JP2024510000A - MEC system - Google Patents

Abstract

The present invention provides MEC stacks having a plurality of MEC cells including at least one gas inlet and at least one degassing element, and methods for improving biocatalyst-catalyzed bioelectrochemical methanation reactions in those MEC stacks. I will provide a. [Selection diagram] Figure 5

Description

TECHNICAL FIELD The present invention relates to microbial electrolysis cell (MEC) systems, and more particularly to MEC systems in which multiple MECs are stacked in an MEC stack for performing bioelectrochemical methanogenesis reactions.

Methane has the highest energy density per carbon atom of any fossil fuel, and its energy conversion potential is greater than that of other natural gases, which can be obtained directly by combustion in the presence of oxygen or by power generation using fuel cells. is also much larger. The energy production potential of methane is gaining increasing importance in the global market.

Methane produced from renewable sources (renewable methane) is a sustainable and renewable energy source that is already becoming an alternative to coal and other fossil fuels today. For this reason, many different processes for producing renewable methane, so-called methanation processes, have been developed and optimized in the prior art.

One methanation process, for example, can be based on microbial electrochemical technology (MET), called bioelectrochemical methanation. This process is realized in a microbial electrolysis cell (MEC), a unique system capable of converting electrical energy into chemical energy using microorganisms as catalysts. This system combines electrolysis and methane production in a single reactor, the so-called MEC. If within the MEC a methanogenic microorganism is present, for example in the cathode compartment or cathode, the MEC is considered a bioelectrochemical methanation cell.

The reactor can include a single compartment, a cathode compartment or chamber, separated from an anode compartment or chamber, for example via a semi-permeable membrane. In some embodiments of the prior art, methane production by methanogenic microorganisms (e.g., methanogens or archaea) occurs directly in the biocathode compartment, and the electron flow required for cathodic reduction of CO2 to methane is It is supplemented by water oxidation in the anode compartment.

More specifically, the process uses electrical power to increase the potential difference between the anode and cathode of the MEC to enable the bioelectrochemical methanation reaction.

In cathodic MEC processes, electrons are generated, eg in the form of hydrogen, which are utilized as electron donors to reduce carbon sources, eg carbon dioxide, to valuable products, eg methane. The relevant bioelectrochemical methanation reactions are catalyzed by microorganisms, so-called biocatalysts.

In the present invention, the term "input gas" is used and is understood to include any gas required or suitable for the catalyst in the MEC to accomplish the chemical reaction. Suitable input gases can be selected from typical carbon donors such as CO2 and CO, but also from waste gases containing other suitable carbon donors.

According to the invention, the input gas may be an atmospheric gas, e.g. from microbial fermentation in ethanol production, the combustion of fossil fuels, e.g. in a coal-fired energy plant, or as a by-product of e.g. a geothermal power plant, or from atmospheric gas, e.g. CO2-rich emissions found as by-products or produced during activities carried out in industrial processes such as fossil fuel or agricultural industries, as a result of any human industrial activity that results in the release of gaseous compositions that diffuse into the Also understood as waste gas. Such gases, depending on their source, can contain very different gas compositions. They mainly have in common that they contain relatively large amounts of CO2 compared to air.

According to another embodiment of the invention, instead of the input gas, another inorganic carbon source containing electronic equivalents can also be used, consisting of the group consisting of sodium carbonate, potassium carbonate and ammonium carbonate, or combinations thereof. selected from among.

To increase the production of methane using bioelectrochemical methanation, MECs are stacked in so-called MEC stacks. A MEC stack is composed of multiple MECs, also referred to herein as MEC cells. MEC can be built from layers. Layers are, for example, membranes, electrodes, sealings, (porous) transport layers, turbulence promoters, electrode-membrane assemblies, bipolar plates, etc. This design simplifies MEC scalability and allows for easy replacement of individual or broken MECs as needed. Therefore, this design can simplify maintenance by the operator, even if the operator does not have specialized knowledge of bioelectrochemical systems in general. Prior art MEC stacks are constructed such that the input gases required for the reactions of all MEC cells are routed to one inlet, usually at the first MEC cell, and then moved or flowed through subsequent MECs. Thus, the input gas is used sequentially throughout the MEC cell for each reaction of the gas production process (eg, methanation).

In the prior art, the use and operation of MEC stacks poses several problems.

Firstly, the issue of volume arises. Large amounts of input gas are required for substantially optimal reaction throughout all MEC cells, thereby increasing both the size and cost associated with the MEC stack.

The second issue is related to reaction efficiency within the MEC stack. During continuous operation of prior art MEC stacks, inefficiencies are always present. For example, carbon supply strategies typically do not meet the carbon source needs of microorganisms within each MEC cell. For this reason, the electron donor in the MEC cell, e.g. hydrogen (reducing power), is often not used or is used inefficiently, resulting in low methane production and unused This results in a substantial amount of hydrogen being contained.

A further problem relates to changes in the physicochemical conditions of the microorganisms/strains caused by the introduction of input gases into the system. Prior art MEC stacks experience gradients of physicochemical conditions for the bacterial strains present, resulting in regions within the stack that do not provide optimal conditions for microbial metabolism or e.g. methane production, resulting in Compared to the theoretically calculated maximum output of such an MEC stack, the conversion of CO2 and H2 to methane is clearly reduced.

It is an object of the present invention to provide a method and system for carrying out an optimized methane production process across the MEC stack that at least partially solves or ameliorates the inefficiency problems of the prior art.

Such a method and system is defined by the independent claim relating to bioelectrochemical methane production using MEC. The dependent claims each specify embodiments of both a method and a system.

