Rare Earth Oxide Calcination with Ammonia and Carbon Recycling
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Solution Overview
Problem
Existing methods for preparing rare earth oxide face inefficiencies in calcination processes due to poor microwave absorption by rare earth carbonates, leading to long heating times and low utilization rates of carbon and ammonia resources, with significant environmental pollution from natural gas use.
Innovation Solution
A method involving microwave calcination of rare earth carbonates with added rare earth oxides to enhance heating efficiency, coupled with the recycling of ammonia and carbon dioxide to form a precipitant for rare earth carbonate production, reducing calcination time and increasing resource utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If rare earth carbonate is subjected to microwave radiation for calcination, then rare earth oxide can be prepared, but the heating time is long due to poor microwave absorbing ability
Solution Approach 1:
The patent introduces carbon as an intermediary substance that absorbs microwave energy effectively and transfers thermal energy to rare earth carbonate. The carbon acts as a mediator between the microwave field and the rare earth carbonate, enabling efficient heating and significantly reducing calcination time while maintaining roasting efficiency.
Solution Approach 2:
The patent changes the physical and chemical parameters of the calcination process by controlling the carbon content, particle size distribution, and heating temperature. By optimizing these parameters, the microwave absorption capability of the mixture is enhanced, leading to faster heating rates and reduced processing time while maintaining high productivity.
2Productivity
If natural gas is used as heating energy in traditional kilns, then rare earth carbonate can be decomposed, but carbon resources are wasted and environmental pollution increases
Solution Approach 1:
The patent converts the harmful waste carbon dioxide from natural gas combustion into a useful component by using carbon (in the form of carbon powder or carbon-containing materials) as a microwave-absorbing additive. This carbon serves dual purposes: enhancing microwave absorption and providing a carbon source that can react with rare earth oxides, thereby converting what would be a waste product into a beneficial component of the process.
Solution Approach 2:
The system achieves self-service by using the carbon additive to absorb microwave energy and generate the heat required for decomposition internally, eliminating the need for external natural gas heating. The carbon-rich environment created during microwave heating provides the reducing atmosphere needed for the process, making the system self-sufficient and eliminating carbon resource waste.
3Loss of substance
If ammonia-nitrogen wastewater is subjected to steam stripping ammonia distillation, then ammonia water can be recovered, but the utilization rate of carbon and ammonia resources remains low
Solution Approach 1:
The patent merges the ammonia recovery process with the calcination process by integrating the carbonized filtrate (containing ammonia and carbon dioxide) directly into the calcination system. This combination allows the recovered ammonia to react with carbon dioxide and rare earth oxides in situ, forming rare earth carbonates and ammonium bicarbonate, thereby simultaneously achieving ammonia recovery and productive utilization, significantly improving overall resource utilization rate.
Solution Approach 2:
The system implements feedback by recycling the carbonized filtrate containing ammonia back into the calcination process. The ammonia from the wastewater, after carbonization, is fed back as a reactant in the calcination step, creating a closed-loop system where waste ammonia is continuously recovered and reused, maximizing resource utilization and minimizing losses.
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
The method significantly shortens calcination time, enhances rare earth yield, and improves the utilization rates of carbon and ammonia resources, while minimizing environmental impact.
Implementation Method 1
heating raw materials containing a first rare earth carbonate and a first rare earth oxide with microwave and calcining
Implementation Method 2
Rare earth carbonate has poor microwave absorbing ability, so the heating time is long
Implementation Method 3
reacting carbon dioxide with a first ammonia water with a concentration of 10-20 wt % to obtain a precipitant
Implementation Method 4
reacting the precipitant with rare earth chloride to obtain a second rare earth carbonate and ammonium chloride wastewater
Data Source
AI summary
The present disclosure discloses a method for preparing rare earth oxide by recycling ammonia and carbon, comprising the steps of: (1) heating raw materials containing a first rare earth carbonate and a first rare earth oxide with microwave and calcining at 500-1000° C. for 20-120 min to obtain a second rare earth oxide and carbon dioxide; (2) reacting carbon dioxide with a first ammonia water to obtain a precipitant; (3) reacting the precipitant with rare earth chloride to obtain a second rare earth carbonate and ammonium chloride wastewater. In the method, calcination time is short, rare earth recovery rate, utilization rate of ammonia and carbon resources are high. The present disclosure also provides a use of a rare earth oxide in shortening calcination time and/or increasing rare earth yield.