Internship Report at SCIL

Internship Report Caustic Soda Plant Sitara Chemical Industries Limited (SCIL) th

th

Training Period (8 June 2010 - 5 July, 2010) (Duration: 4 weeks)

By: Sajjad Rasool Chaudhry (M08-PG12) Ahtisham Arshad (M08-PG16) th 6 Semester B.Sc. Chemical Engineering

Institute of Chemical Engineering & Technology, University of the Punjab Lahore

Internship Report (SCIL)

Acknowledgments We are thankful to the Institute of Chemical Engineering & Technology, University of the Punjab, and Sitara Chemical Industries Limited for providing us such a marvelous and informative professional training program. We are thankful to Dr. Ayyaz Muhammad (Incharge Internship Program, ICET, PU). After that we are also very thankful to Mr. Saeed Akhter (DGM Prod. Area-I)Mr. Muhammad Yousaf (DM Prod. Area-I), Mr. Muhammad Saleem (DPM Prod Area-I), Mr. Faheem Ahmed (Senior Manager ISO) for their kindness and complete guidance throughout our training period. It will also be our pleasure to say thanks to Mr. Sheikh Imran (Tr. Engineer), Mr. Ahmed Waqas (Tr. Engineer), Mr. Zaman Ahmed (Tr. Engineer), Mr. Sharjeel (Tr. Engineer), and Mr. Ahsan Mushtaq (Tr. Engineer) for their friendly behavior and time to time guidance. And at the end, special thanks to Mr. Ramzan (Senior Superindent) and all plant operators for their help and cooperation. coope ration.

Page 2 of 48

Institute of Chemical Engineering & Technology, Punjab University, Lahore

Internship Report (SCIL) TABLE OF CONTENTS

Ch. 1 Company Profile 1.1 Introduction 1.2 Company’s Mission statement 1.3 Achievements 1.4 Safety & Environment Management 1.5 Corporate social responsibilities responsibi lities Ch. 2 Caustic soda plant 2.1 Primary brine section PFD of Primary brine section 2.2 Secondary brine section PFD of secondary brine section 2.3 Cell room PFD of cell room 2.4 Dechlorination 2.5 Evaporation unit PFD of evaporation 2.6 Caustic solidification solidificat ion plant (CSP) Block diagram of CSP Ch. 3 Utilities and protective equipments 3.1 Utilities 3.2 Personal protective equipments (PPEs) Ch. 4 Product Details 4.1 Ammonium chloride 4.2 Carbon dioxide gas 4.3 Bleaching powder 4.4 Calcium chloride 4.5 Liquid Caustic soda (33%) 4.6 Liquid Caustic soda (50%) 4.7 Caustic soda flakes Summary

PAGE NO.

4 4 4 4 5 5 7 8 12 18 23 24 28 29 32 34(b) 35 39 40 40 41 42 42 42 43 44 45 46 47 48

Page 3 of 48


Internship Report (SCIL) Chapter # 1

Company Profile 1.1 Introduction:Sitara Group of Industries is one of the renowned industrial groups of Pakistan. This group started its industrial activity with textile weaving sector in 1956. Sitara Group by now is in textile cloth finishing and processing, textile spinning, chlor alkali industries and power plant.

The chemical production unit of Sitara Group of Industries is known as Sitara Chemical Industries Limited (SCIL). It is situated at 32 km, sheikhupura road, Faisalabad. It was incorporated in 1981 and began producing caustic soda in 1985, initially at a rate of 30 metric tons per day. The plant’s capacity was gradually increased over years to current level of 545 metric tons per day. In addition, various by-product facilities have been added and expanded from time to time to cope with growing demand. Its specialty chemicals and export division was established in 2001 and agri chemicals division in 2003. Besides manufacturing Caustic Soda and various allied chemicals, the company has been able to set up independent plants of some more gases i.e. Oxygen (O 2), Nitrogen (N2), Carbon Dioxide (CO2), Nitrous Oxide (N2O) in the same premises, during last one and half year. 1.2 Company’s Mission Statement:“We believe in stimulating and challenging team oriented work environment that encourages, develops and rewards excellence and diligently serve communities, maintaining high standards of moral and ethical values. We strive to develop and employ innovative technological solutions to add value to business with progressive and proactive approach. As well as work hard for continuing growth and diversification for bottom line results with risks well contained” 1.3 Achievements:Three times winner-Top 25 Companies Corporate Excellence Award by Karachi Stock Exchange. •

•

•

Winner of Corporate Excellence Award of Management Association of Pakistan year 2000 Sitara Chemicals stand amongst top 10 plants of the world based on Denora, Italy, mercury free, membrane technology. Also acquired state of art technology from M / s. Asahi Kasei Japan.

•

Certified ISO-9001: 2008

•

Certified EN14001:2004

Page 4 of 48


Internship Report (SCIL) 1.4 Safety & Environment Management:SCIL is a very much responsible organization. It cares greatly for the environment as well satisfaction of its customers. For this reason they have adapted almost all national and international quality and environment safety policies. QUALITY POLICY :

“Sitara Chemical Industries Ltd. is committed to remain alert and advance, to continuously grow as a Quality Symbol for its products and in meeting industrial and consumer requirements, through training, team work, and procedures, on time, every time.” ENVIRONMENTAL POLICY:

“Sitara Chemical Industries Ltd. is committed to continual improvement of its Environmental Management System (EMS) by adoption of appropriate pollution prevention measures and complying with all relevant training, teamwork and procedures as implemented from time to time. In actual words, SCIL has well developed and recognized Quality Management Systems as well as Environmental Management Systems. SCIL has following certifications in QMS and EMS from SGS under the authority of UKAS Quality Management. •

ISO 9001:2008

ISO 14001:2004 1.5 Corporate Social Responsibilities (CSR):•

For Professional & Industrial growth, training plays an imperative & optimistic role in today’s competitive and rapidly changing work environment. Employee’s development & grooming become more critical & essential for which importance of training & development cannot be denied, as it is a proactive process leading towards building the competencies and capabilities of employees. SCIL is a socially responsible organization. They are investing in healthcare and skills development of their people and peoples of the area as well as education of best of the brains. This industry is well acknowledged for its contribution to socio-economic uplift of the region and strengthening social safety nets. They value their workforce as the most integral part of the organization. A brief discussion on different projects of social welfare run by SCIL is given in the following lines. 1.5.1

Human Development Center:-

SCIL has introduced numerous tools to train, re-train/upgrade their people. In this context, a Human Development Center has been established at Sitara Chemical Industries Ltd where Page 5 of 48


Internship Report (SCIL) internal training sessions are held regularly. The renowned trainers are also called at the center to impart training in the fields of technical, supervisory and management skills. In continuation to its existing training & development activities, the management of SCIL has broadened its internal training activities for fresh graduates and plant workforce in order to make them ready to face the challenges of future and for their career growth. In this perspective, the Senior Executive’s lectures and discussion sessions are being arranged for the fresh graduates & middle management employees. Academic & on job training (OJT) of plant operators and supervisors is being conducted by Senior Manager Training of the company. 1.5.2

Aziz Fatimah Hospital:-

Aziz Fatimah Hospital is the brain child of SCIL and is a welfare wing of sitara group for the people of Faisalabad. The hospital was established in 1979 by the group elders and was inaugurated by, the then, president of Pakistan General Muhammad Zia-ul-Haq. 1.5.3

Sitara Institute of Management & Technology:-

SCIL is not only remaining alert and advance as symbol of its products, but is also very much conscious to the rising need of keeping pace with Technology and Management Sciences. To achieve this potential of Technical & Managerial skills as a key contributor to socioeconomic and educational development, Hence Sitara Group of Industries has established its own institute, which would not only take hold requirement of industries in Faisalabad but will contribute in other nation building projects as well. Thus with this vision, SIMT came into being under Aziz Fatima Trust (Education Wing) as one of the welfare projects. 1.5.4

Aziz Fatimah Girls High School

SCIL has also established a girl’s school for quality education. This school is situated in Gulshan-e-Iqbal to provide quality education at doorstep to the girls residing in this area. It has highly qualified and trained teachers. School has just started its first educational year.

