Design of nonmetallic refractory heating equipment in bulk curing barn and its baking effects

Objective To overcome the defects of 418-type heat interchanger in bulk curing barn, such as being susceptible to corrosion and having short service life, and to optimize the structure and performance of heating equipment in bulk curing barn.

Method A nonmetallic refractory material with high conductivity was choosen to make the heat interchanger. The heat interchanger was structured with three layers of circular horizontal dual pipelines and three heating interchange pipelines in the same vertical plane were connected by an S-shape connector. The heat interchanger was equipped with a squared and vaulted stove (with a cast iron cover)feeding disposable coal. Using bulk curing barn with metal heating equipments as the control, the performances and baking effects of the nonmetallic refractory heating equipment in bulk curing barn were studied.

Result The heating rate of bulk curing barn installed with the nonmetallic refractory heating equipment(5.36 ℃·h^-1) was significantly lower than the control(21.73 ℃·h^-1) without loading tobacco, while its cooling rate was slower than the control. The results showed that bulk curing barn installed with nonmetallic refractory heating equipment showed great temperature stability and the trends at three key point temperatures(38, 42, 55 ℃)were the same. Its plane and vertical temperature difference was less than the control during curing. Compared with the control, the heat efficiencies of baking the middle and upper tobacco leaves increased by 12.42% and 6.74%, the coal consumption rates reduced by 22.50% and 15.13%, the average prices of the dried tobacco leaves after curing increased by 0.84 and 0.20 yuan per kilogram respectively, the proportion of medium-high grade tobacco leaves increased, and the effects of energy saving and quality improving was obvious in the bulk curing barn with nonmetallic refractory heating equipment.

Conclusion The heating equipment made of nonmetallic refractory material with high conductivity has excellent baking performence and high corrosion resistant, and can be applied for heating equipment update in bulk curing barn.