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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.