Minimum Feasible Capacity for Specialty Grades of Hydrate and Alumina Plant

Hi Friends,

In earlier post, we have already discussed about Minimum feasible capacity of smelter grade Alumina refinery which is techno-economically viable to set up in any part of the globe. In present post, we will briefly discuss about minimum feasible capacity of specialty grades of  Alumina Plant.

It is well known fact that specialty grades of hydrate and alumina are marketed at premium price ranging from three times to five times of those of chemical grade hydrate and standard calcined alumina where as the production of specialty grades of hydrate and special alumina are approximately 15% to 20% higher than those of chemical grade hydrate and smelter grade alumina respectively. Because of increasing demand of specialty grades of hydrate and calcined alumina for various non-metallurgical applications all over the World has tremendous market potential with reasonably high profit margin. Thus, it gives us opportunity to think about the minimum feasible capacity of specialty grade alumina plant which can give high returns resulting in low pack back period. 


The preliminary study reveals that specialty grade alumina plant with 25,000 tonnes per annum production capacity is the minimum feasible capacity considering the availability of basic technological equipment for continuous operation on commercial scale. The estimated capital investment for such plant will be around US$ 25 million excluding the investment towards land and infrastructure facilities. The average manufacture cost of specialty grade alumina is estimated at around US$ 310 per tonne inclusive of all financial charges where as minimum  selling price will be ranging from US$ 600 to US$ 1000 per tonne of specialty grade alumina. Taking average level of sales realization at around US$ 800 per tonne of specialty grade alumina, the pay back period for total capital investment works out to less than 3 years. Specialty grades of hydrate have more profit margin compared to specialty grades of calcined alumina.


The preliminary financial indices prompt us to go ahead for execution immediately. However, It is always advisable to check the following basic information before taking final decision for execution-

1. Availability of about 3.0 million tonnes of chemical grade bauxite,
2. Required utilities and services,
3. About 20 hectares of land for plant,
4. About 50 cubic meters per hour of industrial grade water,
5. Other basic input raw materials and skilled workforce.

In addition to all stated above requirements, the detailed feasibility study is a must to confirm the market scenario, fixing of product-mix, finalizing the required process technology and re-look at outcome of final financial parameters. Execution of such plants definitely require technical competence in process expert as a process technology supplier for the project, otherwise execution with superficial knowledge about the process may be detrimental for the stake holders in the project - this is just a word of caution from our expert team.

These are just the basis to initiate working on this lucrative project. Please put your views / suggestions / remarks / comments, if any.

If you like this article, then please press your rating as  +1  .
Thanks and regards.

Kunwar Rajendra

System Design for Setting up Refractory Grade Alumina Production Unit

Hi Friends,

In earlier technical papers, we have already covered the operation, technological options, broad design basis, process engineering and process calculations for metallurgical grade Alumina refineries. Now, we would like to present the glimpse of specifications and production processes including plant design as well as engineering aspects for non-metallurgical grades of hydrates and calcined aluminas. The non-metallurgical grades of hydrate and alumina are also known as specialty grades of products as they have special characteristics particularly with respect to their quality specifications and wide range of industrial applications. Specialty products are value added products mostly manufactured using purer grades of hydrate as the feed stock under strictly controlled process conditions with or without addition of suitable mineralizer. 

Refractory grade alumina (RGA) has high degree of calcination and lower impurities.   In RGA, Na₂O content is controlled at lower level as Na₂O causes formation of voids in refractory at high temperature due to melting and creates cracks which is not desirable.

Previously, we have already published a technical paper on "Market potential of Refractory grade alumina" which was well appreciated by the readers.

In present paper, we would like to discuss about the product specifications, production process route and system design calculations for major equipment of a typical RGA plant of  1 tph production capacity in subsequent paragraphs-

Specifications of Refractory grade alumina:

Al₂O₃ : 99.0% min.

SiO₂ : 0.020% max.

Fe₂O₃: 0.020% min.

Na₂O (total) : 0.35% max.

Na₂O (soluble): 0.15% max.

LOI (at 1100^o C) : 0.30 % max.

α Al2O3 : 90% min.

