KR20200077310A - Apparatus and Method of Producing Methane Gas using Sewage Sludge - Google Patents

Abstract

An embodiment of the present invention relates to a methane gas production apparatus and method using sewage sludge, in which sewage sludge undergoes a hydrothermal carbonization process under conditions of a temperature of 180 to 220°C, a pressure of 10 to 40 bars, and a reaction time of 1 to 6 hours, and then the liquid product is fermented in an anaerobic digestion reactor, so that methane gas capable of increasing the anaerobic digestion rate can be produced. The produced methane gas can be useful as fuel for a heating device for heating a hydrothermal carbonation reactor.

Description

Apparatus and Method of Producing Methane Gas using Sewage Sludge}

The present invention relates to an apparatus and method for producing methane gas using sewage sludge.

As the industry level and economic growth, the number and/or capacity of sewage treatment plants increased, and accordingly, the amount of sewage sludge generated in the sewage treatment plants increased steadily. In the past, sewage sludge was also treated by ocean dumping, but such dumping is prohibited to prevent pollution of the marine environment.

On the other hand, the waste surplus sludge generated after sewage treatment can be said to be an energy source capable of expressing 3,000 to 4,000 kcal/kg of calorific value when dried with a solid content (% by weight, dry) of about 20 to 40%. Therefore, it is necessary to develop a technology that can be used as an energy source at the same time as the current sludge treatment, in which the necessity of energy recycling and the development of new energy resources are urgently needed in the era of high oil prices. However, sewage sludge having a water content of about 80% requires expensive energy in removing cell number (bound water) during the drying process, and thus has many restrictions on treatment and recycling, and also causes environmental problems such as odor generation. have.

In Korea, the amount of sewage sludge generated by about 600 sewage treatment facilities is more than 365 million tons per year. In addition, the Korea Environment Corporation estimates that 4.5 million tons of sewage sludge will be generated in 2020 and 5.3 million tons in 2025.

Accordingly, there is an urgent need to develop technologies that can treat sewage sludge in an eco-friendly, large-scale manner and simultaneously utilize it as an energy source.

Sewage sludge is the main material of the body of microorganisms having a size of 2 μm, and substances having a viscosity form flocs to form particles having a size of 100 to 1000 μm, and a large amount of moisture is contained inside the flocs and cell walls.

Current sewage sludge treatment technology consumes a lot of energy during drying, and has a problem that a large amount of odor is accompanied. In addition, when treated with general anaerobic digestion technology, the digestion efficiency due to the killing of microorganisms is lowered, thereby reducing the efficiency of methane generation. Therefore, there is a need for an apparatus and method for manufacturing methane gas using an environmentally friendly and low energy consumption type treatment technology by preventing air pollution such as odor.

Republic of Korea Patent Publication No. 10-2014-0145038

An object of the present invention is to provide an apparatus and method for producing methane gas using sewage sludge capable of producing methane gas therefrom by increasing the anaerobic digestion rate in treating sewage sludge.

In order to achieve the above object,

The present invention in one embodiment,

A hydrothermal carbonization reactor in which a raw material containing sewage sludge is introduced and hydrothermal carbonized the sewage sludge into a carbonization slurry;

A solid-liquid separator separating the solid product and the liquid product from the carbonized slurry;

An anaerobic digestion reactor for fermenting a liquid product to produce methane gas; And

Methane gas discharged from the anaerobic digestion reactor is supplied, and a heating device for heating the hydrothermal carbonization reactor using the supplied methane gas; It includes,

The hydrothermal carbonization reactor provides a methane gas production apparatus using sewage sludge, characterized in that it is performed under conditions of a temperature of 160 to 220°C, a pressure of 10 to 40 bar, and a reaction time of 1 to 6 hours.

The present invention in another embodiment,

Introducing a sewage sludge into a hydrothermal carbonization reactor to hydrocarbonize the sewage sludge in the hydrothermal carbonization reactor to prepare a carbonized slurry;

A step of fluidizing the carbonized slurry from a hydrothermal carbonization reactor to a solid-liquid separator, separating the solid product and the liquid product from the carbonized slurry;

Fluidly moving the liquid product from a solid-liquid separator to an anaerobic digestion reactor, and fermenting the liquid product to produce methane gas; And

Supplying methane gas to a heating device for heating the hydrothermal carbonization reactor; It includes,

The step of preparing the carbonized slurry provides a method for producing methane gas using sewage sludge, characterized in that it is performed under conditions of a temperature of 160 to 220°C, a pressure of 10 to 40 bar, and a reaction time of 1 to 6 hours.

