1. INTRODUCTION Phthalic anhydride was first reported by Lauret in 1836. In 1872, BASF developed naphthalene oxidation process. Since then phthalic anhydride has been continuously commercially produced. It was the first anhydride of a dicarboxylic acid to be used commercially and its importance is comparable to acetic acid . The most important derivatives of phthalic anhydride are polyesters, alkyl resins, phthalocyanines and plasticizers like PVC . Till 1960, phthalic anhydride was manufactured almost exclusively from naphthalene. The growing demand for phthalic anhydride led to the search for alternative raw materials, such as o-xylene, which is nowadays available in adequate quantities from cracking plants and refineries. Modern commercial processes for phthalic anhydride production are based on the selective gas phase oxidation of o- xylene over V 2 O 5 /TiO 2 catalysts, either in fixed or in fluidized bed reactors. The reaction proceeds at nearly atmospheric pressure and in the temperature range of 360-400°C to give almost complete conversion of o-xylene and selectivities for phthalic anhydride of 70-75%. This process is complex, and involves different by-products resulting from the oxidation of phthalic anhydride, such as o-tolualdehyde, phthalide and carbon oxides (CO2 and CO). Due to the large exothermicity of the main reaction (ΔH=−6800 kJ/mol), heat generation can produce hot spots, increasing the risk of runaway reactions. Fluidized bed processes 1
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1. INTRODUCTION
Phthalic anhydride was first reported by Lauret in 1836. In 1872, BASF developed
naphthalene oxidation process. Since then phthalic anhydride has been continuously
commercially produced. It was the first anhydride of a dicarboxylic acid to be
used commercially and its importance is comparable to acetic acid . The
most important derivatives of phthalic anhydride are polyesters, alkyl resins,
phthalocyanines and plasticizers like PVC . Till 1960, phthalic anhydride was
manufactured almost exclusively from naphthalene. The growing demand for
phthalic anhydride led to the search for alternative raw materials, such as o-
xylene, which is nowadays available in adequate quantities from cracking
plants and refineries.
Modern commercial processes for phthalic anhydride production are
based on the selective gas phase oxidation of o-xylene over V2O5/TiO2
catalysts, either in fixed or in fluidized bed reactors. The reaction proceeds at nearly
atmospheric pressure and in the temperature range of 360-400°C to give almost complete
conversion of o-xylene and selectivities for phthalic anhydride of 70-75%. This process is
complex, and involves different by-products resulting from the oxidation of
phthalic anhydride, such as o-tolualdehyde, phthalide and carbon oxides
(CO2 and CO). Due to the large exothermicity of the main reaction
(ΔH=−6800 kJ/mol), heat generation can produce hot spots, increasing the
risk of runaway reactions. Fluidized bed processes permit more efficient heat
removal and a better temperature control, avoiding yield losses and catalyst
degradation related with hot spots.
Phthalic anhydride is an important chemical intermediate. Its major outlets are phthalate
plasticizers, unsaturated polyesters and alkyd resins for surface coatings while its smaller volume
applications include polyester polyols, pigments, dyes, sweeteners and flame retardants.
It is traded in either molten form (requiring heated tankers) or as a white powder ('flake'). The
manufacture of phthalic anhydríde consumes almost all o-xylene produced so that sourcing a
suitable supply of high purity o-xylene is a critical consideration in the early stages of the
feasibility study.
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Care must be taken in the process handling stages as explosive mixtures form easily
between phthalic anhydride dust and air, and spontaneous reaction occurs with many organic
compounds including skin tissue.
The first indigenous phthalic anhydride unit in India was put on stream by Herdillia
Chemicals Ltd. in a plant on the Thane-Belapur Road near Bombay in early 1968. The plant has
a capacity of 6000 tons/year.
