RU2561016C1 - Plant for measurement and accounting of liquefied hydrocarbon gas - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: plant for measurement and accounting of liquefied hydrocarbon gas relates to devices accounting the amount of liquefied hydrocarbon gas (hereinafter referred to as LHG) and can be used in LHG drain and filling systems of automobile tanks, railway tank cars and other tanks. The plant for measurement and accounting of liquefied hydrocarbon gas includes a mass flow meter, a valve, a controller, the first input of which is connected through the flow rate measuring unit to the mass flow meter, and the first control output is connected to the valve, a reversible mass flow meter connected to the second input of the controller, an additional valve connected to the second output of the controller. The plant includes four hydraulic lines: a return steam line, a drain and filling line, a discharge line and a nitrogen blowdown line. The drain and filling line consists of a filter of a gas separator provided with an automated steam discharge system, a check valve, a set of safety valves, a mass flow meter, a differential valve, an electric control valve and a normally closed cutoff valve. The drain and filling line consists of a filter of a gas separator provided with an automated steam discharge system, a check valve, a set of safety valves, a mass flow meter, a differential valve, an electric control valve and a normally closed cutoff valve.

EFFECT: creation of a high-accuracy automated plant with a dosed filling function.

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Description

The invention relates to a metering device for the amount of liquefied petroleum gas (hereinafter LHG) and can be used in systems for discharging and filling LHG in automobile tanks, railway cars - tanks and other containers.

The closest analogue to the present invention is a metering system for the amount of liquefied hydrocarbon feed (No. 59241 U1, G01F 9/00), comprising a mass flow meter, valve, controller, equipped with an additional mass flow meter, an additional valve located on the gas equalizing collector for returning carbon-based feedstock.

The disadvantages of the closest analogue are:

1. The measurement error caused by the presence of the vapor phase of the LPG in the liquid phase at the entrance to the mass flow meter.

2. The possibility of a reverse flow of LPG through the flow meter of the discharge line.

3. Lack of safety valves on the discharge line of the installation.

4. Lack of shutoff valves capable of automatically blocking the discharge line in the event of an emergency power outage.

5. Lack of pressure monitoring devices.

6. Lack of purge system.

An installation for measuring and metering liquefied petroleum gas is proposed, comprising a mass flow meter, a valve, a controller, the first input of which is connected to a mass flow meter through a flow computer, and the first control output to the valve, a reversible mass flow meter connected to the second input of the controller, an additional valve connected to the second output of the controller. The unit includes four hydraulic lines: steam return, drain, discharge and nitrogen purge line. The drain line consists of a gas separator filter equipped with an automated steam vent system, a check valve, a set of safety valves, a mass flow meter, a differential valve, an electro-control valve and a normally closed shut-off valve. The installation includes an automation unit consisting of a controller, a flow computer, pressure sensors, a grounding device, an indication device, and an external control device.

The technical result of the invention is to obtain an automated installation with a dosed filling function, which has high accuracy of accounting for the dispensed amount of LPG, which meets the necessary safety requirements when performing filling operations. Reducing the likelihood of a measurement error by eliminating the possibility of a two-phase LPG flow passing through a mass flow meter.

Figure 1 presents the hydraulic circuit in conjunction with the automation system of the installation.

Metering system, consisting of an automation unit and four hydraulic lines: steam return, discharge, discharge and nitrogen purge lines. A discharge line, which consists of a gas separator filter 1, equipped with an automated steam discharge system, a check valve 2, a set of safety valves 3.1, 3.2, a mass flow meter 4, a differential valve 5, an electro-control valve 6, and a normally closed shut-off valve 7. The steam return line consists of from the electro-control valve 8 and the mass flow meter 9. The discharge line of the installation is an intermediate link combining the drain and steam return line and serves to connect to the discharge sleep collector. The nitrogen purge line is used to purge the system with nitrogen. The automation node consists of a controller, a flow computer and pressure sensors 10.1, 10.2, 10.3. One of the inputs of the controller 13 is connected through a flow computer to the flow meter 4 of the discharge line, the second input is connected to the flow meter 9 of the steam return line. The outputs of the controller 13 are connected by electrically controlled valves 6, 8 and 7.

During storage and transportation, liquefied gases constantly change their state of aggregation. When boiling liquid is taken from the tanks and transported through the pipeline, part of the liquid evaporates due to pressure losses, a two-phase flow is formed, the vapor pressure of which depends on the flow temperature, which is lower than the temperature in the tank. In the case when the system pressure exceeds the saturated vapor pressure, the LPG passes into the liquid phase.

The use of a gas separator filter 1 equipped with an automated steam discharge system together with a differential valve 5 will increase the pressure of the product passing through the discharge line above the pressure of the LPG vapor. Thus, the medium passing through the mass flowmeter will be a single-phase liquid flow. Given that mass flowmeters are not sensitive enough to measure biphasic liquids, the mass flow rate and / or density readings become incorrect, or in the worst case, the instruments stop working at all. The accuracy of the flow measurement of such media is determined by many physical and technical reasons, the main of which is the difference in the speeds of the phases through the primary transducers of the flow meters used; heterogeneity of phase distribution over the flow cross section; significant fluctuations in velocities, pressures and fractions of phases.

