ABSTRACT The main objective of vocational training program is to provide practical knowledge of the product being manufactured and working process in the factory, besides the theoretical and practical knowledge from their institution. Pulp and paper industry in India and all over the world has grown exponentially it’ it’s over the past few years. Growing at the pace that it is, to understand functionally was my basic objective. To be a part of pulp and paper industry was very exciting and knowledgeable. On site work gave me a better understanding of mechanical systems. Classroom knowledge was insufficient and was given more meaning. Thus suddenly all theories and derivations seemed logical. More over this training gave me a chance to interact with working techniques, and to get familiar with facilities and formalities that one should follow in a factory.
1
OBJECTIVE
1. To facilitates realization of team and effective organization. 2. Create business and strategic thinking. 3. Build management and technical competences. 4. Promote a culture of achievement and excellence. 5. Improve quality of work life in organization. 6. Optimize resource utilization. 7. Atmosphere of east consciousness. 8. Encourage improvements of team and individuals.
2
INTRODUCTION
Century Pulp & Paper (an ISO-9001: 2000 & ISO-14001:2004 Certified Division of Century Textiles and Industries Ltd.), a Division of Century Textiles and Industries Ltd. is a member of B.K. Birla Group of Companies. The company chairman is Shrimati Basant Kumarji Birla. Established in 1984, the Division is situated at Lalkua on the Bareilly-Nainital Bareilly-Nainital Highway. The Head Office Office of the th Division is on the 11 Floor of Industry House, 10, Camac Street, Kolkata. Product range of the CPP comprises a vast range of quality Writing & Printing Paper and superior quality dissolving Rayon Grade Pulp used for Viscose/Staple fiber/filament yarn. It has other uses in preparing urea, formaldehyde, melamine formaldehyde and phenol formaldehyde. CPP has a well equipped and planned department for Environmental Conservation and Pollution Control. CPP pays sincere attention to the overall development of its employees and that of the community. It also has a well organized HRD Department for supervising these activities. CPP maintains an excellent infrastructural set up with modern facilities in order to carry out organizational activities.
ENERGY CONSUMPTION: The power requirement of the plant is met by a 7500 MVA grid connection from UPCL and 21 MW & 6.8 MW own turbo generator sets. The plant consumes approx 6 lacks units per day, 90% of which is met by own generation. The daily thermal energy inputs are from 600 tons of coal and RFO. Black Liquor & Pith generated as liquid & solid wastes are also used for meeting steam and power requirements of the mill. The annual energy bill of the company is 20.64 % of the manufacturing cost. Because of continuous energy conservation efforts, plant optimization and adopting technological advances, there has been a continuous reduction in specific energy consumption. 3
RECIPIENT OF AWARDS 1. Eco-Mark by BIS for its Bagasse based products. 2. Central Pollution Control Board and National Productivity Council have selected the company as a “Model” unit in the field of “Waste Minimization” among pulp and paper industries. 3. CPP’s Effluent Treatment Plant has been selected by Central Pollution Control Board for carrying out studies and data collection for preparation of Minimal National Standards (MINAS) for large pulp and paper industry group. 4. CPP’s waste reduction schemes have been included in the “World Bank” – Data Base on Waste minimization. 5. Awarded Indo German Green tech Award for Environment Excellence for the year 2000-2001. 6. CPP was awarded ‘First Prize’ at All India Farmer’s fair for the year 2004 -2005 for its significant efforts towards farm forestry. 7. CPP was adjudged as the “Efficient Unit” in energy conservation by CII for the year 2004-2005 8. CPP was awarded “First Prize” for energy conservation by Indian Paper Makers Association as well as the “National Award” for Energy Conservation in Pulp & Paper Sector by the Hon’ble Prime Minister of India for the year 2004-2005 2004 -2005
4
C.P.P. PRODUCTS Machinery used Raw Material
: Most Modern Machinery : Bamboo Wood, Vineer Chips, Bagasse, Waste Paper, Soft wood Pulp Products Manufactured : All types of writing and printing papers papers Grade Pulp : Tissue Paper and Packing Board CPP’s range of products includes some of the finest varieties of writing and printing paper which has carved a niche in the market.CPP also manufacturer’s raw material for viscose filament yarn/staple fiber and also paper grade pulp. A. Writing and Printing Printing Papers (45 to 210 gsm) (Wood (Wood based)
1.
Azurelaid
2.
Maplitho White/NS
3.
Maplitho Deluxe CG
4.
SS Maplitho
5.
Dye line base
6.
Offset printing paper
7.
Maplitho NS (ARSR)
8.
Century Parchment
9.
Super Printing
10.
Century Bond
11.
Railway Bond
12.
Copier
13.
Continuous Stationery (HB)
14.
Base Paper for coating
15.
Plain Paper
16.
Opaline Base Paper
17.
Overlay tissue
18.
Century Maplitho
19.
NCR Base Paper
20.
MICR Cheque Paper 5
21.
Color Ptg Paper
22.
Century Excel Ptg
23.
Century Index Paper
24.
Broke cover MF – MF – Sticker Base
(Bagasse Plant) 1.
Copier
2.
Super Maplitho white
3.
Super shine Printing
4.
Plain Paper/ Writing Paper
B. Rayon grade pulp C. Bleach hardwood pulp (paper grade)
6
DIFFERENT UNITS IN C.P.P. Century's rayon and/or paper grade pulp, and writing and printing paper unit were established in 1984 at Lalkua, near Nainital in the state of Uttarakhand. Its second paper unit, based on bagasse manufacturing, is adjacent to the existing pulp and paper plant at Lalkua. It was established in 1995. The company also has a prime-grade tissue paper plant at Lalkua. The company's fiber line (pulp plant), with a capacity of 1.62 lac tonnes per annum, and multilayer packaging board plant, with a capacity of 1.8 lac tonnes per annum, are near completion. Production has begun and is expected to stabilize in due course.
PRODUCTS: The division's range of products includes a large variety of writing and printing paper, tissue paper and paper board. The company also manufactures raw material for viscose filament yarn, staple fiber and paper grade pulp.
