Straw biochar, preparation method thereof and application of straw biochar in enhancing sludge methanogenesis

Abstract

The present application provides a kind of straw biochar and its preparation method and application in the methane production of sludge intensification, belong to solid waste resource processing technical field.The preparation method of straw biochar of the present application is, after the preliminary drying of straw mixture is chopped, is dried, carbonizes, grinds, obtains the straw biochar;The straw mixture includes corn stalk and reed straw;The heating rate in the carbonization process is 5-10 DEG C / min, the pyrolysis temperature when carbonizing is 500-650 DEG C, the holding time under the pyrolysis temperature is 1-2h.The present application uses straw biochar to pretreat livestock and poultry manure wastewater, thereby activating biochar, play the effect of intensifying sludge anaerobic digestion in subsequent stage, provides a more competitive new idea for the application of biochar in anaerobic digestion.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid waste resource processing, and particularly relates to a straw biochar, a preparation method thereof and application of the straw biochar in enhancing sludge methane production. BACKGROUND

[0002] Anaerobic digestion, as a widely used process for the treatment of solid organic waste, has also been applied to the treatment and disposal of livestock manure wastewater, i.e., traditional biogas digesters. Anaerobic digestion can not only effectively reduce the volume of livestock manure, but also effectively utilize the biologically available substances in livestock manure wastewater. In the process of anaerobic digestion of livestock manure wastewater, the biologically available substances therein will be converted into more valuable organic matter, such as methane, hydrogen and short-chain fatty acids. However, the process of anaerobic digestion of livestock manure wastewater has defects such as low hydrolysis rate, poor methane production efficiency and methane production being easily affected by environmental factors, which limits the degree of energy and resource utilization of residual livestock manure waste.

[0003] Biochar is a stable green material rich in carbon, which is usually prepared by pyrolysis of municipal solid waste, agricultural solid waste and residual sludge under limited oxygen conditions. The effectiveness of biochar depends largely on its adsorption performance, pH value, electrical conductivity and surface functional groups. Studies have shown that the addition of biochar in the process of anaerobic digestion can effectively improve the system stability, enhance microbial activity, reduce acid inhibition, and at the same time improve the fermentation rate and methane production of the anaerobic digestion process. The main mechanisms of biochar promoting anaerobic digestion include auxiliary microbial immobilization, buffer effect and promotion of interspecies electron transfer.

[0004] It should be noted that biochar prepared under different raw materials, different carbonization temperatures and different holding times has very different properties. In the past, biochar has been applied to anaerobic digestion as an exogenous additive, and the advantages of biochar have not been fully utilized. Therefore, before the start of anaerobic digestion, biochar is used to pretreat the substrate, providing a new idea and method for further efficient use of biochar to promote anaerobic digestion. SUMMARY

[0005] The present application aims to provide a straw biochar, a preparation method thereof and application of the straw biochar in enhancing sludge methane production. The present application uses straw biochar to pretreat livestock manure wastewater, thereby activating the biochar and achieving the effect of enhancing sludge anaerobic digestion in the subsequent stage, providing a more competitive new idea for the application of biochar in anaerobic digestion.

[0006] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0007] The application provides a preparation method of straw biochar, wherein a straw mixture after preliminary drying is cut, dried, carbonized and ground to obtain the straw biochar.

[0008] The straw mixture comprises corn straw and reed straw.

[0009] The heating speed in the carbonization process is 5-10 DEG C / min, the pyrolysis temperature in the carbonization process is 500-650 DEG C, and the holding time at the pyrolysis temperature is 1-2 h.

[0010] Preferably, the length of the cut straw mixture is 1-5 cm.

[0011] Preferably, the preliminary drying temperature is 10-30 DEG C, and the preliminary drying time is 24-48 h; the drying temperature is 100-110 DEG C, and the drying time is 24-48 h.

[0012] Preferably, the ground mixture is sieved through a 100-140 mesh sieve, and the undersize is the straw biochar.

[0013] The application further provides the straw biochar prepared by the above preparation method.

[0014] The application further provides application of the above straw biochar in enhancing sludge methanogenesis, comprising the following steps.

