International Drying Symposium te at o a y g Sy pos u
MARKET ANALYSIS OF DRYING TECHOLOGIES IN DENMARK AND THE POTENTIAL FOR ENERGY RECOVERY ON DRYING SYSTEMS
Senior Consultant Lars Reinholdt Senior Consultant Peter Schneider Senior Consultant Ebbe Nørgaard
Ebbe Nørgaard, ebn@teknologisk.dk , ph: +4572201273, Energy and Climate division
Content
Background for presentation
Background for presentation
Market analysis on drying
b h (b f)
Basics about heat pumps (brief)
Air vs. steam drying in relation to energy recovery
High temperature heat pumps, relevant for drying
Conclusions
Content
Background for presentation
Background for presentation
Market analysis on drying
b h (b f)
Basics about heat pumps (brief)
Air vs. steam drying in relation to energy recovery
High temperature heat pumps, relevant for drying
Conclusions
Please note that there is no paper behind this presentation, p p p ,
but you are welcome to have a copy of the presentation, and
to discuss further details afterwards!
Content
Background for presentation
Market analysis
Basics about heat pumps (brief)
Air vs. steam drying in relation to energy recovery
High temperature heat pumps, relevant for drying
Conclusions
Background for presentation
I come originally from the refrigeration and heat pump business where the heat source often is at much lower temperature (exergy) levels than what can be realized in many drying facilities by recovering energy in the exhaust stream.
My mission with the presentation is to show the potential of energy
recovery on drying systems by means of new and different types of high temperature heat pumps integrated in closed drying circuits.p p p g y g
Within the last decade 3 new high temperature types have been commercialized, which are relevant for drying applications.
It is not a detailed economical analysis of the feasibility of such system, because it has to be carried out for each individual case and no pinch analysis have been made – it is a generalized approach.
In Denmark electricity is going to be the future energy source, mainly based on wind power – bright future for heat pumps (in Denmark at least).
The Danish Technological Institute is a private and non-for-profit institution that does not sell any products but often develop them in cooperation with industry, and often with co-funding from a third party.
Content
Background for presentation
Market analysis
Basics about heat pumps (brief)
Air vs. steam drying in relation to energy recovery
High temperature heat pumps, relevant for drying
Conclusions
Distribution of the industry's energy consumption in DK Distribution of the industry s energy consumption in DK
Total 91.368 TJ~ 25380 GWh
Boilers and network losses 9%
18%
Boilers and network losses Heating/Boiling
Drying
0%
1%
1% Drying
Evaporation Distillation 3% 27%
Burning/Sintering Meltning/Casting 14%
Other heating up to 150° C Other heating above 150° C
6% 17%
4% Labour transportation
Room heating
Source: Danish Energy agency (2002)
Typical specific energy consumption of different drying processes (Denmark)
[kJ/kg water] [kcal/kg water][MWh/ton]
Convection dryers
Dryer types
Typical energy consumption
processes (Denmark)
Convection dryers
Conveyer dryers 4000‐6000 957‐1435 1,1‐1,7 Tunneldryers 5500‐6000 1316‐1435 1,5‐1,7
Owens 5000‐5800 1196‐1388 1,4‐1,6
Rotorowen 4500‐9000 1077‐2153 1,3‐2,5
l d b d
2460 kJ/kg
Fluid bed 4000‐6000 957‐1435 1,1‐1,7
Flash 4500‐9000 1077‐2153 1,3‐2,5
Spray 4500‐11500 1077‐2751 1,3‐3,2
Steam
Vacuum 2900‐4600 694‐1100 0,8‐1,3
Atmospheric 2500 598 0,7
High pressure 2500 598 0,7
Heat pump 500‐1100 120‐263 0,1‐0,3
Contact dryers
Specific energy consumption above approx.
2460 kJ/kg water evaporated indicate that there are losses in the specific drying process
y
Drum 3200‐6500 766‐1555 0,9‐1,8
Roller 2900‐5700 694‐1364 0,8‐1,6
Spiraltube 3400 813 0,9
Screw 3400‐5600 813‐1340 0,9‐1,6
Specific energy consumption below 2460 kJ/kg can be obtained by using different kinds of recuperators heat pumps or by using the
Gas based infra red dryers 3500‐9500 837‐2273 1,0‐2,6
Radiant dryers
Radiofrequency 5300 1268 1,5
Microwave 6400 1531 1 8
recuperators, heat pumps or by using the exhaust energy from the drying process elsewhere
Microwave 6400 1531 1,8
Freeze drying 10000 2392 2,8
Infrared 3300‐5600 789‐1340 0,9‐1,6
Source: Danish Energy agency (1998)
Economy: Energy saving potential and compressor cost
Economy: Energy saving potential and compressor cost
There is an economical potential for
There is an economical potential for energy recovery on drying systems.
Why is it not realized?
Interview with drying business in Denmark.
200 players within drying in Denmark were identified (consultants, end users, component suppliers)
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users, component suppliers)
104 of these were interviewed
80 of 104 had drying process (food, feed, fertilizer, fiber, fuel)
Main results
- 5 % of the processes are based on steam drying - 95 % are based on air drying
- 50 % does not know the specific energy consumption (efficiency) of their drying process, it must be calculated on behalf of overall energy consumption
- 90 % of processes are more than 10 Years old and require large investments - General requirement regarding pay pack time for investments is 5-7Ge e a equ e e t ega d g pay pac t e o est e ts s 5 Yearsea s - 34 % have heard about steam drying
- Which parameters have top priority for the end users?:
a. Product quality 86 % We do as we usually do, because we
k it k d k
b. Proven technology (working stability) 86 % c. Safety (fire, explosion) 75 %
d. Energy consumption 70 %
L l i t l i t 65 %
know it works and we make money
e. Local environmental impact 65 %
Temperature analysis of drying processes
Supply temperature and Δt between heat source and heat sink temperatures for drying process are important for heat pump driven process.
