Method for preparing liquid organic fertilizer by alkali-thermal hydrolysis assisted by organic solvent in sludge

Abstract

The invention discloses a method for preparing liquid organic fertilizer by using sludge organic solvent-assisted alkaline thermal hydrolysis, which specifically comprises: placing high-water-content urban surplus sludge in a thermal alkaline hydrolysis reaction device, adjusting the pH value, adding ethanol, performing thermal alkaline hydrolysis treatment, obtaining sludge-based liquid organic fertilizer mother liquor, adding strong acid cation exchange resin to the sludge-based liquid organic fertilizer mother liquor, stirring and reacting, separating the strong acid cation exchange resin, obtaining sludge-based liquid organic fertilizer stock solution, and obtaining sludge-based liquid organic fertilizer product after dilution; the invention relates to the technical field of sludge treatment. The method for preparing liquid organic fertilizer by using sludge organic solvent-assisted alkaline thermal hydrolysis, adjusting the pH value of high-water-content urban surplus sludge, adding ethanol for thermal alkaline hydrolysis treatment, and introducing strong acid cation exchange resin for heavy metal ion removal treatment, obtaining sludge-based liquid organic fertilizer, and realizing safe and efficient land utilization of organic matter and nutrients in urban surplus sludge.

Description

Technical Field

[0001] The invention relates to the technical field of sludge treatment, in particular to a method for preparing liquid organic fertilizer by sludge organic solvent-assisted alkaline-thermal hydrolysis. Background Art

[0002] With the continuous improvement of urban sewage treatment facilities, a large amount of urban waste sludge byproducts has been produced, and the annual output has exceeded 80 million tons. Urban waste sludge contains a large amount of organic carbon and organic matter and nutrients such as nitrogen, phosphorus, and potassium required for plant growth, which provides favorable conditions for its land utilization. However, urban waste sludge also contains certain harmful substances such as heavy metals and pathogenic microorganisms, which is the main reason for limiting the land utilization of urban waste sludge.

[0003] At present, the commonly used high-temperature aerobic digestion technology for preparing solid organic fertilizer can stabilize pathogenic microorganisms and organic matter in urban residual sludge, but it is difficult to effectively solve the pollution risk of heavy metals. In addition, compared with liquid organic fertilizer, solid organic fertilizer has the problem of low fertilizer efficiency. Therefore, how to achieve the safe and efficient land utilization of organic matter and nutrients in urban residual sludge still faces technical challenges.

[0004] Based on the search of the above information, a method for preparing liquid organic fertilizer by sludge organic solvent-assisted alkaline-thermal hydrolysis is proposed to achieve safe and efficient land utilization of organic matter and nutrients in urban residual sludge. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method for preparing liquid organic fertilizer by using sludge organic solvent-assisted alkaline-thermal hydrolysis, which solves the problem of poor land utilization rate of urban surplus sludge.

[0006] To achieve the above object, the present invention is implemented by the following technical scheme: a method for preparing liquid organic fertilizer by sludge organic solvent-assisted alkaline-thermal hydrolysis, which specifically comprises the following steps:

[0007] S1. Place high-water-content urban excess sludge in a hot alkaline hydrolysis reaction device, add an alkaline solution, stir and adjust the pH to 9-13 to obtain a sludge solution;

[0008] S2. Add ethanol to the sludge solution and stir it thoroughly to obtain a solution to be treated;

[0009] S3, performing thermal alkaline hydrolysis treatment on the solution to be treated to obtain a solution to be separated;

[0010] S4, performing solid-liquid separation treatment on the solution to be separated, collecting the liquid product, and obtaining the sludge-based liquid organic fertilizer mother liquor;

[0011] S5. Adding a strongly acidic cation exchange resin to the sludge-based liquid organic fertilizer mother liquor, stirring for reaction, and separating the strongly acidic cation exchange resin to obtain a sludge-based liquid organic fertilizer stock solution.

[0012] The present invention is further configured as follows: the alkaline solution in S1 is potassium hydroxide.

[0013] The present invention is further configured as follows: the amount of ethanol added in S2 is 50% to 250% of the amount of dry sludge in the high-water content urban surplus sludge.

