KR20240052705A - Process for recovery of ammonia, methane and hydrogen from waste - Google Patents

Abstract

According to one embodiment of the present disclosure, hydrofermenting a feed to produce a first gaseous product, wherein the first gaseous product comprises hydrogen and carbon dioxide; separating hydrogen from the first gaseous product; methane fermenting the filtrate of the hydrofermentation to produce a second gaseous product, wherein the second gaseous product comprises methane and carbon dioxide; Separating methane from the second gaseous product: separating the filtrate of methane fermentation into solid and liquid; and separating ammonia from the liquid component separated in the solid-liquid separation step. By providing a process for recovering ammonia, methane, and hydrogen from waste, ammonia, methane, and hydrogen can be recovered in high yield.

Description

{Process for recovery of ammonia, methane and hydrogen from waste}

This disclosure relates to a process for recovering ammonia, methane and hydrogen from waste.

In order to discharge wastes such as livestock waste and food waste, a process of decomposing them by microorganisms is required, and the decomposition of wastes by these microorganisms usually proceeds in anoxic conditions. Biodegradation by microorganisms in such anoxic conditions is required. The decomposition of organic matter is called anaerobic digestion. As products of anaerobic digestion, gases such as hydrogen, methane, and carbon dioxide are produced.

In addition, the filtrate of anaerobic digestion contains components that can be reused for other industrial purposes, such as ammonia. Methods for efficiently recovering reusable components from the products, by-products, and filtrate of anaerobic digestion have been actively studied. there is.

US 2016-0206993 A1

The present disclosure provides a process for recovering ammonia, methane and hydrogen from waste.

A process for recovering ammonia, methane and hydrogen from waste according to the first aspect of the present disclosure includes hydrofermenting the feed to produce first gaseous products, wherein the first gaseous products comprise hydrogen and carbon dioxide. and; separating hydrogen from the first gaseous product; methane fermenting the filtrate of the hydrofermentation to produce a second gaseous product, wherein the second gaseous product comprises methane and carbon dioxide; Separating methane from the second gaseous product: separating the filtrate of methane fermentation into solid and liquid; And it may include the step of separating ammonia from the liquid component separated in the solid-liquid separation step.

According to one embodiment, the process of recovering ammonia, methane, and hydrogen from waste may further include thermally hydrolyzing the feed before the hydrogen fermentation step.

According to one embodiment, the process of recovering ammonia, methane, and hydrogen from waste may further include the step of pretreating the filtrate of methane fermentation before the solid-liquid separation step.

According to one embodiment, the pretreatment step may include at least one of gravity sedimentation, filtration, and coagulation sedimentation of the filtrate of methane fermentation.

According to one embodiment, separating hydrogen from the first gaseous product includes supplying a carbon dioxide absorbent to the first membrane separator; and supplying the first gaseous product to the first membrane separator.

According to one embodiment, the first membrane separator may be a gas-liquid membrane separator.

According to one embodiment, the step of separating methane from the second gaseous product further comprises feeding the second gaseous product to a second membrane separator, where the second membrane separator may be a gas-gas membrane separator.

According to one embodiment, the step of separating ammonia from the liquid component separated in the solid-liquid separation step includes supplying an ammonia absorbent to a third membrane separator; And it may further include supplying the liquid component to a third membrane separator.

According to one embodiment, the third membrane separator may include a hydrophobic membrane.

According to one embodiment, the ammonia absorbent may include at least one of sulfuric acid, nitric acid, and phosphoric acid.

According to one embodiment, the third membrane may be a liquid-liquid membrane separator.

According to one embodiment, the process of recovering ammonia, methane, and hydrogen from waste may further include solidifying the recovered ammonia.

According to one embodiment, the step of separating ammonia from the liquid component separated in the solid-liquid separation step includes adsorbing ammonium ions (NH ₄ ⁺ ) contained in the effluent of the third membrane separator using an adsorbent; And it may further include the step of desorbing ammonium ions adsorbed on the adsorbent.

According to one embodiment, the adsorbent may include zeolite.

According to one embodiment, the ammonia absorbent may include at least one of sulfuric acid, nitric acid, and phosphoric acid at a lower concentration compared to the ammonia absorbent used in a process that does not include an adsorption step.

The process for recovering ammonia from waste according to the second aspect of the present disclosure includes the steps of separating feed into solid and liquid; and separating ammonia from the liquid component separated in the solid-liquid separation step, wherein the step of separating ammonia from the liquid component separated in the solid-liquid separation step includes supplying an ammonia absorbent to a third membrane separator; and supplying the liquid component separated in the solid-liquid separation step to a third membrane separator, wherein the third membrane separator includes a hydrophobic membrane.

According to one embodiment, the step of separating ammonia from the liquid component separated in the solid-liquid separation step includes adsorbing ammonium ions (NH ₄ ⁺ ) contained in the effluent of the third membrane separator using an adsorbent; And it may further include the step of desorbing ammonium ions adsorbed on the adsorbent.

According to the first aspect of the present disclosure, hydrogen, methane, and ammonia can be recovered in high yield, and fouling of the separator for recovering each component can be prevented.

