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Case Study: Savings
for the Cement Industry with Alumina
Grinding Media
In February 2000, one our clients, a
cement manufacturer approached us to study
and design a cost-effective grinding
system.
The problems in the current system were:
-
High costs due to the need for regularly
replacing the grinding media.
-
High Wear of the linings, leading to
greater downtimes and assembly costs.
-
Higher power consumption as heavy-duty
motors were being used.
-
Contamination in the end product due to
rapid wearing of the steel media and
lining.
One of the first steps was to really
determine the costs of running the current
system. The enormity of the number came as
a no-surprise. Due to the abrasive nature
of the mix being ground, the wear rate of
the steel media and lining was very high,
leading to a regular replacement schedule
at periodic intervals. The mills were
extraordinarily heavy owing to the weight
of the steel lining and the bulky steel
media.
After looking at the various parameters of
the system such as the purity required in
the end product as well as the grinding
time required, it was determined that
their real need was for a better grinding
media and lining. Naturally, the choice
was for our 92% Alumina lining and media.
The following analysis is the verbatim of
the analysis submitted to Universal
Ceramics for their client.
COST
SAVINGS IN REPLACEMENT OF STEEL GRINDING
MEDIA / LINING WITH 92% ALUMINA MEDIA /
LINING
Conversion of Steel Lining to Alumina
Lining Project (completed in January
2001)
End Product : Porous
Cement Blocks for Construction Industry
Process Examined :
Grinding of Sand in Continuous Mill.
Mill Size
: 1.75 M Φ x 5.75 M
I)
Savings on Media Consumption
Current use: Steel Media 25mm Φ x
25mm Height.
Proposed: 92% Alumina Grinding
Media.
Expenses for Steel Media:
QUANTITY RATE / Kilo VALUE
Initial charge
20 Tons
Annual consumption
150 Tons
(Avg. 500 Kilo / Day x 300 Days)
TOTAL
170 Tons x
65
¢ =
$ 110500
Expenses for Alumina Media
Since the Specific Gravity of Steel
Grinding Media is 2.5 times more than
Ceramic Media, on basis of equivalent
volumes:
The Initial charge - 20 / 2.5 = 8
Tons
Topping up of Ceramic Media - 150 /
2.5 = 60 Tons
Since the minimum expected life is more
than 10 times, the approximate topping up
would be 60 / 10 = 6 Tons
Thus Annual Consumption - 8 Tons +
6 Tons = 14 Tons @ $ 3.37
/Kilo.
Value = $ 47000
Direct Saving in Grinding Media
- ($110500 – $47000 )
-
$87000 / Year
II) Cost Savings in Lining
Weight of Steel
Lining/Sector
- 17 Tons / 6 Months
Total Weight of Steel Lining - 17
x 3.5 - 60 Tons / 6
Months
(3 Sectors + 2 Nos.
Flanges)
Weight of Steel Lining -
60 x 2 - 120
Tons / Year
Cost of Steel
Lining - 120 Tons x
65 ¢
/ Kilo - $ 78000
Cost of Transportation and
Installation -
$13000
TOTAL
- $ 91000 / Year
Cost of Ceramic
Lining
-$ 63500
(Inclusive of material and
fitting)
Life expectancy approx 5 yrs Rs.30 /
5 -$ 13000 /Year
Net Saving on
Lining (91 – 13)
-
$ 78000/Year
Note :- Under normal working
conditions these lining can last about 10
times longer than steel or rubber.)
III ) Cost Saving on Electricity
Weight of Steel Lining - 60
Tons
Weight of Ceramic Lining - 15
Tons
Difference -
45 Tons
Total circumferential load reduction due
to changing over from Steel to Ceramic
Lining- 45
Tons
Total Torque reduction in frictional load
reduction –
Weight of Steel Silpeb
- 20 Tons
Weight of Ceramic Media -
08 Tons
Weight reduction - 14
Tons
Total weight reduction
- 45 Tons + 14 Tons =
59 Tons
Saving in electrical Consumption about 30%
as lesser power motor may be used.
Motor rating
- 165 KW
Considering
- 16
¢
/ KW hr
Electrical Consumption / Year = 165 KW x
14 Hrs x 300 Days = 693000 Units
Cost of
Electricity = 16
¢
x 693000
= $110900
Saving 30%
=
$33000 / Year
IV) Increase in Volume due to reduced
thickness of Ceramic Lining – 5% as
thickness will be 2” instead of 4”
Thus production volume will increase by
2.5 %.
A Summary of Savings:
SAVING (I)
- $87000 / Year
SAVING (II) - $78000 / Year
SAVING (III) - $33000 / Year
TOTAL SAVING -
$198000 mn / Year
V) Payback Period Analysis
Initial Investment – Lining
- $63500
Grinding
Media
- $47000
- $110500
Saving / Year
-
$198000
Pay Back Period: Maximum 7 Months
Net Saving Thereafter $198000 x 5 years
minimum
=
$990000
Notes:
This specially chosen ceramic lining lasts
much longer than other lining material
like rubber, steel or conventional
ceramics, leading to lesser replacement
necessities which is very expensive
considering the downtime, production loss
and the cost of installation.
To ensure the highest installation
efficiency we require a very precise
inside dimensions of the mill shell, door,
lid and frame.
To get the highest efficiency it is
recommended to use both the lining and the
grinding media of the specified material. |
