Heat Exchange Solutions Support Sustainability in the CPI

Developments in heat exchange technologies promote efficiency, reliability and cost effectiveness in the chemical process industries (CPI)

Heat exchange technologies play a pivotal role in industrial sustainability efforts because they are at the forefront of enabling more environmentally friendly chemical processes, while also serving as a core mechanism in evolving clean technology and electrification projects. However, to find success in traditional or developing applications, selection of the right heat exchange technology is essential, as it will provide more energy-efficient performance, greater reliability and lower operational costs. Fortunately, innovative heat-exchange solutions are available to suit every industry need and overcome common process challenges in both existing and emerging applications.

“Chemical processing companies are concerned about their carbon footprint, which is directly related to the energy efficiency of their processes and hence, to their heat exchangers,” says Alasdair Maciver, head of energy storage solutions and vice president of the welded heat exchangers business unit, with Alfa Laval (Lund, Sweden; alfalaval.com). “At the same time, the ‘clean-tech’ space is looking at new, innovative processes in hydrogen, carbon capture and energy storage and these efforts come with new demands for heat exchangers.”

According to the experts, more-efficient heat transfer, increased reliability and more cost-effective operation are of the highest priority for today’s heat exchange technologies, no matter the application.

“Chemical processors are looking for heat exchange systems that meet high standards around performance and reliability, tempered against a reasonable cost of investment,” explains Warren Chung, regional director with Solex Thermal Science (Calgary, Alta., Canada; solexthermal.com). “As operators seek to maximize the useful operating life of their facilities, they have been increasingly considering heat exchange options from the total cost of ownership perspective rather than simply the lowest upfront capital investment. Operators have realized that production disruptions due to failed or underperforming heat exchange systems are significantly costlier than investing in higher quality heat exchange systems with greater longevity.”

“However, the challenge is determining which technology works best for your application and process given the chemicals that will be flowing through it and the reaction,” adds Nathan Thomson, manager business engineers with SWEP (Duluth, Ga.; swep.net). “Operators need an understanding of the innovation around the core heat exchange technologies as they are constantly evolving and each has its own advantages and disadvantages, depending on the application.”

Heat exchange innovations

While selecting the appropriate heat exchange technology depends on the specifications of the application, developments and technologies that focus on improving efficiency and reliability often result in greater cost effectiveness in any operation.

“Many of the challenges associated with heat exchange technologies are the same as in other sectors, although preventing unwanted chemical reactions, corrosion and fouling are key considerations for chemical processors, as they impact reliability and efficiency,” notes Matt Hale, global key account director with HRS Heat Exchangers (Marietta, Ga.; hrs-heatexchangers.com). “But these can be mitigated with appropriate design and construction, depending on each individual project. For example, the use of corrosion-resistant stainless steel and corrugated-tube architecture can minimize and prevent fouling (Figure 1).

“Such steps will also help maximize heat transference and energy efficiency. For example, corrugated tubes are more efficient than smooth tubes in operation. As in all sectors, costs are also a key consideration, although it’s important to look at both capital and operational costs, as a cheaper installation may be more costly in the long run, as it may require more heat for ongoing operations.”

Hale says that HRS’s corrugated-tube technology provides a number of benefits when compared to smooth tubes. “The first is that corrugations create turbulent flow in the product, helping to prevent fouling. In turn, this improved efficiency means that corrugated tubes provide greater levels of heat transfer than smooth tubes of the same length, so corrugated-tube heat exchangers can be up to half the size of their smooth tube equivalents. The turbulence created in the tube also reduces cleaning frequency and simplifies maintenance compared to other heat exchanger designs.”

Meanwhile, Alfa Laval’s Maciver notes that transitioning from shell-and-tube technology to more efficient plate-type heat exchangers, where applicable, can help reduce energy requirements and, consequently, a facility’s carbon footprint and operational costs. “It’s a first, and easy step on the journey to decarbonization and it provides several additional benefits to chemical processes,” notes Maciver.

Because plate heat exchangers have a smaller footprint, they are easier to install, service and maintain. Plate technology also increases reliability by reducing fouling, stress, wear and corrosion to result in better performance and longer operational uptime. Additionally, the technology minimizes energy costs and emissions, contributing to an improved bottom line.

