KR100609000B1 - An apparatus and the method for hydrogen and methane production by using waste activated sludge - Google Patents

Abstract

The present invention relates to an apparatus for producing hydrogen and methane using waste activated sludge, and more particularly, to pre-treatment of waste activated sludge, and upon the generation of hydrogen, conditions suitable for the growth of hydrogen producing bacteria are added. It is characterized by being able to produce hydrogen and methane while maximizing the treatment of waste activated sludge by adding conditions suitable for the growth of methane producing bacteria. According to the present invention, by generating hydrogen and methane using waste activated sludge which is an organic waste, it is possible to solve the problem of disposal and disposal of organic waste and to efficiently produce hydrogen and methane, which are alternative energy, by a biological method.

Waste activated sludge, hydrogen, methane, pretreatment, pH control

Description

An apparatus and the method for hydrogen and methane production by using waste activated sludge}             

1 is a view schematically showing an apparatus for producing hydrogen and methane using waste activated sludge and a treatment process of the method according to the present invention;

* Explanation of symbols for the main parts of the drawings

 10: pretreatment reactor 20: hydrolysis reactor

 30: hydrogenation reactor 40: reactor for pH adjustment

 50: methane production reactor

 11: inflow pump 12: return pump

 13: stirring device 14: heating device

The present invention relates to an apparatus for producing hydrogen and methane using waste activated sludge, and more particularly, to pre-treatment of waste activated sludge, and upon the generation of hydrogen, conditions suitable for the growth of hydrogen producing bacteria are added. It is characterized by being able to produce hydrogen and methane while maximizing the treatment of waste activated sludge by adding conditions suitable for the growth of methane producing bacteria.

Recently, with the increase of population and the development of industry, the sewage treatment plant has increased in number, and the amount of waste activated sludge, which is a waste generated in each sewage treatment plant, is increasing rapidly every year. For example, in Korea, as of the end of 2003, about 6.210 tons of waste activated sludge are generated per day.

One of the biggest problems facing urban sewage treatment plants is the treatment and disposal of waste activated sludge, which is reported to account for more than 50% of the total operating cost of sewage treatment plants (2003, Ministry of Environment). Sewage statistics).

In Korea, most of the final treatment and disposal of waste activated sludge has been reliant on landfill and marine discharge methods, but landfilling is currently banned entirely. It is strengthening.

Therefore, research is underway to recycle waste activated sludge. Given this reality, it is now urgent to recognize waste activated sludge as a product that can be reused as a resource rather than as a waste, and to develop treatment and disposal technologies for effective reduction and reduction of resources.

On the other hand, since hydrogen energy does not emit carbon dioxide, which is the source of greenhouse gases, when it is burned, it is clean, renewable, and shows higher energy efficiency than petroleum, so it is possible to replace fossil fuel, which is a major energy source. Its importance began to be recognized as energy. Hydrogen energy is recently spotlighted as clean energy that can fundamentally solve global warming and various environmental problems.

However, conventionally known methods for generating hydrogen include pyrolysis through naphtha reforming, electrolysis of water, etc. These methods obtain reactive materials from fossil fuels, high or high operating conditions, or excessive operating costs. There are disadvantages.

As another method of hydrogen generation, hydrogen can be produced through fossil fuels, biomass and chemical or biological processes, among which biological hydrogen production is a very economical and ideal method of producing energy with reduction of waste. (Das D, Veziroglu TN, J. Hydrogen Energy , 21 , pp 13-28, 2001).

As a biological hydrogen production process, research is being conducted to generate hydrogen using organic materials in water such as high concentrations of wastewater, solid waste, molasses, glucose, and crystallized cellulose (Lay JJ, et al., Water res , 33 (11), pp 2579-2586, 1999). In particular, anaerobic technology that generates hydrogen by using waste, such as sludge sludge, as an organic source, can improve the recovery rate of organic waste, improve the recovery rate of bioenergy, and secure hydrogen generation technology that is spotlighted as future energy. This is a key technology that needs to be developed. However, although several studies have been conducted overseas on the generation of hydrogen using sludge sludge, most of them are simple studies such as batch type, and the results are almost unknown due to treatment efficiency and operational difficulties.

