-BYMohd Asrar Uddin Soheb

Introduction

Waste heat is heat, which is generated in a process by way of fuel combustion or chemical reaction, and then “dumped” into the environment even though it could still be reused for some useful and economic purpose.

Surroundings(rivers, air, etc.)

Fuel

Heat generation(boilers, heaters)

Process

Cooling

Surroundings(rivers, air, etc.)

Fuel

Heat generation(boilers, heaters)

Process

Cooling

Energy Flow without Waste heat recovery

Energy Flow with Waste heat recovery

S.No Source Quality

1. Heat in flue gases. The higher the temperature, the greater the potential value for heat recovery.

2. Heat in vapour streams. As above but when condensed, latent heat also recoverable.

3. Convective and radiant heatlost from exterior of equipment.

Low grade – if collected may be used for space heating or air preheats.

4. Heat losses in cooling water. Low grade – useful gains if heat is exchanged with incoming fresh water.

5. Heat losses in providing chilled water or in the disposal of chilled water

a) High grade if it can be utilized to reduce demand for refrigeration.

b) Low grade if refrigeration unit used as a form of heat pump.

6. Heat stored in products leaving the process

Quality depends upon temperature.

7. Heat in gaseous and liquid effluents leaving process.

Poor if heavily contaminated and thus requiring alloy heat exchanger.

Waste Source & Quality

Indirect Benefits:

a)Reduction in pollution b) Reduction in equipment sizes

c) Reduction in auxiliary energy consumption

Recuperators

In a recuperator, heat exchange takesplace between the flue gases and theair through metallic or ceramicwalls. Duct or tubes carry the air forcombustion to be pre-heated, theother side contains the waste heatstream.

Metallic Radiation Recuperator

Convective Recuperator

Convective Radiative Recuperator

Heat Wheels•It is a sizable porous disk, fabricated with material

having a fairly high heat capacity, which rotates between two side-by-side ducts: one a cold gas duct, the other a hot gas duct. •The axis of the disk is located parallel to, and on the partition between, the two ducts. As the disk slowly rotates, sensible heat (moisture that contains latent heat) is transferred to the disk by the hot air and, as the disk rotates, from the disk to the cold air. The overall efficiency of sensible heat transfer for this kind of regenerator can be as high as 85 percent. Heat wheels have been built as large as 21 meters in diameter with air capacities up to 1130 m3 / min.

Eight ways to profit from waste heat

1. Save Fuel2. Generate Electricity3. Sell Heat and Electricity4. Reduce Cooling needs5. Reduce Capital

Investment Cost6. Increase Production7. Reduce Greenhouse gas

emission8. Transform The Energy

•The major components contributing to the annual savings are Coal and water.

•Capital Cost can be reduced.

•Reduces the emission of Harmful gases.

•Maintenance cost can be reduced.

QUERIES ???

THANK YOU