1

PROJECT REPORT

ON

Design and Modeling of Gray Paperboard Dryer

Submitted by

Murtaza Husain

Nitin Patil

Guided by

Prof. G. H. Waghmare

Department of Mechanical Engineering

Yeshwantrao Chavan College of Engineering,

Nagpur.

2010-2011

2

Department of Mechanical Engineering

Yeshwantrao Chavan College Of Engineering,

Nagpur.

2010-2011

Certificate

This is to certify that the project titled “Design and Modeling of

Gray Paperboard Dryer” has been duly completed towards the

partial fulfillment of Requirement for the award of degree of

Bachelor of Mechanical Engineering, awarded by Nagpur

University.

Submitted by

Murtaza Husain Nitin Patil

Prof. G. H. Waghmare Prof. S. P. Untawale

Guide H.O.D

3

Content

S. No. Title Page No.

1. Abstract 5

2. List of Figures 6

3. Nomenclature 7

Ch. No. 1: Introduction 08 - 15

1.1 Company’s Profile 9 1.2 Classification and Manufacturing Process 10 1.3 Product’s Applications 15

Ch. No. 2: Problem Definition 16 - 18

2.1 Present Drying Process 17 2.2 Problem in Present Drying Process 17 2.3 Problem Definition 18

Ch. No. 3: Available Drying Techniques 19 - 27

3.1 Flotation Dryer 20 3.2 Steam Cylinder Dryer 21 3.3 Combined system (Gas IR and Air) 22 3.4 Microwave Dryer 25

Ch. No. 4: Dryer Design 28 - 31

4.1 Dryer Design Constraints 29 4.2 Dryer Design and Parts 30 4.3 Working of Dryer 31

Ch. No. 5: Design Calculations 32 - 42

5.1 Heat Requirements 33 5.2 Transmission Power Calculation 38 5.3 Design of Chain Drive 41

4

Ch. No. 6: Drafting and Pictures of Model 43 - 47

6.1 Drafting of the Duct 44 6.2 Drafting of the Structure 45 6.3 Drafting of the Box 46 6.4 Pictures of Dryer Model 47

Ch. No. 7: Conformity of Design 48 - 49

4. Bibliography 50

5. Acknowledgement 51

5

Abstract In the past decade India has slowly and steadily emerged as

world’s second biggest market. On the other hand it has also emerged of one of the best locations for out sourcing goods and services. Because of these developments India’s packaging sector is witnessing the massive growth in the industry. There has been a considerable increase in the sales but there is lack of productivity in the medium and small scale industries which produce raw materials for these packaging industries. This is due to many reasons like technology and cost of technology.

Our project aims to research in the feasible technology for drying of the paperboards used for packaging. Our aim is to propose a dryer which would supplement the conventional drying process. Hence we have designed a dryer to combat the problems arising from conventional drying process.

Chapter 1 contains introduction of Raj Paperboard Mills in which we have done our project. It gives a review how the paperboards are manufactured and what are the main uses to which they are put to.

Chapter 2 describes the conventional drying process and also the problems associated with it.

Chapter 3 gives a review of the conventional dryer product used worldwide for drying paper and paperboards.

Chapter 4 describes the constraints to which the drying process is subjected to and also describes the design of the proposed dryer and parts used in it.

Chapter 5 shows the design calculations done for designing of the chain drive and deciding the heater specification.

Chapter 6 contains the design model and drafting of the dryer.

Chapter 7 shows how the design meets the problem and shows how it is better than other drying techniques discussed in chapter 3.

6

List of Figures S. No. Figure Page No.

1 Different types of paper board 6

2 Sludge form the paper industry 7

3 Pulping machine 8

4 Paperboard rolling machine 9

5 Finished gray paperboard 10

6 Wet gray paperboard 12

7 Flotation dryer 13

8 Flat hood arrangement of flotation dryer 14

9 Steam cylinder dryer 15

10 Combined gas and infra red dryer 16

11 Air supply system for gas IR dryer 17

12 Microwave dryer 20

7

Nomenclature β Inverse of film temperature

ρ Density of material under consideration

µ Absolute viscosity

Pr Prandtl number

K Thermal conductivity

Re Reynolds number

Nu Nusselt number

Gr Grashofs number

h Convective co-efficient

lc Critical length

ΔT Temperature difference

A Surface area

Q Heat transfer Rate

ω Angular velocity

α Angular acceleration

n rotational frequency rpm

t Time

τ Torque

m Mass of the body

g Gravitational pull

µf Co-efficient of friction

8

Chapter No. 1

Introduction

9

1.1 Company profile Raj Paper Board Mills was setup in the year 1993. The purpose

was to cash the increasing demand of the product and boom which was projected in the packaging sector at that time. The plant was setup on kanolibori road wanadongri hingna as it was outside the city and near to a quickly industrializing area MIDC Hingna Road hence considering the cost, availability and use to which it was going to be put to the location was decided. It was started with a humble amount of Rs. 5000 and now after 18 successful years the company’s present setup value is about Rs. 10 crore.

