The compressors form part of a group of technical devices that are widely used at all types of industrial facility.
The compressor plants represent a complex of systems running smoothly as one well-coordinated assembly (in addition to the main compressor unit and engine or motor their delivery sets may include gas treatment equipment, an integrated oil system, various types of cooling system, piping with a full set of valves used in different services, control instruments and other auxiliary equipment). The specific equipment composition of a compressor plant may vary as a function of the type of compressor unit and its driver, equipment service and other parameters. To allow the compressor plant to be monitored and controlled industrial-type PLCs are used that provide smooth operation of all constituent parts in a well-coordinated manner and performance of the whole system as one unit.
Types of compressor unit:
- Screw Compressors
The screw compressors are provided with smooth throughput control and automatic geometric compression ratio control features and are characterized by highly economical operation, minimum noise and vibration levels and compactness in design.
As units with fewer moving parts and simple rotational movement the screw compressors provide reliable compression of gas without pulsations, thus assuring better sealing and dynamic balancing characteristics required for noiseless and efficient running.
Types based on lubrication system:
- With built-in injection of oil in compression chamber
Types based on oil feed:
- With common lubrication system
- With dual-lubrication system
- Gas engine
- Electric motor
ROTARY VANE COMPRESSORS
The rotary vane compressors represent high-quality and reliable equipment assuring trouble-free operation of a plant during its overall service period. Such a type of compressor relates to rotary machines where gas compression takes place in chambers with periodically decreasing volumes.
The main advantage of this type of compressor when it is used to handle gas is that its materials and construction allow assuring complete leakproofness. The cylinders and heads made of special fine-grained iron are provided with a water jacket and are carefully machined to ensure a close fit between the cylinders and the heads. The heads are fixed to the cylinder by means of bolts and pins reducing the amount of maintenance work to a minimum.
The compressor is equipped with a lubrication device reducing friction between the blades and their wear considerably. The material of which the blades are made is resistant to influence of most gases entrapped by the plant.
Types based on driver-compressor connection:
- With direct connection
- With through shaft
- Gas engine
- Electric motor
The reciprocating compressor relates to the displacement type of compressor. In the reciprocating compressor gas is compressed by means of pistons moving in the cylinders reciprocally: gas suction and discharge being controlled by the opening and closing valves.
The compressor comprises a piston, piston rod, cylinders, suction and discharge valves and covers for closing the openings in the cylinders (cylinders heads, valve caps).
Depending on the overall pressure ratio it is possible for gas to be compressed by means of one or several stages (cylinders). Compression of process gas and a mixture of process gases results in compression heat at all times. That is why cooling liquid is supplied to the cylinders.
- Balanced opposed
Types based quantity of stages:
Types based cylinder cooling:
Types based on lubrication system:
- With cylinder lubrication
- Gas engine
- Electric motor
- With integral engine
The centrifugal compressor consists of a casing and a rotor equipped with a shaft with symmetrically located impellers. The centrifugal n-stage compressor is divided into several sections and equipped with several intermediate coolers from which gas is supplied to the channels.
The plant design provides for a gas seal module assuring stable and uninterruptible supply of clean dry gas (usually compressed gas) to the gas seals without penetration of impurities and moisture present in the compressed gas into them and assuring required velocity of gas flow through the labyrinth seals.
To allow stable operation of a compressor station and prevent the compressor from being driven into surge an antisurge protection system should be provided for. It usually consists of a set of required gas flow and pressure transmitters at the inlet and outlet from the compressor and surge valve for bypassing gas to the suction side.
- Mutishaft-type (with built-in step-up gear box)
Types based on quantity of casings:
Types based on casing split:
- Electric motor
- Various types of turbines
In the liquid-ring compressor the transmission of gas from the suction nozzle to the discharge nozzle takes place continuously and evenly .The most widely used operating fluid in the liquid-ring pumps and compressors is water.
From a design standpoint the water-ring compressor is simple, reliable in operation and characterized by a low noise level when running. The presence of the liquid ring in this compressor allows pumping out gases containing vapours, capillary liquids, solid foreign inclusions (dust) and even abrasive particles.
