Bapco’s refinery gas desulphurisation project (RGDP) included several design and specification features which utilised cutting-edge environmental technology.
This demonstrates Bapco’s commitment to ensuring that investment projects at the refinery not only comply with regulations but also meet the best international standards.
FOR THE FUTURE
The RGDP is designed in anticipation of future regulations. SO2 emission limits in Bahrain are currently determined by the emissions from the burning of domestically produced natural gas - known as Khuff gas – which has an H2S content of 600 particles per million (ppm).
Refinery off-gas streams from typical distillation and conversion units may contain H2S in concentration up to 20,000 ppm. Now, the RGDP will desulphurise all untreated off-gas streams so that the H2S content in the treated gas will be below 150 ppm, far below the limit prescribed by current regulations, in anticipation of tighter future regulations.
DOUBLE SEALS
Double seals on pumps, meanwhile, have been installed to limit fugitive emissions, on all mechanical pump seals operating on sour water or amine service when the H2S concentration exceeds 500 ppm. Upon failure of single seals, H2S can be released to the atmosphere, but with double seals, the releases can be contained within the process upon seal failure, thus mitigating fugitive emissions to air and resultant health hazards.
ROUND-THE CLOCK OP
Also unit redundancy will now permit operations 365 days per year
In order to meet air and effluent environmental regulation on a continuous basis without having to shut down revenue generating facilities it is essential to incorporate redundancy into the treating facilities.
In this regard Bapco’s RGDP solution for treating H2S and sour water was to provide 100 per cent redundancy. Thus after the RGDP, Bapco now has two sulphur recovery units and two sour water stripping units, both fully operational. In the event of failure or a planned turnaround of one unit the other immediately takes the load. This way, 365 days of operation are permissible without violating the emission regulations while preserving the cash flow from revenue-generating units.
DEGASSING
Liquid sulphur produced from the sulphur recovery unit contains dissolved H2S. This dissolved H2S is retained in the sulphur, some of it even after pelletisation, but only to be released at some time later. These fugitive H2S emissions are a health concern to personnel working in and around sulphur products.
Under the RGDP, Bapco installed facilities in the liquid sulphur pits to remove this trapped H2S from within the sulphur, thereby creates a healthier and safer environment for those working in and around the process areas.
DISPERSION MODELLING
Bapco commissioned a specialist consultant to carry out an air quality assessment for the RGDP project to predict the ground level concentration of SO2 and nitrogen oxide (NOX) at various residential centres on the island.
Current emissions from the refinery were predicated to exceed limits in some instances. However, the results predicted that emissions would be reduced to 94 per cent of current level and ground level concentrations would be within Bahrain and WHO standards
Thus, the investment in state-of-the-art dispersion modelling technology provided an immediate visual report on predicted outcome.
This assessment was also presented to the Bahrain government’s Environmental Authority to demonstrate the favourable impact of the RGDP project.
SEAL OF APPROVAL
In accordance with the government’s requirements for the environmental assessment of projects, Bapco submitted an environmental screening report to obtain approval for the project. The submission provided full data on chemicals used in the project, fugitive emissions, effluents discharged and process solid wastes, together with Bapco’s environmental management structure and policy.
GREEN BUILDERS
Finally, Bapco adopted the policy to construct the RGDP facilities in full compliance with safety and environmental regulations. Contractors and sub-contractors were provided detailed guidelines to ensure safety and environmental protection. In addition a project specification was in all bidding documents to explain their role and responsibilities for safety and environmental compliance during construction.
