Method for operating a system for producing alcohols and / or hydrocarbons

Abstract

The invention relates to a method for operating a system for producing alcohols and / or hydrocarbons using electrical energy which is particularly generated from renewable resources. According to the invention, water is extracted from the surrounding air by means of a carbon dioxide sorption unit.

Description

[0001] Method for operating a plant for the production of alcohols and / or hydrocarbons

[0002] The invention relates to a method for operating a plant for producing alcohols and / or hydrocarbons according to patent claim 1.

[0003] Plants for the regenerative production of liquid fuels are known from the prior art, in particular WO 2022 / 096 615 A1. The plant according to WO 2022 / 096 615 A1, for example, is a large-scale plant powered exclusively by renewable energy via its own photovoltaic unit. To produce hydrogen, a water supply is required in addition to this self-generated power supply. Therefore, the prior art proposes constructing such plants near bodies of water, particularly near the sea. For example, seawater can be used to produce hydrogen through electrolysis via a desalination plant.

[0004] The dependence on natural water resources limits the choice of locations for such plants. Many areas well-suited for solar energy production have few nearby bodies of water that would meet the high water demand for hydrogen production. In other areas, however, where natural bodies of water are available, a competition arises between the water supply for the region of the site and the water demand for the plant.

[0005] In addition, energy production from a photovoltaic system, as well as relative humidity, exhibits pronounced day-night differences. While relative humidity is usually relatively low during the day, but solar radiation is high at these times of day, solar electricity production is possible at night, but humidity is relatively high. These fluctuations, especially with regard to solar electricity production, impact the operation of a liquid fuel production plant.

[0006] While the day-night differences could be compensated for, for example, by large battery storage systems, this requires high investment costs, and the amortization of these costs is questionable. Alternatively, electricity and water supply lines could be provided over long distances, but this would significantly increase the infrastructure and development costs for the plant site. For practical and economic reasons, the choice of locations for existing plants is therefore limited.

[0007] Therefore, locations near the sea, which offer high annual solar radiation, appear to be the most suitable. The water required to operate the plant can then be provided by desalinating the seawater. However, this leaves behind a highly concentrated saline solution, which is discharged into the ocean. This leads to significant pollution of coastal waters. Water extraction from the sea can contaminate coastal waters and has corresponding consequences for vegetation and biodiversity in these waters. In addition, the service life is longer, as significantly less contaminants are introduced.

[0008] Against the background of these conflicting objectives, the object of the invention is to provide a method for operating a plant for producing alcohols and / or hydrocarbons, which can be used at different locations worldwide, in particular independently of an external, natural water supply.

[0009] According to the invention, this object is achieved by the subject matter of patent claim 1.

[0010] Accordingly, the invention is based on the idea of ​​providing a method for operating a plant for producing alcohols and / or hydrocarbons using, in particular exclusively, electrical energy generated from renewable sources, preferably photovoltaics. In the method according to the invention, water is extracted from the ambient air using a carbon dioxide sorption device.

[0011] The invention is based on the discovery that ambient air, even in desert regions with a high number of hours of sunshine, contains many times more water than carbon dioxide. When extracting CO2 from the ambient air, the amount of water required for the process can therefore also be extracted from the ambient air. Using the water bound in the ambient air to supply the plant with water thus enables the plant to be constructed anywhere.

[0012] In particular, the process according to the invention can be used in plants for the production of hydrogen from purely renewable energies, for example in desert areas without natural water sources.

[0013] A further advantage, particularly compared to processes that use seawater for water supply, is that the water obtained from the ambient air using the process according to the invention has already been distilled in the environment. Therefore, desalination is not necessary, and the water is also significantly cleaner than desalinated seawater. Additional, energy-intensive measures, such as seawater desalination, can thus be dispensed with. This also reduces the energy requirements of such a plant.

[0014] In a preferred embodiment of the process according to the invention, the water extracted from the environment is fed through a water supply line to an electrolysis unit for producing hydrogen and / or its derivatives. The electrolysis unit is preferably operated using electrical energy generated by photovoltaics. In particular, the electrolysis unit's energy supply is preferably entirely from purely renewable energy generation. This can be achieved by a photovoltaic unit. Alternatively, it is also possible to use at least partially renewable energy from wind power. Other renewable energy generation systems can also be used.

