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Recent progress of the superconducting magnet for MHD in China
Fusion Engineering and Design 20 (1993) 299-303 North-Holland
299
Recent progress of the superconducting magnet for MHD in China L . G . Y a n , L . Z . Lin a n d B . H . Jing Institute of Electrical Engineering, Academia Sinica, Bei]ing, China
A coal-fired MHD power generation has been selected as a project for advanced energy technology in the PRC National High-Technology program. In this project, an MHD-steam combined cycle intermediate plant is considered as the most prudent step towards actual commercial demonstration. The conceptual design of the superconducting magnet for the coal-fired MHD intermediate plant is presented in this paper. Construction of the whole superconducting magnet system will be completed in 1999. In the meantime, a middle-size saddle magnet for experimental MHD generator No. 1 is under construction at the Institute of Electrical Engineering, Academia Sinica.
1. Introduction Recent studies on the China energy scene indicate that coal-fired electrical power generation is to be about 70% of the total installed power generation capacity from now to the 50s of the 21st century. Magnetohydrodynamics (MHD) process is a new approach to the coal-fired power generation with significant efficiency and lower emissions than the conventional coal-fired power plant. The MHD-steam combined cycle power plant could increase the efficiencies up to 50-60% which will result in a fuel saving by about 35%. Inherent in the MHD process is the ability to remove sulfur. Its applications could provide a great potential for improving the Chinese backward status in the coal-fired electrical power production. Therefore, a coal-fired MHD power generation has been selected as a project for advanced energy technology in the National High-Technology (863) program in China. In this project, an MHDsteam combined cycle intermediate plant (MI plant) is considered as the most prudent step towards actual commercial demonstration, and the conceptual design effort is a first step to technological demonstration. The MHD conceptual design is jointly conducted by the Institute of Electrical Engineering (lEE), Correspondence to: Dr. L.Z. Zin, Institute of Electrical Engineering, Academia Sinica, P.O. Box 2703, Beijing 100080, China.
Academia Sinica and the University of Tennessee Space Institute (UTSI). The objective of the conceptual design is to evaluate a coal-fired MI plant at ten MW scale to demonstrate the technical feasibility, performance, cost and schedule of an MHD system operating within an electrical utility environment. Since the middle of the 1970s, an MHD superconducting magnet development has been started at the IEE. A series of model saddle magnets have been designed, constructed and tested in sequence. According to the National High-Technology program, a middle-size saddle magnet for experimental MHD generator No. 1 is under construction. The magnet will be ready in 1992.
2. Main characteristics of the magnet According to the MI plant design requirements and contents in the task specification on the conceptual design of the coal-fired MHD intermediate plant in the National High-Technology (863) program, the MHD output should be leveled in ten MW scale. The MI plant steam connection concept is illustrated in fig. 1. The MHD channel design determined that the diameter of warm bore should be 1.1 m, the peak channel field should be 4.5 T and the active length should be more than 5.6 m. Inside the active length the field should not be lower than 68% of the peak channel field. The magnet should be positioned con-
0 9 2 0 - 3 7 9 6 / 9 3 / $ 0 6 . 0 0 © 1 9 9 3 - E l s e v i e r Science Publishers B.V. All rights r e s e r v e d
3(10
L . G . Yah et al. / The superconducting magnet fi)r M H D !
I I
-
TOPPING CYCLE
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=~ | 4 I
=
f I FEEDWATER
I
INVERTER
AE'TRO~ff EX~STIt~ I .
.
.
.
.
.
.
.
.
.
..........
.
