Gas Separator Project

Contents

Table of contents

Introduction

1 Project Feasibility Study

1.1 Overview of separator structures

1.2 Justification of design selection

2 Process Solutions

2.1 Description of the production flow chart

2.2 Process calculation

2.2.1 Calculation of two-phase gas separator

3 Design part

3.1 Material Selection

3.2 Mechanical calculation

3.2.1 Calculation of shell operating under internal overpressure

3.2.2 Calculation of elliptical bottom operating under internal overpressure

3.2.3 Check of hole reinforcement

3.2.4 Reinforcement of hole in elliptical bottom

3.2.5 Reinforcement of holes on the shell

3.2.6 Calculation of flange connection

3.2.7 Calculation of gas separator supports

4 Installation, repair, maintenance

Conclusion

List of sources used

Paper

In order to clean the associated gas at KNPS - PURPE of Vankorneft CJSC, the project proposes to install a gas separator. This will remove most of the water molecules present in the associated gas, and therefore increase the gas quality used in further processes at the plant.

This project contains all the necessary technological and strength calculations, issues of installation and repair are covered.

The course project consists of a calculation and explanatory note and a graphic part. It includes 67 pages of typewritten text in the format A4, 26 literary sources. The graphic part of the project consists of: 4 sheets of A1 format.

Introduction

A gas separator is a necessary device for separating dissolved gas from liquid hydrocarbons and the smallest drops. They are commonly used for gas cleaning, as well as for ensuring the safety of the process of transporting, processing and recycling liquids.

In addition, gas separators are widely used in the production of oil and gas products to protect pumping equipment from gas plugs [1].

The separation technology in our time is able to provide up to 85% of the profit from one well due to the very possibility of the separation process. But what is separation ?

 Separation (lat. Separatio - separation ) - in technology, various processes for the separation of mixed volumes of heterogeneous particles, mixtures, liquids of different densities, emulsions, solid materials, solid particles or droplets in gas [9].

During separation, there is no change in the chemical composition of the separated substances. Separation is possible if there are differences in the characteristics of the components in the mixture: in the sizes of solid particles, in their masses, in shape, density, friction coefficients, strength, elasticity, wettability of the surface, magnetic susceptibility, electrical conductivity, radioactivity and others.

The properties distinguishing the separation products need not coincide with the characteristics by which the mixture of components is separated in production. A very large number of individual fine particles take part in the separation process itself, among which there are particles with intermediate properties with respect to the necessary features. Completely pure fractions of separated components cannot be obtained from the initial mixture after industrial separations, but only products with their predominant content [9].

Project Feasibility Study

Separator Design Overview

A two-phase separator is the simplest equipment (allowed for use) for separating the gas phase from the liquid phase. Separators are horizontal and vertical.

By the nature of the existing forces, separators are divided into:

Gravitational, phase separation in which occurs due to the difference in densities of the gas liquid or solid gas particles.

Packing separators in which the phases are separated by gravity and inertia.

Centrifugal, separation in which occurs due to centrifugal and inertial forces.

According to the shape and position in space, separators are divided into: cylindrical horizontal with one or two tanks; cylindrical vertical; spherical.

There are many separators of different designs, but all of them, as a rule, consist of the following sections [18].

Main separation section. Designed to separate the main part of the liquid (oil, gas condensate, water) from the incoming gas-liquid flow. To ensure high-efficiency preliminary separation and uniform distribution of flow along the cross section of the apparatus, structural devices are used:

tangential flow input, in which liquid under the action of centrifugal force is thrown to the vessel wall and flows along it, and gas is distributed along the cross section of the apparatus and withdrawn;

reflectors (rectangular or circular plates, hemispheres) installed at the inlet of the separator;

a built-in cyclone installed at the inlet of the horizontal separator;

structures allowing separate introduction of gas and liquid into the separator [15]. 

Siege section. In this section, gas bubbles are further released from the liquid in the gas-oil separators. In gas separators, the liquid in this section is separated by gravitational forces, and the gas moves in the vessel at a relatively low speed. In gas separators of some structures, various devices are used to reduce turbulence - plates, cylindrical and semi-cylindrical surfaces [15]. 

