The Investigation Of Calcium Absorbent Desulfurization Products Morphology And Broken Characteristics

Now the wider application of flue gas desulfurization technology generally usescalcium based sorbents in China. The formation of product layer in the desulfurizationprocess, hinders the contact of the effective solid-phase components of absorbent andSO₂, resulting in lower utilization of calcium-based sorbents. To solve this problemresearchers have proposed a variety of process routes, one of which is thedesulfurization product growing roughly, it refers to using of additives or adjustingthe desulfurization reaction conditions to form more rough and low mechanicalstrength desulfurization products on the surface of calcium-based sorbents. In thedesulfurization process, the friction and collision between the particles or between theparticles and the reactor wall can make the rough desulfurization products broken andfell off from the surface of the absorbent, so that the effective solid-phase componentsin the absorbent and SO₂can contact directly, thereby increasing the utilization of theabsorption. Based on previous investigations of other researchers, this workresearched for the impact on the morphology and crushing characteristics ofalcium-based sorbents desulfurization products by different reaction conditions andadditives.In this paper, fixed bed reactor used as a desulfurization test bed, with themercury porosimeter, scanning electron microscopy, XRD, EDS et. testing tools, tofind the impact by different reaction conditions and additives on the morphology ofcalcium-based sorbents desulfurization products were studied. The study found: thepresence of high concentrations of water vapor and NO₂can increase the absorbentdesulfurization efficiency, high concentrations of water vapor and NO₂in favor ofdesulfurization; high concentrations of water vapor made the desulfurization productssurface more dense, NO₂increased surface roughness of the desulfurization products.CO₂concentration rising in flue gas, calcium absorbent desulfurization efficiencydecreased, and the desulfurization product of the surface morphology became moredense, indicating that CO₂was more prone to clog the pores on calcium-basedabsorbent surface. Additives caused the following effects: add1%MgCl₂or1%MgO,calcium-based absorbent utilization increased substantially, the other type and contentof the additives will reduce the utilization of calcium-based sorbents. The addition ofSiO₂caused the pore volume of less than100nm pores decreasing on thedesulfurization product, and surface intensifying more roughly. MgCl₂, MgO and Ba（OH）₂added decreasd the pore volume of "ostioles" in the desulfurization productsand surface roughness.Based on fixed bed desulfurization test, using a sieving mechine tested a varietyof desulfurization products, to find the impact by different reaction conditions andadditives on crushing characteristics of desulfurization products. The study found:low concentration of water vapor, high concentrations of CO₂, the existence of NO₂will improve the broken performance of the desulfurization products; the plus sievesamples of desulfurization products obtained under the conditions in10%water vaporhad more pore volume between100-300nm than the original absorbent; and the porevolume of the "mesopores" in the plus sieve samples of desulfurization productsobtained under the conditions in30%of CO₂increased significantly, the "mesopores"in the plus sieve samples of desulfurization products obtained under the conditions of500ppm of NO₂were constant. Add of SiO₂, MgCl₂and MgO will increase the brokenefficiency of the desulfurization products, the pore volume of "mesopores" in the plussieve samples of desulfurization products added Ba（OH）₂,5%SiO₂,3%of MgCl₂had increased; the pore volume of "mesopores" in the plus sieve samples ofdesulfurization products added1%MgO decreased. With scanning electronmicroscopy, the plus sieve samples generally had more rough surface morphologythan the minus mesh.