DK144834B - Steam power plant with pressurized steam boiler and one with this integrated ECONOMIZER - Google Patents

Description

U4834

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a steam power plant having a pressurized steam boiler and an integral with this economizer, in which the steam boiler is pressurized by means of a charging group consisting essentially of a turbocharger driven by a gas turbine connected to the gas boiler and the speed of the charge group can be regulated. simultaneously with the amount of fuel depending on the pressure or the amount of fresh steam produced in the steam boiler.

Pressurized steam boilers with high flue gas velocities and forced circulation of the water to steam power plants have long been known under the name "Velox boilers". For regulating the charging group, usually a Ward-Leonard group is permanently coupled to the charging group. The amount of fuel is controlled by the steam consumption, which at the same time in a known way also affects the Ward-Leonard group and thus regulates the charge group speed and thus adjusts the supplied air volume 15 to the amount of fuel. At approximately 3/4 load of the steam boiler, the gas turbine's performance precisely meets the compressor's power requirements. At lower partial loads, the charging group consumes electrical energy, and at higher partial loads and at full load, which means the nominal power which is lower than the maximum power, and when overload is applied, the surplus power is supplied to the grid. The Ward-Leonard control permits changes in rpm within wide limits, but presents the disadvantage that the group is constantly running with and, in addition, expensive and complicated.

Steam boilers of this kind usually at full load only have a charge pressure of 2-3 bar and high gas speeds, which means that the exhaust gas temperature after the gas turbine is relatively high, so that a subsequent heating surface is not required which is not below the compressor's final pressure and therefore becomes very bulky and expensive. Since this subsequent heating surface can be practically only a feed water preheater, preheating of the feed water by means of extraction steam must be reduced, which degrades the efficiency of the circuit process and, in addition, the capacitor must be increased.

In addition, it is known to counteract the deterioration of the circulation of the feed water by using a combined process where the gas turbine group, which simultaneously serves to charge the boiler, is operated at the highest permissible temperature before the gas turbine. This reduces the production of steam because the hot gases are cooled less in the boiler, but on the other hand, a utility effect can be extracted over a generator belonging to the gas turbine. In such a combined process it will just be possible to offset the losses incurred as a result of the poorer water heating, but on the other hand significant disadvantages must be accepted. Thus, due to the risk of corrosion, the high gas temperature before the gas turbine only allows the use of very pure ash-free fuel, which results in substantially higher fuel costs. The heat exchanger arranged after the gas turbine is very voluminous and similarly expensive, partly because by increasing the temperature in front of the gas turbine, there is also a sharp increase in the exhaust gas temperature, and thus a large amount of heat must be transferred to keep the chimney losses small, and this because the heat transfer is 10 smaller. because of the lower gas pressure and therefore the gas volumes become large. The heat exchanger surface of this pressurized heat exchanger is many times larger than that of a charged steam generator. The large volume of the heat exchanger also causes greater space requirements and higher costs for foundations. In addition, the output must be divided into two generators, one for gas and 15 for the steam turbine, which costs the construction costs. As the gas turbine group draws a generator, its rpm is constant and the air flow at partial load can either not be reduced or reduced at all by a complicated construction, and thus large exhaust gas losses occur. Admittedly, this could be avoided by using a separate utility power turbine, which would, however, cost the plant a lot.

In order to avoid evaporation in the subsequent feedwater preheater by partial load, the temperature before the gas turbine must be lowered, which decreases the thermal efficiency.

The object of the invention is to provide a steam power plant of the kind mentioned initially of simple construction and of a good overall efficiency, which is designed so that no additional heat exchanger is required on the gas side of the pressurized steam boiler, and nevertheless, can be kept within the limits customary of such plants.

This problem is solved according to the invention by adjusting the charge group speed in the event of a change in the vapor volume or vapor pressure corresponding to a post-load appropriate value while constantly maintaining the equilibrium between the turbo compressor performance and the gas turbine performance and the charge group speed in the event of a disturbance of the load. the equilibrium at otherwise constant vapor flow or constant vapor pressure in the steam power can be regulated via a speed regulator, and in both cases the regulation can be effected by a bypass connection outside the gas turbine as well as a bypass located at the gas pressure of the economizer under full gas pressure. connection.

