Improvements in energy efficiency, reliability and operational boundaries reduce emissions and cut costs

Due to a demand to increase margins and meet sustainability and decarbonization targets, today’s chemical processors are seeking ways to improve energy efficiency and reliability while also reducing emissions. Fortunately, innovations in heat exchangers are helping them meet these goals. Recent and anticipated heat-exchanger developments are pushing traditional operational boundaries to increase heat-transfer efficiency and reduce utility consumption and maintenance needs, while also improving operational performance, even in the severe conditions associated with the chemical process industries (CPI).

“Innovations and new developments in heat exchangers are driven by process needs or the need to operate the plant more efficiently — or more importantly — safely,” says Rutger Theunissen, chief business officer of services and supplies with Lummus Technology (Houston; ). “We continue to look for ways to improve our heat exchangers to meet a variety of needs: improving sustainability and reducing environmental impacts (such as implementing electrification or lowering emissions from firing); using materials-science innovation to ensure the materials of construction can withstand more severe conditions; and improving fouling mitigation and optimizing maintenance requirements to reduce operating expenses.”

 

Boosting heat-exchanger efficiency

As sustainability goals continue to expand, increasing the efficiency of heat transfer is becoming a growing priority for manufacturers of heat exchangers, and they are rising to the challenge with tweaks on existing technologies and the development of new ones that manage to boost efficiency, operational performance and reliability, allowing chemical processors to cut costs, increase profits and reduce their carbon footprint. “All chemical processing industries are developing roadmaps and targets for decarbonizing their processes and reducing emissions,” notes Alasdair Maciver, who is responsible for the development of business and heat exchanger solutions with the clean-technology space, specifically in energy storage applications, at Alfa Laval (Lund, Sweden; ). “The most effective short-term way of doing this is by reducing energy consumption, which means increasing energy efficiency. Plate-type heat exchangers are fundamentally more efficient than tubular types, so this is an obvious low-hanging fruit for them. The more challenging part is to increase the scope of plate heat exchangers, moving plate heat exchangers into larger and more demanding processes in terms of capacity, pressure, temperature and aggressive fluids.” He continues: “We are focusing our heat- exchanger development to make heat exchangers that are even more efficient, reliable and cost competitive from a lifecycle perspective. Specifically, this means working with optimization of the plate design for thermal efficiency, new materials for strength and corrosion resistance, increasing pressure and temperature limits, improving ease of service and connected services.” Samuel Glover, Jr., global product manager for plate heat exchangers with SPX Flow (Charlotte, N.C.; ), adds: “Significant developments continue to take place that are focused on improving heat-transfer efficiency of the heat-exchanger unit. Often, this means working to provide the end user with their required heat transfer in a smaller footprint, both in size and energy consumption, which can result in cost savings. “A more efficient system also means a more sustainable one,” Glover continues. “By helping processors optimize their equipment, in both new builds and existing systems, we can help them reach goals around energy use, as well.” Spirax Sarco Ltd. (Blythewood, S.C.; ) is also working on innovations that increase not only the efficiency, but the performance of their heat-transfer solutions, says Chris Rossi, product manager for thermal energy solutions with the company. “Because processors are always looking to see how they can continue to make products to their internal standards, while also delivering profit to shareholders and trying to be a more sustainable entity, it’s an important goal for us to develop solutions that can deliver.” As such, the company recently updated several heat exchangers, including the Turflow, a high-efficiency heat transfer solution and EasiHeat with dual control. Spirax Sarco’s Turflow heat exchangers (Figure 1) are compact in design and suitable for a range of fluids, including steam. The straight, corrugated-tube design induces turbulence in the flow of the fluid, providing a self-cleaning effect, which reduces scale buildup and, therefore, maintenance needs. And, unlike traditional shell-and-tube heat exchangers, it delivers a more consistent and higher heat transfer rate, creating a solution that also improves heat transfer efficiency.

