The first step in the application of diatomite filter aid in titanium filtration is pre-coating, which means that before the titanium filtration operation, the diatomite filter aid is applied to the filter medium, namely, the filter cloth. The diatomite is prepared into suspension in a certain proportion (generally 1∶8 ~ 1∶10) in the pre-coating tank, and then the suspension is pumped into the filter press filled with clear water or filtrate through the pre-coating pump, and repeated circulation (about 12 ~ 30min) until the circulating liquid is clear.
In this way, a uniformly distributed precoating is formed on the filter medium (press cloth). To prepare suspension, generally use clear water, but also can use relatively clear titanium liquid. The amount of diatomite used for pre-coating is generally 800 ~ 1000g/m2, and the maximum flow rate of pre-coating should not exceed 0.2m3/(m2? H). Precoating is the basic filter bed for titanium liquid filtration, and its quality is directly related to the success of the whole filtration cycle.
Pre-coating should also pay attention to the following points:
(1) During pre-coating, the amount of diatomite should be 1 ~ 3mm thick filter layer. Taking the experience of a factory as an example, the 80m2 plate and frame filter press was used, and 100kg of diatomite filter aid was added each time during pre-coating, which could filter continuously for 5d and produce 17-18T of finished products every day.
(2) When precoating, the plate and frame filter press shall be filled with liquid in advance, and the air shall be discharged from the upper part of the machine;
(3) pre-coating should continue to hit the cycle. Because the filter cake is not formed at the beginning, some fine particles will pass through the filter cloth and enter the filtrate. Circulation can intercept the filtered particles on the surface of the filter cake again. The length of cycle time depends on the degree of clarity required for the filtrate.
The second step is to add filtration. When the titanium liquid containing solid and colloid impurities is filtered, after the pre-coating is done, it is not necessary to add diatomite filter aid to filter directly. When filtering the titanium liquid containing more solid and colloidal impurities, or when filtering the titanium liquid with higher concentration and viscosity, an appropriate amount of diatomite filter aid must be added to the filtering titanium liquid. Otherwise, the surface of the pre-coating will be covered with solid and colloidal impurities soon, blocking the filter channel, so that the pressure drop on both sides of the filter cake will rise rapidly, and the filtration cycle will be greatly shortened.
Post time: Apr-20-2022