U4834 3

With this simple, reliable and very economical plant, the speed control is done by means of the boiler itself, and is done without interference from outside and without supply of energy from outside. The rpm and thus also the airflow is continuously adjusted according to the fuel quantity, so that the excess air in the steam boiler is practically constant at almost all operating situations and immediately after load changes. The high pressure ratio of the charge group also gives a high temperature of the compressed combustion air, whereby even heavy oil can be combusted without difficulty and without additional air heating required. Furthermore, the high pressure ratio enables small dimensions of the steam generator to be dispatched in the mounted state, i.e. as a single unit, and in addition, without the charge group giving effect, low exhaust gas temperatures are obtained, so that it is not necessary to conduct feed water preheating using the exhaust gases, which means that the thermal process can be optimized by preheating the feed water during use. of outlet steam.

In the drawing, an embodiment of the invention is shown schematically and simplified. The steam power plant itself consists essentially of a 20 high-pressure steam turbine 1 and a low-pressure steam turbine 2 jointly operating an electric generator 3, as well as a capacitor 4, a condensate pump 32, a feed water heater 5 heated by extraction steam, and a steam boiler 6. For charging the steam boiler, i.e. to bring its gas side up to the desired pressure, a charging group consisting essentially of a turbo compressor 7, a gas turbine 8, a starter motor 9 and a hydraulic clutch 10. serves all these parts. of the charging group sits on the same shaft.

A fresh steam regulator 12 controlling a drain 13 from a pressure oil line 14 belonging to the primary system, fed at 15 over a throttle location 16, operates in dependence on the vapor pressure or flow rate through a fresh steam line 11. The pressure oil line 14 is connected to both a a servomotor 17 which controls the fuel supply (not shown) via the steam boiler 18 of the steam boiler and with a servomotor 19 which displaces a cylinder 20 associated with the centrifugal regulator 21 of the charging group, whereby the control oil pressure in the secondary system pressure oil line 23 is changed by an outlet 22. The pressure oil line 23 is fed at 24 over a throttle location 25 and leads to a valve 26 in a bypass connecting 27 passing through the gas turbine 8 and to a servomotor 28 operating a valve 29 acting on a bypass connection 30 at the boiler portion 31 gas side. Instead of pressure oil control, an electric control with the same functions can also be used.

The individual parts cooperate and regulate the plant as follows:

At full load, the turbo compressor 7 compresses the combustion air to at least 9 bar, thereby heating the air to approx. 330 ° C, which facilitates the burning of heavy fuel oil. The steam boiler 6 is designed such that the gas temperature at the runoff is approx. 430 ° C, which is also the inflow temperature in the gas turbine 8. This, in connection with the high pressure ratio, results in an exhaust gas temperature after the gas turbine at clinic 150 ° C, which means that the chimney temperature is also only 10 150 ° C, since the chimney inflow end is usually located in the immediate vicinity of the gas turbine exhaust end, and the chimney temperature is always measured at the chimney inflow end. In this connection, it should be mentioned that the values mentioned are found to be particularly advantageous operating values. The upper limit of the exhaust gas temperature and chimney temperature must be set to 165 ° C.

If this limit is exceeded, a heat exchanger should be used to avoid excessive exhaust gas losses. Thus, according to the invention, the exhaust gas loss can be kept very low so that the necessity of a voluminous subsequent heating surface is eliminated. The turbo compressor 20 has no cooling, and thus the feed water must neither be heated by the compressed air nor by the exhaust gas, which allows optimum heating by means of extraction steam.

The temperature before the gas turbine is maintained by means of a regulation, which will be described in greater detail later, so low that the gas turbine just manages to operate the charging group's turbo compressor. This means that the expansion heat of the entire gas turbine, with the exception of bearing and radiation losses, is transferred to the compressor, so that the charge group has the same power as the one required in known plants by means of exhaust gas heated air preheater. At the same time, the group also produces a high pressure, thereby reducing the boiler heating surface to a fraction of a non-charged boiler.