While the Turflow relies on design to increase efficiency, the Spirax EasiHeat implements enhanced control to achieve higher levels of efficiency. EasiHeat is a complete, ready-to-use steam-to-water heat-transfer system that delivers energy efficiency performance in applications with stable load conditions. The dual-control design combines the benefits of both steam and condensate control and provides a high level of set-point accuracy while providing sub-cooled condensate under any operating load changes. The steam-side control allows users to heat only the water that is required and, by reducing steam demand, it helps to reduce CO₂ emissions by using the latent heat from the condensate. The condensate control ensures that all the useful energy in the steam is used within the unit, resulting in less waste, which in turn, reduces both fuel demand and CO₂ emissions.

 

Performance and reliability

However, as heat-exchanger manufacturers understand that even the most efficient heat exchanger is of no use to chemical processors if it cannot handle the operational extremes of the industry, they are working on adapting solutions to meet the performance demands of chemical processing. “In addition to efficiency, the current trend we are seeing is a real drive towards increases in operating temperatures and pressures,” explains Albert Bedell, technical director with Solex Thermal Science (Calgary, Alta., Canada; ). “This seems to be due to an increase in focus on energy recovery and overall efforts to reduce the energy intensity of the process heat. Processors are taking a fresh look at their processes and are taking a ‘nothing-is-sacred’ approach to reimagining things.” He continues: “The rub here is that a lot of these processes are operating at temperatures well beyond what standard heat exchangers can operate at — say north of 600 or 700°C. The low availability of options in this temperature range is a challenge we hear about quite often.” Bedell says Solex is working on finding options to move beyond the temperature limits imposed by using steels as materials of construction. “One of the big shifts we’ve made over the past few years is to rethink the overall geometry of our exchangers for these applications, which gives us a lot more flexibility to use different materials,” he says. “We are currently moving through the development of some prototypes and are very excited to see how far we’ll be able to push the temperature limits of our equipment in 2024.” Also hoping to safely implement heat exchanger technologies at extreme temperatures and pressures, Theunissen says Lummus launched a new Polaris (Figure 2) breech-lock closure for high-temperature, high-pressure heat-exchanger closures used in the hydrocarbon processing industry. The technology incorporates two new features. The ProSeal system, a new gasket loading design, requires no internal split ring, flange or bolts for simplified fabrication, assembly and disassembly. The load to the seal is efficiently distributed and maintained under a wider range of operating conditions. The ProSeal system further protects the components from damage and deformation caused by plant upsets and differential thermal expansion.

And, complementing Polaris’s new sealing system is the ProLock closure system, a securing mechanism using a special appliance that is simpler and safer to operate. The design allows easy access to all threads for maintenance, lubrication and repair and significantly reduces the time needed for inserting and removing the closing plug. High-pressure exchangers with breech-lock- or screw-plug-type closures are used in the hydroprocessing industry, primarily for hydrocracking, hydrotreating, lubricating oil, slurry and residue-upgrade processing. Applications include use in reactor feeds and effluent exchangers, recycle gas exchangers, effluent recovery and gas recovery exchangers and other applications in gas compression and fertilizer processes. SPX also recognized the importance of boosting the performance and reliability of heat-transfer systems and has developed a technology that makes it easier and less time consuming to maintain heat exchangers, helping to reduce operating expenses. The company’s new plate heat exchanger FastFrame (Figure 3) offers improved usability and durability. The new design includes opening and closing via a powered wrench in under two minutes, consistent tightening across the plate pack and improved safety from the leg/foot design. “Using the traditional method, processors spend significant amounts of time and lose valuable production hours cleaning heat exchangers,” says SPX’s Glover. “This frame design speeds up the process, taking only minutes.”

 

New applications

Not only do improvements in heat-transfer efficiency, performance and reliability optimize energy usage, reduce a facility’s carbon footprint and improve the overall performance and efficiency of the plant, but today’s more efficient and effective heat exchangers are opening the door to interesting new applications — many of which are helping the world itself become a more sustainable place.

