How to dry foundry sand?
In order to improve the core strength and permeability of Tongliao foundry sand, reduce the gas generated during the pouring process and improve the quality of castings, the foundry sand manufacturer first sprays a layer of paint on the surface of the sand core, and then sprays the sand core to dry in a drying box. So how should casting sand dry the sand core?
During the drying process, the gas in the high-temperature furnace is constantly in contact with the sand core, so the water in the sand core continues to evaporate, the clay is sintered, or a special binder appears. Dry the sand core to increase strength and penetration strength.
During the heating stage, the furnace temperature rises slowly, and the heat can be quickly transferred from the surface to the inner layer of the sand core, so the water in the sand core is quickly converted into steam and escapes. The main purpose is to evaporate the water in the sand core and drain it out as quickly as possible. When heated to 250-300°C, store the sand core in the furnace for a period of time until all moisture in the sand core evaporates.
During the cooling stage, the exhaust valve should be partially opened and heating should be stopped so that the sand core can continue to discharge the residual water in the furnace. The furnace temperature gradually decreases and the core cools slowly. When the furnace temperature drops to room temperature, the sand core can be released. In the actual production of the foundry sand factory, the drying time of the sand core is 1.4-2.0h, and then the sand core is taken out of the drying furnace and cooled at room temperature for more than 2 hours.
Sand drying equipment
Introduction to the working principle of foundry sand dryer
It is sent to the hopper by a belt conveyor or bucket elevator, and then enters the feeding end through the feeding pipe of the feeding machine of the hopper. The inclination of the feeding pipe should be greater than the natural inclination of the materials so that the materials can flow into the casting sand dryer smoothly. The dryer cylinder is a rotating cylinder, which is slightly inclined with the horizontal line. Materials are fed in through the higher end, and heat carrier enters through the lower end, and contacts with materials in counter-flow. Sometimes heat carrier and materials flow into the cylinder together. As the cylinder rotates, the materials move to the lower end due to gravity. When the wet materials move forward in the barrel, they receive the heat from the heat carrier directly or indirectly, and the wet materials dry. Then, the wet materials are sent out through the discharge end through a belt conveyor or screw conveyor. The inner wall of the barrel of the sand dryer is equipped with a lifting plate. Its function is to lift the materials and scatter them, to increase the contact surface of the materials and the airflow, in order to improve the drying rate and promote the advancement of the materials. Heat carriers are generally divided into hot air, flue gas, etc. After the heat carrier passes through the dryer, a cyclone dust collector is generally required to collect the materials in the gas. If you need to further reduce the dust content of the exhaust gas, it should be discharged after passing through a dust collector.