Footsteps for Enhancing Data Bank on Bauxite, Hydrate, Alumina & Alumina Chemicals

Hi Friends,

In present post, we have put forward our aggressive steps to enhance the inventory of technical data bank pertaining to bauxite, hydrate, alumina and alumina chemicals covering all spheres of activities for all friends of our professional fraternity.

It's my natural temperament to exchange ideas particularly on technical topics. It is also the truth that blessings of my superiors and best wishes of my friends have attributed in enriching my knowledge base which further encouraged me to move forward with accelerated pace in exchanging ideas and opinions. I do not believe in diary culture in hiding information unnecessarily in my desk. I know, I have very limited data / information with me compared to many others in the World. My this approach has given me more than 2500 trust-worthy friends who are directly or indirectly associated with bauxite, hydrate, alumina and aluminium including specialty chemicals. As such, I have faced many road blocks in my career path so is impossible for me to forget the blessings of society and almighty God. Majority of my life, I have enjoyed with smile. What ever work I do, I get immense pleasure in contributing to my fullest satisfaction.  

During early days of my professional careers, I faced acute problems in learning technical things as limited people had the desire to exchange their fresh or outdated perceived ideas as they used to keep those data as very confidential just like keeping the personal property in the Bank lockers. Those days i.e in early eighties, internet in India was available to defense people only. You can imagine the extent of difficulties faced by me in learning the basics and design aspects of process, calculations, equipment, capex, opex and profitability aspects. Truly, it was hard time for me when I recall. I struggled a lot for finding even tiny technical information. You will be astonished to know that people were reluctant to tell even the basic process and operating parameters of Alumina refinery. Can you think of doing process design engineering calculations using scientific calculators and preparation of drawings using Mini Drafters on the Drawing boards. For the first time in 1984, I got opportunity to work on computer that to with 640 kb RAM. Those days, Word star and Lotus-123 were the basic software for  word processing and calculations respectively. In 1990, I got the computer with MS-Excel on which I initiated to take up the assignment for developing a mathematical model for Design of Alumina Refinery during extra hours. I was fortunate to be awarded for development of that mathematical model sometime in 1995. I kept on updating the mathematical model considering it as my person achievement. If I see the model today, I am surprised on myself for completing this unique and wonderful developmental work alone. The outcome of this model has been well tested with the results provided by other leading technology suppliers in the World. This mathematical model has been developed on MS-Excel platform and requires only 150  basic input data and it gives detailed process calculations like material balance, thermal energy balance, water balance, caustic soda balance, alumina balance etc and sizing calculations for all major technological equipment, tailor made equipment and requirement of utilities and services within no time. Utmost accuracy in outcome is the essence of this mathematical model. Since this Mathematical model has been awarded by Internationally reputed Engineering & Consultancy Organization and they are using the same even today for design of Alumina refinery. Thus, I consider it as their asset but as an originator, I keep on updating the Mathematical model incorporating advancements in process technology. 

To summarize the facts of my professional life, I had to face a lot of difficulties which can not be expressed in words. All of us know the fact of our life that we are not going to remain alive on this earth for more than 200 years under any circumstance. Thus, it would be a wiser decision to dissipate the knowledge and expertise acquired by all of us. Though our first forefathers were monkeys, but we can not behave like monkeys today in keeping intact the assimilated information with us as the World has become very small because of advancements in communication technology. I feel proud of myself as I initiated this move of exchanging the ideas of public domain nature among my friends about a decade back which was appreciated by almost all across the globe. Now, I have observed that my friends are contributing much more than what I could and what I am. I have always advised one and all to share the information of public domain nature and never disclose any data, information and drawings of proprietary and confidential nature. My interest  has remained at the same level among the global team but I am contributing little less because of paucity of time due to other pressing assignments.Till date, I have published 283 technical articles on this specialized subject and could present few papers in national and International seminars covering all aspects starting from concept to commissioning of Alumina Refinery.

No matter, I am always (24x7) available for serving the community around and specifically to bauxite, hydrate, alumina, aluminium and alumina chemical fraternity on techno-commercial issues across the globe even during odd hours.

If any individual particularly the young professionals / Entrepreneurs has any question with regard design, engineering, execution, commissioning, process calculations and costing (such as bauxite mining cost, alumina production cost, specific capital cost etc.) related to Bauxite, mining, Hydrate, Alumina and Specialty grades of hydrates and aluminas including Alumina chemicals, please feel free to ask any information / clarification clearly indicating your e.mail ID for receiving your reply. Our team of Experts will definitely put efforts for reply to you. Sometimes, you may be required to wait a while for the reply. Simplicity in our language and authenticity in information are major strength. 

