Abstract:
A system for power generation comprising a turbine system and a power generating system connected to said turbine system, wherein said turbine system comprises: 
     a compressor and inlet means for supplying fluid to said compressor for cooling said oxygen-containing gas; 
     a combustion means; 
     a gas turbine; 
     a recuperator connected with outlet of said compressor means, and the outlet for exhaust gases of said gas turbine means, for mutual heat exchange; 
     means for at least partially condensing water from the exhaust gases from said gas turbine means, said condensing means being connected with said outlet for exhaust gases of said gas turbine and further provided with an outlet for condensate and an outlet for discharging the remaining gas.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a system for power generation. Such systems generally comprise a turbine system, comprising both gas turbines and steam turbines, and a power generating system. At present the efficiency of the best known systems for power generation is about 55-60%. In such systems for power generation there is a need to improve their performance and their efficiency. It is an object of the present invention to provide a system for power generation having an increased efficiency, in particular above 55% and more in particular 58-62%. 
     SUMMARY OF THE INVENTION 
     The invention therefore provides a system for power generation comprising a turbine system and a power generating system connected to said turbine system, wherein the turbine system comprises: 
     a) a compressor means connected with an inlet for oxygen-containing gas, an outlet for compressed oxygen-containing gas and an inlet means for supplying fluid to said compressor means for cooling the oxygen-containing gas; 
     b) a combustion means provided with a fuel inlet and a flue gas outlet, said combustion means being connected with the outlet for compressed oxygen-containing gas of the compressor means; 
     c) a gas turbine means connected with said flue gas outlet of the combustion means and being provided with an outlet for exhaust gases; 
     d) a recuperator means connected with the outlet for compressed oxygen-containing gas of the compressor means, and with the outlet for exhaust gases of the gas turbine means, for mutual heat exchange; 
     e) at least a means for at least partially condensing water from the exhaust gases from the gas turbine means, said means for condensing being connected with the outlet for exhaust gases of the gas turbine means and further provided with at least an outlet for condensate and an outlet for discharging the remaining gas. 
     The cooling of said oxygen-containing gas with the fluid may be carried out directly or indirectly, during and/or after at least one compressor stage. For indirect cooling the fluid may be any conventional gaseous or liquid coolant, such as freon, water and air. For direct cooling the fluid may be water, methanol, ethanol and the like. 
     Advantageously, according to the invention the condensate in the condensate outlet has a temperature of ambient or above ambient or a temperature below ambient, e.g. 1-15° C. 
     In another advantageous embodiment of the present invention the fluid is supplied directly to the oxygen-containing gas during and/or after compression wherein the cooling is essentially obtained by evaporation of the fluid. 
     In still another advantageous embodiment of the invention the condensate is injected into the oxygen-containing gas during and/or after compression. This is particularly important in locations in which water required for that operation will constitute a supply problem. Preferably, therefor recuperator means are further connected with the fuel inlet of said combustion means for heat exchange, resulting in a further increase of the efficiency with 0.5. 
     More advantageously, the exhaust gases from the gas turbine means are expanded in at least one condensing turbine. 
     In another advantageous embodiment of the invention at least part of the exhaust gases from the condensing means are recycled to the inlet of the oxygen-containing gas of the compressor means. 
     Still more advantageously, at least part of the exhaust gases from the condensing means are recycled to a heat exchange means for heat exchange with the oxygen-containing gas supplied to the inlet for oxygen-containing gas of the compressor means. 
     In another advantageous embodiment of the present invention part of the exhaust gases from the condensing means are directly recycled to the inlet of the oxygen-containing gas of the compressor means and another part is recycled to a heat exchange means for heat exchange with the oxygen-containing gas supplied to the inlet for oxygen-containing gas of the compressor means. 
     Further, advantageously, the exhaust gas from a first condensing turbine is further expanded in at least a second condensing turbine. At least part of the exhaust gases from the turbine system are advantageously expanded to a pressure of 0.2-0.8 bara. 
