Hemp-based aerogel for apparel insulation

Riwa Dbouk, Yahya Hassan, Keon Lee, Sherief Omran and Ozan Polat

Community Partner: Baerfell Advanced Materials
Degree:
- Bachelor of Applied Science
Program:
- Chemical Engineering
Campus: Vancouver

Our project

Insulating materials like aerogels are often used in outdoor clothing or firefighter suits because of their thermal, water-resistant and flame-retardant properties. Aerogels are traditionally produced using synthetic inputs in an energy-intensive process.

Hemp-based aerogels represent a promising next-generation insulation material because they combine the exceptional low-density and thermal performance of aerogels with the sustainability advantages of agricultural biomass.

Our partner, Baerfell, has created a process to produce bio-based aerogels derived from hemp at the lab scale.

In this project, we assessed the feasibility of scaling this up to design a demonstration-scale process to convert agricultural waste hemp fibres into 120 tonnes of aerogel sheets annually. Our design evaluates the full process pathway, major equipment, environmental impact and economic feasibility to assess whether hemp aerogel can viably transition from laboratory research to industrial-scale manufacturing.

Baerfell

Our design solution

The process starts with delignification to remove unwanted organic materials from the hemp fibres, including lignin and hemicellulose.

After separating out the delignified hemp, we mechanically blend it with water and a cross-linking agent, PAE, to strengthen the matrix and stabilize the porous structure.

We then dispense this sol-gel mixture onto sheets and trays, according to our dimension specifications. After this, we perform a two-step solvent exchange – first replacing water with ethanol – followed by liquid carbon dioxide.

Once the liquid carbon dioxide has fully displaced the ethanol, conditions are raised to supercritical conditions to vaporize all carbon dioxide, producing our final product without collapsing the aerogel pore structure.

In the final curing stage we heat up the aerogel to activate the cross-linking agent and apply a hydrophobic coating to produce sheets of aerogel that can then be cut and used in applications from clothing to cold transportation for medicines.

Hemp-Based Aerogel Project Capstone Poster.

The technical challenges we faced

Our of the most significant scale-up challenges was replacing the freeze-drying step that was used in the lab. Replicating that process at scale would have taken over 100 freeze dryers at a cost of around $1 million each.

We looked at many different alternatives and settled on a two-step approach of solvent exchange and supercritical drying.

To meet our annual production target of 120 tonnes, this section requires six supercritical drying vessels operating simultaneously, which had a significant impact on both plant economics and layout.

Another issue was the amount of water required in our process.

By significantly increasing our cellulose concentration relative to the lab-scale process, we were able to maintain the thermal insulating properties required by our sponsor while reducing water demand by about four to five times.

Producing aerogel in bulk sheets also presented a manufacturing challenge due to the immense volume of space required. We designed a custom tray-to-rack system that incorporates hydraulic presses and automation to transfer material to the supercritical carbon dioxidedrying station.

What’s next for our project

We’ve shared our design solution with our capstone sponsor. After reviewing the viability of our approach, they may be able to incorporate our ideas as they advance their process from the lab to a pilot-scale facility.

What we’re most proud of

It initially seemed very difficult to achieve the goals of this project both technically and economically. However, we managed to make it work and our calculations suggest that the proposed facility could break even in two to three years.

We’re proud of the level of engineering detail we achieved, particularly in developing the control strategy and producing a clear piping and instrumentation diagram and operating procedures that reflect something that could be realistically implemented.

This project also made us realize the significant responsibility held by process engineers, who are ultimately responsible for every design decision, including HAZOP analysis.

This project exemplifies the interdisciplinary nature of engineering.

Our solution draws on our knowledge of chemical and biological engineering, mechanical engineering, manufacturing engineering and economics. The success of this project also relied on our skills in communication and collaboration, both with each other and with our project sponsor.