A new system for providing heat for the flue-curing of tobacco was developed by modifying the conventional direct combustion of biomass fuel (bio-fuel) such that the energy stored in the fuels was fully utilized. The system consisted of an integrated furnace with a heat dissipation structure for combusting and gasifying bio-fuel including solid fuel as well as combusting the generated gas, and a heat exchanger with a special flue pipe layout. The new device was tested through experiments in different tobacco-growing areas, using the controlled direct combustion of coal and biomass fuel for flue-curing in a bulk curing barn. The results showed that the distribution of temperature in the longitudinal section of the new system exhibited a regular temperature transition pattern corresponding to the solid fuel and gas combustion areas. The amount of carbon monoxide in the flue gas at the chimney exit indicated that the burning of the biomass briquette fuel was more complete, with less than 1.7% carbon monoxide generated. The thermal efficiencies of the biomass briquette fuel and firewood were 55.26 and 53.17%, respectively, which were higher than that of coal (49.52%). The newly developed integrated furnace would be well suited for tobacco curing in tobacco-growing areas, and could be used commercially for drying agricultural products on different scales.
In recent years, excessive carbon dioxide (CO 2) emissions have already led to a series of environmental problems. As the largest flue-cured/Virginia tobacco (Nicotiana tobacum L.) producer in the world, China currently grows about one-third of the world's tobacco annually [1], and tobacco curing (TC) is the most energy-intensive phase of tobacco production [2]. Traditionally, coal is used to directly burn and heat fluecured tobacco in a bulk curing barn [3, 4]. During the annual TC season, millions of tons of CO 2 and fly dust are emitted into the atmosphere from the chimneys, which causes serious environmental pollution [5, 6];
Applying biomass energy for curing flue-cured/Virginia tobacco heating is the best way to realize green tobacco production. Aiming to satisfy the heating demand for flue-cured tobacco curing, a new heating device that uses biomass briquettes as fuel for curing tobacco is adopted the first time, which was developed using modern mature electromechanical and computer technology. The new device consists of automatic feeding, ash cleaning, ventilation, and ignition systems governed by an intelligent tobacco-curing controller designed for specific curing characteristics. The results of experiments conducted with an original direct combustion coal furnace, bulk curing barn, and controlled coal-fired heating indicated that the heat supply of the new device could satisfy the heat demand during the tobacco curing process, with a good performance-controlling difference of ± 0.5 °C between the actual and target dry-bulb temperature in the barn. With its unattended heating management and use of fully burning fuel, the new device sharply decreased the cost of manual operation and tobacco leaves required per kilogram compared to a coal furnace. Considering the shape of its structure, the new device could be used to heat homes or small-scale boilers if the chip procedure of the controller is altered.
Original scientific paper https://doi.org/10.2298/TSCI190406072WIn view of the abundant solar energy available during the tobacco curing season, a solar hot-water installation to provide auxiliary heating for bulk tobacco-curing operations was developed, based on the original concept of a boiler-driven central heating supply that transported hot water over short distances by pipeline, using solar collectors connected in parallel and installed on the unoccupied flat roofs of 20 curing barns. The results showed that daily solar conversion efficiency ranged from 65% to 67%. During the tobacco curing period from 10:00 hours to 14:00 hours each day, in sunny or partly cloudy weather, heating water temperatures exceeding 75 °C were automatically derived for use in the bulk curing barns needed. Use of solar energy as a substitute for coal fuel in tobacco curing, in conjunction with precise automatic control, enabled solar energy to account for 18.4% of the total curing energy consumption in this study. Through comparative analysis, the use of solar hot-water installations can help the local tobacco industry to reduce absolute carbon emissions by more than 10% at the experimental location in the pay-back period.
Using tobacco stalks as a biomass fuel for flue-cured tobacco production creates a closed, green production cycle. Tobacco stalks are rich in cellulose and can be crushed to produce biomass pellet fuel (BPF). However, single flue-cured tobacco stalk (FCTs) BPF can easily slag during flue-cured tobacco heating (FTH), which affects the operation of biomass burners. In this study, five anti-slagging agents (ASAs), one organic (sodium carboxymethyl cellulose, CMC) and four inorganic (kaolin, KLN; diatomite earth, DTE; calcium carbonate, CCO; and calcium dihydrogen phosphate, CHO)], were compared. An ash fusibility test was conducted in two steps to optimize the proportion and treatments that were then screened using FTH. Compared with pure FCT-based BPFs, the slag resistance of 2% CCO and CHO could be controlled below 15%. The emission of particulate matter from chimneys burning BPF with 2% CCO was lower than that with other ASAs. The ASAs achieved complete combustion with low carbon monoxide content in the tail gas. Considering the anti-slagging effect and economic cost, 2% CCO was the best additive for the biomass burner. These results provide a reference for FCT-based BPF production.
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