A pressurized thermogravimetric analyzer for use in studies of gas/solid systems

A TG-151 Thermogravimetric Experimental Station, which measures and records weight changes of a solid material over a wide dynamic temperature range at a wide range of pressures in controlled environments, was purchased from Cahn Instruments, Inc. The TG-151 permits temperature to be programmed to follow a precise temperature profile of ramp and/or isothermal segments while monitoring the changes in weight of solid samples exposed to a gaseous environment of specified composition at a preset pressure. Weight and temperature measurements are made at user-specified time intervals and total time (up to 48 hours). Data are stored on the disk of a dedicated computer. The data can be processed by a data analysis program or exported to spreadsheet programs. The pressure vessel is designed to operate in vacuum to 10(exp -5) torr and over a wide range of pressures. At normal room temperature, the TG-151 can operate up to 100 atm and at 1273 K, it can operate up to 70 atm. The null balance has a sensitivity of 10 micrograms, capacity up to 100 grams, and a dynamic range of 10(exp 6):1. Both reducing and oxidizing environments can be established in the reaction chamber. For our specific needs the instrument had to be slightly modified to allow for two reactant gas streams to enter the pressure vessel at prescribed times. This required the purchase and installation of a gas blending system. The gas blending system permits coal and char samples to be heated at a specified rate to a desired temperature in an inert environment before the sample is exposed to an oxidizing environment.