MANUFACTURE OF FORMALDEHYDE.pdf

download MANUFACTURE OF FORMALDEHYDE.pdf

of 51

Transcript of MANUFACTURE OF FORMALDEHYDE.pdf

  • iii

    MANUFACTURE OF FORMALDEHYDE

    FROM METHANOL

    A PROJECT REPORT

    Submitted by

    S. GAYATHRI (41501203005)

    G. MUTHAMILARASI (41501203014)

    in partial fulfillment for the award of the degree

    of

    BACHELOR OF TECHNOLOGY

    in

    CHEMICAL ENGINEERING

    S.R.M. ENGINEERING COLLEGE, KATTANKULATHUR-603 203, KANCHEEPURAM DISTRICT.

    ANNA UNIVERSITY : CHENNAI - 600 025

    MAY 2005

  • iv

    BONAFIDE CERTIFICATE Certified that this project report "MANUFACTURE OF FORMALDEHYDE FROM

    METHANOL" is the bonafide work of "S. GAYATHRI (41501203005) and G.

    MUTHAMILARASI (41501203014)" who carried out the project work under my

    supervision.

    Prof. Dr. R. KARTHIKEYAN Prof. Dr. R. KARTHIKEYAN

    HEAD OF THE DEPARTMENT SUPERVISOR

    CHEMICAL ENGINEERING PROFESSOR & HEAD

    S.R.M.Engineering College CHEMICAL ENGINEERING

    Kattankulathur - 603 203 S.R.M.Engineering College

    Kancheepuram District Kattankulathur - 603 203

    Kancheepuram District

  • v

    ACKNOWLEDGEMENT

    Our heart felt thanks to the Director, Dr.T.P.Ganesan, and our Principal, Prof.

    R.Venkatramani,M.Tech,F.I.E, for allowing us to carryout our project.

    We express our profound gratitude to Dr.R.Karthikeyan, Head of the

    Department, Chemical engineering, who guided us in the right direction through the

    course of our project.

    We also thank our project co-ordinater Mrs.K.Kasturi,B.Tech, for her valuable

    advice and encouragement.

    Our special thanks to the members of the DTP section and library for their co-

    operation

  • vi

    ABSTRACT

    Formaldehyde, one of the important industrial chemicals, finds its applications

    in polymeric resins like phenol formaldehyde, adhesives, alkali resins for paints and

    coatings etcManufacture of formaldehyde (as formalin) is done by oxidation of

    methanol, mainly by metal oxide process involving Fe/Mo catalyst with 95-99mol%

    conversion of methanol. This project is aimed at designing plant producing 37 wt%

    formalin and checking for feasibility of production.

  • vii

    TABLE OF CONTENTS CHAPTERS TITLE PAGE NO

    ABSTRACT iv

    LIST OF TABLES

    vii

    LIST OF FIGURES

    viii

    LIST OF SYMBOLS

    ix

    1

    INTRODUCTION

    1

    2

    PROPERTIES

    2.1 PHYSICAL PROPERTIES 2.2 THERMAL PROPERTIES

    2.3 CHEMICAL PROPERTIES

    3 3 3 4

    3

    ANALYSIS AND SPECIFICATIONS

    7

    4

    COMMERCIAL USES OF FORMALIN

    8

    5

    LITERATURE REVIEW

    5.1 SELECTION OF PROCESS

    10 11

    6

    PROCESS DESCRIPTION

    6.1 FLOW SHEET

    12 14

    7

    MATERIAL BALANCE

    15

    8

    ENERGY BALANCE

    19

    9

    DESIGN

    23

    10

    PLANT LAYOUT 29

    11 MATERIALS OF CONSTRUCTION 11.1 METALS 11.2 NON-METALS

    39 39 40

    12

    INSTRUMENTATION AND CONTROL

    41

  • viii

    13 STORAGE AND TRANSPORTATION 46 14

    HEALTH AND SAFETY CONSIDERATIONS

    47

    15

    COST ESTIMATION

    49

    16

    CONCLUSION

    56

    REFERENCES

    57

    LIST OF TABLES

    Table Number

    Description Page No

    1

    Heat transfer data

    19

    2 Storage temperatures 46

    3 Dose-response relationship 47

    4 Delivered cost of equipments 49

    5 Direct cost factor 50

    6 Indirect cost factor 50

    7 Auxillary cost factor 52

  • ix

    LIST OF FIGURES

    Page No FIGURE 6.1

    FLOW SHEET

    14

    FIGURE 7.1

    REACTOR BALANCE

    17

    FIGURE 7.2

    ABSORBER BALANCE

    18

    FIGURE 8.1

    ENERGY BALANCE FOR METHANOL VAPORIZER

    19

    FIGURE 8.2

    ENERGY BALANCE FOR REACTOR

    20

    FIGURE 8.3

    ENERGY BALANCE FOR HEAT EXCHANGER 1

    21

    FIGURE 8.4

    ENERGY BALANCE FOR HEAT EXCHANGER 2

    21

    FIGURE 8.5

    ENERGY BALANCE FOR ABSORBER(BOTTOM)

    21

    FIGURE 8.6

    ENERGY BALANCE FOR ABSORBER (TOP)

    22

    FIGURE 10.1

    PLANT LAYOUT

    38

  • x

    LIST OF SYMBOLS

    A Area (m2)

    D,d Diameter (m)

    L Length (m)

    m Mass (Kg)

    Nu Nusselt number

    n Number of tubes

    P Pressure (atm)

    Pr Prandtl number

    Re Reynolds number

    V Volume(m3)

    T Temperature(K)

    U Overall heat transfer

    coefficient(W/ m2.oC)

    Z Height (m)

    GREEK LETTERS T Temperature difference (oC)

    TL Logarithmic mean temperature difference (oC) L

    Viscosity of liquid

    Density (Kg/m3)

  • 11

    1. INTRODUCTION

    Formaldehyde occurs in nature and it is formed from organic material by

    photochemical processes in the atmosphere. Formaldehyde is an important metabolic

    product in plants and animals (including humans), where it occurs in low but

    measurable concentrations. It has a pungent odour and is an irritant to the eye, nose

    and throat even at low concentrations.

    However, Formaldehyde does not cause any chronic damage to human health.

    Formaldehyde is also formed when organic material is incompletely combusted.

    Formaldehyde is an important industrial chemical and is employed in the manufacture

    of many industrial products and consumer articles.

    Formaldehyde was first synthesized in 1859, when BUTLEROV hydrolyzed

    methylene acetate and noted the characteristic odour of the resulting solution. In

    1867,HOFMANN conclusively identified formaldehyde, which he prepared by

    passing methanol vapour and air over a heated platinum spiral. This method, but with

    other catalyst, still constitutes the principal method of manufacture.

    Industrial production of formaldehyde became possible in 1882,when

    TOLLENS discovered a method of regulating the methanol vapour: air ratio and

    affecting the yield of the reaction. In 1886 LOEW replaced the platinum spiral

    catalyst by more efficient copper gauze. A German firm, Hugo Blank, patented the

    first use of a silver catalyst in 1910.In 1905,Badische Anilin and Soda-Fabrik started

    to manufacture formaldehyde by a continous process employing a crystalline catalyst.

