Production of Acrolein

IN THE NAME OF ALMIGHTY ALLAH, WHO IS THE MOST BENEFICENT AND THE MOST MERCIFUL

Production of Acrolein by partial oxidation of Propylene

Project Advisors Madam Saira Bano Sir Abdul Rehman

Project Members Sweeba Zafar

2008-CPE-14

Aleem Naeem

2008- CPE-82

Muhammad Naeem

2008- CPE-38

Muddasar Safdar

2008- CPE-02

DEPARTMENT OF CHEMICAL AND POLYMER ENGINEERING

UNIVERSITY OF ENGINEERING & TECHNOLOGY LAHORE

Production of Acrolein by partial oxidation of Propylene This project is submitted to department of Chemical Engineering, University of Engineering & Technology Lahore-Pakistan for the partial fulfillment of the Requirements for the Bachelor‟s Degree In

CHEMICAL ENGINEERING Internal Examiner:

Sign: _______________ Name: _______________ Sign: _______________ Name: _______________

External Examiner:

Sign: ________________ Name: ________________

DEPARTMENT OF CHEMICAL AND POLYMER ENGINEERING

UNIVERSITY OF ENGINEERING AND TECHNOLOGY LAHORE

All praises to Almighty Allah, Whose uniqueness, oneness & wholeness is beyond any comparison. All respects are for His Holy Prophet, Muhammad (peace be upon him) who enabled us to recognize our Creator.

i

Dedicated to Our loving Parents, their resolute patience and guidance to bring us to this position.

ii

Abstract

This report presents the final year project design of a chemical plant producing 3500 kg/day of Acrolein by partial oxidation of propylene using mixed catalyst. The mixed catalyst is the bismuth molybdate-based catalyst having an average particle size of 3.5mm.We selected this catalyst because it is highly active and selective than other catalysts used for the production of Acrolein. We selected the capacity on the basis of demand and supply of Acrolein worldwide and with respect to Pakistan. The process that we selected for the production of Acrolein is an optimum one because of low cost of propylene. Also propylene is easily available and the yield of Acrolein obtained is maximum by this process than any other process. After selecting the capacity and process for production of Acrolein we did material and energy balance of whole plant and determined the flow rates and fractions of components across each equipment being used in the plant and also the heat load for each unit. We designed the four major units of the plant that are heat exchanger, reactor, absorber and distillation column. Also we did the mechanical design of reactor. After that we applied control scheme to heatexchanger, PFR and distillation column. We did the HAZOP analysis of absorber. We studied the environmental impacts of Acrolein and the also the steps of minimizing these impacts. Finally, we determined the cost of all designed equipments.

iii

Acknowledgement All praise to ALMIGHTY ALLAH, who provided us with the strength to accomplish this main project. All respects are for His HOLY PROPHET (PBUH), whose teachings are true source of knowledge & guidance for whole mankind.

Before anybody else we thank our Parents who have always been a source of moral support, driving force behind whatever we do. We are indebted to our project advisors Madam Saira Bano and Sir Abdul Rehman for their worthy discussions, encouragement, technical discussions, inspiring guidance, remarkable suggestions, keen interest, constructive criticism & friendly discussions which enabled us to complete this report. They spared a lot of precious time in advising & helping us in writing this report.

We are sincerely grateful to Dr. Mahmood Ahmad & Dr. Shaukat Rasool for their profound gratitude and superb guidance in connection with the project.

Authors

iv

Preface It is a design project and purpose is to present the production of Acrolein by partial oxidation of propylene using mixed catalyst. Chapter 1 provides basic knowledge of Acrolein, methods of manufacturing, physical and chemical properties, applications and other uses of Acrolein. Chapter 2 deals with capacity selection and different processes for the manufacturing of Acrolein and the selection of optimum one. Chapter 3 deals with process description. Chapter 4 consists of material and energy balance calculations across all equipments in the plant. Chapter 5 includes detailed design of shell and tube heat exchanger, reactor, absorber and distillation column. It also consists of basic knowledge of these equipments and the specification sheets of all these equipments are also given. Chapter 6 includes mechanical design of reactor. Chapter 7 Instrumentation and control for the process is being discussed in this chapter. Chapter 8 deals with hazard and operability analysis. Why and how HAZOP analysis is done. Chapter 9 includes environmental impacts of Acrolein and what steps are under taken to minimize these impacts. Chapter 10 includes cost estimation of all the designed equipments.

v

Table of Contents Page #

Chapter # 1 Introduction of Acrolein --------------------1 1.1 Acrolein -------------------------------------------------------1 1.2 History and Origin --------------------------------------------1 1.3 Methods of manufacturing------------------------------------1 1.4 Properties of Acrolein ----------------------------------------2 1.4.1 Physical properties of Acrolein--------------------------2 1.4.2 Chemical properties of Acrolein-------------------------3 1.5 Uses and applications of Acrolein----------------------------3

Chapter # 2 Process and Capacity selection ----------------6 2.1 Process Selection-------------------------------------------------6 2.1.1Vapor phase condensation----------------------------------6 2.1.2 Vapor phase oxidation--------------------------------------6 2.1.3 Partial oxidation of propylene------------------------------6 2.2 Capacity Selection-------------------------------------------------7

Chapter # 3 Process Description-----------------------------11 3.1 Process Description -----------------------------------------------11