Thanks to the presence of the liquid ring in this compressor the compression of gas takes place with intensive heat exchange and is close to isothermal, which allows pumping out and transferring easily decomposable, polymerizable, explosion-hazardous gases and mixtures.
Types based on quantity of inlet nozzles:
- Electric motor
Techengoil AO supplies all the above-mentioned types of compressor unit depending on the requirements of its customers.
WORKING AGENT HEATING UNIT
The working agent heating unit is designed for utilization of associated petroleum gas directly on the sites of oil production installations and serves to assure the process of increasing temperature of various media.
The unit is designed for heating the following types of products to required temperature by outlet flue gas:
Advantages of solutions based on working agent heating units:
- It is possible to utilize associated petroleum gas from the first and final stages of separation of oil in accordance with the Russian Federation regulations without paying burning penalties.
- It is possible to arrange for rational use of heat from combustion of flue gases.
- Separation of the processes of gas burning and working agent heating, which considerably reduces the possibility of heat exchanger and other equipment forming part of the delivery set being overheated and damaged.
- It is possible to use a wide fuel gas supply range: 0-100%.
- It is possible to use “fat” gas, water-saturated gas, as well as fuel characterized by a low calorific value in the combustion process.
- Easy control of output and medium temperature at the outlet from a heat exchanger by varying air blower rotor rotational speed and quantity of air being supplied to the chimney stack.
- It is possible to heat several types of media by installation of parallel working agent heat exchangers with their own smoke exhausters on each heating line.
- Efficient associated petroleum gas burning with a conversion degree of up to 99.9% by installation of high-quality imported smokeless burners.
Depending on the service of the working agent heating unit it is possible to use it in different versions: single-flow, double-flow or triple-flow configurations. In the triple-flow configuration it is possible to heat three different agents simultaneously, each heating line being autonomous, which allows it to be switched off if required or in case of absence of supply of a working agent.
GAS TREATMENT PLANT
Gas treatment using the adsorption method
This method is applied either to achieve a low “dew point” (less than minus 20 … minus 300C), or for a selective removal of impurities from the gas. Porous solids with a large specific surface are used as adsorbents.
The adsorption process of on-site natural gas dehydration and treatment is cyclic and includes adsorption, desorption, and refrigeration phases which run in series in a single apparatus. There are different process configurations for adsorption systems. The most common arrangements are two-tower, three-tower, and six-tower configurations. In the two-tower system, tower A is in the adsorption mode, tower B is in the desorption and refrigeration mode. In the three-tower system, each process phase (adsorption, desorption, and refrigeration) takes place in a corresponding tower. The six-tower system allows a plant to operate in a two-tower mode.
Gas treatment using the absorption method
This method is used to extract water vapor, hydrocarbons, and other contaminants from the gas.
The absorption process is performed in a vertical and cylindrical absorber vessel. The gas and absorbent come into a contact on the trays, mounted inside the apparatus, and mix in a counterflow: the gas flows upward from the bottom, and the absorbent flows from the top downward. In the process of its downflow, the absorbent becomes saturated with solutes or moisture and is supplied via the bottom of the tower to regeneration. The dehydrated gas flows via the top of the tower. The efficiency of absorption depends upon the temperature and pressure, the number of trays in the absorber, the absorbent quantity and quality.
Low temperature separation
Low Temperature Gas Separation is a process of natural gas on-site treatment aimed at the removal of liquid hydrocarbons and water by a single-time condensation at lower temperatures and separation of equibalanced gaseous and liquid phases. The process runs at average negative temperatures (approximately from 0 to -30°C).
The low temperature technology is applied mainly as the gas condensate on-site natural gas treatment for a concurrent dehydration and extraction of target components, such as heavy hydrocarbons and inert gases if present in appreciable amounts.
The following refrigeration schemes can be applied to achieve gas chilling:
- The external refrigeration cycle (external chilling feed) when special agents – refrigerants – recirculate in the refrigeration cycle.
- The internal refrigeration cycle which employs the cooling of process flows by means of a pressure drop. For a more comprehensive extraction of hydrocarbon condensate from the natural gas, the gas cooling at the plant is provided by the gas-throttling effect (Joule-Thomson effect).
