The paper is focused on (i) kinetics of trioxane vacuum crystallization from solution in different apparatus volumes, (ii) vapour-liquid equilibrium and (iii) crystals hardness versus process temperature. It has been found that trioxane is a well-crystallized substance with relatively high effective growth rate and, simultaneously, to some extent, crystals are resistant to attrition. Unfortunately, their elongated shape promotes breaking in the forced magma circulation type crystallizers, but still it is easy to reach well-filtrated product. To meet the objective a profitable technology for practical application, the studies in pilot scale using industrial solutions were performed. The discussed newly developed vacuum method seems to be a promising alternative for trioxane crystals production instead of a very energy-consuming and low-efficiency cooling crystallization. The additional advantages are simplicity of operation as well as lower capital cost. (C) 2009 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.