Method for preparing biological crude oil by promoting hydrothermal liquefaction of pig manure through steel rolling oil sludge

Abstract

The invention provides a method for preparing biological crude oil by promoting hydrothermal liquefaction of pig manure through steel rolling oil sludge, and belongs to the technical field of biomass energy. According to the method for preparing the biological crude oil by promoting the hydrothermal liquefaction of the pig manure through the steel rolling oil sludge, the steel rolling oil sludge serves as a catalyst for the hydrothermal liquefaction reaction of the pig manure, under the subcritical condition, the emulsified structure of the steel rolling oil sludge is destroyed, and fatty acid, water and scrap iron are obtained, the iron scrap can be used as a homogeneous catalyst for hydrothermal liquefaction of organic matters in pig manure, and Fe and Fe3O4 in the iron scrap can be used as a heterogeneous catalyst; in addition, under the subcritical condition, fatty acid can be subjected to thermal cracking to generate H2, iron can also react with subcritical water to generate H2, and H2 can promote hydrodeoxygenation of organic matter and is beneficial to improving the oil quality of biological crude oil; meanwhile, unutilized fatty acid can also be used as a raw material to be converted into biological crude oil, so that the oil yield is further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of biomass energy, and in particular relates to a method for producing bio-crude oil by promoting hydrothermal liquefaction of pig manure through steel rolling sludge. Background Art

[0002] Pig manure is a high-water content organic solid waste, with a water content of more than 80% and 15% organic matter. It is a good raw material for producing green and low-carbon bio-crude oil. At present, the main methods for disposing pig manure are drying and composting, which usually require dehydration pretreatment and have low treatment efficiency.

[0003] In recent years, hydrothermal liquefaction has been favored by the market as a new method for treating organic solid waste with high water content. Hydrothermal liquefaction technology directly uses water in organic solid waste with high water content as a green reaction medium and catalyst to convert organic matter such as cellulose, hemicellulose, protein, lipids into green and low-carbon bio-crude oil at 250-350℃ and 5-15MPa. Using hydrothermal liquefaction to treat pig manure not only eliminates the need for dehydration pretreatment of pig manure, but also converts organic matter in pig manure into bio-crude oil, and sterilizes pig manure in a high temperature and high pressure environment, thereby achieving the reduction, harmlessness, resource utilization, and energy utilization of pig manure.

[0004] Since the yield and oil quality of bio-crude oil produced by hydrothermal liquefaction of pig manure are relatively low, it is usually necessary to optimize the hydrothermal liquefaction process and increase the yield of bio-crude oil by adding suitable catalysts. There are two main types of commonly used catalysts. One is homogeneous catalysts, including alkaline catalysts such as Na2CO3 and Ca(OH)2 or acidic catalysts such as CH3COOH and HCOOH; the other is heterogeneous catalysts, including metal catalysts such as Ni, Co, Fe, Ag, and Ru. Among them, homogeneous catalysts are difficult to separate from the water phase, making them difficult to reuse. Although heterogeneous catalysts are easily separated from the liquefied product, they also have problems with poor stability and short service life, resulting in a high cost for the production of bio-crude oil by hydrothermal liquefaction of pig manure. Summary of the invention

[0005] The object of the present invention is to provide a method for producing bio-crude oil by promoting hydrothermal liquefaction of pig manure by using steel rolling sludge. The method provided by the present invention has low catalyst cost, high oil yield and high oil product quality.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for producing bio-crude oil by promoting hydrothermal liquefaction of pig manure using steel rolling sludge, comprising:

[0008] Mixing pig manure, steel rolling sludge and water to obtain a mixed liquid;

[0009] The mixed liquid is subjected to a hydrothermal reaction under subcritical conditions, and then the oil phase is separated to obtain bio-crude oil.

[0010] Preferably, the ratio of the dry mass of the pig manure to the mass of the steel rolling sludge is 2:8 to 8:2.

[0011] Preferably, the sum of the dry mass of the pig manure and the mass of the steel rolling sludge is 2.5-10% of the mass of the mixed liquid.

