Farms annually face the problem of manure disposal. Considerable funds are wasted, which are required for organizing its removal and burial. But there is a way that allows you not only to save your money, but also to make this natural product serve you for the benefit.
Prudent owners have long been using eco-technology in practice, which makes it possible to obtain biogas from manure and use the result as fuel.
Therefore, in our material we will talk about the technology for producing biogas, we will also talk about how to build a bioenergy plant.
Determination of the required volume
The volume of the reactor is determined based on the daily amount of manure produced on the farm. It is also necessary to take into account the type of raw materials, temperature and fermentation time. In order for the installation to work fully, the container is filled to 85-90% of the volume, at least 10% must remain free for gas to escape.
The process of decomposition of organic matter in a mesophilic plant at an average temperature of 35 degrees lasts from 12 days, after which the fermented residues are removed and the reactor is filled with a new portion of the substrate. Since the waste is diluted with water up to 90% before being sent to the reactor, the amount of liquid must also be taken into account when determining the daily load.
Based on the given indicators, the volume of the reactor will be equal to the daily amount of the prepared substrate (manure with water) multiplied by 12 (time required for biomass decomposition) and increased by 10% (free volume of the container).
Construction of an underground structure
Now let's talk about the simplest installation, which allows you to get at the lowest cost. Consider building an underground system. To make it, you need to dig a hole, its base and walls are poured with reinforced expanded clay concrete.
From opposite sides of the chamber, inlet and outlet openings are displayed, where inclined pipes are mounted for supplying the substrate and pumping out the waste mass.
The outlet pipe with a diameter of about 7 cm should be located almost at the very bottom of the bunker, its other end is mounted in a rectangular compensating container into which waste will be pumped out. The pipeline for supplying the substrate is located approximately 50 cm from the bottom and has a diameter of 25-35 cm. Top part pipes enter the compartment for receiving raw materials.
The reactor must be completely sealed. To exclude the possibility of air ingress, the container must be covered with a layer of bituminous waterproofing.
The upper part of the bunker is a gas holder having a dome or cone shape. It is made of metal sheets or roofing iron. It is also possible to complete the structure with brickwork, which is then upholstered with steel mesh and plastered. On top of the gas tank, you need to make a sealed hatch, remove the gas pipe passing through the water seal and install a valve to relieve gas pressure.
To mix the substrate, the unit can be equipped with a drainage system operating on the bubbling principle. To do this, vertically fasten plastic pipes inside the structure so that their upper edge is above the substrate layer. Poke a lot of holes in them. Gas under pressure will go down, and rising up, the gas bubbles will mix the biomass in the tank.
If you do not want to build a concrete bunker, you can buy a ready-made PVC container. To preserve heat, it must be overlaid around with a layer of thermal insulation - polystyrene foam. The bottom of the pit is filled with reinforced concrete with a layer of 10 cm. Polyvinyl chloride tanks can be used if the volume of the reactor does not exceed 3 m3.
Conclusions and useful video on the topic
How to make the most the simplest installation from an ordinary barrel, you will find out if you watch the video:
The simplest reactor can be made in a few days with your own hands, using available tools. If the farm is large, then it is best to buy a ready-made installation or contact specialists.
Over time, "green" technologies are becoming more popular. Earlier this week, LanzaTech announced the production of about 15,000 liters of aviation fuel. The world produces a lot more fuel every day, but this is special, it was obtained from the gaseous emissions of industrial Chinese enterprises. The fuel was handed over to Virgin Atlantic, Richard Branson's company, and the aircraft that was filled with this fuel has already made a successful flight.
This week, the Swiss company Climeworks, which uses atmospheric carbon dioxide, announced the creation of a plant in Italy that will consume CO2 from the atmosphere and produce hydrogen. The latter will be used in the methane production cycle.
The plant has already been built, it was created in July, its launch (so far in test mode) took place last week. It is clear that this type of enterprise is not a cheap pleasure, and it would not be easy for a startup to find funds for the implementation of such a project. The European Union found the money and financed the project.
