IN-PLANT TRAINING REPORT

AT

RELIANCE INDUSTRIES LIMITED DAHEJ MANUFACTURING DIVISION

PO: DAHEJ, TAL: VAGRA, DIST: BHARUCH, GUJARAT, INDIA

PIN: 392130

A TRAINING REPORT SUBMITTED AS A PART

OF

PROJECT

BY

AMIT JAIN

&

SHANTANU FAUGAAT

THIRD YEAR, CHEMICAL ENGINEERING DEPARTMENT (2009-2010)

INDIAN INSTITUTE OF TECHNOLOGY, DELHI (I.I.T- DELHI)

TRAINING PERIOD: 17TH MAY TO 17TH JULY 2010

1

DAHEJ MANUFACTURING DIVISION

RIL-DMD

ACKNOWLEDGEMENT

2

This is to convey our sincere thanks and gratitude to all those people who

generously co-operated and guided us in every aspect to make this project

successful. The time that we spent at the plant of Reliance Industries Ltd. have

been a great learning experience; not just because of training experience, but

also because of the world class working environment and the highly

experienced people with whom we got the chance to work along.

We are grateful to Mr. Sushil Kumar(President) to give us this coveted

opportunity for an internship at RIL-DMD. We are thankful to Mr. A B Patel

(HOD-GCU) and Mr. Sandeep Vipra(Sr. GM) for giving us a deep insight on

our project in GCU Plant and guiding us through various difficulties.

Special thanks to Mr. Felix Gnanaraj(Manager-GCU Plant) and Mr. Krishnamurthy Anand(Manager-GCU Plant) for guiding us properly and plan wise as Mentor and providing us with the requisite data and necessary details of the whole plant. We also thank Mr. Pankaj Tahiliani for showering his unhindered support by all means.

I am also grateful to Mr. Bhavesh R.Makwana Executive (HR) who

helped us with all the formalities during this training.

Our special thanks to the whole staff of GCU for extending their technical and emotional support during our stay. They really helped us with all their time and knowledge. Without the kind and selfless support from all these FOPEs this project would not have been completed.

CERTIFICATE OF TRAINING:

3

Dahej Manufacturing Division

This is to certify that Mr. Amit Jain, student of

Chemical Engineering Department in Indian Institute of

Technology, Delhi has successfully completed his project

training at Reliance Industries Limited- Dahej manufacturing

Division from 17/05/2010 to 17/07/2010

We wish him every success in future endeavors.

Mr. Arvind Patel Mr. Sandeep

Vipra

(HOD-GCU) (Sr. GM-GCU)

CONTENTS

4

Sr. No.

TOPIC SECTION PAGE NO.

1 ACKNOWLEDGEMENT 3

2 CERTIFICATE OF TRAINING 4

3 PREFACE 6

4 INTRODUCTION 7

5 PROJECT DEFINITION 9

6 GCU PLANT SECIFICATIONS 10

7 GAS CRACKING PROCESS OVERVIEW 11

8 PROJECT 1 16

9 DIFFERENT ANTI-COKING METHODS 20

10 PROJECT 2 24

11 REFERENCES 30

5

This report constitutes of two projects done during training at

RIL-DMD, in GCU Plant:

1. Increasing the run length of W-coil in radiant section of

Cracking Furnace so as to delay the Decoking operation.

2. Determining the cause of lower efficiency and below par

performance of C2R compressor compared to design data.

INTRODUCTION

6

DAHEJ MANUFACTURING DIVISION

(GANDHAR COMPLEX)

PLANTS IN RIL, DMD

1) CHLOR ALKALI(CA)

2) VINYL CHLORIDE MONOMER(VCM)

3) POLY VINYL CHLORIDE(PVC)

4) ETHANE PROPANE RECOVERY UNIT(EPRU)

5) GAS CRACKER UNIT(GCU)

6) ETHYLENE OXIDE/ ETHYLENE GLYCOL(EOEG)

7) HIGH DENSITY POLY ETHYLENE(HDPE)

