Tuesday, May 14, 2013

CONGRATULATIONS TO ALL MEMBERS OF BAUXITE-ALUMINA-ALUMINIUM FRATERNITY

Hi Friends,

We congratulate all members of bauxite-alumina-aluminium fraternity for setting a new height of success by achieving the target of 56,000 viewers of our popular technical blog today, the 15th of May 2013. We are thankful for your continued support, feed back and contribution in improving the quality of technical articles published on regular basis.

We celebrate every success and thus it was essentially felt to express our views on this grand occasion.

Let us keep contributing in future for further improvements.
Regards.

Kunwar Rajendra

Monday, March 18, 2013

A Book on "Alumina Technology - Process & Design"

Hi Friends,


We are planning to publish a book on Alumina Technology covering various technical aspects with emphasis on process & design of Metallurgical and Non-Metalurgical (Speciality grades) Alumina Plants including Byproducts. We have structured a Draft Table of Content for the purpose. If everything goes well, this book will be published by early 2014 by a Publisher of International repute.

In our opinion, the proposed new book will be unique with regard to availability of in depth technical data / information generally required by process engineers and plant designers as no such book is available in the market particularly on Bauxite, Hydrates and Aluminas.

Given below, please find the draft table of content seeking your views for addition / deletion / modifications, you feel appropriate, for enrichment.



TABLE OF CONTENT

1.            Introduction
2.            Raw Materials
3.            Process technology
3.1.         Alumina production process
3.2.         Process considerations
3.3.         Quality of Alumina
3.3.1.     Specifications of Metallurgical grade alumina
3.3.2.     Applications of Metallurgical grade alumina
3.4.         Technological options for design of Alumina refinery
3.4.1.     Bauxite crushing
3.4.2.     Bauxite grinding
3.4.3.     Desilication, digestion and slurry flashing
3.4.4.     Residue thickening, washing and disposal
3.4.5.     Heat interchange system
3.4.6.     Precipitation
3.4.7.     Calcination
3.5          Recommended process route
3.6          Process and design features of Alumina refinery
3.6.1       Basic considerations for design of bauxite crushers
3.6.2       Principles of Desilication process
3.6.3       Significance of sodalite factor
3.6.4       Impact of dissolved silica in pregnant liquor on product quality
3.6.5       Desilication methods
3.6.6       Design of efficient digestion system
3.6.7       Techniques of liquor decantation and residue washing
3.6.8       TCA as filter aid for polishing filtration
3.6.9       Heat interchange system
3.6.10    Principles of hydrate precipitation
3.6.11    Techniques of hydrate classification
3.6.12    Multiple effect evaporation system
3.6.13    Hydrate washing and filtration
3.6.14    Energy efficient calcination system
3.7          Major process control parameters
 
4.            Plant Design Criteria
4.1          Basic terminology used in Alumina refinery
4.1.1       Solids concentration in slurry
4.1.2       Liquor concentration
4.1.3       Plant causticity
4.1.4       Alumina to Caustic ratio
4.2          Basis for design capacity of Alumina refinery
4.2.1       Estimated reserves and quality of Bauxite
4.2.2       Fixation of plant capacity
4.2.3       Product-mix and product specifications
4.2.4       Finalization of production process route
4.2.5       Sizing of plant and equipment
4.2.6       Safety and pollution control measures
4.2.7       Planning for green belt
4.3          Plant availability, margin and operating schedule
4.3.1       Overall availability of plant
4.3.2       Design margin
4.3.3       Turndown ratio
4.4          Major efficiency parameters
4.5          Plant operating schedule
4.6          Unit areawise operating and process control parameters
5.            Methodology for Design of Plant and Equipment
5.1.         Basis for Sizing of Pipelines in Alumina refinery
5.2.         Dimensions and drive motor rating for Ball mill
5.3.         Design of test tanks
5.4.         Design of liquor to Ball mill heat exchangers
5.5.         Design of Bauxite slurry heat exchangers
5.6.         Drive motor rating calculations for agitators of Predesilication tanks
5.7.         Design of digester vessels
5.8.         Design of 1st stage regenerative heat exchangers
5.9.         Design of 2nd stage regenerative heat exchangers
5.10.       Design of 3rd stage regenerative heat exchangers
5.11.       Design of live steam heat exchangers
5.12.       Design of 1st stage heat exchanger for heat interchange unit
5.13.       Design of 2nd stage heat exchanger for heat interchange unit
5.14.       Design of precipitation tank chemical cleaning heat exchangers
5.15.       Design of spiral heat exchangers
5.16.       Method of Stack height calculations for boilers and calciners
5.17.       Basis for design of Cogeneration plant
5.18.       Design calculations for raw water supply system

6.            Safety and Environmental Management
6.1.         HAZID and HAZOP study for Alumina refinery
6.2.         Emission of gases and Air quality monitoring
6.3.         Generation and Disposal of Bauxite residue
6.4.         Generation and disposal of fly ash
6.5.         Surface effluent & Concept of Zero effluent discharge

7.            Design Aspects for Civil and Structural Work
7.1.         Geo-technical studies of soil
7.2.         Design features of civil work
7.3.         Design features of structural work
7.4.         Suitability of TMT bars for Alumina refinery

8.            Special Grades of Bauxite, Hydrate and Alumina
8.1.         Chemical grade bauxite
8.2.         Cement grade bauxite
8.3.         Refractory grade calcined bauxite
8.4.         Abrasive grade calcined bauxite
8.5.         Chemical grade hydrate
8.6.         High purity hydrate
8.7.         Dry coarse hydrate
8.8.         Superfine hydrate
8.9.           Fire retardant filler grade hydrate
8.10.         Pharmaceutical grade hydrate
8.11.         Light hydrate
8.12.         SP grade calcined alumina
8.13.         High purity high alpha alumina
8.14.         Activated alumina
8.15.         Tabular alumina