That is, a method is provided for adjusting gas gradients in a process within a microbial electrolysis cell (MEC) stack that includes at least two MEC cells. This method is
a. a step of measuring,
i. MEC cell and/or MEC stack current and voltage, to determine the hydrogen production rate;
ii. Optionally, the pH value of the catholyte in the catholyte circuit, and/or iii. optionally, the redox potential of the catholyte, and/or iv. Optionally, measuring the temperature of the catholyte;
b. determining an input gas amount for one or more gas input points based on the information evaluated in step a);
c. supplying the determined input gas amount via one or more gas input points, thereby adjusting volume requirements for efficient methane production in the MEC stack;
d. Optionally, adjusting the physicochemical conditions for efficient methane production in the MEC stack, such as the pH value and/or temperature and/or the oxidation potential of the catholyte;
e. degassing the MEC stack via one or more degassing elements disposed after the MEC cells of the MEC stack.

The method provides improved reaction conditions for the microorganisms present and improves the efficiency of methane production of the bioelectrochemical methane production process throughout the MEC stack.

In the present invention, the term "gas gradient" is to be understood as a variable amount or mass of gas occupying a certain volume of interconnected MECs in an MEC stack, as well as individual MECs. Furthermore, "gas gradient" refers to a gradient in gas phase composition. Such gradients depend on and vary not only on the physical parameters of catholyte pressure and temperature, but also on biological parameters such as microbial metabolism and reactant availability.

The MEC stack of the present invention includes at least two MEC cells, but is not limited to two. MEC stacks with 3, 4, 5, 6, 7, 8, 9, 10 or more MEC cells are also envisioned. At least two MEC cells of the MEC stack share a catholyte circuit that passes through the cathode compartment of the MEC cells. The catholyte is the fluid in which the growth medium, which also contains the input gases, is supplied to the microorganisms (strains) and/or in which the gases produced within the MEC cell are transported during the reaction.

According to the method, the first step includes measuring current and cell voltage. According to the present invention, the current and voltage of the MEC cell and/or MEC stack for determining the hydrogen production rate is measured in mol/sec based on HPR=CE×e ⁻¹ ×N _A ⁻¹ ×I be done. Here, HPR is hydrogen production rate, CE is Coulombic efficiency, e is elementary charge, _NA is Avogadro's number, and I is current. Coulombic efficiency is given by the ratio of the number of electrons in the product (i.e., hydrogen) to the total number of electrons transferred (current x time/e), and is calculated experimentally based on the MEC's hydrogen mass balance over the MEC's operating voltage range. need to be specified.

Additionally and/or alternatively, the hydrogen concentration within the cathode compartment can be measured by a dissolved hydrogen sensor. The placement of the dissolved hydrogen sensor, ie, before and/or after and/or within the MEC cell or stack, is important for tuning the production process to determine the hydrogen production rate.

This measurement of the hydrogen concentration in the cathode compartment and, in a further embodiment, the optional measurement of the catholyte pH value, the catholyte redox potential, and/or the catholyte temperature all control the reaction conditions within the MEC. The reaction process of the MEC within the MEC stack and the resulting production capacity can thus be adjusted, improved and predicted.

According to some embodiments, methanogenic microorganisms in the MEC convert hydrogen and CO2 to methane. The rate of methane production in a single MEC cell depends on the hydrogen to CO2 ratio supplied to the methanogenic microorganism and the physicochemical conditions provided to the strain/microorganism.

Theoretically, substantially optimal methane production is achieved by methanogenic microorganisms when 4 parts hydrogen and 1 part CO2 are available to them. Under ideal conditions, this results in essentially 100% conversion of starting material to methane according to the present invention. The conversion rate is determined by the activity of the biocatalyst which depends on the physicochemical conditions within the MEC. Therefore, the main objective is to ensure substantially optimal conditions for the strain in order to achieve an optimized conversion rate.

According to the present invention, one very effective way to control these conditions is to monitor the amount of hydrogen occurring (e.g., produced) within the MEC and thus available for further reactions. and to measure. Such measurements are most effectively accomplished by measuring current and/or voltage in the cathode compartment of one or more MECs, as described above.

Depending on the measured current and/or voltage, the theoretical amount of hydrogen produced in the MEC cell is calculated and a corresponding amount of CO2 is provided, thereby providing almost substantially optimal reaction conditions and conversion. achieved.

Further factors influencing the physicochemical conditions of the strain are the pH value and redox potential of the catholyte. According to the method of the invention, those additional measurements are also useful for regulating and improving the physicochemical conditions of the bacterial strain in the catholyte.

The catholyte should preferably have a pH value of 6 to 9, especially a pH value of 7.5 to 8.5, especially a pH value of about 8. Higher or lower pH values inhibit optimal growth and metabolic function behind methane production. For this reason, proper balance is assisted by the optional pH measurement of the method. The pH measurement system may be a commercially available pH sensor.

The redox potential (ORP) of an aqueous solution, such as a catholyte, determines the tendency of the solution to gain or lose electrons. In MEC cells, power is used to provide a potential difference between the anode and cathode. At the anode, water is electrochemically split into protons, electrons, and oxygen. At the cathode, electrons are used as a reducing force, e.g. H2 as an electron carrier, and an electron acceptor, e.g. CO2, is reduced to CH4. The ORP measurement system may be a commercially available ORP sensor.

A pH measurement system and an ORP measurement system are placed on the catholyte circuit. These measuring systems can be included in the degassing element, for example. Therefore, catholyte measurements are performed after the catholyte has been degassed.

Maintaining the ORP below a specified value, preferably about −100 mV, is important for optimal production of hydrogen, and thus methane.

Also, measuring and adjusting the temperature of the catholyte helps to improve the environment of the strain and improve the conversion rate. The cathode side of the MEC cell generates heat, warming the catholyte. Typically, the catholyte exiting the cathode compartment is too hot for the microorganisms in the MEC cell and subsequent MEC cells to efficiently convert CO2 and H2 to methane. Therefore, the adverse effect of increased catholyte temperature negatively limits the size of the MEC stack.

As mentioned above, step a. All possible physicochemical conditions measured in the MEC cell or MEC stack as a whole influence the methanogenesis reaction singly and/or jointly. The quantity and quality of methane-containing gas produced in a MEC stack therefore depends, at least in part, on the conditions within the individual MEC cells and the properties of the catholyte.