This is the third plant of the company involved in the processing of carbon dioxide. The first venture was not very large, rather, it was about creating a small installation that captures CO2 from the atmosphere and releases it into greenhouses, where plants developed faster as a result of increased carbon dioxide concentration. The second plant is built in Iceland, where it converts CO2 from a gaseous state to a bound one. The gas is literally “injected” into the lithosphere of volcanically active regions (the whole of Iceland, in fact, is such a region), where it chemically binds with basalt.
The second option for the utilization of carbon dioxide is quite difficult to implement technically, so the implementation of the project was somewhat problematic. Nevertheless, the company's management stated that the installations had been operating for a long time without failures, "not a single break" was noticed for a sufficiently long period. It should be noted that the design of the second plant is modular, it can be expanded, thus increasing the productivity of the plant.
As for the third option of an industrial enterprise, it will not work around the clock, but only 8 hours a day. Its task is to demonstrate the possibility of producing fuel "out of thin air". It is clear that the fuel, when burned, will release reaction products, including carbon dioxide. But the plant will capture CO2 again and again, thus the "man-made carbon dioxide cycle" will be carried out. If production is scaled up, C02 consumption and aircraft fuel generation will also increase in volume.
So far, the plant's installation includes three air collectors, which, according to the project leaders, are very energy efficient - more than previous versions. In a year, the plant, with the current volume of work, can collect about 150 tons of carbon dioxide. The installation of the plant allows the production of about 240 cubic meters of hydrogen per hour, using energy generated by solar panels.
Aviation fuel made from carbon dioxide
Further, hydrogen binds with CO2 (it is also isolated from atmospheric air) using catalysts. The reactor that performs this operation was developed by the French company Atmostat. Methane is purified and used for industrial purposes. It is then converted to a liquid under pressure and used for industrial purposes.
Despite the fact that the plant is already in operation, it is not economically efficient. Unfortunately, the path to profitability is very long. As mentioned above, production is able to “remove” only about 150 tons of carbon dioxide per year. And the annual volume of emissions of this substance into the atmosphere is 30-40 gigatons, and this figure is increasing every day.
Be that as it may, production is still working, and investors are clearly interested in this technology - the company recently closed another round, having received about $ 30.8 million.
Climeworks is a company that is engaged in similar projects, the number of such startups is gradually increasing, which gives hope that in the end the companies will still reach much higher volumes of carbon dioxide consumption.
Formic acid, whose formula is HCOOH, is the simplest monocarboxylic acid. As it becomes clear from its name, the characteristic secretions of red ants became the source of its discovery. The acid in question is part of the poisonous substance secreted by stinging ants. It also contains a burning liquid, which is formed by the stinging caterpillars of the silkworm.
For the first time, a solution of formic acid was obtained during the experiments of the famous English scientist John Ray. At the end of the seventeenth century, he mixed water and red wood ants in a vessel. Next, the vessel was heated to a boil, and a jet of hot steam was passed through it. The result of the experiment was the preparation of an aqueous solution, the distinguishing characteristic of which was a strongly acidic reaction.
In the middle of the eighteenth century, Andreas Sigismund Marggraf succeeded in obtaining pure formic acid. Anhydrous acid, which was obtained by the German chemist Justus Liebig, is considered the simplest and strongest carboxylic acid at the same time. According to modern nomenclature, it is called methanoic acid and is an extremely dangerous compound.
To date, obtaining the presented acid is carried out in several ways, including a number of successive stages. But it has been proven that hydrogen and carbon dioxide can be converted into formic acid and return to the original state. The development of this theory was carried out by German scientists. The relevance of the topic was to minimize the release of carbon dioxide into the atmospheric air. This result can be achieved by its active use as the main source of carbon for the synthesis of organic substances.
The innovative technique developed by German specialists involves the implementation of catalytic hydrogenation with the formation of formic acid. According to it, carbon dioxide becomes both a base material and a solvent for separating the final product, since the reaction is carried out in supercritical CO2. Thanks to this integrated approach, one-step production of methane acid becomes a reality.
