SYSTEM FOR HIGH-VALUE UTILIZATION OF ORGANIC SOLID WASTE

Abstract

A system for high-value utilization of organic solid waste includes an anaerobic digestion unit, a biogas measurement and collection unit and a methane purification and liquefaction unit. The anaerobic digestion unit includes an organic solid waste pretreatment system and an anaerobic digestion device. The biogas measurement and collection unit includes a gas flow meter and a high-pressure biogas collection device. The methane purification and liquefaction unit includes a high-pressure separation tank, a liquefaction pretreatment system, a heavy hydrocarbon and benzene removal device, a two-stage rectification system, a low-temperature pressure liquid storage tank device and a buffer storage tank. The organic solid waste undergoes an anaerobic digestion treatment to produce methane followed by collection, purification and liquefaction.

Claims

1. A system for high-value utilization of organic solid waste, comprising: an anaerobic digestion unit; a biogas measurement and collection unit; and a methane purification and liquefaction unit; wherein the anaerobic digestion unit comprises an organic solid waste pretreatment device, an anaerobic digestion device and a residue collection tank which are connected in sequence; the biogas measurement and collection unit comprises a gas flow meter and a high-pressure biogas collection device which are connected in sequence; the methane purification and liquefaction unit comprises a high-pressure separation tank, a liquefaction pretreatment device, a heavy hydrocarbon and benzene removal device, a two-stage rectification device and a low-temperature pressure liquid storage tank which are connected in sequence, wherein the two-stage rectification device is also connected to a buffer storage tank; and the buffer storage tank and the low-temperature pressure liquid storage tank are connected; a gas outlet of the anaerobic digestion device is communicated with a gas inlet of the gas flow meter; a gas outlet of the high-pressure biogas collection device is communicated with a gas inlet of the high-pressure separation tank; a liquid outlet of the high-pressure separation tank is connected to a liquid inlet of the two-stage rectification device; the two-stage rectification device comprises a first-stage rectification tower, a two-stage rectification tower, a main heat exchanger, a supercooler, a tower kettle and a tower overhead device; and an ethanolamine absorption device and a dehydration device are provided in the liquefaction pretreatment device.

2. The system of claim 1, wherein the anaerobic digestion device comprises an anaerobic digestion tank, a heating device and a stirring device; the stirring device is provided in a center of an interior of the anaerobic digestion tank; an outside of the anaerobic digestion tank is surrounded by the heating device; a top of the anaerobic digestion tank is provided with a biogas outlet, a solid material inlet, an acid liquor inlet, an alkali liquor inlet, a pH or temperature detector and a stirring motor; and a bottom of the anaerobic digestion tank is provided with a discharge port; the heating device is a water-bath heater, a coil heater or a combination thereof; and the stirring device is selected from at least one of a center shaft mixer, a horizontal mixer, an inclined mixer and a submersible mixer.

3. A method for high-value utilization of organic solid waste using the system of claim 1, comprising: pretreating the organic solid waste by the organic solid waste pretreatment device to obtain a digestion material; performing anaerobic digestion after the digestion material enters the anaerobic digestion device from an outlet of the organic solid waste pretreatment device, so as to yield biogas from a biodegradable organic matter in the organic solid waste and produce a digestion residue from a non-biodegradable organic matter in the organic solid waste; allowing the obtained biogas to flow into the gas flow meter, and converting the biogas into a high-pressure raw gas by the high-pressure biogas collection device; sending the obtained high-pressure raw gas to the high-pressure separation tank to carry out liquid separation treatment to obtain a condensed liquid; sending the obtained condensed liquid into a two-stage rectification system; generating liquid methane after the high-pressure raw gas enters the liquefaction pretreatment device, the heavy hydrocarbon and benzene removal device and the two-stage rectification device in sequence; storing the liquid methane in the low-temperature pressure liquid storage tank; discharging a surplus liquid that undergoes supercooling into the buffer storage tank for accumulation; and sending the surplus liquid into the low-temperature pressure liquid storage tank; and sending the digestion residue into a residue collection tank for recycling.

