ENV-16-79 An Overview of Hydrogen Cyanide Air Emission Test Methods to Measure Emissions from Fluidized Catalytic Cracking Units

Description:

Hydrogen cyanide (HCN) emissions from Fluidized Catalytic Cracking Units (FCCU) have come under scrutiny from regulators. Recent testing, starting with the 2011 Refinery ICR test programs, has indicated emissions may be higher than historical data would indicate. Examination of the data suggests the differences in emission levels may be attributable to the test method. Bias problems were recognized with the original HCN test method (EPA CTM 33) that likely stem from problems in maintaining the sodium hydroxide absorbing solution pH. EPA Conditional Test Method (CTM) 33 was superseded by EPA Other Test Method 29, and while OTM 29 overcomes issues associated with CTM 33, it remains a challenging sampling method and is subject to interferents that are present in refinery emissions. HCN emissions can also be measured using EPA Method 320 by Fourier Transform Infrared (FTIR) spectroscopy. This approach has the advantages of an instrumental test method with real-time, on-site data, fast response time, and low detection limits.