Air Pollution Control Equipment Services, Emissions

Coal-fired opacity technology being demonstrated in the U.S.

Oct. 2, 2003 — A particulate agglomeration technology for coal-fired power plants, developed in Australia and brought to the U.S. by Southern Company and Indigo Technologies, Brisbane, Australia, is now being demonstrated on a Southern Company plant in Mississippi.

The technology now has the additional backing and cooperation of EPRI, Entergy, Cinergy, Ontario Power Generation, First Energy and Duke. Several more U.S. utilities are also considering participation.

The device – the Indigo Agglomerator – works by charging particulate matter both positively and negatively, causing the formation of larger particle clusters that can be removed from stack gases more easily than by electrostatic precipitators alone. “The fine negative particles are attracted to the large positive particles and vice-versa, creating particles of about 10 microns in size,” says Bob Crynack, president of Indigo Technologies LLC.

The first prototype Indigo Agglomerator was installed in December 2000 at Delta Electricity’s Vales Point Power Station in New South Wales, Australia. That installation verified the technology and provided data for the design of a full commercial installation. In March of this year, the first U.S. commercial installation was completed during a four-week outage at Mississippi Power Company’s Watson Plant in Gulfport, Miss.

The device was installed on Unit 4, a 250 MW opposed wall-fired boiler with two separate exhaust gas treatment and monitoring systems. The plant burns a variety of foreign and domestic coals.

Each of the plant’s gas treatment and monitoring systems has an air heater for waste heat recovery, an electrostatic precipitator (ESP) for dust removal and an induced draft fan to maintain a slightly negative furnace pressure and convey gas into a common exhaust chimney.

The monitoring system on each system measures gas flow, gas temperature and opacity (an optical measurement of dust emissions). The agglomerator was installed in the B exhaust gas treatment system between the air heater and the ESP.

Preliminary tests indicate up to 70% reduction in opacity levels, a 45% reduction in outlet dust load, and a reduction in PM 2.5 fine particulate emissions of more than 50%.

The agglomerator uses two key processes to reduce fine particle emissions. A bi-polar charger is used to charge half of the dust positively and half negatively. The bi-polar charger has a series of alternating positive and negative parallel passages that the gas and dust pass through to acquire a positive or negative charge.

The second key process is a specially designed mixing system that causes the fine positive particles to be carried by the gas and mixed with the large negative particles emitting from the adjacent negative passage. This mixing system also causes the fine negatively charged particles to mix with the large positive particles. This results in the oppositely charged particles attaching to each other and forming agglomerates.

The particle size distribution confirms that these results are due to a reduction in fine particle emissions, showing a greater than 350% reduction at 0.8 micron at the ESP outlet. Particles in the 1-micron size range have a large effect on the visibility of emissions, hence the large opacity reduction.

Source: This article is part of the Power Engineering October 2003 issue.

Air Pollution Control Equipment Services, Emissions

Coal-Fired Opacity Technology Being Demonstrated in the U.S.

Issue 10 and Volume 107.

A particulate agglomeration technology for coal-fired power plants, developed in Australia and brought to the U.S. by Southern Company and Indigo Technologies, Brisbane, Australia, is now being demonstrated on a Southern Company plant in Mississippi. The technology now has the additional backing and cooperation of EPRI, Entergy, Cinergy, Ontario Power Generation, First Energy and Duke. Several more U.S. utilities are also considering participation.

The device — the Indigo Agglomerator — works by charging particulate matter both positively and negatively, causing the formation of larger particle clusters that can be removed from stack gases more easily than by electrostatic precipitators alone. “The fine negative particles are attracted to the large positive particles and vice-versa, creating particles of about 10 microns in size,” says Bob Crynack, president of Indigo Technologies LLC.


This view of the agglomerator installation on Mississippi Power’s Watson Unit 4 shows the device between the electrostatic precipitator inlet nozzle (left) and the air heater, (right). Photo courtesy of Mississippi Power Company.
Click here to enlarge image

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The first prototype Indigo Agglomerator was installed in December 2000 at Delta Electricity’s Vales Point Power Station in New South Wales, Australia. That installation verified the technology and provided data for the design of a full commercial installation. In March of this year, the first U.S. commercial installation was completed during a four-week outage at Mississippi Power Company’s Watson Plant in Gulfport, Miss. The device was installed on Unit 4, a 250 MW opposed wall-fired boiler with two separate exhaust gas treatment and monitoring systems. The plant burns a variety of foreign and domestic coals.

Each of the plant’s gas treatment and monitoring systems has an air heater for waste heat recovery, an electrostatic precipitator (ESP) for dust removal and an induced draft fan to maintain a slightly negative furnace pressure and convey gas into a common exhaust chimney. The monitoring system on each system measures gas flow, gas temperature and opacity (an optical measurement of dust emissions). The agglomerator was installed in the B exhaust gas treatment system between the air heater and the ESP.

Preliminary tests indicate up to 70% reduction in opacity levels, a 45% reduction in outlet dust load, and a reduction in PM 2.5 fine particulate emissions of more than 50%.

The agglomerator uses two key processes to reduce fine particle emissions. A bi-polar charger is used to charge half of the dust positively and half negatively. The bi-polar charger has a series of alternating positive and negative parallel passages that the gas and dust pass through to acquire a positive or negative charge. The second key process is a specially designed mixing system that causes the fine positive particles to be carried by the gas and mixed with the large negative particles emitting from the adjacent negative passage. This mixing system also causes the fine negatively charged particles to mix with the large positive particles. This results in the oppositely charged particles attaching to each other and forming agglomerates.

The particle size distribution confirms that these results are due to a reduction in fine particle emissions, showing a greater than 350% reduction at 0.8 micron at the ESP outlet. Particles in the 1-micron size range have a large effect on the visibility of emissions, hence the large opacity reduction.


Study Aims at Reducing Power Plant Water Consumption

Power generation is second only to agriculture as the largest domestic user of water, accounting for 39 percent of all freshwater withdrawals in the nation. A project is currently underway to address one element of power plant water consumption — water contained in the exhaust gas of coal-fired power plants.

The University of North Dakota (UND) Energy & Environmental Research Center (EERC) will conduct a research project on behalf of the U.S. Department of Energy’s National Energy Technology Laboratory to test and evaluate a new process to remove water from plant exhaust gases in the hope of conserving water resources, improving power plant efficiency, and reducing harmful emissions released into the atmosphere.

EERC and Siemens Westinghouse Power Corporation have been selected to perform the two-year demonstration project.