4. A method for high-value utilization of organic solid waste using the system of claim 2, comprising: pretreating the organic solid waste by the organic solid waste pretreatment device to obtain a digestion material; performing anaerobic digestion after the digestion material enters the anaerobic digestion device from an outlet of the organic solid waste pretreatment device, so as to yield biogas from a biodegradable organic matter in the organic solid waste and produce a digestion residue from a non-biodegradable organic matter in the organic solid waste; allowing the obtained biogas to flow into the gas flow meter, and converting the biogas into a high-pressure raw gas by the high-pressure biogas collection device; sending the obtained high-pressure raw gas to the high-pressure separation tank to carry out liquid separation treatment to obtain a condensed liquid; sending the obtained condensed liquid into a two-stage rectification system; generating liquid methane after the high-pressure raw gas enters the liquefaction pretreatment device, the heavy hydrocarbon and benzene removal device and the two-stage rectification device in sequence; storing the liquid methane in the low-temperature pressure liquid storage tank; discharging a surplus liquid that undergoes supercooling into the buffer storage tank for accumulation; and sending the surplus liquid into the low-temperature pressure liquid storage tank; and sending the digestion residue into a residue collection tank for recycling.

5. The method of claim 3, wherein the digestion material stays in the anaerobic digestion device for 20-40 days.

6. The method of claim 5, wherein a temperature of the anaerobic digestion device ranges within 35-39 C., 41-45 C., or 53-57 C. for biogas production.

7. The method of claim 3, wherein after a pressure of biogas collected in the high-pressure biogas collection device reaches 120 bar at 27 C., the biogas enters the high-pressure separation tank.

8. The method of claim 3, wherein in the liquefaction pretreatment device, CO.sub.2 removal, desulfurization and dehydration are carried out; wherein the dehydration is performed after the CO.sub.2 removal; the CO.sub.2 removal and the desulfurization are simultaneously performed; CO.sub.2 is removed by ethanolamine (MEA) through absorption; the dehydration is performed using a molecular sieve dehydration method for further removing sulfide.

9. The method of claim 3, wherein the organic solid waste is one or more combinations of domestic, agricultural and industrial organic waste.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 is a schematic diagram of a system for high-value utilization of organic solid waste according to the present application.

[0033] FIG. 2 is a flow chart of a method for high-value utilization of organic solid waste

[0034] In the drawings: I, anaerobic digestion unit; where 1, organic solid waste pretreatment unit; 2, anaerobic digestion unit; and 3, residue collection tank;

[0035] II, biogas measurement and collection unit; where 4, gas flow meter; and 5, high-pressure biogas collection device; and

[0036] III, methane purification and liquefaction unit; where 6, high-pressure separation tank; 7, liquefaction pretreatment device; 8, heavy hydrocarbon and benzene removal device; 9, two-stage rectification device; 10, low-temperature pressure liquid storage tank; and 11, buffer storage tank.

DETAILED DESCRIPTION OF EMBODIMENTS

[0037] The technical solutions in the embodiments will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the embodiments described herein are only a part of the embodiments, rather than all the embodiments of the present application. Any other embodiments made by those skilled in the art based on the embodiments of the present application without sparing any creative efforts shall fall within the scope of the present application.

[0038] In addition, for the purpose of illustration, a lot of specific details are given in the following embodiments. It should be understood for those skilled in the art that the present application can also be implemented with only a part of the specific details given herein. In some embodiments, the methods and means well-known to those skilled in the art are not described in detail, which is intended to highlight the spirit of the present application. All the units of the raw material content of the present application are based on parts by weight, unless otherwise specified. In addition, the technical indicators in the present application are measured by standard methods used in the field, which can refer to latest national standards in details, unless otherwise specified.

[0039] It should be understood that terms such as have, comprise and include used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0040] In a first aspect, the present application provides a system for high-value utilization of organic solid waste, which includes an anaerobic digestion unit, a biogas measurement and collection unit and a methane purification and liquefaction unit.

[0041] The anaerobic digestion unit includes an organic solid waste pretreatment device, an anaerobic digestion device and a residue collection tank which are connected in sequence.

[0042] The biogas measurement and collection unit includes a gas flow meter and a high-pressure biogas collection device which are connected in sequence.

[0043] The methane purification and liquefaction unit includes a high-pressure separation tank, a liquefaction pretreatment device, a heavy hydrocarbon and benzene removal device, a two-stage rectification device and a low-temperature pressure liquid storage tank which are connected in sequence. The two-stage rectification device is also connected to a buffer storage tank. The buffer storage tank and the low-temperature pressure liquid storage tank are connected.