1.1 Applications
Fig No. 1 Applications of Phthalic Anhydride-2009
There are various applications of phthalic anhydride-
1.1.1 Preparation of phthalate esters
Phthalate esters are widely used as plasticizers. In the 1980s, approximately 6.5×109 kg of these
esters were produced annually, and the scale of production was increasing each year, all from
phthalic anhydride. The process begins with the reaction of phthalic anhydride with alcohols,
giving the mixed esters:
C6H4(CO)2O + ROH → C6H4(CO2H)CO2R
The second esterification is more difficult and requires removal of water:
C6H4(CO2H)CO2R + ROH C6H4(CO2R)2 + H2O
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The most important diester is bis(2-ethylhexyl) phthalate ("DEHP"), used in the manufacture of polyvinyl chloride.
1.1.2 Organic Synthesis
Phthalic anhydride is a precursor to a variety of reagents useful in organic synthesis. Important
derivatives include phthalimide and its many derivatives. Chiral alcohols form half-esters , and
these derivatives are often resolvable because they form diastereomeric salts with chiral amines
such as brucine. A related ring-opening reaction involves peroxides to give the useful peroxy
acid.
C6H4(CO)2O + H2O2 → C6H4(CO3H)CO2H
1.1.3 Precursor to dyestuffs
Phthalic anhydride is widely used in industry for the production of certain dyes. A well-known
application of this reactivity is the preparation of the anthroquinone dye quinizarin by reaction
with para-chlorophenol followed by hydrolysis of the chloride.
1.2 List of companies producing Phthalic Anhydride in India
Now, ∆H1= 80*1000*∫(-3.786 + 0.1424*T – 8.224*10-5*T2 + 1.798*10-7*T3)dT where T is from 423 K to 610.5 K∆H2 = 27555.47 MJ/hr o-xylene stream:Assuming 1% losses,Heat transfer rate supplied by Natural gas to o-xylene stream=4385/0.99 = 4429.3 MJ/hrCalorific Value of Natural gas = 54 kJ/gAmount of Natural gas: m(54) = 4429.3 *1000 kJ/hr m=82 kg/hr
Air stream:Assuming 1% losses,Heat transfer rate supplied by steam to air stream = 27555.47/0.99 = 27833.81 MJ/hrEnergy Balance around the Reactor: Heat transfer rate required to raise the reacting mixture from 320 C to 360 C = 3020.4*1000* 386.08 = 0.1166 *1010 cal/hr = 4881.1 MJ/hrPAN reaction: C8H10 + 3O2 C8H4O3 + 3 H2O∆H 298 K = -371.79 + 3(-242) -19.01 = -1116.8 KJ/mol ∆H 633K = -1116.8 +11.814 = -1104.98 kJ/mol ∆H net(1)= n(∆H 633K ) = 56 *1000*(-1104.98)*1000=-61878.88MJ/hrMAN reaction:C8H10 + 7.5 O2 C4H2O3 + 4 H2O + 4CO2
∆H net(3) = n(∆H 633K ) =16*1000*-4204.38*1000 = -67,270.16 MJ/hrOverall Heat transfer rate liberated = -61878.88 -24315.44-67270.16 = -153464.48 MJ/hrLet us allow the Products to leave the reactor at 400 C.∆HO2 = 288.68 MJ/hr
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∆HN2=(23 22.9*1000)(1218.53)=2830.51 MJ/hr ∆HMAN= (8000)*5392.32= 43.14 MJ/hr∆HCO2 = (160*1000)*1945.38 =(160*1000) * 1945.38 =311.26 MJ/hr∆HH2O = (280*1000)*1479.97=414.39MJ/hr∆HPAN= 600.41 MJ/hrOverall Heat utilized for raising products from 360 C to 400 C = 4488.4MJ/hr Net enthalpy heat rate change with in the reactor =4881.1-153464.5+4488.4 = -144095.01 MJ/hr144095.01 MJ/hr is to be utilized by molten salt.
