KR20160057242A - Apparatus for dry anaerobic digestion and method for dry anaerobic digestion - Google Patents

Abstract

The present invention relates to an apparatus for dry anaerobic digestion and a method for dry anaerobic digestion. According to an embodiment of the present invention, an apparatus for dry anaerobic digestion includes: a thermal hydrolysis tank which thermally hydrolyzes food wastes by heating the food wastes; an acid fermentation tank which acid-ferments the hydrolyzed food wastes; a digestion tank which generates methane gas by methane-fermenting the acid-fermented food wastes; a stabilization tank which stabilizes digestion sludge generated from the methane-fermented food wastes; and an ammonia removal unit which removes ammonia components included in the digestion sludge, wherein an anaerobic digestion activating liquid is supplied to the acid fermentation tank.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a dry anaerobic digestion apparatus and a dry anaerobic digestion apparatus,

The present invention relates to a dry anaerobic digester and a dry anaerobic digestion method.

The London Convention, concluded in 1972, is an agreement to prevent marine pollution by dumping of waste and other substances. The Government of the Republic of Korea has enforced the ban on marine dumping of sludge and livestock manure by 2012 under the London Convention, The prohibition of marine dumping of waste trash (drinking waste water) was carried out. Therefore, it is urgent to secure alternative technologies for the treatment of waste water.

On the other hand, since the byproducts generated in the food waste treatment process are high concentration wastewater, there is a great burden on the installation and operation of wastewater treatment. Therefore, the government announced plans for establishing and implementing the "Waste Resource and Biomass Energy Conservation Measures" and is promoting an expansion project to expand the supply of renewable energy.

In this regard, the anaerobic digestion technology is suitable for the treatment of high-concentration food wastes, and biogas can be converted to electricity and heat and used in the private sector.

In Korea, there has been an attempt to commercialize foreign technologies. However, since the characteristics and reaction characteristics of organic matter contained in food wastes are different from those of other countries, there is a problem that the efficiency of treatment of food wastes using foreign technologies and methane gas generation efficiency are low .

Patent Document: Korean Registered Patent No. 10-0787074 (registered on December 12, 2007) Patent Document: Korean Registered Patent No. 10-1184555 (registered on September 9, 2012)

Embodiments of the present invention provide a dry anaerobic digester and a dry anaerobic digestion method in which methane gas generation stability and operation efficiency are improved.

According to an embodiment of the present invention, there is provided a heat dissolving tank for heating and solubilizing food wastes; An acid fermentation tank for fermenting the solubilized food waste; A digester for generating methane gas by fermenting the acid fermented food waste by methane; A stabilization tank for stabilizing the digested sludge generated from the methane fermented food wastes; And an ammonia removal device for removing the ammonia component contained in the digested sludge, wherein the acid fermentation tank is provided with a dry anaerobic digestion device to which anaerobic digestion active liquid is supplied.

In addition, the acid fermenter may be provided with the dry anaerobic digestion apparatus in which the digested sludge in which the ammonia component has been removed to a predetermined concentration or less is supplied by the ammonia removal apparatus.

In addition, the digester sludge may be provided with a dry anaerobic digester having an ammonia concentration of 3,000 mg / l or less and an alkalinity of 8,000 to 11,000 mg / l.

Also, the digested sludge may be supplied at a mass of 0.5 to 2 times the mass of the food waste, and the dry anaerobic digester may be provided.

Further, the thermal solubilizer may be provided with a dry anaerobic fire extinguisher which is heated by using a generator or waste heat of a boiler.

In addition, the anaerobic digestion active liquid may be a mineral, and may be provided with a dry anaerobic digestion apparatus containing at least one of Fe, Ni, and Co.

The method may further include a crushing separator for crushing and sorting the food waste, and a methane bacteria incubator for culturing the methane bacteria using the leachate of the food waste, which is crushed and sorted from the crushing separator, A dry anaerobic digester may be provided.

According to an aspect of the present invention, there is provided a method of manufacturing a food waste, An acid fermentation step of acidifying the thermally solubilized food waste; And a digestion step of fermenting the acid fermented food wastes by methane to produce methane gas. In the acid fermentation step, a dry anaerobic digestion method in which an anaerobic digestion active liquid is introduced into the acid fermentation tank where acid fermentation is performed may be provided have.

