Process Research Of Salt Treatment And Calcination To Prepare Titanium White Pigment Via Low Concentration Of Titanyl Sulfate Solution

Salt processing and calcinations are the core process of rutile-type titanium white pigment production via sulfate process,directly affecting grain growth and crystal transformation of titanium dioxide,and ultimately determining the properties of titanium pigments.Salt processing and calcinations are contribute to reduce energy consumption and promote quality of product for controllable and stable during sulfate process.For the case of quality of titanium dioxide being fluctuating wildly and the situation of high energy consumption for titanium white pigment production,rutile titanium dioxide white pigments were prepared by low concentration industrial hydrolyzing TiOSO4 solution via calcining seeds,washing,salt processing and calcining in this paper.The effects of the adding amount of calcining seeds,zinc salt,potassium salt,phosphorus salt and the highest calcination temperature and maintaining time of the highest calcination temperature on the pigments properties of rutile titanium dioxide white pigments were staadied.The orthogonal mutual influences of the adding amount of salt treatment agents(zinc salt,potassium salt,phosphorus salt)and the highest calcination temperature were investigated by orthogonal regression test,and the calcination process and calcining mechanism were discussed.The results are as follows:(1)The crystal transformation of titanium dioxide particles was accelerated by adding the zinc salt and calcining seeds(from anatase to rutile),and reducing power increased with the increasing amount of zinc salt and calcining seeds,whereas the blue phase increased before getting reduced.The particle properties of titanium dioxide were regulated and crystal transformation was inhibited by adding potassium salt and phosphorus salt,and blue phase increased with the increasing amount of potassium salt and phosphorus salt,and reducing power was increasing before reducing with increasing amount potassium salt and phosphorus salt.The crystal transform and grain growth of titanium dioxide particles were affected by the highest calcination temperature and the maintaining time of the highest calcination temperature,and reducing power was increasing before reducing with increase of the highest calcination temperature and the maintaining time,and blue phase was reducing.(2)The orthogonal mutual influences between the salt treatment agents and between the salt treatment agents with the highest calcination temperature on the pigments properties of rutile titanium dioxide white pigments were investigated by orthogonal regression test,and the regression equation was established.The influences degree of influence factors to reducing power is zinc salt>the interaction of zinc salt and phosphorus salt>potassium salt>phosphorus salt>the highest calcination temperature>the interaction of potassium salt and phosphorus salt.The influences degree of influence factors to blue phase is zinc salt>the highest calcination temperature>the interaction of zinc salt and phosphorus salt>potassium salt>the interaction of potassium salt and phosphorus salt>phosphorus salt.The optimal salt processing and calcination condtion are zinc salt amount of 0.33%,potassium salt amount of 0.65%,phosphorus salt amount of 0.20%,the highest calcination temperature of 840oC.(3)The calcining process was studied and the results show that:The rutile-type grain size and content of rutile both increased as the calcination intensity was increased after crystal structure transition temperature(807.4OC).The reducing power had a positive linear correlation with calcination intensity before 400134.06 K rnin,after which the linear correlation became negative.The blue phase index had a negative linear correlation with calcination intensity.At the early stage of calcinations,the average grain size of particles gradually decreased from 324.38nm to 145.44nm,and particle size distribution was narrow.Whereas in later period,the average grain size were increased to 206.84nm because of sintering and mixing together for particles,andparticle size distribution turned broaden again.After crystal structure transition temperature,the grain growth of titanium dioxide particles can be divided into three stages:rapid growth of crystal,the growth and mature stage of crystal and sintering fusion of crystal.