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1. INTRODUCTION
OCL is a Chemical Company. The core business of company is manufacturing and marketing of Soda Ash and Sodium Bicarbonate. OCL is the second largest producer of Soda Ash and Sodium Bicarbonate in Pakistan. OCL is part of Olympia group of companies each owned by a member of the Monnoo family. The industrial group has been a success in Pakistan for more than 40 years, today boasting combined annual revenue of $300 million. It has started commercial production in 2000 with approximately 50,000 Tons annually and now we have reached a production capacity of 150,000 tons of Soda Ash and 15,000 tons of Sodium Bicarbonate annually. OCL is a Public Limited Company that employees 1200 people. It has a distribution network spread throughout Pakistan. The majority of OCL customers are glass, paper, soap and detergent manufactures. They are also exporting to UAE, South Africa, India, Sri Lanka and Bangladesh.
1.1 Products:
Light Soda Ash: Light soda ash is a white, odorless, uniform product, free from dirt and other foreign matter. Usage: ➢ Sodium Silicate ➢ Soaps Detergents ➢ Causticisation ➢ Paper Industry ➢ Laundry ➢ Chemical Industries ➢ Textiles Dense Soda Ash: Dense soda ash is a white, odorless and uniform product, free from dirt and other foreign matter.
Usage: ➢ Glass Industry ➢ Bottles, Jars, Sheets ➢ Hollow Glass ➢ Glass Balls ➢ Electric Bulbs ➢ Bangle Industry Sodium Bicarbonate: Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slight alkaline taste resembling that of sodium carbonate. Usage: ➢ Pharmaceuticals ➢ Backing and Confectionary ➢ Beverages ➢ Tannery ➢ Fire Extinguishers ➢ Poultry
1.2 Mission of Company:
The mission of OCL is: ➢ A Company built on sound financial footings that achieve excellent operating results through efficiency and cost control. ➢ A Company that consistently benefits its stakeholders through enhanced quality and profitability. ➢ A Company that achieves a high level of customer care service by providing quality products and positive feedback. ➢ A Company that provides excellent working environment to its employees that assists in enhancing their strengths and abilities create cultures that foster motivation and promote individual growth. ➢ A Company that contributes towards a good corporate citizenship and sets highest standards in serving the society.
1.3 Quality Policy:
➢ Sodium bicarbonate plant All these areas are briefly described0. The report also contains current issues of OCL, some problems highlighted along with their recommendations and their benefits. At the end of this report final conclusion is specified.
2. KILN SECTION
2.1 Objective of Plant:
The main objective of the kiln plant is to produce CO 2 & CaO. CO 2 & CaO can be by the burning of CaCO 3 with coke in kiln. The resulting products CO 2 & CaO used in further production of soda ash. CaCO 3 CO 2 + CaO CO 2 use for the production of soda ash & CaO use to make calcium hydro-oxide or milk of lime Ca(OH) 2. This milk of lime further use to recover ammonia which is also use in the production process of soda ash. Raw Materials: Raw materials uses in kiln plant are:
- Lime stone (CaCO 3 ) The standard size use in kiln plant of lime stone is 4-5 inches. Contents in lime stone are CaCO 3 , MgSO 4 & siliceous matter.
- Coke The standard size for coke to use in kiln plant is 1.25-2.5 inches. It has a calorific value of about 1300 BTU/lb. it contains 8-9% moisture. It is use to generate CO 2 & high temperature for calcination of CaCO 3.
