Study of Emission Rates from Fluidized Catalytic Crackers During Start Up Situations

Abstract

Résumé -Étude des taux d'émission des unités de crackage catalytique pendant le démarrage -Les unités de crackage catalytique (FCCU) sont utilisées depuis de nombreuses années dans l'industrie de raffinage du pétrole. En conditions normales, il y a peu de soucis concernant l'émission dans l'atmosphère de poussière de catalyseur venant de ces procédés. Cependant, au démarrage de l'unité, les taux d'émission sont couramment plus élevés que la normale. Un échantillon d'une souche a été prélevé sur un FCCU durant le démarrage pour confirmer l'ampleur des émissions de particules. Cet article présente les résultats de l'échantillon d'une souche prélevé durant les 19 premiers jours après le démarrage de l'unité et discute les différents régimes de transmission de particules dans l'air, qui ont lieu durant cette période. Abstract -Study of Emission Rates from Fluidized Catalytic Crackers During Start Up Situations

Modeling and Characterization of Air Emissions from Laboratory and Industrial Fluidized Beds

“…None of the correlations predicted this sudden drop in emission rates. The initially high emission rate, followed by a sudden drop over time in the laboratory FCCU is very similar to the fluctuations seen in the industrial FCCU as outlined elsewhere [12]. If only the steady-state' emission rates are required, then any of the three correlations appear to work well.…”

“…The correlation of Zenz and Weil again predicts the lowest emission rate with Tasirin and Geldart predicting the highest at over 11,000 mg/m 3 . From Stack tests conducted during a start-up period (refer to [12]), actual FCCU emission range from a peak of ca. 1000 mg/m 3 to a low of ca.…”

Categorisation of Particulate Emissions from a Fluidised Catalytic Cracking Unit

“…The concentration of the small size particles (2.2 -3 mm) are relatively constant during the start up. A detailed review of the sampling data is presented elsewhere [14]. The changing operational conditions during the start up period, as described earlier are represented in Figure 3.…”

“…These include correct unit monitoring, proper design of air pollution control devices and controlling catalyst attrition rates [11 -13]. However, large variations between the quantity and composition of catalyst emissions during start up situations have been identified [14]. It is commonly assumed that these higher than normal start up emissions are caused by dynamic changes in the operating procedures causing temporary cyclone problems or direct failure of specific equipment [15,16].…”

“…For the purpose of this study, start up is defined as the moment that heating of the FCCU occurs. It is important for refiners to understand start up emissions, as they are often significantly larger than normal operating emission levels [14]. Refineries may need to utilise expensive end of pipe treatment options to adhere to set standards or limits on particle emissions, which may only be broken during a start up.…”