Page 6 of 48



Caustic Soda Plant Although SCIL is manufacturing many important chemicals such as Ammonium Chloride (NH4Cl), Bleaching Powder (Ca(OCl) 2), Chelated Iron, Clorinated Parafin Oil, Hydrochloric acid (HCl), Ferric Chloride (FeCl 3), Ferric Sulphate (Fe 2(SO4)3) etc. But their main product is Caustic Soda (NaOH) chemically known as Sodium Hydroxide. SCIL is selling caustic Soda in three forms: (1) 33% liquid Caustic Soda, (2) 50 % liquid Caustic Soda and (3) 98.5 % caustic flakes Sitara Chemical Industries is manufacturing caustic soda (NaOH) by electrolysis of brine solution. Process is carried out in membrane cells equipped with latest technology. At time, SCIL has three caustic manufacturing plants in working, named as BMR, M-I and M-III. Another plant M-II is being established and is almost in final stages. Overall caustic production of SCIL is 545 MTD with 210 MTD contributed by BMR. Since, our internship program was conducted at BMR; therefore in the following lines we will have detailed discussion of all unit operations and unit processes taking place in the cycle of production of Caustic Soda. Very first step in the production of caustic is the preparation of brine solution from Rock Salt. Rock salt is obtained from Khushab. Since this saturated brine solution contains impurities which can scale within pipelines and other equipment and also damage the electrolyzer membrane, therefore various techniques are employed to filter and purify this brine solution. After necessary preliminary treatments, ultra pure brine solution is sent to the cell room where electrolysis is carried out. Two by products Hydrogen and Chlorine are formed along with caustic soda. The production cycle of NaOH goes through the following series of steps. •

Primary Brine Section This section involves saturation of brine solution, its purification by settling after treatment with certain regents and primary filtration by pressure filters.

•

•

Secondary Brine Section In this section, brine coming from primary brine section is filtered by resins to remove any remaining impurities which may cause damage to membranes of the electrolyzer. De-chlorination Unit Here de-chlorination and other preliminary treatments of depleted brine coming from cell room are carried out before sending it to primary brine section.

Page 7 of 48



•

•

Evaporation Unit Caustic soda obtained from cell room has a concentration of 32 % w/w. in evaporation unit; this concentration is raised to 50 %. Caustic Solidification Plant( CSP) In this section, caustic soda from evaporation unit is concentrated upto 98.5% and solidified for packing in bags and drums.

In next lines is the detailed discussion on each section along with complete description of all unit operations and unit processes involved.

2.1 PRIMARY BRINE SECTION 2.1.1

INTRODUCTION Primary brine section involves three types of activities

•

Brine saturation

•

Brine purification and settling

•

Brine filtration

Main purpose of the brine processing is to resaturate the depleted brine coming from the electrolyzer, by adding the quantity of salt which has been electrolyzed. The impurities which has been introduced in the brine together with the salt are to be removed first by settling and then by chemical treatment and settling. The suspended impurities are removed by filtration 2.1.2

Process Description:-

In this section de-chlorinated depleted brine coming from cell room after electrolysis is concentrated and purified by sedimentation and filtration. After electrolysis, concentration of brine decreases to 180-200 g/l. so it is sent to saturators (DS-5010 A/B) where it is concentrated to 300-310 g/l. The flow rate of the depleted brine is 80m3/hr. Two saturators are present at BMR one in process and one at standby. Saturators are made of concrete, reinforced with steel and internally epoxy lined. Depleted brine is introduced with the help of five nozzles installed at the bottom of each saturator. Saturator is filled with lumps of Rock Salt with the help of tractor blades from salt yard. Water percolates through the salt lumps dissolving the salt in it and over flows in separate overflow line. Makeup de-mineralized water is also fed through a pipeline to cover water losses and maintain the required flow rate. The level of the salt in the brine saturator is kept as constant as possible by feeding salt in the saturator at required rate. The raw salt impurities such as Ca and magnesium salt are dissolved in the depleted brine faster as compared to sodium chloride, so that if excessive amount of salt is loaded into the saturator, the impurities content in the saturated brine would be higher than the normal. Page 8 of 48


Internship Report (SCIL) Follow rate is maintained so that the desired concentration is obtained. If concentration is much higher, salt may crystallize in pipelines, reactors or tanks in cold seasons. When saturator is exhausted (filled with sludge), flow is shifted to second saturator and first one is subjected to cleaning. After concentration brine many suspended and dissolved impurities which are necessary to be remove. Approximate composition of Rock Salt and impurities associated with it are as given below: NaCl ---------------------------------------------------------- 97% w/w +2

Ca -------------------------------------------------------------021%w/w Mg+2------------------------------------------------------------0.06% w/w SO4--------------------------------------------------------------0.9% w/w +

K ---------------------------------------------------------------0.17% w/w Sr----------------------------------------------------------------1.0 ppm SiO2-------------------------------------------------------------5.0 ppm Al ---------------------------------------------------------------0.2 ppm Fe ---------------------------------------------------------------1.0 ppm Mn --------------------------------------------------------------0.5 ppm Ni----------------------------------------------------------------0.05 ppm I -----------------------------------------------------------------0.5 ppm F ----------------------------------------------------------------1.0 ppm Cr, Mo, V------------------------------------------------------0.5 ppm Insolubles -----------------------------------------------------0.69% w/w Moisture-------------------------------------------------------0.97% w/w

So in order to remove these impurities, brine is treated with Calcium Chloride CaCl 2. For this purpose brine coming out of saturator is collected in Brine Collecting Tank (D-510) from where almost 40% of it is sent to CaCl2 pits while 60% overflows from tank to the Settling Pits (D-5610 A/B). Settling pits are working alternatively i.e. one in process and one at standby. Insoluble and suspended impurities are settled down settling pits and brine overflows to the next pit known as Common Pit (D5620). In CaCl2 pits, CaCl2 in the form of solution is infused to maintain 3000-4500 ppm of Ca++ in excess. The CaCl2 pit is made ready twice in a day and transferred in the common pit D-5620. CaCl2 pit is made ready to transfer in 6-8 hrs .CaCl2 which is infused has sp. Gravity 1.1-1.2 and pH in range of 6-9. From the settling pit, the brine over flows into the common pit D-5620 where it is mixed with the brine coming from the CaCl2 pit. From common pit brine is pumped to the first Reactor (R-5020 A) . The flow rate is 105110m3/hr. In this reactor brine is treated with 8% Barium Carbonate solution to remove any left Page 9 of 48


Internship Report (SCIL) over sulphates. After reactor, brine flows to the first Settler (TH- 5010 A) . This settler has a 3 capacity of 1800 m and its material of construction (MOC) is RLS (rubber lined steel). Suspended impurities settle down at the conical bottom of settler and are removed through a drain valve and screw pump by a slow moving rack. Rack rotates at a speed of 0.1 RPH. Nalco solution prepared in tank D-5310A/B is dosed at controlled rate. The amount of flocculants, Nalco, is maintained at 1-2 ppm. Brine over flows from the settler and is collected in a Tank D-515. From D-515, brine is pumped to the second Reactor (R-5020 B) where it is treated with 8% solution of Soda Ash +2 +2 (Na2CO3) and Caustic Soda in order to remove Ca and Mg . Both reactors are equipped with agitators for intimate mixing to facilitate reaction and to avoid settling of insoluble compounds formed, within the reactor instead of settler. After second reactor, brine solution flows by gravity 3 to the second Settler (TH-5010 B) . This settler has a capacity of 2630 m . Flocculent (Nalco) is also added in the settler. This settler is also equipped with a slow moving rake at the bottom to drain settled sludge through a drain valve. This sludge is collected in two Brine Recovery Pits (D-5710 A/B) where any brine which was drained previously with sludge and is sent to Common Pit. From second settler brine overflows to the Pre-filtered storage tanks (D-5060 A/B) . From tanks D-5060 A/B, brine solution is fed to six Pressure Leaf Filters (F-5070 A-F) in parallel manner. Brine filters are required to remove the suspended solids overflowing with the brine from the settler TH-5010B. There are six leaf filters F5070A-F operating in parallel, five normally in operation and one in standby. Brine from tank D-5060 A/B is pumped and distributed to each filter through individual manual valves, before proceeding to the filtration the filters must be pre-coated. For pre-coating, the pre-coat slurry is prepared in the tank D-5100. The pre-coat material Arbocel is thoroughly dispersed in the filtered brine. The end of the filtering cycle is indicated by the pressure drop in the filter .When the filter reaches the maximum operating pressure, the filter must be cleaned. The pressure across the filter should not exceed 3 bars. Filters contain 17 leaves each and total filtering surface of 2 each filter is 38.2 m . Casings of all filters are made HRLS (hard rubber lined steel) and filtering cloth is of FRP (fiber reinforced plastic). 3

