Iron Oxide Scale Removal from Boiler Feed- Water in Thermal Power Plant by Magnetic Separation

Transcription

1 Construction of Low-Carbon Society Using Superconducting and Cryogenic Technology March 7 th 9 th, 2016 Cosmo Square Hotel & Congress, Osaka Japan Iron Oxide Scale Removal from Boiler Feed- Water in Thermal Power Plant by Magnetic Separation Shigehiro NISHIJIMA Osaka University

2 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

3 Iron Oxide Scale Removal from Boiler Feed-Water in Thermal Power Plant by Magnetic Separation Contents 1. 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?

4 1. Why Thermal Power Plant? Changes of electricity generation and CO 2 emission in Japan CO 2 emission (Red line) has been increasing in recent years. Nuclear power generation (Red frame) has decreased, Thermal power generation (Black frame) has increased Efficiency of Thermal power generation is related to CO 2 emission directly. Practically preventing decrease of efficiency is important

5 2. Why magnetic separation (MS)? Preventing decrease of efficiency is important in thermal power plant. The main factor of decline in thermal power generation efficiency is Scale. Formed by corrosion of pipework materials of feed-water system Thermal conductivity : about 10% of pipework scale adhesion Decrease in heat-exchange efficiency Increase in pressure loss Preventing scale adhesion is important to keep the efficiency high.

6 Calculation of CO 2 reduction Heat exchanger Scale Pipe Pump heat Boiller heat Decrease in heat-exchange efficiency 70 μm scale is formed in a boiler every year Removing the scale 0.8% improvement of thermal conversion efficiency ~1,480,000t CO 2 /year reduction Increase in pressure loss 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 CO 2 /year reduction At least in total ~1,600,000t CO 2 /year reduction

7 Scale properties at each temperature Main chemical component Low-temperature area Iron ion Iron Oxyhydroxide(FeOOH) High-temperature area Magnetite(Fe 3 O 4 )/ Hematite(Fe 2 O 3 ) Separation Rate (%) size <0.45μm ~10 μm Saturated magnetization - 50~100emu/g Scale concentration - 10 ppb membrane High gradient Magnetic separation Fluid speed(m/s) Separation efficiency of (ferromagnetic) particles at high speed. at high temperature area easy to remove What kind of filtering system? High Gradient Magnetic Separation (HGMS) for scale removal from feed-water

8 Water purification system in feed water circuit High-pressure turbine Low-pressure turbine Boiler Condenser HGMS Deaerator High-pressure Low-pressure feed-water heater feed-water heater

9 3.Why superconducting MS? High Gradient Magnetic Separation (HGMS) Magnet Flow Field Stainless wires

10 HGMS system for scale removal 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. Line of feed-water system Solenoidal superconducting magnet Magnetic separation unit Valve 1 : open Valve 4 : close Amount of feed-water for treatment : about 400 ~ 500 m 3 /h => Large magnetic area is required. Valve 3 : close Valve 2 : open

11 Why superconducting magnetic separation? Requests for magnet Inner diameter of HGMS system : 50 ~ 60 cm Flow velocity : 70 cm/s Magnetic field : 1 T - 2 T Temperature : 200 C Pressure : 2 MPa Cooling by refrigerator Superconducting Magnet Solenoidal superconducting magnet cm 100 cm Advantages Magnetic filters can be washed and reused. Magnetic filter (ferromagnetic) cm magnetic shielding Low pressure loss Low secondary waste

12 4.Does MS work under high temp & pressure? 4-1 Magnetic separation experiment under high temp & pressure 4-2 Magnetic Filter design for long time operation 4-3 Formation of iron-oxide

13 Does it work at the high-temperature & high pressure? Inner diameter of HGMS system : 50 ~ 60 cm Flow velocity : 70 cm/s Applied magnetic field : 1 T - 2 T Temperature : 200 C Pressure : 2 MPa Two pressure vessel are connected. Initial condition of the pressure vessel Temperature Pressure Vessel A MPa Vessel B MPa Magnetic Separation under high temperature & high pressure Vessel A: Vessel B: 350mL of suspension was encapsulated and heated to ml of distilled water was encapsulated and heated to 200 The suspension flowed through the magnetic filter because of the different pressure

14 Magnetic separation at the high-temperature & pressure Temperature ~200 (473K), Pressure ~2MPa(20 atm) Magnetic fields: 0.5, 1, 2 T Flow velocity : 60~70 cm/s Separation object (simulated scales ) The mixture 80 wt.% of magnetite 20 wt.% of hematite Concentration of suspension: 50 ppm Magnetic separation device Experimental system Magnetic filter Diameter: 6.3 mm Wire diameter:0.1 mm Length: 90 mm Flow velocity 60~70 cm/s Physical properties of iron oxide particles Hematite Magnetite Particle diameter(μm) Magnetic susceptibility(-) Saturated magnetization(t) - 0.4

15 Magnetic separation at the high-temperature & pressure Experimental result Trapped and passed particles at each magnetic field Most of trapped particles are magnetite and passed particles are hematite When the applied magnetic field was 2 T, most of particles were removed Magnetic separation efficiency(%) Magnetic separation efficiency at each magnetic field 88 % 95 % 0.5T 1T 2T Magnetic field 98 % When the applied magnetic field was 2 T, separation efficiency became up to 98% These results show the applicability of the magnetic separation under the condition of the high-temperature and high pressure (200,2 MPa).

16 Experimental setup

17 Verification of designed filters by HGMS experiment Experimental setup Membrane filter Pressure gauge Sampling valve P Circulating pump Solenoidal superconducting magnet Sampling valve Pressure gauge P Magnetic separation unit Static mixer 51 mm Magnetic separation unit Injection pump Tank Magnetic separation unit Inner diameter : 51 mm Magnetic filter (ferromagnetic) Ring spacer (paramagnetic) Spacer width : 5.0 mm

18 Magnetic Filter

19 Water Treatment To 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 system for AVT can be applied. AVT: All Volatile Treatment / Ammonia(NH 3 )Hydrazine (N 2 H 4 ) CWT: Combined Water Treatment / / Ammonia(NH 3 ) Depending the water treatment, different type of scale occurs. Basic research for formation of iron-oxide

20 XRD analysis Ferromagnetic Ferromagnetic Paramagnetic Ferromagnetic Paramagnetic Scale is composed of various components depending on water treatment. 20

21 Developing apparatus Conditions of each part in thermal power plant Schematic diagram of experimental equipment The developing circulation equipment Apparatus for Scale formation under flow By this experiment we can deal with any types of scale. 21

22 Contents 1. 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

23 Not thermal power plant but heater boiler system. Superconducting MS system is introduced in a factory for demonstration.

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26 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.