Iron Oxide Scale Removal from Boiler Feed- Water in ......Iron Oxide Scale Removal from Boiler Feed-Water in Thermal Power Plant by Magnetic Separation Construction of Low-Carbon Society

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

Magnet

FieldFlow

Stainless wires

High Gradient Magnetic Separation (HGMS)

3．Why superconducting MS?

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

Experimental setup

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

Magnetic Filter

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.