    Formaldehyde output was 30 kg/day in the form of an aqueous 30 wt% solution. The

    methanol required for the production of formaldehyde was initially obtained from the

    timber industry by carbonizing wood. The development of high-pressure synthesis of

    methanol by Badische Anilin and Soda-Fabrik in 1925 allowed the production of

    formaldehyde on a true industrial scale

  • 12

    2. PROPERTIES

    2.1 PHYSICAL PROPERTIES

    Formaldehyde is a colorless gas at ambient temperature that has a pungent,

    suffocating odor. At ordinary temperatures formaldehyde gas is readily soluble in

    water, alcohols and other polar solvents. It has following physical properties:

    Boiling point at 101.3 kPa = -19.2oC

    Melting point = -118oC

    Density at 80oC = 0.9151g/cm3

    At 20oC = 0 .8153 g/cm3

    Vapor density relative to air = 1.04

    Critical temperature = 137.2 141.2 (oC)

    Critical pressure = 6.784 6.637 Mpa

    Cubic expansion coefficient = 2.83 x 103 K-1

    2.2 THERMAL PROPERTIES

    Heat of formation at 25oC = -115.9 + 6.3 kJ/mol

    Heat of combustion at 25oC = 561.5 kJ/mol

    Heat of vapourisation at 19.2oC = 23.32 kJ/mol

    Specific heat capacity at 25oC = 35.425 J/mol K

    Heat of solution at 23oC

    In water = 62 kJ/mol

    In methanol= 62.8 kJ/mol

    In 1-propanal = 59.5 kJ/mol

    In 1-butanol = 62.4 kJ/mol

    Entropy at 25oC= 218.8 + 0.4 kJ/mol K

    2.3 CHEMICAL PROPERTIES

    Formaldehyde is one of the most reactive organic compounds known. The

    various chemical properties are as follows:

    Decomposition

    At 150oC formaldehyde undergoes heterogeneous decomposition to form

    methanol and CO2 mainly. Above 350oC it tends to decompose in to CO and H2.

  • 13

    Polymerization

    Gaseous formaldehyde polymerizes slowly at temperatures below 100oC,

    polymerization accelerated by traces of polar impurities such as acids, alkalis or

    water. In water solution formaldehyde hydrates to methylene glycol

    H

    H2C=O + H2O HO C OH

    H

    Which in turn polymerizes to polymethylene glycols, HO (CH2O)nH, also

    called polyoxy methylenes.

    Reduction and Oxidation

    Formaldehyde is readily reduced to methanol with hydrogen over many metal

    and metal oxide catalysts. It is oxidized to formic acid or CO2 and H2O.

    In the presence of strong alkalis or when heated in the presence of acids

    formaldehyde undergoes cannizzaro reaction with formation of methanol and formic

    acid. In presence of aluminum or magnesium methylate, paraformaldehyde reacts to

    form methyl formate (Tishchenko reaction)

    2HCHO HCOOCH3

    Addition reactions

    The formation of sparingly water-soluble formaldehyde bisulphite is an

    important addition reaction. Hydrocyanic acid reacts with formaldehyde to give

    glyconitrile.

    HCHO + HCN HOCH2 - C N

    Formaldehyde undergoes acid catalyzed Prins reaction in which it forms -Hydroxy-

    methylated adducts with olefins. Acetylene undergoes a Reppe addition reaction with

    formaldehyde to form 2- butyne-1,4- diol.

  • 14

    2 HCHO + HC CH HOCH2CCH2OH

    Strong alkalis or calcium hydroxide convert formaldehyde to a mixture of sugars in

    particular hexoses, by a multiple aldol condensation, which probably involves a

    glycolaldehyde intermediate. Acetaldehyde, for example reacts with formaldehyde to

    give pentaerythritol, C (CH2OH)4

    Condensation reactions

    Important condensation reactions are the reaction of formaldehyde with amino

    groups to give schiffs bases, as well as the Mannich reaction.

    CH3COCH3 + (CH3) 2NH.HCl + HCHO

    CH3COCH2CH2N(CH3) 2.HCl + H2O

    Formaldehyde reacts with ammonia to give hexamethylene teteramine and

    with ammonium chloride to give monomethylamine, dimethylamine, or

    trimethylamine and formic acid, depending upon reaction conditions.

    Aromatic compounds such as benzene, aniline, and toluidine combine with

    formaldehyde to produce the corresponding diphenyl methanes. In the presence of

    hydrochloric acid and formaldehyde, benzene is chloromethylated to form benzyl

    chloride. Formaldehyde reacts with hydroxylamine, hydrazines, or semicardazide to

    produce formaldehyde oxime, the corresponding hydrazones, and semicarbazone,

    respectively.

    Resin formation

    Formaldehyde condenses with urea, melamine, urethanes, cyanamide,

    aromatic sulfonamides and amines, and phenols to give wide range of resins.

  • 15

    3. ANALYSIS AND SPECIFICATIONS

    Qualitative Methods:

    Qualitative detection of formaldehyde is primarily by colorimetric methods.

    Schiffs fuchsin-bisulfite reagent is the general reagent used for detecting aldehydes.

    In the presence of strong acids, it reacts with formaldehyde to form a specific bluish

    violet dye.

    Quantitative Methods:

    Physical Methods: Quantitative determination of pure aqueous solutions of

    formaldehyde can be carried out rapidly by measuring their specific gravity. Gas

    chromatography and high-pressure liquid chromatography can also be used for direct

    determination.

    Chemical Methods:

    The most important chemical method for determining formaldehyde is the

    sodium sulfite method. It is based on the quantitative liberation of sodium hydroxide

    when formaldehyde reacts with excess sodium sulfite.

    CH2O + Na2SO3 + H2O HOCH2SO3Na + NaOH

    The stoichiometrically formed sodium hydroxide is determined by titration

    with an acid.

    Formaldehyde in air can be determined with the aid of gas sampling apparatus.

    In this procedure formaldehyde is absorbed from a definite volume of air by a wash

    liquid and is determined quantitatively by a suitable method like pararosanline

    method.

    Formaldehyde is sold in aqueous solutions with concentrations ranging from

    25 56 wt% HCHO. Formaldehyde is sold as low methanol (uninhibited) and high

    methanol (inhibited) grades. Formaldehyde solutions contain 0.5-12 wt% methanol or

    other added stabilizers. They have a pH of 2.5 3.5,the acid reaction being due to the

    presence of formic acid.

    4. COMMERCIAL USES OF FORMALDEHYDE

    Formaldehyde resins are one of the major applications of formaldehyde. Some

    of the derivatives are given below.

    Urea-formaldehyde resins are produced by the controlled reaction of urea and

    formaldehyde. Their major uses are as adhesives for particleboard, fiberboard and

  • 16

    plywood. They are also used for compression molded plastic parts, as wet-strength

    additives for paper treating, and as bonders for glass fiber roofing materials.

    Phenol formaldehyde is produced by the condensation of phenol with

    formaldehyde. The use of these resins is as an adhesive in waterproof plywood. These

    resins are also used for binding glass fiber insulation.