Filtered brine comes out of each filter at a flow rate of 18-20 m /hr and is fed to two Guard Filters (F-5080 A/B) which stops the Arbocel fibers eventually released by pressure leaf 2 filters. These guard filters are of basket type with a total filtering of 2.78 m for each filter. Casing of the filters is made of HRLS (hard rubber lined steel) and filtering cloth is of PP (Polypropylene). Sequence is so that one filters in process and one is at standby. From these guard filters, brine is sent to two Storage Tanks (D-5070 A/B) . From storage tanks, brine is pumped to Secondary Brine section after raising its temperature to 55 C by using a plate type Heat Exchanger (E-5070) . Material of construction of Page 10 of 48


Internship Report (SCIL) the heat exchanger is titanium and its heat duty is 905.0 k Cal/hr. Here low pressure steam and cooling water connections are provided to allow the brine heating or cooling in order to control o the temperature of the brine at 50-60 C. At the end of Primary section, brine has following proportion of impurities in it. +2

•

Ca

•

Mg

+2

----------------------------- 8 ppm (maximum) ----------------------------- 1.92-2 ppm (maximum)

Sulphates (SO 4) -------------- 10 g/l Reactions Involved in Primary Section:•

2.1.3 Sulphates

These are precipitated as barium sulphate by reaction with barium carbonate in 1 reactor R-5020 A. Na2SO4 +

BaCO3

BaSO4 +

st

Na2CO3

Calcium This is precipitated as calcium carbonate by reaction with sodium carbonate in 2 reactor R-5020 B. CaCl2 + Na2CO3

nd

CaCO3 + 2NaCl

Magnesium This is precipitated as magnesium hydroxide by reaction with caustic soda in 2 reactor R-5020 B. MgCl2 + 2NaOH

nd

Mg(OH)2 + 2NaCl

Strontium, This is precipitated mainly as strontium carbonate Sr

++

+ CO3

--

SrCO3

Most of the sulphates in the brine are being removed by treating with calcium chloride. Hence the consumption of barium carbonate is controlled. BaCO3 is an imported commodity and is very costly, where as calcium chloride is a waste produced in HCl neutralization pits. Another advantage is that Calcium sulphate, which is precipitated out, is a good fertilizer where as barium sulphate is dangerous to water bodies and soil.

Page 11 of 48



Page 12 of 48


Internship Report (SCIL) 2.1.4

Equipment Details:-

Tanks, Mixers and Reactors:SATURATOR DS-5010A/B 3

Capacity

312 m

Dimension

6000*8000*2000

M.O.C

Concrete Epoxy Lined

SETTLING PITS D-5610A/B 3

Capacity

280 m

Dimension

7000 * 20000 * 2000

M.O.C


COMMON PIT D5620 3

Capacity

138 m

Dimension

6000 * 11500 * 2000

M.O.C


CALCIUM CHLORIDE PITSA/B/C 3

Capacity

700 m

Dimension

7000 * 40000 * 2500

M.O.C


BRINE RECOVERY PIT D-5710A/B 3

Capacity

256 m

Dimension

8000 * 16000 * 2000

M.O.C


REACTOR R-5020 3

Capacity

50 m

Diameter

3800mm

Height/Depth

4400mm

M.O.C

RLS (Rubber lined Steel) Page 13 of 48


Internship Report (SCIL) TANK D-515 3

Capacity

15 m

Diameter

2000mm

Height/Depth

4500mm

M.O.C

RLS

SETTLER TH 5010A 3

Capacity

50m

Diameter

22000mm

Height/Depth

4500mm

M.O.C

RLS

SETTLER TH 5010B 3

Capacity

2630m

Diameter

26000mm

Height/Depth

4500mm

M.O.C

RLS

TANK D-5060A/B (STORAGE) 3

Capacity

75m

Diameter

3000mm

Height/Depth

11170mm

M.O.C

FRP (Fiber Reinforced Plastic)

TANK D-5070 A/B (STORAGE) 3

Capacity

75m

Diameter

3000mm

Height/Depth

11170mm

M.O.C

FRP Page 14 of 48


Internship Report (SCIL) TANK D-5200A/B (Sodium Carbonate) 3

Capacity

10m

Diameter

2000mm

Height/Depth

3440mm

M.O.C

FRP

TANK D-5210A/B (Barium Carbonate) 3

Capacity

20m

Diameter

2800mm

Height/Depth

3200mm

M.O.C

FRP

TANK D-5310A/B (Nalco) 3

Capacity

10m

Diameter

2000mm

Height/Depth

3050mm

M.O.C

FRP

TANK D-5100(Pre-coat) 3

Capacity

4m

Diameter

1500 mm

Height/Depth

2390mm

M.O.C

RLS

Pumps and Related Motors:P-5610A/B (common Pit Pump)

MOTOR

Type

Cent

Volute size

5*4

Flow rate

120 m /hr

RPM

2900

TDH

20 m

R.kw

15

MOC

Titanium

R.Amp

26

3

Page 15 of 48


Internship Report (SCIL) P-5060A/B (Pre-filtered Brine)

MOTOR

Type

Cent

Volute size

4*3

Flow rate

125 m /hr

RPM

2900

TDH

50 m

R.kw

37

MOC

SS

R.Amp

68

Type

Cent

MOTOR

Volute size

4*3

Flow rate

90 m /hr

RPM

2900

TDH

50 m

R.kw

37

MOC

SS

R.Amp

68

3

P-5070A/B (Filtered Brine)

3

P-5080/B (Resin Regeneration)

MOTOR

Type

Cent

Volute size

4*3

Flow rate

80 m /hr

RPM

2900

TDH

25 m

R.kw

15

MOC

SS

R.Amp

26

Type

Cent

MOTOR

Volute size

3*1.5

Flow rate

50 m /hr

RPM

2900

TDH

25 m

R.kw

5.5

MOC

SS

R.Amp

11

3

P-5100A/B (Precoat)

3

Page 16 of 48


Internship Report (SCIL) P-5200A/B (Sod. Carbonate)

MOTOR

Type

Cent

Volute size

1.5*1

Flow rate

10 m /hr

RPM

2900

TDH

20 m

R.kw

3.7

MOC

SS

R.Amp

6.5

3

P-5210A/B (Barium Carbonate )

MOTOR

Type

Cent

Volute size

1.5*1

Flow rate

10 m /hr

RPM

2900

MOC

SS

R.Amp

6.5

`Type

Cent

MOTOR

Volute size

2*1.5

Flow rate

0.7 m /hr

RPM

2900

TDH

20m

R.kw

3

MOC

SI

R.Amp

5.2

3

P-5310A/B (Nalco)

3

P-515A/B (Reactor 5020 B Supply)

MOTOR

Type

Cent

Volute size

5*4

Flow rate

120 m /hr

RPM

2900

TDH

20 m

R.kw

3.6

MOC

SS

R.Amp

6.5

3

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Internship Report (SCIL) P-5710A/B (Brine Recovery)

MOTOR

Type

Cent

Volute size

2*1.5

Flow rate

120 m /hr

RPM

2900

TDH

20m

R.kw

3.7

MOC

SS

R.Amp

6.5

3

Calcium Chloride Pits (Transfer Pump)

MOTOR

Type

Cent

Volute size

5*4

Flow rate

120 m3/hr

RPM

2900

TDH

20m

R.kw

18.6

MOC

SS

R.Amp

33

Calcium Chloride pits ( Circulation Pump)A/B

MOTOR

Type

Cent

Volute size

5*4

Flow rate

120 m /hr

RPM

2900

TDH

20m

R.kw

18.5A/15B

MOC

SS

R.Amp

33A/29B

3

2.2 SECONDARY BRINE 2.2.1

Nature of Ion Exchange Resin:-

Ion exchange resins are based on solid insoluble polymers supplied in the form of beads, which have fixed active ionic groups. Mobile ions of opposite charge can be exchanged reversibly and stoichiometercally for ions of the same charge present in the solution. ++

++

The resin being used TP-260 has Na ions as mobile ions and exchange with Ca & Mg ++ ++ present in the brine. When most of the Na+ has been exchanged with Ca &Mg , the bed is exhausted and needs to be regenerated. The exhausted column is taken out of the stream and the other two are remained in operation. TP-260 has weak acidic chelating amino methyl phosphonic

Page 18 of 48


Internship Report (SCIL) acid groups which form stable complexes with a number of transition metals and main group elements. 2.2.2


Before feeding brine to electolyzers it is passed through ion exchange resin towers C++, ++ ++ 5040 A/B/C placed in series in order to absorb Ca Mg and Sr contained in brine. The brine feeding to the resin tower has following typical specifications NaCl

