Cement grinding and manufacturing plant process 

Cement Grinding Plant

For making cement, we requires clinker, clay, gypsum or flyash. If we want to make OPC cement then we will use gypsum. If we have to make PPC cement then we will use Flyash.

"Factory of National Cement Share Company by DFID - UK Department for International Development, Wikimedia Commons, CC BY 3.0

 Cement grinding plant is divided into five sections.

1) Storage Yard section

2) Proportioning Hopper section

3) Cement Mill section

4) Cement Silo section

5) Packing section

 

1) Storage Yard section :-

Storage yard should be designed in such a way that raw material can be stored for 7 -10 days. In this section, raw material brought from outside is stored. Raw material may contain clinker, clay, gypsum or flyash and additives. All these have different storage yards.

Charnwood Brick – 1 – Clay conveyor entering the works
cc-by-sa/2.0 - © Alan Murray-Rust - geograph.org.uk/p/5857633

The storage yard consists of ground hoppers. At the bottom of ground hopper has a pin gate or slide gate.. Which prevent the material from escaping. This is followed by vibratory feeders. Which put the material on the belt conveyor. This belt conveyor feeds to the proportioning hoppers.

  2) Proportioning Hopper section:-

The hoppers in this section are made of mild steel or cement concrete. The capacity of these hoppers is prepared at the base of the percentage of material. For example, the percentage of clinker is most commonly used to make cement. Therefore the hopper of the clinker is of the largest size. 

Hanson Cement, Clitheroe
cc-by-sa/2.0 - © Alan Murray-Rust - geograph.org.uk/p/4480158

Other hoppers have a lower capacity, such as gypsum / flyash, clay and additives. The material on these hoppers is inserted with the help of reversible belt conveyor or three way chute. All these hoppers are fitted with pin gate or slide gate. For example, clinker and gypsum for slide gate, flyash and clay for pin gate are used.    

The weigh feeder is used to extract the appropriate quantity of material. All materials are inserted on the belt conveyor with the help of chute. This belt conveyor feeds the cement mill. In the proportioning hoppers, venting connection must always be given. Venting greatly reduces the problem of chocking. Apart from this, also keep in mind that it is very important to provide a manhole connection in Proportioning hoppers so that it can be repaired from time to time.

In MS hoppers, liner should always be used for abrasive material to avoid hopper wear. Nowadays, high level and low level indicators are also being provided in Proportioning hoppers. A poking hole must be provided in the tapper portion of the hoppers so that the largest size of the material can be broken with the help of rod which hinges the outlet of the hoppers.

3) Cement  Mill section:-

     Mill section is the main part of cement plant. It can also be called the heart of an entire plant. We also know Mill section as cement mill section. If we talk about cement mill section, then there are two types.

  a) Open circuit      b) Close circuit

 a) Open circuit:-

The cement mill section in which classifier is not used is called open circuit.

 b) Close circuit:-

The cement mill section in which classifier is used is called close circuit.

 Closed circuit cement grinding comprising an 18’ diam. air separator and a 2600 HP ball mill in Portugal. by N.N.Zoubov Engineers, Wikimedia Commons, CC BY-SA 3.0

Process :-

A two way chute is placed at the discharge end of the belt conveyor which brings the material from the hopper section. One end of the two way chute is attached to the cement mill, while the other end is kept open to check the composition of the material. 

Proper lining of two way chute should be done so that it does not wear. In the cement mill the material is converted into fine powder. This is where cement is manufactured. The fineness of cement depends on the Blaine. 

The capacity of cement mill depends on the capacity of the plant such that if the capacity of the plant is 800 TPD then the capacity of the mill will be 800/20 = 40TPH. After the cement mill, an air slide or screw conveyor is attached which is connected to the outlet of the cement mill through the chute and which is connected to the inlet of the bucket lift through the chute. 

In the close circuit, the bucket elevator sends the material to the classifier via air slide. The classifier separates the coarse and fine material. The coarse material is again poured into the mill via air slide while fine material is sent to the cyclones. On the other hand, if we look in the open circuit, the material is sent directly from the bucket elevator to the cyclones.

The rotary vane feeder (RVF / RAL) is attached below the cyclones. A fine air slide is attached to the rotary vane feeder which is connected to the bucket elevator or air lift feeding in silo. 

4) Cement Silo section :-

The fines air slide which comes from the cement mill section and feed the bucket elevator, the same bucket elevator feed into the silo top air slide. Many plants do not install silo feeding bucket elevator.

Cement Silos by 长城建机编辑处 , Wikimedia Commons, CC BY-SA 4.0

 Air lift is used in those plants. Air lift lifts the fine material and poured into the expander. From expander the material goes into the silo feed air slide. Silo is made of Mild steel or concrete. A bin mounted dust collector is placed on the top of the silo, so that there is no problem of dusting and chocking. 

A high level indicator is placed at the top of the silo. So that the cut can be made after the silo is filled. With this, you should also know that there are two types of silo, one flat bottom type silo and the other conical bottom type silo.

In Silo we store material for two to three days. The capacity of silo depends on the capacity of the plant. If the plant capacity is 800 TPD, the maximum capacity of silo will be 800 X 3 = 2400 tonnes. The areation system is provided inside the bottom part of the silo so that the cement does not get frozen in the bottom and easily exits through the outlet. The slide gate and rotary vane feeder are fitted under the silo.

5) Packing section:-

The cement is packed in bags in the packing section. Many small plants do not have a separate packing section. In small plants, packing is done using a packing machine just below the silo. There are two types of packing machine, one stationary packing machine and the other rotary packing machine / rotary packer. 

The storage bin is attached before the packing machine, so that the material pressure directly from the silo does not affect the packing machine. A high level indicator is put in the storage bin. Proper venting of packing machine and bin is very important. 

Proper venting should also be given to the packing area, as a result there is no dust in that area and in it can be worked easily. The bag which is filled in the packing machine is put on the truck loading belt conveyor or truck loading machine through the chute conveyor. These truck loading belt conveyor or truck loading machine load the bags into the truck by the workers.

Through these sections, cement is prepared and reaches all of us.      

    

   

 

 

 

 

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Ishan Kumar