An Industrial Perspective on Ultrapure Water Production for Electrolysis : A techno-economic assessment of membrane distillation for electrolysis - synergies, performance, costs, and value propositions

Sammanfattning: Sustainable development is one of the most important issues in todays’ industrial sector, and several markets are now looking for alternatives to fossil fuels. One of these solutions is hydrogen; a clean, easily combustible gas which can be used as fuel in several industrial processes, such as steel production and power generation. However, the production of green hydrogen is limited, and this is where the need for electrolysis emerges. Electrolysis is a way to produce green hydrogen by separating water into hydrogen and oxygen using energy. One crucial aspect is that this process requires extremely pure feedwater, also known as ultrapure water. To produce this water two main systems are investigated; reverse osmosis and membrane distillation, and they are compared from a techno-economic standpoint. Firstly, a literature review was made, which gave theoretical background of core concepts such as different types of electrolysis, water purification, as well as several financial models and theories used in the report. Based on this, calculations were made to analyse the possibility of running membrane distillation entirely on waste heat. From the data gathered the results showed that membrane distillation can be run entirely on waste heat from electrolysis, even with a 25% loss factor included. After the technological calculations, financial calculations were made to directly compare a reverse osmosis-based system with membrane distillation. OPEX and CAPEX for both systems were calculated over a 20-year period and then added together, producing a total price for reverse osmosis at 0,67 €/m3, whereas membrane distillation has a total price of 0,60 €/m3. An assessment of both electrolyser systems and the two water purification systems is made. The electrolyser inquiry ends with the conclusion that two of the electrolysis processes, Proton-Exchange Membrane and Alkaline Water, are suitable to combine with membrane distillation. With the comparative analysis between reverse osmosis and membrane distillation, a longer discussion regarding financial viability is made. The key takeaway here is that membrane distillation is cheaper, both in total and when calculating the net present value. Looking specifically at the membrane distillation market, the conclusion is that it is still in the earlier stages of development, and so customer relationships are crucial. This is reinforced through the value proposition model, which shows that the company should put focus on customer relationships with their product model.