US3789806A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Furnace circuit for variable pressure once-through generator
Assignee: Foster Wheeler Inc
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Filing: 1971-12-27
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Granted: 1974-02-05
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Expires: 1991-12-27
Abstract
Abstract A variable pressure vapor generator of the once-through type in which circulation is established at normal loads by the generator feed pump. However, at start-up and loads below about 50 percent, evaporation in the generator furnace enclosure is carried out only to a vapor-liquid mixture. At least a minimum flow, for instance about 10 percent flow, is maintained by the generator feed pump, and circulation in the furnace enclosure is established by natural recirculation of the liquid portion of the vapor-liquid mixture, assisted by the feed pump flow. By the invention, turbine throttle pressure is varied in response to load demand, and fluid pressure within the vapor generator circuit is varied essentially in step with the throttle pressure.
Inventors
- 👤 W Gorzegno
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 23:46
CPC Classifications
F; F22; F22B; F22B29/00; F22B29/06; F22B37/00; F22B37/02; F22B37/26; F22B37/32
Claims Analysis
Total Claims: 31
Claim 1
Independent Claim
191 words
A method of operating a vapor generator of the once-through type comprising the steps of establishing the circulation rate in the generator at normal loads by the generator feed pump, the evaporation rate of the generator being equal to the circulation rate; varying the pressure within the generator in proportion to load; carrying out the evaporation in the furnace enclosure at lower loads only to a vapor-liquid mixture; separating the vapor and liquid portions in said mixture; recirculating the liquid portion of the mixture to the furnace enclosure at such lower loads at a density by which natural circulation in part provides the driving force of recirculation; maintaining at least a minimum generator feed pump flow; mixing said feed pump flow with the recirculated flow at the lower loads in such a way as to effect a transfer of energy from the feed pump flow to the recirculated flow and thereby increase the recirculation rate at the lower loads; and converting the generator from recirculated flow to once-through flow, and vice versa, substantially at that load and pressure at which there is essentially little or no driving force by natural circulation.
Claim 2
Independent Claim
191 words
A method of operating a vapor generator of the once-through type comprising the steps of establishing the circulation rate in the generator at normal loads by the generator feed pump, the evaporation rate of the generator being equal to the circulation rate; varying the pressure within the generator in proportion to load; carrying out the evaporation in the furnace enclosure at lower loads only to a vapor-liquid mixture; separating the vapor and liquid portions in said mixture; recirculating the liquid portion of the mixture to the furnace enclosure at such lower loads at a density by which natural circulation in part provides the driving force of recirculation; maintaining at least a minimum generator feed pump flow; mixing said feed pump flow with the recirculated flow at the lower loads in such a way as to effect a transfer of energy from the feed pump flow to the recirculated flow and thereby increase the recirculation rate at the lower loads; and converting the generator from recirculated flow to once-through flow, and vice versa, substantially at that load and pressure at which there is essentially little or no driving force by natural circulation.
Claim 3
Dependent Claim
40 words
The method of claim 1 wherein the transition from recirculated flow to once-through flow and vice versa occurs at about 50 percent load, evaporation to dryness or to a high quality mixture occurring in the furnace enclosure at said load.
Claim 4
Dependent Claim
15 words
The method of claim 2 in which the generator pressure at full load is supercritical.
Claim 5
Dependent Claim
26 words
The method of claim 1 wherein the ratio of feed pump flow to recirculated flow is increased with increased load and pressure at said lower loads.
Claim 6
Dependent Claim
24 words
The method of claim 1 wherein the minimum driving feed pump flow utilized is approximately 10 percent of the full load feed pump flow.
Claim 7
Dependent Claim
46 words
The generator of claim 5 wherein the feed pump flow is that required to maintain a predetermined circulation rate in the furnace enclosure, further including the step of returning excess liquid flow from the furnace enclosure to constitute at least in part the feed pump flow.
Claim 8
Dependent Claim
31 words
The method of claim 4 further including the step of preheating the feed pump flow in tubes of the furnace enclosure prior to mixing the recirculated flow and feed pump flow.
Claim 9
Dependent Claim
24 words
The method of claim 4 wherein the flow in the furnace enclosure is of the once-up-through type at loads exceeding about 50 percent load.
Claim 10
Dependent Claim
64 words
The method of claim 4 wherein the feed pump flow and recirculated flow are mixed in a jet pump with a portion of the feed pump flow providing the driving force, including the step of bypassing said jet pump with the remaining portion of feed pump flow to maintain a predetermined pressure ratio of the jet Pump driving flow to the driven recirculated flow.
Claim 11
Dependent Claim
161 words
A vapor generator of the once-through type including a radiantly heated furnace enclosure and feed pump means arranged to pass a liquid flow through the enclosure, the improvement comprising means for establishing essentially the same pressure throughout the generator and for varying said pressure in response to load; separator means for receiving the flow from the generator furnace enclosure when such flow is a vapor-liquid mixture; recirculation means for recirculating the liquid portion of said flow back to the furnace enclosure, said separation means and recirculation means establishing with the furnace enclosure a natural circulation loop; means for mixing the recirculated flow with said feed pump flow in such a way as to effect a transfer of energy from the feed pump flow to the recirculated flow and thereby increase the recirculation ratio by the feed pump flow; and valve means for interrupting the recirculated flow permitting the generator flow to be either in part by natural circulation or totally once-through.