290-310g/l

Na2SO4

7-8g/l

NaClO3

15g/l

Ca++

4-6ppm

Mg++

1-2ppm

Sr++

1 ppm max

SiO2

5 ppm max

Cl2

Nil

Suspended solids

0.5ppm

Temperature

50-6 C

PH

9-10

o

The resin bed in the tower stayed on a grid plate. The spargers are fitted on this plate. The purified brine from tank D-5070 is fed in the tower through P-5070A/B at a flow rate of 105-110 m3/hr. As the towers are connected in series, so the brine is fed in the first tower in the series and ultra purified brine is collected from the discharge of the third tower and collected in Ultra Pure Brine Tank (D-5160) . From D-5160 brine is pumped to Brine Head Tank (06D-001) . Then it is sent to the cell room after controlling its temperature through two Heat Exchangers (06E-001) and (06E-002) . 2.2.3

Regeneration of the Resin Bed:-

The chemical nature of the resin functional group is suitable to form complex compounds with a lot of metal ions. The resin at the beginning of the operating cycle is in the sodic form. During the operation it fixes Ca++ & Mg++ to which it has a high affinity, and releases Na+. When the resin is exhausted, means when it has absorb max. Ca & Mg ions, it must be reconverted in the sodic form. This process is referred to as “resin regeneration”. Page 19 of 48


Internship Report (SCIL) The regeneration process requires a sequence of different operations. The most significant of which are a treatment with diluted HCl which displaces the metal ions previously fixed by the resin functional groups followed by a treatment with diluted NaOH solution which makes the resin to change form the acidic form to the sodic form i-e H+ replaced with Na+ STEPS INVOLVE IN THE REGENERATION PROCESS

1. Brine drainage (half empty) 2. Washing with demi water 3. Counter washing with demi water 4. Drainage 5. Washing with 4% HCl solution 6. Drainage 7. Washing with demi water 8. Drainage 9. Counter washing with 5% NaOH solution 10. Drainage 11. Washing with demi water 12. Drainage 13. Water replacement with brine 14. Filling with brine After regeneration resetting is done almost in 60 minutes and brine is circulated between resin towers and brine tanks D-5070. The circulation of brine remains on till the required results of Ca & Mg are achieved. Then the column is taken in operation and placed in the last in series. Some Important points:•

•

•

•

•

•

Resin washing with water has the purpose of removing the brine from the tower and counter washing is done to remove the brine trapped in the resin bed. Brine must be removed completely because the chlorates possibly present in the brine could decompose during the acid washing and give free chlorine, which oxidizes the resin with an increase in resin consumption. During washing with HCl real regeneration of the resin bed is occurred. The metal ions attached by the resin are displaced and the resin is converted into the acidic form. After washing with HCl, the bed is again washed with water in order to reduce the consumption of the caustic soda and to fully remove HCl in the column. The more important is to avoid the possible damage of the resin particles due to heat evolved in the reaction between acid and caustic soda. During the washing with caustic soda, the resin is converted from the acidic form to the + + sodic form. i.e. H replaced with Na Before filling brine in the regenerated column it is emptied so that the conc. of the brine remained within the range, otherwise it may be lowered. Page 20 of 48



2.2.4 Chemical Reaction Involved:Chemical reactions involved in secondary purification and regeneration of resin towers are as given below. BRINE PURIFICATION

Na2(Resin) + Ca

++

Na2(Resin) + Mg

Ca(Resin) + 2 Na

++

+

Mg(Resin) + 2 Na

+

RESIN REGENERATION ++

Ca(Resin) + HCl

H2(Resin) + Ca

Mg(Resin) + HCl

H2(Resin) + Mg

H2(Resin) + NaOH

Na2(Resin) + H2O

2.2.5

++

(Washing by HCl) (Washing by HCl) (Washing by NaOH)

Equipment Details:-

RESIN TOWERS TOWER

RESIN BED

Capacity

13m

3

Volume

4m

Diameter

1900mm

Diameter

1900mm

Height

4600mm

Height

1410mm

MOC

HRLS

No. Of Sparger MOC Openings

3

249 Haste Alloy 0.2mm

TANKS TANK D-5130 (5% NaOH) 3 Capacity 40 m Dia 3000 mm Heights 6190 mm MOC PP-R TANK D-5140 (4% HCl) 3 Capacity 30 m Dia 3000 mm Height 4770 mm MOC FRP TANK D-5150A/B (Effluents) 3 Capacity 75 m Dia 3000 mm Height 11170 mm MOC FRP Page 21 of 48


Internship Report (SCIL) TANK D-5160(ULTRA PURE BRINE) 3 Capacity 75 m Dia 3000 mm Height 11170 mm MOC FRP PUMPS AND RELATED MOTORS P-5130A/B(5%. NaOH) PUMP Type Centrifugal 3 F.Rate 20 m /hr TDH 25 m MOC SS Volute 1.5*1.0 Impeller 5 P-5140A/B(4%. HCl) PUMP Type Centrifugal 3 F.Rate 30 m /hr TDH 25 m MOC FRP Volute 2*1.5 Impeller 5 P-5150A (Effluents) PUMP Type Centrifugal 3 F.Rate 15 m /hr TDH 25 m MOC FRP Volute 1.5*1.0 Impeller 8 P-5150B (Effluents) PUMP Type Centrifugal 3 F.Rate 20 m /hr TDH 25 m MOC SS Volute 1.5*1.0 Impeller 5 P-5160A/B PUMP Type Centrifugal 3 F.Rate 90 m /hr TDH 35 m MOC Titanium

MOTOR Capacity Rated Amp. RPM

5.0 kW 9.8 A 2900


5.5 kW 10.8 A 2900


5.0kW 10.0 A 2900


5.0 kW 10.0 A 2900


15.0 kW 28.5 A 2900

Page 22 of 48



Page 23 of 48



2.3 CELL ROOM 2.3.1

Electrolyzer:-

The equipment used to carry the process of electrolysis is called electrolyzer. The cell room comprises of three electrolyzers A/B/C placed in parallel fashion. Each electrolyzer has capacity of 164 cells. At present electrolyzer A has 162, electrolyzer B has 161 and electrolyzer C has 162 elements. Each element acts as an electrolyzer individually. Each element consists of anode and cathode compartments separated by a membrane. Anodic side is made of titanium while cathodic side is made of nickel. The ion exchange membrane is clamped between the half shells with interposed PTFE gaskets. The half shells are bolted together at the flange, thus constituting a cell element. The ion exchange membrane is made by an organic polymeric matrix incorporating fixed ionic groups neutralized by mobile ions of opposite charge. Fixed group are sulphonic type or carboxylic type, while mobile counter ion is sodium ion. Only the cation exchange selectivity of the membrane can prevent migration of OH-. The flow of Cl across the membrane is about negligible, because membrane selectivity and electric field across the membrane opposes the chloride ions transport. The raw material feeding to the electrolyzer is brine. The brine nearly saturated, is introduced into the anode compartment of the cell. The aqueous solution in this compartment is called anolyte. The membrane separates the anolyte from the catholyte compartment. 32% caustic soda from catholyte tank plus Demineralized water to make a 29-30% caustic solution is admitted to catholyte compartment where sodium hydroxide is formed by the combination of hydroxyl ions and sodium ions, which migrate through the membrane to the cathode. Chlorine gas, usually called cell gas, is formed at the anode while Hydrogen gas and sodium hydroxide are formed at the cathode. 2.3.2


Ultra pure brine is stored in tank D-5160 and pumped via P-5160A/B into over head feed brine tank. 06D001. Brine enters in the overhead tank from the top and over flows by gravity from the top side back in D-5160 . The outlet is from the bottom of the tank and leads to cell room by gravity. The brine is heated in the way before entering cell room through heat exchanger 06E001 to raise its temperature up to 65-75 C. It is a plate type heat exchanger. Heat exchanger is provided with steam as well as cooling water connections. There is also a stand by heat exchanger 06E002 which is either used to fill a single electrolyzer or in case of emergency. In the cell room main feed brine line has three connections to feed each of the three electrolyzers. These supply lines are underneath of each electrolyzer. Brine is fed in the anodic compartment of each cell.

