To develop an understanding of modern industrial technologies that clean up and prevent air pollution, students build and observe a variety of simple models of engineering pollutant recovery methods: scrubber, electrostatic precipitator, cyclone and baghouse. In an associated literacy activity, students become more aware of global environmental problems and play a part in their solution by writing environmental action campaign letters.

One of the biggest challenges environmental and chemical engineers face is devising new techniques to prevent the creation of additional air pollution from manufacturing and industry. Their challenge is compounded by industry owners who do not want the added clean-up steps to slow down or add cost to their manufacturing processes. So, engineers must be creative in designing new pollutant recovery methods and industrial technologies that clean up and prevent air pollution. air pollution atmosphere baghouse cyclone electrostatic precipitator environment industry pollution scrubber technology After this lesson, students should be able to: Describe and explain how a scrubber, an electrostatic precipitator, a cyclone and a baghouse work as pollutant recovery methods. Give examples of when the use of a scrubber, an electrostatic precipitator, a cyclone or a baghouse is appropriate. Describe how engineers create technology to help industry clean up their air pollution. Ask students to suggest ideas: How would you clean up air that is dirty with dust, particulate matter and gases? Would you establish any laws? Who would the laws impact: industries, small businesses, citizens? Write their ideas on the chalkboard. Hopefully, the student suggestions include "washing the air" and, perhaps, using a filter. If not, prompt them by asking how nature cleans the air, and what happens to all the dirt and dust that is suctioned up by a vacuum. Discuss what they think should happen if somebody releases a large amount of pollution into the air. The Clean Air Act of 1970 regulates how much of any pollutant can be released into the air. Two kinds of pollutants are regulated under the Clean Air Act. One type, called "criteria" pollutants, includes these six pollutants: carbon monoxide, nitrogen dioxide, sulphur dioxide, ozone, lead and particulate matter. Criteria air pollutants are discharged in relatively large quantities by a variety of sources, and they threaten human health and welfare across broad regions of the country. The U.S. Environmental Protection Agency (EPA) sets national standards for each of the criteria pollutants, and the states must take action to ensure the standards are met. Failure to meet the standards is called "nonattainment." Many urban areas are classified as "non-attainment areas" for at least one criteria air pollutant. The Clean Air Act establishes "enforcement" methods that can be used to make polluters obey the laws and regulations. Enforcement methods include citations (like traffic tickets), fines and jail terms for violators of the law. As the goals of the law are met, we breathe cleaner air every year. The most common methods of eliminating or reducing pollutants to an acceptable level are: destroying the pollutant by thermal or catalytic combustion (burning the air), changing the pollutant to a less toxic form or collecting the pollution with equipment to prevent its escape into the atmosphere. Explain to the students that in this lesson they will investigate four air pollution cleaning methods developed by environmental engineers and used in industry: scrubbers, electrostatic precipitators, cyclones and baghouses. One of the biggest challenges environmental and chemical engineers face is devising new techniques to prevent the creation of additional air pollution. Manufacturing and industry is a large contributor to air pollution. In this lesson, students take on the role of engineers and experiment with four different methods for cleaning up industrially-polluted air. To do this, conduct four of the activities listed in the Associated Activities section in sequence to model the four technologies used to reduce industrial air pollution: Washing Air (wet scrubber), Cleaning Air with Balloons (electrostatic precipitator), A Merry-Go-Round for Dirty Air (cyclone) and Let's Bag It (baghouse). Air contaminants are emitted into the atmosphere as particulate matter, aerosols, vapors or gases. The most common methods of eliminating or reducing pollutants to an acceptable level are: destroying the pollutant by thermal or catalytic combustion, changing the pollutant to a less toxic form or collecting the pollution with equipment to prevent its escape into the atmosphere. Pollutant recovery may be performed by the use of one or more of the following: scrubbers, electrostatic precipitators, cyclones and/or baghouses. There are also a number of natural ways to clean the air, including: Hurricanes (violent tropical storms of rain, lightning, thunder and high winds) Tornadoes (violent, funnel-shaped windstorms that are very destructive) Raindrops, snowflakes and other precipitation events remove air pollution through the natural water cycle (although this can lead to water and land pollution) Plants (especially spider plants) Mucus inside our noses traps the dirt and germs from the air before they reach our lungs. If the air is really dirty it cannot stop all the pollution, so some of it may reach and damage our lungs (i.e., smoking effects). To help reduce air pollution, over the years, our government has passed many laws, called the Clean Air Act. The first Clean Air Act was passed in 1963. The Clean Air Act tells people everything they must do to reduce air pollution. Several Clean Air Acts have been passed since 1963. The most recent one was passed in 1990. (For more information, see the attached Clean Air Act Reading.) A pollutant recovery method that works very much like a giant vacuum cleaner. Heavy dirt particles fall out and are removed, and smaller particles are trapped by filters (bags) made of cloth, paper or similar materials. Particles are shaken or blown from the filters into a collection hopper. A pollutant recovery method in which dust-laden gas is whirled very rapidly inside a cylinder-shaped collector. Flying dust particles (as well as all matter) like to travel in straight lines unless an external force acts upon them. Because of this, pollutant particles with inertia in a cyclone tend to leave the circular path of the cyclone, collect on the wall, and then slide down the wall into a collection chamber. A pollutant recovery method in which a