Method and system for monitoring combustion source emissions

An emissions monitoring system for monitoring constituent concentration levels in an emission stream flowing through a combustion source exhaust stack, the system comprising:

• a sampling device configured and positioned for extraction of sample gas from the emission stream in the stack, the sampling device comprising a sample probe that includes means for cooling the sample gas in the sample probe to a temperature below about 350° F. but above a dew point temperature of the sample gas;
• a chamber positioned adjacent the stack, the chamber defining a chamber interior;
• means for maintaining in the chamber interior a temperature above a dew point temperature of the sample gas;
• at least one sample gas line in fluid communication with the sampling device, at least a portion of the sample gas line being disposed in the chamber interior;
• means for removing particulate matter from the sample gas, the means for removing particulate matter being disposed in the chamber interior and being in fluid communication with the at least one sample gas line;
• an NO2 converter in fluid communication with a first one of the at least one sample gas line downstream of the means for removing particulate matter, the NO2 converter being operable at temperatures above the dew point temperature of the sample gas to convert NO2 gas in the sample gas to NO gas and being disposed in the chamber interior;
• means for removing water from the sample gas, the means for removing being disposed adjacent the chamber and being in fluid communication with the at least one sample gas line downstream of the NO2 converter;
• and
• a first analyzer in fluid communication with the first one of the at least one sample gas line downstream of the means for removing water, the first analyzer being configured for determination of an NO concentration level in the sample gas.

An emissions monitoring system for monitoring constituent concentration levels in an emission stream flowing through a combustion source exhaust stack, the system comprising:

• a sampling device configured and positioned for extraction of sample gas from the emission stream in the stack, the sampling device comprising a sample probe that includes means for cooling the sample gas in the sample probe to a temperature below about 350° F. but above a dew point temperature of the sample gas;
• a chamber positioned adjacent the stack, the chamber defining a chamber interior;
• a chamber heater disposed in the chamber interior, the chamber heater being adapted for maintaining in the chamber interior a temperature above a dew point temperature of the sample gas;
• at least one sample gas line in fluid communication with the sampling device, at least a portion of the sample gas line being disposed in the chamber interior;
• a filter disposed adjacent the stack, the filter being in fluid communication with the at least one sample gas line so that the sample gas passes through the filter, which removes particulate matter from the sample gas to produce a filtered sample gas;
• an NO2 converter disposed in the chamber interior in fluid communication with a first one of the at least one sample gas line downstream of the filter, the NO2 converter being operable at temperatures above the dew point temperature of the sample gas to convert NO2 gas in the sample gas to NO gas;
• a dryer disposed adjacent the chamber, the dryer being in fluid communication with the at least one sample gas line downstream of the NO2 converter and having a dryer intake for receiving the filtered sample gas and a dryer exit for returning dried filtered sample gas to the at least one sample gas line, the dryer being configured for removing water from the filtered sample gas and for effectively lowering the dew point of the filtered sample gas;
• and
• at least one analyzer in fluid communication with the at least one sample gas line downstream of the dryer, each of the at least one analyzer being configured for determination of a concentration level of a constituent in the dried filtered sample gas.

A method of monitoring a concentration level of NOx in an exhaust stream from a combustion source, the method comprising the steps of:

• capturing sample gas from the exhaust stream using a sample gas probe;
• cooling the sample gas in the sample gas probe to a temperature below about 350° F. but above a dew point temperature of the sample gas;
• converting NO2 in the cooled sample gas to NO by passing the sample gas through a catalytic NO2 converter adapted for operation at temperatures above the dew point temperature of the sample gas;
• removing water from the sample gas by passing the gas through a dryer downstream of the NO2 converter;
• and
• determining a sample gas NO concentration level.

A method of monitoring a concentration level of NOx in an exhaust stream from a combustion source, the method comprising the steps of:

• capturing sample gas from the exhaust stream using a sample gas probe;
• cooling the sample gas in the sample gas probe to a temperature below about 350° F. but above a dew point temperature of the sample gas;
• removing particulate matter from the cooled sample gas;
• converting NO2 in the cooled sample gas to NO by passing the sample gas through a catalytic NO2 converter while maintaining the temperature of the sample gas above the dew point temperature of the sample gas;
• cooling the sample gas to a temperature sufficient to cause water in the sample gas to condense out of the sample gas;
• and
• determining a sample gas NO concentration level;
• wherein the step of converting NO2 precedes the step of cooling the sample gas to a temperature sufficient to cause water in the sample gas to condense out of the sample gas.

A method of monitoring a concentration level of a constituent in an exhaust stream from a combustion source, the method comprising:

• capturing sample gas from the exhaust stream using a sample gas probe;
• cooling the sample gas in the sample gas probe to a temperature below about 350° F. but above a dew point temperature of the sample gas;
• removing particulate matter from the cooled sample gas;
• converting NO2 in the cooled sample gas to NO by passing the sample gas through a catalytic NO2 converter adapted for operation at temperatures above the dew point temperature of the sample gas;
• removing water from the sample gas by passing the sample gas through a dryer downstream of the NO2 converter;
• measuring a sample gas flow rate downstream of the dryer;
• determining a sample gas constituent concentration level;
• introducing a span gas having a known span gas constituent concentration level into the sample gas upstream of the catalytic NO2 converter to form a combined sample and span gas flow;
• measuring a combined sample and span gas flow rate downstream of the dryer;
• determining a combined sample and span gas constituent concentration level;
• and
• determining an overall system bias using the known span gas constituent concentration level, the sample gas constituent concentration level and the combined sample and span gas constituent concentration level.