A separator is a machine that separates mixed substances into two or more different substances. The common separators are centrifugal separator and electrostatic separator.
Equipment introduction
In order to keep good separation effect, the liquid level and pressure of the separator should be controlled. Constant pressure control technology is used to control the liquid level and pressure of traditional separator. In the variable pressure liquid level control of the separator, the float liquid level controller is used to drive the oil and gas regulating valve to make it work together to control the liquid volume of crude oil and natural gas, so as to adjust the liquid level of the separator without controlling the pressure of the separator. The liquid level control method of variable pressure can reduce the throttle of the oil and gas outlet valve to the greatest extent, reduce the pressure of the separator, and improve the separation effect.
Oil gas separator and oil gas water three-phase separator are widely used in oil field transfer station and combined station. In order to keep good separation effect, the liquid level and pressure of separator need to be controlled.
working principle
Centrifugal separator
When the controller is connected to the power supply, a strong negative pressure is generated at the suction port, which forces the oil mist to be sucked into the mist absorber. The oil mist particles collide under the action of the wind wheel in the mist absorber, and the small particles are collected into larger particles that can be controlled, which are intercepted by high-efficiency mist absorbing materials, collected and recovered through the return port.
Electrostatic separator
According to the second-order principle of electrostatic field, the fine oil mist particles enter a strong electric field with the air flow and are positively charged. When the particles with points reach the electric field between the collecting plates of the purifier, the particles are attracted by the metal washing plate and adhere to the metal plate, so as to separate the oil mist from the air and achieve the purification effect.
Comparison between centrifugal and electrostatic oil mist separators
Centrifugal oil mist separator has a wide range of applications, and the requirements of multi workshop environment are not very high; electrostatic oil mist separator can only be used in relatively dry workshop environment, and the electric field of oil mist separator is easy to be short circuited due to the conductivity of water in workshop with very large fog.
The separation effect of centrifugal oil mist separator is not as fine as that of electrostatic separator. The diameter of separable particles in electrostatic oil mist separator can be as small as 0.01 μ M.
Control method
Traditional control
Oil gas two phase separator
The oil-gas two-phase separator separates the oil-gas mixture into single phase crude oil and natural gas. The pressure is controlled by the pressure control valve at the natural gas outlet, and the liquid level is regulated by the oil outlet valve controlled by the controller.
The pressure control valve at the natural gas outlet is usually a self operated regulating valve or a pneumatic diaphragm regulating valve matched with pressure transmitter, controller and gas source. The oil outlet valve is usually a pneumatic diaphragm control valve equipped with liquid level sensor, controller and air source or an oil outlet control valve operated by float liquid level regulator.
In some oil-gas two-phase separators, pneumatic diaphragm control valve is used to control the pressure of the separator, and float liquid level regulator is used to control the liquid level of the separator.
Oil gas water three phase separator
The oil-gas-water three-phase separator can separate part of water from crude oil while separating gas and liquid from oil well products.
Steam water separator
With the development of oil field, the water content of oil well produced liquid increases gradually, and the application of three-phase separator also increases gradually. The control method of three-phase separator is different with different structure. The control principles of the two typical separators are as follows:
(1) After the oil gas water mixture enters the separator, the inlet diverter roughly divides the mixture into vapor-liquid two phases, and the liquid phase enters the liquid collection part. The liquid collecting part has enough volume to make the free water settle to the bottom to form a water layer, on which are crude oil and emulsion oil layers with small water droplets. Crude oil and emulsions spilled over the baffles. The oil level downstream of the baffle is controlled at a constant height by the liquid level controller. The water is discharged from the outlet upstream of the baffle, and the oil-water interface controller controls the opening of the drain valve to keep the oil-water interface at the specified height. The pressure of the separator is controlled by the valve on the natural gas pipeline.
(2) The separator is provided with an oil pool and a water baffle. The crude oil overflows from the oil baffle to the oil pool, and the oil level in the oil pool is controlled by the oil outlet valve operated by the liquid level controller. The water flows under the oil pool and flows into the water chamber through the water baffle. The liquid level of the water chamber is controlled by the outlet valve operated by the liquid level controller.
Problems existing in liquid level and pressure control of traditional separator
In the constant pressure control of the separator, the pressure control valve on the natural gas pipeline throttles the natural gas to a certain extent to ensure the stability of the pressure in the separator. When the gas volume decreases or the pressure at the gas outlet decreases, the throttling degree of the valve increases; on the contrary, the throttling degree of the valve decreases.
Fine powder separator
In the liquid level control of the separator, the oil-water outlet valve also throttles the liquid. When the liquid volume increases, the throttling degree decreases; when the liquid volume is small, the throttling degree increases to keep the liquid level stable.