We wish to have your opinion / comments / remarks on our new move on the very specialized subject like alumina. We will welcome your suggestions.

Kunwar Rajendra
rajendra@ceti.co.in
www.ceti.co.in

CONGRATULATIONS TO ALL MEMBERS OF BAUXITE-ALUMINA-ALUMINIUM FRATERNITY !

Hi Friends,

Our efforts of exchanging our knowledge on the technical platform of Alumina Technology blog has fetched us to a new height of success. All of us who contributed directly or indirectly in achieving this grand success deserves our heartiest Congratulations! We congratulate all members of bauxite-alumina-aluminium fraternity for setting up such a new record of of success in achieving the target of 95,000 viewers of our popular technical blog across the globe today, the 19th June 2015.

The editorial team of Alumina Technology blog is thankful to you all of you for your continued co-operation, support, feed back and contribution in improving the quality of technical articles published on regular basis.

We celebrate every success and thus we are now aiming for the grand occasion for reaching to  a further milestone of success to cross the total viewer target of 100,000 within couple of months from now. We have observed that our younger generation of bauxite-alumina-aluminium fraternity have started taking keen interest in analyzing the articles with due care and expressing their views and suggestion by putting their remarks in the space provided under "Comments" column located just below each technical article. We have truly realized that exchanging knowledge has helped us in enriching the knowledge of all involved persons.

Trust, we will continue to have your cooperation / supports in days to come for further improvements in quality of articles published on this blog. Your comments encourages our team to be more careful while publishing any new article on this popular technical platform. Knowledge sharing, positive attitude towards our assignment and improving skill are the key to success. Let us remember these tools of success for achieving our goals.

Regards

Kunwar Rajendra

Forecast for Primary Aluminium Production in the World

Hi Friends,

After a long time, I have appeared before you to discuss about region-wise projected production capacity of primary aluminium in the World. These data are purely based on information available on public domain. 

During last couple of years, the aluminium market was little sluggish which forced many aluminium producers to cut down the production figures / operate at break even level / even a few Smelters were kept shutdown. It's a well known fact that aluminium price always follows a periodic sinusoidal curves. Majority of people involved in aluminium business are well aware of the facts and habituated to face the challenges in such situation. If we look at the present price trend, the LME price for aluminium has taken upward trend and is hovering at around US$ 2000 per tonne of aluminium. 

In this post, we thought of sharing forecast for primary aluminium production across the globe as tabulated below:

The world aluminium production figure projected for 2017 clearly indicates the compound annual growth rate (CAGR) figure of around 5.9% taking actual production of aluminium for 2013 as the base figure. The project CAGR of 5.9% is a promising figure compared to past CAGR figure of around 3% for previous decades.The tabulated figures have been assimilated from various published literature,  international journals, balance sheets of companies and some data directly collected through interaction with the experts of aluminium field across the globe. These data are authentic and reliable and have been published here in the interest of friends of aluminium fraternity as a piece of information. However, these data may be cross-checked before taking any financial decisions.

The author of this article will be pleased to have additional data / information from experts or any  individual related to the subject.

We will welcome your comments / remarks.

Regards.

Rajendra Kunwar

rajendra@ceti.co.in

www.ceti.co.in

PROMISING ALUMINA REFINERY PROJECTS IN INDONESIA

Hi Friends,

As discussed in previous articles, about 89% of alumina produced in the World is used for manufacture of aluminium metal and remaining 11% for production of chemicals and other non-metallurgical applications. Thus calcined alumina as well as hydrated alumina (Hydrate) is broadly characterized in two categories-

•       Metallurgical grade alumina or Smelter grade alumina (MGA or SGA)) and
•       Non-metallurgical grade alumina or Chemical grade alumina (NMGA or CGA).

Though the volume of CGA market is less compared to that of SGA but the profit margin in CGA is much higher as its selling price ranges from 2 to 5 times of that of SGA. Presently, the market potential of CGA across the globe is estimated at around 5.8 to 6.0 million tonnes per annum. Out of total CGA demand in International market, specialty grade hydrates have market share of over 50% i.e. about 3.0 to 3.2 Mtpa being used as feed stock for manufacture of Aluminium sulphate, Fire retardant fillers, Tooth paste, Sealing rings for rotating equipment, Thread guides, Polish, Paints, Ceramics, Abrasive, High temperature refractory and American diamond. During last couple of years, selling price of CGA has shown increasing trend along with increase in its demand whereas selling price of SGA has shown downward trend hovering at the level of US$ 350-360 per tonne of calcined alumina because of lower LME price of aluminium metal. Now, let me give the brief account of bauxite reserves and alumina scenario with more focus on salient features of Alumina projects in Indonesia in subsequent paragraphs.