Liquid collection section. It is used to collect liquid, from which gas was released almost completely in previous sections at temperature and pressure in the separator. However, there is some gas in it. For separators volume of this section is selected so that it allows to retain separated liquid for time required for gas bubble to come to surface and secondary ingress into gas flow [15].

Dropping section. Designed to capture liquid particles in the gas leaving the separator. The section usually consists of baffles (nozzles) of various types - ceramic rings, louvres, bags of woven wire mesh, etc. The criterion for the efficiency of separating the drip liquid from the gas is the value of the specific carry-over of the liquid, which should be in the range from 10 to 50 mg/m3 of gas.

The efficiency of the baffle nozzles depends on several factors, the main of which are: the permissible speed of gas ingress, a certain amount of liquid supplied with gas, the uniform loading of the nozzle over the area of ​ ​ its cross section.

In addition to the functions performed by the described sections, the structures of the separators should include elements preventing the formation of foam and extinguishing it, as well as reducing the harmful effect of gas-liquid flow pulsation on the separation of liquid and gas [15].

Internals of separators

The separation efficiency depends on the internal arrangement of the separator. It should be noted that many devices that significantly improve separation efficiency are patented. Many suppliers now offer their own special high-performance internals. This manual will consider the main types of internals, the effectiveness of their use, as well as possible shortcomings and complications associated with their installation [19].

As previously shown, inlet partitions are installed at the inlet of the separator; abrupt change of pulse and direction of multiphase flow. The inlet partition may be a flat plate, a structural steel channel, a spherical plate or a cone, Figure 1.1.

The latter two versions create less interference than plates or corner profiles, their use reduces the possibility of problems of repeated carry-over of liquid and formation of emulsions

Centrifugal input devices have also become widespread. In particular, Kvaerner Process Systems developed a two-cylinder input device. When this equipment is used, foam formation is reduced and the distribution of the supplied fluid is improved. Centrifugal devices can be installed on the inlet of a horizontal or vertical tank and can be particularly effective for improving gas throughput through high gas oil separators.

Wave cutters are vertical partitions installed in horizontal apparatuses perpendicular to flow to increase the gap between gas and liquid.

Defoamer. The formation of foam in the gas phase can lead to excessive entrainment of liquid into the gas phase. There is a packing material that can be placed in the gas phase exit path. It restricts flow and creates additional surface area, which contributes to the breakdown of the foam.

Drip breakers are installed to remove small droplets of liquid mist from the gas and reduce the entrainment of liquid into the exhaust gas. Today, mesh and blade drip breakers have received the most use [19].

In the vane drop-breaker, figure 1.3 gas passes by laminar flow through parallel plates that change their direction.

The kinetic energy of the liquid mist changes, causing the droplets on the walls of the blades to collide and merge. Liquid flows down the walls and collects at the bottom of the tank. Vane separators are highly effective in-body devices and are less susceptible to clogging compared to mesh drips [19].

Mesh drop catchers are made of mesh usually 0.05-0.5 mm in diameter, figure 1.4. When using devices of this kind, special attention should be paid to the gas flow rate. Too little velocity will prevent liquid droplets from colliding and draining, and excessive velocity will cause the droplets to be carried away again. Mesh droplets are inexpensive, however, susceptible to clogging. Therefore, they are not suitable for treatment of gas containing solid particles, heavy fractions of oil or paraffins. In addition, the mesh droplets operate efficiently only in a certain range of gas flow rates.

Typically, 99.9% removal of up to 10 micron oil droplets is achieved in paddle or mesh type droplets. Western manufacturers usually guarantee a reduction in the volume of entrained liquid in the treated gas to 12mg/m3. Russian suppliers guarantee that the volume of entrained liquid in separators equipped with drip-catching elements will not exceed 30mg/m3 [19].

Anti-swirlers. The formation of swirls can occur at the exit of the apparatus. These swirls impede the separation process and facilitate the gas to be carried away into the liquid outlet. The formation of swirls can be prevented by maintaining an appropriate liquid level above the outlet nozzle, as well as by installing swirl dampers. Usually, minimum required

a liquid level of 2D for gas/liquid separation and 3D for liquid/liquid separation, where D is the diameter of the outlet nozzle.

