Flyash - High value added products and application (technology & markets)

Code No: TMS101 Price: Rs1440/- Category: Foods & Agriculture: Sugar Industry By Products


Table Of Contents : Exectuvie summary; Introduction; Flyash overview; Current application profiles – Flyash high value added products; Current technology status-Flyash high value adeed products; Current infrastructure status; Technology evaluation – Flyash high value adeed products; Market potential for flyash; Recommended action plan; List of annexures

Flyash-High value added application (technology & markets)


Study Objectives

The report is to carry out a detailed techno market evaluation of various high value added products and applications of flyash with a view to identify the viable technologies available to India and determine the market potential of these technologies within existing constraints. The report is to address whether flyash apart from its high volume low technology uses could also become a resource material for various low volume but high value products and specialized applications, provided the mechanism of its formation is adequately and scientifically understood, users and manufacturers are sufficiently informed and educated and an infrastructure could be evolved for its proper characterization and grading. The objective is to come up with recommendations for appropriate course of action to utilise flyash for high value added applications.

The Scope of the Study

The scope of the report covers the broad techno market evaluation of high value added products and applications of flyash. It is to identify major applications developed internationally and its their status in India; determine the current technology status of various technologies both in India and abroad, understand the likely future trends in this field, outline major infrastructure capabilities and constraints of India in the field of flyash utilization, evaluate the key technologies available to India on various counts – technical, economical, social and environmental and finally attempt to identify specific products/applications that could be explored in the country giving its broad market potential and recommended course of action for its implementation.

Importance of the Topic

Consequent upon increased generation of electricity through thermal route involving combustion of pulverized coal/ignite, concurrent generation of flyash in bulk quantities is a matter of serious concern not only because of issues associated with its disposal and utilization but also because of its threat to public health and ecology. It is anticipated that by the year 2000 A.D. Indian thermal power stations together will be generating around 100 million ton of fly ash per year and the deteriorating quality of coal will be aggravating the situation further.

At present, large quantity of flyash is being dumped in slurry form in large areas close to the power plants without being put to gainful use. Only a very small percentage (<3.5%) of fly ash generated in India is being used for gainful applications whereas the corresponding figures of other countries may vary from 20 to 80%. The main emphasis upto now in our country has been towards the utilization of flyash for low and medium value applications like bricks, part replacement of cement and in mass concrete for dams etc. Such efforts have so far not met with much success as is obvious from the low figures of utilization. Efforts will therefore have to be directed to developments of other commercially viable products, which may yield high value addition to its manufacturers. Such applications include metal extraction and use of flyash as raw material for certain high value products. These kinds of products though consume very low volume of flyash in absolute terms, however have the potential in yielding considerable sales revenues for their end products.

It is estimated that the total mineral wealth of our flyash is approx. of the order of Rs.30,000 crore/year which is expected to grow 2.5 times by the end of the century. Significance of this area could well be understood from the fact that, just 1 million ton of flyash if put to use for different high value added applications has the potential of yielding a total turnover of Rs.500 crore per year. By contrast, if the same amount of flyash is to be used for say manufacturing of bricks, the total output may be to the tune of just Rs.25 crore.

The Methodology

The methodology of the survey includes both secondary and primary survey. All published information involving more than 100 articles in international magazines, journals, reports, seminar proceedings in various libraries have been researched during the secondary survey. For the purpose of primary survey, direct as well as indirect contacts have been established through structured questionnaires with several agencies both in India and abroad.

Keeping in view, the small no. of organizations working in this field, a carefully researched sample had been drawn to get maximum possible coverage. The effort has been made to give equal representation to all possible segments – manufactures, R&D institutes, laboratories, electrical utilities, associations, consultants, Govt. departments, potential users and regulatory agencies.

Current Application Status

Various known applications of flyash that we have been able to identify are given in the following:

As a resource material

As a raw material

Alumina High wear resistant ceramic tile
Magnetic Mineral Wool
Carbon Glazed floor and wall tiles
Cenospheres Ash alloys
Mineral Fillers Synthetic wood
Enhanced Pozzolana Decorative glass
Other Minor and trace items Fire bricks
  Fire abatement applications
  Adsorbent for toxic organics
  Foam insulation products
  Ceramic Fibre
  Oil well Cement
  Domestic cleaning powder
  Continuous casting mould powder
  Ultra light hollow sphere for arid zone cultivation

  Current Market Status

Current market investigation on the utilization of various flyash high value a deed products and application in the country is virtually absent for commercial applications. It can be concluded that currently there is a negligible market for these products though the potential may be substantial.

