US20240003532A1

US20240003532A1 - Green steam industrial steam generator process and system

Info

Publication number: US20240003532A1
Application number: US18/214,663
Authority: US
Inventors: Timothy A. Fuller
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 2022-07-01
Filing date: 2023-06-27
Publication date: 2024-01-04
Also published as: AU2023299167A1; TW202417780A; WO2024006325A1

Abstract

A steam generation system includes a silo, a heater, a material transfer system, and a heat exchanger. The silo is configured to receive granular material into the silo at an upper portion of the silo. The heater is arranged at or in the upper portion of the silo to heat the granular material received into the silo. The material transfer system is arranged to remove granular material exiting from a bottom of the silo. The heat exchanger is disposed in a lower portion of the silo and is arranged to contact granular material flowing downward inside the silo. The electricity for operating the heater may be generated by a renewable energy source such as a solar energy source or a wind energy source.

Description

This application claims the benefit of U.S. Provisional Application No. 63/358,076 filed Jul. 1, 2022. U.S. Provisional Application No. 63/358,076 filed Jul. 1, 2022 is incorporated herein by reference in its entirety

BACKGROUND

The following relates to the green energy arts, steam generation arts, and related arts.

BRIEF SUMMARY

In some illustrative embodiments disclosed herein as nonlimiting examples, a steam generation system includes a silo, a heater, a material transfer system, and a heat exchanger. The silo is configured to receive granular material into the silo at an upper portion of the silo. The heater is arranged at or in the upper portion of the silo to heat the granular material received into the silo. The material transfer system is arranged to remove granular material exiting from a bottom of the silo. The heat exchanger is disposed in a lower portion of the silo and is arranged to contact granular material flowing downward inside the silo.
In some illustrative embodiments disclosed herein as nonlimiting examples, a steam generation method is disclosed which is performed in conjunction with the steam generation system of the immediately preceding paragraph. The steam generation method includes: delivering granular material to the upper portion of the silo of the steam generation system; delivering electricity to operate the heater of the steam generation system; and flowing a heat transfer fluid through the heat exchanger of the steam generation system. In some embodiments, the delivering of the granular material, the delivering of the electricity, and the flowing of the heat transfer fluid are performed concurrently. In some embodiments, the delivering of the electricity to operate the heater comprises generating the electricity from solar energy or from wind energy.
In some illustrative embodiments disclosed herein as nonlimiting examples, a steam generation system includes a silo, a heater, a heat exchanger, a material transfer system, and a storage silo. The silo is configured to receive granular material into the silo at an upper portion of the silo. The heater is arranged to heat the received granular material to generate heated granular material. The heat exchanger is disposed in a lower portion of the silo and is arranged to extract heat from the heated granular material flowing downward in the silo to generate cooled granular material. The material transfer system is arranged to remove the cooled granular material exiting from a bottom of the silo. The storage silo is connected to store the cooled granular material removed by the material transfer system and to transfer granular material from the storage silo to the upper portion of the silo.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 diagrammatically illustrates a green steam system for superheated steam production.

FIG. 2 diagrammatically illustrates a more detailed view of the heat exchanger modules of the illustrative green steam system of FIG. 1 .

FIG. 3 diagrammatically illustrates suitable water/steam circuit of the system of FIGS. 1 and 2 .