Energy balance around the salt cooler: Q = m Cp ∆ T 144095.01 *106 = m *1560*(395-150) m= 377 tons/hr =104.72 kg/sEnergy balance around the heat exchanger – 2(HE-2):
Boiler feed water (bfw) available at 549 kPa,90 C
It is to be delivered at high pressure (4300 kPa)Saturated steam enthalpy (at 4300 kPa and 254 C)=2799.4 kJ/kgAt heat exchanger-2, 144095.01*106= m(2799.4*1000) m = 51473.5 kg/hr Flow rate of boiler feed water = 51473.5 kg/hr
Heat possessed by products leaving reactor at 400 C :∆HO2=221.5 *1000*11633.92 = 2576.9 MJ/hr∆HN2 = (2322.9*1000)*11120.96 = 25832.9 MJ/hr ∆HMAN = 8000*40662.54 = 325.3 MJ/hrBoiling point of water = 406.7 K at 3 atm∆HH2O = 16403.4 MJ/hr∆HPAN=56*1000*82634.21= 4627.52 MJ/hr∆HCO2 =160*1000*16441.09 =2630.58 MJ/hr
Overall Heat possessed by products leaving the reactor = 2576.9 + 25832.9 +325.3 +2630.58 +16403.4+4627.52 = 52396.6 MJ/hrEnergy balance around the heat exchanger – 3(HE-3): Energy possessed by stream after heat exchanger-3 :∆HO2 = 221.5 *1000* (3735.32)=827.37 MJ/hr∆HN2 =2322.9 *1000 *3651.46=8481.97 MJ/hr∆HMAN = 8*1000*8713.958=69711664 cal/hr=291.8 MJ/hr∆HH2O =13929.75 MJ/hr∆HPAN=56*1000*8713.958=487981648 cal/hr=2042.59 MJ/hr
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∆HCO2 = 794.86 MJ/hrTotal Heat = 26368.3 MJ/hr52397-26368=26029 MJ/hr is being utilized by heat exchanger – 3,Boiling Point of water = 427 K at 525 kPa Saturated steam enthalpy =2749.7 kJ/hrm (2749.7*1000) =26029 *106
m= 9466 kg/hrFlow rate of cool water = 9466 kg/hr
Energy balance around the Switch Condenser:Energy possessed by effluent stream:
∆HMAN= 160*9797==1.57 MJ/hr∆HH2O =13832.94 MJ/hr(since B.P of water = 393 K at 2 atm)∆HPAN= 112 * 20480 = 2.29 MJ/hr∆HCO2 =160*1000*4548.34= 727.73 MJ/hrTotal energy possessed by effluent stream =23125.76 MJ/hrSince Cp (MAN) =Cp (PAN) in liquid state, we have
Cp (MAN) =Cp (PAN) = Cp (Feed)Specific enthalpy = 7972.15 Cal/mol = 33369.8 kJ/kmolTotal enthalpy of feed = (55.888+7.84) (33,369.8) = 63.728 *33,369.8 = 2126.6 MJ/hr Energy remaining =26368.3 – (2126.64+23,125.8) = 1115.9 MJ/hrLet cool water be condensing medium and its temperature rise by 10Ci.e., from 30 C to 40C 1115.9 *1000 =m (4.18)(40-30) m=26696.2 kg/hr=26.7 T/hr26.7 T/hr of cooling water is being used.
Energy balance around the Distillation Column:
In W, 55.62 and 1.71 kmol/hr of PAN and MAN are present.In D, 0.01 and 7.67 kmol/hr of PAN and MAN are present.Solidification point of PAN = 130.8CBottom product is at 150CSpecific enthalpy of bottom product (hW ) =8713.96 cal /mol =36474.9 kJ/kmolTotal Enthalpy of bottom product = (55.62+1.71) (36474.9) = 57.33 * 36474.9 = 2091.1 MJ/hrTop Product is at 60C (333K)
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Specific enthalpy of top product (hD) = 2317.48 cal/mol =9700 .5 kJ/kmol Total enthalpy of Top product =(0.01+7.67) (9700.5) =7.68 *9700.5 =74.499 MJ/hr
Composition of MAN and PAN in D are 0.998,0.0013Assuming PAN and MAN obey’s Raoults law, y = ax/ (1+(a-1)x); where a= √( atop* a bottom)Here MAN is more volatile component.Using Antonie’s equation,Vapor pressure of MAN at 333 K, 423 K is 3.536 mm Hg, 186.2 mm Hg.
