Technical Field
The present disclosure relates to a field of electrical/ mechanical energy generation. Particularly,
the present disclosure relates to a process and a system for maximisation of power generation from
gas turbine. More particularly, the present disclosure relates to maximisation of power through a
5 combination of a thermodynamic process by recovering low level heat from gas turbine exhaust
and an absorption refrigeration cycle to produce chilled water that can be used for cooling air to
the inlet of gas turbine. Also, the present disclosure relates to involving heat/ thermal energy
storing devices which help in optimum operation with respect to change in atmospheric
temperature between different climates, day and night or even change in power demand from the
10 gas turbine.
Background
Gas turbines are widely used in various process industries. They are of various capacities directly
generating power in a generator from here which can be referred as GTG and or directly connected
15 to mechanical drives, from here can be referred as GTM. These drives are most reliable but need
clean fluids for firing.
With regards to the efficiency of the gas turbine, it mainly depends on the use of the exhaust gas
coming out of the gas turbine. The exhaust of the gas turbines is hot, and the temperature could
vary from 300oC-700oC and above based on the model of the gas turbine. The heat is generally
20 recovered in heat recovery steam generator, referred as HRSG to produce steam and then in a
make-up water heater, referred as MUH where water generally received at room temperature is
being heated before it goes into deaerators. The MUH is also sometimes referred as condensate
polishing heater (CPH). The temperature of the flue gas at the exit of HRSG and MUH/CPH is
generally maintained above 100- 150 oC and above based on the heat recovered in HRSG and
25 MUH/CPH. The sulphur content in the fuel also plays a role as the temperature of flue gas to the
stack is to be above the dew point to reduce the impact of corrosion.
To further improve the efficiency of the heat recovery system, any bottoming thermodynamic
cycle may be preferred to recover heat from the gas turbine exhaust. In recent years, there have
been substantial improvements in thermodynamic cycles employing multi-component working
3
fluids and a combination of absorption, condensation, evaporation and recuperative heat exchange
operations to reduce irreversible losses typical of conventional Rankine cycles. Generally, the lowlevel heat in the flue gas from the gas turbines could be thus tapped as electrical/ mechanical energy
by a thermodynamic process, like kalina cycle, organic rankine cycle (ORC), goswami cycle etc.
5 The efficiency of the gas turbine, gas turbine + HRSG, gas turbine + HRSG + rankine cycle, gas
turbine+ HRSG+ MUH/CPH, gas turbine + HRSG + MUH/CPH+ rankine cycle could be in the
range of 20-40%, 30-85%, 30-80%,30-90%,30-80%. This is due to heat lost in the flue gas which
could be in the range of 100-700oC and above based on the configuration as discussed above.
The present patent discusses about kalina/ organic rankine cycle (ORC) for the low-level heat
10 recovery. Though it helps in additional heat recovery, it also does not offer sufficient efficiency
improvement of the whole system as most of the heat recovered is lost in the cooling/ condensing
the partially expanded working fluid as well as liquid working fluid coming out of the separator
which is a typical characteristic of a rankine cycle.
The kalina cycle has been the subject of a number of patents including U.S. Pat. Nos. 6,216,436;
15 4,586,340; 4,604,867; 5,095,708 and 4,732,005, the disclosures of which are incorporated by
reference.
Further, to improve the efficiency of gas turbine, inlet air may be cooled. To cool the inlet air,
various techniques or technologies are adopted. In principle, a cold temperature source like simply
cold water or preferably chilled water can be used to cool the inlet air. Production of chilled water
20 again could consume energy in the form of electricity as in case of mechanical refrigeration, vapour
compression refrigeration (VCR) or alternatively by using thermal sources as in Vapour absorption
refrigeration (VAR). Sometimes, chilled water may be a by-product in a process which can be
directly used. The VCR process consumes power thus reduces the net power output whereas a
VAR process uses heat. Sometimes waste heat available in process streams to be air/water cooled
25 for downstream process, excess waste low-grade low-pressure steam etc. could be used, thus
making the process more economically viable.
Generally, if the exhaust temperature of the turbine in kalina/ organic rankine cycle (ORC) is
beyond 100-120oC, absorption cycle or ejector for vapour compression may be utilised for
generation of chilled water. In kalina cycle, the exhaust temperature of the turbine is generally
4
above 30-60oC based on the working fluid pair and its composition and exhaust pressure of the
turbine maintained. In some cases, it could be as high as > 60-80oC. This very low-level heat,
which is generally lost to atmosphere, cannot be used for above mentioned vapour absorption
refrigeration or ejector-based vapour compression refrigeration.
5 However, the continued quest for increased efficiencies in power generation equipment has
resulted in combining the kalina/ organic rankine cycles in an integrated combined cycle power
generating system in accordance with the present invention.