The next step of the method according to the invention comprises determining the amount of input gas at at least one gas input point on the basis of the information evaluated in step a).

In particular, the input gas amount should advantageously be adjusted depending on the amount of hydrogen produced in the MEC cells of the MEC stack, eg so that the ratio of hydrogen to CO2 is optimal for the strain.

Supplying the input gas to the system, particularly the catholyte, influences the pH value, ORP and temperature of the catholyte, and thus also the physicochemical conditions of the bacterial strain in the cathode compartment.

Therefore, based on the information collected in step a), the overall amount of input gas preferably required by the system can be determined and the relative amount of input gas required to balance the system can be calculated. In particular, it is determined how much input gas is to be supplied to the system and optionally to one or more gas inlets of the system.

Accordingly, the next step of the method comprises supplying the determined amount of input gas through at least one gas input point, optionally at least two or more gas input points, thereby increasing efficiency in the MEC. Adjust the volume requirements for organic methane production. Furthermore, in some embodiments, the supply of the determined input gas amount is also used to adjust the pH value and/or temperature and/or oxidation potential of the catholyte, thereby improving the reaction conditions for methane production. Ru.

Determining the required input gas for at least one or more gas inlets and supplying the input gas from at least one or more gas inlets has proven to be particularly advantageous and to provide unexpected synergistic effects. There is.

For exemplary purposes, methods of the invention, including, for example, supplying an input gas at two or more gas inlets, provide an efficient amount of CH4 and also substantially reduce the overall energy input required. reducing the voltage and/or current required for optimal operation, including in particular hydrogen production and cooling of the MEC stack, yet still compared to prior known bioelectrochemical methanation equipment. , can result in apparently efficient methane production.

Additionally, it is also advantageous to increase the electrode-liquid interfacial area (area) of the MEC cell, also referred to herein as "active electrode surface area" or simply "active area." Due to the wide distribution of input gas, individual MEC cells receive on average less input gas, thereby lowering the gas gradient, while at the same time increasing the amount of liquid phase and thus increasing the active area.

By increasing the active area, less stack voltage is required to drive a predefined current through the MEC cells of the MEC stack, or the amount of H2 produced through the MEC stack at a predefined voltage is reduced. With the increase of , higher currents can be achieved. Therefore, the overall energy consumption of the MEC stack is significantly reduced without compromising efficiency.

This power consumption improvement can already be achieved with the presence of two gas inlets in the MEC stack and increases by adding more gas inlets to the MEC stack, e.g. one gas inlet before each MEC cell. . Therefore, according to the present method, the methane production reaction process can be achieved with less electric power, and the impact on the environment can be minimized. Therefore, the method can achieve more efficient methane production and lower power consumption, allowing smaller MEC cells to be constructed and used.

The use of one or more gas inlets, for example two or more gas inlets, for the input gas has the advantage that the influence of the input gas on the catholyte is distributed. For example, the effect of local introduction of CO2 on the pH of the catholyte is a decrease in the pH value. Injecting the input gas through a single gas inlet, as done in the prior art, establishes an unfavorable pH value to support the biomethanation reaction at the catholyte. Therefore, the MEC cell located after such a gas inlet will experience disturbances in the physicochemical conditions, which will adversely affect the conversion rate.

Instead, injecting the gas through multiple gas inlets at different locations in the MEC stack provides a more uniform distribution of the gas and reduces the local influence of the input gas on the pH of the catholyte. As a result, better conditions are created for the strain, thereby increasing the conversion rate.

Similar concepts naturally apply to regulating temperature. The feed gas temperature is typically outside the optimum temperature for biological methanation reactions. Injecting gas through one inlet at a time (as is done in the prior art) creates a gradient in the temperature of the catholyte, causing the first MEC cell (e.g., the cell that receives the cooler catholyte) to become inefficient. Show reaction.

Again, injecting the input gas through multiple inlets (eg, at least two inlets) provides a more uniform temperature distribution. Therefore, the temperature of the catholyte circulated into the MEC cell immediately after one of the two or more inlets deviates less from the optimum conditions than in the prior art, making the reaction more efficient. The need for external heat generators and/or cooling elements is also minimized, thereby minimizing manufacturing costs while providing a more positive impact on the environment.

Efficiency advantages similar to those mentioned regarding the measurement and influence of pH values and temperature occur with ORP. Low redox potential (ORP) in the growth medium is believed to be important for methane production. This parameter can be controlled by the addition of chemical reducing agents such as Na2S. The amount of CO2 and its effect on pH may make it easier for Na2S to be stripped off as H2S, resulting in a decrease in concentration. This fact will increase the ORP to unfavorable conditions. Culture conditions should suitably maintain the redox potential below about -100 mV.

By creating a substantially optimal environment for bacterial strains (eg, methanogenic microorganisms), higher methane conversion rates are achieved. Therefore, according to the present method, more methane can be produced and the production is more efficient.

A further advantage of using multiple gas inlets in the present method is that the size of the MEC cell that can be used in such an optimization method is reduced.

In the prior art, the input gas flows through all connected MEC cells in the MEC stack along with the growth medium. This means that sufficient input gas needs to be supplied to the first MEC cell to meet the demands of all MEC cells for the methanation reaction. Therefore, the MEC cell becomes larger than necessary.

Due to the feasible boundaries on the conditions in the size of prior art MEC cells, the required amount of gas to allow a substantially optimal reaction of the entire MEC stack without compromising proper reaction conditions. Unable to supply input gas. All of this results in a reduction in production efficiency for the methanogenic reactions within the MEC stack, which prevents full utilization of the potential.

The present invention and method of regulating gas gradients in bioelectrochemical methanogenesis processes overcome and minimize such problems. In particular, it is possible to feed more input gas into the system overall, so that the reactions involved in the methanation process are more efficient and the rate of methane production is increased.