[0012] Preferably, the temperature of the hydrothermal reaction is 250-350° C., and the insulation time is 15-60 min.

[0013] Preferably, the hydrothermal reaction is carried out in an inert atmosphere.

[0014] Preferably, the separation includes solid-liquid separation, oil-water separation and organic solvent removal performed sequentially.

[0015] Preferably, the solid-liquid separation method is suction filtration.

[0016] Preferably, the oil-water separation method is extraction, and the extraction agent used for extraction includes dichloromethane, chloroform, ethyl acetate, butyl acetate, butanol or petroleum ether.

[0017] Preferably, the organic solvent is removed by rotary evaporation.

[0018] The present invention provides a method for preparing bio-crude oil by promoting hydrothermal liquefaction of pig manure with steel rolling sludge, comprising: mixing pig manure, steel rolling sludge and water to obtain a mixed liquid; subjecting the mixed liquid to a hydrothermal reaction under subcritical conditions and then separating an oil phase to obtain bio-crude oil. The present invention uses steel rolling sludge as a catalyst for the hydrothermal liquefaction reaction of pig manure. Under subcritical conditions, the emulsified structure of the steel rolling sludge is destroyed to obtain fatty acids, water and iron filings, wherein the fatty acids have carboxyl groups and can be used as homogeneous catalysts for hydrothermal liquefaction of organic matter in pig manure, and Fe and Fe3O4 in the iron filings can be used as heterogeneous catalysts; and under subcritical conditions, the fatty acids can also undergo thermal cracking to produce H2, and iron can also react with subcritical water to produce H2, and H2 can promote hydrogenation and deoxygenation of organic matter, which is beneficial to improving the oil quality of bio-crude oil; at the same time, unused fatty acids can also be used as raw materials to be converted into bio-crude oil, further improving the oil yield. The results of the examples show that, by using the method provided by the present invention, the oil yield of hydrothermal liquefaction of pig manure is 35.33-39.66%, and the calorific value of the obtained bio-crude oil is 33.48-36.94 MJ / kg. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the process of producing bio-crude oil by promoting hydrothermal liquefaction of pig manure using steel-rolling sludge in Example 1 of the present invention. DETAILED DESCRIPTION

[0020] All raw materials of the present invention have no particular limitation on their sources and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0021] There is no particular restriction on the purity of all raw materials in the present invention, and industrial pure raw materials are preferably used in the present invention.

[0022] The present invention provides a method for producing bio-crude oil by promoting hydrothermal liquefaction of pig manure using steel rolling sludge, comprising:

[0023] Mixing pig manure, steel rolling sludge and water to obtain a mixed liquid;

[0024] The mixed liquid is subjected to a hydrothermal reaction under subcritical conditions, and then the oil phase is separated to obtain bio-crude oil.

[0025] The present invention has no special requirements on the source of the steel rolling sludge, and the sludge produced by the steel cold rolling process can be used. In an embodiment of the present invention, the steel rolling sludge comes from the cold rolling process of a large domestic steel enterprise. Steel rolling sludge is a metallurgical solid waste resource with a high viscosity and a mixed emulsified structure of oil-water-iron filings, containing 5-60wt% of grease and 20-90wt% of iron filings. The grease is mainly higher fatty acids such as palmitic acid and oleic acid, and the iron filings are mainly Fe, Fe3O4, Fe2O3, etc.

[0026] The present invention has no special requirements on the source of the pig manure, and the pig manure produced by a pig breeding farm can be used. In an embodiment of the present invention, the pig manure comes from a large breeding farm in Jiangxi Province.

[0027] The present invention has no particular requirements for the specific mixing method, and the conventional mixing method in the art can be used.

[0028] In the present invention, the ratio of the dry mass of the pig manure to the mass of the steel rolling oil sludge is preferably 2:8-8-2, more preferably 4:6-6:4; as an embodiment of the present invention, the ratio of the dry mass of the pig manure to the mass of the steel rolling oil sludge can be 2:8, 3:7, 4:6, 5:5, 6:4, 7:3 or 8:2. The steel rolling oil sludge is used as a catalyst for the hydrothermal reaction of pig manure. The more it is added, the more conducive it is to convert pig manure into bio-crude oil. However, too much steel rolling oil sludge will reduce the utilization rate of pig manure and the production efficiency, and it will also cause the calorific value of bio-crude oil to decrease due to the inability of too many higher fatty acids to be completely converted into bio-crude oil. The present invention limits the ratio of the dry mass of pig manure to the mass of steel rolling oil sludge within the above range, which is conducive to improving the oil yield and oil quality, and has higher production efficiency.