The installed capacities for the various products are:
Item Rayon and/or paper grade pulp Writing and printing paper: A Wood-based paper B Bagasse-based paper C Recycle based paper Total (a + b + c) Prime-grade tissue paper Packaging board Power plant Chemical recovery plant
Metric tonnes per annum 31,320
37,250 84,600 75,960 1,97,810 36,000 500 tons/day
7
PLANTS WITH IN CAMPUS: 1. W.P.P. PLANT: Integrated pulp and paper unit based on Eucalyptus and Bamboo furnish. Two paper machines with 115 T.P.D Capacity. Paper M/c I equipped with size press. press. Capable to manufacture 44-210 GSM(gm/ GSM(gm/ sq.meter). Machine deckle is 2.69 meters. Re-winders are jagenberg make with 1000m/min speed and cutters are of 1.45m width with 200m/min speed.
2. R.G.P PLANT: Based on eucalyptus & popular furnish. Bleaching sequence includes chlorine dioxide treatment. Sheeting machine with 100 T.D.P productions with on machine cutters and bailing press. (Make carcano, italy make). M/c deckle 2.4 meters.
3. BAGASSE PLANT: Based on bagasse furnish 84%, eucalyptus and bamboo 10% are imported pulp 6%. Paper machine equipped with film press for on line coating with 235 t. d. p production. Capable to manufacture 40-120 GSM including light weight coated varieties. M/c deckle 5.2 meters.
4. RECYCLE FIBRE PLANT: A second fiber based plant manufacturing writing/printing paper. DIP plant is equipped with 2 stage floatation and 2 stages bleaching. Latest technology in corporate in this plant facilitates production of finest paper quality in this category. The product range includes writing and printing papers of 52-130 GSM.
5. TISSUE PLANT: Prime grade tissue plant of 100 TPD with hi-speed machine (2000 MPM) supplied by metso is equipped with latest technology to produce finest quality in this category. The product range will include facial, napkin, toilet, C-fold and kitchen towel etc. in the range 13-40 GSM.
6. BOARD PLANT: Based on wood and waste paper voith machine equipped with latest technology capable to produce 500 TPD finest quality packaging board with
8
600 MPM speed. The product range includes 4 layer board of 170-500 GSM, M/c deckle is 3.75 Mtr. 7. POWER BLOCK: Powerhouse has 9 coals and Pith fired boilers and three turbines. The turbines are of 6.8 MW BHEL TG set (extraction back pressure),21MW TDK TG Set and 16 MW BHEL turbine , 43 MW TG (all are double extraction condensing type) 8 boilers are fluidized bed boilers out of which , 1 F. B. C. Boiler is of 100 2
T/hour 62 kg/cm ,480 degree Celsius each , 1 boiler is spreader stoker coal fired boiler of 25 T/hr , 47 ata ,420 degree Celsius and 1 boiler is coal cum pith fired boiler of 60 T/hr , 66 ata , 485 degree Celsius Celsius ,1 new coal boiler of 2
100 T/hr , 65 kg/Cm ,480 degree Celsius . 8. Chemical recovery plant: It recovers cooking chemicals spent during cooking operation in digesters with the help of latest technology available. These chemicals are re used in cooking operation in pulp mill. The liquor received from pulp mill is called black liquor and the liquor supplied back to pulp mill is called white liquor based on their color appearance. The black liquor contains substantial quantity of organic matter like lignin which when burnt in recovery boiler along with the black liquor releases enormous amount of heat which utilized to generate high pressure steam and is sent to turbines to generate power. The black liquor is first concentrated in evaporators, then burn in boilers and their after is reacted with lime (Calcium oxide) in causticizing section to finally recover the spent chemicals.
9
QUALITY CONTROL Century Pulp and Paper, Lalkua has well organized laboratory equipped with modern pulp and paper testing equipments including Auto line from L&W Sweden, Qualified and experienced staff manage the quality control department. For all inputs fibrous/non fibrous, in-process material (digester section, bleaching section, stock preparation); finished material (Paper/Pulp)at paper machine rewinders/cutters, finishing house and Go-downs, standards/ specifications are followed as per guidelines of ISO-9001:2000) quality system (quality Inspection Plant). Inputs and Finished product is allowed only after conforming to standards. Testing/analysis is carried out as per TAPPI/ISO standard. A separate customer cell has been formulated to redress customer grievances and recourse to quick solutions. This cell understands changing needs of customers, caries out periodical market research to improve customer-choice process.
10
ENVIROMENT MANAGEMENT Century pulp & paper maintains a perfect harmony with environment through excellent pollution – –control control measures both for air & water. All initiatives and efforts are made to curb pollution at the grass-roof level. In order to meet the measures set by the board for air & water, C.P.P. has adopted the following control facilities.
Water: Effluent treatment plant having most modern technology, based on activated sludge process involving primary clarifier, anaerobic treatment, biological reactor, Secondary clarifier and sludge handling system. Air : electronics precipitators and bag filter in coal fired boilers: electrostatic precipitators & ventury scrubber in rotary lime kiln; jet condensers for digester blow offs. Green belt developments are an integral part of total environmental management program. C.P.P. maintains it own plant nurseries and has planted species in and around premises. Maintaining a clean and unpolluted environment has been one of the prime objectives of C.P.P. all endeavors have been made right from the inception to incorporate device that can take care of pollution-both of water and air. “ waste control ” forms and integral
part of overall “waste management system” system” -
systematically planned and adopted by C.P.P.
11
PROCESS OF PAPER PRODUCTION Timber Timber used for papermaking comes from well managed forests where more trees are planted than harvested to ensure sustainable growth. Papermakers usually use only the parts of the tree that other commercial industries don't want - such as saw mill mill waste and forest forest thinning. Go to publications publications for details of a Trees used for Paper making Poster.
De-Barker Bark is stripped from the logs by knife, drum, abrasion, or hydraulic barker. The stripped bark is then used for fuel or as soil enrichment.
Chipping Machine Stripped logs are chipped into small pieces by knives mounted in massive steel wheels (used in chemical pulping process). The chips pass through vibrating screens, where by both undersized chips; dust etc and oversized chips are rejected. Accepted chips are then stored in huge bins ready for the next process.