In order to ensure the normal discharge of liquid under the condition of large liquid volume, the separator has high pressure. However, when the liquid volume is reduced, the liquid must be throttled through the oil-water outlet valve to keep the liquid level from decreasing. Therefore, in production, the separator generally works under high pressure, and the liquid phase valve is in throttling state.
Too high separator pressure affects the liquid inlet of the separator, increases the back pressure at the outlet and wellhead of the transfer station or metering station, and is not conducive to oil transportation. Most of the oil wells in China are mechanical oil production, and the wellhead back pressure increases, which increases the energy consumption of oil production. In addition, at higher pressure, the saturated dissolved gas in the oil is separated from the oil when the pressure drops after the outlet valve throttles, which is easy to make the oil pump in the downstream process produce gas turbidity. Therefore, higher separator pressure not only affects the separation efficiency of oil and gas, increases the production energy consumption, but also affects the safety production.
Transformer control
The float level controller drives two control valves, one control valve controls natural gas, the other control valve controls crude oil, which realizes the joint regulation of the valves at the outlet of crude oil and natural gas. When the float rises, the connecting rod mechanism makes the opening of the air way regulating valve decrease and the opening of the oil way regulating valve increase; on the contrary, when the float falls, the connecting rod mechanism makes the opening of the air way regulating valve increase and the opening of the oil way regulating valve decrease. By changing the opening of the control valve and the relative flow of natural gas and crude oil, the liquid level of the separator is controlled. The pressure of the separator is the sum of the pressure at the natural gas outlet or liquid outlet and the pressure difference before and after the natural gas regulating valve or liquid regulating valve. When the gas and liquid volume and the downstream pressure of the separator change, the pressure of the separator changes, so this control method is variable pressure control.
Application of variable pressure liquid level control in oil gas two phase separator
When the liquid quantity and gas quantity in and out of the oil-gas separator are constant, the liquid level is stable at a certain position; when the liquid quantity or gas quantity in the separator changes and the liquid level rises, the float linkage mechanism will make the opening of the natural gas control valve smaller and the opening of the crude oil control valve larger, so that the exhaust volume decreases and the liquid discharge volume increases, until the liquid quantity and gas quantity in and out of the separator are equal, the liquid level will increase When the liquid volume or gas flow into the separator changes and the liquid level drops, the float connecting rod mechanism will make the opening of the natural gas control valve open wider and the opening of the crude oil control valve close smaller, so as to increase the gas discharge and reduce the liquid discharge. Until the liquid volume and gas flow in and out of the separator are equal, the liquid level will be stabilized at a higher level Low position. In this way, with the change of liquid or gas flow into the separator, the float linkage mechanism drives the regulating valve to produce corresponding action, so as to keep the liquid level relatively stable.
Application of variable pressure liquid level control in oil gas water three phase separator
(1) Application of variable pressure liquid level control in oil gas water three phase separation. The control of the crude oil level is the same as that of the oil-gas separator, and the oil-water interface is controlled by the drain valve operated by the oil-water interface controller.
(2) Application of variable pressure liquid level control in oil gas water three phase separator. The liquid level of the oil pool is controlled by the crude oil control valve and the natural gas control valve operated by the liquid level controller, and the liquid level of the pool is controlled by the water outlet control valve and the natural gas control valve operated by the liquid level controller.
Operating procedures
1. Before operation, carefully check whether the inlet and outlet pipelines and valves of the separator are correctly connected, and whether the connecting bolts are tight;
2. Open the natural gas outlet valve and the raw material inlet valve, pay attention to observe the liquid level indication, and keep the liquid level between 1 / 2 ~ 1 / 3. If there is any abnormal phenomenon, adjust the opening of the inlet and outlet valves in time to achieve a stable state;
3. When the equipment is in stable operation, pay attention to observe the liquid level indication, which shall not be less than 1 / 2. If it is too low, turn down the discharge valve of oil and water, and start normal discharge when the liquid accumulation reaches the specified range;
4. Pay attention to observe whether the internal temperature, pressure and pressure of the separator are normal, strictly prevent overtemperature and overpressure operation, make records regularly, and record the liquid level height at the same time;
5. Remove the dirt and sediment inside the equipment once every half a month;
6. Pressure gauge, pressure gauge valve, safety valve and other non operators are strictly prohibited to assemble, disassemble, open and close at will;
7. Pay attention to the change of oil inlet temperature to prevent sand sticking, wax sticking, wax plugging and oil leakage accidents;
8. When the separator is out of service, purge the liquid in the container and pipeline.
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