[0029] As an embodiment of the present invention, the pig manure can be sampled and tested for the dry basis mass ratio, thereby regulating the ratio of the dry basis mass of the pig manure to the mass of the steel rolling sludge.

[0030] As another embodiment of the present invention, the pig manure can be used after pretreatment. The method of pretreatment of the pig manure is: drying the pig manure in an oven at 105°C for 12 hours, fully removing the moisture, grinding and sieving to no less than 400 meshes, obtaining dry pig manure, and placing it in a sealed bag for standby use.

[0031] In the present invention, the sum of the dry mass of the pig manure and the mass of the steel rolling oil sludge is preferably 2.5-10% of the mass of the mixed solution, and more preferably 5-7.5%. The greater the proportion of the dry mass of the pig manure and the steel rolling oil sludge in the mixed solution, the more raw materials will participate in the hydrothermal reaction, but too much raw material will cause incomplete reaction and affect the oil yield; moreover, if the proportion of the dry mass of the pig manure and the steel rolling oil sludge is too large, the fluidity of the mixed solution will also be reduced, increasing the difficulty of mixing and transfer; if the proportion of the dry mass of the pig manure and the steel rolling oil sludge in the mixed solution is within the above range, both the oil yield and the production efficiency can be taken into account.

[0032] In the present invention, the temperature of the hydrothermal reaction is preferably 250-350°C, more preferably 270-300°C. As an embodiment of the present invention, the temperature of the hydrothermal reaction can be 255°C, 265°C, 275°C, 285°C, 295°C or 300°C. The higher the temperature of the hydrothermal reaction, the faster the hydrothermal reaction rate, but too high a temperature may cause side reactions, reduce the calorific value of the bio-crude oil, and cause carbonization of the bio-crude oil, reducing the oil yield; the temperature of the hydrothermal reaction is within the above range, which is conducive to the hydrothermal reaction, and can avoid side reactions and carbonization of the bio-crude oil.

[0033] In the present invention, the holding time of the hydrothermal reaction is preferably 15 to 60 minutes, more preferably 30 to 45 minutes. As an embodiment of the present invention, the holding time of the hydrothermal reaction can be 25 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes or 55 minutes. The longer the holding time of the hydrothermal reaction, the more complete the reaction, but if the time is too long, side reactions may occur, reducing the oil quality of the bio-crude oil; the holding time of the hydrothermal reaction within the above range is conducive to further improving the oil yield and oil quality.

[0034] In the present invention, the hydrothermal reaction is preferably carried out in an inert atmosphere, and the inert atmosphere is preferably a nitrogen atmosphere. Carrying out the hydrothermal reaction in an inert atmosphere can avoid oxidation reaction, which is beneficial to further improve the oil quality of the bio-crude oil.

[0035] In the present invention, the hydrothermal reaction is preferably carried out under stirring conditions, and the stirring speed is preferably 150 to 1500 r / min, more preferably 500 to 1000 r / min. As an embodiment of the present invention, the stirring speed may be 300 r / min, 400 r / min, 500 r / min, 600 r / min, 700 r / min, 800 r / min, 900 r / min or 1000 r / min. Stirring is conducive to the hydrothermal reaction and can further improve the oil yield.

[0036] The present invention has no special requirements for the pressure of the hydrothermal reaction, as long as it can reach the subcritical condition. As an embodiment of the present invention, after the reaction system is replaced with nitrogen, the initial pressure is maintained at 0.1-2 MPa, and then heating is performed to increase the pressure of the reaction system after water vaporization.

[0037] The present invention has no special requirements for the hydrothermal reaction device, and a hydrothermal reaction device commonly used in the art can be used. In an embodiment of the present invention, the hydrothermal reaction is carried out in a high-pressure reactor.