Vapor pressure of PAN at 333 K, 423 K is 0.153 mm Hg, 17.36 mm Hg.atop =3.536/0.153 =23.11; a bottom =186.2/17.36= 10.73
a=sqrt( atop* a bottom) =sqrt(23.11*10.73) = 15.75y = 15.75x/(1+14.75x) is equilibrium relation.Let us assume that boiling point of feed varies linearly with compositionBoiling point of PAN and MAN are 560 K and 473 KFor feed composition,Boiling point of feed =(55.888*560+7.84*473)/(55.888+7.84) = 549.3 KSpecific enthalpy of feed if feed is saturated liquid =18,752.08 cal/mol = 78492.5 kJ/kmolSpecific enthalpy of feed = 7972.15 cal/mol =33369.8 kJ/kmol Normal Heats of vaporization
PAN 11850 cal/mol = 49601.73 kJ/kmolMAN 5850 cal/mol = 24486.93 kJ/kmol Let us assume that latent heat of vaporization of feed varies linearly with compositionλ feed = (55.888*49601.73 +7.84 *24486.93)/(55.888+7.84) = 46511.66 kJ/kmol
Specific enthalpy of feed if feed is saturated vapor = Specific enthalpy of saturated liquid + Latent heat of vaporization of feed =78492.5 +46511.66 =125004.2 kJ/kmolq= (Hv - hF )/(Hv– hL ) = (125004.2-33369.8)/(125004.2- 78492.5) = 1.97Assume that constant Molar overflow rate is prevailing.Feed line is y = qx/(q-1) – xF /(q-1) = 2.03 x -0.127Point of intersection of feed line and equilibrium line is 2.03 x -0.127 = 15.75x / (1+14.75x) x = 0.53 => y = 0.95For minimum reflux (Rm) Top section operating line passes through pinch point (0.53,0.95) and (0.98,0.98)Slope = (0.98- 0.95)/(0.98- 0.53) = 1/15 = Rm / ( Rm + 1) Rm =1/14Ropt = 1.5 Rm =1.5/14 =0.107Mole fraction of MAN in top product =0.998
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Mole fraction of PAN in top product =0.0013Assuming boiling point varies linearly, Boiling point of Top product = 0.998 * 473 + 0.0013 *560 =472.78Kλ top product = 0.998*24486.93 +0.0013 *49601.73 = 24502.43 kJ/kmolSpecific enthalpy of top product if it is saturated vapor = 12628.32 +24.502.43 = 37130.75 kJ/kmol
Energy balance around Total Condenser:
V*HV = D*hD + Lo* hLo + Qc
Using V=(R+1)D, Lo=R*D, hLo= hD
Q c = (R+1) D [HV –hD] =(1+0.107)(0.01+7.67 )[37130.75-9700.5] = 233.20 MJ/hrCooling water is available at 30C and let its temperature rise by 10C mCp∆T = 199182.16 kJ/hr m (4.18)(40-30) = 199182.16 kJ/hr m= 4765.12 kg/hr = 4.765 T/hr
Flow rate of cooling water = 4765.12 kg/hr = 4.765 T/hr
Overall Energy balance around Distillation Column: F*hF + QB = Q c + D*hD + W* hW 2126.6 + QB =233.20 +62.92 +2091.1 QB = 260.62MJ/hrReboiler load :Electrical Power to be supplied to Reboiler at a rate of 260.62 MJ/hr
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10. ENVIRONMENTAL CONSIDERATIONS
The environmental impact due to day-to-day operation and the potential environmental
damage that results from a plant accident or spill have been considered. Potential emissions to
the environment from the proposed phthalic anhydride plant have been assessed in three
categories:
(a) Airborne emissions
(b) Waterborne emissions and
(c) Solid waste.
