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Fouling Focus
Heat exchanger fouling in practice – understand & mitigate
Part 8 – fouling costs and benefits of mitigation
In this series of articles we will look at how heat exchangers foul , how to understand the root causes of fouling , and how to mitigate the impact of fouling . The material presented is based entirely on the author ’ s experience and analysis of operating situations in the Oil & Gas industry . However , many theories and varied experiences exist across the industry and amongst researchers .
By Himanshu Joshi , Heat Exchanger Specialist
If decisions have to be made related to heat exchanger fouling - should any action be taken , what action , can the cost be justified - it is necessary to know how much the fouling issue costs and how much the action will cost . There are many components to the cost ( economic losses ) of fouling , but not all may be applicable
Energy
Loss type
Process losses
Corrosion
Cleaning
Table 1 Fouling related losses
Description Applies to heat exchangers used for heat recovery and if the loss of heat duty has to be accommodated by a furnace . Associated costs are in increased fuel consumption , increased emissions , and in reduced process flow if the furnace is unable to accommodate all the heat duty loss . Also see item ( c ) in the next row . ( a ) If a reboiler fouls , there may not be sufficient heat in the column or the required temperatures to get the desired distillation
( b ) If an overhead condenser fouls it may affect the pressure in the column and impact separation of components .
( c ) A fouled condenser may also affect the temperature , composition , and pressure of the vapor going to a compressor , which in turn affects the energy consumption in the compressor . Some fouling ( cooling water is one example ) leads to underdeposit corrosion which necessitates replacement of the tube bundle . This cost should be included in the benefit / cost analysis . The cost of cleaning is a form of loss . This cost should include everything associated with cleaning including the cost of incomplete cleaning , as shown in Part 6 .
About the author
Himanshu Joshi retired from Shell in 2021 after 34 combined years with ExxonMobil and Shell , during which he specialized in heat exchangers and fouling . He was part of a team that was granted a patent related to fouling deposit analysis at ExxonMobil , and led applied fouling R & D projects at both companies . He has made several presentations about the field aspects of fouling and fouling mitigation , and deployed many mitigation technologies in the field . He can be reached by email at alph . hmj @ gmail . com .
Cost type
Cost of mitigation hardware
Recurring costs
Tube bundle cost
Cleaning
Engineering and field work
Table 2 Fouling mitigation costs
Description For examples refer to Part 4 . The devices mentioned there have a purchase and installation cost . This could be a one-time cost , but see the next item on recurring costs .
Installation cost should also include removal and reassembly of the tube bundle and cleaning if necessary . ( a ) In some cases mitigation devices need to be replaced at regular intervals . ( b ) There may be a continuous cost such as the use of electricity or other utilities . These costs must be part of any benefit / cost analysis . Some techniques may require the use of a redesigned tube bundle which must be purchased new . Same as listed in Table 1 , but mitigation should lead to fewer number of cleanings and thus a lower cost . These two costs often get overlooked . If a new design is made or some hardware is installed , some amount of engineering time is required . Some techniques may also require field work not normally needed , such as electrical connections or extra valves or pumps . www . heat-exchanger-world . com