FIELD OF THE INVENTION
The present invention generally relates to a co generation/combined cycle power
plant using coal as the primary energy source and natural gas as the secondary
energy source. In particular the invention relates to a Heat recovery steam
generator (HRSG) system in a combined cycle/cogeneration plant, adaptable to
downstream of Gas Turbine fired by coal gas. More particularly, the present
invention relates to a device for import steam receiving and distribution and
regulating steam temperature.
BACKGRQUND OF THE INVENTION
The combined or cogeneration power plants which convert fossil fuel energy into
electrical energy is known to be more efficient in comparison to coal fired power
plant, and the formers are relatively easy and inexpensive to construct. In a
typical combined cycle / cogeneration plant the gaseous/liquid fuels are fired in a
gas turbine and HRSG.The exhaust gases leave the gas turbine at about 600
degc and contain a significant source of energy. To recover this energy, the
typical combined cycle or cogeneration plants has a heat recovery steam
generator (HRSG)through which the hot exhaust gases pass to produce steam
for the process and/or, for use the in steam turbine for producing power.
Although, the efficiency of the combined cycle power plants (CCPPs)is higher as
compared to the conventional coal fired power plants, but considering the limited
availability and high cost of the Iiquid/gasous fuels used in the CCPPs,theIGCCswhich uses abundantly available coal as fuel combined with high efficiency
is a preferred choice for the power plants. In the CCPPs,the natural gas/liquid
fuels are fired in a gas turbine, the HRSG installed behind the Gas turbine
recovers the heat from the exhaust by generating steam, which is fed to the
steam turbine. In the IGCC, the syngas required for firing in the gas turbine is
first being generated in a gasifier which is then cooled in a syngas cooler and
cleaned before being admitted into the gas turbine. In the syngas cooler, the hot
syn gases are cooled in a boiler which generates superheated steam for further
use. The degree of superheated steam in the boiler of the syngas cooler decides
the amount of steam generated. The superheated steam generated from the
boiler of the syn gas cooler is either fed to the steam turbine or gas turbine or to
both. The need to use bare tubes in the boiler of the syn gas cooler for handling
dust laden sysgases makes the size of the boiler of the syngas cooler larger. In
order to have a compact syngas cooler, firstly, the saturated steam from the
boiler of the syn gas cooler can be generated, which then can be further
superheated in the Heat recovery boiler installed behind the Gasturbine.
This invention deals with a method of importing the steam from the syngas
cooler boiler into the HRSGfor further superheating and method of controlling
the steam temperature by proper positioning of super heater surface and desuper
heater.
In the known IGCCsteam system, the turbine working steam is made from thesteam generated in the Heat recovery steam generator installed behind the Gas
turbine and the steam from the syngas cooler in the coal gasification system
which is depicted in Fig 1. In this configuration a coal supply device (1) supplies
coal to a gasifier (2), the syn gas from the gasifier (2) is cooled in a syngas
cooler boiler (3) which consists of a super heater (4), an evaporator (5), an
economizer (6). The cooled syn gas is passedthrough a gas cleanup system (8).
The syngas cooler (3) generates steam (7) for feeding to a steam turbine (18).
The cooled cleaned syngas from the gas cleanup system (8) is fed to a gas
turbine combustor (9) of a gas turbine (10). Air for the gas turbine combustor
(9) is provided by an air compressor (11). An exhaust gas heat recovery steam
generator (12) consisting of a super heater (17), an evaporator (14), an
economizer (13) uses the exhaust gas supplied from the gas turbine (10) as the
heat source. The saturated steam-water mixture from the evaporator (14)
passesthrough a drum (15) and after separation of water in the drum (15), it
passes through a link (16) to the super heater (17) for further super heating.
The steam generated by the Heat recovery steam generator (12) is supplied to
the steam turbine (18). The steam exhaust from the steam turbine (18) is
condensed in a condenser (19) is passedthrough a Deaerator (20) and the feed
water from the Deaerator (20) is pumped by a pump (21) to the feed water
system of the syn gas cooler boiler (3) and the exhaust gas heat recovery steam
generator (12).