The main process hazard which may occur during normal operation of phthalic anhydride
plants is the risk of PAN dust clouds forming from minor process breaches. PAN dust clouds are
both toxic and explosive. Air quality monitoring will be utilized to identify process breaches
producing dust clouds before they become hazardous. Appropriate breathing equipment will
always be available.
Safety will be a priority and detailed policies will be developed to ensure safe working
practices are cultivated. Employees from all groups and levels will be involved in safety on a
day-to-day basis. The use of appropriate protective equipment will be mandatory for both
employees and visitors in all process areas. Noise will be controlled through good design and
appropriate insulation, and will not exceed recommended levels.
10.1 Airborne Emissions
The Low Air Ratio process is the cleanest of the processes for phthalic anhydride
production. Normal operating conditions will produce only two significant discharges to the
environment which are shown in Figure.
(a) Non-condensable reaction by-products that remain with the air as it is rejected from the
process to the environment.
(b) Heavy residue from the bottoms of the rectification column.
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The reaction by-products are mostly light organic vapours. A scrubbing unit will be
installed in order to reduce the concentrations of contaminants to less than 25 ppm PAN, 10 ppm
maleic anhydride and 3 ppm benzoic acid prior to discharge to the atmosphere. A 50 m stack
should disperse these concentrations to acceptable levels. The total amount of PAN vented to the
atmosphere will be less than 1 kg/hr. However approximately 15 T/hr of carbon dioxide will be
produced as a by-product of the main synthesis reaction and this gas will need to be vented to the
atmosphere. This is a negligible quantity when compared with the discharges from other local
industries.
10.2 Waterborne Emissions
Water is not part of the phthalic anhydride process and will not come into direct contact
with any process stream in the system. Air coolers will be used to satisfy most of the process
cooling requirements so that cooling water usage will be minimal. The cooling-water circuit is a
closed system and does not use either sea or river water, and it makes only small discharges of
pH-neutral water to the environment. Biological fouling is controlled with phosphate additives
rather than the more environmentally hazardous chromate additives. Steam requirements will be
essentially met by the process itself using the heat generated by the PAN reaction. An
interconnection with the adjoining utilities plant will be installed but will generally only be used
to export steam. Process contaminants that might enter the steam system through exchanger leaks
or other process disturbances will be scrubbed at the shared utilities plant, so that condensate can
be recycled to reduce energy consumption and chemical treatment costs.
10.3 Solid Waste
No solid residue is expected from the phthalic anhydride process. However,
bioremediated waste from the adjoining utilities plant which may be partially sourced from the
PAN plant wastewater can be cleanly incinerated in a combustion unit if the heating value is
sufficiently high. Heat released by this process will be used for boiler feed-water preheating to
minimize energy consumption in the utilities plant. The requirements for an incinerator in the
common utilities plant will have to be assessed. Other options such as extended bioremediation
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of heavy organic residues, may be more economical as the incinerator will require a complex
control system to monitor its performance, to regulate the fuel: air ratio, and to safeguard
operation against process disturbances that could potentially result in unburned product being
emitted directly to the environment.