A number of design features of Russian-designed separators should also be emphasized. They have the following interesting design features:

design of oil pre-degassing inlet pipe

the presence of a droplet tube that activates their fusion prior to deposition

design of devices preventing gas entrainment installed above the main separator.

Design Requirements

A properly designed gas separator shall meet the following requirements:

Dissipate and control the energy of gas movement;

Reduce the rate of gas and liquid entry to provide gravitational separation at the initial stage;

Retain the liquid for sufficient time to separate the dissolved gas from the liquid hydrocarbons;

Prevent re-ingress of liquid;

Position inlet and outlet holes of required value for gas and liquid inlet and outlet. Install safety valve, level controller, level, pressure, temperature sensors and drain pipes;

It shall be provided with liquid storage vessels and a drop deposition compartment.

Types of gas separators

Mainly, manufacturers produce gas separators of two main types: vertical and horizontal. However, it is also possible to find spherical ones, which have appeared relatively recently, and which are intended for medium-pressure gases containing a small amount of liquid [14].

Horizontal separator

Figure 1.6 schematically shows a horizontal two-phase separator arrangement. The fluid flow enters the separator vessel and strikes the inlet partition, which leads to a sharp decrease in the flow pulse. The primary separation of liquid and gas occurs precisely on this partition. Under the influence of gravity, larger drops of liquid carried away by gas fall on the phase interface.

The liquid flowing through the container is settled in the liquid collection section for a period of time necessary to allow the liquid-entrained gas bubbles to float to the surface and join the main gas volume. This section also provides a buffer volume in the event of pulsations of the input stream. The liquid then leaves the vessel through a level control valve which is controlled by the level gauge. The level meter registers the level increase in the tank and accordingly the valve opens [14].

The gas, after passing through the partition, flows horizontally along the secondary separation section above the liquid. While the gas flows through this section, smaller liquid droplets remaining in the gas after the drip breaker settle under gravity and enter the phase interface.

However, some of the liquid droplets have such a small diameter that they are practically unable to settle during the passage of gas through the gravity separation section. Before the gas leaves the vessel, it passes through a coalescing section or a drip. In this section, metal nets, corrugated plate packs, as well as other nozzles can be used, which catch small drops of liquid, helping them to coagulate and, increasing in size, fall on the phase interface [14].

The pressure in the vessel is controlled by a pressure control valve which is installed on the gas outlet line. The pressure sensor detects the pressure deviation in the vessel from normal and provides a signal to open or close the valve. Thus, by controlling the flow rate of the gas leaving the vessel, the required pressure in the vessel is maintained. Typically, horizontal separators are operated with a liquid level of 50% in the vessel, which also provides a maximum interface area of [14].

Vertical separator

As in the case of the horizontal separator, the pre-separation of phases in the case of the vertical separator is carried out on the inlet partition, Figure 1.7. The liquid flows down into the liquid collection section and then exits the container through a nozzle at the bottom of the container. Gas bubbles released from the oil float in the direction

opposite to liquid flow and enter gas section of separator. Level regulators operate in the same way as horizontal separator [14].

The gas separated at the inlet baffle flows vertically upward towards the gas outlet. In the gravitational separation section, liquid droplets carried away by the gas fall vertically down onto the phase boundary. The gas passes through the drip drum before leaving the vessel. The pressure is controlled in a similar manner to a horizontal separator.

Selection of the type of separator (horizontal or vertical) is carried out taking into account the gas factor Figure 1.8. Vertical separators are suitable for separating mixtures or with very high or very low gas factors. It is vertical separators that are used in these two cases because it is more difficult to adjust the phase separation level in a horizontal configuration than in a vertical configuration. In addition, vertical separators require less space for installation, which becomes a fundamental factor in the design of an oil treatment system located, for example, on a platform. It should also be noted that the vertical separator is more easily (compared to horizontal) cleaned of mechanical impurities (sand, proppant, salts, asphaltenes, etc.) [14].