    Acetylenic chemical uses of formaldehyde involve the reaction with acetylene

    to form butynediol, which in turn can be converted to butanediol, butyrolactone and

    pyrrolidones. Their major applications are as specialty solvent and extractive

    distillation agents.

    Polyacetyl resins are produced from the anionic polymerization of

    formaldehyde. These resins are used in plumbing materials and automobile

    components.

    Pentaerythritol is formed by the reaction of formaldehyde, acetaldehyde and

    sodium hydroxide. Its largest use is in the manufacture of alkyd resins for paints and

    other protective coatings.

    Hexamethylene tetramine is formed by the reaction between formaldehyde

    and ammonia. It is used as a partial replacement for phosphates as a detergent builder

    and as a chelating agent.

    Urea-formaldehyde concentrates are used as controlled release nitrogen

    fertilizers.

    Melamine resins are thermosetting resins produced from melamine and

    formaldehyde and are primarily used for surface coatings.

    The direct use of formaldehyde is to impart wrinkle resistance in fabrics.

  • 17

    5. LITERATURE SURVEY

    Most of the worlds commercial formaldehyde is manufactured from methanol

    and air either by a process using a silver catalyst or one using a metal oxide catalyst.

    SILVER CATALYST PROCESS

    The silver catalyst processes for converting methanol to formaldehyde are

    generally carried out at an atmospheric pressure and at 600 720C .The reaction

    temperature depends on the excess of methanol in the methanol-air mixture. The

    composition of mixture must lie outside the explosive limits. The amount of air used

    is also determined by the catalytic quality of the silver surface. The following

    reactions take place

    CH3OH + O2 HCHO + H2O

    CH3OH HCHO + H2

    Methanol conversion is 65 75% per pass.

    METAL OXIDE PROCESS

    In this process formaldehyde is formed by oxidation process only. The

    reactions are

    CH3OH + O2 HCHO + H2O

    HCHO + O2 CO + H2O

    The reactions occur over a mixed oxide catalyst containing molybdenum oxide

    and iron oxide in a ratio 1.5 to 3.The reaction is carried out at 250 350 oC and

    essentially at atmospheric pressure. Methanol conversion is 95 98% per pass.

    5.1 SELECTION OF PROCESS

    It is estimated that nearly 70% of commercial formaldehyde is produced by

    metal oxide process. This process has a very low reaction temperature, which permits

    high catalyst selectivity, and the very simple method of steam generation. The

    conversion is around 95-98% per pass, which is greater than silver oxide process.

  • 18

    6. PROCESS DESCRIPTION

    Metal oxide process: Vaporized methanol is mixed with air and optionally recycled

    tail gas is passed through catalyst filled tubes in a heat exchanger reactor. The

    following reactions take place in the reactor.

    CH3OH+ O2 HCHO +H2O +37 Kcal/g-mol

    HCHO + O2 CO+H2O+51 Kcal/g-mol

    The temperature inside the reactor is maintained at 250-350C.

    The heat released by the exothermic reaction is removed by vaporization of a

    high boiling heat transfer fluid on outside of the tubes. Steam is normally produced by

    condensing the heat transfer fluid. The catalyst is granular or spherical supported

    Fe/Mo and has an effective life of 12 18 months. A typical reactor has short tubes of

    1-1.5m and a large shell diameter of 2.5 m or more. The exit gases from the reactor

    pass through a heat exchanger where the temperature is reduced to 110oC and then to

    the absorption column where water is used as the scrubbing medium.

    The absorber can be either of packed or tray type. It is necessary to remove the

    heat of solution plus the residual sensible heat of the feed gases, and this is done by

    circulating down flow liquid through external heat exchangers and in some cases by

    the use of cooling coils. The bottom stream from the absorber represents the final

    product. Formaldehyde concentration in the product is adjusted by controlling the

    amount of water added to the top of the absorber. Formic acid is removed by ion

    exchange. A large portion of the absorber overhead gas is recycled back to the feed

    system. The methanol conversion ranges from 95-99mol% and depends on the

    selectivity, activity and spot temperature of the catalyst, the later being influenced by

    the heat transfer rate. The overall plant yield of formaldehyde is 88-95 mol%.

  • 19

    The final product contains up to 55wt% formaldehyde and 0.5-1.5 wt%

    methanol.

    ABSORBER

    R E A C T O R

    WATER

    CW

    CW

    DEIONISER

    METHANOL

    RECYCLE GAS

    PURGE GAS

    AIR

    St

    St

    BLOWER

    BFW

    St

    BFW

    2

    1 `

    3 F ORMA L I N

    1. METHANOL VAPORIZER 2. HEAT EXCHANGER 1 3. HEAT EXCHANGER 2

  • 20

    FIG 6.1 FLOW SHEET 7. MATERIAL BALANCE

    Basis: 100 kmoles of methanol in fresh feed per hour

    Molecular weight of methanol = 32 kg/kmole

    Weight of methanol in feed = 3200 kg

    CH3OH + O2 HCHO + H2O

    Assume methanol conversion is 97 %.

    Hence methanol reacted = 97 kmoles

    = 3104 kg

    Assume that 1% of methanol reacts to form formic acid.

    HCHO + O2 CO + H2O

    Actual O2 required = 51.925 kmoles = 1661.60 kg

    Actual O2 supplied (250% excess) = 181.738 kmoles = 5815.62 kg

    Excess O2 = 181.738 51.925

    = 129.813 kmoles =4154.02 kg

    Assume that 57% of oxygen requirement comes from recycle stream and 43% comes

    from fresh feed.

    O2 from fresh feed = 181.738 x 0.43

    = 78.147 kmoles = 2500.70 kg

    Corresponding N2= 78.147 x (79/21)

    = 298.982 kmoles = 8371.50 kg

    Assume that the percentage composition of recycle stream is

    O2 - 7.78%

  • 21

    N2 - 88.3%

    H2O - 3.89% O2 from recycle stream = 103.590 kmoles =3314.88 kg

    N2 in recycle stream = 1175.910 kmoles =32925.48 kg

    H20 in recycle stream = 51.795 kmoles =932.31 kg

    Reactor outlet:

    Unreacted methanol = 2 kmoles=64 kg

    HCHO formed = 92.15 kmoles=2764.50 kg

    H2O formed = 154.64 kmoles=2783.52 kg

    CO formed = 4.85 kmoles= 135.8 kg

    Nitrogen =1484.185 kmoles=41157.20 kg

    Unreacted oxygen =129.813 kmoles =4154.02 kg

    HCOOH formed = 1 kmole = 46 kg

    FIG 7.1

    REACTOR

    Methanol =3200kg

    O2= 3314.82 kg N2 = 32925.48 kg H20 = 932.31 kg

    Air O2=2500.71kg N2 =8231.50 kg

    CH3OH = 64 kg O2=4153.92 kg N2=41157.20kg H20 = 2783.4 kg

    HCHO=2764.5 kg CO=135.8 kg HCOOH=46 kg

    TOTAL INPUT =51104.82 kg TOTAL OUTPUT =51104.82 kg

  • 22

    ABSORBER

    Gms (Ya-Yb) = Lms (Xa- Xb)