The present disclosure overcomes the problems of the current technology by the claimed process
and system. The inventors of present invention have discovered using the low-level heat from
10 exhaust of gas turbines in kalina/ organic rankine cycle (ORC) in adsorption (Solid based)
refrigeration cycle which can perform even at low temperature near and above 50oC for generation
of chilled water. The present invention is simple i.e., it does not have any complex equipment in
the cycles and has improved energy conversion efficiency.
15 Summary of the invention
The present disclosure provides a system and a process for maximisation of power generation from
gas turbine. The present process and system relate to maximisation of power through a
combination of a thermodynamic process by recovering low level heat from gas turbine exhaust
and an adsorption refrigeration cycle to produce chilled water that can be used for cooling air to
20 the inlet of gas turbine. This can help in maximising power generation in case of having a generator
to the gas turbine shaft or increase in mechanical energy output if it is connected directly to a drive.
The thermodynamic process converts the thermal energy from the heat source to the mechanical
energy. The inlet air of gas turbine is cooled using chilled water produced in refrigeration
techniques like absorption/adsorption or a vapour compression through an ejector. The present
25 process and system also employ a heat/ thermal energy storing devices which help in optimum
operation with respect to change in atmospheric temperature between different climates, day and
night or even change in power demand from the gas turbine. The process and system of the present
invention is simple i.e., it does not have any complex equipment in the cycles and has improved
energy conversion efficiency.
5
The present invention produces more mechanical energy/ work/electrical energy and helps in
increasing the efficiency of the entire system, operating the gas turbine process in an optimum
manner. By doing this, the efficiency of the system can also be increased by using the low-level
heat to produce more power. The capital expenditure (CAPEX) of the entire system can be
5 optimised based on the operation, type of gas turbine, atmospheric conditions etc.
Brief description of accompanying drawings
The present invention will be further understood with reference to the accompanying drawings,
wherein:
10 FIG. 1 is a schematic layout of a typical gas turbine configuration.
FIG. 2 is a schematic layout of a typical steam generation in HRSG and a steam turbine
configuration.
FIG. 3 is a schematic layout of a typical gas turbine -HRSG configuration with low level heat
recovery from flue gas.
15 FIG. 4 is a schematic layout of a typical low level heat recovery configuration by kalina cycle.
FIG. 5 is a schematic layout of a typical gas turbine-HRSG configuration with low level heat
recovery system (here kalina cycle) from flue gas along with thermal energy storage device in
upstream of kalina cycle.
FIG. 6 is a schematic layout of a typical low level heat recovery configuration by kalina cycle
20 along with thermal energy storage and adsorption refrigeration cycle.
FIG. 7 is a schematic layout of a system for maximisation of power having a combination of a
kalina cycle for recovering low level heat from gas turbine exhaust and an adsorption refrigeration
cycle by cooling air to the inlet of gas turbine (without HRSG and MUH).
FIG. 8 is a schematic representation of a system for maximisation of power having a combination
25 of a kalina cycle for recovering low level heat from gas turbine exhaust and an adsorption
refrigeration cycle by cooling air to the inlet of gas turbine (with HRSG and MUH).
6
FIG. 9 is a schematic layout of a system for maximisation of power having a combination of a
kalina cycle for recovering low level heat from gas turbine exhaust and an adsorption refrigeration
cycle by cooling air to the inlet of gas turbine (with HRSG and MUH).
5 Detailed description of the invention:
While the disclosure is susceptible to various modifications and alternative forms, specific aspects
thereof have been shown by way of examples and will be described in detail below. It should be
understood, however that it is not intended to limit the invention to the particular forms disclosed,
but on the contrary, the invention is to cover all modifications, equivalents, and alternative falling
10 within the spirit and the scope of the invention.
The applicant would like to mention that the examples and comparative studies are mentioned to
show only those specific details that are pertinent to understanding the aspects of the present
disclosure so as not to obscure the disclosure with details that will be readily apparent to those of
ordinary skill in the art having benefit of the description herein.
15 The present disclosure provides a system and a process for maximising power generation by
recovering low level heat from exhaust of gas turbines to a working fluid which in turn can provide
heat for a thermodynamic process like kalina cycle directly /indirectly. The present disclosure
describes using the low-level heat from exhaust of gas turbines in kalina cycle and in adsorption
(solid based) refrigeration cycle which can perform even at low temperature near and above 50oC
20 for generation of chilled water which can be utilised for inlet air cooling of gas turbine.
