High-Value Treatment System or Method for Urban Wet Garbage

Abstract

The present invention belongs to the field of treatment of urban organic wastes, and specifically relates to a high-value treatment system or method for urban wet garbage. According to the present invention, through the steps such as oil extraction, high-efficiency hydrolysis, high-value biological conversion, simultaneous recovery of released nitrogen and phosphorus and deep utilization of residues, urban wet garbage is converted into acetic acid by high-value treatment, produced by-products including carbon dioxide and hydrogen are biologically converted into acetic acid, released nitrogen and phosphorus are recycled into slow-release fertilizers, and solid residues are used to prepare materials capable of promoting conversion of the wet garbage into acetic acid through high-value treatment. According to the present invention, not only can high-value treatment of the urban wet garbage be realized, but also produced waste gases and waste residues are recycled.

Claims

1. A high-value treatment system or method for urban wet garbage, wherein the urban wet garbage is used as a raw material, and the method comprises the following steps: 1) mixing the urban wet garbage with water and performing oil extraction to obtain an oil-extracted mixture; 2) mixing the oil-extracted mixture with an alkali for performing a hydrolysis reaction to obtain a hydrolysate; 3) performing anaerobic culture on the hydrolysate and a first acetic acid-producing sludge, collecting a produced gas and performing solid-liquid separation after culture is completed to obtain a first liquid and a first solid; 4) introducing the gas into a mixture of municipal sewage and a second acetic acid-producing sludge for performing anaerobic culture and solid-liquid separation to obtain a second liquid and a second solid; and 5) mixing the first liquid with the second liquid, adding a magnesium salt to adjust a pH value, and performing stirring and solid-liquid separation, wherein a precipitate is a fertilizer containing nitrogen and phosphorus, and a supernatant liquid is a liquid containing acetic acid; mixing the first solid, the second solid and humic acid, and performing drying to obtain a third solid, wherein the first acetic acid-producing sludge is an acclimated sludge capable of converting glucose into acetic acid; and the second acetic acid-producing sludge is an acclimated sludge capable of converting carbon dioxide and hydrogen into acetic acid.

2. The high-value treatment system or method for urban wet garbage according to claim 1, wherein an acclimation process of the first acetic acid-producing sludge comprises the following steps: adding glucose into a mixture of sludge and municipal sewage, and performing anaerobic culture at a pH of 6-11 and a temperature of 20° C. to 80° C. to obtain the first acetic acid-producing sludge; and/or, an acclimation process of the second acetic acid-producing sludge comprises the following steps: introducing hydrogen and carbon dioxide into a mixture of sludge and municipal sewage, and performing anaerobic culture at a pH of 5-9 and a temperature of 20° C. to 50° C. to obtain the second acetic acid-producing sludge.

3. The high-value treatment system or method for urban wet garbage according to claim 2, wherein the acclimation process of the first acetic acid-producing sludge comprises three periods: in the first period, a content of solids in the mixture is 3800-4500 mg/L; and/or, in the first period, based on a total volume of the sludge, the municipal sewage and the glucose, a concentration of the glucose is 600 mgCOD/L to 1000 mg/L; and/or, the first period is 3-7 days; and/or, in the second period, the concentration of the glucose is maintained to be 1000-1400 mgCOD/L per day; and/or, the second period is 8-12 days; and/or, in the third period, the concentration of the glucose is daily increased by 80-100 mgCOD/L; and/or, in the third period, acetic acid is also added, and a concentration of the acetic acid is maintained to be 30-70 mgCOD/L per day; and/or, the third period is 30-35 days.

4. The high-value treatment system or method for urban wet garbage according to claim 1, wherein in step 1), a particle size of the urban wet garbage is 0.1-1 mm; and/or, a content of solids in a mixture formed by mixing the urban wet garbage with water is 20-180 g/L; and/or, an oil content of the oil-extracted mixture is lower than 3%.

