RU77649U1 - DEVICE FOR PRODUCING A GAS-AIR MIXTURE OF A UNIFIED COMBUSTION HEAT - Google Patents

Abstract

A device for producing a gas-air mixture of a single heat of combustion, including a supply gas pipe connected to a gas composition analysis unit and a gas flow measuring unit, the output of which is connected to the inputs of the gas reduction unit and the gas-air mixing unit connected in parallel, the outputs of which are combined and connected to the input of the measurement unit the flow rate of the gas-air mixture, the output of which is connected to the consumer’s gas pipeline, and the second input of the gas-air mixing unit is connected to the output of the forced air supply unit and, while the inputs of the automated control system are connected to the gas composition analysis unit, the gas flow measurement unit and the gas-air mixture flow measurement unit, and the outputs of the automated control system are connected to the forced air supply unit, through a pneumatically or electrically controlled valve to the gas mixing unit with air and a reduction unit; the automated control system is configured to generate a signal controlling the air supply, a signal controlling the reduction unit and a signal controlling the gas-air mixing unit.

Description

The utility model relates to the field of gas supply systems, namely, devices for producing gaseous fuel in automatic gas mixing systems, constructed on gas pipelines of the gas supply system of cities and towns and designed to provide natural (gas and oil fields) gases and gas mixtures with an overpressure of not more than 1.2 MPa (12 kgf / cm ² ) of consumers using these gases as fuel.

The predominant type of application of the utility model is the use in gas supply of industrial and domestic facilities.

The main objective of devices for producing a gas-air mixture is to obtain a gas mixture of a single heat of combustion.

When using gas-air mixture production devices and solving this problem, that is, when receiving gas fuel at the outlet of a gas mixing station with stable calorific value obtained by mixing combustible gas and atmospheric air, or gas and low-calorific artificial gases:

- eliminates incomplete combustion of gas in gas burner devices,

- the operation mode of gas burner devices of furnaces and boilers is stabilized

- increases the efficiency of gas consuming installations,

- reduced specific gas fuel consumption per unit of output.

Ultimately, solving this problem allows you to increase the efficiency of the entire gas supply system, and also, by reducing harmful substances released into the atmosphere, improve the environmental situation.

Since the utility model relates to the field of devices for producing gaseous fuel, namely, to the creation of an automatic gas mixing system for producing a mixture of combustible gas with air of uniform heat of combustion and can be used on gas pipelines of the gas supply system of cities and towns, it should be borne in mind the following:

Gas pipelines of the gas supply system, depending on the pressure of the transported gas, are divided into (Gas supply SNiP 2.04.08-87, M. 2001):

- high-pressure pipelines of category I - at a gas operating pressure of more than 0.6 MPa (6 kgf / cm ² ) up to 1.2 MPa (12 kgf / cm ² ) inclusive for natural gas and gas-air mixtures and up to 1.6 MPa (16 kgf / cm ² ) for liquefied petroleum gases (LPG);

- high pressure gas pipelines of category II - at a working gas pressure of more than 0.3 MPa (3 kgf / cm ² ) up to 0.6 MPa (6 kgf / cm ² );

- medium pressure pipelines - at a working gas pressure of more than 0.005 MPa (0.05 kgf / cm ² to 0.3 MPa (3 kgf / cm ² );

- gas pipelines of low pressure - at a working gas pressure of up to 0.005 MPa (0.05 kgf / cm ² ) inclusive.

Combustible gases can be classified by lower heat of combustion - Q _H and combustion temperature (Ravich MB Gas and its use in the national economy. M. Nauka, 1977, p.357).

By lower heat of combustion - Q _H :

- with increased calorific value (high-calorie) - Q _H > 31.40 MJ / m3 (natural, associated petroleum and liquefied);

- with an average combustion heat Q _H = 12,60-31,40 MJ / m3 (coke, shale and generator, obtained by pressure gasification with steam-oxygen blowing);

- with low heat of combustion Q _H <12.60 MJ / m3 (blast furnace, generator, mixed and underground coal gasification gases).

By combustion temperature T (max):

- with T _max = 2000 ° С - natural, oilfield, liquefied, coke, shale gases, which are advisable to use for high-temperature processes;

- with T _max = 1500-1700 ° С - mixed (50% coke oven and 50% blast furnace),

generating gases from bitumen fuels, which are used for medium temperature processes;

- with T _max = 1400-1500 ° C - blast furnace and some generator gases that are used for medium and low temperature processes;

- with T _max = 750-1400 ° С - numerous waste gases (cupola, industrial hydrocarbon plants, purge gases, which are often not utilized);

- with T _max <750 ° С - these gases are not used as fuel.

