KR20190075595A - Process for producing methanol from organicwastes - Google Patents

Abstract

The present invention relates to a method for producing biogas mixed with carbon dioxide and methane gas, which can be a raw material of methanol from organic waste, and producing methanol from the biogas. According to an embodiment of the present invention, the biogas producing method from organic waste includes: a step (a) of lowering the moisture content of organic waste through a dehydration process; a step (b) of decomposing the organic waste into low molecular weight organic materials through a thermal hydrolysis process; and a step (c) of producing biogas mixed with carbon dioxide and methane through an anaerobic digestion process with the low molecular weight organic material. The present invention has effects of: reducing atmospheric diffusion of greenhouse which causes global warming by improving a recovery rate of biogas from organic waste; and improving resource utilization by recycling methane and carbon dioxide, which cannot be used as energy and wasted, by recovering the biogas from the organic waste.

Description

PROCESS FOR PRODUCING METHANOL FROM ORGANICWASTES [0002]

The present invention relates to a method for producing biogas mixed with carbon dioxide and methane gas which can be a raw material for methanol from organic wastes, and to produce methanol from the biogas.

Organisms are substances that result from the life activities of living organisms and are composed of polymer compounds. Sludge, food wastes, and manure that are generated as a by-product of the wastewater treatment process are representative organic wastes. They decompose gradually in the natural world, and they smell and decompose and become a hotbed of pathogens. In the end, they are decomposed into methane gas and carbon dioxide gas, which are greenhouse gases, and cause global warming and environmental pollution.

The components of these organic wastes are composed of polymer organic matter, that is, proteins, carbohydrates, lipids, and fibers. Polymer organic materials have a high water content because they are strong in hydrophilicity and take long time to decompose in a natural state.

Biogas is a mixture of methane and carbon dioxide produced when anaerobic digestion of organic wastes occurs. Methane and carbon dioxide are the most abundant carbon-containing gases in the Earth's atmosphere. These gases play an important role in the greenhouse effect where atmospheric gases absorb infrared radiation and trap it in the Earth's atmosphere. CH ₄ and CO ₂ are also produced when anaerobic digestion of biomass and animal manure occurs, in which the CH ₄ component is 40 to 70% and the remainder is CO ₂ . However, most of these fuels are abandoned without being used as energy.

The reason why such biogas can not be used as energy is that the amount of heat is reduced due to a high CO ₂ concentration and the stability of the mixed gas combustion flame is lowered. As a result, when biogas is burned in an engine, a turbine, or a boiler, carbon monoxide (CO), nitrogen oxides (NO _x ), and unburned hydrocarbons are increased in comparison with pure methane or natural gas. These biogas are often burned without extracting potential chemical energy and released to the atmosphere as CO ₂ and H ₂ O. Incineration is the most common method of disposal of CH ₄ / CO ₂ mixed gas, which consumes the calorific value of CH ₄ .

Although biogas is used as a fuel for power generation engine, turbine or direct heating boiler, it is difficult to reduce pollutants by a large amount of CO ₂ in the biogas. It is economically problematic to use CO ₂ as pure methane does not apply.

Korean Patent Publication No. 10-2002-0010902

It is an object of the present invention to provide a method for producing methanol from recovered biogas by improving the recovery rate of biogas discharged from decomposing and recovering organic wastes.

(A) lowering the water content of the organic waste through a dehydration process; (b) decomposing the organic waste into a low molecular organic material through a thermal hydrolysis process; And (c) producing the biogas in which carbon dioxide and methane are mixed through the anaerobic digestion process of the low molecular weight organic matter. The present invention also provides a method for producing methanol from organic wastes.

In the step (a), the water content may be lowered to 80 to 85%.

The step (b) may be performed at 150 to 200 ° C for 20 to 60 minutes, and the step (b) may be performed at 4.7 to 15.5 bar.

In step (c), hydrogen gas may be removed by reacting with sodium hydroxide or iron chelate after producing the biogas.

(C-1) separating the desorbing liquid from the organic waste having been subjected to the digestion process in the step (c); And (c-2) precipitating struvite from the desalination solution. The present invention also provides another aspect of the present invention to provide a method for producing methanol from organic wastes.