Current Technology Status - Global/India

Mineral Extraction

Different methods of recovering metal values from coal ash have been evolved over the last 50 years. The researches have concentrated on extraction of carbon, alumina, magnetite, cenospheres and other metal values. Of the elements present in coal ash, iron and aluminium have been examined most extensively for recovery. Of the minor and trace elements, the extraction of gallium, germanium, uranium and molybdenum have been investigated most frequently.

Recovery of element constituents from coal ash have been accomplished using both physical and chemical processes.

Chemical processed for the recovery of major constituents of coal ash have been formulated and tested at lab/pilot scale in four general categories. (Mainly at Oak Ridge National Lab., Ames Laboratory and EPRI, USA):

  • Hydrothermal leaching
  • Sinter-leach
  • Gas solid reaction
  • Direct reduction

The commercial viability of these processes are in their early stages of establishment and at present they appear to be viable only under certain circumstances. Polish researches have led to development of sintering disintegration method (a variant of lime soda sinter process) which is found to be a commercial viable process.

Methods have now been developed at lab scale by Israel electric Corporation Ltd. to extract metal oxides using bio leaching process which is considered to be much more economical than acidd leaching process.

Research is on to determine the technological feasibility of extracting alumina through combination of raw materials, the value of different flyashes and technological conditions of sintering process.

The separation of magnetite has been achieved using both dry drum magnetic separators and wet drum magnetic separators. The techniques have also been developed to use both dry and wet magnetic separators in sequence to maximize the quantity of magnetic materials (dry separators) typically and enhancing the quality of the recovered magnetic (wet separators).

In USA, M/s. Cenosphere Research Incorporation and in UK, M/s. Fillite Ltd. have developed and perfected the collecting, separation and classifying technologies for the recovery of cenospheres for variety of filler applications in the industry. Various organizations have developed several applications of cenospheres both in industrial and household sectors.

Technologies for recovering carbon concentrate from flyash by flotation have been successfully developed and is in commercial operations. Similar Scientific Services Incorporation of USA have successfully investigated and tested the use of carbon obtained from flyash as replacement of carbon black in tyre/rubber industry.

Considerable experimentation and testing is going on to classify the spent flyash available after mineral extraction so that different fractions could be supplied to different markets. Pioneering work is being done at EPRI for plastic filler applications and its use as enhanced pozzolanic material for cements.

Use of Fly Ash as Raw Material

Ash Alloy: Pilot scale trials have been successfully conducted for Development of aluminium flyash alloys using inexpensive casting techni-que. This technology can save considerable amount of aluminium, zinc and cast iron.

  • Coal ash mineral wool: Commercial technologies have been developed to substitute mineral wool.
  • Foam insulation products: Precipitated silica mixed with flyash is employed as an insulating Material as a substitute for polyurethane. The technology is at pilot scale.
  • Flyash Fire bricks: Technologies are commercially available.
  • Decorative Glass: Lab scale trials have been successful.
  • Fire Abatement applications: Technologies have been developed for refuse pile fire abatement with flyash slurry injection.
  • Filler application: Cenosphers have been successfully used as plastic fillers while spent ash is substituting conventional fillers in several applications and being used as enhanced pozzolanic material for cement.
  • Light weight refractories: Cenospheres when sintered with certain proprietary aggulutinating agents, form light weight refractories.

In India work is being done on high value added products and applications by CPRI, RRL Bhopal, RRL Bhubneswar, RRL Trivandrum, NML, PDIL, IIT Kharagpur and IFFCO, etc. At CPRI, lab scale trials have been conducted to produce glazed floor and wall tiles, acid resistant bricks, hollow ceramics for arid zone cultivation, high strength insulation bricks and mosaic tiles. NML has developed technologies for manufacturing high wear resistant ceramic tiles as a substitute to high alumina ceramics for applications in wear and abrasive resistant areas. The technologies are now being perfected by PDIL for manufacturing of ceramic fibers from mullite obtained from flyash. IFFCO has successfully carried pilot scale trials for separating unburnt carbon from fluash slurry using hydrocyclones. Indian School of Mines, dhanbad is experimenting with use of flyash as adsorbant for water treatment applications. Nyvelli lignite has successfully demonstrated the use of flyash based distempers and domestic cleaning powders. IIT-Kharagpur has developed on lab scale continuous casting mould powders using flyash for its use in the moulds of continuous casting machines in steel plants. RRL Bhubneswar has developed pilot scale technologies for extraction of alumina, using down draft sintering as well as technology for insulation bricks. RRL-Bhopal has the technology for manufacture of synthetic wood on pilot level.

