Calcium Carbonate Production via Polyhydroxy Solvation
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Solution Overview
Problem
The 'classic' process for producing calcium carbonate from lime results in slow reaction rates, high impurity levels, irregular particle sizes, and the need for energy-intensive milling, making it unsuitable for certain applications due to toxicity and particle shape issues.
Innovation Solution
A method involving an aqueous solution of 10% to 35% polyhydroxy compound and 1% to 5% calcium hydroxide, with controlled carbon dioxide dispersion and pH management to precipitate calcium carbonate, ensuring high purity and uniform particle size through phase control and alkaline reagent addition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the classic process uses CaO slaked with water to produce aqueous suspension of lime hydroxide, then the process is simple and straightforward, but the reaction rate is slow due to limited solubility of Ca(OH)2 in water
Solution Approach 1:
The invention changes the chemical parameters of the system by introducing polyhydroxy compounds (sorbitol, sucrose, glucose, fructose, or mixtures) to alter the solubility and reactivity of calcium hydroxide. These compounds increase the dissolution rate of Ca(OH)2 and accelerate the carbonation reaction, transforming the slow classic process into a faster industrial process while maintaining operational simplicity
Solution Approach 2:
Polyhydroxy compounds act as intermediary substances that facilitate the dissolution of calcium hydroxide and enhance the carbonation reaction. These intermediaries form soluble complexes with calcium ions, increasing the availability of calcium for reaction with CO2, thereby accelerating the overall process without complicating the manufacturing approach
2Quantity of substance
If the classic process is used to produce calcium carbonate from lime, then the process requires minimal additional materials, but the product contains high levels of impurities including toxic metals
Solution Approach 1:
Polyhydroxy compounds serve as selective intermediaries that form soluble complexes with calcium ions while leaving impurities behind. This selective complexation allows the calcium to be extracted and reacted to form pure calcium carbonate, while toxic metals and other impurities remain in the residue and are removed through filtration, producing food-grade and pharmaceutical-grade calcium carbonate
Solution Approach 2:
The invention extracts calcium from the impure lime matrix by forming soluble calcium-polyhydroxy complexes. This extraction process separates calcium from toxic impurities such as lead, arsenic, and other heavy metals. The filtered solution containing only calcium complexes is then carbonated to produce high-purity calcium carbonate, effectively removing harmful substances from the product
3Quantity of substance
If the classic process produces calcium carbonate, then the production cost is low, but the particle size is irregular and requires energy-intensive milling
Solution Approach 1:
The invention performs preliminary action by controlling the nucleation and growth stages of calcium carbonate precipitation through pH management and controlled CO2 addition. By maintaining optimal conditions during these initial stages, the process produces particles with uniform size and spherical morphology directly, eliminating the need for subsequent energy-intensive milling operations while keeping production costs low
4Productivity
If the polyhydroxy compound process is used to dissolve lime, then the dissolution rate increases and reaction is faster, but additional chemical compounds are required
Solution Approach 1:
The invention changes the chemical parameters by introducing polyhydroxy compounds that naturally occur in many forms (sorbitol from agricultural by-products, sucrose from sugar industry). These compounds simplify the overall process by enabling faster dissolution and reaction rates, and the polyhydroxy compounds can be easily removed or recycled, effectively reducing chemical complexity while dramatically improving productivity
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
Produces calcium carbonate with narrow particle size distribution, high purity, and improved brightness, making it suitable for various industrial applications, including food and pharmaceutical industries, with reduced energy consumption and lower impurity levels.
Implementation Method 1
a solution of calcium ions is prepared by dissolving the lime or lime hydroxide in an aqueous solution incorporating a polyhydroxy compound which serves to facilitate dissolution of calcium ions
Implementation Method 2
carbon dioxide is added to a solution of calcium ions, resulting in precipitation of calcium carbonate
Implementation Method 3
Ca(OH)2 + CO2 = CaCO3 + H2O
Data Source
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AI summary
A method of producing calcium carbonate from lime comprises the steps of: (i) providing an aqueous solution comprising 10% to 35% by weight of dissolved polyhydroxy compound and 1% to 5% by weight of dissolved calcium hydroxide (expressed as Ca(OH)2) and having a pH of at least 11.5; (ii) treating the solution prepared in step (i) to remove solids including suspended solids; (iii) dispersing carbon dioxide through the solution so as to form calcium carbonate with a consequential reduction in the pH of the reaction mixture, (iv) during a time period beginning at the start of a sudden, short rise in pH and ended during a subsequent fall in pH but before it reaches 9.5 terminating the dispersion of carbon dioxide and adding an alkaline reagent to maintain a pH for the product mixture of at least 9.5, and (v) recovering precipitated calcium carbonate.