80 % of installations can be
made with commercially
available heat pumps
available heat pumps
Temperature analysis of drying processes
90 % are technologically possible to generate with heat pump
80 % of installations can be
made with commercially
available heat pumps
available heat pumps
Content
Background for presentation
Market analysis on drying
Basics about heat pumps (brief)
Air vs. steam drying in relation to energy recovery
High temperature heat pumps, relevant for drying
Conclusions
Basics about heat pumps
A heat pump is a machine or device that moves heat from one location
(th ' ') t l t t t th l ti (th ' i k'
(the 'source') at a lower temperature to another location (the 'sink' or 'heat sink') at a higher temperature using mechanical or thermal work.
qheat
20 kW
qreject
30 kW Thermal
driven cooling device
4
qcold
10 kW
COP = 0,5
4 1,5
A small temperature difference between hot and cold temperature will increase the Coefficient Of Performance (COP).
Most heat pumps are electrically driven so COP > (kWh power)/(kWh gas) (typically 3
+ return on investment). Typical investment is 250 – 500 €/kW heat capacity.
Content
Background for presentation
Market analysis on drying
Basics about heat pumps (brief)
Air vs. steam drying in relation to energy recovery
High temperature heat pumps, relevant for drying
Conclusions
Air vs. steam drying
For efficiency of energy recovery with heat pump it is
advantageous to operate with small temperature differences
d b f h d bl
Air drying can be faster than steam drying at comparable temperature differences and vise versa – depends on the product.
Possibility to obtain same drying rates with different temperature differences air/steam
It is easier to recover energy from steam process than air process, (higher exergy of pure steam). Plus practical
issues, no heat source heat exchanger.
Air drying process without energy recovery
1. Heating the air (20 to 100° C) 2. Drying (100 to 42° C)
1
2
1
Energy recovery with recuperator
1. Heating the air (20 to 100° C) 2. Drying (100 to 40° C)
1
2
1
3
Energy recovery with heat pump (and recuperator)
1. Heating the air (20 to 100° C) 2. Drying (100 to 40° C)
1
2
5 S ibl t ( 15 %)
1
3
5. Sensible part ( 15 %) 6. Latent part (85 %)
4
Operating conditions heat pump:
Simple heat pump process calculation p g p p
T
cold= 0° C, T
hot= 105° C 3
,
1
3
,
2
=
COP
CO7 ,
3
= 2 COP
nh4 ,
2
4
,
2
=
COP
COp p p p
Osenbrück process may be interesting.
(Low Pressure) Super Heated Steam Drying (SHSD, (Low Pressure) Super Heated Steam Drying (SHSD, LPSHSD)
High temperature steam
From boiler
steamCases:
Heat exhanger
Cases:
100 industrial systems in Europe for drying of
diff t d t many different product groups and drying systems
PC Condensate Exhaust steam
Safety valve Superheat steam
Optimal if the steam can be
fan
used elsewhere, for instance in evaporator (concentration of liquid)
Dryer
For instance in relation to
sugar production, drying of
beet pulp.
SHSD, LPSHSD
and mechanical recompression - and mechanical recompression
Steam
Cases:
Steam
Heat Exchanger
Cases:
MAN Turbo has supplied compressors for such
li ti t “Ab l t
Water compressor
applications at “Absolut Vodka” in Sweden (70- 105° C, 20 Years)
PC Condensate
Safetyvalve Super heated steam
Drying of peat Atlas Copco turbo compressor
fan
(60 tonnes/hour
evaporation, 4-16 bar, 0,17 MWh/ton
Dryer To pilot plants for drying
of sludge, Atlas Copco
To be considered when
Screwcompressors 0,25 MWh/ton
To be considered when
exhaust steam cannot be
used elsewhere.
St d d h t d i SHSD Standard heat pump process used in SHSD
Operating conditions heat pump (peat case):
T = 120° C T
cold= 120 C T
hot= 200° C
Sensible heat
SHSD (120-190° C) Latent heat
69 2 0
,
= 4
realistic
COP P
spec0 , 17 MWh / tonnes 2
, 4
69 ,
0 =
=
High temperature heat pumps
High pressure compressor (80 bar) for Ammonia systems. Max. 100° C
condensation. Possible to use hotgas to increase temperature a little. Supplier in Denmark and Scotland. No temperature glide
CO2 Transcritical systems. Max. 120° C on hot side. Large temperature glide on the heat sink
Osenbrück process, 150° C with 25 bar ammonia compressor. In principle 350°p , p p p C is possible. Large temperature glides on both heat sink and source
Taylormade Mechanical Vapor Recompression systems, has been realized at 200° C (16 bar). Critical pressure is 212 bar (370° C). No temperature glide.( ) p ( ) p g
Typical cost for heat pump: 270 – 540 Euro/kW
Source: Hybrid energy
CO
2Conclusions
There is an economical incentive for recovering energy on drying systems.
New types of high temperature heat pumps with large temperature glides may be relevant in drying
may be relevant in drying.
Temperature difference is important and different types of heat pumps should be considered as they have different characteristics.
Heat pumps can potentially reduce the energy consumption on drying systems below drying temperatures of 200-300° C.
It is off cause not always feasible, individual analysis are required.
Energy consumption is important for end users, but they do not know how efficient their system is. y
Small temperature differences give high efficiencies.
COP > (kWh power)/(kWh gas) (typically 3 + return on investment)
COP > (kWh power)/(kWh gas) (typically 3 + return on investment).