[0014] The present invention is further configured as follows: the hot alkali hydrolysis temperature in the hot alkali hydrolysis treatment in S3 is 100° C. to 180° C., the hydrothermal carbonization reforming time is 1 h to 10 h, and the stirring speed is 0 rpm to 120 rpm.

[0015] The present invention is further configured as follows: the solid-liquid separation treatment method in S4 and the method for separating the strongly acidic cation exchange resin in S5 both include centrifugation treatment and filtration treatment.

[0016] The present invention is further configured as follows: the dosage of the strongly acidic cation exchange resin in S5 is 1-10 mL / g, and the stirring reaction is performed for 10 min to 30 min.

[0017] The present invention is further configured as follows: the sludge-based liquid organic fertilizer stock solution obtained in S5 is diluted 250-1000 times to obtain the sludge-based liquid organic fertilizer product.

[0018] The present invention is further configured that: the sludge-based liquid organic fertilizer stock solution diluent is tap water.

[0019] The present invention provides a method for preparing liquid organic fertilizer by using sludge organic solvent-assisted alkaline-thermal hydrolysis. The method has the following beneficial effects:

[0020] (1) The present invention adjusts the pH of high-water-content urban surplus sludge, adds ethanol for thermal alkaline hydrolysis treatment, obtains sludge-based liquid organic fertilizer, and introduces strong acid cation exchange resin for heavy metal ion removal treatment, thereby providing a guarantee for the safe utilization of sludge-based liquid organic fertilizer, thereby achieving safe and efficient land utilization of organic matter and nutrients in urban surplus sludge.

[0021] (2) The sludge-based liquid organic fertilizer obtained in the present invention is rich in a variety of organic matter including small molecule amino acids, sugars, etc., which can provide the necessary organic carbon source for the growth of plants and soil microorganisms, and is rich in free phosphate ions, ammonium ions and potassium ions, which can provide the necessary macronutrient elements that are easily absorbed and utilized for plant growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1The present invention is a process flow chart of a method for preparing liquid organic fertilizer by ethanol-assisted thermal alkaline hydrolysis of urban surplus sludge. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. 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.

[0024] See also Figure 1 , the embodiment of the present invention provides the following technical solutions:

[0025] Embodiment 1: A method for preparing liquid organic fertilizer by alkali-thermal hydrolysis of sludge with organic solvent, comprising the following steps:

[0026] S1. Place 100.00 g of a high-water-content urban excess sludge sample with a water content of 85% in a hot alkaline hydrolysis reaction device, add 1.00 mol / L potassium hydroxide solution, stir and adjust the pH to 9 to obtain a sludge solution;

[0027] S2. Add 22.50 g of ethanol to the sludge solution and stir thoroughly to obtain a solution to be treated;

[0028] S3, subjecting the solution to be treated to a thermal alkaline hydrolysis treatment at 140° C. for 6 hours, cooling it to room temperature, and obtaining a solution to be separated;

[0029] S4, centrifuging the solution to be separated at 10500 rpm for 10 min, collecting the liquid product, and obtaining the sludge-based liquid organic fertilizer mother solution;

[0030] S5, adding a strong acid cation exchange resin to the sludge-based liquid organic fertilizer mother solution, the addition amount of the strong acid cation exchange resin is 5 mL / g, and stirring the reaction for 20 minutes, separating the strong acid cation exchange resin, and obtaining the sludge-based liquid organic fertilizer stock solution;

[0031] S6. Dilute the sludge-based liquid organic fertilizer stock solution 500 times with tap water to obtain a sludge-based liquid organic fertilizer product.

[0032] Among them, the total amino acid content in the sludge-based liquid organic fertilizer stock solution reached 40.14 mg / mL, among which the contents of aspartic acid, glutamic acid, glycine, alanine, valine, phenylalanine and leucine all exceeded 2.00 mg / mL; the molecular weight distribution of organic matter in the collected sludge-based liquid organic fertilizer stock solution was between 158 and 4923; the ammonium ion content in the collected sludge-based liquid organic fertilizer stock solution reached 2.96 mg / mL; the phosphate ion content in the collected sludge-based liquid organic fertilizer stock solution reached 2.95 mg / mL ; The potassium ion content in the collected sludge-based liquid organic fertilizer stock solution reached 6.43 mg / mL; The heavy metal content in the collected sludge-based liquid organic fertilizer stock solution was lower than 1.80 mg / L; The hydroponic germination rate of barley from the collected sludge-based liquid organic fertilizer products reached 87.5%, which is equivalent to that of commercially available organic fertilizers; The hydroponic root length and root weight of barley from the collected sludge-based liquid organic fertilizer products were 9.4 cm and 94.5 mg respectively; The hydroponic leaf length and leaf weight of barley from the collected sludge-based liquid organic fertilizer products were 10.7 cm and 92.2 mg respectively.

