Research On Preparation Of Activated Carbon From Biomass In The Fluidization Bed

Activated carbon is an important adsorbent. It is extensively used in industry such as environmental protection, chemical industry, food processing, pharmaceutical processing, and military chemistry, etc. China has the plentiful crop stalks resources, but most of them are discarded as waste material or burned out. The abundant crop stalks as agricultural byproduct contains plentiful fixed carbon. It is significant to explore new application of crop stalks.Firstly, to better operate and design a fluidization bed to convert biomass such as wheat stalk, corn stalk and wood powder into activated carbon, the minimum fluidization velocity of biomass mixing with sand is obtained by experiment. The biomass choosed includes wheat stalk, corn stalk or wood powder. For such bi-component mixtures, the weight percent of biomass are fixed at 10%, 20%, 30%, 40%, 50% and 60%. The experiment shows that the minimum fluidization velocity of the mixture increases with increasing weight percent of biomass. The weight percent of biomass is equal or lesser than 10%, the mixtures are characterized by good fluidization behaviors.Using nitrogen and carbon dioxide as fluidized medium, the pressure drops of empty bed and the bed loading specified volume of material under different velocities in a series of temperatures (room temperature, 300℃, 600℃, 700℃, 800℃, 900℃) were examined. The experiment shows that the minimum fluidization velocity of the mixture decreases with the temperature increase.In this study, activated carbon was prepared from biomass such as wheat stalk, corn stalk and wood powder using carbon dioxide as the activating gas in a fluidized bed reactor. The effects of process parameters such as fluidized number, activating temperature and activating time on the adsorption properties were investigated. The products were characterized by iodine value, methylene blue adsorption value and SEM. It was concluded that activating conditions are as follows: the fluidized number of all three kind biomass 1.5, the activating temperature of the three 800℃, and the activating time of wheat stalk and corn stalk 30 min while wood powder 40 min. Finally, activated carbon from biomass was used to adsorb dyeing waste water. The adsorptions of dyes onto activated carbon followed pseudo-second-order kinetics.