The temperature drop of the gas during its treatment is achieved by using a throttle, two- or three-flow vortex tube, as well as a turbo expander.
OTHER TYPES OF OIL AND GAS EQUIPMENT
Gas separators are apparatus for the treatment of gas and gas-condensate well produce, as well as the protection of shutoff and control valves and gas transfer equipment from the condensed moisture, hydrocarbon condensate, and mechanical impurities. Gas separators are part of gas treatment plants equipment configuration.
Three-phase separators are used for the separation of gas condensate from water, hydrocarbon condensate and separation gas.
Its hookup provides for an option to discharge the gas to a low-pressure flare when equipment is shut down for maintenance, or, in the event of an emergency, discharge from safety valves to the flare system.
A separator consists of the following basic parts: casing, gas condensate inlet, stable hydrocarbon condensate outlet, gas outlet, water outlet, gas-liquid mix intake and distribution unit, distributing and coalescing unit, baffle plate, and capillary moisture trap.
Oil and gas separators
Oil and gas separators are intended for crude oil degassing and associated petroleum gas purification at the oil field produce gathering and treatment plants.
Oil and gas separators are used at the inlet, intermediate, and discharge stages of on-site crude oil preparation units.
АО Techengoil supplies customized modular skid packages, modular containerized packages, or prefabricated equipment.
АО Techengoil is an engineering and design company doing its business in the area of capital construction of facilities for oil and gas, energy, and chemical industries, giving particular attention to geological, environmental, and climatic issues.
The company carries out design and engineering of:
- Crude oil and gas pre-treatment, processing, transportation, and storage facilities;
- Technological process automated control systems;
- Solutions for crude oil processing plants, inclusive of chemicals feed to oil refining and reaction units, pressure testing of equipment, disposal of flare gas, etc.;
- Energy sector solutions.
Our company elaborates a complete set of design documentation and provides a follow-up in the course of state expert examination.
Designing services include the following activities:
- Elaboration of a technical specification document;
- Preparation of a land plot layout diagram;
- Preparation of architectural design solutions;
- Preparation of structural design solutions;
- Preparation of data on plant internal utilities, utilities network, and technical performance measures;
- Preparation of data on external utilities network and listing technical performance measures;
- Preparation of process solutions;
- Drafting an environmental protective measures plan;
- Drafting a fire safety measures plan;
- Structural survey of buildings;
- Supervision services.
All activities are exercised by qualified specialists with the use of such modern software as: Aspen Hysys, AutoCAD, Compass, Aspen Plus, SolidWorks, etc. In order to ensure the best results, 3D modelling technologies are employed.
Our company has been certified and awarded necessary permits to perform all the above-mentioned activities.
For more detailed information related to the services and costs, please contact our specialists.
АО Techengoil company carries out equipment procurement projects. Equipment can be supplied prefabricated for on-site erection, or as modular skid packages. The company specializes in the supply of the following types of equipment:
- Micron filters;
- Commercial gas metering units;
- Analytical equipment;
- Gas distribution systems;
- Shutoff valves;
- Tanks and vessels;
- Shelters for equipment.
ERECTION SUPERVISION WORK
The necessity of erection supervision is determined by a high hazardousness of facilities in oil and gas, energy, and chemical industries. The implementation of erection supervision stage of works ensures a proper equipment erection and installation resulting in its fault-free and long-term operation.
Erection supervision services are rendered by АО Techengoil qualified specialists, certified by the State Qualification Board, and hold relevant work authorizations.
The Company specialists have clearances to perform the following types of work:
- Electrical installation;
- Heavy equipment erection and dismantling;
- Electrical arc welding;
- Gas hazardous works;
- Pressure vessels and pipelines testing and opening;
- Operations in the areas with a high gas content in the air, electrocution hazard, and limited time of exposure;
- Technical diagnosis of electrical drives and valves, as well as a number of other activities, considered hazardous by the RosTechNadzor Agency.
The erection supervision, carried out by our company specialists, includes the following basic stages:
- Acceptance of equipment at the Customer site for the verification of equipment configuration and disclosure of possible faults;
- Consultancy in the process of erection of equipment;
- Preparation of necessary supporting documentation for the erection works and subsequent equipment operation.