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Chapter # 4 Material and Energy Balance -----------------14 4.1 Material Balance --------------------------------------------------14 4.1.1 Material Balance across reactor------------------------------14 4.1.2 Material Balance across quench cooler---------------------15 4.1.3 Material Balance across absorption column----------------16 4.1.4 Material Balance across water distillation column---------17 4.1.5 Material Balance across propylene distillation column----18 4.1.6 Material Balance across acrolein distillation column------19 4.2 Energy Balance-----------------------------------------------------19 4.2.1 Energy Balance across mixing point-------------------------19 4.2.2 Energy Balance across preheater-----------------------------20 4.2.3 Energy balance across reactor--------------------------------21 4.2.4 Energy balance across quench cooler------------------------22 4.2.5 Energy Balance across absorption column------------------23 4.2.6 Energy Balance across water distillation column-----------24 4.2.7 Energy Balance across propylene distillation column------25 4.2.8 Energy Balance across acrolein distillation column--------26

Chapter # 5 Designing of Equipments ------------------------27 5.1 Design of Shell and Tube Heat Exchanger ---------------------27 5.1.1Heat Exchanger--------------------------------------------------27 5.1.2 Main Categories of Heat Exchangers------------------------27 5.1.3 Heat exchangers are used--------------------------------------27 5.1.4 Selection of Heat Exchanger----------------------------------28 5.1.5Shell and Tube Heat Exchanger-------------------------------29 5.1.6 Types of Shell and Tube Heat Exchanger-------------------29

vii

5.1.7 Design Calculations--------------------------------------------30 5.1.8 Specification Sheet of heat exchanger-----------------------41 5.2 Design of Reactor--------------------------------------------------42 5.2.1 Selection of Reactor Type-------------------------------------42 5.2.2 Design Calculations--------------------------------------------44 5.2.3 Specification Sheet of reactor--------------------------------54 5.3Design of Absorber-------------------------------------------------55 5.3.1 Packed Columns------------------------------------------------55 5.3.2 Choice of plates or packing-----------------------------------55 5.3.3 Types of packing-----------------------------------------------57 5.3.4 Column Internals-----------------------------------------------60 5.3.5 Packing support----------------------------------------------61 5.3.6 Liquid distributors--------------------------------------------62 5.3.7 Liquid redistributors--------------------------------------------65 5.3.8 Hold-down plates-----------------------------------------------66 5.3.9 Liquid hold-up--------------------------------------------------67 5.3.10Wetting rate-----------------------------------------------------68 5.3.11Column Auxiliaries--------------------------------------------68 5.3.12 Design Calculations-------------------------------------------70 5.3.13 Specification Sheet of absorber------------------------------83 5.4 Design of Distillation Column ----------------------------------84 5.4.1Distillation-------------------------------------------------------84 5.4.2 Types of Distillation Columns-------------------------------85 5.4.3 Choice between plate and packed columns----------------85 5.4.4 Plate Contractors-----------------------------------------------86 5.4.5 Selection of Tray----------------------------------------------86 5.4.6 Factors affecting Distillation Column operation----------87 5.4.7 Design Calculations-------------------------------------------89 5.4.8 Specification Sheet --------------------------------------------103

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Chapter # 6 Mechanical design of Reactor------------------104 6.1 Mechanical Design-------------------------------------------------104

Chapter # 7 Instrumentation and Control ------------------106 7.1 Instrumentation and Process Control---------------------------106 7.2 Process instrument-----------------------------------------------107 7.3 Control------------------------------------------------------------107 7.3.1Temperature measurement and control----------------------107 7.3.2Pressure measurement and control---------------------------107 7.3.3 Flow measurement and control------------------------------108 7.4 Control scheme of distillation column--------------------------108 7.5 Heat exchanger control-------------------------------------------111 7.6 Control Scheme of PFR------------------------------------------111

Chapter # 8 HAZOP Study ------------------------------------ 114 8.1 Introduction ---------------------------------------------------------114 8.2 Background ---------------------------------------------------------114 8.3 Types of HAZOP---------------------------------------------------115 8.4 HAZOP guide words and meanings------------------------------116 8.5 HAZOP study of an absorber--------------------------------------116

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Chapter # 9 Environmental Impact analysis of acrolein -118 9.1Hazards Identification-----------------------------------------------118 9.1.1Potential Acute Health Effects---------------------------------118 9.1.2 Potential Chronic Health Effects------------------------------118 9.2Fire and Explosion Data---------------------------------------------119 9.3Accidental Release Measures---------------------------------------119 9.4 Handling and Storage------------------------------------------------120 9.5Exposure Controls/Personal Protection----------------------------120 9.6First Aid Measures----------------------------------------------------121

Chapter # 10 Cost Estimation -----------------------------------123 10.1 Cost Indexes---------------------------------------------------------123 10.2 Cost Estimation of designed equipments-------------------------124

APPENDICES-------------------------------------129 REFERENCES -----------------------------------155

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CHAPTER NO: 1 INTRODUCTION OF ACROLEIN 1.1 Acrolein Acrolein is the basic compound in the series of unsaturated aldehydes. Its chemical formula is C3H4O and chemical name is 2-propanol. Acrolein is colorless and highly volatile liquid and soluble in many organic liquids.

