Byproducts PowerPlant
Byproducts PowerPlant
Byproducts PowerPlant
Resource efficiency means using fewer virgin raw materials. Increasingly, cement
plants are turning to industrial byproducts and materials that otherwise would be
discarded as sources for the basic elements needed for cement making.
the effect on process chemistry and facility emissions, many cement plants can
utilize byproducts from the electric power industry as a raw material in the
continued
Three general classes of byproducts from electric power plants can be used in the manufac-
ture of portland cement: fly ash, bottom ash / boiler slag, and flue gas desulfurization
THE CEMENT-MAKING PROCESS
(FGD) materials.
Portland cement manufacturing Fly ash and bottom ash/ boiler slag contain large amounts of silica and alumina as well as
is a four-step process: calcium and iron [TFHRC 2002]. All of these components are needed in the cement
1. Raw materials, including limestone manufacturing process. FGD materials can replace the natural gypsum that must be added to
and small amounts of sand and clay, the final product to control the setting of concrete [EPRI 1999]. Currently, over 55% of U.S.
come from a quarry usually located portland cement plants use one or more of these byproducts to produce clinker or cement.
near the cement manufacturing Fly Ash
plant. Limestone is typically about
Fly ash is the fine, powder-like material collected by the particulate matter control devices at
80% of the raw mix and is the
coal-burning power plants. Depending on chemical and physical attributes, some fly ash can
primary source of calcium.The
be blended into the final cement product or used at the ready-mixed concrete plant. In the
remaining raw materials provide appropriate proportions in concrete, fly ash decreases permeability and increases long-term
the silica and the necessary small strength [ACAA undated].
amounts of alumina and iron.
The American Coal Ash Association (ACAA) reported that 70 million short tons of fly ash
2. The materials are carefully analyzed, was produced in 2003, with over 12 million short tons used in concrete, concrete products,
precisely combined and blended, and grout. Over 3 million short tons of fly ash was used in kiln feed for the manufacture of
and then ground for further process- clinker or cement [ACAA 2004].
ing. This is called kiln feed.
In 2005, 39 portland cement plants were using fly ash as a raw material in the manufacture
3. The ground materials are heated in of clinker, and 3 plants were blending fly ash into one or more cement products. (Figure 1
an industrial furnace, called a kiln,
shows the locations of the plants utilizing fly ash.)
that reaches gas temperatures of
1,870°C (3,400°F). The heat caus- FIGURE 1
es the kiln feed to turn into a new Map of U.S. Portland Cement Plants Currently Utilizing Fly Ash
substance called clinker. The kiln
ME
WA
flame is fueled by powdered coal,
MT ND VT
powdered petroleum coke, natural NH
OR MN MA
NY
gas, oil, and/or recycled materials ID
WI
MI
CT
SD
burned for energy recovery. WY
PA
NJ
IA
NE OH MD DE
portland cement.
TX LA
Map of U.S. Portland Cement Plants Currently Utilizing Bottom Ash / Boiler Slag
ME
WA
MT ND VT
NH
OR MN MA
NY
WI CT
ID MI
SD
WY NJ
PA
IA
NE OH MD DE
NV IN
IL
WV
CA
UT CO
VA
USE OF POWER PLANT BYPRODUCTS
KS KY
MO
NC
TN
The Buzzi Unicem plant in
AZ
NM
OK
AR
SC Chattanooga, TN, uses all three
GA byproducts from coal-fired power
MS AL
plants: fly ash, bottom ash, and
TX LA
synthetic gypsum. The fly ash and
bottom ash are part of the kiln feed
FL
and become part of the clinker, while
the gypsum is used in the finish mills
Portland cement plants using bottom ash / boiler slag as a raw material in the manufacture of clinker (21) in the production of portland cement.
FIGURE 3
Map of U.S. Portland Cement Plants Currently Utilizing Flue Gas Desulfurization Materials
ME
WA
MT ND VT
NH
OR MN MA
NY
WI CT
ID MI
SD
WY NJ
PA
IA
NE OH MD DE
NV IN
IL
WV
UT VA
CO
CA KS
MO KY
NC
TN
OK
SC
AZ
NM AR FOR ADDITIONAL INFORMATION
MS
GA PLEASE CONTACT:
AL
References
2003 Coal Combustion Product (CCP) Production and Use Survey, American Coal Ash Association, Aurora, CO,
USA, October 1, 2004.
Coal Ash Fact Sheet, American Coal Ash Association, Aurora, CO, USA, Undated.
Environmental Focus: Flue Gas Desulfurization Byproducts, BR-114239, Electric Power Research Institute, Palo
Alto, CA, USA, 1999.
User Guidelines for Waste and Byproduct Materials in Pavement Construction, FHWA-RD-97-148
(www.tfhrc.gov/hnr20/recycle/waste/index.htm), Turner Fairbank Highway Research Center, Federal Highway
Administration, United States Department of Transportation, McLean, VA, USA, May 2002.
VERTICAL CONFIGURATION
HORIZONTAL CONFIGURATION
Portland Cement Association is a trade association representing cement companies in the United States and
Canada. PCA’s U.S. membership consists of 46 companies operating 102 plants in 36 states. PCA members
account for more than 97% of cement-making capacity in the United States and 100% in Canada.
www.cement.org