The present disclosure relates to a process for maximization of power generation (5), comprising
steps of:
a. passing an inlet air stream (1) through an air cooler (11) and then an air compressor (2)
to a combustion chamber (17) producing a flue gas (3);
25 b. at least a portion of the flue gas (3) is passed through a gas turbine (4) and a generator,
to generate power (5);
c. at least a portion of the flue gas (3) is passed through a kalina (7)/ organic rankine cycle
(ORC) to generate a vapor stream;
7
d. at least a portion of the vapor stream is passed through a turbine and a generator, to
generate power (5);
e. at least a portion of the vapor stream is passed through an adsorption refrigeration cycle
(8), to generate chilled water (9);
5 f. at least a portion of the chilled water (9) is used to cool the inlet air stream (1) through
the air cooler (11);
characterized in that, combination of the kalina (7)/ organic rankine cycle (ORC) and the
absorption refrigeration cycle (8) maximizes the power generation (5) by recovering low level heat
from the flue gas (3) and by cooling the inlet air stream (1), respectively.
10 One of the embodiments of the present invention, wherein at least a portion of the flue gas (3) is
passed through a heat recovery steam generator (HRSG) (6) to generate steam (15).
Yet another embodiment of the invention, wherein at least a portion of the flue gas (3) is passed
through a make-up water heater (MUH) (12) to generate steam (15).
Yet another embodiment of the invention, wherein at least a portion of the steam (15) generated
15 from the heat recovery steam generator (HRSG) (6) is passed through a steam turbine (20) and a
generator, to generate power (5).
Yet another embodiment of the invention, wherein at least a portion of the steam (15) generated
from the make-up water heater (MUH) (12) is passed through a steam turbine (20) and a generator,
to generate power (5).
20 Yet another embodiment of the invention, wherein a thermal energy storage device (10) is a hot
thermal energy storage device and/or a cold thermal energy storage device.
Yet another embodiment of the invention, wherein at least a portion of the steam (15) generated
from the heat recovery steam generator (HRSG) (6) and the make-up water heater (MUH) (12) is
sent to the hot thermal energy storage device (10) for thermal energy storage.
25 Yet another embodiment of the invention, wherein at least a portion of the flue gas (3) from the
gas turbine (4) is sent to the hot thermal energy storage device (10) for thermal energy storage.
8
Yet another embodiment of the invention, wherein at least a portion of the flue gas (3) from the
kalina (7)/ organic rankine cycle (ORC) is sent to the hot thermal energy storage device (10) for
thermal energy storage.
Yet another embodiment of the invention, wherein at least a portion of the chilled water (9) is sent
5 to the cold thermal energy storage device (10) for thermal energy storage.
Yet another embodiment of the invention, wherein at least a portion of the flue gas (3) which is
passed through the kalina cycle (7)/ organic rankine cycle (ORC) exchanges heat with a mixture
of a working fluid (25) in an evaporator (22).
Yet another embodiment of the invention, wherein the working fluid in the kalina cycle (7) is
10 selected from a mixture of ammonia and water, mixture of organic fluids and mixture of alcohols.
Yet another embodiment of the invention, wherein the working fluid in the organic rankine cycle
(ORC) is selected from iso pentane, butane, iso butane, pentane, etc.
Yet another embodiment of the invention, wherein the temperature of the flue gas (3) from the gas
turbine (4) is in the range of 300oC-700oC.
15 Yet another embodiment of the invention, wherein the temperature of the vapor stream produced
in the kalina (7)/ organic rankine cycle (ORC) is in the range of 90-200oC.
Yet another embodiment of the invention, wherein the temperature of the chilled water (9)
produced in the adsorption refrigeration cycle (8) is in the range of 2-20°C.
The present disclosure relates to a system for maximization of power generation (5), comprises
20 - an air cooler (11) configured to cool an inlet air stream (1);
- an air compressor (2) configured to compress the cooled inlet air stream (1);
- a gas turbine (4) and a generator, wherein the gas turbine (4) and the generator are
configured to generate power (5);
- a kalina (7)/ organic rankine cycle (ORC) configured to generate vapor stream;
25 - an adsorption refrigeration cycle (8) configured to generate chilled water (9);
9
characterized in that, combination of the kalina (7)/ organic rankine cycle (ORC) and the
absorption refrigeration cycle (8) maximizes the power generation (5) by recovering low level heat
from the flue gas (3) and by cooling the inlet air stream (1), respectively.
One of the embodiments of the invention, comprises a heat recovery steam generator (HRSG) (6)
5 configured to generate steam (15).
One of the embodiments of the invention, comprises a make-up water heater (MUH) (12)
configured to generate steam (15).
One of the embodiments of the invention, comprises a thermal energy storage device (10)
configured to store thermal energy.
10 Yet another embodiment of the invention, wherein the thermal energy storage device (10) stores
at least a portion of the thermal energy of the flue gas (3) from the gas turbine (4).
Yet another embodiment of the invention, wherein the thermal energy storage device (10) stores
at least a portion of the thermal energy of the steam (15) from the heat recovery steam generator
(HRSG) (6).
