Experimental study on hydrodynamic cavitation-enhanced carbothermic reduction process for production of magnesium carbonate hydromagnesite
In order to enhance microscopic mixing and mass transfer and to increase the Mg(OH)2 carbonation rate,hydro-dynamic cavitation technology was employed to intensify the carbonation reaction of Mg(OH)2 and CO2 to produce the inter-mediate product Mg(HCO3)2,which was then pyrolyzed to produce basic magnesium carbonate[4MgCO3·Mg(OH)2·4H2O].An orthogonal experimental design was used to investigate the factors influencing the carbonation rate of Mg(OH)2.The re-sulting products were characterized by using scanning electron microscopy,X-ray diffractometer,and a multi-parameter testing instrument.The results showed that the important order of factors affecting the Mg(OH)2 carbonation rate was inci-dent angle α>CO2 flow rate q>Mg(OH)2 solid content s>inlet pressure p>throat diameter d0>carbonation time t.Under the process conditions of α=60°,d0=4 mm,p=0.35 MPa,t=60 min,s=1.6%,and q=17 L/min,the carbonation rate reached 92.1% .It was a 31.57% improvement over the carbonation rate(60.53% )of a bubble-stirred reactor.The content of impuri-ties such as CaO and Fe in the product 4MgCO3·Mg(OH)2·4H2O was reduced,and the produced 4MgCO3·Mg(OH)2·4H2O had a uniform flake structure with a crystal thickness of less than 50 nm.The product had good crystallization and rela-tively stable and single composition.Each diffraction peak position of the obtained product was completely consistent with the diffraction peak position of basic magnesium carbonate in the standard hexagonal crystal form.
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