Accordingly, the present invention is to solve the above problems, the present invention solves the problem of disposal and disposal of organic waste and at the same time provide a method capable of stably and continuously generating hydrogen and methane as alternative energy in a biological method. It aims to do it.

That is, the present invention is pre-treated to effectively use the waste activated sludge as a substrate for hydrogen and methane production, and when the hydrogen is generated, conditions suitable for the growth of hydrogen-producing bacteria are added, and conditions for the growth of methane-producing bacteria are added to the methane production It is an object of the present invention to provide an apparatus and method for producing hydrogen and methane using waste activated sludge which can generate hydrogen and methane while maximizing the treatment of waste activated sludge.

Hydrogen and methane generating apparatus using waste activated sludge according to the present invention for achieving the above object is, pretreatment to pre-treat to discharge to the outside by destroying organic matter in the waste activated sludge by adjusting to pH1 to pH2 or pH12 to pH14 Reactor; Reaction tank conditions are adjusted to a pH range of 5 to 6 for hydrogen producing bacteria growth conditions, the hydrogen production reactor for producing hydrogen from the waste activated sludge pretreated by the pretreatment reactor; And a methane generating reactor in which the pH of the reactor is adjusted to neutral for methane producing bacteria growing conditions, and methane is generated from the waste activated sludge treated by the hydrogen generating reactor.

In addition, the hydrogen and methane production method using waste activated sludge according to the present invention, the step of controlling the waste activated sludge by adjusting to pH1 to pH2 or pH12 to pH14; Generating hydrogen from the waste activated sludge pretreated in this step, adjusting the pH to a range of 5 to 6 for hydrogen producing bacteria growth conditions; And producing methane from waste activated sludge which has undergone the hydrogen generation step by adjusting the pH to neutral for methane producing bacteria growth conditions.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

1 is a view schematically showing an apparatus for producing hydrogen and methane using waste activated sludge and a treatment process of the method according to the present invention.

Waste activated sludge used in the present invention is a sludge produced as a result of treatment of waste in a sewage treatment plant by a biological treatment process, and is a high concentration of organic material in which most components are microorganisms.

Waste activated sludge is first introduced into the pretreatment reactor 10 through the inlet pump 11. In the pretreatment reactor 10, the pH is adjusted to be in a strongly acidic state (pH 1 to 2) or a strong basic state (pH 12 to 14), thereby destroying the cell walls and cell membranes of microorganisms, which are components of waste activated sludge, so that the organic matter inside So that it can easily flow out.

In order to adjust the pH in the pretreatment reactor 10, a strong acid solution (concentrated hydrochloric acid) or a strong base solution (10N sodium hydroxide solution) is injected into the pretreatment reactor 10. The pH is monitored through a pH sensor (not shown) installed in the pretreatment reactor 10 to adjust the injection amount of the strong acid solution or the strong base solution to maintain the desired pH. Preferred pH of the pretreatment reactor 10 is pH 1 to 2 for strong acidic conditions, and pH 12 to 14 for strong basic conditions.

In the pretreatment reactor 10, waste activated sludge pretreated in a strongly acidic state or a strong basic state is transferred to the hydrolysis reaction tank 20. In the hydrolysis reaction tank 20, the pH of the pretreated waste activated sludge is adjusted to a range of 6 to 7 in order to prevent the pH from being rapidly changed in the next step of the hydrogen production reactor.

In the case of waste activated sludge pretreated in a strongly acidic state in the pretreatment reactor 10, a strong base solution such as 10N sodium hydroxide solution is directly injected into the hydrolysis reactor 20 to adjust the pH to be in the range of 6 to 7, and pretreatment. In the case of waste activated sludge pretreated in a strong basic state in the reactor 10, a strong acid solution such as a concentrated hydrochloric acid solution is directly injected into the hydrolysis reactor 20 to adjust the pH to be in the range of 6 to 7. While monitoring the pH through a pH sensor (not shown) installed in the hydrolysis reaction tank 20 to adjust the injection amount of a strong basic solution or a strong acid solution to maintain the desired pH. In the hydrolysis reaction tank 20, waste activated sludge whose pH is adjusted in the range of 6 to 7 is transferred to the hydrogenation reaction tank 30.