[0044] A gas outlet of the anaerobic digestion device is communicated with a gas inlet of the gas flow meter.

[0045] A gas outlet of the high-pressure biogas collection device is communicated with a gas inlet of the high-pressure separation tank.

[0046] A liquid outlet of the high-pressure separation tank is connected to a liquid inlet of the two-stage rectification device.

[0047] In an embodiment, the anaerobic digestion device includes an anaerobic digestion tank, a heating device and a stirring device. The stirring device is provided in a center of an interior of the anaerobic digestion tank. An outside of the anaerobic digestion tank is surrounded by the heating device. A top of the anaerobic digestion tank is provided with a biogas outlet, a solid material inlet, an acid liquor inlet, an alkali liquor inlet, a pH or temperature detector and a stirring motor. A bottom of the anaerobic digestion tank is provided with a discharge port.

[0048] In an embodiment, the heating device is a water-bath heater, a coil heater or a combination thereof.

[0049] In an embodiment, the stirring device is selected from at least one of a center shaft mixer, a horizontal mixer, an inclined mixer and a submersible mixer.

[0050] In an embodiment, the two-stage rectification device includes a first-stage rectification tower, a two-stage rectification tower, a main heat exchanger, a supercooler, a tower kettle and a tower overhead device which are connected. Their connection manner is similar to that in the existing two-stage rectification process for producing high-purity methane.

[0051] In a second aspect, the present application provides a method for high-value utilization of the organic solid waste using the system mentioned above. The method includes the following steps.

[0052] The organic solid waste is pretreated by the organic solid waste pretreatment device to obtain a digestion material. Then, anaerobic digestion processes after the digestion material enters the anaerobic digestion device. A biodegradable organic matter in the organic solid waste generates monomers (including monosaccharides, a small amount of amino acids and high fatty acids) under the action of hydrolysis bacteria. The monomers are used to generate an intermediate product, i.e., a volatile organic acid, under the action of acidifying bacteria in the acid production process. In the subsequent process of hydrogen production and acetic acid production, gases (including CH.sub.4, H.sub.2, CO.sub.2 and N.sub.2), acetic acid, methylamine and the like are generated. Next, under the action of methanogens, anaerobic digestion products (including digestion residues and biogas) are generated. The biogas generated in the anaerobic digestion unit flows into the gas flow meter of the biogas measurement and collection unit and is converted into a high-pressure raw gas by the high-pressure biogas collection device. The obtained high-pressure raw gas is sent to the high-pressure separation tank to carry out liquid separation treatment to obtain a condensed liquid. The obtained condensed liquid enters into a two-stage rectification system. The high-pressure raw gas enters the liquefaction pretreatment device for desulfurization, dehydration and CO.sub.2 removal, and then enters the heavy hydrocarbon and benzene removal device to remove heavy hydrocarbons and trace benzene, and then passes through the two-stage rectification device to generate liquid methane, which is stored in low-temperature pressure liquid storage tank. A small amount of a surplus liquid that undergoes supercooling is discharged into the buffer storage tank for accumulation, and the surplus liquid accumulated to a certain amount is taken out and sent into the low-temperature pressure liquid storage tank.

[0053] The non-biodegradable organic matter in the organic solid waste becomes digestion residue through anaerobic digestion and enters a residue collection tank for recycling.

[0054] In an embodiment, the digestion material stays in the anaerobic digestion device for 20-40 days.

[0055] In an embodiment, a temperature of the anaerobic digestion device ranges within 35-39 C., 41-45 C., or 53-57 C. for biogas production.

[0056] In an embodiment, after a pressure of biogas collected in the high-pressure biogas collection device reaches 120 bar at 27 C., the biogas enters the high-pressure separation tank.

[0057] In an embodiment, in the liquefaction pretreatment device, CO.sub.2 removal, desulfurization and dehydration are carried out. The dehydration is performed after the CO.sub.2 removal. The CO.sub.2 removal and the desulfurization are simultaneously performed. CO.sub.2 is removed by ethanolamine (MEA) through absorption. The dehydration is performed using a molecular sieve dehydration method for further removing sulfide.

[0058] In an embodiment, the organic solid waste is one or more combinations of domestic, agricultural and industrial waste.

