The circular economy in special paper production

This doctoral work was carried out almost entirely within Ahlstrom, with which I collaborated for the full duration of the project. Ahlstrom is a company that manufactures cellulose based and non cellulosic fibre materials and applies these materials across several sectors, including filtration for the automotive industry, the sector in which my research is situated. The research comprises two principal projects developed within the company. The first project falls under waste reduction efforts and focused on the development of a thermal treatment to reduce the formaldehyde content in production waste. This treatment is based on the use of saturated steam that leads to the polymerization of the resin consuming Formaldehyde (Formaldehyde is the curing agent of all resins used within Ahlstrom). In this work, the effectiveness of the treatment itself was evaluated, together with an analysis of its waste streams, such as the condensate, with a view to potential reuse. Quantitative analyses were carried out on the condensate to check for the presence of methanol, formaldehyde, formic acid and ammonia. The presence of methanol is mainly due to the polymerisation reactions taking place within the resin, which lead to the release of methanol, but also to the hydrolytic action of water and the high temperature of the autoclave. The presence of formic acid, on the other hand, probably stems from the dismutation reaction of formaldehyde, whilst ammonia is derived directly from urea, which is used in paper grades as a formaldehyde scavenger. The presence of all these analytes, in addition to traces of resin derivatives (phenol and derivatives, melamine and derivatives), makes the purification of this condensate water a highly complex and costly process for the company, which, whilst awaiting the development of a purification strategy, is currently disposing of the contaminated water from the autoclave through a specialist company. The second project concentrated on modifying paper formulations with the aim of eliminating so called mercerized cellulose, which is chemically treated with caustic soda, in order to reduce both the environmental impact (due to the neutralization and the energy required for the purification of caustic soda solutions) and the cost for the company. In order to improve the raw materials using greener technology, it was decided to draw on previous experience gained during waste treatment. It was observed that, following treatment with waste, the cellulose became weakened and frayed. Our hypothesis was to use steam to induce a functional modification in the cellulose, with the aim of increasing its air permeability and porosity. The project aimed at reducing mercerised cellulose produced promising results from the outset, allowing me to witness during my doctoral studies the transition from experimental activity to large scale industrial application. The project also became significant for Ahlstrom as a whole, enabling me to carry out experiments both at the Binzhou plant in China and at the Taylorville facility in the United States