[0033] Embodiment 2: A method for preparing liquid organic fertilizer by alkali-thermal hydrolysis of sludge with organic solvent, comprising the following steps:

[0034] S1. Place 100.00 g of a high-water-content urban excess sludge sample with a water content of 75% in a hot alkaline hydrolysis reaction device, add 1.00 mol / L potassium hydroxide solution, stir and adjust the pH to 13 to obtain a sludge solution;

[0035] S2. Add 22.50 g of ethanol to the sludge solution and stir thoroughly to obtain a solution to be treated;

[0036] S3, subjecting the solution to be treated to a thermal alkaline hydrolysis treatment at 100° C. for 6 h, cooling it to room temperature, and obtaining a solution to be separated;

[0037] S4, centrifuging the solution to be separated at 10500 rpm for 10 min, collecting the liquid product, and obtaining the sludge-based liquid organic fertilizer mother solution;

[0038] S5, adding a strong acid cation exchange resin to the sludge-based liquid organic fertilizer mother solution, the addition amount of the strong acid cation exchange resin is 5 mL / g, and stirring the reaction for 20 minutes, separating the strong acid cation exchange resin, and obtaining the sludge-based liquid organic fertilizer stock solution;

[0039] S6. Dilute the sludge-based liquid organic fertilizer stock solution 500 times with tap water to obtain a sludge-based liquid organic fertilizer product.

[0040] Among them, the total amino acid content in the collected sludge-based liquid organic fertilizer stock solution reached 55.03 mg / mL, among which the contents of aspartic acid, glutamic acid, glycine, alanine, valine, tyrosine, phenylalanine, leucine, lysine and proline all exceeded 2.20 mg / mL; the molecular weight distribution of organic matter in the collected sludge-based liquid organic fertilizer stock solution was between 43 and 4920; the ammonium ion content in the collected sludge-based liquid organic fertilizer stock solution reached 1.17 mg / mL; the phosphate ion content in the collected sludge-based liquid organic fertilizer stock solution reached 2.87 mg / mL; the potassium ion content in the collected sludge-based liquid organic fertilizer stock solution reached 23.21 mg / mL; the heavy metal content in the collected sludge-based liquid organic fertilizer stock solution was lower than 3.00 mg / L except zinc (6.18 mg / L); the hydroponic germination rate of barley from the collected sludge-based liquid organic fertilizer products reached 85.0%; the hydroponic root length and root weight of barley from the collected sludge-based liquid organic fertilizer products were 10.9 cm and 90.0 mg respectively; the hydroponic leaf length and leaf weight of barley from the collected sludge-based liquid organic fertilizer products were 11.5 cm and 95.0 mg respectively.

[0041] Embodiment 3: A method for preparing liquid organic fertilizer by alkali-thermal hydrolysis of sludge with organic solvent, comprising the following steps:

[0042] S1. Place 100.00 g of a high-water-content urban excess sludge sample with a water content of 75% in a hot alkaline hydrolysis reaction device, add 1.00 mol / L potassium hydroxide solution, stir and adjust the pH to 13 to obtain a sludge solution;

[0043] S2. Add 22.50 g of ethanol to the sludge solution and stir thoroughly to obtain a solution to be treated;

[0044] S3, subjecting the solution to be treated to a thermal alkaline hydrolysis treatment at 140° C. for 6 hours, cooling it to room temperature, and obtaining a solution to be separated;

[0045] S4, centrifuging the solution to be separated at 10500 rpm for 10 min, collecting the liquid product, and obtaining the sludge-based liquid organic fertilizer mother solution;

[0046] S5, adding a strong acid cation exchange resin to the sludge-based liquid organic fertilizer mother solution, the addition amount of the strong acid cation exchange resin is 5 mL / g, and stirring the reaction for 20 minutes, separating the strong acid cation exchange resin, and obtaining the sludge-based liquid organic fertilizer stock solution;

[0047] S6. Dilute the sludge-based liquid organic fertilizer stock solution 500 times with tap water to obtain a sludge-based liquid organic fertilizer product.