For example, Lummus recently announced a partnership with NET Power Inc. (Raleigh, N.C.; ) to supply recuperative heat exchangers for near-zero-emissions power generation. “We recognize the design and supply of heat-exchanger systems into supercritical CO₂ power-generation cycles where efficiency and the ability to withstand high pressures (400 bars) and high temperatures (600°C) as an important move for the industry. This is a challenging application, but at the same time extremely interesting and valuable,” says Lummus’s Theunissen. “It is an application that will help operators and their power plants deliver clean, reliable and low-cost energy.”

And, according to Alfa Laval’s Maciver, there is also “enormous potential” around hydrogen and carbon-capture applications. “Hydrogen is such a broad scope, from electrolyzers and fuel-cell components, refueling stations for hydrogen-fueled vehicles, compression stations and other parts of the hydrogen production and distribution infrastructure.” To help support hydrogen efforts, Alfa Laval recently developed its HyBloc Printed Circuit heat exchanger (Figure 4), which was designed for hydrogen precooling in filling stations. HyBloc is small, modular, scalable and designed to fit into existing pump delivery systems. It supports the high operating pressures necessary to shorten the time it takes to fill a vehicle’s tank. The technology also offers a high capacity in the precooler, which reduces wait time between fillings. Durable, fusion-bonded plates make the units robust and allow them to withstand pressures up to 1,250 bars and operating temperatures as low as –70°C.

Also in the realm of carbon capture and hydrogen, Tranter (Solna, Sweden; ) is supplying plate-and-frame heat exchangers constructed of stainless steel and 254 SMO with ethylene-propylene-diene-monomer (EPDM) rubber gaskets to a carbon-capture application in a new “blue” hydrogen plant in Texas. Tranter’s heat exchangers with ThermoFit plates in the Omniflex plate pattern will be used as vent condensers and for heat recovery between the lean and rich solvent, where the rich solvent has absorbed the CO₂ from a gas stream and needs to be heated prior to entering the desorption column where the CO₂ is separated from the solvent, making it lean. The lean solvent in turn needs to be cooled down before being reintroduced into the absorber. The plate-and-frame heat exchangers used for vent condenser will condense any evaporated solvent in the desorption step back into the column.

And, as heat exchanger manufacturers continue to realize the importance of efficient, robust exchanger options for sustainability-based applications, we can expect to see more innovations in the next few years. For example, Solex’s Bedell suggests that there is a tremendous amount of interest in the cement industry in reducing its overall carbon intensity through energy recovery from solids. “When you look at the size of the cement industry, even marginal improvements can have a big impact on global carbon emissions and some of the improvements being developed are more revolutionary than marginal,” he says. Another area where he sees a growing interest is using solids as part of the carbon-capture process, and developments in heat-exchanger technologies will allow them to play a starring role in this application. “For both the carbon-capture and cement applications, there don’t seem to be great off-the-shelf options for moving-bed heat exchangers, so this is really going to be an interesting area to watch for new innovations and developments in the next few years.” Another company, Makai Ocean Engineering (Waimanalo; Hawaii; ) is partnering with Shell Technology’s Marine Renewable Program to develop and test potentially transformative propriety technologies that may advance the engineering and economic viability of an offshore Ocean Thermal Energy Conversion (OTEC) system. Makai’s concepts for OTEC systems and a “cutting-edge” thin-foil heat exchanger technology hold the potential to reduce the capital and operating costs of an offshore OTEC system. The partnership and research are intended to explore how to achieve more value with lower emissions through ocean-based renewable energy systems and an advanced heat exchange solution may be the key. It appears that as chemical processors, power generators and other heavy industries continue to drive toward more efficient and sustainable operations and applications, heat-exchanger developers will strive to create and deliver the necessary heat-transfer technologies to meet these growing needs, helping processors meet sustainability and operational goals along the way.

– Joy LePree