In the present invention, the hydrolysis reactor 20 is an additional component for preventing the pH from changing rapidly between the pretreatment reactor 10 and the hydrogen production reactor 30. Therefore, even when the hydrolysis reaction tank 20 is not provided, that is, waste activated sludge is transferred directly from the pretreatment reaction tank 10 to the hydrogenation reaction tank 30 to adjust the pH to achieve the object and effect of the present invention. There is no problem.

In the hydrogen generation reactor 30, the hydrogen is generated by the hydrogen producing bacteria, and the pH is adjusted to a range of 5 to 6 so as to be suitable for the growth of the hydrogen producing bacteria. If the pH is greater than 6, the activity of the methane producing bacteria is not preferable, and if the pH is less than 5, the activity of the hydrogen producing bacteria itself is lowered.

Hydrogen-generating bacteria are inoculated after heat treatment for 20 minutes at 80 ° C. or higher in the anaerobic digester of a general sewage treatment plant at the beginning of operation. In the present invention, since the hydrogen-producing bacteria are not purely cultured and used, anaerobic microorganisms of a general sewage treatment plant are used, so that initial inoculation is easy and commercialized.

For pH adjustment in the hydrogen production reactor 30, an acidic solution such as 1 N hydrochloric acid or a basic solution such as 1 N sodium hydroxide solution is injected into the hydrogen production reactor 30. The pH is monitored through a pH sensor (not shown) installed in the hydrogen generation reactor 30 to adjust the injection amount of the acidic solution or the basic solution to maintain the desired pH. In addition, in the hydrogen generation reactor 30, a pH 5 to pH 6 buffer solution may be added so that the pH does not change rapidly and remains constant.

Baffles are installed inside the hydrogen generation reactor 30 to minimize the loss of hydrogen producing bacteria, and hydrogen generation reactions occur independently while the waste activated sludge in solid form flows into the hydrogen generation reactor 30. To do that.

Since 2 mol of hydrogen is required to generate 1 mol of methane, it is very important that the hydrogen generating reactor 30 does not generate a methane generating reaction. To this end, in the present invention, not only the pH in the hydrogen production reactor 30 is adjusted to be suitable for the growth of hydrogen producing bacteria, but also the transfer pump 12 and the heating device 14 are added to the rear end of the hydrogen production reactor 30. The waste activated sludge may be further heat-treated to suppress the growth of methane-producing bacteria and then returned to the top of the hydrogen production reactor 30.

Methane-producing bacteria are very weak to heat, whereas hydrogen-producing bacteria are spore-forming bacteria that, when exposed to heat, can form spores and survive at high temperatures. Therefore, methane-producing bacteria in waste activated sludge returned by the heating device 14 are deactivated. Hydrogen-producing bacteria can survive to maximize hydrogen production efficiency.

The heating temperature by the heating apparatus 14 is heated so that it may be 80 degreeC-100 degreeC, Preferably it is 90 degreeC-100 degreeC, and the time for which waste activated sludge stays and heats in a heating apparatus is about 15 to 20 minutes. It is preferable. At this time, if the heating temperature is low, the residence time is relatively long, and if the heating temperature is high, the residence time is relatively short.

Waste activated sludge which passed through the hydrogen production reactor 30 is transferred to the methane production reactor 50, and in the methane production reactor 50, methane is produced by the methane producing bacteria by adjusting the pH to be suitable for the growth of methane producing bacteria. do.

Methane producing bacteria are used by inoculating microorganisms in an anaerobic digester of a general sewage treatment plant at the beginning of operation. In the present invention, since the methane producing bacteria are not purely cultured and used, anaerobic microorganisms of a general sewage treatment plant are used, so that initial inoculation is easy and commercialized.