Chemical Pulping Process Chips from the storage bins are fed into a digester to which chemicals have been added. The woodchips are then 'cooked' to remove lignin. Lignin is the binding material which holds the cellulose fibers together. The chips are 'cooked' by heat and pressure in caustic soda and sulphur. The chemical process is energy self sufficient as nearly all by-products can be used to fire the pulp mill power plant. The chemical pulping process produces lower fiber yield than mechanical pulping, typically 50-60%.
Mechanical Pulping Process Mechanical pulp yields over 90% of the wood as fiber is produced by forcing debarked logs, about two meters long, and hot water between enormous rotating steel discs with teeth that literally tear the wood apart. Alternatively, logs can be pressed against grindstones which is why this process is also known as ground 12
wood pulp. Trees contain up to 30% lignin, a material which is sensitive to light and degrades, and turns brown in sunlight, which explains why papers made from mechanical pulp will discolor. An example of this is newsprint. Newsprint is designed to have a short life span, and if left for a long period of time will lose its whiteness and strength. The special advantages of mechanical pulp are that it makes the paper opaque and bulky.
Hydrapulper When the bales of wood pulp or waste paper arrive at the paper mill they are loaded onto a conveyor and passed into a circular tank containing water. This has a very powerful agitator at the bottom which breaks up the bales into small pieces. The pulp mass created begins to look like thick porridge. This machine is known as a Hydrapulper. It operates automatically and when the disintegrating process is complete it discharges the pulp into large storage tanks. Hydrapulpers used mainly for handling waste paper are fitted with special devices for removing unwanted contraries such as wire, plastic, paper clips, staples etc
Blend Chest The stock passes to a blend chest where numerous chemicals can be added to obtain the required characteristics to the finished paper. Dyes are also added, as necessary, to color the paper. Dyes fix themselves to the cellulose fibers and are fast to light and water. Each grade of paper and board requires a very accurate blend of pulps and additives and the properties of the paper are continually monitored by computers during manufacture.
Waste Paper Waste paper is collected from Waste Paper Banks and Commercial collections. When you deposit your used papers into a waste paper bank, you are sorting the paper into grades before the merchant collects it. This is why you can only put certain papers into a particular bank.
13
Many offices have in place an office recycling scheme. Again the waste paper is usually segregated ready to be collected. Waste paper currently represents 67% of the raw material used in the UK to make paper and board. The waste paper merchant collects the used paper which is then sorted by hand into different grades. Paper not suitable for recycling is removed. The waste paper merchant will then bale the waste paper ready to be taken to the paper mill.
De-inking Before printed paper, such as office waste and newspapers, can be recycled the ink needs to be removed, otherwise it will be dispersed into the pulp and a dull grey paper would result. There are two main processes for de-inking waste paper - these are known as washing and flotation.
Washing The waste paper is placed into a pulper with large quantities of water and broken down into slurry. Contraries -such as staples - are removed using centrifugal screens. Most of the water containing the dispersed ink is drained through slots or screens that allow the dispersed ink particles through, without taking the pulp. Adhesive particles, known as 'stickies' are removed by fine screening. Flotation Again the waste is made into slurry and contaminants removed. Special surfactant chemicals are added which makes a sticky froth on the top of the pulp. Air bubbles are blown through the pulp and these carry the inks to the surface. As the bubbles reach the top foam layer is formed that traps the ink. The foam must be removed before the bubbles break or the ink will go back into the pulp. Because the ink is removed from the flotation machine in a concentrated form, the flotation system does not require a large water treatment plant
14
Refining This is where the cellulose fibers pass through a refining process which is vital in the art of papermaking. Before refining, the fibers are stiff, inflexible and form few bonds. The stock is pumped through a conical machine which consists of a series of revolving discs. The violent abrasive and bruising action has the effect of cutting, opening up and de-clustering the fibers and making the ends divide. This is called fibrillation. In this state, the fibers are pliable and have greater surface area, which significantly improves the fiber bonding. The properties of the paper are directly related to the refining process. Refining used to be called beating.
Screening and Cleaning Pulps contain undesirable fibrous and non-fibrous materials, which should be removed before the pulp is made into paper or board. Cleaning involves removing small particles of dirt and grit using rotating screens and centrifugal cleaners.
Paper making machine The Paper Machine is a very large piece of machinery. A typical machine is about the length of two football pitches and around 4 meters wide. It can run up to speeds of 2000 m per minute - or 60 miles per hour! The machine itself consists of 7 distinct sections. The flow box, wire, press section, drier section, size press, calendar and reeling up. The first section of the machine is called the 'Wet End'. This is where the diluted stock first comes into contact with the paper machine. It is poured onto the machine by the flow box which is a collecting box for the dilute paper stock. A narrow aperture running across the width of the box allows the stock to flow onto the wire with the fibers distributed evenly over the whole width of the paper machine. The machine is operated by computer control. The computer will monitor the paper for moisture content, weight etc and computer screens will show pictures of the process and should any adjustments need to be made, an alarm will sound.
15
Conversion and Printing Once the paper is made, a great deal of it is converted into a product. Converters specialize in transforming reels and sheets of paper and board into a vast array of finished products for distribution such as boxes, cartons and stationery. Converters sell their products to the public or to other manufacturers. Not all paper and board is processed by converters. Some papermakers do their own converting, for example, the manufacturers of soft tissues market their own products and sell directly to the public. p ublic. The printing industry converts large quantities of paper and board, much of which reaches the customer as newspapers, magazines or books.
16
WORKING OF W.P.P PLANT
BLOCK DIAGRAM OF W.P.P. STREET: CHIPPER
BROWN STOCK WASHER 4 STAGES
SCREENING
CHIP SILO
KNOTTER
UNBLEACHED SCREEN PULP STORAGE TOWER 2 NOS.
DIGESTER 3 NOS.
BLOW TANK
BLEACHING
PAPER MACHINE 2 NOS.
