5.3    Major  equipments of mineral mixture plant

 

The mineral mixture plant has been designed in two sections. In first section, pre-determined quantities of trace mineral salts are crushed into fine powder form in a ball mill of capacity

500 litres. In the second section, crushed mineral salts (trace elements) are thoroughly mixed with other ingredients viz. calcite powder, magnesium oxide, sodium thiosulphate and di- calcium phosphate in a ribbon mixer and conveyed through screw conveyor to a storage silo. The mineral mixture plant consists of the following major equipment.

 

Ball Mill

 

 

In the ball mill (Fig. 5.2), pre- determined quantities of trace mineral salts  are  poured   in   the   ball   mill drum   for   grinding.   The  mixture   is then crushed into fine powder form. The ball mill should be of 500 litres capacity  and  SS  304  rotating  drum with minimum 60 kg of EN-31 balls of

 

50 mm  diameter.   Approx.  120 balls are required for crushing the granule to such an extent that 90 per cent of crushed powder should pass through

212 micron IS sieve. The crushed powder  shall  be  collected  in  50  kg bags manually.

 

Intake inclined screw  conveyor

 

 

Di-calcium    phosphate,     magnesium

Fig. 5.2 Ball mill

 

oxide, calcite powder and sodium thio-sulphate along with the trace minerals pre-mix should be dumped into the hopper mounted on the conveyor to feed the ribbon mixer with the desired quantity.

 

Ribbon mixer

 

 

The  ribbon   mixer   (Fig.  5.3)  has  a rated capacity of 500 kg. However, it is designed to  handle maximum  700 kg, which  is 40 per cent higher than the  rated  capacity.  It  has  provision for  forward  and  reverse  rotation  of the ribbon  shaft for  thorough  mixing of various mineral salts and pre-mix, in maximum 30 minutes time. Raw materials are fed from the inlet at the top cover and after thorough mixing discharged from the bottom outlet, having a manually operated valve.

 

 

Silo inclined screw  conveyor

 

The hopper of the conveyor receives

 

the thoroughly mixed mineral mixture powder from the ribbon mixer bottom

Fig. 5.3 Ribbon mixer

 

outlet. The conveyor of 2.0 MT/hr capacity transfers the powder to storage silo.

 

Storage silo

 

The SS 304 storage silo of 700 kg capacity functions as an intermediate storage till the mixed mineral mixture  powder  is packed in bags. The silo (Fig. 5.4) has a top inlet and a bottom outlet, provided with manually operated slide gate valve and motor operated bin discharger.

 

5.4    Start up & shut down procedure

 

Ball mill

 

1.        Check the correct level of oil in the gear box.

2.        Check the correct direction  of  rotation  of the ball mill drum.

3.        Open anyone hand hole cover. Ensure that the hand hole cover on the other side is fully tight.

4.        Remove the cover, place 120 nos. EN-31,

50 mm diameter balls inside the drum.

5.        Load the drum with trace element pre-mix

(as per the formulation).

 

 

 

 

Fig. 5.4 Storage silo

 

6.        Close the hand hole cover tight and close the ball valve mounted on the cover.

7.        Close the hinge cover of the SS shroud.

8.        Now switch on the ball mill. Ensure that it rotates clockwise if viewed from the motor side.

9.        Initially operate for an hour, stop the switch

 

and open the hinge cover of the shroud.

10.      Slowly  open  the ball valve of  the hand hole  and  see  if  any  pressure  releases from the drum. Sometimes the ball valve gets choked with the fine mineral mixture powder.  Insert  a  rod  through  the  ball valve opening  and ensure that  there  is no choking in the ball valve and that all the pressure buildup inside the drum has been released through valve.

If the mineral salts of desired specifications are not taken in the ball mill then all the mineral salts will tend to form

a mass, sticking to the sides of the drum and discharge of such a mass will be difficult

 

11.      Open any one hand hole cover by loosening the opposite side nuts and then remove the cover from the drum.

12.      Take a sample and see the fineness of the powder.  If the desired fineness is not achieved, tighten the hand hole cover, close the ball valve and run the ball mill for one more hour. The ball mill is designed to crush the batch in maximum 4 hours time. However, depending upon the granule size available and the moisture content, the time can be standardized by hit and trial method, which could be from 1 to 2 hours.

13.      Once the desired fineness is achieved, remove the hand hole as mentioned in step 10.

14.      Place SS grill cover on the hand hole and tighten it. Then close the hinge cover of the shroud.

 

15.      Place an empty bag fastened by hooks below the shroud discharge valve and then open the discharge flap valve.

16.      For decanting, start rotating the drum by putting the switch ON.

17.      Once the total crushed powder is collected in the bags, stop ball mill and bring the grilled hand hole position on top.

18.      Remove the grilled cover, re-charge the drum with fresh ingredients and close the hand hole cover.

19.      Repeat the process till the complete batch is crushed to the desired fineness.

20.      Once the batch is over and the ball mill is not required to operate for quite some time, ensure that the drum is completely emptied and the hand hole cover is closed.

21.      Switch off the main switch.

 

Mineral  mixture plant

 

1.        Check the correct level of oil in the gearbox of ribbon mixer, intake inclined screw conveyor, silo inclined screw conveyor and bin discharger.

2.        Check the correct direction of rotation of the ribbon mixer and screw conveyors.

3.        Manually close the ribbon mixer bottom outlet.

4.        Put ON the intake inclined screw conveyor and ribbon mixer. In the auto mode, the ribbon mixer will run in forward and reverse direction for a pre-set time.

5.        Start dumping  all ingredients in the hopper of intake inclined screw conveyor. For dumping of ingredients following sequence should be maintained:

•       First load  DCP in the  intake  hopper.