The total volume of the mixture of phases

V _c = V _W + V _P ,

where V _W - the volume of the liquid phase of the LPG,

V _P - the volume of the vapor phase of the LPG.

The total mass of the mixture of phases

m _C = m _F + m _P or m _C = V _F · ρ _F + V _P · ρ _P ,

where m _W is the mass of the liquid phase of the LPG,

m _P - mass of the vapor phase of the LPG,

ρ _W - the density of the liquid phase of the LPG,

ρ _P is the density of the vapor phase of the LPG.

The relationship between the true fractions of the liquid and vapor phases is determined by the equation

$${\varphi }_P^{\mathrm{ABOUT}}=\mathrm{one}-{\varphi }_F^{\mathrm{ABOUT}};$$

$${\varphi }_P^M=\mathrm{one}-{\varphi }_F^M,$$

и $${\varphi }_{П}^{М}$$

- соответственно объемная и массовая доля паровой фазы СУГ,Where $${\varphi }_P^{\mathrm{ABOUT}}$$

and $${\varphi }_P^M$$

- respectively, the volume and mass fraction of the vapor phase of the LPG,

и $${\varphi }_{Ж}^{М}$$

- соответственно объемная и массовая доля жидкой фазы СУГ. $${\varphi }_F^{\mathrm{ABOUT}}$$

and $${\varphi }_F^M$$

- respectively, the volumetric and mass fraction of the liquid phase of the LPG.

The relationship between the expendable fractions of the liquid and vapor phases is determined by the equation

$${\delta }_P^{\mathrm{ABOUT}}=\mathrm{one}-{\delta }_F^{\mathrm{ABOUT}};$$

$${\delta }_P^M=\mathrm{one}-{\delta }_F^M.$$

The expendable volume fraction of the mixture depends on the average speeds of the vapor and liquid phases of the LPG

$${\delta }_{П}^{О}=\frac{{\varphi }_{П}^{О}\cdot {\upsilon }_{П}}{{\upsilon }_{С}}$$

, $${\delta }_F^{\mathrm{ABOUT}}=\frac{{\varphi }_F^{\mathrm{ABOUT}}\cdot {\upsilon }_F}{{\upsilon }_{\mathrm{FROM}}};$$

$${\delta }_P^{\mathrm{ABOUT}}=\frac{{\varphi }_P^{\mathrm{ABOUT}}\cdot {\upsilon }_P}{{\upsilon }_{\mathrm{FROM}}}$$

,

- расходная объемная доля жидкой фазы СУГ,Where $${\delta }_F^{\mathrm{ABOUT}}$$

- expendable volume fraction of the liquid phase of the LPG,

- расходная объемная доля паровой фазы СУГ, $${\delta }_P^{\mathrm{ABOUT}}$$

- expendable volume fraction of the vapor phase of the LPG,

- скорость жидкой фазы СУГ, $${\upsilon }_{\mathrm{well}}$$

- the speed of the liquid phase of the LPG,

- скорость паровой фазы СУГ, $${\upsilon }_P$$

- the speed of the vapor phase of the LPG,

- скорость смеси фаз СУГ. $${\upsilon }_{\mathrm{FROM}}$$

- the speed of the mixture of phases of LPG.

The expendable mass fraction of the mixture also depends on the average speeds of the vapor and liquid phases of the LPG

- расходная массовая доля жидкой фазы СУГ,Where $${\delta }_{\mathrm{well}}^m$$

- expendable mass fraction of the liquid phase of the LPG,

- расходная массовая доля паровой фазы СУГ. $${\delta }_P^M$$

- expendable mass fraction of the vapor phase of the LPG.

, то расходные доли $${\delta }_{ж}^{о}$$

и $${\delta }_{ж}^{м}$$

жидкой фазы меньше истинных $${\varphi }_{ж}^{о}$$

и $${\varphi }_{ж}^{м}$$

, а паровой фазы, наоборот, больше истинных, т.е. $${\delta }_{п}^{о}>{\varphi }_{п}^{о}$$

и $${\delta }_{п}^{м}>{\varphi }_{п}^{м}$$

.As $${\upsilon }_P>{\upsilon }_{\mathrm{from}}>{\upsilon }_{\mathrm{well}}$$

, then expendable shares $${\delta }_{\mathrm{well}}^{\mathrm{about}}$$

and $${\delta }_{\mathrm{well}}^m$$

liquid phase is less than true $${\varphi }_{\mathrm{well}}^{\mathrm{about}}$$

and $${\varphi }_{\mathrm{well}}^m$$

, and the vapor phase, on the contrary, is larger than the true ones, i.e. $${\delta }_P^{\mathrm{about}}>{\varphi }_P^{\mathrm{about}}$$

and $${\delta }_P^m>{\varphi }_P^m$$

.

