Journey of AFR with indigenous systems

The AFR (alternative fuel and raw material) journey of Dalmiapuram and Ariyalur (Tamil Nadu) plants is dealt with, highlighting the key actions from an in-house team.

Though the Indian cement industry has achieved excellence in energy efficiency, AFR (alternative fuel and raw material) usage still remains an area where much more can be done. The current Thermal Substitution Rate (TSR) in Indian cement industry is less than 4 per cent, as compared to some European countries that have TSR as high as 80 per cent. Increased use of alternate fuel in the Indian cement industry is not only a potential solution towards sustainability, conserving the depleting fossil fuel but also identified as one of the key levers to reduce carbon footprint.

At Dalmia Cement Bharat Ltd, use of AFR is identified as a key focus area, sustainability is rooted in its corporate vision – “Our vision is to become a leader in building materials and evoke pride in all stakeholders through customer-centricity, innovation, sustainability and our values.”

In this article, the AFR journey of Dalmiapuram and Ariyalur (Tamil Nadu) plants is dealt with, highlighting the key actions from in-house team. The way forward for increasing use of AFR in cement industry is also suggested.

AFR utilised at Dalmiapuram plant with an in-house developed feeding system
Objective:

• Maximising AFR consumption, with minimum investment
• Reducing the operating cost
• Reducing the capital cost

Challenges in the earlier system:

• AFR material was fed in to Line 1 Pyro clone, through winch bucket and handled manually
• The lifting height was 45 m from ground level
• Handling the AFR material in bags was laborious
• Low feed rate
• Extra coal consumption due to false air entry
• CO generation due to inconsistent feed
• AFR feeding system supplied by third party had high capital cost not justifying the ROI due to low volumes of available waste materials
• The plant team decided to go for an in house system, using available resources.

Actions taken:

• An available unused lift was modified for bulk handling of solid mixed AFR
• A motorised tippling chute arrangement was made in the ground level to fill the lift cabin
• The lift cabin was modified with bottom trap door arrangement, to unload material in to the storage bin
• 10 tonne capacity surge bin was placed at 45 m level for receiving material from lift
• The extractor in the surge bin fed the material to a belt conveyor with variable speed control
• The belt conveyor discharges to a screw conveyor, which is finally feeding in calciner bottom duct through air lock, i.e., double flap valve

Savings:

• The in-house AFR feeding system project cost was only about 10 to 15 per cent of the price quoted by supplier of a new system
• The power consumption of the installed system was lower

With Innovation …Creativity…Team work, this plant team initiative was a big success. Results achieved at Dalmiapuram plant – TSR 10.75 per cent in FY 2016-17: With various actions including the above in-house feeding system and regular focus and monitoring, our plant team could achieve a TSR of 10.75 per cent, by using various types of waste.

Usage of AFR at Dalmia Ariyalur plant
Alternate fuel is received from nearby area and stored as per allotted space. With the help of tractor or dumper material is shifted to pre heater location. The material is fed to a lifting arrangement to calciner floor. Solid mixed AFR material is filled in the feeding arrangement hopper which is a screw weigh feeder system discharging at calciner bottom portion with proper air sealing arrangement. The feeding system is supplied by a reputed vendor for accurate dosing of AFR. The discharge chute is having two hydraulic flaps and below the hydraulic flap one emergency pneumatic gate is provided for safe operation and fire prevention. Various AFR materials are used through the system and the trend of current usage is depicted in the bar chart.

Safety aspects for AFR utilisation
Incoming material is studied with due respect to safety as per the material safety data sheet. All incoming AFR is received in covered authorised trucks and stored in respective yards under covered condition. AFR handling persons are trained by the competent persons. During AFR handling, all persons are given specified PPEs. Daily safety tool box talk is carried out before starting the feeding activity. Workmen health is checked by the company doctors at regular intervals.

The way forward
Long term supply contracts are required for justifying the capital investment in AFR handling and feeding equipment. The quality variation in the AFR needs to be absorbed by the plant by careful process planning and optimisation. To cover the operation cost and penalties due to high ash, moisture and low net heat value, adequate gate fee needs to be provided that should be an essential element of waste management policy. High volume waste like RDF from MSW is available but as the polluter pays principal is still not applied such waste are not viable for the cement plants. Further cement Industry can also use large volume agricultural residue as AFR in energy efficient and environment-friendly manner provided an encouraging policy framework is developed in this regard.