OCR Text |
Show particles and their accuracy is limited. The optical pyrometer is ideally suited for the task. Like the disappearing filament pyrometer it is a nonintrusive instrument. And with proper calibration it is more accurate. However, its main advantage lies in the fact that it has a fast response time and can therefore gather data during transient processes. The rate of data acquisition is really limited by electronic respose time and data storage capacity. In this paper, the theoretical basis of the concept shall be described in detail. Then, results from actual pyrometry on single char particles will be shown. The types of information that can be derived from these measurements and their influence on understanding combustion phenomena will be demonstrated. Work along similar or complementary lines has been performed by many researchers in the field. The temperature of individual buring particles has been measured by McLean et aJ. [1], Mitchell and McLean [2], Timothy et al. [3], and Jorgensen and Zuiderwyk [4]. The measurements involve either a particle at a particular location in a furnace or the complete temperature-time history of the particle. Our measurements in this paper fall in the latter category. It should be mentioned that the technique can be modified to yield particle sizes and velocities in addition to temperature at fixed locations [2]. 2. EXPERIMENTAL METHODS 2.1 Char Preparation Chars were made from a high-volatile A bituminous coal (PSOC 1451). The coal was ground in a mechanized mortar and pestle grinder in air for approximately 30 seconds and then sieved on a mechanical shaker for 10 minutes into the following size fractions: less than 45J.LID, 45-53J.Lm, 53-74J.Lm, 74-104J.Lm, 104-125J.Lm and greater than 125J.Lm. Chars were then generated from the 53-74J.Lm size fraction of coal. The coal was pyrolysed in an electrically heated drop tube furnace. The furnace consists of an alumina tube of 5 cm internal diameter heated by Kanthal heating 3 |