Power plants – Motive fluid energized by externally applied heat – Having apparatus cleaning – sealing – lubricating – purging,...
Reexamination Certificate
2000-10-12
2001-11-20
Nguyen, Hoang (Department: 3748)
Power plants
Motive fluid energized by externally applied heat
Having apparatus cleaning, sealing, lubricating, purging,...
C060S659000
Reexamination Certificate
active
06318087
ABSTRACT:
This application claims priority under 35 U.S.C. §§119 and/or 365 to Appln. No. 99810956.5 filed in Europe on Oct. 21, 1999; the entire content of which is hereby incorporated by reference.
FIELD OF THE INVENTION
The invention relates to steam power plants from which large amounts of water or process steam are removed from the circuit continuously, for example for industrial purposes. The invention relates in particular to a system for the simultaneous bleeding of the steam condenser and of the degassing system for the make-up water supplied.
BACKGROUND OF THE INVENTION
The power plants from which large amounts of process steam are removed for industrial purposes are generally known. Relatively large amounts of steam are removed from such power plants for a prolonged or even the entire operating time. In various industrial applications for process steam, such as for example in paper factories, there is no return flow into the water/steam circuit of the power plant. Therefore, the amount of condensate and steam in the circuit has to be maintained by continuously supplying correspondingly large amounts of make-up water.
If only small amounts of make-up water are supplied to a power plant, or if this water is supplied only for a brief period, this make-up water is generally supplied directly to the steam condenser, for example by being sprayed over the tube bundles, where it is degassed in coolers which are present. The steam/gas mixture which is formed is extracted by bleed devices.
By contrast, if large amounts of make-up water are supplied to a power plant over a prolonged period or continuously, this make-up water is firstly degassed in a degassing system and is only then supplied to the condenser. Both degassing means and condenser are connected to bleed pumps which remove the steam/gas mixture from the circuit of the power plant. Compared to a power plant to which small amounts of make-up water are supplied, the demands imposed on the capacity of the bleed system are increased. These capacity demands are often determined by desired limits or ranges for the condenser pressure and for the oxygen content in the condensate which is taken out of the condenser for reuse for steam production. The lower these desired limits and the larger the amounts of steam and make-up water, the greater the demands imposed on the capacity of the extraction system.
FIG. 1
diagrammatically depicts part of a steam power plant with an example of a bleed system from the prior art, which removes the steam/gas mixture from a make-up water degassing means and a condenser. In this case, a suction arrangement is connected to the two units via two lines, each of the two lines having a diaphragm of predetermined aperture size, by means of which the suction capacity at the individual subsystems is predetermined. The size of these individual diaphragms and the ratio of the two diaphragm sizes, for a specific operating load of the power plant, that is to say a specific amount of steam to the condenser, and for a specific amount of make-up water, are such that an oxygen content in the condensate and a condenser pressure which are within the respectively desired ranges are established.
However, in power plants from which process steam is removed for industrial purposes, the amount of process steam removed and the supply of make-up water may vary considerably over time. At the same time, the current consumption and thus the amount of steam to the condenser may also fluctuate. However, if the suction capacities at the degassing system and condenser are predetermined by the diaphragm sizes, while the amounts of steam and make-up water vary, there is no guarantee that the overall system will be optimally set. For example, a predetermined distribution of the suction capacity to condenser and degassing means may lead to a very low oxygen content in the condensate, which is well below the desired limit, while, however, the bleeding of the condenser is insufficient, so that the condenser pressure rises. This reduces the condenser capacity and leads to associated losses in electrical output.
To avoid the risk of insufficient suction capacity, the total capacity of the bleed system may be sufficiently great to ensure that there is sufficient suction capacity for any possible current consumption and for any possible amount of make-up water supplied. However, at lower operating loads and with small amounts of make-up water, this would lead to excess capacity on the part of the bleed system and to unnecessary investment and operating costs.
SUMMARY OF THE INVENTION
The object of the invention is to provide a system for simultaneously bleeding the degassing means and the condenser in power plants of the type described in the introduction, in which the total suction capacity and the distribution of the suction capacities to the individual subsystems is optimized, so that in the event of fluctuation of the current consumption and the amount of make-up water supplied, the oxygen content in the condensate of the condenser and the condenser pressure remain below predetermined limits. The intention is that there should be no excess capacity on the part of the suction for the bleed system, together with the associated costs.
A power plant from which large amounts of process steam are removed and to which make-up water is supplied continuously has a degassing system for the make-up water supplied, which as a subsystem of the condensation system is connected to the condenser. The power plant also has a system with bleed pumps and at least two lines, of which a first line connects the bleed pumps and the condenser and a second line connects the bleed pumps and the degassing system. The invention consists in the fact that a control member, such as for example a regulating valve, a regulating diaphragm or a readjustable restrictor, is arranged in at least one of the lines which connect the bleed pumps to the units to be bled, with the result that the suction capacity in that line or those lines can be varied while the power plant is in operation.
The distribution of the suction capacities to the individual lines is regulated or adjusted by the regulating valve or the readjustable restrictor by changing the aperture size in that line. The regulation and readjustment take place via an automatic control circuit or manually on the basis of measured variables in the water/steam circuit, in particular the pressure in the condenser and/or the oxygen content in the condensate or make-up water system.
Setting the distribution of the suction capacities results in the oxygen content and the condenser pressure being within their desired ranges or reaching a set value.
In a first embodiment, a regulating valve, a regulating diaphragm or an adjustable restrictor is arranged in the line from the bleed pumps to the condenser, the line from the degassing system having a diaphragm of predetermined aperture size. In this way, bleeding of the condenser is regulated or adjusted according to the measured condenser pressure, so that the latter reaches or is below a desired set value. The diaphragm size in the line from the degassing system is designed in such a way that, for a predetermined total suction capacity of the bleed pumps, an oxygen content in the condensate which is in the desired set range is achieved even with the maximum amount of make-up water supplied and the maximum aperture of the control member in the first line.
In a second embodiment, a control member is arranged in the line from the degassing system, while the line from the condenser has a diaphragm with a given aperture. The bleeding of the degassing system is regulated or set according to the oxygen content in the condensate. The size of the diaphragm in the line from the condenser is designed in such a way that for all loads and the associated amounts of steam supplied to the condenser, the condenser pressure is within the desired set range.
In a further embodiment, both lines, that is to say that from the condenser and that from the degassing system, have a regulating valve, a regul
Baumann Peter
Blangetti Francisco Leonardo
Novak Walter
Alstom
Burns Doane Swecker & Mathis L.L.P.
Nguyen Hoang
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