This document proposes three options for a waste heat recovery system and heat pump to reduce fuel consumption and improve energy efficiency at a process plant. Option 1 involves using recovered heat from oven exhausts and a compressor to heat pretreatment bath tanks. Option 2 uses recovered heat to pre-heat oven intake air and heat one pretreatment tank. Option 3 combines options 1 and 2 with a heat pump to heat additional pretreatment tanks. Calculations estimate potential heat sources, energy and cost savings for each option. Diagrams illustrate the proposed air to water and air to air heat recovery approaches.

1. Page No : 1
RE-NEXT
Waste Heat Recovery System & Heat Pump
for Reduction of Fuel Consumption, Minimise Thermal
Pollution & Enhancing Energy Efficiency
in process
VVL & ORG

2. Page No : 2
2
 WHRS – Overview of Proposal
 Waste Heat Recovery System – General
 Air source Heat pump options - example
 Present Scenario & Sources of Heat Potential
 Present Scenario & Sink Identification
 Air to Water / Air Recovery System.
 Calculation of Sources & Sink and Cost Saving & ROI
 Proposal Options
 Challenges of WHRS implementation.
Content

3. Page No : 3
 Paint shop all 3 nos of Ovens , Hot Water Generators and Compressors are exhausting the process & flue gases as a waste heat to the Environment. (Heat Sources)
 Hot water generator generates the heat energy for heating the PT tank hot baths & ASU’s intake air to maintain bath temperature & booth RH and temperature.
 In Ovens, amount of fresh air is mixing with the recirculation air for diluting the concentration of oven process hot air. Ambient temperature of Fresh air is getting
heated thro heat exchanger chamber in Hot box oven. (PT hot bath tanks, ASU and Oven Fresh air intakes – Sink)
 Heat Energy requirement of PT hot baths in production mode is approx. 3.25 to 3.5 lac kcal/hr.
 Paint shop waste heat is let out from the system in the form of exhaust from CED, Liquid ovens & Compressor, which have heat potential of 2.95 lac Kcal/hr.
(Burner Stack heat potential recovery is not considered).
 Currently the HWG LPG consumption is 60 -70Kg/ hr for both PT & ASU..
Proposal of the Project
 Utilisation of the waste exhaust gas heat & compressor oil heat by means of Waste Heat Recovery System.
 And Integration of Water Source Heat Pump with existing hot water circuit for heating PT process. Also By product of Heat pump (chilling source) can be used in CED
bath to maintain process temperature.
Overview of Proposal
Option Recovery method LPG saving (Kg/hr) Total cost Saving (In Rs) Investment (In Cr.) ROI (In Months)
Option 1
Air to Water
33 99,37,078 1.46 18
Oil to Water
Option 2
Air to Air
26 79,61,503 1.51 23
Oil to Water
Option 3
Air to Air
45 1,15,85,214 2.17 24
Oil to Water
Air source heat pump -240Kw

4. Page No : 4
Powder coating (Exhaust damper
at 15 %,Heat exhaust is minimal)
Waste heat exhaust (oil/Gas) Chilling requirements
90Kw 90Kw 90Kw 55Kw
Compressor Pretreatment line
CED
chiller
Hot
water
Paint Shop Heating & Cooling Layout
Fresh air requirements
HWG 1 HWG 2
KOD Deg Phos
Oven Exhaust
Heat up
stack F A
Hold
stack
F A
CED
So
So
Si
Si
Si
So-Source
Si-Sink
Oven Exhaust
Stack Exhaust F A
PMR
chiller
Robot line 2
So
Si
Oven Exhaust
Stack Exhaust F A
PMR
chiller
Robot line 1
So
Si
ASU 1
ASU 2
PTCED
Hot water requirements

