Thermal Analysis Applied Research In The Microwave Preparation Of Activated Carbon In The Agricultural And Forestry Wastes

The farming and forestry reject is the low ash content material. It doesn't contain the heavy metal element. In addition in these farming and forestry reject does not include the lignin, the cellulose and so on. Their chemical composition is similar with the lumber. Especially the charcoal content achieved in particular above 40%. Uses the microwave radiation farming and forestry reject to be possible to prepare the high quality active carbon. While the thermal analysis technology applying in the reject converting into resources research is extremely widespread. It may carry on the research analysis that using the thermal analysis technology to the farming and forestry reject thermal decomposition characteristic.This article take the farming and forestry reject (coconut shell, macadamia shell) as material and combine the new technology that uses microwave radiation farming and forestry reject to prepare active carbon. Study on weight loss, enthalpy and stability in heating process of coconut shell by simultaneous measurements of thermogravimetry(TG) and differential thermal analysis(DTA), pyrolysis and charring mechanisms of coconut shell were obtained. In this paper it also studied the influences on pyrolysis temperature and heating rate charring yield and decompose rate of coconut shell. According to the experimental data, thermal analysis curves of coconut shell all have two weight loss stage in 2.3℃/min, 5℃/min, 10℃/min, 20℃/mim 30℃/min five different heating rate. Pyrolysis of coconut shell temperature range is from 200 to 410℃. Controlling the weight loss of second stage is the key for pyrolysis and charring ,in a certain degree increasing heating rate is helpful for pyrolysis reaction of coconut shell. Under the conditions of heating rate is 20℃/min, enthalpy of pyrolysis is 792.15J/g and weight loss is only 31.925%.The optimum final pyrolysis temperature is 575 ℃By the method of Coats-Redfern's law, The pyrolysis behavior and kinetics of coconut shell were investigated at the five different the heating rate The experimental data reveal that the kinetic parameters are much influenced by the operating conditions. And the activation energy and pre-exponential factor of pyrolysis reaction increases with heating rates. Through the kinetics compensation the effect processing. The kinetic models are obtained for the coconut shell pyrolysis at the five different the heating rate.Preparation activated carbon from the charring coconut shell with the water as activeagent by simultaneous measurements of thermogravimetry and differential thermal analysis was studied, Effects of activating mechanisms of the charring coconut shell, soak times, enthalpy and microwave radiation on the preparation of activated carbon by microwave radiation were obtained. According to the experimental data, thermal analysis curves of different the charring coconut shell all have a heat absorption and water loss stage in 40℃ heating rate. Soaked in the water increase the weight loss rate , activating point and heat releasing temperature interval. The soak time was 48h,weight loss reach at 32.048% in temperature range 390℃~998℃, heat releasing temperature interval is from 153.62℃to 855℃, enthalpy of heat releasing is helpful for activating and heat absorption reaction of the charring coconut shell in high temperature from 800 ℃ to 900 ℃ .Water-charring coconut shell is reached at activating reaction temperature rapidly by microwave radiation. Activated time was 3~5minutes,flow rate of water vapor was 3.5~5.5 mL/min, experiment showed that iodine value of activated carbon was 1031mg/g,methylene blue adsorption was 100mL/g.Preparation activated carbon from the macadamia (Macadamia temifolia F.Muell.)shell with the phosphoric acid as active agent by simultaneous measurements of thermogravimetry and differential thermal analysis was studied, effects of pyrolysis mechanisms of macadamia shell , the enthalpy and weight loss on the preparation of activated carbon were obtained. According to the experimental data, thermal analysis curves of macadamia shell all have two weight loss stage and a heat absorption peak or heat releasing peak in different conditions. Pyrolysis of macadamia shell temperature interval is from 200- 410 ℃ .residue is close to zero in 800 ℃. Charring and activating of phosphoric acid-macadamia shell temperature range is from 130 ～ 410 ℃ soak in phosphoric acid 12 and 24 h, residue is 34.431 % and 17.743 %.The best activating temperature is about 400 ℃,soak times is 12 h by phosphorylation. Meanwhile increasing soak times ,temperature of peak DTG curves is gradually tending to lower temperature ,it is from 363.63 ℃ descend to 243.71 ℃ and 238.37 "C Phosphoric acid catalyze charring reaction , phosphoric acid-macadamia shell is beginning pyrolysis and charring at 130 ℃. The study results provide significant theoretical parameters in preparation of activated carbon of the macadamia shell.