Current Infrastructure Status

  • Manufacturing:
  • Metal Extraction from Flyash No commercial or pilot plants in operation.
  • High value added products using flyash as raw material  No commercial plant in operation.
  • Raw material availability: Sufficient raw material is available in the country for metal extraction processes.
  • Flyash testing and characterization: Absolute lack of infrastructure and mechanism for ensuring flyash characteristic and grading at various thermal power stations.
  • Flyash handling and transportation: Inadequate infrastructure for dry collection, handling and transportation of flyash at thermal power stations.
  • R&D Work on high value added products and applications: Certain R&D institutes are working in the areas of  high value added applications.
  • Training, Education and Promotion: Inadequate
  • Govt. Support and Incentives: No special schemes in existence for encouragement of high value added products and applications facilities.
  • Information Dissemination: Considerable lack of information and appreciation among users and prospective investors on the implications and possibilities of high value added applications of flyash.
  • I.S. Standards: Formulated only for cement and bricks.
  • Demonstration Programs: Inadequate

Technology Viability Evaluation

Metal Extraction

Very few metal extraction processes are in operation internationally. Most of the processes are in early stages of commercialization. Coal ash recovery processes using hydro thermal leaching process and sinter leaching process – Calsinter process and lime soda sinter process appear to be most promising for commercial exploitation. Polish developed sinter disintegration process, is also found to be commercially viable and two plants are in operation in Poland. Most of the processes are viable under certain conditions. Hydrothermal leaching of flyash with alkaline solutions has been examined and found to be most viable on high PH ash. Moreover, most of the extraction processes are viable only for flyash with high alumina content above 25%.

Among the technologies investigated, Calsinter process and sinter disintegration process, appear to be most viable at the current stage of development. The viability need to be studied further for the quality and characteristics of flyash that are needed for the extraction. However, economics of none of these processes compare favourably with alumina recovery from bauxite using Bayer’s process. The processes may compete with Bayer’s process, when the alumina content in bauxite is below 50%.

Physical process for recovery of the iron rich fraction of ash from bituminous coal ash by magnetic separators is now commercially viable and a project is in operation in USA. Among the magnetic separation technology, the use of wet magnetic separators hold advantages over dry magnetic separators. The use of wet and dry magnetic separator combination appears to be another viable option offering the benefits of both the technologies.

Technologies for recovering trace elements have been developed. However, the chief road block to ash metal recovery processes developed is the economics of recovering these metals from such a lean ore as flyash.

Technologies for collection and classification of cenospheres is now commercially viable. Recovery of carbon using flotation technology and hydrocyclone separators have been developed and found to be commercially viable.

Flyash as raw material

Various high value added products developed using flyash as raw materials are found to be economically viable as discussed here.

The use of carbon derived from flyash as an adsorbant for waste water treatment and its use as filler for rubber industry has been established.

The use of flyash for manufacture of high wear resistant tiles appears to be viable as a substitute for high alumina ceramics for various abrasion and wear resistant applications.

The use f ash alloys is about to be a commercial reality following its success on pilot scale. The characterisation of mechanical and tribological properties of ash alloys developed show that if possesses superiro abrasion resistance, hardness, compressive proof strength and elastic modulus compared to matrix aluminium alloys without any ash.

Coal ash mineral wool is produced abroad based on well developed reliable technology. Quality of coal ash wool manufactured is comparable to the properties of conventional mineral wool at much lower prices.

Flyash composite wood substitutes developed in India using 25-35% flyash is considered to be low cost an better alternative to ordinary wood. It has advantages over cellulose products, plywood and fiber board for all domestic and household aplications.

Floater based light refractory materials developed are found to save 50% more energy compared to traditional refractory in furnace linings.

Products like ceramic fibers, foam insulation products, continuous casting mould powders, decorative glass are other potential technologies are under development. The full viability implications of the can be assessed, after they are tried on pilot scale level.

Cenospheres are now being successfully used as fillers in plastic like nylon and polypropylene. Size classified coal ash can successfully substitute various other fillers like aluminum hydrate, calcium carbonate, kaolin, mica, tale and ground silica. Their applications have been well established in wall board, joint compounds, carpet backings, vinyl flooring, plastics and industrial coatings,. etc.