1 is a process flow diagram of a process for recovering ammonia, methane and hydrogen from waste according to one embodiment.
Figure 2 is a schematic diagram of a hydrophobic membrane according to one embodiment.
Figure 3 is a schematic diagram of the step of separating ammonia from the liquid component separated in the solid-liquid separation step according to one embodiment.
Figures 4 to 6 are graphs showing the change in ammonium adsorption rate of zeolite with respect to the amount of zeolite according to one embodiment.
7 to 9 are graphs showing changes in the theoretical ammonium adsorption rate of zeolite with respect to the amount of zeolite according to one embodiment.

The objects, advantages, and features of the present disclosure will become more apparent from the following detailed description and preferred embodiments taken in conjunction with the accompanying drawings, but the present disclosure is not necessarily limited thereto. Additionally, in describing the present disclosure, if it is determined that a detailed description of related known technologies may unnecessarily obscure the gist of the present disclosure, the detailed description will be omitted.

Hereinafter, an implementation example of the present disclosure will be described in detail with reference to the attached drawings.

1 is a process flow diagram of a process for recovering ammonia, methane and hydrogen from waste according to one embodiment.

The process of recovering ammonia, methane and hydrogen from waste of the present disclosure includes hydrofermenting the feed to produce first gaseous products, wherein the first gaseous products include hydrogen and carbon dioxide.

Referring to FIG. 1, the feed may be supplied to the hydrogen fermenter 1 to produce a first gaseous product including hydrogen and carbon dioxide.

Feed is waste such as household waste, industrial waste, and livestock waste, and may include waste containing organic matter. The waste may be, for example, food waste, livestock manure, sewage sludge, or agricultural by-products.

The hydrogen fermentation step is a step of decomposing organic matter, which is a component of waste, using microorganisms or fungi. The hydrogen fermentation step may be an anaerobic fermentation step of decomposing organic matter using microorganisms or fungi, preferably under anaerobic conditions. Fermentation of the feed by microorganisms in the hydrogen fermentation step produces a first gaseous product, which includes hydrogen and carbon dioxide as a by-product.

In one embodiment, hydrofermentation may be performed at a temperature of 30 to 60° C. and a pH of 6 to 8.

In one embodiment, the process may further include thermally hydrolyzing the feed before the hydrogen fermentation step. Before the hydrogen fermentation step, under conditions of high temperature and pressure, water vapor is sprayed on the feed to perform thermal hydrolysis to decompose the high molecular substances present in the feed into low molecular substances, thereby making the action of microorganisms active in the hydrogen fermentation step. , As a result, the amount of hydrogen generated as a product of fermentation of the feed by microorganisms can be increased. Specifically, in the thermal hydrolysis step, among the microorganisms present in the feed, hydrogen-producing microorganisms, such as Clostridium sp., survive by forming spores, while the activity of non-hydrogen-producing microorganisms or methanogenic microorganisms, such as Halobacterota, is reduced. This is suppressed, and the amount of hydrogen generated in the hydrogen fermentation stage increases. Thereafter, the suppressed non-hydrogen producing microorganisms can be activated again in the environment of the methane fermentation step, which performs methane fermentation to convert volatile fatty acids produced by metabolism of low-molecular-weight substances obtained in the thermal hydrolysis step into methane. That is, thermal hydrolysis of the feed can increase the amount of products of hydrogen fermentation and methane fermentation. More specifically, the thermal hydrolysis of the feed is carried out for 15 to 30 minutes at a temperature of 100 to 200 ° C. and a pressure of 1.0 atm to 15 atm, preferably at a temperature of 120 to 180 ° C. and a pressure of 1.9 atm to 10 atm. You can.

The process includes separating hydrogen from the first gaseous product. As described above, the first gas product contains hydrogen and carbon dioxide, and in order to recover hydrogen therefrom, a step of separating only the hydrogen is required.

In one embodiment, separating hydrogen from the first gaseous product may further include supplying a carbon dioxide absorbent to the first membrane separator and supplying the first gaseous product to the first membrane separator. Referring to FIG. 1, the first gas product containing hydrogen and carbon dioxide produced in the hydrogen fermentation tank 1 is supplied to the first membrane separator 3, and at this time, the carbon dioxide absorbent is also supplied from the carbon dioxide absorber feeder 4. It is supplied to the membrane separator (3). Hydrogen and carbon dioxide contained in the first gas product have similar diffusion rates, so it is not easy to separate them using a separator that utilizes the difference in gas diffusion rates commonly used to separate components of a gas mixture in the art. In consideration of this situation, one embodiment of the present disclosure supplies a carbon dioxide absorbent and a first gaseous product to the first membrane separator, so that the first gaseous product as a supply flow and the absorption flow as an absorption flow to the first membrane separator. As the carbon dioxide absorbent flows across the membrane, only the carbon dioxide in the supply flow penetrates the membrane to the absorption flow side and diffuses, thereby separating carbon dioxide from hydrogen. Here, carbon dioxide, which has high solubility in the carbon dioxide absorbent, diffuses from the feed flow into the absorption flow, dissolves in the absorption flow, and is separated from the feed flow. The separated hydrogen is recovered, and the mixture of carbon dioxide and carbon dioxide absorbent that has diffused through the membrane is discharged outside the first membrane separator. Referring to FIG. 1, this can be recycled to the carbon dioxide absorbent feeder (4). The carbon dioxide absorbent recycled to the carbon dioxide absorbent feeder may be regenerated under high temperature and high pressure conditions and supplied again to the first membrane separator.

