A method for stabilizing biogas slurry based on natural cold energy and application thereof

Abstract

A kind of treatment method and application based on natural cold energy stable biogas slurry.The present application belongs to the field of agricultural technology.The present application provides a kind of treatment method based on natural cold energy stable biogas slurry to solve the technical problem of how to quickly consume biogas slurry, and the treatment method is: step 1: freeze-thaw treatment;Step 2: configuration of flocculant;Step 3: flocculation and adsorption treatment;Step 4: adjust pH.The present application realizes the efficient utilization of straw and manure through the natural cold energy, the porous adsorption of activated carbon, zeolite powder and bentonite, and the flocculation and bacteriostatic effect of chitosan biology, provides auxiliary materials for fertilizer production, accelerates the rapid stabilization and conversion of biogas slurry, and promotes the efficient and stable operation of biogas engineering.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of biogas slurry treatment, and particularly relates to a treatment method for stabilizing biogas slurry based on natural cold energy and application. BACKGROUND

[0002] As a byproduct of biogas engineering, the bottleneck problem in large-scale biogas engineering at present is how to quickly consume biogas slurry. The difficulty in biogas slurry consumption directly limits the promotion and long-term efficient and stable operation of biogas engineering. Although biogas slurry reflux can partially consume biogas slurry, the treatment capacity is low and cannot meet the large-scale biogas slurry treatment. The traditional aerobic biological treatment method needs to install an aeration system due to the high content of refractory organic matter, thereby increasing the treatment investment and operation cost. Although biogas slurry concentration can recover nutrients and reduce the volume of biogas slurry, pretreatment is required before membrane filtration. The biogas slurry produced by large and medium-sized biogas engineering still has the characteristics of undegraded organic matter and low oxidation-reduction potential after biogas slurry concentration treatment, and there is a great environmental risk if it is directly used as a fertilizer and returned to the soil. Therefore, it is necessary to improve the stability of biogas slurry and reduce the pollution to the atmosphere and soil. The chemical method can achieve the purpose of improving the stability of biogas slurry, but the investment and operation cost is high, secondary pollution is serious, and it is not conducive to agricultural use of biogas slurry. SUMMARY

[0003] To solve the technical problem that the prior art cannot quickly consume biogas slurry, the application provides a treatment method for stabilizing biogas slurry based on natural cold energy and application.

[0004] One of the purposes of the application is to provide a treatment method for stabilizing biogas slurry based on natural cold energy, which comprises the following steps:

[0005] Step 1: freeze-thaw treatment is performed on the anaerobic fermentation stock solution, and solid-liquid separation is performed to obtain freeze-thaw supernatant and freeze-thaw precipitate;

[0006] Step 2: a certain proportion of chitosan is added to the wood vinegar to obtain a flocculating agent;

[0007] Step 3: the flocculating agent obtained in step 2 is added to the freeze-thaw supernatant obtained in step 1, and after being placed for 24 hours, a composite adsorbent is added and continued to be placed for 12-24 hours. The supernatant is absorbed to obtain flocculation and adsorption supernatant and flocculation and adsorption precipitate;

[0008] Step 4: the flocculation and adsorption supernatant is adjusted to neutral to obtain stabilized biogas slurry.

[0009] Further limitation, the flocculating agent in step 2 has a mass concentration of 0.5-2%.

[0010] Further limitation, the addition amount of the flocculating agent in step 3 is 5-11% of the volume of the freeze-thaw supernatant.

[0011] Further limited, the composite adsorbent added in step 3 is 2-3% of the volume of the freeze-thaw supernatant.

[0012] Further limited, the composite adsorbent in step 3 is composed of activated carbon, bentonite and zeolite powder.

[0013] Further limited, the mass ratio of activated carbon, bentonite and zeolite powder in the composite adsorbent is (0.5-1):(0.5-1):1.

[0014] Further limited, the particle size of the composite adsorbent in step 3 is 50-100 mesh.

[0015] Further limited, the pH is adjusted to neutral in step 4 using potassium hydroxide.

[0016] The second object of the present application is to provide an application of the freeze-thaw precipitate obtained by the above treatment method, which is directly used for composting.

[0017] The third object of the present application is to provide an application of the flocculation adsorption precipitate obtained by the above treatment method, which is used as a fertilizer auxiliary material.

[0018] The fourth object of the present application is to provide an application of the stabilized biogas slurry obtained by the above treatment method, which is directly used for biogas slurry field application or concentration.

[0019] The fifth object of the present application is to provide an application of the above treatment method in a biogas project.