2.2 Kiln Operation
Kiln Feeding System: There are total three kilns. Two kilns are in operation one is standby. Raw materials are charged from storage place to kiln top hopper by trolley. Trolley is attached to skip hoist by a steel rope. Skip hoist is driven by a motor. The quantity of raw materials per trolley is as follows: Total weight of lime stone & coke per trolley = 890-913kg Weight of lime stone per trolley = 830-850kg Weight of coke per trolley = 60-63kg Raw materials are charged from top kiln hopper to kiln by hannon flask through combined feeder. The quantity of raw materials per charge as follows: Total weight of lime stone & coke per charge = 1350kg
After cleaning in scrubber gas is passing through cooler. In cooler there are rashing rings of ceramic material. Water is showering from the top of the cooler and gas is passing through from the bottom of the cooler. By rashing rings the contact time between gas and water is increased and by increasing this contact time gas is cool down in short time. The leaving temperature of gas is about 30-32c₀, after cooler gas is entered in electrostatic precipitator (ESP). Electro Static Precipitator: When gas is cooled down to 30-32c₀^ it enters in electro static precipitator. In ESP 62KVA electrostatic charge is produced through 85 corona wires. This is called corona effect. At the end of each wire there is weight of about 0.5kg is hanging by which the wires hanging still. Through positive and negative charge the remaining dust particles attracts to these wires and removes from the gas. As the gas sucked by compressor so after cleaning & cooling gas is sent to compressor section. The cleaning of ESP’s takes place after every 8hrs. Specification of kiln: Height of kiln 75ft Diameter of kiln 12ft Kiln top hopper capacity 550 - 600ton Capacity of kiln 150ton Insulation of kiln Refectory bricks Refectory bricks made of Aluminum oxide & silica Thickness of refectory bricks 2ft Height of refectory bricks in kiln 66ft Operating parameters of kiln: Sr. # Parameters Ranges
- Pre heating zone/Top zone 450 - 600c₀
- Calcining zone/Middle zone 800 - 1100c₀^ (preferably 830-950c₀)
- Cooling zone/Bottom zone ≤100c₀
- Kiln top pressure 0.02-0.05KPa
- Force draft fan pressure 0 - 7KPa
- Force draft fan flow rate 9000m^3 /hr
- Kiln pull Adjust according to compressor pull
- Compressor pull Adjust according to requirements
- Burden height 1 - 2ft (out)
- Hannon flask rotation time 2min & 55sec
- Top hopper level ¾
- Kiln gas exit temperature ≤200c₀^ (preferably 120-150c₀^ )
2.3 Preparation of Milk of Lime (MOL):
Burnt lime is discharged to plate conveyer by plate feeder and air lock. Bucket elevator discharge this burnt lime into burnt lime hopper. Burnt stone is fed to the lime slacker. There are total three slacker two of them are in working and one is standby. Water in hot water storage tank is heated up to 70-80c₀^ by injecting steam which is coming from boiler. To fulfill the requirements of hot water so the hot water is also supplied from combined building through ammonia cooler. Hot water is fed to slacker along with burnt stone and flow of water is adjusted in such a way to get MOL of required strength. To separate out grit from MOL, the MOL flows through a trough into a rotary sieve. Then it is sent to continuous stirred tank and from there it is supplied to distiller and brine purification plant. Specification of slacker: Length of slacker # 1,2 11.5m Diameter of slacker # 1, (at front) 1m Diameter of slacker # 1, (at back) 1.8m Capacity of slacker # 1,2 120ton\day Length of slacker # 3 16m Diameter of slacker # 3 (at front) 1m Diameter of slacker # 3 (at back) 1.8m Capacity of slacker # 3 350ton\day Operating parameters of slacker: Sr. # Parameters Ranges
- Entering temperature of CaO 45 - 55c₀
- Hot water temperature 70 - 80c₀
- Mesh size of rotary sieve # 1 3mesh
- Mesh size of rotary sieve #2 10mesh
- MOL at sieve shoot 120 - 124tt
- MOL tank 140 - 150tt
- Gas exit from cooler ≤30-32c₀
- CO 2 produce in kiln ≥35%
- O 2 produce in kiln ≤3% (excess)
- Exit temperature of CaO 45 - 55c₀
- Gas %age reduce (^) • Improper coke ratio.
- Top pressure increase • Less compressor pull.
- F.D pressure is very high.
- Scrubbing system partially blockage. - Increase the compressor pull. - Start I.D fan. - Increase F.D fan pressure.
- Top pressure decrease (^) • High compressor pull.
- F.D fan pressure is too low.
- Error in top pressure gauge.
- Vent rate is too high.
- Flapper plates are open. - Decrease the compressor pull. - Stop the I.D fan. - Increase F.D fan pressure. - Put on flapper plates in a right way. - Check the pressure gauge.
- O 2 contents in kiln gas are high
- Air quantity is too high.
- There is partial burning in kiln.
- The pressure at top is negative
- Top feeding flapper plates are open.
- Decrease the air input.
- Distribute the raw material properly.
- Keep small positive pressure at top.
- Top feeding flapper plates to be closed.
