Coking inhibition additive for endothermic fuel as well as preparation method and application of coking inhibition additive

Abstract

The invention discloses a coking inhibition additive for heat absorption type hydrocarbon fuel. The coking inhibition additive comprises hydrazine monohydrate, distilled water and stearic acid terminated hyperbranched polyethyleneimine CHPEI. The invention also provides a preparation method of the heat absorption type hydrocarbon fuel coking inhibition additive, which comprises the following steps: weighing hydrazine monohydrate, adding distilled water, and stirring until the hydrazine monohydrate and the distilled water are uniformly mixed; adding CHPEI particles, and stirring until the CHPEI particles are completely dispersed; the mixture is put into a high-speed homogenizer to be stirred, and it is ensured that the mixture is in a uniform sticky paste shape; the invention also provides an application of the heat absorption type hydrocarbon fuel coking inhibition additive. According to the coking inhibition additive and the application thereof provided by the invention, high-temperature coking of aerospace engine fuel can be effectively inhibited; and a pseudo-homogeneous system which is low in freezing point, good in overload resistance stability and uniform in appearance can be formed with hydrocarbon fuel.

Description

Technical Field

[0001] The present invention relates to the technical field of aerospace engines, and particularly relates to an additive for inhibiting coking of endothermic fuels, a preparation method thereof, and an application thereof. Background Art

[0002] Endothermic fuels are a type of liquid propellant mainly composed of hydrocarbon fuels. They can flow through the heat exchange channels on the surface of the aircraft as coolants, participate in the active cooling process of aerospace aircraft, and reduce the overheating risk caused by high-speed air friction of the aircraft. During the endothermic cooling process, the hydrocarbon fuel will heat up and crack, and the cracking reaction will produce coke and block the pipeline. Inhibiting the cracking and coking of the fuel is the key to ensuring the stable operation of the aircraft.

[0003] Most of the academic community uses inert coating technology to inhibit the cracking and coking of hydrocarbons. However, due to the limitations of the heat exchanger structure and the process complexity of the coating technology, using additives is a more commonly used method for coking inhibition. Currently, compared with "hydrogen-supplying" coking inhibition additives such as tetrahydroquinoline and benzyl alcohol, "free radical trapping type" coking inhibitors have received more attention because they have better effects and a wider effective use temperature under the same addition amount. Such additives release free radicals that can form p-π conjugated stable products with coking precursors to inactivate coking precursors and hinder the growth of aromatics, thereby achieving coking inhibition.

[0004] For example, the patent with the application number CN202110231081.6 discloses a preparation method and application of a new type of hydrocarbon fuel coking inhibitor. Using glycerol, water, and hydroxyl-terminated hyperbranched polyester can release hydroxyl free radicals, thereby effectively inhibiting the cracking of the fuel. The patents with the application numbers CN202110154121.1 and CN201810035986.4 respectively disclose a series of composite coking inhibitors containing elements such as S and P, and a series of sulfur-containing SO2 and H2S coking inhibitors. Using compounds containing elements such as S and P or sulfur-containing gaseous compounds can effectively achieve coking inhibition by releasing mercapto and phosphino free radicals.

[0005] However, due to the inherent high polarity of the small molecule compounds formed by the above elements such as O, S, and P, the above coking inhibitors cannot be miscible with hydrocarbon fuels. When applying the related inventions, an independent sampling system must be set at the inlet of the high-temperature fuel cracking device of the aerospace power engine to mix the fuel and the additive. In addition, when the aircraft maneuvers, the heterogeneous system may also be separated by the overload effect (acceleration ~ 50×G), affecting the stable operation. Compounds such as water may also increase the freezing point of the fuel and affect the anti-icing performance of the fuel. Therefore, how to simultaneously solve the problems of solubility, overload stability, and high freezing point of such coking inhibitors in hydrocarbon fuels is a research difficulty in this field at present. Summary of the Invention

[0006] The object of the present invention is to provide an anti-coking additive for endothermic fuels, a preparation method thereof and an application thereof; the anti-coking additive provided by the present invention can effectively inhibit the high-temperature coking of aerospace engine fuels, and can form a quasi-homogeneous system with low freezing point, good anti-overload stability and uniform appearance with hydrocarbon fuels.

[0007] The object of the present invention is achieved by the following technical solutions:

[0008] An anti-coking additive for endothermic hydrocarbon fuels, the additive comprising hydrazine monohydrate, distilled water and stearic acid-capped hyperbranched polyethyleneimine CHPEI.

