US 3376857 A
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April 9, 1968 R. J. 5. SMITH 3,376,857
STEAM CQNDENSERS Filed Feb. 7, 1966 United States Patent 3,376,857 STEAM CONDENSERS Robert J. S. Smith, 7 New Park Crescent, Falsgrave, Yorkshire, Scarborough, England Filed Feb. 7, 1966, Ser. No. 525,703 6 Claims. (Cl. 122-1) ABSTRACT OF THE DISCLOSURE A method of and a system for the recovery of waste heat from the exhaust steam of a steam engine operated by a steam raising plant using low pressure compression to liquify the exhaust steam so as to form superheated water and feeding the superheated water so obtained back to the boiler of the steam raising plant.
This invention relates to a method of and a system for the recovery of waste heat from the exhaust steam of a steam engine or other prime mover or apparatus from which steam is exhausted at a temperature and pressure suitable for recovery.
The principal object of the present invention is the provision of means enabling waste heat from exhaust steam to be recovered in a simple and effective manner thereby increasing the thermal etficiency of the engine or apparatus to which the invention is applied.
In accordance with the method of the invention, waste heat is recovered from the exhaust steam of apparatus operated by steam raising plant by partially cooling the exhaust steam, compressing the partially cooled steam to a pressure lower than that at which the steam raising plant operates, and feeding the superheated water so obtained back to the boiler of the steam raising plant.
The system for recovering waste heat from the exhaust steam of apparatus operated by steam raising plant comprises a cooler into which the exhaust is directed and partially cooled and a compressor receiving the partially cooled steam and compressing it to a pressure lower than that at which the steam raising plant operates, the superheated water produced by the compressor being fed to a feed pump for return to the boiler.
The invention is applicable to modern high efficiency steam plants operating at 1,000 to 1,500 pounds per square inch or more.
In one embodiment of the invention exhaust steam is passed to a cooler maintained at around atmospheric pressure, thence to a compressor operating at a low pressure in which it is liquified before being passed into a combined receiver surge tank and oil separator maintained in a pressurised condition by an outlet valve through which the condensate is directed to the feed pump.
In order that the invention may be clearly understood reference will now be made to the accompanying drawing in which FIGURE 1 shows a specific line diagram of the waste heat recovery system and FIGURE 2 shows a sectional view of a receiver vessel. While the specific application described relates to the exhaust from a reciprocating steam engine it will be understood that the invention is not limited in this way and is applicable to other prime movers such as steam turbines.
The reciprocating engine 1 delivers its exhaust steam to a cooler 2 (either Water or air cooled) which is closely controlled to extract only sufficient latent heat to reduce the volume of the steam and also to increase its density at an internal cooler pressure maintained at a neutral or slightly positive pressure in the order of 0 to 1 pound per square inch (gauge). This pressure may be varied bet-ween any limits, positive or negative, however, if so desired.
3,376,857 Patented Apr. 9, 1968 ice The partially cooled steam is then extracted by the compressor 3 in which it is liquified by compression and passed to a combined receiver surge tank and oil separator 4, the outlet from which is controlled by a suitable valve 5 to give a pressure in the order of 22 to 25 pounds per square inch (gauge).
The liquified steam is finally drawn from the receiver by the normal boiler feed pump 6 and so returned to the boiler 8 without any further loss of heat.
The receiver surge tank and oil separatof 4 is provided with a spring loaded venting valve 7 set to 35 pounds per square inch, the purpose of which is to relieve any excess pressure in the receiver too great for the normal outlet to pass out such as entrapped air when starting up. The engine, compressor and boiler feed pump may be mechanically coupled as indicated in the figure.
The outlet valve 5 controls the receiver pressure and is constructed to maintain the steady liquifying pressure mentioned above under all conditions.
The receiver surge tank and oil separator 4 is shown with a cone shaped top 9 to reduce the amount of entrapped air, the air venting valve 7, the inlet valve 10 and the oil bafile 11.
It will be noted from the above that the receiver surge tank and oil separator 4 has a number of functions.
Firstly it acts as a controller of the liquifying pressure, the pressure being governed by the outlet valve 5.
Secondly it acts as a storage vessel for the liquified steam, and thus as a surge tank to even out variations in the quantity of liquified steam delivered from the cooler and so from the compressor.
Thirdly, by incorporating an oil bafile or other means, it acts as an oil separator to ensure oil free feed water to the boiler.
As the pressure of compression is moderate, at most 25 pounds per square inch, the expenditure of compres sor power on waste heat recovery will be correspondingly low and this enables a comparatively large compressor to be used with the result that a large volume of partially cooled steam can be liquified without further loss of latent heat, the cooler being only required to remove sufii-cient latent heat to keep the cooler pressure at the figure mentioned above.
Tests with an experimental steam plant indicate that a compressor 14% of the swept volume of the engine would recover approximately 70% of the waste heat in the exhaust steam.
A further improvement in the overall efiiciency of the plant may be obtained in the case of reciprocating engines by the employment of an exhaust driven rotary motor interposed between the engine and the cooler, for driving the compressor, boiler feed pump and cooler circulating pump (or radiator fan). The compressor itself can also be of the rotary positive displacement type.
This arrangement enables the condensing components to work automatically according to exhaust conditions irrespective of engine speed or load.
The waste heat recovery method and system described in this specification is supplementary to other methods and systems of heat saving such as conventional economisers, bled steam feed water heaters and air pre-heaters.
What I claim is:
1. A method of recovering waste heat from the exhaust steam of apparatus operated by a steam raising plant, said method comprising partially cooling the exhaust steam to a degree causing it to lose only sufiicient latent heat to reduce the volume of the steam and increase its density, causing said partially cooled steam to be accepted in unmodified form by a compressor, and causing said compressor to compress the steam to a pressure lower than that at which the steam raising plant operates so as to condense the steam to superheated water, and feeding the water so obtained back to the boiler of the steam raising plant.
2. In a steam raising plaint having a boiler, a system for recovering waste heat from the exhaust steam of apparatus operated by said steam raising plant, said system comprising a cooler into which the exhaust steam is directed and partially cooled to a degree causing it to lose only sufiicient latent heat to reduce the volume of the steam and increase its density, and a compressor receiving the partially cooled steam and compressing it to a pressure lower than that at which the steam raising plant operates to condense the steam to superheated water, a surge tank having an inlet and an outlet, said inlet communicating with said compressor and a feed pump communicating with said surge tank outlet and said boiler, the superheated water produced by the compressor being delivered to said surge tank and fed therefrom to said feed pump for return to said boiler.
3. The system for recovering waste heat set forth in claim 2 and wherein a spring loaded venting valve is in communication with said surge tank.
4. The system for recovering waste heat set forth in from the surge tank is controlled by a valve to maintain CTI claim 2 and wherein the outlet for the superheated Water a predetermined pressure in said surge tank.
5. The system for recovering waste heat set forth in claim 4 and wherein said valve maintains said predetermined pressure in the order of 22 to 25 pounds per square inch gauge.
6. The system for recovering waste heat set forth in claim 2 and wherein an oil separator is part of said surge tank.
References Cited UNITED STATES PATENTS 1,282,080 10/1918 Hawley 60-96 1,601,384 9/1926 Vianello 60-92 1,661,900 3/1928 McCallum et al. 6096 X 1,924,341 8/1933 Schellens et al. 60-96 OTHER REFERENCES A.P.C. Application of Heller, Serial No. 428,655, published June 1, 1943.
KENNETH W. SPRAGUE, Primary Examiner.