10.4 Process Hazard
The most serious process hazard is the potential for phthalic anhydride dust clouds to
form following process breaches. The condensers will be the primary point of risk but other
equipment; including the storage tanks and the reactor are also possible sources. At low
concentrations (less than 1%), PAN dust is a serious health risk. At higher levels (1.5-10.5%),
PAN dust is a major explosion hazard. A level of 10,000 ppm (1 %) PAN in the atmosphere is
immediately dangerous to life, but a lower concentration also poses a health risk and is an eye,
nose and skin irritant. Health and safety standards require a minimum of 3 ppm PAN and 0.05
ppm MAN for safe working environments before acute or chronic effects are detectable. These
standards will be met through appropriate process design and operating precautions. Phthalic
anhydride dust is explosive at concentrations of 1.5-10.5% in air. As there is always the
possibility of process leaks, all sources of ignition and non-intrinsically safe equipment will be
excluded from the site, except within the main buildings. High-risk zones will be identified and
equipped with air quality monitors to detect dust before it reaches a hazardous level. The three
areas of highest risk are the condensers, reactor and storage vessels. The areas where these items
are located are separated from other items of equipment to prevent an explosion in one area
triggering an explosion in another. Major fires in the plant will burn hot and be difficult to
extinguish, but will not release large quantities of harmful vapours. A fire station, manned by
specially trained process operators, will be located near the process equipment in order to access
and contain any fires before they become difficult to manage.
10.5 Accidental Spills & Tank Breaches
Significant volumes of reactants, products and intermediates will be held on site in the
three product storage tanks, two reactant storage tanks and an intermediate PAN pretreatment
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tank. Spills from these sources are clearly the most serious due to the potential volume of
material that could be lost. Subsequently, all of these vessels require containing walls (or bunds)
to be built around them to prevent loss of hazardous materials in the event of a tank breach.
Ortho-xylene is a flammable and moderately toxic liquid at ambient temperatures and represents
a serious hazard if a significant volume is spilled. Process operations will be paused during a
spill until satisfactory recovery can be completed using temporary storage facilities which will be
readily available on the site. Phthalic anhydride is solid up to 131oC, although it will be held as a
liquid in the main product tanks and intermediate pretreatment tank. Consequently, any spill will
solidify quickly after contact with cool air. This helps to contain spills and aids the recovery
process, but increases the risk of dust cloud formation and may block drains. Recovery can be
affected with shovels and drums, but adequate protective equipment must be provided for the
workers. The recovered product can then be returned to the pretreatment tank to avoid any
discharge to the environment. Hot water will be used to clean up any remaining residue.
10.6 Personal Safety Precautions & Procedures
Safety will be the primary priority for the plant management. The senior operator will
have full authority over the process area and will be required to approve any activities, including
routine maintenance, undertaken in the process area.
Protective equipment will be made available to all employees and a mandatory policy for the use
of safety glasses and hard hats will be implemented. Dust respirators and filters will be available
in the control room at all times. Monitoring programs will be established to ensure that the time-
weighted average daily exposure of workers to PAN or MAN is below the acceptable safety
limits. Similar regulations will apply to visitors. The primary air compressor (providing air feed
to the reactor) is the only loud noise source in the process. Appropriate design modifications will
be made to limit noise from the compressor, and it will be housed in an insulated isolation
enclosure to further restrict noise emissions.
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FIGURE: Phthalic anhydride process block diagram with emission sources.
11. PLANT LOCATION
11.1 Plant Location and Site Selection
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The major requirements for an Ethylene Glycol plant are ethylene oxide and water. Glycol plants are almost always located very close to Ethylene oxide plants to reduce transportation expenses, as the transportation of ethylene oxide is expensive due to its explosive tendencies. The plant considered here is located adjacent to an Ethylene oxide plant. The most optimum location would be in a petrochemical industrial area where there is a market for fiber grade glycol.
The other considerations are as follows:
11.1.1 Raw Materials Availability
Probably the location of the raw materials of an industry contributes more toward the choice of plant site than any other factor in most chemical operations low delivered cost of raw materials must be weighed up against other operating costs.This is especially noticeable in those industries in which the raw materials areinexpensive and bulky and is made more compact and obtain a high bulk value during the process of manufacture. The supply of basic raw materials should be controlled directly be user. Physical distance is not the only controlling factor in source of raw materials, for purchase price and buying expense, base point procuring, reserve stock and reliability of supply are also determinants.