According to the apparatus and method for producing methane gas using sewage sludge of the present invention, after the sewage sludge undergoes a hydrothermal carbonization process at a temperature of 160 to 220° C., a pressure of 10 to 40 bar and a reaction time of 1 to 6 hours, the liquid product is anaerobic. By fermenting in a digestion reactor, methane gas capable of increasing the anaerobic digestion rate can be produced.

1 is a schematic diagram of a methane gas production apparatus using sewage sludge according to an embodiment of the present invention.
2 is a schematic diagram of a discharge system of a hydrothermal hydrocarbon reactor according to an embodiment of the present invention.
3 is an overall conceptual diagram of a methane gas production apparatus using sewage sludge according to an embodiment of the present invention.
4 is a flowchart illustrating a method for producing methane gas using sewage sludge according to an embodiment of the present invention.
5 is a view evaluating the total solid (TS) of the process water in the experimental example of the present invention.
6 is a view showing the results of the BMP test performed in the experimental example of the present invention.

The present invention can be applied to various changes and can have various embodiments, and specific embodiments will be illustrated in the drawings and described in detail in the detailed description.

However, this is not intended to limit the present invention to specific embodiments, and it should be understood that all modifications, equivalents, and substitutes included in the technical scope of the present invention are included.

In the present invention, terms such as “comprises” or “have” are intended to designate the existence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and one or more other features. It should be understood that the existence or addition possibilities of fields or numbers, steps, actions, components, parts or combinations thereof are not excluded in advance.

In the present invention, the term "hydrothermal carbonization (HTC)" means that a material having a low water content and a water-mixed material or a material having a high water content is heated in a closed reactor and water is saturated by this heating. Refers to a process in which the carbonization reaction proceeds without evaporation of water as water vapor pressure is generated. Particularly, such hydrothermal carbonization is an easy technique for treating high-functional sewage sludge, and can remove moisture by mechanical dehydration after reaction without latent heat of evaporation, and thus has less energy consumption than drying techniques.

On the other hand, since the sewage sludge in the present invention has a high water content, a carbonization reaction may occur in the hydrothermal carbonization reactor without supplying additional water. Specifically, as heat is applied to the hydrothermal hydrocarbon reactor, the carbon content of the sewage sludge supplied to the hydrothermal hydrocarbon reactor may increase. In other words, oxygen and nitrogen of the sewage sludge are reduced by the hydrothermal reaction, and accordingly, the carbon content of the sewage sludge is relatively increased. The "sewage sludge" may mean organic wastes such as wastewater sludge and food waste including dyeing sludge.

In the present invention, “anaerobic digestion reaction” refers to a method of treating wastewater using microorganisms in an anaerobic state, also called anaerobic decomposition, and anaerobic bacteria reduce and decompose by ingesting organic matter in sludge, and useless It can mean releasing inorganic compounds. In the present invention, the anaerobic treatment process in the mesophilic temperature range can achieve a higher level of methanation and treatment stability than the thermophilic treatment.

The present invention relates to an apparatus and method for producing methane gas using sewage sludge.

Conventionally, in the treatment of sewage sludge, a lot of energy is consumed during drying, and there is a problem that a large amount of odor is accompanied. In addition, when treated with general anaerobic digestion technology, the digestion efficiency due to the death of microorganisms was lowered, resulting in a decrease in methane generation efficiency. In order to overcome this problem, the present invention provides an apparatus and method for hydrothermal carbonization of sewage sludge and improving digestion efficiency through an anaerobic digestion reaction of a liquid product generated at this time.

According to the present invention, the sewage sludge is fermented in an anaerobic digestion reactor by fermenting a liquid product subjected to a hydrothermal carbonization process at a temperature of 160 to 220° C., a pressure of 10 to 40 bar and a reaction time of 1 to 6 hours, thereby increasing the anaerobic digestion rate. Methane gas can be produced.

The methane gas thus produced can be usefully used as a fuel for a heating device for heating a hydrothermal carbonization reactor.

Hereinafter, the present invention will be described in detail. 1 is a schematic diagram of a methane gas production apparatus using sewage sludge according to an embodiment of the present invention.

