power plant water treatment

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Power Plant Water Treatment

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Welcomes

SKS POWER GENERATION CHHATTISGARH LIMITED

TATA POWER COMPANY LIMITED


An Overview of Plant Water System

At

SPGCL, Raigarh, Chhattisgarh.


Water Cycle for DM Water

• Source of Raw Water – Mahanadi River (44KM)• Raw Water Reservoir• Stilling Chamber• Solid Contact Clarifier• Clarified Water Storage Tank• Pressure Sand Filter• Basket Filter• Ultra-Filtration• Micron Cartridge Filter• High Pressure Pump• Reverse Osmosis• Degasser Tower• Mixed Bed• DM Water Storage Tank


Water Storage Facility• Raw Water Reservoir

• Quantity : 2 Nos (1W + 1S)

• Capacity : 500000 M3 (each)


Design Raw Water QualityS.No Parameter Units Result

1 pH --- 8.402 Conductivity µs/cm 3353 Total Dissolved Salts ppm 2014 Total Suspended Salts ppm 2005 Turbidity NTU 2006 Alkalinity ppm 747 Chloride ppm 308 Silica ppm 119 Colloidal Silica ppm 3310 Sulphate ppm 2911 Sodium ppm 2112 Magnesium ppm 2113 Calcium ppm 4714 Iron ppm 2


Water Treatment Facility• Solid Contact Clarifier

(SCC)

• Quantity : 2 Nos

• Flow : 2011 M3/Hr

• Chemical Used in SCC :

• NaOCl

• FeCl3

• Lime

• Polyelectrolyte


Pretreatment Terminology• Turbidity• Turbidity is the cloudiness or haziness of a fluid caused by large numbers of

individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality

• Clarifier• A clarifier is a settling tank used to remove solid waste particles from water.

When the clarifier separates the concentrated impurities, the sludge formed by the process discharges from the bottom of the tank.

• Thickener• An apparatus for the sedimentation of solids from suspension in a liquid.

• Decanter Centrifuge• A centrifuge is a device, which employs a high rotational speed to separate

components of different densities. A decanter centrifuge separates solid materials from liquids in slurry and therefore plays an important role in wastewater treatment.


Operations involved in removal of un-dissolved Impurities


Purpose of Pretreatment Chemicals• Coagulation• Coagulation is a process to neutralize charges and then to form a gelatinous

mass to trap particles thus forming a mass large enough to settle or be trapped in the filter.

• Flocculation• Flocculation is gentle stirring or agitation to encourage the particles thus formed

to agglomerate into masses large enough to settle or be filtered from solution.


Uses of Pretreatment Chemicals• NaOCl: Chlorination.• NaOCl + H2O → HOCl + NaOH• HOCl → HCl + O

• Lime: pH correction & Alkalinity• CaO + H2O → Ca(OH)2

• FeCl3: Coagulation.• 2 Fe Cl3 + 3 Ca(HCO3)2 → 2 Fe(OH)3 + 3CaCl2 +

6CO2

• Polyelectrolyte: Flocculation.


SCC Outlet Water QualityS.No Parameter Units Result

1 Turbidity NTU ≤ 102 Total Suspended Salts ppm ≤ 103 Colloidal Silica (Without

Lime)ppm ≤ 10

4 Colloidal Silica (With Lime) ppm ≤ 35 Heavy Metals ppm NIL


Water Treatment Facility

• Sludge Thickener

• Quantity : 1 No

• Flow : 201 M3/Hr

• MOC : RCC

• Centrifuge System


• Flow : 30 M3/Hr


Thickener Outlet Water QualityS.No Parameter Units Result

1 Turbidity NTU ≤ 1002 Total Suspended Salts ppm ≤ 503 Colour & Appearance - Clear4 Sludge % 4 - 5


Water Treatment Facility

• Pressure Sand Filter (PSF)


• Flow : 132.75 M3/Hr


PSF Outlet Water QualityS.No Parameter Units Result

1 pH --- 8.402 Conductivity µs/cm 3353 Total Dissolved Salts ppm 2014 Total Suspended Salts ppm ≤ 105 Turbidity NTU ≤ 106 Silica ppm 117 Chloride ppm 30


Basket Filter

Basket Filters have a pore size around < 50 micron.


Water Treatment Facility• Ultra - Filtration (UF)


• Flow : 112.75 M3/Hr

• Type : Dead End – Flow

• Membranes : 18 Nos

• Chemicals Used in UF :

• HCl

• NaOH

• NaOCl


Ultra – filtration (UF)

• A membrane type system that removes small colloids and large molecules from solutions. Ultrafiltration removes particles in size range between 0.01 to 0.1 micron range. The process falls between reverse osmosis and microfiltration as far as the size of particles removed is concerned

• What can UF remove?• Non-reactive silica, Colloids, Algae, Bacteria, Coliform, Viruses, Proteins

etc.