15 Yet another embodiment of the invention, wherein the thermal energy storage device (10) stores
at least a portion of the thermal energy of the steam (15) from the make-up water heater (MUH)
(12).
Yet another embodiment of the invention, wherein the thermal energy storage device (10) stores
at least a portion of the thermal energy of the vapor stream from the kalina cycle (7).
20 Yet another embodiment of the invention, wherein the thermal energy storage device (10) stores
at least a portion of the thermal energy of the chilled water (9) from the absorption refrigeration
cycle (8).
A typical gas turbine consists of mainly two sections, cold section and hot section. Typically, air
inlet, intake system, air compressor becomes part of cold section whereas combustion chamber,
25 turbine and exhaust system become part of hot section. This may vary from design to design. The
gas turbine also includes auxillary systems like fans, lube oil systems, fuel system etc. for safer
and optimum operation. The gas turbine operates by Brayton cycle with air as the working fluid.
The air as a working fluid passes through air inlet system to the air compressor. The compressed
10
air at higher pressure passes to combustion chamber where energy is supplied by combustion of
fuel and the temperature raises. This high-temperature and high-pressure gas, generally referred as
flue gas, enters a turbine, where it expands to produce shaft work. To produce power, the shaft is
connected to a generator. This combination of gas turbine along with generator is referred as gas
5 turbine generator, GTG. Alternatively, the mechanical energy can be used directly to other drives
like compressors, pumps etc. Generally, the air compressor of the gas turbine also lies in the same
shaft and thus energy required for compression of air is met by the mechanical energy generated
by gas turbine.
The gas turbines are constant volume machines. Thus, the power output from these machines
10 directly depends on the inlet air temperature. Thus, for gas turbines that receive air directly from
atmosphere, power production is low in summer compared to winter due to higher ambient
temperature in summer in comparison to winter. So, during summers when temperature is above
ISO conditions, to maintain constant power production or to increase power production to meet
peak demands generally observed in summers, the temperature of air going to the gas turbine is
reduced by cooling the inlet air to around 10-15o
15 C where the gas turbine provides good
performance as per ISO conditions. Reducing the temperature further may sometimes pose
problems related to ice formation of water in air etc. Formation of ice may increase pressure drop,
clogging the air filters etc. They can even damage the air compressor blades.
FIG. 1 is a schematic layout of a typical gas turbine configuration. Referring to FIG. 1, air (1) from
20 atmosphere is conpressed in an air compressor (2) for which the shaft work is provided from the
gas turbine (4). Air (1) and fuel (16) then burns in a burner section (17) to form flue gas (3) which
is then sent via a turbine (20) to produce power (5). The flue gas (3) is then further sent to heat
recovery systems (6) like HRSG or vented out simply to atmosphere.
Coming to the efficiency of the gas turbine (4), it mainly depends on the use of the exhaust gas
25 coming out of the gas turbine. The exhaust of the gas turbines is hot, and the temperature could
vary from 300oC-700oC and above based on the model of the gas turbine. The heat is generally
recovered in heat recovery steam generator (6), referred as HRSG to produce steam and then in a
make-up water heater (12), referred as MUH where water generally received at room temperature
is being heated before it goes into deaerators. The MUH is also sometimes referred as condensate
30 polishing heater (CPH). The temperature of the flue gas (3) at the exit of HRSG (6) and MUH
11
(12)/CPH is generally maintained above 100-150 oC and above based on the heat recovery area in
HRSG and MUH/CPH. The sulphur content in the fuel also plays a role as the temperature of flue
gas to the stack is to be above the dew point.
For example, if the area in the HRSG and MUH/CPH is not limiting, for natural gas firing, the
temperature of flue gas measured at the stack can be as low as 100oC-120o
5 C. In some designs,
there is a provision of auxiliary firing in HRSG for generating more steam, which increases the
potential of low-grade heat. In facilities where power is only required, and where steam is not
desired, the heat available in flue gas at the exit of gas turbine is not recovered and flue gas
temperature could be 300oC-700oC and above. Though a HRSG may be employed followed by a
10 steam Rankine cycle could increase the power generation efficiency of the whole system. Also,
some facilities may not have MUH/CPH if in case the water may not be required to be preheated
before further use or to deaerator thus flue gas temperature could be 100oC-700oC and above based
on supplementary firing or different levels of steam produced in HRSG. Further, if the MUH/CPH
exists still the temperature could be around 100-300 oC and above based on the heat recovery
15 capacity of the HRSG and MUH and the dew point of the flue gas based on the sulphur content of
fuel.
FIG. 2 is a schematic layout of a typical steam generation in HRSG and a steam turbine
configuration. Referring to FIG. 2, the flue gas (3) exchanges heat with incoming boiler feed water.