Claim 12
Dependent Claim
161 words
A vapor generator of the once-through type including a radiantly heated furnace enclosure and feed pump means arranged to pass a liquid flow through the enclosure, the improvement comprising means for establishing essentially the same pressure throughout the generator and for varying said pressure in response to load; separator means for receiving the flow from the generator furnace enclosure when such flow is a vapor-liquid mixture; recirculation means for recirculating the liquid portion of said flow back to the furnace enclosure, said separation means and recirculation means establishing with the furnace enclosure a natural circulation loop; means for mixing the recirculated flow with said feed pump flow in such a way as to effect a transfer of energy from the feed pump flow to the recirculated flow and thereby increase the recirculation ratio by the feed pump flow; and valve means for interrupting the recirculated flow permitting the generator flow to be either in part by natural circulation or totally once-through.
Claim 13
Dependent Claim
44 words
The generator of claim 10 wherein the transition from natural to once-through flow and vice versa occurs at an intermediate load point, the generator furnace enclosure being sized to evaporate the flow to a high quality mixture or to dryness at said load point.
Claim 14
Dependent Claim
21 words
The generator of claim 10 including at least one downcomer, the recirculated flow from said separator means being into said downcomer.
Claim 15
Dependent Claim
51 words
The generator of claim 12 in which the means for mixing the recirculated flow with the feed pump flow is a jet pump comprising a venturi section interposed in said downcomer, a nozzle for introducing a jet stream into said venturi section, and means connecting said nozzle with said feed pump.
Claim 16
Dependent Claim
69 words
The generator of claim 13 further including conduit means for receiving a portion of the flow from said feed pump means and for mixing said portion with the recirculated flow at a point downstream of the jet pump, said conduit means including valve means arranged to maintain a predetermined pressure ratio between the pressure in said nozzle and the recirculated flow in said downcomer upstream of the venturi section.
Claim 17
Dependent Claim
63 words
The vapor generator of claim 10 including header means for receiving the liquid flow from said separator means, flow detection means for detecting the rate of flow from said feed pump means, and bypass means for bypassing at least part of the flow from said header means to a point upstream of said flow detection means to prevent flooding of said separator means.
Claim 18
Dependent Claim
20 words
The generator of claim 15 wherein said bypass means includes a valve responsive to liquid level in said separator means.
Claim 19
Dependent Claim
24 words
The generator of claim 16 wherein the bypass flow is routed to the generator deaerator or high pressure heaters for recovery of heat therein.
Claim 20
Dependent Claim
18 words
The generator of claim 10 wherein said furnace enclosure comprises a circuitry which is of the once-up-through type.
Claim 21
Dependent Claim
15 words
The generator of claim 18 in which said furnace enclosure is oil or gas fired.
Claim 22
Dependent Claim
65 words
The generator of claim 18 wherein said furnace enclosure comprises a plurality of upright panels, each panel comprising a plurality of parallel upright tubes, the enclosure including cross-over means intermediate the upper and lower elevations of the enclosure by which the flow in panels in a high heat absorption area of the enclosure is transferred to an area of low heat absorption, and vice versa.
Claim 23
Dependent Claim
16 words
The generator of claim 20 wherein the cross-over means is positioned above the enclosure burner zone.
Claim 24
Dependent Claim
27 words
The generator of claim 20 further including a plurality of resistances interposed at the entrance to the furnace enclosure circuits for equalizing the flow in the circuits.
Claim 25
Dependent Claim
72 words
The generator of claim 10 including a plurality of separator means, each separator means comprising an outer cylindrical upright vessel, an inner conduit extending axially within the vessel including a closed upper end, a plurality oF curved arms extending radially from said conduit upper end for transmitting the flow in said conduit tangentially along the inner wall of the vessel, the conduit being arranged to receive the flow from the furnace enclosure.
Claim 26
Dependent Claim
62 words
The generator of claim 10 in which said generator ic coal fired, further including means for transmitting the feed pump flow first to at least one flow circuit constituting a portion of the furnace enclosure and then mixing said feed pump flow with recirculated flow, the combined recirculated and feed pump flow then being transmitted through remaining circuits of the furnace enclosure.
Claim 27
Dependent Claim
28 words
The generator of claim 24 in which said at least one flow circuit constitutes panels in the center portions of the lower side walls of the furnace enclosure.
Claim 28
Independent Claim
101 words
A method of operating a vapor generator of the once-through type at low loads and start-up comprising the steps of: carrying out evaporation in the furnace enclosure only to a vapor-liquid mixture; separating the vapor and liquid portions of the mixture; recirculating the liquid portion of the mixture to the furnace enclosure at a density by which natural circulation in part provides the driving force for the recirculation; maintaining at least a minimum generator feed pump flow; and mixing said feed pump flow and recirculated flow so that the feed pump flow provides the remainder of the driving force for recirculation.
Claim 29
Independent Claim
101 words
A method of operating a vapor generator of the once-through type at low loads and start-up comprising the steps of: carrying out evaporation in the furnace enclosure only to a vapor-liquid mixture; separating the vapor and liquid portions of the mixture; recirculating the liquid portion of the mixture to the furnace enclosure at a density by which natural circulation in part provides the driving force for the recirculation; maintaining at least a minimum generator feed pump flow; and mixing said feed pump flow and recirculated flow so that the feed pump flow provides the remainder of the driving force for recirculation.
Claim 30
Dependent Claim
25 words
The method of claim 26 wherein the ratio of feed pump flow to recirculated flow is increased with increased load and pressure in the generator.
Claim 31
Dependent Claim
41 words
The method of claim 27 wherein the flow in the generator is converted from recirculated flow to once-through flow, and vice versa, substantially at that load and pressure at which there is essentially little or no driving force by natural circulation.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-02-04 | 1977-08-06 | 1978-02-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-02-04 | 1981-08-06 | 1982-02-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-02-04 | 1985-08-06 | 1986-02-05 | $7700.00 | Window Closed / Lapsed |