In order to adjust the pH in the methane production reactor 50, the pH is adjusted to neutral by injecting an acidic solution such as 1N hydrochloric acid solution and 1N sodium hydroxide solution in a reactor 40 for separate pH adjustment. It may then be transferred to the methane production reactor (50).

The present invention will be described in more detail with reference to the following examples. However, the following examples are merely illustrative of the present invention and the present invention is not limited thereto.

<Example 1>

In Example 1, in order to produce hydrogen and methane using the waste activated sludge of the present invention, the following experiment was performed to find the most effective as a pretreatment method.

First, the waste activated sludge is treated in a laboratory scale pretreatment tank 10 with chemical methods (pH control, ozone treatment), physical methods (crushing, heat treatment, sonication, electrolysis treatment) and biological methods (hydrolysis treatment). After each pretreatment, the change value of the sludge carbon source (SCODcr) was measured. PH control of the chemical method was adjusted to a strongly basic state of pH 12. The results are shown in Table 1 below.

As a result, as shown in Table 1, when adjusting the pH, the sludge carbon source (SCODcr) value showed the highest value, the rate of increase was 14.6% compared to raw water.

Through this, it can be seen that by adjusting the pH, the cell wall and the cell membrane of the microorganisms in the waste activated sludge are destroyed and the organic matters are eluted to increase the SCODcr level.

<Example 2>

In Example 2, the following experiment was carried out to determine the efficiency of hydrogen generation for each waste activated sludge pretreated in Example 1.

First, each 160 ml test bottle was used as a hydrogen production reactor 30, and each test bottle was subjected to 90-100 ° C of microorganisms in the anaerobic digester of the J sewage treatment plant (where waste activated sludge was obtained in Example 1). 20 ml of the obtained microorganisms were inoculated by heating for about 20 minutes at 100 ml, and 100 ml of waste activated sludge pretreated by each method was added in Example 1, and MES (C ₆ H ₁₃ NO ₄ S.H ₂ ) was added as a buffer solution. About 5 ml of O) was injected at 3 M to prevent a sudden change in pH during the operation period so that the pH in the test bottle was maintained at pH 5.5, and a small amount of nutrients was injected. Then, nitrogen gas was sufficiently injected into each of the test bottles to make the anaerobic condition, and the mixture was stirred in a stirring incubator while maintaining a temperature of 30 ° C., and then cultured in a test bottle so as to mix well.

In addition, the amount of hydrogen generated according to the culture time was measured using a syringe, and the amount of hydrogen generated was measured by measuring the content of hydrogen in the generated gas using GC (Hewlett Packard 5880A). The results are shown in Table 2 below.

<Example 3>

In Example 3, the following experiment was carried out to determine the properties of the gas generated when the pretreated waste activated sludge was not heat treated and when heat treated.

At this time, the hydrogen production reactor 30 as shown in FIG. 1 was used, and the concentration of TSS (Total Suspended Solid; total suspended solids) was concentrated by adjusting the pH-activated waste activated sludge in Example 1. 30,000 mg / L was injected into the reactor 30 using a metering pump in an amount of 1 L per day. In addition, the internal volume of the hydrogen generation reactor 30 is 3 L, so that the residence time is 3 days, the hydrogen generation reactor 30 is acid (1N) so that the pH electrode is installed to maintain the pH in the range of 5 to 5.5 HCl) and base (1N NaOH) were added automatically. Meanwhile, the generated gas was collected in the gas collecting tube to measure the amount of generated gas, and the generated gas was measured using GC (Hewlett Packard 5880A).

In the initial operation, the waste activated sludge in the reaction tank 30 was operated under a condition that no heating device was installed, and after a certain period of time, the waste activated sludge was conveyed from the rear end to the front end of the reactor for more stable hydrogen generation. The waste activated sludge was heated by passing through a stainless steel tube. The waste activated sludge was controlled by the pump so that the residence time of the tube was about 10-20 minutes, and the stainless steel was wound with a heating tape to maintain the temperature of about 100 ° C.