[0009] In the present invention, hydrazine monohydrate, distilled water and stearic acid-capped hyperbranched polyethyleneimine (CHPEI) are uniformly mixed to form an anti-coking additive. The anti-coking additive is added to the hydrocarbon fuel and stirred evenly to form a stable quasi-homogeneous system, thereby achieving coking inhibition.

[0010] The technical concept of the present invention is as follows:

[0011] (1) In terms of coking inhibition: Research in other fields has shown that during pyrolysis, hydrazine can release free radicals such as H·, NH2·, and ·NH· (Combustion and Flame, 2001, 124(1), 106-126). For fuel coking, the hydrogen free radical H· can reduce the alkyl free radical R· to form the product RH, delaying the pyrolysis conversion of the fuel. Free radicals such as NH2· and ·NH· contain lone pairs of electrons, and can capture conjugated π-bond-stabilized coking precursor free radicals such as cyclopentadienyl and phenyl free radicals to form stable products with p-π conjugation, thereby hindering secondary reactions and inhibiting coking growth. On the one hand, water can consume coking through the water-gas reaction C + H2O → CO + H2, and on the other hand, it can also act as a diluent to strip coking from the wall surface.

[0012] (2) In terms of the formation of a quasi-homogeneous system: The stearic acid-capped hyperbranched polyethyleneimine (CHPEI) is hydrophilic inside and lipophilic outside. When dispersed in the fuel in the form of micelles, the inner core can encapsulate hydrazine monohydrate, and the outer shell can achieve the solvation of "hydrazine monohydrate + polymer micelles", and droplets with a size much smaller than that of ordinary emulsions can be obtained. Relying on the nano-size effect of the micelles, the freezing point of water can be reduced and the anti-overload ability can be improved to construct a stable quasi-homogeneous system. In addition, as described in patents CN201910701494.9 and CN201711131229.9, hyperbranched polyethyleneimine also has additional functions such as promoting fuel conversion, enhancing the fuel heat sink, and inhibiting oxidative coking.

[0013] The coking inhibition additive includes hydrazine monohydrate with a mass fraction of 30% - 50%, distilled water with a mass fraction of 10% - 30%, and stearic acid-capped hyperbranched polyethyleneimine CHPEI with a mass fraction of 20% - 60%.

[0014] Preferably, the coking inhibition additive includes hydrazine monohydrate with a mass fraction of 30% - 50%, distilled water with a mass fraction of 10% - 30%, and stearic acid-capped hyperbranched polyethyleneimine CHPEI with a mass fraction of 40%.

[0015] The present invention also provides a preparation method of the above-mentioned endothermic hydrocarbon fuel coking inhibition additive. The preparation method includes:

[0016] (1) Weigh hydrazine monohydrate with a mass fraction of 30% - 50%, add distilled water with a mass fraction of 10% - 30% thereto, and stir until evenly mixed;

[0017] (2) Add stearic acid-capped hyperbranched polyethyleneimine CHPEI particles with a mass fraction of 20% - 60% to the solution, and continue to stir until the polymer particles are completely dispersed;

[0018] (3) Put the mixture into a high-speed homogenizer and stir to make the mixture into a uniform viscous paste to obtain the coking inhibition additive.

[0019] The present invention also provides an application of the above-mentioned endothermic hydrocarbon fuel coking inhibition additive. The coking inhibition additive can be added to the hydrocarbon fuel and dispersed to form a colorless transparent or milky white translucent homogeneous liquid.

[0020] When the fuel is used for active cooling of an aerospace engine, adding 1% - 20% of the coking inhibition additive based on the fuel mass can effectively inhibit the pyrolysis coking of the fuel.

[0021] Preferably, the hydrocarbon fuel is RP-3 or JP-10.

[0022] Compared with the prior art, the coking inhibition additive and its application provided by the present invention, or the so-called application method, have the following advantages and outstanding effects:

[0023] (1) It can effectively inhibit the high-temperature coking of aerospace engine fuel;

[0024] (2) It can form a pseudo-homogeneous system with a uniform appearance with the fuel;

[0025] (3) It has a low freezing point and good anti-overload stability. Description of the Drawings

[0026] Figure 1 The hydrocarbon fuel containing the coking inhibition additive prepared in Application Example 2;

[0027] Figure 2 A hydrocarbon fuel sample containing water and hydrazine prepared for Application Example 2;

[0028] Figure 3 Temperature and pressure monitoring diagram of the operation process of RP-3 fuel in Application Example 3;

[0029] Figure 4 Temperature and pressure monitoring diagram of the operation process of RP-3 fuel containing a coking inhibition additive in Application Example 3.