Technical specifications for combustible natural gases for industrial and domestic purposes are established in accordance with GOST 5542-87.

Requirements for equipment and calculation methods used to determine and control the volumetric heat of combustion of natural gas, its component composition and density are regulated by GOST R 8.577-2000 “Volumetric heat (energy) of combustion of natural gas”, GOST 27193-86 “Natural combustible gases, method determination of the calorific value of water with a water calorimeter ”, GOST 23781-87“ Natural combustible gases, a chromatographic method for determining the composition ”, GOST 22667-82“ Natural combustible gases, a calculation method for determining the calorific value, relative Wobbe numbers and numbers. ”

Gas fuel is used in all industries and in public utilities. At the same time, the non-renewability of fossil fuels raises the question of its rational and efficient use. In practice, combustible gas with different heat of combustion and density is supplied to gas burner devices of furnaces and boilers, where it is independently mixed with air before being supplied for combustion. The processes of formation of gas-air mixtures, as a rule, occur directly in the gas burner devices of furnaces and boilers and consist of successively proceeding stages: the formation of a homogeneous gas-air mixture, heating

mixtures to a flash point and chemical reaction - the actual combustion reaction. The stage of mixture formation has a significant effect on combustion and can be carried out either as a preliminary (preparatory) stage, or occur in parallel with other processes. Numerous gas burner devices are known with various methods of mixing gas with air, which practically do not provide quick and complete combustion of fuel, since the resulting gas-air mixture in the mixing chambers of these gas burner devices does not have a constant composition, density and the required (calculated) heat of combustion. All this leads to a change in the thermal power of gas burner devices and a deterioration in the technical and economic indicators of the plants as a whole.

A gas-air mixing plant is widely used (A.K. Kortunov, E.S. Korshunov, P.L. Kuznetsov, B.V. Barabash, A.I. Prromtov, M.Z. Shakirov, M.A. Ali -Zade, A.K. Khodjaev, U.S. Gas Industry, Moscow, Nedra, 1964, p. 190-191, Fig. 112.

The installation consists of an air filter, an air duct, a throttle valve, a natural gas pipeline, a mixing chamber, an automatic calorimeter, an automatic gas heat meter, an actuator on the throttle valve, and an automatic gas density recorder directed to consumers.

Due to the fact that the density and composition of the natural gas entering the installation inlet are not uniform, the resulting air-gas mixture is also uneven. In order to equalize its parameters at a certain distance from the mixers, a continuous sampling takes place, which enters both the automatic calorimeter and the automatic recorder of the density of gas directed to consumers. The calorimeter readings are constantly compared with the set value, if they deviate from the set calorie value, a signal is sent to the actuator, after which the throttle valve increases or decreases the bore for the air entering the mixing chamber.

The disadvantage of this scheme is the significant inertia of the operation of both the control system and the actuator as a whole, which is not

allows you to accurately maintain the required output indicators of the gas-air mixture in the "real time", the consequence of which is the inability to quickly achieve a constant uniform heat of combustion of the gas-air mixture and its density.

A known installation for producing a mixture of combustible gas with air based on the use of liquefied gas of the propane-butane fraction from soil tank installations (N.L. Staskevich, G.N.Severinets, D.Ya. Vigdorchik, Handbook of liquefied hydrocarbon gases, L. Nedra 1990, pp. 405-409).

The installation includes gas storage tanks, heaters for drying gas, air compressors, ejectors for the formation of gas-air mixture. Gas consumption during the day is uneven, therefore, the installation is equipped with three or four ejectors, which are automatically switched on and off depending on the amount of gas consumption. The installation is equipped with expensive air compressors and sophisticated instrumentation, which increases the cost of fuel. The resulting gas-air mixture has a calorific value of 8400-8500 Kcal / nm3. The disadvantage of this solution is that, as a result of using such a gas-air mixture, a part of the gas (10-15% of the volume) is not oxidized to CO2 and, in the form of unsaturated hydrocarbons (Сn Н2n) and carbon monoxide (СО), enters the atmosphere as a part of the combustion products.

In this case, part of the valuable hydrocarbon fuel is lost, there is pollution of the atmosphere of the combustion zone (industrial and domestic premises), as well as rapid wear of gas burner devices.

The closest analogue is a block automatic gas mixing system for producing a mixture of combustible gas with air of uniform heat of combustion (Eurasian patent EA 006716 B1, 2006.02.24, Bulletin No. 1, author - applicant - patent holder - AGAEV SHAMIL MIRZA OGLY, Azerbaijan).

