Once through sliding pressure steam generator

Claim 2

A supercritical pressure once-through type steam generator for sliding pressure operation into the subcritical pressure range at reduced loads, comprising: control means for operating said steam generator at supercritical pressure at high loads and at subcritical pressure at low loads; a furnace; vertical tubes lining the walls of said furnace around the periphery thereof, said tubes in parallel flow arrangement and continuous throughout the height of said furnace; internal flow agitating means located within said tubes throughout substantially the entire heated length thereof; a steam-water separating means; means for conveying fluid leaving said tubes to said separating means; a superheater; means for conveying steam from said separating means to said superheater; means for selectively directing substantially the entire flow of fluid leaving said tubes through said superheater; feedwater supply means; means for conveying feedwater to said tubes; means for passing a flow through said tubes exceeding the flow through said superheater during very low load operation of said steam generator; and fixed means for apportioning flow to various of said vertical tubes in proportion to the predicted full load heat absorption of the various tubes.

Claim 3

An apparatus as in claim 1 wherein said means for passing a flow comprises: means for conveying water from said steam separating means to said tubes; and pump means for recirculating water from said separating means through said tubes at low loads.

Claim 4

An apparatus as in claim 2: wherein said pump is sized to recirculate less than 50 percent of the full load flow.

Claim 5

An apparatus as in claim 3: wherein said pump is sized to recirculate less than 30 percent of the full load flow.

Claim 6

An apparatus as in claim 1: wherein said internal flow agitating means comprises internal rifling within said vertical tubes.

Claim 7

An apparatus as in claim 1: wherein said fixed means comprises orifices arranged to throttle the flow entering said vertical tubes.

Claim 8

An apparatus as in claim 2: wherein said internal flow agitating means comprises internal rifling within said vertical tubes.

Claim 9

An apparatus as in claim 7: wherein said fixed means comprises orifices arranged to throttle the flow entering said vertical tubes.

Claim 10

An apparatus as in claim 8: wherein said pump is sized to recirculate less than 50 percent of the full load flow.

Claim 11

An apparatus as in claim 9: wherein said pump is sized to recirculate less than 30 percent of the full load flow.

Claim 12

An apparatus as in claim 2: wherein said fixed means comprises orifices arranged to throttle the flow entering said vertical tubes.

Claim 13

An apparatus as in claim 11: wherein said pump is sized to recirculate less than 50 percent of the full load flow.

Claim 14

A supercritical pressure once-through type steam generator for sliding pressure operation into the subcritical pressure range at reduced loads, comprising: control means for operating said steam generator at supercritical pressure at high loads and at subcritical pressure at low loads; a furnace; vertical tubes lining the walls of said furnace around the periphery thereof, said tubes in parallel flow arrangement and continuous throughout the height of said furnace, and internally rifled throughout a substantial heated length; a steam-water separator; means for conveying fluid leaving said tubes to said separator; a superheater; means for conveying steam from said separator to said superheater; means for selectively directing substantially the entire flow of fluid leaving said tubes through said superheater; feedwater supply means; means for conveying feedwater to said tubes; means for conveying water from said separator to said tubes; pump means for recirculating water through said tubes from said separator during very low load operation of said steam generator; and orifices for apportioning flow to various of said vertical tubes in proportion to the predicted full load heat absorption of the various tubes.

Claim 15

A supercritical pressure once-through type steam generator for sliding pressure operation into the subcritical pressure range at reduced loads, comprising: control means for operating said steam generator at supercritical pressure at high loads and at subcritical pressure at low loads; a furnace; vertical tubes lining the walls of said furnace around the periphery thereof, said tubes in parallel flow arrangement and continuous throughout the height of said furnace, and internally rifled throughout a substantial heated length; a steam-water separator; means for conveying fluid leaving said tubes to said separator; a superheater; means for conveying steam from said separator to said superheater; means for selectively directing substantially the entire flow of fluid leaving said tubes through said superheater; feedwater supply means; means for conveying feedwater to said tubes; means for conveying water from said separator to said tubes; pump means for recirculating water through said tubes from said separator during very low load operation of said steam generator; and orifices for apportioning flow to various of said vertical tubes in proportion to the predicted full load heat absorption of the various tubes.

Claim 16

An apparatus as in claim 13: wherein said pump is sized to recirculate less than 50 percent of the full load flow.

Claim 17

An apparatus as in claim 1: wherein the tube spacing and sizing is selected such that the mass flow entering said vertical tubes at full load is greater than 1,000 kilograms per second per meter squared.

Claim 18

An apparatus as in claim 10: wherein the tube spacing and sizing is selected such that the mass flow entering said vertical tubes at full load is greater than 1,000 kilograms per second per meter squared.

Claim 20

An apparatus as in claim 1 or 10: wherein the sizing and spacing of said tubes is such that the inside diameter measured in millimeters greater than 0.0125 w minus 5 where w is the full load mass flow entering said tubes measured in kilograms per second per meter squared.