[0015] (1) pretreating livestock and poultry manure wastewater with the straw biochar to obtain a pretreated mixture;

[0016] (2) mixing the pretreated mixture with anaerobic digestion sludge and performing anaerobic digestion.

[0017] Preferably, the mass ratio of the straw biochar to VS in the livestock and poultry manure wastewater is (0.5-2.0):1, and the mass ratio of VS in the livestock and poultry manure wastewater to VS in the anaerobic digestion sludge is 1:(1-2).

[0018] Preferably, the rotation speed in the pretreatment is 100-150 rpm, the pretreatment temperature is 30-40 DEG C, and the pretreatment time is 1-24 h.

[0019] Preferably, the pH of the mixed system in step (2) is 6.9-7.1.

[0020] Preferably, the rotation speed in the anaerobic digestion is 100-150 rpm, the anaerobic digestion temperature is 33-38 DEG C, and the anaerobic digestion time is 35-40 days.

[0021] The present application provides a kind of straw biochar and its preparation method and application in enhancing sludge methanogenesis.The present application is based on corn straw and reed straw raw material after high-temperature carbonization treatment method is prepared to obtain straw biochar (preparation flow as shown in Figure 1 The present application is based on corn straw and reed straw raw material after high-temperature carbonization treatment method is prepared to obtain straw biochar (preparation flow as shown in

[0022] The present application is based on corn straw and reed straw raw material after high-temperature carbonization treatment method is prepared to obtain straw biochar (preparation flow as shown in BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The present application is based on corn straw and reed straw raw material after high-temperature carbonization treatment method is prepared to obtain straw biochar (preparation flow as shown in

[0024] Figure 2 The present application is based on corn straw and reed straw raw material after high-temperature carbonization treatment method is prepared to obtain straw biochar (preparation flow as shown in DETAILED DESCRIPTION

[0025] The present application provides a kind of straw biochar and its preparation method and application in enhancing sludge methanogenesis.The present application is based on corn straw and reed straw raw material after high-temperature carbonization treatment method is prepared to obtain straw biochar (preparation flow as shown in

[0026] In the present application, the straw mixture preferably includes corn straw and reed straw.

[0027] In the present application, the temperature of the preliminary drying is preferably 10-30℃, and further preferably 25℃.

[0028] In the present application, the time of the preliminary drying is preferably 24-48h, and further preferably 24h.

[0029] In the present application, the length of the chopped straw mixture is preferably 1-5 cm, and more preferably 4 cm.

[0030] In the present application, the chopped straw mixture (mainly corn straw and reed straw) is preferably rinsed with deionized water to completely remove dust and other impurities on the surface of the raw material.

[0031] In the present application, the drying temperature is preferably 100-110°C, and more preferably 105°C.

[0032] In the present application, the drying time is preferably 24-48h, and more preferably 24h.

[0033] The moisture content of the dried straw mixture is preferably 8%-10%, and more preferably 10%.

[0034] In the present application, the heating rate during carbonization is preferably 5-10°C / min, and more preferably 10°C / min.

[0035] In the present application, the pyrolysis temperature during carbonization is preferably 500-650°C, and more preferably 600°C.

[0036] In the present application, the holding time at the pyrolysis temperature is preferably 1-2h, and more preferably 1h.

[0037] In the present application, the ground product is preferably passed through a 100-140 mesh screen, and the undersize is the straw biochar, and more preferably a 120 mesh screen.

[0038] The present application also provides a straw biochar prepared by the above method.

[0039] The present application also provides a use of the above straw biochar in enhancing sludge methanogenesis, comprising the following steps:

[0040] (1) pretreating livestock and poultry manure wastewater with straw biochar to obtain a pretreated mixture;

[0041] (2) mixing the pretreated mixture with anaerobic digestion sludge and performing anaerobic digestion.

[0042] The present application pretreats livestock and poultry manure wastewater with straw biochar to obtain a pretreated mixture.

[0043] In the present application, the mass ratio of the straw biochar to the VS in the livestock and poultry manure wastewater is preferably (0.5-2.0):1, and more preferably 2:1.

[0044] In the present application, the rotation speed during the pretreatment is preferably 100-150 rpm, further preferably 120 rpm.

[0045] In the present application, the temperature during the pretreatment is preferably 30-40℃, further preferably 35℃.