In another prior art of the IGCCsystem of power generation, through generationof saturated steam in the syngas cooler boiler and importing this steam into the
exhaust gas heat recovery steam generator drum for further superheating for
use in the steam turbine which is described in (Fig 2). The fig 2 discloses a
system, wherein the syngas cooler boiler (3) consists of an evaporator (5) and
an economiser (6). The saturated steam (7) generated is fed to the drum (15) of
the exhaust gas steam generator (12). This steam along with the steam
generated for the HRSGis superheated in a super heater (17). The drum (15) is
sizedto accommodate larger steam quantity.
The major disadvantages of the prior art as depicted in fig 1 is that it limits the
amount of steam generated from the syngas cooler as superheated steam is
generated. Further the use of bare tubes for the surfaces, combined with
superheated steam production makes the syngas cooler size larger. The major
disadvantage of the prior art as depicted in Fig 2 is that the requirement of a
larger size of the drum along with separator.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose an import steam
receiving and distribution device, which receives the imported saturated steam
from the syn gas cooler boiler and from the HRSGdrum for further feeding to
the HRSGsuper heaters. Another object of the present invention is to propose an import steam receiving
and distribution device, in which a super heater system generate rated
parameters in both combined cycle (CC) and IGCCmodes of operation by proper
disposition of super heaters and de super heaters.
A further object of the present invention is to propose an import steam receiving
and distribution device, in which the super heater system is provided with a
bypass device in the HRSG,which facilitates operation of HRSGin either in CC
mode or IGCC mode thereby ~liminates the requirement of multiple de super
heater.
A still further object of the present invention is to propose an import steam
receiving and distribution device, in which the super heater system in the HRSG,
can accommodate a wide variation of steam quantities from the syngas cooler
boiler and the HRSG.
Yet further object of the present invention is to propose a method of receiving
imported saturated steam from syngas cooler boiler of the IGCe into HRSG,
including regulating the steam temperature in HRSGsuper heaters during normal
combined cycle mode of operation and during IGCe Mode of operation.
SUMMARY OF THE INVENTION
In accordance with the present invention an import steam receiving and
distribution device is provided in the Heat recovery steam generator (HRSG)inthe IGCC system, for operation of a super heater system at rated parameters
with and without import of steam from the boiler of the syngas cooler. The heat
recovery steam generator (HRSG) system, being f10wably connected to a gas
turbine via a transition duct acting as a passage for the exhaust gas from the gas
turbine, the HRSG comprising : a super heater formed of a plurality of tubes, de
super heater system consisting of plurality of de super heaters, a super heater
with or without a bypass system consisting of plurality of valves, an evaporator
consisting of a plurality of configured tubes; an economizer located downstream
of the evaporator; and an import steam receiving and distributing header device.
The saturated steam from the boiler of the syngas cooler is supplied to the
import steam receiving and distributing device of the HRSG, which also receives
saturated steam generated by the HRSG evaporator system. The mixed steam
enters the system of super heaters, de-super heaters for superheating the mixed
saturated steam for supply to the steam turbine. In accordance with the present
invention, a bypass device is provided in the superheater system of IGCC, which
is opened or closed on the mode of operation of the plant. The mode of
operation can be normal combined cycle with natural gas in gas turbine (gasifier
not in operation) or IGCC (With import steam from syn gas cooler boiler) for
achieving the rated steam temperature.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
FIGURE 1 is a schematic presentation of a HRSG in IGCC system as per prior
art. Figure 2 is a schematic presentation of an yet another HRSGin IGCCas per
prior art.
Figure 3 is a schematic view of the IGCCHRSGsystem that incorporates an
import steam receiving and distribution device constructed in
accordance with and embodying the present invention.