AO Techengoil company carries out start-up preparation, adjustment, and start-up of equipment for oil and gas, energy, and chemical industries.
The following basic work stages are carried out by company specialists in order to check out the reliability and safe operation of equipment:
- Study and analysis of design documentation;
- Formulation of commissioning program;
- Comprehensive inspection of equipment and detection of installation defects;
- Drawing up a report and issuing recommendations for the elimination of installation defects;
- Provide training in the integrated testing of equipment to operating personnel;
- Integrated testing of equipment;
- Load testing of equipment under different operating conditions and using the response data of instrumentation;
- Drawing up a technical report and preliminary process flow diagram for the maintenance and operating personnel;
- Formulation of Documentation Package following the results of commissioning.
Commissioning is performed by the company engineers who are trained in the commissioning procedures, certified by the State Qualification Board, and hold certificates authorizing them to do commissioning works.
Improvement of crude oil recovery efficiency
Crude oil reservoirs recovery improvement – the enhancement of oil recovery rate from subsurface – is one of the major problems in the energy supply of the country in the coming decades. The efficiency of currently known methods of recovery will provide a high ultimate oil recovery factor.
The residual reserves, or unrecoverable, using the currently applied industrial methods of oil-fields development, reach high values (approximately from 55 to 75 %) of the initial geological in-situ oil reserves thus representing a large resource for ramping up the recoverable reserves, applying the methods of enhancing crude oil reservoirs recovery efficiency.
In this connection, АО Techengoil company proposes different gas drive methods for the enhancement of oil recovery rate from the currently developed oil-fields by the application of the following progressive formation stimulation methods:
- Air injection into an oil reservoir;
- Carbon dioxide injection into an oil reservoir;
- Nitrogen, flue gas, etc. injection into an oil reservoir.
Crude oil pretreatment
All recovered crude oil is subject to integrated treatment.
There are the following basic stages of crude oil treatment:
- Crude oil preparation for processing (dewatering, desalting);
- Primary crude oil processing (distillation);
- Secondary crude oil processing (thermal methods: coking, pyrolysis, thermal cracking; catalytic methods: reforming, catalytic cracking, hydrogenation);
- Petrochemical products treatment.
Crude oil degassing
Crude oil recovered from subsurface typically contains solved gas, referred to as the associated petroleum gas. Prior to crude oil transportation and feed to processing, the gas has to be separated from crude oil. The removal of the gas from crude oil, or degassing, is performed by means of separation and stabilization.
In the conditions of an oil reservoir at a high pressure, gases are solved in oil. When oil is rising to the surface, the pressure drops, and the solved gas breaks out. It is critical to entrap it at this moment. There are several schemes of an on-site oil and gas separation that differ in the conditions of gas and oil transfer. The schemes of Group 1 are characterized by the separation of gas from oil at the shortest distance from the well. After the gas is separated, only crude oil is transferred to the central gathering point.
Crude oil stabilization
Even after a multistage oil-field separation, a considerable quantity of C1 – C4 hydrocarbons is still left in crude oil. A substantial part of these hydrocarbons can be lost whilst pumping from one tank to another, during storage, and oil transportation. Along with the gases, valuable light naphtha fractions can be lost.
In order to eliminate gas and light naphtha fractions losses, prevent air pollution, and entrap valuable gaseous components, it is necessary to extract maximum amounts of C1 – C4 hydrocarbons from oil prior to transporting it to oil refineries. This objective is resolved at crude oil stabilization units, typically located in the immediate vicinity of the site of crude oil recovery. There are different methods of crude oil stabilization.
Crude oil emulsions
The presence of water and salts in oil delivered for processing is harmful for the operation of refineries. With a high water content, the pressure in oil distillation equipment increases thus reducing their performance; besides, extra heat is consumed for water evaporation and heating.
Water and salts are removed immediately after crude recovery from the subsurface in oil-fields and at crude oil processing plants. There are two types of technological processes that are employed for water and salts removal: dewatering and desalting. Both processes are based on demulsification. However, during dewatering, natural emulsions, the ones that formed as a result of an intensive mixing of crude with the drilling fluid, get broken. Dewatering is carried out in the oil fields and, along with degassing, represents the first stage of crude oil preparation for transportation and processing.
