Dealing with mercury from coal-fired power plants

Where does airborne mercury come from, and how do we get rid of it?

12/22/2011


Dear Control Engineering: When I read about new EPA regulations on mercury emissions from coal-fired power plants, I want to know where the mercury comes from, and how to get rid of it.

Power plants do not create mercury, lead, arsenic, or other heavy metals any more than they would be able to create gold. Those pollutants are elemental metals and present in coal. The problem is that when you burn coal, you vaporize those metals and send them out the stack. There is some controversy as to exactly what happens in the atmosphere, but eventually those metals condense, either in their elemental form or after reacting with something else in the process (e.g., chlorine), and fall to earth in rain drops. Rain goes into rivers and lakes, and fish accumulate the metals.

(There are other types of pollutants, such as dioxin, that can be formed in a combustion process, but that’s a different issue.)

Mercury emissions have gone down, at least as a function of total electricity produced, but many plants still have little in the way of abatement equipment. Conventional FGD scrubbers can help with mercury to some extent, but if you really want to cut it down, activated charcoal injection is usually best. If the fluegas is at the right temperature, mercury will condense and stick to finely-ground activated carbon particles blown into the stream. The particles are then removed in a baghouse.

This process works, but the result is contaminated charcoal. The usual disposal method is landfilling or burial. If you put it in an old coal mine, you’re returning it whence it came.

Peter Welander, pwelander(at)cfemedia.com



No comments
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2013 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
The Leaders Under 40 program features outstanding young people who are making a difference in manufacturing. View the 2013 Leaders here.
The new control room: It's got all the bells and whistles - and alarms, too; Remote maintenance; Specifying VFDs
2014 forecast issue: To serve and to manufacture - Veterans will bring skill and discipline to the plant floor if we can find a way to get them there.
2013 Top Plant: Lincoln Electric Company, Cleveland, Ohio
Case Study Database

Case Study Database

Get more exposure for your case study by uploading it to the Plant Engineering case study database, where end-users can identify relevant solutions and explore what the experts are doing to effectively implement a variety of technology and productivity related projects.

These case studies provide examples of how knowledgeable solution providers have used technology, processes and people to create effective and successful implementations in real-world situations. Case studies can be completed by filling out a simple online form where you can outline the project title, abstract, and full story in 1500 words or less; upload photos, videos and a logo.

Click here to visit the Case Study Database and upload your case study.

Bring focus to PLC programming: 5 things to avoid in putting your system together; Managing the DCS upgrade; PLM upgrade: a step-by-step approach
Balancing the bagging triangle; PID tuning improves process efficiency; Standardizing control room HMIs
Commissioning electrical systems in mission critical facilities; Anticipating the Smart Grid; Mitigating arc flash hazards in medium-voltage switchgear; Comparing generator sizing software

Annual Salary Survey

Participate in the 2013 Salary Survey

In a year when manufacturing continued to lead the economic rebound, it makes sense that plant manager bonuses rebounded. Plant Engineering’s annual Salary Survey shows both wages and bonuses rose in 2012 after a retreat the year before.

Average salary across all job titles for plant floor management rose 3.5% to $95,446, and bonus compensation jumped to $15,162, a 4.2% increase from the 2010 level and double the 2011 total, which showed a sharp drop in bonus.

2012 Salary Survey Analysis

2012 Salary Survey Results

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.