MARKET - REGULATIONS

Mercury Reduction Status and Programs around the World

The U.S., with less than 5 percent of mercury emissions, is leading the way and setting reduction examples for the rest of the world.  Approximately 2,000 tons of mercury are emitted yearly due to human activities. Much of this, in vapor form, travels from continent to continent. So it is a worldwide problem.

The present emissions reflect big reductions both intentional and accidental. Coal-fired power plants in China have installed SO₂ scrubbers and are capturing at least 30 percent of the mercury previously emitted. Most European countries require scrubbers for SO₂ and SCR for NO_x. There is no mercury limit but the scrubber/SCR combination removes much of the mercury.  As a result, coal burning worldwide now accounts for only 600 tons of mercury emissions per year as opposed to gold mining which is 25 percent greater.

Most of the world’s waste incinerators have some form of mercury control, so actual emissions are approximately 50 tons per year. More than 100 tons is captured by pollution control devices.

The U.S. has tough regulations which require compliance over the next three years. They affect coal-fired power plants, cement plants, and industrial boilers. The regulations are based on mercury weight limits per unit of energy consumed or produced.  Regulations elsewhere are based on weight per unit of stack gas discharged.  By taking the details for an average plant one calculates the required limit for existing U.S. coal-fired power plants at 1.7 ug/m³ to 4 ug/m³.

So the U.S. has set limits which are an order of magnitude lower than other countries. But there are local rules and pending rules which are equally stringent.

In Germany power plants burning sewage sludge as well as coal must meet the 30 ug/m³ but one plant is facing a local regulation of 3 ug/m³. One coal-fired power plant in the Netherlands is facing a 2.4 ug/m³ limit. The China Council for International Cooperation has recommended that the limit for coal-fired power plants be reduced from 30 ug/m³ to 5 ug/m³ by 2015 and to 3 ug/m³ by 2020.

The coal-fired power plants in China and Germany need some level of mercury reduction to meet the 30 ug/m³ requirement. Typically the particulate collector and scrubber combination will provide adequate capture. However, mercury levels in the raw coal vary. This means that measurement is necessary and in some cases additional controls will be required.

At this point there are stringent requirements for mercury control from waste incinerators  in most countries. Cement plants, industrial boilers, and utility boilers in the U.S. also now have stringent requirements. The reduction solution varies somewhat from industry to industry but in general, all the same options are available. Decisions are complicated by the fact that mercury removal takes place along with the capture of other pollutants. So all the factors listed below need to be considered:

a.       Process

                                i.            Particulate Type

1.      Electrostatic Precipitator-dry

2.      Electrostatic Precipitator-wet

3.      Fabric Filter

                              ii.            FGD Process

1.      Wet limestone

2.      Spray dryer

3.      Circulating dry scrubber

4.      Dry sorbent injection

                            iii.            Capture Mechanism

1.      Bromine

2.      Chlorine

3.      Activated carbon

4.      Non carbon sorbent

5.      Membrane

6.      Gold amalgamation

                            iv.            Selection Criteria

1.      Efficiency

2.      Performance

3.      Maintenance

4.      Cost

b.      Process Components

                                i.            Capture device in conjunction with particulate device or scrubber

1.      Activated carbon injection systems

2.      Halogen slurry injection systems

3.      Liquid bromine injection

4.      Advanced SCR catalyst

5.      Post scrubber membrane

                              ii.            Monitoring

1.      Continuous emissions monitor

2.      Sorbent trap

                            iii.            Re-emissions Prevention

1.      Chemicals

2.      Activated carbon

                            iv.            Wastewater Treatment

1.      Physical-chemical

2.      Biological

3.      Zero liquid discharge

a.       Thermal evaporation

b.      Pressure evaporation

c.       Flue gas drying

d.      Sidestream spray drier

Ten years ago when U.S. EPA started its investigation process it appeared that activated carbon injection was the best solution across the board. It now is apparent that there are many options which should be considered. McIlvaine has created a free website to help polluters around the world make the best decisions for their plant. Mercury Removal - Continuous Analyses