NOx Reduction
Throughout the world, environmental considerations and regulations have made NOx reduction a priority. Emissions requirements are increasingly stringent, and regulations have in many areas sharply reduced the allowable levels of various types of emissions from fired equipment.
OnQuest was established in California and our professionals are therefore highly aware of and mindful of regulatory oversight. As a result, OnQuest has for years specialized in designing furnace applications that incorporate technologies to reduce NOx emissions, volatile organic compounds (VOCs), and hazardous air pollutants (HAPs). A number of methods—including both pre- and post-combustion technologies—can be used to achieve lower levels during start-up and operation of heaters and process plants, and in retrofitted equipment.
Current Burner Design: Efficiency in Controlling Emissions
The designs for new and evolving ultra-low NOx burners largely rely on different flame length and new requirements for burner-to-burner interaction. These changing parameters must be taken into account during design; often, floor-plate or sidewall panel dimensions must be modified to accommodate the new characteristics of these burners. Moreover, burner piping must typically be re-examined to account for the reduced port dimensions of the burner tips.
NOx Reduction Retrofits of Older Burners
Many existing heaters can be retrofitted with ultra-low NOx burners to achieve NOx levels as low as 25 ppm(v). In special cases, emission levels may be even lower. However, incorporating these technologies requires precise design engineering and construction oversight; retrofitting an existing burner design is rarely a straight-forward one for one "change-out" of the burners.
The Ultra-Low Alternative: Selective Catalytic Reduction
In some jurisdictions, regulatory constraints on allowable emissions are particularly tight. When requirements approach the single digit ppm(v), another method for effectively reducing NOx is to use the post-combustion technology called a Selective Catalytic Reduction unit, or SCR unit.
Many innovative retrofits of existing heaters have been performed to accommodate SCR units and their associated real estate needs, pressure drop requirements, and instrumentation and controls for the associated Ammonia Injection. Optimal temperature zones assist in the economic application of an SCR unit, and the means to create these zones often results in significant modifications to the convection sections of the fired heaters.
Experience = Success
OnQuest’s long-term expertise with NOx control in the Los Angeles basin refineries and power plants has made our professionals highly adept at optimizing both installation procedures and project costs for achieving and sustaining the required NOx levels for a given application. Often, we can combine adjacent units for economies of scale. |