Page 24 of 48


Internship Report (SCIL) Catholyte (33% NaOH) is stored in the storage tank 31D002. Its temperature is about 8085 C. It is cooled in 31E001 before transferred in overhead tank 31D001.A temperature of 7075C is usually required to feed in cells. 31E001 is a plate type heat exchanger which is provided steam as well as cooling water connections. There is also a stand by heat exchanger/cooler 31E003 which is used in case of emergency or for single electrolyzer filling. This heat exchanger can be used only for cooling purpose as there is no steam connections associated with it. Catholyte enters into catholyte overhead tank 31D001 from the top and over flows from top side. Outlet is from the bottom and leads to cell room by gravity. In the cell room three electrolyzers are arranged in parallel. In each electrolyzer 164 elements are placed in series. At present Electrolyzer A has 162 ELZ-B has 161 and ELZ-C has162 elements. Brine is introduced in the anodic compartment of the cell while caustic soda is introduced in cathodic compartment of the cell. When current is introduced, electrolysis takes place. As a result of it caustic soda is produced in the cathodic compartment together with hydrogen gas where as chlorine gas is produced in the anodic compartment. 2.3.3

Electric Supply Circuit:-

11KV power is supplied from grid station. It is passed through transformer to step it down to 440 V. Then it is passed through rectifiers to convert it into DC which is then supplied to electrolyzers via bus bars and flexibles. There are 2 bus bars and 9 flexibles associated with each electrolyzer. 2.3.4

Reactions:-

Following reactions takes place in the cells Sodium chloride and water are dissociated in the brine solution according to the equations +

-

NaCl

Na

+

Cl

H2O

H

+

+

OH

-

The principal anode reaction involves the oxidation of the anion Cl- to produce chlorine gas -

2Cl

Cl2

+

-

2e

The primary cathode reaction is the reduction of the cation H+ to produce hydrogen gas +

2H

+

-

2e

H2

The sodium cation Na+ then combines with the OH- ions to form third overall product NaOH +

Na

-

+ OH

NaOH

The overall cell reaction is 2NaCl + 2H2O

2NaOH + Cl2 + H2 Page 25 of 48



Side Reactions:-

The predominant side reactions in the anodic compartment of the cell are -

O2 + 2H2O + 4e

-

ClO + Cl- + H2O

4OH

-

2OH + Cl2 -

2ClO3 + 4Cl + 3/2 O2 + 6H+ + 6e

-

ClO3 + 2Cl

6ClO + 3H2O 3ClO

-

-

-

-

-

-

-

-

The source of the OH ions in these reactions is the migration of OH ions through the membrane from the catholyte solution, caused by attraction to the positively charged anode. 2.3.6

Products Handling:-

31.5-32.5% caustic soda is produced in cathodic compartment of the cell and is collected in the catholyte header along with hydrogen gas. It leaves the catholyte header by gravity in the main caustic soda header and passes through hydrogen gas separator 31F002 .Then it is stored in the catholyte storage tank 31D002 to maintain its level about 50% for circulation through the cells. The excess caustic is transferred in the caustic buffer tank D2000 from where it is fed to evaporators for concentration. It is also transferred to storage tanks as such 32% caustic soda as finished product. The stream leaving the cells, composed of depleted brine and chlorine gas, is discharged in the anolyte header and termed as anolyte. The depleted brine leaves the anolyte header by gravity in the depleted brine header and chlorine gas is separated in the vertical gas header which is connected to main chlorine gas header. The depleted brine is passed through the chlorine gas separator in order to remove maximum chlorine gas contents carried with it. The depleted brine is acidified in the acidification pot 07D005 and then stored in the depleted brine storage tank 07D001U . In the anodic compartment of the cell chlorine gas is produced as a result of electrolysis. It is separated from depleted brine in the vertical gas header as well as in the gas separator 07F001 and is collected in the main chlorine gas header. Hydrogen gas is produced together with caustic soda in the cathodic compartment of the cells and discharged in the catholyte header. It is disengaged from caustic soda in the vertical gas header as well as in the hydrogen gas separator 31F002 and is collected in the main hydrogen gas header Hydrogen gas is also cooled before it is transferred to furnaces for HCl production through heat exchanger E2310Aand B.

Page 26 of 48



Equipment Details

BRINE OVERHEAD TANK 06D001 3 Capacity 28m ID 3000mm Height/length 3450mm MOC PP+FRP CAUSTIC O/H TANK 31D00 3 Capacity 8m ID 1800mm Height/length 3248mm MOC Ni CATHOLYTE TANK31D002 3 Capacity 31m ID 24mm Height/length 5228mm MOC Ni HYDROGEN SEPARATOR31F002 3 Capacity 1.6m ID 700mm Height/length 4175mm MOC Ni Allowable pressure 0.5bar CHLORINE SEPARATOR07F001 3 Capacity 1.2m ID 600mm Height/length 4150mm MOC Ti ACIDIFICATION POT07D005 3 Capacity 0.54m ID 800mm Height/length 1200mm MOC FRP DEPLETED BRINE TANK07D001 3 Capacity 42m ID 2600mm Height/length 8300mm MOC FRP

PUMPS ANOLYTE PUMP07P001A/B Type Centrifugal 3 Flow rate 140 m /h TDH 30m MOC Tit CATHOLYTE PUMP31P001A/B Type Centrifugal 3 Flow rate 100m /h TDH 30m MOC Ni Page 27 of 48



Page 28 of 48



2.4 DECHLORINATION 2.4.1

Introduction:-

Depleted brine from electrolyzer usually contains 0.3 g/lit dissolved chlorine at a pH about 3.5-4.0 and 1.0 g/lit as available chlorine in the form of hypochlorite ions. Depleted brine also carries 2000-2500 ppm of free chlorine. The process of removal of chlorine from the depleted brine is termed as “Dechlorination” Chlorine must be removed from brine because of the following facts. •

•

•

The removal of impurities in the primary brine purification becomes difficult. In the presence of high contents of chlorine, the impurities in the rock salt are more easily dissolved during brine saturation. Chlorine oxidizes ion exchange resins, hence increasing its consumption.

The chlorates are necessary to remove because •

•

It decreases the sodium chloride solubility resulting in decreased efficiency, possible salt precipitation and potentially adverse chlorate conc. in the caustic soda product. Chlorates have a strong oxidizing effect which is more evident at high concentrations.

Chlorates are formed in the anodic compartment of the cell of electrolyzer via chemical or electrochemical reactions as mentioned before. Chlorates removal rate is a function of the chlorate concentration so that it is convenient to operate at a relatively high chlorate concentration in the feed brine. High temperature also favors the chlorates removal, so a temperature of 85- 90C is recommended. The third parameter affecting chlorates removal is pH. A low pH less than 2.0 is favorable. 2.4.2


Dechlorination is carried out in three successive steps •

By vacuum stripping

•

By Sodium Sulphite treatment

•

With activated carbon

Depleted brine leaving the electrolyzers flows into the acidification pot 07D005 where it is mixed with acidified stream of brine from reactor R-5050. Then it is collected in depleted brine Page 29 of 48


Internship Report (SCIL) storage tank 07D001 , from here the brine is pumped through 07P001A/B . The discharge of the pump is divided into two streams, one leads to vacuum stripper C-5010 and second leads to acid mixing drum DM-5050 . Normally 70 to 75% material goes to C-5010 and 25-30% in DM-5050 for decomposition of chlorates. In DM-5050, 33% HCl is added to lower down its pH almost zero, after acidification the brine flows down by gravity into the reactor R-5050 where it is mixed with chlorinated steam coming from the vacuum stripper C-5010. In R-5050 at low pH and high temperature, chlorates are decomposed, producing free chlorine which is vented in the chlorine sniff line. The over flow of R-5050 entered in the acidification pot and lower the pH of the depleted brine ranging 1.5-2.0

NaClO3 + 6HCl

NaCl + 3Cl2 + 3H2O

a) By Vacuum Striping Brine containing absorbed chlorine enters from the upper part of the packed tower C5010 where vacuum is generated by means of steam ejector J-5600 . In such condition brine leaving the tower has 20-50ppm of chlorine. The wet chlorine stripped from the brine leaves the tower and is cooled in the shell and tube type heat exchanger E-5010 . The condensed chlorinated water is returned in the depleted brine tank 07D001 while the chlorinated steam is sent to reactor R-5050. The brine flows down by gravity in the dechlorinated brine tank D-5020. The tank is vented to chlorine sniff line. b) By Sodium Sulphite Treatment: Sodium sulphite is added to the depleted brine leaving the tank D-5020 by means of an in line injection on suction of the pump P-5020A/B. Sodium sulphite solution is prepared in the tank D-5250B by absorbing of SO 2 in sodium carbonate solution and sent in D-5300 by means of pump P-5250A/B. Sulphur dioxide (SO 2) is prepared by burning sulphur mud in the sulphur furnace which is sucked through an absorber by a suction fan. The gas is entered from the bottom of the absorber and left from the top. The sodium carbonate solution is fed from the upper side of the absorber and flows down back to the same tank. When the solution is ready it is transferred in tank 5250A. During chlorates decomposition following reaction takes place Na2SO3 + Cl2 + H2O

