NEWS RELEASE                                                                                                                JUNE 2015

Sulfuric Acid Mist Is a Problem Created By Pollutant Reduction

China is among the countries finding that solution of their NOx and SO2 problems create sulfuric acid mist.  The environmental impact is serious and has created an urgency for solution.  Companies with the solution have a big opportunity to expand their worldwide reach.  McIlvaine is conducting a discussion of the problem and the solutions on June 18. More Information

Plants which install NOx control systems and scrubbers are creating sulfuric acid mist.  The mist plumes are often more visible than the exhaust before the major air pollution control investments.  Furthermore, the nearby structures can be quickly damaged by condensing acid mist.

This problem creates a major opportunity for a number of companies.  Suppliers of processes, sorbents, catalysts, filters and heat exchangers have experience which is now applicable around the world.

This acid mist problem affects the design of all the other air pollution control equipment. Knowledge of the solution empowers international suppliers.  In pursuit of the solution, suppliers have discovered ways to make the entire plant more efficient. So this knowledge is even more valuable.

The first knowledge need involves regulatory implications.  SO2 in the flue gas is converted to SO3 in the catalytic reactor used for NOx reduction.  The stack gas is cooled in the scrubber and the SO3 leaving the stack is mostly condensed sulfuric acid mist.  It is small in total mass but very visible and also destructive to nearby buildings.  The mist is often treated as particulate by regulators.  Since limits on particulate are an order of magnitude lower than on SO2, the regulatory impact is very significant.  There are many unresolved issues on measurement and limits on the mist.

The solutions to the SO3 problem are different for each of three air pollution control processes: Wet Calcium, Dry Scrubber and Hot Gas Filter.

Flow Sequence Wet Calcium Dry Scrubber Hot Gas Filter
Fuel High   Sulfur Medium/Low Medium/Low
Combustion LNB,   FGR,  SNCR,  Br LNB,   FGR,  SNCR,  Br LNB,   FGR,  SNCR,  Br but also CaCO3
After   Economizer SCR   with catalyst to deal with SO3, NOx and Mercury ACI,   SCR with catalyst to deal with SO3, NOx and mercury

Ceramic   Catalytic Filter

With   DSI
Air   Pre Heater Sorbent   injection for SO3 and acid gas trim Sorbent   injection for SO3 and acid gas trim Extract   all heat and reduce exit to 200oF
Particulate ESP   or FF Dry   scrubber/FF Already   captured
SO2 Wet   calcium FGD Captured   with particulate Already   captured
Trim   Wet   ESP Not   available Mercury   module

 LNB= low NOx burner, FGR= flue gas recirculation, Br= bromine addition with fuel. SNCR= selective non-catalytic reduction, CaCO3 = pulverized limestone addition in furnace, ACI= activated carbon injection, SCR= selective catalytic reduction, DSI= dry sorbent injection, HE= heat exchanger, ESP= electrostatic precipitator, FF = fabric filter, FGD= flue gas desulfurization .

Each of these alternatives will be reviewed in depth during the discussion.  Each step in the flow sequence will be analyzed.  Also site specific variables will be addressed.  The discussion will be led by world experts.  The webinar will be free to power plants and subscribers to44I Power Plant Air Quality Decisions (Power Plant Decisions Orchard). There is a charge for others.  Details are found at: More Information