE6.

[0079] The analysis process of gasification, gas washing, standing and oil-water separation is completely consistent with that of Example 3, except that the composite aid therein is replaced by the block polyether prepared with polyethyleneimine as a starter (aid CE6) prepared in the comparative example. The measured oil yield is 46.1%, and oil-water separation occurs after 40 min. Although the aid can be used as a demulsifier, it cannot effectively promote the absorption of ammonia water to the raw coal gas.

[0080] Table 4: Measured oil quality, oil yield and oil-water separation time in the examples and comparative examples

[0081]

[0082] Among them, samples CE1, CE2, CE4, CE5 can only achieve partial oil-water separation and cannot achieve complete oil-water separation; CE6 can achieve oil-water separation, but cannot effectively promote the absorption of ammonia water to the raw coal gas, so its oil recovery rate (oil yield) is low.

[0083] The above examples are preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods, which are all included in the protection scope of the present application.

Claims

1. A method for preparing a composite additive for crude coal gas absorption and oil-water separation, characterized in that, Includes the following steps: (1) Add the initiator dimethylaminopropanol and catalyst to the pressure reactor, introduce inert gas, heat to the polymerization reaction temperature, add propylene oxide in three batches to carry out the polymerization reaction, control the feeding rate during each addition of propylene oxide to maintain the pressure in the reactor below 0.4 MPa, and carry out the polymerization reaction until the pressure in the reactor no longer continues to decrease. Cool to obtain polypropylene oxide fragments; (2) The pressure reactor containing the polypropylene oxide fragment obtained in step (1) is heated to the polymerization reaction temperature, and ethylene oxide is added in three batches to carry out the polymerization reaction. During each addition of ethylene oxide, the feeding rate is controlled to maintain the pressure inside the reactor below 0.4 MPa. Each addition of ethylene oxide carries out the polymerization reaction until the pressure inside the reactor no longer continues to decrease. The reactor is then cooled to obtain block polyether. (3) The block polyether obtained in step (2) is dissolved in water by heating, cooled, and then hyperbranched polyethyleneimine solution is added dropwise under stirring. The mixture is thoroughly mixed and matured to obtain a composite additive.

2. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of block polyether to hyperbranched polyethyleneimine is (8-15):

1.

3. The preparation method according to claim 1 or 2, characterized in that, In step (1), the mass ratio of propylene oxide added three times is (2.5-4):(3-4.5):(2-4); And / or, in step (2), the mass ratio of the three additions of ethylene oxide is (2-4):(2.5-4.5):(2-5); And / or, the ratio of the total mass of propylene oxide in step (1) to the total mass of ethylene oxide in step (2) is (1.1~1.5):1; And / or, the number average molecular weight of the block polyether in step (2) is 2000-6000; the weight average molecular weight is 3000-7000; and the dispersity is 1.0-1.

5.

4. The preparation method according to claim 1 or 2, characterized in that, In step (3), the number average molecular weight of hyperbranched polyethyleneimine is 10,000 to 20,000; And / or, the degree of hyperbranching of hyperbranched polyethyleneimine is 0.4 to 0.7; And / or, the molar ratio of primary amine, secondary amine and tertiary amine groups in hyperbranched polyethyleneimine is (1-2):(1-3):

1.

5. The preparation method according to claim 1 or 2, characterized in that, The initiator dimethylaminopropanol mentioned in step (1) accounts for 3-8% of the total molar amount of propylene oxide added in three steps; And / or, the catalyst in step (1) comprises at least one of an alkali metal hydroxide, a bimetallic cyanide complex, and an alkali metal alkoxide; And / or, the catalyst described in step (1) accounts for 1 to 2‰ of the total mass of the three propylene oxide additions.

6. The preparation method according to claim 1 or 2, characterized in that, The inert gas in step (1) includes at least one of nitrogen, helium and argon; And / or, the polymerization reaction temperature in step (1) is 90–150 °C; And / or, the polymerization reaction temperature in step (2) is 100 to 130°C.

7. The preparation method according to claim 1 or 2, characterized in that, In step (3), the mass ratio of the block polyether to water is 1:(6-10). And / or, the mass concentration of the hyperbranched polyethyleneimine solution in step (3) is 30–60 wt.%; And / or, the heating temperature in step (3) is 60–70 °C; And / or, the time for adding the hyperbranched polyethyleneimine solution in step (3) is ≥15 min; And / or, after the hyperbranched polyethyleneimine solution in step (3) is added dropwise, stir at 60-90 °C for 45 min or more.

8. The preparation method according to claim 1 or 2, characterized in that, The ratio of the total mass of propylene oxide in step (1) to the total mass of ethylene oxide in step (2) is 1.3:1; And / or, the number-average molecular weight of the block polyether in step (2) is 3000-4000; the weight-average molecular weight is 3300-4500; and the dispersity is 1.1-1.3; And / or, the mass ratio of the block polyether to the hyperbranched polyethyleneimine in step (3) is 10:

1.

9. A composite additive obtained by the preparation method according to any one of claims 1 to 8.

10. The application of the composite additive as described in claim 9 in crude coal gas absorption and oil-water separation.

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