As per data available on public domain, bauxite is available in Tayan, Munggu Pasir, Mempawah and West Kalimantan region in Indonesia. West Kalimantan is having total bauxite reserves of over 2000 million tonnes with proven reserves of over 800 million tonnes of bauxite. The bauxite is predominantly gibbsitic in nature with average quality of about 43% total alumina, about 38.6% available alumina and around 3% reactive silica. The bauxite in Indonesia has been seen in low lying hills with overburden varying from 0.60 m to 3.8 m and nodular bauxite horizon from 2.2 to 5.2 m. The geographical studies indicate that these bauxite deposits were formed by in-situ weathering. Till last year, the country was exporting bauxite to china and other countries but in the recent past, the Indonesian government has totally banned the export of bauxite and putting more focus on processing of bauxite for production of value added products.

In Indonesia, there are two major Alumina projects in West Kalimantan namely Tayan Alumina Project and Mempawah Alumina Project under execution and active consideration as outlined here under.

Tayan CGA Project: Tayan bauxite mine commenced its operation in early 2010 and was exporting bauxite to China and Japan. Construction of Tayan Alumina Project was started in April 2011 aiming to mechanical completion schedule in December 2013 and trial production in January 2014. The capacity of this plant is 0.300 million tonnes for production of wide varieties of Chemical grade hydrates and aluminas. The estimated investment in this project was US$ 500 million with the technology supplied by Showa denko (SDK), Japan. The actual mechanical completion of this project was done in December 2014 and commercial production commenced in February 2015.

Mempawah SGA Project: The capacity of this plant is 1.2 million tonnes of SGA to be supplied as feed stock to Aluminium Smelter. The estimated capital investment will be about US$ 1.5 billion. The construction of this plant will be started by early 2015 with mechanical completion target of December 2017.

Both Alumina projects have promising future because of locational advantages, availability of good bauxite reserves, adequate coal reserves and adoption of advanced technology. I wish grand success of both projects.

We seek your valued comments / opinions / additional information, if any.

Regards.

Rajendra Kunwar
rajendra@ceti.co.in
www.ceti.co.in

Is Low Silica in Bauxite a Problem in Bayer Alumina Plant ?

Hi Friends,

After a long gap, I have appeared before you to interact on a small but very critical process issue of Bayer Alumina Plant.

In the past, we have always discussed about the negative impact of high silica in bauxite specifically with regard to operational problems, process control issues, higher consumption of input materials and deterioration in quality of product hydrate or alumina. In previous articles, this issue was elaborated at length with measureable / quantifiable approach so as to focus on its importance in Bayer Alumina Refineries.

In present post, we will briefly discuss about the advantages and disadvantages of low silica in processing bauxite for production of calcined alumina.  The question mark (?) on the subject itself forces us to think and re-think about the positive and negative aspects of low silica in bauxite.

It’s a well-known fact that all Alumina producers wish to have low silica bauxite for obvious reasons discussed earlier. Now, before coming to the subject directly, following questions arise-

(i)  What type of silica is harmful for Bayer’s process?

(ii) What should be the cut-off silica content in bauxite for acceptable quality of alumina?

Though we have discussed   these issues in several articles, still it is prudent to freshen up with salient features as outlined below-

We are well aware that predominantly there are two types of silica in bauxite designated with regard to Bayer process of alumina (a) Non-reactive silica and (b) Reactive silica. ROM bauxite mined adopting either open cast or underground mining methodology contains a number of metallic oxides including silica. This mined silica as percentage of total dry bauxite is termed as total silica. The part of total silica which reacts with caustic soda and forms sodalite complex through sodium silicate route is termed as Reactive silica. Majority of Reactive silica is found in form of Kaolinite. And thus, the non-reacting component of total silica with caustic soda is popularly known as Non-reactive silica. Quartz is non-reactive silica. The silica being abrasive in nature causes erosion in components of various process equipment like heat exchangers, pipelines, valves, pump casing and impellers etc. Thus higher silica content affects the capital investment of Alumina refinery because robust material of construction for equipment component in contact with bauxite slurry. Hence higher silica in bauxite causes higher initial investment for the plant and higher repair maintenance cost for routine replacement of critical components of equipment.

Generally, it has been seen from bauxite analysis that Reactive silica in bauxite ranges from 50% to 80% out of Total silica in bauxite. Plant operation is affected because of high silica in bauxite as it has high settling velocity and abnormally high abrasive nature.