8) CAPTIVE POWER PLANT(CPP)

9) NITROGEN/ OXYGEN PLANT(N2/O2)

10)WASTE WATER TREATMENT PLANT(WWTP)

PLANTS RAW MATERIALS

PRODUCTS

7

VCM C2H4, Cl2, O2 VCM, HCl, EDC

PVC VCM PVC

CA NaCl NaOH, HCl, Cl2

EPRU Natural Gas C2H6, C3H8

GCU C2H6, C3H8 C2H4, C3H6

EOEG C2H4, O2, CH4 Ethylene Oxide/ Glycol

HDPE C2H4, H2, C4H8 High Density Polyethylene

CPP Naphtha/ fuel gas(Lean gas)

Power

N2/O2 Air N2 and O2

WWTP Waste Water Water

PROJECT DEFINITION:

8

The overall project work was carried out under the guidance of my Mentor, Mr. Felix Gnanaraj and Mr. Krishnamurthy Anand as follows:

WEEK 1: Understanding the GCU manufacturing Process by studying the Operating Manual. Taking an overall feel of the plant.

WEEK 2: Focusing on our Project 1 and learning the furnace operations in detail referring the Process Flow Diagrams (PFDs) and Operating manuals.

WEEK3: Referring the various available papers and doing extensive search on the internet for details regarding various available anti coking technologies.

WEEK 4: Comparing different alternatives with respect to their Expensiveness and capacity utilization.

WEEK 5: Preparation of Report for Project 1 and submission.

WEEK 6: Understanding the whole refrigeration cycle of C2R and C3R compressors and the problem of underperformance of C2R compressor.

WEEK 7: Referring the Data Sheets for comparing the designed load (tonne/hr) values for compressor with the Actual data on C2R efficiency excel sheet.

WEEK 8: Calculation of % efficiency for the Compressor on Excel and suggested ways to maximize the efficiency by increasing load on later stages and decreasing the intermediate temperature.

WEEK 9: Preparation of Report and submission

GCU PLANT SPECIFICATIONS:

9

Plant licensor: STONE & WEBSTER ENGG. CORP. LTD.

Commissioning Date: 12.02.2000

Production capacity: 400,000 TPA Ethylene, with 5th furnace

Capacity utilization: 118.379%

Area of Plant : 64400 m2 (Excluding CT 01)

BUSINESS DETAILS:

Initial Investment : 750 Crores

Finished Products :

Ethylene : Polymer Grade

Propylene : Polymer Grade

Area of Usage : Polyethylene, Polypropylenes

 

Gas cracking process overview:

10

Cracking:

Cracking is the process whereby complex organic molecules or heavy hydrocarbons are broken down into simpler molecules (e.g. light hydrocarbons) by the breaking of carbon-carbon bonds in the precursors.

The rate of cracking and the end products are strongly dependent on the temperature and presence of any catalysts.

Cracking, also referred to as pyrolysis, is the breakdown of a large alkane into smaller, more useful alkanes and an alkene. Simply put, hydrocarbon cracking is the process of breaking long chain hydrocarbons into short ones.

In Gas cracker unit, C2/C3and Imported Propane are the feed stocks and are cracked to Ethylene, Propylene With hydrogen, Methane, C4 mix, RARFS, Mix oil, Light fuel oil as byproducts.

Components of the GCU plant :

1. Ethane Propane Fractionator

2. Furnace

3. quench water tower

4. Cracked Gas compressor

5. De-Methanizer Section

6.De-Ethanizer section

7. Acetylene Hydrogenation and Ethylene Tower

8. Depropanizer

9. Propylene Tower

10. Debutaniser

11. Gasoline Fractionator

11

The gas cracker plant which is mainly put up to produce Ethylene and Propylene as value added products by cracking various feed stocks available from ONGC/GAIL and by import of Propane.

This feed gas has two storage spheres at OSBL and can store about 1300 MT put together.

The feedstock comes to Ethane propane fractionator, Ethane and propane are fractionated and Ethane is recovered at top and propane at bottom after preheating up to 54oC this feed is send to furnace for cracking separately.

