Technical paper
Moving Targets: How Ever Changing Air Quality Regulations are Driving Process Decisions
Historically, the concern of process engineers was the design and operation of plants to do primarily one thing, efficiently meet product specifications. In today's changing regulatory environment, there are additional concerns design engineers may neglect. These concerns include Volatile Organic Compounds (VOCs) and Hazardous Air Pollutants (HAPs) emissions as exceeding thresholds can limit throughput, increase liability to the operator, and add significant lead time to plant construction or modifications. A case study aimed at debottlenecking a large cryogenic gas plant is presented to investigate a legacy VOC and HAP issue as well as maximize overall plant production. The debottlenecking study focused on multiple amine sweeting units and their associated still vent emissions. Interestingly, methanol was found in surprising amounts in the still vent emissions. Control devices were assessed and subsequently installed to alleviate any future VOC and/or HAP issues and allow for increased production. The regulation of Green House Gases (GHGs) has changed significantly of late, with the likely outcome that treating will be performed in the field at "minor sources". Producers operating large plants already categorized as "major sources" of air pollutants must pay careful attention to these GHGs. A case study of a cryogenic gas plant is presented where increasing plant throughput was potentially bottlenecked due to emissions of CO2 in excess of Prevention of Significant Deterioration (PSD) permitting thresholds. A thorough analysis was performed of the plant to manage CO2 emissions while still maintaining product specifications. This allowed the operator to avoid a long, costly regulatory review and permitting process while still increasing production. With current GHG regulations likely to push gas treating into the field, sour gas streams may be the new bottleneck as SO2 emissions may curtail production due to the National Ambient Air Quality Standard (NAAQS) for SO2. Designers will need to begin evaluating the technologies best suited to work around this issue.
Historically, the concern of process engineers was the design and operation of plants to do primarily one thing, efficiently meet product specifications. In today’s changing regulatory environment, there are additional concerns design engineers may neglect. These concerns include Volatile Organic Compounds (VOCs) and Hazardous Air Pollutants (HAPs) emissions as exceeding thresholds can limit throughput, increase liability to the operator, and add significant lead time to plant construction or modifications. A case study aimed at debottlenecking a large cryogenic gas plant is presented to investigate a legacy VOC and HAP issue as well as maximize overall plant production. The debottlenecking study focused on multiple amine sweeting units and their associated still vent emissions. Interestingly, methanol was found in surprising amounts in the still vent emissions. Control devices were assessed and subsequently installed to alleviate any future VOC and/or HAP issues and allow for increased production. The regulation of Green House Gases (GHGs) has changed significantly of late, with the likely outcome that treating will be performed in the field at “minor sources”. Producers operating large plants already categorized as “major sources” of air pollutants must pay careful attention to these GHGs. A case study of a cryogenic gas plant is presented where increasing plant throughput was potentially bottlenecked due to emissions of CO2 in excess of Prevention of Significant Deterioration (PSD) permitting thresholds. A thorough analysis was performed of the plant to manage CO2 emissions while still maintaining product specifications. This allowed the operator to avoid a long, costly regulatory review and permitting process while still increasing production. With current GHG regulations likely to push gas treating into the field, sour gas streams may be the new bottleneck as SO2 emissions may curtail production due to the National Ambient Air Quality Standard (NAAQS) for SO2. Designers will need to begin evaluating the technologies best suited to work around this issue.