U.S. patent application number 13/991709 was filed with the patent office on 2013-09-26 for retrofitting a heating steam extraction facility in a fossil-fired power plant.
The applicant listed for this patent is Andreas Pickard, Thomas Schneider, Gerald Stief, Johannes-Werner Wein. Invention is credited to Andreas Pickard, Thomas Schneider, Gerald Stief, Johannes-Werner Wein.
Application Number | 20130247571 13/991709 |
Document ID | / |
Family ID | 45349165 |
Filed Date | 2013-09-26 |
United States Patent
Application |
20130247571 |
Kind Code |
A1 |
Pickard; Andreas ; et
al. |
September 26, 2013 |
RETROFITTING A HEATING STEAM EXTRACTION FACILITY IN A FOSSIL-FIRED
POWER PLANT
Abstract
A method for retrofitting an existing steam turbine with a steam
extraction facility is provided. The stem turbine has a plurality
of pressure stages and is integrated into a fossil-fired steam
power plant. A steam extraction line is connected to one pressure
stage or between two pressure stages of the steam turbine, and a
heating steam turbine is connected into the steam extraction
line.
Inventors: |
Pickard; Andreas;
(Adelsdorf, DE) ; Schneider; Thomas; (Aurachtal,
DE) ; Stief; Gerald; (Nurnberg, DE) ; Wein;
Johannes-Werner; (Gerhardshofen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Pickard; Andreas
Schneider; Thomas
Stief; Gerald
Wein; Johannes-Werner |
Adelsdorf
Aurachtal
Nurnberg
Gerhardshofen |
|
DE
DE
DE
DE |
|
|
Family ID: |
45349165 |
Appl. No.: |
13/991709 |
Filed: |
November 28, 2011 |
PCT Filed: |
November 28, 2011 |
PCT NO: |
PCT/EP11/71180 |
371 Date: |
June 5, 2013 |
Current U.S.
Class: |
60/648 ;
60/670 |
Current CPC
Class: |
F01K 7/38 20130101; Y02E
20/14 20130101; Y02E 20/16 20130101; F01K 17/00 20130101; F01K
17/02 20130101; F01K 23/10 20130101; F01K 7/22 20130101 |
Class at
Publication: |
60/648 ;
60/670 |
International
Class: |
F01K 17/00 20060101
F01K017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 8, 2010 |
DE |
10 2010 062 623.6 |
Claims
1-5. (canceled)
6. A method for retrofitting a steam turbine with a steam
extraction capability, the steam turbine comprising a plurality of
pressure stages and being integrated into a fossil-fired steam
power plant, comprising: connecting a steam extraction line to one
pressure stage or between two pressure stages of the steam turbine;
and connecting a heating steam turbine into the steam extraction
line.
7. The method as claimed in claim 6, wherein the steam extraction
line is connected to a hot reheat line of the steam turbine.
8. The method as claimed in claim 6, wherein the steam extraction
line is connected to a cold reheat line of the steam turbine.
9. The method as claimed in claim 6, wherein the steam extraction
line is connected to an overflow line of the steam turbine.
10. A fossil-fired power plant, comprising: a steam turbine
comprising a plurality of pressure stages and being integrated into
the fossil-fired steam power plant, wherein the steam turbine is
adapted to perform a method for retrofitting the steam turbine with
a steam extraction capability as claimed in claim 6.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the US National Stage of International
Application No. PCT/EP2011/071180 filed Nov. 28, 2011 and claims
benefit thereof, the entire content of which is hereby incorporated
herein by reference. The International Application claims priority
to the German application No. 10 2010 062 623.6 DE filed Dec. 8,
2010, the entire contents of which is hereby incorporated herein by
reference.
BACKGROUND OF INVENTION
[0002] There is a need to adapt existing fossil-fired power plants
to changing requirements. Steam power stations or combined-cycle
gas and steam power stations in particular are often subject to
demands for adaptation, especially for a retroactive implementation
of the capability to extract steam from the steam section of the
power station. This additionally extracted steam can be required as
process or heating steam for internal processes within the power
station process or for supplying other processes outside of the
actual power station process. Extracting steam from the steam
turbine process reduces the remaining steam volume which is still
available for the steam turbine process and which now can make no
further contribution to the generation of steam. As a consequence
the extraction of steam from the steam turbine process reduces the
efficiency of a steam power plant.
