We are exploring opportunities for installation of WHRS at other plants
ACC Ltd-one of India´s leading manufacturers of cement and concrete with operations spread throughout the country with 17 modern cement factories, more than 50 RMC plants, 21 sales offices, and several zonal offices-successfully installed a waste-heat recovery system (WHRS) at its Gagal cement plant in Bilaspur district of Himachal Pradesh, with an investment of Rs 100 crore in 2013.
"WHRS are the requirement of waste heat for drying of raw material, fuel as well as additives. Most of our plants have been optimised for heat recuperation in the preheater as well as clinker cooler," says KN Rao, Director - Energy & Environment, ACC Limited, during an exclusive interview with the ICR team. He speaks at length about how to reduce energy consumption and ACC´s future plans.
As one of the important players of the industry, how do you assess the scope of upgrade of your existing pyro-processing system in your plant?
A robust and technically strong in-house team reviews, identifies and implements actions to continually improve thermal efficiency of the plants. Besides, close monitoring of operational measures like reduction of infiltration of air through continuous focus, burner momentum, raw-mix, etc. are taken to sustain/reduce thermal energy consumption.
Computatation Fluid Dynamics (CFD) studies are carried out on a continuous basis through in-house expertise to improve heat recuperation in preheater cyclones, besides reduction of pressure drop.
Please elaborate on your initiatives/improvements taken in terms of optimisation. Plants took up various debottlenecking/optimisation activities to improve the kiln productivity. Some of the activities are mentioned below:
- The kiln and calciner coal firing systems were upgraded for consistency and accurate coal feeding
- Modificationon in preheater cyclones
- Re-routing of coal injection and reduction of calciner outlet temperature with optimisation of degree of calcinations (DOC)
- Controlling fine coal residue and moisture(grinding media change and taking hot air directly from kiln
b)Use of high efficiency coolers:
- Control Flow Grate (CFG) to reduced fall through (RFT) conversion in clinker cooler and compartment modification fan replacement
- Modification of cooler inlet with addition of new fans to improve rate and recuperation, which resulted in reduction in average PH tower O/L temp by 50C
c)Upgrade in process fans:
- Replacement of process fans (preheater fan, raw mill fan, etc) with high efficiency fan and installation of medium voltage drives for speed control of major process fans
- Replacement of impellers to improve operating efficiency
- Modification in fan circuit to reduce pressure drop
- Replacement of existing PA fan by high pressure turbo blower along with burner tip modification to improve burner momentum, reduce primary air and Nox and improve combustion.
d)Improved refractory technology:
- Focussed monitoring of radiation and prompt action for any abnormality.
If you have already gone ahead with the improvements could you brief us on the results in terms of reducing energy consumption, and bringing down cost of operation?
The various initiatives, some of which have been detailed above resulted in reduction of 16 MJ of specific thermal energy/tonne of clinker to 3,050 MJ in 2014 as compared to 3066 MJ in 2013. In terms specific CO2 emissions per tonne of cement, the same reduced to 526 kg CO2/tonne of cement from 538 kg CO2/tonne of cement.
A significant portion of the energy requirement can be sourced through utilisation of waste heat from the pre-heater and cooler. Could you brief us on the initiatives (installing WHR system) taken by your company?
ACC has commissioned WHRS system at Gagal, during 2013. The potential for generation of WHRS depends on the thermal efficiency of the clinker cooler and the pre-heater. Other factors influencing WHRS are the requirement of waste heat for drying of raw material, fuel as well as additives. Most of our plants have been optimised for heat recuperation in the preheater as well as clinker cooler. We are exploring opportunities for installation of WHRS at other plants where waste heat is available for recovery through economically viable WHRS.