static charge makes dirt particles stick to electrified plates (much the same way that static electricity in clothing attracts small bits of dust and lint). The dirt is knocked loose, collected and removed. A funnel-shaped chamber in which materials are collected temporarily and later discharged through the bottom. A pollutant recovery method that traps solid particles and gases as they pass through a fine water mist inside the scrubber. Sometimes the mist is injected with limestone powder to help extract the dirt particles. Washing Air Cleaning Air with Balloons A Merry-Go-Round for Dirty Air Let's Bag It What's a Kid to Do? Write on the chalkboard the following information on the four air pollutant removal methods explored in the four activities in the Associated Activities section: Baghouses: 98% efficiency Cyclones: 95% efficiency Electrostatic precipitators: 98% efficiency Wet scrubbers: 94% efficiency Ask the students the following questions to help clarify their understanding of the industrial air pollutant recovery methods in use today, and discuss as a class: Does a wet scrubber clean up all of the pollutants? (Answer: No, it removes 94% of them.) Do any of these cleaning methods remove all pollutants from the air? (Answer: No. They range from 94-98% efficient.) Which type of air cleaning process would be the best for removing particles? Which method is most efficient? (Answer: The baghouses and precipitators are the most efficient.) Which method is least efficient? (Answer: Cyclones.) Which type of air cleaner would be the best for removing waste gases? (Answer: Wet scrubbers work better on acidic, basic or corrosive gasses. Cyclones work better on other gases.) When might one type of pollutant recovery method be better than another? (Answer: It would depend on the type of pollutant(s), cost, location, etc.) If the baghouses and precipitators are the most efficient, why would you ever want to use a wet scrubber or cyclone? (Answer: It depends on the type of pollutant(s) and the industrial conditions. Wet scrubbers work better on acidic, basic or corrosive gases with high water solubility. Cyclones are best at removing solid pollutants from dust-laden gases.) What problems arise by having too many pollutants in the air we breathe? (Answer: The most important problems are adverse health effects.) Have the students complete the attached Cleaning Up Worksheet - Four Methods to summarize their understanding of the various pollutant recovery methods explored in the activities. Read the attached Clean Air Act Reading. Explain to students that during this lesson they have only considered industrial changes and technologies for controlling air pollution. Ask for suggestions about what we can personally do to control and/or prevent the amount of air pollution that we cause? Conduct the literacy activity, What's a Kid to Do?, for this lesson and/or assign the attached Clean Air Act Worksheet and Letter as homework. Brainstorming: As a class or in small groups, have the students engage in open discussion. Remind students that in brainstorming, no idea or suggestion is "silly." All ideas should be respectfully heard. Take an uncritical position, encourage wild ideas and discourage criticism of ideas. Have them raise their hands to respond. Write their ideas on the board. Ask the students: How would you clean up air that is dirty with dust, particulate matter and gases? Class Discussion: Ask the students and discuss as a class: Can you think of any ways that nature helps clean up the air? (Answer: Hurricanes, violent tropical storms with rain and high winds, tornadoes, raindrops/snowflakes/other precipitation remove air pollution through the water cycle, plants [especially spider plants], and mucus inside our noses traps some of the dirt and germs from the air before they reach our lungs.) Do you think engineers use nature as a model for the air cleaning technologies they design? (Answer: We will find out as we learn about industrial air cleaning methods.) Drawing/Journaling: If your class conducted all four Air Pollution unit, Lesson 10, pollutant recovery method activities, have students complete the attached Cleaning Up Worksheet - Four Methods to capture their observations and summarize their understanding of the various methods. Otherwise, depending on the students' age, have them draw a picture or write in their own words a description of how the studied industrial air cleaner methods clean air. Ask for volunteers to share their descriptions with the class. It's a problem all over the world! Imagine that you are an engineer at a meeting of great leaders from around the world. They are waiting to hear you speak about what is happening to our fresh air. You want to convince more of them to begin using the new technologies that you have just studied. What will you tell them? How will you get them to work together? Write down your ideas. Now What? Have the students brainstorm about what to do with the pollutants that are removed from the air with the pollution recovery methods investigated in the activities of this lesson. Clean Air Act: Have students complete the Clean Air Act Worksheet and Letter, which asks them to describe what they would include in their own "clean air act" and write a letter to the National Clean Air Coalition about what they have learned. If you have the time and ability to let the students build the models described in the Associated Activities section, consider having one group build a different model and present it to the class. Have students research the Clean Air Act. What is it? What is the goal? When was it started? Have students compare the U.S. to other countries in its air quality and regulations for controlling air quality. Assign students some of the lesson concepts to research on the Internet. Lead a small discussion of the findings during the next class period. Air Pollution Control. The Chemical Engineer's Resource Page, Midlothian, VA. Accessed November 27, 2004. (Description of cyclone, scrubber and electrostatic precipitator air pollution control methods.) http://www.cheresources.com/pollcontrolzz.shtml Markle, Sandra. The Kids' Earth Handbook. Atheneum, NY: John Wiley & Sons, Inc, 1991. Mock, Lyn. Air Pollution Control. Last updated August 2, 2004. Lesson Plans for Teachers, TCEQ, Texas Natural Resource Conservation Commission. Accessed September 18, 2006. http://www.tceq.state.tx.us/assets/public/assistance/education/air/air_pollution_control.pdf Cleaning Up Worksheet - Four Methods (pdf) Clean Air Act Reading (pdf) Clean Air Act Worksheet and Letter (pdf)