In one embodiment, the step of separating hydrogen from the first gaseous product is performed at room temperature between 20 and 30° C., with a feed flow rate of 500 to 800 mL/min and an absorption flow rate of 300 to 500 mL/min. You can.

The carbon dioxide absorbent is not limited as long as it is a material that can absorb carbon dioxide flowing through the membrane from the feed flow. For example, the carbon dioxide absorbent may be NaOH, KOH, and amine-based absorbent such as monoethanolamine and triethylamine.

In one embodiment, the first membrane separator may be a gas-liquid membrane separator. As described in the present disclosure, when a gas such as a supply flow and an absorption flow are supplied together to the first membrane separator, the gas supply flow and the liquid absorption flow flow across the membrane in the membrane separator. The expression "gas-liquid" membrane separator in the present disclosure refers to the state of two flows flowing across the membrane in the membrane separator. When the first membrane separator is a gas-liquid membrane separator, the gas is supplied to the first membrane separator. The carbon dioxide absorbent used is in a liquid state.

In one embodiment, the first membrane separator may include a hydrophobic membrane. A hydrophobic membrane is a membrane that has high hydrophobicity and high gas permeability, allowing non-liquid substances to selectively pass through a separator containing an aqueous system, and can be used to separate carbon dioxide gas in the above-mentioned gas-liquid membrane separator.

In one embodiment, the process may further include supplying the first gas product from which carbon dioxide has been removed to a desiccator. Referring to Figure 1, the first gaseous product comprising hydrogen and water is supplied to the desiccator (5). In the process of separating carbon dioxide from the first gas product into an absorption flow in the first membrane separator, water derived from the carbon dioxide absorbent described above passes through the membrane in the form of water vapor, is contained in the first gas product, and flows out from the first membrane separator. The desiccator removes water contained in the first gas product by drying it, allowing pure hydrogen to be recovered.

The process includes methane fermentation of the filtrate of the hydrofermentation to produce second gaseous products, wherein the second gaseous products include methane and carbon dioxide. As used herein, the term “filtrate of hydrofermentation” means liquid and solid products of the hydrofermentation step of the feed, excluding the first gaseous product, and the portion of the feed that is not fermented in the hydrofermentation step. Referring to FIG. 1, the filtrate from the hydrogen fermentation tank is supplied to the methane fermentation tank 2, and a second gas product including methane and carbon dioxide is produced in the methane fermentation tank. The methane fermentation step is a step of decomposing organic matter, which is a component of the filtrate of hydrogen fermentation, using microorganisms or fungi, similar to the hydrogen fermentation step, and is preferably an anaerobic fermentation step of decomposing organic matter using microorganisms or fungi under anaerobic conditions. It can be. By fermentation of the filtrate of hydrogen fermentation by microorganisms in the methane fermentation step, a second gaseous product is produced, which includes methane and carbon dioxide as a by-product.

In one embodiment, methane fermentation can be performed at the same temperature and pH as hydrogen fermentation.

The process for recovering ammonia, methane and hydrogen from waste of the present disclosure includes separating the methane from the second gaseous product. As described above, the second gas product contains methane and carbon dioxide, and in order to recover methane therefrom, a step of separating only the methane is required.

In one embodiment, the step of separating methane from the second gaseous product may be performed at room temperature between 20 and 30° C. and with a feed flow rate of 500 to 800 mL/min.

In one embodiment, separating methane from the second gaseous product may further include feeding the second gaseous product to a second membrane separator, where the second membrane separator may be a gas-gas membrane separator. . Referring to Figure 1, a second gaseous product comprising methane and carbon dioxide is fed to the second membrane separator (6). The second gaseous product supplied to the second membrane separator may flow in one membrane-separated zone as a feed flow, and air may flow as a permeate flow in another membrane-separated zone. Therefore, in one embodiment, the second membrane separator may be a gas-gas membrane separator, and methane and carbon dioxide have different membrane permeation rates, so that carbon dioxide permeating the membrane by diffusion toward the permeate flow side due to the difference in permeation rate is methane. can be separated from The separated methane is recovered, and the carbon dioxide can be released into the atmosphere.

There is no limitation in the method of generating the permeate flow as long as it is a separate gas flow separated from the supply flow by a membrane in the second membrane separator. In one embodiment, the process may further include blowing the second membrane separator using a blower. Referring to Figure 1, the blower 7 blows air to the second membrane separator 6. Blowing by the blower is performed in a direction perpendicular to the membrane, whereby the supply flow flows in the direction of the membrane, and at this time, carbon dioxide diffuses toward the permeate flow side due to the difference in membrane permeation speed. The permeation flow may receive carbon dioxide flowing through the membrane and discharge it to the outside of the second membrane separator. Through this process, a second gaseous product containing methane separated from carbon dioxide is recovered.