1.2 History and origin Acrolein is highly toxic and flammable material with extreme lachrymatory properties. Degussa has produced Acrolein commercially since 1938.The process was based on vapors phase condensation of acetaldehyde and formaldehyde. By following the Degussa method of acrolein production the first plant to manufacture acrolein first started in 1942. In 1945 shell started the production of acrolein by pyrolysis of diallyl ether, a byproduct of synthesis of allyl alcohol by saponification of allyl chloride. In 1959 shell began producing acrolein by partial oxidation of propylene. Acrolein, low mole weight aldehyde containing a C=C solid bond, is a clear to yellow, flammable, poisonous liquid with a disagreeable odor; boiling at 52.7 0C; soluble in water, alcohol, and ether; causing tears. Commercial acrolein is produced by gas-phase oxidation of propylene in the presence of bismuth or molybdenum oxide. It is also produced as a by-product during the production of acrylic acid or acrylonitrile.

1.3 Methods of Manufacturing 

It was produced commercially starting in 1938 by the vapor-phase condensation of acetaldehyde & formaldehyde. In 1959, the direct oxidation of propylene in presence of a catalyst became the preferred commercial

1

process, & variations of this process are the only methods currently used commercially. The acetaldehyde-formaldehyde route was last used in the USA in 1970 

Manufactured: By oxidation method I-e (A) by oxidation of acetaldehyde; (B) by oxidation of propylene in liquid phase; (C) by oxidation of propylene in vapor phase; (D) by oxidation of allyl alcohol;

 

By heating glycerol with magnesium sulfate. Prepared industrially by passing glycerol vapors over magnesium sulfate heated to 330-340 0C.

1.4 properties of acrolein 1.4.1 Physical properties of acrolein Molecular weight

56.06 kg/kg mole

Odor

Extreme sharp, pungent and disagreeable

Color

Colorless or yellowish

Boiling point

52.50C at 760 mmHg

Melting point

-880C

Density

0.8389 g/cm3 at 200C, 0.8621 g/cm3 at 00C

Heat capacity

2139 kJ/kg.K (17 to 440C, liquid) 1200 kJ/kg.K (3000C, vapor) -74.483 kJ/mol

Standard heat of formation Heat of combustion

-29098 kJ/kg

Heat of vaporization

542.191 kJ/kg

Heat of

-80.4 kJ/mol

polymerization PH

6 in 10% solution in water at 250C

Surface tension

0.024N/m at 200C

2

Vapor density

1.94 (Air =1)

Viscosity

0.35 cp at 200C

1.4.2 Chemical properties CH2=CH-CHO the carbonyl group in the conjugate with the C=C bond is present in molecule of acrolein because of its two functional group; acrolein is highly reactive, easily polymerized compound. Its reactive centre can be reacted selectively and simultaneously. The reaction of acrolein can be understood as typical of olefin activated for nucleofilic attack by influence of electron attracting carbonyl group or as a reaction of aldehyde that is unsaturated. The tendency of acrolein to polymerize is very great; the acrolein can only be stored in the presence of considerable amounts of stabilizers. In spite of the presence of stabilizer, small amounts of polymerization catalysts which are able to initial radical, anionic or cationic propagating polymerization are sufficient to cause highly polymerization reaction.

1.5 Uses and applications of acrolein Some of direct and indirect uses of acrolein are Manufacturing of Acrylic Acid The largest single use for acrolein is as an isolated intermediate in the manufacturing of acrylic acid, most of which is converted to its lower alkyl esters. Preparation of Polyester Resin Acrolein is used in the preparation of polyester resin, polyurethane, propylene glycol, acrylic acid, acrylonitrile and glycerol. Production of Methionione Acrolein is basic raw material for the production of essential amino acid methionine because of lack of methionine in many nutrient protein compounds

3

with the average biological demand, it is necessary to add methionine to the natural food materials for boilers to improve their biological efficiency which is a protein supplement used in animal feed. Manufacturing of Glycerol The chemical reduction of acrolein via alkyl alcohol is the technical process for the manufacturing of synthetic glycerol. Microbiological Activity of Acrolein In biological systems one may expect rapid reactions with any reactive N-H, S-H, O-H or C-H bond which would lead to molecular modification. In the subsurface injection of waste waters the addition of 6-10 ppm acrolein controls the growth of microbes in the food lines thereby preventing plugging and corrosion. The microbiological activity is further utilized in protecting the liquid fuel against microorganism. About 400

1 to 2500

Pressure drop between fluids is 3 sec. so, result is satisfactory.

Entrainment (un) actual velocity (based on net area) = Maximum volumetric flow rate/ Net area (un) actual velocity Velocity at flooding condition uf

= 2.871 m/sec = 3.586 m/sec

So Percent flooding =un/ uf = 0.80 = 80%

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Liquid flow factor = FLv =0.033 From Appendix B figure 15 , Fractional entrainment (ψ) = 0.05 Well below the upper limit of (ψ) which is 0.1. Below this effect of entrainment on efficiency is small.

