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Список литературы 3. Скороход А.В., Слободенюк Н.П.
1. Вентцель А.Д. Курс теории случайных Предельные теоремы для случайных блужданий -процессов-M: Наука, 1975. Киев.: Наукова думка, 1970.
2. Диткин В.А., Прудников А.П. Интегральные 4. Ширяев А.Н., Булинский А.В. Теория преобразования и операционное исчисление - М.: случайных процессов - М.: Физматлит., 2005. Наука, 1974.
СОПОСТАВИТЕЛЬНЫЙ АНАЛИЗ РАЗЛИЧНЫХ ВИДОВ БИОГАЗОВЫХ УСТАНОВОК
Саламов О.М.
Ведущий научный сотрудник, Доктор философии по физики, доцент Институт Радиационных Исследований НАН Азербайджана,
Мамедова Л.Г. Доцент кафедры «Экологии», Доктор философии по биологическим наукам Азербайджанский Университет Архитектуры и Строительства,
Алиев Ф.Ф. Вице-президент МЕА, Доктор философии по техническим наукам Международная Экоэнегетическая Академия,
Салманова Ф.А. Старший научный сотрудник, доцент Доктор философии по техническим наукам Институт Радиационных Исследований НАН Азербайджана
Юсупов И.М. Старший инженер
Институт Радиационных Исследований НАН Азербайджана
COMPARATIVE ANALYSIS OF DIFFERENT TYPES OF BIOMAS PLANTS
Salamov O.
Leading Researcher, Doctor of Philosophy in Physics, Associate Professor Institute of Radiation Research of NAS of Azerbaijan,
Mamedova L.
Associate Professor, Department of Ecology, Doctor of Philosophy in Biological Sciences Azerbaijan University of Architecture and Construction,
Aliyev F. MEA Vice President Doctor of Philosophy in Engineering International Eco-Energy Academy, Salmanova F.
Senior Researcher, Associate Professor, Doctor of Philosophy in Engineering Institute of Radiation Research of NAS of Azerbaijan,
Yusupov I. Senior engineer
Institute of Radiation Research of NAS of Azerbaijan
Аннотация
В работе приводятся результаты сопоставительного анализа конструкций и принципов работы биогазовых установок (БГУ) для получения биогаза (БГ), из биомассы (БМ) растительного и животного происхождения и органических отходов (ОО), содержащего большое количество (до 70%) метана. Приводятся подробные разъяснение процессов, происходящих в отдельных конструктивных частях БГУ и механизмы осуществления этих процессов.
Abstract
The present study is devoted to a comparative analysis of the designs and principles of operation of biogas plants (BGP) for biogas (BG) production from plant and animal origin biomass (BM), as well as organic waste (OW) containing a large amount (up to 70%) of methane. A detailed explanation of the processes occurring in the individual structural parts of the BGP and the mechanisms for implementing these processes are given.
Ключевые слова: биогаз, биогазовая установка, нагревательная система, теплообменник, измельчитель, биореактор, мешалка, сепаратор, анаэробное брожение, минеральный остаток.
Keywords: Biogas, biogas plants, heating system, heat exchanger, shredder, bioreactor, mixer, separator, anaerobic fermentation, mineral residue.
Introduction
BG production has great importance, from the energy, economic and environmental points of view. In first, it should be note that the plant or animal origin, as well as industrial and household waste saturated with hydrocarbons and valuable inorganic trace elements, industrial sewage and human waste can be used as raw materials for BG production. The main raw materials for obtaining BG are cattle and small-cattle manure, and other livestock, in particular pig, horses, etc. as well as bird droppings. A number of environmental problems are simultaneously solved, related to pollution of both soil and groundwater, and the atmosphere, greenhouse gases such as CO2, CH4, N2O, etc. with processing this type of wastes. All these gases are released during the natural fermentation of the above types of BM, other types of OW and are directly released into the atmosphere. Given that the available reserves of all types of conventional fuels (solid, liquid and gaseous) will be exhausted in the near future, the role of BG in electricity and heat supply to the population becomes obvious. Based on the above, starting from the second half of the last century, in all developed countries of the world, especially oil
producers are intensively works to develop various biogas technologies and biogas plants for BG production from various types of raw materials. The historical development of biogas technology in various countries of the world is briefly reviewed below [1].
