&EPA
United States August,
Environmental Protection - 1984
Agency
Lime
Handling
Systems
Problems
and
Remedies
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Lime Loading/ Unloading
Problems associated with the lime . .
loading/unloading operation include generation of
lime dust, severe damage of dry lime transport
piping due to abrasion at sharp elbows and bends,
and rupture of the lime bin due to buildup of
excessive pressure inside the bin. To minimize
these problems, dust collection baghouses should
be installed on lime storage bins and checked after
each loading operation; pressure relief valves
should be installed on lime bins; and long-radius
piping should be used for Hme transport.
Lime Storage
In lime storage bins, the flow of lime to the dry lime
feeders is often interrupted by "arching" or
"bridging" of the dry lime above the hopper opening.
Moisture in the storage bin can cause the lime
powder to "cake," thereby preventing it from flowing
freely. The lime storage bin should have a minimum
60° bottom slope to facilitate the flow of material info
the feed hopper. A vibrating "live bin" bottom helps
to minimize "arching" and "bridging" problems. To
prevent the entry of moisture info the bin, a rotary
ball valve should be installed at the bottom of the bin.
In cases where bagged lime is used, the bulk
storage area should be adequately ventilated and •
the humidity controlled to avoid "caking" problems.
Lime Slaking
Incorrect slaking temperature and water to lime
ratios in the slaking operation can result in poor
quality hydrated lime. If the slaker is not operated
under negative pressure, steam and moisture travels
back into the feeder and lime bin and causes
"caking" problems. Instrumentation panels located .
on or adjacent to the slaker are often covered with
lime dust and grit resulting in frequent breakdown of
equipment.
Lime slakers should be airtight and operated under
negative pressure. A fan may be used to draw out
vapors to help maintain negative pressure in the
slaker. Instrumentatfon panels should be separately
housed and located away from the slaker.
Lime Slurrying
A severe problem of abrasion occurs if fiber rein-
forced plastic (FRP) tanks are used for slurry pre:
paration. Tanks made of corrosion resistant metal
should be used to avoid abrasion problems.
Probes used for level control in the slurry tank are
often coated with lime solids and rendered
ineffective. Sonic-type slurry level sensor systems
can be used to mitigate this problem.
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The performance of existing lime handling systems'
can be significantly improved by incorporating rem-
edial measures at a reasonable cost A summary of
the major problems with Ifme handling; systems and
suggested improvements is presented in Table 1.
Remedy
• Install baghouse on lime silos.
• Use long radius bends and heavy duty
elbows.
Install "live" bin systems.
• Operate slaker under negative pressure and
install rotary valve under the feeder.
• Maintain proper temperature and water
content in slaker.
» Locate instrumentation away from slaker.
Use corrosion resistant metal tanks (not FRP).
Use sonic-type level sensor systems.
• Install lime slurry recirculation loops; flush
transport lines with water; use flexible
hoses; avoid sharp bends; use minimum f!£
to 2 inches diameter piping.
Minimize distance between recirculation loop
and feeder^ use open/close type valves; Use
rotary cup type feeder.
• Rotate the use of alternate pH' probes.
Remedies
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For Additional Information:
EPA Offices:
EPA-OWPO (WH-547)
401 M Street SW
Washington, DC 20460
(202)382-7365/7368
EPA-MERL (443)
26 West St. Clair Street
Cincinnati, OH 45268
(513)684-7613
&EPA
United States
Environmental Protection
Agency
Washington, DC 20460
Official Business
Penalty for Private Use
$300
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