STOCK PREPARATION
BLEACHED PULP STORAGE TOWER NO. 1
RE-WINDING AND CUTTING
FINISHING FINISHIN G
WARE HOUSE
3 NOS.
17
WOOD BASED PAPER PLANT (W.P.P. STREET) 1. PLANT CAPACITY 2. RAW MATERIAL 3. GENERAL PROCESS
: 115 TONNES PULP PER DAY PRODUCTION : EUCALYPTUS, BAMBOO VINEER CHIPS : SHOWN IN ATTACHED FLOW DIAGRAM
PLANT/ PROCESS DESCRIPTION: Wood based paper is made with eucalyptus, bamboo & vineer chips as raw material. All types of writing and printing papers are made in this plant. Quality parameter is very stringent in its production.
The main units in W.P.P plant are as mentioned below: 1. Chipper house : for chipping the wood logs 2. Digester house : for cooking the chips 3 Washing plant : for washing the fiber 4. Bleaching plant : for bleaching the fiber 5. Stock preparation : for addition of additive in pulp 6. Paper machine : paper sheet making 7. Converting : for cutting paper reels to desired size & length 8. Finishing : for cutting the reels in paper of desired size 9. Packing : for packing the reels and reams CHIPPER HOUSE:
Eucalyptus logs & bamboo are fed to the chipper through feeding conveyors to obtain wood chips of size 1” to 11 -1/2”. In chipper house, 3nos. drum type chippers each having capacity of 10 tons/hour chipping capacity are installed for this purpose. The accept size chips are stored in a chip silo while over size portion is recycled for re-chipping. To avoid any foreign material/wood dust to enter to a process, the chips are washed in chips washing equipments before processing.
DIGESTER HOUSE: The washed chips are fed to the digester in the pulp mill for cooking operation of the chips. There are 3 nos. digester, each having capacity of 6.5 kg/cm2. The cooked chips (pulp) are pumped to blow down tank to release the pressure by venting out the vapors. The cooked pulp is passed through the two separate un 18
cooked, or partially cooked chips/knots which are re-cooked in the digester. The accept from the knotter contains the pulp, spent chemicals and the organic material obtained from wood during cooking the total mass is now sent for washing in brown stock washer.
WASHING AND SCREENING: The washing of the pulp is counter currently done with hot water on nos. brown stock washers washers which are basically rotary rotary vacuum vacuum filters. This is is done to to get pure pure fiber by separating spent chemicals and organic content of the wood from it. During washing of the pulp, the organic and inorganic contents in the form of black liquor are sucked with the help of vacuum and stored in the seal tank from where these are pumped to recovery plant. Air pressure is used through the drum dru m surface of the washer for effective washing of the pulp After washing, washed pulp is sent to centrifugal screen to remove fine specs. This is a section with a rotating drum and stationary screen. When drum rotates, fine shrives, fiber bundles and specs are separated from the Pulp due to centrifugal force. The screened pulp is stored and diluted again before pumping to bleaching section.
BLEACHING PLANT: For manufacturing packing paper, bleaching sequence is by passed but for producing writing paper, it has got the utmost importance. Bleaching of the pulp is done to remove its inherent brown color and achieved desired whiteness and brightness necessary for writing and printing paper. This operation involves heavy cost and is to be done in a controlled manner to preserve the strength of the wood fibers. The bleaching sequence is done with the help of chlorine, hypo &chlorine dioxide & hydrogen peroxide. Bleached pulp stored in high density tower (HTD) STOCK PREPARATION: The bleached pulp is transferred to this section to further refine it and adding the additive in it for getting the desired properties in paper. The pulp is first refined in double refiner and then a number of additive are added to it in pre decided and specified amount as per the set formulation. Some of these are alum, talcum, rosin, starch, retention aid, optical brightening agents etc. with the addition of these additives, surface finishing , durability of paper, folding 19
strength, bursting strength are established .Very carefully supervision at every stage is required otherwise even a slight negligence may result in rejection of whole lot of paper.
PAPER MACHINES: There are to paper machines in total paper production capacity of 115mt/day. The prime operation of paper machine is to convert pulp into paper sheet of uniform thickness and GSM (gm per square meter). Paper machine contains of four main parts wiz. Wire part, press part, dryer part, and calendar part. In first two parts, water accompanying the pulp is drained and pulp sheet is spread. In dryer part, rolls are heated with the help of steam and paper sheet is dried gradually in a controlled manner. Dried paper sheet is passed through calendar section where calendar rolls compacts the web , smoothen the surface of the paper and even even out its otherwise rough rough surface .only after calendaring , the surface becomes suitable for writing/printing purpose. The paper sheet is then scanned to ensure uniformity in its formation and wrapped on roll called “pope reel”. CONVERTING SECTION: It consists of re-winder section and sheet cutter section. In re-winder section, the pope reel of 2.69 meter width is cut in smaller size and length as per order. FINISHING SECTION: The paper sheets are finished, counted and stacked. PACKING SECTION: Here reels and reams are packed, labeled and all specification mfg. date, mfg lot are mentioned and lot is stored in go-downs prior to dispatch.