Also, the digested sludge generated in the digestion step is supplied to an acid fermentation tank where the ammonia contained in the digested sludge is removed to a predetermined concentration or less by the ammonia removal device, and then the food waste is acid-fermented. Can be provided.

Also, the thermal solubilization step may include a dry anaerobic digestion method of heating the food waste using waste heat of a generator or a boiler, and pulverizing the food waste with a fine pulverizing rotary blade.

Also, the anaerobic digestion activated liquid may be a mineral, and the mineral may include at least one of Fe, Ni, and Co.

Also, a dry anaerobic digestion method in which the ammonia concentration of the digested sludge is 3,000 mg / l or less may be provided.

Also, a dry anaerobic digestion method in which the ammonia concentration of the digested sludge is 3,000 mg / l or less and the alkalinity thereof is 8,000 to 11,000 mg / l may be provided.

Also, a dry anaerobic digestion method in which the pH of the acid fermentation tank is maintained at 5.0 to 6.0 and the pH of the digestion tank is maintained at 7.2 to 8.0 can be provided.

In addition, the digested sludge may be supplied at a mass of 0.5 to 2 times the mass of the food waste, and the dry anaerobic digestion method may be provided.

Further, before the heat-solubilization step, a step of crushing or sorting the food waste is performed. Culturing the methane bacteria using leached water of the food waste, which is crushed or selected; And a step of introducing the methane bacteria into the digester after the cultured methane bacteria are introduced into the digester.

Embodiments of the present invention can provide a dry anaerobic digestion apparatus and a dry anaerobic digestion method in which methane gas generation stability and operation operation efficiency are improved.

1 is a schematic view of a dry anaerobic digestion apparatus according to an embodiment of the present invention.
2 is a flowchart of a dry anaerobic digestion method according to an aspect of the present invention.
FIGS. 3 and 4 are graphs showing the rate of biogas production per volume of the anaerobic digestion tank under conditions in which no minerals are added to food waste. FIG.
5 is a graph showing the rate of biogas production under the condition that minerals are added to food wastes.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

A dry anaerobic digestion apparatus according to one aspect of the present invention is a device for producing methane gas (biogas) by fermenting food wastes using anaerobic bacteria. The apparatus includes a crushing separator (10), a methane bacteria incubator (100) A high temperature heat solubilization tank 20 having a pulverizing rotary blade, an acid fermentation tank 30 and a digester 40, a stabilizer tank 60 and an ammonia removing device 90.

In this embodiment, the dry anaerobic digestion process can be understood as a process involving organic wastes having a total solids concentration (TS) of 10 to 40%, and the food wastes can be used not only for general food waste but also for sewage sludge, It can be used to mean organic wastes such as livestock manure and organic wastes generated from biological wastes. In the food waste according to the present embodiment, the pretreatment step can be reduced to one stage or two stages or less.

The crushing and sorting machine 10 can sort contaminants or foreign substances contained in the high-concentration food waste to be introduced through the input hopper 11 and can crush the selected food waste in a predetermined size range of 5 to 30 mm. The selected contaminants or foreign matter in the crushing separator 10 can be buried.

The crushing and sorting machine 10 comprises a ball mill for putting a plurality of balls into a cylinder and crushing the crushing by the motion of the ball, a rod mill as a rotary crusher using a steel rod as a crushing medium, A mechanical device such as a crusher, a jaw crusher, an impact crusher, and a wheeler mill, or an ultrasonic device, a physical / chemical device such as a thermal treatment, etc. may be applied.

Although not shown, the food wastes that have been crushed and sorted by the crushing separator 10 may be stored in a storage tank or the like, and the food waste stored in the storage tank may be optionally supplied to the heat dissolution tank 20 as needed.

Meanwhile, the liquid leachate extracted from the food waste can be supplied to the methane bacteria incubator 100, and the methane bacteria incubator 100 can cultivate the methane bacteria using the leachate. When methane bacteria are cultured from leachate, the amount of methane bacteria to be cultured can be increased. The methane gas generated during the methane bacterial cultivation process can be transferred to the gas storage tank 50.