Raj paper board mill’s present setup has a built up area is 25000 sq. ft. and another 2 acres for drying boards and unloading, filtering and processing of raw material. In their present setup they have 6 rolling mills which work approximately 16 hrs a day and 20 hrs a day in summer. They have 5000 sq. ft. storage shade used to stock the paper boards during summer for monsoon and it is also used for drying the boards in winter during night time. Processes like sorting, inspection and straightening are also done here other than stocking.

Raj Paper Board Mills produce gray paper boards of thin gauge (6-12 ounce), medium gauge (14-24 ounce) and thick gauge (28-70 ounce). But their main produce is of sheets weighing 16 to 40 ounces i.e. medium and thick gauge. Their present facility enables them maximum production of 4 tons/day and a turnover of Rs. 6 crore which is huge considering the laborers required and the capital involved.

They have an associate setup in Chandrapur by the name of Vidarbha Paper Board Mills who together with them manufacture gray paper boards for their retail store named Goodwill Traders and for their packaging agency Goodwill Packaging both located at Gandhi Bagh, Itwari. Considering their retail sales these two companies serve only 60% of their requirement and hence they need to purchase paper boards from other factories in Chandrapur. The kind of potential which is being seen in the market in recent years they have projected that there present rate of production will suffice only 40% of the demand posed by their packaging and retail business. Hence there is a need to increase the productivity and the production rate. Gray paper board mills require

10

sludge of paper industry and hence are located near paper industry. Considering this Chandrapur is mass producing region of this product and hence a serious competitor. Raj paper board mills have two advantages to them over others that they are located very near to the market region hence the transportation cost is very less and also that their product need not be sold to retailers but they have their own store.

1.2 Classification and Manufacturing Process Paperboard is a thick paper based material. While there is no rigid

differentiation between paper and paperboard, paperboard is generally thicker (usually over 0.25 mm/0.010 in or 10 points) than paper. According to ISO standards, paperboard is a paper with a basis weight (grammage) above 224 g/m2, but there are exceptions. Paperboard can be single or multi-ply. Sometimes it is referred to as cardboard, which is a generic, lay term used to refer to any heavy paper pulp based board.

In 1817, the first paperboard carton was produced in England. Folding cartons first emerged around the 1860s and were shipped flat to save space, ready to be set up by customers when they were required. 1879 saw the development of mechanical die cutting and creasing of blanks. In 1911 the first kraft sulphate mill was built in Florida and in 1915 the gable top milk carton was patented and in 1935 the first dairy plant was observed using them. Ovenable paperboard was introduced in 1974.

Terminology and classifications of paperboard are not always uniform. Differences occur depending on specific industry, locale, and personal choice. In general, the following are often used:

Boxboard or carton board – paperboard for folding cartons and rigid set-up boxes

o Folding boxboard (FBB) – a bending grade capable of being scored and bending without fracture

o Chipboard – all recycled, low quality board o Kraft board – a strong virgin fiber board often

used for beverage carriers. Often clay coated for printing

11

o Laminated board – a lamination of paperboards and other materials, for example Liquid packaging board

o Solid Bleached Board (SBB) or Solid Bleached Sulphate {SBS) – clean white board used for foods etc

o Solid unbleached board (SUB) – board made from unbleached chemical pulp

o White lined chipboard (WLC) – a white, often clay coated, chipboard

Containerboard – a type of paperboard manufactured for the production of corrugated fiberboard

o Corrugated medium – the inner fluted portion of corrugated fiberboard

o Linerboard – a strong stiff board for one or both sides of the medium

Other

o Binder's board – a paperboard used in bookbinding for making hard covers.

Different types of paperboards

12

Raw materials

Used paper is collected and sorted and usually mixed with virgin fibers in order to make new material. This is necessary as the recycled fiber often loses strength when reused; the added virgin fibers enhance strength. Sludge from paper industry is the source of virgin fibers. Mixed waste paper is not usually deinked (skipping the deinking stage) for paperboard manufacture and hence the pulp may contain traces of inks, adhesives, and other residues which together give it a grey color. Other raw material required for the production of gray paper board is abundant supply of water.

Sludge of paper industry

Pulping

Pulping is the process of separating plant fibers in order to recast it in the form of paper board. In manufacturing of Gray paper board recycled paper, sludge from paper industry in put in a pulping machine with large volume of water. The pulping machine has a mixing / cutting blade in it which when the machine starts churns the mix and converts it into a slurry of fiber. This slurry is then stored in a huge tank with agitator in it which prevents the settling of the pulp at the bottom.

