CAV – dosing, conveying, mixing - Avoidance of explosions using nitrogen

12.02.2019 11:00
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Article CAV 12-2018


Inertisation in bulk material process engineering with the aid of self-generated nitrogen

Bulk material is used in many sectors of industry. The granular or powdery solids have the property of being easily pourable and are also used as precursors in the chemical, pharmaceutical and plastics industries. Bulk materials include granulates and pellets as well as powdery colour pigments and fillers. However, bulk materials can often form an ignitable mixture both during storage and processing if there is contact with oxygen. In order to avoid so-called dust explosions, inerting measures must be taken in many process steps of bulk material process engineering. Many companies in the bulk materials industry therefore use INMATEC nitrogen generators to avoid explosions.

Bulk material plants process the bulk material in several process steps. First, the tankers filled with bulk material or sacks and big bags that have been delivered are emptied. After sieving, in which solidified accumulations are dissolved, the bulk material is usually transported to the storage and day silos via pneumatic conveyors. The granulate or powder to be recycled is then dosed and continuously fed to the agitator tanks and mixers, where it is ultimately filled as an end product in the form of tablets or lacquers, for example. Accidents in the bulk materials industry often involve explosions in connection with dry and flammable or explosive bulk materials. This creates fine dust wherever bulk materials are handled. Such dust is removed via pneumatic suction lines. If this dust comes in contact with the ambient air, there is a danger of a dust explosion e.g. in the filter or silo. There are high ignition potentials – particularly in grinding or mixing processes – which can lead to dust explosions. However, the storage or transport of bulk material in pipelines is also not without its problems. Here, too, chemical reactions can take place due to interaction with oxygen, resulting in an explosion. In order to prevent explosions both during storage and mixing, nitrogen is added to the storage and production vessels.


A new generation of nitrogen generators

Nitrogen can be obtained in the form of gas cylinders, tanks or bundles. However, as economic efficiency and independence from supply shortages as well as environmental compatibility are playing an increasingly important role for companies, more and more companies in the bulk materials industry are deciding to produce nitrogen on-site in their own plants. INMATEC, the market-leading manufacturer of nitrogen generators from Germany, offers a wide range of nitrogen generators, from small standard plants up to plants specially designed for the customer, which produce the desired amount of nitrogen on-site from the ambient air. INMATEC has now developed the IMT PNC with PSA technology (pressure swing adsorption). This new generation of nitrogen generators will have its market launch in January 2019. Technical compressed air flows through an adsorption vessel filled with a carbon molecular sieve in the generator. Oxygen and carbon dioxide molecules from the ambient air are caught in the sieve, while the free nitrogen molecules flow into the product tank. Novel flow technology combined with innovative vortex technology reduces compressed air requirements and increases efficiency. This makes it possible to extract more nitrogen from every cubic metre of air and saves energy costs. The dry nitrogen, from which the plant can extract up to 3,000 m³ per hour depending on requirements, has a purity of at least 95.0%. This corresponds to the ATEX guidelines of the European Union for protection against the emergence of explosions. The dry nitrogen can be used in the various process steps of the bulk materials industry, e.g. for filling the head space of silos, mixers and filters.

Several thousand INMATEC nitrogen generators are used across the globe. With more than 25 years of experience in plant construction, INMATEC offers the right solution for every process: In-house nitrogen production for explosion protection in chemical processes for the production of aromas, chemical base materials, paints, insecticides, lacquers, crop protection agents and detergents, pharmaceutical processes such as the production of pharmaceuticals, cosmetics and vitamins as well as processes for the production of plastics, to name just a few.

 

 

published in CAV 12-2018
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