Asphaltene Removal in Oil Refinery's Wastewater
Client: Major North American Oil Refinery
This oil refiner contracted with Chester Engineers to discuss the oil/solids at their existing wastewater treatment facility. The issue was two-fold as the oil refiner had first increased their production from 75,000 barrels per day to 120,000 barrels per day thus stressing the hydraulic capacity of the existing wastewater treatment plant (WWTP). Secondly, the frequency of processing heavy/sour Canadian crude blends had increased over nearly the same duration thus increasing the contaminant and in particular the asphaltene loadings through the wastewater treatment plant. The combination of these two influences had substantially increased upsets in the WWTP and the potential for violations.Other process challenges in developing a solution where:
- The frequency and variability in processing sweet and sour crudes.
- High and frequent variability in flows causing chemical control and surge problems with the API Separator.
- pH spikes above 11 causing difficulty in breaking emulsions.
- TSS, TOC, oil and solid variations which resulted in exceeding regulatory requirements.
- Occasional dumping of the rag layer.
Other engineering firms had attempted to develop a process solution prior to Chester Engineers' contract without success.
Once a process solution was developed, a key challenge was to install a temporary system in four months to avoid regulatory actions that could have resulted in the refinery having to limit or curtail production.
The Interdisciplinary Approach
The design-build portion of the project required extensive coordination between the oil refiner (i.e. their safety, environmental, engineering, reliability, maintenance and operations groups), Chester Engineers (as the prime contractor) and each of Chester's subcontractors (i.e. civil, mechanical and electrical) to develop a technically sound and economical design-build approach.
The Sustainable Result
Through extensive testing of several options, Chester Engineers successfully developed a process to remove the asphaltenes from the wastewater. The essence of the process was to intercept and treat the desalter effluent prior to entering the facilities main wastewater treatment plant. Once the process was finalized, the oil refiner contracted with Chester Engineers to install a temporary system through a design-build contract.
Close coordination between the owner, Chester Engineers and subcontractors resulted in the installation of the temporary pre-treatment system that was fully operational within four months. The project was executed on a fast-track design/build basis and was completed within budget and ahead of schedule. To facilitate project collaboration, Chester Engineers developed an extensive 3-D model of the plant which incorporated value-added input from the oil refiner's operations and engineering groups, the sub-contractors for constructability reviews and a review by safety personnel to eliminate any hazards from the design. . To reduce schedule Chester Engineers used early procurement, a design/build contracting format and innovative designs such as modification of frac tanks to function as clarifiers and thickeners to shorten fabrication and construction durations.
The temporary system was finished within four months and the results were beyond expectations as the plant significantly reduced the solids loading on the main wastewater treatment plant bringing it into compliance. Other project benefits included an overall decrease in treatment chemical usage.
The oil refinery then agreed to a design-build contract with Chester Engineers to install the permanent system. Again Chester Engineers developed an extensive 3-D model of the pre-treatment plant with the input of the oil refiner and sub-contractors. The permanent system included not only the pre-treatment plant, but also a new chemical building and polishing sand filters on the back end of the facilities main wastewater treatment. The project was completed ahead of schedule and within budget. The results of the permanent system were even better than the temporary system as the permanent incorporated actual clarifiers and thickeners which enhanced sludge compaction. Better system controls also significantly reduced chemical consumption.
Both the temporary and permanent design-build projects were constructed with zero lost time incidents and zero accidents.