Typical physical properties of Refractory grade alumina:-

Appearance: White crystalline,

Melting point: 2040^oC,

Specific surface area: 0.50 to 1.0g/m²,

Refractive index: 1.76

Hardness: 9 on Moh scale.

Typical sieve analysis:-

+ 100 Mesh: 5 to 20%,

+ 200 Mesh: 40 to 90%,

-325 Mesh: 5 to 10%.

Production Process Route:-

Chemical grade hydrate, the intermediate product of Metallurgical grade Alumina plant, is used as the feed stock for production of Refractory grade calcined alumina. As such, the calcination system with associated material handling and alumina cooling system are the basic facilities of RGA plant but it is preferred to install hydrate washing and filtration equipment at the 1^st operating stage of the plant to ensure desired control on leachable Na₂O content in the feed hydrate to Kiln. The washed and filtered hydrate is calcined in Rotary kiln at about 1400^oC and passed through Air cooler and water cooler for recovery of thermal energy so as to minimize specific HFO consumption for alumina production.

Operating parameters for Rotary vacuum filters:-

Solids in feed hydrate slurry: 45% (w/w),

Cake thickness: 40 mm max.,

Heel thickness: 5 mm,

Vacuum requirement: 700 mm Hg min.

Moisture in filtered cake: 10% max.,

Hot water requirement: 1 m³ per tonne of hydrate,

Specific filtration rate: 1.5 t/m².hr.

Specifications of Fuel oil:-

Type of fuel oil: Heavy furnace oil (HFO),

Calorific value of oil: 9600 k.cals./kg,

Specific heat of oil: 0.56 k.cal./kg,

Flash point of oil: 250^oC.

Typical analysis of Fuel oil:-

C = 87%,          H=10.5%,          S =1.0%,

O=0.10%,         N=0.20%           Moisture=1.2%.

Sizing of Required Horizontal Rotary Vacuum Filter:-

It is assumed that 0.5% of alumina will be lost with flue gas through stack.

Alumina production rate = 1.0 tph

                                                             1.0 *156

Thus dry hydrate to Rotary kiln = ------------- = 1.54 tph.

                                                          0.995*102

No. of washing stages on filter =2

Number of filtration stage = 1,

Total no. of washing & filtration stages =3.

Specific filtration rate = 1.5 t Hydrate/m².hr.

Total filtration area required = 3*1.5/1.54 = 3.1 m².

Nearest available filter = 4.2 sq.m.

Sizing Calculations for Required Rotary Kiln:-

Let effective inner diameter of Kiln = 1.80 m,

Thickness of refractory bricks = 150 mm.

Thus inner shell diameter of Kiln=1.80 m + 2*0.15 m =2.10 m.

                                                                            K*L*D²

Throughput rate of Kiln, tonnes per day = ------------

                                                                               3

Where,

L = Length of Kiln in meters,

D = Diameter of Kiln in meters and

K = Constant.

For alumina, K =1.10.

Thus 1.0*24 = 1.10*L*(2.1)²

Hence, Length of Kiln, L =14.85 meters.

Rotational Speed of Kiln:-   

                 

For production of specialty grade alumina,

Kiln rotates at N*D = 2.40,

Where,

N=Rotational speed of Kiln in rpm and

D = Diameter of Kiln.

Thus N*2.10 = 2.40

Hence Rotational speed Rotary Kiln = 1.14 RPM.

Trust, the system design calculations for RGA have been described systematically. We will welcome your comments and remarks.

Kunwar Rajendra

Principal Consultant - Engineering

Consultancy, Engineering and Training Institute (CETI), India.

www.ceti.co.in

Minimum Feasible Capacity of Specialty Grades of Alumina Refinery

Hi Friends,

In earlier post, we have already discussed about minimum feasible capacity of smelter grade Alumina refinery which is techno-economically viable to set up in any part of the globe. In present post, we will briefly discuss about minimum feasible capacity of specialty grades of  Alumina Plant.