In order to be able to reduce the rpm of the charge group by partial load, which gives the advantage that the combustion air quantity can be adjusted at any time according to the load of the steam boiler or according to the amount of fuel, the starter motor 9 is separated from the charging group by the clutch 10 and stopped as soon as the charging group after ignition in the combustion chamber has achieved the required speed for the balance between compressor power and turbine power. The group is then left to itself and controlled by the installed regulator. In this arrangement, the combustion air flow rate at a boiler load of approx.

50% is reduced to approx. 55% of the full-load combustion air volume, so that a practically constant excess of air can be kept in the steam boiler between full and half-load, which is very important to achieve clean combustion and 5 correspondingly less environmental pollution.

If the fresh steam pressure decreases because the steam turbine group, due to a desired increase in power, requires a larger amount of steam, the fresh steam regulator 12 will block the drain oil line 14 drainage, thereby increasing the pressure in the primary system and causing the servomotor 17 to open the steam boiler 18 and the fuel nozzle 18. the cylinder 20 of the centrifugal regulator 21 is displaced by the servomotor 19 so that the drain 22 is closed, thereby increasing the control oil pressure in the independent secondary system pressure oil conduit 23. This causes the valve 26 in the bypass gas 27 passing through the gas turbine 8 to be blocked. and that valve 29, and thus the bypass connection 30, at the gas side of the steam boiler is opened by the servomotor 28. This results in an increased flow rate through the gas turbine and a higher temperature before the gas turbine, and thus the charge group rpm and the combustion air flow respectively are adjusted to the new larger fuel 20. amount.

With temporarily rising fresh vapor pressure, i.e. in the case of falling loads, the same regulation process takes place, but in the reverse order.

In view of the efficiency, it is advantageous that the valves 26 and 29 are not simultaneously activated, but that with increasing 25 need for combustion air, the bypass connection 27 leading outside the gas turbine 8 is first closed and then the the bypass connection 30 at the gas side of the steam boiler, and that in case of decreasing need for combustion air, the bypass connection 30 is first closed at the gas side of the steam boiler and then opening of the bypass connection 27.

30 The two regulatory areas may then overlap somewhat, but may also have a narrow, neutral zone between them. All these possibilities can be easily realized, e.g. by appropriate dimensioning of the spring force of the valve 26 and the servomotor 28, the spring force of the servomotor having to be the strongest.

In this embodiment, it may be most economical to select the spring forces such that both bypass connections are blocked at full load. If the operating load exceeds full load, the bypass connection 30 at the gas side of the steam boiler 6 will at least temporarily open to supply the required combustion air quantity 6 as quickly as possible to the larger fuel quantity, and then close again when the operating load is again reduced. If the operating load falls below full load, the bypass junction 27 will be temporarily opened to adjust the charge group speed according to the smaller amount of fuel.

5 In this mite, the rpm and the combustion air quantity respectively can be adjusted as quickly as possible according to the fuel quantity.

These events can be accelerated by the use of gradient controllers that are activated at the rate of change instead of the usual controllers. In addition, it may occur that the charge group, by constantly adjusting the fresh vapor regulator 12, i.e. at constant load, changes its speed. This happens, e.g. when the ambient air temperature fluctuates strongly. In this case, too, the controller fully fulfills its task.

15 If the ambient air temperature under otherwise constant conditions in the steam power plant rises, the weight of the air transported by the turbo compressor 7 decreases, thereby disturbing the charge group equilibrium and the group rpm starts to decrease. The control oil drain 22 is closed by the centrifugal regulator 21 and the control oil pressure in the secondary system pressure oil line 23 begins to rise. Thereby the bypass valve 26 is closed and / or the valve 29 is opened, thereby increasing the flow rate of the gas turbine and / or the temperature before the gas turbine until the desired speed is reached again.

In addition, the entire regulation may be so dimensioned that the pressure in the pressure oil lines 14 and 23 decreases with decreasing fresh vapor pressure, but the result remains the same.