    Gms =molar flow rate of gas on solute free basis

    Lms =molar flow rate of liquid on solute free basis

    Xa =% of solute in liquid at inlet

    Xb =% of solute in liquid at outlet

    Ya =fraction of solute in gas at inlet

    Yb =fraction of solute in gas at outlet

    Gas flow rate = Gms= 1653.645 kmoles/hr M= 0.0678 (VLE data) M= (Lms) min Gms (Lms) min = 112.117 kmoles Yb = 5/95 = 0.0526 Ya = 3.14 X104 Xa = 0 Xb =0.7758 Assume Lms = 1.4 (Lms) min Lms = 157.71 kmoles

  • 23

    FIG 7.2

    8. ENERGY BALANCE DATA TABLE 1:

    Latent heat of vaporization, (KJ/Kg)

    Specific heat capacity Cp(KJ/Kg oC)

    Methanol 1099.90 (at 64.7 oC) 2.513 O2 - 0.928 N2 - 1.04 H2O 2255(at 100 oC)

    3278.20 (at 400 oC) 2228.69(at 110 oC)

    1.88

    CO - 1.13 HCOOH - 0.6 HCHO - 0.5 Oil - 1.75 1) Methanol vaporizer RECYCLE AIR (25oC) H20 (400 oC) O2 :3314.8 Kg N2: 32925 Kg H20:932.31 Kg CH3OH = 3200 Kg AIR(285 oC) METHANOL

    CH3OH=64 kg HCOOH=46 kg

    H20=1165.39 kg O2=4153.92 kg N2=41156.64 kg

    PRODUCT STREAM HCHO=2764.5 kg H20=4593.02 kg

    HCHO=2764.5 kg CO =135.8 kg HCOOH=46 kg

    FROM REACTOR CH3OH = 64 kg O2=4153.92 kg N2=41157.20kg H20 = 2783.4 kg ABSORBER

    SOLVENT H20=2838.78 kg

    RECYCLE STREAM

    TOTAL INPUT = 53943.46 kg TOTAL OUTPUT = 53943.46 kg

    Methanol Vaporizer

  • 24

    FRESH AIR O2: 2500 Kg N2: 8231.5Kg (400 oC) SUPERHEATED STEAM

    FIG 8.1

    mCp T(inlet stream) = m (steam) (m Cp (recycle) + m Cp (air) +m Cp (methanol liq)+m(methanol) +m Cp (methanol gas) )(285-25) = 18.08x105 = m x 3278.20

    Steam required m = 551.52 Kg

    2)Reactor CH3OH = 3200 Kg CH3OH = 64 Kg O2 = 5815.6 Kg O2 = 4153.92 Kg N2 = 41157.2 Kg N2 = 41157.20 Kg H20 = 932.31 Kg H20 = 2783.61 Kg (285 oC) CO = 135.80 Kg HCOOH = 46 Kg HCHO = 2764.50 Kg

    FIG 8.2 Reactions: CH3OH + 1/2 O2 HCHO + H20 Ho = -4839 KJ/Kg HCHO + 1/2 O2 CO + H20 Ho = -7115.35 KJ/Kg For an isothermal reaction: H(products) + Ho - H(reactants) =H (H = m CP T) (T=285-25=260) Substituting values from table 1, H = 13.8687x106 KJ H (reactor) = m CpT(cooling oil) 13.8687x106 = m x 1.75x 110

    Oil required m = 72045.058 Kg

    Isothermal

    Reactor

  • 25

    3) Heat exchanger 1: Oil (120 oC) H20 (25 oC) Steam (100 oC) Oil (230 oC)

    FIG 8.3

    mCp T(cooling oil) = mCP T(H20) + m (steam) 13.8687x106 = m x 1.88 x 75 + m x 2255

    Water required m = 5144.19 Kg

    4) Heat exchanger 2:

    Steam (100 oC) Reactor outlet (285 oC) (110 oC) H20 (25 oC)

    FIG 8.4

    mCp T(products) = m CpT(H20) + m (steam) 9.1815x106 = m x 1.88 x 75 + m x 2255

    Water required m = 3405.60 Kg

    5)Absorber:

    Bottom: Water (50 oC)

    Products (gases) H20 (liquid)

    (110 oC) (110 oC)

    Water (25 oC)

    FIG 8.5

    mCp T(cooling H20) = m (condensing water) m x 1.88 x 25 = 2783.61 x 2228.7

    Cooling water required m = 13996.121 Kg

    Top:

    Water (50 oC)

  • 26

    Products (gases) Products (gases)

    (110 oC) (30 oC)

    Water(25 oC)

    FIG. 8.6

    mCpT(cooling H20) = mCpT (product gases) m x 1.88 x 25 = mCp (110-30)

    Cooling water required m = 81457.60 Kg

  • 27

    9. DESIGN

    HEAT EXCHANGER 1

    U0A0TL = (m CPT) OIL Where U0 = Overall heat transfer co-efficient (KW/m2 oC)

    A0= Outside tube area (m2)

    TL = Logarithmic mean temperature (oC) TL = (230 100) (30 -25) ln (130/5)

    = 38.3659 oC

    U0x 2 x R x L x n x TL = 3852.409

    U0 = 1

    1/h0 + (A0/Ai) ( 1/hi)

    Nu =0 .023 (Re)0.8 (Pr)0.3

    Assume that d0 = BWG NO = 16

    d0= 0.0191 m

    di = 0.0157 m

    m = AV

    V = m / A = (72045.05 /3600)

    x (0.0157/2)2 x 864.9939

    = 119.56 m/s

    Nu = 0.023 x (120262.0154) (1.9989)

    = 5504.1158

    hi = 44.87 kW/ m2 oC

    Assume ho = 1.7201 kW/ m2 oC

  • 28

    1

    Uo =

    (1/1.7021) + (1.216/44.87)

    Uo = 1.6270 kW/ m2 oC

    Assume L = 2.7432 m

    1.6270 x 3.14 x 0.0191x111 x 2.7432 x n = 3852.409

    HEAT EXCHANGER 2

    U0A0 TL = (m CPT) PRODUCTS

    TL = (285 100) ( 110 -25) ln (185/85)

    = 128.584 oC

    U0x 2 x R x L x n x TL = 2550.4324

    U0 = 1

    1/h0 + (A0/Ai) (1/hi)

    Nu =0 .023 (Re)0.8 (Pr)0.3

    Assume that d0 = BWG NO = 16

    d0= 0.0191 m

    di = 0.0157 m

    m = AV

    V = m / A = (51105.03/3600)

    x (0.0157/2)2 x 900

    = 81.517m/s

    n = 147 tubes

  • 29

    Nu = 0.023 x (138695.051) (0.6795)

    = 21676.058

    hi = 181.714 kW/ m2 oC

    Assume ho = 1.7201 kW/ m2 oC

    1

    Uo = (1/1.7021) + (1.216/181.714)

    Uo = 1.682kW/ m2 oC

    Assume L = 3.048 m

    1.682 x 3.14 x 0.0191x128.5842 x 3.048x n = 2550.4324

    REACTOR DESIGN

    Specification: Packed multiple tubular reactor

    Assumption:

    Shell diameter of each reactor =39

    = 0.99 m

    Tube specifications: 1 1/2" BWG (No 16)