20
WORKING OF R.G.P. PLANT FLOW CHART OF R.G.P. STREET: WOOD STORAGE YARD CHIPS PREPARATION CHIPS SILD CHIPS WASHING DIGESTER BATCH BLOW TANK
BLAC BLACK K LI UOR UOR
RECO RECOVE VERY RY
WASHING AND SCREENING BLEACHING CENTER CLEANERS CLEANED PULP STORAGE APPROACH FLOW SHEETING MACHINE SHEET CUTTER BALING PRESS PACKING WARE HOUSE
21
RAYON GRADE PULP PLANT (R.G.P.STREET) 1. PLANT CAPACITY
: 100TONNES PULP PAPER DAY PRODUCTION
2. RAW MATERIAL
: EUCALYPTUS
3. GENERAL PROCESS
: SHOWN IN ATTACHED FLOW DIAGRAM
PLANT /PRODUCTION DESCRIPTION: Rayon grade pulp is used as the raw by Textile and rayon industries to the manufacturer yarn and clothes from it. Hence quality parameters are very stringent in its production. The main units in the R. G. G . P .Plant are mentioned below: Chipper house : For chipping the wood logs. Digester house : For cooking the chips. Washing plants : For washing the fibers. Bleaching plant : For bleaching the fibers. Chemical plant : for preparation of chemical in the fiber. Sheeting machine : for converting R.G.P into sheets. Packing section/go-down: for cutting and packing the sheets and before dispatch. The details of the section are brief here under: 1. CHIPPER HOUSE: Eucalyptus logs are thoroughly washed in high pressure gets of water and then fed to chippers through feeding conveyors. In chipper 3 nos. disc this type chippers are installed having 9 tons/hour chipping capacity. The accept size of the chip produced is “1 to 1 -1/2” size. The accept size chips are stored in chip silo while oversize portion is recycled to re-chipper the main chipper has 335 H.P. ,drive motor while rechipper has 60 H.P. ,drive motor. 2. DIGESTER HOUSE : The washed chips are then fed to digester in pulp mill for cooking operation. There are 5 nos. digesters each having a capacity of50-55 tons/cooking batch. In R.G.P. plant, cooking process has a difference then the process in W.P.P. plant. Here it is carried in 2 stages
22
PRE-HYDROLYSIS STAGE(PH STAGE): This stage has been acquired to reduce the pentagon’s in the pulp and to decompose hemi cellulose. It is further divided into four stages viz., PH steaming, PH cooking, PH venting, and PH draining. Before starting this cooking operation, the chips are charged into digester along with hot water and washed twice. The steaming is done 90-120 mts , cooked for 90-150 mts. At a 175 centigrade and after that vent is open to release the exhaust steam. Then water is drained from the bottom of the digester
SULPHATE COOKING: This is the second stage in cooking of the chips the cooking chemical is known as white liquor are charged in certain portion into the digester and bath ratio is maintained by adding adding hot water as per per requirement. Cooking process is done for 75 min. at a temperature of 165 centigrade. During this process, de-lignifications and hydrolysis of fiber takes place. The cook chips are pumped to blow down tank to release the pressure by venting out the vapors. The cooked pulp is passed through knotters to separate out un-cooked partially cooked chips which are refed to digester. The accept from the knotter contains, spent chemicals and organic material obtained from wood during cooking. The total mass is now sent for washing in brown stock washers. 3. WASHING AND SCREENING: The washing operation is carried out with the help of three nos. counter current brown stock washers. Water is used as the median of washing. The pulp is taken into the vat of the washers. The difference between the washing operation of bagasse pulp and W.P.P. pulp is that here instead of vacuum, air pressure is used in washing through the drum surface of the washer. High pressure air jets spray compressed air on the rotating vat of pulp on the drum surface and taps over the drum spray hot wash liquor from the subsequent washer over the rotating vat. After washing, washed pulps are sent to buffer screen to remove the fine specs. This is a screen with a rotating drum and stationary screen. When drum rotates, fine shives, fiber bundle and specs are separated from the pulp due to centrifugal force. The screened pulp is sent to Decker thickener which helps to drain water and
increased the consistency of the pulp. The pulp is stored in un bleached high density tower and then goes to un bleached low density tower where it is diluted with water to bring consistency to 4% which facilitates pumping of the pulp to further stages. 23
4. BLEACHING PLANT: For manufacturing packing paper, bleaching sequence is by passed but for producing writing printing papers, it has got the utmost importance. With this operation, the brown inherent color of the pulp is bleached to white and the desired brightness of the pulp can be obtained which is very crucial for establishing in the present market. The bleaching sequence consists of the following steps: Chlorination
Alkali extraction
Hypo chloride
Alkali extraction II
Chlorine dioxide bleaching
Hypo chloride II The bleached pulp is sent to bleach knotter and bleached centricleaners where knots and other impurities are removed from the pulp and then thickened over the Decker thickener and stored in clean pulp tower (C.B.T.).From this tower, the pulp is supplied to sheeting machine. 5. CHEMICAL PLANT: In this section bleaching chemical like ClO 2, Cl2 ,hypo, SO2
are prepared and are distributed to the main plants.
6. SHEETING MACHINE: The Sheeting machine is same as paper machine with difference that is a slow speed machine for making high gsm sheet. The specifications of the machine are as follows: : four drainer type right hand sheeting machine. a. Type : carcano, Italy and modified by mechano, Kolkata. b. Make :95t/day c. Capacity : 40 meters/min. d. Operating speed :700-800 gsm e. Basis weight : 2.81mts f. Wire deckle : 32.05 mts g. Wire length :40(endless wire) h. wire mesh The prime operation of the sheeting machine is to convert the pulp into pulp sheet of uniform thickness and gsm(gm per square meter).The pulp from head box is distributed over the mesh from where maximum water is removed from the pulp but still the sheet remains wet. The pickup section picks up the sheet and forwards it to press section where the water is removed by pressing the sheet 24
between rollers .The sheet is still not completely dry. It is then forwarded to drier section where it is passed in between steam heated rollers. It is the longest section of the machine with 36 driers and the balance moisture of the sheets get evaporated during the passing of the sheet through driers. The machine mainly consists of the following parts: DISTRIBUTOR: It is a tapered type distributor which distributes the pulp to head box of the machine. HEAD BOX: The open typed head box is provided with one sided inlet and a free adjustment from wall. The hydraulic capacity is 4960 – 4960 – 14880 lit/min.
SLICE: It is opening of 2670 mm width in the head box along the deckle from where the pulp comes out and falls on the running wire mesh. It can be opened up to max 100 mm opening.
WIRE MESH: It is endless very fine mesh.
PICK UP SECTION
PRESS SECTION
DRIER SECTION
SHEET CUTTER:
After driers, the sheet is passed through sheet cutter where it is cut into required size. It is continuous operation. Its maker is pizzolato Vicenza (Italy).The cut sheets are then piled one over the other and with the help of a conveyor are sent to Bailing press machine. Of sunds defibrator make with hydraulic pressure of 302
170 kg/cm .The pile of sheets are compressed and packed with packing paper and tied with the help of wire. The packed bails are kept in go down and dispatched from there.