     Advantageously, according to the invention the relatively cold condensate or gas is applied for cooling purposes and heat developed in the process is applied for heating purposes. 
     Preferably fluid to be supplied to the compressor is atomized in the oxygen-containing gas to be fed to the compressor means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described in more detail by way of example by reference to the accompanying drawing, in which: 
     FIG. 1 represents schematically a power generating system according to the present invention; 
     FIG. 2 represents schematically an advantageous embodiment of the present invention; 
     FIG. 3 represents schematically another advantageous embodiment of the present invention; 
     FIG. 4 represents schematically still another advantageous embodiment of the present invention; 
     FIG. 5 represents schematically a further advantageous embodiment of the present invention; and 
     FIG. 6 represents schematically a preferred embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a power generating system  1  according to the present invention. The power generating system  1  comprises a compressor means  2  provided with an inlet for oxygen-containing gas  3 , an outlet for compressed oxygen-containing gas  4  and a water inlet means  5  for quasi-isothermal compression of oxygen-containing gas in the compressor means  2 . It is noted, that the water inlet means  5  may be arranged such that for the quasi-isothermal compression of oxygen-containing gas water is added in and/or after the compressor means  2 . The water inlet means  5  are designed as required for the compressor means  2 . That is, the compressor means  2  may consist of one compressor with several compression stages and one or more of these stages are provided with water inlet means and/or water is injected after one or more compressor-stages. Alternatively the compressor means  2  may consist of several consecutive compressors provided with water injection means during or after each compressor in such a way that the compression is carried out quasi-isothermally. The compressed oxygen-containing gas outlet  4  passes through a recuperator  6  for heat exchange and is connected to a combustion means  7  which is also provided with a fuel inlet  8  and a flue gas outlet  9 . 
     The compressed flue gas present in the flue gas outlet is expanded in a gas turbine means  10  mounted on a shaft  11  for driving the compression means  2  and connected to the generator  12  for power generation. The expanded gas leaves the gas turbine means  10  via a turbine exhaust gas outlet  13  and passes through the recuperator  6 . Accordingly, heat exchange is effected between the hot exhaust gas (550 20   C.) from the gas turbine means flowing through duct  13  and the fuel (25° C.) in the fuel duct  8  and the compressed oxygen-containing gas in the compressed oxygen-containing gas duct  4 . 
     Subsequently, the turbine exhaust gas outlet  13  passes through a water inlet heat exchange means  14  for heat exchange of water supplied via the water inlet  15 . Accordingly, the water temperature is raised from 25° C. to about 200° C. 
     Finally, the cooled exhaust gas of 100-250° C. is supplied to a condensing turbine means  16  in which the exhaust gas is expanded further in this case to a pressure of 1 bara resulting in water condensation. The remaining cooled exhaust gas is supplied via an exhaust gas exit  17  to a stack  18 . The formed condensate is recycled via the pump  19  and the condensate recycling pipe  20  to the water inlet  15 . 
     FIG.2 shows another power generating system  22 . Equivalent means and other equipment items are referred to by the same reference numbers. 
     In contrast to the power generating system  1  of FIG. 1, in the power generation system  22  of FIG. 2, part of the exhaust gas leaving the condensing turbine means  16  is recycled via the exhaust gas recycling duct  23  to the oxygen-containing gas inlet  3 . 
     FIG. 3 shows a power generating system  24  according to the present invention, which comprises an exhaust recycling gas duct  23  connected to the oxygen-containing gas outlet  3 , whereas the remainder of the exhaust gas is branched off via duct  25  and to a heat exchange unit  26  for heat exchange with oxygen-containing gas supplied via the oxygen-containing inlet  3 , after which the exhaust gas is released via stack  27 . 