It is well known fact that specialty grades of hydrate and alumina are marketed at premium price ranging from three times to five times of those of chemical grade hydrate and standard calcined alumina where as the production of specialty grades of hydrate and special alumina are approximately 15% to 20% higher than those of chemical grade hydrate and smelter grade alumina respectively. Because of increasing demand of specialty grades of hydrate and calcined alumina for various non-metallurgical applications all over the World has tremendous market potential with reasonably high profit margin. Thus, it gives us opportunity to think about the minimum feasible capacity of specialty grade alumina plant which can give high returns resulting in low pack back period. 

The preliminary study reveals that specialty grade alumina plant with 25,000 tonnes per annum production capacity is the minimum feasible capacity considering the availability of basic technological equipment for continuous operation on commercial scale. The estimated capital investment for such plant will be around US$ 25 million excluding the investment towards land and infrastructure facilities. The average manufacture cost of specialty grade alumina is estimated at around US$ 310 per tonne inclusive of all financial charges where as minimum  selling price will be ranging from US$ 600 to US$ 1000 per tonne of specialty grade alumina. Taking average level of sales realization at around US$ 800 per tonne of specialty grade alumina, the pay back period for total capital investment works out to less than 3 years. Specialty grades of hydrate have more profit margin compared to specialty grades of calcined alumina.

The preliminary financial indices prompt us to go ahead for execution immediately. However, It is always advisable to check the following basic information before taking final decision for execution-

1. Availability of about 3.0 million tonnes of chemical grade bauxite,
2. Required utilities and services,
3. About 20 hectares of land for plant,
4. About 50 cubic meters per hour of industrial grade water,
5. Other basic input raw materials and skilled workforce.

In addition to all stated above requirements, the detailed feasibility study is a must to confirm the market scenario, fixing of product-mix, finalizing the required process technology and re-look at outcome of final financial parameters. Execution of such plants definitely require technical competence in process expert as a process technology supplier for the project, otherwise execution with superficial knowledge about the process may be detrimental for the stake holders in the project - this is just a word of caution from our expert team.

We feel that you will like the article on "Marketing potential of Special Hydrates and Aluminas".

These are just the basis to initiate working on this lucrative project. Please put your views / suggestions / remarks / comments, if any.

If you like this article, then please press your rating as  +1  .
Thanks and regards.

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

Market Potential for Specialty Grades of Hydrate and Alumina

Hi Friends,

We all are well aware that about 10 to 11% of total alumina produced in the World is used for non-metallurgical applications. The hydrate or alumina used for non-metallurgical grades are categorized as Specialty grade or Specialty grades of hydrate and alumina. Generally, these specialty grades of hydrate and alumina are marketed at about 2 to 5 times of metallurgical grade hydrate and alumina. The production of specialty grade hydrates and alumina require additional facilities to attain the desired product quality particularly with respect to purity level, fineness and other specified properties depending on their various industrial applications. The production of specialty grades of hydrate and alumina are 15 to 20% higher than standard hydrate and alumina.

In present scenario, the increasing demand for a few selected grades of hydrate and alumina in domestic as well as International market has pushed the selling price to reasonably high level. Thus, all special alumina producers have jacked up the selling price of their products to a level beyond imagination.  

Here, I would like to put the example of Chemical grade hydrate which is used for manufacture of chemicals like Non-ferric alum, Sodium aluminate, Zeolite-4A and Fire retardant fillers. The production cost of Chemical grade hydrate lies between US$90 to US$100 per tonne in moderately efficient Alumina refineries. Presently, Chemical grade hydrate is being sold at a price between US$330 to US$350 per tonne depending on the geographic location of the plant and proximity to consumers. Similar is the market scenario for many other grades of specialty grade hydrate and alumina.

Observing the tremendous market potential for specialty grades of hydrate and alumina, existing alumina producers are modifying the process circuit for converting the plant from Metallurgical grade to Specialty grades of hydrate and alumina. Also, a few specialty grade alumina plants are under execution and planning stage in the World.

Looking at the past and the present trend, it can be concluded that market potential for specialty grades of hydrate and alumina in future is promising.

Seek your views / comments, if any.

If you like this article, then please press your rating as  +1  .
Thanks and regards.

Kunwar Rajendra