(D) modifying a biogas mixed with carbon dioxide and methane gas produced through the biogas production method to produce a synthesis gas, which is a methanol feedstock mixed with carbon monoxide and hydrogen; And (e) producing methanol from the syngas. In another aspect of the present invention, there is provided a process for producing methanol from organic wastes.

The step (d) may be carried out using nickel (Ni), cobalt (Co), rhodium (Rh), ruthenium (Ru), Mo ₂ C, palladium (Pd) or platinum , And the step (d) may be performed at 600 to 1,000 ° C and 1 to 20 bar.

The step (e) may be performed at 200 to 300 ° C.

The present invention has an effect of reducing the occurrence of diffusion of greenhouse gases into the atmosphere, which causes global warming and the like, by improving the recovery rate of biogas from organic wastes.

Also, by recovering biogas from organic wastes, methane and carbon dioxide that can not be used as energy but are discarded can be recycled to improve resource utilization.

FIG. 1 is a process diagram of a synthesis process of biogas and methanol according to an embodiment of the present invention.

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

Referring to FIG. 1, a method for producing methanol from organic wastes according to an embodiment of the present invention includes the steps of: (a) lowering the water content of organic wastes through a dehydration process (S100); (b) decomposing the organic waste into a low molecular organic material through a thermal hydrolysis process (S200); And (c) a step (S300) for the low-molecular-weight organic substance to produce carbon dioxide (CO ₂₎ and methane (CH ₄₎ is a bio-gas mixture through the anaerobic digestion process, referred to as biogas in the present description means the organic Means a mixture of methane and carbon dioxide gas generated when anaerobic digestion of waste is effected.

The step (a) (S100) is a first dehydration process of the organic waste, The wastewater sludge has a water content of about 97 to 99%, which is high in water content. Therefore, a large capacity facility is required to treat the wastewater sludge. It is a process to lower the water content to 80 to 85% in order to reduce the capacity of facilities. The first dehydration process in step (a) (S100) may be performed by using a belt press or a centrifugal separator. After the dewatering process, the dehydrated organic material is stored in the organic material storage tank, and the dehydrated organic material is supplied through the thermal hydrolysis process in step (b) (S200).

The step (b) (S200) is a step of decomposing the polymer organic material of the organic waste dehydrated in step (a) into low molecular organic materials such as sugar, amino acid, fatty acid and the like under high temperature and high pressure conditions.

The heat hydrolysis process in step (b) (S200) may be performed at a temperature of 150 to 200 ° C for 20 to 60 minutes, and preferably at a pressure of 4.7 to 15.5 bar.

The step (c) (S300) is a step of producing biogas in which carbon dioxide and methane are mixed through the anaerobic digestion process of the low molecular organic material.

Organic matter is decomposed into methane and carbon dioxide when it is left in the natural environment and diffuses into the atmosphere. This diffusion into the atmosphere wastes energy resources and adversely affects global warming. However, when the organic matter is decomposed in a short time, the waste is treated, the energy of methane is recovered from the waste, and the warming can be solved by collecting the carbon dioxide together.

The anaerobic digestion process in step (c) (S300) proceeds to a hydrolysis step, an acid production step, an acetic acid production step, and a methane production step. Microorganisms such as bacteria act on the reaction. In anaerobic condition (oxygen-free environment), the reaction takes place at a middle temperature (30 to 40 ° C) or a high temperature (about 55 ° C) .

[Reaction Scheme 1]

_{C x H y O z N v} S w + 1/4 (4x-h-2z + 3v + 2w) H 2 O → 1/8 (4x-y + 2z + 3v + 2w) CO 2 + 1/8 ( 4x-y + 2z + 3v + 2w) CH 4 + vNH 3 + wH 2 S

(x, y, z, v, w mean the molar ratio of each element or molecule, and is an integer of 1 or more).

Since the biogas contains impurities such as hydrogen sulfide, ammonia, and siloxane in the step (c), a cleaning process (digestion gas cleaning process) for removing impurities before using the biogas as a raw material for methanol production can be performed. As the cleaning method, high pressure water scrubbing, pressure swing adsorption (PSA), amine adsorption, membrane osmosis, etc. can be applied. The biogas produced in the step (c) S300 contains a small amount of hydrogen sulfide of about 1,000 to 5,000 ppm. Hydrogen sulphide causes bad smell and reacts with mol, it has strong acidity and causes corrosion of machine. The sulfur component can be removed by reaction with sodium hydroxide or iron chelate.