Na2SO4 + 2HCl

c) With Activated Carbon After treatment with sodium sulphite, brine is passed through an activated carbon bed in tower C-5020. Care must be taken that the carbon should work with acidic brine pH less than 2 and chlorine less than 50ppm. High chlorine contents in brine feeding the tower causes to violent Page 30 of 48


Internship Report (SCIL) reaction with the carbon, relatively high pH in the feed brine to tower causes carbon degradation in the form of fine particles which can plug the tower. The brine passing out of the tower is made alkaline by the addition of dilute caustic effluent from tank D-5150B. The pH is raised up to 6.09.0 before it is transferred in primary brine section. When the carbon is packed down it is necessary to counter wash the carbon bed tower. When the pressure drop across the carbon bed became more frequent, then it is packed with fresh activated carbon. Normally this situation occurs after 40-45 days. 2.4.3

Equipment Details:-

DEPLETED BRINE TANK-07D001 3 Capacity 42 m ID 2600 mm Length/Height 8300 mm MOC FRP 07P001 (DEP. BRINE PUMP) Type Cent 3 F.R 100 m /hr TDH 20 m MOC Titanium ACIDIFICATION POT (07D005) 3 Capacity 0.54 m ID 800 mm Length/Height 1200 mm MOC FRP DM-5050 3 Capacity 0.5 m ID 800 mm Length/Height 1400 mm MOC FRP D-5020 3 Capacity 15 m ID 2000 mm Length/Height 5100 mm MOC FRP P-5020A/B Type Cent 3 F.R 120 m /hr TDH 34 m MOC Titanium D-5250A/B 3 Capacity 5m ID 1800 mm Length/Height 2028 mm MOC FRP Page 31 of 48


Internship Report (SCIL) P-5250A/B Type F.R TDH MOC D-5300 Capacity ID Length/Height MOC R-5050 (REACTOR) Capacity ID Length/Height MOC C-5010 (VACUUM STRIPPER) ID Length/Height Packing height Packing material MOC C-5020 (ACTIVATED CARBON) ID Length/Height Packing length Packing material

Cent 3 5 m /hr 20 m AISI 316 3

5m 2000 mm 1840 mm FRP 3

20 m 2500 mm 4372 mm FRP 1300 mm 3650 mm 1200 mm ceramic saddles Titanium 2200 mm 3800 mm 1600 mm Activated carbon

2.5 EVAPORATION UNIT 2.5.1

Introduction:-

The plant is designed for continuous concentration of caustic soda 31-32% to 50%. The concentration is improved by evaporation in a triple effect counter flow falling film evaporator. The plant consists of three falling film evaporators. At first there was only one unit of capacity 120mt/day, with the passage of time capacity of caustic soda plant was enhanced so another evaporation unit of capacity 250 MT/day was designed to meet industrial and consumer’s needs. Falling film evaporator is a tube bundle heat exchanger with a separator at the bottom. In the separator vapors and thick liquor are separated. The feed liquor is uniformly distributed in the tubes by a distribution device, thus the liquid moves down forming a thin film along inside wall of the tube. That is why it is called a falling film evaporator. 2.5.2


The caustic is fed to the first evaporator EV-201 by a pump P-2000A/B installed at the discharge of caustic buffer tank D-2000. On product side the first evaporator is operated under a vacuum. the caustic leaves the first evaporator effect Ev-201at a concentration of 36-37%. The first evaporator is heated with vapors formed in the second evaporator EV202. The shell of the Page 32 of 48


Internship Report (SCIL) evaporator EV-201 is also under vacuum about 250-270mmHg. The condensate of the EV-201 collected in the same tank. This vacuum is produced by connecting the condenser 201,duct D201and shell condensate lines of EV-201 to TK-201. The vapors of EV-201 are condensed in E201. The cooling water is fed in the shell and the vapors are condensed in the tubes. The condensate is collected in the tank TK-201.The vacuum in E-201 is produced through steam ejectors. After the EV201, pump 201A/B pumped the caustic soda to the second evaporator EV202 via heat exchangers E-202 & E-203. The discharge of the pump P- 201 is divided into two streams; one admitted to the shell of E-202 and second is admitted in the tubes of the E-203. These two streams rejoined before entering the EV-202. This evaporator effect is heated with the vapors from EV-203.the pressure in the shell of EV-202is about 1.9-2.0.The caustic soda enters EV-202 at conc. range 36-37%, and temp. range110 -115C and leaves at conc. 42-43% and temp.120-125C.This caustic soda is fed to the third evaporator EV-203 through pump P-202 via E-204 & E205. The condensate is collected in condensate tank TK-202 and then transferred in TK-201 from where it is transferred in D-5150B. The discharge of pump P-202 is again divided into two streams; one admitted to the shell of E-204 and second is admitted in the tubes of the E-205. These two streams rejoined before entering the EV-203. This evaporator effect is heated with the steam at a pressure of about 14bars.The caustic side is under a pressure of 2 bars. The vapors produced here are used to heat the second evaporator and the condensate is collected in the tank TK-203.The caustic leaves this evaporator at 50% conc. at temp. of 175-185C. Now it is to be cooled before storage. For this purpose it is first passed through tube side of E-204. Here it’s temp. is reduced to 155-160C. Then it is pumped via P-203 through the tube side of the E-202 and E-206, the final temp is about 55-65C. The condensate of the evaporator EV-203 also bears a sufficient amount of heat, which is recovered by passing it through the shells of E-205 & E-203.The steam condensate at a temp about 97-98C is returned to boiler section. 2.5.3

Equipment Detail:-

EVAPORATION PLANT

Equipment EV-201 EV-202 EV-203 E-201 E-202 E-203 E-204 E-205 E-206

No. of tubes 139 116 81 405 48*3=144 20*2=40 48*3=144 24*3=72 26*3=78

Length (mm) 6000 6000 6000 6000 6000 6000 6000 6000 6000

Diameter Thickness (mm) (mm) 48.3 1.65 48.3 1.65 48.3 1.65 25.0 1.00 26.7 1.65 26.7 1.65 26.7 1.65 26.7 1.65 26.7 1.65

Material of Construction SS.904L Ni-201 Ni-201 SS.904L Ni-201 Ni-201 Ni-201 Ni-201 Ni-201

Page 33 of 48



CONDENSATE TANKS TK-201 Capacity Diameter Height TK-202 Capacity Diameter Height TK-203 Capacity Diameter Height

2.5.4

3

2.8 m 1400 mm 2000 mm 3

1.54 m 1100 mm 1400 mm 3

2.2 m 1100 mm 2000 mm

Normal Operating Data:Plant capacity Feed flow rate Steam pressure Pressure in duct 203 Vacuum in E-201 Vacuum in D-201 Vacuum in EV-201 Vacuum in TK-201 Evaporator 201 Feed inlet temperature Feed concentration Product concentration Product temperature Evaporator 202 Feed temperature Product temperature Feed concentration Product concentration Evaporator 203 Feed temperature Product temperature Feed concentration Product concentration

250 ton/day 3 15-25 m /h 14-15 bar 1.9-2.0 bar (safety blows at 2.1bar) 600-650 mm Hg 550-570 mm Hg 260-280 mm Hg 0.70-0.75 bar o

75-80 C 30-32 % 35-36 % o 75-80 C o

90-100 C o 120-125 C 35-36 % 41-42 % o

150-160 C o 150-160 C 41-42 % 50-51 %

HEAT EXCHANGERS E-201(surface condenser) Vacuum 600-650 mmHg o Condensate temp. 58-60 C 3 Cooling water flow rate 250-280 m /h o Cooling water temp. 28-32 C Cooling water pressure 1.2 bar Parameter Tubes Shell Material flow 35-36 % Caustic cooling water o o Inlet temperature 75-80 C 28-32 C o o Outlet temperature 55-60 C 35-40 C Page 34 of 48



E-202

Parameter Material flow Inlet temperature Outlet temperature

Tubes 50 % Caustic o 130-135 C o 90-95 C

Shell 35-36 % Caustic o 75-85 C o 110-120 C

E-203

Parameter Tubes Shell Material flow 35-36 % caustic steam condensate o o Inlet temperature 75-85 C 150-160 C o o Outlet temperature 110-120 C 90-100 C E-204 Parameter Tubes Shell Material flow 50% caustic 41-42% caustic o o Inlet temperature 170-180 C 120-130 C o o Outlet temperature 140-150 C 150-160 C E-205 Parameter Tubes Shell Material flow 41-42 % caustic steam condensate o o Inlet temperature 120-130 C 180-185 C o o Outlet temperature 150-160 C 150-160 C E-206 Parameter Tubes Shell Material flow 50% caustic cooling water o o Inlet temperature 90-100 C 28-32 C o o Outlet temperature 55-65 C 35-40 C

2.6

CAUSTIC SOLIDIFICATION PLANT 2.6.1

Introduction:-

Caustic solidification plant is designed in order to concentrate 50 % caustic soda to 9798% caustic soda in solid form. For this purpose a single effete tube bundle falling film evaporator is used as pre-concentrator. 50% NaOH is concentrated up to 60% NaOH using vapors produced in the final concentrator for heating in this equipment. In the final concentrator the concentration is improved up to 97-98% using outside heating media. Due to increasing demand of the solidified caustic soda three CSP units are designed on same pattern named as CSP-I capacity, CSP-II and CSP-III. Another plant named as CSP-IV is under construction yet.