DETAILED DESCRIPTION OF THE INVENTION

Steam generation systems and methods disclosed herein provide either saturated or superheated steam for industrial process use from renewable energy sources such as solar and wind. Hence, such steam generation systems are also referred to herein as green steam systems. Solid particles are used to absorb and store energy from the available renewable sources. When steam is needed, energy is transferred from the solid particles to a heat transfer fluid in a suitably designed heat exchanger. In embodiments in which the heat transfer fluid is water, steam is generated directly and sent to the industrial process. In embodiments in which the heat transfer fluid is not water, a second heat exchanger is suitably used to generate steam from the hot heat transfer fluid. The green steam system is flexible and can be configured with different heat transfer surfaces for different applications. A nonlimiting illustrative example configuration for producing superheated process steam is described in the following.
With reference to FIG. 1 , an illustrative green steam system is shown. Also shown in FIG. 1 are an industrial facility F operatively connected with the illustrative green steam system, and grade level G is also indicated with an illustrative truck T disposed thereon. In this system, sand or other granular material is passed by gravity through an electric heater 10 where the temperature of the particles is raised to (in one nonlimiting illustrative embodiment) between 600° C. (1112° F.) and 650° C. (1202° F.). The temperature the granular material is heated to is controlled by the rate at which the granular material is delivered and the electricity delivered to the heater 10 (i.e., how hot the heater 10 is run). In some embodiments these parameters are set to ensure the granular material is heated to a temperature of at least 600° C.
The electric heater 10 operates on renewable energy and is located above an insulated silo 12 where the hot sand is stored. Hence, the insulated silo 12 is also referred to herein as a hot silo 12 or hot sand silo 12. The illustrative heater 10 is disposed above the silo 12, between a hopper 14 and a top 12 _Tof the silo 12; however, it is also contemplated for the heater to be integrated into an upper portion of the silo. The electricity for operating the electric heater 10 may, by way of nonlimiting illustrative example, be generated by a renewable energy source such as electricity from solar energy generated by photovoltaic solar panels, solar thermal collectors, concentrated solar power systems, or so forth; electricity from wind energy produced by a wind turbine farm or the like; or another type of renewable energy. The hot sand particles exit a bottom 12 _Bof the silo 12 and flow under the force of gravity through multiple heat exchanger modules 20, 22, 24, 26 where the sand transfers its energy to the water and steam. The sand exits the heat exchangers modules 20, 22, 24, 26 as cold sand at (in one nonlimiting illustrative embodiment) a temperature between 150° C. (302° F.) and 200° C. (392° F.) and is conveyed to a bucket elevator or other sand transfer system 30 which lifts the cold sand to a top 40 _Tof a second insulated silo 40, also referred to herein as a cold sand silo 40 or cold silo 40, or as a storage silo 40. In the illustrative example, the sand transfer system 30 lifts the cold sand to a hopper 42 at the top 40 _Tof the second insulated silo 40. The delivering of the granular material and the delivering of the electricity and the flowing of the heat transfer fluid can be adjusted to cool the granular material exiting from the bottom 12 _Bof the hot silo 12 to a temperature of 200° C. or lower in some embodiments. When renewable energy is available for the electric heater 10, the sand is removed from a bottom 40 _Bof the second (i.e., storage) silo 40 by a screw conveyor or other sand transfer system and is fed to a bucket elevator or other sand transfer system 44 which lifts the sand to the inlet of the electric heater 10 (e.g., the sand is delivered by the sand transfer system 44 to the hopper 14 located above the heater 10 in the illustrative example of FIG. 1 ).
With reference to FIG. 2 , a more detailed view of the heat exchanger modules 20, 22, 24, 26 of the illustrative green steam system of FIG. 1 is shown. The illustrative heat exchanger modules are arranged in two parallel particle flow paths P1 and P2. Particle flow path P1 is also referred to herein as sand flow path #1; and similarly particle flow path P2 is also referred to herein as sand flow path #2. Each particle flow path P1, P2 contains two heat exchanger modules arranged in a series configuration. In the first flow path P1 (“Sand flow path #1), the sand passes through a generating bank module 20 for producing saturated steam and then through an economizer module 22 for heating the feed water to near saturation. In the second flow path P2 (“Sand flow path #2), the sand passes through a superheater module 24 for producing superheated steam and then through a second economizer module 26 for heating the feed water to near saturation. During operation, all heat exchanger modules 20, 22, 24, and 26 are full of slow moving, loosely packed sand particles.
The generating bank module 20 and the superheater module 24 are designed with heat exchanger tubes oriented vertically, as diagrammatically shown in FIG. 2 , parallel to the sand flow direction (i.e., parallel with flow paths P1 and P2). This advantageously reduces the flow resistance to the sand presented by the heat exchanger tubes of the generating bank module 20 and the superheater module 24. The heat exchanger tubes of the generating bank module 20 are connected to an inlet header 20 _Inat the bottom of the generating bank module 20 and an outlet header 20 _Outat the top of the generating bank module 20. Likewise, the heat exchanger tubes of the superheater module 24 are connected to an inlet header 24 _Inat the bottom of the superheater module 24 and an outlet header 24 _Outat the top of the superheater module 24. This provides a flow of water/steam which is countercurrent to the sand flow (i.e., countercurrent to the direction of the sand flow paths P1 and P2). This counterflow arrangement advantageously maximizes heat transfer from the hot sand to the water/steam. The headers 20 _In, 20 _Out, 24 _In, 24 _Outas well as the connecting tubes are suitably covered with a refractory material to protect them from erosion caused by the sand flow. The heat transfer tubes are arranged in a staggered bundle. Flow disruptors are optionally attached to each tube in a pattern so as to move cold sand away from the outer tube wall and move hot sand toward the outer tube wall. The optional flow disruptors cover the entire surface of each tube and can be a pin stud design or a fin design, as two nonlimiting examples.
