Heat exchanger fouling can be frustrating at the best of times. Especially in heavy fouling applications, where inflated maintenance costs compound inevitable energy and production losses.
Severe fouling results from many contributing factors, making it hard to define the best way to deal with the problem.
Industry experts use a multi-pronged strategy to address fouling. They combine a thorough understanding of the process environment, operating best practices and advanced technologies like heat exchanger coating. This approach leads to the design and manufacture of a unit that delivers substantial value in use.
Let’s take a look at today’s key heat transfer solutions.
Optimizing the Design Factors
When a heat exchanger is destined for harsh operating conditions, designers can tackle the issue of fouling from the get-go. An understanding of initial variables combined with thoughtful design can lead to big savings in the long run.
Pinpointing the “optimal” design for heavy fouling is anything but straightforward, and engineers must blend science with experience.
Heat exchanger models balance numerous considerations, including:
- Process fluid characteristics
- Material properties (i.e., thermal conductivity)
- Temperature & pressure differentials
- Surface area and effective heat transfer
- Fouling factors
The first step to optimizing an exchanger for fouling is to employ industry best practices for design, manufacture and operation. These methods are often low cost and easy to implement—and are typically sufficient to address low-to-moderate fouling. Only for certain cases do more cutting-edge antifouling technologies become necessary.
After more than 60 years of providing industrial heat transfer solutions, Exchanger Industries Limited has a profound understanding of heat transfer in heavy fouling applications. Our engineers apply this expertise during design and manufacture to ensure a unit pays off with increased efficiency over its service life.
Using an Oversized Unit
It’s standard practice to estimate a default fouling factor based on an exchanger’s operating conditions and the properties of the process fluids involved. This factor leads to an increase in the required heat transfer surface area and, as a result, every unit is oversized to some degree.
While more surface area should take longer to foul, the truth is that oversizing often exacerbates the problem by lowering pressure drop and flow velocity. This reduces the shear forces acting at the tube wall and gives foulants more residence time to deposit.
The other obvious problem with specifying an oversized exchanger is that larger units come with larger costs. In heavy fouling applications, units can easily be oversized by 50% or more—the resulting inflated capital costs directly offset any anticipated maintenance or uptime savings.
Implementing a Cleaning Program
Perhaps the most well-established response to heat exchanger fouling is cleaning. Removing accumulations restores at least some of the heat transfer efficiency for a time—until the foulant builds up again.
Typical cleaning tactics include:
- Steam or chemical clean-in-place techniques that do not require opening the unit up
- Aggressive mechanical scrubbings (i.e., hydroblasting or pigging) that require access to fouled surfaces
Cleanings are a manageable response to fouling; however, this approach becomes costly and endlessly infuriating when fouling is severe. Even if redundant units are available, operators must constantly juggle the units during cleanings to avoid downtime. In all cases, the expenses, such as additional workforce and waste disposal fees, rack up quickly.
Investing in Heat Exchanger Coating
Antifouling technology has seen remarkable advancements in recent years, resulting in cost-effective solutions for heavy fouling applications, especially where downtime has a significant impact. Exchanger Industries (partnered with a global chemicals manufacturer) supplies a proprietary fluoropolymer coating that addresses fouling by preventing it in the first place.
Applied tube-side, the coating’s unique low-surface energy chemistry acts to minimize adhesive forces, essentially repelling deposits at the molecular level. The coating keeps tubes clear of foulant, upholds the peak heat transfer efficiency and dramatically reduces (or even eliminates) the need for cleaning.
The additional benefits of heat exchanger coating can include:
