Hydrogen Generation Plant

M. Nageswar Rao, Sr.Mgr.(EMD)

Date: 09.10.2015Venue: EDC, Simhadri

Presentation layoutNeed for HydrogenFacts & Merits of HydrogenTechnologies of Hydrogen productionHydrogen generation at SimhadriSafety aspectsStatutory requirements

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Need for HydrogenGenerator cooling

Stator coreRotor coreRotor winding

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Facts about hydrogenLightest element

Atomic number 1.Density of Hydrogen =0.07

Most abundant element in the Universe. Not naturally found in atomic state on earth. Bound to other elements as Compound.

Normal boiling point of – 253°C (- 423°F)Flammable Colourless & OdorlessNon Toxic & Non Corrosive

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Merits of hydrogenThermal conductivity 5 times more than air.Higher specific heat

3.42 at 0 degC as compared to 0.237 of air. 538 degC is ignition temp in air. Low density& light gas (14 times lighter) Very good heat transfer property. Less drag, Low windage & frictional losses.

Better circulation.

BUT ITS MIXTURE WITH AIR IS EXPLOSIVE

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Technologies of H2 production

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Electrolysis of waterElectro-chemical cellNatural H2 extraction

H2 production in SimhadriAlkaline Electrolysis

Suited for stationary applicationsproduce high purity hydrogen. significantly costlier.High rate of gas generation

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Alkaline Electrolysis

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Inputs requiredDM water (Conductivity < 1 μS/cm)Rectifier (Direct current)KOH electrolyte solution (Caustic Potash

Solution sp.gr. of 1.25 @15.5degC) – increase conductivity

Cooling waterInstrument Air

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Process flow

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Process flow

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Main componentsRectifiers : Make M/s HIND, (DC 9V, 2270A)Electrolyser (Stuart Cell)Gas Holders (Liquid Floating Type)Compressors (Diaphragm Type)Purification SkidManifold Vacuum Pump

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RectifierParameter RatingInput 3-ph, 415V ac, 45A Output DC 9V,

2270A (20% -100% operating range), 6pulse o/p

Type of control Constant current by means of SCRSpecification IEC-146Cooling Air forced (Rectifier & control

panel)

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Rectifier6-pulse centre-tap

converter with Inter group reactor.

It is formed by 2 no.s of 3-ph half wave converters with a phase shift of л connected in parallel through IGR.

Each SCR conducts for 2 л /3 (л /3 if no IGR)

IGR absorbs instantaneous Potential difference between common cathodes.

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Stuart Cell Sealed Unipolar type Cells 3- plate cell having

1 nickel plated iron anode plate 2 iron cathode plates

MOC: Mild Steel / IS: 2062 / 1079

KOH solution (concentration of 28-30%)

Low Voltage system to ensure safe condition (2.2 volts Each)

Capacity : 3.75 cum/hr @2800A Two streams in service Capacity 2X 3.75 =7.5 cum/hr Generated H2 Gas Purity >

99.8%

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Gas holderTwo gas holders

One for receive gas from generation

Other for supply gas to the compressors.

Buffer vesselWater sealed liquid floatingMOC : mild steelTank & Bell construction Operating Pressure 125 mmwcLimit Switches on both high and

low levels of the tank to maintain right amount of Gas within the vessel with all necessary interlocks.

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CompressorsDiaphragm Type Two Stage compression

1 st 20 kg/cm2

2nd 170 kg/cm2

Isothermal Process of compression

Hydraulic oil is the motivating force

Cap: 4.7 cum/hr (Each)Two in service , One as

stand by.18

Purification skidRemoval of O2 impurity in H2 gas

by means of a Catalytic purifier (Palladium based).

Coalescing Filters to remove moisture in H2 gas.

Dual Tower regenerative Desiccant Dryer (Molecular Sieve) to achieve the necessary Dew Point.

Filters to remove particulate carry over traces in the product H2 gas

Generated H2 gas purity > 99.99% , Due point < - 40 Deg.C.

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ManifoldFilling of high purity H2 in

cylinders at high pressure @ 140 kg /cm2

Provision for connecting to vacuum pump for ensuring “No foreign gas/ positive hydrogen

Provision for venting to atmosphere in case of purity less than required.

Maintain positive pressure in hydrogen cylinder to prevent introduction of air

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Process parameters

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Parameter ValueDM water conductivity < 4 μS/cmSp.gr. of electrolyte KOH

1.20 -1.23

Cell voltage 2.2VCurrent

2000AmpsOperating Temp 50 degCPurity >99.99%Dew point < -40 deg

CFilled Cylinder Pressure

140kg/cm2

Generation capacityGeneration @ 2800A

Hydrogen (99.8%) : 7.5 cum/hrOxygen : 3.75 cum/hr

BottlingHydrogen (>99.9%) : 1 Cyl @ 140 kg/cm2

Oxygen : To ventDaily average : 5-6 Cyls.

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Safety aspectsKOH is strong Alkali , hazardous,

Use PPE Ensure Availability of Emergency Shower

Oxygen generated is combustible & hence to be vented . Ensure no open flames near venting area.

H2 is flammable and may form mixtures with air that are flammable or explosive.

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Statutory Requirements

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License/ Testing FrequencyLicense from ministry of explosives for• Generation• Filling• Storage • Night Shift operation

Expiring on 30.09.2015

Hydro static Stretch test of Cylinders @250kg/cm2

Every 5 years

Thank you all

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