No . Waste Origin
1 Spent clay
2
3 CTP
4 RIB
5 VGO
Spent activated carbon
Used clay filter from kerosene treating unit
Water content Ignition Loss Oil Content % % mg / kg-dry
14.3 7.2 162,000
Demin water treatment 18.6 78.3 3,800
Sludge from effluent water treatment ( physical chemical treatment )
Oily surface water in remote impounding basin that contains sludge
Vacuum gas oil from tank maintenance and desludging
75.9 34.2 206,000
29.9 91.8 684,000
25.0 95.3 874,000
Table 1 : Identified refinery hazardous wastes for testing and initial characterisation results .
significantly ( 80-90 % from the initial waste weight ), reducing the footprint for disposal , the treatment costs and further treatment . Carbonisation also produces charcoal that can be used as fertiliser or soil conditioner and reduces greenhouse gas from waste as the carbonisation process stabilises the organic matter in waste , thus reducing gas emissions from decomposition . The targeted waste for assessment is sludge waste from wastewater operations and oily sludge from tank cleaning activities , with other types of wastes such as used activated carbons being considered .
Pilot Testing Procedures
The pilot testing programme was planned in two phases — in 2022 and 2023 . Phase 1 was conducted using a smaller 200L carbonisation kiln in December 2022 ( see Photos 1 & 2 ). Phase 1 was conducted using refinery hazardous waste samples as in Table 1 . The samples were selected based on waste availability and generation amount . The baseline results before carbonisation testing showed that Compagnie Technique des Petroles ( CTP ) system sludge had the highest water content of 75 % while spent clay had the lowest water content of 14.2 %. Vacuum Gas Oil ( VGO ) sludge and remote impounding basin ( RIB ) sludge samples have the highest oil content ( 684,000- 874,000 mg / kg-dry ) and aligned with ignition loss of 91.8 % and 95.3 %. Spent clay , CTP and RIB samples have significant amounts of hydrocarbon content with low boiling points . In general , most of the waste was high in hydrocarbon content and suitable for testing with a carbonisation unit , since the unit can recover significant amounts of hydrocarbon content based on the volatilisation process .
After the baseline characterisation analysis , all five samples were assessed using a 50kg carbonisation kiln . The testing process is simplified as follows :
The carbonisation system was installed at the pilot site in the MRCSB refinery in the identified area equipped with a low-pressure steam utility line . Waste samples were then prepared with a predetermined amount in treatment trays , with a calculated oil load . Low-pressure steam was then injected and the kiln door was sealed . Steam was continuously supplied to drive away oxygen for an inert atmosphere and efficient heating , and initially , diesel was burned to start indirect heating . Then , hydrocarbon gases , which volatilise at higher temperatures , replaced diesel as heating fuel . The heating was stopped when the carbonisation chamber hits 600 ° C , completing the carbonisation process . To prevent damage to equipment , blowers automatically run until temperatures drop . The system was then allowed to cool overnight . When the carbonisation chamber temperature fell below 50 ° C , the
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