Number of holes = (π/4) Dhole2

Area of 1 Hole

= 0.0000196 m2 Area of N Holes = 0.0307 m2 Number of Holes = 1566.3

Height of Distillation Column Height of column Hc = (Nact -1)Hs+ ∆H+ plates thickness No. of plates

= 27

Tray spacing Hs = 0.45 m ∆H= liquid hold up and vapor disengagement ∆H=0.55+0.55=1.1 m Total thickness of trays = 0.005× 27 = 0.135 m Height of column

= (26 ×0.45) + 1.1+0.135 = 12.9 meters

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5.4.8 Specification Sheet of Distillation Column Identification: Item

Distillation column

Equipment-Code

T-104

Tray type

Sieve tray

Function:

Separation of Acrolein from propylene and water

Operation:

Continuous

Design Data No. of trays

27

Weir height

50mm

Pressure drop per

1.1kPa

Weir length

0.7688 m

1566.3

Minimum Reflux

0.414

tray No of Holes

Ratio Height of column

12.9m

Reflux ratio

0.621

Column-Diameter

0.96m

Hole size

5mm

Tray spacing

0.45m

Entrainment

0.05

Tray thickness

5mm

Hole area

0.0307 m2

Flooding

80 %

Active area

0.512m2

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CHAPTER NO: 6 MECHANICAL DESIGN OF REACTOR 6.1Mechanical Design Shell Thickness Shell thickness can be calculated by following relationship 𝑒=

𝑃𝐷 + 𝐶 2𝑓𝐽 − 𝑃

Where, e = Design thickness of shell in mm f = Design stress = 137895 k Pa for carbon steel J=1 D = Shell diameter = 0.908 m=908mm P = Maximum allowable pressure = 205 k Pa C = Corrosion allowance = 3.2 mm under sever conditions Shell thickness = 3.87 mm Material of construction For the reactor shell, carbon steel is proposed as material of construction as it is both cheap and also compatible with water. The reactor tubes are suggested to be of stainless steel so that any contamination of maleic anhydride due to corrosion products is avoided. Heads for reactor shell Standard torispherical heads are most commonly used for pressure up to 15bar. Thus as ASME standard torispherical heads have been designed for the reactor. The proposed material of construction is plain carbon steel.

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Thickness of the head

e

Pi Rc Cs 2 Jf  Pi (Cs  0.2)

Cs = Stress concentration factor torispherical head

1 Rc = Crown radius 4 

  3  Rc / R  k 

   

Rc = 2.15 m Rk= Knuckle radius = 0.06 x Rc= 0.129 m Cs = 1.77 Thickness = 6.2 mm Reactor Support The types of support used for vessels are: 

Saddle support



Skirt support



Bracket support

Saddle supports are used for horizontal vessels while other two types are used for vertical vessels. For the reactor in this case, a skirt support is proposed as it is safer than bracket support and can more efficiently bear the weight of the reactor and water as a cooling media circulating through the reactor.

105

CHAPTER NO: 7 INSTRUMENTATION AND CONTROL 7.1 Instrumentation and Process Control Measurement is a fundamental requisite to process control. Either the control can be affected automatically, semi automatically or manually. The quality of control obtainable also bears a relationship to accuracy, reproducibility and reliability of measurement methods, which are employed. Therefore, selection of the most effective means of measurements is an important first step in design and formulation of any process control system. Design of control system involves large number of theoretical and practical consideration such as quality of controlled response, stability, the safety of operating plant, the reliability of control system, the range of control, easy of start up, shutdown or changeover, the ease of the operation and cost of control system. Traditionally one under takes the design of control system for chemical plant only after the process flow sheet has been synthesized and designed. This allows the control designer to know 

What units are in plant and their sizes



How they are interconnected



The range of the operating conditions



Possible disturbance, available measurements and manipulations



What problem may arise during shutdown and start up

7.2 Process instrument Process instrument is a device used directly or indirectly to perform one or more of the following three functions 

Measurement



Control

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

Manipulation

The primary purpose of control in process industry is to aid in the economics of industrial operations by improving quality of product and efficiency of production.

7.3 Control Control means methods to force parameters in environment to have specific value. There is some control on different parameters as follows

7.3.1Temperature measurement and control Temperature measurement is used to control the temperature of outlet and inlet streams in heat exchangers, reactors, etc. Most temperature measurements in the industry are made by means of thermocouple to facilitate bringing the measurements to centralized location. For local measurements at the equipment bimetallic or filled system thermometers are used to a lesser extent. Usually, for high measurement accuracy, resistance thermometers are used. All these measurements are installed with thermo wells when used locally. This provides protection against atmosphere and other physical elements.

7.3.2 Pressure measurement and control Like temperature, pressure is a valuable indication of material state and composition. In fact, these two measurements considered together are the primary evaluating devices of industrial materials. Pumps, compressors and other process equipments associated with pressure changes in the process material are furnished with pressure measuring devices. Thus pressure measurement becomes an indication of an energy decrease or increase.

107

Most pressure measuring devices in industry are elastic element devices, either directly connected for local use or transmission type to centralized location. Most extensively used industrial pressure measuring device is the Bourdon Tube or a Diaphragm or Bellow gauges.

7.3.3 Flow measurement and control Flow indicator is used to control the amount of liquid. Also all manually set streams require some flow indication or some easy means for occasional sample measurement. For accounting purposes, feed and product streams are metered. In addition utilities to individual and grouped equipments are also metered. Most flow measuring devices in the industry are Variable Head devices. To a lesser extent variable area is used as many types are available as special metering situation arise.

