A Stacked Continuous Vacuum Pan, A World Class Innovation For Sugar Cane Mill

The vacuum pans is necessary for sugar mills in terms of sugar manufacturing process. And, it is known that batch vacuum pan and continuous vacuum pan are generally used in many sugar mills. However, there is the high quality vacuum pans which is provided significant advantages such as complete automation and minimal supervision, steam economy, better exhausting, uniform crystal, high rate of evaporation, high throughput and maximum capacity utilization in a minimum footprint, it is called stacked continuous vacuum pans.

The crystallization process in general
Sugar typically comes from sugarcane or sugar beets. Once harvested, the sugar is extracted and then undergoes purification and clarification followed by evaporation. Crystallization is the next step in the sugar manufacturing process.

This crystallization process typically takes place under vacuum and involves the simultaneous processes of mass transfer and evaporation. Vacuum is used to keep the temperature at a low enough level to minimize color formation as well as the inversion/degradation of sucrose. Crystallization has typically been carried out in batch vacuum pans, although more recently, continuous systems have been introduced.

Nevertheless, the process of initiating crystallization is still carried out on a batch basis. When sucrose concentration reaches the desired level, the dense mixture of syrup and sugar crystals, called massecuite, is discharged into large containers, known as crystallizers. Crystallization continues in the crystallizers as the massecuite is slowly stirred and cooled. Massecuite then flows into centrifugals, where molasses is separated from the raw sugar by centrifugal force. The sugar crystals may then be dried and packaged in solid and/or liquid form.

What is stacked continuous vacuum pan
a stacked continuous vacuum pan system comprised at least three horizontal modules, each module having a horizontal shell and a vertical calandria mounted along the horizontal shell, wherein each of the at least three horizontal modules may be mounted on a separate floor of the system in a stacked configuration and the system may operate as a single unit such that syrup, molasses and product massecuite may flow continuously down through the at least three horizontal modules. The vertical calandria may be formed of stainless steel. The vertical calandria may be a single bank of vertical tubes within a housing, wherein the vertical tubes may be sealed in a polygonal formation at the ends.

Each of the at least three horizontal modules may have at least two compartments and massecuite may flow from one compartment to another compartment. An internal surface of the horizontal shell of each of the at least three horizontal modules may have a non-stick surface, which may be polytetrafluoroethylene (PTFE). The vertical calandria may provide for up to approximately 25% greater heating surface than a tubular calandria.

This crystallization process typically takes place under vacuum and involves the simultaneous processes of mass transfer and evaporation. Vacuum is used to keep the temperature at a low enough level to minimize color formation as well as the inversion/degradation of sucrose. Crystallization has typically been carried out in batch vacuum pans, although more recently, continuous systems have been introduced.

Nevertheless, the process of initiating crystallization is still carried out on a batch basis. When sucrose concentration reaches the desired level, the dense mixture of syrup and sugar crystals, called massecuite, is discharged into large containers, known as crystallizers. Crystallization continues in the crystallizers as the massecuite is slowly stirred and cooled. Massecuite then flows into centrifugals, where molasses is separated from the raw sugar by centrifugal force. The sugar crystals may then be dried and packaged in solid and/or liquid form.

KEY BENEFITS
• Suitable for cane, beet and refinery massecuites.
• Compact modular design using a honeycomb calandria.
• High Circulation Rate without the use of mechanical stirrers.
• Lower turndown ratio during the cleaning cycle.
• Small footprint.
• Fast track installation and assembly.
• Modules can be added for required increase in capacity.
• Improved steam economy with the use of low pressure vapors.
• Each module can be operated using different vapor pressures.
• Fully automated.

How is the stacked continuous vacuum pan working?
The stacked continuous vacuum pan in a first horizontal module; processing massecuite in the first horizontal module; flowing massecuite from the first horizontal module to a second horizontal module; processing massecuite in the second horizontal module; and flowing massecuite from the second horizontal module to a third horizontal module, wherein each of the first horizontal module, the second horizontal module and the third horizontal module may have a horizontal shell and a vertical calandria mounted along the horizontal shell, and wherein the first horizontal module, the second horizontal module and the third horizontal module may be formed in a stacked configuration with each module mounted on a separate floor to allow massecuite to flow continuously down through the modules.

Each of the at least three horizontal modules may be separately removable from the system to be cleaned while continuing a boiling process at a reduced rate through remaining ones of the at least three horizontal modules. The system may be suitable for use with A massecuite, B massecuite, C massecuite, raw massecuite, refined massecuite and high-purity, high-viscosity massecuite. The system may be used for both recovery and refinery operations in cane and beet sugar refineries. The shape of the system may provide a smooth massecuite flow-path without stagnant areas or short circuiting.

The method of the stacked continuous vacuum pan
The stacked continuous vacuum pan method is consisted of each of the first horizontal module, the second horizontal module and the third horizontal module may have at least two cells where the processing steps occur. The vertical calandria may have a honeycomb structure. The method also may comprise bypassing one of the first horizontal module, the second horizontal module and the third horizontal module while continuing a boiling process at a reduced rate through the other two horizontal modules.

Each module having a horizontal shell and a honeycomb-shaped calandria mounted along the horizontal shell, wherein each of the at least three horizontal modules may be mounted on a separate floor of the system in a stacked configuration such that massecuite may flow down through the stacked configuration, and wherein each of the at least three horizontal modules may be separately by-passable such that the system may be capable of being continuously used at a reduced rate through the remaining horizontal modules. Each of the at least three horizontal modules may have at least two cells through which massecuite flows. An internal surface of the horizontal shell of each of the at least three horizontal modules may have a non-stick surface. The shape of the system may provide a smooth massecuite flow-path without stagnant areas or short circuiting.

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