13

Pulping machine pulping sludge and garbage paper

Rolling of paperboard

This is the stage in which the cardboard takes shape. The pulp from the agitator is supplied to the over head tank through a pump. These overhead tanks are connected to the paper board rolling mill machine. The Rolling machine has a fine net belt conveyor, the net traps the fiber in the pulp at the submerged drum. The net then transports the fiber to the main rolling drum where water gets squeezed out of the fiber and the fiber gets rolled over the main drum and the contact point of main drum and rubber roll. As per the required thickness the main drum is allowed to take rotations before the wet paper board is cut and taken out from over the drum.

14

Drying

The paper boards thus obtained needs to be dried to get rid of the water. On an average a paperboard even after so much squeezing on the rolling mill contains 60% to 70% moisture. Hence the most economical way of getting rid of this excess moisture in this region (Nagpur) is by drying it using sun light. The paperboards are spread outside in the open. And in about 6 to 7 hours these paperboards get perfectly dried. But the paperboard thus obtained is deformed because of the uneven surface of the ground and also because of uneven heating. Hence therefore the paperboards are calendared and then are sorted by weight. The product thus obtained is then cut into proper rectangular shapes of required sizes as ordered by the customer.

Water circuit through the plant

The water circuit starts from the bore well from where the makeup water is taken from and supplied to the storage tank with agitator. The water here is in the form of slurry which is from here supplied to the overhead tanks and to the rolling mills. The water separates out from the slurry in two stages on each drum the water which remains on the cardboard is lost. The remaining water is the supplied to the pulpper where it again forms slurry and is sent to the agitator. The total process water is changed every week as the decay process starts in the pulp present in the water and it starts to stink.

15

1.3 Uses of Paperboard

There many uses of virgin and recycled paperboards out of which few uses are enumerated below:-

Advertising: Advertising boards, signs, shop, window displays, popup displays, exhibition board, picture frame backing, POP advertizing screen printing.

Building: models, partitions, wall cladding, indoor or outdoor decoration, air conditioning ducts, windows and false ceilings.

Industrial field: wall claddings, control cabinets and panels, structures for corrosive environments, ducts.

Packaging: Food Packaging, textile packaging, stationary, etc.

Gray paper board cut down to customer specification

16

Chapter No. 2

Problem Definition

17

2.1 Present Drying Process The paper boards obtained after the rolling process needs to be

dried to get rid of the water. On an average 24 ounce sheet weighs 60 to 70 ounce in wet condition. This means that the sheet contains 60% to 70% moisture.

Hence the most economical way of getting rid of this excess moisture in this region (Nagpur) is by drying it using sun light. As there is abundant supply of it, the ambient temperature is also high enough in summers and there is very little vegetation which grows in the summer by itself. Hence the ground is clear of the wild plants. Therefore the paperboards can be spread outside in the open. And in about 6 to 7 hours these paperboards get perfectly dried.

2.2 Problems in Present Drying Process The problems posed by the present drying technique are as

follows:-

As there is no equipment meant for drying of these paper

boards, during monsoon season the company cannot

function as it cannot dry their product. If the paperboards

are kept in wet condition for long about 2 days then they

start to decay hence all the money spent on the process is

lost.

Another problem encountered by the company is that there

is considerable due in the winter season during the night

hence they cannot dry product during the night time which

in turn increases the no. of boards to be dried during day

time which causes problem of availability of space.

In seasons other than summer the ground has vegetation

and insects breading in them which makes it difficult and

dangerous for the laborer to work and also for the product

to dry.

18

No matter how plain a land may be there is always

unevenness present. This unevenness causes deformation

of the surface of the dried paperboard.

Also a huge capital cost is required just to purchase land for

drying the paperboard which is not expectable.

The strong winds blowing round the year in this region

causes considerable loss of product. Also increases the

labor involved in prevention of such events.

This process slows the production rate to a considerable

extend. Considering the increasing market demand some

alternative needs to be searched.

2.3 Problem Definition The problem definition is to design a dryer which could be used in

monsoon and in winter in order to dry these sheets to an acceptable

limit of 80% within the time constraint. Hence enabling the company to

function during monsoon and winter.

Gray paper before drying

19

Chapter No. 3

Available Drying Techniques

20

3.1 Flotation dryers Flotation dryers typically use a single heat source and fan system

to provide heated air to both sides of the web. Using a dual heat source system as shown in Fig. 17 allows the use of differential temperatures on each side of the sheet.

The object of this arrangement is to operate the drying arrangement with increased temperatures on the “wet” side of the sheet versus the dryer side of the sheet. This will result in increased evaporation from the wet side causing the fibers to contract more than on the opposite side which is being subjected to lower temperature air. As mentioned, this system is effective for moderate curl control and is more suitable for gas fired arrangements than for steam fired arrangements due to temperature limitation of steam fired systems. Properly designed systems can obtain 75 to 100oF (25 to 40oC) differential temperatures between top and bottom sections. It is difficult to achieve higher differentials because the spent air streams have a tendency to mix due to the design arrangement of the nozzles and exhaust areas. Even with this consideration, a dual zone arrangement can effectively help control troublesome curl in paperboard operations.