     FIG. 4 shows a power generating system  28  having a lay-out similar to the power generating system  1  of FIG.  1 . However, the power generating system  28  of FIG. 4 comprises a condensing turbine system consisting of a first condensing turbine  16  expanding exhaust gas to atmospheric pressure, and a subsequent second condensing turbine  29  further expanding the exhaust gas to 0.4 bara. Relatively cold condensate (5° C.) is removed via condensate pipe  30 . The exhaust gas leaving the second condensing turbine  29  via the duct  31  is supplied to a compressor  32  for compressing exhaust gas to atmospheric pressure prior to release via duct  33  and stack  18  to the atmosphere. 
     Cold condensate is pumped via pump  34  through a heat exchange means  35  and the relatively warm condensate (25 20   C.) is supplied to the condensate recycling pipe  20 . 
     In the heat exchange means  35  air  36  is cooled. This cooled air may be used for space cooling. 
     FIG. 5 shows a power generating system  37  according to the present invention. The compressor means comprises two compressors  38  and  39  for compressing oxygen-containing gas in a first stage to 3 bar and in a second stage to 9 bar. For quasi-isothermal compression water is added after each compression stage. To that end the water inlet means  5  comprises water inlets  40  and  41  supplying water to the outlet  42  of the compressor  38  and the outlet  4  of compressor  39 , respectively. 
     The gas turbine means  43  expands the flue gas from the combustion means to subatmospheric pressure (about 0.6 bara (700° C.)). After heat exchange in the recuperator  6  and the water inlet heat exchange means  14 , the exhaust gas is cooled in a condensor  44  to about 20° Co. Condensate formed is partly recycled via pump  34  and condensate recycling pipe  20  through heat exchange means  14  to the water inlet means  5 . The other part of the condensate is supplied via pipe  45  to a space heating means (not shown). 
     The cool exhaust gas leaving the condensor  44  is supplied via duct  46  to the compressor  32  for compression to atmospheric pressure and release via release duct  33  and stack  18  to the atmosphere. The efficiency of the power generator system  37  of the invention is about 60%. 
     Although subsequent to the second condensing turbine  29  exhaust gas is to be compressed in compressor unit  32 , still the efficiency is improved by about 2-4% because only a relatively small amount of dry and cool gas has to be compressed. 
     Finally, FIG. 6 shows a power generating system  47  according to the present invention. The lay-out of this power system  47  is similar to that of the power system  37  shown in FIG.  5 . Similar and equivalent unit operations and processes are referred to by the same reference numbers. 
     Condensate formed and separated in the condensor  44  (25° C.) is recycled via the condensate recycling pipe  20  directly to an atomizing unit  48 . In this atomizing unit  48  condensate is atomized in air supplied via the air inlet  3 . Air comprising atomized water (12-15 wt % on the oxygen containing gas in the form of droplets having a size of 1-5 μm) is supplied to the compressor  49  of the compressor means  2 . Condensate is not preheated in order to avoid an increase of the compression energy. The power system  47  has an efficiency of about 59%. 
     In relation to the various illustrating embodiments it is noted, that although the turbines  10  and  43  and  16  (and if appropriate also  29 ) are mounted on a common shafts  11  together with the compressor means  2  and  32 , and the generator  12 , in equivalent embodiments these shafts may be split into respective separate shafts driving separate generators and compressor means. 
     Although lower hydrocarbon fuels, such as methane are preferred, other fuels may be used as well. 
     In relation to condensation it is noted that preferable condensation is carried out in several steps. In a first step a small amount of condensate is formed. This first amount of condensate is relatively contaminated with some salt and/or particulates and is therefore less suitable for use in the quasi-isothermal compression. The bulk of the condensate though is pure and can be used for this purpose and both the contaminated condensate and the surplus pure condensate are suitable for irrigation, etc. 
     It will be appreciated that various modifications of the present invention will be apparent to those skilled in the art from the foregoing description. Such modifications are intended to fall within the scope of the appended claims.