Calcium Hydroxide Production via Ammonia Cycle Process
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Solution Overview
Problem
The cement production industry is a significant contributor to global CO2 emissions, primarily due to the thermal decomposition of limestone and fossil fuel burning, with existing methods offering limited opportunities for decarbonization, especially given the reluctance of major producers to adopt new technologies.
Innovation Solution
A novel low-temperature ammonia cycle process is developed to produce calcium hydroxide from calcium-bearing industrial waste streams, such as recycled concrete and coal ashes, utilizing an aqueous solution of ammonium chloride to extract and precipitate calcium hydroxide, which can be recycled, reducing the carbon footprint of cement production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional thermal decomposition of limestone is used to produce calcium oxide, then calcium oxide can be produced, but CO2 emissions increase significantly
Solution Approach 1:
The invention changes the fundamental chemical reaction parameters by replacing thermal decomposition with aqueous chemical reactions. Instead of heating limestone to high temperatures (which releases CO2), the process uses ammonium chloride solution to react with calcium-containing materials at ambient or moderate temperatures, producing calcium hydroxide directly without CO2 emissions. This parameter change transforms the manufacturing approach from thermal to chemical-aqueous processes.
Solution Approach 2:
The invention utilizes phase transitions of water and ammonia to drive the chemical reactions. Water serves as the reaction medium and reactant, while ammonia cycles between dissolved and gaseous phases to facilitate calcium extraction and precipitation. The phase behavior of these substances enables the continuous operation of the process and the separation of products from reaction mixtures.
2Productivity
If conventional cement production methods are used, then cement can be produced to meet growing demand, but the carbon footprint increases
Solution Approach 1:
The invention extracts calcium from waste materials using ammonium chloride solution, separating calcium from other components in the waste streams. This extraction process recovers valuable calcium content that would otherwise be discarded, converting waste into a useful cement ingredient while avoiding the CO2-intensive limestone quarrying and processing required by conventional methods.
Solution Approach 2:
The invention converts industrial waste materials (coal combustion residues, steel slag, recycled concrete) into valuable calcium hydroxide for cement production. These waste materials, which would require landfilling or special disposal, are transformed into resources that replace limestone, thereby converting environmental harm into economic and environmental benefit while eliminating CO2 emissions from raw material processing.
3Ease of manufacture
If limestone quarrying and thermal processing are used, then calcium oxide is produced, but energy consumption increases
Solution Approach 1:
The invention replaces the mechanical-thermal system (crushing, heating, and processing limestone at high temperatures) with a chemical-aqueous system. Instead of applying mechanical force to crush limestone and thermal energy to decompose it, the process uses chemical reactions in aqueous solution to dissolve and precipitate calcium compounds at much lower energy inputs, fundamentally substituting one technological paradigm for another more efficient one.
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 process significantly reduces CO2 emissions by over 50% and offers a pathway for cement production to become carbon-negative, enabling direct capture of atmospheric carbon as precipitated calcium carbonate, surpassing conventional methods in emission reduction.
Implementation Method 1
The method includes the step of contacting a material comprising calcium-containing molecules with an aqueous solution comprising a water-soluble salt comprising ammonium cation and a counter-anion
Implementation Method 2
contacting a material comprising calcium-containing molecules with an aqueous solution comprising a water-soluble salt comprising ammonium cation and a counter-anion, for a time, and at a temperature, pH, and pressure effective to yield a compound comprising calcium and the counter-anion
Implementation Method 3
Supernatant from the first step is reacted with ammonia and water for a time, and at a temperature, pH, and pressure effective to yield calcium hydroxide, which precipitates from the reaction solution
Implementation Method 4
calcium hydroxide, which precipitates from the reaction solution
Data Source
AI summary
A method of making a composition of matter comprising calcium hydroxide. The method includes the steps of contacting a calcium-containing molecule with an aqueous solution of a water-soluble salt having ammonium cation and a counter-anion, under conditions effective to yield a compound containing calcium and the counter-anion; and reacting the compound comprising calcium and the counter-anion with ammonia and water under conditions to yield calcium hydroxide.