21

3.2 Steam Cylinder Dryers Steam cylinder dryers have been used in the production of

coated paper and paperboard for many years due to the many advantages offered by this arrangement. Specifically, steam cans offer:

• Positive web support with the elimination of long draws

• The coated sheet is dried on a flat surface reducing paper stress, cockle and curl.

• A reasonably efficient conversion of steam latent heat to drying energy resulting in an economical drying method

• Ease of threading and broke handling

A steam cylinder operates by introducing saturated steam through rotary unions. Drying is accomplished by conduction heat transfer from the internal steam source to the surface of the paper. As the steam condenses inside the dryer shell energy is transferred from the steam (heat of vaporization) to the web by conduction

22

through the dryer shell and to the coated paperboard. Since all paper mills have a supply of saturated steam available this is the most widely used heat source. Typical steam cylinder diameters range from 4 to 6 feet (1220 to 1830 mm). Fig. 9 depicts a typical cross section of a steam cylinder.

3.3 Combined Systems (Gas IR and Air)

While it has previously been stated that high performance drying and gas IR drying offer alternative systems, it has long been considered that the ideal drying system for coating applications would be the combination of the two systems. Using gas IR to provide sensible heat together with the excellent mass transfer effect of the high performance air drying system described above is an ideal combination.

Infra-red or IR is an excellent means of imparting an intense concentration of sensible energy to the web, and this helps to both immobilize the coating and minimize the binder migration effect. Drying, however, is a combination of both heat and mass transfer and for a major amount of evaporation to take place within a given system; an external air system is necessary to carry away the evaporated water vapor. Seeing the advantages of having gas IR closely coupled with

23

convective air flotation drying, has led several manufacturers to offer a combination system (Fig. 46).

In this arrangement which is conveniently packaged in a single enclosure, gas IR is used to provide sensible heat and the drying of the coating to the immobilization point. An air drying section uses the energy from the gas IR exhaust as make-up air to the preceding air flotation section resulting in improved energy efficiencies. The amount of gas IR and convective air can be tailored to meet the application requirements. A major step forward in the development of the combined dryer is the ability to provide stable sheet flotation by the application of high velocity air movement at the sheet surfaces, while simultaneously ensuring that air movement does not adversely affect the function of the highly sensitive infra-red emitters. Careful nozzle design also prevents overspill of high temperature air from the dryer enclosure.

24

The air system depicted in Fig. 47 shows that the return air from both the air flotation dryer and the infra-red system are combined so that none of the energy is lost as would normally be the case with a conventional, stand alone, infrared system where a substantial volume of the recirculation air is exhausted at each pass. The exhaust air which will ultimately be sent to the atmosphere is at relatively high temperature and humidity which makes it suitable to be passed through an “air to air” heat recovery unit in order to pre-heat make up fresh air and gas burner combustion air. In addition, the energy normally lost in the conventional infrared system through reflection, transmission and side scatter, etc. is fully maintained in the insulated enclosure of this dryer arrangement. The overall thermal efficiency of the combined system will naturally be better than the efficiencies of the individual systems. In fact, efficiency levels far in excess of 60% are predicted for the combined system. A major feature of the combined system is that a highly efficient overall energy balance can be achieved. The compact design, energy efficiency and web stability of combined systems provides many advantages in coating applications. Benefits of the combined IR/HPC dryer can be summed up as follows:

Maximum drying rate with minimum machine space requirement

25

Correctly proportioned IR/air for high productivity and product quality

Stable web flotation throughout both sections for improved runability

Integration of techniques and equipment

Efficient energy usage

The combination of infra-red sensible energy input and convected air mass transfer enables extremely high drying rates to be achieved within a confined space, without any compromise in coat quality and resultant surface printability.

3.4 Microwave Dryer Microwave cardboard, paper tube drying equipment is modern

high-tech production equipment, it has changed the traditional method of heating the heat transfer drying board. Microwave does not require preheating and heat transfer, directly to the board while heating from the inside out. And heating uniformity is good, does not produce coking phenomenon, not easily lead to the phenomenon of coke endogenous. Paper microwave drying equipment can be continuous production, simple process, can be single-handling equipment, labor saving. Mainly used in paper, cardboard, paper tubes, paper tubes, gray cardboard, paper Fu film, tape and other paper industry drying board. The devices are suitable for all kinds of cardboard, gray cardboard, kraft paper, cardboard, pulp, paperboard, pulp drying model stereotypes. It has following advantages:

fast heating, energy efficient

heating uniformity, improve product quality microwave can penetrate to the interior materials, exterior materials as the same time production of heat, does not produce endogenous phenomena of coke. With the continued evaporation of water surface materials, material surface temperature will be slightly lower than the inside surface temperature, the formation of the temperature gradient from inside to point to things, and the heating process with