11.1.2 Markets and Transportation
The existence of transportation facilities has given too many of the greatest track centers of world. A location should be chosen, if possible which has several competitions will help to maintain low rates and give better service. Often times, a location is selected outside the city in order to have a rail road siding available and thus eliminate trucking costs to freight years from excessive costs of transportation. There will be more long distance water transportation used in the future to reduce the cost of freight years from excessive costs of transportation. There will be long-distance water transportation used in the future to reduce the cost of freight, with the spread between production cost and sales cost constantly narrowing. We would see that the product has a ready market at a close distance from the plant site so that transportation will not become a big problem. Also we have to see that the product has as a ready market so that there will be demand throughout the year for the product.
11.1.3 Climate
The plant site should be at a place where the climate is mild. Excessive cold, torrid heat and excessive humidity should not be present where the plant is situated for this will reduce the productivity part of the workmen. Also if excessive of conditions is present then the air conditioning and other facilities also will increase the expenditure.
11.1.4 Power supply The Chemical Engineering industries are the largest users of electric power equipment among the industries today because the modern demand is for extreme flexibility that sometimes errors on the side of too many individual drives. Power for chemical industry is primarily from
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coal water and oil: in as much as they provide for the generation of steam both for processing and of electricity production. A plant should establish near a hydraulic power generated project. By keeping the availability of power and deep water transportation overweight all other considerations including that of extremely severe winter weather making for difficult operating conditions.
11.1.5 Water supply
Water for industrial purpose can be obtained from one of two general sources: the plant’s own source of municipal supply, if the demand for water is large it is more economical for the industry to supply its own water. Such supply may be obtained from drilled wells, rivers, lakes, dammed steams, or other impounded supplier, before a company enters upon any project, it must ensure itself if a sufficient supply of water for all industrial, sanitary and fire demand, both present and future. Data on temperature of water and on maximum, minimum and average rain fall can be obtained from governmental agencies if surface water is to be pounded or the date on stream flow of reverse can be acquired likewise if wells are to be relied on, Geologists and practical well drillers should be consulted.
11.1.6 Labor supply
A certain careful study of the supply of a cheap labor should be made. Factors to be considered in labor studies are supply, kind diversity, intelligence, wage scales regulation efficiency and costs. The success of many of organizations depends upon the means by which its labor gets to and from their works. A cheap site may have to be avoided if the laborers cone a long distance they will be tired in coming to the plant. Also technical skill should be given due importance.
11.1.7 Community and Site characters
The nature of the sub soil is very important while considering the plant of the industry. Also due consideration should be given for the expansion of the plant. The cost of the land is important, as well as local building costs and living conditions. Also even if there is no immediate plan for expanding, a new plant should be constructed at a location where additional space is available.
11.2 Plant Layout
Plant layout in its broadest sense is a part of the overall system. It includes everything from the original of the building to the location and movement of a small component. It is an integral part of: PRODUCTION PLANNING: It allows, promotes and aids the creation of utility. MAINTENANCE: It affects the amount, difficulty and time required for it. MATERIAL HANDLING: This is necessitated by the design & layout of the plant. ORGANIZATION: Physical layout often determines areas of authority, spheres of personnel influence.
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Obviously machines, equipment, materials, employees, fixtures and all the necessary facilities for engaging in an activity must be given a place of work. How they are located and where they are located, may well determine the firm’s efficiency, its profit potential and its existence. Noise, color, tight and dictate work environment. Proper work environment will increase the productivity to optimum levels, boost the morale and job satisfaction.
Good layout design requires through knowledge of work flow, product flow and information flow. Engineering, management & future expansion are to be imbibed into the layout design. Technology is continuously upgrading making better manufacturing techniques available and correct layout will accommodate these challenges. Consideration is to be given for backward integration and forward integration of the product.