Referring to FIG. 1, in the methane gas production apparatus using sewage sludge according to an embodiment of the present invention, a raw material containing sewage sludge is input, and a hydrothermal carbonization reactor 107 hydrothermal carbonizing the sewage sludge into a carbonization slurry. ; A solid-liquid separator 115 separating the solid product and the liquid product from the carbonized slurry; An anaerobic digestion reactor 200 for fermenting a liquid product to produce methane gas; And a heating device 108 for supplying methane gas discharged from the anaerobic digestion reactor 200 and heating the hydrothermal carbonization reactor 107 using the supplied methane gas. Including, the hydrothermal hydrocarbon reactor, the temperature is 160 to 220 ℃, pressure 10 to 40 bar and the reaction time is carried out under conditions of 1 to 6 hours.

According to an embodiment of the present invention, after the hydrothermal carbonization process under the above-described conditions, methane gas capable of increasing the anaerobic digestion rate can be prepared by fermenting the liquid product in an anaerobic digestion reactor. For example, the anaerobic digestion rate in the anaerobic digestion reactor of the present invention may be 75 to 85%, wherein, in the biogas produced in the anaerobic digestion reactor, the content of the methane gas may be 75 to 80%.

Hereinafter, a manufacturing apparatus and a process for producing methane gas using sewage sludge according to the present invention will be described in detail.

2 is a schematic view of the discharge system of the hydrothermal hydrocarbon reactor. Referring to Figure 2, the hydrothermal carbonization reactor 107, the reaction raw material is introduced through the inlet line, the reactant is completed through the outlet line is discharged. In the present invention, the hydrothermal carbonization reactor may be made in a hydrothermal carbonization reactor having a closed structure having an inflow line and an outflow line.

The hydrothermal hydrocarbon reactor is a high-pressure reactor, the reaction may proceed at a pressure higher than atmospheric pressure, and the allowable internal pressure of the hydrothermal hydrocarbon reactor may be 10 bar or more. In one example, the hydrothermal hydrocarbon reactor may have an allowable internal pressure in the range of 10 to 40 bar, 15 to 35 bar, 15 to 30 bar, 15 to 20 bar, or 16 to 19 bar.

The reactant that has flowed out through the hydrothermal carbonization reactor 107 outlet line is transferred to the reservoir 113a via the discharge member 112. The storage tank 113a may have a structure having a stirring means therein, and a solid-liquid separator 115 separating a solid component and a liquid component is sequentially connected to the rear end. The solid-liquid separator 115 separates and discharges the solid component and the liquid component. Here, the reaction raw material means sewage sludge, and the reactant after the reaction is completed may mean a carbonized slurry.

On the other hand, the discharge member 112 serves to continuously flow out the reaction is complete reaction in the hydrothermal carbonization reactor 107. The discharge member 112 may be a decompression means including a section in which pressure is sequentially or continuously depressurized along a fluid flow direction inside the member. In addition, the discharge member 112 may be a structure in which reactants flow out along a direction in which the screw rotates. In addition, the discharge member 112 is designed, for example, to have a structure in which the inner diameter increases sequentially or continuously along the fluid flow, or a structure in which the pressure decreases sequentially or continuously along the fluid flow. Here, the meaning of the'sequentially or continuously depressurized section' means that the pressure in the pipe through which the fluid moves is not temporarily lowered, but the pressure is sequentially or continuously lowered according to a certain distance or a certain time interval. it means. This is a concept different from a general discharge pump or a valve type discharge structure in which the pressure is temporarily lowered when the reactant is discharged.

3 is an overall conceptual diagram of a methane gas production apparatus using sewage sludge according to an embodiment of the present invention. Referring to FIG. 3, the sewage sludge, which is a reaction raw material, flows into the storage tank 101, and the sewage sludge accommodated in the storage tank 101 flows into the hydrothermal carbonization reactor 107 through the supply member 102. When the reactor water level is above a certain level, the supply member 102 stops the operation of the supply member or reduces the supply flow rate of the supply member. At this time, the hydrothermal carbonization reactor 107 is formed with a water level sensor for measuring the water level inside.

Auxiliary reactors 103a and 103b are located on the fluid flows of the supply member 102 and the reactor 107. If necessary, the auxiliary reactors 103a and 103b are structures in which two reactors are formed in parallel positions. In the auxiliary reactors 103a and 103b, preliminary carbonization is performed by preheating the sewage sludge in the range of 70 to 80°C or heating it in the range of 100 to 110°C.