In some nonlimiting illustrative embodiments, the economizer modules 22 and 26 are designed with heat exchanger tubes oriented horizontally, as diagrammatically shown in FIG. 2 , and parallel to the long axis of the module. The tubes are connected in a serpentine manner with tubes connecting to tubes at the next higher elevation using a “U” bends. The tubes are arranged in a staggered bundle as viewed from the ends of the tubes. The staggered bundle assists in keeping the sand mixed, so the tubes see a more uniform sand temperature. The tubes are connected to an inlet header at the bottom of the module and an outlet header at the top of the module (not shown in FIG. 2 ). This provides an overall water flow which is counter to the sand flow even though each individual tube is in cross flow.
In the illustrative embodiment, the bottom of each economizer module 22 and 26 includes screw conveyors 50 oriented parallel to the long axis of the economizer module. The screw conveyors 50 are adjacent to each other with no gaps in between. The screw conveyors 50 control the flow of sand through the heat exchanger modules 20, 22, 24, 26 by removing sand from the bottom of the economizer modules 22, 26 and transporting it to the inlet (e.g., hopper 42) of the cold silo bucket elevator 30 (see FIG. 1 ). Because there are multiple screw conveyors 50, the sand flow in vertical lanes corresponding to the respective screw conveyors 50 can be adjusted independently to account for uneven sand temperature distributions or flow imbalances in the heat exchangers 20, 22, 24, 26. While mutually parallel screw conveyors 50 are illustrated, in alternative embodiments other types of sand transport are contemplated, such as a bank of mutually parallel conveyor belts oriented perpendicular to the long axis of the economizer modules 22 and 26.
FIG. 2 shows a vertical channel 52, referred to herein as a silo drain 52, located below the centerline of the hot silo 12 in between the heat exchanger modules 20, 22 of the first particle flow path P1 and the heat exchanger modules 24, 26 of the second particle flow path P2. This vertical channel 52 provides a sand flow path P3 that feeds one (as shown, or optionally more) of the screw conveyors 50. The silo drain 52 is used to remove sand from the hot silo 12 during maintenance activities, during extended shutdowns, or in the event of a situation calling for rapid removal of the hot sand. The screw conveyors 50 are water cooled and transport the sand to the inlet of the cold silo bucket elevator 30 (see FIG. 1 ). Under normal operating conditions, the drain 52 is full of non-moving sand.
With reference to FIG. 3 , a water/steam circuit suitably employed in the illustrative green steam system of FIGS. 1 and 2 is shown. Warm condensate is returned via a pipe or the like 60 from the industrial process (e.g., the illustrative industrial facility F shown in FIG. 1 ) and is mixed with fresh makeup water delivered via a water line 61, and the mixture is delivered via a pipe or the like 62 to the inlet of a feed pump 64 (also indicated in FIG. 1 ). The high-pressure water downstream of the feed pump is split into parallel streams 66 and 68 which are sent through the two economizer modules 22 and 26 (e.g., economizer banks #1 and #2 of FIG. 2 ). Nearly saturated water exits the economizer modules 22 and 26 and is sent via a riser 69 to a steam separator 70 (also indicated in FIG. 1 ), which in the illustrative example is a vertical separator 70. Water exits a bottom 70 _Bof the vertical separator 70 and travels through downcomers 71 to the inlet header 20 _inof the generating bank module 20. A saturated steam/water mix exits the generating bank module 20 at the outlet header 20 _outand returns through risers 72 to the vertical separator 70. This sets up a natural circulation loop where the flow is driven by density differences between the separator 70 and the generating bank 20. The vertical separator 70 also has a blowdown line 76 where water can be removed from the system to control the buildup of dissolved solids within the system. In the illustrative embodiment, the vertical separator 70 is used instead of a steam drum because the vertical separator 70 has a better form factor for the green steam application (e.g., it can be conveniently mounted on the hot silo 12 as diagrammatically shown in FIG. 1 ) and because the vertical separator 70 responds more quickly to changes in steam demand. However, it is contemplated to substitute a steam drum or the like for the illustrative vertical separator 70.
Saturated steam exits the top 70 _Tof the vertical separator 70 and goes through a pipe or the like 78 to a steam accumulator 80 (also indicated in FIG. 1 ) before going through the superheater module 24, by flowing into the inlet header 24 _Inof the superheater module 24. The superheated steam exiting the outlet header 24 _Outof the superheater module 24 is sent via a pipe or the like 82 to the industrial process F (labeled “Steam to process” in FIG. 3 ). The steam accumulator 80 is used in the illustrative green steam system to provide a more rapid response to a change in steam demand than changing the sand flow can achieve. Excess steam is stored in the accumulator 80 when the system produces more steam than is utilized by the industrial process F. The stored steam can later be released to meet a rapid increase in steam demand or to cover some gaps in the availability of the renewable energy source.
The green steam system can also be configured to deliver saturated steam instead of superheated steam by using a second generating bank module instead of the superheater module 24.
The heat exchanger modules 20, 22, 24, 26 may in some embodiments be self-contained devices which can be disconnected from the system and removed via a monorail system for maintenance or replacement.
The illustrative heat exchanger modules are arranged in two particle flow paths. However, more than two sands paths are also contemplated for use in the green steam system.
The illustrative examples employ sand as the granular material. Sand is advantageously low cost, with high heat capacity and good flowability. However, other granular materials are contemplated for use in the green steam system, such as gravel, crushed stone, synthetic granular materials, or so forth.
While the above description constitutes the preferred embodiment of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.

