NEWS RELEASE                                   JANUARY 2007

Coal-fired Power Plant Becomes A “Green” Chemical Producer

Coal-fired power plants can become major producers of hydrochloric acid and calcium chloride in a win-win situation.  Environmental emissions from the power plant including mercury are reduced.  Environmental emissions from hydrochloric acid manufacture are eliminated.  The net cost of electricity goes down instead of up.  These are the conclusions reached by the McIlvaine Company in its online, Power Plant Air Quality Decisions service.

Power plants emit more than 90 percent of the hydrogen chloride (HCl) escaping stacks in the U.S.  If this HCl were converted to hydrochloric acid, as much as one million tons per year of acid could be generated with a value of $200 million.

By installing a chloride prescrubber ahead of the conventional limestone scrubbing system, the HCl is easily captured and concentrated.  This scrubber will also capture more than 90 percent of the mercury.  The diluted acid is recirculated until equilibrium is reached.  Then a steady stream of dirty acid is removed and cleaned.  The mercury is concentrated in a solid form and easily disposed.  The cleaned acid can be sold or converted to calcium chloride.

The advantage of calcium chloride production by the power plant is that this chemical could be used on unpaved roads in the vicinity of the plant to reduce fugitive dust emissions.  Dust from unpaved roads is ten times greater than that from power plant stacks.

Calcium chloride sprayed on these roads regularly would reduce dust and more than offset any emissions from the plant.  However, because of the high cost of the chemical, states have not been able to fund this beneficial procedure.  If power plants provided calcium chloride at affordable prices, they would become net reducers of dust in their vicinity.

The additional cost for the prescrubber is more than offset by reductions in the SO₂ scrubber and the wastewater treatment.  So when the sales value of the acid is included, the levelized cost of electricity is reduced.

Total emissions from both air and water are reduced.  These include reductions in mercury, HCl, and chlorinated compounds in the water discharges.  The avoided environmental emissions from conventional hydrochloric acid manufacture are also significant.

This is not new untried technology.  A number of prescrubbers are already in use in coal-fired plants around the world.  Waste incinerators are already producing hydrochloric acid and calcium chloride.  The two step scrubbing system is more reliable than the single stage system.  It is also more flexible so it is actually a safer choice.  For example, part of the acid can be reinjected ahead of the SCR to increase mercury removal to whatever efficiency is needed.  This is an important consideration for power plants who are concerned about stringent mercury rules.

There are two reasons why this is now the time to implement the technology.  First, there is now a need to remove the mercury and concern that the capture does not result in transfer to the water or the gypsum.  Secondly, there are now materials of construction to handle the highly acidic conditions.  There is also the knowledge to take advantage of materials savings in the down stream portion of the plant once the chlorides have been removed.