The separation of Ethane and Propane allows us more control over cracking.

12

Furnace:

4 furnaces where cracking takes place at 830-840oC in single furnace – 24 W coils distributed iin 3 zones.

furnace consists of 2 sections: Convection section and Radiant section.

Convection section:

main purpose of convection section is to utilise the heat energy associated with flue gases leaving furnace.

The convection section is having 6 convection banks   1. Hydrocarbon feed preheat bank no1 2. Boiler Feed water preheat bank no 2 (Economiser) 3. Hydrocarbon Feed preheat bank no 2 4. Very High pressure Steam superheat bank 5. Hydrocarbon plus Dilution steam preheat bank 6. Dilution Steam preheat bank: Dilution steam is added in a ratio of 1:3,

to reduce the partial pressure of hydrocarbon so as to suppress formation of undesired products and to reduce coking

Radiant Section:

Cracking takes place in radiant section in 24 W coils. Coils are distributed in 3 zones each zone havin 8 W coils each. We have

separate control on each zone on feed and temperature. The residence time for feed in coil is .285 seconds. The product coming out of coils are sent to ultra selective heat

exchangers, there are 12 USX. After cracking the the mixture is sent to primary and secondary transfer

line heat exchangers for quenching and cooling upto 232oC.  Fuel used is fuel gas which is a mixture of Methane and Hydrogen. There are total 144 wall burners and 24 floor burners. There are total 72

burner on each wall arranged as 12 burners each row so total 6 rows are there.

Quench water tower:

The cracked stream from radiant section goes to Quench water tower in which Heavy oils and some tar materials are separated along with water,

13

After separation in Oil water Separator the fuel oil is send as product for storage and water is routed to Dilution Steam Generator. Here the cracked gas is quenched up to 40o C.

Cracked gas compressor:

The cracked gases from quench tower comes to compressor where the pr. Of gas is raised from 0.4 Kg/cm2 is raised up to 25 Kg/cm2

This is a 4 stage centrifugal compressor. In between the 3rd and 4th stage a caustic tower removes the acidic

impurities(CO2 and H2S). After compressor the outlet gases are cooled down to 15oC and then

passed through a molecular sieve dryer dryer (3 Ao) to remove moisture before it is cooled further by various refrigeration streams.

Demethanizer Section:

The Chilling takes place in 3 stages i.e. up to -40oC by Propylene refrigeration and to -70oC in 2nd stage and -90oC in the 3rd stage by Ethylene Refrigeration.

The Hydrocarbon condensates from 1st stage at -40oC is sent to Demethanizer Prestripper where in the C2+ Stream is split from C1 stream and sent to Deethanizer, which also receive the Hydrocarbon condensate from the -70oC & -98oC levels.

Here also the C1 stream is fractionated and sent to Demethanizer Rectifier and the bottom C2+ steam is sent to Deethanizer.

The Demethanizer Rectifier overhead stream is cooled to a temp of -130oC in the Demethanizer overhead rectifier and in that process the slipping C2 are condensed and put back to Demethanizer.

The gases coming out at -130oC is a mixture of Methane, Hydrogen, and CO and is called Rich Gas. The chillness up to -130oC is obtained by Demethaniser reflux recycle stream, which is chilled by expansion in Expander Compressor.

14

Deethanizer, Acetylene Hydrogenation and Ethylene Tower:

The Deethanizer is operated at 20.6-kg/cm2g pressure, separates C2s from the top at -19.3oC and the C3+ from bottom at a temperature of 68.2oC.

The C2s are a mixture of Ethylene, Acetylene and Ethane. since Acetylene is a poison for polymers product, therefore it is hydrogenated in a reactor using palladium catalyst. The hydrogenated product is taken to an Ethylene/Ethane Fractionator. Ethylene is separated in pure form from 8th tray and the bottom ethane is sent for cracking back in pyrolysis heater as recycle ethane. The column is operated at 17.2 kg/cm2 with top and bottom temp at -33oC and -11o C respectively.

