Introduction

The following proposal is based on a program created by the Duquesne Light Power Company for the retro-fit of power plants.

Company Background

Duquesne Light, founded in 1880, is the first utility to have installed a plant-wide scrubber system to improve air quality, and also operate the nation’s first nuclear power station. Currently, Duquesne Light and 20 other electric utility companies in the U.S. have joined to form the Clean Air Strategy Group which provides valuable technical and policy related data and information to key U.S. stakeholders and decision makers. In addition to being active in the design of clean air policy, Duquesne Light is involved in the development of technical data and related health effects information. As a member of the Electric Power Research Institute (EPRI), Duquesne Light participates in the EPRI annual ozone and particulate research program.

Duquesne Light’s environmental management program combines and incorporates elements from the International Standards Organization (ISO-14001), the Edison Electric Institute (EEI) and Strategic Environmental Management (SEM) standards. The program is based on a customized approach to meeting the unique needs of each company. It relies on careful planning to set environmental objectives, develop environmental strategies and monitor the achievement of these objectives and strategies.

 

Pollution Control Strategy

Duquesne Light suggests the use of three separate technologies to ensure control of SOx, NOx and particulate matter. The first of these technologies is an electrostatic precipitator (ESP), which will remove a significant percentage of all suspended particulates as they leave the combustion center. Dry flue gas desulfurization will be used to remove compounds containing sulfur and oxygen, thus reducing the possibility of acid rain for the atmosphere in the area surrounding the power plant. Finally, selective catalytic reduction will reduce the emission of large quantities of Nitrogen-Oxygen gases. A detailed description of each of the technologies is provided below.

Electrostatic Precipitator (ESP):

Efficient removal of particulates from stack emissions will be achieved with an electrostatic precipitator (ESP). An ESP is a device that uses electric forces to separate particles from gases. The particles are charged and attracted to plates in the precipitator. Three parameters that have a direct affect on the efficiency of the system are the gas flow rate, area of the plates, and the drift velocity of the particles. Drift velocities are heavily affected by the characteristics of the electric field, including the voltage and currency maintained in the precipitator. These must be controlled in order to keep efficiencies high. Another challenge in retaining maximum performance is the electronic charge distribution, which must be kept uniform in order to ensure that the electric field is fully utilized by the particles.

The collected particles are removed from the charged plates by means of an electronic zapper, which takes time to strike the plates, causing them to vibrate and knock the particle cake into collection bags, or hoppers. The collected fly ash, or waste, is usually placed in landfills, although portions of it can be sold to cement manufacturers. A drawback to this process includes corrosion, which occurs when acidic particles such as sulfur are left on the plates. This can be partially avoided by heating the ESP during start-up and shutdown.

Low-pressure drops, range of particle size collection, simple maintenance, and the ability to handle high gas flow rates characterize the effectiveness of the ESP. Collection efficiencies are on the order of 99.9%, making the ESP a reliable pollution control tool.

Estimated Percent Reduction: 99.3%

Recommended Provider: Hyandai Heavy Industries Co. Ltd. Hong Kong Office

Dry Electrostatic Precipitator (500 MW design)

Dry Flue Gas Desulfurization (FGD):

SO2 can be removed from the gas after it has gone through both the Tangent and ESP and most of the particulates have been removed In the desulfuruization process dry limestone is injected into the boiler creating CaO. In order to collect SO2 properly excess reagent must be added. Although this increases the cost of the system and the load on the ESP, it allows for high collection efficiencies.

Similar to the wet flue gas desulfurization system, the dry FGD system also has a large waste stream that necessitates landfilling, yet the installation costs are less than that of wet FGD systems. The waste from the dry FGD, unlike the wet FGD, can also be separated and sold for cement and other forms of manufacturing, thus creating a secondary source of revenue.

Efficiencies of the dry FGD system are very high with today’s technologies. This system is also proven compatible with the ESP, which allows for high efficiency of removal.

Estimated Percent Reduction: 80.1%

Recommended Provider: Babcock and Wilcox Ltd.

Beijing Office

Selective Catalytic Reduction (SCR):

Although SCR has a higher cost for reducing NOx emissions than comparable technologies, it is more efficient, with 10 percent greater removal rates. Additional systems such as Natural Gas Reburning were considered for simultaneous use with the SCR, however, NGR requires a steady supply of supporting natural gas to enhance the combustion reaction thereby, making this option less desirable. Our models concluded that adding on this system, when the SCR was already in place had a limited effect on total reduction in emissions so the addition cost could not be justified. Therefore we are proposing only the incorporation of an SCR system.

Percent Reduction 73.5%

 

Labor Considerations

We estimate an approximate labor force of 800-1000 employees in the retrofitted plant. Of these employees 50 to 100 will be required to oversee environmental controls. Employees from all engineering disciplines with degrees ranging from undergraduate degrees to doctorates degrees are required. Salaries will range from $25,000 to $150,000. All training will be done internally and take 3-4 years for average plant and environmental control operations. Training will cost approximately $120,000 per employee.

Predicted Averages: for an environmental control employee

Cost Considerations for power plant operations

Process

Capital Cost

Continual/ Maintenance Cost

Hot Side Selective Catalytic Reduction

$24.04 M

$3.16 M

Cold Side Electro-Static Reduction

$19.67 M

$1.74 M

Dry Flue Gas Desulfurization

$64.13 M

$10.13 M

Total for Pollution Control Systems

$107.84 M

$15.03 M

We accept the financial situation put worth in the Proposal Request for overall capital funding.

Future Pollution Control Strategies

Updating of technology and training programs will include the following:

On an international basis, there are guidelines set by the International Standards Organization, known

as ISO 14001, that provide direction and advice on a wide variety of environmental issues, such as

compliance, training and performance measurement.

Future investments could include:

 

Using a pilot software, called IECM (Integrated Environmental Control Module), in order to simulate and see results from a coal-powered power plant, we input the following data. The program allowed us to control our imaginary power plant, by giving us many different options for the separate pollution control systems. Our simulation used such pollution control systems as NOx control, TSP control, and SO2 control. By tinkering with the types of technologies, we were able to obtain a set of data for our specific pollution control systems. There were six main inputs that we adjusted and they are the furnace type, the NOx control during combustion, the NOx control after combustion, the particulate control after combustion, the SO2 control after combustion, and the fly ash disposal.

Our choices are listed below:

Combustion Control

Post- Combustion Controls

Solids Management

Furnace Type

NOx Control

NOx Control

Particulates

SO2 Control

Fly Ash Disposal

Tangential

Low NOx Burners

Hot-Side SCR

Cold-Side ESP

Dry FGD

Mixed w/ Landfill