Reduction in energy consumption can be achieved through productivity optimisation

Reduction in energy consumption can be achieved through productivity optimisation

Sujit Sen, Vice-president, Process, PENTA India

Penta, a highly successful cement plant consultant, has carried out operational and energy audits and plant optimisation for many clients. "While most of our efforts have brought about improvements in productivity, they have also resulted in reducing operating costs. We have also been able to set right some unsuccessful projects which had been underperforming due to bad system design or incorrect operation," says Sujit Sen, Vice-president, Process, Penta India. Excerpts from the interview.

What are the external factors that affect energy consumption in cement plants?
There are certain macro factors that determine the focus on energy efficiency within the cement plants. These are the forces from outside which govern the decisions within the plant. The first one would be the price and availability of fuel. India has always seen higher fuel costs as well as electrical energy costs compared to many other parts of the world, so most of our cement plants have been installed with highly energy efficient processes and technology.

Market forces are another factor that one has to contend with. Running the plants at 70 - 80 per cent of installed capacity will drive out any of the benefits perceived in installing good equipment or carrying out energy management drives. In that case any discussion on energy efficient operation of the plant is purely academic. Productivity is the denominator in this equation and as long as plants cannot work at design or higher capacity, the specific energy consumption will not reduce. Operating at capacity for half the month and then shutting down or operating continuously with lower than design throughput is also not a viable solution as it will reduce the life of equipment and increase the cost of expensive consumables like refractories, lubricants, etc. Sustained energy efficiency is possible only when plants run continuously with hundred percent runtime and greater than hundred percent production factor.

Energy intensive industries are taking up a lot of green initiatives such as reducing one's carbon footprint. This awareness is another external factor that can drive cement industries towards continuous energy efficiency improvement. The use of alternative fuels and waste derived fuels in cement industry will also depend upon the environmental regulations that will either promote or dissuade the use of such fuels.

Which section or process in cement plant has the highest scope for improvement in terms of energy efficiency?
Most energy consuming sections in a cement plant are the grinding and pyro-processing sections. Any attempt to improve the productivity of mills and kilns will reduce electrical and thermal energy. There is scope of improvement in energy consumption in the selection of fans, compressors and pneumatic transport system, too.

What are the major challenges in retrofitting or setting up new cement plants?
Reduction in the energy consumption in cement plants can be achieved through productivity optimisation of the existing cement plants and or by modernising with state- of- the- art technology wherever viable. Major challenges during retrofitting are layout and space constraint, safety of plant personnel during modification and above all, the downtime of the plant. However at present scenario when capacity utilisation is 65-80 per cent the downtime should not come in the way.

In setting up new plants, any efforts towards energy efficiency will result in increasing the capital cost, since top quality grinding systems, VFD controllers for process fans, etc, will be warranted. In the face of the sluggish market and low cement consumption, these will be tough choices for the cement plant owners.

What is the scope for greenfield projects?
The per capita consumption of cement in India is far below than that of the average values for developing countries and therefore there is ample scope. . Even within India, there is a wide gap of per capita consumption of cement between rural and urban India. All major players are now applying limestone reserves mining lease and block the mines, keeping in mind the future growth of the country and increase of demand of cement.

At present, brownfield expansion of an existing cement plant installation is more encouraging over the greenfield projects. This is mainly due to less investment required per tonne of cement, less hassle in obtaining government clearances and at the same time, the brown field project can achieve the very close saving on both thermal and electrical energy as that of the green field project.

How much can an existing plant improve its energy efficiency?
The improvement of energy depends on the age of the plant and how the plant is operating. It is generally observed depending on the technology used in the plant and the kind of equipment, both thermal and electrical energy efficiency can be improved from 5 per cent to 30 per cent.

What is your outlook on the PAT scheme introduced by the Bureau of Energy Efficiency?
The PAT scheme in theory is a mandated energy management scheme which has benchmarked energy consumption for designated consumers and is now compelling these plants to undertake continuous improvement. The first three-year assessment period ends in 2014 and it is possible that most companies will be able to meet their targets this time. However, the next round will prove to be more difficult as the base line will be at improved levels. The success of the energy market place that is to arise from these efforts remains to be seen.

Could you give us with examples where you helped cement companies reduce energy bills?
As cement plant consultants we have carried out both operational and energy audits for our clients as well as plant optimisation. While most of our efforts have brought about improvements in productivity, they have resulted in reducing operating costs. We have also been able to set right some of their unsuccessful projects which had been underperforming due to bad system design or incorrect operation. Some of the examples are cited below. In one instance, kiln productivity has increased by 25 per cent; thermal power consumption reduces by 9 per cent and reduction of electrical power 12 per cent by carrying out a plant audit and setting right the operation parameters.

In another case, we carried out some minor modifications of the cooler and optimized its operation resulting on reducing thermal energy consumption of the kiln by 15 kcal/kgcl. In the case of one plant, the installation of pre grinder was not achieving desired results. We studied the operating data of the grinding circuit, identified the bottlenecks and suggested some minor changes. Subsequently with the joint efforts of plant personnel, equipment suppliers and consultants from PENTA, the productivity of the cement grinding circuit increased by 50 per cent and energy saving of around 7 Kwh/ tonne was achieved. In one plant, we were suggested some operational changes without any added expenditure which could enhance to production of the pyro-processing system by 15 per cent and thereby reduce specific fuel consumption.

How much can a plant expect to save in energy costs by applying IT solutions?
The implementation of MIS (management Information systems) helps to keep track of the key performance indicators. Management is able to monitor both plant operations and the productivity in a continuous manner. The plant operation is better controlled through proper automation and instrumentation to eliminate human error. Information Systems can be used to obtain idea of plant problems and discrepancy of plant operation. This data can be used to identify and solve recurring problems and increase the availability of the equipment. Thus run factor goes up, increasing the production and hence lower specific energy consumption. Moreover better control over inventory and spares can also be obtained through IT systems. Many MNCs have successfully used IT systems for years. However, in India, it is often observed that the plant personnel do not fully utilise these tools which are then limited to generating reports rather than help in decision making. It is also necessary to ensure that all sensors are calibrated and are working properly. Proper implementation of IT systems will enable to reduce not only energy costs but all operating costs as well. However the exact value of the savings depends on the maturity of the owners and plant personnel in exploiting these tools to their best capabilities.

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