Page 35 of 48


Internship Report (SCIL) 2.6.2 Process Description a) Pre-Concentrator:50% caustic soda stored in caustic buffer tank is pumped via PBT-1&2 to feed into pre-concentrator. The flow of the feed is controlled by LCV-9.11. There are temperature and pressure gauges to indicate the feed temperature and pressure respectively. Pre-concentrator is heated with vapors formed in final concentrator. The pre-concentrator is designed as tube bundle falling film evaporator. Above the tubes there are vertical slits through which caustic soda feed flows evenly into the tubes and form an unbroken film along the inner wall of the tube. The pre-concentrator works at 0.93 bar vacuum on the product side. This vacuum is created in the system by steam ejector. A two stage ejector, 14 bar steam, is used for this purpose. The vapors produced in the pre-concentrator are removed by steam ejector and are condensed in a condenser. Vapors are introduced in the shell side of the condenser while cooling water is introduced in the tubes. Vapors condensed in the condenser are collected in the condensate tank. The condensate of the pre-concentrator also goes into condensate tank by gravity. From condensate tank it may transfer in M-II plant under level control where it is stored it the D-5150B. The condensate may be overflow into the drain. This condensate is also used for sugar solution preparation and for heating the seal of 60% caustic pump A/B. b) Final Concentrator:60% caustic soda obtained from pre concentrator is pumped via P8.11A/B to feed it into final concentrator. The feed rate is controlled by FIC-9.09. The final concentrator is basically consisting of 6 individual concentrator tubes and the vapor separator. The caustic soda feed is evaporated in the falling film concentrator at atmospheric pressure by means of heat applied by salt heating medium. The feed liquor is uniformly distributed to each concentrator element. It flows evenly with the inner wall of the tubes from top to bottom. The heat transfer medium moves counter currently from bottom to top inside the heating jackets surrounding the concentrator tubes. The vapor produced in the course of the concentration process reached the horizontal collecting channel together with concentrated caustic side. The collecting channel is provided with conic baffle which separate vapors and molten caustic side. The vapors leads to the separator which retains caustic droplets contained in the vapor. These vapors leave the separator from the top and are used to heat the pre concentrator. The molten caustic soda leaves the separator through its lower part and is directed by the distributing device to the flaker and/or drum filling device. The heating medium is a mixture of following salts in a particular composition. KNO3

53%

NaNO2

40%

NaNO3

7% Page 36 of 48


Internship Report (SCIL) c) Sucrose System:All the equipment and piping in contact with caustic melt is made of pure nickel are low carbon nickel because of corrosive resistant of nickel. Oxygen acts corrosively, particularly when combines with high temperature and form nickel oxide which would contaminate the product i.e. caustic melt, so it is very important to prevent the penetration of atmospheric oxygen into the equipment. For this purpose system is blanketed with nitrogen or steam. In addition by adding 0.15 Kg sugar solution into the system just after the feeding valve to pre concentrator, the nickel pickup of the caustic soda melt is reduced to 2 ppm approximately. 5% aqueous solution of sugar is prepared by using food grade sugar in the water/vapor condensate in the sugar tanks and dosed into the caustic system by pumping via sugar pump at a rate of 3 - 5 lit/hr. Flow rate of sugar dose is very important, low flow may cause increasing nickel ppm and excessive flow may leads to blackish particles in the caustic melt. d) Flaker:The flaker consists of a rotating drum/cylinder which dips in the vat containing caustic o melt. The cylinder is cooled to 60-55 C by showering cooling water on its inner walls thus a thin film of caustic melt is formed over the drum surface which is scrapped by a sharp blade/scrapper. The flakes thus formed are directly made to fall into the duct which conveys them to the filling hopper where it is provided with an automated weighing and then filling in PPW bags lined with polyethylene bags which is tied with cable ties and then stacked inserting tag cards in the stitching. e) Dust Collector:For purpose of operational safety and to facilitate the operator working at filling station, a dust collection system is provided. The system consists of a suction fan .It sucks dry air from the flaker, passed through the duct, weighing system and also from the bags. The suction pipe is dipped into a water tank where the caustic soda is precipitated in water in seal pot when its concentration is about 5 to 10%, it is replaced by another water filling. 2.6.3

Normal Operating Conditions:-

PRECONCENTRATOR Caustic feed concentration Caustic feed flow rate Caustic feed temperature Caustic feed pressure Temperature in the separator Vapor inlet temperature Vapor outlet temperature

50% 3 1.0-1.25 m /hr o 60-65 C 6.4-6.5 bar o 90-110 C o 350-360 C shell side o 160-165 C product side Page 37 of 48


Internship Report (SCIL) Vacuum Caustic outlet temperature Caustic outlet concentration Sugar dose flow rate CONDENSOR Cooling water inlet temperature Cooling water outlet temperature Cooling water flow rate STEAM EJECTOR Steam pressure Water flow rate BURNER Fuel gas flow rate Salt inlet temperature Salt outlet temperature Salt coil temperature Flue gas temperature FINAL CONCENTRATOTR Caustic feed concentration Caustic feed flow rate Caustic feed temperature Caustic temperature in distributor Caustic temperature in vat Salt inlet temperature Salt outlet temperature Vapor outlet temperature FLAKER DRUM Cooling water inlet temperature Cooling water outlet temperature Cooling water flow rate Cooling water pressure Air pressure

0.9-0.95 bar o 68-72 C 60-61 % 3-5 lit/hr o

30-32 C o 35-40 C 3 150-200 m /hr 13-14 bar 900-1000 lit/h 190-210 390-405 420-430 420-435 475-500

3

Nm /hr o C o C o C o C

60-61 % 1.0-1.25 m3/hr o 68-70 C o 360-380 C o 325-330 C o 420-430 C o 390-405 C o 360-370 C o

30-32 C o 35-40 C 3 50 m /hr 1.3-1.5 bar 1 bar

Page 38 of 48



Page 39 of 48



Utilities and Protective Equipments 3.1 Utilities Different utilities used during process along with their use and required amounts are given in the following lines 3.1.1

Water:-

Uses:

Electrolysis feeding, Resin regeneration, Preparation of Brine, Caustic soda and HCl dilution, Flocculent preparation Amount : s

15 m /h Source:

Tube well water Types:-

Demineralized water, R.O. water Specifications :-

3.1.2

pH

6-7

Conductivity

10 micron siemen/cm (max)

Fe

100 pbb (max)

SiO2

100pbb (max

Suspended Solids

Nil

Instrument Air :-

Uses:

For controlling Auto valves etc. Specifications:-

Design pressure

7 ATA

Temp.

40 C

Dew point at 7 ATA

-25 C

Oil and dust

free

o

o

Page 40 of 48



Nitrogen:-

Uses:

For purging Hydrogen and Nitrogen lines Types:

Industrial nitrogen in cylinders N2 (99.5% v/v)

O2 (0.5% v/v)

3.2 Personal Protective Equipments (PPEs):Following personal protective equipments are exclusively used at SCIL by workers, operators, engineers and all other related persons. • • • • • • • •

Face sheet Goggles Rubber gloves Safety boots Gas masks/ Filter masks Air mask OBA Safety helmets

Besides these PPEs many other safety devices are used such as fire extinguishers, anti firing gas cylinders etc.

Page 41 of 48



Product Details Besides producing Caustic Soda, SCIL manufactures many important chemicals. A brief detail on quality and specifications of some of the products is given in the following lines. 4.1 Ammonium Chloride:Installed Annual Production Capacity

3,000 MT

Technology Developed by

Mannesmann (Germany)

Specifications Physical Appearance

White Crystals

Quality

99.7 ± 0.2%

Moisture

0.1 % max.