[0038] After the hydrothermal reaction is completed, the present invention separates the product of the hydrothermal reaction to obtain bio-crude oil.

[0039] In the present invention, after the hydrothermal reaction is completed, the reaction system is preferably cooled and depressurized in sequence. The present invention has no particular requirements for the specific method of cooling, and a conventional cooling method in the art can be used. In an embodiment of the present invention, cooling water is used to cool the reaction system, and the pressure is released after the temperature drops to room temperature.

[0040] After cooling and depressurizing the reaction system, the present invention preferably further comprises collecting the product of the hydrothermal reaction. The present invention has no particular requirements for the specific method of the collection, and the operation method familiar to those skilled in the art can be adopted. In one embodiment of the present invention, after collecting the product of the hydrothermal reaction, the reaction device is also washed with acetone, and the washing liquid is mixed with the product of the hydrothermal reaction.

[0041] In the present invention, the separation preferably includes solid-liquid separation, oil-water separation and organic solvent removal performed sequentially.

[0042] In the present invention, the solid-liquid separation method is preferably suction filtration. The present invention has no special requirements for the specific operation of the suction filtration, and the conventional operation in the art can be used. In one embodiment of the present invention, after suction filtration, the filter cake is washed with acetone, and the filter cake is dried and reused as a raw material for the iron ore sintering process.

[0043] In the present invention, the oil-water separation method is preferably extraction, and the extractant used in the extraction preferably includes dichloromethane, chloroform, ethyl acetate, butyl acetate, butanol or petroleum ether. The use of the above-mentioned extractant is conducive to separating the bio-crude oil from the water phase.

[0044] In the present invention, the organic solvent is preferably removed by rotary evaporation, and the parameters of the rotary evaporation preferably include: a water bath temperature of 40 to 60°C, a vacuum degree of 100 to 1000 kPa, and a rotary evaporation time of 15 to 60 minutes. The present invention separates the bio-crude oil from the organic solvent by rotary evaporation, and recycles the acetone used for washing and the extractant used for extraction.

[0045] The present invention uses steel rolling sludge as a catalyst for the hydrothermal liquefaction reaction of pig manure. Under subcritical conditions, the emulsified structure of the steel rolling sludge is destroyed to obtain fatty acids, water and iron scraps. The fatty acids have carboxyl groups and can be used as homogeneous catalysts for the hydrothermal liquefaction of organic matter in the pig manure. Fe and Fe3O4 in the iron scraps can be used as heterogeneous catalysts. Moreover, under subcritical conditions, the fatty acids can also undergo thermal cracking to generate H2. Iron can also react with subcritical water to generate H2. H2 can promote the hydrogenation and deoxygenation of organic matter, which is beneficial to improving the oil quality of bio-crude oil. Meanwhile, unused fatty acids can also be used as raw materials to be converted into bio-crude oil, further improving the oil yield.

[0046] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] Example 1

[0048] The raw materials are pig manure from a large breeding farm in Jiangxi Province and steel rolling sludge from a well-known domestic steel plant.

[0049] Pre-treat the pig manure: dry the pig manure in an oven at 105°C for 12 hours, then grind and sieve to no less than 400 mesh to obtain dry pig manure, which is then sealed for later use.

[0050] Industrial analysis of dry pig manure was performed and the results are shown in Table 1.

[0051] Table 1 Industrial analysis results of dry pig manure

[0052] Fixed Carbon Volatile Matter Ash Moisture 10.24％ 66.29％ 22.13％ 1.34％

[0053] The elemental analysis and calorific value calculation of dry pig manure and steel rolling sludge were carried out, and the results are shown in Table 2.

[0054] Table 2 Elemental analysis and calorific value of pig manure and steel rolling sludge on dry basis

[0055] name C(％) H(％) N(％) S(％) O*(％) Calorific value / (MJ / kg) Pig manure 39.56 5.85 2.22 0.16 52.37 12.379 Steel rolling sludge 46.04 7.46 0.10 0.20 46.40 17.969

[0056] Note: *Value calculated by subtraction.

