Like many other substances, water can exist in the form of either a solid, liquid, or gas. We will focus largely onliquid and gas phases and the changes that occur duringthe transition between these two phases. Steam is the vaporized state of water which contains heat energy intended for transfer into a variety of processes from air heating to vaporizing liquids in the refining process.

Why we use steam

• Steam produced by evaporation of water which isrelatively cheap and plentiful commodity.

• Its temperature can be adjusted very accuratelyby controlling its pressure using a simple valve.

• Its carries relatively large amount of heat in asmall mass.

Steam Formation

1kg of water @ O0c

Zeroenthalpy datum point

Total energy (enthalpy) held in 1kg of water (mass) is called “specific enthalpy of saturated water –(hf)

1atm

1000c 1000c

Water steam

1000c

Steam

Extra energy to be added is called “specific enthalpy of evaporation” (hfg)

Total = hf + hfg

energy (hg)

O0c 1000cWater water @ 1atm

Sensible heat (hf)

Basic Principles in Thermodynamics

Volume of 100 times Volume of 1000c

1000c water @ Volume steam @ 1atm

1atm

Load (Compress)

Water molecules not easy to break, hence boiling point of water (tB.P.) moreases.

Basic Principles in Thermodynamics

Enthalpy – Total energy due to pressure andtemperature of a fluid / vapour @any given time & condition.

Unit: Joule (J) KJ

Specific heat capacity – A measure of the ability of a substance to absorb heat. It is the amount of heat required to raise 1kg of substance by 10c.

Unit: KJ/Kg0c (eg. Water 4.186kj/kg0c)

Basic Principles in Thermodynamics

Absolute Pressure :Pressure above the absolute zero.

Absolute zero is the theoritical pressureless state of a perfect vacuum.

Pressure excorted by the atmosphere at sea level is 1.013 bar abs ( 1 bar)

Gauge PressureGauge pressure is the pressure above atmosphereicpressure.

Pressure gauge shows Gauge Pressure in bar g or kgf/cm2

Basic Principles in Thermodynamics

P tB.P hfg

Basic Principles in Thermodynamics

Steam Table

Relationship exists between steam pressure, saturated

temperature, evaporation of staturation ethalpy.

Basic Principles in Thermodynamics

Steam Table

Gauge Pressure Temp.

Enthalpy in kj/kg

Volume Dry Sat.

Water Specific Enthalpy of Evoporation

Steam

Bar kPa 0C Hf Hfg hg M3/kg

0123456789

1011121314

0100200300400500600700800900

10001100120013001400

100120134144152159165170175180184188192195198

419506562605671641697721743763782799815830845

225722012163213321082086206620482031201520001986197319601947

267627072725273827492757276327692774277827822785278827902792

1.6730.8810.6030.4610.3740.3150.2720.24

0.2150.1940.1770.1630.1510.1410.132

Basic Principles in Thermodynamics

Steam GenerationSteam Generator is called “Boiler”

Two Types of Boilers

• Water Tube Boilers

• Fire Tube Boilers

Boiler Tubes

WaterTube

Boilers

• Generate high pressure steam even 50 bar

• Generate super steam 2000 – 3000c

– Application• Steam turbine to produce electricity (Combine cycle plant)

• High temperature steam requirement

Fire Tube Boilers

• Generate low pressure max. up to 17.5 bar

• Most common boiler generate saturated steam

Fire Tube Boiler

• Design Types :

Two Pass Boiler

Two Pass reverse flame

Three Pass Boiler

Three pass - wet back

Three pass – dry back

Two Pass Boiler

Two Pass reverse flame

Three Pass Boiler

Three pass - wet back

Three pass – dry back

Selection of Boiler

• Steam load

• Pressure operating / maximum

• Future expansion

• Efficiency %

• Maintenance

Types of Fuel Use

• Diesel

• Furnace Oil Low / Medium / Heavy

800 RS 1000RS 1500 RS

• Natural Gas

• Bio Mass (Wood, Saw dust, Paddy husk, etc.,)

Steam Distribution and Condensate Recovery System

Steam Cycle

Feed Water Tank Management System

Feed Water Tank Management System

Steam ejector

Water

It might be good enough to drink,

but is it good enough for the Boiler?

Steam Distribution

Steam Line Pipe Sizing

On the basis of :

Fluid Velocity

Pressure Drop

Pipe Sizing• Greater Cost

• Greater Heat Loss

• Greater Volume of Condensate Formed

• Lower Pressure to Steam Users, or

• Not Enough Volume of Steam

• Water Hammer and Erosion

Pipeline Capacities at Specific Velocities

Kg/h

Pressure bar

Velocity m/s

15mm 20mm 25mm 32mm 40mm 50mm 65mm 80mm 100mm 125mm 150mm

0.4 152540

71017

142535

244064

3762102

5292142

99162265

145265403

213384576

3946751037

6489721670

91714572303

0.7 152540

71218

162537

254568

4072106

59100167

109182298

166287428

250430630

4317161108

68011451712

100615752417

1.0 152540

81219

172639

294871

4372112

65100172

112193311

182300465

260445640

4707301150

69411601800

102016602500

2.0 152540

121930

254364

4570115

70112178

100162275

182295475

280428745

4106561010

71512151895

112517552925

158025204175

3.0 152540

162641

375687

60100157

93152250

127225375

245425595

3856321025

5359101460

92515802540

150524804050

204034405940

Steam Metering

• Measurement in mass flow rate kg/hr• Density compensation

– Measure the velocity Q = Av m2 =

– Measure temp Spe. volume υ

– Density ρ =

– Mass flow rate m = Qρ =

– Efficiency of the boler or the process equipment

Pressure Reduction

• Process temperature required (0C)

• Equvalent steam pressure (bar)

• Steam consumption (kg/hr)

• Available steam pressure (bar)

Source

Pressureup stream

Kg/hr consumption

Size ?