1. The development of biogas technology in various countries of the world.
The first BG research was conducted by Italian researcher Allesandro Volta. In 1770, he began to collect marsh gases from swamps located in the northern part of Italy, and later he conducted research on the combustion of these gases. English scientist Faraday determined that marsh gases are consists of hydrocarbon at the end of the XVIII century. Only in 1821, the Italian researcher Avogadro found that the chemical composition of the marsh gas consists of methane. In 1884, the famous French bacteriologist Pasteur conducted full-scale research on BG. Moreover, he used solid manure as a raw material. Considering the results obtained from the experiment, he proposed to lighting the streets with biomethane obtained using Parisian horses manure. At the end of the XIX century, new method for anaerobic fermentation of animal origin BM was found, which
makes it possible to processing of sewage wastes. Namely, this discovery gave a significant impetus to the development of BG production. Further, in 1907, the BG was used as fuel for generating electricity. In the same years, valuable work was carried out in Germany to develop and create various types of BGP. Anaerobic purification plant with two level was created which simultaneously obtained BG. In 1875, Popov investigated the effects of temperature on the amount of released gas. He found that river sediments begin to release BG even at temperatures around 60C. In the beginning of the 1895, street lamps in one of the districts of the Exeter city were supplied with BG, obtained by wastewater fermentation. In 1887, India was created new BGP for lighting one of the hospitals using obtained BG and in 1897 the BG was used as motor fuel in various engines for the first time in Bombay. BGP began using in European countries only during the First World War, which was due to a fuel shortage. The first large-scale BG production facility was created in Birmingham in the 1911, to disinfect sewage sludge of this city and obtained BG was used to electricity generation. During the Second World War, the main attention was paid to obtaining BG from livestock manure in Germany and France due to the lack of fuel. Therefore, these works developed rapidly, and already 40 years in France were commissioned about 2000 biogas plants operating with manure. In the same years, the BG production factories also existed in Hungary. However, all pre-war plants in the post-war time were not able to compete with heat and power plants operating on the basis of cheap traditional energy sources, and were dismantled. In the 70s of the last century, the second phase of the energy crisis began, which gave a new impetus to the development and implementation of biogas technology. In particular, the works has begun on the introduction of biogas technologies in the Southeast Asia countries, as part of national and international programs. Currently, more than 46 million families use BG for lighting and heating homes and cooking in these countries. The sole leader in the use of biogas technologies is China, where 40 million small units are currently in operation, with a bioreactor (BR) volume of not more than 10 m3, and it is planned to increase their number to 80 million in 2020. There are using 4.4 million units in India, and 355 thousand units in Nepal and South Asian countries. Moreover, the state programs for the implementation of small biogas plants in China and India. More than 70,000 units were planned in 2013 in Senegal, Burkina Faso, Ethiopia, Uganda, Kenya and Tanzania. In Latin America, where includes Argentina, Brazil, Chile and Mexico, there are several biogas plants which many these have been operating since the beginning of the last century. However, the total number of them is only from 15 to 45 operating or planned biogas plants. Currently, 18% of the energy balance needs are provided through BG in Denmark. But Germany is the sole leader among European countries with a total number of biogas plants with 8 million units. In Austria
The scientific heritage No 48 (2020) there are more than 350 units with 2000 m3 bioreactor volume, and in Denmark there are more than 20 large biogas plants with 850-14600 m3 volume of bioreactor and a large number of small biogas plants. 68 biogas plants are used in England to partially cover the energy needs of agriculture. Despite the presence of numerous biogas plants, only 4 biogas plants work on manure in France. In Western Europe, almost half of poultry farms are heated using BG. Currently, the well-known corporations such as Volvo and Scania produce buses operating on the basis of BG, which are widely used in the Swiss cities of Bern, Basel, Lucerne, Lausanne and Geneva. In the USA, there are more than 170 large biogas plants with a volume of more than 2000 m3 of BR, of which 153 of these produce electrical and thermal energy [2-4].