[0057] A method for producing bio-crude oil by promoting hydrothermal liquefaction of pig manure by steel rolling sludge, as shown in the schematic diagram Figure 1 , the specific steps are:

[0058] Take 4.054 g of the pretreated dry pig manure and steel rolling sludge mixture into a high-pressure reactor with a mass ratio of dry pig manure to steel rolling sludge of 8:2, add 50 g of deionized water, seal the reactor, and introduce sufficient N2 to fully replace the air in the reactor to maintain the initial pressure in the reactor at 2 MPa, and close the reactor valve.

[0059] The hydrothermal reaction temperature was set to 300°C, the holding time was set to 30 min, and the stirring speed was set to 150 r / min. After the reaction was completed, the cooling water was turned on to fully cool the reactor. After the temperature in the reactor dropped to room temperature, the pressure in the reactor was released. After the reactor was opened, the products of the hydrothermal reaction in the reactor were collected, and the reactor body and the stirring paddle were washed with 50 mL of acetone.

[0060] The product of the hydrothermal reaction and the washing liquid are filtered, and then the filter cake is washed with 100 mL of acetone to obtain a filtrate and a solid residue; 100 mL of dichloromethane is added to the filtrate for extraction, and an aqueous phase solution and an oil phase solution containing a mixed organic solvent and bio-crude oil are separated; the solid residue is dried to obtain a solid product generated by the reaction.

[0061] Under the conditions of a water bath temperature of 50° C. and a vacuum degree of 500 kPa, the oil phase solution was subjected to rotary evaporation to remove dichloromethane and acetone in the oil phase mixed solution to obtain bio-crude oil.

[0062] Example 2

[0063] A method for producing bio-crude oil by promoting hydrothermal liquefaction of pig manure by using steel-rolling sludge, wherein the raw materials and preparation method are the same as those in Example 1, except that the mass ratio of dry-basis pig manure to steel-rolling sludge is 6:4.

[0064] Example 3

[0065] A method for producing bio-crude oil by promoting hydrothermal liquefaction of pig manure by using steel-rolling sludge, wherein the raw materials and preparation method are the same as those in Example 1, except that the mass ratio of dry-basis pig manure to steel-rolling sludge is 4:6.

[0066] Example 4

[0067] A method for producing bio-crude oil by promoting hydrothermal liquefaction of pig manure by using steel-rolling sludge, wherein the raw materials and preparation method are the same as those in Example 1, except that the mass ratio of dry-basis pig manure to steel-rolling sludge is 2:8.

[0068] Example 5

[0069] A method for producing bio-crude oil by promoting hydrothermal liquefaction of pig manure by using steel rolling sludge, wherein the raw materials and preparation method are the same as those in Example 2, except that the temperature of the hydrothermal reaction is 275°C.

[0070] Example 6

[0071] A method for producing bio-crude oil by promoting hydrothermal liquefaction of pig manure by using steel rolling sludge, wherein the raw materials and preparation method are the same as those in Example 2, except that the temperature of the hydrothermal reaction is 250°C.

[0072] Example 7

[0073] A method for producing bio-crude oil by promoting hydrothermal liquefaction of pig manure by using steel rolling sludge, wherein the raw materials and preparation method are the same as those in Example 2, except that the temperature of the hydrothermal reaction is 350°C.

[0074] Comparative Example 1

[0075] A method for preparing bio-crude oil by hydrothermal liquefaction of pig manure, wherein the preparation method is the same as that of Example 1, except that no steel rolling sludge is added.

[0076] Comparative Example 2

[0077] A method for preparing bio-crude oil by hydrothermal liquefaction of pig manure, wherein the preparation method is the same as that of Example 5, except that no steel rolling sludge is added.

[0078] Comparative Example 3

[0079] A method for preparing bio-crude oil by hydrothermal liquefaction of pig manure, wherein the preparation method is the same as that of Example 6, except that no steel rolling sludge is added.

[0080] Comparative Example 4

[0081] A method for preparing bio-crude oil by hydrothermal liquefaction of pig manure, wherein the preparation method is the same as that of Example 7, except that no steel rolling sludge is added.

