Express Publishing is a highly respected publisher who continuously raises the standards of English Language Teaching (ELT). Upstream 1 & 2 comprise a. Upstream 1 & 2 comprise a modular language course for learners from CEF A1+ to The DVD along with the DVD Activity Book constitute a short listening and. Upstream Series. Sample Modules. To view the samples below click on the image of the Student´s Book or the CD-ROM: Upstream Beginner A1+. Express.
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Upstream series is specially designed for students from absolute beginner to intermediate level. Each book consists of five modules and provides systematic. Student's Book. Express Publishing . This book is not meant to be changed in any way. . English as this is the language that is used most frequently. One way to attract customers is to build a shop that makes people look twice! Some buildings have got bright colours, others have got strange.
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Supplementary Material. In some processes where the initial temperature is low, it might be necessary to heat the liquid again in a heat exchanger before the flash drum to achieve good separation of the heavy components. There are level and pressure control loops. As an alternative, when production is mainly gas, and remaining liquid droplets have to be separated out, the two-phase separator can be a knockout drum K. In this unit, water content can be reduced to below 0.
The coalescer is completely filled with liquid: water at the bottom and oil on top. Internal electrodes form an electric field to break surface bonds between conductive water and isolating oil in an oil-water emulsion. The coalescer field plates are generally steel, sometimes covered with dielectric material to prevent short-circuits. The critical field strength in oil is in the range of 0. Field intensity and frequency as well as the coalescer grid layout are different for different manufacturers and oil types.
Photo: Burgess Manning Europe PLC If the separated oil contains unacceptable amounts of salts, they can be removed in an electrostatic desalter not used in the Njord example.
The salts, which may be sodium, calcium or magnesium chlorides, come from the reservoir water and are also dissolved in the oil. The desalters will be placed after the first or second stage separator depending on GOR and water cut. The environmental regulations in most countries are quite strict.
Figure 6. Produced water treatment It also places limits on other forms of contaminants. This still means that the equivalent of up to one barrel of oil per day in contaminants from the above production is discharged into the sea, but in this form, microscopic oil drops are broken down quickly by natural bacteria.
Various pieces of equipment are used. This illustration shows a typical water treatment system. Water from the separators and coalescers first goes to a sand cyclone, which removes most of the sand. The sand is further washed before it is discharged. The water then goes to a hydrocyclone, a centrifugal separator that removes oil drops. The hydrocyclone creates a standing vortex where oil collects in the middle and water is forced to the side.
Finally the water is collected in the water de-gassing drum. Dispersed gas slowly rises and pulls remaining oil droplets to the surface by flotation.
The surface oil film is drained, and the produced water can be discharged to sea. Recovered oil in the water treatment system is typically recycled to the third stage separator. MP compressor A typical stage is shown above. Incoming gas on the right is first cooled in a heat exchanger. It then passes through the scrubber to remove liquids and goes into the compressor. The anti-surge loop thin orange line and the surge valve UV 23 allow the gas to recirculate.
The components are described below. The lower the temperature, the less energy will be used to compress the gas for the given final pressure and temperature. However, both gas from separators and compressed gas are relatively hot.
This ends up as a temperature increase. Plate heat exchanger Heat exchangers of various forms are used to cool the gas. Plate heat exchangers picture above consist of a number of plates where the gas and cooling medium pass between alternating plates in opposing directions. Tube and shell exchangers picture below place tubes inside a shell filled with cooling fluid. The cooling fluid is often pure water with corrosion inhibitors.
Tube heat exchanger. Heat should be conserved, e. Excess heat is dispersed, e.
However, hot seawater is extremely corrosive, so materials with high resistance to corrosion, such as titanium must be used. Drops of water and hydrocarbons also form when the gas is cooled in the heat exchanger, and must be removed before it reaches the compressor. If liquid droplets enter the compressor, they will erode the fast rotating blades.
A scrubber is designed to remove small fractions of liquid from the gas. There are various types of gas-drying equipment available, but the most common suction compressor scrubber is based on dehydration by absorption in triethylene glycol TEG. The scrubber consists of many levels of glycol layers. A large number of gas traps enlarged detail force the gas to bubble up through each glycol layer as it flows from the bottom to the top of each section.
Processed glycol is pumped in at the top from the holding tank. It flows from level to level against the gas flow as it spills over the edge of each trap. During this process, it absorbs liquids from the gas and comes out as rich glycol at the bottom. The holding tank also functions as a heat exchanger for liquid, to and from the reboilers. The glycol is recycled by removing the absorbed liquid.
Usually there is a distillation column on the gas vent to further improve separation of glycol and other hydrocarbons. For higher capacity, there are often two reboilers which alternate between heating rich glycol and draining recycled processed glycol.
On a standalone unit, the heat is supplied from a burner that uses the recovered vaporized hydrocarbons. In other designs, heating will be a combination of hot cooling substances from other parts of the process and electric heaters, and recycling the hydrocarbon liquids to the third stage separator.