The heat-solubilization tank (20) has a function of heat-solubilizing and refining the selected food wastes, and the food wastes can be heat-solubilized by heating the crushed food waste. In addition, the food waste can be crushed and refined by having a grinding-type rotary blade. The hydrolysis in the acid fermentation tank 30 can be promoted as the food waste is thermally solubilized and refined in the heat-solubilization tank 20.

The heat source used in the heat-solubilization tank 20 may be waste heat supplied from a generator or a boiler 80. [ For example, the heat-solubilization tank 20 can heat the food waste to about 50 to 80 DEG C, and the heating time can be about 5 to 30 minutes. Here, the generator 80 may be a cogeneration power generator.

As the food waste is thermally solubilized and refined by the solubilization tank 20, the efficiency of digesting the food waste in the acid fermentation tank 30 and the digestion tank 40 can be improved, thereby improving the methane gas production rate have.

In addition, the heat dissolving tank 20 can directly heat the food waste, and the food waste can be thermally solubilized by injecting steam directly supplied or produced from the outside into the food waste. Further, although not shown, the heat-solubilization tank 20 may further include a heat exchanger for exchanging food waste with waste heat.

The acid fermentation tank 30 has a function of hydrolyzing and acidifying fermented food wastes. The fermented food wastes can be mixed with the digested sludge recovered from the digestion tank 40.

Specifically, the acid fermentation tank 30 is capable of hydrolyzing polysaccharides, proteins, and lipids contained in high-concentration food wastes into monosaccharides, amino acids, glycerol, higher fatty acids, etc., ₃ COOH) or butyl acid (C ₃ H ₇ COOH).

In this case, it is important to maintain the optimal environmental conditions in which the activity of the tuber-anaerobic bacteria can be activated in order for the smooth hydrolysis and the acid fermentation process to proceed. The pH and the mineral concentration on the acid fermentation tank 30 can be kept within a certain range and the digestion sludge of the digestion tank 40 is supplied to the acid fermentation tank 30 or the Fe, Minerals such as Co can be added. The acid fermentation tank 30 may include a stirring screw so that food waste, digested sludge, minerals and the like can be mixed evenly.

In general, the pH of food wastes is between 4.2 and 4.8, which means that lactic acid-producing bacteria or alcohol-producing bacteria can actively act at such pH. Therefore, the production of organic acid is lowered and lactic acid fermentation or alcohol fermentation can be actively performed.

On the other hand, since the pH concentration suitable for the growth of tuber-anaerobic bacteria, that is, organic acid-producing bacteria is 5.0 to 6.0, the pH of the food waste can be stabilized by supplying the acid fermentation tank 30 containing digester sludge containing an appropriate range of carbonate. The pH of the acid fermentation tank 30 may be maintained at 5.0 to 6.0, and the mass of the digested sludge may be 0.5 to 2 times the mass of the food waste.

At this time, the alkalinity of the circulated digestion sludge can be adjusted by the ammonia removal device 90. The ammonia removing device 90 will be described later.

Table 1 shows that the amount of organic acid such as acetic acid, propionic acid, and butyric acid was increased as the digested sludge was mixed with the food waste.

unit

Acid fermenter
Digester Mixing ratio
(Amount of digestion sludge
/ Food quantity)
0
0.5
One
0
0.5
One
Acetic acid

mg / l
4,672
3,809
2,537
252
22
31
Propionic acid

mg / l
562
357
186
65
53
64
Butyl Acid

mg / l
2,152
2,963
3,956
350
0
0

On the other hand, the anaerobic digestion active liquid can be added to the acid fermentation tank 30. The anaerobic digestion active liquid is a substance capable of activating anaerobic digestion, and may be, for example, a mineral. The anaerobic digestion active liquid may be a substance that helps the growth of the thermogenic anaerobic bacteria in the acid fermentation tank 30 or the methane bacteria of the digestion tank 40. The efficiency and rate of organic acid and methane gas generation may be increased as the anaerobic digestion active liquid is added . When the anaerobic digestion activating liquid is a mineral, the type of the minerals may be one or more of Fe, Ni, and Co.