The water is heated up in stages to form steam. The steam (15) generated can be either directly
20 utilised or part of it can be used to produce power (5) by passing it through a steam turbine (20)
where in the steam pressure reduces.
FIG. 3 is a schematic layout of a typical gas turbine -HRSG configuration with low level heat
recovery from flue gas. Referring to FIG. 3, the fuel (16) is fired in the gas turbine (4) and
corresponding amount of air (1) is consumed. Further, the flue gas (3) generated goes in to HRSG
25 system (6) where steam (15) of various grades can be generated for which boiler feed water is sent
into the system. Further, part of the steam (15) that is generated can be let down in a turbine (20)
to a low grade (pressure) steam but producing power. The flue gas (3) after HRSG (6) can be
generally vented out. But to recover further energy, the flue gas (3) further passes into low level
heat recovery units like kalina (7)/ organic rankine cycle (ORC). In a typical kalina cycle, flue gas
30 (3) exchanges heat with a mixture of ammonia-water (25) before it vents into atmosphere.
12
In operation, a simple kalina cycle has these major steps:
1. Pumping a liquid flow of the working medium at an increased pressure;
2. Evaporation of liquid flow using the heat available.
5 3. Separation of total working fluid to gas and liquid in a separator
4. Expansion of the gaseous working medium flow in a gas expander, conversion of its energy
into a usable form and creation of the expanded working medium flow; and
5. Condensation of the partially condensed, expanded working medium flow to form the
liquid working medium flow.
10 In this cycle, the working fluid is generally a mixture of ammonia and water and other working
fluid pairs may also be utilised. Various kalina cycles are designed based on the composition of
working fluid, operating temperature and pressure. The efficiency of a simple kalina cycle is
around 10-15 %. Also, by additional equipments like recuperators, absorbers, super heaters, liquid
expanders/turbines ejectors, etc., the efficiency of the cycle is further improved. In a typical
15 recuperator (23), the heat available in the liquid working fluid from the bottom of the separator
(21) is used to preheat the cold working fluid coming out of the pump before going to the
evaporator (22). The absorbers are employed to recover the partially condensed, expanded working
fluid coming out of the expander. Superheaters are employed to further heat the gas coming out of
the separator with another heating medium before going to expander/turbine. Liquid
20 expanders/turbines are employed to recover the pressure energy in the liquid coming from the
bottom of the separator to generate electrical or mechanical energy. Ejectors are also employed for
a similar purpose but generally to raise the pressure of the gas coming out of the gas expander.
Other modifications like employing various heat exchangers based on heat available to raise the
temperature of working fluid, employing multiple turbines/ expanders etc. are also practiced. Thus,
25 the efficiency is further improved by 0.5-5 % and above. Not all these above-mentioned equipment
or modifications may be observed, and it is case to case basis.
FIG. 4 is a schematic layout of a typical low level heat recovery configuration by kalina cycle.
Referring to FIG. 4, the flue gas (3) exchanges heat with a mixture of ammonia and water (25) in
an evaporator (22). The process starts with an ammonia water mixture (25) is pumped to a high
30 pressure. It passes through an evaporator (22) where the vapour phase is generated. The mixture
13
then goes to a separator (21) wherein the vapour phase leaves to turbine (20) for generating power
(5). The liquid phase then mixes with the turbine outlet fluid before it is condensed in a condenser
(24) using cooling water (14). To improve the efficiency, the liquid from the separator (21) bottom
is used to preheat the feed from the pump outlet before the evaporator (22).
5 Further, in any operation process units, demand varies and also demand may vary between climate,
day-night etc. Similarly, the operation and power generation of gas turbine also gets effected with
ambient conditions. For the same machine the power production may drop by 1-10 % based on the
ambient temperature following the heat rate curves.
To address this, the present process and system employs a thermal energy storage device (10)
10 which optimises the power production and meets varying demand of power. The storage device
could be used to either produce constant power at varying process conditions, gas turbine operation
etc. The heat storage device (10) can be installed either on the flue gas (3) side at the exit of gas
turbine (4), HRSG (6), MUH (12) or at the exit of kalina (7)/ organic rankine cycle (ORC) turbine
exhaust or wherever suitable based on the operational and safety aspects.