7.4 Control scheme of distillation column Objectives In distillation column any of following may be the goals to achieve. 1. Overhead composition 2. Bottom composition 3. Constant over head product rate 4. Constant bottom product rate

Manipulated variables Any one or any combination of following may be the manipulated variables. 1. Steam flow rate to reboiler 2. Reflux rate 3. Overhead product with drawn rate 4. Bottom product withdrawn rate

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5. Water flow rate to condenser

Loads or disturbances Following are typical disturbances. 1. Flow rate of feed. 2. Composition of feed. 3. Temperature of feed. 4. Pressure drop of steam across reboiler. 5. Inlet temperature of water for condenser.

Control scheme Here is control scheme on acrolein distillation column. Consider the feed to this column as binary mixture composed of acorlein and water. We can specify four control variable for this distillation column are 

Acrolein product quality



Fractional recovery of acroelin in overhead product (distillate rate)



Liquid level in overhead accumulator



Liquid level at bottom of column

Overall product rate is fixed and any change in feed must be absorbed by changing bottom product rate. The change in product rate is accomplished by direct level control of reboiler if the stream rate is fixed, feed rate increases then vapor rate is approximately constant and the internal reflux flow must increase. Trying to control the liquid level at the bottom of column with reflux flow or distillate flow rate involves very long time response because action of manipulated variable must travel the whole length of distillation column before it is felt by the controller variable so it cannot be done. A long time response is involved when we try to control the level in the overhead accumulator by manipulating the bottoms flow rate & stream flow rate. It is quite complicated to control the distillate composition or flow rate with bottom flow

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rate. Since an increase in feed rate increases reflux rate with vapor rate being approximately constant, then purity of top product increases.

Explanation First on the cold day or in rainstorm the temperature of cold water in overhead condenser drops and overhead vapors passing through condenser produces sub cooled liquid. When sub cooled liquid returns back from reflux to the top tray of distillation column it causes less vapors to go overhead. Low vapors in overhead causes less liquid level in accumulators. If the accumulator level is controlled by reflux flow the latter will decrease thus the disturbance causes by the cooling water temperature drop does not propagate down the column in terms of increased liquid level overflow. The acrolein product composition is controlled by distillate flow. The scheme shown is cascade scheme for distillation column.

Figure 7.1. Control scheme of distillation column

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7.5 Heat exchanger control

Figure 7.2. Control scheme of heat exchanger The control objective is to maintain the temperature at desired value and to allow particulate heat exchange. The manipulated variable is flow rate of utility stream. The external disturbance that will affect the operation of heat exchanger is surrounding temperature, inlet temperature and steam pressure and steam temperature or its flow rate in case when utility is steam. The output variable is the temperature of outlet process stream and temperature of outlet utility stream. The above is feedback control scheme for heat exchanger. The control system of complete plant must permit smooth, safe and relatively fast startup and shutdown of plant operation.

7.6 Control Scheme of PFR Objectives In PFR control any of following may be the goals to achieve 1. Constant Temperature inside the reactor 2. High quality of Product

111

Reactor Variable The independent variables for the PFR may be divided into following categories 1. Uncontrolled variables 2. Manipulated variables 3. Controlled Variables

Uncontrolled Variables The variables, which cannot be controlled by controller, are called uncontrolled variables. The Uncontrolled variables include 1.Vent gases rate 2.Temperature of feed, etc

Manipulated Variables The independent manipulated inputs are variables, which are adjusted to control the chemical reaction. Any one or any combination of following may be the manipulated variables 1.Flow rate of cooling water 2.Flow rate of Feed 3.Flow rate of Product stream

Controlled Variables Any process variable that is selected to be maintained by a control system is called a controlled variable. Following are the controlled variables 1.Inside reactor Temperature 2.Inside reactor Pressure

Temperature Control Scheme The simplest method of cooling a PFR is shown in diagram. Here we measure the reactor temperature and manipulated variable the flow of cooling water to the shell side in shell and tube type reactor. Using a shell side for cooling has two advantages. First, it minimizes the risk of leaks and thereby cross contamination between the cooling system and the process. Second, heat transfer rate is increased by using baffles.

112

A temperature sensor measures the inside reactor temperature and transfer signal to temperature transducer, transducer converts these signals in other form and the output of transducer is accepted by controller and controller transfer its signal to final control element. Final control element takes step to overcome these disturbances.

PFR Control Configuration

Figure 7.3. Control Scheme of PFR

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CHAPTER NO: 8 HAZOP STUDY 8.1Introduction A HAZOP survey is one of the most common and widely accepted methods of systematic qualitative hazard analysis. It is used for both new or existing facilities and can be applied to a whole plant, a production unit, or a piece of equipment It uses as its database the usual sort of plant and process information and relies on the judgment of engineering and safety experts in the areas with which they are most familiar. The end result is, therefore reliable in terms of engineering and operational expectations, but it is not quantitative and may not consider the consequences of complex sequences of human errors.

8.2 Background The technique originated in the Heavy Organic Chemicals Division of ICI, which was then a major British and international chemical company. The history has been described by Trevor Kletz . In 1963 a team of 3 people met for 3 days a week for 4 months to study the design of

a

new phenol plant.