Figure 4 is a schematic view of the HRSGsuper heater system utilizing a
bypass device constructed according to the present invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
Figure 3 shows a coal handling system (1) feeding coal to the gasifier (2) which
generates high temperature coal gas (syn gas). This high temperature syn gas is
cooled in a syn gas cooler boiler (3) having an evaporator (5) and economizer
(6) which generates saturated steam (7) which is supplied to an import steam
receiving device (20). The cooled syn gases after cleaning in the gas cleanup
system (8) is fed to the combustion chamber (9) of the Gas turbine (10). The
compressor (11) of the gas turbine (10) supplies air to the combustion chamber
(9) of the gas turbine (10). The exhaust gases leaVing the gas turbine (10) is
fed to the Heat recovery steam generator (12) consisting of a superheater
system (17), an evaporator (14), an economizer (13). The steam water mixturegenerated from the evaporator (14), is passed through the drum (15) for
separating the water from the steam water mixture and the separated saturated
steam is supplied to the import steam receiving and distributing device (22)
through at least one first link (16). The steam received from the syn gas cooler
evaporator (5) is also fed to the import steam receiving and distributing device
(22), the mixed steam (23) is supplied to the superheater system (17). The
steam from the HRSG super heater system (17) is supplied to a steam turbine
(18), the exhaust of the steam turbine (18)is condensed in a condenser (19).
The condensate is heated in a deaerator (20) and the deaerated water from the
deaerator (20) is pumped through a feed pump (21) to the economizer (6) of the
syngas cooler boiler (3) and the economizers (13) of the heat recovery steam
generator (12).
According to the present invention, as indicated in Figure 3, the saturated steam
generated from the syngas cooler boiler (3) is fed to the import steam receiving
and distributing device (22). The saturated steam from the drum (15) of the heat
recovery steam generator system (12) is fed to the import steam receiving and
distributing device (22) through the first links (16). The mixture of the saturated
steam received from the syngas cooler boiler (3) and the HRSG (12) received in
the import steam receiving and distributing device (22) is further fed to the super
heater (17) through at least one second distributing links (23). The introduction
of the import steam receiving and distributing device (22) eliminates the need for
a larger drum for the heat recovery steam generator (12) as the steam from thesyn gas cooler boiler (3) is not fed to the HRSGdrum (15) and there is no need
for an extra separating devices in the drum. Since a larger drum is avoided due
to introduction of the import steam receiving and distributing device (22), the
startup / shutdown of the HRSGcan be faster compared to a system in which
import steam from the syn gas cooler boiler (3) is fed into the drum (15) of the
HRSG(12).
Another aspect of the present invention is the connecting links (7) between the
syn gas cooler boiler (3) and the import steam receiving and distributing device
(22), the first connecting links (16) between the HRSGdrum (15) and the import
steam receiving and distributing device (22), the second distribution links (23)
between the import steam receiving and distributing device (22) and the super
heater (17), can be of single or multiple connection for ease of manufacture/use
and for better flow distribution.
A further aspect of the present invention as indicated in fig 3, is the super heater
system designed for achieving the rated temperature both during IGCC mode
wherein the steam flow through the super heater (17) will be higher and during
normal CCPPmode, wherein the steam flow through super heater (17) will be
less as there will be not any steam flow from the syn gas cooler boiler (3), and
with the proper positioning of the de-super heater, and by proper selection of
single or multiple desuperheaters and selection of materials. Referring to figure 4, in another aspect of the present invention, a superheater
bypass device is introduced between the superheater sections for achieving the
rated steam temperature both during IGCC mode, wherein the steam flow
through the super heater becomes higher and during normal CCPP mode,
wherein steam flow through the super heater is lessened as there will not be any
steam flow from the syn gas cooler boiler (3). In IGCC mode, the syn gas
required for firing in the combustor (9) of the GT (10) is generated from the
gasifier (2) which is then cooled in the syn gas cooler (3), then cleaned in a gas
clean up system (8), after which it is fed into the combustor (9) of the gas
turbine (10). The exhaust gases leaVing the gas turbine exhaust is fed to the
Heat recovery steam generator (12) consisting of a superheater system (24, 25,
26, 27, 28), an evaporator (14), an economiser (13). The steam water mixture
generated from the evaporator (14) is passed through the drum (15) for
separating the water from the steam water mixture and the separated saturated
steam is supplied to the import steam receiving and distributing device (22)
through the first links (16). The steam received from the syn gas cooler
evaporator (5) is also fed to the import steam receiving and distributing device
(22), the mixed steam (23) is supplied to the superheater system. The steam
from the HRSGsuper heater system is supplied to a steam turbine (18), the
exhaust of the steam turbine (18) is condensed in a condenser (19). The
condensate is heated in a deaerator (20) and the deaerated water fron the
deaerator (20) is pumped through a feedpump (21) to the economiser (6) of the
syngas cooler boiler (3) and the economizer (13) of the heat recovery steam
generator (12). According to the present invention, as indicted in Figure 4, the saturated steam
generated from the syngas cooler boiler (3) is fed to the import steam receiving
and distributing device (22). The saturated steam from the drum (15) of the heat
recovery steam generator system (12) is fed to the import steam receiving and
distributing device (22) through the first links (16). The mixture of the saturated
steam received from the syngas cooler boiler (3) and the HRSG (12) received in
the import receiving and distributing device (22) is further fed to the superheater
through the second distributing links (23). The superheater system consists of
three parts. The first superheater system comprises a super heater (24), a desuperheater
(25); the second super heater system comprises a superheater (26)
separated by a bypass valve (30); and the third superheater system comprises a
superheater (28). The first super heater system shall be bypassed by an
operating bypass system device (27, 29 and 30). The bypass valve (30) shall be
opened and the valves (27, 29) are closed in the normal combined cycle mode of
operation when the gasifier is not in operation, and the bypass valve (30) shall
be closed and the valves (28, 29) are opened during IGCC mode of operation.