15 FIG. 5 is a schematic layout of a typical gas turbine-HRSG configuration with low level heat
recovery system (here kalina cycle) from flue gas along with thermal energy storage device in
upstream of kalina cycle. To improve the efficiency and availability of the system, thermal energy
storage devices (10) can be utilised. For example, for gas turbine-HRSG configuration along with
low level heat recovery from flue gas, as shown in FIG. 3, the system can be optimised by placing
20 a thermal energy storage device (10) at the flue gas (3) ide that is going to low level heat recovery
system, here in this case kalina cycle (7) as shown in FIG. 5. This can help is continuous operation
of kalina cycle though the load changes happen in the gas turbine due to demand changes, time of
operation viz. day and night or due to seasonal changes. In some examples, HRSG (6) is having
supplementary firing to produce more steam (15). In few configurations, the HRSG can operate as
25 a standalone boiler with auxiliary air provision. Thus, having thermal energy storage can also help
in optimising the operation and also in proper sizing of downstream low level heat recovery system
though handling both peak and off-peak gas turbine and HRSG operation scenarios. Various high
temperature thermal energy storage materials viz. oils/wax, molten salts, liquid metals etc. can be
incorporated.
30 The adsorption refrigeration cycle comprises
14
- desorbing the refrigerant from the chamber, by heating the chamber;
- liquifying the refrigerant;
- evaporating the refrigerant to produce a cooling effect.
This chilled water can be utilised for cooling the air going to the inlet of air compressor of the gas
5 turbine thus maximising the power generation from the existing gas turbine assembly.
FIG. 6 is a schematic layout of a typical low level heat recovery configuration by kalina cycle
along with thermal energy storage and adsorption refrigeration cycle.
The efficiency of kalina cycle is generally very less may be around 10-15 %. Further, it requires
cooling water in the condenser to bring back the temperature of ammonia-water mixture to the
10 feed conditions. To improve the energy efficiency further, low level heat from the mixed stream
of turbine outlet and hot side fluid coming out of recuperator is recovered into an adsorption cycle
to produce chilled water. The adsorption refrigeration cycle requires hot stream preferably above
50o C to produce chilled water. It further requires cooling water and power for its operation. This
chilled water is also having multiple applications. As, the operation of kalina cycle is dependent
15 on the upstream gas turbine and HRSG, to provide a uniform and continuous hot water flow
required for an adsorption refrigeration cycle, high temperature thermal energy storage may be
utilised. Application of adsorption refrigeration cycle helps in reduction of overall cooling water
going into the system. To maintain hot temperatures for the adsorption refrigeration cycle, the
process changes viz. change in flow rate of ammonia-water mixture, composition of ammonia20 water mixture, upstream/ downstream temperature of low-level heat etc may be employed. The
configuration with a typical kalina cycle (7) with high temperature thermal energy storage (10)
and adsorption refrigeration cycle (8) is as shown in FIG. 6.
FIG. 7 is a schematic layout of a system for maximisation of power having a combination of a
kalina cycle for recovering low level heat from gas turbine exhaust and an absorption refrigeration
25 cycle by cooling air to the inlet of gas turbine (without HRSG and MUH). Referring to FIG. 7, an
inlet air stream (1) flows to an air compressor (2). The compressed air then flows to a combustion
chamber (17) where energy is supplied by combustion of fuel (16) and the temperature raises. This
high-temperature and high-pressure gas, generally referred as flue gas (3), enters a turbine (4),
where it expands to produce shaft work. To produce power, the shaft is connected to a generator.
15
The exhaust exiting the gas turbines flows as an inlet in kalina cycle (7). In operation, the working
fluid is pumped at an increased pressure into an evaporator (22). The total working fluid then goes
to a separator (21) providing a gas and liquid stream. The gaseous stream expands in a gas
expander, converting its energy into a usable form. The liquid stream from kalina cycle (7) enters
5 the adsorption refrigeration cycle (8) to generate chilled water (9). The chilled water (9) from
absorption refrigeration cools the inlet air stream (1) completing the loop.
FIG. 8 and FIG. 9 is a schematic representation/ layout of a system for maximisation of power
having a combination of a kalina cycle for recovering low level heat from gas turbine exhaust and
an absorption refrigeration cycle by cooling air to the inlet of gas turbine. Referring to FIG. 8, an
10 inlet air stream (1) flows to an air compressor (2). The compressed air then flows to a combustion
chamber (17) where energy is supplied by combustion of fuel (16) and the temperature raises. This
high-temperature and high-pressure gas, generally referred as flue gas (3), enters a turbine (4),
where it expands to produce shaft work. To produce power (5), the shaft is connected to a
generator. The exhaust exiting the gas turbines flows to a heat recovery steam generator (6),
15 referred as HRSG and a make-up water heater (12), referred as MUH. The exhaust of the gas
turbines is hot, and the temperature could vary from 300oC-700oC and above based on the model
of the gas turbine. The HRSG (6) and MUH (12) recovers waste heat from flue gas to produce
steam (15). The steam (15) leaving the HRSG (6) and MUH (12) is routed to a power generation
unit with steam turbine. In one of the embodiments, flue gas leaving the HRSG and MUH can be
20 routed to heat/ thermal energy storing devices (10).
