Switching to AFR using emerging & efficient technology
KHD Humboldt Wedag has vast experience in the field of providing latest state-of-the-art technologies and keeping-up the solutions ahead of the market requirement. The consistent market share for last 160 years is the benchmark that we have set-in and this legacy is continued with much more thrust in last 10 years. Coming to Alternative Fuels and Raw material (AFR) applications, we have diversified solutions depending up on the type of alternative fuel the end Customer wants to use. Snapshot of the product portfolio is summarised below:
PYRO-JET® AFR Kiln Burner: KHD has specially designed PYRO-JET® AFR kiln burner for maximum utilisation of alternative fuels. The unique features of this burner enables perfect flame shaping and mixing of fuels with oxygen from primary air and secondary air, faster AFR burn-out in the entrained phase, stable ignition and maintaining hot sintering zone due to better flame characteristics. For higher alternative fuel substituiton rates, the specially designed AFR retractable swirl nozzle is also configured in the system to make surte that fracturing, mixing of the AF flow achieved shortly before entering the kiln with appropriate spraying angle and improving the mixture within the flame core and with oxygen.
Alternative fuels such as plastic, paper foil, rice husk, RDF, saw dust, wood ships etc. with acceptable feed size can be fired in the kiln with this burner. Also, liquid alternative fuels such as solvent, pharmaceutical waste, etc. can be used in this burner with additional guide tube and associated valve train system.
PYROCLON® Calciner: Over the years, KHD has continuously improved the calciner systems to accommodate firing options to use wide range of alternative fuels. The KHD trade mark tubular calciners are perfect choice for firing coarse solid AFR, due to well balanced velocity and retention time inside the calciner. Patented PYROTOP«, part of the calciner takes care of mixing of fuel with gas & meal and also increases the retention time.
PYROCLON® R Calciner: Suitable for solid fuels with 2D size of <40 mm which can be lifted in the gas and easy to ignite.
PYROCLON® R Extended Calciner: Suitable for solid fuels with 2D size of <50 mm which can be lifted in the gas and easy to ignite.
PYROCLON® R Calciner + Combustion Chamber: Suitable for solid fuels with 2D size of <100 mm which are coarse and difficult to ignite. High calciner volume and additional residence time will be achieved with Combustion chamber. Start of combustion in pure tertiary air, open flame and center of combustion chamber is nearly kept free from meal leads to faster ignition. Additional mixing will be achieved at transition point of combustion chamber to calciner tube.
What are the advantages of this equipment and where they are installed?
In greenfield cement plants, the solutions discussed above can be integrated in the system design with minimal Capex to achieve maximum benefits. Also, in existing plants, most of these solutions can be introduced looking in to the layout feasibility. Solutions such as Burner, calciner, etc. are anyway required for clinker manufacturing process. Adopting them for suitable AFR usage can lead to advantages in terms of higher AFR substitution. The process advantages of these solutions are already discussed above.
We have AFR feeding and dosing installation references with renowned cement houses like UltraTech, Lafarge (now Nuvoco), Jaypee Cement (now UltraTech), J K Cement, etc.
What are the changes that have to be made in the process for installing these equipment?
In existing systems suitable adoptions in layout to be accounted for and in some cases tailor-made solutions to be exercised due to compact layouts. Further, looking in to the chemical composition, physical properties such as moisture etc. of fuels and its heat value, one has to review the capacity of Preheater fan. More often than not, the exhaust gas volume tend to increase with AFR usage at base clinker production rate.
It is necessary to have certain design margin for trouble free operation. Further, with respect to the chemical composition and circulating elements viz. Cl and S, necessary precautions to be incorporated in the system to avoid heavy build-ups, jamming issues by installing air blasters, compressed air rings at appropriate locations and if necessary bypass arrangement of kiln gases to minimise the operational constraints. Also, raw mix to be reviewed and optimised with respect to type of AFR usage.
How do they impact operating and capital costs? What are the factors one has to look into while selection of AFR materials?
For any alternative fuel usage, a detailed study is mandatory before going ahead with the execution of project. Of course, the availability of alternative fuels is one of the main criterions to be taken in to consideration. The capital costs are one time investment and should be evaluated on case to case basis looking in to the technology, reliability, availability of the system.
The overall operating cost is combination of lot of factors such as impact of AFR on specific power consumption, specific fuel consumption due to increased moisture and excess air requirement. Further detailed analysis to be exercised on the critical chemical components, which will influence the clinkerisation process such as sulphur, chlorine etc. High amount of such components can lead to continuous operational disturbances with clogging, coating, etc. which in turn influences the production rate. Such parameters to be critically analysed during the project inception stage itself. The following factors has influence on operating costs which needs to be reviewed thoroughly.
Influence on energy balance thus specific heat consumption
- Increased waste gas volumes (higher fuel moisture, fuel chemical composition, higher excess air demand, more fuel to maintain hot sintering zone).
- Higher amount of primary air (transport air) and leakage air, decrease of recuperation air from clinker cooler.
- In case of bypass system losses due to bypass gas extraction.
Influence on plant operation stability thus production rate
- High demands on fuel dosing equipment, continuous fuel feed.