The process includes the step of separating the filtrate of methane fermentation into solid and liquid. As used herein, the term "filtrate of methane fermentation" refers to the liquid and solid products of the products of the methane fermentation step, excluding the second gaseous products, and the portion of the filtrate of the hydrogen fermentation that is not fermented in the methane fermentation step. There are no limitations to the method for solid-liquid separation of the filtrate of methane fermentation as long as the solid and liquid components of the filtrate of methane fermentation can be separated. Referring to FIG. 1, the filtrate of methane fermentation is supplied to the solid-liquid separator 8 and separated into a liquid component, which is an anaerobic centrate, and a sludge, which is a solid component.

In one embodiment, the process may further include pretreating the filtrate of methane fermentation before the solid-liquid separation step. In Figure 1, the pretreatment step is not shown. The filtrate of methane fermentation is separated into solid and liquid, and the separated liquid component is supplied to a third membrane separator including a membrane. In the solid-liquid separation step, contaminants such as sludge, which is in an intermediate state between solid and liquid, may be included in the separated liquid component. This may accumulate on the membrane surface or pores of the third membrane separator and cause fouling, a phenomenon that reduces the performance of the membrane separator. By pretreating the filtrate of methane fermentation before the solid-liquid separation step, components in an intermediate state between solid and liquid, such as sludge, can be separated into solid components, preventing the components from being supplied to the third membrane separator, and the pretreatment step As a result, membrane fouling can be prevented. The pretreatment step is not limited to the method as long as it can reduce contaminants that may be contained in the liquid component among the solid-liquid separated components to prevent membrane fouling of the third membrane separator.

In one embodiment, the pretreatment step may include at least one of gravity sedimentation, filtration, and coagulation sedimentation. Gravity sedimentation, filtration and coagulation sedimentation correspond to pretreatments that help separate contaminants as solid components rather than liquid components so that they are not supplied to the third membrane separator in the solid-liquid separation step.

The process includes the step of separating ammonia from the liquid component separated in the solid-liquid separation step. The separated liquid components may contain contaminants such as phosphates, pathogens, and antibiotics.

In one embodiment, the step of separating ammonia from the liquid component separated in the solid-liquid separation step includes supplying an ammonia absorbent to a third membrane separator and supplying the liquid component separated in the solid-liquid separation step to the third membrane separator. More can be included. Referring to FIG. 1, the anaerobic desorption liquid, which is a liquid component, and the ammonia absorbent from the ammonia absorbent feeder 10 are supplied to the third membrane separator 9. The liquid component separated in the solid-liquid separation step supplied as a feed flow to the third membrane separator is an ammonia aqueous solution containing a large amount of ammonia (NH ₃ ), and the ammonia absorbent supplied as a recovery flow to the third membrane separator does not contain ammonia. It may be a liquid component. In the case of the third membrane feeder, one part separated by the membrane is supplied with the feed flow and the other part separated by the membrane is supplied with the recovery flow, and the membrane of the third membrane separator provides a passage through which ammonia gas from the feed flow moves to the recovery flow. can perform its role. This movement of ammonia gas may be due to a difference in partial pressure of ammonia gas between the supply flow and the return flow. Dissolved ammonia in the feed flow evaporates into gas phase at the interface between the feed flow and membrane pores according to the gas phase-aqueous liquid phase equilibrium relationship, and can penetrate the membrane and diffuse toward the recovery flow.

In one embodiment, the amount of ammonia diffusing from the feed flow toward the return flow can be controlled by controlling the pH of the feed flow and return flow. Here, the pH adjustment of the feed flow and return flow is not limited to any method. As the pH of the feed flow increases, solubility decreases, causing ammonia (NH _3(g) ) in the feed flow to increase, and as pH decreases, ammonium ions (NH ₄ ⁺ _(aq) ) in the feed flow may increase. At the membrane pore interface in contact with the supply flow, the partial pressure of ammonia gas increases due to pH control, and at the membrane pore interface in contact with the recovery flow, ammonia is converted to ammonium ions due to a relatively low pH compared to the supply flow, so the partial pressure of ammonia gas decreases. You can. Therefore, a partial pressure difference of ammonia gas occurs between the supply flow and the recovery flow, and this partial pressure difference can induce selective diffusion in which ammonia gas continues to move from the supply flow to the recovery flow.

In one embodiment, since the main components of the feed flow and return flow of the third membrane separator are both liquid as described above, the third membrane separator may be a liquid-liquid membrane separator.

In one embodiment, the step of separating ammonia from the liquid component may be performed at room temperature of 20 to 30 °C, flow rates of the feed flow and return flow of 500 to 800 mL/min, and pH conditions of 8 to 12.

