The Skinny on Boiler Emissions

Emissions

Because of all the political dialogue, as a population, we tend to have heard about emissions in one form or another.  With my recent blogs on Boiler MACT regulations, I thought it would make a good article to talk about the types of emissions we see in our industry and what can be done to do away with emissions or mitigate their effects.  Although my slant as an employee of E-Tech, Inc. is to offer solutions to emission issues, boiler economizers such as we design and manufacture, can only moderate these pollutants to a certain degree.  Furthermore, my knowledge base is limited to our products to an extent.  Boiler manufacturers have more impact on this and therefore, more smarts.

At E-Tech, my company, we concern ourselves primarily with:

·         Nitrogen compounds (NO_X)

·         Sulfur Oxides (SO_X)

·         Volatile Organic Compounds (VOC’s)

Certainly there are other things to worry about such as particulates but that is not within the scope of this blog.

NITROGEN COUPONDS (NO_X)

NO_X is a generic term for nitric oxide (NO) and nitrogen dioxide (NO2) and is formed from the reaction of nitrogen and oxygen during the combustion process.  NO_X is not to be confused with nitrous oxide (laughing gas, for example).   Although this discussion is related to boilers, NO_X is produced from any combustion process, particularly from automobiles.  NO_X Pollution from cars, trucks, planes, etc., can be particularly high in areas of high motor vehicle activity and around densly populated parts of the country. 

While it is true that NO_X can encourage the formation of acid rain, it is not the main reason we look at reducing them.  It is because of the effects on the production of ozone that we endeavor to lower this pollutant.  To reduce NO_X a variety of methods have been introduced over the years, and as time has gone on, improvements have been made.  Here, in no order, are several.

·         Selective Catalytic Reduction (SCR) – In this method, ammonia is injected in the boiler exhaust gases with a catalyst that allows the ammonia to reduce the NO_X

·         Flue Gas Recirculation (FGR) – This is been around for a while and is an effective means of reducing emissions on smaller boilers (30,000 PPH or less is a good range).  In essence FGR involves recirculating cooler exhaust gases back into the combustion process to lower the temperature.

·         Burner Modifications – Fifteen years ago or more, burners having NO_X levels of 30-50 PPM were considered pretty cutting edge.   Since then, some of the ultra-low NO_X burners offer as low as 5 PPM

·         Efficiency – Finally, this is where E-Tech comes in.  By adding heat recovery equipment to the boiler, the firing rate for any given output is reduced, thereby lowering emissions.

SULFUR COMPOUNDS (SO_X)

I remember years ago when I first heard about acid rain.  It was in New England where I was born and it was having an impact on the lakes and trees of the area.  Although I didn’t understand it at that time, I remember there were certain parts of the country – the rust belt (before it got rusty) – that were blamed for the phenomenon.  While acid rain has been around for centuries the issue became more urgent in the 1970s and 1980s in the US.  Many laws have been promulgated through Congress and the EPA to help turn back the clock to cleaner times.  One of the biggest culprits in acid rain is sulfur.  Even though sulfur compounds can be naturally formed (volcanoes, etc.), much is produced by man through the burning of sulfur-laden fuels such as coal and heavy oil.

As a large portion of our nation’s utilities produce electricity through the burning of coal, the industry has done much to reduce its pollution footprint.  Many coal-burning plants use flue gas desulfurization, a process by which 95% or more of the SO₂ will be removed.  In addition, as natural gas has become more plentiful and less costly, it is being used more and more; its future looks bright not only in the boiler market but also for fleets of cars and trucks.

Although I wish I could plug economizers here, there’s not much an economizer can do except lower the firing rate of the boiler.

VOLATILE ORGANIC COMPOUNDS (VOC)

VOCs are compounds with high vapor pressures and low water solubility.  They are comprised mainly of carbon and hydrogen.  Many VOCs are dangerous to both human health and the environment and may include both manmade as well as naturally occurring elements.  E-Tech has worked with many companies involved in the design and manufacturing of thermal oxidizers, one method of destroying hazardous pollutants.

My blog quote for the day is about autumn, my favorite time of year.

Autumn is a second spring when every leaf is a flower.  ~ Albert Camus