Pollution Control in Coal-fired Power Plants: Various Technologies

By: Frank Caprio | On: August 8, 2018

Pollution control in coal power plants is critical. In this blog, we explore the different technologies used and the differences between them.

Pollution Control

Thermal Power Plants produce electricity by first creating heat, and the U.S.A. still produces most of our energy by burning fossil fuels (coal, natural gas, or oil) to create this heat. Despite our nation’s move towards clean, renewable energy production, coal-fired plants still produce about 30% of our electricity. The exhaust fumes from these plants contain coal ash and pollutants that must be removed before being released into the atmosphere. Long gone are the days where power plants belched black smoke laden with particulate matter, heavy metals, greenhouse gases, and the constituents of acid rain. In order to remove these pollutants effectively and economically, several different technologies are employed, and they all use hoses and expansion joints. It is important to understand which pollution control technologies are being utilized so you can recommend the best products for the job.

Flyash

When burning coal to produce power, there are two main combustion technologies: pulverized coal and fluidized bed systems. Pulverized coal systems grind the coal into a very fine powder, which is then sprayed into the furnace, where it ignites. Fluidized bed systems use one of several designs where the coal is combined with other materials (sand, lime, etc.) and is suspended by airflow as the combustion occurs. In fluidized bed systems, the coal feedstock can vary greatly in size, quality, and energy content. While pulverized coal systems are still fairly common, most newer coal-fired plants use a Circulating Fluidized Bed (CFB) combustion system.

Regardless of which technology is used, both produce coal ash. Most of this ash is airborne (called “flyash”), while some ash settles out of the flue gas (“bottom ash”). Historically, coal ash would be mixed with water, and pumped as a slurry to an ash retention pond, where the water is gradually removed and the ash is covered over. However, due to several accidents involving ash retention ponds, the industry has moved toward dry conveying and storage of ash. Ash removal systems use blowers, pumps, baghouses, and silos to convey and store the removed ash, and all of these systems use hose and expansion joints, both metallic and non-metallic. We are uniquely qualified to help conduct hose and expansion joint surveys, provide suggestions to improve reliability, and recommend the best products for any flyash removal system.

Flue Gas

Once the particulate matter has been removed, the flue gas must then be treated to remove heavy metals and acid gases. Again, there are several techniques that can accomplish this, including Flue Gas Desulfurization (FGD), Selective Catalytic Reduction (SCR), and other specialized systems. FGD systems can utilize wet scrubbers, dry scrubbers, or dry-spray scrubbers that inject either a wet or a dry sorbent into the flue gas to neutralize and remove acid gases. CFB plants generally do not require additional equipment to remove acid gases; they operate at temperatures below those where Nitrogen oxides are created, and any sulfur present in the coal reacts with sorbents added to the fluidized bed. If a pulverized coal plant uses a dry sorbent injection system to remove acid gases, then additional equipment must be installed to remove mercury. These mercury removal systems inject activated carbon or some similar media to react with the mercury, which then settles out of the flue gas. All of these scrubbers, SCRs, and mercury removal systems require the use of hoses and expansion joints.

Miscellaneous Applications

There are many other applications where hoses and expansion joints are used for emission control. Induced draft fans, flue gas heaters, steam lines, and sluicing water pumps are just a few of the applications where our products increase safety, improve reliability, and provide unmatched value. And remember, power plants aren’t just the utility plants that keep the lights on; most large industrial complexes also have power plants onsite.

Which technology does my plant use?

There are numerous factors that determine the optimal emission control system for a power plant: the size of the plant, the sulfur content of the coal and how much of it must be removed, energy costs, water scarcity issues, and local regulations are a few considerations. Some FGD systems can even be designed to operate using sea water, which can create other corrosion-related problems.

The important thing is to have a thorough knowledge of the technologies used in these plants, and to understand how flexible metal products are expected to perform. How can the distributor and the end user work together to improve productivity and reduce downtime? Conduct a hose survey. Read the blog posts on our website. But first, contact us or call 800-221-2319 and let us help by providing insight on how our products will benefit the equipment, the technology, and the applications. With a thorough understanding of the operations, we can all work together help solve the toughest emission system challenges.