WO2010068053A2 - Method for preparing methane gas using red algae extract - Google Patents

Abstract

The present invention relates to use of a red algae extract for preparing methane gas, generated during a pulp manufacturing process using red algae. More specifically, the present invention provides a method for directly preparing methane gas from red algae extract and a method for preparing methane gas using distillery wastewater remaining after ethanol preparation from red algae. The direct method for preparing the methane gas comprises: (a) a step of hydrolyzing red algae extract; (b) a step of removing impurities from red algae extract from step (a); and (c) a step of performing methane fermentation of the extract obtained through step (b) using methane-fermenting fungi. The other method for preparing methane gas using distillery wastewater comprises: (a) a step of hydrolyzing red algae extract; (b) a step of removing impurities from red algae extract from step (a); (c) a step of neutralizing the pH of red algae extract obtained through step (b); (d) a step of inoculating distiller's yeast to red algae extract from step (c); (e) a step of performing alcohol fermentation of red algae extract from step (d); (f) a step of distilling alcohol fermentation liquid obtained through step (e) and collecting ethanol; and (g) a step of performing methane fermentation of distillery wastewater remaining after collecting the ethanol from step (f) using methane-fermenting fungi.

Description

Methane gas production method using red algae extract

The present invention uses the red algae extract generated in the pulp production process using red algae for the production of methane gas. Specifically, the present invention comprises the steps of (a) hydrolyzing the red algae extract; (b) removing impurities of the red algae extract which passed through step (a); (c) The method of directly producing methane gas from red algae extract comprising the step of fermenting methane using the methane fermentation of the extract after the step (b).

Methane is the simplest carbon compound and has a structure in which four hydrogens are bonded to one carbon, and exist in the form of a gas at room temperature. Methane gas itself is odorless, but for industrial use, some odors are mixed to make it easier to detect leaks. Such methane gas is produced through the methane fermentation process. Methane fermentation occurs as anaerobic bacteria break down organic matter, producing methane and carbon dioxide. Methane fermentation has been used for the treatment of manure and industrial waste. Recently, attempts have been made to use the methane gas collected through the fermentation of methane produced during the treatment of manure or industrial waste.

Korean Unexamined Patent Publication No. 1997-0069903 discloses a device for obtaining methane gas from organic wastewater, and Korean Unexamined Patent Publication No. 1999-0083953 discloses a method and device for methane gasification of household waste and animal carcasses. In addition, the Republic of Korea Patent Publication No. 2000-0001131 "Livestock waste food waste purification and methane gas extraction device" is disclosed, and the related technology has been continuously developed to date.

As such, methane fermentation requires organic materials that can be used as substrates by anaerobic bacteria that methane fermentation, and the range of these organic materials can be considered in various ways, as described above. Use as a substrate for fermentation would be desirable when considering aspects of efficient use of resources.

Recently, a method of producing paper as pulp produced using red algae has been developed, and industrialization thereof has been actively attempted. Red algae inhabit relatively deeper water than other algae, and are relatively small in size. There are more than 4,000 species, and the algae grow wider than green algae and brown algae, and grow from shallow depths to deep water rays. Republic of Korea Patent No. 0811193 discloses "pulp made of red algae and its manufacturing method". The patent goes through the steps of washing red algae, oxygen pretreatment, extracting the gel components of red algae to produce pulp from red algae, which is a gel component and low-molecular-weight carbohydrates, such as ummu and carrageenan present in the algae When the red algae is composed of pulp fibers, it is a step for treating this because it causes problems such as increasing drug consumption and preventing dehydration.

As such, the gel component (woom; also called agar or Agar), which is a constituent of red algae, may be extracted from red algae according to the characteristics of the paper to be manufactured, and then paper may be produced. You may. The higher the content of the gel component can produce a paper with high transparency and density, the lower the content of the gel component can produce a paper with high opacity and excellent bonding. In other words, this is a part that can be adjusted by the manufacturer according to the needs of the consumer, in any case, the gel component extracted from the red algae is bound to be discarded.

As such, when pulp is produced from red algae, the production cost is lower than the cost of purchasing raw timber, and the use of chemicals for lignin removal and bleaching is significantly reduced compared to the cost of purchasing raw wood. It can be, and the final product also does not contain harmful chemicals, there is an advantage to produce a product that is harmless to the human body and the environment, but as described above, there was a problem that the gel component generated in the process must be discarded.