Refuse fire abatement using flyash injections ahs proved to be a safe and effective technique. Control of the process using temperature criteria has been shown to be reliable. One projects where steep slopes are burning or access to the burning area is difficult, flyash injection has been the most economical and at times the only effective method of fire abatement.

Market Potential, Share & Expected Investment

The market prospects for high value added products is not easy to determine as the product is not in commercial use and the technology is in its early stages of commercialization. However, the market potential has been indicated for the products, that it may substitute in future. The exact market share that the flyash based products could achieve will depend upon different factors including Govt. regulation, incentives, user perceptions and attitudes, techno economic criteria for the process technologies developed and availability for infrastructural support.

The total market potential that exists for high value added products by 2000 AD is estimated to be Rs.5000 crore. The actual market size has been estimated for metal extraction under two different scenarios assuming setting up of a 1 lakh ton and 1 million ton flyash processing plant. Whereas for all other products, very low penetration levels have been assumed. Experience of other countries have been relied to estimate the penetration levels.

The expected market share and investment required are given below

Table A: Expected Market for Flyash Products/Technologies
and Investments


Item Category

Total Market Potential
2000 AD

Expected* Share of a Technologies

Expected Investment

Expected Utilization of FA
2000 AD

Metal Extraction:
Alumina, Titania, Magnetite, Cenospheres, Mineralfillers, carbon etc
Rs.4000 Crore Rs.45-450 Crore Rs.100-400 Crore 1 Lakh ton / yr to 1 million ton / yr
FA High Value Added Products/ Applications: Ash alloys, ceramic tiles, fire bricks, insulation products, mineral wool, ceramic fibre, distemper, synthetic wood, fire abatement applications Rs.1000 Crore Rs.75-80 Crore Rs.35-40 Crore 1200-1500 ton/yr


Rs.5000 Crore Rs.120-530 Crore Rs.135 – Rs.440 Crore 1 Lakh ton / yr to 1 million ton / yr

* Expected share range vary based on processing of 1 lakh ton / yr to 1 million ton /yr flyash for metal extraction applications.

Recommended Action Plan

Consistent long-term support from the Govt. of in terms of evolving appropriate guide-lines for promoting gainful utilization of flyash.

Giving due importance to high value added applications of flyash by creating proper demonstration program and other awareness building measures.

Evolving institutional arrangements / mechanism for coordinating matters relating to flyash handling, transportation characterization and availability of dry flyash.

Vigorous well-directed R&D and technical development efforts in developing high value added products/applications of flyash.

Setting up piilot / demonstration cum production plant in different parts of the country on various high value added applications of flyash.

Pilot Plants Recommended

  • Extraction of alumina, magnetite cenospheres, mineral fillers, and other oxides.
  • Coalash mineral wool
  • Fire bricks/Heat insulation bricks
  • Ceramic fibres
  • Continuous casting mould poweders
  • Floater based light refractories
  • Glazed tiles

R&D Program Recommended

  • Ash alloys
  • Use of cenospheres and spent ash as filler in plastic, paper, pesticide, paints and textile coatings, etc.
  • Use of carbon as adsorbent for toxic organics.

To Evaluate and if found viable to promote the technology developed by NML for high wear resistant ceramic tiles for various industrial applications.

Govt. giving initial subsidy for a couple of years to flyash beneficiation plants in order to ensure their viability in comparison to conventional processes.

All prospective users/industries like aluminium plants, steel plants, cola plants, and other core sector industry to be directed to give preference to flyash products.

All thermal power plants to evaluate the possibility of going in for hydrocyclones to separate the combustibles (unburnt carbon) from flyash and recycle the same into the boiler.

Development of mechanism for effective inter-institute coordination and cooperation and dissemination of information to potential users through conducting national seminars, workshops, etc.

Study Limitations

As very few organizations have been involved in this area compared to low and medium value applications, if took a very long time to identify organizations working specifically in high value added applications of flyash.

Most of the developments and usages are taking place in foreign countries. It became difficult to asses the exact status of technologies and its evaluation without physically carrying out a survey abroad. Problem was compounded due to absolute lack of knowledge and appreciation for these applications among large segment of prospective end users and investors. Also response from one of the leading R&D institute which is known to have done work in this area was inadequate. The study had to rely mostly on indirect sources of information.