The process of hydrogenation of carbon dioxide with the formation of methane acid is currently one of the objects of active research. The main goal pursued by scientists is to obtain chemical compounds waste generated from the combustion of fossil fuels. In addition to the wide distribution of formic acid in various industries, its participation in the storage of hydrogen should be noted. It is possible that the role of fuel for vehicles equipped with solar panels will be played by this acid, from which hydrogen can be extracted by catalytic reactions.
The formation of methane acid from carbon dioxide by homogeneous catalysis has been the subject of study by specialists since the 1970s. The main difficulty is the shift of equilibrium towards the starting materials, which is observed at the stage of the equilibrium reaction. To solve the problem, it is necessary to remove formic acid from the composition of the reaction mixture. But on this moment this can only be achieved by converting methane acid into a salt or other compound. Therefore, it is possible to obtain pure acid only in the presence of an additional stage, which consists in the destruction of this substance, which does not allow to achieve the organization of an uninterrupted process of formic acid formation.
However, a unique concept is becoming increasingly popular, which is being developed by scientists from the Walter Leitner group. They suggest that the integration of the stages of hydrogenation of carbon dioxide and the isolation of the product with their implementation within the same apparatus makes it possible to make the process of obtaining pure methane acid uninterrupted. How did scientists manage to achieve maximum efficiency? The reason for this was the use of a two-phase system in which the mobile phase is represented by supercritical carbon dioxide, and the stationary phase is represented by an ionic liquid, liquid salt. It should be noted that the ionic liquid was used to dissolve both the catalyst and the base to stabilize the acid. The flow of carbon dioxide in conditions where the pressure and temperature exceed the critical figures, contributes to the removal of methane acid from the composition of the reaction mixture. It is important that the presence of supercritical carbon dioxide does not lead to the dissolution of ionic liquids, catalyst, base, ensuring the maximum purity of the resulting substance.
In industry, the main methods for the production of carbon dioxide CO2 are its production as a by-product of the reaction of converting methane CH4 into hydrogen H2, combustion (oxidation) of hydrocarbons, the reaction of decomposition of limestone CaCO3 into lime CaO and water H20.
CO2 as a by-product of the steam reforming of CH4 and other hydrocarbons into hydrogen H2
Hydrogen H2 is required by industry primarily for its use in the production of ammonia NH3 (Haber process, catalytic reaction of hydrogen and nitrogen); ammonia is needed for the production of mineral fertilizers and nitric acid. Hydrogen can be produced in many ways, including water electrolysis, which is beloved by ecologists - however, unfortunately, at given time all methods of hydrogen production, except for hydrocarbon reforming, are absolutely economically unjustified on the scale of large-scale production - unless there is an excess of "free" electricity in production. Therefore, the main method of hydrogen production, during which carbon dioxide is also released, is methane steam reforming: at a temperature of about 700 ... 1100 ° C and a pressure of 3 ... 25 bar, in the presence of a catalyst, steam H2O reacts with methane CH4 with the release of synthesis gas (the process is endothermic, that is, it goes with the absorption of heat):
CH4 + H2O (+ heat) → CO + 3H2
Propane can be steam reformed in the same way:
C3H8 + 3H2O (+ heat) → 2CO + 7H2
As well as ethanol (ethyl alcohol):
C2H5OH + H2O (+ heat) → 2CO + 4H2
Even gasoline can be steam reformed. There are more than 100 different chemical compounds in gasoline, the steam reforming reactions of isooctane and toluene are shown below:
C8H18 + 8H2O (+ heat) → 8CO + 17H2
C7H8 + 7H2O (+ heat) → 7CO + 11H2
So, in the process of steam reforming of one or another hydrocarbon fuel, hydrogen and carbon monoxide CO (carbon monoxide) were obtained. At the next stage of the hydrogen production process, carbon monoxide in the presence of a catalyst undergoes the reaction of moving an oxygen atom O from water to gas = CO is oxidized to CO2, and hydrogen H2 is released in free form. The reaction is exothermic, it releases about 40.4 kJ / mol of heat:
CO + H2O → CO2 + H2 (+ heat)
In industrial environments, the carbon dioxide CO2 released during the steam reforming of hydrocarbons is easy to isolate and collect. However, CO2 in this case is an undesirable by-product, simply releasing it freely into the atmosphere, although now the prevailing way of getting rid of CO2, is undesirable from an environmental point of view, and some enterprises practice more "advanced" methods, such as, for example, pumping CO2 into declining debit oil fields or pumping it into the ocean.