•       Then  load  the  remaining ingredients  (Pre-mix,  MgO,  calcite  powder, sodium

thio-sulphate) and,

•       At the  end,  load  remaining DCP in the  hopper.

6.        In the first batch, add approx. 25 kg of DCP extra and load in the intake hopper at the end. This extra DCP will remain in the Intake screw conveyor. The net batch size for the ribbon mixer shall therefore be of 500 kg.

7.        From second batch onwards, load the material as per the Sr. No. 5.

8.        Run the ribbon mixer in auto mode for 15 minutes. The mixer is set for forward and reverse rotation in auto mode and will mix all the ingredients thoroughly.

9.        Close the discharge valve of the storage silo and start the silo inclined screw conveyor to transfer mineral mixture powder from ribbon mixer to silo.

10.      Put the ribbon mixer in the forward rotation mode and open the bottom  discharge valve of the ribbon mixer.

11.      Mineral mixture will start pouring into the small hopper of silo inclined screw conveyor and convey to the storage silo.

12.      At the end when material stop coming out from the outlet valve, quench the ribbon mixer by reverse and forward operation for some time, so that all the powder drops into the hopper of silo inclined screw conveyor.

13.      Close the bottom outlet valve of the ribbon mixer.

14.      With a time lapse, stop the silo inclined screw conveyor.

15.      Repeat the procedure for next batch.

 

Cleaning procedure

 

If the plant is not in operation for a longer period, it is advisable to completely unload the material.

 

1.        The ribbon mixer can be emptied completely by quenching in forward and reverse movement.

2.        In the intake feed screw conveyor and silo inclined screw conveyor, a hinge door has been provided at the lower most portion of the conveyor. By partially opening the hinge door, the accumulated material in the screw conveyor can be collected in the bag. Initially the material will fall down due to gravity; entire material can be removed by quenching the screw in the forward direction.

3.        Silo is an intermediate storage facility before bagging the entire batch. However, it should not be used as storage for longer period. The mineral mixture has tendency to  absorb moisture  if  it  is  exposed to  atmosphere for  long  time.  If  the  mineral mixture remains in silo for long, it might absorb atmospheric moisture and chances of material choking the silo increases. Hence, mineral mixture should be transferred to bags immediately and not stored in silo for long time.

 

 

 

Table 5.3 Technical details of mineral mixture plant
Ribbon mixer	Capacity –500 kg mineral mixture/batch Bearing both end- UCF 212 Motor – 12.5HP, 3 Phase, 1455 rpm, H X F 160ml, B4 – Crompton/ABB make Gear box – AS-60-PP-160, Ratio- 18:55, mounting B5 X B3, Bonfiglioli make Gear box output to Ribbon mixer shaft –Flexible coupling size- FC 9”
Intake inclined screw conveyor	Capacity –2MT/hr. Bearing both end – UCF 208 Thrust bearing on bottom – 51408 ZKL Motor – 5HP, 3 Phase, 1425 rpm, Crompton /ABB make Gear box – AS-45-PP-112, Ratio- 15:83, Mounting B5 x B3, Bonfiglioli  make Gearbox output to conveyor shaft – Coupling – Chain type-3/4’’, 18 teeth
Silo inclined screw conveyor	Capacity –2MT/hr Bearing both end – UCF 208 Thrust bearing on bottom – 51408 ZKL Motor – - 5HP, 3 Phase, 1425 rpm, Crompton/ ABB make Gear box –AS-45-PP-112, Ratio- 15:83, mounting position-B3, Bonfiglioli make Gearbox output to Intake screw conveyor shaft – Chain type-3/4’’, 18 teeth
Bin discharger	Capacity–700kg/hr Bearing both end – UCF 204 Motor –2HP, 3 Phase, 1421 rpm, Crompton/ ABB make Gear box – AS-25-PP-90, Ratio- 11:51, mounting position-B3, Bonfiglioli make Gearbox output to Bin discharger shaft – Chain type-1/2’’, 18 teeth
Ball mill	Capacity – 500 litre (200 kg trace mineral salts) Bearing on both end shaft – 22216K Pedestal Size – S 516 Sleeve size     - H 316 Motor –7.5HP, 3 Phase, 1430 rpm, flange mounted- ABB make Gear box – AS-60-PP-132, Ratio- 25:47, mounting position-B3, Bonfiglioli make Gear box output to Ball mill shaft – Chain type-3/4’’, 22 teeth

 

Table 5.4 Maintenance schedule for mineral mixture plant
Equipment	Description and schedule
Intake dumping hopper with magnet grill	Clean the magnet grills everyday (remove iron particles).
Intake screw conveyor	Check gear box oil level every 15 day. Tight all drives bolts and nut every week. Greasing all bearings every 20 days. Open bottom  lead and remove material at the end of production ever day.
Ribbon blender	Clean filter bag of blender every day. Greasing both end bearings every 20 days. Tight graphite gland packing every week. Replace gland packing after 3 to 4 months if adjustment is no more. Tight every drives nut and bolts every week. Check oil of gear box every 20 days.
Manually operated disc valve	Check nut & bolts and put oil drops in both the bush if find operating hard.
Silo feed conveyor	Check gear box oil every 15 days. Tight all drives bolts and nut every week. Greasing all bearings every 20 days. Open bottom  lead and remove material at the end of production every day.
Storage silo	Check nut bolts and cable connection of vibrator every week. Clean the filter bags on top of silo every day.
Discharge conveyor	Check gear box oil every 15 days. Tight all drives bolts and nut every week. Greasing all bearings every 20 days. Open bottom lead and remove material at The end of production every day.
Ball mill	Check gear box oil every 15 days. Tight all drives bolts and nuts every week. Greasing all bearings every 20 days.
Motor control centre	Clean dust in inside panel with blower. Tight the terminals if found loose.