Acrylonitrile Production by Propylene Ammoxidation PDF

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2013 Acrylonitrile by Propylene Ammoxidation Submitted by Guided by Aman Agrawal Dr. R.G.Pala Ankesh Kumar Singh Pratik Chaplot Rahul Gupta Raju Mishra Sachin Goel 1/5/2013 Table of Contents 1 Introduction .................................................................................................

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Acrylonitrile Production by Propylene Ammoxidation Ankesh Kumar Singh

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2013 Acrylonitrile by Propylene Ammoxidation

Submitted by Guided by Dr. R.G.Pala

Aman Agrawal Ankesh Kumar Singh Pratik Chaplot Rahul Gupta Raju Mishra Sachin Goel 1/5/2013

Table of Contents 1

Introduction ................................................................................................................................... 2

2

Price and Demand ......................................................................................................................... 3

3

Health Effects ................................................................................................................................. 3

4

3.1.1

Sources and Potential Exposure ................................................................................... 4

3.1.2

Assessing Personal Exposure ....................................................................................... 4

Sohio Process ................................................................................................................................. 7 Reactor ............................................................................................................................................... 8 Effect of different variables on Conversion ..................................................................................... 9

5

Aspen Simulation......................................................................................................................... 12 Reactor ............................................................................................................................................. 12 Quencher .......................................................................................................................................... 13 Absorber........................................................................................................................................... 15 Recovery Unit (Re-boiled Stripper) ............................................................................................... 17 Overall .............................................................................................................................................. 19

6

Plant Wide Control System Design ............................................................................................ 21 Pressure Driven Overall Flow Sheet .............................................................................................. 21 Dynamic Stripper: ........................................................................................................................... 22 Dynamic Absorber and Stripper: ................................................................................................... 22

7

Liquid Separation Scheme .......................................................................................................... 23 Materials to be recovered ............................................................................................................... 23 Development of Separation Sequence ........................................................................................... 23 Simplifying Assumptions ................................................................................................................ 26 Simulation of Separation Steps and Equipment Sizing ................................................................ 26 Distillation Columns .................................................................................................................... 28 Overall Process Balance .............................................................................................................. 28 Water Recovery ........................................................................................................................... 29

8

Pollutants And Their Control...................................................................................................... 30

9

Modifications to Design .............................................................................................................. 31 Quench Column (Acidic) ................................................................................................................. 31

10

Plant Location .......................................................................................................................... 36

11

References ................................................................................................................................ 43

12

Appendix .................................................................................................................................. 44

1 | Acrylonitrile by Propene Ammoxidation

1

Introduction

Acrylonitrile is a chemical compound with the formula C3H3N. This colourless liquid often appears yellow due to impurities. It is an important monomer for the manufacture of useful plastics such as polyacrylonitrile. In terms of its molecular structure, it consists of a vinyl group linked to a nitrile.

FIGURE 1: Lewis Structure.

Acrylonitrile (AN) is commercially produced by a reaction of propylene and ammonia in the presence of a catalyst. Having both olefinic (C=C) and nitrile (C-N) groups permits a large variety of reactions and makes ANa versatile chemical intermediate. The nitrile group can undergo hydrolysis, hydrogenation, esterification and reduction. Reactions of the carbon double bond include polymerization, copolymerization, cyanoethylation, cyclization and halogenation. One of the reasons for the versatility of acrylonitrile is that it can form copolymers with other unsaturated compounds, such as styrene and butadiene, for example a raw material for acrylic acid, acrylic esters, acrylic amide in the synthesis of compounds used for the production of adhesives, antioxidants, binders and emulsifiers. In its liquid state, acrylonitrile has a tendency to polymerize, which is prevented by the addition of phenolic or amine-based stabilizers and small quantities of water. Most industrial acrylonitrile is produced by catalytic ammoxidation of propene: 2CH3-CH=CH2 + 2NH3 + 3O2 → CH =CH-C≡N + 6H2O