Depropaniser:

In this part C3 s are taken out from the overhead and the bottom temperature at 14oC and 71oC, the C3 s are taken out from the overhead and the bottom C4+ stream is sent to Debutaniser.

Propylene tower:

In propylene tower propylene is obtained as overhead product and rest propane and are sent to pyrolysis heater for further cracking.

Debutanizer:

The C4 stream which entered the debutaniser is split into mixed C4 stream from top of the column at a pressure of 4.5 kg/cm2 and at a top temperature of 50oC and the balance C4stream goes to storage at PTD for sending to Baroda complex for recovery of 1:3 Butadiene in future.

Gasoline fractionator:

C5+ from bottom of Debutaniser is sent here, the Pyrolysis gasoline is taken out as overhead product and sent to PTD (Product Transfer Department). The bottom product of gasoline fractionator is sent to fuel oil stripper where the fractionation is done under vacuum to separate aromatic gas oil from the stream from the top for use as wash oil in the charge gas compressor internal. The bottom product is sent as light fuel oil.

15

PROJECT-1:

Increasing the run length of W-coil in radiant section of

Cracking Furnace so as to delay the Decoking operation.

Causes of coke formation:

1. Surface catalyzed reactions - lead to formation of filamentous(catalytic) coke (alloy surface has Ni, and Fe)

2. Bulk gas polymerization - from secondary reactions leading to:

a) condensation on the wall giving smooth hard coke

b) formation of coke in the gas phase - amorphous coke

16

Reactions in Furnace:

The desired products in steam cracking are light olefins such as ethylene, propylene, butadiene. The desired reaction is the decomposition of the hydrocarbon molecule (typically of paraffinic structure) to its olefinic equivalent. The simplest illustration is decomposition of ethane into an ethylene molecule, where the overall reaction is:

The mechanism as proposed by Rice and Herzfeld is as follows

17

Two major undesired reactions that occur simultaneously with the desired cracking of alkanes are dehydrogenation and condensation. Dehydrogenation is the phenomenon where an olefin molecule further decomposes into a diolefin or the C≡C group.

Condensation is a reaction where two or more small molecules combine to form a larger stable structure such as cyclo-diolefins and aromatic. This secondary reaction occurs in the latter stage of pyrolysis and the residence time of the reactor is high.

Coke Formation:

The extreme of dehydrogenation and condensation is coke formation. Coke forms when hydrogen atoms are removed from the hydrocarbon radicals until the extreme of leaving only a layer of elemental carbon or coke. Although,

18

aromatic are relatively stable molecules, they can however further react via condensation to form a chain of its benzene ring structure. These condensation products leave the gas phase and settle on the inner walls of the radiant coils as a layer of hard coke.

Four main consequences of coking process can be singled out in cracking furnaces:

The external tube skin temperature continuously rises and can reach its maximum allowable value. This fact can limit the on-stream time of the unit.

The pressure drop increases with the running time and can influence the process selectivity.

The furnace thermal efficiency is progressively reduced.

The reaction volume progressively declines.

The primary reactions involved in the formation of coke on the metal surface of radiant tubes and quench section are as follows:

These are kinetically controlled reactions. Initially after decoking the inner metal surfaces are in highly oxidized state. With time as O2 and H2O partial pressure on surface decreases due to formation of coke layer the coking rate also decreases.

Factors affecting Coking:

Feedstock (Character of hydrocarbon impurities etc.)

19

Temperature control problems

Flow rate control problems

Reactor and TLX design

Metallurgy and surface characteristics of the coil (MOC, composition and roughness of inner surface, metal fines from decoking)

Different Anti-Coking Methods:

Coke can be classified in generally two ways, catalytic and non-catalytic coke. It is believed that catalytic coke plays a more significant role in coking of furnace coils. Hence our aim is to suppress the metal catalyzed coking reaction.