True density of the mixture

$${\rho }_{\mathrm{from}}={\rho }_{\mathrm{well}}-{\varphi }_P^{\mathrm{about}}\left({\rho }_{\mathrm{well}}-{\rho }_P\right),$$

and the flow rate of the mixture

$${\rho }_{\mathrm{from}R}={\rho }_{\mathrm{well}}-{\delta }_P^{\mathrm{about}}\left({\rho }_{\mathrm{well}}-{\rho }_P\right).$$

Subtracting the last equation from the previous one, we get:

. $${\rho }_{\mathrm{from}}-{\rho }_{\mathrm{from}R}=\frac{{\delta }_P^{\mathrm{about}}-{\varphi }_P^{\mathrm{about}}}{{\rho }_{\mathrm{well}}-{\rho }_P}$$

.

.Whence it follows that the consumption density is less than true, since $${\delta }_P^{\mathrm{about}}>{\varphi }_P^{\mathrm{about}}$$

.

Due to the inhomogeneity of the flow structure, the fractions of the individual LPG phases change throughout the entire pipeline.

Therefore, measuring the flow rate of a two-phase LPG flow entails an additional error. Flowmeter manufacturers are also investigating the effect of the presence of different phases of flow on the occurrence of measurement errors. The effects causing additional measurement errors, such as the “Bubble” effect, the resonator effect, and the effect of inhomogeneity of the bubble distribution, were revealed.

The use of a check valve 2 at the outlet of the gas separator filter 1 will allow the discharge line to be constantly filled and exclude the possibility of the formation of a reverse flow discharge line.

The use of safety valves 3.1 and 3.2 on the discharge line will ensure the safety of the installation. And if the pressure is higher than the pressure, the safety valve settings will dump it into the discharge line.

The use of pressure sensors in the installation will determine the degree of contamination of the filter elements of the gas separator filter, designed to filter the LPG before entering the flowmeter with the necessary purity of filtration. Also, pressure sensors will allow you to control the operating pressure of the installation between the locking elements.

The possibility of closing the drain line in the event of an emergency power outage is carried out by installing a normally-closed shut-off valve after the electro-control valve.

The system is as follows.

A serial connection is made to the accumulator nipples of the tank or to technological pipelines.

The operator on the external control device 12 (hereinafter AWP) produces a dose set and gives permission to release the product at the selected post. The controller 13 processes the received information from the operator’s workstation 12. Monitors the signals of readiness for filling from the grounding device 14 and issues a command to smoothly open the valve 8 located on the steam return line in order to equalize the pressure of the filled tank with the steam return line. The pressure equalization is controlled according to the readings of the mass flow meter 9. After reaching the flow readings on the mass flow meter 9 below the set by the installation program, the controller 13 sends a signal to open valves 6 and 7, and liquefied hydrocarbon gas is poured through the discharge line pipe.

When filling the filter-gas separator 1 through the valve 11 installed in the lid of the filter-gas separator, LPG vapors formed during the liquid flow are removed before they reach the flow meter 4, and when the set filling level is reached, the valve 11 is closed. The differential valve 5, installed after the mass flow meter 4, closes the system with a force exceeding the vapor pressure of the LPG, for this the working cavity of the valve 5 is connected with the steam return line. When the pressure in the system is higher than the pressure setting valve 5 is the opening of its flowing part. Given the properties of LPG, a single-phase fluid moves along the discharge line.

At the same time, part of the product that has fallen into the filled tank is evaporated and, through the steam return line, is discharged into the supply tank. Pressure sensors 10.1, 10.2, 10.3 monitor the pressure in the system.

The controller 13 processes the incoming information about the dispensed mass of the liquefied petroleum gas from the mass flow meter 4 of the discharge line and the returned mass of the vapor phase of the LPG from the mass flow meter 9 of the steam return line. It subtracts from the mass of the LPG dispensed the mass of the LPG returned to the supply tank through the steam return line and outputs it to the indicating device 15 and the AWG of the LPG 12 loading operator. Upon reaching a certain value close to the LPG mass specified by the operator, the controller 13 issues a valve 6 to reduce speed loading the product, and when the specified mass is reached, it gives a command to completely close the valves 6 and 7 and gives a signal to the workstation of the loading operator 12.

Normally closed shut-off valve 7 is designed to shut off the flow of LPG along the discharge line in automatic mode, in the event of an emergency power failure to the system.

The nitrogen purge line allows manual purging of the system with nitrogen.

The above control measurements using an exemplary measuring device showed that the accuracy of accounting for LPG filling is in the range 0-0.15% of the released mass.

Claims (1)

Installation for measuring and metering liquefied petroleum gas, containing a controller, the first input of which through a flow computer is connected to the mass flow meter of the discharge line, and the first control outlet to the discharge line valve, provided on the steam return line with an additional valve connected to the second output, characterized in that the discharge the line consists of a gas separator filter equipped with an automated steam discharge system, a non-return valve, a set of safety valves, mass of flowmeter, the differential valve elektroreguliruyuschego valve and a normally closed shut-off valve, and having in its composition parovozvratnuyu line line nitrogen purge and automation assembly consisting of the controller, the calculator flow, pressure sensors, earthing devices, display devices and an external control device.