TABLE 1: Chemical properties of Acrylonitrile

Chemical Name Regulatory Name Molecular formula Molecular weight Density Boiling point Melting point Vapor pressure Solubility Conversion factor DOT Label

Acrylonitrile 2-Propenenitrile, Acrylonitrile C3H3N 53.1 g/mol 0.81 g/cm3 at 25oC 77.3oC -82oC 100 torr at 23oC Soluble in isopropanol, ethanol, ether, acetone, and benzene 1 ppm = 2.17 mg/m3 at 25°C Flammable Liquid

Acrylonitrile (AN), also known as vinyl cyanide (CH2=CH-C≡N), is a high volume commodity chemical with worldwide production of more than 10 billion pounds per year. It contributes billions annually to the U.S. economy. Acrylonitrile is used as a monomer in the production of acrylic and modacrylic fibers, which accounts for approximately 50% of its global use.

2 | Acrylonitrile by Propene Ammoxidation

Acrylic fiber is used for clothing, carpeting and other fabrics and in the production of rugged plastics for automotive components, computers, and appliances. Acrylic fiber is also used in the manufacture of polyacrylonitrile (PAN)-base carbon fibers; which are increasingly important materials for lightweight, high-strength applications in aeronautics, automotive, engineering, etc. Acrylonitrile is used as a comonomer the production of acrylonitrile, butadiene, styrene (ABS) and styrene acrylonitrile (SAN) polymers, which accounts for an additional 31% of use. These polymers are used in a wide range of oiland chemical-resistant nitrile rubber for industrial hoses, gaskets and seals. Acrylonitrile is also used as an intermediate in the production of other industrial chemicals, such as adiponitrile and acrylamide.

2 Price and Demand

FIGURE 2: Price of Acrylonitrile (ACN Highlights from 01-15, Feb 2013)

In the first half of the last fortnight, selling offers for ACN went up at slow and steady pace. In the early first half of the last fortnight, ACN prices firm up in Asian market due to rise in feedstock rates, which supported the price rise. Prices were stable in European market due to poor energy market. In the early second half of the last fortnight, ACN prices surged in Asian market due to increase in feedstock value coupled with improved demand from the downstream market. It is produced in very large amounts (2.5 billion pounds in 1993) by five companies in the United States. U.S. demand is likely to increase 2 to 3 percent per year for the next several years. The largest users of acrylonitrile are companies that make acrylic and modacrylic fibers. Companies also use AN to make: high impact acrylonitrile-butadienestyrene (ABS) plastics used in business machines, luggage, and construction material; styreneacrylonitrile (SAN) plastics used in automotives and household goods and in packaging material; adiponitrile, a chemical used to make nylon; and dyes, drugs, and pesticides.

3 Health Effects

FIGURE 3: MSDS Label

Chemicals can be released to the environment as a result of their manufacture, processing, and use. EPA has developed information summaries on selected chemicals to describe how you might be exposed to these chemicals, how exposure to them might affect you and the environment, what happens to them in