The remaining flue gas leaving the HRSG and MUH is generally maintained above 100- 150 oC
and above based on the heat recovery area in HRSG and MUH/CPH. Typically, additional area is
provided after the HRSG and MUH/CPH end on the flue gas side before the stack (13). The
working fluid of the kalina cycle can be passed through this additional area. Sometimes,
25 modifications in the HRSG side may be done to reduce the additional pressure drop that may be
envisaged due to additional area. Further, in kalina cycle (7), the exhaust temperature of the turbine
is generally above 30-60oC based on the working fluid pair and its composition and exhaust
pressure of the turbine maintained. In some cases, it could be as high as > 60-120
oC.
In adsorption refrigeration, the refrigerant or adsorbate vapour molecules adsorb onto the surface
30 of a solid instead of dissolving into a liquid. In adsorption system, an adsorber adsorbs the
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refrigerant vapour into a solid, while in absorption system, an absorber absorbs the refrigerant
vapour into a liquid. Adsorption refrigeration also includes a generation process where refrigerant
vapour molecules desorbing from the solid. Though various combinations of adsorbent and
refrigerant are used, one pair is active carbon fiber and ammonia being an adsorbent and refrigerant
5 respectively. The following are the advantages of absorption refrigeration cycle in the system and
the process of the invention:
• efficient process of utilising energy;
• Even lower temperature (energy) 70 to 80oC can be recovered by the present invention;
• Adsorption cycle consumes less power;
10 • Less corrosion and air leakages.
• Environment friendly
• Economical process
The chilled water (9) from absorption refrigeration cycle (8) cools the inlet air stream (1) through
an air cooler (11) completing the loop.
15 Referring to FIG. 9, an inlet air stream (1) flows to an air compressor (2). The compressed air then
flows to a combustion chamber (17) where energy is supplied by combustion of fuel and the
temperature raises. This high-temperature and high-pressure gas, generally referred as flue gas (3),
enters a turbine (4), where it expands to produce shaft work. To produce power (5), the shaft is
connected to a generator. The exhaust exiting the gas turbines flows to a heat recovery steam
20 generator (6), referred as HRSG. The exhaust of the gas turbines is hot, and the temperature could
vary from 300oC-700oC and above based on the model of the gas turbine. The HRSG (6) recovers
waste heat from flue gas to produce steam (15). The steam (15) leaving the HRSG (6) is routed to
a power generation unit with steam turbine. In one of the embodiments, flue gas (3) leaving the
HRSG (6) is routed to heat/ thermal energy storing device (10).
25 The remaining flue gas (3) and the mixture of ammonia and water (25) as a working fluid enters
the kalina cycle (7) to generate vapor stream. This vapor stream is routed to a power generation
unit. In one of the embodiments, flue gas (3) leaving the kalina cycle (7) is routed to heat/ thermal
energy storing device (10). A portion of vapor stream is passed through an adsorption refrigeration
cycle (8), to generate chilled water (9). The chilled water (9) is used to cool the inlet air stream (1)
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through an air cooler (11). In one of the embodiments, chilled water (9) leaving the adsorption
refrigeration cycle (8) is routed to cold/ thermal energy storing device (10).
Thus, the present invention helps in increasing the efficiency of the entire system, operating the
gas turbine process in an optimum manner. By doing this the efficiency of the system can also be
5 increased by using the low-level heat to produce more power. The capital expenditure (CAPEX)
of the entire system can be optimised based on the operation, type of gas turbine, atmospheric
conditions etc.
The advantages of the disclosed invention are thus attained in an economical, practical, and facile
manner. While preferred aspects and example configurations have been shown and described, it is
10 to be understood that various further modifications and additional configurations will be apparent
to those skilled in the art. It is intended that the specific embodiments and configurations herein
disclosed are illustrative of the preferred nature of the invention and should not be interpreted as
limitations on the scope of the invention.

We Claim
1. A process for maximization of power generation (5), comprising steps of:
a. passing an inlet air stream (1) through an air cooler (11) and then an air compressor (2)
to a combustion chamber (17) producing a flue gas (3);
b. at least a portion of the flue gas (3) is passed through a gas turbine (4) and a generator,
to generate power (5);
c. at least a portion of the flue gas (3) is passed through a kalina (7)/ organic rankine cycle
(ORC) to generate a vapor stream;
d. at least a portion of the vapor stream is passed through a turbine (20) and a generator, to
generate power (5);
e. at least a portion of the vapor stream is passed through an adsorption refrigeration cycle
(8), to generate chilled water (9);
f. at least a portion of the chilled water (9) is used to cool the inlet air stream (1) through
the air cooler (11);
characterized in that, combination of the kalina (7)/ organic rankine cycle (ORC) and the
absorption refrigeration cycle (8) maximizes the power generation (5) by recovering low level heat
from the flue gas (3) and by cooling the inlet air stream (1), respectively.