5. The high-value treatment system or method for urban wet garbage according to claim 1, wherein in step 2), the alkali is sodium hydroxide, and conditions of the hydrolysis reaction are that a pH value is 8-12 and a temperature is 5° C. to 80° C.

6. The high-value treatment system or method for urban wet garbage according to claim 1, wherein in step 3), a volume ratio of the first acetic acid-producing sludge to the urban wet garbage is (6-10):100; and/or, conditions of anaerobic culture are that a pH value is 6-12 and a temperature is 20° C. to 80° C.

7. The high-value treatment system or method for urban wet garbage according to claim 1, wherein in step 3), the third solid is also added into the hydrolysate and the first acetic acid-producing sludge, and an added amount of the third solid is not higher than 70% of a dry weight of the first acetic acid-producing sludge.

8. The high-value treatment system or method for urban wet garbage according to claim 1, wherein in step 4), based on a total volume of the mixture, a concentration of the second acetic acid-producing sludge is 500-7000 mg/L; and/or, conditions of anaerobic culture are that a pH value is 6-8.

9. The high-value treatment system or method for urban wet garbage according to claim 1, wherein in step 5), the magnesium salt is magnesium chloride; and/or, the pH value is adjusted to 8-10; and/or, a stirring time is 5-50 minutes; and/or, after the magnesium salt is added, an ammonia nitrogen salt and/or a phosphate salt is also added.

10. The high-value treatment system or method for urban wet garbage according to claim 1, wherein an added amount of humic acid is 10% to 100% of a total dry weight of the first solid and the second solid; and/or, a drying temperature is 20° C. to 120° C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0065] FIG. 1 is a flowchart showing a high-value treatment method for urban wet garbage in the present invention.

DETAILED DESCRIPTION

[0066] The following describes implementations of the present invention by using specific examples. A person skilled in the art may easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0067] Before specific examples of the present invention are further described, it should be understood that the protection scope of the present invention is not limited to the following specific examples, and terms used in examples of the present invention are used to describe the specific examples rather than limit the protection scope of the present invention. If test methods of specific conditions are not indicated in examples below, it shall be carried out in accordance with the conventional conditions or the conditions recommended by the manufacturer.

[0068] When numerical ranges are given in the examples, it should be understood that, unless otherwise specified in the present invention, two endpoints of each numerical range and any value between the two endpoints can be used. Unless otherwise defined, meanings of all technical and scientific terms used in the present invention are the same as those generally understood by a person skilled in the technical field to which the present invention belongs. In addition to specific methods, equipment and materials used in the examples, those skilled in the art can also use any methods, equipment and materials in the prior art similar or equivalent to the methods, equipment and materials described in the examples of the present invention based on the knowledge of the prior art and the description of the present invention.

[0069] FIG. 1 is a flowchart showing a high-value treatment system or method for urban wet garbage in the present invention, and the method includes the following steps:

[0070] 1) mixing the urban wet garbage with water and performing oil extraction to obtain an oil-extracted mixture, where, a particle size of the urban wet garbage is 0.1-1 mm, and a concentration of solids in the mixture formed by mixing the urban wet garbage with water is 20-180 g/L;

[0071] 2) mixing the oil-extracted mixture in step 1) with an alkali for performing a hydrolysis reaction in a reactor R to obtain a hydrolysate, where, the alkali is sodium hydroxide, and conditions of the hydrolysis reaction are that a pH value is 8-12, a temperature is 5° C. to 80° C. and time is 1-96 hours;

[0072] 3) performing anaerobic culture on the hydrolysate in step 2), a first acetic acid-producing sludge W1 and a third solid in a reactor R1, collecting a produced gas G and performing solid-liquid separation after culture is completed to obtain a first liquid L1 and a first solid S1, where, a volume ratio of the first acetic acid-producing sludge W1 to the urban wet garbage is (6-10):100; conditions of anaerobic culture are that a pH value is 6-12, a temperature is 20° C. to 80° C. and time is 1-12 days; and an added amount of the third solid is not more than 70% of a dry weight of the first acetic acid-producing sludge;

