Combustion Emissions
The cement industry has an enviable record in reducing air pollutants. It is working closely with the Environmental Protection Agency and state regulators to develop new standards and technology to assure air quality. Investment in new equipment and technology to reduce emissions totals in the millions of dollars per year.
Cement companies also work with state and local officials to meet the National Ambient Air Quality Standards (NAAQS). For example, the industry is conducting ongoing cooperative efforts with federal, state, and local officials to study emissions controls of fine particulates and other pollutants. Further emission reductions are achieved by utilizing waste fuels that would otherwise be burned unproductively in incinerators.
In a perfect world combustion products
would be limited to just water and carbon dioxide.
But we don't live in a perfect world. Nitrogen
oxides known as thermal NOX
is generated in and around the flame at temperatures
greater than 1200° C. A short hot burning
zone can reduce the formation of thermal NOX.
Sulfur dioxide, or SO2,
is formed as sulfide or elemental sulfur is oxidized
at temperatures of 300 to 600° C. Limiting
the source of sulfur or the necessary oxygen can
limit the potential for SO2
formation. Carbon monoxide (CO) formation is another
concern; it is either formed because of incomplete
combustion or the rapid cooling of combustion
products below the ignition temperature of 610°
C. The particulate matter from the raw materials
can become entrained in the exhaust gas and carried
out of the kiln system. The vast majority if it
is removed by the fabric filters, know as baghouses,
or by electrostatic precipitators.
The portland cement industry was among the first to tackle the issue of climate change, and it has remained at the forefront of developing policies and improving the manufacturing process. Since 1975, the cement industry has reduced emissions by 33 percent. In 2000, the industry created a way to measure carbon dioxide (CO2) emissions, and by the year 2020, the industry plans to voluntarily reduce CO2 emissions by 10 percent below the 1990 baseline.
The most recent progress involves newly introduced guidelines that will allow for greater use of limestone as a raw material of cement, which will ultimately reduce CO2 by more than 2.5 million tons per year.
Today, the cement industry accounts for less than 1.5 percent of U.S. CO2 emissions, well below other sources such as electric generation plants for heating and cooling (33 percent), transportation (27 percent), and industrial operations (19 percent).
By 2020, the industry aims to reduce CO2 emissions by 10 percent below the 1990 baseline levels. To achieve this goal, the cement industry has adopted a three-part strategy:
- Improve the energy efficiency by upgrading plants with state-of-the-art equipment
- Improve product formulation to reduce energy of production and minimizes the use of natural resources
- Conduct research and develop new applications for cement and concrete that improve energy efficiency and durability
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