The paper presents gross and net calorific values, ash content, conversion factors, and bulk density for different-sized spent cones of Scots pine Pinus sylvestris L., Norway spruce Picea abies L., European larch Larix decidua Mill., and Silver fir Abies alba Mill. harvested from various sites. Gross and net calorific value and bulk density were measured in accordance with the relevant EN and ISO standards. The density conversion factors were determined based on free space measurement by means of water immersion. Gross calorific value for Scots pine, Norway spruce,
A significant amount of waste is generated in the food industry, which is both an environmental and an economic problem. The recycling of this waste has become an important area of research. The processing of grapes produces 20–30% of the waste in the form of grape pomace and stalks. This article assesses the fuel values of these materials before and after torrefaction. The input materials were grape pomace samples from the varieties Riesling (Vitis vinifera “Welschriesling”) and Cabernet Sauvignon (Vitis vinifera “Cabernet Sauvignon”) from the South Moravia region and stalks from the variety Welschriesling. The torrefaction process was performed using a LECO TGA 701 thermogravimetric analyzer under nitrogen atmosphere at set temperatures of 225 °C, 250 °C, and 275 °C. The residence time was 30 min. Elemental analysis, calorific value, and gross calorific value were determined for all samples. The analyses show a positive effect of torrefaction on fuel properties in the samples. Between temperatures 250 °C and 275 °C, the carbon content increased by 4.29 wt.%, and the calorific value increased with the increase in temperature reaching a value of 25.84 MJ·kg−1 at a peak temperature of 275 °C in the sample grape pomace from blue grapevine.
In this article, the author investigates the change of weight and temperature of pine cones in a microwave oven over the following range of microwave irradiation power (PMF): 800, 620, 440, 260 and 130 W.
Cones were divided into groups according to their weight and the author examined the influence of PMF on their water content and drying rate. The process is described with the help of mathematical equations and curves. The cones were irradiated in the microwave until all cones of the given group began to open the first scales. Small cones required longer exposure times to PMF than medium and large cones in order to cause scale opening. The most efficient of the five settings was a irradiation power of 620 W with an exposure time to microwaves for no longer than 20 seconds.
In the second part of the study, the author analyses the changes of temperature on the cone surface using a thermal imaging camera. The values of surface temperature depended on irradiation power and the duration of irradiation.
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