Pressure down stream Process

Pressure Reduction

• Safety of the equipments

• Increase the ‘enthalpy of evaporation’

• Condense water convert into flash steam

Distribute at High PressureThis will have the following advantages:

Smaller bore steam mains needed and therefore less heat (energy) loss due to the smaller surface area.

Lower capital cost of steam mains, both materials such as pipes, flanges and support work and labour. Lower capital cost of insulation (lagging)

Dryer steam at the point of usage because of the drying effect of pressure reduction taking place.

The boiler can be operated at the higher pressure corresponding to its optimum operating condition, thereby operating more efficiently.

The thermal storage capacity of the boiler is increased, helping it to cope more efficiency with flcuating loads, and a reduced risk of priming and carryover.

Selection of Working Pressure

Gauge Pressure Temp.

Enthalpy in kj/kg

Volume Dry Sat.

Water Specific Enthalpy of Evoporation

Steam

Bar kPa 0C Hf Hfg hg M3/kg

0123456789

1011121314

0100200300400500600700800900

10001100120013001400

100120134144152159165170175180184188192195198

419506562605671641697721743763782799815830845

225722012163213321082086206620482031201520001986197319601947

267627072725273827492757276327692774277827822785278827902792

1.6730.8810.6030.4610.3740.3150.2720.24

0.2150.1940.1770.1630.1510.1410.132

Types of PRVs

Direct acting

Pilot operated

Pressure Reducing Station

Best practices in steam distributionPipe alignment and drainage

This will eleminate water hammer

Eleminate water hammerBest practices in steam distribution

Best practices in steam distribution

• Strainer - Remove pipe scale & dirts

Best practices in steam distribution

• Eleminate air in the pipe lines

Best practices in steam distributionPipe laying with slope

Branch Connections

Best practices in steam distributionDrainage in steam lines

Best practices in steam distributionSteam Line Reducers

Best practices in steam distribution

• Expansions

Best practices in steam distribution• Types of steam expansions

Best practices in steam distribution• Close / plug the steam leaks

Cost of steam – Rs. 7.50/kg

5mm hole @ 10 bar press – 80 kg/hr

Steam leak per day (12 hrs) - 960 kg

Loss in 5mm hole per day – Rs. 7.50 x 960 kg = Rs. 7,200.00

Loss in 5mm x 5nos holes per day – Rs. 7,200.00 x 5= Rs. 36,000.00

Loss Per month (26 days) – Rs. 36,000.00 x 26= Rs. 936,000.00

Loss Per Annum – Rs. 936,000.00 x 12

= Rs. 11,232,000.00

Best practices in steam distribution

Lagging the steam pipe lines

Q = UA (ΔT)

Insulation Material Properties – Glass wool of 64 kg/m3

density

Thumb rule :Steam lines – 50mm thick glass wool pipe coversCondensate lines – 25mm thick glass wool pipe covers

Steam Traps

• Why traps required?

• What is the function of the steam trap?

• What are the types of traps?

• How to select the trap?

• Utilise maximum energy from the steam

• Trap steam & release condensate

Steam Traps

Why traps required?

Types of Steam Traps

Thermodynamic Traps

Thermostatic Traps

Balanced Pressure Traps

Liquid Expansion Traps

Bimetallic Expansion Traps

Mechanical Traps

Ball Float Traps

Inverted Bucket Traps

Thermodynamic Steam Trap

Application

Ball Float Trap

Application

How to select the trap?

• Refer the catalogues

Trap Module

Trap Monitoring System• Steam Leak • Water clogg

Condensate Management

1. Why Return Condensate?

2. Sizing Condensate Return Lines

3. Condensate Pumping

4. Long Delivery Lines

5. Lifting Condensate

6. Flash Steam

Water, 85%

Flash Steam, 15%

Approximate Amount of Flash Steam in Condensate

Water

Flash Steam

Water and Chemical Savings by Returning Condensate

Total Savings by Condensate Recovery

Fuel + Water + Blowdown

Condensate Pipe SizingKg/h

Pressure downstream of trap, bar g

15mm 20mm 25mm 32mm 40mm 50mm 65mm 80mm 100mm 125mm 150mm

0.0 6.2 11.0 17.8 30.3 41.9 69.0 98.4 152.0 261.8 411.4 594.1

0.1 6.8 12.0 19.4 33.2 45.8 75.5 107.6 166.2 286.3 449.9 649.7

0.2 7.4 13.0 21.1 36.0 49.7 81.8 116.7 180.3 310.5 488.1 704.7

0.3 8.0 14.0 22.7 38.8 53.5 88.2 125.8 194.3 334.7 526.0 759.5

Methods of Condensate Return

• Two types of recovery systems

Without pump

With pump

Condensate lifting without Pump

Back Pressure on Traps

Pressure at end of return line

Hydrostatic head

Frictional resistance to flow

BACK PRESSURE

Condensate lifting with Pump

Condensate lifting with Pump

Where to go recovered condensate

Complete system of steam distribution & condensate Recovery

system

Srilal MidellawalaJoint Managing Director / Director Marketing

Tritech Group of CompaniesNo. 87, Makola South,

Makola,Kiribathgoda.

Email : srilal@tritech.lk Web : www.tritech.lk