[0003] In order to enable a thermodynamically optimized concept to
be realized in a steam extraction retrofit that is now to be
implemented, the use of an extraction turbine would recommend
itself already at the time of construction of the power plant.
However, this concept would lead to an increased initial investment
since the turbine cannot be optimized simultaneously for operation
without extraction and with extraction. Retrofitting a steam
turbine plant with steam extraction capability is often technically
demanding and complex, as well as cost-intensive in terms of
implementation. If a steam extraction capability is realized only
as a result of a retrofit, substantial losses in efficiency are
likely into the bargain.
[0004] Converting an existing steam turbine plant to provide a
retroactive steam extraction capability, in particular for tapping
low-pressure steam, can be very complicated and labor-intensive,
however. Thus, for example, the dimensions of the power house may
not be sufficiently large to accommodate the additional piping for
extracting the steam, or the steam turbine or, as the case may be,
the power station process is not suitably configured for steam
extraction. In steam turbines having a separate casing for the
medium- and low-pressure stages it is at least easily possible to
tap low-pressure steam at the overflow line. In steam turbines
having a medium- and low-pressure stage housed in a single casing,
on the other hand, it is often not feasible to carry out retrofits
in order to extract the large volume of steam required, for which
reason the turbine has to be replaced in this situation. In any
event, however, when low-pressure steam is tapped into the
low-pressure section from the overflow line, the low-pressure
section needs to be adapted to handle the changed swallowing
capacity (steam volume flow).
[0005] Extracting steam from other sources within the power station
process is often likewise not cost-effective or possible in a
suitable manner. Thus, for example, extracting steam from a reheat
line of the steam turbine leads to load imbalance in the boiler if
no further expensive and complex measures are taken. Extracting
higher-value steam for the carbon dioxide separator must also be
ruled out unless further measures are undertaken, since this leads
to unacceptable energy losses.
[0006] A further problem that arises with the retrofitting of a
steam extraction capability is that when the steam extraction is
discontinued the steam that is now not required abruptly
accumulates to excess. This surplus steam now cannot simply be
returned to the steam turbine process, because the latter is
configured for operation with steam extraction, in other words for
a lower volume of steam.
SUMMARY OF INVENTION
[0007] The object of the invention is therefore to disclose a
method for retrofitting a steam extraction capability in order to
tap steam from the steam process of a fossil-fired power plant,
which capability can be realized in a simple and cost-effective
manner, and which in addition is thermodynamically favorable, so
that the efficiency losses due to the additional steam extraction
are minimized.
[0008] The object is achieved according to the invention by the
features of the independent claims. Also provided according to the
invention is a heating steam turbine which is connected to the
overflow line of the steam turbine.
[0009] The invention permits an extraction point to be chosen which
lies outside of the turbine. This enables retrofit capability to be
integrated without high initial investments. The use of a
back-pressure turbine with extraction points permits multistage
heating to be realized, which is more beneficial thermodynamically
than single-stage heating. Moreover, this retrofit concept permits
retroactive thermodynamic optimization, since the extractions are
only specified at the time of the retrofitting.
[0010] According to the invention the heating steam extraction is
decoupled from the main process through the use of the
back-pressure steam turbine. Because the back-pressure steam
turbine is not supplied until the time of conversion, no extraction
points need to be provided on the main steam turbine. This means
that retrofitting is possible even in a power station in which
heating steam extraction was not included in the planning at the
time of installation. In this case, however, it might be necessary
to carry out a modification to the low-pressure turbine.
[0011] Advantageously the steam extraction line is connected to a
reheat line. In the event of a deactivation of the steam extraction
function the low-pressure steam continues to be tapped from the
overflow line. For this reason an auxiliary condenser is connected
in parallel with the steam extraction line. The auxiliary condenser
is provided so that in the event of failure or intentional
deactivation of the steam extraction function the accumulating
excess steam will be condensed in the auxiliary condenser.
BRIEF DESCRIPTION OF DRAWINGS
[0012] Exemplary embodiments of the invention are explained in more
detail below with reference to figures, in which:
[0013] FIG. 1 is a schematic diagram of a steam turbine arrangement
comprising a back-pressure steam turbine according to the
invention,
[0014] FIG. 2 is a schematic diagram of a steam turbine arrangement
having steam extraction from the overflow line according to the
prior art.
