Pyrolysis of a Single Asphaltene Particle

Pyrolysis of a Single Asphaltene Particle 1

Satarupa Dhir1*, Nirlipt Mahapatra1, Mehdi Alipour1, Rajender Gupta1 Department of Chemical and Materials Engineering, University of Alberta, Canada

Oilsands found in Athabasca and Cold Lake regions of Northern Alberta form Canada’s primary source of energy reserves. Asphaltene, a significant part of bitumen is often considered to be the least valuable component of crude oil due to various factors such as difficulty in transporting and processing. However, utilization of asphaltene plays a crucial role in overall economics of oilsands extraction. Gasification of asphaltene can result in much needed hydrogen for upgrading of bitumen. Pyrolysis is the first step in gasification that directs formation of soot formation on one hand and char formation on the other hand. Very limited study has been carried out on pyrolysis of asphaltenes in entrained bed conditions. Single particle investigations are useful since they are conducted in a well-controlled environment allowing elimination of complexities arising from particle-particle interactions. In this work, pyrolysis of pulverised Asphaltene feedstock is carried out in a drop tube furnace (DTF) maintained in atmospheric pressure. The furnace constitutes of a quartz tube which is electrically heated to temperature ranging from 600-1000 ˚C. The volatiles produced passes through a bed of activated carbon and water scrubber before being released to the vent. Pulverised Asphaltene particles ranging from 1.7mm- 250µm are passed one particle at a time through a double valve feeder. Effect of particle temperature and particle size on char formation and char characteristics were investigated. The primary objective is to determine, if the pyrolysis takes place on the surface or from the whole particle forming a hollow char particle. Chars obtained from higher particle size (1.7mm to 0.85mm) at 600 ˚C exhibited similar morphology to that of pure asphaltenes. This can be attributed to the incomplete pyrolysis, as the particle does not reach the required temperature during dropping down in the furnace. The pyrolysis of particle sizes ranging from 425µm-250µm at higher temperatures 700-900 ˚C showed better results with 10-2% volatile matter remaining in char. SEM images as well as cross sectional images of char particles indicated that cenospheres with hollow structure starts to form at temperature greater than 800 ᵒC for particle size smaller than 425µm. Fragmentation of char particles occurs at higher temperature. Cross-sectional images shows that the cenospheres are hollow in nature with porosity increasing at higher temperature. Further, characterisation techniques such as FTIR and EDX are being carried out to understand the presence of functional group and elemental composition in char at varying operating conditions.

Figure 1: Experimental setup for pyrolysis of asphaltenes

Figure 2: SEM and CS SEM of char at 800 ᵒC

Figure 3: SEM and CS SEM of char at 900 ᵒC

Q1. Industrial gasification occurs at high temperatures, Why is the temperature kept low for this study? Q2. What is the significance of morphology/SEM study? Q3. Why Potassium emission is low compared to sodium? Or Alkali metal compounds have low boiling point, why are they present in significant amount at higher temperatures as 900C?