    Corresponding number of tubes = 307

    Volume of one tube:

    ID = 0.03479 m L = 1.5 m

    Volume = R2L = x0.01742 x 1.5=1.426 x10-3 m3

    Volume of 307 tubes =0.4379 m3

    Void fraction = 0.4 (assumption)

    Volume occupied by catalyst/reactor = 0.4379 x 0.6

    = 0.2627 m3

    Space velocity = 5 m3 of gas charged to the reactor (assumption)

    (at NTP) hr- m3 of catalyst per tube

    Space velocity for 307 tubes = 1535 m3 of gas charged to the reactor

    n = 65 tubes

  • 30

    hr- m3 of catalyst

    Volumetric flow rate: (at NTP)

    No of moles entering the reactor/hr = 1803.43 Kmol/hr

    Pressure = 1.1 atm; Temperature = 298 K

    R = 0.08206 atm m3 / Kmol K

    PV= nRT

    V = 1803.43 x 0.08206 x 298 = 40,091.70 m3 of gas/hr

    1.1

    Volumetric flow rate

    Volume of catalyst = = 26.1183 m3

    Space velocity

    Number of reactors required = volume of catalyst Volume occupied by

    Catalyst per reactor

    = 26.1183/0.2627

    = 99.42 ~ 100 reactors

    ABSORBER DESIGN

    Absorber height Z =Noy x Hoy

    Noy = yb - ya ; YL = (yb-yb *)- ( ya-ya * ) YL ln ((yb-yb *)/ ( ya-ya * ))

    Hoy = Gms / Kya ; where Gms = mass flow rate of gases (Kg/s)

    K ya = overall mass transfer coefficient based on

    gas phase (Kmol/m3 s )

    Calculation of Noy:

    ya = 3.13 x 10 4 xa = 0

    yb = 0.0499 xb = 0.4368

  • 31

    Kya = 0.4 Kmol/m3s (assumption)

    Gms (ya-yb) =1.32 Lms (xb-xa ) (x,y are mole fractions of HCHO in

    liquid and gas phase resp)

    xb = 0.5877

    yb * = 0.067 xb * (equilibrium data)

    yb * = 0.039

    substituting the above values,

    YL = 0.00298 Noy = 16.69 ~ 17 transfer units

    Calculation of Hoy:

    Gms = 2764.50 Kg/hr = 0.7679 Kg/ s

    Gas density at 110oC = 0.90 Kg/m3

    Liquid density = 1000 Kg/m3

    Viscosity = 0.0009 Kg/ms

    K4 = 0.9; FP = 1 0.5

    Mass flow rate per unit area V = K4 v (l - v )

    (Kg/m2s ) 13.1 FP ( l /l )0.1 Substituting the values,

    V = 1.4616 Kg/m2s

    Column area = Gms/V =0.5252 m2

    Column diameter =(0.5252 x 4/)0.5 = 0.8179 m

    Hoy = Gma/Kya=Gms/(column area x Kya )

    = 0.19 m

    Calculation of height: (for the top of the absorber)

    Z = 17 x 0.19

    Z= 3.33m

  • 32

    10. PLANT LAYOUT

    INTRODUCTION

    The economic construction and efficient operation of a process unit will

    depend upon how well the plant and equipment specified on the process flowsheet is

    laid out and on the profitability of the project with its scope for future expansion.

    Plant location and site selection should be made before the plant layout.

    Plant location and site selection:

    The location of the plant has a crucial effect on the profitability of the project.

    The important factors that are to be considered while selecting a site are:

    1. Location, with respect to market area

    2. Raw material supply

    3. Transport facilities

    4. Availability of Labour

    5. Availability of utilities

    6. Availability of suitable land

    7. Environmental impact and effluent disposal

    8. Local community considerations

    9. Climate

    10. Political and strategic considerations

    1. Marketing area

    For materials that are produced in bulk quantities, such as cement, mineral

    acids, and fertilizers where the cost of product per tone is relatively low and the cost

    of transport a significant fraction of the sales price, the plant should be located close

    to the primary product. This consideration will be less important for low volume

    production, high-priced products, such as pharmaceutical.

    2. Raw materials

    The availability and price of suitable raw materials will often determine the

    site location. Plants producing bulk chemicals are best located close to the source of

  • 33

    major raw material, where this is also close to the marketing area. For the production

    of formaldehyde the site should be preferably near a methanol plant.

    3. Transport

    Transport of raw materials and products is an important factor to be

    considered. Transport of products can be in any of the four modes of transport.

    4. Availability of labour

    Labour will be needed for construction of the plant and its operation. Skilled

    construction workers will usually be brought in from outside the site area, but there

    should be an adequate pool of unskilled labours available locally; and labour suitable

    for training to operate the plant. Skilled tradesman will be needed for plant

    maintenance. Local trade union customs and restrictive practices will have to be

    considered when assessing the availability and suitability of the local labour for

    recruitment and training.

    5. Environmental impact and effluent disposal

    All industrial processes produce waste products, and full consideration must

    be given to the difficulties and cost of their disposal. The disposal of toxic and

    harmful effluents will be covered by the local regulations and the appropriate

    authorities must be consulted during the initial survey to determine the standards that

    must be met.

    6. Local community consideration

    The proposed plant must fit n with and be acceptable to the local community.

    Full consideration must be given to the safe location of the plant so that it does not

    impose a significant additional risk to the community on a new site, the local

    community must be able to provide adequate facilities for the plant personnel.

    7. Land

    Sufficient suitable land must be available for the proposed plant and for future

    expansion. The land should ideally be flat, well drained and have suitable load-

    bearing characteristics full site evaluation should be made to determine the need for

    piling or other special foundations.

    8. Climate

  • 34

    Adverse climatic conditions, at a site will increase costs. Abnormally low

    temperatures will require the provision of additional insulation and special heating for

    equipment and pipe runs.

    9. Political and strategic considerations

    Capital grants, tax concessions and other inducements are often given by

    governments to direct new investment to preferred locations; such as areas of high

    unemployment. The availability of such grants can be overriding consideration in the

    site selection.

    After considering the location of the site the plant layout is completed. It

    involves placing of equipment so that the following are minimized:

    1. Damage to persons and property in case of fire explosion or toxic release

    2. Maintenance costs

    3. Number of people required to operate the plant.

    4. Construction costs

    5. Cost of planned expansion.

    In plant layout first thing that should be done is to determine the direction of the

    prevailing wind. Wind direction will decide the location of the plant.

    List of items that should be placed upwind and downwind of the plant is given down.

    Items that should be located upwind of the plant.

    Laboratories

    Fire station

    Offices building

    Canteen and Change house

    Storehouse

    Medical facilities

    Electrical substation

    Water treatment plant

    Water pumps

    Workshops

  • 35

    Items that should be located downwind of the plant

    Blowdown tanks

    Settling tanks

    Burning flares

    The various units that should be laid out include

    1. Main processing unit

    2. Storage for raw materials and products

    3. Maintenance workshops

    4. Laboratories for process control

    5. Fire stations and other emergency services

    6. Utilities: steam boilers, compressed air, power generation, refrigeration

    7. Effluent disposal plant

    8. Offices for general administration

    9. Canteens and other amenity buildings,such as medical centers

    10. Car parks

    1. Processing area

    Processing area also known as plant area is the main part of the plant where

    the actual production takes place. There are two ways of laying out the processing

    area

    1.) Grouped layout

    2.) Flowline layout

    Grouped layout

    Grouped layout places all similar pieces of equipment adjacent. This provides

    for ease of operation and switching from one unit to another. This is suitable for all

    plants.