I
t
FEE~ATER
BOILER
1
HEAT RECOVERY CONTROLS
Fig. 1. The MI plant steam connection integration concept. sistent with the channel space requirement and requirements for thermal insulation of the coil windings. The selected major parameters of the coil are given in table 1 [1]. A saddle winding is used to produce the transverse field for the M H D generator. It has many advantages, such as: saddle winding requires less conductor compared with racetrack or circular coils, the stored magnetic energy is smaller, the magnetic field in the channel is more uniform and the peak field in the conductor is lower. But the design and construction technology for the saddle coil is much more complicated due to its three-dimensional winding. The magnet will consist of eight coil layers. Each coil layer, having two circular saddle coils will be assembled on the bore tube by spiral banding. When all of the coils have been installed on the bore tube, collars around the coils will be mounted. It cannot support the electromagnetical force, but it can ira-
prove the force transmission. Then the outer He vessel will be mounted and welded, and the 'superstructure' will be installed. Table 1 Major coil parameters Coil overall length Coil overall width (without supcrstructurc) Stored energy Peak channel field Superconductor Operating current Ampere turns Winding average Current density Cooling Coil configuration Number of coil layers Weight of conductor
7.5 m 2.04 m 192 MJ 4.5 T NbTi 3675 A I(I.9 MA 2.07 kA/cm: LHc at 4.2 K, pool boiling circular saddle 8 61.5t
301
L.G. Yan et al. / The superconducting magnet for M H D
The 'superstructure' was designed to carry the Lorentz force in an efficient manner [2]. It is in the vacuum vessel and not in the He vessel, so the latter will be smaller and the quantity of helium stored in the He vessel will be reduced. The assembly layout of this design is given in fig. 2. The cross section of SC magnet for MI plant is shown in fig. 3.
3. Conductor design Conductor design chosen for the MHD SC magnet is similar to the SC magnet for Coal Fired Flow Facility (CFFF/SM) conducted by ANL [2]. It is a monolithic, pool-boiling, He-I cooled conductor. The conductor consists of the superconducting region which contains NbTi superconducting filaments in a copper matrix. This region is surrounded by highpurity copper stabilizer. Its ]gurpose is to carry all of current in case a normalization event occurs in the conductor. To minimize both the winding cost and the induced voltage in the winding when the magnet becomes normal, and also to compromise with the heat leak requirements of the cryostat, an operating current of 3675 A is chosen.
5(3(33 Fig. 3. The cross section of the MHD magnet. As shown in fig. 4, the selected conductor like C F F F / S M will be 3.1cm high with conductor thickness varying according to the field grades. The conductor will be graded into three grades. The turn to turn insulation will be provided by
ff
~
"~.t . . . . . . . . . . . . . . . .
]]1i "~
- ...
-
•
~ ""
J
'
885O 92~ Fig. 2. Assembly layout (cutaway) of the SC magnet design.
302
L.G. Yan et al. / The superconducting magnet for M H D
4. Schedule and cost Aches~ve
/
/
St~bilizer
L
The expected schedule for design, manufacturing and installation of the M H D intermediate plant is expected to be seven years. The operating test including c o m p o n e n t check-out, plant start-up and acceptance testing will be scheduled for the last three years. According to this schedule, the superconducting magnet will be completed in the middle of 1999. The total cost estimated for MI plant is about 1.6 hundred million Yuans (Chinese money). A m o n g which, the cost for superconducting magnet is about 23.5 million Yuans.
~ t o r
5. Saddle magnet for experimental MHD generator
K e y s ~ Pultruc~d Fi~_,-eAass
.4
Fig. 4. The conductor design chosen for the MHD magnet. fiberglass strip. It will be made in a fishbone-like pattern, so that vapor locking will be avoided and that about 40% of broad face of conductor will be cooled. We have considered the possibility of using a conductor developed by the Institute for High Temperature ( I V T A N ) in Moscow. As shown in fig. 5, the conductor designed with an operating current of 4250 A at 5 T will be cryostable. The cooling face is bigger and the cross section of the conductor is smaller as compared with the C F F F / S M conductor. The insulation between turns is inserted in the front face of the conductor, so it is more simple for coil winding. T h e r e f o r e , if later studies show significant advantages, the conductor could be adapted for use on M H D coils.
Stabilizer Fiberglass Insulation~
•4
I
;2'
"××
rYx, I _ _ _ _ _ u ~ t o r /
/t ~. ,4.:~ -J " - J
Fig. 5. A cryostable superconductor.
I
A superconducting saddle magnet for the experimental M H D generator is under construction at the Institute of Electrical Engineering, Academia Sinica [3]. The magnet consists of 17 coil layers. Each layer has two circular saddle windings with a 54.5 ° segment cross section [4]. The conductor is 2 m m × 10 mm NbTi monolithic provided by Supercon Co. According to the field grades the conductor is graded into two grades. They are fully superconducting at l l 0 0 A in a field of 6 . 5 T and at l l 0 0 A in 4 . 5 T respectively. The coils are assembled on the bore tube by spiral bandings. The main parameters of the saddle m a g n e t are shown in table 2. Table 2 Main parameters of a saddle magnet Central field Operating current Stored energy Total cold weight Inner diameter of winding Outer diameter of winding Length of winding Number of layers Number of turns Height of LHe channel Diameter of warm bore Effective magnetic length Cross section of conductor Number of filaments Grade A filament Diameter Grade B filament Diameter Cu/S.C. ratio grade A grade B
4.1 T 905 A 9.4 MJ 11 tons 690 mm 1200 mm 1760 m m 17 5796 5 mm 420 mm 850 mm 2 mm x 10 mm 61 172 ~m [4() txm 13.1 20.3
Note: There are some differences between the completed magnet and the original design.