Claims

1. A steam generation system comprising:

a silo configured to receive granular material into the silo at an upper portion of the silo;

a heater arranged at or in the upper portion of the silo to heat the granular material received into the silo;

a material transfer system arranged to remove granular material exiting from a bottom of the silo; and

a heat exchanger disposed in a lower portion of the silo and arranged to contact granular material flowing downward inside the silo.

2. The steam generation system of claim 1 wherein the heat exchanger comprises at least one bank of steam-generating tubes.

3. The steam generation system of claim 2 wherein the steam-generating tubes of the at least one bank of steam-generating tubes are oriented vertically.

4. The steam generation system of claim 3 wherein the heat exchanger further includes at least one economizer disposed beneath the at least one bank of steam-generating tubes.

5. The steam generation system of claim 4 wherein the tubes of the at least one economizer are horizontally and the material transfer system comprises a plurality of mutually parallel screw conveyors or conveyor belts arranged parallel with the horizontal tubes of the at least one economizer.

6. The steam generation system of claim 2 further comprising:

a steam separator or steam drum operatively connected with the at least one bank of steam-generating tubes.

7. The steam generation system of claim 6 wherein the heat exchanger further includes:

a superheater connected to receive water or steam from the steam separator or steam drum.

8. The steam generation system of claim 7 further comprising:

a steam accumulator interposed between the steam separator or steam drum and the superheater.

9. The steam generation system of claim 1 further comprising:

a storage silo connected to

receive granular material removed from the silo by the material transfer system at an upper portion of the storage silo, and to

transfer granular material from the storage silo to the upper portion of the silo.

10. A steam generation method comprising:

providing a steam generation system including a silo configured to receive granular material into the silo at an upper portion of the silo, a heater arranged at or in the upper portion of the silo to heat the granular material received into the silo, a material transfer system arranged to remove granular material exiting from a bottom of the silo, and a heat exchanger disposed in a lower portion of the silo and arranged to contact granular material flowing downward inside the silo;

delivering granular material to the upper portion of the silo of the steam generation system;

delivering electricity to operate the heater of the steam generation system; and

flowing a heat transfer fluid through the heat exchanger of the steam generation system.

11. The steam generation method of claim 10 wherein the delivering of the granular material, the delivering of the electricity, and the flowing of the heat transfer fluid are performed concurrently.

12. The steam generation method of claim 10 wherein the delivered granular material comprises sand.

13. The steam generation method of claim 10 wherein the delivering of the electricity to operate the heater comprises generating the electricity from solar energy or from wind energy.

14. The steam generation method of claim 10 wherein the delivering of the granular material and the delivering of the electricity is effective to heat the granular material to a temperature of at least 600° C.

15. The steam generation method of claim 10 wherein the delivering of the granular material and the delivering of the electricity and the flowing of the heat transfer fluid is effective to cool the granular material exiting from the bottom of the silo to a temperature of 200° C. or lower.

16. A steam generation system comprising:

a heater arranged to heat the received granular material to generate heated granular material;

a heat exchanger disposed in a lower portion of the silo and arranged to extract heat from the heated granular material flowing downward in the silo to generate cooled granular material;

a material transfer system arranged to remove the cooled granular material exiting from a bottom of the silo; and

a storage silo connected to store the cooled granular material removed by the material transfer system and to transfer granular material from the storage silo to the upper portion of the silo.

17. The steam generation system of claim 16 wherein the heat exchanger comprises at least one bank of vertically-oriented steam-generating tubes.

18. The steam generation system of claim 17 wherein the heat exchanger further includes at least one economizer comprising horizontally-oriented tubes disposed beneath the at least one bank of steam-generating tubes.

19. The steam generation system of claim 18 wherein the material transfer system comprises a plurality of mutually parallel screw conveyors or conveyor belts arranged parallel with the horizontally-oriented tubes of the at least one economizer.

20. The steam generation system of claim 16 further comprising:

a steam separator or steam drum operatively connected with the at least one bank of steam-generating tubes; and

a steam accumulator connected to accumulate steam output by the steam separator or steam drum;

wherein the heat exchanger further includes a superheater connected to receive steam from the steam accumulator.