[0046] In the present application, the time during the pretreatment is preferably 1-24 h, further preferably 6 h.

[0047] In the present application, the pretreated mixture is mixed with anaerobic digestion sludge, and anaerobic digestion is performed.

[0048] In the present application, the mass ratio of VS in the livestock and poultry manure wastewater to VS in the anaerobic digestion sludge is preferably 1: (1-2), further preferably 1:2.

[0049] In the present application, the pH of the mixed system is preferably 6.9-7.1, further preferably 7.0.

[0050] In the present application, the rotation speed during the anaerobic digestion is preferably 100-150 rpm, further preferably 120 rpm.

[0051] In the present application, the temperature during the anaerobic digestion is preferably 33-38℃, further preferably 35℃.

[0052] In the present application, the time during the anaerobic digestion is preferably 35-40 days, further preferably 40 days.

[0053] The technical solutions provided by the present application will be described in detail below in conjunction with examples, but they should not be understood as limiting the scope of protection of the present application.

[0054] Example 1

[0055] The present example provides a kind of straw biochar, and its method for strengthening sludge methanogenesis, specific process as follows:

[0056] (1) preparation of straw biochar

[0057] Corn straw and reed straw are collected and mixed as straw mixture raw materials, washed with tap water, and then placed in a ventilated place at room temperature for 24 h. The straw mixture is preliminarily dried. The preliminarily dried straw mixture is cut and treated to an average length of 4 cm, then washed with deionized water to completely remove dust and other impurities on the surface of the raw material; the straw mixture is dried in an oven at 105℃ for 24 h to obtain a straw mixture with a water content of 10%.

[0058] The dried straw mixture was placed in a vacuum tube furnace, and the temperature rising rate was set to 10°C / min. When the temperature rose to 600°C, pyrolysis was carried out at this temperature for 1 h. During the pyrolysis process, 99.999% high-purity nitrogen was continuously introduced to ensure an oxygen-free environment in the tube furnace, and corn straw biochar was obtained. The biochar was ground with a mortar and sieved through a 120-mesh sieve. The undersize was the straw biochar.

[0059] (2) Methane production

[0060] Into a 300 mL serum bottle, 86.4 mL of livestock and poultry manure wastewater (VS in livestock and poultry manure wastewater was 15.824 ± 0.15 g / L) was added. According to the mass ratio of straw biochar:VS in livestock and poultry manure wastewater = 2:1, the straw biochar prepared in step (1) was added, and the serum bottle was shaken uniformly without adjusting the pH. The serum bottle was placed in a constant temperature shaker at 35°C and 120 rpm for 6 h of pretreatment. After the pretreatment was completed, a pretreatment mixed system was obtained.

[0061] According to the mass ratio of VS (livestock and poultry manure wastewater):VS (anaerobic digestion sludge) = 1:2, anaerobic digestion sludge was inoculated into the pretreatment mixed system, and the pH of the system was adjusted to 7.0. The VS of the anaerobic digestion sludge was 19.190 ± 0.043 mg / L.

[0062] The serum bottle reactor was aerated for 2 min using 99.999% high-purity nitrogen to remove oxygen in the serum bottle and headspace, and to maintain anaerobic conditions throughout the serum bottle. The serum bottle reactor was sealed with a butyl rubber plug and an aluminum cap, and the bottle opening was wrapped with sealing film. Finally, the serum bottle was placed in a constant temperature shaker at 35°C and 120 rpm for incubation. The anaerobic digestion reactor was continuously operated for 40 days.

[0063] The above treatment is the pretreatment group. In order to verify the strengthening effect of straw biochar and livestock and poultry manure wastewater on sludge methanogenesis, a control group (Control) and a non-pretreatment group were also set up in this embodiment.

[0064] The difference between the control group and the pretreatment group is that no straw biochar is added. The other operations are the same as those of the pretreatment group.

[0065] The difference between the non-pretreatment group and the pretreatment group is that after mixing the straw biochar with the livestock and poultry manure wastewater, no pretreatment is performed, and the anaerobic digestion sludge is inoculated directly. The other operations are the same as those of the pretreatment group.

