The history of the discovery and use  of cement

Cements are adhesive particles that are capable of attaching to each other  to make a unified body of their constituent particles .

Cement is a composition of the oxide   Calcium (lime) with other oxides such as aluminum oxide, silicon oxide, iron oxide,   Magnesium oxide and alkaline oxides that have affinity to combine with water in the air and become resistant or hard in  the air or  under water .

According to these characteristics, the cement can have different composition and basically is considered as hydraulic mortars. Hydraulic mortars  were known in the old time. Limestone is among these mortars made by Romans and Greeks by mixing it with volcanic ash, soil and water facilities to obtain a type of lime and water  with a high hardening and pressurerizing capability. The Romans were able to apply the mortar to build large buildings that still remain stable after several thousand years.

In Iran, from ancient times in wet areas especially northern area of  Persian Gulf a kind of mortar was used with interesting hydraulic properties nd high compressive strength. The best kind of mortar is  Khamir  mortar used in Khamir Port .  

Port installations made  with this type of mortar are still standing in  areas such as Lengeh and Bushehr port.  

About 200 years ago following investigation of the hydraulic properties of volcanic material used in the construction works of the Romans, it was discovered that  existence of clay compositions in limestone increaseshydrulic properties. One of the forerunners of this discovery was English man John Smeaton   English who found this successful result for construction of eddy stone (1756 AD) . Next, extensive studies by Mr. Vicat ,  French scientist  on hydraulic lime (lime which have the effect of setting under water) succeeded for the first time in history to produce synthetic raw material for mortars. The mentioned study can be considered as the first bases of  Portland Cement Manufacturing ( cement Portland ).

Following this discovery, about 200 years ago, the artificial mixture of limestone and clay   was used to make ​​a hydraulic limestone called Portland cement. However, the cement  was the different from what today is known as Portland cement. The difference (in   Indeed defects) were improved over the next years and its result was a cement called ordinary cement (Portland) used by human. The first  building built with this type of cement was 1824 constructed in the British parliament building  between 1825-1840.

After considering the amazing properties of this new phenomenon, 180 years a go the demand for cement consumption increased last year and obtained a kind of  qualitative and quantitative aspects growth raised as a credible and extended industry .
With increasing   demand for consumption, the issue of the quality of cement and quality control was raised. Following this demand, standardization of  tests, and cement   were considered more seriously .

Following this need, for the first time in history  the  cement production factory in 1877 was established by the ANSI standard cement producers in Germany. Then in 1904,  the Engineering Standards Committee   in England was founded that later renamed as British Standards Institution.  On that year, the first US standards developed for cement production .  

With respect to   background of some tests on cement in Germany, it can be noted  that  cement is the first industry product that has been standardized .

Raw materials mines  and their extraction

Raw materials for cement factory are "Marley" clay and lime.

To provide raw materials for Firoozabad cement factory,  two lime and clay Marley mines localized and purchased. These mines are Mook Marley limestoneof Esmaeelabad at 2 and 15 km from the factory.

 Raw materials in mentioned mines, both of  which are operated openly are produced in an explosion method and transported to the plant by truck   .

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Crusher

Crusher  is the first cement production line at the cement factories. The raw material  shipped to the factory with maximum dimensions   of 80 cm entered in to crusher. After crushing by belt conveyor mounted below the crusher, they moved in to mixing of raw materials saloon.  

A part of equipments in   this part of plant in China are  purchased and mounted  by local experts in the depth of 16 m  of ground that crushed 850 stone per hour .

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Mixing  raw materials saloon

Mixing  raw materials saloon is the second production line of plant . The asymmetrical silo with length of 278 meters and a width of 54 meters can hold 60 tons of raw materials  to maintain them in a chopped form .

In this saloon , there are two devices named "Stacker" and   "Reclaimer" both of which purchased from China   .

Stacker transfers 1,200 tons of raw material on the conveyor belt to the middle of the  sallon per hours and makes them stacked. Reclaimer with removing power of 560 tons of raw material per hour   put materials on the conveyor belt and  guide them  outside.

In this section materials become homogenous to provide conditions for sustainability of the quality of the final product in addition to storing about Sixty thousand tons of raw materials.

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Feed bunkers of raw materials

Homogeneous raw materials in the mixing saloon of the raw materials by conveyor  will be transferred to the next section , i.e. feed bunkers of raw materials. In this section, there are four metal bunkers with  capacities of 240, 280, 560 and 850 tons which are respectively used to store silica, iron, lime and mix raw materials.

Under each of these bunkers a weighing device is made that allows the entry of raw materials to the production line based on the certain weight percentage.

It should be mentioned that lime, silica and iron after crushing by the crusher are directly entered in to related bunkers without entering the mixing saloon inorder to be used  in a mixture of Marley in the next section.

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Raw materials milling

Raw materials with specified weights are  entered into raw materials milling section. These materials are dried using hot air before entering the mill.

In  this mill, raw material are changed in to powder and transferred to silo of raw materials for storage. Milling of raw materials in Firoozabad Cement Plant  is bullet type which converts  270  tons  of raw materials to powder  per hour.

To move this 14 meters long and 4.5 meters diameter mill, about 6200   KW energy is required. Percent of output material powdering in this mill is 12% on a 90 micron sieve.   steel balls with 20 to 90 mm ​​diameter and a certain weight ratio enter   the mill and by its rotational motion with a combination of pressure, abrasion and  impact will powder the raw material.

A mill for raw materials  is purchased from FLSmidth Denmark Company  and installed and   adjusted in this section by local contractors. .

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Storage of raw materials    (Silos of raw materials)

Raw materials after converting into powder materials are transferred to silos  for storage. Silos of raw materials of the plant are two concrete structures  with height of 52 meters and a diameter of 18 meters and a storage capacity of about ten thousand  tons of raw materials.

