Training Programme for Energy Professionals 26 November 2010

New Trends in Waste Heat Recovery & Co-generation

ORGANISED BY

MAHARASHTRA ENERGY DEVELOPMENT AGENCY (MEDA) and BEE

WASTE HEAT RECOVERY SOLUTIONS

• Flue gas as a heat source – Condensing Economizer– Heat Recovery In Carbon Industry– Engine Heat Recovery Systems– Incinerator Heat Recovery System– Boiler exhaust heat recovery– Heat Pump

• Condensate flash steam as heat source– Condensate and flash steam heat recovery – Blow down flash steam heat recovery

Condensing Economiser – Flue gas heat recovery (Natural gas)

Present Scenario :

• Stack temp - 240 deg c • Efficiency - 88 % • Losses - Dry flue gas loss- 8.8 % (8%)

- Moisture loss - 2.2 % (10.7%) - Unburnt loss - 0.5 % (0.5%) - Radiation loss - 0.5 %(0.5%)Challenges :

• Reduction in heat transfer Performance • Low end corrosion

Flue gas heat recovery (Fuel Oil)

• Conventional heat recovery System Air pre heater - 4% Economiser/Water pre heater - 4%

• Limitations of conventional system- It targets only sensible heat loss. Low end corrosion limits heat recovery opportunity

• Heat recovery opportunity (Extra) Sensible heat loss - 6.5 % Latent heat loss - 8 %

Condensing economiser (Opportunity & Limitations)

Opportunity• Designed to increase the efficiency by reducing fluegas temp. below

dew point temp. • Maximises benefit of sensible heat recovery & recovers latent heat to

increase the efficiency beyond 100% (On NCV basis)• Partially reduces SOX emission• Gaseous fuels with higher hydrogen contents (Recommended)

Less FG volume, Less heat transfer area, Attractive payback Less Sulphur, Less severity of corrosion, Freedom for

material selection

Limitations • Criticality of material selection • Chimney corrosion • Poor heat transfer due to lower LMTD • Higher cost

* Flue gas condensing system independent of boiler system *Flue gas reheating *Economiser selection based on makeup water quantity

Heat recovery in Carbon Industry

Before Heat Recovery • For activated carbon production steam is used. The source for the steam is

fired boiler. • Flue gases generated in process were vented to atmosphere at around 550

deg.C

After Heat Recovery • Flue gases from process are utilized to generate a steam. • The steam generated by WHRB is use for activated carbon production. Thus

fired boiler remained as stand by.

KEY FEATURES• Steam Generation from Process waste Gases• Proven and reliable system design• Fuel Saving• Attractive Payback Period

P & I Diagram - Heat recovery in Carbon Industry

CASE STUDY: Heat recovery in Carbon Industry

A] WASTE HEAT RECOVERY DETAILS• No of kilns : 12 nos.• Approx. Activated carbon production : 30,000 kg/hr• Total Flue gas quantity : 93,229 kg/hr• Flue gas inlet temp. : 550 DEG.C• Steam generation ( F&A 100) : 9,800 kg/hr• No. of WHRB : 4 Nos.(2 tphx2 Nos. + 2.8 tphx1 no. + 3 tphx1no)

B] SAVINGS IN TERM WOOD FIRED BOILER• boiler capacity(F&A 100) : 9,800 kg/hr• boiler efficiency (considered) : 65%• Wood consumption : 2626 kg/hr• Wood Price : 3 Rs/kg.• Saving in terms of Wood : 567 Lacs( for 7200 hrs annual working hrs.)• Savings in terms of Energy : 38 Billion kcal/annum.• Quantity of wood saved : 18900 Tons / annum• Nos of Trees saved : ?????????????

Application note Carbon Inds.pdf

Engine Heat Recovery Systems

Before Heat Recovery System

The exhaust gases generated from NG fired engine sets are of temp. 400 – 450 deg.C. These gas were directly passed to chimney before installation of heat recovery system

After Heat Recovery System

The exhaust gases coming from Engine are used for heating Thermal oil which is required for some process in the plant.

KEY FEATURES

• Proven system

• Easy to operate

• Fuel Saving

• Heat recovery in the form of Steam, water also possible.

P&I Diagram - Engine Heat Recovery System

CASE STUDY: Engine Heat Recovery System

A] WASTE HEAT RECOVERY DETAILS• No of engines : 1 No• Flue gas quantity : 10,688 kg/hr• Flue gas inlet temp. : 427 Deg.C• Flue gas outlet temp after Heat recovery : 360 Deg. C (Passed to VAM)• Heat Recovery in terms of Thermal oil heating : 1,72,000 kcal/hr

B] SAVINGS IN TERMS OF FURNACE OIL FIRED THERMAL OIL HEATER• Heater capacity : 1,72,000 kcal/hr• Heater efficiency (considered) : 85%• FO consumption : 24.66 lit/hr• FO Price : 30 Rs/lit.• Saving in terms of FO : 53.26 Lacs( for 7200 hrs

annual working hrs.)• Savings in terms of Energy : 1238.4 million kcal/annum.• Quantity of FO saved : 1,77,552 lit/annum

Incinerator Heat Recovery System

Before Heat Recovery System

The exhaust gases (700-800 deg.c) from incinerator are passed through scrubber to reduce its temperature. After scrubber the waste gases are let out through chimney.