Although the above mentioned development of biogas technology, in other countries of the world, unfortunately, the necessary attention is not paid to biogas technologies in Azerbaijan. In this regard, the exception is biogas plants, created under the guidance of prof. F.G. Aliyev, according to the joint project of the "International Eco-Energy Academy" and the "Azerbaijan Engineering Academy", which was applied in the village of Khinalig, Guba region of Azerbaijan. However, unfortunately these works were suspended due to insufficient funding. Another biogas plant was established in the Gobustan region of Azerbaijan by State Agency for Alternative and Renewable Energy Sources (SAARES) of the Republic of Azerbaijan. However, this plant was did not work even one day since created due to due to the lack of specialists in the field of biogas technology. All this is due to the fact that biogas plant was assembled on the basis of equipment purchased abroad and it was completely assembled by the representatives of manufacturers (foreign experts), which required significant financial costs and since biogas plants are complex plants that require sufficient knowledge of all processes occurring in the BR, and since biogas plants are complex equipments that require sufficient knowledge of all processes occurring in the BR which should be automatically monitored and regulated. Therefore, in the future, the existing SAARES employees could not manage the work of this BGP due to the shortage of specialists in this field and over time it failed. This plant is currently in an idle, decayed state (see Fig. 1). It should be noted that, not only this plant, as well as all other power plants installed by the "specialists" of the SAARES, in different territories of Azerbaijan, have only the appearance, but at this moment, none of them work normally. Therefore, Azerbaijan takes the last place in the development of alternative and renewable energy, not only among developed, but also among developing countries, including among the CIS countries. However, it should be note that in the second half of the last century, our republic was one of the leading countries in the world in the development of solar and wind energy [5-9].
Figure 1. General view of the BGP mounted by the SSARES in the Gobustan region of the
Republic of Azerbaijan
2. Classification, block diagrams and functional diagrams of various types of BGP
Technological processes occurring at BGP depend on technical, chemical, biological, energy, structural, organizational and other factors mutually related to each other. The technical factors include all the structural components of the BGP.
Figure 2 shows a schematic relationship between the individual structural units of the BGP for the BG production from BM of plant or animal origin and OW, by their anaerobic digestion.
The main structural units of the BGP include a loading hatch, chopper, bioreactor, primary assembly chamber for BG (shown as "Biogas" in Fig. 2), separator, water trap, gas separation chamber, filter-drier for methane, gas holder, compressor, and also receivers for the accumulation of CO2 and CH4. The scheme shown in Fig. 1 is simplified, since it contains only those nodes that belong to many types of biogas plants, including non-automated, simple and low-power installations.
So, in industrial biogas plants with high performance, in addition to the structural elements shown in Fig. 2, also consists of stirrers with a vertical or horizontal shaft located inside the BR, water heating systems for displacement with grinded BM and OW, intended for the circulation of the heat-transfer agents through the pipes of the heat exchanger (HE) located inside the BR, water pumps used to supply the loading hatch with warm water from the hot water storage tank, or with liquid fermentation waste, from the bottom of the separator, an alarm device associated with the
analyzer gas connected to the gas outlet of the BR, maximum pressure relay to protect the BR from depressurization under the possible increase in the BG pressure above the maximum value, an electrical pressure gauge designed to automatically turn the compressor on and off depending on the amount of excess pressure of the BG in the gas tank. Moreover, automated industrial biogas plants are also supplied with some thermal relays, with thermosensitive elements installed respectively inside the BR and the hot water storage tank, which serve to automatically control the temperature inside the BR, as well as the temperature of hot water in the storage tank for hot water and heat transfer agent circulating through the heat exchanger pipe by means of a circulation pump.
The diagram of one of the simple versions of the Belarusian State University, designed for medium and large peasant farms is shown in Figure 3 [10]. According to the authors of the work, a distinctive feature of the BGP is that for the preparation of raw materials. There is a separate capacity and the BM (manure) crushed and diluted with warm water is fed to the loading hopper from there using compressor.