As an example of the benefits that can be achieved, Maciver points to a collaboration between Alfa Laval and Dow Chemical (Midland, Mich.; www.dow.com), in which a number of heat exchanger positions at different sites were upgraded to improve sustainability and profitability. Specifically, in a project at a Dow site in Terneuzen, the Netherlands, the existing shell-and-tube solution used in a heat recovery role in the ethylene oxide plant was replaced with two Alfa Laval Compabloc heat exchangers to achieve substantial energy savings and reduced CO₂ emissions. The replacement also mitigated severe fouling problems, which increased uptime and improved product yield.

Also aimed at increasing efficiency, Roy Niekerk, director of application engineering at Kelvion GmbH (Monzingen, Germany; kelvion.com), explains his company’s offerings: “The challenge given by our customers is to have an as-close-as-possible temperature approach in their heat exchangers, which is often achieved by a fully welded plate heat exchanger, such as the K°Flex, which is a high-performance plate heat exchanger designed for optimal flexibility and efficiency in heat transfer applications (Figure 2).

“It features a modular design that enables easy customization to suit specific operational requirements,” Niekerk continues. “The system offers efficient heat exchange, compact size and simplified maintenance, making it ideal for industries such as chemical processing and power generation. Its robust construction and adaptability enhance energy efficiency and operational sustainability.”

And, as an alternative solution to increase reliability in difficult-to-handle process streams that are incompatible with traditional heat exchangers, Solex’s Chung suggests the use of heat-pipe heat exchanger (HPHE) solutions from Econotherm, a Solex Thermal Science company (Figure 3). “HPHEs reduce the risks and the consequences of failure that commonly plague traditional heat exchanger types through the inclusion of multiple redundancies in the heat exchanger design,” he says. “By using HPHEs, operators realize fewer process disruptions and longer run lengths without having to sacrifice performance, especially in particulate-rich and corrosive process streams.

“Due to the technical limitations of traditional exchanger types, these process streams were previously inaccessible from a heat-recovery perspective and otherwise considered wasted,” Chung explains. “However, HPHEs now enable chemical processors to unlock incremental energy-recovery opportunities within their operations and present a viable solution for meeting the evolving challenges.”

He points to the use of an HPHE developed by Econotherm for use as an air preheater in a petrochemical complex. “The application had a failed plate-style recuperator that needed to be replaced. The heat exchanger outage was causing the consumption of significantly higher fuel quantities at the gas-powered burners with increased associated emissions,” he says.

“A HPHE unit was custom built to match the complicated dimensioning of the existing unit, which minimized capital investments in fan/duct work. The HPHE was used to cool the fluegas to near the acid-gas dewpoint, enabling incremental heat recovery from the primary stream of corrosive fluegas, while minimizing corrosion risk and lowering fuel consumption to below the requirements from when the plate-style recuperator was in operation.”

Additionally, developments in heat-exchanger coating technologies can also provide a cost-effective means of managing corrosion and fouling in an effort to boost reliability, according to SWEP’s Thomson. “We have been working on innovating coatings that we can apply to the heat exchanger, which allow our customers to use a less expensive heat exchanger in complicated systems where they previously would have needed more noble materials of construction,” he says. “Instead, we coat it with a specifically formulated chemical and it provides protection to stainless steel or less noble materials in these applications, allowing a lower cost of ownership and the use of efficient and compact solutions.”

For example, he says, brazed plate heat exchangers bring benefits in terms of thermally efficient and compact products, but there were some obstacles with the use of brazed plate heat exchangers, including interactions between media, which can result in corrosion, fouling, scaling and leaching and a decrease in the performance and efficiency. “But, by looking at these processes, we found using coatings provided a way to mitigate the occurrence,” says Thomson. “The use of coatings and innovating applications of coatings allows better resistance to corrosion, scaling and leaching, and opens markets for less expensive heat exchange solutions, while also allowing customers to replace older technology with newer, more efficient versions in support of reaching sustainability and cost goals.”

Emerging applications

While improvements in energy efficiency and reliability help overcome challenges and provide lower operational costs in traditional chemical processing applications, they are also fundamental in the development of newer sustainable-technology and electrification innovations, according to the experts.

“Everyone is keen on efficiency right now because it directly reduces the carbon footprint. Further, the more efficiency you can achieve with a heat exchanger, the less additional steam you need to create in the process, which is typically done in oil- or gas-fired burners, so you instantly reduce fuel consumption,” explains Alfa Laval’s Maciver. “While this is the biggest driver in traditional chemical processes, it is especially true in the new clean-tech space, which is looking at new processes in hydrogen, carbon capture and energy storage.”

