The Nature of Fouling
Defined –
Fouling in industry is defined as the undesirable accumulation of material
on equipment surfaces such that function, performance, efficiency or operation
of the equipment is degraded. Some fouling mechanisms are well understood
and yield to numerous mediation methods. Others are as wide spread as
the ocean, and require site specific strategies for minimization and control.
Bridger Scientific develops technologies to aid in the understanding and
control fouling phenomena.
Examples of Fouling and its deleterious effects:
Micro biologic growth on heat exchanger heat transfer
surfaces (biofilm) |
thermal performance loss |
Ship hull macrobiological accumulations (macro organic fouling
– barnacles) |
speed, drag and weight |
Calcium carbonate scale on home water heater elements (mineral
scale) |
premature failure |
Plaque on human teeth (biofilm) |
bad breath / cavities |
Rime ice build up on aircraft wings (clear ice) |
reduced lift / crash |
Cholesterol build up on human arteries (organic deposit) |
heart attack / death |
The Interdisciplinary Nature of Fouling –
A holistic view
Many different people with various skill sets and objectives are involved
with fouling in industry. I’ll speak primarily about electric utility
power plants, as that is what I am most familiar with. But the stage is
similar for many industries using industrial quantities of water - The
actors:
- The plant operator – wants to
operate the plant as requested without limitations or restrictions
- The regulator – federal or state
monitoring of NPDES permit compliance
- The biologist – protecting the
environment by monitoring aquatic organisms and quantifying impacts
- The performance engineer – monitoring
plant thermal performance and calculating efficiency
- The chemist – monitoring and
adjusting the biocide, scale and corrosion inhibitor schedule as required
- The maintenance foreman – scheduling
the work and shutdowns to clean heat exchangers as necessary
- The accountant – juggling the
relative economic costs of water pollution and air pollution
- The plant owner – wants to maximize
profits and productivity
- The local public – they want
jobs, electricity, a clean lake/river/beach/ocean, and skies overhead
!
All these people have a vested interest in the plants
operation. And all their goals are different and sometimes mutually contradictory.
Information must flow between them and somebody must act as the coordinator
of their actions. Neglect the needs or desires of anyone of them at your
peril! We sell instrumentation that is used to improve the understand
of fouling problems for many of these people. And we never know into which
direction we will be pulled next – engineering/biology/regulatory
compliance…
History
Numerous methods have been used to control fouling in nature. Early sailing
ships applied copper plates to their sides to inhibit marine biological
fouling. They also sailed up river from the ocean to expose the attached
ocean organisms to fresh water so they would die and fall from the ship
to improve speed. It was not until the modern age of wide spread plumbing
and sanitation (and high population density) that humanity has had to
deal with fouling in a more significant way.
The primary systems we are concerned with are industrial
users of cooling water. In the US, a NPDES (national pollution discharge
elimination system) permit is required of all water users who take and
then discharge large quantities of water to the environment. The permits
program, originally started circa 1972 with the clean water act. The permits
typically restrict large users of water to discharging water with known
toxins above a specific threshold. The bar is changing as our knowledge
of the environment and the sensitivity or fate of various chemicals improves.
Other nations have similar issues and have instituted similar programs.
The greatest motivation for understanding and improved control comes from
those areas with high population density and scarce water resources.
A Breakdown by type
- Biological – Macrobiological
(barnicles, mussels, hydroids…)
Microbiological (biofilms)
- Mineral Scale - calcium carbonate
(inverse solubility scales)
- Product fouling - petrochemical coking
milk sterilization/scalding
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