GB2117056A

GB2117056A - Steam- and gas-turbine power plant

Info

Publication number: GB2117056A
Application number: GB08301939A
Authority: GB
Inventors: Zoltan Vadas; Bela G Wenczel; Zoltan Belcsak; Geza Takacsy
Original assignee: Energiagazdalkodasi Intezet
Current assignee: Energiagazdalkodasi Intezet
Priority date: 1982-01-27
Filing date: 1983-01-25
Publication date: 1983-10-05
Also published as: IT8283487A0; GB2117056B; GB8301939D0; JPS58133407A; SU1517765A3; FR2526482B1; CH663448A5; IT1158321B; DE3302733C2; FR2526482A1; DE3302733A1; NL8203867A

Abstract

The heat from gas turbine exhaust is used to generate steam in a boiler and the steam generated is used to power a steam turbine. When, for example, two gas turbines 1 and one steam turbine 3 are provided in a station, and when it is desired to operate at full load in driving generators or compressors 2, both gas turbines 1 are operated and the heat from their exhaust generates enough steam to drive the steam turbine. However, when it is desired to operate at partial load only one gas turbine 1 is operated and additional steam is generated in associated boiler 4 by supplemental fuelling equipment 5. In this way, a combined cycle station can be operated at near maximum efficiency when running below peak power. <IMAGE>

Description

SPECIFICATION A method of operating turbines and an apparatus for use therein The invention can be used for driving the pressure intensifying stations of natural gas and oil lines and the power plants in combined gassteam cycle.

The so-called combined cycle, otherwise known as gas-steam cycle, offers excellent total efficiency, as a result of the further driving power gained from utilization of the waste heat of the gas turbines.

The combined cycle is employed particularly in electric power plants, but recently it has gained acceptance even in driving compressor stations of natural gas lines in combined cycle. The solutions according to the present level of engineering, however, do not sufficiently concentrate on changing the total power of the station at a high efficiency, which is of great importance, due to the operational character of said equipment.

Accordingly, the gas turbines are characterized by - apart from numerous advantageous features - a very low efficiency during their partly-loaded operation. In addition, the efficiency of the steam turbine also decreases during minor steam absorptions, thus the facility of gas-steam cycle can be operated only at a power being lower than the nominal one with low efficiency. An example of these disadvantages is that the efficiency of a 3 x 10 MW station at 30 MW power is 41 percent, at 22.5 MW power 35 per cent, while at 1 5 MW merely 25 per cent.

In many applications (island operated power plants, compressor stations) partial loading occurs frequently, thus an actual demand for a flexible, system and a system of high efficiency arises. The invention is aimed at essentially improving the total efficiency of facilities of gas-steam cycle mainiy in case of partial loading.

The essence of the invention lies in that the ratio of the machine units driven by gas, and steam turbines, respectively, of similar, or approximately similar performance is changed to 2:1, 1:1 or to the combination and/or multiple of said values at a similar, or approximately similar (+5 per cent) unit performance and cycle efficiency in such way, that - by way of a supplementary fuelling employed in the flue gas utilizing boilers (hereafter called flue gas boilers) and utilizing also the 02 content of the flue gas the 1 6-60 bar value of steam pressure being advantageous for the 2 ::1 gas turbine/steam turbine ratio is increased to a value of 40-1 50 bar, simultaneously increasing the superheating temperature of the steam from 300-4800C to advantageously 400--5400C, and the desired identical, or approximately identical unit performance is obtained in the steam turbine suitable for a steam operation of adjustable (sliding) parameters, by way of the steam of such increased working performance.

The essence of the apparatus according to the invention lies in that it has a flue gas boiler supplying steam with a working performance varying in a ratio 1:2 under varying steam pressure and steam temperature, where said boiler is provided with a supplementary fuel equipment utilizing also the 02 content of the flue gas for supplementary fuelling and it is connected to each gas turbines of the station (power plant) on the flue gas side, the spare parts of which (steamgas separating apparata, chambers, ducts, pumps) are all produced in an embodiment suitable for the levels of pressure and temperature during the operation and for adjusting them and/or their technical characteristics (cross section, speed of rotation) can be varied; the station (power plant) comprises one or two steam turbine driven machine unit(s) of identical, or approximately identical (+5 per cent) unit performance corresponding to one or two gas turbine driven machine unit(s), where said gas turbines are internally formed for supplying identical, or approximately identical (+5 per cent) shaft performance under various steam parameters, they are provided with Fittings distributing the loading between the two turbine parts suited for processing of the two steams of various pressure and temperature, and with an accordingly formed protecting and regulating system; the system made up of the gas turbines, the flue gas boilers, the supplementary fuelling equipment and the steam turbine(s) has a regulating apparatus controlled by the desired power requirements of the steam turbine(s) which is accomplished by changing the supplementary fuelling of the flue gas boilers.

The method and apparatus according to the invention will now be further described, purely by way of example, with reference to the accompanying figures 1 and 2.

The plant (compressor station or power plant) shown in figure 1 is made up of three machine units, two of which are driven by the gas turbine 1, while one of them by the steam turbine 3.

The driven machine 2 can be a compressor or a generator. Both gas turbines 1 are provided with a flue gas boiler 4 each comprising a supplementary fuelling equipment 5 utilizing also the 02 content of the flue gas. All the three machine units are in operation here, the flue gas boilers 4 of the gas turbines 1 develop from the flue gas of the gas turbines 1 - not using or using the supplementary heating equipment to a small extent only - sufficient steam for utilizing the full nominal performance of the machine 2 driven by the steam turbine 3. The steam is applied to the steam turbine 3 through the steam duct 6.