[0020] The present application has the following remarkable effects compared with the prior art:

[0021] The present application provides a treatment method for stabilizing biogas slurry based on natural cold energy, which utilizes natural cold energy, the porous adsorption of activated carbon, zeolite powder and bentonite, and the flocculation and bacteriostatic effect of chitosan organisms, to realize efficient utilization of straw and manure, and accelerate the rapid stabilization and conversion of biogas slurry.

[0022] (1) The present application utilizes the natural cold energy of winter in cold northern regions to realize rapid separation of biogas slurry and biogas residue by freeze-thaw treatment, and the separated biogas slurry is not viscous, and the freeze-thaw precipitate can be used for organic fertilizer and soil improvement.

[0023] (2) The wood vinegar is prepared by carbonization of straw, which improves the resource utilization rate of crop straw, and the present application realizes rapid flocculation and sterilization of the suspended matter in the biogas slurry by the flocculating agent prepared by wood vinegar and chitosan, to ensure that the flocculation adsorption precipitate can be utilized without causing secondary pollution.

[0024] (3) The composite adsorbent realizes the effects of decolorization, deamination, deodorization and turbidity removal on the biogas slurry, accelerates the rapid stabilization and conversion of the biogas slurry by adjusting the pH to improve the oxidation-reduction potential, and promotes the efficient and stable operation of the biogas project; meanwhile, the pretreatment process of the biogas slurry fertilizer is reduced, and the stabilization period is shortened.

[0025] (3) The treatment method for stabilizing biogas slurry based on natural cold energy provided by the application has the characteristics of energy saving, environmental protection, short cycle and quick effect, and the stabilized biogas slurry can be directly used for biogas slurry field or concentration, and the freeze-thaw precipitation and flocculation adsorption precipitation can be used as compost raw materials or directly as fertilizer auxiliary materials, which can promote plant growth and soil improvement. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The turbidity detection comparison chart of the fermentation liquid treated by the flocculant in Examples 1, 5-6 and Comparative Example 1 is shown in the following figure.

[0027] Figure 2 The turbidity detection comparison chart of the fermentation liquid treated by the flocculant in Examples 1-4 and Comparative Examples 2-3 for 24 hours is shown in the following figure. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the application clearer, the application will be further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the application, and are not used to limit the application.

[0029] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained by commercial channels by those skilled in the art.

[0030] The terms "comprise", "include", "have", "contain", or any other variant thereof, used in the following examples, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article or device comprising the listed elements does not necessarily limit to only those elements, but can include other elements not explicitly listed or inherent to such composition, step, method, article or device.

[0031] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range. In this specification and claims, range definitions may be combined and / or interchanged, unless otherwise stated, these ranges include all subranges contained therein.

[0032] The indefinite articles “a” and “an” preceding an element or component of this invention do not impose any limitation on the quantity (i.e., number of times) of the element or component. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers only to the singular form.

[0033] In this invention, "an embodiment" or "embodiment" refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments.

[0034] Example 1

[0035] S1: Place 500ml of anaerobic fermentation stock solution (biogas project of Heilongjiang Ruiyuan Biomass Energy Investment Co., Ltd.) at -20℃ for freezing treatment first, and then place it at room temperature for thawing treatment. Take out the supernatant to obtain freeze-thaw supernatant and freeze-thaw precipitate. The obtained freeze-thaw precipitate is directly used for composting.

[0036] S2: Add chitosan (molecular weight of 400,000) to 100ml of wood vinegar (agricultural wood vinegar from Shijiazhuang Hongsen Activated Carbon Co., Ltd.) to obtain a flocculant with a mass concentration of 1%.

[0037] S3: Add 5% of the volume of flocculant to the freeze-thaw supernatant obtained in S1, let stand for 24 hours, then add 3% of the volume of composite adsorbent (1wt% activated carbon + 1wt% bentonite + 1wt% zeolite powder), let stand for another 24 hours, and then remove the supernatant to obtain flocculation adsorption supernatant and flocculation adsorption precipitate. The obtained flocculation adsorption precipitate can be directly added to fertilizer additives.

[0038] S4: Add potassium hydroxide to the flocculation and adsorption supernatant obtained in S3 to adjust the pH to neutral to obtain stabilized biogas slurry. The stabilized biogas slurry can be directly returned to the field or concentrated.

[0039] Example 2

[0040] The difference between this embodiment and Embodiment 1 is that the amount of flocculant added is 7% of the volume of the freeze-thaw supernatant, while the rest is the same as in Embodiment 1.