Now coming to the topic with raised question mark, it’s true that low reactive silica in bauxite is considered as a serious process problem as it directly affects the quality of product alumina because of higher silica content in alumina. The SiO₂ content in calcined alumina produced in all modern alumina a refinery is controlled at around 0.015%. The alumina having higher silica content is considered as inferior quality. For achieving 0.015% SiO₂ in alumina, the SiO₂ in aluminate liquor feeding to crystallizers / precipitators should be around 0.45 gpl.  The ineffective desilication because of delay in achieving super-saturation of silica across desilicators, gpl SiO₂ in liquor increases to much higher level which ultimately deteriorates the product alumina quality.

The above elaboration concludes that moderate level of Reactive silica in bauxite at around 1.5% in bauxite is considered to be the best with regard to plant efficiencies and product quality as well.

Trust, the subject has been covered here to your desired level of satisfaction in understanding the criticality of the subject issue. We would welcome your  valued comments / remarks to further substantiate the subject.

Regards.

Kunwar Rajendra

Capex, Opex and Techno-economic Viability for Green-Field Alumina Refinery in India

Hi Friends,

Today is the great day for all of us who are deeply associated with this knowledge sharing technical blog on Alumina processing technology. It is needless to mention here that our blog has earned a prestigious position among the people of Bauxite-alumina-aluminium fraternity in short span of time. Congratulations to all concerned on the eve of crossing the total viewer mark of 130,000 today. This glorious moment is remarkable and memorable as we are proceeding ahead in setting the new height of success. We are continuously receiving appreciations from our learned friends for high level of quality of content published so far and feedback for further improvements. 

In present post, we are bringing out some special facts which will be useful for the top notch officials in taking strategic decisions with regard to capital investments, Operating cost and techno-economic viability aspects for setting up new Alumina refineries in India. 

As such, only a few Alumina refineries were constructed and commissioned across the globe during last decade. Broad details and present status of new refineries executed over last 15 years / under execution presently  in India are outlined in subsequent paragraphs-

1. 1.4 Mtpa Vedanta Alumina Refinery, India: This plant was designed for 1.4 Mtpa alumina with two streams each stream having 0.70 Mtpa production capacity. One of the stream of this plant was commissioned  in 2006 with non-designated source of bauxite as Niyamgiri deposits could not be cleared  by the Government of India for carrying out bauxite mining activities.  The specific capital investment for this plant was very low as the company took advantage of volatile market of equipment and facilities during execution period. But processing of low alumina content and high reactive silica content in bauxite of unidentified areas during commissioning itself made the plant uneconomical. Finally, the shutdown of the plant was forced on 9th December 2012 because of non-availability of bauxite. Plant remains shutdown as yet. However, the Vedanta management is striving to restart the operation of this plant shortly even with imported bauxite.
2. 1.4 Mtpa Anrak Alumina Refinery, India: This plant is located at about 70 km from Visakhapatnam in the state of Andhra Pradesh in India. This Alumina refinery has two streams of 0.70 Mtpa each and the execution is expected to be completed for commissioning by end of the current year - 2013. Most of the equipment and facilities of this plant have been installed and one of the process streams out of two are in readiness for trial but no adequate bauxite available as the earmarked Jarrella bauxite deposits are yet to be cleared by the Government. The trial run for Stationary calciner supplied by Outotec Germany was done in early first week of April 2013 with purchased hydrate and a few thousand tonnes of calcined alumina could be produced. HSD was used as the fuel for firing followed by HFO for calcination during commissioning trial. The estimated specific capital investment of this plant was much higher than that of Vedanta. But this plant could save substantially on technology, engineering and site activities during implementation.
3. 1.5 Mtpa Utkal Alumina Refinery, India: This plant is owned by Aditya Birla group of companies. The execution of this plant was conceived sometime in 1996. The construction of this plant is in advance stage and mechanical completion of this plant is expected by the end of 2013. This plant has been designed by Rio Tinto Alcan Australia who are considered leader in process technology across the globe. But because of inordinate delay in implementation because of various socio-political reasons, the capex of this project has increased substantially. Thus the specific capital investment of Utkal alumina plant was much higher than targeted figure. 
4. 1.4 Mtpa JSW Alumina Refinery, India: Under diversification plan, JSW group company decided to set up alumina refinery in Vijaya Nagaram district of Andhra Pradesh with state of the art and most modern plant associating Rio Tinto Alcan Australia as technology supplier in the year 2005. The company has acquired adequate land but execution of project is under hold awaiting clearance from Government of India for bauxite mining from Araku group of deposits.
5. 1.0 Mtpa NALCO Alumina Refinery, India: National Aluminium Company (NALCO) has initiated studies for setting up 1.0 Mtpa Alumina refinery near Mandavi in Gujarat. As per our estimates, the specific capital investment for this project will be high at around US$ 1000 per   tonne of Calcined alumina mainly because of Lignite based Co-generation plant, required Desalination plant, marginally bigger size equipment requirement because of lower alumina recovery from available bauxite in Gujarat and additional expenditure towards development of infrastructure facilities like port etc. for the project.

