Study On The Desulfurization Characteristics Of Activated Carbon Modified By Microwave

Flue gas desulfurization (FGD) by activated carbon is an efficient, widely applied recycling technology that can not only remove sulfur dioxide (SO2), but also recover the sulfur resource. Therefore, the promising FGD technology has been under intensive research. The SO₂ adsorption and oxidation capability and the regeneration technique of activated carbon are key factors to the successful performance of this technology and hot research arenas in the world. This dissertation focused on the modification of activated carbon and its regeneration by using microwave technology in order to find a cost-effective and technically feasible FGD process.The effects of the microwave power, dosage of activated carbon, and flow rate on the behavior of activated carbon were investigated under microwave radiation. The rise of temperature can be divided into two phases: rapid change phase (0- 60 seconds) and slow change phase (60-120 seconds). In about 120 seconds, the temperature approaches a stable value. The stable temperature of activated carbon is primarily determined by the power of microwave. The dosage of activated carbon only affects the stable temperature but shows little influence on the rate of the temperature rise. The flow rate of gas has little effect on the heating rate of the activated carbon. The behavior of activated carbon's temperature rise can be described by the logarithm or the second order polynomial.Activated carbons in different sizes were processed under various powers ofmicrowave with different time. The pore structures, surface groups, elemental composition, and microstructures of both conventional and modified activated carbon were tested. It was found that modified activated carbon had little change in the surface, modest shrink on pore volume and substantial change in the mediate-size pore, a little change in pore size distribution, compared with the conventional activated carbon. The fundamental crystallites of modified activated carbon aggrandize and its graphitizing increases as well. Heating with microwave induces dissociation of surface groups over activated carbon to form COx. The less the oxygen content and the more content of N element in the form of pyrrole-N were observed under stronger microwave power radiation.It was affirmed that the desulfurization capability of activated carbon could be greatly increased by microwave modification. According to the analysis on surface physical and chemical characteristics, a mechanism was concluded: Modified by microwave, functional groups begin to dissociate, alkalescency is enhanced, and surface oxygen content is reduced; the amount of active sites produced by dissociation of oxygen-containing groups increased, so did the pyrrole-N groups. Apparently, the activated energy of SO₂ adsorption decreased. In the process of microwave processing, in addition to heat effect of microwave, non-heat effect of microwave also exists, which increases the rate of activation process and decreases activated energy of reactionThe effects of power of microwave, radiation time and activated carbon sizes on desulfurization were studied by a Crossover experiment. The power of microwave is a key factor for SO₂ adsorption capability. The increase of the power of microwave can enhance adsorption capability of activated carbon. The radiation time can play a significant role on modified activated carbon in 4-5 minutes. The higher adsorption capability of the modified activated carbon was obtained using smaller activated carbon.The results of the dynamic experiment of SO₂ adsorption show that microwave-modified activated carbon has a high desulfurization capability and a long breakthrough time. A higher influent concentration of SO₂ and a lower flow velocity will prolong the breakthrough time and increase the SO₂ adsorption capability. The operation temperature is suggested between 60 ℃and 80℃. Theoxygen and vapor concentration in flue gas greatly affects on the SO₂ adsorption capacity.A one-dimension mathematical...