5. Page No : 5
S.no Locations Area Category Purpose Required parameter
Heating / Cooling Equip &
Fuel source
1
PT
Hot water Heating Pretreatment process requirement 60* C HWG / LPG
2 KOD Heating Pretreatment process requirement 58* C HWG / LPG
3 Degrease Heating Pretreatment process requirement 60* C HWG / LPG
4 Phosphate Heating Pretreatment process requirement 52* C HWG / LPG
5 CED CED Cooling To maintain CED bath temp 30-32* C Chiller
6
CED oven
CED oven heat up Heating For baking 213* C Burner / LPG
7 CED oven hold up Heating For baking 213* C Burner / LPG
8
Liquid line
Line 1 oven Heating For baking 170* C Burner / LPG
9 Line 2 oven Heating For baking 170* C Burner / LPG
10 Line 1 PMR Cooling To maintain Paint temp 27-30* C Chiller
11 Line 2 PMR Cooling To maintain Paint temp 27-30* C Chiller
12 ASU 1 Heating To maintain booth temp & RH 27-30 *C & 65 (+-5) HWG / LPG
13 ASU 2 Heating To maintain booth temp & RH 27-30 *C & 65 (+-5) HWG / LPG
14 VPC Powder Coating Heating For baking 185 & 210 * C Burner / LPG
Paint Shop Heating & Cooling Requirements
Heating Ckt Cooling Ckt

6. Page No : 6
Sources of Heat Potential
Name
Process
Temperature
Oven Exhaust
Temperature
Oven exhaust
flow rate
Cool down to
Oven Exh Mass
flow rate
Oven Exh Heat content
Total Exh Heat
content
deg C deg C m3/hr deg C kg/hr kCals/hr kW
ED Oven exhaust 215 185 6238 100 4743 86,712 101
TC Oven 1 exhaust 165 150 4169 100 3432 36,910 43
TC Oven 2 exhaust 170 160 4878 100 3923 50,627 59
Compressor 1,21,238 141
Total Available Heat Potential 2,95,486 344
 Paint shop all 3 no’s Ovens (CED & Robot line – 1 & 2), Hot Water Generators and Compressors are exhausting the process & flue gases as a waste
heat to the Environment.
 In Ovens, burner flue gas stack heat potential is not considered in waste heat recovery system due to system provider not recommending considering
safety aspect. ( M/S. Durr ).
 Hot water generator stack flue gas heat potential is not considered due to temperature is < 120 deg.
Source 1 Source 2,3
Source 4

7. Page No : 7
Calculation–Sources and Saving
Name
Process
Temperature
Oven Exhaust
Temperature
Oven
exhaust
flow rate
Cool
down
to
Ambient
Temp
Density @
ambient
Oven Exh
Mass flow
rate
Cp @
ambient
Oven Exh
Heat
content
10% losses
of Kcal/hr
40% losses
in
Compressor
Kcal/hr
Capacity
LPG
saving
deg C deg C m3/hr deg C Deg C kg/m3 kg/hr kCals/kg kCals/hr Kw Kg/hr
CED Oven 215 185 6238 100 30 1.1492 4743 0.239
96,346
86,712 - 101 9.4
TC Oven 1 165 150 4169 100 30 1.1492 3432 0.239
41,011
36,910 - 43 4.0
TC Oven 2 170 160 4878 100 30 1.1492 3923 0.239
56,252
50,627 - 59 5.5
Compressor - - - - - - - -
2,02,063
-
1,21,238
141 13.2
3,95,672 1,74,249 1,21,238 344 32.2
2,95,486
Heat Sources Calculation from Oven Common Exhaust & Compressor
Note:

8. Page No : 8
Option 1: Air to Water
Utilization of waste exhaust gas heat from all 3 ovens common exhaust & heat recovery from compressor,
both can utilize to heat up PT hot bath tanks in production mode. (Air to Water)
Option 2:
Air to Air,
Oil to Water
a) Utilization of waste exhaust gas heat from all 3 ovens common exhaust to pre heating the same oven
fresh air intake from ambient to 90*C. (Air to Air)
b) Heat recovery from compressor oil to heat up any one of the hot bath tank of PT. (Oil to Water)
Option 3:
Air to Air,
Oil to Water &
Heat pump
a) Utilization of waste exhaust gas heat from all 3 ovens common exhaust to pre heating the same oven
fresh air intake from ambient to 90*C. (Air to Air)
b) Heat recovery from compressor oil to heat up any one of the hot bath tank of PT. (Oil to Water)
c) Remaining tanks of PT can be heat up by means of Water source heat pump system. (Heat pump)
 Utilisation of the waste exhaust gas heat & compressor oil heat by means of Waste Heat Recovery System.
 And Integration of Water Source Heat Pump with existing hot water circuit for heating PT process. Also the By product of Heat pump
(chilling source) can be used in CED bath to maintain process temperature.
 Arrived the following three options….
Proposal of the Project