In one embodiment, the third membrane separator can include a hydrophobic membrane. A hydrophobic membrane is a membrane that has high hydrophobicity and high gas permeability, allowing non-liquid substances to selectively pass through in an aqueous system, and can be used to separate ammonia gas in the liquid-liquid membrane separator described above. Referring to Figure 2, by controlling the pH of the supply flow and the recovery flow, a partial pressure difference of ammonia gas is generated between the supply flow and the recovery flow, and according to Henry's law, ammonia gas is released from the supply flow with a high concentration of ammonia gas. It can diffuse through the pores of the hydrophobic membrane towards the recovery flow side where its concentration is low. Membrane separators containing such hydrophobic membranes have compressibility and modularity, occupy a small installation space, have excellent scalability, and are energy efficient by transferring substances through diffusion rather than mechanical pressure. In addition, membrane separators containing hydrophobic membranes can control the flow rate, preventing phenomena affecting separator performance such as emulsion creation, flooding, and foaming, and improving separation performance. It is excellent and makes it possible to recover high purity ammonia.

In one embodiment, the ammonia absorbent may include an acid. For example, the ammonia absorbent may include at least one of sulfuric acid, nitric acid, and phosphoric acid. The ammonia absorbent supplied as the recovery flow to the third membrane separator contains an acid, so that the pH of the recovery flow can be controlled to be lower than the pH of the supply flow, which is the difference between the supply flow and the recovery flow bordering the membrane as described above. By generating a partial pressure difference of ammonia gas, continuous diffusion of ammonia gas toward the recovery flow can be induced. In addition, by containing the above acid, the ammonia absorbent can have the advantage of being able to obtain the recovered ammonia in the form of a salt such as ammonium sulfate, ammonium nitrate, or ammonium phosphate.

In one embodiment, the process may further include solidifying the recovered ammonia. As mentioned above, the ammonia recovered, for example in the form of ammonium salts, may be transferred to other components present in the recovery flow, e.g. H ₂ S which can migrate to the gas phase if an ammonia absorbent comprising sulfuric acid is used as the recovery flow. It may contain ingredients such as impurities, which cause bad odor. In order to remove such impurities and recover pure ammonium salt that can be used as a solid fertilizer with high added value, the process involves evaporating and crystallizing ammonia in the form of recovered liquid ammonium to evaporate the impurities and crystallize the ammonium salt in solid form. can be obtained.

In one embodiment, the step of separating ammonia from the liquid component separated in the solid-liquid separation step includes adsorbing ammonium ions (NH ₄ ⁺ ) contained in the effluent of the third membrane separator using an adsorbent; And it may further include the step of desorbing ammonium ions adsorbed on the adsorbent. Figure 3 schematically shows the ammonia separation step as described above.

The third membrane separator effluent is the return flow of the third membrane separator and contains ammonia gas in the form of ammonium ions that has passed through the membrane by diffusion from the feed flow as described above. As shown in FIG. 3, when ammonium ions contained in the third membrane separator effluent are adsorbed with an adsorbent in the adsorption column 11, the third membrane separator effluent, that is, in the recovery flow of the third membrane separator, Ammonia accumulation and an increase in pH of the recovery flow as measured by the pH meter (12) can be prevented. This prevents a decrease in the pH difference between the feed flow and the recovery flow, thereby preventing a decrease in ammonia recovery efficiency. In other words, the adsorption step after treatment by the third membrane separator prevents the pH of the recovery flow from increasing, so that a low-concentration acid solution can be used as an ammonia absorbent in the recovery flow compared to the third membrane separation step without the latter adsorption step. do. The use of a low-concentration acid solution can increase the safety and economic efficiency of the process compared to using a high-concentration acid. In one embodiment, the ammonia absorbent may include at least one of sulfuric acid, nitric acid, and phosphoric acid at a lower concentration compared to the ammonia absorbent used in a process that does not include an adsorption step.

In one embodiment, the adsorbent may include zeolite. Zeolites are porous crystalline bodies composed of hydrated aluminosilicates, have high mechanical and thermal stability, and low processing costs. In particular, zeolites have high selectivity for ammonium ions even in the presence of competing cations such as sodium, calcium, potassium, and magnesium in the third membrane separator effluent, making it possible to exclude impurities from entering the recovered ammonium ions. It has the advantage of being

In one embodiment, the zeolite used as an adsorbent in the ammonia separation step may be natural zeolite, and natural zeolite is economically advantageous compared to synthetic zeolite. Natural zeolite has a negative charge and is combined with weakly acidic cations such as sodium ions (Na ⁺ ) and potassium ions (K ⁺ ) located at cation exchange sites to maintain electrical neutrality. When this natural zeolite is introduced into the third membrane separator effluent, H ⁺ in the third membrane separator effluent is exchanged with weakly acidic cations located at the cation exchange sites of the natural zeolite, resulting in an increase in the pH of the third membrane separator effluent. There is a possibility that it will happen. To prevent such pH changes, the natural zeolite can be used with improved adsorption capacity by pre-treating it with an acidic solution to remove impurities such as weakly acidic cations inside the pores and increase porosity.