The final step of the method includes degassing the MEC stack through at least one degassing element positioned after the MEC cells of the MEC stack. In this step, at least the last cell of the MEC stack is vented with a first gas, a first portion of the output gas. The first gas may be, for example, methane, but is not limited thereto. It can also be a combination of various process gases produced during the reactions of individual MEC cells. Catholyte degassing may take place, for example, in a catholyte reservoir located after the last MEC cell.

The method improves the energy efficiency of gas production (eg, methane production) because resources are used more efficiently and substantially completely, as can also be seen in FIG. Thereby, the present method and system minimize the production costs through efficient utilization of resources and also improve the quality of the produced gas (e.g. methane) by allowing better control and regulation of the production process. can be improved.

According to one embodiment, step a), i.e. measuring at least one of the various parameters of the catholyte, comprises measuring and/or calculating the hydrogen production in at least two MEC cells of the MEC stack, as described above. include. This can be done, for example, by measuring the current in each cathode compartment.

As mentioned above, knowledge of the amount of hydrogen produced helps determine the virtually optimal amount of input gas (e.g., CO2) that needs to be fed to the catholyte to achieve the ideal reaction efficiency. useful for. Measurements can be performed, for example, at the first and last MEC cells, at the first and intermediate MEC cells, or at any two or more different MEC cells. Furthermore, it can also be calculated based on current.

Also, measurements and/or calculations of hydrogen production for all MEC cells are contemplated and included in this application. As mentioned above, the present invention provides a more energy efficient process, which means higher currents in the MEC cells are possible or the stack voltage can be lowered. Therefore, more hydrogen can be produced with a given input of electrical energy. The targeted addition of CO2 based on this data also allows for the production of more methane. In particular, by controlling the current via the voltage, hydrogen production in the MEC cell and/or the MEC stack can be regulated. Therefore, the amount of hydrogen to be generated can be set, and according to the present invention, target addition of CO2 can be performed based on the amount of hydrogen, so the efficiency of the MEC stack can be increased.

According to a further embodiment of the method, step a) comprises additionally measuring the pH value of the catholyte through a pH measuring system placed before and/or after the two or more gas input points.

If the pH measuring system is arranged before the gas input point, it is suitable for example to determine the required input gas amount. The measurement system can be placed, for example, in the catholyte reservoir or directly on the catholyte circuit just before the gas inlet.

If the pH measurement system is after the gas inlet, it is also useful to check the effect of the input gas on the pH value of the catholyte. This may be used to determine the amount of input gas delivered from another gas inlet and/or whether the amount of input gas delivered from the gas inlet before the pH measurement system is actually , may act as a control mechanism to ensure the expected influence on the pH value of the catholyte.

Combinations of positions are also encompassed by this application. The pH measuring device can be placed before some gas inlets and/or after other gas inlets. Further, the pH measurement system is also envisioned before and after a certain gas inlet, or before and after each gas inlet.

They are therefore mechanisms for controlling and/or regulating the physicochemical conditions of the catholyte and for stabilizing and improving the growth conditions of microorganisms or fungal strains.

According to a further embodiment, the method includes further degassing the MEC stack using a further degassing element. A further degassing element can be added, for example after some MEC cells or all MEC cells, so as to have the effect of degassing the output gas (e.g. methane) immediately after its generation in the individual MEC cells of the MEC stack. may be placed.

In this way, some gas, such as product gas, is extracted from the system at one or more locations. By extracting gases at multiple locations in the MEC stack, minimizing the storage requirements of each gas in each MEC cell is achieved while increasing the active area in each MEC.

For example, the produced methane is degassed from each MEC cell instead of being transported by the catholyte through all fluidly connected MEC cells. Therefore, the MEC cell does not require additional volume to hold the methane produced by the preceding MEC cell. Therefore, the MEC cell can be made smaller, or the additional volume can be used more efficiently, for example, for additional conversion of hydrogen and/or carbon dioxide to methane. This greatly improves production efficiency.

Therefore, degassing can be used to further stabilize conditions and adjust the catholyte to create substantially optimal growth and/or methanation conditions for the strain.

Additionally, degassing the MEC stack at various locations also affects the physicochemical conditions for the strain. By degassing the MEC stack, the pH value, temperature and/or ORP can be influenced through the evacuation of gases, so that an improvement or optimization of the conditions for the bacterial strain can be achieved.

Therefore, the present method of adjusting gas gradients maximizes control and regulation of the physicochemical conditions of the catholyte and thus of the methanation reaction in each MEC cell of the MEC stack. For this reason, many degrees of freedom in the physicochemical conditions for the microorganisms related to methanogenic efficiency are influenced by the presence of one or more gas inlets and one or more degassing elements.

Accordingly, the present method and embodiments thereof produce methane more efficiently and with substantially less energy.

According to the invention, there is also provided a system that can achieve regulation of gas gradients in a bioelectrochemical methanogenesis process.

According to one aspect of the invention, an MEC stack in a bioelectrochemical methane production plant is provided. The MEC stack comprises at least two MEC cells, each MEC cell comprising a cathode compartment and an anode compartment. The MEC cells are fluidically connected in parallel or series, and the MEC stack includes at least one catholyte circuit connecting cathode compartments of two or more MEC cells of the MEC stack. The invention is characterized in that two or more gas inlets are arranged in at least one catholyte circuit.

According to the present application, a bioelectrochemical methane production plant is a system, plant, container, facility, etc. in which a process for producing methane using at least one MEC stack is carried out.

As mentioned above, the MEC stack according to the present invention includes at least two MEC cells that are fluidly connected. Each MEC cell includes a cathode compartment and an anode compartment. MEC cells are fluidly connected to each other in parallel or series.

In this application, when discussing "MEC connections", parallel or series fluid connections via at least one catholyte circuit are intended. A fluidic connection between two MEC cells according to the invention is such that at least one fluid (eg catholyte and/or gas) can pass through and reach the connected MEC cells. Fluid connections can be achieved using, for example, conduits.