- Formation of build-ups in case of Cl- and S- rich alternative fuels in the area at kiln inlet, riser duct, bottom most cyclone etc. This requires more manual cleaning efforts or else Bypass System is necessary.
Influence on clinker quality and market demand
- "Raining" of unburnt fuel out of the kiln flame to the clinker bed => reduced burning conditions.
- Cooling down of the sintering zone.
- Possible enrichment of harmful elements in clinker, e.g. MgO, P2O5 (depending on Alternative Fuel ash composition).
- Adaption of raw mix, e.g. high Fe- content in Alternative Fuel.
Influence on emissions / fossil fuel availability
- Positive influence on avoiding NOx formation and / or NOx reduction.
- CO formation in case of inadequate calciner technology or unsuitable secondary fuels.
- Saving of primary fossil fuel.
What are the advanced technologies available for AFR? How receptive have Indian cement manufacturers to these innovations?
As already explained above, we have state-of-the-art solutions for wide range of fuels and the same are being updated from time to time as per the demands of industry. Looking in to the difficulties in preparing the alternative fuels to the required size to be fed in already known solutions such as kiln burner, Calciner, Combustion chamber etc., we have recently come up with more robust latest generation solution i.e, PYROROTOR, suitable for firing coarse alternative fuels. Two such installations are under execution stage Globally and after reviewing the results we would like to introduce the same in Indian market. We are sure that this latest technology will change the course of AFR utilisation process in cement industry.
Features of PYROROTOR®: PYROROTOR, unique combustion reactor for cement plant applications for the thermal treatment of alternative fuels and raw materials. Due to high temperature process and longer residence time it is suitable for nearly all types of alternative fuels. Tertiary air is used as combustion air in PYROROTOR. Mechanical fuel transport through the reactor provides sufficient residence time. PYROROTOR is generally located above rotary kiln, between tertiary air duct and kiln riser duct. Indian cement manufacturers have always welcomed such new innovations. The cement market in India is competitive and manufacturers always strive for achieving price advantage by implementing new technologies. Higher AFR substitution rates can reduce the overall fuel cost which is one of the major cost input factor in clinker/ cement manufacturing. Solutions like PYROROTOR should become instant hit due to its unique advantages of suitability for using wide range of alternative fuels with minimum processing which reduces the preparation cost significantly.
What are the challenges companies face in sourcing AFR materials and what are the strategies they follow?
The majority of cement plants in India are using alternative fuels as an alternative energy source to minimise the operating cost by substituting usage of expensive fossil fuels. This gives competitive edge in terms of reduced manufacturing cost of clinker/cement. Also, there are few cement groups who has taken alternative fuels usage as a corporate social responsibility to minimise waste. However, in future, alternative fuels usage in cement industry works on sustainable basis if there is reasonable advantage to manufacturers in terms of cost reduction. As of now, the main challenge lies in availability of waste alternative fuels of consistent quality throughout the year.
Depending upon their geological locations and availability, the plants which are closer to the waste generation locations like pharmaceutical waste, treated RDF municipal solid waste, plastics, agriculture waste etc., are using AFR. The negative fuel cost in comparison to fossil fuels is working in cement plants favor as of now as these wastes are available at negative cost or at very marginal cost. The per kcal cost of prepared alternative fuel inclusive of sourcing, transportation, preparation, feeding etc. is lower than fossil fuel specific rate which keeps the balance to use AFR in cement plants. Looking in to this derivative, plants are sourcing and using alternative fuels on case to case basis. The evergreen economics rule of demand vs supply vs price will prevail and such situation may arise in future as the case is now for flyash, petcoke, etc. However, there should be some strict legislation from Government with well-modulated incentives to increase total substitution rate.
At what level is AFR used in Indian cement plants when compared to global benchmarks, and how long the industry may take to reach that level of efficiency?
The AFR substitution rate in Indian cement industry is less than 5 per cent TSR, which is remarkably low when compared to the standards of Europe where the AFR substitution rate is more than 40 per cent. There is huge scope for improving the figures that we are clocking today. It needs continuous support from Government and associated bodies. A critically reviewed vision plan to be laid out involving all the stakeholders to target the TSR levels of developed nations. Actions by all stakeholders are critical for realisation of the vision to become reality. Government and industry must take collaborative action to create a favorable framework for accelerating and implementation of AFR usage in cement plants.
Government should create and enable level playing field for the AFR users by providing interim financial stimulus packages that compensate and provide an edge in pricing pressures. Also, Government should take initiatives to establish latest state-of-art waste treatment plants, crop waste processing units, etc. in collaboration with cement plants in that particular cluster to supply segregated and treated alternative fuels.
Putting latest and innovative technological change into action is another aspect to improve the AFR usage. All stakeholders should intensify collaborative action to increase the implementation of state-of-the-art technologies and share best operating practices. Governments and industry should ensure sustained funding and supportive risk-mitigating mechanisms to promote the development and demonstration of new technologies and processes that offer increase in AFR utilisation. Such measures will act as springboard to improve the AFR utilisation and TSR in Indian cement industry.
About the authors: Authored by: Ashok Kumar Dembla, Managing Director & President, Humboldt Wedag India Pvt Ltd
Co-authored by: Sita Ram Sharma, Head - Parts & Services, Humboldt Wedag India Pvt Ltd.