Abstract
The economic viability of the split-phase glycolysis process for the recycling of any kind of flexible polyurethane foam waste employing crude glycerol as cleavage agent has been demonstrated. First, experiments at pilot plant scale were carried out to check that the process can be extrapolated to larger scales. With the goal of scaling-up the process from laboratory scale to pilot plant, geometric similarity criteria were applied together with dynamic similarity for laminar flow in agitated tank reactors. Hence, a pilot plant installation was designed with geometrically similar equipment to those used for lab scale, obtaining analogous results in terms of recovered polyol properties. Then, the basic design of a split-phase glycolysis industrial plant with a capacity for treating 270 Tm per year of flexible PU foams scraps was proposed. Finally, the economic feasibility of such recycling process was confirmed because of the obtention of a Net Present Value (NPV) of 1,464,555€, with an Internal Rate of Return (IRR) of 27.99%, and a payback time between 4 and 5 years.
Highlights
A pilot plant installation was designed with geometrically similar equipment to those used for lab scale in a previous work from our research group, obtaining analogous results in terms of recovered polyol properties and mass balance
To achieve a proper scale-up of the glycolysis process, it was necessary to take into account several points: shape factors requirements in the tank reactor, agitator dimensions, required agitator head power, and rotational speed
The optimal values of these three shape factors are between 0.7 and 1.0 for the D/T in laminar flow, Z/T can range from 0.5 to 1.0, and C/T must be in the range between 0.1 and 0.4 [10, 11]
Summary
Polyurethanes (PUs) are plastic polymers made by combining isocyanates and polyols. The global polyurethane market was valued at USD 76,600 in 2020 and will reach USD 94,160 million by the end of 2027, growing at a compound annual growth rate (CAGR) of 3.5% during 2022–2027 [1]. The wide diversity of polyols and isocyanates allows the synthesis of numerous different compounds covering a huge range of applications. The polyurethanes are classified mainly in foams (flexible and rigid) and in the denominated CASEs (Coatings, Adhesives, Sealants, and Elastomers) [2]. The flexible foams can be separated into three main groups: conventional, viscoelastic and high resilience foams [3]. PU-recycling processes are one of the most important goals of the research and industrial worlds as a
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