Claims
- 1. The combination of an unfired boiler having a high pressure steam generating circuit means and a low pressure steam generating circuit means, a source of thermal energy for said boiler, means for effecting a flow of feedwater to said boiler, a controller for controlling the operation of said boiler, said controller including means for periodically calculating the energy available to said boiler from said thermal energy source and the quantity of dry steam that can be generated by the transfer of said energy to said feedwater, means under the direction of said controller for so modulating the flow of feedwater to said boiler as to supply to said boiler the quantity of feedwater that can be turned into steam as aforesaid by the transfer of said thermal energy thereto, and means for proportioning the flow of feedwater between said high pressure steam generating circuit means and said low pressure steam generating circuit means in accord with the ratio
- W.sub.HP /W.sub.LP,
- where:
- W.sub.HP is the mass flow of the steam generated in the high pressure steam generating circuit means, and
- W.sub.LP is the mass flow of the steam generated in the low pressure steam generating circuit means.
- 2. A combination as defined in claim 1 wherein said controller has calculating means as aforesaid for calculating the quantity of steam having a setpoint temperature which is an assigned or calculated number of degrees lower than the temperature of the thermal energy source that can be generated by the transfer of said energy to the feedwater supplied to said high pressure steam generating circuit means, means for measuring the temperature of the steam discharged from said high pressure steam generating circuit means and for adding a signal representative of that temperature to a signal representative of the setpoint temperature to generate an error signal, means for converting said error signal to a feedwater flow correction signal, means for adding said feedwater flow correction signal to a flow indicative signal generated in said predictive mode of operation to generate a corrected flow command signal, and means for transmitting said corrected flow command signal to said flow modulating means.
- 3. A combination as defined in claim 1 which has a feedwater flow proportioning means upstream of said high and low pressure steam generating circuit means and wherein said controller has means for generating first and second signals indicative of the flow of the feedwater actually passed through said boiler and through said low pressure steam generating circuit means, means for converting said first and second signals to a flow split signal in accord with the ratio ##EQU5## where:
- W.sub.FW is the total measured flow of feedwater through the boiler, and
- W.sub.LPFW is the measured flow of the feedwater through the low pressure steam generating circuit means;
- means for adding the just mentioned flow split signal to the flow split signal indicative of the proportioning of said feedwater between said high and low pressure steam generating circuit means to create a flow split error signal, means for converting said error signal to a flow split command signal, and means for transmitting said flow split command signal to said feedwater flow proportioning means.
- 4. A combination as defined in claim 3 wherein said controller has calculating means as aforesaid for calculating the quantity of steam having a setpoint temperature which is an assigned or calculated number of degrees lower than the temperature of the thermal energy source that can be generated by the transfer of said energy to the feedwater supplied to said high pressure steam generating circuit means, means for measuring the temperature of the steam discharged from said high pressure steam generating circuit means and for adding a signal representative of that temperature to a signal representative of the setpoint temperature to generate an error signal, means for converting said error signal to a feedwater flow correction signal, means for adding said feedwater flow correction signal to a flow indicative signal generated in said predictive mode of operation to generate a corrected flow command signal, and means for transmitting said corrected flow command signal to said flow modulating means.
- 5. A combination as defined in claim 1 wherein said controller has calculating means as aforesaid for calculating the quantity of steam having a setpoint temperature which is an assigned or calculated number of degrees lower than the temperature of the thermal energy source that can be generated by the transfer of said energy said to the feedwater supplied to said low pressure steam generating circuit means, means for measuring the temperature of the steam discharged from said low pressure steam generating circuit means and for adding a signal representative of that temperature to a signal representative of the setpoint temperature to generate an error signal, means for converting said error signal to a flow split correction signal, means for adding said flow split correction signal to the flow split correction signal generated in accord with the aforesaid ratio W.sub.HP /W.sub.LP to generate a corrected flow split command signal, and means for transmitting said corrected flow split command signal to said flow proportioning means.
- 6. A combination as defined in claim 5 wherein said controller has means as aforesaid for calculating the quantity of steam having a setpoint temperature which is an assigned or calculated number of degrees lower than the temperature of the thermal energy source that can be generated by the transfer of said energy to the feedwater supplied to said high pressure steam generating circuit means, means for measuring the temperature of the steam discharged from said high pressure steam generating circuit means and for adding a signal representative of that temperature to a signal representative of the setpoint temperature to generate an error signal, means for converting said error signal to a feedwater flow correction signal, means for adding said feedwater flow correction signal to a flow indicative signal generated in said predictive mode of operation to generate a corrected flow command signal, and means for transmitting said corrected flow command signal to said flow modulating means.