The system consists of an air compressor unit; unit of a gas and air mixer including a gas mixer, an adjustable ejector mixing unit, including four centrifugal fans and four

adjustable ejector mixers containing an adjustable nozzle, a mixing chamber, a diffuser, a confuser and a nozzle; and a proportionality unit including an air flow meter, an air flow control valve, a check valve, a gas flow control valve, a gas flow meter and a gas to air ratio regulator.

In this solution, pre-prepared gas (purified and heated), pressure P = 3-12 kgf / cm3, is fed to the inlet of the gas mixer unit with air of an automatic gas mixing station. Air from the air compressor through the receiver, the reduction unit and the proportional device is supplied to the automatic gas mixing device. Air is also supplied there from an automatic controlled ejector installation, which is included in the gas and air mixer unit. The low pressure air is supplied to the adjustable ejector unit by centrifugal fans. In a gas mixer, gas and air are mixed in a ratio close to stoichiometric (1.01-1.02). The ratio of gas and air is regulated depending on the change in gas flow. The regulation of the ratio of gas and air is carried out automatically using a proportional device.

The disadvantage of this solution is the lack of accuracy in determining the ratio of gas and air required for supply to the ejector for mixing, which results in significant variations in the parameters of the outlet air-gas mixture by such indicators as calorific value and density.

As can be seen from the technical solutions described above, which have both their pros and cons, all existing technical solutions aimed at obtaining a gas-air mixture with constant values of calorific value use, to varying degrees, control and measuring equipment of varying degrees of complexity. In all known solutions, this equipment determines the composition of an already prepared gas-air mixture by sampling with their subsequent analysis - which ultimately creates an inertia in the operation of such monitoring and control systems and, as a result, delay in adjusting the operation of actuators, which leads to unstable characteristics of the calorific value obtained gas-air mixture. All technical

Improvements in the control and management system using a similar principle can only reduce the inertia and the size of the deviation of the mixture parameters from the set value, but fundamentally they cannot completely prevent such deviations.

The technical result of the claimed solution is such a layout of the system’s components that provides the system with exact preset parameters of the gas-air mixture, in particular its calorific value, in which deviations from the set parameters do not exceed the error values of the measuring equipment by minimizing the inertia in the operation of the monitoring and control system .

This technical result is ensured by the fact that one of the components of the monitoring and control system, namely, the gas composition analysis unit, is installed at the inlet of the gas supply system, and the gas-air mixing unit is connected in parallel to the output of the gas flow metering unit and reduction unit, their outputs are combined and connected to the input of the gas-air mixture flow measuring unit, the output of which is connected to the consumer’s gas pipeline, the second input of the gas mixing unit the air is connected to the output of the forced air supply unit, while the inputs of the automated control system are connected to the gas composition analysis unit, the gas flow measurement unit and the gas-air mixture flow measurement unit, and the outputs of the automated control system are connected to the forced air supply unit, through an electrically operated valve to the unit mixing gas with air and a reduction unit.

This arrangement, due to the location of the gas composition analysis unit at the inlet, and not at the outlet of the system, as in existing analogues, eliminates the inertia of the system.

The device consists of the following main units: reduction unit (BR), a unit for measuring gas flow (BIRG), a unit for mixing gas with air (BSGV), a unit for measuring the flow of gas-air mixture (BIRGVS),

forced air supply unit (BPPV), gas composition analysis unit (BASG) and automatic control system (ACS).

The reduction unit includes a pressure regulator, safety shut-off and relief valves, and shut-off valves. The reduction unit is necessary to create the necessary pressure drop on the BSGV to ensure the necessary vacuum at the suction of the ejector, which is part of the BSGV.

The gas flow measurement unit (BIRG) consists of shut-off valves and a gas flow meter with an electronic corrector, a gas flow meter, an absolute gas pressure sensor and a temperature sensor.

The gas-air mixing unit (BSGV) consists of an air filter, shut-off valves, a safety shut-off valve that prevents gas from entering the outside and an electrically-controlled valve that regulates the air flow, and an ejector that takes air from the atmosphere, mixes it with the incoming gas and delivers it the resulting gas-air mixture into the consumer gas pipeline. The air-gas mixture flow measuring unit (BIRGVS) is a gas flow meter with an electronic corrector, a gas flow meter, an absolute gas pressure sensor and a temperature sensor.

The forced air supply unit (BPPV) consists of an air compressor, with the possibility of its external control, as well as an air filter.