[0041] Example 3

[0042] The difference between this embodiment and Embodiment 1 is that the amount of flocculant added is 9% of the volume of the freeze-thaw supernatant, while the rest is the same as in Embodiment 1.

[0043] Example 4

[0044] The difference between this embodiment and Embodiment 1 is that the amount of flocculant added is 11% of the volume of the freeze-thaw supernatant, while the rest is the same as in Embodiment 1.

[0045] Example 5

[0046] The difference between this embodiment and Embodiment 1 is that the molecular weight of chitosan is 700,000, while the rest is the same as in Embodiment 1.

[0047] Example 6

[0048] The difference between this embodiment and Embodiment 1 is that the molecular weight of chitosan is 900,000, while the rest is the same as in Embodiment 1.

[0049] Comparative Example 1:

[0050] The difference between this embodiment and Embodiment 1 is that the flocculant was added and left to stand for 12 hours; otherwise, it is the same as Embodiment 1.

[0051] Comparative Example 2:

[0052] The difference between this embodiment and Embodiment 1 is that the amount of flocculant added is 1% of the volume of the freeze-thaw supernatant, while the rest is the same as in Embodiment 1.

[0053] Comparative Example 3:

[0054] The difference between this embodiment and Embodiment 1 is that the amount of flocculant added is 3% of the volume of the freeze-thaw supernatant, while the rest is the same as in Embodiment 1.

[0055] Comparative Example 4:

[0056] The difference between this embodiment and Embodiment 1 is that the composite adsorbent is changed from 1wt% activated carbon + 1wt% bentonite + 1wt% zeolite powder to 1wt% activated carbon + 1wt% bentonite, while the rest is the same as in Embodiment 1.

[0057] Example of effect 1:

[0058] The turbidity of the fermentation broths of Examples 1, 5-6, and Comparative Example 1 after treatment with flocculant was measured, and the results are as follows: Figure 1 As shown, from Figure 1 As can be seen, the effects of chitosan with different molecular weights on flocculation are not significantly different. In actual operation, considering the processing cost, chitosan with a moderate molecular weight can be selected. As for the flocculation time, complete flocculation can be achieved after standing for 24 hours.

[0059] Example 2:

[0060] The turbidity of the fermentation broth after 24 hours of flocculation treatment in Examples 1-4 and Comparative Examples 2-3 was measured, and the results are as follows: Figure 2 As shown, from Figure 2 As can be seen, different flocculant addition ratios have a significant impact on flocculation. A 5% addition can achieve complete flocculation of biogas slurry. Depending on the suspended matter content in the biogas slurry and the cost of flocculation, a treatment concentration of 5%-11% can be selected.

[0061] Example of effect 3:

[0062] The physicochemical properties of the stabilized biogas slurry obtained in Example 1 and Comparative Example 4 were tested, and the results are shown in Table 1. As can be seen from Table 1, the combination of chitosan, activated carbon, bentonite and zeolite powder has the lowest turbidity, ammonium nitrogen and total protein content, high redox potential and the best treatment effect in its biogas slurry.

[0063] Table 1. Effects of different treatment methods on the properties of biogas slurry

[0064]

[0065] The contents not described in detail in this specification are well-known to those skilled in the art. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for treating biogas slurry based on natural cold energy stabilization, characterized in that, Includes the following steps: Step 1: The anaerobic fermentation broth is subjected to freeze-thaw treatment to separate the solid and liquid components, resulting in a freeze-thaw supernatant and a freeze-thaw precipitate. Step 2: Add a certain proportion of chitosan to the wood vinegar to obtain a flocculant; Step 3: Add the flocculant obtained in Step 2 to the freeze-thaw supernatant obtained in Step 1, let it stand for 24 h, then add the composite adsorbent, and continue to stand for 12-24 h. Take off the supernatant to obtain the flocculation adsorption supernatant and the flocculation adsorption precipitate. Step 4: Adjust the supernatant of flocculation and adsorption to neutral to obtain stabilized biogas slurry; The flocculant concentration mentioned in step 2 is 0.5-2% by mass. In step 3, the amount of flocculant added is 5-11% of the volume of the freeze-thaw supernatant, and the amount of composite adsorbent added is 2-3% of the volume of the freeze-thaw supernatant. The composite adsorbent described in step 3 is composed of activated carbon, bentonite, and zeolite powder; The mass ratio of activated carbon, bentonite, and zeolite powder is (0.5-1):(0.5-1):1; The composite adsorbent described in step 3 has a particle size of 50-100 mesh.

2. The application of the processing method according to claim 1 in biogas engineering.

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