  • 36

    Flowline layout

    Flowline layout uses the line system, which locates all the equipment in the

    order in which it occurs on the flowsheet. This minimizes the length of transfer lines

    and therefore reduces the energy needed to transport materials. This is used mainly for

    small volume products.

    2. Storage house

    The main stage areas should be placed between the loading and unloading

    facilities and the process they serve. The amount of space required for storage is

    determined from how much is to be stored in what containers. In raw material storage,

    liquids are stored in small containers or in a pile on the ground. Automatic storage and

    retrieving equipment can be substantially cut down storage

    3. Laboratories

    Quality control laboratories are a necessary part of any plant and must be

    included in all cost estimates. Adequate space must be provided in them for

    performing all tests, and for clearing and storing laboratory sampling and testing

    containers.

    4. Transport

    The transport of materials and products to and from the plant will be an

    overriding consideration in site selection. If practicable, a site should be selected that

    is close to at least two major forms of transport: road, rail, waterway or a seaport.

    Rail transport will be cheaper for long distance transport of bulk chemicals.

    Road transport is being increasingly used and is suitable for local distribution. Road

    area also used for fire fighting equipment and other emergency vehicles and for

    maintenance equipment. This means that there should be a road around the perimeter

    of the site. No roads should be a dead end. All major traffic should be kept away form

    the processing areas. It is wise to locate all loading and unloading facilities ,as well as

    plant offices, personnel facilities near the main road to minimize traffic congestion

    within the plant and to reduce danger.

    5. Utilities

  • 37

    The word Utilities is now generally used for ancillary services needed in the

    operation of any production process. These services will normally be supplied from a

    central site facility and will include:

    Electricity

    Steam for process heating

    Cooling water

    Water for general use

    Inert gas supplies

    Electricity

    Electrical power will be needed at all the sites. Electrochemical processes that

    require large quantities of power need to be located close to a cheap source of power.

    Transformers will be used to step down the supply voltage to the voltages used on the

    purpose.

    Steam for process heating

    The steam for process heating is usually generated in water tube boilers using the

    most economical fuel available. The process temperature can be obtained with low-

    pressure steam. A competitively priced fuel must be available on site for steam

    generation.

    Cooling water

    Chemical processes invariably require large quantities of water for cooling. The

    cooling water required can be taken from a river or lake or from the sea.

    Water for general use

    Water is needed in large quantities for general purpose and the plant must be

    located near the sources of water of suitable quality, process water may be drawn

    from river from wells or purchased from a local authority.

    Offices

    The location of this building should be arranged so as to minimize the time

    spent by personnel in travelling between buildings. Administration offices in which a

  • 38

    relatively large number of people working should be located well from potentially

    hazardous process.

    Canteen

    Canteen should be spacious and large enough for the workers with good and hygienic

    food.

    Fire station

    Fire station should be located adjacent to the plant area, so that in case of fire or

    emergency, the service can be put into action

    Medical facilities

    Medical facilities should be provided with at least basic facilities giving first aid

    to the injured workers. Provision must be made for the environmentally acceptable

    disposal of effluent.

    The layout of the plant can be made effective by

    1. Adopting the shortest run of connecting pipe between equipments and the least

    amount of structural steel work and thereby reducing the cost.

    2. Equipment that need frequent operator attention should be located convenient to

    control rooms.

    3. Locating the vessels that require frequent replacement of packing or catalyst

    outside the building

    4. Providing at least two escape routes for operators from each level in process

    buildings.

    5. Convenient location of the equipment so that it can be tied with any future

    expansion of the process.

  • 39

    CANTEE

    WORKSHO

    FINISHED PRODUCT STORAGE

    ADMINISTRATIVE OFFICE

    SECURITY OFFICE

    CANTEEN

    WORKSHOP

    RAW MATERIAL STORAGE

    PROCESSING AREA

    EXTENSION AREA

    ENTRY EXIT

    SAFETY HEALTH DEPT CENTER

    MAIN ROAD

    FIG 10.1 PLANT LAYOUT

  • 40

    11. MATERIALS OF CONSTRUCTION

    Materials of construction may be divided into two general classifications of

    metals and non-metals.

    11.1 Metals

    Pure metals and metallic alloys are included under this classification. Some

    commonly used metals are discussed in the following section.

    Iron and steel

    Although many materials have greater corrosion resistance than iron and steel,

    cost aspects favor the use of iron and steel. As a result, they are often used as

    materials of construction when it is known that some corrosion will occur.

    In general, cast iron and carbon steel exhibit about the same corrosion

    resistance. They are not suitable with dilute acids, but can be used with strong acids,

    since a protective coating composed of corrosion products forms on the metal surface.

    Carbon steel plates for reactor vessels are a good example. This application

    generally requires a minimum level of mechanical properties, weldability, formability,

    and toughness as well as some assurance that these properties will be uniform

    throughout.

    Stainless steel

    There are more than 100 different types of stainless steels. These materials are

    high chromium or high nickel-chromium alloys of iron containing small amounts of

    other essential constituents. They have excellent corrosion-resistance and heat

    resistance properties.

    The addition of molybdenum to the alloy increases the corrosion resistance

    and high temperature strength. If nickel is not included, the low temperature

    brittleness of the material is increased and the ductility and pit type corrosion

    resistance are reduced. The presence of chromium in the alloy gives resistance to

    oxidizing agents.

    Aluminum

  • 41

    The lightness and relative ease of fabrication of aluminum and its alloys are

    factors favoring the use of these materials. Aluminum resists attack by acids because a

    surface film of inert hydrated by aluminum oxide is formed. This film adheres to the

    surface and offers good protection unless materials, which can remove the oxide, such

    as halogen acids or alkalis, are present.

    11.2 Non-metals

    Plastics

    In comparison with metallic materials, the use of plastics is limited to

    relatively moderate temperature and pressures.generally,plastics have excellent

    resistance to weak mineral acids and are unaffected by inorganic salt solutions-areas

    where metals are not entirely suitable. One of the most chemical resistant plastics

    commercially available today is tetrefluoroethylene.This thermoplastic is practically

    unaffected by all alkalis and acids except fluorine and chlorine gas at elevated

    temperatures and molten metals.

    Epoxies reinforced with fiberglass have very high strengths and resistance to

    heat. Chemical resistance of the epoxy resin is excellent in non-oxidizing and weak

    acids not good against strong acids.

    12. INSTRUMENTATION AND CONTROL

    Instruments are provided to monitor key process variable during plant

    operation. It is desirable that the process variable to be monitored be measured

    directly; often however this is impractical and some dependent variable, that is easier

    to measure, is monitored in its place. The temperature instrument may form part of a

    control loop controlling, say, reflux flow; with the composition of the overheads

    checked frequently by sampling and laboratory analysis.