3 | Acrylonitrile by Propene Ammoxidation

the environment, who regulates them, and whom to contact for additional information. EPA is committed to reducing environmental releases of chemicals through source reduction and other practices that reduce creation of pollutants. Acrylonitrile is highly flammable & toxic. It undergoes explosive polymerization. The burning material releases fumes of hydrogen cyanide and oxides of nitrogen. It is classified as a Class 2B carcinogen (possibly carcinogenic) by the International Agency for Research on Cancer (IARC), and workers exposed to high levels of airborne acrylonitrile are diagnosed more frequently with lung cancer than the rest of the population. Exposure to acrylonitrile can occur in the workplace or in the environment following releases to air, water, land, or groundwater. Exposure can also occur when people smoke cigarettes or breathe automobile exhaust. Acrylonitrile enters the body when people breathe air or consume water or food contaminated with AN. It can also be absorbed through skin contact. It does not remain in the body due to its breakdown and removal. There are two main excretion processes of acrylonitrile. The primary method is excretion in urine when acrylonitrile is metabolized by being directly conjugated to glutathione. The other method is when acrylonitrile is metabolized with 2-cyanoethylene oxide to produce cyanide end products that ultimately forms thiocyanate, which is excreted via urine, or carbon dioxide and eliminated through the lungs. Acrylonitrile evaporates when exposed to air. It dissolves when mixed with water. Most releases of acrylonitrile to the environment are to underground sites or to air. Acrylonitrile evaporates from water and soil exposed to air. Once in air, AN breaks down to other chemicals. Microorganisms living in water and in soil can also break down AN. Because it is a liquid that does not bind well to soil, acrylonitrile that makes its way into the ground can move through the ground and enter groundwater. Plants and animals are not likely to store acrylonitrile. Exposure to acrylonitrile is primarily occupational. It is used in the manufacture of acrylic acid and modacrylic fibers. Acute (short-term) exposure of workers to acrylonitrile has been observed to cause mucous membrane irritation, headaches, dizziness, and nausea. No information is available on the reproductive or developmental effects of acrylonitrile in humans. Based on limited evidence in humans and evidence in rats, EPA has classified acrylonitrile as a probable human carcinogen (Group B1).

[The main sources of information for this fact sheet are EPA's Integrated Risk Information System (IRIS), which contains information on inhalation chronic toxicity of acrylonitrile and the RfC and the carcinogenic effects of acrylonitrile including the unit cancer risk for inhalation exposure, EPA's Health Effects Assessment for Acrylonitrile, and the Agency for Toxic Substances and Disease Registry's (ATSDR's) Toxicological Profile for Acrylonitrile.] 3.1.1

3.1.2

Sources and Potential Exposure

 Human exposure to acrylonitrile appears to be primarily occupational, via inhalation.  Acrylonitrile may be released to the ambient air during its manufacture and use. Assessing Personal Exposure

 Acrylonitrile can be detected in the blood to determine whether or not exposure has occurred.  Metabolites may be detected in the urine, but some breakdown products are not specific to acrylonitrile.

Acute Effects 



Workers exposed via inhalation to high levels of acrylonitrile for less than an hour experienced mucous membrane irritation, headaches, nausea, feelings of apprehension and nervous irritability; low grade anaemia, leukocytosis, kidney irritation, and mild jaundice were also observed in the workers, with these effects subsiding with the ending of exposure. Symptoms associated with acrylonitrile poisoning include limb weakness, laboured and irregular breathing, dizziness and impaired judgment, cyanosis, nausea, collapse, and convulsions. A child died after being exposed to acrylonitrile by inhalation, suffering from respiratory malfunction, lip cyanosis, and tachycardia before death. Several adults exposed to the same concentration of acrylonitrile exhibited eye irritation, but no toxic effects.

4 | Acrylonitrile by Propene Ammoxidation

 

Acute dermal exposure may cause severe burns to the skin in humans. Acute animal tests in rats, mice, rabbits, and guinea pigs have demonstrated acrylonitrile to have high acute toxicity from inhalation and high to extreme acute toxicity from oral or dermal exposure.