Inhibitors/Additives –

In these method chemical additives are used to suppress coke formation. Coke inhibitors work by passivating catalytically active metal sites through chemical bonding interactions, and/or forming a thin layer to physically isolate the metal sites from coke precursors in a process stream, and/or interfering with those radical reactions leading to coke formation by blocking active radical sites on surfaces.

Various Inhibitors:

Generally Sulphur or Phosphorus containing species are used as additives, It is believed that compounds forms a metal sulfide or phosphate passivating layer on reactor metal surfaces and that these layer isolates gas phase coke precursors from active metal sites on surfaces, thereby resulting in coking reduction. These compounds can be entered anywhere before the crossover point on an inert carrier(steam or N2).These are added in pre-treatment as more passivation can be done on clean coils.

The sulfide formation is kinetically faster but thermodynamically unstable at temperature above 670 C on the other hand phospates form at a relatively smaller rate but are thermodynamically stable at higher

20

temperatures. Therefore a combination of sulphur and phosphorus compound can serve better for our purpose.

Other combinations such as of tin- and phosphorus containing compounds, or antimony- and phosphorus-containing compounds, or tin- antimony- and phosphorus containing compounds are also used.

Another method is to cover the inner tube with catalytically inert coke which is formed through inhibitor additives such as alkyl benzenes, alkyl naphthalene, alkyl triaromatics. These are the compounds from which benzyl radicals are easily formed. These inhibitors are added prior to adding the hydrocarbon and they form an inert coke layer to prevent coke growth. They are added in 100ppm to 10% of the carrier. The problem with is that this procedure does not deal with the change separation process at the later stages due to a modified feed.

Metallurgy:

In this we modify the composition of the coil so as to change there properties making them more temperature resistant and more coke repellant.

ET45 Micro (45Ni/35Cr Micro):

In this alloy protective and dense, strongly adhering oxide layers of chromium oxide is formed which prevents the deposition of coke filaments from catalytic coke.The problem with this is if the tube metal temperatures exceed 1050°C, as the Chromium oxide is converted under high carbon activity into non-protective scales.

Centralloy 60 HT:

The new alloy Centralloy 60 HT is a cast nickel base alloy containing about 60 weight% Nickel, 25 to 30 weight% Chromium, 2 to 5 weight% Aluminum plus additions of Niobium, Titanium and other minor alloying

21

elements. Aluminum additions lead to the generation of - compared to Chromium oxide – a thermodynamically more stable Aluminum oxide layer which is formed at relatively low oxygen partial pressures and is stable over a wide range of temperatures

This alloy is sold by the company Schimdt-Clemens

Surface treatment:

ANK400:

Based on novel surface chemistry and technology: Spinels having composition of MnxCr3-xO4 are desired on the urface layer. Simultaneously Fe and Ni atoms migrate inward forming a sublayer enriched in these two elements.

Very stable and very inert to total coke production. Demonstrates longer run length

22

Advantages:

Increased and sustained on-stream time Lower pressure build-up More linear temperature profiles Reduction in coke formation and spalling in coil and TLE Less carburization Reduced CO production and start-of-run CO spikes Better heat transfer to the process gases

Disadvantages:

High cost For optimum results, need to apply ANK 400 to whole furnace.

23

Recommendation

On analyzing all the commercially available Anti-Coking technologies, it is recommended that ANK-400 is the best possible option as it provides longer run length and is stable at higher temperatures relevant to this cracking furnace, as compared to the other alternatives.

Project 2:

Determining the cause of lower efficiency and below par

performance of C2R compressor compared to design data.

The products of cracking have to separated to get the desired products this is achieved through distillation, which requires chilling. This chilling is provided through two refrigeration systems – C2R (ethylene refrigeration system) which provides chilling upto – 100 C and C3R (propylene refrigeration system) which provides chilling upto – 40 C.

This refrigeration is provided by Joule -Thompson effect by sudden decrease in pressure of the gas in various vessels. Ethylene is initially compressed up to 27 kg/cm2 and then slowly depressurized to .01 kg/cm2 in 4 stages with final stage providing chilling up to -100 C and other stages provide temperature of -84.4 C, -67.8 C, -48.8 C. Compression is done through centrifugal 4 stage compressor.