The capital expenditure data analysis clearly reveal that specific capital investment in setting up Alumina refineries in India varies from US$ 650 to US$ 1000 per tonne of calcined alumina depending on geographic location of the plant in the country. The capex will be lowest for the plant in Orissa, Gujarat and Jharkhand where as the same will highest in Gujarat.  The reasons are well known to all concern as elaborated in above paragraph. Also, the opex will be higher mainly because of poor plant efficiency figures due to wide variation in mineralogical and chemical composition of basic input material, Bauxite. Also, the volume effect of plant capacity because of low reserve of Bauxite in Gujarat is the other reason. It will be prudent to mention that comparatively lower grade of bauxite, non-availability of desalinated water, availability of low calorific value solid fuel source (Lignite) for co-generation plant are the main reasons for highest capex. Again, on opex part, the same will be abnormally high because of poor plant efficiency figures coupled with low grade of bauxite in Gujarat. At current price level of Caustic soda, Heavy furnace oil and Lignite, even the economic viability for Alumina refinery in Gujarat is a question mark because of high specific capital investment of around US$1000 per tonne and estimated operating cost excluding financing charges (interest & depreciation) at around US$ 200 per tonne of Calcined alumina as per preliminary estimates.However, the actual figures of Capex and Opex can be ascertained by Project Owner with detailed studies before taking financial decision on the matter. In spite of all these facts stated above, Green-field Alumina refineries will be installed mostly in India and Vietnam in coming decade because of huge bauxite reserves of comparatively improved quality than other countries across the globe. In other words, India and Vietnam are the future destinations for green-field Alumina refineries in years to come.

Trust, the above deliberation will give a glimpse of required capex, opex and economic viability aspects for setting up green-field Alumina refinery to one and all across the globe. The author of this technical article will welcome your comments on the subject, if any. Please feel free in sharing your views.

Regards.

Rajendra Kunwar
rajendra@ceti.co.in
www.ceti.co.in

BENEFICIATION OF BAUXITE FOR ENRICHMENT IN QUALITY

Hi Friends,

In continuation to my earlier posts, I thought of sharing my views on beneficiation of Bauxite with the objective to optimum utilization of natural resources available with us. I am presenting here my views on the subject as outlined here under in subsequent paragraphs.

The mineral, Bauxite, is a rich source of alumina for making aluminum. The aluminium metal and its alloys have strong growth potential in international market for wide range of industrial applications. Bauxite is also used in refractory, cement, absorbents, steel, abrasives, rubber, plastic, cosmetics, paints, paper, polishes, glass, enamel and ceramics.

Since bauxite is a mineral occurring in earth’s crust, it has a number of impurities, like iron, silica, titania, calcium, and small quantities of phosphorous, sulfur, zinc, magnesium and various carbonate and silicate minerals. These impurities create quality problems during processing thereby increase production costs. Therefore, the removal of impurities to the extent possible economically is essential before processing further for any application.

Most mines abroad subject their run of mine ore (ROM) to the mineral dressing operation most suitable for their material. Crushing the ROM, usually in hammer mills, is an operation practiced worldwide. Depending on the bauxite, and the quality/grade required, the next stages are screening, scrubbing and washing, magnetic separation and drying. Magnetic separation is done to remove iron, however, is normally practiced in a limited way to produce high value, special grade bauxites. At present, the production of bauxite in most operative mines in India is not sufficiently high as to warrant a capital-intensive beneficiation plant, which usually requires a large capacity to be really economical. Hence, ore dressing efforts have been mainly confined to removal of silica by manual and/or mechanized breaking, crushing, manual sorting and dry screening.

Efforts towards research are being emphasized in most bauxite producing countries to develop cheap and innovative bauxite beneficiation processes. Many new methods of magnetic separation are also being tried out. These include rare earth roll separators, super conducting high gradient magnetic separators and open gradient, non-cryogenic high gradient magnetic separators. Other methods being researched include fluidized bed acid leaching, hydrogen assisted beneficiation and bio leaching. However, despite decades of intensive studies, economical bauxite beneficiation technology for removal of impurities satisfactorily is not available as on date.