The anaerobic digestion activity liquid may be a mixed solution supplied by mixing Fe, Ni, and Co, or may be mixed in an acid fermentation tank 30 after separately supplying Fe, Ni, and Co from the respective feeders.

FIG. 3 and FIG. 4 show the rate of biogas production under the condition that minerals are not added to the food waste, and FIG. 5 shows the rate of biogas production under the condition that minerals are added to the food waste.

3 and 4, when the mineral is not introduced into the acid fermentation tank 30, the stop period of the continuous operation varies depending on the mixing ratio with the sludge. However, in the digestion tank 40, After this time, biogas (methane gas) production was not achieved.

4, compared to the control experiment in FIG. 3, the anaerobic digestion activity was maintained at a level of soluble Fe of 100 to 300 mg / l and a concentration of Ni and Co of about 0.5 to 5 mg / l during the experiment And then put into the fermenter (30). It can be seen that when minerals are added, methane gas production continues at a similar rate to that at the beginning, even after a lapse of time.

The Fe component can enhance the activity of the hydrogenase enzyme present in the acid fermentation tank 30 and help to convert it into a fermentation form of hydrogen and organic acid (acetic acid, butyric acid). In addition, the Fe, Ni, and Co components increase and maintain the activity of methanogenase present in the digester 40 and become essential components for the growth of anaerobic microorganisms.

On the other hand, the digester 40 is capable of fermenting organic acids with methane. Methane can be produced by methane fermentation of the organic acid by methane bacteria, which is a kneading anaerobic bacteria. The gas generated during the fermentation of the organic acid by methane may include methane, carbon dioxide, etc., and the methane gas may be stored in the gas storage tank 50. And the gas stored in the gas reservoir 50 may be supplied to the generator / boiler 80.

The digester 40 may include an active reaction between a food waste containing organic acid (hereinafter referred to as "digestive liquid") and methane bacteria, and a circulation device capable of circulating the digestive juice to maintain the carbonate circulation cycle.

Methane bacteria cultured from the methane bacteria incubator 100 may be introduced into the digester 40. When the methane bacteria are further added to the digester 40, the digester 40 can be operated stably even when the organic acid load included in the food waste is excessively increased. For example, depending on the type of food waste, the concentration of organic acid contained in the food waste may be changed. In this case, methane bacteria may be added depending on the concentration of the organic acid, so that the digestion efficiency of the digester 40 can be stably maintained have.

Meanwhile, the stabilization tank 60 can precipitate the extinguishing sludge discharged from the digestion tank 40, and as the extinguishing sludge is settled in the stabilization tank 60, it can be separated into a solid layer and a liquid-phase independent layer , The high concentration ammonia component in the digested sludge can be removed by the ammonia removal device 90 before it is circulated to the acid fermentation tank 30.

The ammonia removing device 90 is a device for removing ammonia from the digested sludge discharged from the stabilizing tank 60. The ammonia removing device 90 may be a stripping device for removing the ammonia gas after gasifying the ammonia component dissolved in the digested sludge. The ammonia removal device 90 may be operated at a reaction temperature of 50 ° C to 80 ° C to improve the gasification reaction rate of ammonia, and hydrogen peroxide (H 2 O 2) may be added to improve the removal efficiency of the ammonia component.

The alkalinity of the digested sludge in which the ammonia component is removed by the ammonia removing unit 90 can be maintained at 8,000 to 11,000 mg / l and the ammonia concentration can be maintained at 3,000 mg / l or less.

Then, the digester sludge having an appropriate alkalinity is transferred again to the acid fermentation tank 30 to maintain the pH of the acid fermentation tank 30 at an appropriate pH, for example, in the range of 5.0 to 6.0, and the pH of the digester 4 It can be maintained at an appropriate pH, for example, 7.2 to 8.0.

Meanwhile, the dehydrator 70 dehydrates the digested sludge, the sludge cake among the dehydrated digested sludge is buried, and the wastewater can be treated by a separate wastewater treatment apparatus or the like.

Hereinafter, a dry anaerobic digestion method according to one aspect of the present invention will be described.

First, the collected food waste can be introduced into the crushing sorter 10 through the input hopper 11. The crushing and sorting machine 10 can filter out the impurities contained in the food waste and crush the food waste to a predetermined size (S100).