They

started

with

a

technique

called critical

examination which asked for alternatives, but changed this to look for deviations. The method was further refined within the company, under the name operability studies, and became the third stage of its hazard analysis procedure (the first two being done at the conceptual and specification stages) when the first detailed design was produced. In 1974 a one-week safety course including this procedure was offered by the Institution of Chemical Engineers (IChemE) at Teesside Polytechnic.Coming

114

shortly after the Flixborough disaster, the course was fully booked, as were ones in the next few years. In the same year the first paper in the open literature was also published. In 1977 the Chemical Industries Association published a guide .Up to this time the term HAZOP had not been used in formal publications. The first to do this was Kletz in 1983, with what were essentially the course notes (revised and updated) from the IChemE courses. By this time, hazard and operability studies had become an expected part of chemical engineering degree courses in the UK.

8.3Types of HAZOP 1. Process HAZOP The HAZOP technique which was originally developed to assess plants and process systems 2. Human HAZOP It is a family of specialized HAZOPs that are more focused on human errors rather than technical failures. 3. Procedure HAZOP It is a review of procedures or operational sequences, sometimes also denoted as SAFOP, SAFE Operation Study. 4. Software HAZOP It deals with the identification of possible errors in the development of software.

Advantages 1. Systematic examination 2. Multidisciplinary study 3. Utilizes operational experience

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4. Solutions to the problems identified may be indicated 5. Reduces risks 6. Better contingency 7. More efficient operations 8. Considers operational procedures

8.4 HAZOP guide words and meanings Guide Words

Meaning

No

Negation of design intent

Less

Quantitative decrease

More

Quantitative increase

Part of

Qualitative decrease

As well as

Qualitative Increase

Reverse

Logical opposite of the intent

Other than

Complete substitution

8.5 HAZOP study of an Absorber Item

Deviation

Causes

Consequences

Safeguards

Actions

Low flooding

Use pressure

Use blower

packing

efficiency

controller at

upstream

High liquid

Flood can

above stream

and also use

loading

occur

of absorber

suitable

No.

AB1

Low pressure Unsuitable

packing for absorber High

Low

Good

Use pressure

Use blower

pressure

pressure

absorption

controller

working

116

drop Low

Chocking

Efficiency of

Use

Use control

temperature

can occur in

absorber

temperature

valve and

the packing

reduces also

controller for

controller at

pressure drop

the

upstream of

increases

measurement

absorber

of temperature of inlet gases and stream High

Quencher is

Low

Use

Use control

temperature

not working

absorption

temperature

valve and

properly

Damage to the

controller for

controller at

packing

temperature

upstream of

measuring of

absorber

inlet gases and stream High

More water is

Check CO2

concentration wood

required to

concentration controller

of CO2

composition

remove CO2

after cracker,

for

Increase in

Increase in

use wood of

controlling

CO2

operating cost

constant

composition

and vice versa

composition

of CO2

Low

Change in

Less

concentration conversion of CO2

in cracker, more carbon remains as it is

117

Use

CHAPTER NO: 9 ENVIRONMENTAL IMPACT ANALYSIS OF ACROLEIN 9.1Hazards Identification 9.1.1Potential Acute Health Effects Acrolein is very hazardous in case of skin contact (irritant), of eye contact (irritant), of ingestion, of inhalation. Liquid or spray mist may produce tissue damage particularly on mucous membranes of eyes, mouth and respiratory tract. Skin contact may produce burns. Inhalation of the spray mist may produce severe irritation of respiratory tract, characterized by coughing, choking, or shortness of breath. Severe over-exposure can result in death. Inflammation of the eye is characterized by redness, watering, and itching. Skin inflammation is characterized by itching, scaling, reddening, or, occasionally, blistering.

9.1.2 Potential Chronic Health Effects Acrolein is mutagenic for mammalian somatic cells and for bacteria and/or yeast. The substance is toxic to lungs, upper respiratory tract. The substance may be toxic to skin, eyes. Repeated or prolonged exposure to the substance can produce target organs damage. Repeated or prolonged contact with spray mist may produce chronic eye irritation and severe skin irritation. Repeated or prolonged exposure to spray mist may produce respiratory tract irritation leading to frequent attacks of bronchial infection. Repeated exposure to a highly toxic material may produce general deterioration of health by an accumulation in one or many human organs.

118

9.2Fire and Explosion Data Flammability of the Product: Flammable. Auto-Ignition Temperature: 220°C (428°F) Flammable Limits: LOWER: 2.8% UPPER: 31% Products of Combustion: These products are carbon oxides (CO, CO2). Fire Hazards in Presence of Various Substances: Acrolein is highly flammable in presence of open flames and sparks, of heat also in presence of oxidizing materials.

Explosion Hazards in Presence of Various Substances: There is a risk of explosion of the product in presence of mechanical impact and slightly explosive in presence of heat.

Fire Fighting Media and Instructions: Flammable liquid, soluble or dispersed in water. In case of small fire use dry chemical powder while for large fire alcohol foam, water spray or fog may be used.

Special Remarks on Fire Hazards: Vapors may form explosive mixtures with air. Vapor may travel considerable distance to source of ignition and flash back. When heated to decomposition it emits toxic fumes of carbon monoxide, peroxides.

Special Remarks on Explosion Hazards: Vapors may form explosive mixtures with air.

9.3Accidental Release Measures Small Spill: Dilute with water and mop up, or absorb with an inert dry material and place in an appropriate waste disposal container.

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Large Spill: Acrolein is flammable, corrosive and Poisonous liquid. Keep it away from heat also from sources of ignition. Absorb with dry earth, sand or other noncombustible material. Do not get water inside container. Do not touch spilled material. Use water spray curtain to divert vapor drift. Use water spray to reduce vapors. Prevent entry into sewers, basements or confined areas; dike if needed. Call for assistance on disposal.