Fig. 2 shows another, alternative way of operation of the plant according to figure 1. In this case, merely two of the three machine units are in operation, e.g. because only the 2/3 part of the total performance is required. This is achieved by stopping one machine 2 driven by the gas turbine 1 and by operating the two operating machine units at full loading and at good efficiency in such a way, that the supplementary fuelling equipment 5 arranged on the flue gas boiler 4 of the gas turbine 1 of the machine unit Il is started at full capacity (at about 100 per cent excess boiler performance).Due to the steam turbine 3 of the machine unit Ill being suitable for operation of varying parameters, an identical performance with that of the way of operation shown in Fig. 1 is obtained by the steam developed at a higher energetics potential, preserving a practically good total efficiency. The machine unit I is not operated in this way of operation.

In addition to, or instead of the plant consisting of three, i.e. an odd number of machines, a plant consisting of two, i.e. an even number of machine units shown in Figure 2 can also be formed.

Accordingly, a plant of four machine units can be formed from two machines each, a plant of five machine units from 3 + 2 machines, etc. In order to increase operational reliability of the two machine arrangements (a gas turbine, a steam turbine), the boiler utilizing the flue gas can be provided with a heating equipment which is able to operate the steam turbine machine unit even when the gas turbine is out of operation.

The advantages of the method and apparatus according to the invention are: The known advantages of employing combined cycle are extended to the partially loaded operation of the plants, preserving the good efficiency of their operation.

Operational reliability of the plants of combined cycle is increased by the new way of operation.

- Easier investment and operation are obtained, due to the adjustable ratio of the gas turbine/steam turbine.

- Employing machines of identical performance results in advantages in operation and maintenance, as well as in easier installation of the new way of driving.

Claims

1. A method of economically varying the total performance of producing machine units driven in combined (gas-steam) cycle in pressure intensifying stations of natural gas and oil lines and in power plants, characterized in that the ratio of the machine units driven by gas turbine 1, and by steam turbine 3, respectively, is changed to 2 :1, 1 :1, and to the multiple of them, respectively, while preserving identical, or approximately identical (+5 per cent) unit performance and cycle efficiency in such a way, that the value of 1 6-60 bar of steam pressure being advantageous for a 2 :1 ratio of gas turbine 1 steam turbine 3 is increased to a value of 40-1 50 bar being advantageous for the 1::1 ratio of gas turbine/steam turbine by way of a supplementary fuelling equipment 5 applied in the flue gas boilers 4 of the gas turbines 1 which utilizes also the 02 content of the flue gas, simultaneously increasing the expedient 300-4800C superheating temperature of the steam to 400-5400C, and then the desired identical, or approximately identical unit performance is obtained in the steam turbine 3 being suited for an operation of varying (sliding) parameters, by way of steam of such increased working performance.

2. An apparatus for accomplishing the method as ciaimed in claim 1, in which it comprises a flue gas boiler 4 connected to each gas turbine 1 of the station (power plant) on their flue gas side and provided with a supplementary fuelling equipment 5 utilizing also the 02 content of the flue gas, said flue gas boiler developing steam of varying working performance in about a 1:2 ratio, where the spare parts of said flue gas boiler (gas-steam separating apparata, chamber, ducts, pumps) are all suitable for the levels of pressure and temperature during the operation and for adjusting them during the operation and/or their technical specifications (cross section, speed of rotation) can be adjusted; the station (power plant) is provided with one or two steam turbine 3 driven machine unit(s) of identical, or approximately identical (+5 per cent) unit performance corresponding to one or two gas turbine driven machine unit(s), where said gas turbine(s) 3 are internally formed for supplying identical or approximately identical (+5 per cent) shaft performance under various steam parameters; they are provided with fittings distributing the loading between the two turbine parts suited for processing of the two steams of different pressure and temperature, and with an accordingly formed protecting and regulating system; the system made up of the gas turbine(s) 1, flue gas boilers 4, supplementary fuelling equipment 5 and system turbine(s) comprises a regulating unit controlled by the desired power requirements of the steam turbine(s) 3 which is accomplished by changing the supplementary fuelling of the flue gas boilers 4.

3. A method of operating a station comprising at least one gas turbine, a steam boiler for raising steam from the gas turbine exhaust, at least one steam turbine powered by steam from the boiler and supplementary fuelling equipment for raising steam in the boiler, wherein the ratio of gas turbines to steam turbines in the station is in the range of from 2:1 to 1 the number of gas turbines operating being variable but the ratio always lying within the said range, the method comprising operating the fuelling equipment when the number of gas turbines operating is insufficient to run the steam turbine at or nearly at maximum efficiency.

4. A station comprising at least one gas turbine, a steam boiler for raising steam from the gas turbine exhaust, at least one steam turbine powered by steam from the boiler and supplementary fuelling equipment for raising steam in the boiler, wherein the ratio of gas turbines to steam turbines in the station is in the range of from 2:1 to 1 :1, means for varying the number of operating gas turbines within the above range, and means for controlling the fuelling equipment to provide sufficient steam from the boiler(s) to operate the steam turbine at or nearly at maximum efficiency.

5. A method of operating a station substantially as hereinbefore described, with reference to Figures 1 and 2 of the accompanying drawings.

6. A station substantially as hereinbefore described with reference to and as illustrated in Figures 1 and 2 of the accompanying drawings.