Superheated Steam Spray Drying as an Energy-Saving Drying Technique: A Review

Abstract

Drying is an extremely energy-intensive process. Superheated steam as a drying medium can improve the energy efficiency of the drying processes. In superheated steam drying, waste heat can be recovered by condensing the exhaust steam or raising its specific enthalpy. Spray drying is widely used in industry, even though its energy efficiency is often low. Substitution of air by superheated steam as a drying medium in a spray dryer may reduce the energy consumption of the drying process by 20–30%; moreover, if excess steam generated by moisture evaporation is upgraded to a higher temperature level and reused for drying, the energy demand could be decreased by even 80%. A literature review showed that superheated steam spray drying was successfully applied for both thermally resistant and a wide range of thermally sensitive materials. Superheated steam drying gives a number of advantages in terms of product properties, i.e., higher particle porosity due to rapid moisture evaporation results in improved powder rehydration properties. Additionally, steam drying may be applied for in situ particle crystallization. Taking into account the advantages of superheated steam drying and the potential application of this technology in spray drying systems, there is a great need for further research in this field. This literature review aimed to present an energy-saving solution, i.e., superheated steam spray drying process, showing its advantages and potential applications, followed by drying kinetics, providing analysis of the research papers on experimental studies as well as mathematical modeling of this drying technique.

A Review of Energy-Efficient Technologies and Decarbonating Solutions for Process Heat in the Food Industry

“…Energies 2024, 17, 3051 7 of 50 organic matter is subject to the steps illustrated in Figure 7 [33] and further described in Table 1. The analysis of this process has drawn a lot of research to improve historical procedures [34][35][36] in which all steps and energy provided were considered individually. Uçal et al [37] analyzed a whole milk powder (WMP) production line principally based on natural gas for heating purposes and showed that pasteurization, evaporation, and drying represented 98.3% of the energy consumption and 95.7% of the CO2 emissions-for a total of 10.2 MJ/kgWMP and 0.588 kgCO2/kgWMP.…”

“…From the energy utility point of view, high-temperature heat pumps and solar thermal technologies present great potential. Solar thermal implementation has been studied by Camci [35] and Sobulska et al [36], showing that the production of superheated steam with solar collectors leads to energy efficiency gains of 75% and 70% on the drying process, and Shah [39], showing a reduction of 60% of conventional boiler duties with solar thermal collectors' integration at the process level in a dairy plant in Dubai. Regarding heat pumps, Bühler et al [40] showed a potential energy savings of 65% for central heat pump systems and 56% for decentralized heat pumping systems, with a carbon emissions reduction impact of around 80% in the frame of Denmark's electricity mix.…”

Production of functional spherical particles with porous hollow structures in water via oiling-out directional agglomeration

“…10,[13][14][15] Spray drying granulation usually has the problems of complex equipment, a large floor space, a low thermal efficiency and high energy consumption. 20,21 Studies have shown that drying processes, including spray drying, account for about 10-25% of energy consumption in the industrial sector in developed countries and are a significant contributor to the production of greenhouse gases. 22,23 As a typical spherical crystallization process, quasi-emulsion solvent diffusion requires compli-cated and large amounts of multi-solvent systems (such as biohazardous solvents like dichloromethane, tetrachloromethane, and methylbenzene) to satisfy the demanding diffusion relationship between the continuous and dispersed phases.…”