MILLED PEAT DRYING IN CASE OF DIFFERENT SIZE OF FEED AND CONDITIONS

Drying of milled peat is suggested to be considered as a special case of heat and mass exchange process. This issue is of great practical importance since natural peat contains up to 10 grams and more of moisture per 1 gram of dry matter. In order to obtain various peat products, peatland can be drained, which removes only 20% of moisture, while drying allows peat dehumidification to 30–40%. This article is focused on one of the issues of peat production industry—enhancement of milled peat production efficiency by means of creating a new process flow aimed to boost seasonal output per unit area by means of reducing thickness of dried layer and using more drying cycles per season. A detailed description is devoted to experimentation in an environmental chamber designed at the Tver State Technical University. The study object was milled valley peat with a decay degree of 30–35%, particles 2 and 4 mm in size. The peat samples were subjected to three types of drying conditions at different feeds from 0.129 to 1.81 kg/m2. The features of the mechanism of drying in thin layers are revealed with regard to moisture exchange between milled valley peat and underlying peatland. It is found how radiation intensity influences drying efficiency, for instance, under low intensity radiation (convection drying), the drying rate is constant for all values of thickness of the test peat layers (from 4 to 16 mm). As radiation increases from 0.50 to 0.86 kW/m2, the rate of drying grows too while fraction composition has no influence on the drying process. The optimal layer thickness to ensure the maximum rate of drying is determined. The scope of the discussion encompasses the mechanism of peat drying on wet bedding and the related explanations are given. The mechanisms of drying peat chips directly on peatland and with moisture proofing are compared in case of different moisture contents and radiation intensities. The maximum drying rates are compared at different radiation intensities and the optimal drying period is determined as 5–6 hours depending on feed. Two process flows are proposed to increase seasonal output of milled peat: two cycles of milling, drying and gathering per day (10–12 h); one-cycle deep milling per two days of drying and gathering of dried upper layers as they are dehumidified up to standard. Output per gathering cycle is decreased in this case, and number of gathering cycle increases more than 4 times. However, the overall seasonal output per unit production area grows.

Keywords

Peat, chips, drying period, evaporation rate, moisture, layer, spreading, moisture exchange, production cycle, radiation, drying conditions, maximum drying rate zone, final product gathering.

Issue number: 5
Year: 2018
ISBN:
UDK: 622.331.002.5
DOI: 10.25018/0236-1493-2018-5-0-65-73
Authors: Stolbikova G. E., Kuporova A. V.

About authors: Stolbikova G.E., Candidate of Technical Sciences, Assistant Professor, e-mail: gtp1938@mail.ru, Kuporova A.V., Senior Lecturer, e-mail: borale@inbox.ru, Tver State Technical University, 170026, Tver, Russia.

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