[0073] 4) introducing the gas G produced in step 3) into a mixture of municipal sewage and a second acetic acid-producing sludge W2 for performing anaerobic culture in a reactor R2 and solid-liquid separation to obtain a second liquid L2 and a second solid S2, where, based on a total volume of the mixture, a concentration of the second acetic acid-producing sludge is 500-7000 mg/L; and conditions of anaerobic culture are that a pH value is 6-8; and

[0074] 5) mixing the first liquid L1 with the second liquid L2 in a reactor R3, adding magnesium chloride, adding ammonium chloride or sodium phosphate as needed to make a molar ratio of magnesium ions to ammonium ions to phosphate ions in a solution reach 1:1:1 to adjust a pH value, and performing stirring and solid-liquid separation, where a precipitate is a fertilizer containing nitrogen and phosphorus, and a supernatant liquid is a liquid containing acetic acid. The pH value is 8-10, and the stirring time is 5-50 minutes. At the same time, the first solid S1, the second solid S2 and humic acid are mixed and dried to obtain a third solid P. The added amount of humic acid is 10% to 100% of the total dry weight of the first solid and the second solid; the drying temperature is 20° C. to 120° C.

[0075] In the present invention, the first acetic acid-producing sludge is an acclimated sludge capable of converting glucose into acetic acid. An acclimation process of the first acetic acid-producing sludge includes the following steps: adding glucose into a mixture of sludge and municipal sewage, and performing anaerobic culture at a pH of 6-11 and a temperature of 20° C. to 80° C. to obtain the first acetic acid-producing sludge.

[0076] In the present invention, the second acetic acid-producing sludge is an acclimated sludge capable of converting carbon dioxide and hydrogen into acetic acid. An acclimation process of the second acetic acid-producing sludge includes the following steps: introducing hydrogen and carbon dioxide into a mixture of sludge and municipal sewage, and performing anaerobic fermentation at a pH of 5-9 and a temperature of 20° C. to 50° C. to obtain the second acetic acid-producing sludge.

[0077] Compared with traditional methods, the yield of acetic acid can be increased by at least 157% by using the high-value treatment method for urban wet garbage in the present invention to treat urban wet garbage.

[0078] The pH values in examples of the present application are all achieved by adjusting with 10 mol/L sodium hydroxide.

Example 1

[0079] In this example, a method for preparing a first acetic acid-producing sludge and a second acetic acid-producing sludge includes the following steps:

[0080] An acclimation process of the first acetic acid-producing sludge includes the following steps: adding surplus sludge of a sewage treatment plant and municipal sewage into a biological acclimation reactor for mixing, where the content of solids in a mixture of the sludge and municipal sewage in the biological acclimation reactor is 4000 mg/L; in a first period, adding glucose to make a concentration of the glucose reach 800 mgCOD/L based on a total volume of the sludge, municipal sewage and glucose; maintaining the pH value and the temperature in the acclimation reactor to be 6 and 20° C. respectively and performing stirring for 5 days under anaerobic conditions; in a second period, namely from the 6th day, increasing the concentration of the glucose to 1200 mgCOD/L per day, adding fresh municipal sewage per day, discharging the same amount of a supernatant per day and continuously performing anaerobic stirring for 11 days; in a third period, namely from the 16th day, increasing the concentration of the glucose by 100 mgCOD/L per day, adding acetic acid at the same time to maintain the concentration of the acetic acid to be 50 mgCOD/L per day, and discharging a supernatant and sludge per day to maintain the volume of the mixture and the concentration of the sludge in the reactor same as those on the 15th day. Acclimation was performed for 48 days to obtain the first acetic acid-producing sludge.