Obtaining CO2 from the complete combustion of hydrocarbon fuels
When hydrocarbons such as methane, propane, gasoline, kerosene, diesel fuel, etc. are burned, that is, oxidized with a sufficient amount of oxygen, carbon dioxide and, usually, water are formed. For example, the combustion reaction of methane CH4 looks like this:
CH 4 + 2O 2 → CO 2 + 2H 2 O
CO2 as a by-product of H2 production by partial oxidation of fuel
Approximately 95% of the industrially produced hydrogen in the world is produced by the above-described process of steam reforming of hydrocarbon fuels, primarily methane CH4 contained in natural gas. In addition to steam reforming, hydrogen can be obtained from hydrocarbon fuel with a fairly high efficiency by the partial oxidation method, when methane and other hydrocarbons react with an amount of oxygen insufficient for complete combustion of the fuel (recall that in the process of complete combustion of the fuel, briefly described above, carbon dioxide is obtained CO2 gas and H20 water). When a less than stoichiometric amount of oxygen is supplied, the reaction products are predominantly hydrogen H2 and carbon monoxide, also known as carbon monoxide CO; in small quantities, carbon dioxide CO2 and some other substances are obtained. Since, in practice, this process is usually carried out not with purified oxygen, but with air, there is nitrogen at the inlet and outlet of the process, which does not participate in the reaction.
Partial oxidation is an exothermic process, that is, heat is released as a result of the reaction. Partial oxidation is generally much faster than steam reforming and requires a smaller reactor. As seen in the reactions below, initially partial oxidation produces less hydrogen per unit of fuel than steam reforming does.
Reaction of partial oxidation of methane CH4:
CH 4 + ½O 2 → CO + H 2 (+ heat)
Propane C3H8:
C 3 H 8 + 1½O 2 → 3CO + 4H 2 (+ heat)
Ethyl alcohol C2H5OH:
C 2 H 5 OH + ½O 2 → 2CO + 3H 2 (+ heat)
Partial oxidation of gasoline using the example of isooctane and toluene, from more than a hundred chemical compounds present in gasoline:
C 8 H 18 + 4O 2 → 8CO + 9H 2 (+ heat)
C 7 H 18 + 3½O 2 → 7CO + 4H 2 (+ heat)
To convert CO into carbon dioxide and produce additional hydrogen, the water → gas oxygen shift reaction already mentioned in the description of the steam reforming process is used:
CO + H 2 O → CO 2 + H 2 (+ small amount of heat)
CO2 in sugar fermentation
In the production of alcoholic beverages and bakery products from yeast dough, the process of fermentation of sugars - glucose, fructose, sucrose, etc., is used, with the formation of ethyl alcohol C2H5OH and carbon dioxide CO2. For example, the glucose fermentation reaction C6H12O6 is:
C 6 H 12 O 6 → 2C 2 H 5 OH + 2CO 2
And the fermentation of fructose C12H22O11 looks like this:
C 12 H 22 O 11 + H 2 O → 4C 2 H 5 OH + 4CO 2
Wittemann CO2 production equipment
In the production of alcoholic beverages, the resulting alcohol is a desirable and, one might even say, a necessary product of the fermentation reaction. Carbon dioxide is sometimes released into the atmosphere, and sometimes left in the drink to carbonate it. In baking bread, the opposite is true: CO2 is needed to create bubbles that cause the dough to rise, and ethyl alcohol is almost completely evaporated during baking.
