Mondi South Africa is a wholly owned subsidiary of Anglo American plc. Its operations are focused on the production of pulp, paper, board, mining support systems and corrugated containers. Activities range from forestry operations to highly technical manufacturing and converting processes.
The increasingly competitive and demanding international pulp market has given rise to Mondi’s R2.3 billion RB720 expansion project, which raises the mill’s production capacity by 25% to 720,000 tonnes per annum, and accommodates a 40% increase in timber supply from over 2,800 small growers who form part of Mondi’s Khulanathi timber growers scheme.
The project began in 2001 with an engineering study that was followed by a detailed Environmental Impact Assessment in 2002. The regulatory authorities ultimately approved it in March 2003. Mondi’s policy is to operate in accordance with Best Available Technology (BAT) in terms of processes, operating equipment and infrastructure.
The mill operates two co-generation steam turbines for on-site power generation with a total capacity of 60 MW. Electricity is also imported from the national grid, comprising between 7 and 15% of the total energy used.
Targets
Primary objectives of the project were:
- Ensuring the long-term sustainability of the mill;
- Optimizing the capacity of two existing recovery boilers;
- Improving operational efficiencies;
- Reducing the water consumption and wastewater discharge resulting from the process;
- Reducing bleaching chemicals consumption by the introduction of an improved, new state-of-the-art bleaching sequence;
- Reducing raw material (wood) consumption per metric ton of product through the implementation of new cooking technology which increases the product yield in the cooking process;
- Reducing cooking chemicals consumption by improving process control.
In order to reduce future energy costs and maximize energy efficiency, it was important to:
- Understand the energy usage pre-RB720. The energy-intensive parts of the process were known from historical data as were the energy costs associated with it;
- Identify opportunities to reduce the energy usage. The mill wanted to implement cost-effective equipment that would maximize energy efficiency. It was also important to focus on alternative operational measures before investing in technological measures. This involved matching usage to requirement, maximizing system efficiencies and optimizing the energy supply; and
- Verify that energy efficiency targets were met continuously. This would be achieved by continually measuring and monitoring energy consumption throughout the operation against predicted energy consumption figures.
- Installation of a new hardwood continuous digester able to deliver improved steam economy due to its lower operating temperatures;
- Installation of a bleach plant to lower the usage of bleach chemicals;
- Adding a lime kiln, an evaporation plant and a pulp drier machine;
- Upgrading an existing causticizing plant;
- Adding a new super-concentrator to increase the solid content of the black liquor biomass to 80%.
The increased solids produce an additional amount of biomass available for steam generation in the two recovery boilers. The improved energy balance of the mill results in a lower coal demand for steam generation in the power boilers. A decrease in coal consumption from 562 metric tons per day to 234 metric tons per day has been realized, an improvement due to the increased amount of wood waste utilized as a source of energy generation.
The engineering challenges facing the project were unique. They included the fact that the commissioning and tying in of new equipment to the existing plant had to fit in with a working mill without loss of production at any stage. Technology interface of old and new plants added to the complexity of the project. Despite these demands, project was completed on schedule and within budget.
Results
The Richards Bay mill operates a Process Information system (PI) that tracks and records monitored information continuously. Information and data used in the calculations were verified by an external audit. A baseline was established using energy and production information for 2003. A comparison was done using information obtained during 2005 after implementation of the project.
A short overview of the results is provided in the table below:
For 2005 the emission reductions to the atmosphere compared with 2003 are the following:
- SO2 – 2,177 tons representing a 50% reduction;
- NOx – 509 tons representing a 35% reduction;
- CO2 – 297,121 tons representing a 50% reduction;
- Total reduced sulfur (TRS) emissions were reduced by approximately 60%.
By the end of 2005, Richards Bay achieved total energy and water cost-savings of R 38,678,843 compared with the projected energy and water costs without the introduction of energy-saving measures. This represents a net cost saving of 27.2% for purchased energy and water.
The energy cost savings that will be achieved over the life of the project will add to the bottom line, thus improving the competitiveness and financial performance of Mondi Business Paper Richards Bay.
Conclusions
In summary, the conclusions are:
- Mondi Business Paper Richards Bay embarked on a R2.3 billion expansion project (RB720) to optimize production capacity, increase energy efficiency and improve the environmental performance of the mill;
- Various energy-efficient technologies were chosen in the design stage of the project on the basis that they would help to realize a real reduction in water consumption and energy purchased;
- Richards Bay Mill used 44.3% less purchased energy in 2005 compared the baseline year 2003 due to the implemented energy-saving measures, in comparison with what it would have used if no energy-saving measures had been introduced;
- During 2005, Richards Bay reduced its energy and water costs by 27% compared with what it would have paid if no energy and water saving measures had been introduced;
- By the end of 2005, Mondi Business Paper Richards Bay achieved total energy and water cost-savings of R 38,678,843 due to the implemented energy saving measures compared with what it would have paid if no energy-saving measures had been introduced;
- A reduction of water use by some 13,000 cubic meters per day was realized as a result of the implementation of new technology, and wastewater volumes were reduced by more than 25%;
- During 2005 the following emission reductions were achieved:
- SO2 2,177 tons
- NO6 509 tons
- CO2 297,121 tons
- Total reduced sulfur (TRS) emissions were reduced by approximately 60%.
About the NBI and this case study
As a voluntary business coalition of 140 leading South African and international companies, the National Business Initiative (NBI) seeks to enhance the business contribution to sustainable growth and development in South Africa.
Partnerships with the Department of Minerals and Energy, the Capacity Building, Leadership and Action Programme, and the World Business Council for Sustainable Development aided NBI's work in this area and led to the signing of an Energy Efficiency Accord between business and government. The Accord offers business and industry an opportunity to meet national energy efficiency targets through collective action.
To this end, an Energy Efficiency Technical Committee has been established to overcome challenges, unlock opportunities and establish best practice. Holcim is one of 38 companies and industry associations that have signed the Accord.
The case studies that have been developed as part of the Accord show how energy efficiency can be achieved at commercial and industrial levels and how challenges have been overcome.
To Download the complete case study --> HeRe !
Source: World Business Council for Development Sustainable
1 comment:
World Business Council for Development Sustainable , para mas información sobre este tipo de estudios, puedes acudir a http://www.wbcsd.org/
atte. Manuel Torres Laveaga
Post a Comment