Vertical separators found the most use in the oil industry for separating oil and gas flows with average gas factors Figure 1.9. Their great advantage is the ease of installation and the ability to process well products with a high tendency to foaming. The processes of foam formation at the interface are themselves caused by gas bubbles formed during the passage of fluid through the inlet partition or emitted

directly from the liquid collection section. It should be emphasized that the foaming process reduces the throughput of the separator and reduces the efficiency of its operation. Vertical separators are better able to cope with foaming processes, since the interface area between the two phases is larger in the case of vertical orientation of the separator

Technical specifications

Gas separators of the first type have a capacity of up to 0.95 million cubic meters per day. The vertical gas separator of the second type (Figure 1.10) provides cleaning of 5.6 million cubic meters over the same period of time . Gas separator GS 1 remains operable in a wide temperature range - from minus 30 ° С to + 100 ° С. Domestic gas separators are installed in the geographical zones of the Russian Federation from the first to the fifth. Permitted seismicity - up to 9 points inclusive. The vertical gas separator can also operate in the Far North. In this case, gas separators are equipped with a special heater

Principle of gas separator operation

In any type of gas separator, gas movement is ensured, which can be carried out both by tangential input and by means of a coil located inside the structure. Centrifugal force allows dropping drops onto the vessel walls, preventing their re-entry into the gas. At the same time, the principles of deposition can vary depending on the design of the gas separator [14].

Among the nine main types, filtration, centrifugal force and gravity can be distinguished. After the inlet to the separator, the substance typically passes through the primary separation step and then enters the secondary separation section, in which the gas is separated from the liquid and further purified in the drop-catching section.

At the same time, the liquid drains, entering the section for its collection. Gas separators are also equipped with discharge branch pipes, which subsequently allow gas and liquid to be discharged.

The principle of operation of the separators is based on the differences in physical properties that the components of the mixture possess. Swirling of medium is created inside gas separator housing. Under the influence of centrifugal force, the flow deviates due to the influence of special nozzles of various configurations on it. Thus, the heavier hydrocarbons are separated from the gas and discarded onto the stripper, whereby the purified gas is drawn upwards and impurities are deposited on the walls of the housing and drained into the separated liquid collector. Thus, gas separators very efficiently purify a gas in which the amount of impurity at the outlet does not exceed one percent. Thanks to such high efficiency of the gas separator , the price of which is quite democratic, pays off as soon as possible [14].

Nevertheless, the principle of separation in the oil and gas industry is used not only in separating the produced gas from impurities, but also in removing drip liquid from the gas discharged to the burners of flare plants. Such a device is called a flare separator, and it is an indispensable element of flare systems that equip gas condensate, gas and oil fields, as well as oil and gas processing plants. Structurally , flare separators are a cylinder, inside of which an angle and mesh vertical nozzle is installed. For ease of maintenance and stable maintenance of a certain mode of operation, flare separators are equipped with process nozzles for gas-liquid mixture injection and liquid discharge, as well as separate nozzles for instrumentation.

The crude mixture of liquid and gas is supplied to the flare separator through an inlet nozzle, then to an angle nozzle, where the mixture flow is evenly distributed along the internal volume of the separator, and the drop liquid settles on its walls. Next steps of fine cleaning of gas from liquid are carried out in vertical mesh nozzle and then in zone of gravitational deposition. After that, liquid separated from the gas is discharged through the connector to a special drain tank, and the gas is discharged to the flare. Separators are installed in open areas and are able to function both in the tropics and in the Far North, where the average temperature of the coldest five-day period reaches 60 degrees Celsius [16].

Gas Separator Selection

When selecting a gas separator, it is necessary to take into account the characteristics of the gas to be treated, the characteristics of the liquid flow and the volumes of liquid storage tanks. It should also be borne in mind that almost any type of gas separator will give good results if the loading corresponds to its capacities. Therefore, the choice depends primarily on the economic feasibility of the design and its cost

1.2 Justification of design selection

On the basis of the above literary review, a two-phase vertical gas separator with a mesh drop trap is accepted for course design.

This type of design allows to achieve removal of liquid from gas up to 99.9% of water molecules contained in it. This is achieved by passing the gas-liquid mixture flow through the inlet assembly, where already at the first stage we observe the formation of liquid droplets during flow into the gas separator and as a result, the gas flow swirls. The gas, in turn, is directed to the upper part of the separator, passing through a mesh drop trap, which is made using a mesh corrugated hose RSG made in the form of a mesh, usually 0.05-0.5 mm in diameter, where the smallest particles of moisture remain.