[0030] Figure 5 Temperature and pressure monitoring diagram of the operation process of JP-10 fuel in Application Example 4;

[0031] Figure 6 Temperature and pressure monitoring diagram of the operation process of JP-10 fuel containing a coking inhibition additive in Application Example 4;

[0032] Figure 7 Particle size distribution of the additive package in RP-3 fuel measured by dynamic light scattering method at an addition amount of 10%;

[0033] Figure 8 Schematic structure of hyperbranched polyethyleneimine capped with stearic acid in Example 1. Detailed implementation manners

[0034] The following application examples can enable professionals in the field to understand the present invention more comprehensively, but do not limit the present invention in any way. Without conflict, the following examples and the features in the examples can be combined with each other.

[0035] Example 1

[0036] A hydrocarbon fuel coking inhibition additive, comprising hydrazine monohydrate with a mass fraction of 30% - 50%, distilled water with a mass fraction of 10% - 30%, and stearic acid-capped hyperbranched polyethyleneimine (CHPEI) with a mass fraction of 40%.

[0037] As an implementation manner, the hydrocarbon fuel coking inhibition additive comprises hydrazine monohydrate with a mass fraction of 30%, distilled water with a mass fraction of 30%, and stearic acid-capped hyperbranched polyethyleneimine (CHPEI) with a mass fraction of 40%.

[0038] As an implementation manner, the hydrocarbon fuel coking inhibition additive comprises hydrazine monohydrate with a mass fraction of 40%, distilled water with a mass fraction of 20%, and stearic acid-capped hyperbranched polyethyleneimine (CHPEI) with a mass fraction of 40%.

[0039] As an implementation, the coking inhibition additive for hydrocarbon fuel comprises hydrazine monohydrate with a mass fraction of 50%, distilled water with a mass fraction of 10%, and stearic acid-capped hyperbranched polyethyleneimine (CHPEI) with a mass fraction of 40%.

[0040] The preparation method of the above coking inhibition additive for hydrocarbon fuel is as follows:

[0041] (1) Weigh hydrazine monohydrate with a mass fraction of 30% - 50% using an analytical balance, add distilled water with a mass fraction of 10% - 30% thereto, and slowly stir with a glass rod until evenly mixed;

[0042] (2) Add stearic acid-capped hyperbranched polyethyleneimine (CHPEI) particles with a mass fraction of 20% - 60% to the solution, and continue to slowly stir for 5 minutes until the polymer particles are completely dispersed;

[0043] (3) Put the mixture into a high-speed homogenizer and stir for 10 minutes to ensure that the mixture is in a uniform viscous paste state.

[0044] Application Example 1

[0045] According to Example 1, hydrazine monohydrate with a mass fraction of 30%, distilled water with a mass fraction of 30%, and stearic acid-capped hyperbranched polyethyleneimine (CHPEI) with a mass fraction of 40% are mixed to prepare coking inhibition additive A. Hydrazine monohydrate with a mass fraction of 40%, distilled water with a mass fraction of 20%, and stearic acid-capped hyperbranched polyethyleneimine (CHPEI) with a mass fraction of 40% are mixed to prepare coking inhibition additive B. Hydrazine monohydrate with a mass fraction of 50%, distilled water with a mass fraction of 10%, and stearic acid-capped hyperbranched polyethyleneimine (CHPEI) with a mass fraction of 40% are mixed to prepare coking inhibition additive C.

[0046] Add additive A to RP-3 jet fuel at addition amounts of 5%, 10%, 15%, and 20% respectively. The freezing point of the fuel is measured according to the standard of GB / T 2430 "Determination Method for Freezing Point of Aviation Fuel", and the results are -61°C, -63°C, -65°C, and < -65°C respectively.

[0047] Add additive B to RP-3 jet fuel at addition amounts of 5%, 10%, 15%, and 20% respectively. The freezing point of the fuel is measured according to the standard of GB / T 2430 "Determination Method for Freezing Point of Aviation Fuel", and the results are -62°C, -65°C, -66°C, and < -65°C respectively.

[0048] Additive C was added to RP-3 jet fuel at 5%, 10%, 15%, and 20% addition levels respectively, and the fuel freezing points were measured in accordance with the standard of GB / T 2430 "Determination Method for Freezing Point of Aviation Fuel". The results were -63°C, -65°C, -66°C, and < -65°C respectively.

[0049] The results show that the above fuels containing the coking inhibition additive meet the standard of GB / T 6537 "Jet Fuel No. 3" with a freezing point < -60°C.

