Preparation Of A New High-Performance Calcium-Based Desulfurizer Using A Steam Jet Mill And Study Its Driving Effect

Dry flue gas desulfurization technology has great potential and broad prospects in the field of flue gas desulfurization.At present,the commonly used calcium-based desulfurizers are difficult to meet the desulfurization efficiency requirements of dry flue gas desulfurization technology.Na HCO₃desulfurizers can meet the requirements of desulfurization efficiency,but the high price and the difficulty in handling desulfurization products make it quite difficult to realize the large-scale application of Na HCO₃Desulfurizers.To improve the desulfurization performance of calcium-based desulfurizer,we utilize CFD numerical simulation to analyze the internal flow field of the steam jet mill and the driving effect of quicklime,study the mechanism and process parameters of the steam jet mill digesting quicklime and evaluate the apparent performance and desulfurization performance of calcium-based desulfurizer prepared by a steam jet mill,ordinary dry digestion,and Na HCO₃desulfurizer.The main conclusions are as follows:(1)Using liquid water and steam as dry digestion medium to digest quicklime,the results show that the specific surface area of the digested product and the digestibility of quicklime increased with the decrease of the particle size of the quicklime and the increase of the degree of mixing.The surface area increased with the temperature of liquid water and steam,and the digestibility of quicklime increased with the temperature of the liquid water and decreased with the temperature of the steam,which is due to the increase of the temperature of the steam,the chemical reaction rate between Ca O and water vapor is greater than the gas-phase diffusion of water vapor,which causes the passage of water vapor into the quicklime to be easily blocked,resulting in a decrease in the digestibility of quicklime.When the quicklime particle size is less than D₅₀=3.523?m,the digestibility of dynamic steam digestion is the same as that of liquid water,but the specific surface area of the digested product is higher than that of liquid water digestion,and the dispersibility and fluidity of the digested product are better.(2)This research utilized an LNGS-80 steam jet mill to prepare a desulfurizer at a steam temperature of 150?260?,the pressure of 0.5 MPa,and the speed of the classifier is 150,750,and 1350 r/min,our results show the digestion in the steam jet mill can transform all the calcium oxide into calcium hydroxide.Desulfurizer via steam jet mill technique has a much better apparent activity than the calcium-based desulfurizer prepared by traditional dry digestion.By increasing the steam temperature and the speed of the classifier,the calcium-based desulfurizer by steam jet mill digestion has a larger specific surface area,higher porosity,finer particle size,more uniform particle distribution,and more obvious honeycomb structure,and better fluidity.(3)Combined with the numerical simulation of FLUENT fluid dynamic simulation software and the experiment of digesting quicklime by the steam jet mill,the results show that when the steam pressure of 0.5 MPa and the steam temperature is 150?260?,the nozzle outlet velocity obtained is greater than 795 m/s,and the crushed particle size D₅₀=1.331?3.930?m,which indicates that the steam jet mill has a high crushing intensity and obtain a finer particle size.The main area of quicklime digested by the steam jet mill occurs in the jet collision zone,and the total length of the jet is about 0.1 ms.Under different inlet steam temperatures,the smaller the particle size is,the shorter the distance required to accelerate to the maximum speed,the greater the maximum speed obtained by the accelerated particles,and the easier the particles are crushed and digested.The steam jet mill forms a supersonic high turbulence flow field in the steam injection zone,which is conducive to full contact between the quicklime and the steam.The huge momentum created by the high-speed collision allowed the formation of largely abundant small particles and freshly formed super active surface which could further accelerate the digestion rate of quicklime.In the steam jet mill,better environmental conditions are provided for quicklime digestion,and the obtained digested product has better activity.A small quantity of undigested quicklime will be sent back to pulverizing zone by a centrifugal force,produced by the impeller of the high-speed rotating classifier,to be further digested.(4)The calcium-based desulfurizer prepared by steam jet mill digestion,with the increase of the steam temperature and speed,the time to maintain 100%desulfurization efficiency and the“break-through”time increase.The calcium-based desulfurizer prepared by the steam jet mill operating time with 100%desulfurization efficiency and the“break-through”time is longer than that of ordinary calcium-based desulfurizers,especially at 0-20%flue gas relative humidity.As for the desulfurizer prepared by the steam jet mill under the indicated conditions(steam temperature of 260?,classifier speed of 1350 r/min,relative humidity of10%),the“break-through”time is 6 times that of the optimal desulfurizer prepared by water dry digestion.When the humidity is 20%and 60%,it is 4 times and 1.6 times,respectively.(5)The desulfurizer prepared by the steam jet mill at a steam temperature of 260?and classifier speed of 1350 r/min compared,and conventional Na HCO₃desulfurizers and ultrafine Na HCO₃desulfurizers,tested the desulfurization performance at a relative humidity of 10%.The time operating time for the three desulfurizers with 100%desulfurization efficiency is 420,360,and 100 min,and the“break-through”time is 460,400,and 120 min.When the flue gas temperature of 100?300?,the desulfurizers“break-through”temperature is 260,200,and 200?,expanding the use range of desulfurizer flue gas temperature.(6)Compared with the desulfurizer by conventional dry digestion,the desulfurizer prepared by the steam jet mill in this research had significantly superior performance and even better desulfurization performance than Na HCO₃desulfurizers.And its preparation cost is much lower than the Na HCO₃desulfurizer.This research provides a new method and process for preparing high-performance desulfurizer by digesting quicklime,which is an important step in pushing forward the application of dry flue gas desulfurization.