The liquid wastewater from the food wastes discharged from the crushing separator 10 may be extracted S110 and supplied to the methane bacteria incubator 100. Methane bacteria may be cultured by the methane bacteria incubator 100 have. The methane bacteria generated in this process may be introduced into the digester 40 (S130). Methane gas or the like may be extracted (S140) and then transferred to the gas storage tank 50 for storage.

Further, the leachate may be supplied to the high-temperature heat-solubilization tank 20 having the fine-pulverized rotary blade of the separated food waste to be thermally solubilized (S200).

The heat-solubilization tank 20 can heat-treat the food waste using the waste heat supplied from the generator or the boiler 80, and the food waste can be easily dissolved in an acid fermentation tank in a state of being easily decomposed. The heat-solubilization tank 20 can use steam as a heat source as waste heat, and can heat treat the waste water by using steam or the like to spray food waste.

In this case, since the thermal solubilization step (S200) is performed before the introduction of the digestion sludge (S320), the anaerobic bacteria contained in the digestion sludge can be prevented from being killed.

The food waste having undergone the pretreatment process such as crushing / sorting and heat-solubilization can be acid fermented (S300) in the acid fermentation tank 30. The digested sludge recovered from the digestion tank 40 is introduced into the ammonia removal unit 90 through the stabilization tank 60. The digested sludge recovered from the digestion tank 40 may be introduced into the anaerobic digestion activated sludge, (S610) with the ammonia removed from the acid fermentation tank 30.

At this time, the ammonia removal device 90 can maintain the ammonia concentration in the digested sludge to 3000 mg / l or less and the alkalinity to 8,000 to 11,000 mg / l or less. The digestion sludge from which ammonia has been removed from the acid fermentation tank 30 is introduced into the acid fermentation tank 30 and the digester 40 to maintain the proper alkalinity.

Also, circulating digestion sludge titratable alkalinity can be controlled by lowering the hydrogen partial pressure of acid fermentation to produce an organic acid fermentation pattern of acetic acid and butyric acid. Meanwhile, nutrients or enzymes necessary for the growth of the anaerobic bacteria can be supplied by inputting the anaerobic digestion active liquid into the acid fermentation tank 30. Therefore, the acid fermentation tank 30 can be maintained in an optimized state for the growth of anaerobic bacteria, and organic acid fermentation centered on acetic acid (CH ₃ COOH) or butyl acid (C ₃ H ₇ COOH) have.

In addition, when the anaerobic digestion activating liquid is a mineral, the mineral component generally exists in an ionized state in the solution, and minerals such as Fe, Ni, Co and the like can be combined with OH constituting H ₂ O, The concentration can be increased. That is, when only minerals are simply added to the acid fermentation tank 30, the pH of the acid fermentation tank 30 may be lowered so that the effect of activating acid fermentation may not be conspicuous. Therefore, by adding minerals and digested sludge to the acid fermentation tank 30, the effect of pH adjustment of the acid fermentation tank 30 can be enhanced.

The digestion liquid in which acid fermentation is completed can be extinguished in the digester 40 (S400). That is, an acid fermentation broth containing an organic acid in which hydrolysis and acid fermentation are completed due to action of acid-producing bacteria such as tuberous anaerobes may be methane fermentation by methane bacterium, which is a combined anaerobic bacteria, and organic acids may be converted into methane gas . At this time, the methane bacteria cultivated from the methane bacteria incubator 100 may be introduced into the digester 40 (S130), so that even when the concentration of the organic acid is excessively increased, the methane fermentation can be smoothly performed, 40) can be stabilized by methane fermentation.

Also, since the pH of the digestive juice flowing into the digestive tank 40 at this time is maintained at 5.0 to 6.0, it is possible to prevent the pH of the digestive tank 40 from being excessively elevated due to methane fermentation.

Meanwhile, the methane gas generated in the digester 40 may be stored in the gas storage tank 50 and used for power generation of the generator 80 or heating of the boiler 80.

