| Making full use of biomass is one of the effective way to solve the problem of energy crisis and environmental pollution. Pyrolysis is one of the most basic and effective methods to convert the biomass to high-quality fuel. To evaluate the raw material, understand the pyrolysis mechanism, guide the pyrolysis processing and yield the wanted products, it is of significance to measure the fundamental parameters of raw material, pyrolysis processing parameters and product fuel parameters rapidly. This study is supposed to rapidly measure the fundamental parameters of the raw material, the processing parameters, such as activation energy of the pyrolysis, and the fuel properties of the solid product from the pyrolysis. The results of the study will provide the theory and data support for trading the straw according to the quality, evaluating the applicability of straw, understanding the pyrolysis reaction process and mechanism of straw, predicting the reaction rate and feasibility, and setting up the operating parameters. The main innovation achievements obtained are as followed.1. It is feasible to rapidly predict the cellulose, semi-cellulose, lignin, soluble carbonates, moisture, ash, volatile matter, fixed carbon, C, H, O, N, K, Mg and calorific value contents of the crudely crushed corn and wheat straw using NIRS. However, for S content, the model can only tell which is higher or lower of the crudely crushed sample. The models of the finely milled sample are more accurate than the crudely crushed sample’s. The results also show that, for different particle sizes, different processing methods are needed for the spectra.2. The influence of NIRS on-line acquisition parameters such as focal distance, speed of the belt, integration time on the spectral repeatability was studied using two different spectrometers. The results show that different parameters are needed for different spectrometers to get high-quality spectra. Using the optimal spectrometer and collecting parameters, the NIRS online models can predict the cellulose, semi-cellulose, lignin, soluble carbonates, moisture, ash, volatile matter, fixed carbon, C, H, O, N, K, Mg and calorific value contents rapidly. For the accuracy of the models, the online models match or are more accurate than the static spectra models.3. The pyrolysis profile of the corn straw and the wheat straw are really different. With the RSD of the models smaller than 10%, it is feasible to predict the extrapolated onset and end temperature, total weight loss ratio, weight loss ratio, peak rate and temperature at the peak point. The activation energy of the corn straw is higher than wheat straw. The activation energy of the peak rate point keep stable. It means the reaction is different at different heating rate, but the reaction at peak rate point is probably the same. The NIRS models can predict the average activation energy and activation energy where the reaction conversion ratio between 0.3 and 0.6 accurately and rapidly with the RSD lower than 10%.4. The ending temperature has a significant influence on the fuel properties of the solid product. For the solid product produced from ending temperature lower than 300 ℃, the fuel properties are approaching the low grade coal following the increase of the ending temperature. The fuel properties of solid product produced from ending temperature higher than 300 ℃ are between the low grade coal and high grade coal according to the Van Krevelen diagram. And the fuel properties of corn straw biochar are closer to the coal than that of wheat straw. The NIRS models can predict the mass yield, energy yield, heat value, volatile matter, fixed carbon, ash, C, H and O of the com and wheat straw biochar accurately and rapidly with the RSD being smaller than 9%. |
PDF Full Text Request