Experimental Study on the Spray Characteristics in the Spray Drying Absorber

Abstract

A pilot-scale spray drying absorber (SDA) system was set up to evaluate the effect of spray characteristics on flue gas desulfurization efficiency. Varying spray injection conditions and inlet gas conditions, SO 2 concentrations were measured using a combustion gas analyzer. As a reagent, a slaked lime (Ca(OH) 2 ) slurry was treated with flue gas containing SO 2 . The influence of each parameter is determined by the compromise between the droplet absorption capability and SO 2 gas supply to the region of the droplet cloud. When the SO 2 molecules are sufficiently supplied to the wet droplet surface, the variation of the total droplet surface area plays a dominant role in the desulfurization process. The conditions of low inlet gas temperature and low slurry feed rate are included in this case. However, when the droplets of sprayed slurries are too small or evaporation proceeds too fast, the SO 2 molecules cannot be sufficiently transferred to the droplet surface. The excess calcium sorbents in the droplets dry out before they react with the hot gas. Consequently, the desulfurization efficiency as well as the utilization efficiency of Ca decreases for the smaller droplets. This trend appears to be dominant in conditions of high gas temperature and large slurry feed rate with the small Sauter mean diameter (SMD) of spray droplets. From the experimental results, we proposed two empirical models for the desulfurization efficiency and operating conditions.

Spray-Dry Desulfurization of Flue Gas from Heavy Oil Combustion

“…Additional options to enhance the performance of the spray dryer have been reported. 7,[11][12][13]22 These rely on an accurate control of the average size of lime particles dispersed in the slurry and of the atomization characteristics (drop size). The size of dispersed lime particles depends on the lime slaking process and on the properties of the parent quicklime.…”

“…In particular, drop sizes below 10 -20 m lead to a low Ca utilization. 12,22 It must be emphasized, however, that the largest droplet size that can be used in practice is limited by the length of the spray-dry column: an important design criterion is, in fact, that, to avoid deposition and corrosion on the duct walls at the spraydryer outlet, only solid material must be present. In this work, the droplet (Sauter) mean size in the spray was measured offline to be between 20 and 40 m. With the atomizer used in this work, the droplet mean size in the spray depends on the slurry and atomization air feed rates and on the flue gas flow rate.…”

Numerical simulation on semi-dry flue gas purification of MSW incineration

“…This paper presents the numerical simulation about spray dry purification flue gas of MSW incineration. Spray drying process is a very complex of flows, heat and mass transfer and chemical reaction [1,3,4] . And then, in this paper, on the basis of the status quo in-depth analysis of spray drying technology, optimal design the purification devices of spray drying in flue gas flow rate of 600 Nm 3 /h.…”

Modelling of trona based spray dry scrubbing of SO2

“…The kinetic studies on the reaction between trona and SO 2 are also based only on TGA experiments and it is concluded that the reaction occurs at dry base. On the other hand, all model approaches for spray dryer scrubbing of SO 2 are based on lime or limestone slurries [8,9,[12][13][14].…”