Pore Performance: One 3D-printing firm's ambition to re-engineer membranes

Article by Adam Duckett

Adam Duckett interviews Tom Pugh and Andrew Walker about Evove’s push to improve separations

EVOVE wants to disrupt membrane technology. Using modelling and 3D printing, it has ambitions to change how membranes are designed, made, and who makes them while improving filtration performance, cutting energy use, and championing water conservation. These ambitions received a significant boost in November when the UK-based firm was picked from among more than 1,700 applicants to demonstrate its technology with brewing giant AB InBev (of Budweiser and Stella Artois fame) and Coca-Cola.

The company, which is based in Daresbury and employs around 30 staff, is developing various products that it says enhance the performance of membranes used to process liquids and recycle discharged waters. These include graphene-oxide coatings to reduce fouling of ceramic hollow-fibre membranes; 3D-printed inserts that are designed to optimise fluid dynamics in tubular and hollow fibre membranes; 3D-printed spacers with novel geometries to reduce energy use in the likes of spiral-would membranes; and 3D printed membranes that have more uniform porosity than those manufactured conventionally.

I spoke with Tom Pugh, a materials chemist, who says two crises led him to Evove where he now works as the VP of Customer Success. His role involves managing the technical aspects of the business and working with customers to understand their needs.

His first “existential crisis” struck while studying for a post-doctorate in magnetic materials.

“The overall feeling was ‘I don’t think anything I’m doing is ever going to see the light of day within my lifetime’. So, I was in search of something where I could have an impact on the industrial world.”

Pugh moved into sales for film materials but after a time he realised that technical development was what he really enjoyed, which brought him to Evove. The diversity of his colleagues’ backgrounds and expertise is helping Evove to approach membrane design from a fresh direction unencumbered by conventional thinking, he says.

“We have some expertise in fluid dynamics, engineering chemistry, but we’re not specifically coming from a [water industry] background…What that means is we look at things and we scratch our heads and ask: ‘Why is that the case?’.”

Prototype: Evove’s 3D-printed ceramic membrane technology

Membrane elements redesigned

“So let’s start with spacers,” Pugh says. “Perhaps the spiral element is one of the most well-known membrane types for the reason that it packs a large amount of area into quite a small volume.”

Spacers sit atop the membrane so that when it’s rolled into a spiral, they separate the layers, providing a cavity for the liquid to flow. Conventionally, they are made by extruding a polymer but this limits the geometries of the spacers that can be created.

Evove is 3D-printing its spacers to create novel shapes, and using computational fluid dynamics to model flow through the membrane to optimise spacer design and the effective use of the membrane surface area. Pugh says the technology can help reduce pressure drop and the extra energy required to overcome it.

“The input pressure will reduce over the course of the membrane to an output pressure generating a middle value, which is the TMP or transmembrane pressure,” he says.

“If you’ve got a big pressure drop, you have to have big input pressure. It is as simple as that. Big input pressure and big input flow, which means high energy costs. So, the geometries and designs that we produce are tailored and modelled and understood to minimise pressure drop. We can identify high performance spacers, ones that are generating a higher permeate flow, so we’re getting more out of each membrane element.”

Pugh says it’s helpful to think of the efficiency gains in terms of specific energy consumption, that is how much energy it costs to process a unit of volume. If the flux can be increased by 20% while maintaining the input pressure and flow then the operation has 20% less specific energy consumption, he explains. Consider the number of desalination operations running today and the growth in installations required to meet rising freshwater demands and Pugh says the implications of a 20% saving are huge.

“A 10-20% increase in in flux is what we can achieve right now and these are non-optimised designs, at prototype stage. Realistically we see this being further towards 50%. In terms of the specific energy consumption, again if we manage pressure drop, the figures are probably more like 30% or 40% energy savings.”

The company is also modelling and designing asymmetric inserts, which can be thought of as spacers for tubular membranes, that save energy use by increasing surface velocity to help reduce fouling but reduce feed flow input.

“We can reduce the capital expenditure of the systems using these inserts because we’re not delivering as much feed flow volume. We use less steel. We have smaller ID [inside diameter] pipes. We have a smaller pump. All of which gives you an initial capex saving but then also your ongoing opex.

“Off the back of pilots, we’ve done with juice processing clarification for example, we’ve seen energy savings in the region of 70-75% as an operational saving in addition to a capex saving in the region of probably 15-20%.” Evove’s coatings range and inserts are commercialised. Pugh says the 3D-printed spacers are at technology readiness level (TRL) 6 and he expects to demonstrate and perform pilot tests in the coming months. The company is also working to develop 3D-printed membranes.