After Heat Recovery System

The exhaust gases from Incinerator are used for heating water which is required in process plant

KEY FEATURES

Proven system

Easy to operate

Fuel Saving

Heat recovery in the form of Steam, thermal oil also possible.

P&I DIA. Incinerator Heat Recovery System

P & I Diagram – Incinerator waste heat Recovery System

CASE STUDY: Incinerator Heat Recovery System

A] WASTE HEAT RECOVERY DETAILS• No of Incinerators : 1 No• Total Flue gas quantity : 4341 kg/hr• Flue gas inlet temp. : 700 Deg.C• Flue gas outlet temp after Heat recovery : 350 Deg. C• Heat Recovery in terms of Thermal oil heating : 5,50,000 kcal/hr

B] SAVINGS IN TERM FURNACE OIL FIRED THERMAL OIL HEATER• Heater capacity : 5,50,000 kcal/hr• heater efficiency (considered) : 85%• FO consumption : 78.85 lit/hr• FO Price : 30 Rs/lit.• Saving in terms of FO : 170 lacs( for 7200 hrs

annual working hrs.)• Savings in terms of Energy : 3960 million kcal/annum.• Quantity of FO saved : 5,67,720 lit / annum

BOILER EXHAUST HEAT RECOCERY

Boiler/Thermic Fluid heater exhaust is available at around 250 to 300 deg C. Heat from exhaust may be recovered for following purposes …

1. Boiler Feed water heating / Process water heating

2. Boiler Combustion Air preheating / Fuel drying

3. Operation of Hot Air / Gas fired VAM

Saving :

Approx 1% fuel saving may be achieved by reducing flue gas temperature by 20 to 22 Deg C through heat recovery unit.

Advantages of Preheating combustion air

HEAT PUMP

Heat Pump is a Device that pumps heat from lower temperature to medium temperature using High Grade Energy.

PROCESS

Water at 36 deg C

Water at 32 deg C

HEAT REJECTED TO ATMOSPHERE

COOLING TOWER

In the Cooling tower heat from condenser of Chiller is rejected to the atmosphere.

IS IT POSSIBLE TO PUMP HEAT FROM LOWER POTENTIAL AT 36O C TO HIGHER POTENTIAL AT 90O C ???

Feed Water Temp. 55 Deg C

FEED WATER TANK

50% Condensate

Water to Boiler

STEAM

ABSORPTION CHILLER

Q3

12°C

7°C CONDENSATE

Q1 Q2

32°C 36°C

Q1+Q2=Q3

Chilled Water

Cooling Water

ABSORPTION CHILLER

CONDENSATE

ABSORPTION HEAT PUMP

ABSORPTION HEAT PUMP

Q3

36°C

32°C

STEAM

Q1 Q2

30°C90°C

Q1+Q2=Q3

Cooling Water

Hot Water

ABSORPTION CHILLER AND HEAT PUMP

FOR EVERY 1.7 KCAL OF HEAT GIVEN BY HEAT PUMP

0.7 KCAL IS FREE

ENERGY SAVINGS BY HEAT PUMP

WHICH MEANS 41% IS FREE HEAT

PROPOSED SYSTEM

CONDENSER OF CHILLER

36O C34O C

32O C

HEAT PUMP30O C

90O C

PROCESS

MAKEUP WATER TANK

HOT WATER TANK

BOILERFEED

WATERTANK

CONDENSATE HEAT RECOVERY-WHY?

Steam when used as a heating medium, around 75% percent of total energy is used in the

heating process, which is termed as latent heat.

If one recovers the condensate, remaining 25% energy which is normally wasted through steam trap discharge, is recovered as sensible heat of condensate water & latent heat of flash steam.

FLASH STEAM HEAT RECOVERY

E.g.10 bar(g) condensate discharged

from steam trap at atmospheric pressure

The amount of flash steam will be 15% of the total condensate.The energy content of flash steam shall be about 50% of the total

energy content of condensate.

Condensate-SCHEME.xls

s24-1_1.swf

BLOWDOWN FLASH STEAM RECOVERY

More appropriate for boilers with very high FW TDSPlants having no / less condensate recoveryHigh Pressure / Power Boilers

• AUTO BD & FLASH REC. SYS.pdf

Thank You