Many enterprises, primarily distilleries, for which CO 2 is a completely unnecessary by-product, have set up its collection and sale. The gas from the fermentation tanks is fed through alcohol traps to the carbon dioxide plant, where CO2 is purified, liquefied and bottled. In fact, it is the distilleries that are the main suppliers of carbon dioxide in many regions - and for many of them, the sale of carbon dioxide is by no means the last source of income.
There is a whole industry of production of equipment for the release of pure carbon dioxide in breweries and distilleries (Huppmann / GEA Brewery, Wittemann, etc.), as well as its direct production from hydrocarbon fuels. Gas suppliers such as Air Products and Air Liquide are also installing CO 2 recovery and purification stations, liquefaction and cylindering.
CO2 in quicklime production CaO from CaCO3
The production process for the widely used quicklime CaO also has carbon dioxide as a reaction by-product. The decomposition reaction of limestone CaCO3 is endothermic, needs a temperature of the order of +850°C and looks like this:
CaCO3 → CaO + CO2
If limestone (or other metal carbonate) reacts with acid, then carbon dioxide H2CO3 is released as one of the reaction products. For example, hydrochloric acid HCl reacts with limestone (calcium carbonate) CaCO3 as follows:
2HCl + CaCO 3 → CaCl 2 + H 2 CO 3
Carbonic acid is very unstable, and under atmospheric conditions quickly decomposes into CO2 and water H2O.
Chemists have developed a photocatalyst based on copper oxide and zinc oxide, which allows you to convert carbon dioxide into methane when exposed to sunlight, and the use of such a catalyst made it possible to completely avoid the formation of by-products. Research published in Nature Communications.
An increase in carbon dioxide in the atmosphere is called one of the possible causes global warming. In order to somehow reduce the level of carbon dioxide, scientists propose to use it as a chemical source in the conversion to other carbon-containing substances. For example, recently there has been the reduction of atmospheric carbon dioxide to methanol. Many attempts have been made to develop effective ways conversion of carbon dioxide into hydrocarbon fuels. Typically, catalysts based on titanium oxide (IV) are used for this, however, their use leads to the production of a large number of by-products - in particular, hydrogen.
In their new work, chemists from Korea proposed a new configuration of a photocatalyst consisting of zinc oxide and copper (I) oxide, which makes it possible to reduce atmospheric carbon dioxide to methane with high efficiency. To obtain the catalyst, chemists used a two-stage synthesis from copper and zinc acetylacetonates. As a result, it was possible to obtain spherical zinc oxide nanoparticles coated with small cubic copper(I) oxide nanocrystals.
Scheme for the synthesis of catalyst nanoparticles
K.L. Bae et al./Nature Communications, 2017
It turned out that such nanoparticles are photocatalysts for the conversion of carbon dioxide into methane. The reaction takes place at room temperature when irradiated with light in the visible and ultraviolet regions in an aquatic environment. That is, it involves carbon dioxide, previously dissolved in water. The activity of the catalyst was 1080 micromoles per hour per gram of catalyst. The concentration of methane in the resulting mixture of gases exceeded 99 percent. The reason for such a high efficiency of the catalyst, the authors of the work say, is the ratio of band gap energies in copper and zinc oxides, which leads to a more efficient charge transfer between the components.
Change in the concentration of substances during the conversion of carbon dioxide into methane using the proposed catalyst
K.L. Bae et al./Nature Communications, 2017
In addition, the scientists compared the properties of the proposed catalyst with the most efficient catalyst that has been used for carbon dioxide conversion before. It turned out that a catalyst of the same weight for the same time allows you to get about 15 times less methane than a new one. In addition, the hydrogen content in the resulting mixture is about 4 times greater than the methane content.
According to the scientists, the catalyst proposed by them can not only be used for efficient conversion of carbon dioxide into methane, but is also a source of information on the mechanisms of such reactions with the participation of photocatalysts.
Other methods are used to reduce the amount of carbon dioxide in the atmosphere. For example, recently at one of the power plants in Iceland, a module that captures atmospheric carbon dioxide.
Alexander Dubov
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