Microwave Drying of Boric Acid Crystals to Reduce Energy and Dust
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Solution Overview
Problem
Current boric acid production methods result in excessive energy consumption, product fracturing leading to dust, and a significant portion of the product being obtained as powder boric acid, along with the need for cooling and additional processing steps.
Innovation Solution
A method involving the use of colemanite, ulexite, and tincal ores to produce boric acid, where wet mixtures are filtered, dewatered, and dried using a microwave band conveyor dryer without vibration, eliminating the need for centrifuges, dry dust precipitators, and other equipment, resulting in 98% of the product being within -1+0.063 mm size with 0.03% humidity and 99.99% purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hot air drying systems are used to dry boric acid crystals, then the drying efficiency is improved, but energy consumption increases excessively and product fracturing occurs
Solution Approach 1:
The patent replaces the conventional hot air drying system with a microwave drying system. The microwave dryer uses electromagnetic radiation to directly heat and evaporate moisture from boric acid crystals, eliminating the need for large volumes of hot air circulation. This substitution reduces energy consumption while maintaining high drying efficiency and preventing product fracturing.
Solution Approach 2:
The patent utilizes the phase transition of water from liquid to vapor through microwave heating. The microwave energy directly heats the water molecules within the boric acid crystals, causing rapid evaporation and drying. This phase transition approach achieves efficient moisture removal without the energy-intensive hot air circulation required by conventional systems.
2Speed
If hot air drying systems are used to dry boric acid crystals, then the drying process is accelerated, but product fracturing and dust formation increase
Solution Approach 1:
The patent replaces the mechanical hot air drying system with a microwave drying system that uses electromagnetic radiation. This substitution allows for controlled internal heating of the crystals without the mechanical force of hot air circulation, preventing crystal fracturing and dust formation while maintaining rapid drying speed.
Solution Approach 2:
The patent changes the heating parameter from thermal convection (hot air) to electromagnetic radiation (microwave). This parameter change enables uniform internal heating of the boric acid crystals, preventing the external surface cracking and internal stress fracturing that occur with conventional hot air drying, thereby eliminating dust generation.
3Productivity
If conventional drying and cooling systems are used, then the drying capacity is increased, but the process complexity and equipment requirements increase
Solution Approach 1:
The patent merges the drying and cooling functions into a single microwave drying system. The microwave dryer simultaneously removes moisture and cools the boric acid crystals to ambient temperature, eliminating the need for separate cooling equipment and processes. This integration maintains high drying capacity while significantly reducing process complexity and equipment requirements.
Solution Approach 2:
The microwave drying system performs multiple functions: it dries the boric acid crystals by evaporating moisture, cools the crystals to ambient temperature, and prevents fracturing. This multi-functional approach replaces the conventional multi-stage process requiring separate drying and cooling systems, thereby reducing device complexity while maintaining or improving productivity.
4Manufacturing precision
If centrifuges and dust precipitators are used in the process, then the separation efficiency is improved, but the equipment investment and maintenance costs increase
Solution Approach 1:
The patent extracts and eliminates the need for centrifuges and dust precipitators from the process. By using microwave drying, the system achieves complete moisture removal and prevents dust formation at the source, making these separation equipment unnecessary. This extraction of unnecessary equipment reduces both initial investment and ongoing maintenance costs while maintaining high separation efficiency.
Solution Approach 2:
The microwave drying system performs preliminary action by completely removing moisture and preventing crystal fracturing before the material would require separation. By preventing dust formation in the first place through gentle internal heating, the process eliminates the need for subsequent dust removal equipment, thereby reducing equipment investment and maintenance requirements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method reduces energy consumption, minimizes product loss, eliminates dust, and simplifies the production process, achieving a cleaner and more efficient operation with lower maintenance costs, while ensuring 98% of the product is within the desired size and humidity specifications.
Implementation Method 1
dried in the microwave energy tunnel type band conveyor dryer
Implementation Method 2
Humid boric acid crystals on the band conveyor are dried by applying 1000 watt/unit magnetron power
Implementation Method 3
wet mixtures are dissolved in reactor with acid... are fed to thickener. While top current of the thickener is returned to dissolving unit as a dilute solution, the bottom current which consist of 40-70% H3BO3 crystalline is dewatered
Implementation Method 4
bottom current which consist of 40-70% H3BO3 crystalline is dewatered to reduce SO4 value to maximum 300 ppm and to obtain boric acid crystalls with maximum 20% humidity rate at vacuumed filter
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Wet mixtures which are solved by acid in reactors by using colemanite, ulexide and tincal ores in boric acid factories, filtrated and containing 30-60% solid (boric acid crystals) in the crystallizer unit, are fed to the thickener. The upper current of the thickener is returned to the solution unit as dilute solution; in order to dewater the wet solution whose bottom current is 40-70% H3BO3 crystalline, and to reduce SO4 value, boric acid crystals with maximum %20 humidity rate are obtained by vacuuming at maximum 300 ppm, Humid boric acid crystals taken to vibrating screen from filter exit are fed on the microwave dryer band conveyor at 10 cm. The humid boric acid crystals on the band conveyor are exposed to 1000 watt/unit magnetron power, and dried at 2m/min. Band speed without being subject to vibrating activity. In order to prevent crustation (caking) to take place during production and to ensure that crystal surface temperatures are distributed homogenously, fixed mixers, diffusers, roll grinders are utilized. The dried boric acid crystals are lastly treated in roll and vibrating screen and technical boric acid with 98% -1+0,063 mm size, at maximum 40 °C degrees, with maximum 0,03% humidity, at 0,74-0,95 g/cm3 bulk density, with 99,99% purity and with H3BO3 chemical formulation with minimum 56,25 % B2O3 is produced.