Zero liquid discharge in mdf boards production

Medium-density fiber (MDF) boards are wood fiber agglomerates, which are mainly used for furniture manufacture. This product has been on the increase for years, given its high resistance, stability and quality finish coupled with reasonable costs.

In brief, the MDF boards manufacturing process involves the removal of barks from tree trunks, which are shredded to obtain fibers that are agglomerated together with synthetic resins through high heat and pressure.

This process generates effluents containing fiber residues and various chemicals found in wood, as a result of the humidity in wood trunks, which can range between 1% and 15% in dry conditions. These are effluents with high levels of solid contents and chemical oxygen demands (COD’s).

A very common process in the sector includes effluent purification by physicochemical means. The problem is that the resulting water cannot be discharged, since its COD levels are not low enough. A solution that some manufacturers have tried in order to dispose of this water is throwing it into the ovens in which the boards are treated, so that it evaporates in the high heat. This, however, has not proven to be an efficient solution, since it leaves residues and stains on the boards.

Without any doubt, the most suitable alternative for the treatment of effluents generated in the MDF boards manufacturing process is vacuum evaporation, given it allows the reuse of both evaporation rejects (distilled water and residue concentrate),   which leads to the achievement of zero discharge.

The effluent is effectively introduced into the vacuum evaporator, which separates water from its waste content (fibers and other wood chemical components) producing, as a result, distilled water, that can be sent to the boilers to generate vapor instead of being discharged, as well as a wood fiber concentrate and other components, which can be sent to the biomass boiler to be mixed with other materials to generate energy.

To complete the cycle enabling the reuse of resources, it must be noted that  any tree waste which is not used for the production of MDF boards (such as bark, branches, leaves, etc.) can be combusted  to produce the energy necessary to power the evaporator, which means that the installation of this solution will have near-zero  energy costs.

By Sergio Tuset

Over 30 years’ experience in management of industrial companies. Specially focused on environmental projects for customers, recognized specialist in conceptual engineering applied in wastewater, liquid &solid wastes, and air pollution. Teamwork, leadership, and expertise in Project Managing. Industrial process consulting