However, as in the figure explanation, nothing is indicated for supplying raw materials to the loading hopper. Perhaps, regarding the use of a compressor for this purpose, the authors made a fortuitous mistake, since usually, centrifugal pumps are used for this purpose but not chemical compressors. In addition, the places of the gas holder and receiver are also confused in the presented scheme.
Figure 2. Schematic relationship between the individual structural units of the BGP for obtaining BG from plant or animal origin BM and OW by their anaerobic digestion
Biogas plants are classified according to the following criteria: 1) the shape of the reservoir for collecting BG; 2) design features; 3) the number of levels; 4) temperature condition; 5) BR loading method; 6) the relative amount of dry matter; 7) the purpose of the received BG; 8) the type of raw materials used.
Currently, various types of reservoirs are used to collect BG, which include ovoid, spherical, cubic, elastic, cylindric, in the form of a trench with a cone up and down on both sides.
First of all, the design features refers the number of used bioreactors, according to which biogas plants are single-reactor and multi-reactor.
Simultaneously, single-reactor biogas plants are used for gas supply and heat supply to residents living in rural areas, and multi-reactor biogas plants are used
for heat supply and electricity supply to larger gas consumers, including vehicles.
BGPs are divided into three groups by the number of stages of the ongoing process: single-stage, two-stage and multi-stage.
BGPs are divided into three groups according to the temperature regime: psychophilic (20-250C) with an optimal temperature value of 250C, mesophilic (at 32-400C) with an optimal temperature value of 370C and thermophilic (at 45-600C) with an optimal temperature value of 550C.
Three loading options are used: batch, quasi-continuous and continuous. In addition, BGP are divided into installations for the implementation of dry or wet fermentation depending on the amount of dry matter.
Figure 3. The scheme of one of the BGP options: 1- manure receiver ; 2 - water heating boiler; 3 - loading hopper 4 - BR; 5 - hydro gate 6 - safety valve; 7 - electro-contact manometer; 8 - compressor; 9 - gas mixer; 10 - receiver; 11 - storage for biofertilizers; 12 - pipe removal for loading into transport; 13 - gas holder; 14 - gas reducer.
BGPs are also divided into three groups on the principle of subsequent application of the obtained BG: 1) in block mini thermoelectric stations, in order to obtain electricity and thermal energy; 2) in a heating boiler, for centralized and individual heat supply; 3) in gas appliances, for cooking and hot water, as well as motor fuel (after cleaning BG from CO2 and other impurities).
BGPs are divided into three groups by the type of used raw materials:
- agricultural, in which untreated green mass, or livestock farming waste is used;
- co-fermented, in which a mixture of pre-processed plant origin BM and OW saturated with carbohydrates is used;
- recycling, in which various types of biological waste are used in the fermentation process which the environment is not exposed to pollution;
- among the above options, the most suitable are single-stage biogas plants operating in the mesophilic mode with quasi-continuous loading the raw materials.
