ENVIRONMENTAL PROTECTION IN THE FIELD OF THERMAL POWER PLANT

8/13/2019 ENVIRONMENTAL PROTECTION IN THE FIELD OF THERMAL POWER PLANT

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ENVIRONMENTAL PROTECTION IN THE FIELD

OF THERMAL POWER PLANT

By: Goverdhan Shrestha


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Power Plant and Pollution

Thermal Pollution

Air pollution


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Air pollution in Thermal Power Plant

Fuel

Storage

Facilities

Combustion

Equipment

Exhaust

Gas

Treatment

Facilities

In Plant

Waste

Treatment

SOX

,NOX, CO2, Trace

Substances Particles

Ash, Heavy MetalThermal Power Plant

Dust,

HydrocarbonDust


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Ways to reduce emissions from Fossil Fuel power stations

Flue Gas Cleaning

Capture and Storage of CO2

Range of technologies arebeing used and developed

De- NOX

Dust

collector

De-SOX


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Pollutants and Pollution Control in Coal Fired Power Plant

Coal De- NOX EP De-SOXBoiler

St

a

c

k

Ash Pond

Gypsum

Ash

SOX,NOX, CO2

Dust

Thermal Power Plant

Flue Gas

Cleaning


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At present, mainstream technology

Flue Gas Denitrification

high efficiency in reduction (80% to 90%)

SCR (SelectiveCatalytic

Reduction)

Catalyst: TiO2-Ceramic (with V, W, Mo

additives)

To keep emission of nitrogen oxides

as low as possible

use ammonia as the reducing agent

by catalytic reaction, into nitrogen gas and

water

Method Applicability NOx red. (%)

Flue gas recirculation T-NOx 70~80

Low Nox burner T-NOx , F-NOx 20~50

Staged burners F-NOx, T-NOx 40~50

SCR F-NOx, T-NOx 80~90

SNCR F-NOx, T-NOx 60~80

Nox Abatement Method


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Selective Catalytic Reduction Method

reducing NOxby injecting ammonia as a

reductant in the upstream of air pre-heater

the flue gas temperature ranges from 300 to

400

NOx is reduced into N2 and H2O in the reactor

with catalyst TiO2-Ceramic

Basic reaction formula:

4NH3 4NO + O2 4N2 6H2O

8NH3 6NO2 7N2 12H2O


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NOxreduction potential at different flue gas temperatures


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Dust Collector

remove 99% of particulates from the flue gas.

method of dust collection that uses electrostatic forces, and consists of discharge

wires and collecting plates

Electrostatic Precipitator (EP)

Schematic Diagram of EP

a system used to enhance the quality of air released from the boiler

more effective to remove very small particles like smoke, mist and fly ash


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Dust Separation Mechanism of the Electrostatic Precipitator

Gas Ionization by Corona Discharge

Charging

Precipitation

Dust Removal

Source: smmec.co.jp


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Desulfurization with Limestone-Gypsum Process

Schematic design of the absorber of an FGD

Flue Gas Desulphurization (FGD)

worlds most widely used FGD technologylimestone slurry acts as an absorbent

limestone slurry absorbs SO2 then it is

oxidized by air at the lower part of absorber to

produce calcium sulphate

extracted from the absorber as gypsumslurry and finally dewatered and reused in the

form of gypsum powder


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Ash Treatment

Fly ash bricks

Fly ash in manufacture of cement

Fly ash in distemper

Fly ash in road construction


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Greenhouse Gas Emissions

way to reduce CO2 emissions from fossil fuels power stations:

Carbon capture and storage

CCS applied to a modern conventional power

plant could reduce CO2 emissions to the

atmosphere by approximately 8090%

compared to a plant without CCS

CCS is made up of three key stages.

1. Capture: Carbon capture is the

separation of CO2 from the other

gases produced when fossil fuels are

burnt for power

2. Transport: Once separated, the

CO2 is compressed and transported

to a suitable sites.

3. Storage: in geological formations, inthe ocean, in mineral carbonates, or for

use in industrial processes

CCS refers to a set of CO2 capture,transport and storage technologies that are

put together to abate emissions

Illustration by

Belle Mellor


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Capture

Transport

Storage

Three Options;

Post-combustion Pre-combustion

Oxyfuel

Two Options; Pipelines

Ships

CCS VALUE CHAIN


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CO2 capture systems


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CO2 Storage

Structural/stratigraphic trappingtrapping of CO2below low-permeability seals (caprocks)

Solubility trappingsome CO2 dissolves in water, the water becomes denser,

and begins to sink downwards

it no longer exists as a separate entity, thereby eliminating

the buoyant forces that drive it upwards

Hydrodynamic trapping (Saline aquifers)displaces saline formation water and then migrates buoyantly

upwards through permeable rock

fluids migrate very slowly over long distancescontinues to migrate as a separate phase until it is trapped as residual

CO2 saturation or in local structural or stratigraphic traps


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CO2pumped into disused coal fields displaces

methane which can be used as fuel

CO2pumped into oil fields helps maintain pressure,

making extraction easier

Mineral storage

dissolved CO2 reacts with the reservoir rock, carbonate minerals can

form and precipitate

the time line for this trapping mechanism is over thousands of years

the permanence of mineral storage, combined with the potentiallylarge storage capacity present in some geological settings, makes this a

desirable feature of long term storage


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Current maturity of CCS system components

IPCC Special Report on Carbon dioxide Capture and Storage


21/21Thank You

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ENVIRONMENTAL PROTECTION IN THE FIELD OF THERMAL POWER PLANT