The heating of waste activated sludge is continuously performed for a long time. As a result, the dynamic system can reduce the hydrogen producing bacteria which are very sensitive to the environmental conditions and increase the methane producing bacteria. In order to inhibit the activity of, but to ensure the presence of heat-producing hydrogen bacteria. The results are shown in Table 3, below, for the production rate of each gas.

If not heat treated When heat treated H ₂ 2.1% 34.7% N ₂ 10.5% 11.6% CH ₄ 35.7% 12.7% CO ₂ 51.8% 41.1%

As a result, as shown in Table 3, the hydrogen production rate was 34.7% of the total gas components when the heat treatment was performed, while only 2.1% when the heat treatment was not performed. In addition, the methane production rate was 12.7% of the total gas components when the heat treatment, while 35.7% was not the heat treatment.

Through this, it can be seen that when generating hydrogen in the hydrogen generating reactor 30, the hydrogen production rate can be increased by using heat treatment in combination.

Although the invention has been described in detail above, it will be apparent to the inventors that various modifications and changes are possible within the scope and spirit of the invention, and it is obvious that such modifications and modifications fall within the scope of the appended claims.

As described above, according to the present invention, by generating hydrogen and methane using waste activated sludge, which is an organic waste, it is possible to solve the problem of disposal and disposal of organic waste and to efficiently replace hydrogen and methane, which are alternative energy, by a biological method. Has the effect of producing.

Claims (19)

a pretreatment reactor for adjusting the pH to pH 2 or pH 12 to pH 14 to pretreat the organic matter in the waste activated sludge to be discharged to the outside; Reaction tank conditions are adjusted to a pH range of 5 to 6 for hydrogen producing bacteria growth conditions, the hydrogen production reactor for producing hydrogen from the waste activated sludge pretreated by the pretreatment reactor; And Reaction tank conditions are hydrogen and methane using waste activated sludge, characterized in that the pH is set to neutral for methane production bacteria growth conditions, and includes a methane production reactor for generating methane from the waste activated sludge treated by the hydrogen production reactor Generation device. The hydrogen and methane using waste activated sludge according to claim 1, further comprising a heating conveying means for heating and transporting a part of the waste activated sludge treated by the hydrogen generation reactor to 80 ° C to 100 ° C. Generating device. delete delete delete The waste tank according to claim 1, further comprising a hydrolysis reaction tank installed at a rear end of the pretreatment reaction tank and an upper end of the hydrogen production reactor to adjust the pH of the pretreated waste activated sludge in the range of 6 to 7. Hydrogen and methane generator using activated sludge. delete The apparatus for producing hydrogen and methane using waste activated sludge according to claim 1, wherein the hydrogen generation reactor is provided with a partition wall. delete pretreatment of waste activated sludge by adjusting to pH1 to pH2 or pH12 to pH14; Generating hydrogen from the waste activated sludge pretreated in this step, adjusting the pH to a range of 5 to 6 for hydrogen producing bacteria growth conditions; And The method for producing hydrogen and methane using waste activated sludge, comprising the step of generating methane from the waste activated sludge which has been subjected to the hydrogen generation step by adjusting the pH to neutral for methane producing bacteria growth conditions. 11. The method of claim 10, wherein the hydrogen generating bacteria in the hydrogen generation step, hydrogen and methane production method using waste activated sludge, characterized in that the inoculation of the microorganisms of the anaerobic digestion tank of the sewage treatment plant is used to inoculate. The method of claim 10, wherein the methane generating bacteria in the methane production step, hydrogen and methane production method using waste activated sludge, characterized in that the inoculation of the microorganisms of the anaerobic digestion tank of the sewage treatment plant in the initial operation. The waste activated sludge according to claim 10, further comprising the step of returning a portion of the waste activated sludge that has undergone the hydrogen generation step to be heated at 80 ° C to 100 ° C for 15 minutes to 20 minutes, and being returned. Hydrogen and methane generation method using. delete delete delete The method of claim 10, further comprising a hydrolysis reaction step of adjusting the pH of the waste activated sludge passed through the pretreatment in the range of 6 to 7. delete delete

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