26

the migration occurred in the direction of vapor pressure and heat transfer in the same direction. According to drying theory, this state is extremely beneficial to heat the dry material.

thermal inertia is small, easy to control instant heating

safety and environmental protection technical parameters: a microwave output power: ≥ 60KW (adjustable) 2 input apparent power: ≤ 75KVA 3 device operating voltage: Three-phase 380V ± 10% 4 microwave operating frequency: 2450MHZ ± 50HZ

Work Environment: 5 ~ 55 ℃, relative humidity ≤ 80%

around the non-corrosive gases and explosive gases

energy, cost: 75 kilowatt / hour (approximately)

Microwave dryer

27

The Techniques discussed above are standard and are used in manufacturing of higher end product i.e. paper and paper board manufactured from wood pulp. These techniques increase the productivity and production rate and make the process independent of ambient conditions. But they have following drawbacks:

High capital investment.

High maintenance cost.

Unavailability of the technology.

Skilled laborer requirement for operation and maintenance.

The manufacturing price of gray paper board will drastically increase and at market price it won’t be able to reach the breakeven point.

28

Chapter No. 4

Dryer Design

29

4.1 Design Constraints Considering the drying technique available for drying of higher

end paper boards we can design a hot chamber dryer similar to a flotation dryer. This dryer would use heating coils to heat the air and fans to circulate the air within the chamber. The parameters or constraints considering which the dryer is designed are as follows:

Dimension constraints:

The sheet has a standard size of 36 x 42 inches

Time constraints:

Considering the design for a 24 ounce sheet as it is their main selling product. The time required for production of two (as they are manufactured in pairs) 24 ounce sheets is 1.5min. Hence the time available for drying of each sheet in order to make the drying process continuous is 45 sec.

Weight constraints:

On an average 24 ounce sheet weighs 60 to 70 ounce in wet condition. This means that the sheet contains 60% to 70% moisture. Hence the power supply to the heating coil must be so adjusted so that it is able to dry the sheet to an acceptable level within the time constraints.

30

4.2 Design and Parts of Dryer List and Design of various parts of dryer:

Box or the Hot Chamber

To accommodate the paper board sheet and various other equipments we take up a box of dimension of 40 x 50 x 20 inches. The box is made out of 3 mm thick mild steel sheet and is insulated from inside by a 5 mm thick asbestos sheet.

Structure

Box is to be mounted on four legs of Square L beams and the rollers on L beams running across the side of the box from outside. The square L beams are of cast iron and 3mm gauge. The height of structure is 5 ft. The structure is to be bolted to the ground so that it can be easily unbolted and the dryer can be relocated (detail dimensions shown in drafting).

Roller Conveyor system

A Roller conveyor system is used to hold the paper board sheet and move it forward in the box. There are seven 2 inch dia rollers and four 4 inch dia rollers. These are mounted from outside the box on antifriction bearings on the L beams running across the sides of the box. These rollers are GI pipes which are plugged on ends and then mounted. Mounting is done on shaft of dia 1 inch for smaller rollers and 2 inch dia for larger rollers. These plugs are of two different length different for left and right side 5 and 3 inches respectively.

Chain Drive

The rollers are given rotary motion with the help of a chain drive. The chain drive consists of 9 sprockets 2 big and 7 small. There is only one chain which will drive all the sprockets. The design calculations are shown in the next chapter.

31

Circulation Duct and Fans

The circulation duct is used to circulate the air from top to bottom side of the box and vice versa. The duct has a cross sectional area of 81 sq. inches and has a diffusing frustum attached at its one end. The duct in insulated with 0.5 mm thickness aluminum fiber glass cloth from outside. It has a circulation fan attached to it which forces air through the duct. There is another fan attached to the bottom side of the box this use used to introduce make up air to maintain the humidity inside the box to a desired level and also to maintain heat transfer coefficient between inside air and sheet.

Heating Coil

Two heating coils are provided in the box as a source of heat for drying. These are located above and below the rollers so that they supply there heat directly to the sheet. The specification of the heater based on the heat required for drying and heat losses through walls of duct and box is discussed in the next chapter.

Other Mountings

Other accessories required for the controlling of parameters within the box are thermostat for controlling the internal temperature of the box, regulator to control the speed of rollers, on/off switches for motor, circulation fans and heater coils.

4.3 Working of Dryer This is a single pass dryer which can be installed just after the

rolling machine so that the wet paperboard can be directly put through the dryer. The inside temperature of the dryer is maintained by the heater coils. The sheet is brought into the box by the roller conveyor and is positioned there for a certain interval of time so that the water present in the paperboard gets evaporated. After the interval the conveyor moves this sheet out of the box and brings another one in hence continuing the process.

