25 Environmental and Economic Impacts of Biofouling on Marine …
389
Heat Exchanger Tubing Alloys in Natural and Synthetic Seawaters’ published by
Sheldon et al. in 1984 evaluates the impact of fouling on heat transfer efficiency of
a condenser using tubing material Type 439 Stainless Steel (T439SS) (Sheldon and
Polan 1984). The case study shows that one month of exposure to a biofouling environment reduced the heat transfer efficiency of the condenser by 19% (Sheldon and
Polan 1984). Six months exposure of the same condenser in an inorganic depositing
environment (calcareous or slit) only caused 9% reduction (Sheldon and Polan 1984).
Thus biofouling could increase the heat transfer resistance to a greater degree in a
much shorter time when compared to inorganic deposits (Sheldon and Polan 1984).
Therefore, to compensate for this energy loss at the heat exchanger surface, additional energy has to be supplied. In most cases, fossil fuels are the main energy source
of heat exchangers that are used for heating purposes. Thus marine biofouling will
directly result in additional consumption of fossil fuels (Casanueva-Robles and Bott
2005). More and more consumption of fossil fuels will increase the emission of
air pollutants like CO 2 , SO 2 & NO X and thereby a subsequent rise in the global
warming potential (GWP). The case study article ‘The Environmental Effect of Heat
Exchanger Fouling’ published by Müller-Steinhagen et al. in 2005 proves that there
is a direct relationship between the biofilm thickness on the heat exchanger surface
and the overall CO 2 emissions in seawater cooled power plants (Casanueva-Robles
and Bott 2005). A 550 MW coal-fired power station was considered for the case
study (Casanueva-Robles and Bott 2005). In the power station, steam is condensed
in seawater cooled high and low pressure condensers (Casanueva-Robles and Bott
2005). The steam is condensed in order to reduce the steam pressure, which will help
to increase the pressure driving force across the turbines (Casanueva-Robles and Bott
2005). The biofouling affected the proper functioning of the condensers and increased
the steam pressure, which resulted in the reduction of driving force across the turbines
(Casanueva-Robles and Bott 2005). This resulted in subsequent energy loss and
affected the plant’s efficiency (Casanueva-Robles and Bott 2005). To compensate
for this energy loss, more steam has to be produced and this caused more CO 2
emissions (Casanueva-Robles and Bott 2005). The CO 2 emissions were compared
to different values of biofilm thickness on the condenser surface (Casanueva-Robles
and Bott 2005). For both high and low pressure condensers, the biofilm thickness was
considered from 0 to 10
3
µm (Casanueva-Robles and Bott 2005). The percentage
increase in CO 2 discharge was 0.75% for low pressure condenser and 0.69% for
high pressure condenser (Casanueva-Robles and Bott 2005). Thus for the thickest
biofilm studied (10
3
µm), the total additional CO 2 produced was 6.2 tonnes per hour
(Casanueva-Robles and Bott 2005). The case study concluded a significant proportional increase in power plant’s overall CO 2 discharge with an increase in biofilm
thickness on the condenser surfaces (Casanueva-Robles and Bott 2005).
Another example regarding CO 2 emissions caused by heat exchanger fouling is
provided in the article ‘Heat Exchanger Fouling: Environmental Impacts’ published
by Müller-Steinhagen et al. in 2011 (Müller-Steinhagen et al. 2009). In the article,
the authors provide an approximate estimation of the overall annual CO 2 emissions
caused by heat exchanger fouling in the oil refinery operations. To heat the crude
oil, the oil refineries generally rely on a battery of shell & tube heat exchangers also
389
Heat Exchanger Tubing Alloys in Natural and Synthetic Seawaters’ published by
Sheldon et al. in 1984 evaluates the impact of fouling on heat transfer efficiency of
a condenser using tubing material Type 439 Stainless Steel (T439SS) (Sheldon and
Polan 1984). The case study shows that one month of exposure to a biofouling environment reduced the heat transfer efficiency of the condenser by 19% (Sheldon and
Polan 1984). Six months exposure of the same condenser in an inorganic depositing
environment (calcareous or slit) only caused 9% reduction (Sheldon and Polan 1984).
Thus biofouling could increase the heat transfer resistance to a greater degree in a
much shorter time when compared to inorganic deposits (Sheldon and Polan 1984).
Therefore, to compensate for this energy loss at the heat exchanger surface, additional energy has to be supplied. In most cases, fossil fuels are the main energy source
of heat exchangers that are used for heating purposes. Thus marine biofouling will
directly result in additional consumption of fossil fuels (Casanueva-Robles and Bott
2005). More and more consumption of fossil fuels will increase the emission of
air pollutants like CO 2 , SO 2 & NO X and thereby a subsequent rise in the global
warming potential (GWP). The case study article ‘The Environmental Effect of Heat
Exchanger Fouling’ published by Müller-Steinhagen et al. in 2005 proves that there
is a direct relationship between the biofilm thickness on the heat exchanger surface
and the overall CO 2 emissions in seawater cooled power plants (Casanueva-Robles
and Bott 2005). A 550 MW coal-fired power station was considered for the case
study (Casanueva-Robles and Bott 2005). In the power station, steam is condensed
in seawater cooled high and low pressure condensers (Casanueva-Robles and Bott
2005). The steam is condensed in order to reduce the steam pressure, which will help
to increase the pressure driving force across the turbines (Casanueva-Robles and Bott
2005). The biofouling affected the proper functioning of the condensers and increased
the steam pressure, which resulted in the reduction of driving force across the turbines
(Casanueva-Robles and Bott 2005). This resulted in subsequent energy loss and
affected the plant’s efficiency (Casanueva-Robles and Bott 2005). To compensate
for this energy loss, more steam has to be produced and this caused more CO 2
emissions (Casanueva-Robles and Bott 2005). The CO 2 emissions were compared
to different values of biofilm thickness on the condenser surface (Casanueva-Robles
and Bott 2005). For both high and low pressure condensers, the biofilm thickness was
considered from 0 to 10
3
µm (Casanueva-Robles and Bott 2005). The percentage
increase in CO 2 discharge was 0.75% for low pressure condenser and 0.69% for
high pressure condenser (Casanueva-Robles and Bott 2005). Thus for the thickest
biofilm studied (10
3
µm), the total additional CO 2 produced was 6.2 tonnes per hour
(Casanueva-Robles and Bott 2005). The case study concluded a significant proportional increase in power plant’s overall CO 2 discharge with an increase in biofilm
thickness on the condenser surfaces (Casanueva-Robles and Bott 2005).
Another example regarding CO 2 emissions caused by heat exchanger fouling is
provided in the article ‘Heat Exchanger Fouling: Environmental Impacts’ published
by Müller-Steinhagen et al. in 2011 (Müller-Steinhagen et al. 2009). In the article,
the authors provide an approximate estimation of the overall annual CO 2 emissions
caused by heat exchanger fouling in the oil refinery operations. To heat the crude
oil, the oil refineries generally rely on a battery of shell & tube heat exchangers also