Figure 1: CFD model of Evove’s 3D-printed insert technology

Improving poor porosity

Evove is convinced that the methods being used to design and manufacture membranes are outdated. Firstly, Pugh says that the process of manufacturing a membrane involves significant use of water and chemicals; and secondly, if you look really closely at the membranes produced you will find that their pores have a range of sizes and shape and others will be closed pores that are effectively dead ends.

“We’ve measured these things and we’ve seen that the active porosity is only in the region of 17-18%.” Evove sees 3D printing as an opportunity to produce more uniform membranes that optimise separation, and enable the manufacture of custom designs that further boost performance and can be tailored to specific plants.

The company is completing laboratory trials of its production process, which includes a novel reactive binder jet method that it hopes will allow the company to produce ceramic membranes without sintering.

Andrew Walker, Evove’s Chief Marketing Officer, says: “The big expense with ceramics comes from having to put them in an oven at 1,500°C for 3-5 days. We have a method still under development but showing promising results whereby we’ll be able to reduce, probably eliminate sintering entirely.”

He says the saving could reach 60% of manufacturing costs and this should make ceramic membranes affordable for a wider set of sectors. Walker sees two possible approaches: one is offering membranes designed to fit the existing systems that industries have invested in and the second is producing novel designs for greenfield plants. Speaking in October, Walker said he expects the company will commercialise the technology within 12-14 months.

Early adopters of Evove’s technology will involve traditional liquid processing applications like desalination in the Middle East where operators have to deal with harsh ambient conditions

“They will not yet be at full scale all around the world, so it will be available in smaller quantities. But the advantage of additive manufacturing is you can copy and paste that reasonably easy. It’s more of a question of deploying a bit of hardware and a bit of software. And you can empower end users to print their own membranes if they want to, or to at least print it locally using designs from Evove.”

He expects the early adopters of Evove’s technology will involve traditional liquid processing applications like desalination in the Middle East where operators have to deal with harsh ambient conditions.

Pugh adds: “Ultimately, where we see membrane technology going is 3D-printed polymer membranes with 100% active porosity. And the design capability to fundamentally change a membrane from a flat sheet, for example, into an intricate structure that has controlled flow. We’ve done modelling on this and realistically this technology is more towards 2024. We’re talking about orders of magnitude in performance gains.”

Figure 2: Pressure drop profile in biplanar commercial spacer (left) vs Evove 3D-printed spacer

Trials and resistance

We spend some time discussing the need for improved separations and the opportunities for improved membrane technology.

“It’s no secret that the world is focused quite solely on CO2 emissions, greenhouse gases, global and climate change. Quite rightly but often what’s overlooked is the impact of all that’s happening on water,” Pugh says.

The WWF estimates that by 2025, two-thirds of the world’s population could face water shortages. Climate change is exacerbating the issue, but also many of the plans for combating climate change require greater water use.

A shift from fossil fuels has spurred greater electrification. Yet much of the lithium needed for batteries is made using evaporative techniques in water-stressed regions that the IEA reports require about 2m L of water for every tonne of lithium produced. Similarly, the race for green hydrogen produced using electrolysis will require greater volumes of pure water in the short-term pending development of techniques that can make use of impure or contaminated water. This will place increased demand on freshwater supplies, competing with agricultural and domestic needs, and will likely see greater use of desalination, which in turn would benefit from improved separations requiring less energy use.

“I think people are starting to realise the true value of water, which is far beyond what the current value is set at,” Pugh says.

As well as its membrane pilot studies with AB InBev and Coca-Cola, Evove is in discussions with UK-based developers about supporting lithium extraction from geothermal waters. And it has a pilot project running in the US on filtering produced water from the oil and gas industry.

Among the risks to Evove’s success that the pair identify are regulatory hurdles; proving the sintering-free production method for its 3D-printed membranes; and convincing conservative industries to break with incumbent systems and supply chains.

The company is raising funds for plans to build an industrial-scale manufacturing facility for its membranes and components, which is likely to be in the northwest of England.

“There’s no shortage of interest in the technology. I think people are very much aware of the cost increase, the water scarcity, and the environmental concerns,” Pugh says.

“Will people adopt it? Will they be resistant? It’s up to us to prove the benefit of the technology.”

Article by Adam Duckett

Editor, The Chemical Engineer

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