The efficiency of the BGP depends on the following requirements:
- reduction of heat costs to ensure the temperature regime inside the BR, with the exact choice
of design and location of heat exchangers, as well as using thermal insulation on the surfaces of the BR and the battery tank for hot water;
- reduction of energy costs for grinding the feedstock and moving the substrate in the BR;
- increasing the rate of fermentation of the substrate, i.e. transformation processes of BM and OW on BG;
- creating the optimal conditions for the life of all types of microorganisms involved in all stages of the substrate fermentation process;
In most biogas plants, about 50% of the resulting BG is used to ensure energy costs, which negatively affects the overall performance and overall efficiency of BGP. Recently, various BGPs have been developed in the form of inventions at the technical solutions level, in which wind and solar (photovoltaic power sources or flat solar collectors) energy sources are used to ensure energy costs. The scheme of the BGP, which is heated by the flat solar collector is presented in Fig. 4 [11]. As can be seen from the given BGP scheme, the solar collector is connected in the natural circulation mode of heat-carrier, which requires the BR to be placed at several meters above the BR
Figure 4. BGP with heat supply from the solar collector: 1- BR; 2- reservoir; 3- water jacket; 4- solar collector; 5- spherical cover; 6 - free end of the loading hatch 7; 8- fermented BM; 9- mixer; 10-BG;
11-gas holder; 12- unloading hatch; 13 - temperature regulator; 14- expansion tank; 15- the layer of thermal insulation; 16 - containers; 17- heat storage substance with phase transition
This is one of the main disadvantages of this plant, since it places a high demand on the thermal insulation of the BR. Otherwise, large heat losses may occur, especially during the winter periods of the year, as well as under windy weather conditions. Moreover, the heating process of the BR is carried out only with the using solar collector in this BGP, which is also one of the disadvantages of this plant, since, despite the fact that heat-accumulating substance with a phase transition is placed in special containers inside the BR, but this is not enough ensuring the necessary temperature at different times of the year, in particular in the winter season. Since the BGP is not equipped with an automatic temperature control system inside the BR, its temperature can reach up to 200-2500C due to boiling of the heat-storage substance with a phase transition, which is absolutely unacceptable for the BGP operating even in the thermophilic mode. Since at such a high temperature none of the microorganisms involved in the fermentation process will be able to continue its life activity.
Figure 5 presents a diagram of another BGP [12], in which the rotational movement of the shafts shredder and mixers is carried out from a wind turbine, and the necessary temperature regime inside the BR is provided by using a flat solar collector. This plant also has certain drawbacks in that temperature regime in the BR is ensured only by the solar collector, which is
unacceptable for such installations, since flat solar collectors work only in the sunny time of the day, and in non-sunny days (overcast), as well as at night, their work stops completely. Therefore, the continuity of the required temperature regime is violated, which leads to a significant weakening of the vital activity of microorganisms that carry out the fermentation processes of BM. In addition, the input and output of the solar collector pipes are directly connected to the heat exchanger in this BGP, i.e. without using an additional battery tank for hot water, due to which, on clear sunny days, especially at noon in the summer season, the temperature inside the BR is understood to be up to 1000C, which leads to the complete death of all types of microorganisms involved in certain stages of substrate fermentation. Another serious drawback of this BGP is the use for rotating the shredder shafts and both mixers of the mechanical wind turbine, since it is not possible to constructively connect the shaft between this wind turbine and the shredder and mixer shafts located at distances greater than 100 m from each other.
The next important factor is the lack of access to wind energy in every place with a speed above the minimum operating speed of 4 m/s, especially in mountain and foothill areas, where mainly objects of the agricultural sector, as well as farms with rich reserves of various types of raw materials are located.
/2 2 '5
Figure 5. BGP with power supply from wind turbine and solar collector: 1-BR; 2- heat exchanger; 3 4- separate BR cameras; 5- pipe for receiving BM and OW; 6- pipe for removal of biofertilizers; 7 - loading hatch; 8- hatch for unloading bioferti-lizers; 9 - BM shredder; 10 - the shaft of the first mixer; 11 and 12 are the upper and lower blades of the first mixer, respectively; 13 - the shaft of the second mixer; 14 and 15 - the upper and lower blades of the second mixer, respectively; 16 - couplings; 17 -rotational motion transmission system; 18- wind turbine; 19 - gas holder; 20 - gas distributor; 21-flat solar collector (heater); 22 - expansion tank; 22 and 23-heat exchanger pipe; 25- insulating layer
The Institute of Radiation Problems of the Azerbaijan National Academy of Sciences, together with the International Eco-Energy Academy are developed an automated BGP with automatic control mode work on the signals of various signal sensors, considering the indicated shortcomings of the well-known biogas plants for which alternative current sources, in particular, flat solar collectors and power units, are used for energy supply (electric and thermal). This BGP is simultaneously used flat solar collectors, wind and photoelectric current sources, as well as the centralized electrical network as a backup source to provide the necessary temperature conditions inside the bioreactor. In this case, two types of storage systems are used: electric, consisting of a battery block, and thermal, consisting of a storage tank for hot water with a large capacity, which ensures uninterrupted operation of the plants, regardless of the season and climatic conditions.