9.                    By-Products & Alumina Chemicals
9.1.                 Vanadium Sludge
9.2.                 Gallium metal
9.3.                 Ferric alum from Bauxite
9.4.                 Non-Ferric alumum from hydrate
9.5.                 Specifications and Production of Zeolite
9.6.                 Production of Zeolite from Bauxite
9.7.                 Production of Zeolite from hydrate
10.          Basic Process Calculations
10.1.       Calculations for bauxite consumption factor
10.2.       Calculations for Caustic soda losses
10.3.       Material flow balance for typical Alumina refinery
10.4.       Broad break of process steam requirement
10.5.       Estimated electrical power requirement
10.6.       Process water requirement
10.7.       Make up water requirement for cogeneration plant
10.8.       Water requirement for drinking and sanitation in plant

11.          Project Engineering and Execution
11.1.       Engineering stages of Alumina refinery
11.2.       Execution Methodology
11.3.       Testing & commissioning Procedure


Your views / suggestions on the matter will be appreciated.
Thanks and regards.

Kunwar Rajendra

Tuesday, March 5, 2013


                                                 BENEFICIATION OF BAUXITE

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.

I will welcome your comments on the elaborated topic.
Regards.

                      Kunwar Rajendra

Wednesday, January 9, 2013

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

Thursday, January 3, 2013

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


Thursday, June 21, 2012

Operational Sequence for Start up & Commissioning of Alumina Refinery

Hi Friends,
In present post, we will discuss the operational sequence for starting and commissioning of Alumina refinery. As such, there may be many permutations and combinations of operational sequence for starting and commissioning of Alumina refinery. We are presenting here one of them which may be simple and most appropriate. The schematic diagram is presented here under-

Start up and commissioning of Alumina refinery is taken up after following activities-
  • Thorough checking for Mechanical completion,
  • Readiness of raw water supply system and DM plant,
  • Synchronization of boilers and turbo-generators,
  • Cold water run and 
  • Hot water run.
  • Ensuring the availability of adequate input materials.
Caustic concentration build up and raising its temperature to around 85 degree centigrade are pre-commissioning activities required for start up of Alumina refinery. Sequence of caustic concentration build up, temperature raising, start up and commissioning steps are taken up in following sequence-

  1. Fresh caustic lye received by road / rail tankers are stored in Caustic storage tanks (CSTs) and 6 or 7 nos. precipitators of 2nd line as 1st line precipitators shall be taken into range for commissioning.
  2. Initially, Evaporator feed tank, Liquor preparation tank, Digesters, Flash tanks, Heaters and one of the Decanters are taken into range for concentration build up and temperature raising. Accordingly closed circuit with these equipment is made by temporary connections for circulation of liquor before start up. 
  3. Water is taken in Evaporator feed tank through temporary lines and operation of evaporator is initiated at low vacuum and operation is stabilized slowly with boiling. This ensures the adequate condensate supply to boilers as well as hot water for dilution of caustic lye to around 150 to 200 gpl caustic in Liquor preparation tank. 
  4. Run the Test tank pump at about 50% flow for filling Heaters, Digesters and Decanter connected in the circuit. Keep the drain valves of Heaters in open condition in the beginning  for purging out entrapped air in pipelines otherwise it may cause damage to chambers of heaters.
  5. Open steam in Live steam heater maintaining the outlet temperature below 100 degree centigrade. 
  6. Circulation of liquor in this circuit is continued for about 24 hours for checking the readiness of process circuit.
  7. Start Bauxite charging to grinding mill at about 50% digestion liquor flow and taking charging ratio at around 0.300. Bauxite charging to grinding circuit is considered as start of plant commissioning i.e. Zero hour of plant commissioning.
  8. Two desilication tanks will be filled up with slurry taking Bauxite slurry heaters into service. After attaining about 16 hours of desilication time, temporary circuit of Red area will be discontinued and permanent process circuit will be energized for generation of spent liquor.
  9. Start flocculent preparation and dosing to settler as required.
  10. Initially Security filters will be operating as a spool but will be taken into range afterwards for ensuring required purity of plant liquor.
  11. Heat Interchange Unit will be kept bypassed and filling of precipitators shall be started taking only five (5) precipitators in range for the purpose of adequate seed generation.
  12. Continue circulation of Precipitation liquor through Evaporators and Digesters for slowly raising the temperature profile of liquor.
  13. Slowly increase the digestion liquor concentration to around 250 gpl caustic and step up charging ratio to around 0.620 level for raising the ratio profile of aluminate liquor to the level of pregnant liquor. 
  14. Take Residue washers into circuit.
  15. After attaining the aluminate liquor ratio above 0.600 in feed liquor of Precipitation tanks, start seeding with purchased solid hydrate at controlled rate for generation of seed hydrate. For the purpose, solid hydrate will be mixed in Seed mixing tank with Pregnant liquor and pumped to those five (5) Precipitation tanks taken in range.
  16. Maximize charging ratio to the desired saturation level and increase Bauxite charge at increase digestion liquor flow.
  17. Hydrate generated in Precipitation circuit will be used as seed till adequate hydrate is built up in the process.
  18. Discontinue all temporary connections and continue operation as normal by taking desired number of equipment and vessels of one line of process circuit.
  19. Start hydrate classification circuit and transfer of product hydrate to Hydrate storage shed.
  20. After making a stock of about 20,000 tonnes of hydrate in storage shed, commission Calciner for production of calcined alumina.
  21. Stabilize plant operation for maximizing alumina production level.
Hope, starting and commissioning procedure for Alumina refinery has been covered with clarity in understanding.

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

Kunwar Rajendra