MXPA98006343A - Separation plant of a - Google Patents

Abstract

An air separation plant 2 includes a compressor 4 of air, a gas turbine 10, arranged to drive the air compressor 4, a compressor 6 of the product nitrogen, and a steam turbine 14, arranged to drive the Compressor 6 of the nitrogen product. This water vapor turbine is part of a circuit that includes a generated 22 of water vapor, in which the current is capable of being raised in temperature by the heat exchange of the water with the hot gaseous exhaust, coming from the turbine 10 gas or other turbine of g

Description

AIR SEPARATION PLANT The invention relates to an air separation plant. An air separation plant is often provided with a product compressor, in addition to one or more air compressors. In large plants, which produce more than 1000 tons per day of the product, the separation is usually done by rectification. US-A-4 382 366 refers to an air separation plant, which produces an oxygen product. A compressor of the oxygen product is directly driven by a steam turbine. A stream of waste nitrogen, which contains sufficient oxygen to support combustion, is taken from the rectification column in which this oxygen product is separated and introduced, without further compression, into a chamber, where the combustion of combustible gas. The resulting combustion products are expanded in a turbo-expansion apparatus. The current, supplied to the steam turbine, is raised in temperature by the exchange of heat with the combustion gases that escape from the separation plant, the steam turbine and the turbo-compressor, all coupled together. Such a plant can not produce a nitrogen product in large quantities. Larger plants can produce up to 10,000 tons per day of the product nitrogen at high pressure. Therefore, large compressors are required for the product nitrogen. Conventionally, such compressors are driven by electric motors. These electric motors are often large and problems can arise when starting motors. Traditionally, starter motors are supplied. An object of the present invention is to provide an air separation plant, which does not require an electric motor to drive the air compressor or the compressor of the product nitrogen. According to the present invention, an air separation plant is provided, which includes an air compressor, a gas turbine, arranged to drive the air compressor, a compressor of the product nitrogen, a steam turbine, arranged to drive the product nitrogen compressor, in which this water vapor turbine is part of a circuit in which the water vapor can be raised in temperature by the heat exchange of the water with the hot exhaust gases from the turbine of gas.

