With the advancement of modern sciences and technologies and the development in the high-tech, new energy and other strategic emerging industries, more and more high performance materials are used, e.g. the superfine powder, due to the small particle size, large specific surface area, high surface activity, etc. The jet milling system is one of the most effective equipment for the dry preparation of superfine powder, in which the fluidized bed jet mill is the type used most widely in the dry superfine pulverization of many materials.
Now flammable, explosive and oxidative products used in many fields of the modern industries feature the superfine particle size and the higher risk of explosion, because oxidation or explosion may occur when such products are pulverized with air as the medium, and the smaller powder size is, the lower explosion limit (LEL) is, and the lower minimum ignition energy is.
- Micronization Fineness Scope of D97= 2～15 µm;
- Applied to the Flammable, Explosive, Oxidative & Hygroscopic materials;
- Oxygen percentage can be monitoring & controlling automaticon line by PLC;
- Low consumption of N2, remains required rate & purity controlled within 1 ppm;
Ex-proof Working Principle:
The explosion of dust powder is dependent on three factors, i.e. oxygen, ignition source and the flammable substance, and an explosion can be prevented by eliminating any of the three conditions. When pulverizing any flammable, explosive and oxidative material, the key points of explosion proof are to control the oxygen content and eliminate the ignition source.
The inert gas circulation jet mill system operates with Nitrogen gas or other inert gases as the pulverizing media, and in the entire system, from material feeding, pulverizing, classifying, conveying, separating to packaging, the materials are shielded with inert gas. In the fully closed micro-positive pressure system, the oxygen content is controlled within the safe range, with the online oxygen analyzer and the automatic oxygen supply device, and the oxygen content in the mixture of dust powder and inert gas shall decrease to the level not causing propagation of the flame; and the decrease of the oxygen content will increase the ignition temperature, ignition energy and the lower explosion limit of the dust cloud, causing decrease of the ignition capability of the dust cloud. When the volume fraction of oxygen is below a given limit, the dust cloud will not explode regardless the dust concentration, which is called the limit oxygen content of such dust powder (in the actual applications, a safety coefficient is usually set for the limit oxygen content, to obtain the maximum allowable oxygen content). The inert media include N2, He, Ar, CO2, etc. N2 is the commonly used medium, as the static spark loses its ignition capability in N2 under the general condition, but some metal powders can burn even in nitrogen, e.g. Mg powder, and Ar or He must be used for protection.
Applications of superfine micronizing of flammable, explosive and oxidative materials, meeting the requirements for the high quality of products, and ensuring the safety, environmental and energy saving production. Advanced automatic PLC control, and real time display of operation status. The system has been widely used in Chemical, Pesticide, Pharmaceutical, Metal, Rare metal, New energy and New materials and other industries.
Ex-Proof Jet Mill Micronizing System Flowchart