[0015] It is particularly preferred if the hydrogen and / or its derivatives are further processed in a synthesis unit to produce alcohol and / or a hydrocarbon, in particular methanol. Further processing to produce alcohol and / or a hydrocarbon, in particular to produce a liquid energy source, is particularly advantageous because such liquid energy sources can be transported easily and safely. This applies in particular to methanol, which can be used worldwide as a liquid energy source and can be transported safely, for example, via train tankers, tank trucks, and / or tank ships. In this way, the process makes it possible to produce a liquid energy source in regions of the world that offer high renewable energy generation capacity, for example in the sunbelt, which can then be distributed and used worldwide.

[0016] It is preferably provided that the hydrogen production in the carbon dioxide sorption unit and / or the further processing of the hydrogen and / or its derivatives in the synthesis unit takes place continuously, in particular 24 hours a day, preferably without interruption. The energy-efficient electrolysis of the water, on the other hand, essentially takes place when renewable energy is highly available. Water production in the carbon dioxide sorption unit is subject to daily fluctuations. In particular, higher air humidity is often present at night, so that the water production capacity is increased at this time. Nevertheless, water can also be extracted from the ambient air during the day to operate the plant, in particular by adding temporarily stored water that was produced at night. The synthesis unit can also be operated continuously, so that methanol or other hydrocarbons orAlcohols can be produced. This increases the overall efficiency of the process according to the invention.

[0017] It is particularly advantageous if the further processing of hydrogen and / or its derivatives at night takes place primarily, or even exclusively, from pressure storage tanks that are filled during the day by gas compression. The electrical energy available during the day is thus additionally used to fill pressure storage tanks, which can then be used at night to operate the synthesis unit. This intermediate energy storage is particularly efficient and increases the efficiency of such a plant.

[0018] Furthermore, the water extracted from the ambient air can be temporarily stored, particularly at night, before being fed to the electrolysis unit via the water supply line, particularly during the day. This process step is based on the knowledge that water extraction via the carbon dioxide sorption unit is more efficient at night than during the day. Water is preferably extracted from the ambient air using a highly concentrated lye that is passed through the carbon dioxide sorption unit. The lye also serves to cool the remaining system components and can therefore absorb and dissipate waste heat from the electrolysis unit and / or the synthesis unit. The system's cooling requirements are lower at night than during the day, which means that the lye can absorb more water. In this respect, the water absorption capacity is higher at night than during the day, making water extraction particularly efficient at night.Electrolysis, for which water is required, is very energy-intensive and can therefore be operated primarily during the day when solar energy is available to power the electrolysis. Therefore, it is advisable to store the water produced at night in a buffer storage facility for use in the electrolysis during the day. Alternatively, or in addition, the produced water can also be stored seasonally for a longer period (weeks to months).

[0019] It is also possible for a portion of the hydrogen produced by the electrolysis unit to be burned at night to generate electrical energy in a heat engine, particularly a hydrogen turbine. This allows the necessary energy quantities to be provided at night to continuously operate at least the carbon dioxide sorption unit and the synthesis unit. The combustion water produced during combustion in the hydrogen turbine can be temporarily stored and, particularly during the day, fed to the electrolysis unit to produce hydrogen. In this way, waste products generated during the energetic recovery of hydrogen at night are efficiently utilized within the process to produce hydrogen again during the day. This increases the overall efficiency of the process.

[0020] The heat engine, in particular a hydrogen turbine, can also be operated with oxygen, which is generated, especially during the day, by the electrolysis unit. Instead of releasing the oxygen thus generated into the environment, at least a portion of it can be temporarily stored to power the combustion process in a heat engine or fuel cell, in particular a hydrogen turbine. In this way, the ambient substances generated during electrolysis are utilized and increase the efficiency of the process.