The air separation plant, according to the invention, offers a number of advantages. First, the need for large electric motors to drive the compressor and product air compressor is eliminated. Second, the water vapor cycle can be operated more efficiently than if the water vapor were to raise its temperature directly by burning a fuel. Third, if it is required to change the pressure of the product nitrogen in a period of time, the impulse of the compressor of the product nitrogen by means of the steam turbine and the gas turbine, provides greater flexibility to adjust the pressure of the product, compared to when an electric motor is used. The gas turbine, which is arranged to drive the air compressor is preferably the same gas turbine from which the hot exhaust gases are emitted. Preferably, the air separation plant further includes a turbine of more water vapor, adapted to initiate operation of the air compressor. This additional steam turbine is preferably located in a starter circuit, which includes a boiler to supply pressurized steam to the additional steam turbine and a condenser to condense the expanded water vapor emitted from the additional turbine of water vapor. The air separation plant additionally includes an adsorption apparatus to remove water vapor and carbon dioxide from the compressed air, a heat exchanger, to reduce the air to a temperature at which it is capable of being separated by rectification, at least one rectification column to separate the nitrogen from the air, and at least one turbo-expansion apparatus, to generate cooling. Preferably, the rectification column is a double rectification column, comprising a higher pressure stage, a lower pressure stage, and a reboiler condenser, thermally bonding the upper region of the higher pressure stage to a lower region of pressure. the lower pressure stage, the arrangement being such that, during operation, the condenser supplies the reflux for both stages of the double rectification column. If desired, in order to maximize the average pressure at which nitrogen is taken from the rectification column, a gaseous nitrogen stream can be taken from both the lower pressure stage and the higher pressure stage. In order to increase the rate at which reflux occurs, a portion of the nitrogen vapor, taken from the lower pressure stage, can be condensed and fed back to the lower pressure stage. The cooling necessary for this additional condensation can be supplied by taking a stream of liquid enriched with oxygen from the bottom of the lower pressure stage, reducing its pressure and thus reducing its temperature and exchanging the heat of the reduced pressure stream of the enriched liquid with oxygen with the nitrogen that is going to be condensed. An air separation plant, according to the invention, will now be described in exemplary form, with reference to the accompanying drawing, which is a schematic flow diagram of an air separation plant and the associated power generation plant. The drawing is not to scale. Similar parts in the Figures are identified by the same reference numbers. With reference to the drawing, an air separation plant 2 is shown by rectification. Plant 2 attempts to supply a nitrogen product, at high pressure. It includes a main compressor 4 of air, typically comprising a plurality of compression stages, and a compressor 6 of the nitrogen product, also typically comprising a plurality of compression stages. The remaining components of the air separation plant are indicated by the reference number 8. For ease of illustration, the remaining parts are represented by a rectangular symbol and need not be described here further. They are well known and the invention relates primarily to the operation of the compressors 4 and 6. In normal operation, the air compressor 4 is driven by a turbine 10, preferably through a gear arrangement 12. The components of the gas turbine 10 is not shown in Figure 1, but traditionally comprises a separate air compressor, a combustion chamber, having an inlet for air from the separate air compressor and an inlet for the fuel gas, and a turbo-expansion apparatus, to expand the combustion product emitted from the combustion chamber. The turbo-expansion apparatus and the separate air compressor are all mounted on the same shaft. The compressor 6 of the nitrogen product is driven by a steam turbine 14, preferably through a gear arrangement 16. The steam flows in a circuit from which the steam turbine 14 forms a part. Starting with the steam outlet from the steam turbine 14, this circuit comprises a water condenser 18, a reservoir 20, a heat recovery steam generator 22 and the inlet to the steam turbine 14 of water. In operation, the water vapor escaping from the turbine 14 is condensed in the condenser 18 and fed to the tank 20. The water is pumped at a high pressure by means of a pump (not shown) to the steam generator 22, in which this pressurized and superheated water vapor is elevated in temperature by the indirect heat exchange between the pressurized water and the hot exhaust gases from the gas turbine 10. Downstream of its passage through the steam generator 22, the gaseous exhaust from the turbine 10 is discharged into the atmosphere via the chimney 24. It traditionally takes several hours to start the air separation plant and take it to a state operation. stable. The nitrogen compressor 6, therefore, is typically ripped off after the air compressor 4. Therefore, if the gas turbine 10 is used to start the air compressor 4, alternative arrangements to the steam generator 22 need to be made to cool the hot combustion gases, emitted from the outlet of the gas turbine 10 . As shown in the drawing, the air compressor 4 is also operatively associated with a steam turbine 26. This steam turbine 26 is operated during the starting period of the air separation plant 8 to drive the air compressor 4, as shown, directly, or through a gear arrangement (not shown). In order to generate water vapor for the steam turbine 26, a start-up boiler 28 is provided, in which the water vapor is raised to the temperature and pressure desired by the combustion of a suitable fuel, for example , natural gas. In addition, the steam turbine 26 has a starter capacitor 30 associated with it, to condense the steam escaping from the steam turbine 26. The arrangement is that where the boiler 28 receives water from the tank 20 and raises the temperature of the water vapor. This water vapor expands in the turbine 26 and the resulting expanded vapor condenses in the condenser 30 and returns to the tank 20. Typically, an auxiliary pump (not shown) is used to pass the water under pressure from the tank 20 to the tank. boiler 28. Although the machines described above do not require any power supply in order to supply the power needed to power them, such supply is typically required for the purpose of operating the water pumps (not shown) and to control the operation of the water pump. boiler 28. The apparatus shown in the drawing may need to be operated in a place where there are no major electricity supplies. In order to generate the necessary electricity, a gas turbine or additional gas turbines can be operated. As shown in the drawing, there are two additional gas turbines 40. Each gas turbine 40 drives an electric generator 36 through a gear array 38. The generators 36 supply electrical power to an electrical system 38 adapted to supply electricity to the pumps (not shown) and other auxiliary systems associated with the apparatus shown. in the drawing, as for other uses. In particular, it may be required, in order to generate very large volumes of nitrogen for the increased recovery of the oil, to operate a plurality of plants of the same kind, as shown in the drawing. The gas turbines 32 can be used to supply electric power to the pumps and other auxiliary parts of these other plants. Several changes and modifications can be made to the plant shown in the drawing. For example, in the increased recovery of oil or gas, it is typically convenient to have a nitrogen source available at a pressure greater than 100 bar. Traditionally, to supply such pressure, an additional multi-stage nitrogen compressor (not shown) (not shown) is used in series with the nitrogen compressor 6. This compressor over nitrogen can also be driven by the steam turbine 14 by means of a separate arrangement of gears (not shown). Alternatively, an additional steam turbine (not shown) can be supplied for this purpose and can be supplied with superheated steam, pressurized, from the generator 20 and the expanded water vapor can return the condenser 18. Typically, the nitrogen is supplied to the compressor 6 of the product nitrogen at an elevated pressure in the range of 3 to 6 bar from the separation plant 2 of air. If desired, a further stream of nitrogen can be supplied at an intermediate stage of the nitrogen compressor 6 from the air separation plant 2 at a pressure greater than 10 bar.

Claims (4)

1. REVTf ICACIONEB 1. An air separation plant, which includes an air compressor, a gas turbine, arranged to drive this air compressor, a product nitrogen compressor, and a steam turbine, arranged to drive the compressor of the product nitrogen, in which the water vapor turbine forms part of a circuit in which water vapor is able to raise its temperature by exchanging heat from the water with the hot gaseous exhaust coming from the gas turbine. An air separation plant according to claim 1, in which the gas turbine, arranged to drive the compressor of the product nitrogen, is the same gas turbine that emits the hot gaseous exhaust. 3. An air separation plant, as claimed in claim 1 or claim 2, which additionally includes a turbine plus steam, to initiate operation of the air compressor. An air separation plant, as claimed in claim 3, in which the additional steam turbine is located in a starter circuit, which includes a boiler for supplying steam under pressure to the additional turbine of steam, and a condenser to condense the expanded water vapor, emitted from the additional steam turbine.