- 7. The combination of an unfired boiler, a source of thermal energy for said boiler, means for effecting a flow of feedwater to said boiler, means for effecting a flow of hot gases from said thermal energy source to and through said boiler, a controller for periodically calculating the energy available to said boiler from said thermal energy source and the quantity of dry steam that can be generated by transfer of thermal energy said to feedwater from said hot gases to said feedwater in accord with the algorithm: ##EQU6## where W.sub.FW =the mass flow of feedwater through the boiler,
- W.sub.gas =the mass flow of hot gases supplied to the boiler from the thermal energy source,
- T.sub.gas =the change in temperature of the hot gases in the boiler, and
- T.sub.HP SETPOINT =the selected temperature at which steam is to be discharged from the boiler, and
- flow control means for modulating the flow of feedwater to said boiler at the rate W.sub.FW calculated by said controller and thereby supplying to said boiler the quantity of feedwater that can be turned into said steam by the transfer of said thermal energy thereto from said hot gases.
- 8. A combination as defined in claim 7 wherein said controller has means for adding a correction factor to the feedwater flow value W.sub.FW to compensate for drift in accord with the algorithm:
- FW.sub.TOTAL =W.sub.FW +W.sub.CLCF,
- where
- W.sub.CLCF =-[(T.sub.GAS -T.sub.APP)-T.sub.HP ] K.sub.CLCF and:
- FW.sub.TOTAL =the newly computed feedwater flow including the correction,
- T.sub.HP =the measured high pressure outlet steam temperature,
- T.sub.APP =T.sub.GAS -T.sub.HP,
- T.sub.CLCF =a gain coefficient for converting temperature to feedwater flow,
- T.sub.APP =80 if T.sub.GAS >720, and
- T.sub.APP =68-(751-T.sub.GAS/ 8) if T.sub.GAS <720.
- 9. The combination of an unfired boiler; a source of thermal energy for said boiler; means for effecting a flow of feedwater to said boiler; means for effecting a flow of hot gases from said thermal energy source to and through said boiler; a controller for periodically calculating the energy available to said boiler from said thermal energy source and the quantity of dry steam that can be generated by transfer of said energy from said hot gases to said feedwater in accord with the algorithm: ##EQU7## where: W.sub.FW =the mass flow of feedwater through the boiler,
- C.sub.PFW =the average specific heat of the steam of the water side of the boiler at design point,
- .DELTA.T.sub.FW =T.sub.out -T.sub.in =increase from feedwater temperature to steam outlet temperature,
- h.sub.fg =the latent heat of vaporization of water,
- .DELTA.T.sub.gas =the change in temperature of the hot gases in the boiler,
- W.sub.as =the mass flow of hot gas as supplied to the boiler from the thermal energy source, and
- C.sub.gas =the specific heat of the hot gases supplied to the boiler;
- flow control means for modulating the flow of feedwater to said boiler at the rate W.sub.FW calculated by said controller and thereby supplying to said boiler the quantity of feedwater that can be turned into said steam by the transfer of said thermal energy thereto from said hot gases; and means for adding a correction factor to the feedwater flow valve W.sub.FW to compensate for drift in accord with the algorithm:
- FW.sub.TOTAL =W.sub.FW +W.sub.CLCF'
- where
- W.sub.CLCF =-[(T.sub.GAS -T.sub.APP)-T.sub.HP ]K.sub.CLCF
- and
- FW.sub.TOTAL =the newly computed feedwater flow including the correction,
- T.sub.HP =the measured high-pressure outlet steam temperature,
- T.sub.APP =T.sub.GAS -T.sub.HP, and
- K.sub.CLCF =a gain coefficient for converting temperature to feedwater flow.
Parent Case Info
This is a continuation of application Ser. No. 497,132, filed May 23, 1983 now abandoned.
US Referenced Citations (4)
Foreign Referenced Citations (1)
Number |
Date |
Country |
0114837 |
Sep 1980 |
JPX |
Non-Patent Literature Citations (1)
Entry |
Wardall et al., "The Outlook for Combined Cycle Efficiency with Small Turbines"; Energy Processing/ Canada Mar.-Apr. 1976. |
Continuations (1)
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Number |
Date |
Country |
Parent |
497132 |
May 1983 |
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