Biogas engine. Use of biogas

Experience in gas pipeline aggregates on biogas

1. Introduction

The task of modern energy is to ensure reliable and long-term power supply while maintaining fossil fuel resources and protection ambient. This requires an economical approach to the use of existing energy resources and the transition to renewable sources. The study conducted by the European Commission proved that this is possible.

During the study, only technology available today was taken into account, and it was assumed that the standard of living in European countries would be equalized. So, by 2050, 90% of energy consumed by European countries may well be produced using renewable energy resources (Fig. 1). At the same time, the price of electricity will increase twice, but at the same time consumption of energy carriers will double. Almost a third of the energy will be made from biomass.

Figure 1 - Energy consumption in Europe (European Commission study)

Biomass is a general term for the designation of organic products and waste (liquid manure, grain residues, oilseeds and saham-containing cultures), industrial and household waste, wood, food industry waste, etc. Dry biomass can be immediately used as fuel, in other cases it can be immediately You can convert to biogas by "fermentation", gasification or evaporation (Fig. 2).

Figure 2 - Use of biomass

2. Biogas formation

In nature, biogas is formed during the decomposition of organic compounds in anaerobic conditions, for example, in swamps, on the shores of water bodies and in the digestive tract of some animals. Thus, physics of natural natural processes shows us the path of obtaining biogas.

For industrial production, the development of an integrated technology is required, which includes components such as a biomass drive, a biogas reactor (enzymator), in which the biogas reservoir is leaving and the cleaning system (Fig. 3).

Figure 3 - Production electrical Energy When using biogas

Almost all organic substances decompose by fermentation. In anaerobic conditions, microorganisms involved in the process of fermentation or decomposition are adapted to the source substrate. Due to the fact that fermentation occurs in a wet environment, the biosubstrate must contain approximately 50% of the water. Biological decomposition is carried out at a temperature of from 35 ° C to 40 ° C. In anaerobic fermentation, a multistage process of converting organic substances from high molecular compounds into low molecular weight, which can be dissolved in water. At one stage, dissolved substances decompose, forming organic acids, low-grades alcohol, hydrogen, ammonia, hydrogen sulfide and carbon dioxide. On the other, the bacteria transform substances into acetic and formic acids and in the process of methanogenesis they split them, forming methane.

4 HCOO H → CH 4 + 3 CO 2 + 2 H 2 O

At the same time, the CO 2 content decreases due to hydrogen, as a result of which methane is also formed.

CO 2 + 4 H 2 → CH 4 + 2 H 2 O

Liquid manure is often used as a raw material for biogas. To increase the gas yield, you can add so-called coenses, due to which the production of biogas is homogenized, the volume of which depends on the substrate used (Table 1).

Table 1 - Biogas Output for various types of biomass

3. Biogas quality and its preparation for use

The quality of biogas and the preparation of fuel gas depends on the source raw materials used and the speed of the process. In tab. 2 A comparison of the composition of various types of gas is presented.

Table 2 - an exemplary comparative composition of fuel gases

Since biogas contains such harmful components such as sulfur, ammonia, sometimes silicon, as well as their compounds, the possibilities of using it are limited. These components may cause wear and corrosion engines. internal combustion, Therefore, their content in Gaza should not exceed the norms established by MWM. In addition, the spent gases can not be cooled to a temperature of less than 140 ... 150 ° C, otherwise, in heat exchangers and at the bottom of the system of channels for the spent gas will accumulate acid condensate.

There are several ways to remove sulfur from fuel gas. When biological cleaning in the gas zone in the fermenter is served air. As a result of the oxidation of hydrogen sulfide bacteria, sulfur and sulfate are separated, which are removed with liquid components. Another way is chemical deposition. In this case, the iron trichloride is added to the solution in the fermenter. These methods have proven themselves in wastewater treatment plants.

The most optimal results are achieved when cleaning the gas using activated carbon, and not only sulfur is removed from the gas, but also silicon. In this case, the quality of biogas corresponds to the quality of natural gas, and the use of an oxidative catalytic gas-oil device provides an additional decrease in the level of emission of exhaust gases.

4. Use of biogas for CHP based on gas engines

MWM GmbH (in the past Deutz Power Systems) produces gas pipelines with turbocharging, operating on the depleted mixture in the rated power range from 400 to 4,300 kW (Fig. 4). These engines are adapted to oscillations in the component composition of the biogas and are optimized to work on the gases of complex compositions.