32

Chapter No. 5

Design Calculation

33

5.1 Heat Requirement Calculation

Calculating heat loss through walls of the box:-

For forced convection inside the box considering:-

Film temperature (assuming minimum) = 100oC

Velocity of air in the box = 40 m/s

Length = 1.15 m

β = 1/ (100 + 273) = 2.681 x 10-3 ρ = 0.946 Kg/m3

µ = 21.87 x 10-6 Ns/m3 Pr = 0.688 K = 0.0321 W/m-K

Re = ρ v l / µ = (0.946 x 40 x 1.15) / (21.87 x 10-6) = 1.989 x 106

Nu = [0.037 x Re0.8-871] x Pr1/3

Nu = [0.037 x (1.98 x 106)0.8-871] x 0.6881/3 = 2804.67

havg0 = Nu x K / l = 2804.67 x 0.0321 / 1.15 = 78.29 W/m2-K

For Natural convection outside the box considering:-

Film temperature (assuming avg value for monsoon) = 30oC

β = 1/ (30 + 273) = 3.3 x 10-3 ρ = 1.165 Kg/m3

µ = 18.63 x 10-6 Ns/m3 Pr = 0.701 K = 0.02675 W/m-K

Box side heat transfer coefficient calculation:-

Length lc = 0.5 m

Gr = g x β x ΔT x ρ2 x lc3 / µ2

= 9.81 x 3.3 x 10-3 x 10 x 1.1652 x 0.53 / (18.63 x 10-6)2

= 1.58 x 108

Ra = Gr x Pr

34

= 0.701 x 1.58 x 108 = 1.11 x 108

Nu = 0.59 x Ra0.25

= 0.59 x (1.11 x 108)0.25 = 60.54

havg1 = Nu x K / l = 60.54 x 0.02675 / 0.5 = 3.239 W/m2-K

Box top side heat transfer coefficient calculation:-

Length lc = As / P = 1.25 / 4.5 = 0.277m

Gr = g x β x ΔT x ρ2 x lc3 / µ2

= 9.81 x 3.3 x 10-3 x 10 x 1.1652 x 0.2773 / (18.63 x 10-6)2

= 2.69 x 107

Ra = Gr x Pr

= 0.701 x 2.69 x 107 = 1.88 x 107

Nu = 0.27 x Ra0.25

= 0.27 x (1.88 x 107)0.25 = 17.786

havg2 = Nu x K / l = 17.786 x 0.02675 / 0.277 = 1.717 W/m2-K

Bottom side heat transfer coefficient calculation:-

Length lc = As/P= 0.277 m

Gr = g x β x ΔT x ρ2 x lc3 / µ2

= 9.81 x 3.3 x 10-3 x 10 x 1.1652 x 0.2773 / (18.63 x 10-6)2

= 2.69 x 107

Ra = Gr x Pr

= 0.701 x 2.69 x 107 = 1.88 x 107

Nu = 0.54 x Ra0.25

= 0.54 x (1.88 x 107)0.25 = 35.5576

havg3 = Nu x K / l = 35.5576 x 0.02675 / 0.5 = 3.434 W/m2-K

35

Resistance offered by different parts of the box to heat flow

Steel sheet thickness Ls = 0.003 m

Insulation (asbestos) sheet thickness Li = 0.005 m

Thermal conductivity of steel Ks = 15 W/m-K

Thermal conductivity of asbestos Ka = 15 W/m-K

Lateral sides:-

A = 0.5 m2

RL = 1 / (havg1 x A) + Ls / (Ks x A) + Li / (Ka x A) + 1 / (havg0 x A)

= 1 / (3.239 x 0.5) + 0.003 / (15 x 0.5) + 0.005 / (0.1105 x 0.5) + 1 / (78.29 x 0.5) = 0.7339

Inlet and outlet side:-

A = 0.11 m2

Rs1 = 1 / (havg1 x A) + Ls / (Ks x A) + 1 / (havg0 x A)

= 1 / (3.239 x 0.11) + 0.05 / (15 x 0.11) + 1 / (78.29 x 0.11)

= 2.953

A = 0.515 m2

Rs2 = 1 / (havg1 x A) + Ls / (Ks x A) + Li / (Ka x A) + 1 / (havg0 x A)

= 1 / (3.239 x 0.515) + 0.003 / (15 x 0.515) + 0.005 / (0.1105 x 0.515) + 1 / (78.29 x 0.515) = 0.7125

Top side:-

A = 1.25 m2

RT = 1 / (havg2 x A) + Ls / (Ks x A) + Li / (Ka x A) + 1 / (havg0 x A)

= 1 / (1.717 x 1.25) + 0.003 / (15 x 1.25) + 0.005 / (0.1105 x 1.25) + 1 / (78.29 x 1.25) = 0.5125

Bottom side:-

36

A = 1.25 m2

RB = 1 / (havg3 x A) + Ls / (Ks x A) + Li / (Ka x A) + 1 / (havg0 x A)

= 1 / (3.434 x 1.25) + 0.003 / (15 x 1.25) + 0.005 / (0.1105 x 1.25) + 1 / (78.29 x 1.25) = 0.2795