Figure 7. Glycol regeneration 4. The overview given here will therefore be referenced from other sections. Several types of compressors are used for gas compression, each with different characteristics such as operating power, speed, pressure and volume: Reciprocating compressor. Photo: Ariel corp. Reciprocating compressors, which use a piston and cylinder design with cylinders are built up to about 30 MW power, around —1, rpm lower for higher power with pressure up to 5MPa bars.
Used for lower capacity gas compression and high reservoir pressure gas injection. Screw compressor. Two counter-rotating screws with matching profiles provide positive displacement and a wide operating range.
Typical use is natural gas gathering. Axial compressor. Applications include air compressors and cooling compression in LNG plants. Centrifugal compressor. Pressure differential up to Most compressors will not cover the full pressure range efficiently.
The lowest pressure is atmospheric, for gas to pipeline, some 3 to 5 MPa 30—50 bar pressure is used, while reservoir reinjection of gas will typically require 20 MPa bar and upwards, since there is no liquid in the tubing and the full reservoir pressure must be overcome. Therefore, compression is divided into several stages to improve maintenance and availability.
Also due to single unit power limitations, compression is often divided in several parallel trains. This is not the case in this example, since gas is not exported and reinjection can be interrupted during maintenance periods. Compressors are driven by gas turbines or electrical motors for lower power also reciprocating engines, steam turbines are sometimes used if thermal energy is available.
Often, several stages in the same train are driven by the same motor or turbine. The main operating parameters for a compressor are the flow and pressure differentials. The product defines the total loading, so there is a ceiling set by the maximum design power.
Furthermore, there is a maximum differential pressure Max Pd and choke flow Max Q , the maximum flow that can be achieved. At lower flow, there is a minimum pressure differential and flow before the compressor will "surge" if there is not enough gas to operate. If variations in flow are expected or differences between common shaft compressors occur, the situation will be handled with recirculation.
A high flow, high pressure differential surge control valve will open to let gas from the discharge side back into the suction side. Since this gas is heated, it will also pass through the heat exchanger and scrubber so as not to become overheated by circulation. Figure 8. Compressor state diagram The operating characteristics are defined by the manufacturer.
In the diagram above, the blue lines mark constant speed lines. The maximum operating limits are set by the orange line as described above. The surge domain is the area to the left of the red surge curve.
The objective of compressor performance control is to keep the operating point close to the optimal set point without violating the constraints by means of control outputs, such as the speed setting.
However, gas turbine speed control response is relatively slow and even electric motors are not fast enough, since surge response must be in the ms range. Anti-surge control will protect the compressor from going into surge by operating the surge control valve. The basic strategy is to use distance between operating point and surge line to control the valve with a slower response time, starting at the surge control line.
Crossing the surge trip line will cause a fast response opening of the surge valve to protect the compressor. Operation with recirculation wastes energy which could result in unnecessary emissions and produces wear and tear, particularly on the surge valve.
Each vendor supplies several variants of compressor control and anti-surge control to optimize performance, based on various corrective and predictive algorithms.
Some strategies include: Set point adjustment: If rapid variations in load cause surge valve action, the set point will be moved to increase the surge margin. Equal margin: The set point is adjusted to allow equal margin to surge between several compressors. Model based control: Outside the compressor itself, the main parameter for the surge margin is the total volume from the surge valve to the compressor suction inlet, and the response time for the surge valve flow.
A model predictive controller could predict surge conditions and react faster to real situations while preventing unnecessary recirculation.
Since compressors require maintenance and are potentially expensive to replace, several other systems are normally included: Load management: To balance loading among several compressors in a train and between trains, the compressor control system often includes algorithms for load sharing, load shedding and loading. Compressors are normally purged with inert gas, such as nitrogen during longer shutdowns, e. Therefore, startup and shutdown sequences will normally include procedures to introduce and remove the purge gas.
Vibration: Vibration is a good indicator of problems in compressors, and accelerometers are mounted on various parts of the equipment to be logged and analyzed by a vibration monitoring system. Speed governor: If the compressor is turbine driven, a dedicated speed governor handles the fuel valves and other controls on the turbine to maintain efficiency and control rotational speed. For electrical motors this function is handled by a variable speed drive. The final function around the compressor itself is lube and seal oil handling.
Most compressors have wet seals, which are traps around shafts where oil at high pressure prevents gas from leaking out to atmosphere or other parts of the equipment. Oil is used for lubrication of the high speed bearings.
This oil gradually absorbs gas under pressure and may become contaminated. It needs to be filtered and degassed. This happens in smaller reboilers, in much the same way as for the glycol reboilers described earlier. Often, custody transfer also takes place at this point, which means transfer of responsibility or title from the producer to a customer, shuttle tanker operator or pipeline operator.
Although some small installations are still operated with a dipstick and manual records, larger installations have analysis and metering equipment. To make sure readings are accurate, a fixed or movable prover loop for calibration is also installed.
The illustration shows a full liquid hydrocarbon oil and condensate metering system.