[0048] Among them, the total amino acid content in the collected sludge-based liquid organic fertilizer stock solution reached 78.15 mg / mL, among which the contents of aspartic acid, glutamic acid, glycine, alanine, valine, tyrosine, phenylalanine, leucine, lysine and proline all exceeded 3.50 mg / mL; the molecular weight distribution of organic matter in the collected sludge-based liquid organic fertilizer stock solution was between 154 and 4182; the ammonium ion content in the collected sludge-based liquid organic fertilizer stock solution reached 1.87 mg / mL; the phosphate ion content in the collected sludge-based liquid organic fertilizer stock solution was 1.87 mg / mL. The content reached 3.12 mg / mL; the potassium ion content in the collected sludge-based liquid organic fertilizer stock solution reached 46.15 mg / mL; the heavy metal content in the collected sludge-based liquid organic fertilizer stock solution was lower than 3.00 mg / L except zinc (3.72 mg / L); the barley hydroponic effect of the collected sludge-based liquid organic fertilizer product was equivalent to that of commercially available organic fertilizer, with a germination rate of 87.5%, root length and root weight reaching 10.9 cm and 100.8 mg respectively, and leaf length and leaf weight reaching 12.5 cm and 106.5 mg respectively.

[0049] Embodiment 4: A method for preparing liquid organic fertilizer by alkali-thermal hydrolysis of sludge with organic solvent, comprising the following steps:

[0050] S1. Place 100.00 g of a high-water-content urban excess sludge sample with a water content of 85% in a hot alkaline hydrolysis reaction device, add 1.00 mol / L potassium hydroxide solution, stir and adjust the pH to 13 to obtain a sludge solution;

[0051] S2. Add 22.50 g of ethanol to the sludge solution and stir thoroughly to obtain a solution to be treated;

[0052] S3, subjecting the solution to be treated to a thermal alkaline hydrolysis treatment at 140° C. for 6 hours, cooling it to room temperature, and obtaining a solution to be separated;

[0053] S4, centrifuging the solution to be separated at 10500 rpm for 10 min, collecting the liquid product, and obtaining the sludge-based liquid organic fertilizer mother liquor. At this time, the sludge-based liquid organic fertilizer mother liquor will reset the nutrient elements and generate a new nutrient element molecular structure;

[0054] S5, adding a strong acid cation exchange resin to the sludge-based liquid organic fertilizer mother solution, the addition amount of the strong acid cation exchange resin is 5 mL / g, and stirring the reaction for 20 minutes, separating the strong acid cation exchange resin, and obtaining the sludge-based liquid organic fertilizer stock solution;

[0055] S6. Dilute the sludge-based liquid organic fertilizer stock solution 500 times with tap water to obtain a sludge-based liquid organic fertilizer product.

[0056] Among them, the total amino acid content in the collected sludge-based liquid organic fertilizer stock solution reached 52.72 mg / mL, among which the contents of aspartic acid, glutamic acid, glycine, alanine, valine, tyrosine, phenylalanine, leucine and proline all exceeded 2.38 mg / mL, which was 15.18% higher than that without adding ethanol; the molecular weight distribution of organic matter in the collected sludge-based liquid organic fertilizer stock solution was between 154-4182, which was 97.95% lower than that without adding ethanol; the ammonium ion content in the collected sludge-based liquid organic fertilizer stock solution reached 1.16 mg / mL; the phosphate ion content in the collected sludge-based liquid organic fertilizer stock solution reached 2.86 mg / mL, which was 1.0% higher than that without adding ethanol. 4.86%; the potassium ion content in the collected sludge-based liquid organic fertilizer stock solution reached 31.79 mg / mL, which was 30.13% higher than that without adding ethanol; the heavy metal content in the collected sludge-based liquid organic fertilizer stock solution was lower than 1.30 mg / L, among which heavy metals such as chromium, nickel, and arsenic were reduced by 8.60%-34.85% compared with those without adding ethanol; the hydroponic germination rate of barley in the collected sludge-based liquid organic fertilizer products reached 87.5%, which was equivalent to that of commercially available organic fertilizers and increased by 9.38% compared with those without adding ethanol; the hydroponic root length and root weight of barley in the collected sludge-based liquid organic fertilizer products were 9.3 cm and 89.4 mg, respectively, which were 10.06% and 3.89% higher than those without adding ethanol.

