Iron Oxide Scale Removal from Boiler Feed-Water in Thermal Power Plant
by Magnetic Separation
Construction of Low-Carbon Society Using Superconducting and Cryogenic Technology
March 7th–9th, 2016Cosmo Square Hotel & Congress, Osaka Japan
Shigehiro NISHIJIMAOsaka University
Osaka Univ. Saori SHIBATANI, Motohiro NAKANISHI, Nobumi MIZUNO,
Fumihito MISHIMA, Yoko AKIYAMA
NIMS : Hidehiko OKADA, Noriyuki HIROTA
Shikoku Research Institute Inc.
:Hideki MATSUURA, Tatsumi MAEDA, Naoya SHIGEMOTO
Contents1. Why Thermal Power Plant?2. Why magnetic separation (MS)?3. Why superconducting (MS)?4. Does MS work under high temp & pressure?5. Does MS work in a factory?
Iron Oxide Scale Removal from Boiler Feed-Water in Thermal Power Plant
by Magnetic Separation
Efficiency of Thermal power generation is related to CO2 emission directly.Efficiency of Thermal power generation is related to CO2 emission directly.
1. Why Thermal Power Plant?
CO2 emission (Red line) has been increasing in recent years .
Changes of electricity generation and CO2 emission in Japan
Practically preventing decrease of efficiency is important
Nuclear power generation (Red frame) has decreased ,Thermal power generation (Black frame) has increased
The main factor of decline in thermal power generation efficiency is Scale.
Decrease in heat-exchange efficiencyIncrease in pressure loss
Formed by corrosion of pipework materials of feed-water systemThermal conductivity : about 10% of pipework
scale adhesion
2. Why magnetic separation (MS)?
Preventing scale adhesionis important to keep the efficiency high .
Preventing decrease of efficiency is important in thermal power plant.
PumpPipe
Boiller
Heat exchanger
Decrease in heat-exchange efficiency
Increase in pressure loss
~1,480,000t‐CO2/year reduction
Scale
Due to Scale adhesion to pipes or pumps, energy consumption of water supply pump is increased
Removing the scale →thermal conversion efficiency of 0.1%
↓
~130,000t‐CO2/year reduction
At least in total ~1,600,000t ‐CO2/year reduction
Calculation of CO2 reduction
heatheat
70 μm scale is formed in a boiler every yearRemoving the scale →
0.8% improvement of thermal conversion efficiency
Low-temperature area High-temperature area
Main chemical component Iron ionIron Oxyhydroxide(FeOOH)
Magnetite(Fe3O4)/Hematite(Fe2O3)
size <0.45μm ~10 μm
Saturated magnetization - 50~100emu/g
Scale concentration - 10 ppb
Scale properties at each temperature
High Gradient Magnetic Separation (HGMS) for scale removal from feed-water
at high temperature areaeasy to remove
Separation efficiency of (ferromagnetic) particles at high speed.
0
20
40
60
80
100
0 0.2 0.4 0.6 0.8
Fluid speed(m/s)
Sepa
ratio
n Ra
te(%
)
What kind of filtering system?High gradient Magnetic separation
membrane
Boiler
High-pressure turbine
Low-pressure turbine
Condenser
Low-pressurefeed-water heater
Deaerator High-pressure
feed-water heater
HGMS
Water purification system in feed water circuit
HGMS device is installed in bypassed line of feed-water system.
Scale is captured in magnetic separation unit.
Magnetic separation is performed continuously under operation of thermal power plant.=> Magnetic filters are washed and reused.
Amount of feed-water for treatment: about 400 ~ 500 m3/h
=> Large magnetic area is required.
Line of feed-water system
Valve 4 : close
Valve 3 : close
Valve 2: open
Valve 1 : open
Solenoidal superconducting magnet
Magnetic separation unit
HGMS system for scale removal
Inner diameter of HGMS system : 50 ~ 60 cm Flow velocity : 70 cm/sMagnetic field : 1 T - 2 T Temperature : 200 °CPressure : 2 MPaCooling by refrigerator
Requests for magnet
Solenoidal superconducting magnet
Magnetic filter (ferromagnetic)
50 – 60 cmmagnetic shielding
90 – 100 cm
100 cm
Magnetic filters can be washed and reused.Low pressure lossLow secondary waste
Advantages
Superconducting Magnet
Why superconducting magnetic separation?