Figure 4 - Power Range gas engines MWM GmbH (former Deutz Power Systems)

The nominal parameters are specified in accordance with ISO 3046. The characteristics are given only for information and are not mandatory values.

MWM GmbH has a wealth of operation of gas pipeline engines on gas dumps and wastewater (the first such models began to work almost 100 years ago on the sewage gas) and uses accumulated experience for further improvement model Row and improving the reliability of manufactured cogeneration systems. (Fig. 5)

Figure 5 - Development of gas pipelines (for the period 1988 - 2002)

The main task is to make engines more resistant to exposure. harmful substancescontained in gas. Various impurities form acids that negatively affect the components of the engines, primarily on the bearings. Such a negative impact can be eliminated, on the one hand, optimizing the mode of operation and change in the technology of manufacturing bearings, on the other.

If you exploit installation with temperature lubricant oil About 95 ° C (at the engine inlet) and avoid frequent stops and starts, it is possible to reduce the risk of acid formation due to the occurrence of condensate in the cooling phase. In connection with the foregoing, as soon as the engine should work without stopping. Gas accumulation in a sufficient volume in the gas storage will provide a continuous supply of fuel, which is necessary for the uninterrupted operation of the gas engine.

The experience gained during the operation of engines operating on biogas showed that special materials need to use for bearings. Since the efficiency of the engine and the working pressure increases, you need bearings with a higher rated load. Currently, bearings are widely used, which provide all reliability requirements. Due to the solid solid surface, they are more resistant to the effects of aggressive substances contained in gas and lubricant oil than traditional ball bearings with a groove (Fig. 6).

Figure 5 - Comparison of peak pressure of lubricant

The quality of lubricating oil has a significant impact on the service life and wear of the engine. Consequently, during operation, only those oil grades should be used, which manufacturer of the gas engine approved for this type of gas. Oil replacement intervals are determined by entering the power plant to operate according to the results of oil quality analysis. During the operation of the engine, constant monitoring of the quality of lubricating oil is carried out, after which the decision is made to replace it. The first oil analysis is performed after 100 hours of operation, regardless of the type of fuel gas. Intervals maintenance For valves is defined in the same way.

In order to extend the intervals of the lubricant oil, its number in the frame base of the engines should be increased. For this purpose, MWM offers its customers an aggregate with an increased oil volume in the engine frame. The oil is constantly fed into the lubricant circuit, passing through the frame-base diagonally (Fig. 10):

Figure 6 - Lubricating oil supply

In addition to the design features of the Motors themselves, the TEM control and management system (Total Electronic Management Company MWM) is played in ensuring the safe and reliable operation of biogas aggregates. It defines all operating conditions, temperature indicators, pressure, etc. and based on the data obtained sets the optimal output power of the engine at the maximum efficiency, without leaving the installed emission limits. In the TEM system, there is an option to compile analytical graphs of changes in the operational parameters of the station - this allows timely to identify violations in work and quickly respond to them.

The company supplies complete energy attitudes working on biogas. Their composition includes a gas pipeline unit, a utilizer boiler, silencer, catalytic gas-lathers, a gas purification system with activated carbon and, if required, additional system Subsequent cleaning of exhaust gases. (Fig. 7).

Figure 7 - Sample layout Mini CHP ( click on the image to enlarge)

In fig. 8 shows the specific investment and the average maintenance costs of biogas installations. The data summarizes the experience of operating the TBG 616 and TBG 620 settings. They include the costs of a gas pipeline unit, heat exchangers for coolant and exhaust gases, noiselessness, as well as distribution costs, including mounting and pipeline system. Since 2005, the TBG series has been upgraded in the TCG 2016 C and TCG 2020 series, respectively.

Figure 8 - Investments and maintenance costs

In 2009, after conducting the next modernization of the model range, for the TCG 2020 series, it was possible to reach an electric efficiency of 43.7% for the TCG 2020 V20 cogeneration unit, and the electrical power of 12 and 16 cylindrous gas engines would be brought to 1200 and 1560 kW. Serious modernization also touched the TCG 2016 V08 aggregate. The electrical power of this unit is increased to 400 kW, and the electric efficiency rose to 42.2%. Moreover, the electric efficiency and the output power is the same as using natural gas and for biogas.

5. Practical use of various types of raw materials for energy generation

In Brandenburg (Germany) The power plant generates biogas from food and household waste (photo 1). About 86,000 tons of biosoises are disposed of about 86,000 tons.

