Robert Michael Thorogood

Developments in air separation

Important developments over the past few years are reviewed. The products of air separation are key commodity chemicals in the USA. Production levels of nitrogen and argon have increased by 50 to 60% during the last decade. Significant improvements have been made to cryogenic processes to reduce the energy consumption of nitrogen and increase argon recovery. New oxygen technology has focused on integration with coal-gasification gas-turbine combined cycle power generation. Non-cryogenic separation technologies have become established for smaller scale nitrogen and oxygen production. Methods for computer modelling are aiding the development of efficient adsorption processes for oxygen and nitrogen production. New membrane materials and processes have been developed for nitrogen production.

Production of medium pressure nitrogen by cryogenic air separation

Abstract This paper concentrates on cryogenic process cycles for producing medium pressure nitrogen (pressure over 5.5 bar (abs.)) at relatively high purity (oxygen concentration under 5 ppm). The major inefficiencies of the conventional waste-expander cycle in a single distillation column were identified as a starting point. These were removed by synthesizing a series of novel cryogenic nitrogen generators in which the expander bypass flow was reduced and converted to a recycle flow to the distillation column. The novel generators retain the convenient and efficient features of the conventional waste-expander cycle while achieving applicability over a much wider range of production rates and product pressures.

Particle Contamination Control and Measurement in Ultra-Pure VLSI Grade Inert Gases

particle microcontamination in the inert gases, such as nitrogen, used in the manufacture of integrated circuits greatly affects the yield loss of semiconductors. With the continuously increasing complexity of integrated circuits, there are no particles so small that their presence in the inert gas supply systems can be safely ignored. It is, therefore, necessary to accurately measure and control the level of particle contamination in gas delivery systems in order to supply virtually particle free gas. The key factors in production and supply of particle-free gas are ultra-high efficiency membrane filters, total integrity of the filter installations, and absolute cleanliness of all surfaces in contact with supplied gas.

THE DUAL-ZONE BRAZED ALUMINUM PLATE REBOILER-CONDENSER

The boiling process and characteristics of conventional thermosyphon reboilers using plate-fin or enhanced boiling surface geometries are briefly reviewed. The limitations of these configurations can be overcome by the use of separate heat transfer surfaces in two sequential boiling zones. The heat transfer improvement obtained with the new configuration is described. Data are presented for a pilot scale test unit which demonstrate the capability for reduction of reboiler-condenser temperature difference by more than 1/3.

Large-Scale Filter Testing for High-Purity Gas Supply Systems Used in Semiconductor Processing

The development of controlled aerosol generation technology at pressure has made possible fundamental performance measurements on commercial and developmental filters over a wide range of operating conditions. Aerosols were generated by dispersing sodium chloride solution into dry, clean nitrogen at pressure using a modified TSI, Inc. constant output atomizer. The size distributions of the aerosols were measured using a TSI, Inc. differential mobility particle sizer. The geometric mean particle diameter x g and geometric standard deviation of the aerosols were found to vary with atomizer operating condition. The diameter x g was found to depend upon the nitrogen pressure and solution concentration in the atomizer. The salt concentration was varied from 0.001 to 0.1 g/cm3. The aerosol size distribution deviated from log-normal behavior at each operating condition. The size distributions were stable and reproducible. The pressurized aerosols were then used as particle challenges in large-scale performance t...