Improvement Of Air-Network in Cement mills at CEMEX company

Improvement of Air-Network efficiency on cement mills at CEMEX Company

Project Objectives

What's Cement ?

Cement combination

1- Limestone to extract lime(Calcite)

2- clay to extract, Iron Oxides (fe2o3), Bauxite (Al2O3), sand (SiO2)

A cement is a binder, a substance used in construction that sets and hardens and can bind other materials together. The most important types of cement are used as a component in the production of mortar in masonry, and of concrete, which is a combination of cement and an aggregate to form a strong building material.

Raw material storage and Pre-homogenization:

Quarry

Raw mill grinding process

Cement plants are usually located closely either to hot spots in the market or to areas with sufficient quantities of raw materials. The aim is to keep transportation costs low. Basic constituents for cement (limestone and clay) are taken from quarries in these areas.

In the storage area is limestone storage and clay in two separate pile and homogeneous

The raw mills grinding particles and Large granules of the raw and increasing its smoothness and decreasing its diameter from 25 mm to 75 micrometer to made the raw that feed the ovens more smooth and Increasing the surface area of the interactions and made the particles agreeing to the interactions more close.

At CEMEX Assiut factory there is two quarry :

Interactions Ratios Raw material needed:

Cement Manufacturing Process

• 75% of the limestone
• 20% of the clay
• 3 % of the sand
• 2 % of the iron ore

Methods of cement industry :

• limestone quarry
• clay quarry

1-Wet process :

2-Dry process :

Stacker types

Crushing

To reduce the maximum size of the material to 3.7 centimeters.

Crushers used in CEMEX Assiut is :

Hammer crusher

2- Round Yard or circular

1- Rectangular Yard

• X-ray fluorescence (XRF) device

Reclaimer

2-Objectives:

Comminution circuits accomplish three actions

• Size reduction .
• Blending .
• Drying .

Size reduction is required to increase specific surface area in order to increase reaction rates.

• Heat transfer in preheater/kiln .
• Combustion of solid fuels .
• Cement hydration .

• High reduction ratios
• Very little oversize
• Cannot tolerate sticky
• materials or abrasive feed
• High wear rates.
• Low tonnage capacity
• compared to size.
• High speed of rotor
• Hammer replacement ~ 6 months turn ~ 12 months replace

- Suitable for dry to moderately sticky-materials

- Direct feed of free flowing materials

- Optimum utilization of space

- Fully automatic continuous operation

Clay and limestone samples

X-ray fluorescence (XRF) devices

Hoppers and weigh feeder:

Weight feeder

Types of mills :

1 – ball mill

2- vertical mill

Ball Mill grinding

Separators

• Purpose of Air Separators:

-To segregate coarse and fine particles as specified by the operator.

-Overgrinding is avoided by removing the particles that are fine enough to be classified as product and returning the coarse particles to the mill for further size reduction.

Types of Air Separators :

3-Dynamic Separators

2- Static Separators

1- Cyclone

Cement storage silos

Pneumatic conveyors

• Transporting materials from one point to another Using a gas flow
• Economical to install and operate
• Without moving parts
• Flexible for rerouting and expansion.

Bucket fixation to the chain

Bucket Elevators

• Transported material properties
• Method of loading & unloading

• Conveying belt
• Conveying chain

• Deep buckets
• Shallow buckets
• V-shaped buckets
• Round bottom buckets

Bucket fixation to the belt

• Conveying Element:

Buckets

• Selection

• Types

Types of Pneumatic Conveying

1- Dilute-phase conveying

• High velocity
• Low pressure
• Low product to air ratio.

3- Air Slides

2- Dense-phase conveying

• Low velocity
• High pressure
• High product to air ratio

TYPES OF DILUTE – PHASE SYSTEMS

Design Objective :

1. Conveying capacity is inversely proportional to conveying distance

2. Conveying pressure is directly proportional to conveying distance

PIPING

1- X-pump [ Screw conveyors ]

2- Blow Feeder [ for sticky materials ]

3- Jet feeder

4- Air lift [ Vertically ]

5- Pressure Vessel [ champer Pump]

1. Filling

2. Pressurizing

3. Conveying

4. Venting

Advantages of pneumatic conveying systems

Disadvantages of pneumatic conveying systems :

1. Wear occurs in pipelines, especially in elbows, when conveying cement.

2. The air used to convey must be cleaned in dust collectors before discharge to the atmosphere, thus resulting in an increase of the equipment investment.

1. Small space requirements and dust-free operation.

2. Pipe lines can be easily installed into existing plants, since these conveying lines allow the by passing of possible construction obstacles.