Photo 1 - biogas installation in Alto

The biogas preparation process is carried out in a certain sequence. After removing the non-researchable components, the bio currents are crushed and mixed, the resulting mass is heated to 70 ° C to kill pathogenic organisms. Then the waste is sent to two fermenters, each of which accommodates 3300 m3 biomass. Microorganisms split biomass (about 20 days), as a result of which the biogas is formed and the residual amount of fluid, which is then pressed, and the dry residue passes biological processing as compost.

On biogas, two TBG 616 V16K gas pipes produced by DEUTZ Power Systems are operating, the electrical power of each of them is 626 kW, thermal - 834 kW. Generated electrical energy is supplied to power, and heat is used to generate gas. The levels of emissions of harmful substances are lower than the boundary values \u200b\u200bspecified by the German Ta-LUFT standard.

Installation on bioagzea works also in Ayhigte At Agrofarm 2000 GmbH livestock economy. The company handles 2,200 hectares of arable land and 1100 hectares of pastures in Eichigt / Vogtland. Part of the crop grown farm culture is used as feed for 1550 cows, from which 10,650,000 kg of milk are obtained per year. At the same time, it is formed daily from 110 to 120 m 3 of liquid manure - it "ferments" in the enzymator, resulting in 4000 ... 4400 m 3 biogas. The remnants of feed (up to 4 tons per day) are added to the manure, due to which gas production increases by 20%.

Mini CHP is installed in the container (photo 2), the engine TBG 616 V16 K is used as the drive, the electrical power of which is 459 kW, thermal - 225 kW. Electricity is supplied to the power system, and heat is used for the needs of the economy. Liquid manure is used as biogas raw materials.

Photo 2 - MWM Cogeneration Unit (former Deutz Power Systems) in container design with TBG 616 V16 engine

The biomass utilization cycle is almost without waste. The remains formed in the process of anaerobic "fermentation" do not smell, and they can be used in the fields as a fertilizer throughout the year.

conclusions

• The use of agricultural waste as biofuels allows you to provide a closed cycle of agricultural production. The balance of anaerobic fermentation has no smell and can be exported to the fields in the form of fertilizer. This type of fertilizer is immediately absorbed by plants without soil contamination or groundwater.
• The production of energy from biogas, in the light of regular energy crises, refer to promising renewable energy sources. Biogas plants convert solar energy accumulated by plants into biogas during the biological decomposition process. This process is neutral with respect to CO 2 ballage, since only the amount of carbon dioxide is released into the atmosphere, which was previously absorbed by plants during photosynthesis.
• The production of electrical and thermal energy in biogas installations is a promising technology that helps humanity to become independent of the limited reserves of fossil fuels, and also protects the environment.
• MWM GmbH offers its customers installation to generate electricity and heat based on modern, safe and reliable gas engines.

The original article was printed for: Vith International Scientific Conference Gas Engines 2003 in Poland, 02 - 06 June 2003

One of the main trends in the design of modern car engines is the improvement of their environmental characteristics. In this regard, one of better options is an bioflee EngineThe most popular view of which is bioethanol.

Bioethanol is an ethyl alcohol, which is obtained by processing plant raw materials. The cordial crops are becoming the main source for its production.

Engine features on biofuel

It should be noted that at the moment there are practically no speech about the engine, which would fully worked on bioethanol. This is explained by a number of objective restrictions, to overcome which has not yet been found effective solutions.

To date, Biotenol is used to refuel cars, mainly in the mixture with traditional fuels - gasoline and diesel fuel. Work on such fuel can only vehicles With an FFV type engine (Flexible-Fuel Vehicle - Flexible Fuel Selection).

The FFV type motor is an internal combustion engine that has some differences from traditional engines. So, the mains distinctive features are:

• the presence of a special oxygen sensor;
• the use of special material for the manufacture of a number of gaskets;
• eCU software that allows you to determine the percentage of alcohol content in fuel and adjust the operation of the motor accordingly;
• some changes in the design to increase the compression ratio, which is necessary due to a higher octane number of ethanol, compared to gasoline.

Today, automotive fuel with the content of bioethanol is quite highly popular in a number of countries. The leaders here are the US and Brazil. In Brazil today, it is almost impossible to buy gasoline, in which the content of bioethanol would be less than 20%. This technology is popular and in some European countries, especially in Scandinavian countries.

Advantages and disadvantages

Bioethanol as fuel has both significant advantages and substantial disadvantages. The main advantages of biofuels include, first of all, to environmental indicators.