9.4 Handling and Storage Precautions: Acrolein should be kept away from sources of ignition. Ground all equipment containing material. Do not ingest. Do not breathe gas/fumes/ vapor/spray. Never add water to this product. In case of insufficient ventilation, wear suitable respiratory equipment. If ingested, seek medical advice immediately and show the container or the label. Avoid contact with skin and eyes. Keep away from incompatibles such as oxidizing agents, acids, alkalis.

Storage: It should be stored in a segregated and approved area. Keep container in a cool, well-ventilated area also keep it tightly closed and sealed until ready for use. Avoid all possible sources of ignition (spark or flame). Do not store above 8°C (46.4°F).

9.5Exposure Controls/Personal Protection Engineering Controls: Provide exhaust ventilation or other engineering controls to keep the airborne concentrations of vapors below their respective threshold limit value. Ensure that eyewash stations and safety showers are proximal to the work-station location.

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Personal Protection: Face shield, full suit and vapor respirator should be used. Be sure to use an approved/certified respirator with gloves and boots.

Personal Protection in Case of a Large Spill: A self contained breathing apparatus should be used to avoid inhalation of the product. Suggested protective clothing might not be sufficient; consult a specialist before handling this product.

9.6First Aid Measures Eye Contact: Check for and remove any contact lenses. Immediately flush eyes with running water for at least 15 minutes, keeping eyelids open. Cold water may be used. Get medical attention immediately.

Skin Contact: In case of contact, immediately flush skin with plenty of water for at least 15 minutes while removing contaminated clothing and shoes. Cover the irritated skin with an emollient. Cold water may be used. Wash clothing before reuse. Thoroughly clean shoes before reuse. Get medical attention immediately.

Serious Skin Contact: Wash with a disinfectant soap and cover the contaminated skin with an antibacterial cream. Seek immediate medical attention.

Inhalation: If inhaled, remove to fresh air. If no breathing is possible, give artificial respiration. If breathing is difficult, give oxygen. Get medical attention immediately.

Serious Inhalation: Evacuate the victim to a safe area as soon as possible. Loosen tight clothing such as a collar, tie, belt or waistband. If breathing is difficult, administer oxygen. If the victim is not breathing, perform mouth-to-mouth resuscitation.

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WARNING: It may be hazardous to the person providing aid to give mouth-tomouth resuscitation when the inhaled material is toxic, infectious or corrosive. Seek immediate medical attention.

Ingestion: If swallowed, do not induce vomiting unless directed to do so by medical personnel. Never give anything by mouth to an unconscious person. Loosen tight clothing such as a collar, tie, belt or waistband. Get medical attention immediately.

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CHAPTER NO: 10 COST ESTIMATION A plant design must present a process as capable of operating under conditions which will yield a profit and net profit equals total income minus all expenses. It is essential that chemical engineer be aware of the many different types of cost involved in manufacturing processes. Capital must be allocated for direct plant expenses; such as those for raw materials, labor, and equipment. Besides direct expenses, many other indirect expenses are incurred, and these must be included if a complete analysis of the total cost is to be obtained. Some examples of these indirect expenses are administrative salaries, product distribution costs and cost for interplant communication.

10.1Cost Indexes All cost-estimating methods use historical data and are themselves forecasts of future costs. The prices of the materials of construction and the costs of labor considerably increase with time due to changes in economic conditions .Therefore the cost index is used to update the historical cost data available .A cost index is merely an index value for a given point in time showing the cost at that time relative to a certain base time. If the cost at some time in the past is known, the equivalent cost at the present time can be determined by use of cost indexes. Cost in year A = Cost in year B × (Cost Index in year A/Cost Index in year B) The common indexes permit fairly accurate estimates if the time period involved is less than 10 years. Many different types of cost indexes are published regularly in Chemical Engineering Journal .The most common of these indexes are the Marshall and Swift all-industry and process-industry equipment indexes, the Engineering News-Record construction index, the Nelson-Farrar refinery construction index, and the Chemical Engineering plant cost index.

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10.2Cost of designed equipments Cost is being calculated by using following formula Cost of equipment in year A=Cost of equipment in year B × Cost index in year A Cost index in year B Using Marshall and Swift Equipment Cost Index (MS)

Heat Exchanger From appendix B figure 16, For carbon steel shell, stainless steel tubes and floating head, Material adjustment factor = 1 Pressure adjustment factor = 1 Bare cost = $ 140,000 Purchased cost of shell & tube Condenser (Mid 2004) = 140000 × 1 × 1 = $ 140,000 From appendix B figure 17, using Marshall & Swift equipment cost index Cost index in year 2004 = 1200 Cost index in year 2012 = 1700 Cost in 2012=140000 × 1700/1200 = $ 198,333

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Reactor From appendix B figure 16, For carbon steel shell, stainless steel tubes and fixed head, Material adjustment factor for fixed tube sheet= 0.8 Pressure adjustment factor for 2.05 bar = 1 Bare cost = $ 31,000 Purchased cost of muti tubular reactor (Mid 2004) = 31000 × 0.8 × 1 = $ 24,800 From appendix B figure 17, using Marshall & Swift equipment cost index Cost index in year 2004 = 1200 Cost index in year 2012 = 1700 𝐶𝑜𝑠𝑡 𝑖𝑛 2012 =

