Energy Management

Replacement of Existing Cyclones with Low Pressure Drop (LP) Cyclones

Background

The Pre-heaters comprising of 4/5/6 stages of cyclones is an important part of the Kiln section in a Cement Plant. In the pre-heaters the waste gas coming out of the Kiln system is used for pre-heating the kiln feed material. With increased focus towards more heat recovery from the waste gas, the number of pre heater stages have been increased from 4 to 5 / 6. The increase in the number of stages however led to increase in the pressure drop across the system and hence higher fan power. This led to the development of cyclones, which have a lower pressure drop. The low pressure drop (LP) cyclones have the advantage of

Low pressure drop. Hence, lower Pre-heater fan power consumption.
Higher output rate with the same Pre-heater fan
Reduction in thermal energy consumption

Previous status

In a million tonne dry process pre-calciner plant, there were 4 stages of conventional cyclones with a twin cyclone at the top. The pressure drop across the top twin cyclone was about 100 – 125 mmWg.

Energy saving project

The existing top stage twin cyclone was replaced with a low pressure drop cyclone.

Implementation methodology & time frame

The top cyclone was at a height of nearly 106 metres. The implementation of this project involved removal of the existing cyclone and fixing of the new LP cyclone. The normal procedure involves the following steps:

Removal of the bricks inside the existing top cyclone
Removal of the old cyclone
Installation of the new cyclone
Refractory lining of the new cyclones

This procedure however needs a stoppage of the plant of more than 90 days. The plant could not afford such a long stoppage and the consequent loss of production.

Hence, the procedure was improvised to reduce the plant stoppage time. The improvised procedure adopted by the plant is as below:

The entire cyclone was assembled at the ground floor
The inside brick lining was also done at the ground floor only
The plant was then stopped and the existing cyclones removed
The entire twin cyclone along with brick lining was lifted to the top and fixed. A special crane was used for lifting the cyclones of about 150 MT to a height of about 106 metres. In this manner, the project could be implemented with a stoppage of only 20 days.

Benefits of the project

There was an increase in the output of the Kiln, reduction in pressure drop of the pre-heater, reduction in Kiln section power consumption and reduction in Kiln specific thermal energy consumption. The comparison of the conditions and the energy consumption before and after installation of the LP cyclones are as below:

Parameter Before Implementation After Implementation

Clinker Production 2650 TPD 2850 TPD

DP across Top Cyclone 100 – 125 mmWg 70 – 90 mmWg

Kiln section Power 30 kWh /ton 28.5 kWh / ton

Heat Consumption 830 kCal / kg 810 kCal / kg

The implementation of this project resulted in a power saving of 1.5 units / ton of Clinker, which annually amounted to 14 lakh units / year. Additionally there was also the thermal energy reduction of about 20 kCal / kg. The increased output of 200 TPD of clinker also aided in reducing the fixed cost component.

Financial analysis

The total benefits amounted to a monetary annual savings of Rs. 240 lakhs. The investment made was around Rs. 220 lakhs. The simple payback period for this project was 11 months.

Benefits of low pressure drop cyclone