Chronic Effects (Non-Cancer)  In one study, headaches, fatigue, nausea, and weakness were frequently reported in chronically (long-term) exposed workers.  In rats chronically exposed by inhalation, degenerative and inflammatory changes in the respiratory epithelium of the nasal turbinates and effects on brain cells have been observed.  The Reference Concentration (RfC) for acrylonitrile is 0.002 milligrams per cubic meter (mg/m3) based on degeneration and inflammation of nasal respiratory epithelium in rats. The RfC is an estimate (with uncertainty spanning perhaps an order of magnitude) of a continuous inhalation exposure to the human population (including sensitive subgroups) that is likely to be without appreciable risk of deleterious noncancer effects during a lifetime. It is not a direct estimator of risk but rather a reference point to gauge the potential effects. At exposures increasingly greater than the RfC, the potential for adverse health effects increases. Lifetime exposure above the RfC does not imply that an adverse health effect would necessarily occur.  EPA has medium confidence in the study on which the RfC was based because, although it was a well-conducted chronic study in an appropriate number of animals, it was performed on only one species, did not identify a no-observed-adverse-effect level (NOAEL), was confounded by the early sacrifice of rats with large mammary gland tumors and the target organ (nasal turbinates) was examined only at the end of the study in relatively few animals; medium to low confidence in the database because of the lack of chronic or subchronic inhalation data in a second species, the lack of reproductive data by the inhalation route and the existence of an oral study showing reproductive effects; and, consequently, medium to low confidence in the RfC.  EPA has calculated a provisional Reference Dose (RfD) of 0.001 milligrams per kilogram body weight per day (mg/kg/d) for acrylonitrile based on decreased sperm counts in mice. The provisional RfD is a value that has had some form of Agency review, but it does not appear on IRIS. Reproductive/Developmental Effects  No information is available on the reproductive or developmental effects of acrylonitrile in humans.  Fetal malformations (including short tail, missing vertebrae, short trunk, omphalocele, and hemivertebra) have been reported in rats exposed to acrylonitrile by inhalation.  In mice orally exposed to acrylonitrile, degenerative changes in testicular tubules and decreased sperm count were observed. Cancer Risk    

A statistically significant increase in the incidence of lung cancer has been reported in several studies of chronically exposed workers. However, some of these studies contain deficiencies such as lack of exposure information, short follow up, and confounding factors. In several studies, an increased incidence of tumors has been observed in rats exposed by inhalation, drinking water, and gavage. Astrocytomas in the brain and spinal cord and tumors of the Zymbal gland (in the ear canal) have been most frequently reported, as well as tumors of the stomach, tongue, small intestine in males and females, and mammary gland in females. EPA has classified acrylonitrile as a Group B1, probable human carcinogen (cancer-causing agent). EPA uses mathematical models, based on human and animal studies, to estimate the probability of a person developing cancer from breathing air containing a specified concentration of a chemical. EPA calculated an inhalation unit risk estimate of 6.8 × 10-5 (µg/m3)-1. EPA estimates that, if an individual were to continuously breathe air containing acrylonitrile at an average of 0.01 µg/m3 (1 x 10-5 mg/m3), over his or her entire lifetime, that person would theoretically have no more than a one-in-a-million increased chance of developing cancer as a direct result of breathing air containing this chemical. Similarly, EPA estimates that breathing

5 | Acrylonitrile by Propene Ammoxidation



air containing 0.1 µg/m3 (1 x 10-4mg/m3) would result in not greater than a one-in-a-hundred thousand increased chance of developing cancer, and air containing 1.0 µg/m3 (1 x 103 mg/m3) would result in not greater than a one-in-ten thousand increased chance of developing cancer. For a detailed discussion of confidence in the potency estimates, please see IRIS. EPA has calculated an oral cancer slope factor of 0.54 (mg/kg/d)-1.

Hence, In conclusion the effects of acrylonitrile on human health and the environment depend on how much acrylonitrile is present and the length and frequency of exposure. Effects also depend on the health of a person or the condition of the environment when exposure occurs. Breathing acrylonitrile for short periods of time adversely affects the nervous system, the blood, the kidneys, and the liver. These effects subside when exposure stops. Nervous system effects of AN range from headaches and dizziness to irritability, rapid heartbeat, and death. Symptoms of acrylonitrile poisoning may occur quickly after exposure or after levels of breakdown products like cyanide build up in the body. Direct contact with acrylonitrile liquid severely damages the skin. Acrylonitrile liqu...