Total heat loss through walls of box

Q box = ΔT / R = 80 x (1 / 0.2795+ 1 / 0.5125 + 2 / 0.7125 + 2 / 2.953 + 2 / 0.7339) = 939.91 W

Calculation of heat loss through walls of duct:-

Duct heat transfer coefficient calculation:-

A = 1.875 m2

RD = 1 / (havg1 x A) + Ls / (Ks x A) + Li / (Ka x A) + 1 / (havg0 x A)

= 1 / (3.239 x 1.875) + 0.002 / (15 x 1.875) + 0.0005 / (0.0465 x 1.875) + 1 / (78.29 x 1.875) = 0.1773

Total heat loss through walls of duct

Q box = ΔT / R = 80 / 0.1773 = 451.26 W

Calculation of heat required for drying of sheet:-

Initial temperature of sheet = 30oC

Dryer internal temperature = 110oC

Heat required by the sheet at 110oC = hg at 110oC – hf at 30oC

= 2691.3 KJ/Kg - 125.7 KJ/Kg

= 2565.6 KJ/Kg

37

Considering the drying process for a 24 ounce sheet

The water content in 24 ounce sheet before drying is 60% to 70% which is around 1.2 Kg. To dry it to an expectable level 1Kg of water needs to be evaporated during the drying process. The time available for drying of one 24 ounce sheet is 45sec hence:

Power required for drying sheet = 2565.6/45 Watt

= 57 KW

Considering the losses through walls of box and duct power or heat requirement from the heater is:

Total heat required = Heat requirement of paper board sheet

+ Heat loss through walls of box and duct

= 57000 + 939.91 + 451.26

= 58.391 KW

Hence it is suggested that two heaters of 30 KW capacity should be installed one above and one below the rollers near to the sheet.

38

5.2 Transmission Power Calculation

Power required by Rollers:-

Density of cast iron ρ = 8238 Kg/m3

Mass of smaller rollers = ρ x A = 8238 x 2 x π x 1 x 50 x 0.003 x 0.0252

= 4.8525 Kg

Mass of smaller rollers = ρ x A = 8238 x 2 x π x 2 x 50 x 0.003 x 0.0252

= 9.705 Kg

Moment of Inertia of small roller = 4.8525 x (1 x 0.025)2

= 3.0328 x 10-3 Kg m2

Moment of Inertia of larger roller = 9.705 x (2 x 0.025)2

= 30.47 x 10-3 Kg m2

Required angular velocity ω2 = 2 x π x n / 60 (consider n = 60)

= 6.283 rad/s

Therefore angular acceleration α = ω2 – ω1 / t

(Time available for roller get to ω2 from rest = 5 sec)

= (6.283 – 0) / 5

= 1.256 rad/s2

Torque required by small roller = 3.0328 x 10-3 x 1.256

= 3.809 x 10-3 N-m

Torque required by larger roller = 24.26 x 10-3 x 1.256

= 30.47 x 10-3 N-m

Power required by small roller = τ x ω = 3.809 x 10-3 x 6.283

= 23.93 x 10-3 W

Power required by small roller = τ x ω = 30.47 x 10-3 x 6.283

= 0.191 W

39

Total power required by rollers to overcome their inertia

= 23.93 x 10-3 x 7 + 0.191 x 4

= 0.93151 W

Power required for moving the paperboard ahead:-

Coefficient of friction µsp between steel and paper board = 0.84

Mass of card board = 2.5 Kg

Frictional force f = µsp m g = 0.84 x 2.5 x 9.81

= 20.601 N

Torque required = f x r (roller radius) = 20.601 x 1 x 0.025

= 0.515 N-m

Power required = τ x ω = 0.515 x 6.283 = 3.24 W

Power required to make the contact rollers roll:-

Coefficient of friction µsp between steel and paper board = 0.84

Mass of card board = 9.705 Kg

Frictional force f = µsp m g = 0.84 x 9.705 x 9.81

= 79.973 N

Torque required = f x r (roller radius) = 79.973 x 2 x 0.025

= 3.9986 N-m

Power required = τ x ω = 3.9986 x 6.283

= 25.124 W

Total power required by 2 rollers = 25.124 x 2

= 50.248 W

Hence total power requirement by the drive

40

= Power required by rollers to overcome inertial force

+ Power required to move the cardboard forward

+ Power required to roll the contact rollers

= 0.93151 + 3.424 + 50.248

= 54.419 W

Hence a motor of 1/8 hp and 350 rpm should be used to supply power to the chain drive.

41

5.3 Chain Drive Calculation Design power Pd = Pr x KL

Load factor KL for heavy shock load = 1.7

= 54.419 x 1.7 = 92.5123 W

= 1/8 hp

Required RPM = 60

Considering the design power and rpm select roller chain of ISO no. 06B Simplex.