    Objectives

    The primary objectives of the designer when specifying instrumentation and

    control schemes are:

    1) Safe plant operation:

  • 42

    To keep the process variables within known safe operating limits.

    To detect dangerous situations as they develop and to provide alarms and automatic

    shut down systems.

    To provide interlocks and alarms to prevent dangerous operating procedures.

    2) Production rate:

    To achieve the design product output

    3) Product quality:

    To maintain the product composition within the specified quality standards.

    4) Cost:

    To operate at the lowest production cost, commensurate with the other objectives.

    In a typical chemical processing plant these objectives are achieved by a

    combination of automatic control, manual monitoring and laboratory analysis.

    Guide rules:

    The following procedure can be used when drawing up preliminary piping and

    instrumentation diagrams.

    1. Identify and draw in those control loops that are obviously needed for steady

    plant operation, such as:

    Level controls

    Flow controls

    Pressure controls

    Temperature controls

    2. Identify the key process variables that need to be controlled to achieve the

    specified product quality. Include control loops using direct measurement of

    the controlled variable, where possible, if not practicable, select a suitable

    dependent variable.

    3. Identify and include those additional control loops required for safe operation,

    not already covered in steps 1 & 2

  • 43

    4. Decide & show those ancillary instruments needed for monitoring of the plant

    operation by the operators; and for trouble-shooting and plant development. it

    is well worthwhile including additional connections for instruments, which

    may be needed for future troubleshooting and development ,even if the

    instruments are not installed permanently. This would include extra thermo

    wells, pressure tapings, orifice flanges, and extra sample points.

    5. Decide on the location of sample points.

    6. Decide on the need for recorders and the location of the readout points, local

    or control room. This step would be done in conjunction with step 1 to 4

    7. Decide on the alarms and interlocks need, this would be done in conjunction

    with step 3.

    Typical control Systems

    Level control

    In any equipment where an interface exists between two phases some means

    of maintaining the interface at the required level must be provided. This may be

    incorporated in the design of the equipment. The control valve should be placed on

    the discharge line from the pump.

    Pressure control

    Pressure control will be necessary for most systems handling vapor or gas.

    The method of control will depend on the nature of process.

    Flow control

    Flow control is usually associated with inventory control in a storage tank or

    other equipment. There must be a reservoir to take up the changes in flow rate. To

    provide flow control on a compression or pump running at a fixed speed and

    supplying a near constant volume output, a by-pass would be used.

    Heat Exchangers

    Here, the temperature can be controlled by varying the flow of the cooling or

    heating medium. If the exchange is between two process streams whose flows are

    fixed, by-pass control will have to be used.

  • 44

    Cascade control

    With this arrangement, the output of one controller is used to adjust the set

    point of another. Cascade control a give smoother control in situations where direct

    control of variable would lead to unstable operation. The slave controller can be

    used to compensate for any short-term variations in, say, a service stream flow, which

    would upset the controlled variable, the primary controller and long term variations.

    Reactor control

    The schemes used for reactor control depend on the process and type of

    reactor. If a reliable on-line analyzer is available and the reactor dynamics are

    suitable, the product composition can be monitored continuously and the reactor

    conditions and feed flows controlled automatically to maintain the desired product

    composition and yield. More often, the operation is the final link in the control loop,

    adjusting the controller set points to maintain the product within specification, based

    on periodic laboratory analyzer.

    Reactor temperature will normally be controlled by regulating the flow of the

    heating or cooling medium. Pressure is usually held constant. Material balance control

    will be necessary to maintain the correct flow of reactants to the reactor and flow of

    product and unreacted materials from the reactor.

    Alarms and safety trips, and interlocks

    Alarms are used to alert operators of serious and potentially hazardous,

    deviations in process conditions. Key instruments are fitted with switches and relays

    to operate audible and visual alarms on the control panels. Where delay or lack of

    response from the operator may lead to a hazardous situation, the instrument would be

    fitted with trip system to take action automatically to avert the hazard. Interlocks are

    included to prevent operations departing from the required sequence. They may be

    incorporated in the control system design, as pneumatic or mechanical locks.

  • 45

    13. STORAGE AND TRANSPORTATION

    Formaldehyde solutions can be stored and transported in containers made of

    stainless steel, aluminum, enamel or polyester resins. Iron containers lined with

    epoxide resin or plastic may also be used, although stainless steel containers are

    preferred, especially for higher formaldehyde concentrations. Unprotected vessels of

    iron, copper, nickel and zinc alloys must not be used.

    With a decrease in temperature and/or increase in concentration, aqueous

    formaldehyde solutions tend to precipitate paraformaldehyde. On other hand, as the

    temperature increases, so does the tendency to form formic acid. Trace metallic

    impurities such as iron can boost the rate of formation of formic acid. Therefore, an

    appropriate storage temperature must be maintained. Stabilizers can also be added to

    prevent polymerization. Methanol is generally used as a stabilizer. Other compounds

    used as a stabilizer for formaldehyde are ethanol, propanol, urea, melamine, hydrazine

    hydrate and bismelamines.

    Table 2 Storage temperatures for commercial formaldehyde solutions Formaldehyde content,wt% Methanol content,wt% Storage

    temperature,oC 30 1 7-10 37

  • 46

    irritation does not generally occur until concentrations of 1 ppm, based on controlled

    human chamber studies.

    Table 3 Dose response relationship following human exposure to gaseous formaldehyde Effect Exposure level,ppm

    Odor threshold 0.05 1.0

    Irritation threshold in eyes ,nose, or throat 0.2 1.6

    Stronger irritation of upper respiratory

    tract,coughing,lacrimination,extreme

    discomfort

    3 - 6

    Immediate dyspnea,burning in nose and throat,

    heavy coughing and lacrimation

    10- 50

    Necrosis of mucous membranes,

    laryngospasm,pulmonary edema

    >50

    Formaldehyde is classified as a probable human carcinogen by the

    International Agency for Research on Cancer(IARC).Lifetime inhalation studies with

    rodents have shown nasal cancer at formaldehyde concentrations that are

    overwhelmed cellular defense mechanisms,ie,6 to 15 ppm.No nasal cancer was seen

    at 2 ppm or lower levels.

    Available data do not indicate that formaldehyde produces mutagenic,

    tetrogenic, embryo toxic effects in man at concentrations which humans are exposed

    to or can tolerate.

  • 47

    15. COST ESTIMATION ESTIMATION OF THE TOTAL CAPITAL INVESTMENT

    The total capital investment I involves the following:

    A: FIXED CAPITAL INVESTMENT IN THE PROCESS AREA, IF

    B: THE CAPITAL INVESTMENT IN THE AUXILLARY

    SERVICES,IA

    C: THE CAPITAL INVESTMENT AS WORKING CAPITAL, IW

    i.e., I=IF+IA+W A. FIXED CAPITAL INVESTMENT IN THE PROCESS AREA, IF

    This is the investment in all processing equipment within the processing area.