Sewage sludge that has passed through the auxiliary reactors 103a and 103b flows into the hydrothermal carbonization reactor 107 under pressure at a pressure in the range of 10 to 40 bar. In addition, the catalyst stored in the chemical storage tank 105 is added into the hydrothermal carbonization reactor 107 via the chemical pump 106. Sulfuric acid is used as the catalyst. If necessary, the use of a catalyst can be excluded. On one side of the hydrothermal carbonization reactor 107, a separate heating device (heat oil heater) 108 is provided. Through the heating device 108, the hydrothermal carbonization reactor 107 is heated or the temperature is maintained. The inside of the reactor 107 is heated and pressurized in a temperature range of 160 to 220°C, a pressure of 10 to 40 bar, and a reaction time of 1 to 6 hours. For example, the inside of the reactor 107 may be heated and pressurized in a temperature range of 180 to 200°C and a reaction time of 4 to 5 hours. Under the heating and pressurizing conditions, the sewage sludge inside the reactor 107 is converted to a carbonized slurry (solid-liquid slurry) containing a solid product and a liquid desorption liquid through a carbonization process.

The reactant flows out through the outlet line of the hydrothermal hydrocarbon reactor 107. The reactant that flows out flows into the discharge member 112 through the first heat exchanger 109 and the second heat exchanger 110. The first heat exchanger 109 supplies the heat generated from the high temperature reactant discharged from the reactor 107 to the auxiliary reactors 103a and 103b. If necessary, the first heat exchanger 109 supplies heat to the auxiliary reactors 103a and 103b through the heating oil. In this case, the heat exchanger pump 104 is positioned between the first heat exchanger 109 and the auxiliary reactors 103a and 103b. In addition, a separate cooler 111 is formed on one side of the second heat exchanger 110. Through the second heat exchanger 110, the temperature of the reactants flowing into the discharge member 112 is cooled to 60 to 70°C.

The reactants introduced into the discharge member 112 undergo a process of being depressurized while passing through the discharge member 112. While passing through the discharge member 112, the pressure of the reactants is reduced from 10 to 40 bar to atmospheric pressure (about 1 bar). The discharge member 112 continuously discharges the reactant, and at the same time, the pressure of the reactant is sequentially or continuously lowered along the fluid flow direction inside the member. When the water level of the gas separator 113b is higher than a certain level, the discharge member 112 stops the operation of the discharge member or reduces the flow rate of the discharge member. At this time, the gas separator 113b is formed with a water level sensor for measuring the water level inside.

The reactant passed through the discharge member 112 flows into the solid-liquid separator 115. In the solid-liquid separator 115, the reactants are separated into a solid product and a liquid stripping liquid. The solid product may be utilized as a solid fuel such as a thermal power plant, and the liquid desorption liquid is supplied to an anaerobic digestion reactor and reused to generate methane gas.

For example, the solid-liquid separator 115 may be a filter press including a filter plate in which membranes are fused on both sides.

Specifically, the carbonized slurry may be introduced into the filter chamber formed between the filter plate and the filter plate, and the carbonized slurry may be primary dehydrated while being compressed on the filter plate by pressure introduced into the filter chamber. Next, when the pressure inside the filtration chamber exceeds a certain pressure, the primary dehydration is stopped, and the membrane can be expanded. Thus, the primary dehydrated carbonized slurry can be secondary dehydrated by a defined membrane.

As such, as the carbonized slurry is dehydrated twice, dehydration efficiency may be improved.

However, in this embodiment, the case where the solid-liquid separator is a membrane filter press is described as an example, but the spirit of the present invention is not limited thereto. For example, the solid-liquid separator may be a vacuum filter capable of mechanically dehydrating hydrothermal carbonized wastewater sludge, a centrifugal separator, a belt press, a filter press having a drying function, or the like.

Next, the anaerobic digestion reactor may be a reactor for producing methane gas.

Specifically, the anaerobic digestion reactor can hydrolyze polysaccharides, proteins, lipids, etc. included in the process water into monosaccharides, amino acids, glycerol, higher fatty acids, etc., and then induce the production of organic acids such as acetic acid or butyric acid. have.

The organic acid produced in this way can be fermented with methane. At this time, the gas generated in the process of fermenting the organic acid to methane may include methane, carbon dioxide, etc., of which methane gas may be supplied to the boiler. The anaerobic digestion reactor may be an anaerobic digestion reactor such as Continuous Stirred Tank Reactor (CSTR), Anaerobic Filter (AF), Upflow anaerobic sludge blanket digestion (UASB), and preferably UASB (Upflow anaerobic sludge blanket digestion) reactor. .