Dewatered oil during desalting is mixed with fresh water, forming an artificial emulsion, which lately gets broken.. Crude oil desalting.
GAS TREATMENT AND TRANSPORTATION
Gas transportation system by pipelines is subdivided into gas mains which transport gas from the place of its production to the large cities and industrial facilities, and municipal gas pipelines which distribute gas and supply it to the consumers.
Long-distance gas transportation results in a significant pressure drop due to the need to overcome resistance. The volume of gas expands at that, and the carrying capacity of gas pipelines reduces. Gas pipelines normal operation is maintained in this case by the placement of intermediate booster compressor stations.
Gas mains compressor stations arrangement includes compressors, gas scrubbers, gas cooling units, reduction units, oil traps, gas odorizing units, etc.
Positive displacement compressors are used in the low and medium capacity compressor stations with internal combustion engines as the drives. High capacity compressor stations are equipped with turbine compressors.
Treatment of gas before feeding it to the gas main and other needs
Before feeding gas to gas mains, it is required to prepare it for transportation at a gas processing plant located nearby the gas field. The gas treatment process includes gas cleaning of mechanical impurities, removal of gas condensate and free liquid water, and removal of byproducts, such as hydrogen sulfide, carbon dioxide, etc.
The raw gas is cleaned of mechanical and liquid impurities using the following equipment:
- Gas separators;
- Oil mist dust collectors;
- Cyclone dust collectors;
- Gas filter-separators;
- Three-phase separators;
- Oil and gas separators;
Methods of gas dehydration:
- Adsorption method of gas dehydration;
- Absorption method of gas dehydration;
- Low temperature separation;
- 3S technology for gas dehydration and purification;
- Gas dehydration and purification using membrane technologies.
Methods of H2S and CO2 impurities removal:
- Chemisorption technique of gas purification using amines;
- Physisorption technique of gas purification;
- Gas purification by the method of physical and chemical absorption;
- Gas purification using the adsorption method.
A gas processing plant for small, medium, and large gas fields has a typical configuration from a gas well to a commercial gas metering station located at the gas processing plant site. Its infrastructure is intended to provide gas and gas condensate recovery, gathering, and processing for a subsequent transportation or utilization of resources for plant needs.
The choice of a gas treatment process flow diagram depends upon the type and structure of the facility and the costs and benefits analysis.
POWER GENERATION AT GAS TURBINE AND GAS PISTON-ENGINE POWER PLANTS
GAS TURBINE POWER PLANT (GTPP)
Gas turbine power plants can be used in various spheres, from electric power supply of civil and agricultural buildings to industrial facilities and oil and gas fields. Besides, using this type of equipment, it is possible to supply electric power not only to stand-alone objects but also to whole settlements and residential complexes.
The core of a gas turbine power plant is one or several gas turbine engines which are power units connected mechanically with a power generator and integrated in a single power complex by a control system. It is practical to use such equipment at independent enterprises with a continuous electric power consumption. Gas turbine power plants are more appropriate as an off-line source of electric power. As a rule, gas turbine power plants are installed for a higher power consumption than piston-engine power plant capabilities. This equipment is considered to be more robust, and it has a higher MTTR.
GAS PISTON-ENGINE POWER PLANT (GPEPP)
Gas piston-engine power plants are used to generate electric and heat power of set parameters from gaseous fuel. For heat power generation, a gas piston-engine power plant has to be geared with a heat utilization system.
Practically, all of the existing models of gas piston-engine power plants can operate in the cogeneration mode. This particular case makes the use of these plants as a basis for mini-CPP possible. Besides, the electric and heat powers, generated by gas piston-engine power plants are more or less equal. Gas piston-engine power plants can be fitted into containers or special premises intended for a continuous operating mode.
Gas treatment for GTPP/GPEPP
In order to maintain power plant operation, it is required to install an additional gas treatment unit. The configuration of the unit can vary, and it depends directly upon many factors, for instance, the source of fuel gas, fuel gas pressure, fuel gas composition, turbine type, and other parameters. For the determination of the units’ configuration, it is advisable to familiarize with the GTPP/GPETT manufacturer basic requirements for the fuel gas.
