Lowering Emissions

Ask an Expert From: Products Finishing, , from Ti6 Consulting International

Posted on: 1/11/2011

We are facing lowering the CO2 emissions from our factory. Our biggest emission point is our electrocoat system. What areas can we change or better, to meet the stringent limits we have on our emissions?

Q. We are facing lowering the CO2 emissions from our factory. Our biggest emission point is our electrocoat system. What areas can we change or better, to meet the stringent limits we have on our emissions? We are using an epoxy resin with cathodic application in a monorail conveyor dip. J.K.L.

 
 
 
A. The Kyoto agreement went into effect in 2009, after the final endorsement of the world two biggest industrialized powers, the United States and China. Some of the objectives of the existing Kyoto guidelines is to reduce green house CO2 gas emissions worldwide. Many countries have already implemented monitoring, reporting and release emissions limitations to the biggest polluters and considering long term strategies for the low contributors.  
 
Although electrocoaters, including those using the latest electrocoat technologies offered by major worldwide suppliers, are not major contributors to country-wide CO2 emissions, some like you, and because of specific location, face the dilemma of what to do. Some companies will choose buying credits to offset emissions, others will implement renewable energy sources to offset emissions, and others will choose to make process modifications. 
 
Your question indicates that you are considering process modifications and as such I will focus my answer in that direction. From that perspective, the best alternative for electrocoaters is to review the newest technologies offered by electrocoat suppliers and to look at alternative cure systems. Installing renewable energy sources to generate negative CO2 emissions and reduce overall loads could be the subject of another answer. 
 
In order to evaluate the newest technologies materials and decide which one provides the lowest CO2 overall emissions you may have to perform some carbon (C) material balances in your overall electrocoat process. Although the material balance involved may seem complicated, it may be easier if the balance is made in sub-systems and evaluated individually to determine the best overall emission load. 
 
The five major contributing factors to CO2 emissions from a typical electrocoat system operation come from the type of resin and paste used, the solvent additives you use, the oven emissions due to the combustion products released by the type of fuel used to cure the electrocoat, and the polymerization by-products released in the oven during cure and shrinking of the electrocoat material. Lastly, CO2 is released during the pretreatment stages of the electrocoat system from the combustion gases needed to heat the high temperature stages such as cleaners and phosphates.
 
To properly evaluate and compare technologies, you must look at the organic carbon concentration (in C or VOCs), in mg/liter or Lbs/gal, of the components and solvents of your 1K or 2 K electrocoat material. The lower the organic content or concentration, the lower the potential CO2 load in mass units in Kgs or Lbs. You can minimize CO2 emission loads by using best available electrocoat technologies containing zero VOC materials.  
 
Also you must look at your solvent usage: You either add to the electrocoat tank directly, or thru permeate make-up additions. Look at your overall solvent monthly usages and determine how many Kgs or Lbs you use. The best technologies nowadays are those that do not require solvent additions and need only DI or RO water to make-up direct or indirect additions to the electrocoat tank. Some suppliers now have electrocoat systems that are VOC free and therefore contribute to zero CO2 emissions loads. Some of those electrocoat systems are of wide use and have OEM specification approvals in the automotive, truck, construction, agricultural, appliance and other industries. Additionally those electrocoat systems are very friendly to operate.
 
Then you must look at your oven and your cure emissions.
 
These COemissions are the result of burning the fuel used in your specific oven to reach temperature and cure the electrocoat, plus the amount of COcoming from the by-products of crosslinking or poly-merization of the electrocoat materials during cure. 
 
As an overall rule, the lower the electrocoat cure temperature, the lower the overall material losses or shrinkage and therefore lower CO2 emissions. Typically those low temperature technologies are the ones that provide the lowest resin weight loss (shrinkage) and lowest CO2 emissions. Not only do you benefit from the lower weight loss but you also benefit from the lower cure temperature and the less fuel burning, significantly reducing your COemissions.
 
Best available electrocoat technologies cure at relatively low temperatures (280–325°F) and are offered by several worldwide suppliers (as a comparison, older electrocoat technologies cure at 350 or 375°F). These best available electrocoat technologies provide epoxy materials that provide CO2 levels of less than 0.1% by weight. 
 
Additionally you must look at alternative fuels or cure systems such as infrared IR. Eliminating the combustion fuel used (natural gas, propane, LPG, etc) can eliminate the direct generation and release of combustion CO2. Today many parts are cured with IR technologies that contribute to lower CO2 emissions and more sustainable systems. Additionally, those systems require less floor space and shorter process cycle times.
 
Lastly, you must look at your pretreatment system to evaluate potential sources of CO2. Although typical pretreatments for electrocoat systems are inorganic based and do not contribute directly to CO2 load emissions, the combustion fuels used to heat cleaner and phosphate stages must be evaluated to determine their CO2 contribution. 
 
Heating systems that are based on alternative energy such as solar hot water can significantly contribute to lower overall CO2 loads not only by eliminating the combustion CO2 but also by generating negative CO2 and offsetting other process emissions. Your best decision will involve performing several material and energy balances, and deciding which ones provide the lowest emissions. Good luck with your review and evaluation! 


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