Energy Management

Replacement of the Air-lift with Bucket Elevator for Kiln Feed Transport to the Silo

Background

The kiln feed after blending in the silo is conveyed to the top of the pre-heater for further processing. The transport of kiln feed is normally done through pneumatic conveying systems such as air-lift. The pneumatic conveying system consumes more power, nearly 3 to 4 times that of the mechanical conveying system. Also, the pneumatic conveying system adds additional cold air to the pre-heater system, thus reducing the thermal efficiency of the system. Conventionally, the pneumatic conveying system was being preferred as the mechanical system (particularly the Bucket elevator) was not very reliable. In the recent years with the improvement in the metallurgy, bucket elevators that can operate continuously in a reliable manner have been developed. These have been installed in many plants with substantial benefits.

Previous status

In a million tonne dry process pre-calciner plant, the Kiln feed was being conveyed with the help of an air-lift.

Energy saving project

The air-lift was replaced with a bucket elevator. The air-lift was retained to meet the stand-by requirements.

Implementation methodology & time frame

The installation of the Bucket elevator took about 6 months. There was no stoppage of the plant, and the installation of the Bucket elevator was done parallely. The bucket elevator was hooked up during the regular stoppage of the Kiln and a separate stoppage was avoided.

Benefits of the project

The implementation of this project resulted in reduction of power from 146 kW for the air-lift to 51 kW for the Bucket elevator. The air handled by the pre-heater fan also got reduced resulting in pre-heater fan power consumption by 14 kW. The thermal saving was about 3.2 kCal/kg of clinker.

The saving annually amounted to

Electrical saving - 8.6 lakh units / year
Thermal saving - 2112 MMkCal / year

Financial analysis

The total benefits amounted to a monetary annual savings of Rs. 34.0 lakhs (@ Rs.3.1/unit & Rs.350/mmkCal) The investment made was around Rs. 75.0 lakhs. The simple payback period for this project was 27 months.

Benefits of installing bucket elevator for Kiln feed