[0081] An acclimation process of the second acetic acid-producing sludge includes the following steps: adding surplus sludge of a sewage treatment plant and municipal sewage into another biological acclimation reactor for mixing, where the content of solids in a mixture of the sludge and municipal sewage in the biological acclimation reactor is 4500 mg/L; then adding hydrogen and carbon dioxide (a molar ratio of hydrogen to carbon dioxide is 2:1), maintaining the pH value and the temperature in the acclimation reactor to be 5 and 20° C. respectively and performing stirring under anaerobic conditions; and from the 4th day, adding hydrogen and carbon dioxide per day (the molar ratio is 2:1), and discharging a supernatant per day to maintain the volume of the mixture in the reactor same as that on the 3rd day. Acclimation was performed for 43 days to obtain the second acetic acid-producing sludge.

TABLE-US-00001 TABLE 1 Acclimation conditions of a first acetic acid-producing sludge and a second acetic acid-producing sludge in Examples 1-14 First acetic acid-producing sludge Sludge Second acetic acid-producing sludge concentration/ Acclimation Acclimation Acclimation Sludge Acclimation Acclimation Acclimation mg/L pH temperature/° C. time/d concentration/mg/L pH temperature/° C. time/d Example 1 4000 6 20 48 4500 5 20 43 Example 2 3800 11 20 52 4700 9 20 40 Example 3 4300 6 80 40 4500 5 80 35 Example 4 4200 11 20 52 4600 9 80 34 Example 5 4100 9 40 43 4400 5 20 43 Example 6 4200 9 40 43 4100 7 25 38 Example 7 4300 9 40 43 4300 9 80 34 Example 8 4200 9 40 43 4900 7 25 38 Example 9 4400 9 40 43 4500 7 25 38 Example 10 4400 9 40 43 4900 7 25 38 Example 11 4400 9 40 43 4900 7 25 38 Example 12 4500 6 80 40 4300 7 25 38 Example 13 4100 9 40 43 4900 9 50 36 Example 14 4500 9 40 43 4400 6 25 39

Example 15

[0082] In this example, a high-value treatment method for urban wet garbage by using the first acetic acid-producing sludge and the second acetic acid-producing sludge obtained in Example 1 includes the following steps:

[0083] 1) mixing the urban wet garbage with a particle size of 0.1-1 mm with water to obtain a mixture, where a concentration of the urban wet garbage in the mixture is 20 g/L; and performing boiling and oil extraction to obtaining an oil-extracted mixture;

[0084] 2) placing the oil-extracted mixture in step 1) in a hydrolysis reactor R for a hydrolysis reaction to obtain a hydrolysate, where conditions for hydrolysis are that a pH is 8, a temperature is 5° C. and time is 1 hour;

[0085] 3) placing the hydrolysate obtained in step 2) and the first acetic acid-producing sludge prepared in Example 1 in a reactor R1, adding a third solid for performing anaerobic culture, collecting a produced gas G and performing solid-liquid separation after culture is completed to obtain a first liquid L1 and a first solid S1, where, an added amount of the first acetic acid-producing sludge is 8% of the volume of the urban wet garbage; conditions of anaerobic culture are that a pH value is 6, a temperature is 20° C. and time is 1 day; and an added amount of the third solid is 0% of the dry weight of the first acetic acid-producing sludge;

[0086] 4) introducing the gas G produced in step 3) into a mixture of municipal sewage and the second acetic acid-producing sludge prepared in Example 1 in a reactor R2 for performing anaerobic culture and solid-liquid separation to obtain a second liquid L2 and a second solid S2, where, the concentration of the second acetic acid-producing sludge in the mixture is 500 mg/L; and conditions of anaerobic culture are that a pH value is 6 and time is 1 hour; and

[0087] 5) mixing the first liquid L1 with the second liquid L2 in a reactor R3, measuring the concentration of ammonia nitrogen and a phosphate salt, adding a magnesium salt, adding ammonium chloride or sodium phosphate as needed to make a molar ratio of magnesium ions to ammonium ions to phosphate ions in the R3 reach 1:1:1 to adjusting the pH value to be 8, and performing stirring for 5 minutes and solid-liquid separation, where a precipitate is a fertilizer containing nitrogen and phosphorus, and a supernatant liquid is a liquid containing acetic acid. At the same time, the first solid S1, the second solid S2 and humic acid were thoroughly mixed and dried to obtain a third solid P. An added amount of humic acid was 10% of the total dry weight of the first solid S1 and the second solid S2, and the drying temperature was 20° C. In this example, the third solid obtained was not added in step 3).