L.G. Yan et al. / The superconducting magnet for MHD
The bore tube is the main structural support for the cold mass and electromagnetic forces. Made up of two end flanges and a cylindrical section, the assembly weighs 3.6t. In addition to the magnetic forces, the bore tube assembly is designed for a 5 kg/cm 2 pressure in the helium vessel. The banding is 3 mm by 10 mm stainless steel strip. It is insulated with a 50% overlap wrap of mylar film. Between coil layer and banding a fiberglass blanket
303
with a thickness of 1 mm is employed. There are many cooling down grooves on it, so that about 50% of the narrow face of the conductor will be cooled. In each layer, the space between saddle coil ends and the end flanges of bore tube is filled with end filler of fiberglass strips and epoxy putty to form a cylindrical shape. Figure 6 shows the saddle magnet under construction. The magnet will be completed in the spring of 1992.
5. Summary A conceptual superconducting magnet has been designed for the coal-fired M H D intermediate plant in China. Reliability of the magnet and possibility in the technology were considered to be extremely important for this plant. The M H D superconducting magnet will be completed in 1999.
References
Fig. 6. A saddle magnet under construction.
[1] Conceptual Design of a Coal Fired MHD Retrofit Plant, Technical Report (December 1990). [2] MHD Magnet Technology Development Program Summary, MIT (September 1982). [3] L.G. Yan and B.H. Jing, Progress of the MHD Superconducting Magnet Development in China, 10th Int. Conf. MHD Power Generation, December 4-8, 1989. [4] R.J. Thome and J.M. Tarrh, MHD and Fusion Magnets, MIT (1982) p. 29.
299
Recent progress of the superconducting magnet for MHD in China L . G . Y a n , L . Z . Lin a n d B . H . Jing Institute of Electrical Engineering, Academia Sinica, Bei]ing, China
A coal-fired MHD power generation has been selected as a project for advanced energy technology in the PRC National High-Technology program. In this project, an MHD-steam combined cycle intermediate plant is considered as the most prudent step towards actual commercial demonstration. The conceptual design of the superconducting magnet for the coal-fired MHD intermediate plant is presented in this paper. Construction of the whole superconducting magnet system will be completed in 1999. In the meantime, a middle-size saddle magnet for experimental MHD generator No. 1 is under construction at the Institute of Electrical Engineering, Academia Sinica.
1. Introduction Recent studies on the China energy scene indicate that coal-fired electrical power generation is to be about 70% of the total installed power generation capacity from now to the 50s of the 21st century. Magnetohydrodynamics (MHD) process is a new approach to the coal-fired power generation with significant efficiency and lower emissions than the conventional coal-fired power plant. The MHD-steam combined cycle power plant could increase the efficiencies up to 50-60% which will result in a fuel saving by about 35%. Inherent in the MHD process is the ability to remove sulfur. Its applications could provide a great potential for improving the Chinese backward status in the coal-fired electrical power production. Therefore, a coal-fired MHD power generation has been selected as a project for advanced energy technology in the National High-Technology (863) program in China. In this project, an MHDsteam combined cycle intermediate plant (MI plant) is considered as the most prudent step towards actual commercial demonstration, and the conceptual design effort is a first step to technological demonstration. The MHD conceptual design is jointly conducted by the Institute of Electrical Engineering (lEE), Correspondence to: Dr. L.Z. Zin, Institute of Electrical Engineering, Academia Sinica, P.O. Box 2703, Beijing 100080, China.
Academia Sinica and the University of Tennessee Space Institute (UTSI). The objective of the conceptual design is to evaluate a coal-fired MI plant at ten MW scale to demonstrate the technical feasibility, performance, cost and schedule of an MHD system operating within an electrical utility environment. Since the middle of the 1970s, an MHD superconducting magnet development has been started at the IEE. A series of model saddle magnets have been designed, constructed and tested in sequence. According to the National High-Technology program, a middle-size saddle magnet for experimental MHD generator No. 1 is under construction. The magnet will be ready in 1992.
