Experimental Studies of the Kinetics of Infrared Drying of Spent Coffee Grounds

The object of research is drying of spent coffee grounds. In modern production, the issues of rational use of energy in all processes of food technology, including drying, are urgently raised. In many food technologies, 2–3 times more energy is used than is physically necessary for the process. This determines the energy intensity of production and the quality of products. Drying processes are among the most energy-intensive, and in many cases the proportion of energy in the cost of production is up to 30 %. When drying of spent coffee grounds, convective dryers are mainly used, the energy consumption of which is 5 MJ/kg of removed moisture and above. Convective drying uses 40 % of the supplied energy to evaporate moisture. Also, a significant drawback of convective dryers is the discharge of waste coolant into the atmosphere, which has a heat content of only 10–15 % less than the hot air supplied to the drying chamber. The paper proposes the use of infrared radiation for drying of spent coffee grounds in periodic and continuous units. This will allow in the future to reduce specific energy consumption. During the study, the influence of the energy supply intensity, temperature, air flow rate, product layer thickness and specific load on the kinetics of periodic infrared drying of spent coffee grounds is determined. The influence of the energy supply intensity, specific load, tape speed, and the number of infrared modules on the kinetics of continuous infrared drying of spent coffee grounds is determined. The results are compared with convective drying in terms of specific energy consumption. A feature of the use of infrared radiation is its high efficiency and high rate of moisture removal from the surface layers of spent coffee grounds, and as a result, an increase in the productivity of the drying method and a decrease in specific energy consumption. The specific energy consumption obtained during operation of infrared drying of spent coffee grounds is 3.2 MJ/kg. This is below existing convection dryers

Development of Power­efficient and Environmentally Safe Coffee Product Technologies

Based on the energy and environmental audit, analysis of material flows, energy conversion, emissions into atmosphere and lithosphere in the production of instant coffee was carried out.To raise energy efficiency and reduce environmental burden, innovative flow diagrams and equipment for waste processing and production of new coffee products have been developed.Experimental modeling was carried out: kinetics of microwave extraction of water-soluble substances and oil from coffee slurry; hydraulics of the extractant flow through cassettes of the microwave extractor. The experimental data were summarized in the form of a criterion equation.As a result of experimental modeling of the extraction kinetics, it was found that the duration of the process in a microwave field is approximately 20 times less than in a thermostat. The microwave field affects the extraction rate to a greater extent than the process temperature. The growth of microwave power results in a more than the two-fold rise of the yield of extractives from a coffee slurry.Specification of the microwave oil extractor was defined. The extractor sample was tested at a specific power of 180...240 W/kg in the mode of boiling extractant. Ethanol (93...96 % concentration) was used as an extractant. As a result of the tests, a high-quality coffee oil was obtained. It is characterized by a pronounced aroma, coffee taste and an intense dark brown color.Flow diagram of pre-extraction of coffee from slurry was worked out. Additional extraction of water-soluble extractive substances from coffee slurry increased the extract yield by 10...12 %. The temperature regime of extraction was significantly reduced plus duration and energy intensity of the process were reduced.An innovative flow diagram has been developed for the production of liquid coffee concentrate as a basis for coffee-based drinks ready for immediate use. The concentration of solids is 50...65