25
EQUIPMENTS IN W.P.P. AND R.G.P. PLANT CENTRIFUGAL PUMPS These are so called because energy is imparted to the fluid by centrifugal action of moving blades from the inner radius to the outer radius. The main components of centrifugal pumps are (1) the impeller (2) the casing and (3) the drive shaft with gland and packing Additionally suction pipe with one way valve (foot valve) and delivery pipe with delivery valve completes the system. The liquid enters the eye of the impeller axially due to the suction created by the impeller motion. The impeller blades guide the fluid and impart momentum to the fluid, which increases the total head (or pressure) of the fluid, causing the fluid to flow out. The fluid comes out at a high velocity which is not directly usable. The casing can be of simple volute type or a diffuser can be used as desired. The volute is a spiral casing of gradually increasing cross section. A part of the kinetic energy in the fluid is converted to pressure in the casing. Figure shows a sectional view of the centrifugal pump.
Figure: Volute type centrifugal pump. Gland and packing or so called stuffing box is used to reduce leakage along the drive shaft. By the use of the volute only a small fraction of the kinetic head can 26
be recovered as useful static head. A diffuser can diffuse the flow more efficiently and recover kinetic head as useful static head. A view of such arrangement is shown in figure Diffuser pump are also called as turbine pumps as these resembles Francis turbine with flow direction reversed. Impeller: The impeller consists of a disc with blades mounted perpendicularly on its surface. The blades may of three different orientations. These are (i ) Radial, ( ii ) Backward curved, and ( iii ) Forward curved. Backward and forward refers to the direction of motion of the disc periphery. Of these the most popular one is the backward curved type, due to its desirable characteristics, which reference to the static head developed and power variation with flow rate. This will be discussed in detail later in this chapter. A simple disc with blades mounted perpendicularly on it is called open impeller. If another disc is used to cover the blades, this type is called shrouded impeller .This is more popular with water pumps. Open impellers are well adopted for use with dirty or water containing solids. The third type is just the blades spreading out from the shaft. These are used to pump slurries. Impellers may be of cast iron or bronzes or steel or special alloys as required by the application. In order to maintain constant radial velocity, the width of the impeller will be wider at entrance and narrower at the exit.
27
GEARS: CLASSIFICATION OF GEARS In order to avoid the slipping, a number of projections (called teeth) are provided on the periphery of the wheel, which will fit into the corresponding recesses on the periphery of the wheel B. A friction wheel with the teeth cut on it is known as toothed Wheel toothed Wheel or gear .
The gears or toothed wheels may be classified as follows: 1. According to the position of axes of the shafts. The axes of the two shafts between which the motion is to be transmitted, may be (a) Parallel, (b) Intersecting, and (c ) Non-intersecting and non-parallel. The two parallel and co-planar shafts connected by the gears these gears are called spur gears and the arrangement is known as spur gearing. These gears have teeth parallel to the axis of the wheel. Another name given to the spur gearing is helical gearing, in which the teeth are inclined to the axis. The double helical gears are known as herringbone gears.A pair of spur gears are kinematically equivalent to a pair of cylindrical discs, keyed to parallel shafts and having a line contact. The two non-parallel or intersecting, but coplanar shafts connected by gears. These gears are called bevel gears and the arrangement is known as bevel gearing. The bevel gears, like spur gears, may also have their teeth inclined to the . bevell gear gear s face of the bevel, in which case they are known as helical beve The two non-intersecting and non-parallel i.e., non-coplanar shaft connected by gear. These gears are called skew bevel gears or spiral gears and the arrangement is Known as skew bevel gearing or spiral gearing .This type of gearing also have a line contact, the rotation of which about the axes generates the two pitch surfaces known as hyperboloids . Notes: (a) When equal bevel gears (having equal teeth) connect two shafts whose axes are mutually perpendicular, then the bevel gears are known as mitres. (b) A hyperboloid is the solid formed by revolving a straight line about an axis (not in the same plane), such that every point on the line remains at a constant distance from the axis. 28
(c ) The worm gearing is essentially a form of spiral gearing in which the shafts are usually at right angles. (a) Single helical gear. ( b) Double helical gear. ( c) Bevel gear. (d ) Spiral gear. 2. According to the peripheral velocity of the gears . The gears, according to the peripheral velocity of the gears may be classified as: (a) Low velocity, (b) Medium velocity, and (c ) High velocity. The gears having velocity less than 3 m/s are termed as low velocity gears and gears having velocity between 3 and 15 m/s are known as medium velocity gears. If the velocity of gears is more than 15 m/s, then these are called high speed gears.
(a)
(b)
Fig. a & b - Spiral gears
(c)
(d)
Fig. c & d - Helical & double helical gears
3. According to the type of gearing. The gears, according to the type of gearing may be classified as: 29
(a) External gearing, (b) Internal gearing, and (c ) Rack and pinion. In external gearing , the gears of the two shafts mesh externally with each other. The larger of these two wheels wh eels is called spur wheel and the smaller wheel is called pinion. In an external gearing, the motion of the two is always unlike, In internal gearing, the gears of the two shafts mesh internally with each other as shown in. The larger of the two wheels is called annular wheel and the smaller wheel is called pinion. In an internal gearing, the motion of the two wheels is always like, Sometimes, the gear of a shaft meshes externally and internally with the gears in a *straight line, such type of gear is called rack and pinion. The straight line gear is called rack and the circular wheel is called pinion. A little consideration will show that with the help of a rack and pinion, we can convert linear motion into rotary motion and vice-versa.
4. According to position of teeth on the gear surface. The teeth on the gear surface may be (a) straight (b) Inclined and (c ) Curved. We have discussed earlier that the spur gears have straight teeth where as helical gears have their teeth inclined to the wheel rim. In case of spiral gears, the teeth are curved over the rim surface.
30
ROPES OR BELTS Introduction: The belts or ropes are used to transmit power from one shaft to another by means of pulleys which rotate at the same speed or at different speeds. The amount of power transmitted depends upon the following factors: 1. The velocity of the belt. 2. The tension under which the belt is placed on the pulleys. b elt and the smaller pulley. 3. The arc of contact between the belt 4. The conditions under which the belt is used.