4-1 Magnetic separation experiment under high temp & pressure4-2 Magnetic Filter design for long time operation4-3 Formation of iron-oxide
4.Does MS work under high temp & pressure?
Does it work at the high-temperature & high pressure?
The suspension flowed through the magnetic filter because of the different pressure
Two pressure vessel are connected.Initial condition of the pressure vessel
Temperature Pressure
Vessel A 235 ℃ 2.9MPa
Vessel B 200℃ 1.4MPa
350mL of suspension was encapsulated and heated to 235℃
50 mL of distilled water was encapsulated and heated to 200 ℃
Vessel A:
Vessel B:
Inner diameter of HGMS system : 50 ~ 60 cm Flow velocity : 70 cm/sApplied magnetic field : 1 T - 2 T Temperature : 200 °CPressure : 2 MPa
Magnetic Separation under high temperature & high pressure
Length:90 mm
Diameter:6.3 mm
Magnetic separation device
Flow velocity60~70 cm/s
Wire diameter:0.1 mm
◦Separation object (simulated scales )
◦Magnetic fields: 0.5, 1, 2 T
Physical properties of iron oxide particlesHematite Magnetite
Particle diameter(μm) 1.47 1.36Magnetic susceptibility(-) 2.0×10-3 -Saturated magnetization(T) - 0.4
The mixture 80 wt.% of magnetite 20 wt.% of hematite
Magnetic filter
◦Concentration of suspension: 50 ppm
◦Flow velocity : 60~70 cm/s
Magnetic separation at the high-temperature & pressureExperimental system Temperature ~200℃(473K),
Pressure ~2MPa(20 atm)
These results show the applicability of the magnetic separation under the condition of the high-temperature and high pressure (200℃,2 MPa) .
0
20
40
60
80
100
0.5T 1T 2T
Mag
netic
sep
arat
ion
effic
ienc
y(%
)
Magnetic field
88 %98 %
・Most of trapped particles are magnetite and passed particles are hematite
When the applied magnetic field was 2 T, separation efficiency became up to 98%
Magnetic separation efficiency at each magnetic field
Trapped and passed particles at each magnetic field
95 %
Magnetic separation at the high-temperature & pressureExperimental result
・When the applied magnetic field was 2 T, most of particles were removed
Magnetic separation unit
51 mm
Magnetic filter(ferromagnetic)
Ring spacer(paramagnetic)
Inner diameter : 51 mm
Spacer width : 5.0 mm
Magnetic separation unit
Solenoidal superconducting magnet
Tank
Circulating pump
Injection pump
Static mixer
P
PPressure gauge
Sampling valve
Pressure gauge
Sampling valve
Membrane filter
Magnetic separation unit
Experimental setup
Verification of designed filters by HGMS experiment
Water TreatmentTo prevent the occurrence of scale, water treatment is performed
such as All Volatile Treatment , Combined water treatment.
The treatment can not avoid the scale occurrence completely.This is the reason why the scale removal technique is needed.
AVT prevails now
CWT will predominant in future
In this research we have focused.
Developed superconducting HGMS systemfor AVT can be applied.
Basic research for formation of iron-oxide
Depending the water treatment, different type of scale occurs.
AVT: All Volatile Treatment / Ammonia(NH3)Hydrazine(N2H4 )
CWT: Combined Water Treatment / / Ammonia(NH3)
20
Scale is composed of various components depending on water treatment.
Ferromagnetic
Ferromagnetic
Paramagnetic
FerromagneticParamagnetic
XRD analysis
21
Schematic diagram of experimental equipment
The developing circulation equipment
Conditions of each part in thermal power plant
Apparatus for Scale formation under flow
Developing apparatus
By this experiment we can deal withany types of scale.
Contents1. Why Thermal Power Plant?2. Why magnetic separation (MS)?3. Why superconducting (MS)?4. Does MS work under high temp & pressure?5. Does MS work in a factory?
Safety , efficiency, long-time reliability are to be proven.
Demonstration experiment
Not thermal power plant but heater boiler system.Superconducting MS system is introduced in a factory for demonstration.
Conclusion
1. Scale removal from feed water in thermal power plant is effective to keep the efficiency high.2.Supreconducting high gradient magnetic separation is suitable to remove scale.3. Superconducting magnetic separation can be operated at high temperature and high pressure.4. Superconducting magnetic separation is demonstrated to be operated in a factory.
This work is supported by Advanced Low Carbon Technology Research and Development Program (ALCA) of JST Strategic Basic Research Programs.