Internal structure and atomization process of spray dryer
Spray dryer is a form with rapid development and wide application in drying field, which is suitable for liquid raw materials such as solution, emulsion and pumpable suspension to generate powder, granular or block solid products. The different drying characteristics of dry materials, such as thermal sensitivity, viscosity, and flowability, as well as the quality requirements of product particle size, particle size distribution, residual moisture content, bulk density, particle shape, etc., determine the use of different atomizers, airflow movement methods, and drying chamber structures.
The ball milled slurry is further stirred evenly and heated to above 35 ℃ in the mixing tank. Then, pressure is applied to the mixing tank, and under the action of pressure, the slurry is sent to the atomizer. After atomization by the atomizer, it is sprayed into the tower from the bottom. The N2 heated by the oil and gas heat exchanger is sent to the gas distributor at the top of the tower by the blower. After passing through the gas distributor, the N2 enters the tower uniformly and in a whirlwind shape to dry and pelletize the atomized slurry. After the particles come into contact with hot gas, the liquid on their surface evaporates rapidly, while the internal gas migrates to the surface and is carried away by the hot gas during the subsequent drying process. The dried particles fall to the bottom of the tower and are recycled through a pair of disc valves in a gap style.
The gas after drying the slurry contains vaporized hexane and a small amount of tiny dust. The gas is first sent to the cyclone separator by a pressure fan for preliminary separation of the dust, and then sent to the condensation and rinsing tower. In the rinsing tower, the gas is thoroughly washed, and the hexane gas contained in the gas is condensed and collected at the bottom of the rinsing tower. The washed gas is then sent to the oil gas heat exchanger for heating and reuse. During operation, the system maintains a slightly positive pressure state and is automatically controlled by an air supply valve and an exhaust valve. Avoiding the drawbacks of hot air vortex and axial flow, a hot air rectification chamber is installed. A honeycomb shaped fixed blade similar to the guide impeller of a rotary turbine is installed at the outlet of the rectification chamber. The hot air flows out from the radius direction of the fixed blade, further changing the direction of the hot air and blowing towards the drying tower. In this way, the fixed blades convert the hot air of the vortex into the axial supply of the drying tower, achieving the purpose of rectification, which has a very significant effect on solving the problem of product adhesion in the drying tower. And after rectification, it prevents the hot air from rotating, so that when the fog drops, the heating is uniform, and the thermal changes of the finished product can be maintained within a small limit, thus improving the quality of the finished product.
The spray dryer is a thermal process that enables liquid materials to be atomized into fine atomized droplets through nozzles, and then contact with hot media in the drying tower to dry into powder. The feed can be a solution, suspension, or paste, and atomization can be achieved through rotary atomizers, pressure atomizers, and air flow atomizers. The operating conditions and design of the drying equipment can be selected according to the required drying characteristics of the product and the specifications of the powder particles. The spray dryer spray, drying and collection system is made of transparent high-quality high borosilicate heat-resistant glass material, so that the drying process can be carried out in a pollution-free environment. Built in imported oil-free air compressor, the particle size of the powder spray is normally distributed, the fluidity is very good, the noise is very low, less than 60db. The atomization structure of the two fluid spray, the whole machine is made of high-quality stainless steel materials, and the design is compact, without the need for auxiliary equipment. Equipped with a nozzle cleaner (needle), it will automatically clear when the nozzle is blocked, and the frequency of needle passing can be automatically adjusted.