3. Pneumatic conveying pipes require no lubrication and there are not complicated and expensive parts as drive-chains, belts, speed reducers. to repair or to replace.

4. Costly labour charges and the necessity of stocking spare parts are greatly reduced.

• The preheater consists of a series of large cyclones connected in line and placed in an enormous vertical building.
• Each level of cyclones is called a stage with current preheaters having up to six stages.
• The stages are usually numbered from top to bottom.
• increasing the raw meal temperature to nearly 900°C before it is fed to the kiln.

Preheater

Cyclone

Dust collector types :

Dust collectors :

• Gravity settling chamber (drop-out box)
• Cyclone
• Bag house filters
• Electrostatic precipitator
• Gravel bed filter

• The purpose of dust collectors is to remove dust from a gas stream and return it to the process in a de-aerated form

Dust collectors :

Baghouse Filters:

1. Shaker (Differential pressure 50-65 mmWG [2.0-2.5 inWG]

2. Reverse Air (Differential pressure 50-65 mmWG [2.0-2.5 inWG]

3. PulseJet ((Differential pressure 100-115 mmWG [4.0-4.5 inWG]

• The benefit of this tower is:

1-Heating the raw material and flatten it to enter the kiln .

2-Converting the CaCo3 to CaO

The cement is then housed in storage silos, from where it is hydraulically or mechanically extracted and transported to facilities where it will be packaged in sacks or supplied in bulk. In either case, it can be shipped by rail car, freighter truck or ship.

•  Bags: 50 Kg/bag
•  Jumbo plastic bags: 500 Kg/bag, 1000 Kg/bag, 1500 Kg/bag
•  It is also available in bulk.

Process description

Packing

Case ٍStudy

Material gas flow

Air cycle in cement grinding

problem statement :

Improvement of air network efficiency in Cement mills

at CEMEX

schematic:

Description of air network system :

• There are four Russian compressors ( every two compressor are connected together in parallel) .
• The compressed air discharge from the compressors and transported to the five tanks by pipelines .
• the production line number one has five cement mills (1 ,2,3,4,5)
• the one cement mill has one tank from the five tanks and this tank feeds another small tank that feeds two chamber pump .
• one cement mill system:
• the cement outlet from the mill and inlet one chamber pump
• fill it during another chamber pump pumps the cement to silos .

Conclusion

Any Questions

Rotary kiln

Given data

The operation condition in the cemex company

• The power of one compressor= 950 kw
• The air flow rate from one compressors =135m3/min
• Diameter of pipe from chamber pump to silo for the cement mill number (3&4,, Q=100ton/hr)

(dp= 26.7 27cm=11'')

• Diameter of pipe from the chamber pipe to silo for the cement mill number (5,,Q=140ton/hr)

(dp= 26.7 27cm=11'')

• The cement kiln burns rawmix to produce clinker, which is then ground to make cement .
• The kiln is the most expensive and technically complex part of the plant, and because it must be run all the time (unlike other sections of the plant) it effectively defines the output capacity of the plant.

The optimum condition we recommended it :

• The power of one compressor = 375 kw .
• The air flow rate from one compressor = 76 m3/min
• Diameter of the pipe from chamber pump to silo for the cement mill number (3& 4,,Q=100ton /hr)

(dp=0.186 m=18.6 cm= 8").

• Diameter of the pipe from the chamber pump to silo for the cement mill number (5,Q=140ton / hr)

(dp=0.2327m= 23.24cm 10'' ).

Assumptions

&

Approximation

Physical laws

Calculations

CEMENT GRINDING SYSTEM ARRANGEMENT (Using draft fan):

Cement mills :

• Used to grind cement.
• The temperature should not exceed 110°C in order to prevent gypsum dehydration.
• The fine material captured by the main grinding system dust collector or by the respective electrostatic filter is called cement. It is conveyed to the storage silos by rain and wind-proof belt conveyors or by pneumatic pumping.

Kiln Reactions

• Steel-plated cylinder .
• 5m diameter.
• Length of 60 to 100 meters.
• Rotates with a speed of 2 to 2.6 rpm.
• This product, containing nodules with a maximum size of 3 to 4 centimeters is called clinker .

- Grates cooler

-Planetary coolers

- Grates cooler (Cross Bar Cooler)

- Rotary Cooler

Clinker Storage :

Clinker Cooler Types :

- The clinker discharged from the kiln has a temperature close to 1450°C.

-It falls onto the cooler and quickly cooled by a current of air.

Clinker Coolers