Bioethanol is a non-toxic type of fuel, which is completely dissolved in water. With its combustion, it is not formed dangerous to the environment and health of people connections. Adding bioethanol to gasoline reduces the amount of harmful emissions to 30% or more. In addition, bioethanol is made from natural renewable raw materials. Often it is a by-product of the waste-free production of other types of products.

In addition, due to the high octane number, the use of bioethanol allows you to improve some characteristics of the internal combustion engine. Including its efficiency increases.

One of the main disadvantages of biofuels is its instability to low temperatures. In the cold, it can smear with the formation of a film from paraffin on the surface. This determines the difficult start in the winter. To overcome this disadvantage, it has to equip cars with a fuel heater or a small gas tank, designed specifically for a cold start.

Another an important flaw lies in a weak calorific value. When combustion of bioethanol is released at 37-40% less thermal energy, compared with traditional species automotive fuel. It significantly limits the power characteristics of the engine.

Engines on biofuel are essential advantages, but they have where to develop.

The main method of using biogas is to transform it into a source of thermal, mechanical and electrical energy. However, large biogas installations can be used to create industries to obtain valuable chemical products for the national economy.

Biogas can work gas-incorporating devices that produce energy, which is used for heating, lighting, feeding cord machines, for the operation of water heaters, gas stoves, infrared emitters and internal combustion engines.

Most simple way It is burning biogas in gas burners, as the gas can be lifted to them from low pressure gas producers, but more preferably the use of biogas to produce mechanical and electrical energy. This will lead to the creation of its own energy base that ensures the operational needs of farms.

Table 18. Biogas components

Gas-burners

Fig.34. Gas stove working
on biogas in p. Petrovka

The basis of most household appliances in which biogas can be used is the burner. In most cases, atmospheric type burners are preferred, operating on pre-mixed with air biogas. Gas consumption The burners are difficult to calculate in advance, so the design and tuning of the burners should be determined for each individual case experimentally.

Compared to other gases, biogas need less air for fire. Consequently, ordinary gas devices need wider gibrels to pass the biogas. For complete combustion of 1 liter of biogas, about 5.7 liters of air is necessary, while for Bhutan - 30.9 liters and for propane - 23.8 liters .

Modification and adaptation of standard burners is a matter of experiment. In relation to the most common household appliances, adapted to use Bhutan and Propane, it can be noted that butane and propane have a calorific value of almost 3 times higher than biogas and give 2 times more flames.

The translation of burners to work on biogas always leads to more low levels Devices work. Practical measures for modifying burners include:
Increased buses 2-4 times to gas passage;
Change the volume of air supply.

Gas plates
Before using the gas stove, the burners must be carefully adjusted to achieve:
compact, bluish flame;
The flame should be spontaneously stabilized, i.e. Not burning burners should also light up for 2-3 seconds.

Fig.35. Water heating boiler
For home heating with radiating ceramic heaters in with. Petrovka

Emitting heaters
Radiating heaters are used in agriculture to obtain the desired temperatures for growing young, for example, piglets and chickens in a limited space. The temperature required by piglets starts from 30-35 ° C in the first week and then slowly drops to a temperature of 18-23 ° C in 4 and 5 weeks.

As a rule, temperature adjustment consists in raising or lowering the heater. Good ventilation is a necessity to prevent CO or CO2 concentration. Consequently, animals must be under constant supervision, and the temperature is checked through regular intervals. Heaters for piglets or chickens consume about 0.2 - 0.3 m3 biogas per hour.

Heaters thermal radiation

Fig.36. Gas pressure regulator

Photo: Vedenov Ag .., of "Fluid"

Radiating heaters implement infrared thermal radiation through a ceramic body, which heats up to a bright red state at temperatures of 900-1000 ° C with flame. The heating possibility of the radiating heater is determined by multiplying the volume of gas to clean calorific value, since 95% of biogas energy turns into heat. The output of thermal energy from small heaters is
from 1.5 to 10 kW of thermal energy8.

Fuse and air filter
Eating biogas radiating heaters should always be equipped with a fuse, which stops supplying the gas in the event of a decrease in temperature, that is, in the case when the gas is not burned.

Biogas consumption
Household gas burners consume 0.2 - 0.45 m3 biogas per hour, and industrial - from 1 to 3 m3 biogas per hour. The required volume of biogas for cooking can be determined on the basis of time, daily spent on cooking.

