Safety analysis and safety technology of the hotte

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The safety analysis and safety technology of the continuous expansion process are both a challenge P>

the continuous expansion ammonium nitrate process is a mature and reliable process technology in the current industrial explosive production, from the crushing, metering, dissolution and spiral transportation of the raw material ammonium nitrate. The expansion of ammonium nitrate is essentially different from the vacuum drying crystallization process in the current industrial powdery ammonium nitrate production in terms of its chemical principle, Up to now, many ammonium nitrate production enterprises in China still use this process to produce industrial ammonium nitrate, which has been proved to be safe and reliable in practice; The crushing, dissolving and conveying methods of ammonium nitrate are basically the same for all manufacturers in the civil explosive industry, but the expansion methods are different

1 determination of continuous expansion scheme

the key to the continuous expansion production process of expanded ammonium nitrate explosive is the continuous expansion of ammonium nitrate, and the determination of continuous expansion scheme is very important. Through the analysis of the preparation methods of the current production enterprises of ammonium nitrate, the discontinuous preparation of expanded ammonium nitrate and the characteristics of expanded ammonium nitrate, various possible ways to realize continuous expansion are demonstrated and studied in detail, and the continuous expansion scheme of "dynamic feeding and static expansion" is finally determined. The scheme mainly consists of continuous expansion crystallizer, condenser and vacuum pump to form a complete continuous vacuum expansion crystallization system

2 structure and working principle of continuous expansion crystallizer

the expansion crystallizer is an outer cylinder made of stainless steel and placed vertically. Its middle part is a fixed torus with steam interlayer for thermal insulation and rectangular cross section. It is the crystallization disk expanded by ammonium nitrate, which divides the interior of the expansion crystallizer into expansion space and storage (bin) space along the up and down directions. The center of the expansion crystallizer runs through a transmission main shaft composed of upper and lower shafts with a through hole in the center of the upper shaft, which is the transmission shaft of the expansion crystallizer. At the same time, the central through hole is the channel for the

ammonium nitrate solution to enter the expansion crystallizer. The channel is always connected to the top of the crystallizer, which is called the suction pipe of the expansion crystallizer: at the same time, the A scraper connected with the driving spindle and rotating together is arranged adjacent to the suction pipe, which has the "shovel, turn over and lift" function, which is similar to the "plough" of rural ploughing. In addition, a group of discharge scrapers are evenly distributed on the disk surface of the storage space. The suction pipe, scraper and discharge scraper are fixed on the driving spindle and move in a circular direction with the driving spindle, The elongation at break of PE is 90% ~ 950% (among which the elongation of LLDPE is higher) and the range is the perimeter of the crystallizing disk. 4. the precision positioning system of the instrument

continuous expansion is that the ammonium nitrate solution with expansion agent is continuously and evenly sucked into the space formed behind the crystallization disk surface and the scraper plate through the suction pipe rotating together with the driving spindle under the vacuum of less than -0.092mpa, so as to form a dynamic feed. Because the crystallization disk is fixed, the ammonium nitrate solution entering the crystallization disk evaporates and expands instantly, that is, a static expansion is formed. Then, after the driving spindle rotates for one cycle, the expanded ammonium nitrate on the crystallizing disc is loosened by a multifunctional scraper connected with the driving spindle and adjacent to the suction pipe. It falls into the storage space from the center of the crystallizing disk. As the scraper and the suction pipe move in a circular motion together with the driving spindle, as soon as the expanded ammonium nitrate is shoveled out of the crystallizing disc by the scraper, the ammonium nitrate solution is quickly sucked into the crystallizing disc for instant expansion, thus forming a continuous expansion of ammonium nitrate: in addition, the drying time of expanded ammonium nitrate on the crystallizing disc is the time required for the driving spindle to rotate for one cycle, about 1 minute 45 seconds. The expanded ammonium nitrate which falls into the storage bin from the crystallization tray is further dried. Ten minutes later, the storage bin of the expansion crystallizer is full Stop feeding. Break the vacuum, open the discharge door, and a group of discharge scrapers will discharge the expanded ammonium nitrate into the screw outside the machine through the discharge port. The continuous production of expanded ammonium nitrate is realized by two expansion crystallizers alternately sucking, expanding and discharging materials

during the vacuum evaporation of ammonium nitrate solution, the formation of vacuum degree depends on the condensation of evaporation steam and the suction of vacuum pump. Most of the components of evaporation steam are steam generated during the evaporation of water in ammonium nitrate solution, and only a small amount of non condensing gas such as air that can effectively reduce the deformation of main shaft. When they are pumped from the expansion crystallizer into the condenser, they are immediately condensed into liquid. The volume shrinks rapidly, thus forming a vacuum. The condensate and cooling water mix along the drainage pipe and flow into the water sealed pool on the ground. The non condensing gas is sucked in by the vacuum pump and emptied, thus obtaining a higher vacuum

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