[0021] It is also possible to temporarily store intermediate products formed during operation of the plant, in particular aqueous salt solution, sodium carbonate, sodium bicarbonate, sodium hydroxide, hydrogen, carbon monoxide, carbon dioxide, oxygen and / or water, in order to decouple the operation of the plant from ambient conditions. The operation of a plant or of the process described here is heavily dependent on the ambient conditions in the respective region. This applies in particular to the climatic conditions, the weather conditions and the day and night cycle. The operating parameters for carrying out the process must therefore be continuously adjusted. In order to be able to make appropriate adjustments, it is advantageous to temporarily store the intermediate products formed in the plant in order to, for example, interrupt parts of the process at night when less energy is available and continue it during the day.

[0022] In particular, it is advantageous if the operating parameters of the carbon dioxide sorption unit, in particular the concentration and / or temperature and / or circulation rate of a lye in the carbon dioxide sorption unit, are adjusted at night for water extraction. As already mentioned, water extraction is particularly efficient at night because the cooling requirements of the plant or the subsequent process are lower than during the day. This allows for increased water absorption in the carbon dioxide sorption unit.

[0023] The efficiency of the process can be further increased if predictive data, particularly weather forecast data, is used to adjust the operating parameters. Such predictive control makes it possible, for example, to adjust the combustion of hydrogen in a hydrogen turbine at night to ensure continuous operation of the process, even if, for example, partial cloud cover is expected the following day. For example, hydrogen for nighttime combustion can be rationed to continue energy generation by the hydrogen turbine for as long as possible if no direct solar radiation is expected the following day to cover the plant's energy needs using photovoltaics. Other control systems are also possible.

[0024] In a further preferred embodiment of the process according to the invention, waste heat generated during the day in the plant, in particular in the electrolysis unit, is temporarily stored in a heat storage unit, in particular a water heat storage unit, and used at night to heat a lye in the carbon dioxide sorption unit. This intermediate heat storage allows the heat demand, which varies throughout the day, to be compensated. Especially at night, when heat demand is higher but the heat supply is low, temporarily stored heat can be used to operate the process.

[0025] It is also possible for the water obtained in the carbon dioxide sorption unit and / or the combustion water from the hydrogen turbine and / or a lye circulating through the carbon dioxide sorption unit to be cooled to ambient temperature at night and used as a cooling medium in the plant during the day, particularly for condensation processes. This allows additional use of water not directly used for electrolysis. This also increases the efficiency of the process.

[0026] The invention will be explained in more detail below with reference to the attached schematic diagrams.

[0027] Fig. 1 and 2 each show a diagram of the equilibrium concentration of sodium hydroxide solution as a function of the partial pressure of water in the ambient air and the ambient temperature;

[0028] Fig. 3 a table with different values ​​for setting the

[0029] Concentration of caustic soda at different times of day at a location; and

[0030] Fig. 4 is a cross-sectional view of a carbon dioxide sorption unit for

[0031] Implementation of the method according to the invention.

[0032] The process described here serves to extract additional water from the ambient air using a carbon dioxide sorption unit, the purpose of which is to extract carbon dioxide from the ambient air. A lye, preferably sodium hydroxide solution, typically circulates within the carbon dioxide sorption unit. This solution can absorb water in addition to binding carbon dioxide. The water absorption depends on the concentration of the lye.

[0033] This relationship is illustrated in Figs. 1 and 2, with particular emphasis on ambient air parameters, namely the ambient temperature and the partial pressure of water in the ambient air. Figs. 1 and 2 each show the equilibrium concentration of caustic soda as a function of the partial pressure of water and the ambient temperature. Fig. 1 also shows case 1, shown in Fig. 3, while Fig. 2 highlights case 2, shown in Fig. 3.

[0034] In both cases, the assumption is that the CO2 content in the air remains constant at 420 ppm. The molecular weight of CO2 is 44 grams. The molecular weight of air is assumed to be constant at 29 grams. In the example cases shown in Fig. 3, a location for carrying out the procedure is in Baghdad. Case 1 shows the conditions at approximately 3 p.m. with a comparatively high ambient temperature and low relative humidity. Case 2 represents the conditions at the same location at 6 a.m., where the ambient temperature is comparatively low, but the relative humidity is increased.