DETAILED DESCRIPTION OF INVENTION
[0015] FIG. 2 shows a steam turbine arrangement having steam
extraction from the overflow line according to the prior art. The
steam extraction serves in this case to provide a district heating
supply using two heating condensers HZ-K. The district heating
system is connected to the gas and steam turbine power plant via
the overflow line of the steam turbine. There, steam (NAA) is
extracted and ducted by way of a steam line from the power house
UMC to the district heating building UND. The actual district
heating system in the form of 2.times.50% heating condensers is
located in the district heating building UND. Depending on the
required district heating capacity, provision of the district
heating is effected using a single stage. The two district heating
preheaters in combination can thermally transfer 265 MW at the
maximum into the district heating system during normal
operation.
[0016] Alternatively the district heating system can also be
operated with steam from the cold reheat cycle (KZU) (emergency
operation during steam turbine downtime). Capacity transfer into
the district heating grid is thermally limited in this case.
[0017] The district heating return-circuit water that is to be
heated is provided at the transfer point at a pressure of approx.
5-22 bar and flows via the two steam-heated district heating
preheaters (HzVW1 and HzVW2) back into the district heating flow
line to the district heating loads. The district heating flow line
and the district heating return line can each be separated from the
district heating water grid by means of a motorized butterfly
valve. Each HzVW can be shut off individually by means of a
manually operated shutoff valve on the input side and by means of a
motorized butterfly valve on the output side. They possess a common
bypass fitted with a motorized valve.
[0018] The steam for the two HzVWs is tapped during steam turbine
operation from the overflow line to the low-pressure (ND) steam
turbine (DT) by way of a motorized bleeder valve. Two nonreturn
valves in the line prevent backflow to the DT. A steam inspection
probe monitors compliance with the maximum permitted pressure in
this line. If the set value is exceeded the medium-pressure (MD)DT
quick-action shutoff valve is closed. The DT steam extraction lines
are drained via drainage lines fitted with motor-driven shutoff
valves to the condenser MAG and preheated. In order to achieve an
energetically favorable mode of operation the HzVWs are connected
to the system in a staggered manner: For that purpose the bypass of
the HzVWs is set to fully open before the district heating steam
extraction process is placed into service. The control butterfly
valves at the outlet of the HzVWs are closed and the heat
extraction begins with the opening of the outlet valve of the
HzVW1. After the open position is reached the control butterfly
valve in the bypass closes in a controlled manner in order to
increase the district heating capacity. As the demand for heat
increases the control butterfly valve at the outlet of the HzVW2 is
opened in a controlled manner and, as previously in the case of
HzVW1, closes the control butterfly valve in the HzVW as the demand
for heat increases further until the entire volume flows through
the HzVWs. If both HzVWs are in operation with the bypass closed
and the requirement for heating capacity continues to increase, the
steam pressure in both HzVWs is raised with the aid of the control
butterfly valve in the overflow line to the ND turbine and as a
result the heat output is increased in a controlled manner. In
bypass operation of the steam turbine the steam is tapped from the
KZU by way of a steam converter station. A steam inspection probe
monitors to ensure compliance with the maximum permitted pressure
on the low-pressure side. If the set value is exceeded the
corresponding converter valve is immediately closed. Any valve
leakages that could lead to a further increase in pressure are in
each case ducted to the atmosphere via a downstream safety valve.
The injection water for cooling the steam of the steam converter
station is taken from the condensate system downstream of the
condensate pumps. In order to protect against contamination of the
injection control fittings the injection water lines are fitted
with an upstream dirt strainer. In addition the section of pipeline
up to the control valve may be protected by means of a safety valve
in certain cases in order to ensure it cannot be damaged due to
heating of the enclosed condensate. The steam lines upstream of the
steam converter stations are preheated and drained to the drainage
system LCM via drainage lines fitted with motor-driven shutoff
valves. As the requirement for district heating capacity decreases
the HzVWs are powered down in precisely the reverse order to the
connection sequence.