3. COMPRESSORS
Compressors are an important part of the process industries. Compressors increase the pressure of gases and vapors so they can be used in applications that require higher
pressures. For example, they can be used in a wide variety of applications like compressing gases such as carbon dioxide, nitrogen, and light hydrocarbons, or providing the compressed air required operating instruments or equipment. The two most common compressor types are positive displacement and dynamic. Positive displacement compressors use pistons, lobes, screws, or vanes to reduce a fixed volume of gas through compression and deliver a constant volume. Dynamic compressors use impellers or blades to accelerate a gas and then convert that velocity into pressure. Dynamic compressors are more commonly used than positive displacement compressors because they are less expensive, more efficient, have a larger capacity, and require less maintenance. All compressors require a drive mechanism such as an electric motor or turbine to operate, and all are rated according to their discharge capacity and flow rate. Most compressors require auxiliary components for cooling, lubrication, filtering, instrumentation, and control. Some compressors require a gearbox between the driver and compressor to increase the speed of the compressor.
3.1 Compressor Basics:
The principle of operation of a compressor is the same as that for a pump. The compressor driver supplies kinetic energy that the compressor converts to pressure energy. Some energy is wasted because of fluid friction; this turns kinetic energy to heat energy. Like all other machines, compressors efficiency is always less than 100%. Effects of Pressure on a Gas: The main difference between liquids and gases is that:
- Liquids are incompressible —pressure has almost no effect on a liquid’s volume.
- Gases are compressible —pressure has a great effect on the volume of a gas. There is a law that describes how a change of pressure changes the volume of a gas. It is called Boyle’s Law and it says something very simple: as long as the temperature of the gas does not change, increasing the pressure on a gas always decreases its volume. This is probably obvious: a gas is squashed by pressure.
- If double the pressure, the volume is halved.
- If halve the pressure, the volume doubles. Normally, pressure also has an effect on the temperature of a gas. As pressure of a gas increases its temperature also increases. To give the exact relationship between pressure and volume described by Boyle’s Law—doubling pressure halves volume—the gas must kept cool to stop its temperature increasing.
3.2 Types of compressors:
Working principal of Reciprocating compressor: In piston-type reciprocating compressors, the pistons connect to a crankshaft that converts the rotational motion of a driver to the reciprocating motion of the piston. The piston’s motion pulls gas into a cylinder from the suction line, and then displaces it from the cylinder through the discharge line. Check valves (compression valves) on the suction and discharge allow the flow of the gas in one direction only. Piston-type compressors can be single or double-acting. Double-acting compressors trap the gas during the suction stroke on one side of the piston, while compressing the gas on the discharge side of the piston at the same time. Two stage reciprocating compressor: CO 2 coming from kiln has a concentration of 38-40% and the gas coming from calciner has a concentration of 88-90%. Gas coming from kiln has a small amount of moisture, to remove these water vapors gas is passes through coconut bed separator where water vapors removes from the gas, after passing through coconut bed separator the gas sent to compressors through cyclone to remove remaining water vapors. Two stage reciprocating compressor is two single stage reciprocating compressor in series, with the discharge of first compressor (1st^ stage) feeding to the suction of the compressor (2nd^ stage). The 1st^ compressor increases the pressure of the gas & then the 2nd^ compressor increases the pressure even further. For example 1 st^ stage compressor - 1.0 bar inlet pressure 2.0 bar outlet pressure 2 nd^ stage compressor - 2.0 bar inlet pressure 5.0 bar outlet pressure When the gas is compressed it becomes hot. Hot compressed gas could cause a compressor to overheat, & overheating can damage a compressor. In two stage compressor, the compressed gas from stage 1 must be cooled before it enters in 2nd^ stage. To cool the gas, an inter cooler is installed between the first & second stage. The inter cooler is a heat exchange, normally shell & tube type & as the gas passes through the tubes it is cooled by water flowing around the shell. When the gas pressure increased in the second stage, this also increases the temperature of the gas. This high temperature can damage the downstream equipments so the gas is cooled in cold gas tower. In cold gas tower gas is passes from bottom to top through rashing rings & water is showering from the top of the cooler through nozzles. These rings increase the
contact time between gas and water. The temperature of gas is down then it passes through cyclone to remove water vapors in gas. Now the gas is sent to carbonating tower. The kiln gas is used as top gas as its concentration is low & calciner gas is used as bottom gas as its concentration is high. Also kiln gas is used as cleaning gas. Cleaning of carbonating tower takes place after 75hrs. Operation safeties of reciprocating compressor: ➢ Operator must read & understand the service manual carefully. ➢ Before start-up, strictly inspect whether each piping & facility connection are fixed. ➢ Check oil level. ➢ Supply cooling water to each cooling piping & check whether there is any leakage. ➢ Safety devices must be test. ➢ Check all valves. ➢ Start main motor to check if there is any problem. ➢ After completing operation, start-up carried at on site also at control room depending on actual situation. Compressor may be started if everything is okay. ➢ Before starting up compressor the vent valve and suction valve should be open. ➢ Open cooling water supply valve and discharge valve. ➢ Now start compressor & check when the torque load is stable. ➢ When torque load is stable slowly close down the vent valve as well as slowly open the gas discharge valve. ➢ Regulating the water injecting quantity. ➢ Regulating the gas filling pressure. ➢ In normal operation after completing 1st^ pressure rise, pressure may gradually increases to specified value. ➢ When pressure reaches to specified value fully close the vent valve. ➢ When compressor shut down; all pressure must be relieved by opening the vent valve & closing the inlet valve & discharge valve. ➢ Upon compressor is shut down power should be off. Reciprocating Compressor Data: There are total 9 reciprocating compressors. There data as below: **Sr.