1700 1200

× 24800

= $ 35,133

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Absorber The purchased cost of packed column can be divided into the following components;  Cost for column shell, including heads, skirts, manholes and nozzles.  Cost for internals including packing, support and distribution plates. Diameter = D = 10.26 m Height =

H = 28.62 m

From Appendix B figure 18, Material of Construction =C.S(Carbon Steel) Material Adjustment factor =1 Pressure Adjustment factor =0.5 Bare cost of Absorber = 3×105× 0.5×1 = $150000 From Appendix B figure 19, Material of Construction =C.S (Carbon Steel) Packing Material Adjustment factor =1.2 Packed Height =28.26 m Cost of Absorber (Includes column internal support and distribution) = 5×105× 1.2 = $600000

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Total Cost of Absorber Column =$150000+$600000 =$210000

Distillation Column

Diameter of column = D = 0.96 m Height of column = H = 12.9m Plate type = Sieve plate Total pressure drop =29787.36pa Number of plates = 27 Material of construction = Carbon steel

Cost of distillation column= cost of vertical column+ cost of sieve plates

From Appendix B figure 20

Cost of column in 1998 = (bare cost from fig) ×material factor ×pressure factor Cost of column in 1998 = (7×1000) ×1×1 Cost of column in 1998 = $7000

From Appendix B figure 21

Cost of plate in 1998 = (bare cost from fig) ×material factor Cost of plate in 1998 = (320) ×1 Cost of plate in 1998= $320

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Cost of plate in 1998 = 320×27 = $8640

Cost of distillation column in 1998 = 8640+7000

=$15640 Marshall and Swift Equipment Cost Index using Appendix B figure 17, Cost index in 1998 = 1092 Cost index in 2012=1500 Cost of column in 2012=Cost of column in 1998× Cost index in 2012 Cost index in 1998

=15640× (1500/1092) =$21483.

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APPENDICES APPENDIX A Table 1. Heat exchanger and condenser tube data

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Table 2. Tube sheet layouts.(Tube counts) Triangular Pitch

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Table 3.Fouling factor (Coefficients) typical values

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Table 4.Fouling factor (Coefficients) typical values

Table 5.Data for different packings

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Table 5. Continued

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APPENDIX B

Figure 1. Relation between Reynolds number and friction factor

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Figure 2. Relation between Reynolds number and friction factor with respect to baffle cut

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Figure 3. Overall Coefficients

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Figure 4. Tube patterns

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Figure 5. Tube side heat transfer factor

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Figure 6. Shell side heat transfer factor, segmental baffles

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Figure 7. Shell side friction factor

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Figure 8. Shell side heat transfer curve

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Figure 9. Generalized pressure drop correlation, adapted from a figure by the Norton Co. with permission

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Figure 10. Flooding velocity, sieve plates

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Figure 11. Selection of liquid flow arrangement

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Figure 12. Weep point correlation (Eduljee, 1959)

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Figure 13. Relation between downcomer area and weir length

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Figure 14.Discharge coefficients, sieve plates

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Figure 15. Entrainment correlation for sieve plates

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Figure 16. Purchased cost of shell and tube heat exchanger

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Figure 17. Variation of cost indices

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Figure 18. Purchased cost of absorber column

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Figure 19. Purchased cost of packing

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Figure 20. Purchaesd cost of distillation column

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Figure 21.Purchaesd cost of column plates

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REFERENCES 1. McCabe, W.L, Smith, J.C., & Harriot, P., “Unit Operation of Chemical Engineering”, McGraw Hill, 5th ed., Inc, 1993. 2. Sinnot R.K., “Coulson and Richardson‟s Chemical Engineering”, 3rd ed., Vol. 6, Butterword Heminann, 1999. 3. Coulson J.M. and Richardson J.F.,“Chemical Engineering”, 5th ed., Vol. 2, Butterword Heminann, 2002. 4. Branan C.R., “Rules of Thumbs For Chemical Engineers”, Gulf Publishing Company, 1994. 5. Yaw‟s C.L., “Handbook of Thermodynamics and Physical Properties of Chemical Compounds”, Knovel Publishing Company, 2003. 6. R.H.Perry, Don W.Green, “Perry„s Chemical Engineer„s Handbook”, McGrawHill, 7th ed. 7. Max S.Peters, Klaus D.Timmerhaus, Ronald E.West,” Plant Design And Economics for Chemical Engineers”, McGraw Hill, 5th ed. 8. O. Levenspiel, “Chemical Reaction Engineering”, 2nd and 3rd ed‟s., John Wiley and Sons, 1972, 1999. 9. J.M. Smith, “Chemical Engineering Kinetics”, McGraw Hill, 3rd ed., 1981. 10. Kirk-Othmer: Encyclopedia of Chemical Technology, “Reactor Technology”, Vol. 19, 3rd ed., John Wiley, 1982. 11. http://www.google.com.pk/patents?hl=en&lr=&vid=USPAT2270705&id= QxJEAAAAEBAJ&oi=fnd&dq=production+of+acrolein&printsec=abstra ct#v=onepage&q=production%20of%20acrolein&f=false 12. http://www.atsdr.cdc.gov/toxprofiles/tp124-c5.pdf - United States 13. http://www.che.cemr.wvu.edu/publications/projects/large_proj/Acrolein.P DF

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