It is also known to remove up to 90% of the oil droplets contained in the gas up to 10 microns in mesh type droplets. Western manufacturers usually guarantee a reduction in the volume of entrained liquid in the treated gas to 12mg/m3. Russian suppliers guarantee that the volume of entrained liquid in separators equipped with drip-catching elements will not exceed 30mg/m3 [23].

In this regard, the optimal equipment for this separation process will be a vertical type gas separator with a mesh drop trap

Technological solutions

2.1 Description of the production flow chart

The technological scheme is submitted on the MAPT format 000000.071 T3 on A1 format.

The fuel gas system is designed to supply fuel from the gas separator to the PTB10E furnaces and the boiler plant .

Gas from the existing gas pipeline UPSV "Gubkinsky" at a pressure of 0.20.6 MPa is supplied through the gate valve assembly to the UZTG fuel gas measurement unit. 

The UTG measures the fuel gas flow rate using Emerson diaphragms and measures the gas pressure and temperature. Manual sampler [2] is also installed in USTG unit.

Local monitoring of gas overpressure before and after the UTG is also provided with pressure gauges PI52459, PI-52460.

The USTG unit provides for monitoring of air temperature and gas content. When 10% of the LPSL is reached, the exhaust fan is automatically switched on if it is in the OFF state.

Signals from UZTG sensors are transmitted to the information processing system cabinet located in the local control room of the administrative building [2].

After UTG, gas for condensate separation enters the gas separator installed at the fuel gas treatment site. Condensate from the gas separator is discharged to the condensate collection tank by opening the electrified gate valve, from where it is pumped out by the submersible pump.

Monitoring of temperature and gas content of the air medium is provided in the condensate collection tank shelter. When 10% of the LPSL is reached, the exhaust fan is automatically switched on if it is in the OFF state [2].

After the gas separator, part of the gas in the amount of 1000 m3/h enters the boiler house, the rest of the gas is supplied to the fuel of the furnaces. In the furnace, gas is supplied through the gas control stations of GRPSH No. 1,2,3, where the pressure is reduced to 0.050.15 MPa using the pressure regulator. In the event of an accident at the furnaces, the fuel gas supply is stopped using electrified gate valves MOV 357G, 356G, 354G. The fuel gas flow rate for each furnace is determined by the gas pressure regulator RDG80V included in the furnace configuration [2].

2.2 Process calculation

Calculation of two-phase gas separator

The main purpose of the process calculation is to determine the diameter and height of the separator. The type of separator was initially defined, so it is necessary to determine the dimensions of the two-phase separator to separate the gas-liquid mixture.

Design Part

3.1 Material Selection

The separation process is carried out at relatively elevated temperatures from 10 to 115 ° C, and operating pressure of 0.2-0.6 MPa. The medium in the working apparatus is gas, having aggressive properties.

These operating conditions make special requirements for the selection of materials of the apparatus design. Steels must be heat-resistant, having simultaneously heat-resistant properties, well-welded, mechanically strong.

Structural low alloy steel for welded structures meets these requirements. The mechanical properties of steels of this class meet the requirements.

Housing, connectors, flanges, internal devices are made of 09G2S steel. Fasteners are made of similar material. Low-alloy 16GS steel is used for supports [14].

Brief description of steel grade

Steel of 09G2S grade (domestic analogues 09G2, 09G2DT, 09G2T, 10G2S)

Class: Low alloy structural steel for welded structures, steel grade 09G2S is widely used in the production of pipes and other rolled metal.

Use in industry: various parts and elements of welded steel structures operating at a temperature of - 70 to + 425 ° C under pressure.

Type of delivery : rolled stock, including shaped : GOST 1928173 , GOST 2590-2006 , GOST 25912006 , GOST 8239-89 , GOST 824097. Thick sheet GOST 1928273, GOST 5520-79, GOST 552193 , GOST 19903-74. Thin sheet GOST 1706694, GOST 19904-90. Strip GOST 1032006, GOST 82-70. Forging and forged blanks GOST 113371.