Although the MEC cells in the MEC stack are also electrically connected, the present invention does not refer to electrical connections unless explicitly stated.

According to the invention, the MEC stack is not limited to having MEC cells connected exclusively in parallel or in series. Further, a stack in which at least two groups of MEC cells are connected in series, and a stack in which at least two groups of MEC cells are connected in parallel are also envisioned.

According to the invention, the MEC stack comprises at least one catholyte circuit connecting the cathode compartments of two or more MEC cells of the MEC stack. The catholyte cycle transports the growth medium required for the maintenance and metabolic activity of methanogenic microorganisms through catholytes. A catholyte circuit includes a catholyte and one or more gases that are supplied to, for example, a cathode compartment of an MEC cell.

According to the invention, the MEC stack includes at least one catholyte circuit. This means that a plurality of catholyte circuits can be included, for example 2, 3, 4, 5, 6, 7 or more circuits. Some MEC cells of the MEC stack may be fluidly connected by a first catholyte circuit, and some MEC cells of the MEC stack may be fluidly connected by a second catholyte circuit. According to further embodiments, the first and second catholyte circuits may also be fluidly connected to each other.

According to some examples, each odd "number" (e.g., 1st, 3rd, 5th, etc.) of MEC cells is connected by a first catholyte circuit, and every even numbered (e.g., 2nd, 5th, etc.) 4, 6, etc.) may be connected by a second catholyte circuit. Other combinations are also considered and envisioned in this application.

According to the invention, the MEC cells in the MEC stack are arranged conceptually such that each MEC stack includes the first and last MEC cells, and optionally the second, third and fourth MEC cells, etc. It is designed to include.

According to one embodiment, the MEC stack comprises at least two gas inlets arranged in at least one catholyte circuit. As mentioned above with respect to the present method, it has proven surprisingly advantageous to supply input gas to the system, for example at two different locations within the MEC stack and/or within the catholyte circuit.

By distributing the input gas volume throughout the circuit, we efficiently use the size and volume of the MEC cells at hand, maximizing the active area of each individual MEC cell, thereby increasing the efficiency of the electrochemical methanation reaction. Maximize efficiency.

By minimizing the amount of input gas in the various cells and maximizing the active area of the MEC cell, higher current is produced at the same voltage and/or the voltage required to carry the same current is reduced. As a result, the overall power consumption of the MEC stack is minimized and significantly reduced compared to theoretical calculations.

A further advantage is that the catholyte can be better regulated with respect to the pH value, the redox potential of the catholyte and/or the temperature of the catholyte, thereby better regulating the physicochemical conditions for the bacterial strain within the MEC cell. .

By supplying gas from various locations, the effects on the catholyte can be distributed and at the same time variations around a single gas input point can be minimized. The strain conditions are improved so that the methanogenic microorganisms are not faced with or impeded by peak rises/falls in the pH value, temperature and/or ORP of the catholyte through only a single inlet (as in the prior art). As a result, a surprisingly high efficiency of the methanation reaction in the MEC cell is achieved.

According to a further embodiment, at least two gas inlets according to the invention can be placed at any stage in the catholyte circuit, but if at least one gas inlet is placed before the first MEC cell. It has been proven to be advantageous.

According to further embodiments, more than two gas inlets are used. According to one such embodiment, at least one of the gas inlets is arranged in one or more individual MEC cells of the MEC stack. According to a further embodiment, a gas inlet may be arranged, for example every two MEC cells, in front of them.

In this way, for example, the amount of input gas required for a substantially optimal reaction in two subsequent MEC cells is inserted into the catholyte before the first of the two MEC cells. After the second MEC cell, the input gas is completely used for the methanation process. This can be repeated for every two subsequent MEC cells in the stack of MEC cells.

For this reason, it is also envisaged to provide a gas inlet before each MEC cell. In such embodiments, the gases inserted into the catholyte before each MEC cell correspond to substantially optimal requirements for a single MEC cell. This is an efficient way to feed input gas to the catholyte and thus to the MEC cell for conversion to methane. In this way, the conversion of the input gas is efficiently regulated, the effect on the catholyte is taken into account and efficiently controlled, and the optimized growth and methanation conditions of the biocatalyst (e.g. strain) ensure that the methane Generation increases. All this is achieved with less energy input than prior art MEC stacks.

According to a further embodiment, the MEC stack comprises at least one gas inlet in the cathode compartment of one or more individual MEC cells. In some embodiments, more than one gas inlet can be provided per cathode compartment.

In this embodiment, the gas inlet is inserted directly into the catholyte within the cathode compartment. By doing so, the influence of the input gas on the physicochemical conditions of the catholyte can be better controlled, and thus the efficiency of the MEC cell can be further tuned.

According to a further embodiment, each gas inlet comprises a respective flow controller for selectively regulating the gas input from the gas source. According to other embodiments, only some flow controllers are placed in the MEC stack.

The flow rate control is, for example, a valve. Flow control is a computerized method that evaluates data received from measurements in the methods described above, or directly from sensors placed at various locations in the MEC stack, and adjusts the amount of input gas passing through each gas inlet. It is also possible to include means that are

According to a further embodiment of the invention, the MEC stack comprises at least one degassing element for extracting at least a first gas from the MEC stack, at least one of the at least one degassing element comprising: Placed after the last MEC cell in the MEC stack.

The degassing element is used to extract at least a first gas from the MEC stack, the first gas being any product gas produced within the MEC stack during the catalytic reaction (e.g., methane and/or hydrogen) and/or any other gas already present in the MEC stack. After extraction of the first gas, the catholyte can be recycled through the catholyte circuit.

Using at least one degassing element in a MEC stack system is a further method for efficiently managing and operating a MEC stack. By using at least one degassing element, in particular two or more degassing elements, the first gas can be extracted while at the same time converting additional hydrogen and/or for new input gas and/or more A volume space for hydrogen production can be created within the MEC cell.