9. Page No : 9
 Waste heat is the energy lost in industrial process to the environment. Reuse of the lost heat of industrial process that can be used
to provide useful energy & reduce the overall energy consumptions.
 Heat loss mainly classified into High temp, Medium temp & Low temp grades.
 The selection of Heat recovery methods & techniques largely depend on key factors such as the quantity ,quality & the nature of the
heat sources in terms of heat suitability & effectiveness.
 The identification of the heat sources is an important aspect when looking into waste heat recovery methods for industrial process
in order to achieve optimum results & efficiency. There are many different heat recovery technologies available for capturing the
waste heat by the means of Heat exchangers & Waste heat recovery system.
Waste Heat Recovery System
Water/Air In
From
Oven
Exhaust
To Atm

10. Page No : 10
Water Source Heat Pump
 A heat pump is a device that transfers heat energy from a source of heat to what is called a thermal reservoir.
 Heat pumps move thermal energy in the opposite direction of spontaneous heat transfer, by absorbing heat from a cold space.
 Heat pumps usually can be used either in heating mode or cooling mode, as required by the user.
 In paint shop 3 nos chiller are using to maintain the CED bath temp 30-32*C & Paint temp 25-28 *C respectively.
 In Heat pump system 1 KW of electrical input is equal to 3 KW of thermal output.
 Heat Pumps work on a similar principal to a refrigerator; they are able to absorb energy from the return chilled water/Air and transfer this
energy into a refrigerant. The heat energy is upgraded using a refrigerant cycle and this energy is transferred into the water.

11. Page No : 11
Method
Source Sink
Energy
Utilisation
Kcal / Hr.
%
Utilisation
Against
Potential
WHRS - Annual
electricity
consumption
(KWH)
LPG
Saving
Kg/ Hr.
Total
Kg / Hr.
Annual
electricity
consumptio
n cost (In
Rs)
Annual
maint cost
(In Rs)
Total Cost
saving
( In Rs)
Investmen
t
( In Cr.)
ROI
( In
Months)
Area
Potential
Kcal / Hr.
Area Purpose
Energy
Requirement
Kcal/Hr
Air to
Water
CED Oven
Exhaust
1,74,249
PT 3 tanks PT Heating
3,25,000
1,74,249
100%
86,400 19.0
32
5,53,824 3,00,000 55,69,455
1.16
18
TC 1 Oven
Exhaust
TC2 Oven
Exhaust
Oil to
Water
Compressor
1,21,238
PT - 1 tank PT Heating
1,21,238
100%
15,840 13.2 1,01,534
-
43,67,624
0.3
2,95,486 3,25,000 2,95,486 99,37,078
1.46
Proposal Option-1
Option 1: Utilization of waste exhaust gas heat from all 3 ovens common exhaust & heat recovery from compressor, both can utilize to
heat up pretreatment hot bath tanks in prod mode.
Note:

12. Page No : 12
DI No. :
WHRS - Air to Water Recovery Method
From compressor
heat recovery
Oil to Water System
(Compressor)

13. Page No : 13
Proposal Option-2
Option 2: Utilization of waste exhaust gas heat from all 3 ovens common exhaust to pre heating the same oven fresh air intake from
ambient to 90*C. Heat recovery from compressor oil to heat up any one of the hot bath tank of pretreatment.
Method
Source Sink
Energy
Utilisation
Kcal / Hr.
%
Utilisation
Against
Potential
Annual
electricity
consumption
(KWH)
LPG
Saving
Kg/ Hr.
Total
Kg / Hr.
Annual
electricity
consumptio
n cost (In
Rs)
Annual
maint cost
(In Rs)
Total Cost
saving
( In Rs)
Investmen
t
( In Cr.)
ROI
( In
Months)
Area
Potential
Kcal / Hr.
Area Purpose
Energy
Requirement
Kcal/Hr
Air to Air
CED Oven
Exhaust
1,74,249
ED Ovens -
Heat up
FA Pre
heating
1,13,895 1,13,895
65%
47,520 12.41
25.61
3,04,603 3,00,000 35,93,879
1.21
23
Ed Ovens -
Hold up
FA Pre
heating
TC 1 Oven
Exhaust
TC Oven 1
FA
FA Pre
heating
TC2 Oven
Exhaust
TC Oven 2
FA
FA Pre
heating
Oil to
Water
Compressor
1,21,238
PT - 1 tank PT Heating
1,21,238 1,21,238
100%
15,840
13.2
1,01,534
-
43,67,624
0.3
2,95,486 2,35,133 2,35,133
80%
79,61,503
1.51
Note:

14. Page No : 14
CED
HOLDING HEATER BOX
HEAT RECOVERY
UNIT
CED
HEATUP HEATER BOX
˚C ˚C
Blower
9000CF
M
Blower
8000CF
M
Fresh Air 30-35˚C
GAS 200 Deg
C
PRE HEATED
AIR 120 ˚C
FLUE GAS POST HEAT
RECOVERY 140 ˚C
PRE
HEATED
AIR 120 ˚C
Gas Exhaust to
Atmosphere
Option 2 - Schematic for Air to Air Heat Recovery
Air to Air System
 Ovens exhaust air is recovered and reuses for Pre heating the Fresh air intake which is suction from atmosphere with ambient temperature and
preheating upto 90 deg C based on the flow rate requirements.
 Due to the above process, the burner load will get reduce and LPG saving.
 In oven circuit resource is excess. There is no necessity to utilize compressor heat source in Oven circuit. Compressor heat potential can be utilized
for PTCED hot bath.
Pre heat air 90*C
FLUE GAS POST HEAT
RECOVERY 110*C
BLOWER
Pre heat air 90*C
BLOWER

15. Page No : 15
60
*C
90
*C
110*
C
50*
C
110*
C
50*
C
110*
C
50*
C
110*
C
50*
C
90k
w
90k
w
90k
w
55k
w
90*
C
60*
C
60*
C
85*
C
45*
C
60*
C
Buffer Tank
45*
C
60*
C
H/W
KOD/DE
G
45*
C
45*
C
Bigger HEX to recover
compressor heat energy
Exixting HEX in PT line
Option 2 - Schematic for Compressor Heat Recovery
Oil to Water System (Compressor)

16. Page No : 16
Option 3: Utilization of waste exhaust gas heat from all 3 ovens common exhaust to pre heating the same oven fresh air intake from ambient
to 90*C. Heat recovery from compressor oil to heat up any one of the hot bath tank of pretreatment & remaining tanks of PT can
be heat up by means of Water source heat pump system.
Proposal Option-3
Method
Source Sink
Energy
Utilisation
Kcal / Hr.
%
Utilisation
Against
Potential
Annual
electricity
consumption
(KWH)
LPG
Saving
Kg/ Hr.
Total
Kg / Hr.
Annual
electricity
consumptio
n cost (In
Rs)
Annual
maint cost
(In Rs)
Total Cost
saving
( In Rs)
Investme
nt
( In Cr.)
ROI
( In
Months)
Area
Potential
Kcal / Hr.
Area Purpose
Energy
Requirement
Kcal/Hr
Air to Air
CED Oven
Exhaust
1,74,249
ED Ovens -
Heat up
FA Pre
heating
1,13,895 1,13,895
65%
47,520 12.41 12.41 3,04,603 3,00,000 35,93,879
1.21
21
Ed Ovens -
Hold up
FA Pre
heating
TC 1 Oven
Exhaust
TC Oven 1 FA
FA Pre
heating
TC2 Oven
Exhaust
TC Oven 2 FA
FA Pre
heating
Oil to
Water
Compressor
1,21,238
PT - 1 tank PT Heating
1,21,238 1,21,238
100%
15,840
13.2
35
1,01,534
-
43,67,624
0.3
Water
source
heat
pump -
270Kw
Ambient - PT - 3 tank PT Heating
2,03,762 2,03,762
100% 4,86,753 22
31,20,089 4,55,000 46,38,911 0.74
Note: In heat pump system chiller running cost included. 1,26,00,414
2.25
Note:

17. Page No : 17
Piping
diagram
of
installed
system
4 – 60 KW water Source Heat pumps
HP-Cold water Buffer tank
HP-Hot water Primary storage tank.
Cold side Plate
Heat Exchanger
From compressor heat
recovery
Cold well
Hot well Process In/Out
CED Chiller
Option 3 – Schematic Compressor Heat Recovery & Heat Pump
Oil to Water System
(Compressor)
Heat Pump
(Water Source)

18. Page No : 18
Parameters Option 1 Option 2 Option 3
Surface area Compact design Larger area Larger area
HEX type Fin tube type Shell & tube type Shell & tube type & PHE
Recovery heat potential (WHRS) 2.95 lac kcal/hr 1.74 lac kcal/hr 1.74 lac kcal/hr
Heat transfer rate
Higher heat transfer coefficient (Air to
water)
Lesser heat transfer coefficient(Air to
water)
Coefficient of performance - upto 2.5 to 3
(referigrant to water)
Hex area req ( for y kcal/hr) 1x sq.m 4x sq.m 1x sq.m
Investment (In cr.) 1.46 1.51 2.25
Running cost 6,55,358 4,06,138 35,26,226
AMC cost NA NA 4.5 lac/year
Availiability Availiable in during process Availiable in during process Availiable in during process
Tangible benefits HWG on stand by in prod mode Burner & HWG running load will reduce HWG & Chiller on stand by in prod mode
Intangible benefits Eco friendly Eco friendly Eco friendly
Layout constraint In side plant In side plant
In side plant( Dependant on heat pump
unit space req)
Net benefits 99,37,078 79,61,503 1,26,00,414
ROI 18 23 21
Comparison Between Various Options

19. Page No : 19
 M/s.Durr comments: Not recommending WHRS for burner flue gas stack.
 Flue gas duct draft may influence burner back pressure , due to that burner efficiency may get dropped.
 Burner flue gas volume is very less & not advisable to connect to heat recovery system.
 On account of safety issues like proposed safety device is not functioning properly may have adverse reaction on total system safety as well
as work forces protection & may have severe impact on the adjoining system installation.
Oven Burner Flue Gas Stack
Source Calculation – Burner Flue Gas Stack
Name
Process
Temperature
Oven
stack
Temperatu
re
Oven
stack
flow rate
Cool down
to
Ambien
t Temp
Density
@
ambient
Oven
stack
Mass
flow rate
Cp @
ambient
Oven stack
Heat
content
10% losses
of Kcal/hr
LPG
saving
Annual LPG
saving
Total Annual
saving
Investment ROI
deg C deg C m3/hr deg C Deg C kg/m3 kg/hr kCals/kg kCals/hr Kwh Kg/hr Rs Rs Cr. M
ED Ovens - Heat
up
215 200 694 100
30 1.1492 511 0.26 13,283
11,955 14
1.3 4,40,697
24,54,729
Concept
Under
discussion
Ed Ovens -Hold up 215 200
697
100 30 1.1492
513 0.26 13,341
12,007 14
1.3 4,42,602
TC Oven 1 stack 165 195 763 100
30 1.1492 568 0.26 14,022
12,620 15
1.4 4,65,205
TC Oven 2 stack 170 227 1450 100
30 1.1492 1010 0.26 33,344
30,009 35
3.3 11,06,225
73,990 66,591 77 7.3 24,54,729

20. Page No : 20
Challenges for WHRS Implementation
 The acid dew point of a exhaust gas (i.e. a combustion process gas) is the temperature, at a given pressure, at which any gaseous acid
in the exhaust gas will start to condense into liquid acid.
 It is very important not to cool a exhaust gas below its acid dew point because the resulting liquid acid condensed from the flue gas can
cause corrosion problems for the equipment used in transporting, cooling and emitting the flue gas.
 Heat exchangers tend to be larger to recover significant quantities which increases capital cost for the same capacity of air to water will
have lesser area comparative with air to air heat exchanger.

21. Page No : 21
WHRS Reference Images

22. Page No : 22
Water source heat pump supplying both heat and cooling to Durr CED line in Hosur

23. Page No : 23