[0082] The oil yield of each embodiment and comparative example was calculated based on the weight of the obtained bio-crude oil, and the calorific value of the bio-crude oil was tested. The results are recorded in Table 3.

[0083] Table 3 Hydrothermal liquefaction oil yield and bio-crude oil calorific value records of various embodiments and comparative examples

[0084]

[0085]

[0086] By comparing Examples 1 to 4 with Comparative Example 1, it can be seen that at 300° C., when the mass ratio of dry-based pig manure to steel rolling oil sludge is 8:2, 6:4, 4:6, and 2:8, respectively, the yield and calorific value of the bio-crude oil are improved to a certain extent, and as the mass of the steel rolling oil sludge added increases, the oil yield of the bio-crude oil also gradually increases. When the mass ratio is 2:8, the yield is as high as 39.659%, which is 36.600% higher than that of Comparative Example 1; however, the calorific value of the bio-crude oil shows a trend of first increasing and then decreasing. When the mass ratio is 4:6, the calorific value is as high as 36.940 MJ / kg, which is 12.622% higher than that of Comparative Example 1; this is because as the mass of the steel rolling oil sludge added increases, more homogeneous catalysts and heterogeneous catalysts participate in the reaction, and more oil phase is converted into bio-crude oil, thereby improving the oil yield and calorific value of the bio-crude oil; however, adding too much steel rolling oil sludge may cause incomplete conversion of higher fatty acids in the oil phase, so the calorific value of the bio-crude oil is reduced instead.

[0087] It can be seen from Examples 2 and 5 to 7 that when the reaction temperature is too high, the oil yield will decrease and the calorific value of the bio-crude oil will also decrease; this is because too high a temperature will cause side reactions, reducing the quality of the oil, and too high a temperature will cause carbonization of the bio-crude oil, reducing the oil yield.

[0088] By comparing Examples 2, 5 to 7 with Comparative Examples 1 to 4, it can be seen that at different reaction temperatures, by adding an appropriate amount of steel rolling sludge, the oil yield and low calorific value of the bio-crude oil can be improved. At 250° C., when the mass ratio of dry pig manure to steel rolling sludge is 6:4, compared with Comparative Example 3, the yield of bio-crude oil can be increased by 34.759%, and the low calorific value of bio-crude oil is also increased by 13.423%.

[0089] It can be seen from the above embodiments and comparative examples that the method for producing bio-crude oil by promoting hydrothermal liquefaction of pig manure by using steel rolling sludge provided by the present invention can improve the oil yield of hydrothermal liquefaction of pig manure at different reaction temperatures and further improve the calorific value of bio-crude oil.

[0090] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for producing bio-crude oil by promoting hydrothermal liquefaction of pig manure using steel rolling sludge, comprising: Mixing pig manure, steel rolling sludge and water to obtain a mixed liquid; The mixed liquid is subjected to a hydrothermal reaction under subcritical conditions, and then the oil phase is separated to obtain bio-crude oil.

2. The method according to claim 1, characterized in that The ratio of the dry mass of the pig manure to the mass of the steel rolling sludge is 2:8 to 8:

2.

3. The method according to claim 1, characterized in that: The sum of the dry basis mass of the pig manure and the mass of the steel rolling sludge is 2.5-10% of the mass of the mixed liquid.

4. The method according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 250-350°C.

5. The method according to claim 4, characterized in that The heat preservation time of the hydrothermal reaction is 15 to 60 minutes.

6. The method according to claim 1, characterized in that The hydrothermal reaction is carried out in an inert atmosphere.

7. The method according to claim 1, characterized in that The separation includes solid-liquid separation, oil-water separation and organic solvent removal performed sequentially.

8. The method according to claim 7, characterized in that The solid-liquid separation method is suction filtration.

9. The method according to claim 7, characterized in that: The oil-water separation method is extraction, and the extraction agent used in the extraction includes dichloromethane, chloroform, ethyl acetate, butyl acetate, butanol or petroleum ether.

10. The method according to claim 7, characterized in that The organic solvent is removed by rotary evaporation.

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