Methanol production process from the organic waste in accordance with one aspect of the present invention is (c-1) separating talriaek from organic waste digestion process is completed in the step (c) (S300) (2 primary dehydration step) (S310) ; And (c-2) precipitating struvite from the desalination solution ( MAP Struvite crystallization reaction process ) (S320).

The organic waste having been subjected to the digestion process in the step (c) (S300) is composed of a refractory substance and an inorganic substance difficult to digest and contains 80 to 90% of water. The step (c-1) S310), a secondary dehydration process for final treatment of the organic waste can be performed. At this time, the second dehydration process in step (c-1) (S310) may be performed in the same manner as the first dehydration process in step (a) The phosphorus (P) and nitrogen (N) contained in the organics in step (c) S300 are dissolved in the desolvation solution generated in the second dehydration process in step (c). The final treatment can minimize the volume of organic wastes that have undergone the digestion process, or make them available for other purposes by drying, incineration, or composting.

The step (c-2) is a step of precipitating struvite from the desolvation solution generated in the second dehydration step in the step (c-1) (S310). In the secondary dehydration process, a large amount of phosphorus and nitrogen are dissolved in the form of ammonium (NH ₄ ⁺ ) and phosphate (PO ₄ ⁺ ). If the desalination liquid is discharged into a river or a river, it becomes a cause of water pollution as a nutrient salt, and when it is returned to the water treatment process for purification, it overloads the water treatment process.

In order to prevent this, Struvite is precipitated as shown in the following reaction formula (2) by adding magnesium to the desalting solution.

[Reaction Scheme 2]

Mg ²⁺ + NH ₄ ⁺ + PO ₄ ^3- → MgNH ₄ PO ₄ (MgNH ₄ PO ₄ O 6 H ₂ O)

When the above struvite is precipitated and recovered, resources can be recovered from the pollutant and used as the best fertilizer.

The method for producing methanol from organic wastes according to an embodiment of the present invention comprises the steps of (d) modifying the biogas mixed with carbon dioxide and methane gas produced in the step (c) (S300) to produce a methanol raw material mixed with carbon monoxide and hydrogen Producing a syngas (S400); And (e) producing methanol from the methanol feedstock (S500).

The step (d) (S400) is a step of producing the synthesis gas which can be used as a raw material for producing methane from the biogas produced in the step (c) (S300) ( biogas reforming reaction ). The composition of the biogas produced in step (c) (S300) may include about 50 to 70% of CH ₄ gas and about 30 to 50% of CO ₂ gas. In step (d) The reaction scheme of the biogas reforming is shown in the following reaction scheme 3.

[Reaction Scheme 3]

CO ₂ + CH _{4 -} > 2CO + 2H ₂

The components of the synthesis gas produced in the reforming process (Scheme 3) in step (d) (step S400) are carbon monoxide (CO) and hydrogen (H ₂ ), and the CO to H ₂ ratio is 1: 1 .

Catalyst used in the reforming reaction in the step (d) (S400) is a nickel (Ni), cobalt (Co), rhodium (Rh), ruthenium (Ru), Mo ₂ C, palladium (Pd) or platinum (Pt) Lt; / RTI > The reforming reaction in step (d) (S400) is an endothermic reaction, and the reforming reaction can be carried out at a temperature of 800 to 1,000 ° C and a pressure of 1 to 20 atm. Through the reaction according to Reaction Scheme 2, the biogas is reformed into a carbon dioxide hydrogen synthesis gas. The gas hourly space velocity (GHSV) in the reforming reaction in the step (d) ranges from 1 to 23 Sv [h < ^-1 >].

The step (e) (S500) comprises a step ( methanol synthesis step ) of producing methanol from the synthesis gas containing the methanol raw material modified through the step (d) (step S400) To 300 < 0 > C.

The step (e) (S500) by using a synthesis gas of carbon monoxide (CO) and hydrogen (H ₂₎ produced in the reforming process in the step (d) (S400), and the synthesis of methanol, to as Scheme 4 And reacts.

