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1.2.1. Identifying components 
Each regulated component must be assigned a unique identification number, recorded and 
located in the facility and on the Piping and Instrumentation Diagrams. 
1.2.2. Leak definition 
Leak definition means the threshold standard (in ppm). It depends on regulation, component 
type, service and monitoring interval. Leak definition can also be based on visual inspections 
and observations, sound and smell. A leak is detected whenever the measured concentration 
(ppm) exceeds the leak definition. 
1.2.3. Monitoring components 
For many regulations with leak detection provisions, the method for monitoring to detect 
leaking components is EPA Reference Method 21. This procedure uses a portable detecting 

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instrument. Monitoring intervals depend on component type and periodic leak rate but are 
typically weekly, monthly, quarterly, and yearly. 
1.2.4. Repairing components 
Components have to be repair as soon as possible after the leak is detected. The following 
practices can be applied: 
- Tightening bonnet bolts.
- Replacing bonnet bolts.
- Tightening packing gland nuts.
- Injecting lubricant into lubricated packing.
If the repair of any component is technically infeasible without a process unit shutdown, the 
component may be placed on the Delay of Repair list. 
1.2.5. Record keeping 
For each regulated process, a list of ID number for all equipment subject, detailed schematics, 
equipment design specifications, piping and instrumentation diagrams and results of 
performance testing and leak detection monitoring must be maintain. 
For leaking equipment, records, instrument and operator ID numbers and the date the leak 
was detected must be maintained. The dates of each repair attempt and an explanation of the 
attempted repair method is noted. Dates of successful repairs and results of monitoring tests to 
determine if the repair was successful are included. 
2. Flue gases from process heaters and boilers
1,5,6,7,8,13 
Fuel combustion in process heaters and boilers is an important pollutants and greenhouse 
gases emission source. Carbon dioxide (CO
2
) is the principal gas released but nitrogen and 
sulfur oxides (NOx and SOx), carbon monoxide (CO), organic compounds and particulate 
matters (PM) are also released in non negligible quantities. In order to reduce the overall air 
emissions of a refinery or a petrochemical plant, these emissions must be taken into account. 
Several technologies exist to reduce these emissions. The present report synthesizes them. 
2.1. General 
In process heaters and boilers in refineries and petrochemical plants, two major types of fuel 
are burned by combustion sources: fuel gas and fuel oil.
Refinery fuel gas is a collection of light gases generated in a number of processing units in the 
refinery. It contains principally hydrogen and methane and variable amounts of light 
hydrocarbons such as ethane, ethylene or propane. It can also contain hydrogen sulfide in 
trace amounts.
Fuel oil is a fraction obtained from petroleum distillation. It can be divided in two categories: 
distillate oils and residual oils, further distinguished by grade numbers with 1 and 2 being 
distillate oils and 5 and 6 being residual oils: 
- Grade 1: Light domestic fuel oil-distillate. 
- Grade 2: Medium domestic fuel oil-distillate. 
- Grade 3: Heavy domestic fuel oil-distillate. 
- Grade 4: Light industrial fuel oil. 

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- Grade 5: Medium industrial fuel oil. 
- Grade 6: Heavy industrial fuel oil. 
There are four major types of boilers used in industrial applications: watertube, firetube, cast 
iron and tubeless design. Boilers design and size, orientation of heat transfer surfaces and 
burner configuration are factors that influence strongly emissions and the potential for 
controlling emissions. 
Emissions depend also on type and composition of the fuel. Because the combustion 
characteristics are different, their combustion can produce significantly different emissions. 
Among these emissions can be found: 
- Particulate emissions, filterable or condensable, which depends on the completeness of 
combustion and the initial fuel ash content. 
- Nitrogen oxides emissions, due either to thermal fixation of atmospheric nitrogen in the 
combustion air (thermal NOx), or to the conversion of chemically bound nitrogen in the fuel 
(fuel NOx). 
- Sulfur oxides emissions, that are generated during combustion from the oxidation of sulfur 
contained in the fuel. 
- Carbon monoxide and organic compounds emissions, which depends on the combustion 
efficiency of the fuel. 
- Trace metals emissions, which depend on the initial fuel metals content. 
All these emissions can be estimated thanks to emission factors available in EPA literature. 
Control techniques for the reduction of NOx, SOx and particulate matters are described and 
compared below as these three types of emission are the most relevant. 
2.2. Control techniques for NOx emissions reduction 
NOx reduction in boilers and process heaters can be achieved with combustion modification 
and flue gas treatment or a combination of these. The choice of the technique depends on the 
type and size of the boiler or heater, the fuel characteristics and the flexibility for 
modifications. Practically, NOx reductions consist in thermal NOx* reduction and fuel NOx** 
reduction. When fuel with low nitrogen content is used, such as fuel gas or distillate oil, 
thermal NOx is the only component that can be controlled. 
* Thermal NOx is produced by combination at high flame temperature of nitrogen and 
oxygen contained in the combustion air supply. It is produced during the combustion of both 
fuel gases and fuel oils. 
** Fuel NOx is produced by combination of nitrogen contained in the fuel with excess 
oxygen contained in the combustion air. It is only a problem with fuel oils containing bound 
nitrogen. 
Combustion control involves consequently three main strategies: 
- Reducing peak temperatures in the combustion zone. 
- Reducing the gas residence time in the high-temperature zone. 
- Reducing oxygen concentrations in the combustion zone. 

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These changes can be achieved with process modifications or operating conditions 
modifications.
Finally, the flue gas treatment allows reducing NOx emissions.
Here below different technologies are generally and shortly described. The table synthesized 
information available concerning efficiency and applicability of these technologies on process 
heaters or boilers in petroleum industry, using fuel oil or fuel gas. Only methods that have 
been used for industrial process heaters or boilers are considered here but many others 
techniques exist.