Hybrid steam supply system for saving fuel gas and reducing carbon footprint of the oil & gas industry
ADNOC Gas Processing has more than 5,000 TPH steam generation capacity which is equivalent to 3.84 GW thermal energy load. Steam is primarily generated by firing fuel gas. Significant portion of this demand can be alternatively supplied by Solar CSP. Aforementioned magnitude of total steam demand as well as few individual users with 80 to 100 MWth demand indicates application of utility scale Solar CSP. As of now, utility scale use of Solar CSP is mainly for power generation only with just few examples of steam generation for EOR. Continuous downward trend of Levelized Cost of Electricity (LCOE) for Solar CSP has been observed in last few years. In Year 2017, Dubai Electricity and Water Authority (DEWA) awarded the contract to build the 700 megawatt (MW) fourth phase of the Mohammed bin Rashid Al Maktoum Solar Park at LCOE bid of USD 7.3 cents per kilowatt-hour. Significant reduction in CAPEX and accordingly decrease of LCOE to around USD 5.0 cents per kWh is envisaged by eliminating power block and directly utilizing the steam for process heating in industrial applications.
This paper reviews technical viability of hybrid system to supply steam for process heating in the Oil & Gas Industry. Proposed hybrid system is to integrate Solar CSP based steam generation with the existing auxiliary boilers based steam generation by fuel gas. Paper addresses adequacy of available Direct Normal Irradiance for Solar CSP plants with special emphasis on the Middle East region. Paper discusses temperature profiles of end-use applications (like gas sweetening and dehydration etc.) in conjunction with the existing steam system network operating conditions. It also describes supply temperatures of parabolic trough and solar tower CSP technologies along with operating temperature ranges of Heat Transfer Fluids (HTFs) encompassing organic & mineral oils and molten salts. Review of tie-ins for steam supply from Solar CSP to existing network and return of condensate from existing network to Solar CSP has also been presented. Instrumentation & Control philosophy for the proposed hybrid process has also been discussed with focus to minimize additional instrumentation. Paper also examines repercussions of existing auxiliary boilers sustained low load operation due to supply of steam from Solar CSP.
Cost analysis of the proposed hybrid steam supply system has also been presented. It addresses expected LCOE of steam generation from Solar CSP and its feasibility as an alternative to fuel gas based steam generation from existing boilers. Overall impact in terms of reduction in carbon footprint has also been discussed.