A REVIEW ON FLASH CHROMATOGRAPHY AND ITS PHARMACEUTICAL APPLICATIONS

Earlier column chromatography was used for preparative purposes as well as for reaction control in organic synthesis. Column chromatography is an extremely tedious stage in any laboratory and can quickly become a point of congestion for any process lab. Flash chromatography is a technique developed as a modification of preparative column chromatography. This is an air pressure driven technique comprising of medium and short column chromatography, optimised for rapid separation of organic compounds. Modern flash chromatographic system consists of pre- packed plastic cartridges where in the solvent is pumped through the cartridge. By employing high pressure gas, the efficiency and speed of classical column chromatography can be increased. Flash chromatography is an easy & quick approach that is economical to preparative liquid chromatography. The content mentioned in this article mainly focuses on the various components, general principles, procedures and applications of flash chromatography.

COMPRESSOR PUMP UNIT FOR CO2 LIQUIDATION AND SUPPLY IT FOR CARBAMIDE SYNTHESIS

Carbon dioxide, as well as ammonia, are widely used in large-scale chemistry for the production of urea. Currently, the most common technology for producing carmabide is according to which liquid NH3 is pumped into the synthesis column by a pump at a pressure of 15 MPa, and gaseous CO2 is supplied by a compressor with the same pressure as ammonia. Gaseous CO2 is compressed in a multi-stage compressor to a pressure of 15 MPa before it enters the urea synthesis unit, in which it reacts with ammonia. The specific energy consumption for compressing carbon dioxide in a compressor unit is 0.13 kWh/kg. Reducing energy for producing CO2 and also urea can be achieved when it is possible to supply carbon dioxide in liquid form under a pressure of 15 MPa to the urea synthesis column. The analysis showed that to solve this problem it is necessary to implement two processes: compression to 1.8–3.0 MPa, and then cooling and liquefaction of gaseous CO2 due to the cold of liquid ammonia. Liquefied CO2 can then be pumped to the urea column. In order to introduce carbamide into production, a new carbon dioxide compressor and pumping unit has been created. The installation scheme for compressing CO2 to a pressure of 15 MPa and its subsequent supply to the production of urea is given. A cold liquid ammonia stream with an initial temperature of –30 °C is used as a source of cold in the installation. The performance and power consumption of the compressor unit depend on the compression pressure of CO2. After the CO2 is compressed to 1.8 MPa, it is possible to cool 2.3 t/h of carbon dioxide with cold liquid ammonia and then direct it to the synthesis of urea using a pump under a pressure of 15 MPa. The specific energy consumption in the installation will be 0.1 kWh/kg. When CO2 is compressed up to 3 MPa, the plant capacity is 8.78 t/h, and the unit costs are 0,108 kWh/kg. Urea production in this case may increase from 1400 to 1680 t/day. Ref. 5, Fig. 3, Tab. 3.

Optimal Design of Welded Plate Heat Exchanger for Ammonia Synthesis Column: An Experimental Study with Mathematical Optimisation

The production of ammonia, consuming up to 5% of natural gas global production, accounts for about 2% of world energy. Worldwide, the Haber–Bosch process is the mainly used method of ammonia catalytic synthesis, involving temperatures up to 600 °C and pressures up to 32 MPa. In this paper, the results of the development and study of the special welded construction of plate heat exchanger (WPHE) for a column of ammonia synthesis are presented. The heat transfer and hydraulic performance of developed WPHE are investigated on a one-pass model in laboratory conditions. An equation for the relation between heat transfer effectiveness and the number of heat transfer units is proposed. A mathematical model of multi-pass WPHE is developed using these results. The validity of this model is confirmed by results of industrial tests performed with the prototype WPHE installed in operating column of ammonia synthesis at temperatures about 500 °C and pressure about 32 MPa. The tests confirmed the reliability of WPHE and its efficiency compared to a tubular heat exchanger. A method of optimal design of WPHE that allows finding the optimal height of corrugations and the number of passes in WPHE for specified conditions of operation is developed.