Read part 2 here.
Example project: Myanmar cement plant
Change of product portfolio (OPC to composite cements)
Currently only OPC according to EN 197–1 is produced at the plants. The actual cement-to-clinker factor is 1.05 due to the addition of only 5% gypsum to the cement. The cement has a fineness of 3400 Blaine and its compressive strength still remains below 59 MPa at 28 days. At present, the products are produced in accordance with the current market requirements in Myanmar.
A change in the cement product portfolio, reducing the production of OPC cements and increasing the production of composite cements, results in a reduction in specific CO2 emissions. A reduction in the specific production cost per tonne of cement produced a direct financial benefit. Such changes in the product portfolio are directly linked to the sales and marketing strategy of the owner. In this example the owner is vertically integrated downstream and as such can channel a significant portion of the plant’s production capacity within their own value chain and define product requirements.
Trass is available in the vicinity of the plants. The initial target is to produce a composite cement with 15% trass addition. Furthermore, limestone could be added as another additive in the range of 5% according to EN 197–1. The resulting composite cement would have a cement-to-clinker factor of 1.25. This will result in indirect energy consumption and a CO2 conservation of 20% of actual specific thermal energy and CO2 emission. Compared to OPC production of the upgraded/modernised plant at 2100 tpd and coal firing, thermal energy savings of 160 kcal/t of cement and 0.18 t CO2/t of cement (117 180 tpa CO2) could be achieved. These savings are of a secondary character based on the “dilution” of the OPC, but are an efficient method of conserving energy and CO2.
In many cases production of composite cements requires a higher electrical energy consumption due to an increase of cement fineness and increased material grindability of cement additives (e.g. industrial blastfurnace slags). Naturally occurring mineral components, such as pozzolan and trass, typically have lower material grindabilities as compared to clinker. When no specific data is available, and the grindability of trass normally reaches similar figures compared to clinker, a 10% increase in electrical grinding energy has been considered.
Frequency controlled MV motors
In many plants, including this case study, only fixed speed MV electro motors are installed at the major drives of the plant (limestone crusher, raw mill, kiln fan, cement mill and coal mill). As part of the modernisation project, new equipment will be installed, including frequency controlled MV motors. This will result in a specific saving potential of electrical energy of 10%/t of cement for all MV drives.
Motor controllers at LV motors
LV motors typically run at a fixed speed under the provision of rated load requirement. In many applications in a cement plant (e.g. at bucket elevators, belt conveyors, etc.), fluctuations in material load could save electrical energy. To do so, LV motors could be equipped with power saving controllers. Such controllers could reduce the power consumption of selected LV motors by up to 20%.
Minor energy conservation measures
Besides the major energy conservation measures identified at this cement plant, a series of minor but mentionable energy saving measures have also been recognised:
- Optimisation of mining machinery could reduce transportation costs of raw materials.
- Optimisation of the composition and burnability of the raw mixture (LSF, SM) could result in savings of thermal energy.
Energy conservation passport
The ECA results in the issue of an energy conservation passport for qualified measures, or according to the relevant department of a cement plant.
The energy conservation passport of a specific energy saving measure (thermal and/or electrical) includes the existing energy consumption, the future energy consumption, the financial impact (saving potential of energy and cost, as well as the environmental impact) and the CO2 emission balance, if applicable.
An ECA and corresponding energy conservation passport(s) provide a basis for the application of energy conservation funds of loaning institutions. The given example of a large capital project does not include the complete spectrum of options of energy and CO2 savings within a cement plant project, but it provides a clear and targeted overview of the environmental and financial performance possibilities.
The option to fund a large capital cement plant project (at least partially) through energy conservation funds should not be underestimated or neglected.
Written by Piet Heersche and Dr Hans Wilhelm Meyer, Cemcon AG, Switzerland. This is an abridged version of the full article, which appeared in the February 2014 issue of World Cement. Subscribers can view the full article by logging in.
Read the article online at: https://www.worldcement.com/asia-pacific-rim/12022014/project_funding_for_energy_conservation_part_3_730/