External equipments of this section has been purchased from Germany  IBAU  Company  and it is installed by a company company named "Step Company"  .

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Preparation of raw materials for entry into the oven and baking  (preheater)

Raw materials stored in silos are transferred to preheater section through the feed oven. The structure with about 90 meters high is the most famous structure in cement factories.

The preheater  is of an  ILC , 5 cyclonic type.

Raw materials enter  the top of cyclones and through passing  them gradually will be heated to 800 ° C and are ready to oven. The capacity of this section is about 3450 tons per day.

Hot exit gases of preheater for controlling the temperature first enter the cooling tower. Hot gas enters the top of  tower and decreases up to 150 ° C in the tower using its temperature geyser.The gas is used as dehumidifier of input raw material in the mill and eventually  enters into the electrofilter, its dust  will be removed and  exit from the main stack.

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Raw materials Kiln and cooler

Firozabad cement company raw materials kiln  include a 4/35meters diameter  and 67 meters long steel cylinder .

The kiln is installed with a slope of 4 °   and with a rotational motion produces about 3,000 tonnes of clinker per day.  

Raw materials  with  initial temperature of 800 ° C  are imported to the kiln and heated to maximum 1400 ° C . At this temperature , the desired chemical interactions are    performed and dark grains called clinker are exit from the klin. .
The torch used in the klin is made by FLSmidth Company in Denmark and it can use any of gas or oil fuels separately or in combination.  The clinker produced in kiln enters  the "grate cooler" to reduce the temperature.  

Firozabad Cement Plant cooler is of SF Cooler   type. This cooler for the frst time  installed in this plant and is welcomed by newly established cement factories due to its high capabilities.

To reduce energy consumption,  a part of hot temperature in cooler is transmitted to preheater through kiln or  by air duct. The other part of that is full of clinker dust enters in to electrofilter cooling and exit from stack after dust removing.  Energy consumption of this device with 23 meters long and 3.9 meters wide is 240 kw.

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Clinker silos

Cooller clinkers are transferred to clinker silos for storage.

In Firozabad cement company,  three clinker silo are built  the first of which is returned clinker silo. This silo will be removed if the exit clinker lack required standards and its operation will be stopped. However, usually the produced clinker discharges in main silos , i.e. two 25,000 tons silos with a height of 37 meter and 28 meter diameter.

A tunnel is built under the silos and its built internal clinker transmission system is purchased from Aumund Company in Germany.

Silos are discharged from beneath part and clinker passed into mill for changing in to cement.

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Cement milling and cement production section

In milling section of Firoozabad Cement factory, there are  two installed mills made by China. Both of them are bullet mills that convert 110 tons clinker to  cement powder per hour. Each of these mills with 14/5 meters long and 2.4 meters diameter moves with only 4,000 kw energy.  

It should be noted that an amount of gypsum (about 4%) is also mixed with clinker in the mills to be changed in to powder.

The addition of gypsum is for align produced cement ground to perform masonry works on cement. This is because cement produced by pure clinker will be  hardened quickly after contact with water and it is not possible to work with it.

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Cement storage and delivery (cement silos and packing center  )

Cement powder produced in cement mills are transferred to the cement silos for storage. These silos are structurally similar  to silos  of raw materials which are mentioned at the beginning of the production line. about 10,000 tons of cement is stored in each silo.

The only difference between cement silos  and raw material silo is two bascules placed under each of the silos for cement bulk delivery .

Bulk cement bunkers put on bascules for weighting and loading.    Then they are exit from the other hand.

The pocket cement for sale  as represented in issued bills is transferred to packing  center and are loaded for delivery to customer  using the two "Rotary Packer" devices  made ​​in China.

 
Each machine can simultaneously fill 8 pockets. (2400   pockt of 50 kg per hour)
It is should be mentioned that the storage of produced pocket cement includes high costs and losses. Therefore, cement packaging never conducted before purchase order  and the only  method of cement storing in all cement plants   is keeping them in silos .

Filtering of exhaust air

One of the main concerns regarding the construction of a cement factory is exhaust air emissions. In this regard , by considering sensitivities of the management of Firoozabad company operation based on the preservation and development of environmental and natural resources,  filters of the plant selected and purchased among productions with the best world technology.

Two main electrofilters  of this plant were purchased from a Swiss Elex  company. Construction and installation of the interior part was designed and conducted by Nooavaran Sanaat Sabz Company (a subsidiary of Fars and Khoozestan Cement Company of Engineering services) that is installed under license of   Elex  Company.            

The electrofilter exhaust gas concentration is 50 mg per cubic meter, which has less emission compared to other similar industries.

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Material Transport Systems

In cement plants, different transportation methods are used according to type   and size of materials. In this factory also until  materials are  in the form of debris , ordinary conveyor belt will be used (before materials entrance in to mill). The clinker also transports by metal conveyor belt due to its structure.  
But for transferring powders produced in parts such as raw materials milling and cement mills , there are some different instrumental  silos called    Air lift   and  Air Slide .

It can be said in this company there are  several systems for material handling in different forms , the most important of which are:

Air lift, Air Slide, Screw , Belt conveyer, Bucket Elevator, Pan Conveyer

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Installations Channel

Transmission of electricity, water, fuel and oil over the course of the production line is conducted through a concrete tunnel called tunnel of installations. The tunnel has a length of about three kilometers that connecrs all electricity substations, oil refineries and tanks to building of the production line.

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Treatment Plant

Water Treatment Plant consists of two concrete tank with the capacity of 3,900 cubic meters of pure water and 5 small concrete tank for industrial and irrigation water.

Between the two series of tanks covered with soil,  transfer facilities treatment plant is installed and provides a variety of plant water requirements.