[0059] In an embodiment, the domestic waste may be originated from urban sludge, household garbage, garden waste, etc. The agricultural waste may be originated from agricultural straw, mulching film, livestock and poultry manure, etc. The industrial waste may be originated from oil sludge, bacterial residue, industrial organic solid waste, etc.

Embodiment 1

[0060] 1000 kg organic solid waste is originated from municipal sludge.

[0061] The process of high-value utilization of the organic solid waste is described as follows. In the organic solid waste pretreatment system, the organic solid waste is hydrolyzed for 20 min at a temperature of 165-180 C. and a pressure of 1 MPa to obtain the digestion material. The digestion material enters the anaerobic digestion unit to carry out anaerobic digestion for 30 days at a temperature of 35-39 C. to generate biogas. The obtained biogas with 300-500 m.sup.3 flows into the gas flow meter of the biogas measurement and collection unit. The biogas becomes the high pressure raw gas by the biogas high pressure collection device to have a pressure of 120 bar at 27 C. The obtained high-pressure raw gas is sent to the high-pressure separation tank of the methane purification and liquefaction unit to carry out liquid separation treatment to obtain a condensed liquid. The obtained condensed liquid enters into a two-stage rectification system. The high-pressure raw gas enters the liquefaction pretreatment system for desulfurization, dehydration and CO.sub.2 removal. Specifically, the dehydration is performed after the CO.sub.2 removal. The CO.sub.2 removal and the desulfurization are simultaneously performed. CO.sub.2 is removed by ethanolamine (MEA) through absorption. The dehydration is performed using a molecular sieve dehydration method for further removing sulfide. Next, the high-pressure raw gas enters the heavy hydrocarbon and benzene removal device to remove heavy hydrocarbons and trace benzene, and then passes through the two-stage rectification device to generate liquid methane, which is stored in low-temperature pressure liquid storage tank. A small amount of a surplus liquid that undergoes supercooling is discharged into the buffer storage tank.

[0062] The non-biodegradable organic matter in the organic solid waste becomes digestion residue through anaerobic digestion and enters a residue collection tank for recycling.

[0063] Finally, 200-300 kg liquid methane is produced. After testing, the purity of the obtained liquid methane is 99.9%, which can meet the demand of a liquid oxygen methane engine for methane fuel.

Embodiment 2

[0064] The present embodiment differs from Embodiment 1 in that in the present embodiment, the anaerobic digestion processes for 30 days at a temperature of 53-57 C. Finally, 300-500 kg liquid methane is produced. After testing, the purity of the obtained liquid methane is 99.9%, which can meet the demand of a liquid oxygen methane engine for methane fuel.

Embodiment 3

[0065] The present embodiment differs from Embodiment 1 in that the 1000 kg organic solid waste is originated from kitchen waste. In the organic solid waste pretreatment system, the organic solid waste is crushed and then hydrolyzed for 2 h at a temperature of 110-130 C. and a pressure of 1 MPa. Anaerobic digestion processes for 30 days at a temperature of 35-39 C. Finally, 550-650 kg liquid methane is produced. After testing, the purity of the obtained liquid methane is 99.9%, which can meet the demand of a liquid oxygen methane engine for methane fuel.

Embodiment 4

[0066] The present embodiment differs from Embodiment 1 in that the organic solid waste is originated from agricultural straw. In the organic solid waste pretreatment system, the organic solid waste is crushed and then hydrolyzed for 10 min at a temperature of 160-270 C. and a pressure of 2 MPa. Anaerobic digestion processes for 30 days at a temperature of 53-57 C. Finally, 600-700 kg liquid methane is produced. After testing, the purity of the obtained liquid methane is 99.9%, which can meet the demand of a liquid oxygen methane engine for methane fuel.

Embodiment 5

[0067] The present embodiment differs from Embodiment 1 in that the organic solid waste is originated from oil sludge. In the organic solid waste pretreatment system, the organic solid waste is crushed and then hydrolyzed for 30 min at a temperature of 160-200 C. and a pressure of 1 MPa. Anaerobic digestion processes for 30 days at a temperature of 41-45 C. Finally, 300-400 kg liquid methane is produced. After testing, the purity of the obtained liquid methane is 99.9%, which can meet the demand of a liquid oxygen methane engine for methane fuel.