[0066] During the entire experiment, the biogas production was determined periodically by the drainage method, the composition of the biogas was determined by a gas chromatograph, and the methane content was determined. The methane production of each group was summarized, and the results are shown in Table 1. Figure 2As shown in the figure, compared with the control group and the non-preprocessing group, the cumulative methane production per unit biomass of the preprocessing group was significantly improved. Compared with the control group, the methane production of the anaerobic digestion process was increased by 108.85%. This may be because the rich C-OH, C=C and C=O oxygen-containing functional groups on the surface of the biochar accelerate the conversion of volatile fatty acids and other substances to methane. In contrast, the non-preprocessing group added the same concentration of straw biochar without preprocessing, which not only did not improve the cumulative methane production, but also inhibited the cumulative methane production of the anaerobic digestion process by 50.91%. This shows that using straw biochar to pretreat livestock and poultry manure wastewater can significantly improve the energy production effect of the anaerobic digestion process.

[0067] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the scope of protection of the present application.

Claims

1. Use of a straw biochar in enhancing methanogenesis in sludge, characterized in that, The method comprises the following steps: (1) pretreating livestock and poultry manure wastewater with straw biochar to obtain a pretreated mixed system; (2) mixing the pretreated mixed system with anaerobic digestion sludge and performing anaerobic digestion; The mass ratio of the straw biochar to VS in the livestock and poultry manure wastewater is (0.5-2.0):1; The mass ratio of VS in the livestock and poultry manure wastewater to VS in the anaerobic digestion sludge is 1:(1-2); The rotation speed during the pretreatment is 100-150 rpm, the pretreatment temperature is 30-40 DEG C, and the pretreatment time is 1-24 h; The rotation speed during the anaerobic digestion is 100-150 rpm, the anaerobic digestion temperature is 33-38 DEG C, and the anaerobic digestion time is 35-40 days.

2. The use according to claim 1, characterized in that, The preparation method of the straw biochar comprises the following steps: cutting a preliminarily dried straw mixture, drying, carbonizing, and grinding to obtain the straw biochar; The straw mixture comprises corn stalks and reed stalks; The heating rate during the carbonization process is 5-10 DEG C / min, the pyrolysis temperature during the carbonization is 500-650 DEG C, and the holding time at the pyrolysis temperature is 1-2 h; The length of the cut straw mixture is 1-5 cm.

3. The use according to claim 2, wherein The preliminary drying temperature is 10-30 DEG C, and the time is 24-48 h; the drying temperature is 100-110 DEG C, and the time is 24-48 h.

4. The use according to claim 2, characterized in that, The ground product is sieved through a 100-140 mesh sieve, and the undersize is the straw biochar.

5. The use according to claim 1, characterized in that, The pH of the mixed system in step (2) is 6.9-7.

1. The method comprises the following steps: (1) pretreating livestock and poultry manure wastewater with straw biochar to obtain a pretreated mixed system; (2) mixing the pretreated mixed system with anaerobic digestion sludge and performing anaerobic digestion; The mass ratio of the straw biochar to VS in the livestock and poultry manure wastewater is (0.5-2.0):1; The mass ratio of VS in the livestock and poultry manure wastewater to VS in the anaerobic digestion sludge is 1:(1-2); The rotation speed during the pretreatment is 100-150 rpm, the pretreatment temperature is 30-40 DEG C, and the pretreatment time is 1-24 h; The rotation speed during the anaerobic digestion is 100-150 rpm, the anaerobic digestion temperature is 33-38 DEG C, and the anaerobic digestion time is 35-40 days. The preparation method of the straw biochar comprises the following steps: cutting a preliminarily dried straw mixture, drying, carbonizing, and grinding to obtain the straw biochar; The straw mixture comprises corn stalks and reed stalks; The heating rate during the carbonization process is 5-10 DEG C / min, the pyrolysis temperature during the carbonization is 500-650 DEG C, and the holding time at the pyrolysis temperature is 1-2 h; The length of the cut straw mixture is 1-5 cm. The preliminary drying temperature is 10-30 DEG C, and the time is 24-48 h; the drying temperature is 100-110 DEG C, and the time is 24-48 h. The ground product is sieved through a 100-140 mesh sieve, and the undersize is the straw biochar. The pH of the mixed system in step (2) is 6.9-7.1.

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