RMD is a new type of spray dryer

Multi Radial Drying project kicks off


In March 2018 the Radial Multi-zone Dryer (RMD) will start. RMD is a new type of spray dryer which combines low Capex, low Opex, premium product properties and low specific energy consumption. The RMD is an intensified spray drying technology which combines a very short residence time of droplets in a central zone with high- temperature air injection with rapid transfer of initially dried particles to a peripheral zone with mild-temperature air injection.

The imposed droplet trajectory yields better product properties than in conventional spray dryers. Furthermore, high temperature drying improves the energy efficiency, thus reducing the specific energy consumption and carbon footprint of dried (dairy and other) products. Improved product properties relates to nutritional value or functionality (e.g. solubility) of the product. Due to intensified drying, the size, viz. footprint, of the dryer will be significantly smaller than of conventional spray dryers, thus reducing investments in equipment, building and operation. In addition, centrifugal forces generated in the dryer efficiently separate the particles from the drying air. Integration of particle separation in the dryer chamber further reduces investments in equipment by eliminating the need for particle separation downstream of the dryer.

The Radial Multi-zone Dryer (RMD) was defined tested and patented following fundamental research on the fluid dynamics of a vortex chamber spray dryer. The technology was extensively studied on a small lab scale dryer and by means of Computation Fluid Dynamics (CFD) and the principle of the technology was proven. Coming to a working prototype requires, however, addressing a number of fundamental questions concerning control of the product quality, the specific energy consumption and optimal air usage, the particle trajectories in relation to drying properties, and wall contamination and fouling of the atomization nozzle. The RMD project aims at getting a fundamental understanding of the various phenomena determining the RMD performance by combining experimental research, detailed CFD modelling and energy optimization scenarios. An important part of the project is the design and construction of a dryer of sufficiently large scale (100-250 kg water evaporation per hour) to observe fluid dynamics and product properties representative for an industrial scale unit. Milk powder has been selected as challenging model system. Product properties will be carefully analyzed and compared with those obtained with a reference drying technology.

The new RMD unit and CFD simulations will also give insight in design rules and the operation window for pilot plant and production units and will make it possible to make a proper analysis on potential energy saving compared to reference drying technology. One of the deliverables of the project will be a conceptual pilot plant design (e.g. 500 kg/hour water evaporation capacity) which meets the requirements with regards to capital investment, operational costs, product quality and energy efficiency. Finally, collaboration with an equipment manufacturer will be initiated in preparation of the design and construction of a pilot plant unit.


This project is co-funded by TKI-E&I with the supplementary grant 'TKI- Toeslag' for Topconsortia for Knowledge and Innovation (TKI’s) of the Ministry of Economic Affairs and Climate Policy.