Since, the invention for this plant has been submitted to the State Committee on Intellectual Property of Azerbaijan which undergoes relevant expert stages. Therefore, at present, we cannot provide a diagram of this installation and a more detailed explanation of the principles of its operation.
3. The classification of BGP by design and function of individual nodes
The classification of BGP was noted in the previous paragraph. It should be noted that biogas plants are also classified according to the amount of produced BG: family (small), up to 50 m3 of capacity per day; farm (BGP with medium capacity), with 50 to 300 m3 of capacity per day; centralized (high power BGP), with a capacity of over 300 m3 per day.
As mentioned above, BGP also differs in loading methods of raw materials, methods of collecting BG, according to used raw materials, use of additional nodes, in particular, automation of various processes and regulate the main parameters (temperature and pressure in the BR, grinding the initial BM, mixing substrate, heat carriers circulation through heat exchanger pipes, etc.), as well as according to the location and design of the BR, design of the BG assembly system (gas holder and receiver) and the assembly of the mineral residue of the fermentation process (separator for separating the solid part of the mineral fertilizer from the liquid).
Existing BGP uses two types of loading: portion and continuous. The BR is loaded with raw materials completely when batch loading, and after a certain time (at the end of the BM fermentation process) the mineral residue of fermentation is released and the BR loading process is carried out again. Such loading methods are used, usually in bioreactors with a psychophilic operation mode. BGP of any design and any type of raw material are suitable for this loading method. The disadvantage of these types of BGP is the instability of the production of BG.
BGP of continuous loading is loaded daily in small portions of raw materials, and each time, an equal portion of the processed sludge is unloaded when loading new raw materials. The main requirement for the use of this type of loading is that the raw materials processed in such plants must be liquid and homogeneous. The advantage of continuous loading of raw materials is stability and the achievement of a large amount of the obtained BG. Currently, the biogas plants
with continuous loading of raw materials are used in most developed countries.
The following types of biogas plants exist according to the BG collection method: 1) balloon; 2) channel type; 3) with a fixed dome; 4) with a floating dome. At the balloon type of biogas plants, a heat-resistant plastic or rubber bag (balloon) is used to accumulate the resulting BG, in which the reactor is combined with a gas holder. Pipes for loading and unloading raw materials are mounted directly to the plastic of the reactor. Gas pressure is achieved due to the extensibility of the bag and due to the additional load that lies on the bag. The advantage of such type of BG assembly system consists of the simplicity of the design, low cost of the process, ease of movement of the substrate, the presence of the optimal temperature conditions for the psychophilic regime of substrate fermentation, the simplicity of the BR cleaning processes, as well as the loading and unloading of raw materials. The disadvantages are: short operational period (up to 5 years), dependence on external influences and low possibility of job. Channel-type biogas plants are analogs of balloon-type biogas plants, which in many cases are closed by plastic and protected from direct sunlight on the BR, and they are often used for wastewater treatment. Installations of this type of BGP can be used with a low probability of damage to the rubber shell of the BR and at sufficiently high ambient temperatures. The fixed-domed BGPs are consists of the covered domed BR and separator. In this case, the resulting gas is collected in the dome located in the upper part of the BR. The processed raw material is pushed into the separator tank when the BR is loaded with another portion of the raw materials. The level of processed raw materials in the separator rises with increasing gas pressure. The only drawback of these types of biogas plants is the change in gas pressure at the time of its use in household appliances. Floating domes are usually used in semi-buried BGPs that use mobile gas holder floating directly in raw materials or inside a special cylindrical tank filled to half with water. The BG accumulates in the gas holder, the internal capacity of which depending on the change in gas pressure rises (with increasing pressure) or falls (with decreasing pressure).The gas holder is usually made of stainless metal.