The following are the ethylene refrigerant users :

10-E-65 Demethaniser precooler no. 5 -100 C 0.2 kg/cm2

10-E-82 Demethaniser O/H condensor

-100 C 0.2 kg/cm2

10-E-168 Ethylene Prod. Chiller no.3 -100 C 0.2 kg/cm2

10-E-64 Demethaniser precooler no. 4 - 84.4 C 1.8 kg/cm2

10-E-167 Ethylene Prod. Chiller no.2 -84.4 C 1.8 kg/cm2

10-E-63 Demethaniser precooler no. 3 - 67.8 C 4.8 kg/cm2

10-E-166 Ethylene Prod. Chiller no.1 -67.8C 4.8 kg/cm2

24

10-E-62 Demethaniser precooler no. 2 -48.3 C 10.4 kg/cm2

10-E-77 Demethaniser reflux cycle - 38.9 C 28.0 kg/cm2

Centrifugal Compressor

The machine in which pressure and velocity are provided to the air or gas in the radial direction by one or more impeller is called a centrifugal compressor.

25

Calculating Compressor Efficiency

C2R compressor has four stages & each stage has individual suction and discharge. Hence polytropic efficiency and power of individual stage can be calculated separately. Summation of all stage power gives the toal compressor power. Then compressor shaft power is calculated using mechanical efficiency of 98 %.

In Cracked gas turbine , the exhaust side is having some wetness in it. (Normal design is about 88 % ). So the exhaust enthalpy needs to be back calculated from compressor power. Cracked gas turbine power delivered is calculated using a mechanical efficiency of 98 % in turbine side.Then from enthalpy balance actual exhaust enthalpy can be calculated.

In C2R machine since there is no discharge in between polytropic efficiency needs to be calculated for the entire unit. This needs to be calculated by iterative calculation.

Cracked Gas Compressor

26

First stage

Inler pressure = P1 Kg/cm2a

Outlet pressure = P2 Kg/cm2a

Inlet temperature = T1 Degree Kelvin

Outlet temperature = T2 K

ln P2/P1

n = ln P2/P1 - ln T2/T1

n/(n-1) *100 Polytropic Efficiency -% = kavg//(kavg-1)

kavg is to be calculated for the average condition of inlet & outlet.

Normally CG first stage suction hydrocarbon analysis is available, which

needs to be corrected for saturated water in suction.

(n-1)/n

Polytropic head in KJ/Kg = n* Z avg *R* T1 [ ( P2/P1 ) -1 ]

( n-1) * MW

Anomaly

27

The compressor has been underperforming as can be seen by discrepancy in design and actual data in above table.

Even at the higher RPM it is operating at lower load and providing lower discharge pressures.

The anomaly to observe here is that though the compressor should have surged under these conditions due to lower flow rate as can be seen from the graph shown below but that is not happening. So it means that inside the compressor there must be more flow rate than we are observing outside. It means that there is some kind of internal circulation happening with the compressor because of which it is operating at lower efficiency.

28

Recommendation

After going through all the data available to us and calculating the intermediate temperatures we found out that the intermediate temperatures of different stages in C2R are well above their design conditions. This can be understood from the fact that the compressor is working at lower efficiency. Although the lower efficiency seem to be due to some mechanical problems within the compressor and nothing related to the process. One solution to increase the efficiency we would like to suggest is to increase the load of the latter stages simultaneously decreasing the load of initial stages keeping the overall heat load same. This will increase the overall efficiency as the gases have to be compressed in shorter range and the intermediate temperatures will also decrease coming closer to the design conditions.

29

REFERENCES:

1) PLANT OPERATING MANUAL

2) PROCESS FLOW DIAGRAMS (PFDs)

3) PIPING & INSTRUMENTATION DIAGRAM (P& IDs)

4) DATA SHEETS

5) PERRY’S CHEMICAL ENGINEERS’ HANDBOOK- SEVENTH EDITION

30