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Engineering Properties
and Construction Applications of Phosphogypsum
Wen F. Chang - Murray I. Mantell, University of Miami
1990
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There
are more than 900 million tons of phosphogypsum stockpiled on
more than 20 stacks in Florida. Another 30 million tons are
generated annually when producing the phosphoric acid used in
fertilizer. Phosphogypsum is stacked because the U.S. Environmental
Protection Agency (EPA) currently bans its use due to the low-level
radiation associated with it. However, during the past 25 years,
FIPR research showed many ways phosphogypsum can be used safely,
and EPA is considering FIPR research and requests for exemptions
to the rule that bans all use.
One of the most promising uses of phosphogypsum in Florida,
due to the state's road-building needs, is as a road base
material. FIPR research showed it would be as effective and
less expensive than traditional road building materials and
could cut state road-building costs. This study built two
experimental roads using phosphogypsum and found the phosphogypsum
to be a suitable building material from an engineering standpoint.
Based on studies conducted before construction and for two
years after construction, it was also found that the environmental
effects of the gypsum on the local environment, especially
groundwater, were minimal.
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Literature Review
on Gypsum as a Calcium and Sulfur Source for the Southeastern
United States
Malcolm Edward Summer
1995
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Phosphogypsum
is a good source of sulfur and calcium and Florida soils need
more of both. In pastures, for example, adding phosphogypsum
to the soil would mean an economic gain to the farmer. Such
a pasture could support more cattle per acre and the cattle
would show a 20% weight gain. Phosphogypsum is an inexpensive
source of the sulfur needed to produce protein-rich forage that
the double-stomached animal digests easily.
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Phosphate Rock
Treatment for Waste Reduction: Phase II
Glenn A. Gruber,
Jacobs Engineering Group, Inc.
1999
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One
of the questions of the day is how to reduce the amount of phosphogypsum
being produced so as to cut down on the amount of acidic process
water that is stored in ponds on top of phosphogypsum stacks.
It is this water that spilled into the Alafia River in 1999
and caused a massive fish kill. It is this water that the Florida
Department of Environmental Protection (DEP) is trucking and
barging 140 miles into the Gulf of Mexico to dump in an attempt
to keep a pond at Piney Point I Manatee County from spilling
into Bishop's Harbor -- a prized estuary. Using this cost-effective
phosphate rock treatment could reduce the amount of phosphogypsum
produced as well as reduce the cost of producing DAP (diammonium
phosphate) fertilizer. |
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Rail-Veyor Bulk
Material Transport System
Merton F. Dibble, PE,
Rail-Veyor Technology, Inc.
2002
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It
takes millions of gallons of water to pump the matrix that the
phosphate industry mines to the plant each year. It is also
an energy-intensive operation that includes mixing the phosphate
matrix with water to create a slurry that can be pumped to the
washer. In addition, there is always a danger of a pipeline
leak or break in the current pumping system.
This FIPR project designed, tested and proved a possible
replacement for slurry pipelines by combining the best features
of a railroad and overland conveyor without high capital cost
requirements. Since the Rail-Veyor system can move phosphate
matrix at a much higher percent solids than pipelines, there
will be some savings in the amount of water used, but the
real savings will be in the energy needed to move the matrix
from the mine to the beneficiation plant. Environmental problems
associated with pipe breaks or leaks would also be reduced,
since Rail-Veyor carries solids that will not flow into surface
waters if a car accidentally dumps its load. Rail-Veyor could
also be used to transport the sand and clay that are now pumped
to storage areas after they are separated from the phosphate.
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Proceedings of
the Phosphogypsum Fact-Finding Forum. December 1995
Florida Institute of Phosphate Research and Florida Center
for Public Management, Florida State University.
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In
1995, The Florida Institute of Phosphate Research hosted a forum
on phosphogypsum - its potential uses and its potential risks
- to air the facts about this controversial by-product of phosphate
processing. The intent was to get people talking about whether
it is really better to keep stacking the phosphogypsum when
there were already about 700 million tons on the ground and
about 30 million more are generated each year. Today there are
more than 1 billion tons stacked.
The US Environmental Protection Agency (EPA) has banned the
use of most phosphogypsum because it is slightly radioactive.
To discuss
whether phosphogypsum is a health hazard or a wasted resource,
speakers were those who have conducted research about how
phosphogypsum can be used and the risk of putting it to use.
FIPR Board Members and staff have tried to get the EPA to
participate in the forum, hoping to present a balanced program
on the pros and cons of phosphogypsum use. The regulatory
agency in the end declined, saying they were involved in litigation
concerning phosphogypsum, but adding that they wanted to continue
discussion about the issue. That discussion is ongoing today.
Data generated by FIPR-funded projects led the Institute's
Board of Directors (past and present) to believe phosphogypsum
is a wasted resource. At the time of the forum the Board adopted
a position that based on experimental studies of phosphogypsum
and its characteristics, much of the official concern about
its perceived environmental and public health risks is misplaced.
Most of the proposed phosphogypsum uses involve minimal risk,
and that minimal risk can be readily mitigated using common
sense and well established practices. Therefore, in the light
of the economic advantages of several proposed phosphogypsum
uses, the EPA should be strongly urged to reevaluate its restrictions
on phosphogypsum use.
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