Research in India is along international lines but still confined to the laboratory. The Indian Bureau of Mines, Nagpur (IBM), the Jawaharlal Nehru Research Development and Design Center, Nagpur (JNARDDC), and the Regional Research Laboratory, Bhubaneswar (RRL), all claim to have laboratory scale processes that are ready to be up scaled to pilot plant levels. The IBM has done numerous beneficiation tests, using different methods, on various bauxites found in India. The RRL claims to have developed a beneficiation process to produce non-metallurgical grade bauxite, whereas the JNARDDC says it has processes for both metallurgical and non-metallurgical grades.

As per the available published literatures and analysis, the savings on raw ore cost brought by JNARDDC's process through beneficiating metallurgical grade bauxite appears to be over 17% and that of non-metallurgical grade at least 19%. Bauxite users in India have indicated that they are willing to pay between 10-50% higher for a reduction in impurities by a similar amount. This would make the production and marketing of beneficiated bauxite more profitable.

We will welcome your comments / remarks on the elaborated topic.

Regards.

                        Kunwar Rajendra

Reasons for Such a High Popularity of Alumina Technology Blog

Hi Friends,

It gives me immense pleasure to analyse the basic reasons for such a high popularity of this Alumina Technology Blog among the people across the globe. On this issue, we have received many views of our friends of alumina fraternity which we thought of sharing with you.

Main reasons for such a high level of popularity are listed below-

• It's a great deal of what the Author learnt in last three decades in the field.
• It's a simple compilation of technical thoughts based on practical experience in the field of conceptualization, design, engineering, execution, testing and commissioning of various plants in the World.
• The language of this blog is simple.
• Assimilation of authentic and reliable technical data / information.
• It covers all facets of bauxite, alumina and aluminium field available on public domain without disclosing any proprietary information.
• Unique platform to share the views of technical professionals on variety of subjects.

The Author has presented this blog as a Gift to the friends of Bauxite, Alumina and Aluminium fraternity across the Globe.

We will continue our efforts to cover the balance topics in future. We solicit your views for enriching this blog further.

Regards.

Kunwar Rajendra
www.bauxite2aluminium.blogspot.com

It's Right Time to Write Our Success Story

Hi Friends,

It gives me immense pleasure to share this moment of achieving a record number of viewers of over 50,000 of our popular technical blog in such a short span of time. With this achievement, we have reached to a new height of success. All of us have contributed in this remarkable  success thus it is the right time to celebrate.

Let us recall in brief the moments of this glorious event as Success Story. Initially, I had no idea about sharing the knowledge through known and unknown friends as I have limited knowledge about the computers and internet as well. I would like to express my sincere thanks to my elder son, Vivek, for educating me about the blog. Vivek being a Computer engineering professional inspired me to write something about my areas of expertise. 

Soon after, I took the lead and published a few lines assuring my friends to share the technical knowledge of public domain nature pertaining to bauxite, alumina and aluminium. Till date, we have followed this strict ethical principle in publishing each and every technical article on this blog. We have never copied any information from any published literature. We have always used our simple language in expressing our own personal thoughts. 

Of course, right in the beginning itself, I had a dream to achieve a number of 100,000 viewers in  a time span of five (5) years and today on auditing of data, we find that we made a very conservative target.

So far, we have published over 265 technical articles and from last few months we have not added new article because of paucity of time. However, my friends all over the World are enjoying the published articles every moment.

This blog has given me thousands of global friends in every corner of the World as this blog has the in-built translation facility to read in any international language.

At this moment, I would like to thank to Google Management to provide such a lovely platform free of cost for sharing our knowledge.

Let us join hands to assimilate technical data related to design, operation, engineering, technology, execution, commissioning and other related issues on bauxite, alumina and aluminium and enrich our knowledge by exchanging those data with one other. This technique will make all of us more knowledgeable in the field. Trust you will agree with my views.

I take the opportunity to wish you a very happy, healthy and prosperous new year.
Thanks and regards.

Kunwar Rajendra
www.bauxite2aluminium.blogspot.com

Technology Driven and Equipment Oriented Units of Alumina Refinery

Hi Friends,

We have studied so far in detail the design and operating features of Alumina refinery. We have also made ourselves well acquainted with the technological advancements as well as modifications and improvements in major equipment considered for efficient operation of Alumina refinery.