Claim 22

A once-through type steam generator for sliding pressure operation in the subcritical pressure range, comprising: a furnace; vertical tubes lining the walls of said furnace around the periphery thereof, said tubes in parallel flow arrangement and continuous throughout the height of said furnace; internal flow agitating means located within said tubes throughout substantially the entire heated length thereof; a steam-water separating means; means for conveying fluid leaving said tubes to said separating means; a superheater; means for conveying steam from said separating means to said superheater; means for selectively directing substantially the entire flow of fluid leaving said tubes through said superheater; feedwater supply means; means for conveying feedwater to said tubes; means for passing a flow through said tubes exceeding the flow through said superheater during very low load operation of said steam generator; fixed means for apportioning flow to various of said vertical tubes in proportion to the predicted full load heat absorption of the various tubes; and the size and spacing of said vertical tubes being such that the mass flow of water entering said tubes at full load and measured in kilograms per second per meter squared is less than d+5 divided by 0.0125 where d is the inside diameter of the tube measured in millimeters.

Claim 23

A once-through type steam generator for sliding pressure operation in the subcritical pressure range, comprising: a furnace; vertical tubes lining the walls of said furnace around the periphery thereof, said tubes in parallel flow arrangement and continuous throughout the height of said furnace; internal flow agitating means located within said tubes throughout substantially the entire heated length thereof; a steam-water separating means; means for conveying fluid leaving said tubes to said separating means; a superheater; means for conveying steam from said separating means to said superheater; means for selectively directing substantially the entire flow of fluid leaving said tubes through said superheater; feedwater supply means; means for conveying feedwater to said tubes; means for passing a flow through said tubes exceeding the flow through said superheater during very low load operation of said steam generator; fixed means for apportioning flow to various of said vertical tubes in proportion to the predicted full load heat absorption of the various tubes; and the size and spacing of said vertical tubes being such that the mass flow of water entering said tubes at full load and measured in kilograms per second per meter squared is less than d+5 divided by 0.0125 where d is the inside diameter of the tube measured in millimeters.

Claim 24

A supercritical pressure once-through type steam generator for sliding pressure operation into the subcritical pressure range at reduced loads, comprising: control means for operating said steam generator at supercritical pressure at high loads and at subcritical pressure at low loads; a furnace; vertical tubes lining the walls of said furnace around the periphery thereof, said tubes in parallel flow arrangement and continuous throughout the height of said furnace; internal flow agitating means located within said tubes throughout substantially the entire heated length thereof; a steam-water separating means; means for conveying fluid leaving said tubes to said separating means; a superheater; means for conveying steam from said separating means to said superheater; means for selectively directing substantially the entire flow of fluid leaving said tubes through said superheater; feedwater supply means; means for conveying feedwater to said tubes; means for passing a flow through said tubes exceeding the flow through said superheater during very low load operation of said steam generator; fixed means for apportioning flow to various of said vertical tubes in proportion to the predicted full load heat absorption of the various tubes; and wherein at full load, the frictional pressure drop through said vertical tubes is less than 4 times the static head of the fluid in said tubes.

Claim 25

A supercritical pressure once-through type steam generator for sliding pressure operation into the subcritical pressure range at reduced loads, comprising: control means for operating said steam generator at supercritical pressure at high loads and at subcritical pressure at low loads; a furnace; vertical tubes lining the walls of said furnace around the periphery thereof, said tubes in parallel flow arrangement and continuous throughout the height of said furnace; internal flow agitating means located within said tubes throughout substantially the entire heated length thereof; a steam-water separating means; means for conveying fluid leaving said tubes to said separating means; a superheater; means for conveying steam from said separating means to said superheater; means for selectively directing substantially the entire flow of fluid leaving said tubes through said superheater; feedwater supply means; means for conveying feedwater to said tubes; means for passing a flow through said tubes exceeding the flow through said superheater during very low load operation of said steam generator; fixed means for apportioning flow to various of said vertical tubes in proportion to the predicted full load heat absorption of the various tubes; and wherein at full load, the frictional pressure drop through said vertical tubes is less than 4 times the static head of the fluid in said tubes.

Claim 26

An apparatus as in claim 20 or 21 wherein said means for passing a flow comprises: means for conveying water from said steam separating means to said tubes; and pump means for recirculating water from said separating means through said tubes at low loads.

Claim 27

An apparatus as in claim 22: wherein said pump is sized to recirculate less than 50 percent of the full load flow.

Claim 28

An apparatus as in claim 23: wherein said internal flow agitating means comprises internal rifling within said vertical tubes.

Claim 29

An apparatus as in claim 24: wherein said pump is sized to recirculate less than 30 percent of the full load flow.

Claim 30

An apparatus as in claim 25: wherein said fixed means comprises orifices arranged to throttle the flow entering said vertical tubes.

Claim 31

An apparatus as in claim 22: wherein said internal flow agitating means comprises internal rifling within said vertical tubes.

Claim 32

An apparatus as in claim 27: wherein said fixed means comprises orifices arranged to throttle the flow entering said vertical tubes.