In the step of desorbing the ammonium ions adsorbed on the adsorbent, the ammonium ions are desorbed and recovered. There is no limit to the method for desorbing the ammonium ions from the adsorbent, but preferably a method of desorbing the adsorbed ammonium ions by applying heat to the adsorbent. This can be used. Referring to FIG. 3, a thermal desorber 13 is used as a method of desorbing the adsorbed ammonium ions. The recovery form of ammonium ion is not limited to solid ammonium salts. For example, in the desorption step, ammonium ions may be recovered as ammonia gas or ammonia solution, or may also be recovered as a solid such as ammonium sulfate crystals. The adsorbent from which the ammonium ions are desorbed can be used again as an adsorbent for adsorbing ammonium ions in the effluent from the third membrane separator. In one embodiment, when the adsorbent is natural zeolite, the natural zeolite after ammonium ion desorption can be used in the adsorption step without separate pretreatment.

In other words, the adsorption and desorption steps after the third membrane separation step can not only increase the safety and economic feasibility of the ammonia recovery process by tempering the strength of the acid used as a recovery flow in the third membrane separator, but also increase the form of ammonia to be recovered. It has the advantage of being able to be more diversified.

The process for recovering ammonia from waste of the present disclosure includes the step of separating the feed into solid and liquid. Here, the feed is waste such as household waste, industrial waste, and livestock waste, and may include waste containing organic matter. The waste may be, for example, food waste, livestock manure, sewage sludge, or agricultural by-products. The solid-liquid separation step is not limited to a method as long as it can separate solid components and liquid components from the feed. In one embodiment, the feed is supplied to a solid-liquid separator and separated into a liquid component, which is an anaerobic desorbed liquid, and a sludge, which is a solid component.

The process includes the step of separating ammonia from the liquid component separated in the solid-liquid separation step. Separated liquid components may contain contaminants such as phosphates, pathogens, and antibiotics.

The step of separating ammonia from the liquid component separated in the solid-liquid separation step includes supplying an ammonia absorbent to a third membrane separator and supplying the liquid component separated in the solid-liquid separation step to the third membrane separator. The step of separating ammonia from the liquid component in the above process can be performed in the same manner as in the process of recovering ammonia, methane and hydrogen from waste.

The third membrane separator includes a hydrophobic membrane. In one embodiment, the third membrane separator may be the same as that used in the ammonia separation step of the process for recovering ammonia, methane, and hydrogen from waste.

In one embodiment, the step of separating ammonia from the liquid component separated in the solid-liquid separation step includes adsorbing ammonium ions (NH ₄ ⁺ ) contained in the effluent of the third membrane separator using an adsorbent; And it may further include the step of desorbing ammonium ions adsorbed on the adsorbent. In one embodiment, the adsorption and desorption steps may also be the same as the steps for separating ammonia in a process for recovering ammonia, methane, and hydrogen from waste.

In addition, the process conditions and equipment used, ammonia absorbent, and adsorbent of the process for recovering ammonia from waste of the present disclosure may be the same as those used in the process for recovering ammonia, methane, and hydrogen from waste.

Hereinafter, embodiments of the present invention will be further described with reference to specific experimental examples. The examples and comparative examples included in the experimental examples only illustrate the present invention and do not limit the scope of the appended patent claims, and various changes and modifications to the examples are possible within the scope and technical idea of the present invention. It is obvious to those skilled in the art, and it is natural that such variations and modifications fall within the scope of the appended patent claims.

Experimental Example 1 - Comparison of the effect of acidic solution pretreatment on zeolite

Comparing the ammonium adsorption rate of zeolite according to changes in pretreatment conditions for zeolite used as an adsorbent in the step of adsorbing ammonium ions (NH ₄ ⁺ ) contained in the effluent of the third membrane separator using the adsorbent of the process of the present disclosure. For this purpose, zeolite with a solid-liquid ratio (S/L, g/ml) of 1:10 was modified by immersing it in a sulfuric acid (H ₂ SO ₄ ) solution with a normal concentration (N) of 0 to 5 and then used to carry out the adsorption step. The concentration of ammonia in the adsorption solution was measured. The above measurements were made by varying the concentration of the sulfuric acid solution used for zeolite modification and the immersion time of the zeolite in the sulfuric acid solution.

The ammonia concentration in the initial adsorption solution was 2451.2 mg-N/L, and only in the case of zeolite pretreated with 5 N sulfuric acid, the ammonia concentration in the initial adsorption solution was 2857.85 mg-N/L. The adsorption rate of ammonium in zeolite measured for each experimental condition is shown in Table 1 below.

Ammonium adsorption rate according to pretreatment acid concentration and pretreatment time of zeolite sulfuric acid concentration
(N) steeping time
(minute) Ammonia concentration in adsorption solution after adsorption
(mg-N/L) Ammonium adsorption rate of zeolite
(%) 0 10 964 61 0 30 1146 53 0 90 1066 57 0.01 10 1205 51 0.01 30 899 63 0.01 90 1013 59 0.1 10 1027 58 0.1 30 1020 58 0.1 90 1065 57 One 10 1173 52 One 30 1223 50 One 90 1236 50 5 90 2328 19

Experimental Example 2 - Comparison of the degree of adsorption according to the amount of zeolite used for adsorption

The sulfuric acid concentration of the adsorption solution was set to 0.001N, 0.1N, and 5N, and the adsorption step was performed using the same zeolite as in Experimental Example 1 as an adsorbent. After performing the adsorption step by varying the amount (weight) of zeolite used in each adsorption step, the ammonium adsorption rate in the zeolite was evaluated, and the evaluation results are shown in Tables 2 to 4 below.