 Decryption of grade 09G2C: The designation 09G2C means that 0.09% of carbon is present in steel, since 09 goes to letters, followed by the letter "G" which means manganese, and the number 2 - a percentage of up to 2% manganese. Then follows the letter "C," which means silicon, but since there is no number after C, this means a silicon content of less than 1%. Thus, decoding 09G2C means that before us steel has 0.09% carbon, up to 2% manganese, and less than 1% silicon, and since the total number of additives varies in the region of 2.5%, this is low alloy steel.

Steel grade 16GS (substitutes: 17GS, 15GS, 20G2GS, 20GS, 18G2GS).

Class: Low alloy structural steel for welded structures

Delivery type: thick sheet GOST 1928273, GOST 5520-79 , GOST 1990374. Thin sheet GOST 1706694,  GOST 19903-74, GOST 1990490. Strip GOST 8270.

Industrial use : parts and parts of steam boilers and pressure vessels. Hulls, bottoms, flanges and other parts operating at temperatures from 40 to + 475 deg. under pressure. Elements of welded steel structures operating at temperature 70 ° С.

Decryption of the 16GS brand: assumes that the chemical composition of the steel of this brand belongs to silicone-manganese, that is, silicon and manganese are the dominant additives. In percentage terms, the content of these additives is: Si - up to 0.7%, Mn - up to 1.2%. In addition, the following are used for the production of 16GS steel: carbon, nickel, sulfur, phosphorus, chromium, nitrogen, copper.

Installation, repair, maintenance

4.1 Preparation of the article for installation

The specifics of installation and repair of gas separators are due to the overall dimensions of these devices, a special internal device, and the location of the device.

Installation works for installation of the gas separator on the foundation are carried out by a specialized installation control of the SMU.

Before the start of work, the representative of the SMU takes the foundation for the separator from the construction organization. The act "Reception - surrender" is drawn up. It is possible to install the separator on the foundation only after the concrete retention period has ended within the time specified in the specification. Wells for anchor bolts, as well as the entire open surface of the foundation, must be cleaned from construction debris, the threaded part of the bolts must be cleaned and lubricated for corrosion protection [11].

Delivery of the apparatus and equipment to it from the manufacturer's factory is carried out by rail. The weight of the apparatus is 1715 kg, height is 3.5 m, diameter is 0.6 m. From the point of unloading from the railway transport to the place of installation, the gas separator is transported along the highway. 

When receiving equipment for installation, its external inspection is carried out, completeness is checked. The completeness of the equipment is specified in the technical documentation. The body of the apparatus shall bear hairlines or other signs ensuring orientation of its main axes and control of their position in plan relative to the axes of the foundation or adjacent equipment. The same signs shall be affixed to the supports [11].

Assembly hairlines shall be applied in detachable joints of assembly units and parts removed during transportation and storage, or control pins shall be installed to assemble equipment without marking and fitting works. Loading and unloading operations and installation of the gas separator on the foundation are carried out using a crane.

After completion of all construction and installation works, the object is prepared for delivery to the customer.

Before delivery, the device is subjected to hydrotest. If there are no defects, a control test is carried out in the presence of the customer and a certificate of delivery is drawn up. Comprehensive testing is performed by the customer.

Contractors eliminate certain shortcomings observed both during testing and during the period when the facility is put into normal operation.

The repair of the separator consists in the restoration of all worn-out units and parts by welding, surfacing, patches or complete replacement.

Major and average repairs are made once a year [11].

Conclusion

This course design contains all the necessary technological and strength calculations, issues of installation and repair are covered. As a result of the calculation, such design data were determined as: design and actuating thicknesses of the apparatus elements, dimensions of flange joints, strengthening of holes, and also the selection and calculation of the apparatus supports were carried out. The necessary stability and strength test calculations were carried out.

The course project consists of: explanatory note and graphic part. The note includes 67 sheets of typewritten text in the format A4, 26 sources of used literature. The graphic part of the project consists of: 4 sheets of A1 format.

According to the task and taking into account the methodological guidelines, an apparatus for separation of associated gas was designed. The selection of the apparatus and related parts is made according to GOST catalogs. Calculation error does not exceed 5%.