[0088] Compared with Comparative Example 1, the yield of acetic acid can be increased by 157% without adding the third solid P in the present invention.

[0089] A first acetic acid-producing sludge and a second acetic acid-producing sludge obtained in Example 2 were used in Example 16;

[0090] a first acetic acid-producing sludge and a second acetic acid-producing sludge obtained in Example 3 were used in Example 17;

[0091] a first acetic acid-producing sludge and a second acetic acid-producing sludge obtained in Example 4 were used in Example 18;

[0092] a first acetic acid-producing sludge and a second acetic acid-producing sludge obtained in Example 5 were used in Example 19;

[0093] a first acetic acid-producing sludge and a second acetic acid-producing sludge obtained in Example 6 were used in Example 20;

[0094] a first acetic acid-producing sludge and a second acetic acid-producing sludge obtained in Example 7 were used in Example 21;

[0095] a first acetic acid-producing sludge and a second acetic acid-producing sludge obtained in Example 8 were used in Example 22;

[0096] a first acetic acid-producing sludge and a second acetic acid-producing sludge obtained in Example 9 were used in Example 23;

[0097] a first acetic acid-producing sludge and a second acetic acid-producing sludge obtained in Example 10 were used in Example 24;

[0098] a first acetic acid-producing sludge and a second acetic acid-producing sludge obtained in Example 11 were used in Example 25;

[0099] a first acetic acid-producing sludge and a second acetic acid-producing sludge obtained in Example 12 were used in Example 26;

[0100] a first acetic acid-producing sludge and a second acetic acid-producing sludge obtained in Example 13 were used in Example 27;

[0101] a first acetic acid-producing sludge and a second acetic acid-producing sludge obtained in Example 14 were used in Example 28; other steps were the same as those in Example 15. Specific parameters and results are shown in the following table.