Pitch p = 9.525 mm Roller dia dr = 6.35 mm

Width between inner plates b = 5.9 mm

Bearing pin body dia d2 = 3.28 mm inner plate depth h2 = 8.15 mm

Number of teeth on smaller sprocket T = 17

Pitch diameter of smaller Sprocket dc = p / (sin (180/T))

= 9.525 / (sin (180/17))

= 51.836 mm

Number of teeth on larger sprocket T = 34

Pitch diameter of larger Sprocket dcL = p / (sin (180/T))

= 9.525 / (sin (180/34))

= 103.23 mm

Centre distance C = 31 x 25 = 775 mm

Length of chain Lp = π x dcL + 2 x C

= π x 103 + 2 x 775 = 1874.30 mm

Tip dia = d + 1.25p – dr = 51.836 + 1.25 x 9.525 – 6.35

= 57.39 mm

Roller seating radius ri = 0.505dr = 0.505 x 6.35 = 3.206 mm

42

Root dia = d – 2ri = 51.836 – 2 x 3.206 = 45.42 mm

Tooth flank radius = 0.12dr (T + 2) = 0.12x6.35x (17 + 2)

= 14.478 mm

Roller seating angle = 140 – 90 / T = 120 – 90 / 17

= 134.7o

Tooth height above the pitch polygon = 0.5 (p – dr) = 0.5 x (9.525 – 6.35)

= 1.5875 mm

Tooth side radius = p = 9.525 mm

Tooth width = 0.93 x b1 = 0.93 x 5.9 = 5.487 mm

Tooth side relief = 0.1p = 0.1 x 9.525 = 0.9525 mm

Design of V belt drive:-

Design power Pd = 1/8 hp

Considering the design power belt of type A is selected

Motor speed Nm = 280 rpm Chain drive speed Nd = 60 rpm

Dia of smaller pulley ds = 80 mm

Dia of larger pulley dl = 80 x 280 / 60 = 280 mm

43

Chapter No. 6

Drafting and Pictures of dryer model

44

6.1 Drafting of the Duct

45

6.2 Drafting of the Structure

46

6.3 Drafting of the Box

47

6.4 Pictures of Dryer Model

48

Chapter No. 7

Conformity of design

49

The company Raj Paperboard Mills has shown a positive response

towards the proposed design of dryer and is planning to install a test model

for the upcoming year, as the design promising and has following advantages

associated with it:

The design is robust and made from simple mechanical

components and has no sophisticated technology involved.

Hence the capital investment which the increased production

will be able to recover quickly.

The design offers a production rate of 1.33 sheets / min (for 24

ounces).

The drying rate gets adjusted automatically with the changing

production rate and the change in product.

The power requirement of the drive is very less and the heat

losses through the walls are also minimum, hence the operating

cost in minimum and unskilled laborer can be used for operating

the machine. The maintenance cost is low as the design is simple

and it does not require specialization of labor.

The present design can be used with gas burners in place of

heating coils and will give same results. Hence the design is quite

flexible.

The company’s problem of drying in odd seasons i.e. during

monsoon and winter is handled and promises to give satisfactory

results.

As it is not a part of paperboard drying machine it can be

installed at any part of the plant where it is convenient. It can be

made dysfunctional if wanted during dry weather i.e. summer.

50

Bibliography

www.madeinchina.com

www.wikipedia.com

“DRYING SYSTEMS AND NEW TECHNIQUES FOR PAPERBOARD COATING” By: James M. Rennes, P.E. Global Technologies, LLC Green Bay, WI 54307 USA.

Feasibility of recycling pulp and paper mill sludge in the paper and board industries. Jesús A.G. Ochoa de Alda, A Faculty of Experimental Sciences, IE Universidad, c/Cardenal Zúñiga 12, 40003 Segovia, Spain

J. Perry, “Flotation, Infrared Drying Boosts Efficiency of Paper Coating Stage”, Pulp and Paper, May 1989.

E.Bowden, “Non-contact Drying and Turning—the ‘On-Machine’ Technology of the Nineties”. Paper presented at the 44th Annual General Conference, 1990.

J. Dunlop, “Contactless Web Handling and Drying”, ting Conference, TAPPI Press: Atlanta 1991.

Spooner’s REDair Combi TM Brochure

51

Acknowledgement

Failure is the first step towards success. But repeated failure

also has the risk of abandonment of mission. So, behind every

successful project there has to be a person who can show the small

streak of light far away, who can motivate and guide all along the way

properly with his experience and wisdom.

We got such a person along with us throughout the course of

our project as our project guide Prof. G. H. Waghmare. He has been

guiding us through all the difficult stages of the project, helping us

through difficulty and encouraging us to do better every time.

We dedicate our project to our project guide Prof. G. H.

Waghmare for his valuable guidance and painstaking attention for

helping us in our endeavor.

We are also grateful to the staff of Mechanical engineering

department for their help to us especially to Oke sir, Chadge sir and

Anwar sir.

PROJECTEES