Meanwhile, the capacity of the anaerobic digestion reactor may range from 1/30 to 1/3 of the general anaerobic digestion tank. This can be on the order of one-third the capacity of a conventional anaerobic digestion reactor. This, prior to the anaerobic digestion reaction, the sewage sludge undergoes hydrothermal carbonization, thereby destroying the sludge floc to induce the release of protoplasm in the cell, thereby reducing the volume of the sludge, and through the dehydration process, only the liquid product flows into the anaerobic digestion reactor. The capacity of the digestion reactor can be reduced.

In addition, the methane gas production apparatus using the sewage sludge of the present invention is fluidly connected to the anaerobic digestion reactor 200 and the heating device 108, receiving methane gas from the anaerobic digestion reactor 200, sulfur component contained in the methane gas It may further include a desulfurizer 300 for removing.

Specifically, the desulfurizer 300 may remove hydrogen sulfide as a source of sulfur oxides contained in the methane gas. The desulfurizer 300 may be a conventional desulfurization device capable of removing hydrogen sulfide. For example, the desulfurizer 300 may include dry filtering means that substantially removes hydrogen sulfide contained in methane gas supplied therein. The dry filtering means may be a hepa filter capable of adsorbing and filtering fine foreign matter including hydrogen sulfide.

The methane gas that has passed through the desulfurizer 300 is supplied to a heating device 108 that heats the hydrothermal carbonization reactor 107, and may be used as fuel for the hydrothermal carbonization reactor 107.

Method for producing methane gas using sewage sludge according to an embodiment of the invention,

A step in which a sewage sludge is introduced into a hydrothermal carbonization reactor to hydrocarbonize the sewage sludge in the hydrothermal carbonization reactor to prepare a carbonized slurry (S100);

The carbonized slurry is fluidly transferred from a hydrothermal carbonization reactor to a solid-liquid separator, and separating a solid product and a liquid product from the carbonized slurry (S200);

A step of fluidly transferring the liquid product from the solid-liquid separator to the anaerobic digestion reactor, and fermenting the liquid product to generate methane gas (S300); And

The methane gas is supplied to a heating device for heating the hydrothermal carbonization reactor (S400); It includes,

The step of preparing the carbonized slurry is characterized in that it is performed under conditions of a temperature of 160 to 220°C, a pressure of 10 to 40 bar, and a reaction time of 1 to 6 hours (see FIG. 4).

Sewage sludge supplied to the hydrothermal carbonization reactor may refer to organic wastes such as wastewater sludge including dyeing sludge and food waste. In particular, the sewage sludge supplied to the hydrothermal carbonization reactor may be an organic waste having a high water content, specifically, the water content of the sewage sludge is 70 to 90%, 72 to 88%, 73 to 86% or 71 to 84% days Can.

For example, since the sewage sludge has a water content in the above-described range, a carbonization reaction may occur in the hydrothermal carbonization reactor without supplying additional water.

In the method for producing methane gas, the step (S100) of preparing a hydrocarbon slurry by hydrothermal carbonization of sewage sludge in a hydrothermal carbonization reactor is performed at a temperature of 160 to 220°C and a pressure of 10 to 40 bar and a reaction time of 1 to 6 hours, or Temperature 180 to 210 ℃ and pressure 15 to 35 bar and reaction time may be a 2 to 5 hours condition, preferably 180 to 200 ℃ and pressure 15 to 30 bar and reaction time may be 2 to 4 hours condition, more preferably It can be carried out in a hydrothermal hydrocarbon reactor at 180 ℃ and a pressure of 15 to 20 bar and a reaction time of 5 hours.

In the temperature range and pressure, it is possible to effectively improve the dehydration property of the reactants (sewage sludge) and to produce biogas having a high methane gas content. For example, when the reaction temperature is less than 160 °C, the organic content of the liquid product (process water) is low, so the amount of methane generation is limited. When the reaction temperature exceeds 220 °C, the ammonia concentration of the liquid product (process water) It can increase rapidly and adversely affect anaerobic digestion.

In addition, the reaction time in the hydrothermal carbonization reaction may be preferably 4 to 5 hours, and the organic material content (COD) in the liquid product increases in the above range to increase the amount of methane generated.