[Reaction Scheme 4]

CO + 2H _{2 -} > CH ₃ OH

The step (e) (S500) may supply H ₂ in the form of steam, and supplement the deficient H ₂ through the steam.

The synthesis of methanol in step (e) (S500) may be performed at a temperature of 473 to 573 K (200 to 300 ° C).

The methanol synthesis reaction (Scheme 4) in the step (e) (S500) may use a catalyst to support a reaction for bonding a single CO and two H ₂ molecules to produce methanol, A copper containing catalyst may be used, and the copper containing catalyst may be Cu / ZnO / Al ₂ O or Cu / ZnO / Cr ₂ O ₃ . This is a highly exothermic process in the catalyst bed. This reaction produces a significant amount of heat, which can usually be used for steam or electricity production for use in the plant.

In step (e) (S500), methanol may be separated through distillation after the methanol synthesis reaction. In the preparation of methanol by the above reaction scheme 4, the product is composed not only of methanol but also water and a small amount of alcohol having a high molecular weight.

Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited by the examples.

Example 1. Preparation of biogas

Mixed sludge (100% by weight) in which 50% by weight of raw sludge (primary precipitate in water treatment process) and 50% by weight of surplus sludge (microorganism grown in bioreaction as a main component as a secondary precipitate in water treatment process) The sludge was subjected to a dewatering process using a belt press or a centrifuge at a pressure of 4.7, 6.2, 7.9, 10.2, 12.5 and 15.5 bar at 150 to 200 ° C for 20 minutes After hydrothermal hydrolysis, the anaerobic digestion process was carried out under anaerobic conditions (oxygen free environment) at a moderate temperature (30-40 ° C) or high temperature (55 ° C or so), and digestion efficiency and biogas production rate (1 M ³ / kg × digestion efficiency (%)). The results are summarized in Table 1 below.

Reaction time Temperature (℃) Pressure (bar) Digestion Efficiency (%) Biogas production rate 20 minutes 150 4.7 40.3 1 M ³ / kg × digested organic matter (digestion efficiency) 160 6.2 42.0 170 7.9 43.7 180 10.2 44.2 190 12.5 41.5 200 15.5 36.0

Example 2. Production of biogas

The hydrolysis and the anaerobic digestion were carried out in the same manner as in Example 1 except that the reaction time was 30 minutes. The results are summarized in Table 2 below.

Reaction time Temperature (℃) Pressure (bar) Digestion Efficiency (%) Biogas production rate 30 minutes 150 4.7 42.5 1 M ³ / kg × digested organic matter (digestion efficiency) 160 6.2 44.2 170 7.9 45.9 180 10.2 46.4 190 12.5 43.7 200 15.5 38.2

Example 3: Biogas production

The hydrolysis and anaerobic digestion were carried out in the same manner as in Example 1 except that the reaction time was 40 minutes. The results are summarized in Table 3 below.

Reaction time Temperature (℃) Pressure (bar) Digestion Efficiency (%) Biogas production rate 40 minutes 150 4.7 47.2 1 M ³ / kg × digested organic matter (digestion efficiency) 160 6.2 48.9 170 7.9 50.6 180 10.2 51.1 190 12.5 48.4 200 15.5 42.9

Example 4. Production of biogas

The hydrolysis and anaerobic digestion were carried out in the same manner as in Example 1 except that the reaction time was 50 minutes. The results are summarized in Table 4 below.

Reaction time Temperature (℃) Pressure (bar) Digestion Efficiency (%) Biogas production rate 50 minutes 150 4.7 46.8 1 M ³ / kg × digested organic matter (digestion efficiency) 160 6.2 48.5 170 7.9 50.2 180 10.2 50.7 190 12.5 48.0 200 15.5 42.5

Example 5. Production of biogas

The thermal hydrolysis and the anaerobic digestion were carried out in the same manner as in Example 1 except that the reaction time was 60 minutes. The results are summarized in Table 5 below.

Reaction time Temperature (℃) Pressure (bar) Digestion Efficiency (%) Biogas production rate 60 minutes 150 4.7 47.1 1 M ³ / kg × digested organic matter (digestion efficiency) 160 6.2 48.8 170 7.9 50.5 180 10.2 51.0 190 12.5 48.3 200 15.5 42.8

Comparative Example.