The valves (27, 29, and 30) shall be opened or closed fully/partially also.
Another aspect of the present invention, is that the bypass device may comprise
one or multiples valves thereof.
Yet another aspect of the present invention is that the bypass device maycomprise any type of valves for example, gate / globe / control valves, which
shall be opened or closed fully or partially and shall be controlled as part of the
operation requirement.
In a further development of the present invention, the tubes of the first
superheater system and the second super heater system can be bare or finned
or combination of bare and finned tubes based on the functional performance
requirements.
A further advantages feature of the present invention is that the valves of the
bypass device (27, 29 and 30) can be made up of any material to suit the
temperature requirement.
A still further advantageous development of the present invention is that the
bypassdevice (27, 29 and 30) automatically sensesthe mode of operation either
normal combined cycle mode (no import steam from syngas cooler boiler) or in
IGCCmode (Import steam from gasifier) and either closes or opens the bypass
device.
WE CLAIM
1. An import steam receiving and distribution device for operation of a super
heater system at rated parameters with or without import of stem from
the boiler of the syngas cooler, the device being disposed in the Heat
Recovery Steam Generator (HRSG) system in an Integrated Gasification
combined cycle (IGCC) power plant employing a super heater system, the
HRSGbeing f10wably connected to a gas turbine (10) of the IGCCvia a
transition duct acting as a passage for the exhaust gas from the gas
turbine (10), the HRSGcomprising a super heater formed of a plurality of
tubes, a de superheater system having a plurality of de superheaters, at
least one super heater with or without a bypass device having a plurality
of valves, and disposed in the super heater system, an evaporator having
a plurality of an economizer disposed downstream of the evaporator,
configured tubes, and the import steam receiving and distribution device,
the device comprising:
- a first of incoming single or multiple links (7) supplying steam from
the boiler (3) of the syngas cooler;
- a second set of single or multiple incoming links (16) supplying
steam from the evaporator (15) of the HRSG(12) of the IGCC;and
- a third set of single or multiple outgoing links from the header (22)
supplying the mixed steam to the superheater (17). 2. The superheater system as claimed in claim 1 shall have single or
plurality of desuperheaters.
3. The device as claimed in claim 1, wherein the superheater system
comprises a first superheater device having a superheater (24), and a de
super heater (25); a second superheater device having a superheater
(26) separated by a bypass valve (30); and a third superheater device
comprising a superheater (28), and wherein the first superheater device
is bypassed by an operating bypass system device (27, 29, 30).
4. The device as claimed in claim 1 or 2, wherein the bypass valve (30) is
opened, and the valves (27, 29) are closed in normal CCPP'smode, and
wherein the bypass valve (30) is closed and the valves (28, 29) are
opened during IGCCmode.
5. An import steam receiving and distribution device for operation of a super
heater system at rated parameters with or without import of stem from
the boiler of the syngas cooler as sUbstantially described and illustrated
herein with reference to the accompanying drawings.