Table 19. Biogas consumption for household needs

Biogas engines
Biogas can be used as fuel for automotive engines, and its effectiveness in this case depends on the content of methane and the presence of impurities. On methane can work both carburetor and diesel engines. However, since biogas is high-octane fuel, its use is more efficient in diesel engines.
For the operation of the engines, a large amount of biogas is needed and installed on the internal combustion engines of additional devices that allow them to work both on gasoline and on methane.

Fig.37. Gasoelectrogenerator in with. Petrovka

Photo: Vedenov Ag .., of "Fluid"

Gasoelectrogenerators
Experience shows that biogas is economically appropriate to use in gas-electrose generators, while burning 1 m3 biogas allows you to produce from 1.6 to 2.3 kW of electricity. The effectiveness of such use of biogas increases due to the use of thermal energy, which is generated during the cooling of the motor of the electric generator, for heating the biogas plant reactor.

Purification of biogas

To use biogas as fuel for internal combustion engines, it is necessary to pre-purify the biogas from water, hydrogen sulfide and carbon dioxide.

Reducing the content of moisture

Biogas is saturated with moisture. Purification of biogas from moisture consists in cooling it. This is achieved by passing biogas by an underground pipe for moisture condensation at lower temperatures. When the gas is warmed again, the moisture content in it is significantly reduced. Such driving biogas is especially useful for used dry gas meters, since they are necessarily filled with moisture.

Reducing sulfide content

Fig.38. Hydrogen sulfide filter and absorber for carbon dioxide separation. Petrovka
Photo: Vedenov Ag .., of "Fluid"
A hydrogen sulfide mixing in biogas with water forms an acid causing metal corrosion. This is a serious limitation of the use of biogas in aqueous heaters and engines.
The simplest and economical way to clean the biogas from hydrogen sulfide is dry cleaning in special filter. As an absorber, a metal "sponge" is used, consisting of a mixture of iron oxide and wooden chips. With the help of 0.035 m3 of the metallic sponge from biogas, you can remove 3.7 kg of sulfur. If the hydrogen sulfide content in biogas is 0.2%, then this volume of the metal sponge can be cleaned of the hydrogen sulfide of about 2500 m3 of the gas. For the regeneration of the sponge it is necessary to hold some time in the air.
The minimum cost of materials, the simplicity of filter operation and the regeneration of the absorber make this method with a reliable means of protection of the gas golder, compressors and internal combustion engines from corrosion caused by the continuous exposure to the hydrogen sulfide contained in biogas. Zinc oxide is also an effective hydrogen absorbent, and this substance has additional benefits: it also absorbs organic sulfur compounds (carbonyl, mercaptan, etc.) 18

Reducing carbon dioxide
Reducing the content of carbon dioxide is a complex and expensive process. In principle, carbon dioxide can be separated by absorption into lime milk, but this practice leads to the formation of large volumes of lime, and is not suitable for use in large-volume systems. Carbon dioxide itself is a valuable product that can be used in various industries.

Fig.39. Biogasi UAZ
in p. Petrovka
Photo: Vedenov Ag .., of "Fluid"

Use of methane
Modern studies of chemists reveal great possibilities for using gas - methane, for the production of soot (coloring substance and raw materials for the rubber industry), acetylene, formaldehyde, methyl and ethyl alcohol, methylene, chloroform, benzene and other valuable chemical products based on large biogas settings18.

Biogas consumption engines
In p. Petrovka Chui region KR biogas installation of the Association "Farmer" with a volume of 150 m3 provides biogas for household needs 7 peasant farms, the operation of the gasoelectric generator and 2 cars - UAZ and ZIL. To work on biogas, the engines were reinformed by special devices, and cars - steel cylinders for gas injection.
The average values \u200b\u200bof biogas consumption for the production of 1 kW electricity by the engines of the Association "Farmer" - about 0.6 m3 per hour.

Table 20. Use of biogas as motor fuel in C. Petrovka

Fig.40. Burning burner for burning biogas surplus in with. Petrovka
Photo: Vedenov Ag .., of "Fluid"

Biogas use efficiency
The efficiency of biogas use is 55% for gas stoves, 24% for internal combustion engines. The most effective way to use biogas - as a combination of heat and energy, in which 88% of efficiency can be achieved. Use of biogas for the operation of gas burners in gas stoves, heating boilers, antpars and greenhouses - best view The use of biogas for farms of Kyrgyzstan.

Surplus biogas
In the case of an excessive biogas generated installation, it is recommended not to throw it into the atmosphere - this will lead to adverse effects on the climate, and burn. To do this, a torch device is installed in the gas distribution system, which must be at a safe distance from the buildings.