The same procedure as in Example 1 was carried out except that the thermal hydrolysis process was not performed. As a result, the digestion efficiency of the sludge was about 35%.

Example 6. Modification process

The biogas produced in Example 3 was subjected to a biogas reforming process according to the nickel-based catalyst conditions and the reaction conditions shown in Table 6 below to produce CO and H ₂ synthesis gas. The resulting CH ₄ / CO ₂ The H ₂ / CO conversion was measured.

Sample No. Catalyst
(Weight ratio) Reaction conditions CH ₄ / CO ₂ Of H ₂ / CO conversion rate Temperature GHSV
(Sv [h ^-One ]) pressure One Ca / Ni / K
(2: 1: 0.1) 860 ° C 5.04 1 atm 95% / 95% 2 Ni / K-MgO-ZrO ₂ 750 ℃ - 1 atm 85% / 85% 3 _{Ni / Al 2 O 3 -K-} Sn-Mn-Ca 750 ℃ 15 1 atm 80% / 85% 4 _{Ni / ZrO 2 -CeO 2 -La 2} O 3 -K 2 O 500 to 700 ° C 0.95 1 atm 70% / 70% 5 Ni / (Co, Ca, K , Ba, La, Ce) -MgO-ZrO 2 750 ℃ 144 1 atm 53% / 60% 6 Ni-Al ₂ O ₃ -K 700 ℃ 22.5 1 atm 57% / 67% 7 Ni-MgO-K 650 ° C 5.5 1 atm 32% / 42% 8 _{Ni-Al 2 O 3 -K-} CeO 2 -Mn
600 ℃ 2.85 1 atm 85% / 85%

Example 7. Synthesis of methanol

Methanol was synthesized from the CO / H ₂ synthesis gas modified through Example 6 according to the following Reaction Scheme 5.

[Reaction Scheme 5]

Methanol synthesis: CO + 2H ₂ → CH ₃ OH

The methanol synthesis reaction uses a Ni / Fe catalyst to support the reaction of a single CO and two H2 molecules to form a methanol product. Since the reaction is an exothermic reaction, a considerable amount of heat is generated, and the generated heat is used for production of steam or electricity for use in the manufacturing site. For methanol synthesis, the ratio of hydrogen molecules to carbon monoxide molecules is 2: 1.

Having described specific portions of the present invention in detail, those skilled in the art will appreciate that these specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereby. something to do. Accordingly, the actual scope of the present invention will be defined by the appended claims and their equivalents.

Claims (9)

(a) lowering the moisture content of the organic waste through a dehydration process;
(b) decomposing the organic waste into a low molecular organic material through a thermal hydrolysis process; And
(c) producing the biogas in which carbon dioxide and methane are mixed through the anaerobic digestion process of the low molecular organic material.
The method according to claim 1,
Wherein the step (b) is carried out at 150 to 200 ° C for 20 to 60 minutes.
3. The method of claim 2,
Wherein the step (b) is carried out at 4.7 to 15.5 bar.
The method according to claim 1,
Wherein the step (c) comprises producing biogas and then reacting with sodium hydroxide or iron chelate to remove hydrogen sulfide.
The method according to claim 1,
(c-1) separating the desorbing liquid from the organic waste having undergone the digestion process in the step (c) ( secondary dehydration process ); And (c-2) precipitating struvite from the desalination solution ( MAP Struvite crystallization reaction process ).
The method according to claim 1,
(d) modifying the biogas mixed with carbon dioxide and methane gas produced in the step (c) to produce a synthesis gas in which carbon monoxide and hydrogen are mixed; And
(e) synthesizing methanol from the synthesis gas.
The method according to claim 6,
The step (d) is performed using nickel (Ni), cobalt (Co), rhodium (Rh), ruthenium (Ru), Mo ₂ C, palladium (Pd) ≪ / RTI >
8. The method of claim 7,
Wherein the step (d) is performed at a temperature of 600 to 1,000 ° C. and 1 to 20 bar.
The method according to claim 6,
Wherein the step (e) is performed at 200 to 300 < 0 > C.

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