[0019] The condensate in the HzVWs drains off geodetically or due
to the pressure difference into the main condenser, being ducted in
the process through a main condensate preheater in order thereby to
operate more energy-efficiently. A control valve in the drain line
keeps the fill level in the HzVWs constant within the predefined
limits. The two HzVWs remain under pressure on the hot water side
when the district heating system is not in operation so that an
escape of steam is reliably prevented. Both HzVWs are fitted with a
safety valve on the hot water side in order to discharge the
expanding heating water in the event of heating and enclosed
medium. Valves and fittings that are operated in the vacuum range
have a water seal adapter or are implemented with vacuum-tight
stems. The impulse lines of the fill level measurements of the
HzVWs are kept filled at all times by way of bubbler lines. A
safety valve is installed on both HzVWs in order to enable the
accumulating heating water to be ducted away in the event of
pipeline rupture or leaks.
[0020] The district heating system according to FIG. 2 has the
following tasks: [0021] ensuring heat input into the district
heating grid [0022] regulating the flow line temperature [0023] the
mass flow rate is regulated on the power station side
[0024] Example process parameters: [0025] return line temperature:
60-75.degree. C. [0026] flow line temperature: 90-110.degree. C.
[0027] heating water mass flow rate: max. 1400 kg/s [0028] district
heating capacity: approx. 20-265 MW.
[0029] The district heating system consists of the following main
components: [0030] two 50% district heating preheaters [0031]
heating condensate system without heating condensate pumps [0032]
steam provisioning via steam turbine extraction (NM) [0033] steam
provisioning system from cold ZU/KZU(LBC) incl. condensate
injection cooling (LCE).
[0034] FIG. 1 shows a steam turbine arrangement comprising a
back-pressure steam turbine according to the invention.
[0035] The district heating system is connected to the gas and
steam turbine plant exactly as in FIG. 2. Steam (NM) is extracted
from the overflow line of the steam turbine (DT) and ducted by way
of a steam line from the power house UMC to the district heating
building UND. Located there is a heating steam turbine including
all ancillary equipment necessary for operation, such as e.g.
lubricating oil system, evacuation system and drainage facilities.
The steam from the NM system is ducted either to the steam turbine
only or additionally to a third heating condenser (HzVW3). The
heating power output of the district heating system is realized in
up to three stages depending on the district heating capacity
required. Accordingly, two or even three heating condensers are
operated on the steam side as a function of demand. A heating
condenser (HzVW1 and HzVW2) is located under each steam turbine
outflow. Operating in combination at maximum steam turbine load,
these heating condensers can transfer, for example, 120 MW
equivalent thermal energy from the NM steam system into the
district heating grid. If an increased steam output of more than
120 MW equivalent thermal energy is to be extracted, steam is
injected into the heating condenser 3 (HzVW3) in addition. The
latter is supplied directly with steam from the NM system.
Alternatively the district heating system can also be operated with
steam from the cold reheat cycle (KA) (emergency operation during
steam turbine downtime). Capacity transfer into the district
heating grid is thermally limited to, for example, 220 MW in this
case. In the event of downtime/failure of the heating steam turbine
the entire district heating output can be transferred into the
district heating grid by way of the HzVW3. In this case the steam
supply to the heating steam turbine is interlocked and the steam is
supplied exclusively to the HzVW3.
[0036] The district heating system according to FIG. 1 has the
following tasks: [0037] ensuring heat input into the district
heating grid [0038] regulating the flow line temperature [0039] the
mass flow rate is regulated on the power station side
[0040] Example process parameters: [0041] return line temperature:
60-75.degree. C. [0042] flow line temperature: 90-110.degree. C.
[0043] heating water mass flow rate: max. 1400 kg/s [0044] district
heating capacity: approx. 20-265 MW.
[0045] The district heating system consists of the following main
components: [0046] double-flow heating steam turbine with a max.
terminal output power of, for example, approx. 14 MW [0047]
3.times. district heating preheaters [0048] heating condensate
system including heating condensate pumps steam provisioning via
steam turbine extraction (NM) steam provisioning systems from cold
ZU (KZU) LBC incl. condensate injection cooling (LCE).
[0049] The district heating system can be housed in a separate
building UND. A larger district heating building may be necessary
on account of the increased space requirement for the heating steam
turbine incl. ancillary equipment.
* * * * *