Suction Discharge Motor capacity (Kw) Motor RPM Compressor RPM Flow capacity (m**^3 /min)
Kiln Cleaning 95 975 --- 20
Kiln + calciner Top + bottom 200 742 556 42
Kiln Cleaning + top 135 728 516 28
CO 2 coming from kiln has a concentration of 38-40% and the gas coming from calciner has a concentration of 88-90%. Gas coming from kiln has a small amount of moisture, to remove these water vapors gas is passes through coconut bed separator where water vapors removes from the gas, after passing through coconut bed separator the gas sent to compressors through cyclone to remove remaining water vapors. Most screw compressors have two meshing helical screw rotors. They may be single flow, with gas entering at one end and leaving from the other, or double-flow, with gas entering at both ends and leaving at the centre. These are the same arrangements as for screw pumps. Gas is compressed as it is ‘screwed’ along the lengths of the rotors and force out of the discharge. Wet screw compressors are lubricated by oil sprayed into the gas as it enters. These can operate without synchronizing gears. One of the screw rotors then becomes an idler and is turned by the drive rotor. If the gas must be oil-free, non-lubricated dry compressors are used. These need synchronizing gears to avoid metal-to-metal contact between the screws. After compression gas is sent to cold gas tower to cool down and then through cyclone it is sent to carbonating tower. Lubrication System of Screw Compressor: Normally, when gases are compressed, the bearings and seals become hotter. Some of the heat is transmitted to the seals and bearings. This heat is removed by cooling the lubricants. Lubrication systems circulate and cool sealing and lubricating oils. In some applications, the sealing and lubricating oils are the same. The oil piping system of screw compressor is as below: Lube oil Motor, gear box,^ Lube oil oil distributer Each oil injection point of compressor Oil return pipe Lube oil unit
Oil is circulated to lubricate all parts of screw compressor. After passing through all parts of compressor oil is recycled back to oil storage tank, by passing through shell and tube heat exchanger (in shell there is oil and in tubes there is cold water) to cool down the temperature of oil and it is filtered to remove impurities. The compressor adopts high quality E-46 turbine oil, which features better anti rust and anti-oxidation and higher anti-halogenations. Moreover, lubricant must be clean and no moisture is permitted in lubricant. Also turbine oil features longer life generally oil replacement once every two to three years. Alarms or Tripping Values of Different tags of screw compressor: **Sr.
