Study On Absorption/Desorption SO₂ And Basic Properties Of NHD/HPP-H₂SO₄ Composite Absorbents

In order to overcome the problems associated with the high energy consumption during desorption for 1,4-N,N’-bis(2-hydroxypropyl)piperazine(HPP)sulfate aqueous solutions,we tended to incorporate a physical absorbent Polyethylene glycol dimethyl ether(NHD),into the absorbent with certain amount to probe its influences upon SO2 absorption and desorption on.At the same time,the physical properties closely related with the absorption and desorption,such as density,viscosity and surface tensions of the original absorbent and those after SO2 load.The probable constituents such as F-,Cl-,and SO32-(in order to simulate the flue gas composition in metallurgy)upon the process were also investigated.The results turned out that for 1,4-N,N’-bis(2-hydroxypropyl)piperazine(HPP)sulfate aqueous solutions with a concentration of,the optimal NHD incorporation was 3.0 wt.%of the total solution,with about molar ratio between NHD and HPP about 1/2.Under those circumstances,the saturated SO2 load reached 0.619 moles SO2 per mole HPP.Under desorption working conditions of T = 101 ℃ with N2 sweeping,the desorption rate reached 91.9%.After five cycles,the absorbent solution showed no obvious deteriorated performance.Low concentration of Cl-applied in showed little influences upon SO2 absorption and desorption.Low concentration of F-showed no influences upon absorption but promoted desorption.SO32-promoted the saturated absorption of SO2 but deteriorated the desorption performances.Incorporation of NHD can increase the desulfurization rate in the absorption process;it can also reduce the thermal desorption temperature and increase the desorption rate.The densities of the absorbent solutions were measured by using a 10-mL Gay-Lussac pycnometer.The viscosities of the amine solutions were measured using an Ubbelohde capillary viscometer.The surface tension measurements were carried out using a bubble pressure meter,which uses the maximum bubble pressure method.The temperatures of the absorbent solutions were in the range of 303.15～333.15 K,NHD mass fraction in the range of 0.03～0.12 and HPP mass fraction in the range of 0.05-0.30.The results turned out that the densities,viscosities and surface tensions all decreased with temperature.The densities and viscosities increased with HPP(or NHD)mass fraction.The surface tensions decreased with HPP(or NHD)mass fraction.NHD incorporation slightly increased the densities and viscosities but efficiently decreased the surface tension,which may associated with the enhanced desorption performances.