    Fixed capital investment in the process area, IF= Direct plant cost + Indirect plant cost

    The approximate delivered cost of major equipments used in the proposed

    Formaldehyde manufacturing plant are furnished below:

    (Table 4)

    S.NO EQUIPMENT UNITS Cost in Lakhs /Unit

    Cost in Lakhs

    1 Heat Exchanger 3 20 60

    2 Reactors 100 3.85 385

    3 Absorption column 1 50 50

    4 Deionizer 1 1 1

    5 Pumps 3 0.3 0.9

    6 Blower 1 0.1 0.1

    7 Storage tank sealed 1 1.5 1.5

    8 Miscellaneous 1

    Total 500

  • 48

    DIRECT COST FACTOR (Table 5)

    S.No Items Direct Cost Factor

    1 Delivered cost of major equipments 100

    2 Equipment installations 15

    3 Insulation 15

    4 Instrumentation 15

    5 Piping 75

    6 Land and building 30

    7 Foundation 10

    8 Electrical 15

    9 Clean up 5

    Total direct cost factor 280

    Direct plant cost = (Delivered cost of major equipments)

    X (Total direct cost factor)/100

    Direct plant cost = (500 x 280)/100

    = 1400 lakhs

    INDIRECT COST FACTOR (Table 6)

    S.NO ITEMS INDIRECT COST FACTOR

    1 Over head contractor etc 30

    2 Engineering fee 13

    3 Contingency 13

    Total indirect cost factor 56

    Indirect plant cost = (Direct plant cost) x (Total indirect cost factor)/100

    = (1400 x 56)/100

    = 784 lakhs

    Fixed capital investment in process area, IF = Direct plant cost

    + Indirect plant cost

    = 1400 + 784

    = 2184 lakhs

  • 49

    B.THE CAPITAL INVESTMENT IN THE AUXILLARY SERVICES,IA

    Such items like steam generators, fuel stations and fire protection facilities are

    commonly stationed outside the process area and serve the system under

    consideration.

    Table 7:

    S.No

    Items Auxillary Service Cost Factor

    1 Auxiliary buildings 5

    2 Water supply 2

    3 Electric main substation 1.5

    4 Process waste system 1

    5 Raw material storage 1

    6 Fire protection system 0.7

    7 Roads 0.5

    8 Sanitary and waste disposal 0.2

    9 Communication 0.2

    10 Yard and fence lighting 0.2

    Total 12.3

    Capital investment in the auxillary services = (Fixed capital investment in process

    area) x (Auxiliary services cost )/100

    = (2184 x 12.3)/100

    = 268.632 lakhs

    Installed cost = Fixed capital investment in the process area

    + Capital investment in the auxiliary services

    = 2184 + 268.632

    = 2452.632 lakhs

  • 50

    C.THE CAPITAL INVESTMENT AS WORKING CAPITAL, IW

    This is the capital invested in the form of cash to meet day-to-day operational

    expenses, inventories of raw materials and products. The working capital may be

    assumed as 15% of the total capital investment made in the plant (I)

    Capital investment as working capital, IW = ((2184 + 268.632) X 15) /85

    = 432.817 lakhs

    Total capital investment, I = IF+ IA + IW

    = 2184 + 268.632 + 432.817

    = 2885.449 lakhs

    ESTIMATION OF MANUFACTURING COST

    The manufacturing cost may be divided into three items, as follows

    A. Cost proportional to total investment

    B. Cost proportional to production rate

    C. Cost proportional to labour requirement

    A. COST PROPORTIONAL TO TOTAL INVESTMENT

    This includes the factors, which are independent of production rate and

    proportional to the fixed investment such as

    - Maintenance- labour and material

    - Property taxes

    - Insurance

    - Safety expenses

    - Protection, security and first aid

    - General services, laboratory, roads, etc.

    - Administrative services

    For all this purpose we shall charge 15% of the installed cost of the plant

    =( Installed cost x 0.15)

    = 2452.632 x 0.15

    = 367.894 lakhs

    B. COST PROPORTIONAL TO PRODUCTION RATE

    The factors proportional to production rate are

    - Raw material costs

    - Utilities cost-power, fuel, water, steam, etc.

    - Maintenance cost

    - Chemical,warehouse,shipping expenses

  • 51

    Assuming that the cost proportional to production rate is nearly 60% of total capital

    investment,

    Cost proportional to production rate = (Total capital investment x 0.6)

    = 2885.449 x 0.6

    = 1732.269 lakhs

    C. COST PROPORTIONAL TO LABOUR REQUIREMENT

    The cost proportional to labour requirement might amount 10% of total

    manufacturing cost.

    Cost proportional to labour requirement = (367.894 + 1731.269) x

    (0.1)/(0.9)

    = 233.240 lakhs

    Therefore, manufacturing cost = (364.894 + 1731.269 + 233.240)

    = 2332.403 lakhs

    SALES PRICE OF PRODUCT

    Market price of Formaldehyde = Rs.15 /kg

    Production rate = 21196.8 TPA

    Total sales income = 3179.52 lakhs

    PROFITABILITY ANALYSIS

    A.DEPRICIATION

    According to sinking fund method: R= (V- VS) I/ (1+I)n

    R = Uniform annual payments made at the end of each year

    V = Installed cost of the plant

    VS = Salvage value

    N = Life period (assumed to be 15 years)

    I = Annual interest rate (taken as 15%)

    R = (2452.632 x 0.15) / ((1+ 0.15)15 -1)

    = 51.547 lakhs

    B.GROSS PROFIT

    Gross profit = Total sales income Manufacturing cost

    = 3179.52 2332.40

    = 847.117 lakhs

  • 52

    C.NET PROFIT

    It is defined as the annual return on the investment made after deducting

    depreciation and taxes. Tax rate is assumed to be 40%

    Net profit = Gross profit Depreciation (Gross profit x Tax rate)

    = 847.117- 51.547-(847.117x 0.4)

    = 456.723 lakhs

    D.ANNUAL RATE OF RETURN

    RATE OF RETURN = (100 x Net profit) /Installed cost

    = (100 x 456.723)/2452.632

    = 18.619%

    E.PAYOUT PERIOD

    Payout period = Depreciable fixed investment /(Profit + Depreciation)

    = 2452.632 / (456.723 + 51.547)

    = 4.825 years

    16. CONCLUSION

    The metal oxide process was selected for the manufacture of formaldehyde.

    From mass balance and energy balance, the various equipments were designed

    and cost estimation was made. The payout period was found to be 5 years. Hence the

    project is feasible .

  • 53

    REFERENCES

    1. Austin , G.T. Shreves Chemical Process Industries,Fifth edition McGraw-Hill,1984

    2. Charles E.Dryden , Outlines of Chemical Technology for 21st Century, Third

    edition , NEW YORK PRESS,1997

    3. John Mc.Ketta - Encyclopedia of Chemical Technology,vol 8,1997

    4. Kirk and Othmer - Encyclopedia of Chemical Technology,vol 11,1997

    5. Mccabe, Smith and Harriot - Unit Operations in Chemical Engineering ,sixth edition,McGraw Hill,2001

    6. Perry, R.H., and D.W. GREEN , Perrys chemical engineers Handbook,

    Seventh edition, McGraw-Hill,1997.

    7. Robert E.Treybal - Mass Transfer Operations, Third edition, 1984. 8. Ullmann - Encyclopedia Of Chemical Technology, Vol. A11, 1997.