Further the arrangement of the equipment and facilities specified in the process flow sheet is a necessary requirement for accurate pre-construction cost estimation of future detailed design involving piping, structural and electrical facilities. Careful attention to the development of the plot and the elevation plans will point out unusual plant requirements and therefore, give reliable information on building site costs required for precise pre-construction cost accounting.The following list will suggest some of the reasons for what good layout is about:1. Reduce manufacturing costs.2. Increase employee safety.3. Better service to the customer.4. Reduce capital investment.5. Increase flexibility.6. Improve employee morale through improved employee comforts and conveniences in work area.7. Better quality of the product.8. Effective utilization of floor space.9. Reduce work in process to a minimum.10. Reduce work delays and stoppages.11. Better work methods and utilization of labor.12. Improve control and supervision.13. Easier maintenance.14. Reduce manufacturing cycle.15. Better utilization of equipment and facilities.16. Eliminate congestion points.
In developing an effective layout for an enterprise, we should in mind several fundamentals, which exert a significant influence in achieving a good and workable arrangement.
The following are among the major fundamentals most often citied:
11.3 Storage layout
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Storage facilities for raw materials, intermediate and finished products may be located in isolated areas or in adjoining areas. Hazardous materials become a menace to life and property when stored in large quantities and should be kept isolated. Arranging storage of materials so as to facilitate or simplify handling is a point to be considered in design. Where it is possible to pump a single material to an elevation so that subsequent handling can be accomplished by gravity into intermediate reaction storage units.
11.4 Equipment layout
In making layout, ample space should be assigned to each piece of equipment accessibility is an important factor for maintenance. Unless a process is well seasoned, it is not always possible to predict just how its various units may have to be changed in order to be in harmony with each other. It is extremely poor economy to put the equipment layout too closely to a building. A slightly larger building will cost little more than that is crowded. The extra cost will indeed be small in comparison with the penalties that will be extracted if the building was to be extracted. The relative levels of the several pieces of equipment and their accessories determine their placement. Although gravity flow is usually preferable, it is not altogether.
Necessary because liquids can be transported by blowing or by pumping and solids can be moved by mechanical means. Access for initial construction and maintenance is a necessary part of planning, for example, over head equipment must have space for lowering into place, and heat exchange equipment should be located near access areas here trucks or hoists can be placed for pulling and replacing tube bundles. Thus space should be provided for movement of cranes and fork trucks as well as access way around doors and underground hatches. Therefore each plant presents its own challenges that need to be incorporated in the layout.
11.5 Plant expansion
Expansion must always be kept in mind. The question of multiplying the number of units or increasing the size of the prevailing unit or units merit more study than it can be given here. Suffice it to say that one must exercise engineering judgment. Correcting inconsiderate layout plan may involve scrapping the serviceable equipment or shut down the running equipment. Nevertheless the cost of change must be borne for economics of large units and in the end make replacement inevitable.
11.6 Floor space
Floor space mayor may not be major factor in the design of a particular plant. The value of land may be considerable item. The engineer should, however, follow the rule of practicing economy of floor space, consistent with good house keeping in the plant and with proper consideration given to line flow of materials, space to permit working on parts of equipment that need servicing , safety and comfort to the operators.
11.7 Utilities servicing
The distribution of gas, air, water, steam, power and electricity is not always a major item of consideration but flexibility of designing these items should permit to meet almost any
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condition. Regard to the proper placement of each of these services practicing good design reduces the cost of maintenance.
11.8 Workshop
A workshop is also provided to supply tools on demand from laboratory and process. Therefore, this is laid out nearer to the process area.
11.9 Safety units
These are located to the processing area, because probably accidents occur at the processing. Thus they can be easily controlled.
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FIGURE: PHTHALIC ANHYDRIDE PLANT LAYOUT WITH RELEVANT ENVIRONMENT AND SAFETY ADDITION