Bagasse drying with superheated steam offers the advantage of producing approximately 15% more power than with a conventional co-generation plant. Based on a fibre content of 14% on cane a power export of up to 140 kWh/t cane is achievable compared to 122 kWh/t cane in case of a conventional highly efficient co-generation plant. The operational results of a 12 t/h bagasse drier in Australia are briefly described and a concept of integrating a bagasse steam drier system in a modern highly energy efficient cane sugar plant is explained. This encompasses changes in the boiler capacity, turbogenerators and evaparation plant lay-out. Based on power export prices in the range of USD50–85/MWh the payback period of a bagasse steam drier system can be estimated with 3–6 years.
Decarbonization of sugar factories for minimising the CO2-footprint has become a focus for sugar factories to survive in the contemporary world. Heat pumps can be a piece of the puzzle for meeting the challenge of elaborating the path to a green future. This paper explains the technological principles and shows some exemplary scenarios for integrating heat pumps into beet sugar factories. The scenarios demonstrate reductions between 2% and 30% of the total factory’s CO2-emissions. The potentials are limited by the local electricity-gas-price-relationship, which defines a lower limit in regards to operating costs equality.
The export of power from cane sugar factories makes possible the production of “green energy” and proves nowadays to be a substantial source of revenue as well. Looking to the co-generation potential of the cane sugar industry, the power export is in fact still at a very early stage. This report gives an overview of concepts and measures that are required to achieve a low steam demand and high electrical power export for different factory concepts. The impact of sugar extraction by mills and diffusers as well as the option of producing refined sugar in an attached refinery is investigated. The factory models investigated allow steam demands to reduce to the range of 26–34% steam on cane. Such factory concepts are not theoretical any more but have been implemented and successfully proven in several plants in India, Brazil and Pakistan in the last five years. The report gives an overview of the actual achievements.
Optimization of process steam requirement in order to maximize sugar recovery and export power along with manpower optimization is a must for sugar factories to survive under difficult conditions and to earn additional revenues. The process steam demand of greenfield and revamped plants has been reduced to levels of 32–38% from originally more than 50% steam on cane in the case of the brownfield plants. In addition, significant improvement in the power requirement of the plants has been achieved. Bagasse drying offers a good potential to improve the power export. Different available concepts are compared with a focus on bagasse steam drying and low temperature bagasse drying. In order to set up an optimized highly efficient plant or to optimize an existing plant to achieve competitive benchmarks, good process design and the right equipment selection are very important. Experience has been gained with multiple stage or double effect crystallization in the beet sugar industry offering further steam optimization potential. Vapour recompression is also an option to substitute live steam by electrical power. This even provides options to reduce the steam demand from the power plant for the sugar process down to zero. Key aspects concerning the process design and equipment selection are described.
There are still large differences in process steam consumption, sugar recovery and plant availability when comparing sugar production from beet versus that from cane on a global scale. These are partly due to higher sugar contents and purities of sugar beet, but also due to more developed process technologies enabling a more efficient usage of steam and energy. Specific areas of a cane factory that can benefit from adaption technologies typically employed in European beet sugar production are: heat-transfer equipment especially evaporators and condensers, sugar-house work including seed magma systems by cooling and improved crystallizer designs, close monitoring and reduction of water input at all stages of the process, modern layout of the plant in order to reduce pressure drops and enable good supervision, and efficient electrical drives and automation systems. As a result, the improved factories have been able to increase significantly sugar yield and cogeneration power for sale to the national grid and have an increased profitability. Some specific examples of the technological improvements and benefits obtained in some cane factories as a result of the above measures are presented. A further example of the possibilities to process sugarcane and sugar beet in a highly efficient dual-use plant is also shown. Due to the low process-steam consumption of the plant, enough surplus bagasse is produced during the cane crop in order to be self-sufficient in fuel during the beet crop.
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