[0050] Application Example 2

[0051] According to Example 1, hydrazine monohydrate with a mass fraction of 30%, distilled water with a mass fraction of 30%, and stearic acid-capped hyperbranched polyethyleneimine (CHPEI) with a mass fraction of 40% were mixed to prepare the coking inhibition additive. The additive was added to RP-3 jet fuel at 5%, 10%, 15%, and 20% addition levels respectively. It was treated for 5 minutes at 50 times the relative surface gravity acceleration to simulate the maneuvering situation under extreme conditions. The results are as Figure 1 shown, and the fuel systems are homogeneous and stable.

[0052] For comparison, hydrazine monohydrate with a mass fraction of 50% and distilled water with a mass fraction of 50% were mixed to obtain a hydrazine hydrate solution. The hydrazine hydrate solution was added to RP-3 jet fuel at 3%, 6%, 9%, and 12% addition levels respectively. It was treated for 5 minutes at 50 times the relative surface gravity acceleration. The results are as Figure 2 shown, and the fuel systems showed stratification.

[0053] The comparison shows that hyperbranched polyethyleneimine (CHPEI) has the function of a stabilizer, which can disperse hydrazine hydrate in hydrocarbon fuels. Thus, a stable pseudo-homogeneous system that can resist high gravity acceleration is obtained.

[0054] Application Example 3

[0055] According to Example 1, hydrazine monohydrate with a mass fraction of 30%, distilled water with a mass fraction of 30%, and stearic acid-capped hyperbranched polyethyleneimine (CHPEI) with a mass fraction of 40% were mixed to prepare the coking inhibition additive.

[0056] Taking RP-3 jet fuel as the sample, a continuous heat exchange experiment was carried out using a simulated engine surface micro heat exchange channel heat exchange device (GH3128 round tube, total length 1000 mm, heating section length 900 mm, outer diameter 3 mm, inner diameter 2 mm) under the conditions of 1 g / s, 3.5 MPa, and a fuel actual heat sink of 3.5 MJ / kg. The results are as Figure 3As shown. After the test, the heat exchange tube was removed, and the coke was converted into CO and CO2 by high-temperature oxidation method and measured. The total amount of coke on the wall was calculated to be 225 mg.

[0057] As a comparison, taking No. 3 jet fuel (RP-3) as the sample, adding 5% by mass of coke inhibition additive and dispersing it, using the same micro heat exchange channel heat exchange device on the simulated engine surface (GH3128 round tube, total length 1000 mm, heating section length 900 mm, outer diameter 3 mm, inner diameter 2 mm) to conduct continuous heat exchange experiments under the same conditions (1 g / s, 3.5 MPa, fuel actual heat sink 3.5 MJ / kg). The results are as Figure 4 shown. After the test, the heat exchange tube was removed, and the coke was converted into CO and CO2 by high-temperature oxidation method and measured. The total amount of coke on the wall was calculated to be 73 mg, and the coke inhibition rate on the wall was 67.5%.

[0058] The comparison shows that: in the experiment without adding coke inhibitor, the pressure increased to 5 MPa when running for 700 s, and it got out of control at 850 s after manually releasing the pressure. When the fuel with coke inhibition additive was running for 1200 s, the pressure was 1.55 MPa, the pressure difference decreased significantly and was generally controllable.

[0059] Application Example 4

[0060] According to Example 1, 30% by mass of hydrazine monohydrate, 30% by mass of distilled water and 40% by mass of stearic acid-capped hyperbranched polyethyleneimine (CHPEI) were mixed to prepare a coke inhibition additive.

[0061] Taking high-density aviation kerosene JP-10 as the sample, using the micro heat exchange channel heat exchange device on the simulated engine surface (GH3128 round tube, total length 1000 mm, heating section length 900 mm, outer diameter 3 mm, inner diameter 2 mm) to conduct continuous heat exchange experiments under the conditions of 1 g / s, 3.5 MPa and fuel actual heat sink 2.8 MJ / kg. The results are as Figure 5 shown.

[0062] As a comparison, taking high-density aviation kerosene JP-10 as the sample, adding 10% by mass of coke inhibition additive and dispersing it, using the same micro heat exchange channel heat exchange device on the simulated engine surface (GH3128 round tube, total length 1000 mm, heating section length 900 mm, outer diameter 3 mm, inner diameter 2 mm) to conduct continuous heat exchange experiments under the same conditions (1 g / s, 3.5 MPa, fuel actual heat sink 2.8 MJ / kg). The results are as Figure 6 shown. After the test, the heat exchange tube was removed, and the coke was converted into CO and CO2 by high-temperature oxidation method and measured. The total amount of coke on the wall was calculated to be 251 mg.