The gas composition analysis unit (BASG), necessary for the operational control of gas parameters and their transmission to the ACS, consists of a calorimeter. It is also possible to use a gas chromatograph as a BASG.

Automatic control system (ACS) consisting of a control controller (for example, type 750 firm WAGO) and a personal computer;

ACS is designed to automatically maintain a given composition of the gas-air mixture.

All units of the system are connected to the ACS and operate under its control.

Figure 1 shows a schematic diagram of a device for producing a gas-air mixture of a single calorific value.

1. Gas supply pipe

2. Gas flow measurement unit (BIRG)

3. Forced air supply unit (BPPV)

4. The unit for mixing gas with air (BSGV)

5. Reduction unit (BR)

6. The unit for measuring the flow rate of the gas-air mixture (BIRGVS)

7. Gas composition analysis unit (BASG)

8. Automated control system (ACS)

9. Consumer gas pipeline.

A device for producing a gas-air mixture of a single heat of combustion works as follows.

Gas pre-purified, with a pressure of not more than 12 kg / cm2, from the supply gas pipeline 1 enters the gas flow measuring unit 2. At the same time, gas is sampled from the supply gas pipeline 1 and entering the gas composition measuring unit 7. Data on gas flow, pressure gas, gas temperature and lower heat of combustion of gas, gas density, gas component composition in the system enter the automated control system ACS 8, where the parameters of the gas entering the system are analyzed. Based on a comparison of the actual with the given gas parameters in terms of gas flow, gas pressure, gas temperature and lower heat of gas combustion, gas density, gas component composition, the ACS sets the required lower heat of combustion and gas flow rate for the gas-air mixing unit BSGV

4 by calculating the required amount of air added to the active gas in the BSHV and ensuring its maintenance by adjusting the position of the BSGV electrically controlled valve at the suction of the ejector, while a gas-air mixture is formed in the mixing chamber of the BSGV ejector, which is close in relation to the stoichiometric one.

The necessary air flow rate at the suction port of the ejector is possible if there is a certain value of the gas pressure drop before and after the BSGV ejector and a certain gas flow rate through the BSGV, which is implemented by the ACS by calculating the values of these values, based on a comparative analysis of the actual pressure and gas flow rate at the inlet and outlet BSGV, namely, on the basis of the obtained gas parameters from the gas flow measurement unit 2 and the air-gas mixture from the air-gas mixture measurement unit 6. Directly support of desired for stable operation of the ejector pressure drop and gas flow rate is carried out using the ACS Block reducing the pressure regulator 5, which provides a constant gas pressure of the ejector BSGV. If it is not possible to maintain the required pressure drop, for example, with a significant decrease in gas pressure at the system inlet, a forced air supply to the BSGV is provided by means of the BPPV 3 forced air supply unit. Air from the BPPV is supplied directly to the inlet path of the BSGV ejector, in front of the air filter. The BPPV is controlled and controlled by the amount of air supplied to it for mixing with gas by means of an automatic control system, based on continuous monitoring and analysis of actual data on gas pressure and flow rate.

As a result, at the inlet to consumer’s gas pipeline 9, when this system is operating in automatic mode, natural gas is mixed with methane (CH4) in it from 70.0 to 98.5 vol.%, Moving under pressure from 0.5 to 12 , 0 kg / cm2 and atmospheric air in a predetermined ratio of 0.01 to 4.76 vol.%, Which makes it possible to obtain a gas-air mixture of uniform heat of combustion at the outlet of the installation with the minimum possible deviation from a given value in terms of calorific value.

Claims (4)

1. A device for producing a gas-air mixture of a single calorific value, comprising a gas supply pipe connected to a gas composition analysis unit and a gas flow measuring unit, the output of which is connected to the inputs of the gas reduction unit and the gas-air mixing unit connected in parallel, the outputs of which are combined and connected to the input a gas-air mixture flow measuring unit, the output of which is connected to a consumer gas pipeline, the second input of the gas-air mixing unit being connected to the output of the forced air supply unit ear, while the inputs of the automated control system are connected to the gas composition analysis unit, the gas flow measurement unit and the air-gas mixture flow measurement unit, and the outputs of the automated control system are connected to the forced air supply unit, through a controlled valve to the gas-air mixing unit and the reduction unit . 2. The device according to claim 1, characterized in that the automated control system is configured to generate a signal controlling the air supply, a signal controlling the reduction unit, and a signal controlling the gas-air mixing unit. 3. The device according to claim 1, characterized in that the controlled valve is made in the form of a valve with a pneumatic actuator. 4. The device according to claim 1, characterized in that the controlled valve is made in the form of valves with an electric drive.