Meanwhile, the digested sludge remaining in the digestion tank 40 is transferred to the stabilization tank 60 and undergoes the stabilization step S600. Among them, the ammonia component contained in the digested sludge is transferred to the acid fermentation tank 30 through the ammonia Removed by the removal device 90, and then introduced into the acid fermentation tank 30 (S610). And the other digested sludge is dehydrated (S700). The sludge cake can be composted by the composting device or can be used as a raw material for the compost without a composting device. The wastewater can be subjected to a separate wastewater treatment (S800) Wastewater from which components have been removed can result in lower operating costs than existing plants.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand. For example, a person skilled in the art can change the material, size and the like of each constituent element depending on the application field or can combine or substitute the embodiments in a form not clearly disclosed in the embodiments of the present invention, Of the range. Therefore, it should be understood that the above-described embodiments are to be considered in all respects as illustrative and not restrictive, and that such modified embodiments are included in the technical idea described in the claims of the present invention.

10: crushing separator 20: thermal solubilization tank
30: acid fermentation tank 40: digester
50: gas storage tank 60: stabilization tank
70: Dehydrator 80: Generator
90: Ammonia removal apparatus 100: Methane bacteria incubator

Claims (15)

A heat-solubilization tank for heating and solubilizing food waste;
An acid fermentation tank for fermenting the solubilized food waste;
A digester for generating methane gas by fermenting the acid fermented food waste by methane;
A stabilization tank for stabilizing the digested sludge generated from the methane fermented food wastes; And
And an ammonia removing device for removing the ammonia component contained in the digested sludge,
The acid fermentation tank is supplied with the anaerobic digestion active liquid
Dry anaerobic digester. The method according to claim 1,
In the acid fermentation tank,
And the digester sludge in which the ammonia component has been removed to a predetermined concentration or less is supplied by the ammonia removing apparatus
Dry anaerobic digester. 3. The method of claim 2,
Wherein the ammonia concentration of the digested sludge is less than or equal to 3,000 mg / l and the alkalinity is from 8,000 to 11,000 mg / l. 3. The method of claim 2,
Wherein the digested sludge is fed at a mass of 0.5 to 2 times the mass of the food waste. The method according to claim 1,
The heat-
The dry anaerobic digester is heated by using the waste heat of the generator or the boiler. The method according to claim 1,
The anaerobic digestion active liquid may be,
Mineral, and comprising at least one of Fe, Ni, and Co. The method according to claim 1,
A crushing separator for crushing and sorting the food waste, and
Further comprising a methane bacterium culture device for cultivating methane bacteria using leachate of the food waste which has been crushed and selected from the crushing separator, wherein the methane bacteria cultivated are supplied to the digestion tank. Heating food wastes to heat-solubilize them;
An acid fermentation step of acidifying the thermally solubilized food waste;
And an extinguishing step of producing methane gas by fermenting the acid fermented food wastes by methane,
In the acid fermentation step,
In the acid fermentation tank in which the acid fermentation is performed, a dry anaerobic digestion method 9. The method of claim 8,
The digested sludge generated in the digestion step may include:
Wherein ammonia contained in the digested sludge is removed to a predetermined concentration or lower by an ammonia removing device, and then the food waste is fed into an acid fermentation tank where acid fermentation is carried out, 9. The method of claim 8,
Wherein the heat-
A method of dry anaerobic digestion wherein the food waste is heated using waste heat of a generator or a boiler, and the food waste is pulverized by a fine pulverizing rotary blade. 9. The method of claim 8,
The anaerobic digestion active liquid is a mineral,
Wherein the mineral comprises at least one of Fe, Ni, and Co. 10. The method of claim 9,
Wherein the ammonia concentration of the digested sludge is less than or equal to 3,000 mg / l and the alkalinity is less than or equal to 8,000 and less than or equal to 11,000 mg / l. 10. The method of claim 9,
Wherein the pH of the acid fermentation tank is maintained at 5.0 to 6.0, and the pH of the digestion tank is maintained at 7.2 to 8.0. 10. The method of claim 9,
Wherein the digested sludge is fed at a mass of 0.5 to 2 times the mass of the food waste. 9. The method of claim 8,
Before the heat-solubilization step,
Crushing and sorting the food waste;
Culturing the methane bacteria using leached water of the food waste, which is crushed or selected; And
And introducing the methane bacteria into the digestion tank.

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