The main constructive part of all types of BGP is BR, which all four stages of fermentation of BM or OW occur. Bioreactors differ from each other both in terms of location and material. The geometrical location of the BR depends on the loading method and the availability of free place for its location in the required territory. At present, horizontal and vertical BRs are used. Horizontal bioreactors are used mainly at the BGP with a continuous loading method when there is sufficient place for the construction of this type of BR. The vertical bioreactors are more suitable for portion loading of raw materials and are used if necessary to reduce the occupied place. Another important factor is that to reduce the amount of heat loss through the walls of the BR, in particular above-ground and half-buried in the ground, they should be covered with thermal-insulating coating.
Three types of BR are distinguished in terms of design: 1) concrete; 2) brick; 3) metal.
Concrete bioreactors usually have a cylindrical shape and are built underground. Such types of bioreactors belong to the category of low-power plants with a capacity of up to 6 m3 per day. The advantage of these bioreactors is low cost and ease of construction, as well as the possibility of massive production. Concrete BRs also have some disadvantages in that they require high-quality concrete, high qualifications from builders and a large number of wire mesh, as well as compliance with special requirements to ensure the hermeticity of the gas holder.
One of the disadvantages of such BRs is the need to use special coatings to ensure high hermeticity of the gas holder. Moreover, the uniform heating of brick types of BRs is very complicated and the implementation of this process is expensive.
Currently, metal types of BRs are most used, as they are suitable for any type of biogas plants. The advantages of such bioreactors are hermeticity, endurance to high pressures, ease of manufacture and the possibility of reusing the existing BR. The disadvantage of metal bioreactors is that the material is relatively expensive and requires activity to protect it from corrosion.
The effectiveness of the BGP in many respects depends on the intensity of the vital activity of microorganisms performing various stages of BM fermentation, and this in turn depends on many physical, chemical, biological, organizational and technical factors. One of these factors is the surface area of the particles of raw materials, which directly affects the productivity of BGP. It was found that the maximum particle sizes of BM should not exceed 3 cm and maximum performance is achieved with particle sizes of BM up to 3 mm. For this purpose, BM grinders are used in industrial BGPs, consisting of the housing with a grinding blade placed inside it. Thus, the initial BM enters the BR capacity after mixing with warm water and grinding to the desired size, passing through the perforated partition, where subsequently occur all stages of fermentation. Grinding is carried out manually in the ordinary simple, single-family biogas plants and industrial plants using electric motors.
Achieving maximum performance, for all BGPs, it also depends on regular mixing of the substrate using a mixer consisting of a vertical or horizontal shaft and blades attached to them from several places. Vertical shaft mixers are commonly used for large industrial-scale biogas plants. In this case, the blades are attached to the upper, middle and lower parts of the shaft. This is very important, since the lower blades serve to ensure the uniformity of the substrate, as well as the uniform distribution of temperature along the height of the BR, and the upper blade to completely destroy the gas-tight rigid crust accumulated on the upper part of the BR. This ensures optimal conditions for the intensification of the vital activity of microorganisms. Large biogas plants also use hydraulic and gas mixing devices.
The heat exchangers are used to heat the substrate in the BR which circulate the heat carriers (hot water) using a circulating pump. The processes of switching
on and off which are carried out automatically, by means of the thermal relay, according to the signal of the sensing element installed inside the BR.
However, the maximum conditions for the life of all types of microorganisms are provided, due to which the maximum productivity of the biogas plant and the high quality of the obtained BG are achieved when using alternative energy sources for this purpose, in particular, a wind (wind power unit) or solar (photoelectric current source and solar collectors) electrical circuit automatic control systems are much more complicated. In particular, the wind (wind power unit) or solar (photoelectric current source and solar collectors) circuitry of the automatic control system is much more complicated when using alternative energy sources for this purpose. However, the maximum conditions for the life of all types of microorganisms are provided, due to the maximum productivity of BGP and high quality of obtained BG.
Thus, in conclusion we can say that the use of biogas plants in Azerbaijan has great importance as in other countries of the world. Since Azerbaijan has rather strong resources of solar and wind energy, the creation of combined biogas plants working in conjunction with solar and wind power sources is possible. This is of particular importance for the creation of the large-capacity biogas plant, serving both for gas, heat and power supply of residential areas and farms located far from centralized gas and electricity networks.
References
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