2. Main characteristics of the magnet According to the MI plant design requirements and contents in the task specification on the conceptual design of the coal-fired MHD intermediate plant in the National High-Technology (863) program, the MHD output should be leveled in ten MW scale. The MI plant steam connection concept is illustrated in fig. 1. The MHD channel design determined that the diameter of warm bore should be 1.1 m, the peak channel field should be 4.5 T and the active length should be more than 5.6 m. Inside the active length the field should not be lower than 68% of the peak channel field. The magnet should be positioned con-
0 9 2 0 - 3 7 9 6 / 9 3 / $ 0 6 . 0 0 © 1 9 9 3 - E l s e v i e r Science Publishers B.V. All rights r e s e r v e d
3(10
L . G . Yah et al. / The superconducting magnet fi)r M H D !
I I
-
TOPPING CYCLE
-I
=~ | 4 I
=
f I FEEDWATER
I
INVERTER
AE'TRO~ff EX~STIt~ I .
.
.
.
.
.
.
.
.
.
..........
.
I
t
FEE~ATER
BOILER
1
HEAT RECOVERY CONTROLS
Fig. 1. The MI plant steam connection integration concept. sistent with the channel space requirement and requirements for thermal insulation of the coil windings. The selected major parameters of the coil are given in table 1 [1]. A saddle winding is used to produce the transverse field for the M H D generator. It has many advantages, such as: saddle winding requires less conductor compared with racetrack or circular coils, the stored magnetic energy is smaller, the magnetic field in the channel is more uniform and the peak field in the conductor is lower. But the design and construction technology for the saddle coil is much more complicated due to its three-dimensional winding. The magnet will consist of eight coil layers. Each coil layer, having two circular saddle coils will be assembled on the bore tube by spiral banding. When all of the coils have been installed on the bore tube, collars around the coils will be mounted. It cannot support the electromagnetical force, but it can ira-
prove the force transmission. Then the outer He vessel will be mounted and welded, and the 'superstructure' will be installed. Table 1 Major coil parameters Coil overall length Coil overall width (without supcrstructurc) Stored energy Peak channel field Superconductor Operating current Ampere turns Winding average Current density Cooling Coil configuration Number of coil layers Weight of conductor
7.5 m 2.04 m 192 MJ 4.5 T NbTi 3675 A I(I.9 MA 2.07 kA/cm: LHc at 4.2 K, pool boiling circular saddle 8 61.5t
301
L.G. Yan et al. / The superconducting magnet for M H D
The 'superstructure' was designed to carry the Lorentz force in an efficient manner [2]. It is in the vacuum vessel and not in the He vessel, so the latter will be smaller and the quantity of helium stored in the He vessel will be reduced. The assembly layout of this design is given in fig. 2. The cross section of SC magnet for MI plant is shown in fig. 3.
3. Conductor design Conductor design chosen for the MHD SC magnet is similar to the SC magnet for Coal Fired Flow Facility (CFFF/SM) conducted by ANL [2]. It is a monolithic, pool-boiling, He-I cooled conductor. The conductor consists of the superconducting region which contains NbTi superconducting filaments in a copper matrix. This region is surrounded by highpurity copper stabilizer. Its ]gurpose is to carry all of current in case a normalization event occurs in the conductor. To minimize both the winding cost and the induced voltage in the winding when the magnet becomes normal, and also to compromise with the heat leak requirements of the cryostat, an operating current of 3675 A is chosen.
5(3(33 Fig. 3. The cross section of the MHD magnet. As shown in fig. 4, the selected conductor like C F F F / S M will be 3.1cm high with conductor thickness varying according to the field grades. The conductor will be graded into three grades. The turn to turn insulation will be provided by
ff
~
"~.t . . . . . . . . . . . . . . . .
]]1i "~
- ...
-
•
~ ""
J
'
885O 92~ Fig. 2. Assembly layout (cutaway) of the SC magnet design.