It may be noted that: (a) The shafts should be properly in line to insure uniform tension across the belt section. (b) The pulleys should not be too close together, in order that the arc of contact on the smaller pulley may be as large as possible. (c ) The pulleys should not be so far apart as to cause the belt to weigh heavily on the shafts, thus increasing the friction load on the bearings. (d ) A long belt tends to swing from side to side, causing the belt to run out of the pulleys, which in turn develops crooked spots in the belt. (e) The tight side of the belt should be at the bottom, so that whatever sags is present on the loose side will increase the arc of contact at the pulleys. ( f f ) In order to obtain good results with flat belts, the maximum distance between the shafts should not exceed 10 meters and the minimum should not be less than 3.5 times the diameter of the larger pulley.
Types of Belts 1. Flat belt. The flat belt is mostly used in the factories and workshops, where a moderate amount of power is to be transmitted, from one pulley to another when the two pulleys are not more than 8 meters apart. 2. V-belt . The V-belt is mostly used in the factories and workshops, where a moderate amount of power is to be transmitted, from one pulley to another, when the two pulleys are very near to each other.
31
3. Circular belt or rope . The circular belt or rope, is mostly used in the factories and workshops, where a great amount of power is to be transmitted, from one pulley to another, when the two pulleys are more than 8 meters apart. MATERIALS USED FOR BELTS: The material used for belts and ropes must be strong, flexible, and durable. It must have a high coefficient of friction. The belts, according to the material used, are classified as follows:
1. Leather belts. The most important material for the belt is leather. The best leather belts are made from 1.2 metres to 1.5 metres long strips cut from either side of the back bone of the top grade steer hides. The hair side of the leather is smoother and harder than the flesh side, but the flesh side is stronger. The fibers on the hair side are perpendicular to the surface, while those on the flesh side are interwoven and parallel to the surface. Therefore for these reasons, the hair side of a belt should be in contact with the pulley surface, This gives a more intimate contact between the belt and the pulley and places the greatest tensile strength of the belt section on the outside, where the tension is maximum as the belt passes over the pulley.
(a) Single layer belt. (b) Double layer belt. The leather may be either oak-tanned or mineral salt tanned e.g. chrome tanned. In order to increase the thickness of belt, the strips are cemented together. The belts are specified according to the number of layers e.g. single, double or triple Ply and according to the thickness of hides used e .g. light, medium or heavy. The leather belts must be periodically cleaned and dressed or treated with a compound or dressing containing neat foot or other suitable oils so that the belt will remain soft and flexible.
2. Cotton or fabric belts. Most of the fabric belts are made by folding canvass or cotton duck to three or more layers (depending upon the thickness desired) and stitching together. These belts are woven also into a strip of the desired width and thickness. They are impregnated with some filler like linseed oil in order to 32
make the belts water proof and to prevent injury to the fibers. The cotton belts are cheaper and suitable in warm climates, in damp atmospheres and in exposed positions. Since the cotton belts require little attention, therefore these belts are mostly used in farm machinery, belt conveyor etc.
3. Rubber belt. The rubber belts are made of layers of fabric impregnated with rubber composition and have a thin layer of rubber on the faces. These belts are very flexible but are quickly destroyed if allowed to come into contact with heat, oil or grease. One of the principal advantages of these belts is that they may be easily made endless. These belts are found suitable for saw mills, paper mills where they are exposed to moisture.
4. Balata belts. These belts are similar to rubber belts except that balata gum is used in place of rubber. These belts are acid proof and water proof and it is not affected by animal oils or alkalis. The balata belts should not be at temperatures above 40° C because at this temperature the balata begins to soften and becomes sticky. The strength of balata belts is 25 per cent higher than rubber belts.
33
BEARING Introduction:
Bearing: A bearing is a machine element which supports another moving machine element (known as journal). It permits a relative motion between the contact surfaces of the members, while carrying the load. A little consideration will show that due to the relative motion between the contact surfaces, a certain amount of power is wasted in overcoming frictional resistance and if the rubbing surfaces are in direct contact, there will be rapid wear. In order to reduce r educe frictional resistance and wear and in some cases to carry away the heat generated, a layer of fluid (known as lubricant) may be provided. The lubricant used to separate the journal and bearing is usually a mineral oil refined from petroleum, but vegetable oils, silicon oils, greases etc., may be used.
Classification of Bearings Though the bearings may be classified in many ways, yet the following are important from the subject point of view:
1. Sliding bearing 2. Roller bearing
34
Roller bearing 1. Depending upon the direction of load to be supported . The bearings under this group are classified as:
(a) Radial bearings, and (b) Thrust bearings.
In radial bearings, the load acts perpendicular to the direction of motion of the moving element. In thrust bearings, the load acts along the axis of rotation.
2. Depending upon the nature of contact. The bearings under this group are classified as:
(a) Sliding contact bearings, and (b) Rolling contact bearings.
In sliding contact bearings, the sliding takes place along the surfaces of contact between the moving element and the fixed element. The sliding contact bearings are also known as plain bearings. In rolling contact bearings, the steel balls or rollers, are interposed between the moving and fixed elements. The balls offer rolling friction at two points for each ball or roller.
35
Types of Sliding Contact Bearings: SLIPPER BEARING:
The sliding contact bearings in which the sliding action is guided in a straight line and carrying radial loads may be called slipper or guide bearings. Such type of bearings is usually found in cross-head of steam engines.
JOURNAL BEARING:
The sliding contact bearings in which the sliding action is along the circumference of a circle or an arc of a circle and carrying radial loads are known as journal or sleeve bearings. When the angle of contact of the bearing with the journal is 360°then the bearing is called a full journal bearing. This type of bearing is commonly used in industrial machinery to accommodate bearing loads in any radial direction. When the angle of contact of the bearing with the journal is 120°, then the bearing is said to be partial journal bearing. This type of bearing has less friction than full journal bearing, but it can be used only where the load is always in one direction. The most common application of the partial journal bearings is found in rail road car axles. The full and partial journal bearings may be called as 36
clearance bearings because the diameter of the journal is less than that of bearing.
Sliding contact bearing used in steam engines When a partial journal bearing has no clearance i.e. the diameters of the journal and bearing are equal, then the t he bearing is called a fitted bearing, The sliding contact bearings, according to the thickness of layer of the lubricant between the bearing and the journal, may also be classified as follows: 1. Thick film bearings . The thick film bearings are those in which the working surfaces are completely separated from each other by the lubricant. Such types of bearings are also called as hydrodynamic hydrodynamic lubricated bearings.