General Product Information Evolves ammonia when reacting with alkali. Exhibits endothermic nature in aqueous media. Absorbs water & moisture when exposed to atmosphere. Shelf Life: Long life is expected in airtight bags. Product Handling and Safety Instruction It is supplied in the packing of 25 kg Polypropylene bags, having polyethylene liner in bags. Must be stored in well-ventilated and covered area. Do not store it along with caustic soda and other alkaline materials If ammonium chloride contacts the eyes, then eyes must be irrigated immediately with plenty of water for at least 15 minutes. 4.2 Carbon dioxide Gas:Specifications Appearance/ Colour

Normal/Colorless gas.

Purity

99.9 % min

Taste

None

Odor

None/Characteristics

Uses Large quantities of solid carbon dioxide (i.e. in the form of dry ice) are used in processes requiring large scale refrigeration. Carbon dioxide is also used in fire extinguishers as a desirable alternative to water for most fires. It is a constituent of medical gases as it promotes exhalation. It is also used in carbonated drinks.

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Internship Report (SCIL) Product Handling & Safety Instructions Dry carbon dioxide can be handled in most common structural materials. Moist carbon dioxide is generally corrosive by its formation of carbonic acid. Ferrous Nickel alloys are slightly susceptible to corrosion. At normal temperatures carbon dioxide is compatible with most plastics and elastomers. Use local exhaust to prevent accumulation of high concentrations so as to reduce the oxygen level in the air to less than 19.5% and the carbon dioxide concentration below the exposure limit. Protective gloves of any material appropriate for the job. Positive pressure air line with full-face mask and escape bottle or self-contained breathing apparatus should be available for emergency use. 4.3 Bleaching Powder:Installed annual production capacity

4,500 MT


Davy mc-kee (Germany)

Specifications Physical Appearance

White fine Powder

Available Chlorine

30 % ± 1

Moisture

0.50 % max.

Stability

On heating at 100 ± 2 ºC it does not lose more than 1/15th of the available chlorine.

General Product Information Stable below 0.5 % moisture contents. Produces chlorine odor or HOCl in case of high moisture contents and start decomposing. Decomposes by absorption of CO2 from air. Decomposition by oxygen separation with low water contents, which is accelerated in the presence of heavy metals (Fe+3, Ni and Co etc). Shelf Life: One year in airtight drums; 03 months in airtight bags, if stored at room temperature and dry place Product Handling and Safety Instruction It is supplied in 25 kg Polypropylene bags having polyethylene liner in bags. Airtight packing protects decomposition of bleaching powder due to carbon dioxide from air. Must be stored separately in well-ventilated and covered area. Avoid contact with other chemicals especially from all acids. It catches fire on exposure to naked flame and high temperature.

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Internship Report (SCIL) 4.4 Calcium Chloride Purity

Minimum 77%w/w

Physical Appearance

White granules /powder

Specifications Calcium Chloride

77% Min

Magnesium Chloride

2.0% Max

Calcium Hydroxide

0.3% Max

Calcium Sulfate

0.3% Max

Alkali Chloride

0.5% Max

Water Insoluble

0.5% Max

pH (5% w/v solution)

4.5-9.2

Arsenic As

3.0 ppm (max)

Lead Pb

10.0 ppm(max)

Iron Fe

20.0 ppm(max)

Barium Ba

10.0 ppm(max)

Sodium Na

20000.00 ppm(max)

Principal Application Additive to oil well completion. Drying petroleum fractions. Beverages for removing Sodium ion. Mining as dust proofing and freezing resisting ore & coal. Drying air and gases, remove moisture by Hygroscopicity. Fungicides as oxidizing agent. Pharmaceutical as drying and desiccating agent. Water Treatment. Material Handling Must be store in well-ventilated, covered and dry area. Long life is expected in airtight bags. If calcium chloride contacts the eyes, then eyes must be irrigated immediately with plenty of water for at least 15 minutes. Packing Supplied in packing of 25 kg PP Laminated bags having polyethylene line

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Internship Report (SCIL) 4.5 Caustic Soda Liquid (33%) Installed Annual Production Capacity

129,500 MT


Denora(Italy),AKCC(Japan)

Grade

Commercial

Specifications NaOH

50 + 0.5 %

Na2CO3

0.5 % max

NaCl

0.02 % max

NaClO3

0.01 % max

Na2SO4

0.01 % max

Iron

10 ppm max

Silica

10 ppm max

Hg

free

General Product Information Caustic attacks body tissue upon contact. The degree of injury depends upon the extent and duration of contact, temperature and concentration of the caustic. Its corrosive action on tissues causes burns and frequently deep ulcerations. Its contact with the eyes rapidly causes severe damage. Caustic solution is detectable by a slippery feeling like soapy water. Toxic limits are TLV = 2 mg. / cubic meter of air. Shelf Life: Long life if protected from air & contamination. Product Handling and Safety Instruction Immediately remove all contaminated clothing and equipment effected by the Caustic, Flush the exposed area thoroughly with a lot of water, followed by washing with a solution of 5 % ammonium chloride in water. If caustic contacts the eyes, they should be irrigated immediately with plenty of water for at least 15 minutes. Hold the eyelids opened during irrigation. The eyes should be then washed with a dilute boric acid solution and wash the eye with water for an additional 15 minutes. A physician should be seen immediately after the eye is thoroughly washed. For personal protection, use face shields, gloves, gum-boots and protective suites. Use safety shower and wash with plenty of water for at least 15 minutes. Caustic soda (liquid) is transported in Mild Steel tanks.

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Internship Report (SCIL) 4.6 Caustic Soda Liquid (50%) Installed annual production capacity

129,500 MT



Grade

Commercial

Specifications NaOH

50 + 0.5 %

Na2CO3

0.5 % max.

NaCl

0.02 % max.

NaClO3

0.01 % max.

Na2SO4

0.01 % max.

Iron

10 ppm max.

Silica

20 ppm max.

General Product Information Caustic attacks body tissue upon contact. The degree of injury depends upon the extent and duration of contact, temperature and concentration of the caustic. Its corrosive action on tissues causes burns and frequently deep ulcerations. Its contact with the eyes rapidly causes severe damage. Caustic solution is detectable by a slippery feeling like soapy water. Toxic limits are TLV = 2 mg. / cubic meter of air. Shelf Life: Long life if protected from air & contamination. Product Handling and Safety Instruction Immediately remove all contaminated clothing and equipment effected by the Caustic, Flush the exposed area thoroughly with a lot of water, followed by washing with a solution of 5 % ammonium chloride in water. If caustic contacts the eyes, they should be irrigated immediately with plenty of water for at least 15 minutes. Hold the eyelids opened during irrigation. The eyes should be then washed with a dilute boric acid solution and wash the eye with water for an additional 15 minutes. A physician should be seen immediately after the eye is thoroughly washed. For personal protection, use face shields, gloves, gum-boots and protective suites. Use safety shower and wash with plenty of water for at least 15 minutes. Caustic soda (liquid) is transported in Mild Steel tanks

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Internship Report (SCIL) 4.7 Caustic Soda Flakes

Installed Annual Production Capacity

129,500 MT



Grade

Commercial

Specifications NaOH

97.0 ± 1 %

Na2CO3

1.0 % max.

NaCl

0.04 % max.

NaClO3

0.02 % max.

Na2SO4

0.01 % max.

Iron

20 ppm

Silica

20 ppm

General Product Information Caustic attacks any body tissue upon contact. The degree of injury depends upon the extent and duration of contact and the temperature and concentration of the caustic. Its corrosive action on tissues causes burns and deep ulcerations. Its contact with the eyes rapidly causes severe damage. Caustic solution is detectable by a slippery feeling like soapy water Toxic limits are TLV = 2 mg. / cubic meter of air. Shelf Life: Long life if protected from air & moisture. Product Handling and Safety Instruction Immediately remove all contaminated clothing and equipment effected by the Caustic. Flush the exposed area thoroughly with a lot of water, followed by washing with a solution of 5 % ammonium chloride in water. If caustic contacts the eyes, they should be irrigated immediately with plenty of water for at least 15 minutes. Hold the eyelids opened during irrigation. The eyes should then be washed with a dilute boric acid solution and wash the eye with water for an additional 15 minutes. A physician should be seen immediately after the eye is thoroughly washed. For personal protection, use face shields, gloves, gum-boots and protective suites. Caustic soda (Flakes) is packed in 25 kg polypropylene bag having polyethylene liner in it.

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Internship Report at SCIL

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