Different Tags**
630KW 1400KW
Alarm Tripping Alarm Tripping
- Radial Bearing 65c⁰^ 70c⁰^ 75c⁰^80 c⁰
- Thrust bearing 65c⁰^ 70c⁰^ 75c⁰^ 80c⁰
- Gear Box 85c⁰^ 95c⁰^ 85c⁰^ 95c⁰
- Discharge pressure 0.39MPa 0.43MPa 0.39MPa 0.41MPa
- Oil pressure 0.18MPa 0.15MPa 0.18MPa 0.15MPa
- Discharge temp. 90c⁰^ 100c⁰^ 105c⁰^ 110c⁰
- Vibration 1.5ge 2.5ge 0.150mm 0.200mm Operation safeties of screw compressor: ➢ Operator must read & understand the service manual carefully. ➢ Before start-up, strictly inspect whether each piping & facility connection are fixed. ➢ Oil piping is cleaned by circulated oil supplied by oil console. ➢ Supply cooling water to each cooling piping & check whether there is any leakage. ➢ Safety devices must be test. ➢ Open small cover on gear box & check whether there is non-balance & no friction shock. ➢ Start main motor to check if there is any problem. ➢ After completing operation, start-up carried at on site also at control room depending on actual situation. Compressor may be started if everything is okay. ➢ Start oil pump. Emergency tank
- Dissolved impurities To remove these types of impurities water treatment has to be done. To remove these impurities there are two treatments:
- Physical treatment
- Chemical treatment Physical treatment is for suspended particles or impurities and chemical treatment is done to remove dissolved impurities.
- Physical treatment I. Screening II. Sedimentation III. Filtration
- Chemical treatment I. Coagulation II. Flocculation
4.1 Physical & Chemical Treatment of Water:
1. Screening: Screening is the process to remove impurities from water of large size such as large size stones, shopping bags, wood pieces & other organic material. Screening is done by places screen or sieve or strainer at suction of each pump, so that these large size impurities can never chock the pump. 2. Coagulation: As large size impurities remove by screening & some impurities which have large molecular weight settles down at reservoir. But some impurities which do not settle down & suspended in water are removed by coagulation process. There are attractive & repellent forces between these particles, when the attractive & repellent forces between the particles are of same amount then particles do not settle down & suspended in water. To remove these particles a chemical aluminum sulfate (Al 2 SO 4 ) or it is named as alum is added in water, by addition of this chemical the attractive & repulsive force between the particles break. So the particles with negative charge attract towards aluminum ions & the particles having positive charge attracts towards sulfate ions, by the attraction of these particles they made coagulates and settle down. The settling time given to a reservoir is about 1-2days. The amount of adding aluminum sulfate in water is according to requirements. Other chemicals that can be added instead of aluminum sulfate are: potassium sulfate, ferric chloride, aluminum-potassium salts etc. 3. Flocculation: The particle which does not remove by coagulation can be removed by flocculation. In this process the chemical flocculent is added in clean water tank having a capacity
of 1m^3 , and then the doze of this solution is added in water having impurities in it. By the addition of this chemical solution the suspended particles stick with each other & make flocks of large molecular size. These large size flocks and remaining impurities remove by sedimentation process.
4. Sedimentation: Sedimentation takes place on sand bed filter. Sand bed filter is made of four layer bed. Top layer of sand bed filter is of silica sand, second layer is of gravel stones having size of about 2-4mm, and third layer is of also gravel stones with a size of 4-8mm & the fourth layer is of porous bricks. Water passes through these layers and the flocks and the remaining impurities settles down on these layers. The capacity of sand filters is about 1290m^3. The settling time given to sand filter is about 1-2hrs in winter & 2-3hrs in summer. Water after passing through sand bed filter sent to multimedia filters for filtration. 5. Filtration: Filtration is the process by which the particles having very low molecular weight can b removed. The process of filtration is takes place in multimedia filters. In multimedia filters there are also layers of different materials as in sand bed filter. In multimedia filters the top layer is of thickness of 400mm of anthracite, second layer is of quartz sand having size of about 0.8- 1mm & thickness of this layer in fitter is about 600mm. the third or last layer is of gravel stones of size of 2-4mm & the thickness of this layer is about 200mm. Nozzles are fitted at the beneath of multimedia filters. Water from sand bed filter is entering in multimedia filter from top and discharge from bottom through those nozzles. Those nozzles can bear a pressure of about 6bar. When water passes through these layers very small particles settles on these layers and clean water pass through and sent to use in process.
4.2 Water Softening:
➢ Raw water is taken into a tank called catalyzer where it is heated up to 40c⁰-60c⁰^ by the help of steam. ➢ Milk of lime Ca(OH) 2 is added into this heated water which reacts & helps to remove Mg+2^ ions. ➢ Heavier particles from precipitates formed in catalyzer are also removed along with lime grit from the bottom of catalyzer. ➢ Heated water with addition of lime over flows to a tank called settler where almost all fine particles settle down & form sludge. This drained from bottom of settler once in a shift & in way clear water is obtained.