2. Thin film bearings. The thin film bearings are those in which, although lubricant is present; the working surfaces partially contact each other at least part of the time. Such types of bearings are also called boundary lubricated bearings. 3. Zero film bearings. The zero film bearings are those which operate without any lubricant present. 4. Hydrostatic or externally pressurized lubricated bearings. The hydrostatic bearings are those which can support steady loads without any relative motion between the journal and the bearing. This is achieved by forcing externally pressurized lubricant between the members.
37
MECHANICAL MAINTENANCE Maintenance costs are a major part of the total operating costs of all manufacturing or production plants. Maintenance costs at century pulp and paper industry represent up to 60 percent of the total production costs .
PREDICTIVE MAINTENANCE Predictive Maintenance (PdM) offers increased equipment reliability and sufficient advance information to improve planning, thereby reducing unexpected downtime and operating cost. To promote the early detection of abnormal conditions through predictive maintenance, it is essential that common objectives be set for the maintenance and production groups and that the ownership of the equipment, the roles and responsibilities as well as communication and reporting be clearly defined. The first step in preparing to conduct the diagnosis is to identify the physical parameters to be monitored and the corresponding Predictive, Testing & Inspection (PT&I) technology to be used. Having defined the engineering limit for the physical parameters so that a problem can be detected during routine monitoring before excessive damage occurs, a certain number of diagnosticians should be trained and a comprehensive diagnostic system established. On that basis, diagnosticians will then be able to perform measurements, and to analyze and collate the results. If the equipment diagnostic indicates that a repair is required, the repair will be planned and implemented, and the deterioration should be assessed. To refine the predictive maintenance approach, integrating the predictive maintenance techniques with the Work Management process will further enable the asset management strategy to be driven by condition data for improved maintenance decisions. The predictive maintenance efforts are very expensive hence a careful study or plant-wise feasibility survey for deciding the machines to which the predictive maintenance technique is to be applied is carried out, so that those equipment 38
and machines which do not require. So much maintenance and care will not get mixed into predictive maintenance system. For selecting the machines which need predictive maintenance following points are to be carefully studied. 1) Criticality of the machine 2) Downtime costs 3) Downstream effects 4) Age of machine 5) Severity of utilization 6) Stand by availability 7) Hazards involved in the event of failure 8) Skill availability 9) Maintenance support facility and infrastructure 10) Use skill and operating environment 11) Condition of usage
PREVENTIVE MAINTENANCE: Pulp and paper mills are conducive to harsh environments producing lots of dust and heat. Elimination or reduction of the effects of heat and dust is critical to the healthy performance of pulp and paper mills. A preventive maintenance campaign means that equipment failures which result in production downtime and cut profits can be kept to a minimum or even prevented entirely.
POINTS FOR ENSURING MAXIMUM MAXIMUM SYSTEM AVAILABILITY AVAILABILITY THROUGHOUT A PULP AND PAPER MILL. 1. KEEP IT CLEAN If dust is not controlled, then it can cause many potential risks in terms of measurement accuracy and overheating of critical electronic components. Dust is controlled using a well-developed head package design and well-engineered air wiping devices. 2. BE SYSTEMATIC A good preventive maintenance schedule is one that is based on first class record keeping. A logbook should track what has been checked; what was found; and any 39
corrective action that was taken. These records form a platform on which to base preventive maintenance schedules.
3. INSPECT REGULARLY Weekly checks on the quality control scanners can mean inspecting the sensor window material for damage or wear. Early detection of these problems will ensure sensor accuracy and hence more efficient production costs. 4. MAINTAIN SCANNERS Scanners and their onboard sensors are fundamental to maintaining quality Preventive maintenance for scanners should involve:
Visual inspection of the system and its environmental conditions inspection of the connections inspection of the ribbon and fiber optic cables Functional inspection of the fan and cooling system Inspection of the health pages and alarm history h istory Inspection and storage of the parameters Functional testing of the system under normal conditions Basic measurements with supply voltage Inspection of the spare part inventory Cleaning of the system
5. APPLY REGULAR MAINTENANCE TO DRIVES Variable speed drives keep the plant moving, so regular preventive maintenance is vital to maintain their health. Keeping drives and motors clean ensures they are within their operating temperatures and helps achieve the best possible efficiency 6. UPGRADE MOTORS Motors are another essential in the drive chain and those designed for high reliability will help maintain availability. A new motor for process industries has a 20-30 percent greater cooling surface than its predecessor, reducing the internal temperature considerably 7. ASSIGN THE RIGHT PEOPLE FOR MAINTENANCE A key strategy is to control who implements the preventative maintenance procedures and to have an agreed planned programme of work. The best results 40
are achieved when specific people with the correct training are given personal ownership. 8. Give the right training Employees should be trained in correct normal operation, so as not to exceed the device’s parameters, and in what to do when problems occur. Shift engineers need the training so they know all about the operation of the system. Training the staff only when the equipment is commissioned and not be concerned about maintaining current training can lead to more call outs to service engineers than needed, resulting in production delays.
9. GET PROFESSIONAL HELP Many vendors will also perform on site preventive maintenance. The best vendors will assign dedicated field service engineers to a mill to develop a close relationship with customers. This means that the field engineers are informed about the shutdown schedules so they can plan the more intensive maintenance activities and ensure that the installed base is operating in peak condition.
41
CONCLUSION
Maintenance is one of the largest controllable costs in the pulp & paper industry. It is also a critical business function that impacts commercial risk, plant output, product quality, production cost, safety and environmental performance. Although improving maintenance is not difficult, it does require common sense and a systematic approach. In most cases technical solutions are only part of the solution; employees can contribute in significant ways to the success of the program and should be provided coaching
42
REFRENCES
BOOKS:
Theory Of Machine by R. S. Khurmi
Fluid Mechanics by R. K. Bansal
WEB LINKS:
www.substech.com
www.scibd.com
www.abb.com/pulpandpaper
43