The degassing element is further used as a system for regulating the physicochemical conditions for the bacterial strain. Degassing affects the pH value, temperature, ORP of the catholyte, which in turn affects the condition of the strain. By venting the MEC stack at more locations, those physicochemical conditions can be better adjusted, resulting in better and more efficient methane production.

Similarly, as described with respect to the present method, the active phase within the plurality of MEC cells is increased, and the MEC stack requires less energy to operate, thus becoming more environmentally friendly.

As mentioned above, according to further embodiments, one or more degassing elements are placed after one or more other MEC cells. In this way, the product gas and other gases, considered as part of the first gas according to the invention, are extracted immediately after production, passed through all the different MEC cells and degassed in the last MEC cell. The active surface of the MEC cell can also be maximized as a result. Therefore, even less energy is required for efficient methanation reactions and corresponding methane production.

According to a further embodiment, the MEC stack comprises at least one device selected among a pH measurement system, an ORP measurement system, a temperature measurement system, and a current/voltage measurement system. According to a further embodiment, a pH measuring system and/or an ORP measuring system and/or a temperature measuring system and/or a current measuring system are arranged before and/or after the at least one gas inlet.

As already mentioned with respect to the method, the reaction efficiency of the MEC stack and each MEC cell is influenced by one or more of the values mentioned above. The gas input from the gas inlet or the gas output from the degassing element destabilizes the temperature and/or pH values and/or ORP values of the catholyte, for example by lowering or increasing them.

Therefore, there is a need for a measurement system that can measure these values and assess how much gas should be injected through the gas inlet and how much gas should be extracted from the degassing element.

Furthermore, some of the measurement devices can be placed before the gas inlet on the catholyte circuit and measure the catholyte value before the input gas is supplied. By doing so, the adjustment of those values of the catholyte can be controlled and adjusted.

The measuring system can also be placed directly after the gas inlet of the catholyte circuit. This system therefore acts as a control mechanism to control whether those values (e.g. pH, temperature, ORP) are actually having the expected effect on the catholyte (flowing through one or more MEC cells). do.

According to the invention, along the lines described above, an MEC with multiple gas inlets and at least one degassing element is described.

A further alternative, which provides substantially the same advantages and technical effects as a system with two or more gas inlets, is a system with one gas inlet and two or more degassing elements.

To this end, the MEC stack of the bioelectrochemical methanogenesis plant comprises at least two MEC cells, each MEC cell comprising a cathode compartment and an anode compartment. The MEC cells are fluidly connected in parallel or series, and the MEC stack includes at least one catholyte circuit for a catholyte connecting cathode compartments of two or more MEC cells of the MEC stack.

The MEC stack comprises, in this embodiment, one gas inlet for input gas located in the first MEC cell of the MEC stack, and the MEC stack comprises at least two gas inlets for extracting at least one first gas. It is characterized by comprising a degassing element. At least one degassing element is also placed after the last MEC cell of the MEC stack.

In this embodiment, input gas is supplied at the first MEC cell. The entire amount of input gas required by the entire MEC stack is supplied from a first gas inlet located at the first MEC cell. Since the MEC stack of this embodiment includes at least two degassing elements, one degassing element is placed in the last MEC cell to extract gas at the end of the MEC stack. The at least one other degassing element may be placed at any suitable location along the MEC stack, such as in an initial or intermediate MEC cell, in particular.

By having multiple degassing elements, it is possible to increase the active surface of the MEC cell, thereby lowering the required voltage and/or increasing the current for hydrogen production necessary for the reaction process. As a result, the power consumption of the MEC stack can be minimized.

Furthermore, degassing the MEC stack at different locations via two or more degassing elements has the advantage of stabilizing the gas gradient in the catholyte. Regulation of degassing, as discussed above, can help create substantially optimal physicochemical conditions for the strain.

According to another embodiment of the invention, at least one degassing element is placed after one or more of the other MEC cells.

A further inventive idea is to extend an individual MEC stack into an MEC module containing two or more MEC stacks each having at least two MEC cells. The MEC stacks are fluidly connected to each other within the MEC module, thereby allowing them to be fluidly connected both in series or in parallel.

In this way, the above-mentioned features and advantages of the MEC stack of the present invention make it possible to increase the output of large plants and at the same time improve efficiency.

According to the invention, a single MEC is also provided as an individualizable cell for bioelectrochemical methanogenesis reactions. The MEC cell is suitable for use in MEC stacks and corresponding MEC models of bioelectrochemical methanogenesis plants.

According to the invention, the MEC cell is characterized by one gas inlet for input gas and two or more degassing elements, alternatively by two or more gas inlets for input gas and one or more degassing elements. It will be done. Thus, as described above with respect to the MEC stack, each MEC cell may also have at least two gas inlets. Either option has a regulating effect on the catholyte and thus has a direct effect on the efficiency of methane production within the MEC cell.

Next, specific embodiments of the present method and system are disclosed through the following drawings.
FIG. 1a shows a schematic MEC stack with two MEC cells including two gas inlets and one degassing element, according to an exemplary embodiment of the invention. FIG. 1b shows a schematic diagram of an alternative more compact embodiment of an MEC stack with two MEC cells including two gas inlets and one degassing element, according to an exemplary embodiment of the invention. ing. FIG. 2 shows a schematic MEC stack with two MEC cells including one gas inlet and two degassing elements according to another exemplary embodiment of the invention. FIG. 3 is a graph showing the methane production rate as a function of the number and position of gas inlets for the example of FIGS. 1a and 1b. Although the same amount of input gas (CO2 feed) was used in all three experiments, this simple experiment shows that differences in the location of one or more gas inlets have a dramatic effect on the methane production rate of the MEC stack. It has already been shown that it will give FIG. 4 shows an exemplary schematic configuration of the cathode compartment of a prior art MEC stack with n MEC cells. A gas inlet is located before the first MEC and, as shown, the total amount of gas is fed into the MEC stack through this inlet, thereby increasing the proportion of liquid phase (corresponding to the active area) in the first MEC. The above-mentioned volume problem arises in that the MEC cathode compartment volume is considerably limited, while a high proportion of the MEC cathode compartment volume is occupied by educts (CO2, H2) and product gases (CH4), and the proportion of product gases increases as the number of cells increases. increases with FIG. 5 is an illustration of a MEC stack having n MEC cell cathode compartments including a gas inlet before each MEC cell and one degassing element of the last MEC cell, according to an exemplary embodiment of the present invention. It shows the general configuration. FIG. 6 shows a MEC stack having n MEC cell cathode compartments including a gas inlet before each MEC cell and one degassing element after each MEC cell, according to an exemplary embodiment of the present invention. An exemplary schematic configuration is shown.

