Fluidized Calcination Of Sodium Carbonate: Technology Study And Apparatus Development

The calcination of the soda ash dense is very important in the soda ash producing industry. Now domestic and overseas traditional calcining technology and equipments have many disadvantages, such as big investment, large area occupation, long working process and high expense of run and maintenance, etc.According to the disadvantages of the calcining technology and equipments of the soda ash dense, in the base on the analyzing of the important facts that influence the heat transfer of the fluidized bed calcining machine, this article combines the soda ash dense calcining theory with the heat transfer theory of the fluidized bed with in-built heat exchanger. By means of lab experiment and industrial experiment, we have developed a new soda ash dense calcining technology and equipment.We used multilayer fluidized bed with in-bed heat exchanger as main calcining machine and sodium carbonate monohydrate with 4% moisture as raw materials in the lab experiment. We found that the heat efficiency is between 75% and 82%, and in certain temperature the heat efficiency is decreased along with the increase of operative air speed, increased along with the increase of feeding speed and material moisture content. The heat exchange coefficient of the new fluidized bed calcining machine will change along with operation parameter such as: operative air speed, material moisture content, amount of return soda ash, etc.On the base of successful theory analysis and lab experiment, we completed debug and optimize of the new machine in the jobsite. The new technology and equipment has the following advantages:1,Using the fluidizing calcining theory, the calcining and cooling of the dense soda ash are completed in one fluidized bed with short working process, low energy consumption, small area occupation and low investment.2,Main machine adopts multilayer in-built heat exchanger structure. The height of fluidizing section is 4 to 5 times of the ordinary fluidized bed with in-built heat exchanger. We can get large heat exchange area, so the occupied area and flow air speed is reduced, the investment of whole set equipment is low.3,We used pre-mixing feeding device, the return product enters into the fluidized bed through the pre-mixing device. The material moisture content is reduced, the phenomenon of sticking to pipe and forming soda granule is few, so the long period operation of equipment is guaranteed.The new technology and equipment has been used in 200,000 t/y soda ash dense calcining and achieved good social and economic benefits.