processing

2. Waste management
Eman abd el-raouf ahmed

3. The story –visiting 2013

5. What is cement?
Cement is a fine powder which sets after a few
hours when mixed with water, and then hardens
in a few days into a solid, strong material.
Cement is mainly used to bind fine sand and
coarse aggregates together in concrete. Cement
is a hydraulic binder, i.e. it hardens when water
is added.

6. Process of cement

7. Process of cement

9. Process of cement Step 1: Mining
mining of raw
materials that are
used in cement
manufacturing, mainly
limestone and clays.
A limestone quarry is inside the
plant area and a clays quarry is
as far from the plant area as 25
km. The limestone is excavated
from open cast mines after
drilling and blasting and loaded
onto dumpers which transport
the materials and unload into
hoppers of limestone crushers.
The clays are excavated from
open cast mines and loaded
onto dumpers which transport
the materials and unload into
open yard storage

10. Step 2: Crushing, stacking, and reclaiming of raw materials
The limestone is
crushed in the first
crusher called a jaw
crusher and then fed
into the second
crusher called an
impact crusher with
mixing of clays to
reduce particle
size below 50mm.
The discharged raw mix
(limestone 70%, clays 30%)
is fed onto a belt conveyor
and passed across a bulk
material analyzer. The raw
mix is fed into a circular
storage unit called a raw
mix storage.
The other raw materials that are
used in cement manufacturing,
called additives, are high purity
limestone, sand and iron ore. The
high purity limestone is crushed in
a lone in jaw crusher and then
crushed more in a secondary
crusher to reduce the size to
completely pass through a 50mm
sieve.

11. Step 3: Raw meal drying, grinding, and homogenization
The raw mix, high grade limestone, sand, and iron ore
are fed from their bins to raw mills, called air swept
mills, for drying and fine grinding. The raw mill
contains two chambers, separated by diaphragm,
namely a drying chamber and a grinding chamber.

12. Step 4: Clinkerization
Cement clinker is made by
pyro processing of kiln feed
into the preheater-kiln
system.

13. Main Process of cement
manufacture
Basically, cement is produced in
two steps: first, clinker is
produced from raw materials. In
the second step cement is
produced from cement clinker.
The first step can be a dry, wet,
semi-dry or semi-wet process
according to the state of the raw
material.
A two-step process

14. Making clinker
The raw materials
are delivered in bulk,
crushed and
homogenised into a
mixture which is fed
into a rotary kiln.
this is an
enormous rotating
pipe of 60 to 90 m
long and up to 6 m
in diameter. This
huge kiln is heated
by a 2000°C flame
inside of it.
The kiln is slightly
inclined to allow for
the materials to
slowly reach the
other end, where it
is quickly cooled to
100-200°C.
Cement is made by
heating limestone with
clay in a kiln
CaCO3 + clay (clay is
not represented by a
chemical formula)
(arrow) cement

15. Four basic oxides in the correct proportions make cement clinker:
calcium
oxide
(65%),
silicon oxide
(20%),
alumina
oxide (10%)
and iron
oxide (5%).
These elements mixed
homogeneously (called
“raw meal” or slurry) will
combine when heated by
the flame at a
temperature of
approximately 1450°C.
New compounds are
formed: silicates,
aluminates and ferrites of
calcium. Hydraulic
hardening of cement is
due to the hydration of
these compounds.

16. From clinker to cement
The second phase is
handled in a cement
grinding mill, which
may be located in a
different place to
the clinker plant.
Gypsum (calcium
sulphates) and possibly
additional cementitious
(such as blastfurnace
slag, coal fly ash, natural
pozzolanas, etc.) or inert
materials (limestone) are
added to the clinker.
All constituents are ground leading to a fine
and homogenous powder. End of phase two.
The cement is then stored in silos before
being dispatched either in bulk or bagged.

18. Cement and pollution
Cement kiln dust (CKD) is the fine-grained, solid,
highly alkaline waste removed from cement kiln
exhaust gas by air pollution control devices.
Because much of the CKD is actually unreacted
raw materials, large amounts of it can and are,
recycled back into the production process. Some
CKD is reused directly, while some requires
treatment prior to reuse.

19. Reduce pollution

20. Methane gas reducing energy
recycle the value in energy-
bearing secondary
materials by using them as
fuel in kilns that produce
Portland cement. CKRC
also represents companies
that collect, process,
manage, and
market alternative fuels for
use in cement kilns.
the process differs from
conventional methods of
drying bio solids by using
less heat to remove water
from sludge and using
methane gas created
during anaerobic
digestion to power the
dryers within the plant,
reducing the need for
natural gas or other
sources of energy.

21. The methane created
during anaerobic digestion
provides approximately
80% to 85% of the energy
needed to fuel the dryers.
Natural gas provides the
rest.

22. Waste of cement
miscellaneous cement plant
waste fuel streams such as wood
chips, used tires, rice hulls, and
filter cake generally fit within a
state's solid waste management
regulations. Some materials can
be state regulated special
wastes or industrial wastes.
A considerable waste oil
volume already moves
through the hazardous waste
fuel system, with the used oil
collection and transport
activities regulated in some
states as special waste
operations.

23. References:
http://www.eeaa.gov.eg/arabic/main/g
uides/Cement-Ar.pdf
http://gcisolutions.com/HWF&CKS.htm