2. The process as claimed in claim 1, wherein at least a portion of the flue gas (3) is passed
through a heat recovery steam generator (HRSG) (6) to generate steam (15).
3. The process as claimed in claim 1, wherein at least a portion of the flue gas (3) is passed
through a make-up water heater (MUH) (12) to generate steam (15).
4. The process as claimed in claim 2, wherein at least a portion of the steam (15) generated
from the heat recovery steam generator (HRSG) (6) is passed through a steam turbine (20) and a
generator, to generate power (5).
5. The process as claimed in claim 3, wherein at least a portion of the steam (15) generated
from the make-up water heater (MUH) (12) is passed through a steam turbine (20) and a generator,
to generate power (5).
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6. The process as claimed in claim 1, wherein a thermal energy storage device (10) is a hot
thermal energy storage device and/or a cold thermal energy storage device.
7. The process as claimed in claim 1, wherein at least a portion of the steam (15) generated
from the heat recovery steam generator (HRSG) (6) and the make-up water heater (MUH) (12) is
sent to the hot thermal energy storage device (10) for thermal energy storage.
8. The process as claimed in claim 1, wherein at least a portion of the flue gas (3) from the
gas turbine (4) is sent to the hot thermal energy storage device (10) for thermal energy storage.
9. The process as claimed in claim 1, wherein at least a portion of the flue gas (3) from the
kalina (7)/ organic rankine cycle (ORC) is sent to the hot thermal energy storage device (10) for
thermal energy storage.
10. The process as claimed in claim 1, wherein at least a portion of the chilled water (9) is sent
to the cold thermal energy storage device (10)for thermal energy storage.
11. The process as claimed in claim 1, wherein at least a portion of the flue gas (3) which is
passed through the kalina cycle (7)/ organic rankine cycle (ORC) exchanges heat with a mixture
of a working fluid (25) in an evaporator (22).
12. The process as claimed in claim 11, wherein the working fluid (25) in the kalina cycle (7)
is selected from a mixture of ammonia and water, mixture of organic fluids and mixture of
alcohols.
13. The process as claimed in claim 11, wherein the working fluid (25) in the organic rankine
cycle (ORC) is selected from iso pentane, butane, iso butane, pentane, etc.
14. The process as claimed in claim 1, wherein the temperature of the flue gas (3) from the gas
turbine (4) is in the range of 300oC-700oC.
15. The process as claimed in claim 1, wherein the temperature of the vapor stream produced
in the kalina (7)/ organic rankine cycle (ORC) is in the range of 90-200
oC.
16. The process as claimed in claim 1, wherein the temperature of the chilled water (9)
produced in the adsorption refrigeration cycle (8) is in the range of 2-20°C.
17. A system for maximization of power generation (5), comprises
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- an air cooler (11) configured to cool an inlet air stream (1);
- an air compressor (2) configured to compress the cooled inlet air stream (1);
- a gas turbine (4) and a generator, wherein the gas turbine (4) and the generator are
configured to generate power (5);
- a kalina (7)/ organic rankine cycle (ORC) configured to generate vapor stream;
- an adsorption refrigeration cycle (8) configured to generate chilled water (9);
characterized in that, combination of the kalina (7)/ organic rankine cycle (ORC) and the
absorption refrigeration cycle (8) maximizes the power generation (5) by recovering low level heat
from the flue gas (3) and by cooling the inlet air stream (1), respectively.
18. The system as claimed in claim 17, comprises a heat recovery steam generator (HRSG) (6)
configured to generate steam (15).
19. The system as claimed in claim 17, comprises a make-up water heater (MUH) (12)
configured to generate steam (15).
20. The system as claimed in claim 17, comprises a thermal energy storage device (10)
configured to store thermal energy.
21. The system as claimed in claim 20, wherein the thermal energy storage device (10) stores
at least a portion of the thermal energy of the flue gas (3) from the gas turbine (4).
22. The system as claimed in claim 20, wherein the thermal energy storage device (10) stores
at least a portion of the thermal energy of the steam (15) from the heat recovery steam generator
(HRSG) (6).
23. The system as claimed in claim 20, wherein the thermal energy storage device (10) stores
at least a portion of the thermal energy of the steam (15) from the make-up water heater (MUH)
(12).
24. The system as claimed in claim 20, wherein the thermal energy storage device (10) stores
at least a portion of the thermal energy of the vapor stream from the kalina cycle (7).
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25. The system as claimed in claim 20, wherein the thermal energy storage device (10) stores
at least a portion of the thermal energy of the chilled water (9) from the absorption refrigeration
cycle(8)