302
L.G. Yan et al. / The superconducting magnet for M H D
4. Schedule and cost Aches~ve
/
/
St~bilizer
L
The expected schedule for design, manufacturing and installation of the M H D intermediate plant is expected to be seven years. The operating test including c o m p o n e n t check-out, plant start-up and acceptance testing will be scheduled for the last three years. According to this schedule, the superconducting magnet will be completed in the middle of 1999. The total cost estimated for MI plant is about 1.6 hundred million Yuans (Chinese money). A m o n g which, the cost for superconducting magnet is about 23.5 million Yuans.
~ t o r
5. Saddle magnet for experimental MHD generator
K e y s ~ Pultruc~d Fi~_,-eAass
.4
Fig. 4. The conductor design chosen for the MHD magnet. fiberglass strip. It will be made in a fishbone-like pattern, so that vapor locking will be avoided and that about 40% of broad face of conductor will be cooled. We have considered the possibility of using a conductor developed by the Institute for High Temperature ( I V T A N ) in Moscow. As shown in fig. 5, the conductor designed with an operating current of 4250 A at 5 T will be cryostable. The cooling face is bigger and the cross section of the conductor is smaller as compared with the C F F F / S M conductor. The insulation between turns is inserted in the front face of the conductor, so it is more simple for coil winding. T h e r e f o r e , if later studies show significant advantages, the conductor could be adapted for use on M H D coils.
Stabilizer Fiberglass Insulation~
•4
I
;2'
"××
rYx, I _ _ _ _ _ u ~ t o r /
/t ~. ,4.:~ -J " - J
Fig. 5. A cryostable superconductor.
I
A superconducting saddle magnet for the experimental M H D generator is under construction at the Institute of Electrical Engineering, Academia Sinica [3]. The magnet consists of 17 coil layers. Each layer has two circular saddle windings with a 54.5 ° segment cross section [4]. The conductor is 2 m m × 10 mm NbTi monolithic provided by Supercon Co. According to the field grades the conductor is graded into two grades. They are fully superconducting at l l 0 0 A in a field of 6 . 5 T and at l l 0 0 A in 4 . 5 T respectively. The coils are assembled on the bore tube by spiral bandings. The main parameters of the saddle m a g n e t are shown in table 2. Table 2 Main parameters of a saddle magnet Central field Operating current Stored energy Total cold weight Inner diameter of winding Outer diameter of winding Length of winding Number of layers Number of turns Height of LHe channel Diameter of warm bore Effective magnetic length Cross section of conductor Number of filaments Grade A filament Diameter Grade B filament Diameter Cu/S.C. ratio grade A grade B
4.1 T 905 A 9.4 MJ 11 tons 690 mm 1200 mm 1760 m m 17 5796 5 mm 420 mm 850 mm 2 mm x 10 mm 61 172 ~m [4() txm 13.1 20.3
Note: There are some differences between the completed magnet and the original design.
L.G. Yan et al. / The superconducting magnet for MHD
The bore tube is the main structural support for the cold mass and electromagnetic forces. Made up of two end flanges and a cylindrical section, the assembly weighs 3.6t. In addition to the magnetic forces, the bore tube assembly is designed for a 5 kg/cm 2 pressure in the helium vessel. The banding is 3 mm by 10 mm stainless steel strip. It is insulated with a 50% overlap wrap of mylar film. Between coil layer and banding a fiberglass blanket
303
with a thickness of 1 mm is employed. There are many cooling down grooves on it, so that about 50% of the narrow face of the conductor will be cooled. In each layer, the space between saddle coil ends and the end flanges of bore tube is filled with end filler of fiberglass strips and epoxy putty to form a cylindrical shape. Figure 6 shows the saddle magnet under construction. The magnet will be completed in the spring of 1992.
5. Summary A conceptual superconducting magnet has been designed for the coal-fired M H D intermediate plant in China. Reliability of the magnet and possibility in the technology were considered to be extremely important for this plant. The M H D superconducting magnet will be completed in 1999.
References
Fig. 6. A saddle magnet under construction.
[1] Conceptual Design of a Coal Fired MHD Retrofit Plant, Technical Report (December 1990). [2] MHD Magnet Technology Development Program Summary, MIT (September 1982). [3] L.G. Yan and B.H. Jing, Progress of the MHD Superconducting Magnet Development in China, 10th Int. Conf. MHD Power Generation, December 4-8, 1989. [4] R.J. Thome and J.M. Tarrh, MHD and Fusion Magnets, MIT (1982) p. 29.