As can be seen in Tables 2 to 4, it was found that the ammonium adsorption rate of zeolite increased as the amount of zeolite used as an adsorbent increased, regardless of the initial ammonia concentration in the adsorption solution.

Figures 4 to 6 show zeolite according to the amount of zeolite pretreated with various concentrations of sulfuric acid solution, when the sulfuric acid concentration of the adsorption solution is 0.001N, 0.1N, and 5N, and the initial ammonia concentration is 2000 mg-N/L, respectively. This is a graph of the ammonium adsorption rate. Since all of the above graphs are linear, it can be seen that the amount of zeolite used and the ammonium adsorption rate are directly proportional to each other.

In addition, the graphs of Figures 4 to 6 show the theoretical initial ammonia concentration (C _e ) and C _e /q _e derived by the Langmuir isothermal adsorption equation (where q _e corresponds to the amount of ammonium ions that can be adsorbed per unit weight of zeolite. 7 to 9, which are graphs of the relationship with ) (Figures 7 to 9 are the isothermal adsorption equation when the sulfuric acid concentration of the adsorption solution is 0.001N, 0.1N, and 5N, and the initial ammonia concentration is 2000 mg-N/L, respectively. When compared to (corresponding), considering that the graph appears linear and shows a similar slope, it can be confirmed that the experimental data is consistent with the theoretical values.

Experimental Example 3 - Comparison of the effect of acidic solution pretreatment on zeolite in the ammonium ion adsorption step associated with a membrane separator

Supplying an aqueous ammonia solution as a feed flow to a third membrane separator including a hydrophobic membrane, and using an ammonia absorbent containing a low concentration of sulfuric acid as a recovery flow, recovery containing ammonia that is selectively diffused by a partial pressure difference of ammonia gas. I got the flow. Thereafter, the recovery flow was introduced into an adsorption column containing a zeolite adsorbent, and the ammonia contained in the recovery flow was adsorbed by the zeolite adsorbent. The ammonium concentration in the feed flow according to the above series of processes and the ammonium adsorption rate by zeolite in the adsorption column were measured over time while changing the pretreatment acid concentration of the zeolite. The results of measuring the ammonium concentration in the feed flow are shown in the table below. In 5 to 7, the results of measuring the ammonium adsorption rate by zeolite in the adsorption column were shown in Tables 8 to 10.

Table 11 shows the results of measuring the change in concentration of ammonium ions in the feed flow under the same conditions as the above process, except that there was no treatment process using an adsorption column containing a zeolite adsorbent.

From the above measurement results, it was found that the ammonium removal rate in the feed flow in the process linking the third membrane separator and the adsorption column was higher than that in the process using the third membrane separator alone. The transfer of ammonium ions in the feed flow to the recovery flow by the membrane separator is achieved due to the ammonia concentration gradient in the feed and recovery flows. In other words, the greater the difference in ammonia concentration between the supply flow and the recovery flow, the greater the ammonium removal rate in the supply flow. Considering this, when using the same acid as an ammonia absorbent, in a single membrane separator process, the hydrogen ions inside the absorption flow are quickly consumed and ammonium ions can no longer be captured, so the concentration gradient decreases and the ammonium in the feed flow is reduced. While the removal rate is relatively low, in the membrane separator and adsorption column linkage process, the zeolite in the adsorption column can maintain the concentration gradient by adsorbing ammonium ions and releasing hydrogen ions at the same time, so it can be inferred that the ammonium removal rate in the feed flow is relatively high. You can.

In addition, in the process linking the third membrane separator and the adsorption column, it was confirmed that the ammonium removal rate in the feed flow and the ammonium adsorption rate in the zeolite were high when the zeolite in the adsorption column was pretreated with a higher concentration of acid.

Experimental Example 4 - Comparison of the degree of ammonium adsorption and desorption according to the type of zeolite and the presence or absence of pretreatment with acid.

Natural zeolite with or without acid pretreatment and 6 g of synthetic zeolite not pretreated with acid were added to a 0.03 L recovery flow with a predetermined ammonia concentration, and stirred for 30 minutes to allow ammonium ions to be adsorbed on the zeolite. Afterwards, the zeolite was recovered and the ammonium adsorption capacity of the zeolite was measured. The recovered zeolite was introduced into a desorber set at a temperature of 200 to 400°C to desorb the ammonium ions adsorbed on the zeolite in the form of ammonia to improve the desorption capacity and thermal desorption efficiency of the zeolite. Measured. Ammonia gas released from zeolite through thermal desorption was collected using a sulfuric acid solution as a collection solution, and the amount of desorbed ammonia was evaluated by measuring the ammonia concentration in the collection solution. The measurement results are shown in Tables 12 to 16.