A modular gas treatment unit (MGTU) is intended to condition gas to meet the required parameters prior to feeding it to the power generation unit.
The designed MGTU are compact, easily maintainable, highly robust, and they guarantee the quality of the associated gas purification.
The MGTU can comprise (but is not limited to) the following subunits: valves switchover system, coarse filters assembly, coarse filter separators, gas condensate gathering tank, gas flow meter (commercial gas meter), booster compressors stations (BCS), gas fuel heating system, gas pressure reduction system, fine filters assembly, and other types of equipment the configuration of which may vary in some specific cases.
A fuel gas treatment unit conditions the associated petroleum gas for the feed to gas turbine and gas piston-engine power plants. The process of conditioning includes fuel gas cleaning of mechanical impurities and condensed moisture, dehydration, pressure reduction, and fuel gas pressure set point maintenance at the MGTU outlet.
EXTRACTION OF MARKETABLE PRODUCTS
Associated petroleum gas processing
Associated petroleum gas (APG) processing is the second in its significance, after crude oil, source of raw feed for the petrochemical industry. The processes of valuable fractions extraction from the APG are based on two principles. The first one is implemented in the low temperature condensation (LTC) units where gases are separated as per their liquefaction temperatures. The second principle is implemented in the low temperature absorption (LTA) units and is based on the difference in the solubility of gases in liquids. LTA towers may be filled, for instance, with circulating liquid propane though which feed gas bubbles flow.
Natural gas and gas condensate processing
Gas and gas condensate fields also supply valuable raw materials for petrochemistry. The natural gas, the main component of which is methane (around 82 – 98%), has in its composition some other hydrocarbons. In this respect, the natural gas is less rich in C2+ fractions than the oil field APG, but the natural gas production is much higher, thus resulting in its high significance for the petrochemical industry.
From the technological point of view, the processing of natural gas and extraction of valuable fractions is akin to the APG processing: both processes are based on the difference in the boiling points of gases. Speaking with certain reservations, the dehydrated and sweetened gas undergoes multistage refrigeration accompanied by a gradual extraction of its components.
The gas condensate is, in itself, a gasoline and kerosene hydrocarbon liquid with dissolved light gases: methane, ethane, propane and butanes.
Condensate processing, or stabilization, is the extraction of gases, dissolved in it. Thereby, condensate processing plants yield two types of raw materials for the petrochemistry: wide-cut light NGL (natural gas liquids) and stabilized gas condensate which is, in itself, a good quality straight-run gasoline.
One of the critical stages in the way of raw hydrocarbons conversion into petrochemical products is gas fractionation, i.e. the separation of wide-cut light NGL, or similar mixtures, into constituents – separate hydrocarbons.
Liquefied hydrocarbon gases (LHG) have a broad application as fuel in industry and households. The second important area of LHG application is the utilization as motor fuel.
Gas separation at gas fractionation plants is based on the same principles of varying boiling point temperatures. However, if the gas processing plant’s main objective is to separate fatty fractions from methane and ethane, the separation at a gas fractionation plant has to be more thorough and more fractional with the extraction of separate hydrocarbon fractions.
That is why Gas Fractioning Plants are represented as imposing cascades of towers where liquified gases or mixtures are consecutively extracted. The main products are: technical grade of propane-butane, propane and butane fractions, technical grade of butane (less pure), isobutane fraction, and others.
A compressor station is a complex of buildings and equipment for increasing gas compression during its recovery, transportation, storage, supply to technological processes at oil refineries, and other needs.
Depending upon the location, it can be possible to compress various types of gas: air, nitrogen, hydrocarbon gases, carbon dioxide, hydrogen, inert gases, special gases yielded during crude oil refining and gas fractionation, corrosive gases.
Subject to the specific purpose of a compressor station, conditions, requirements for the gas after compression, type of compressor, and other requirements, the type of compressor, engine, cooling system, and material design of equipment is selected.
Following are the examples of the implemented projects of compression of corrosive hydrogen-bearing gases and process gases produced at various types of units at oil refineries.