Of course, the gel component of radish has been used for food or medicine for a long time, but the gel component of radish, which is a waste generated in the process of preparing pulp from red algae, goes through a washing step and a bleaching step. There was a limit to use, and it has been required to derive its use.

The present inventors first developed a method for producing red algae into pulp, and as a inventor of a source patent registered and patented, the red algae after researching to produce methane gas using the gel extract extracted in the process of manufacturing the red algae into pulp The methane gas production method using the extract was completed.

That is, an object of the present invention is to regenerate resources that are discarded as the methane gas is produced using the gel extract generated during the manufacture of pulp from red algae.

In order to achieve the above object, the present invention provides a method of directly producing methane gas from red algae extract and a method of producing methane gas using ethanol from the red algae extract and the remaining distillation waste.

1. Method of producing methane gas directly from red algae

First, the method of directly producing methane gas from the red algae extract includes the steps of: (a) hydrolyzing the red algae extract; (b) removing impurities of the red algae extract which passed through step (a); (c) methane fermentation using the methane fermentation of the extract after the step (b).

Red algae extract used in the present invention can be obtained using the method described in the existing Korean Patent No. 0811193 and the like by the present inventors. First, the red algae may be immersed in an acidic aqueous solution to remove impurities and calcium carbonate, and then the red algae may be immersed in an extraction solvent capable of dissolving the red algae gel component. In the present invention, such red algae extract gel components will be referred to as red algae extract. Red algae extract refers to a daikon (agar, also called agar) present in red algae.

The red algae extract, having undergone this process, is subjected to (a) hydrolysis step. The hydrolysis step is to bring the red algae extract into a reducing sugar state that is suitable for methane fermentation as a substrate. In general, hydrolysis may be considered hydrolysis using an acid or an enzyme, but in the present invention, an acid hydrolysis method is used. The acid may preferably be oxalic acid, sulfuric acid, phosphoric acid, and particularly, in the case of oxalic acid, it is preferable to proceed in an environment having a temperature of 130 to 140 ° C and a pH of 3.0 or less. In addition, the hydrolysis is preferably carried out for 1 to 2 atm, for 30 to 60 minutes.

The red algae extract that passed through step (a) is subjected to an impurity treatment step (b). The impurity treatment step is characterized by consisting of an air blowing step and an alkali treatment step. The air blowing step is a step for removing furfural which is a fermentation blockage generated in the acid hydrolysis step (a). The air blowing step is preferably carried out by blowing the steam of 95 ~ 105 ℃.

Alkali treatment step is to remove the hydroxy methyl furfural (Hydroxy Methyl Furfural) as the air blowing step. In the alkali treatment step, it is preferable to use chemicals such as calcium oxide, sodium hydroxide, potassium hydroxide, etc. to maintain the environment of pH 10 ~ 10.5.

The red algae extract of step (b) is a state in which methane fermentation bacteria have been changed into a form of reducing sugar which is good for use as a substrate, and furfural and hydroxy methyl furfural, which are obstacles to fermentation, have been removed. As it goes through the step (c) methane fermentation. The methane fermentation step (c) may use a general methane fermentation tank. Preferably it is possible to use a fermentation tank that is sufficiently mixed with the temperature range of 10 ~ 40 ℃ and circulation. Methane fermentation bacteria is not particularly limited and is a mesophilic archaeaMethanobacterium                                  bryantii                 ,                 Methanococcus                                  vannielii                 , Methanosarcina                 mazei                  And thermophilic archaea                 Methanobacterium                                  thermoformicicum                 , Methanothermus                 fervidus                 ,                 Methanosarcina                                  thermophilaAll methane fermentation bacteria, including

.

It is possible to produce methane gas from the red algae extract through the steps (a), (b) and (c) as described above.

2. Method of producing methane gas using the remaining distillation waste after producing ethanol from red algae extract

Next, a method of producing methane gas using the remaining distillation waste after producing ethanol from the red algae extract comprises the steps of: (a) hydrolyzing the red algae extract; (b) removing impurities of the red algae extract which passed through step (a); (c) pH neutralization step of the red algae extract that passed through step (b); (d) judo inoculation to the red algae extract that passed through the step (c); (e) alcohol fermenting the red algae extract having undergone the step (d); (f) distilling the alcohol fermentation broth from step (e) to recover ethanol; (g) The step of (m) recovering the ethanol and the remaining distillation waste consists of methane fermentation using methane fermentation bacteria.