[0063] Comparison shows that in the experiment without the coking inhibitor, the pressure increased to 4 MPa when running for 900 s, and it got out of control at 1000 s after manually releasing the pressure. When the fuel with the coking inhibition additive was running for 1200 s, the pressure was 1.65 MPa, the pressure difference decreased significantly and was generally controllable. After the test, the heat exchange tube was removed, and the coking was converted into CO and CO2 by high-temperature oxidation method for determination. The total coking amount on the wall was calculated to be 74 mg, and the coking inhibition rate on the wall was 70.5%.

[0064] Application Example 5

[0065] According to Example 1, a coking inhibition additive was prepared by mixing hydrazine monohydrate with a mass fraction of 50%, distilled water with a mass fraction of 10%, and stearic acid-capped hyperbranched polyethyleneimine (CHPEI) with a mass fraction of 40%.

[0066] Taking high-density aviation kerosene JP-10 as a sample, a continuous heat exchange experiment was carried out using a heat exchange device for tiny channels on the surface of a simulated engine (GH3128 round tube, total length 1000 mm, heating section length 900 mm, outer diameter 3 mm, inner diameter 2 mm) under the conditions of 1 g / s, 3.5 MPa, and the actual heat sink of the fuel being 2.8 MJ / kg.

[0067] As a comparison, taking high-density aviation kerosene JP-10 as a sample, 10% by mass of the coking inhibition additive was added and dispersed, and the same heat exchange device for tiny channels on the surface of a simulated engine (GH3128 round tube, total length 1000 mm, heating section length 900 mm, outer diameter 3 mm, inner diameter 2 mm) was used to carry out a continuous heat exchange experiment under the same conditions (1 g / s, 3.5 MPa, and the actual heat sink of the fuel being 2.8 MJ / kg). After the test, the heat exchange tube was removed, and the coking was converted into CO and CO2 by high-temperature oxidation method for determination. The total coking amount on the wall was calculated to be 251 mg.

[0068] Comparison shows that in the experiment without the coking inhibitor, the pressure increased to 4 MPa when running for 900 s, and it got out of control at 1000 s after manually releasing the pressure. When the fuel with the coking inhibition additive was running for 1200 s, the pressure was 1.65 MPa, the pressure difference decreased significantly and was generally controllable. After the test, the heat exchange tube was removed, and the coking was converted into CO and CO2 by high-temperature oxidation method for determination. The total coking amount on the wall was calculated to be 51 mg, and the coking inhibition rate on the wall was 79.7%.

[0069] The above has made an exemplary description of the present invention. Without departing from the core of the present invention, any simple deformation, modification (including the addition amount of the coking inhibition additive, the water content of the coking inhibition additive, the hydrazine content, the water content, the pressure, flow rate, temperature, etc. of the heat exchange test) or other equivalent replacements that those skilled in the art can make without creative efforts all fall within the protection scope of the present invention.

Claims

1. An endothermic hydrocarbon fuel coking inhibition additive, characterized in that, The additive includes hydrazine monohydrate, distilled water, and stearic acid-capped hyperbranched polyethyleneimine CHPEI.

2. The anti-coking additive for endothermic hydrocarbon fuel according to claim 1, characterized in that The coking inhibition additive includes 30% - 50% by mass of hydrazine monohydrate, 10% - 30% by mass of distilled water, and 20% - 60% by mass of stearic acid-capped hyperbranched polyethyleneimine CHPEI.

3. The anti-coking additive for endothermic hydrocarbon fuels according to claim 2, wherein The coking inhibition additive includes 30% - 50% by mass of hydrazine monohydrate, 10% - 30% by mass of distilled water, and 40% by mass of stearic acid-capped hyperbranched polyethyleneimine CHPEI.

4. A preparation method of the coking inhibition additive for the endothermic hydrocarbon fuel according to any one of claims 1-3, characterized in that, The preparation method includes: (1) Weigh 30% - 50% by mass of hydrazine monohydrate, add 10% - 30% by mass of distilled water thereto, and stir until evenly mixed; (2) Add 20% - 60% by mass of stearic acid-capped hyperbranched polyethyleneimine CHPEI particles to the solution, and continue to stir until the polymer particles are completely dispersed; (3) Put the mixture into a high-speed homogenizer and stir to make the mixture into a uniform viscous paste to obtain the coking inhibition additive.

5. Use of the anti-coking additive for endothermic hydrocarbon fuels according to any one of claims 1-3, characterized in that, Add the coking inhibition additive to the hydrocarbon fuel and disperse it to form a colorless transparent or milky white translucent homogeneous liquid.

6. The application according to claim 5, characterized in that, The addition amount of the coking inhibition additive is 1% - 20% of the mass of the hydrocarbon fuel.

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