As shown in FIGS. 1a and 1b, this exemplary embodiment of the MEC stack 1 includes two MEC cells 10a, 10b. Each MEC cell 10a, 10b includes a cathode 12a, 12b and an anode 14a, 14b. The left part of FIGS. 1a and 1b shows the anode side of the MEC stack, but a detailed description thereof will be omitted. The cathode side of the MEC stack 1 comprises a catholyte circuit 18 that fluidly connects the two MEC cells 10a, 10b.

The MEC stack 1 of FIGS. 1a and 1b comprises two gas inlets 22a, 22b, and a respective gas source 20a, 20b is used to supply input gas to the catholyte. The gas sources 20a, 20b include, but are not limited to, carbon dioxide CO2 in this example. As shown, two gas inlets are placed in front of each MEC cell 10a, 10b, respectively.

A degassing element 30 is arranged above the catholyte circuit 18 and after the second MEC cell 10b to degas the catholyte of the catholyte circuit 18. Furthermore, a pH measurement system 32 and an ORP measurement system 34 are arranged on the catholyte circuit 18. These measuring systems are included in the degassing element 30 in this example. Therefore, measurements on the catholyte are made after the catholyte has been degassed.

As shown in FIG. 2, this exemplary embodiment of the MEC stack 1 comprises two MEC cells 10a, 10b. Each MEC cell 10a, 10b includes a cathode 12a, 12b and an anode 14a, 14b. The left side of FIG. 2 shows the anode side of the MEC stack, but its description will be omitted here.

The cathode side of the MEC stack 1 includes a catholyte circuit 18 that fluidly connects the two MEC cells 10a, 10b. The MEC stack of FIG. 2 includes one gas inlet 22a with a respective gas source 20a. In this example, the gas source 20a is carbon dioxide. According to this embodiment, the MEC stack 1 comprises two degassing elements 30a, 30b, both arranged on the catholyte circuit 18. A first degassing element 30a is placed after the first MEC cell 10a and a second degassing element 30b is placed after the second (or last) MEC cell 10b.

Furthermore, a pH measurement system 32 and an ORP measurement system 34 are arranged on the catholyte circuit 18. These measurement systems are included in the degassing element 30b in this example. For this reason, measurements on the catholyte are made after the catholyte has been degassed.

FIG. 3 shows the methane conversion of the system of FIG. 1a with two different CO2 feed configurations.

The first bar shows the methane conversion with only one gas inlet 22a in FIG. 1a, which represents the prior art. The second bar shows the methane conversion with two gas inlets 22a, 22b according to the exemplary embodiment of the invention of FIG. As can be seen from the graph, when two gas inlets 22a and 22b are arranged in the MEC stack 1, the methane conversion rate is highest. As mentioned above, this is because the distributed and targeted input gas supply provides better physicochemical conditions for the strain.

FIG. 4 shows the distribution of gas and catholyte (liquid phase) within the MEC cell of a prior art MEC stack. As can be seen from this figure, the input gas (CO2 in this example) is supplied from a single gas inlet 22a point in front of the first MEC cell. The first MEC cell also has a limited volume of liquid phase and also shows hydrogen produced by electrolysis. In the first MEC cell, a portion of the CO2 is converted to methane (CH4), and the methane and the remaining CO2 are transferred to the catholyte compartment 12b of the second MEC cell by the catholyte in the catholyte circuit.

Further reactions occur in the second MEC cell and more methane is produced which is sent along with the remaining CO2 to the catholyte compartment 12c of the third MEC cell. This process continues until the catholyte compartment 12n of the last MEC cell, where most of the gas is methane produced, and at least one more round to produce methane in the catholyte compartment 12b of the last MEC cell. Sufficient CO2 is present for the reaction. The generated methane 97 is then degassed after the last MEC cell via the degassing element 30a. The remaining catholyte is then sent back through the circuit to the first MEC cell where it is again enriched with input gas.

As can be seen, in this system of the prior art, the MEC cells face a large amount of input gas (e.g. CO2) and both the produced methane and the remaining CO2 move through all MEC cells. Considerable energy and efficiency is wasted.

The liquid phase in this figure indicates the active area of each MEC cell.

FIG. 5 shows the distribution of gases and substances within the MEC cells of an MEC stack according to an exemplary embodiment of the invention, in which a respective gas inlet is placed in front of each MEC cell. The catholyte compartments 12a-12n of the MEC cells are connected by a catholyte circuit 18, in which a gas inlet 22a-22n is provided before each MEC cell catholyte compartment 12a-12n. It is located. As can be seen from the distribution within the first MEC cell, the average liquid phase is much larger than in the example of FIG. Therefore, the active area within the MEC cell of FIG. 5 is increased and more efficient reactions can be achieved with less power consumption.

Via the gas inlet 22a, the amount of CO2 required for the methanation process of the catholyte compartment 12a of the MEC cell is supplied to the catholyte compartment 12a of the MEC cell. Via the gas inlet 22b, the amount of CO2 required for the methanation process of the catholyte compartment 12b of the MEC cell is supplied to the catholyte compartment 12b of the MEC cell. The same applies to the remaining MEC cells. Therefore, the methane fraction in the second MEC cell will be larger than the methane fraction in the second MEC cell of FIG.