• What UF Reduce• TOC, Colour components, SDI etc.

• What UF will not remove?• Salts, Gasoline, Sugar, Alcohol, Smaller molecular weight molecules etc.


Schematic Representation of UF Dead – End Filtration

Feed

Membrane

Filtrate


UF Outlet Water QualityS.No Parameter Units Result

1 SDI --- ≤ 2.502 Total Suspended Salts ppm NIL3 Turbidity NTU 0.104 Colloidal Silica ppm NIL


Micron Cartridge Filter

Micron Cartridge filters have a pore size around < 5 micron.


Water Treatment Facility• Reverse Osmosis (RO)


• Flow : 106 M3/Hr

• Permeate Flow : 85 M3/Hr

• Reject Flow : 21 M3/Hr

• Chemicals Used in RO :

• SMBS

• HCl

• Antiscalant


How Reverse Osmosis Works


Reverse Osmosis Terminology• Osmosis:• The movement of water molecules towards concentrated solutions

• Reverse Osmosis:• Liquid filtering process in which a contaminated (more concentrated) liquid is forced

to pass through a semi-permeable membrane that block most dissolved or suspended contaminants. It is called 'reverse' because in normal osmosis a less-concentrated liquid passes into a more concentrated one. Reverse osmosis filters have a pore size around 0.0001 micron.

• Feed: • Input to Reverse Osmosis system, Feed Flow = Permeate flow + Reject Flow

• Permeate: • The stream that passes through Reverse Osmosis Membrane


Reverse Osmosis Terminology• Reject:• Waste stream from Reverse Osmosis which carries the rejected salts.

• Rejection % : ( 1 – Product Concentration ) X 100• Feed Concentration

• Recovery % : It is the ratio of Permeate flow to Feed flow

• = Permeate Flow x 100 • Feed Flow

• Salt passage % : 100 - % Rejection


Schematic Representation of Typical RO System

Water Solution

High Pressure Pump

RO Module

Reject

Permeate


What can RO remove?


UF & RO Membranes


Reverse Osmosis Membrane view


Membrane Process Characteristics


Type of fouling – Chemical agent (RO)• Colloidal: • NaOH solutions, chelating agents and surfactants• Organic: • NaOH solutions, chelating agents and surfactants• Silica: • NaOH solutions with high pH• Biofilms:• NaOH solutions, chelating or sequestration agents, Surfactants and disinfectants• Carbonate scales (CaCO3):• Citric acid or HCl with low pH• Metal oxides: • Citric acid with low pH or Na2S2O4• Sulphate scales (CaSO4, BaSO4):• HCl solutions or sequestration agents (EDTA)


RO Outlet Water QualityS.No Parameter Units Result

1 pH --- 5.80

2 Total Dissolved Salts ppm ≤ 10

3 Silica ppm ≤ 1.0

4 Colloidal Silica ppm NIL


Degasser Tower

• Degasser• Degasser is an integral part of any

demineralization plant, where it is generally placed between cation and anion exchanges and removes Carbon Dioxide, which is generated by dissociation of carbonic acid at cation outlet water.

• Unstable H2CO3 breaks into H2O and CO2 as per the Henry’s Law.

• Henry’s Law• It’s states that at constant temperature

the mass of the gas dissolved in a given quantity of solvent is directly proportional to its partial pressure. i.e., m = k p

• H2CO3 H2O + CO2


Water Treatment Facility• Mixed Bed (MB)


• Flow : 85 M3/Hr

• OBR : 20 Hrs

• Output : 1700 M3/Day

• Chemicals Used in MB :

• HCl

• NaOH


MB Regeneration Process• At Service• R – H+ + NaCl → R – Na+ + HCl• R – OH- + HCl → R – Cl- + H2O

• At Regeneration• R – Na+ + HCl → R – H+ + NaCl • R – Cl- + NaOH → R – OH- + NaCl

• Reduces residual ions leaked from cation and anion from the water system.


MB Outlet Water QualityS.No Parameter Units Result

1 pH --- 6.50 - 7.502 Conductivity µs/cm ≤ 0.103 Total Hardness ppm NIL4 Sodium ppm ≤ 0.015 Silica ppm ≤ 0.01


Water Storage Facility• Clarified cum Fire Water

Storage Tank

• Quantity : 1No

• Capacity : 41812 M3

• MOC : RCC

• Neutralization Pit (N Pit)



• MOC : RCC


Water Storage Facility• Filter Back Wash Tank

• Quantity : 1


• UF Permeate Tank

• Quantity : 1


• Degasser Water Storage Tank

• Quantity : 1



Water Storage Facility• DM Water Storage Tank



• MOC : MSEP


Presentation byRama Chandra Reddy Butcha

Group Head – Chemical & EnvironmentTata Power Company Limited

power plant water treatment

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