In the step of preparing a hydrocarbon slurry by hydrothermal carbonization in a reactor having a temperature of 180 to 220°C and a pressure of 10 to 40 bar and a reaction time of 1 to 6 hours, the sewage sludge is preheated to a temperature of 50 to 150°C. It can be introduced into the reactor. Specifically, the sewage sludge flows in a preheated state in the range of 50 to 110°C, which can prevent a rapid temperature change inside the reactor. Alternatively, the sewage sludge is introduced in a preheated state in the range of 120 to 150°C, in which case the sewage sludge is preliminarily or partially carbonized. This has the effect of increasing the carbonization efficiency of sewage sludge.

In one example, the carbonization slurry may be fluidly moved from a hydrothermal carbonization reactor to a storage tank, and may be performed through a step (S200) of separating a solid product and a liquid desorption solution from the carbonization slurry.

The solid product that has undergone the solid-liquid separation process may be dried to produce solid fuel, or may be subjected to a step of molding it. For example, in the step of forming the solid fuel, it may be molded into pellets or the like, and may be molded to a size of 50 mm in diameter and 100 mm in length or less. And, the liquid product can be transferred to an anaerobic digestion reactor to produce biogas containing methane gas.

Specifically, in the step of generating methane gas (S300), the liquid product may be anaerobic digested in the anaerobic digestion reactor 200 to generate methane gas, and the methane gas may be supplied as an energy source of a heating device.

The step of generating the methane gas may be performed under a condition of 15 to 40 hours at a temperature of 30 to 38 °C, for example, in the temperature range, 15 to 35 hours, 15 to 30 hours, or 15 to 20 hours Can be performed. According to an embodiment of the present invention, after a hydrothermal carbonization process, an anaerobic digestion reaction is performed, and methane gas can be generated in a relatively short time. For example, organic matter (COD) in a liquid product can be converted to biogas within 20 hours.

Next, the methane gas generated in the step (S400) for generating methane gas, may perform a step of removing the sulfur component contained in the methane gas. In addition, the methane gas from which the sulfur component has been removed may be supplied as an energy source of a heating device for heating the hydrothermal carbonization reactor 107.

According to an embodiment of the present invention, after the hydrothermal carbonization process under the above-described conditions, methane gas capable of increasing the anaerobic digestion rate may be prepared by fermenting the liquid product in an anaerobic digestion reactor. For example, the anaerobic digestion rate in the anaerobic digestion reactor of the present invention may be 75 to 85%, wherein, in the biogas produced in the anaerobic digestion reactor, the content of the methane gas may be 75 to 80%.

Hereinafter, the present invention will be described in more detail through examples. These examples are only for illustrating the present invention, it will be apparent to those skilled in the art that the scope of the present invention is not to be construed as limited by these examples.

<Example>

Example 1.

Methane gas was produced from sewage sludge using a methane gas production system. Specifically, 2 kg of the sewage slurry having a water content of 80% was heated and pressed for 4 hours in a hydrothermal carbonization reactor at a temperature of 180° C. and a pressure of 30 bar before and after the hydrothermal carbonization. Then, the fluid was transferred to a storage tank to separate the solid product and the liquid desorption liquid (hereinafter referred to as process water). The process water was fluidly transferred to an anaerobic digestion reactor, and fermented for 2 days at a temperature of 30 to 38° C. to prepare methane gas.

Comparative Example 1.

Methane gas was produced from sewage sludge using a thermal hydrolysis device and an anaerobic digestion device. The same sewage sludge as in Example 1 was thermally hydrolyzed for 90 minutes in a thermohydrolysis apparatus under conditions at 165°C and 6 to 9 atmospheres. Then, in the same anaerobic digestion apparatus as in Example 1, methane gas was prepared by fermenting at a temperature of 38 to 42° C. for 15 days.

Comparative Example 2.

Methane gas was produced from sewage sludge using an anaerobic digestion system. Methane gas was prepared by fermenting the same sewage sludge as in Example 1 in an anaerobic digestion apparatus for 25 days.

The results according to the main variables of Example 1 and Comparative Examples 1 and 2 are shown in Table 1 below.

