Improvement On The Equipment For Agro-stalks Smoldering And Experiments

Agro-stalks are the main energy resources in many rural places in China. And smoldering of them is one of the traditional space heating methods. In this study, smoldering of ordered piled corn stalk and wheat straw was investigated via experiments based on previous work. It is of great significance in providing experience on developing new technology to utilize the agro-stalks via smoldering.Problems related to the previous equipment were analyzed and improvements were made on flue gas tube, the furnace, the software to mitigate the effect of environment.Density of corn stalk (mass of a single stalk/ volume of the stalk) and components of several typical agro-stalks was detected. Results showed that: (1) Density of corn stalk is about 170 kg/m~3, much less than that of wood (400-700 kg/m~3), even less than that of stalk powder (200-300 kg/m~3). This is because of the numerous poles in the stalk after dried in the air. It showed that it is not easy to reduce volume of piled stalk by packing. (2) Components of different agro-stalks differed significantly in spite of no obvious difference in elemental analysis. And there is no obvious relationship between component and elemental composition.Smoldering experiments of ordered piled wheat straw, corn stalk at the bulk density of 50 kg/m~3 have been repeated several times. Results showed that: (1) Relationship of bed shrinkage with bulk density of wheat straw and corn stalk can beexpressed as: sh = 1-ρ×0.5869% and sh = 1-ρ×0.4366% , and the shrinkageoccurred mainly along the depth and length of stalks. (2) Mass loss rate, component of gas product, temperature outside the furnace was affected significantly by the ash above the agro-stalks. (3) Mass loss rate of wheat straw smoldering is much higher than that of corn stalk at the same bulk density. (4) In most cases, smoldering propagated randomly and it is very hard to control smoldering via changing bulk density or piled method.Based on the experimental results, a new method which combines smoldering of agro-stalks powder with excess-enthalpy combustion of flue gases was proposed to solve the problem of mass loss rate controlling and gas pollution of smoldering.