The present disclosure has been described in detail above through specific implementation examples. The implementation examples are for specifically explaining the present disclosure, and the present disclosure is not limited thereto. It will be clear that modifications and improvements can be made by those skilled in the art within the technical spirit of the present disclosure.

All simple modifications or changes to the present disclosure fall within the scope of the present disclosure, and the specific scope of protection of the present disclosure will be made clear by the appended claims.

1 Hydrogen fermenter 2 Methane fermenter
3 First membrane separator 4 Carbon dioxide absorbent feeder
5 Desiccator 6 Second membrane separator
7 Blower 8 Solid-liquid separator
9 Third membrane separator 10 Ammonia absorbent feeder
11 Adsorption column 12 pH meter
13 Thermal desorber

Claims (17)

A process for recovering ammonia, methane and hydrogen from waste, comprising:
hydrofermenting the feed to produce a first gaseous product, wherein the first gaseous product comprises hydrogen and carbon dioxide;
separating hydrogen from the first gaseous product;
methane fermenting the filtrate of the hydrofermentation to produce a second gaseous product, wherein the second gaseous product comprises methane and carbon dioxide;
Separating methane from the second gaseous product:
Separating the filtrate of methane fermentation into solid and liquid; and
A process for recovering ammonia, methane and hydrogen from waste, comprising the step of separating ammonia from the liquid component separated in the solid-liquid separation step. In claim 1,
A process for recovering ammonia, methane and hydrogen from waste, further comprising the step of thermally hydrolyzing the feed prior to the hydrogen fermentation step. In claim 1,
A process for recovering ammonia, methane and hydrogen from waste, further comprising pre-treating the filtrate of methane fermentation before the solid-liquid separation step. In claim 3,
A process for recovering ammonia, methane, and hydrogen from waste, wherein the pretreatment step includes at least one of gravity settling, filtration, and coagulation precipitation of the filtrate of the methane fermentation. In claim 1,
Separating hydrogen from the first gaseous product involves
supplying a carbon dioxide absorbent to the first membrane separator; and
A process for recovering ammonia, methane and hydrogen from waste, further comprising feeding a first gaseous product to a first membrane separator. In claim 5,
A process for recovering ammonia, methane and hydrogen from waste, wherein the first membrane separator is a gas-liquid membrane separator. In claim 1,
Separating the methane from the second gaseous product further includes feeding the second gaseous product to a second membrane separator, wherein the second membrane separator is a gas-gas membrane separator to separate ammonia, methane and hydrogen from the waste. recovery process. In claim 1,
The step of separating ammonia from the liquid component separated in the solid-liquid separation step includes supplying an ammonia absorbent to a third membrane separator; and
A process for recovering ammonia, methane and hydrogen from waste, further comprising feeding the liquid component separated in the solid-liquid separation step to a third membrane separator. In claim 8,
A third membrane separator is a process for recovering ammonia, methane and hydrogen from waste, comprising a hydrophobic membrane. In claim 8,
A process for recovering ammonia, methane, and hydrogen from waste, wherein the ammonia absorbent includes at least one of sulfuric acid, nitric acid, and phosphoric acid. In claim 8,
A process for recovering ammonia, methane and hydrogen from anaerobic digestion products, wherein the third membrane is a liquid-liquid membrane separator. In claim 1,
A process for recovering ammonia and hydrogen from anaerobic digestion products, the process further comprising solidifying the recovered ammonia. In claim 8,
The steps for separating ammonia from the liquid component separated in the solid-liquid separation step are:
Adsorbing ammonium ions (NH ₄ ⁺ ) contained in the third membrane separator effluent using an adsorbent; and
A process for recovering ammonia, methane and hydrogen from waste, further comprising the step of desorbing ammonium ions adsorbed on the adsorbent. In claim 13,
A process for recovering ammonia, methane and hydrogen from waste, wherein the adsorbent includes zeolite. In claim 13,
A process for recovering ammonia, methane and hydrogen from waste, wherein the ammonia absorbent contains a lower concentration of at least one of sulfuric acid, nitric acid and phosphoric acid compared to the ammonia absorbent used in processes that do not include an adsorption step. A process for recovering ammonia from waste, comprising:
Separating the feed into solid and liquid; and
It includes the step of separating ammonia from the liquid component separated in the solid-liquid separation step,
The step of separating ammonia from the liquid component separated in the solid-liquid separation step includes supplying an ammonia absorbent to a third membrane separator; and
Comprising the step of supplying the liquid component separated in the solid-liquid separation step to a third membrane separator,
A third membrane separator is a process for recovering ammonia from waste, comprising a hydrophobic membrane. In claim 16,
The steps of separating ammonia from the liquid component separated in the solid-liquid separation step are:
Adsorbing ammonium ions (NH ₄ ⁺ ) contained in the third membrane separator effluent using an adsorbent; and
A process for recovering ammonia from waste, further comprising the step of desorbing ammonium ions adsorbed on the adsorbent.