As described above, the red algae extract may be obtained using a method described in Korean Patent No. 0811193, which is an existing registered patent by the present inventors, and the like. Such extracts may preferably undergo a "concentration step" before the hydrolysis step corresponding to step (a). Concentration step is preferably evaporation concentration using a temperature of 100 ~ 160 ℃ the temperature when the red algae extract comes out of the extractor. When the concentration step is performed using the temperature of the red algae extract from the extractor, it is possible to obtain an effect of reducing energy consumption in the distillation process in the ethanol production process.

It is then subjected to (a) hydrolysis step, (b) impurity treatment step, which is the same as the method for producing methane gas directly from the red algae extract described above. However, preferably, in the process between (a) hydrolysis step and (b) impurity treatment step, ammonium hydroxide and magnesium hydroxide may be added to supply the essential nutrients necessary for the strain.

Then, the step of neutralizing the pH of the red algae extract through the above steps. This is to create an environment in the pH range 5.5 to 6.5 in which alcohol fermentation can be made properly. The acid used herein is not limited to a specific acid as long as the acid can adjust the pH range of the red algae extract that has undergone the impurity treatment to the range of 5.5 to 6.5.

Then, (d) the main vaccination step. The strain used for this is preferablySaccharomyces                                  cerevisiaeCan be used in pre-culture, butSaccharomyces                 cerevisiaeon Without limitation, any microorganism which ferments alcohol can be used.

Next, (e) the alcohol fermentation step may be proceeded as anaerobic effect tablets, preferably at 30 ° C. for 5 to 7 days. After the alcohol fermentation step (f) after distilling the alcohol fermentation broth to recover ethanol, a distillation waste solution is obtained. This can be used as a substrate of methane fermentation. Methane gas can be produced using methane fermentation bacteria in the same way as the method discussed above.

As described above, when the method of producing methane gas from red algae extract according to the present invention is carried out, waste products can be efficiently recycled as fuel by reproducing by-products generated by producing pulp from red algae as methane gas. Will be. It is environmentally friendly and methane gas produced by this method can be used for transportation, heating, and natural gas for power generation.

1 is a schematic diagram of a process for producing methane gas from red algae extract according to the present invention.

Example

1. Direct production of methane gas from red algae

(1) red algae extract acquisition step

The red starfish, a type of red algae, was immersed in an acidic solution at pH 2-3 for 55 minutes to remove impurities and calcium carbonate mixed in the algae. At this time, the pH of the acid solution was adjusted using hydrochloric acid and the temperature was 20 ℃. When the washing was completed, 10 kg of whole loaf of wormwood, that is, the weight of 10 kg when completely dried, was immersed in an aqueous sodium hydroxide solution containing 4% by weight of sodium hydroxide compared to the whole lodge, and then treated for 90 minutes in a 120 ℃ water bath. . After the treatment of the water bath at 40 ° C. was completed, the wood starch was removed, washed with tap water, and then immersed in an aqueous sodium hydroxide solution containing 5% by weight of sodium hydroxide compared to the whole starch starch and treated in an 80 ° C. water bath for 3 hours. At this time, the weight ratio of water and mantle was 10: 1. The red algae extract extracted by treating in this way is low molecular weight in the extraction process to maintain the liquid state at room temperature.

(2) Hydrolysis step

The red algae extract extracted in the above step was hydrolyzed with oxalic acid at 1.5 atmosphere for 50 minutes. 6.2 kg of red algae extracts were obtained, and the hydrolysis resulted in 3.5 kg of reducing sugars.

(3) impurities removal step

Water vapor at 103 ° C. was blown to the red algae extract which had undergone the hydrolysis step, and the environment of pH 10.3 as quicklime (CaO) was removed to remove the fermentation obstacles, pulpfural and hydroxy methyl furfural.

(4) methane fermentation step

The red algae extract, which has undergone the step of removing impurities, is added to CSTR (Continous Stirrer Tank Reactor), a R-201 series reactor system manufactured by Reaction Engineering Co., Ltd.Methanococcus                                  vannielii                  3.85m of methane-coated tablets under standard temperature and pressure conditions after inoculating strains³Methane gas was obtained.