In present post, we will discuss the highlights of our previous posts with more specific to technology and equipment oriented unit operations and unit processes of Alumina refinery. The process sequence of various units of Alumina refinery has been shown below-

As such, unit operations are complicated and unit processes of Alumina refinery are complex in nature because of inter dependence on the major operating and process parameters of upstream and downstream units as even minor deviations / fluctuations in process control parameters abruptly affects the plant efficiency figures. Over a period of time, lots of developments in process technology as well as improvements and modifications in equipment have occurred which has resulted in drastic reduction in overall energy consumption and raw material consumption as well ultimately improving the profitability of the plant. 

Based on our studies and experience in the field, we have clearly depicted in above diagram, the technology driven and equipment oriented process and operating areas of Alumina refinery. Selection of right technology and right equipment matching with optimized process and operational parameters will result in improved efficiency figures thereby lower capex and opex of Alumina refinery. 

Please put your views / suggestions / remarks / comments, if any.

Regards.

Kunwar Rajendra

Design of Air Coolers and Water Coolers for Alumina Refinery

Hi Friends,

In previous posts, we have discussed in detail the design calculations associated with System design, Material balance and Thermal energy balance for setting up Refractory grade alumina production unit. For small capacity plant, sophisticated fully mechanized  alumina cooling facilities may not be cost effective, thus installation of semi-mechanized equipment like Air cooler and Water cooler are considered for the purpose.

In present post, we will broadly discuss the methodology adopted for sizing of air cooler and water cooler including the calculations for working out the rating of their drive motors required for their successful operation. Here, production rate of 1.00 tph Refractory grade alumina (RGA) has been considered in the sample calculations for sizing the Air cooler and Water cooler used as Primary cooler and Secondary cooler for lowering down the temperature of alumina to desired level.

Sizing of Air Cooler:-

In first step, hot calcined alumina coming out from Rotary Kiln at around 1400^oC is cooled with air in Air cooler. The generated hot air is passed in counter-current direction of alumina flow through cooler. Let the temperature of alumina drops to about 300^oCand temperature of air rises from 30^oC to 95^oC. The hot air generated is fed to the Kiln for combustion of HFO.

Heat given by alumina = 1000*0.27*(1400-300) = 297000 k.cals/hr.

Heat lost by radiation = 25% of total heat = 0.25*297000 = 74250 k.cals/hr.

If  w kg of air is passing through the Air cooler for absorbing heat,

Then heat taken by air = w*0.24*(95-30) = w*15.6 k.cals/hr.

Since Heat In = Heat Out.

Thus w*15.6 + 74250 = 297000.

Therefore, w = 14279 kg/hr.

Hence, air flow through Air cooler = 14279 kg/hr.

For design of Air cooler, mass velocity of air through Air cooler is taken as 45,00 kg/hr.m^{2 .}

Thus, the cross sectional area of Air cooler = 14279 / 4500 m² = 3.17 m².

∴  (π/4)*D² = 3.17

∴ D = 2.0 meters.

For Air coolers, L/D =4; therefore, L = 8.0 meters.

Drive motor rating for Air cooler = 4.D² = 4* (2)² = 16.0 kW.

Sizing of Water Cooler:-

Calcined alumina coming out from Air cooler is further cooled in Water cooler. Here, cooling water is sprayed over rotating shell, but the contact of water with alumina is completely avoided. In this case, rise in temperature of water is less but desired cooling of product alumina is easily achieved. It is assumed that final temperature of product alumina is controlled at 90 deg.C and temperature of water rises from 30 to 40 deg.C.

Hence heat given by alumina = 1000*0.27*(300-90) = 56700 k.cals/hr.

Heat taken by water = w*1.0*(40-30) = 10*w k.cal/hr.

Since heat loss = heat gain,

Thus 10*w = 56700

Therefore, w = 5.67 m3/hr.

Thus water flow to Water cooler ~ 6 m3/hr.

Overall heat transfer co-efficient for water cooler = 50 k.cals/hr.m2.deg.C.

So, 56700 = 50*A*(40-30).

Therefore, A = 113.4 sq.m.

For Water cooler, L/D = 7.

Hence, π*D*L = 113.4,

or. π*D*7D = 113.4

Thus, D =2.27 m and L = 15.9 m.

Drive motor rating for Water Cooler = 4.(D)² = 4*(2.27)² =20.6 kW.

Trust, design calculations for sizing of Air cooler and Water cooler required for Alumina refinery have been described systematically. Please put your views / suggestions / remarks / comments, in case you have something better to share with friends of Alumina-aluminium fraternity.

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Thanks and regards.