TABLE-US-00002 TABLE 2 Parameters and results of Examples 15-28 and Comparative Examples 1-15 in step 3) in step 1) Proportion of Content of the added amount solids in a Volume ratio of of the third mixture of the first acetic solid in the dry step 4) the urban acid-producing weight of the Concentration wet garbage in step 2) sludge to the Conditions first acetic acid- of sludge in a and water Hydrolysis urban wet of anaerobic producing sludge mixture (mg/L) conditions garbage culture (%) (mg/L) Example 15 20 pH value 8, 8:100 pH value 6, 0 500 temperature temperature 5° C. and 20° C. and time 1 hour time 1 day Example 16 180 pH value 8, 8:100 pH value 6, 5 500 temperature temperature 5° C. and 20° C. and time 1 hour time 1 day Example 17 20 pH value 8, 8:100 pH value 6, 8 500 temperature temperature 5° C. and 20° C. and time 1 hour time 1 day Example 18 40 pH value 8, 8:100 pH value 6, 13 500 temperature temperature 5° C. and 20° C. and time 1 hour time 1 day Example 19 20 pH value 8, 8:100 pH value 6, 0 500 temperature temperature 5° C. and 20° C. and time 1 hour time 1 day Example 20 20 pH value 8, 8:100 pH value 6, 8 500 temperature temperature 5° C. and 20° C. and time 1 hour time 1 day Example 21 180 pH value 8, 8:100 pH value 6, 5 500 temperature temperature 5° C. and 20° C. and time 1 hour time 1 day Example 22 180 pH value 10, 8:100 pH value 12, 70 7000 temperature temperature 80° C. and 80° C. and time 4 days time 12 days Example 23 50 pH value 8, 8:100 pH value 7, 15 7000 temperature temperature 20° C. and 30° C. and time 1 day time 3 days Example 24 90 pH value 10, 8:100 pH value 9, 40 4000 temperature temperature 50° C. and 40° C. and time 2 days time 6 days Example 25 70 pH value 9, 8:100 pH value 9, 30 4000 temperature temperature 50° C. and 40° C. and time 1.5 days time 5 days Example 26 20 pH value 8, 8:100 pH value 7, 40 1000 temperature temperature 20° C. and 30° C. and time 1 day time 3 days Example 27 100 pH value 8, 8:100 pH value 7, 20 1300 temperature temperature 30° C. and 30° C. and time 2 days time 3 days Example 28 50 pH value 9, 8:100 pH value 9, 25 6000 temperature temperature 25° C. and 35° C. and time 4 days time 2 days step 6) Proportion of the added amount of humic acid in the total dry Comparative step 4) weight of the Example Conditions step 5) first solid and Drying Content of of anaerobic Adjustment Stirring the second solid temperature the urban culture of pH time (%) (° C.) wet garbage Results Example 15 pH value 6 8 5 min 10 20 Comparative 157 and time 1 Example 1: hour 20 g/L Example 16 pH value 6 8 5 min 10 20 Comparative 269 and time 1 Example 2: hour 180 g/L Example 17 pH value 6 8 5 min 10 20 Comparative 196 and time 1 Example 3: hour 20 g/L Example 18 pH value 6 8 5 min 10 20 Comparative 288 and time 1 Example 3: hour 40 g/L Example 19 pH value 6 8 5 min 10 20 Comparative 176 and time 1 Example 4: hour 20 Example 20 pH value 6 8 5 min 10 20 Comparative 257 and time 1 Example 5: hour 20 Example 21 pH value 6 8 5 min 10 20 Comparative 314 and time 1 example 6: hour 180 Example 22 pH value 8 10 50 min 100 120 Comparative 383 and time 1 example 7: hour 180 Example 23 pH value 7 8 10 min 20 30 Comparative 270 and time 1 Example 8: hour 50 Example 24 pH value 7 9 20 min 40 65 Comparative 614 and time 1 Example 9: hour 90 Example 25 pH value 7 10 50 min 30 30 Comparative 453 and time 1 Example 10: hour 70 Example 26 pH value 8 8 30 min 25 60 Comparative 298 and time 1 Example 11: hour 20 Example 27 pH value 7 9 15 min 30 100 Comparative 418 and time 1 example 12: hour 100 Example 28 pH value 7 9 20 min 50 120 Comparative 347 and time 1 Example 13: hour 50

[0102] It can be seen from Table 2 that compared with corresponding comparative examples using traditional methods, the yield of acetic acid in urban wet garbage can be increased by 157% or above by using the methods in examples of the present invention to treat the urban wet garbage. Compared with a treatment method without addition of the third solid, the yield of acetic acid can be increased by 1.4 times or above by adding the third solid into the hydrolysate in step 3) and the first acetic acid-producing sludge.

Comparative Example 1

[0103] In this comparative example, a traditional treatment method for urban wet garbage includes the following steps:

[0104] 1) mixing the urban wet garbage with a particle size of 0.1-1 mm with water to obtain a mixture, where a concentration of the urban wet garbage in the mixture is 20 g/L; and performing oil extraction to obtain an oil-extracted mixture; and 2) directly performing anaerobic culture on the oil-extracted mixture at a pH of 7 and a temperature of 25° C. for 6 days without adding a first acetic acid-producing sludge, a second acetic acid-producing sludge, a magnesium salt and humic acid.

[0105] Only the concentration of the urban wet garbage in the mixture in Comparative Examples 2-14 is different from that in Comparative Example 1, and others are the same as those in Example 1. The concentration of the urban wet garbage in the mixture in Comparative Examples 2-14 is shown in Table 2.

[0106] The above examples only exemplarily illustrate the principles and effects of the present invention, but are not used to limit the present invention. Any person skilled in the art may make modifications or changes on the foregoing examples without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by a person of ordinary skill in the art without departing from the spirit and technical idea of the present invention shall be covered by the claims of the present invention.