2. Methanol gas is produced by using ethanol from red algae extract and distillation waste.

(1) red algae extract acquisition step

The red starfish, a type of red algae, was immersed in an acidic solution at pH 2-3 for 55 minutes to remove impurities and calcium carbonate mixed in the algae. At this time, the pH of the acid solution was adjusted using hydrochloric acid and the temperature was 20 ℃. When the washing was completed, 10 kg of whole loaf of wormwood, that is, the weight of 10 kg when completely dried, was immersed in an aqueous sodium hydroxide solution containing 4% by weight of sodium hydroxide compared to the whole lodge, and then treated for 90 minutes in a 120 ℃ water bath. . After the treatment of the water bath at 40 ° C. was completed, the wood starch was removed, washed with tap water, and then immersed in an aqueous sodium hydroxide solution containing 5% by weight of sodium hydroxide compared to the whole starch starch and treated in an 80 ° C. water bath for 3 hours. At this time, the weight ratio of water and mantle was 10: 1. The red algae extract extracted by treating in this way is low molecular weight in the extraction process to maintain the liquid state at room temperature.

(2) Hydrolysis step

The red algae extract extracted in the above step was hydrolyzed with oxalic acid at 1.5 atmosphere for 50 minutes. 6.2 kg of red algae extracts were obtained, and the hydrolysis resulted in 3.5 kg of reducing sugars.

(3) impurities removal step

Water vapor at 103 ° C. was blown to the red algae extract which had undergone the hydrolysis step, and the environment of pH 10.3 as quicklime (CaO) was removed to remove the fermentation obstacles, pulpfural and hydroxy methyl furfural.

(4) pH Neutralization stage

Phosphoric acid was added to the red algae extract after the impurity removal step to adjust the pH to 5.7.

(5) Main hair vaccination step

Saccharomyces cerevisiaePrecultured 2 × 10^-7 cfu ml^{- One} At the level of it was inoculated into the red algae extract.

(6) Alcohol fermentation stage

remindSaccharomyces                                  cerevisiaeRed algae inoculated were anaerobic fermented at 30 ° C. for 6 days.

(7) distilling alcohol fermentation broth to recover ethanol

After the alcohol fermentation step, it was distilled to recover only ethanol.

(8) step of recovering ethanol and methane fermentation of remaining distillation waste using methane fermentation bacteria

After distilling the alcohol fermentation broth to recover ethanol, the remaining distillate waste liquid was added to CSTR (Continous Stirrer Tank Reactor), a product of R-201 series reactor system manufactured by Reaction Engineering Co., Ltd.Methanococcus                                  vannielii                  The methane-balancing effect tablet was carried out using the strain under standard temperature and pressure conditions.³Methane gas was obtained.

When the method of producing methane gas from red algae extract according to the present invention is carried out, by-products generated by producing pulp from red algae can be recycled to methane gas to efficiently recycle waste resources and used as fuel. It is environmentally friendly, and methane gas produced by this method can be used for transportation, heating, and natural gas for power generation.

Claims (9)

1. Method for producing methane gas from red algae extract comprising the following steps:

   (a) hydrolyzing the algae extract;

   (b) removing impurities of the red algae extract which passed through step (a);

   (c) methane fermentation using the methane fermentation of the extract after the step (b).
2.  The method according to claim 1, wherein the step (b) comprises the step of blowing air into the red algae extract that passed through the step (a) and alkali treatment of the red algae extract.
3. The method of claim 1, wherein step (a) is a method of producing methane gas from red algae extract, characterized in that the acid hydrolysis method.
4. The method of claim 1, wherein step (C) is methane gas production from red algae extract, characterized in that the alkali treatment using calcium oxide, sodium hydroxide, potassium hydroxide.
5. Method for producing methane gas from red algae extract comprising the following steps:

   (a) hydrolyzing the algae extract;

   (b) removing impurities of the red algae extract which passed through step (a);

   (c) pH neutralization step of the red algae extract that passed through step (b);

   (d) judo inoculation to the red algae extract passed through step (c);

   (e) alcohol fermenting the red algae extract having undergone the step (d);

   (f) distilling the alcohol fermentation broth from step (e) to recover ethanol;

   (g) methane fermentation using the methane fermentation of the remaining distillation waste after recovering the ethanol in the step (f).
6. The method according to claim 5, wherein the step (b) comprises the step of blowing air to the red algae extract that passed through the step (a) and alkali treatment of the red algae extract method of producing methane gas from the red algae extract.
7. The method of claim 5, wherein step (a) is a method of producing methane gas from red algae extract, characterized in that the acid hydrolysis method.
8. The method of claim 5, wherein step (C) is methane gas production from red algae extract, characterized in that the alkali treatment using calcium oxide, sodium hydroxide, potassium hydroxide.
9.  The method of claim 5, further comprising the step of concentrating the red algae extract before step (a).

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