Mechanistic Study of Water/Solids Settling in a Diluted Bitumen System: Statistical and Image Analysis

Mechanistic study of Water/Solids Settling in a Diluted Bitumen System: Statistical and Image analysis

Nitin Arora¹ (nitin@ualberta.ca)

Suzanne M. Kresta¹ (kresta@ualberta.ca)

Samson Ng² (ng.samson@syncrude.com)

Sujit Bhattacharya² (bhattacharya.sujit@syncrude.com)

1.      Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 2V4, Canada

2.      Syncrude Canada Ltd., Edmonton, AB T6N 1H4, Canada

 

Keywords: nearest neighbor analysis, froth, sweep flocculation, clays, floc size

 

Abstract

The removal of water and solids (clays and heavy minerals) from bitumen froth is a key step in bitumen extraction from Athabasca oil sands ¹. Bitumen froth contains approximately 60% bitumen, 30% water and 10% solids by mass ¹. Bitumen froth is diluted with naphthenic solvent followed by demulsifier addition to remove water and solids. To achieve the desired level of dewatering, process specifications for both the  bulk concentration of demulsifier and the mixing  conditions (injection concentration, energy dissipation  and mixing time) must be determined². The presence of asphaltenes, naphthenic acids and bi-wettable solids on bitumen-water interface¹ makes water/solids separation from bitumen, a slow and difficult process. The goal of this work is to determine the settling mechanism (sweep flocculation, coalescence) and interactions between particles and drops (water-water, water-solid and solid-solid) using spatial statistics and image analysis.

An image analysis protocol for drop size distribution of spherical water drops was previously developed for diluted bitumen system ³. However, the protocol could not be applied to bitumen froth because of non-spherical water drops and higher solids content (Figure 1). There is a need for development of image analysis algorithm for froth. 

Figure 1: Microscope image with 40X objective containing spherical and non-spherical drops and solids.

Figure 2: Cluster identification after pre-processing of Figure 1.

We have developed a protocol which isolates objects (solids and water) from a microscope image and determines their location. A series of test images containing two objects (A and B corresponding to water and solids) with varying amounts of clustering have been developed to test the point-nearest-neighbor (PNN) method for cluster detection. PNN method provides an overall clustering tendency in an image; however, the method cannot quantify the number, size and location of clusters in an image space. A separate protocol is being developed to obtain this information (Figure 2). Once developed, the image analysis protocol will be integrated with a real time imaging system to monitor clustering and hence detecting operational problems.

Highlights

·         Demulsifier performance can be monitored by cluster detection of bitumen froth images.

·         The composition of the clusters: clay-water, water-water, clay-clay, can also be detected.

·         The water/solid settling mechanism affects demulsifier performance and settling time.

 

References

1.        Masliyah, J.; Xu Z.; Dabros M ;Czarneck. J. Chapter 7. Froth Treatment, Tipman R. In: Handbook on Theory and Practice of Bitumen Recovery from Athabasca Oil Sands Volume II: Industrial Practice. Kingsley Knowledge Publishing; 2013:211-250.

2.        Chong JY. Mixing Effects on Chemical Demulsifier Performance in Diluted Bitumen and Froth. 2013.

3.        Leo SS. Measurement and Analysis of Changes in Drop Size Distribution during Bitumen Clarification using Image Analysis. 2013.