Kunwar Rajendra

Heartiest Congratulations for the New Record of 29,000 Viewers

Hi Friends,

Please accept my heartiest congratulations for associating yourself with our technical blog in achieving this new height of success in short span of time. I am delighted to express my sincere thanks to all of you for your cooperation and supports on every steps of our journey in stepping beyond  the prestigious record of 29,000 viewers. So far, our journey had been joyous and adventurous as well particularly in maintaining the quality standard set since start of this technical blog. Till date, we have published over 235 technical articles on this blog and will continue to add variety of new technical articles full of technical data, information and calculations in days and years to come. We are confident to honor our commitments with our valued viewers.

You must have observed and realized that each and every member of our team has made concerted efforts in improving the quality of articles in all respect. We have published many unique articles which have been developed by our team and well appreciated by our learned viewers. Many of our viewers have expressed on several occasions that such technical documents / articles / papers on such a very specialized topics are rarely available in any published literature other than this particular platform. It is an honor to our team. We are thankful for your appreciation.

On continual basis, our team will put efforts in presenting articles with enriched data, information and calculations pertaining to project and equipment engineering in particular. We will welcome and appreciate your valuable remarks / comments on published articles for further improvements. As a routine, we keep on updating our old articles with modified and latest information. Hence, you are advised to keep a track of updated old articles also. You may find something better than what you have experienced earlier. In case, you have paucity of time because of your busy schedule, just run through the articles, I am sure, you will love the article and will enjoy the content as well. Never ignore the presented articles as we have put lot of efforts for sharing these data, information and calculations with you only.

Please put your valued suggestions / remarks / comments, if any. 


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Kunwar Rajendra

Plate Thickness Calculations for Digesters and Other Pressure Vessels

Hi Friends,

In earlier posts, we have discussed in detail the process design and equipment design calculations for various technological equipment including pressure vessels used in Alumina refineries. I admire your level of stamina and patience in going through such complicated calculations with utmost interest. In present post, we wish to present the design calculations used for estimating the plate thickness of the pressure vessels like Digesters and Flash tanks operative in Alumina refineries. We have carried out sample calculations for Digester vessel installed in medium pressure digestion circuit of Alumina refinery.

As such, many methods and empirical relations have been developed by designers and equipment manufacturers based on their rich experience on the subject. Here, we will discuss the simplified  formula which gives most authentic and reliable results compared to others. Since the plate thickness of pressure vessels is directly proportion to its pressure and diameter and inversely proportion to allowable stress of material of vessel, thus the engineering formula used for thickness calculation can be presented as follows-

                                                                      P x D

                                                  t = -----------

                                                        2 x J x f

Here, P = Design pressure of vessel in kg per cm2,

          D = Diameter of vessel in mm,

          J  = Joint efficiency of welding,

          f  = Maximum permissible stress for material of plate in kg per cm2.
          t  = Plate thickness of vessel in mm.

Welding of pressure vessels are done by duly qualified and certified welders. The welding joint efficiency figures for thickness calculations is taken as per the following norms-
J = 1.00 for class-A type, J = 0.85 for class-B type and  J = 0.50 for class-C type.
The maximum permissible stress for plates of carbon steel as well as stainless steel ranges from 1000 kg/cm2 to 1800 kg/cm2 thus for design calculation purpose, lower value at 1000 kg/cm2 is generally considered. The sample calculations for estimation of plate thickness of Digester vessels are given below for clarity in explanation.


Sample Calculation:
Let us work out the plate thickness for the Digester vessels for Alumina refinery adopting Medium pressure digestion technology. The maximum operating pressure for such Digesters is 7.0 kg per cm2,
Thus design pressure for Digesters, P = 1.20 x 7.0 = 8.40 kg per cm2.
Diameter of Digester = 4.00 meter = 4 x 1000 mm (assumed),
For class-A type welding, Joint efficiency J = 1.00,
Maximum permissible stress of steel plate, f = 1000 kg/cm2,
                                                                                 8.4 x 4.0 x 1000
Thus the plate thickness of Digester vessel, t = ------------------------  = 16.80 mm.
                                                                                  2 x 1.0 x 1000 
Taking the design margin of 15%, 
Plate thickness = 1.15 x 16.80 = 19.32 mm.
Hence, the minimum plate thickness for Digester vessels operative for Medium pressure digestion technology must be 20 mm.


The specifications, drawings and fabrications of pressure vessels are carried out as per the guidelines and standards of American Society of Mechanical Engineers (ASME). Trust, the subject has been elaborated in simplified manner. Please put your views / suggestions / remarks / comments, if any.


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Thanks and regards.


Kunwar Rajendra