Jul-2004

FCC additive demonstrations: Part 1

A review of the issues associated with the FCC additive testing, data collection and analysis required by the US Environmental Protection Agency’s consent degrees

Guido W Aru
Intercat (Johnson Matthey)

Article Summary

The US Environmental Protection Agency (EPA) consent decrees negotiated with many US refiners require reductions in SO2 and NOx emissions from refinery fluid catalytic cracking (FCC) units. Depending on the negotiated settlement, the refiner may be required to implement hardware solutions, additive solutions or a combination of both to achieve the agreed- upon emissions reductions. Additive-based solutions to SO2 and NOx emissions reductions help refiners avoid expensive capital projects such as construction of wet-gas scrubbers or selective catalytic reduction (SCR) units. However, additive solutions require extensive and complex testing and analysis to support eventual negotiation of final emissions limits.

The EPA and the US Department of Justice (DOJ) have pursued civil enforcement actions against many US refineries under their National Petroleum Refinery Initiative. This initiative is targeted to address four primary compliance and enforcement concerns under the Clean Air Act:
— Prevention of significant deterioration/new source review (NSR)
— New source performance standards (NSPS)
— Leak detection and repair requirement (LDAR)
— Benzene national emissions standards for hazardous air pollutants.

Of the approximately 150 petroleum refineries in the USA, the government has reached settlements covering 42 refineries. These voluntary settlements are known as consent decrees. The settling refiners agree to pay civil penalties when applicable, but more significantly agree to perform significant environmental projects to reduce future emissions. The projects are required for various process units throughout a given refinery. The scope and extent of the remedial environmental investment required is derived through negotiation of the consent decree.

The negotiation of a consent decree for a given company and refinery is a complex process that is in principle driven by the strength and severity of the Clean Air Act violations alleged against a company by the government and the company’s desire to avoid litigation. Relative to the FCC, the EPA has target goals for SO2 (25ppm) and NOx (20ppm) emissions limits. In some agreements, the government is also targeting reductions in CO and particulate matter (PM) emissions, but are beyond the scope of this article. The refiner’s goals are generally to minimise costs and operational impacts of any required environmental projects.

 The SO2 and NOx emissions limits from FCCs and the methods by which to achieve them are all subject to negotiation. When a refiner agrees to implement a hardware solution, such as wet-gas scrubber and/or SCR, FCC SO2 and/or NOx emissions limits are specified in the consent decree. This requires the refiner to design and implement an appropriately-sized unit to meet these limits. With FCC additive solutions or hybrid solutions combining hardware and additives (such as a hydrotreater and SOx additive), final emissions limits are not generally defined in the consent decree. Instead, a testing and demonstration program is defined to determine the performance of the additive(s) in the FCC unit at optimised concentrations. Upon completion of the negotiated protocol, a second negotiation occurs to establish the final limits on SO2 and NOx emissions from the FCC (Figure 1).

In some cases the EPA has insisted on implementation of hardware-based solutions for the consent decree. This provides the government guaranteed emissions limits from the FCC, but at significant financial cost to the refinery. Table 1 shows the comparative costs and benefits discovered by one refiner of a wet-gas scrubber versus an additive solution for a 20000bpd FCC.

The addition system for the SOx additive mentioned in Table 1 is supplied at no-cost by Intercat, with less than $50000 in installation expenses (foundation, piping etc) incurred by the refinery. Baseline SO2 emissions are of the order of 1200 to 1500ppm. In this case, the community around the refinery was particularly concerned with the increased traffic of acid-carrying trucks resulting from the operation of the wet-gas scrubber. This was a significant factor in favour of an additive solution.

 Although the EPA may have a predisposition to a hardware solution at a given refinery, the refiner can use political pressure to obtain a more favourable settlement. In a recent negotiation, for example, one refiner was able to use the regional (state) EPA to influence the federal EPA office and allow an SOx additive solution where a wet-gas scrubber was previously mandated. The refiner agreed to use Intercat’s proprietary additive (Super SOxGetter) at a 10% addition rate until an FCC feed hydrotreater project is completed and the unit brought on-stream. After which, the refiner agreed to conduct an SOx additive testing protocol as previously outlined in Figure 1.

Additive testing requirements
The EPA has greatly expanded the specificity of the consent decrees as they relate to FCC additive testing and demonstration. The consent decrees now generally require:
— EPA approval of additives used, testing protocols and emissions models
— Comparative performance testing of multiple additives to determine best performer
— Specific data collection and reporting requirements.

The increased structure and rigor of the consent decrees increases the complexity of executing FCC additive testing and demonstrations, and requires commitment of greater resources by the refiner. However, the cost savings compared with the implementation of emissions control hardware makes additive-based solutions very attractive. Also, by applying a rigorous and thorough approach to the FCC additive testing process, the refiner is ensured a smoother negotiation process with the EPA to establish final FCC emissions limits.

Testing and demonstration
The FCC SOx and NOx additive testing and demonstration requirements delineated in the consent decrees have evolved to a high-level of specificity. The protocols provide detailed requirements for testing, analysis and EPA approvals of additive selection and finalised testing protocols developed by the refinery.