In FIG. 5, the liquid phase within the MEC cells is decreasing between the MEC cells. The catholyte compartment 12n of the last MEC cell contains the complete amount of methane produced in the catholyte compartment of the previous MEC cell 12a to 12n-1, 98, required for the last reaction in the catholyte compartment 12n of the MEC cell. It has the lowest amount of input carbon dioxide and liquid phase of all MEC cells in the MEC stack. In this embodiment, the energy consumption is minimized compared to the example according to FIG. 4 due to the overall increased liquid phase and thus larger active area. This makes the entire MEC stack more efficient.

FIG. 6 shows a further development of the exemplary MEC stack according to the invention. The MEC stack of FIG. 6 is similar to that of FIG. 5, except that in addition to multiple gas inlets before each individual MEC cell, it includes multiple degassing elements after each individual MEC cell. In this way, as can be read from the figure, the active area is constantly increasing since the liquid phase is almost constant at a high level within the catholyte compartment of each MEC cell. In this example, power consumption is less than the MEC stack of FIG. 5, and methane production 99a-99n is still more efficient.

Remarkably, the energy consumption of the entire MEC stack is less than the sum of the energy consumption of all individual MEC cells while still maintaining a more efficient methanation rate and higher methane production per unit energy. It is clear that

Claims (15)

A method of adjusting gas gradients of a bioelectrochemical methane production process in a microbial electrolysis cell (MEC) stack comprising at least two MEC cells, the method comprising:
a. measuring the stack current and/or voltage of the MEC and/or MEC stack in the cathode compartment;
b. determining an input gas amount for at least one gas input point based on the information evaluated in step a);
c. supplying the determined input gas amount through at least one gas input point, thereby adjusting volume requirements for efficient methane production in the system;
d. degassing the MEC stack via one or more degassing elements located after the MEC cells of the MEC stack. The method according to claim 1,
In step a), further
(i) pH value of the catholyte in the catholyte circuit;
(ii) the redox potential of the catholyte;
(iii) the temperature of the catholyte;
A method characterized in that, in step c), the pH value and/or the temperature and/or the oxidation potential of the catholyte are adjusted accordingly. The method according to claim 2,
A method characterized in that step a) comprises measuring the pH value of the catholyte via a pH measuring system placed before and/or after the two or more gas input points. A MEC stack (1) in a bioelectrochemical methane production plant, comprising:
comprising at least two MEC cells (10a, 10b);
Each MEC cell (10a, 10b) comprises a cathode compartment (12a, 12b) and an anode compartment (14a, 14b);
The MEC cells (10a, 10b) are fluidly connected in parallel or series,
the MEC stack comprises at least one catholyte circuit (18) connecting cathode compartments (12a, 12b) of two or more MEC cells (10a, 10b) of the MEC stack;
MEC stack, characterized in that two or more gas inlets (22a, 22b) are arranged in said at least one catholyte circuit (18). In the MEC stack (1) according to claim 4,
A MEC stack, characterized in that one or more individual MEC cells (10a, 10b) of the MEC stack (1) are provided with at least one gas inlet (22a, 22b). In the MEC stack (1) according to claim 5,
A MEC stack characterized in that it comprises at least one gas inlet (22a, 22b) in the cathode compartment (12a, 12b) of one or more individual MEC cells (10a, 10b). In the MEC stack (1) according to any one of claims 4 to 6,
A MEC stack characterized in that each gas inlet (22a, 22b) is provided with a respective flow controller for selectively regulating gas input from a gas source (20a, 20b). The MEC stack according to any one of claims 4 to 7,
The MEC stack (1) comprises at least one degassing element (30) for extracting at least one of the first gas/process gas from the MEC stack (1), said degassing element (30) An MEC stack, wherein one of the MEC cells is disposed after the last MEC cell of the MEC stack. The MEC stack according to claim 8,
A MEC stack, characterized in that one or more degassing elements are arranged after one or more other MEC cells. The MEC stack (1) according to any one of claims 4 to 9,
An MEC stack comprising at least one device selected from a pH measurement system (32), an ORP measurement system (34), a temperature measurement system, a volume measurement system, and a current measurement system. In the MEC stack (1) according to claim 10,
A pH measuring system and/or an ORP measuring system and/or a temperature measuring system and/or a volume measuring system and/or a current measuring system are arranged before and/or after the at least one gas inlet (22a, 22b). MEC stack featuring. An MEC stack (1) of a bioelectrochemical methane production plant, comprising:
comprising at least two MEC cells (10a, 10b);
Each MEC cell (10a, 10b) comprises a cathode compartment (12a, 12b) and an anode compartment (14a, 14b);
The MEC cells (10a, 10b) are fluidly connected in parallel or series,
the MEC stack comprises at least one catholyte circuit (18) for a catholyte connecting cathode compartments (12a, 12b) of two or more MEC cells (10a, 10b) of the MEC stack;
the MEC stack (1) comprises one gas inlet (22a) for input gas located in the first MEC cell (10a) of the MEC stack;
The MEC stack (1) comprises at least two degassing elements (30a, 30b) for extracting at least one output gas, one of the degassing elements (30a, 30b) ) is arranged after the last MEC cell (10b) of the MEC stack. The MEC stack (1) according to claim 12,
MEC stack, characterized in that at least one degassing element (30a, 30b) is arranged after one or more of the other MEC cells. An MEC module (100) comprising two or more MEC stacks (10a, 10b) according to any one of claims 6 to 16,
An MEC module characterized in that the two or more MEC stacks (10a, 10b) are fluidly connected via the catholyte circuit (18). A MEC cell for use in a bioelectrochemical methane generation plant, the MEC cell comprising:
An MEC cell characterized in that it comprises one gas inlet for input gas and two or more degassing elements, or it comprises two or more gas inlets for input gas and one or more degassing elements.

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