Power plants – Combustion products used as motive fluid – With addition of steam and/or water
Reexamination Certificate
2000-05-18
2002-09-24
Gartenberg, Ehud (Department: 3746)
Power plants
Combustion products used as motive fluid
With addition of steam and/or water
C060S728000, C123S541000, C123S542000
Reexamination Certificate
active
06453659
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns a device for the compressing of a gaseous medium and systems that apply such compressing devices, such as energy generating systems, gas separators, compressors and compressor systems for natural gas, air, and chemicals—such as ammoniac.
2. Brief Description of the Prior Art
Compressing a gaseous medium requires compression work, which work is directly proportional to the absolute temperature of the medium to be compressed. This means that compression work may be reduced by cooling the medium before and during the compression, and in the event of recycling, also after compression. This applies also if the medium is compressed successively in various stages. The main objective is a virtually ideal or quasi-isothermal compression.
The medium is cooled by introducing a liquid evaporation agent (usually water). The evaporation agent is introduced in the form of droplets that evaporate. The heat required for evaporation is provided by the medium, which consequently cools.
In principle, it is not necessary that the sprayed droplets of the evaporation agent evaporate completely. Incomplete evaporation of the droplets, however, may result in droplets of the evaporation agent coming into contact with the interior of the compressor unit, which may lead to erosion and corrosion of parts of the compressor unit.
The objective, therefore, is to introduce as tiny droplets as possible (1-10 &mgr;m). The smaller the droplets, the likelier the possibility that they will evaporate completely, but also the less likely that they will come into contact with the structure of the compressor unit. However, if the medium has a high velocity and/or the air residence time in the compressor unit is short, there usually is insufficient time for full evaporation.
DE-A-41 14 678 relates to a method for the atomisation of a fluid for a gas turbine. The atomisation of the fluid has to take place over the entire length of the compressor at a spraying pressure of 5-20 bar above the compressor pressure. The maximum quantity of fluid to be atomised—water in particular—lies between 0 to 0.2 kilogram per kilogram air and may not be exceeded. Finally, it is indicated that the manner wherein the fluid is atomised in the compressor has not yet been constructively solved.
U.S. Pat. No. 4,478,553 relates to the isothermal compression in the compressor of a gas turbine. Atomising means are strategically positioned in the rotor structure. The water to be dispersed is not pre-heated and the size of the droplets of the atomised evaporation agent is preferably maintained at between 2 and 10 &mgr;m.
U.S. Pat. No. 5,388,397 relates to a method for operating a turbocompressor, whereby air is compressed in two stages and cooled in between in an intercooler. The warm water of the intercooler is cooled in subsequent evaporating vessels and the resulting steam is transferred very compactly to the environment by spontaneous evaporation according to a flash method. The evaporated amount is made up to by a corresponding amount of fresh water.
EP-A 0 821 137 describes a system for generating energy, whereby the gas to be compressed is cooled by atomising water droplets with a drop size of 1-5 &mgr;m. Under certain conditions, however, the required flow rate of atomised water droplets is too small.
SUMMARY OF THE INVENTION
The present invention aims to provide a compressor device in which a gaseous medium may be compressed at relatively low temperatures by applying very small droplets of evaporation agent (the median is smaller than 5 &mgr;m, generally smaller than 3 &mgr;m, preferably smaller than 2 &mgr;m, e.g. 1.2 &mgr;m) whereas sufficient flow rate of this type of atomised droplets may be generated in dependency of the flow rate of the medium to be compressed.
Simultaneously, the present invention aims to provide a very adequate manner of cooling a gaseous medium, so that the cooling capacity of existing or required gas coolers (intercoolers) may be reduced or that they may be replaced.
This is achieved according to the invention by a device for compressing a gaseous medium, generally including a compressor unit provided with a medium inlet, an outlet for the compressed medium and of means for atomising a liquid evaporation agent in the medium, wherein the atomising means have at least one flash atomisation unit, mounted and arranged such, that the atomised evaporation agent fragmentises by the formation of gas in the atomised evaporation agent.
The atomising means of this compressor unit includes an inlet for evaporation agent and an outlet for evaporation agent into the gaseous medium line. It is possible that this gaseous medium still has to be compressed, is in the process of being compressed or has already been compressed. In the latter instance, the compressed medium may still be added to a subsequent compressing unit or may in part be recirculated. The atomising means usually also contain a very large number of atomisers via which the evaporation agent is sprayed into the gaseous medium.
In principle, any known type of atomiser may be used in the flash atomisation unit. Suitable ones are, for example, swirl atomisers, slot atomisers, orifice atomisers, rotating bowl atomisers and, if necessary, pen atomisers. Of importance is only that the atomiser gives off droplets or a film of evaporation agent to the gaseous medium, under circumstances changed to such extent that flash atomisation takes place subsequently. Flash atomisation means that the liquid evaporation agent arrives in the gaseous medium under such conditions that as a result of the pressure drop over the atomiser, boiling bubbles or gas bubbles are generated in the droplets or film of the evaporation agent, i.e. gas or vapour is formed in the evaporation agent. This so-called flashing or precipitation results in the explosion or fragmentation of the droplets or film of the evaporation agent as a result of the sudden partial boiling or gas precipitation. Such fragmentation results in the generation of very tiny droplets of evaporation agent in the gaseous medium. After fragmentation, the median size of the evaporation agent is less than 5 &mgr;m, in general smaller than 3 &mgr;m, preferably smaller than 2 &mgr;m, e.g. 1.2 &mgr;m.
This means that atomisers may be employed in the atomising means insofar as they result in droplets of the said median size after fragmentation. Of importance in this respect is that the atomising means, the flash atomisation units in particular, are mounted and arranged such that the atomised evaporation agent fragments by the generation of gas in the atomised evaporation agent.
Preferably, a flash atomisation unit is used that is provided with swirl atomisers. In such a known swirl atomiser, the evaporation agent is put in swirling motion in a swirl chamber. The swirling evaporation agent exits via an outlet. It has appeared that the thickness of the exiting layer of evaporation agent is only a fraction (e.g. 10%) of the diameter of the outlet passage. The subsequent flash fragmentation results in droplets having (dependent on the pressure drop, temperature and diameter of the outlet passage) a median size of 5 &mgr;m or less. Because of the reduced size of the droplets of evaporation agent, there will be less risk of contact with the interior of the compressor unit, which means that the entire length of the compressor unit can be cooled.
It will be clear that in order to realise this fragmentation, it is important that the conditions (in particular the changing of conditions) under which the evaporation agent is atomised in the gaseous medium must be optimal for fragmentation. Important conditions for flash fragmentation are the temperature of the evaporation agent, the atomisation pressure under which the evaporation agent is atomised in the gaseous medium, and the outlet passage diameter. Therefore, the flash atomisation unit preferably, has means for adjusting the temperature of the evaporation agent and/or the atomisation pressure.
As indicated above
Van Liere Jacobus
Van Paassen Cornelis Adrianus Antonius
Gartenberg Ehud
N. V. Kema
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