He continues, pointing out that these applications put new demands on heat exchange solutions. “High temperatures and working with molten salts are two common challenges that we work with in this space,” says Maciver.

“We are actively looking to extend our portfolio of heat exchangers for these applications, including organic R&D development and forming partnerships to bring specific products and expertise into our offerings,” continues Maciver. “For example, we are in a partnership to market our header-coil heat exchanger technology, which has a long tradition in working with molten salts and those that involve significant thermal cycling, which is an issue that often leads to fatigue failures in conventional heat exchangers.

“Reliable and responsive heat exchangers are critical to the energy transition and essential for the future energy market, where an increasing share of intermittent renewable energy sources is being integrated into the grid,” he says.

The Alfa Laval Aalborg header-coil offers innovative header-coil technology that absorbs thermal stress, minimizes equipment strain and eliminates leakage risks (Figure 4). The design features and production techniques ensure a low approach point, as well as high long-term reliability and thermal efficiency, making them suitable for concentrated solar power, energy storage and power-to-X plants.

Kelvion also offers heat exchange technologies that support sustainable and efficient solutions in the clean tech space, including green hydrogen production. “Electrolysis systems are considered to be a promising option for producing hydrogen from renewable resources,” says Alexander Gernhardt, senior application engineer, green technologies, with Kelvion. “However, these systems have a 60 to 80% efficiency rate, which represents the level of electrical energy that will be transformed into hydrogen. The remaining 20 to 40% becomes heat that can either be recovered or reused in, for example, district heating, or emitted by air coolers into the ambient air. This means that an electrolyzer system with 10-MW capacity will transform around 2 to 4 MW of the electrical energy supplied to the process into heat.

“To ensure that the electrolysis occurs in stable and efficient conditions, it is essential that all equipment interacting with the process, especially the heat exchangers, is carefully chosen and designed,” Gernhardt says. “Our plate heat exchangers, shell-and-tube heat exchangers, dry coolers, air fin coolers and cooling towers are specifically designed to enhance the efficiency of the electrolysis plant and help to provide a holistic approach by optimizing the different interconnected heat exchangers to each other. This is of high importance for proton exchange membrane (PEM) and alkaline water electrolysis (AWE) processes as the working temperatures are moderate and temperature differences to the ambient are limited.”

And, as electrification of process heating becomes a major initiative, particularly in certain areas where the electric grid is already decarbonized since it offers a straightforward approach to reducing direct and indirect emissions, heat transfer is of growing importance, say Richard Jibb, technology director, and Roberto Groppi, senior director for heat exchangers, with Lummus Heat Transfer (Houston, Texas; lummustechnology.com).

“Electric heaters, furnaces, heat pumps and boilers are all examples of heat transfer equipment that can be used to reduce reliance on fossil fuels,” says Jibb. “However, using renewable energy effectively can be challenging due to fluctuations in energy production based on the time of day, weather conditions and seasonal variations, such that energy-storage technologies are needed to bridge this gap by storing excess energy during times of high production and releasing it when needed. Energy storage technologies such as compressed-air energy storage, liquid-air energy storage and molten salt or thermal storage all rely significantly on advanced heat exchanger technologies capable of operating at extreme temperatures and under cyclic conditions. In addition, the scale of many industrial heating operations presents an issue, as the electrical infrastructure required may present a practical limit to the amount of heating that can be converted to electrical power.”

Groppi explains: “An alternative approach investigated by Lummus is to use hybrid heating technologies that can combine electrical heating with conventional heat sources or can use electric heating when it is available in excess, in essence balancing the grid and reducing the electricity supply cost.”

As such, Lummus has developed a portfolio of solutions for electrification. The company is involved in joint studies related to the industrial demonstration of Lummus’s SRT-e electric cracking heater to decarbonize a Braskem (São Paulo, Brazil; www.braskem.com.br) site in Brazil (Figure 5). The SRT-e electric cracking heater leverages Lummus’ proven Short Residence Time (SRT) technology modified to operate using electricity and incorporates a modular unit-cell design that can be replicated for plants to accommodate any commercial capacity. The technology uses commercially demonstrated components, plus an optimum heat-flux profile, leading to a longer radiant coil life and longer run length. In addition, decoking can be carried out on a unit-cell basis so maintaining a spare heater is not required.

Whether the application is existing or cutting-edge, heat exchange technology is evolving to provide more efficiency and reliability, as well as a lower cost of ownership, helping to make any operation more sustainable and profitable.

Joy LePree