[0035] At an ambient temperature of 44 °C in case 1 at 3 pm and a relative humidity of 5% at an air pressure of 1006 mbar, the water content is 3.12 g / m 3 . Under these ambient conditions, the air density is 1 .106 kg / m 3, resulting in a CO2 amount of 0.7 g / m 3 This means that the amount of water in one cubic meter of air is 4.4 times the amount of CO2. The diagram in Fig. 1 also shows that a very highly concentrated alkali, particularly caustic soda, is required to remove the water from the air. In particular, a concentration of more than 50% of the alkali is required to remove the water from the ambient air.

[0036] In the second case, the ambient temperature is 28 °C and the relative humidity is about 20%. The air pressure is similar at about 1007 mbar. The water content is therefore 5.45 g / m 3 .

[0037] Due to the lower temperatures, the air density is increased and is 1 ,166 kg / m 3 , resulting in a CO2 amount of 0.74 g / m 3Thus, in case 2, one cubic meter of air contains approximately 7.4 times the amount of water compared to the amount of carbon dioxide. At the same time, Fig. 2 shows that a lower concentration of caustic soda is required to absorb the water from the ambient air. A 40% caustic soda is sufficient to remove the water from the ambient air.

[0038] The above examples clearly demonstrate that water extraction is significantly more efficient, especially at night than during the day. Therefore, it makes sense, and is also intended for the process described here, to choose a dynamic mode of operation. The process can be operated particularly economically if it is adapted to the different environmental conditions.

[0039] The process described here ensures that the water requirements of a hydrogen production plant are met by the water contained in the ambient air. The carbon dioxide sorption unit also comes into play. Unlike previous solutions that rely on desalinated seawater for hydrogen production, the process described here eliminates the need for desalination. The water extracted from the ambient air is already distilled and requires no further post-treatment. This, in turn, increases the service life of the plant and the efficiency of the process.

[0040] As the above examples show, even in dry desert conditions, the air contains an order of magnitude more water than carbon dioxide. With a sufficiently highly concentrated caustic soda, it is therefore possible to extract sufficient water from the air humidity. The advantage of using caustic soda is that it automatically adjusts its concentration to the outside air conditions; it absorbs water and then releases it back into the outside air. The concentration of the caustic soda is thus automatically adjusted.

[0041] Fig. 4 shows a carbon dioxide sorption unit with which the process according to the invention can be carried out. The carbon dioxide sorption unit enables both the extraction of carbon dioxide and the simultaneous recovery of water from the ambient air.

[0042] The carbon dioxide sorption unit comprises a housing 1 in which several fillers 11 are arranged on a perforated grid or grate 6. The grate 6 retains the fillers 11. Below the grate 6, an air inlet 3 opens into the housing 1. The air inlet 3 includes a fan 2, which draws in ambient air and blows it into the housing 1 via the air inlet 3.

[0043] Above the filler elements 11, the housing 1 has an air outlet funnel 7, which opens into an air outlet 8. The air outlet 8 is spatially separated from the air supply 3. The purified ambient air is released into the environment via the air outlet 8.

[0044] A lye distribution unit 10 is arranged above the packing elements 11. The lye distribution unit 10 can have several spray devices that spray the lye 9 over the packing elements 11. As a result, the packing elements 11 are wetted with the lye 9. The lye 9, which is represented by framed arrows in Fig. 4, flows through the packing elements 11 or the bed of packing elements 11. In the opposite direction to the flow direction of the lye 9, the ambient air flows through the bed of packing elements 11. The ambient air flows around the packing elements 11.

[0045] The flow direction of the ambient air is shown in Fig. 4 by solid arrows. On the one hand, the lye 9 exchanges carbon dioxide with the ambient air, binding carbon dioxide in the lye. At the same time, the lye 9 absorbs water from the ambient air. The low-carbon ambient air exits the housing 1 via the air outlet funnel 7 and the air outlet 8.

[0046] The now aqueous lye 9, enriched with carbon dioxide, falls through the grate 6 into a basin at the bottom of the housing 1. There, the collected and carbon dioxide-enriched aqueous lye 9 is pumped out via a lye pump 4 and passed through a water separation unit 5. In the water separation unit, the absorbed water is separated, with the separation quantity being adjusted such that the lye 9 regains its original concentration. The lye 9, now reconcentrated by the separation of the additionally absorbed water from the ambient air, reaches the lye distribution unit 10 and is distributed by it via the packing elements 11. This forms a lye circuit that comprises the lye pump 4, the water separation unit 5, the lye distribution unit 10, and the housing 1 of the carbon dioxide sorption unit. The lye 9 circulates continuously within the lye circuit.The separation of water in the water separation unit 5 can be achieved, for example, by a multi-stage thermal process (evaporation of the water), which heats the lye 9 in the water separator 5. This utilizes waste heat from the plant for producing alcohols and / or hydrocarbons (aFuel plant). Alternatively, membrane processes, such as reverse osmosis, can also be used.

[0047] List of reference symbols

[0048] 1 housing

[0049] 2 fans

[0050] 3 Air supply 4 Drain pump

[0051] 5 Water separation unit

[0052] 6 Rust

[0053] 7 air outlet funnels

[0054] 8 Air outlet 9 Lye

[0055] 10 Lye distribution unit

[0056] 11 packing

Claims

Patent claims 1. A method for operating a plant for producing alcohols and / or hydrocarbons using electrical energy, in particular energy obtained from renewable sources, in which water is extracted from the ambient air by means of a carbon dioxide sorption unit.

2. Process according to claim 1, characterized in that the water obtained from the environment is passed through a water supply line to an electrolysis unit for the production of hydrogen and / or its derivatives.

3. Process according to claim 2, characterized in that the hydrogen and / or its derivatives are further processed in a synthesis unit to alcohol and / or a hydrocarbon, in particular methanol.

4. Process according to one of the preceding claims, characterized in that the water extraction in the carbon dioxide sorption unit and / or the further processing of the hydrogen and / or its derivatives in the synthesis unit takes place continuously, in particular 24 hours a day, preferably without interruption.

5. A method according to claim 4, characterized in that the further processing of the hydrogen and / or its derivatives at night takes place mainly, in particular exclusively, from pressure accumulators which are filled during the day by gas compression.

6. Method according to one of the preceding claims, characterized in that the water obtained from the ambient air, in particular at night, preferably in the form of a diluted salt solution, before it is fed through the water supply line to the electrolysis unit, especially during the day.

7. A method according to any one of the preceding claims, characterized in that a portion of the hydrogen produced by the electrolysis unit is burned at night to generate electrical energy in a heat engine or fuel cell, in particular a hydrogen turbine, the waste heat being utilized in the plant.

8. The method according to claim 7, characterized in that the combustion water produced in the heat engine is temporarily stored and, in particular during the day, is fed to the electrolysis unit for the production of hydrogen, wherein the heat engine, in particular hydrogen turbine, is operated with oxygen which is obtained, in particular during the day, by means of the electrolysis unit.

9. Method according to one of the preceding claims, characterized in that intermediate products formed during operation of the plant, in particular dilute salt solution, sodium carbonate, sodium bicarbonate, sodium hydroxide, hydrogen, carbon monoxide, carbon dioxide, oxygen and / or water, are temporarily stored in order to decouple the operation of the plant from ambient conditions.

10. Method according to one of the preceding claims, characterized in that Operating parameters of the carbon dioxide sorption unit, in particular the concentration and / or temperature and / or circulation rate of a lye and the air flow rate in the carbon dioxide sorption unit, are adjusted at night for water extraction. 1 1. A method according to claim 10, characterized in that forecast data, in particular weather forecast data, are used to adjust the operating parameters.

12. A method according to one of the preceding claims, characterized in that waste heat generated in the plant, in particular in the electrolysis unit, during the day is temporarily stored in a heat storage unit, in particular a water heat storage unit, and used at night to heat a lye in the carbon dioxide sorption unit.

13. A method according to any one of the preceding claims, characterized in that the water obtained in the carbon dioxide sorption unit and / or the water originating from the power generation and / or a lye circulating through the carbon dioxide sorption unit is cooled to ambient temperature at night and used as a cooling medium in the plant, in particular for condensation processes, during the day.

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