Main variables Example 1 Comparative Example 1 Comparative Example 2 Anaerobic digestion residence time (days) 1-2 12~15 20~25 Digester capacity 0.03 0.3 One pH 6.5~8.0 7.5~8.0 6.8~7.5 Temperature (℃) 30-38 38-42 35~37 Methane content (%) 75-80 65-68 60-65 Digestion efficiency (%) 75~85 55-65 35~50

Referring to Table 1, when methane gas was prepared using the apparatus of Example 1 compared to Comparative Examples 1 and 2, the produced methane content and digestion efficiency were the highest, and the anaerobic digestion residence time of the process water was the shortest. In particular, the methane content in the biogas generated in Example 1 occupied 75 to 80%. In addition, Example 1 drastically reduced the residence time of the anaerobic digestion reactor.

This is considered to increase the amount of methane generated by hydrothermal carbonization of sewage sludge, increasing the organic matter content in the process water.

<Experimental Example>

Experimental Example 1. Process water evaluation

2 kg of sewage sludge having a water content of 80% was heated in a hydrothermal carbonization reactor at a temperature of 180° C. and a pressure of 30 bar before and after the hydrothermal carbonization. Then, the process water (liquid desorption liquid) was separated from the carbonized slurry. At this time, the hydrothermal carbonization process was performed hourly, and the COD _Cr and TS of the process water were evaluated after it was performed.

COD _Cr was analyzed by the method based on the water pollution process test standard (Es 04315.3 chemical oxygen demand-titration method-potassium dichromate method).

And the results are shown in Table 2.

unit 2 hours 3 hours 4 hours 5 hours COD _Cr mg/L 93,000 93,000 95,000 121,000 TS mg/L 111,270 110,000 103,000 97,040

Referring to Table 2, COD _Cr increased and TS material decreased as the reaction time increased.

Experimental Example 2. Process water evaluation-2

Hydrothermal carbonization was performed by heating and pressurizing 2 kg of sewage sludge having a water content of 80% in a hydrothermal carbonization reactor at a temperature of 220° C. and a pressure of 30 bar for 4 hours. Then, TS was measured by separating the process water (liquid desorption liquid) from the carbonized slurry, and this was compared with TS evaluated in 1 in the experiment, and this is shown in FIG. 5.

Referring to FIG. 5, TS values were lower when hydrothermal carbonization at 220° C. than when hydrothermal carbonization at 180° C. for 4 hours. On the other hand, the TS value decreased as the reaction time increased.

Experimental Example 3. Evaluation of BMP Test (Biochemical Methane Potential)

BMP Test is a living organism in a sample by measuring the amount of gas generated by anaerobic decomposition of the sample over time while placing a certain amount of sample in a container, inoculating a new anaerobic microorganism, and then sealing it to incubate at the optimum temperature (35~37 ℃). It is a method to evaluate the maximum amount of gas (methane) that can be generated from decomposable organic matter. Specifically, 1.5% NaOH solution is prepared by adding 1 L of each to the serum-bottle, 250 mL of granular microorganisms and 1.2 g of sodium bicarbonate, and 250 mL of the sample in the other serum-bottle (liquid product in the first serum-bottle (sewage sludge ) 250 mL, 250 mL of liquid product (food waste) was prepared in the second serum-bottle), and the amount of NaOH that was dropped into the graduated cylinder was measured every hour to calculate the converted amount of methane.

Referring to FIG. 6, as a result of the BMP test, both liquid products had a methane production amount in parallel within 8 hours, and it was determined that the biodegradable liquid product contained a large amount of organic matter as it appeared that the anaerobic decomposition of microorganisms was actively performed. Became.

So far, the present invention has been focused on the preferred embodiments. Those skilled in the art to which the present invention pertains will understand that the present invention may be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments should be considered in terms of explanation, not limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the equivalent range should be interpreted as being included in the present invention.

100: hydrothermal carbonization reactor
101: sludge storage tank 102: no supply
103a, 103b: auxiliary reactor 104: heating oil pump
105: chemical storage tank 106: chemical pump
107: reactor 108: heating device
109: first heat exchanger 110: second heat exchanger
111: cooler 112: exhaust member
113a: reservoir or gas separator 113b: gas separator
114: exhaust purifier 115: solid/liquid separator
200: anaerobic digestion reactor
300: desulfurizer

Claims (15)