[0057] The high-water content urban waste sludge samples in Example 1, Example 2, Example 3 and Example 4 are all selected from municipal sewage treatment plants.

[0058] In summary, the sludge-based liquid organic fertilizer prepared by ethanol-assisted hot alkaline hydrolysis of urban residual sludge is rich in a variety of organic matter including small molecule amino acids, sugars, etc., which can provide the necessary organic carbon source for the growth of plants and soil microorganisms.

[0059] The sludge-based liquid organic fertilizer prepared by ethanol-assisted thermal alkaline hydrolysis of urban surplus sludge is rich in free phosphate ions, ammonium ions and potassium ions, which can provide the necessary macronutrients that are easily absorbed and utilized for plant growth.

[0060] The heavy metal concentration in the sludge-based liquid organic fertilizer prepared by ethanol-assisted hot alkaline hydrolysis of urban surplus sludge is much lower than the relevant standard requirements for liquid organic fertilizer, which provides a guarantee for the safe use of sludge-based liquid organic fertilizer.

[0061] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0062] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing liquid organic fertilizer by alkali-thermal hydrolysis of sludge with organic solvent, characterized in that: The specific steps include: S1. Place high-water-content urban excess sludge in a hot alkaline hydrolysis reaction device, add an alkaline solution, stir and adjust the pH to 9-13 to obtain a sludge solution; S2. Add ethanol to the sludge solution, stir it thoroughly, and obtain a solution to be treated. The amount of ethanol added is 50% to 250% of the dry sludge in the high-water content urban surplus sludge; S3, performing thermal alkaline hydrolysis treatment on the solution to be treated to obtain a solution to be separated; S4, performing solid-liquid separation treatment on the solution to be separated, collecting the liquid product, and obtaining the sludge-based liquid organic fertilizer mother liquor; S5. Adding a strongly acidic cation exchange resin to the sludge-based liquid organic fertilizer mother liquor, stirring for reaction, separating the strongly acidic cation exchange resin, and obtaining a sludge-based liquid organic fertilizer stock solution.

2. The method for preparing liquid organic fertilizer by assisted alkaline-thermal hydrolysis of sludge organic solvent according to claim 1, characterized in that: The alkaline solution in S1 is potassium hydroxide.

3. The method for preparing liquid organic fertilizer by assisted alkaline-thermal hydrolysis of sludge organic solvent according to claim 1, characterized in that: In the thermal alkaline hydrolysis treatment in S3, the thermal alkaline hydrolysis temperature is 100° C. to 180° C., the hydrothermal carbonization reforming time is 1 h to 10 h, and the stirring speed is 0 rpm to 120 rpm.

4. The method for preparing liquid organic fertilizer by assisted alkaline-thermal hydrolysis of sludge organic solvent according to claim 1, characterized in that: The solid-liquid separation treatment method in S4 and the method for separating the strongly acidic cation exchange resin in S5 both include centrifugation treatment and filtration treatment.

5. The method for preparing liquid organic fertilizer by assisted alkaline-thermal hydrolysis of sludge organic solvent according to claim 1, characterized in that: The dosage of the strong acid cation exchange resin in S5 is 1-10 mL / g, and the reaction is stirred for 10 min to 30 min.

6. The method for preparing liquid organic fertilizer by assisted alkaline-thermal hydrolysis of sludge organic solvent according to claim 1, characterized in that: The sludge-based liquid organic fertilizer stock solution obtained in S5 is diluted 250-1000 times to obtain a sludge-based liquid organic fertilizer product.

7. The method for preparing liquid organic fertilizer by assisted alkaline-thermal hydrolysis of sludge organic solvent according to claim 6, characterized in that: The sludge-based liquid organic fertilizer stock solution diluent is tap water.

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