A hydrothermal carbonization reactor in which a raw material containing sewage sludge is introduced and hydrothermal carbonizing the sewage sludge into a carbonization slurry;
A solid-liquid separator separating the solid product and the liquid product from the carbonized slurry;
An anaerobic digestion reactor for fermenting the liquid product separated from the carbonized slurry to produce methane gas; And
Methane gas discharged from the anaerobic digestion reactor is supplied, and a heating device for heating the hydrothermal carbonization reactor using the supplied methane gas; It includes,
The hydrothermal carbonization reactor, methane gas production apparatus using sewage sludge, characterized in that is carried out under conditions of a temperature of 160 to 220 ℃, pressure of 10 to 40 bar and reaction time of 1 to 6 hours.
According to claim 1,
The hydrothermal carbonization reactor, methane gas production apparatus using sewage sludge, characterized in that is carried out under conditions of a temperature of 180 to 200 ℃ and reaction time of 4 to 5 hours.
According to claim 1,
In the hydrothermal carbonization reactor, an inflow line flowing into the sewage sludge and an outflow line flowing through the carbonized slurry are formed,
Methane gas production apparatus using sewage sludge, which is fluidly connected to the inflow line, and includes a supply member for supplying sewage sludge.
According to claim 3,
An auxiliary reactor which is formed on a fluid line between the supply member and the hydrothermal carbonization reactor, and preheats or precarbonizes the sewage sludge supplied to the hydrothermal carbonization reactor;
A discharge member fluidly connected to the outlet line of the hydrothermal hydrocarbon reactor to discharge the carbonized slurry;
A heat exchanger formed on the fluid line between the hydrothermal carbonization reactor and the discharge member, and supplying heat generated from the high temperature carbonized slurry discharged from the hydrothermal carbonization reactor to the auxiliary reactor through heat transfer oil; And
A storage tank accommodating the carbonized slurry flowing out of the discharge member; Methane gas production apparatus using sewage sludge comprising a.
According to claim 4,
The discharge member is a methane gas production apparatus using sewage sludge, which is a decompression means that includes a section in which pressure is sequentially or continuously depressurized along a fluid flow direction therein.
According to claim 1,
A methane gas production apparatus using sewage sludge further connected to an anaerobic digestion reactor and a heating device, and further receiving a methane gas from the anaerobic digestion reactor to further remove a sulfur component contained in the methane gas.
According to claim 1,
Methane gas production apparatus using sewage sludge, characterized in that the water content of the sewage sludge supplied to the hydrothermal reactor is in the range of 70 to 90%.
According to claim 1,
Methane gas production apparatus using sewage sludge, characterized in that the capacity of the anaerobic digestion reactor is in the range of 1/30 to 1/3 of the general anaerobic digestion tank.
Introducing a sewage sludge into a hydrothermal carbonization reactor to hydrocarbonize the sewage sludge in the hydrothermal carbonization reactor to prepare a carbonized slurry;
The carbonized slurry is fluidly transferred from a hydrothermal hydrocarbon reactor to a solid-liquid separator, and separating the solid product and the liquid product from the carbonized slurry;
Fluidly moving the liquid product from a solid-liquid separator to an anaerobic digestion reactor, and fermenting the liquid product to produce methane gas; And
Supplying methane gas to a heating device for heating the hydrothermal carbonization reactor; It includes,
The step of preparing the carbonized slurry is a method for producing methane gas using sewage sludge, characterized in that it is performed under conditions of a temperature of 160 to 220°C, a pressure of 10 to 40 bar, and a reaction time of 1 to 6 hours.
The method of claim 9,
The step of preparing the carbonized slurry is a method for producing methane gas using sewage sludge, which is performed under conditions of a temperature of 180 to 200°C and a reaction time of 4 to 5 hours.
The method of claim 9,
Method for producing methane gas using sewage sludge, characterized in that the water content of the sewage sludge supplied to the hydrothermal carbonization reactor is in the range of 70 to 90%.
The method of claim 9,
In the step of manufacturing the carbonized slurry, the sewage sludge is a method for producing methane gas using sewage sludge, characterized in that it is supplied to the hydrothermal carbonization reactor in a preheated state to a temperature of 50 to 150 ℃.
The method of claim 9,
Methane gas using sewage sludge, characterized in that the carbonized slurry prepared in the step of preparing the carbonized slurry is discharged from the hydrothermal hydrocarbon reactor in a depressurized state via a section that is sequentially or continuously depressurized along the fluid flow direction. Manufacturing method.
The method of claim 9,
Methane gas produced in the step of generating methane gas, a method for producing methane gas using sewage sludge, characterized in that to perform the step of removing the sulfur component contained in the methane gas.
The method of claim 9,
The step of generating methane gas is a method for producing methane gas using sewage sludge, which is performed at a temperature of 30 to 38° C. for 15 to 40 hours.

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