Arsenic Removal from Borate Minerals via Reductive Roasting
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Solution Overview
Problem
Current methods for removing arsenic from pyrite-free materials like colemanite and howlite are inefficient, particularly due to the use of sulphuric acid, which poses waste disposal challenges, and existing fluidized bed technologies are not applicable to non-pyrite materials.
Innovation Solution
A method involving roasting pyrite-free materials in reducing conditions at temperatures below 900°C, using preheated hydrogen or gases from natural gas combustion, in a fluidized bed reactor, to convert arsenic into volatile forms that can be purified and removed without sulphuric acid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sulphuric acid is used to remove arsenic from borate minerals, then arsenic removal is achieved, but waste disposal problems arise and the process becomes less environmentally friendly
Solution Approach 1:
The invention converts the harmful arsenic impurity into a beneficial volatile form that can be easily removed. By using reductive roasting with carbon monoxide or hydrogen, arsenic is transformed into volatile arsenic compounds (As4, As2O3, As2S3) that can be separated from the borate mineral, turning the waste removal problem into an efficient purification process without generating acid waste
Solution Approach 2:
The invention changes the chemical parameters of the roasting process by using reducing conditions (carbon monoxide or hydrogen atmosphere) instead of oxidizing conditions. This parameter change transforms the arsenic removal mechanism from acid dissolution to reductive volatilization, eliminating the need for sulphuric acid and its associated waste disposal issues
2Reliability
If conventional fluidized bed roasting is used for pyrite materials, then arsenic removal is effective, but the technology is not applicable to non-pyrite materials like colemanite and howlite
Solution Approach 1:
The invention creates a universal roasting process that can handle both pyrite and non-pyrite borate minerals. By using reductive roasting conditions with carbon monoxide or hydrogen, the process becomes adaptable to different mineral types (colemanite, howlite, and other borate minerals), making the arsenic removal technology universally applicable across various borate ore types
Solution Approach 2:
The invention modifies the roasting parameters by using reducing conditions and lower temperatures (below 900°C) compared to conventional high-temperature oxidation roasting. This parameter adaptation allows the fluidized bed process to work effectively with non-pyrite materials that have different thermal and chemical properties than pyrite
3Reliability
If high temperatures (900-1100°C) are used for arsenic removal from oxidic ores, then arsenic can be removed as arsenic trioxide, but energy consumption increases and the process becomes less efficient for borate minerals
Solution Approach 1:
The invention changes the temperature parameter from conventional high temperatures (900-1100°C) to lower temperatures (below 900°C, preferably 400-800°C). This temperature reduction is made possible by using reductive conditions with carbon monoxide or hydrogen, which enable arsenic volatilization at lower energies, thereby reducing energy consumption while maintaining effective arsenic removal for borate minerals
Solution Approach 2:
The invention uses the reducing atmosphere (carbon monoxide or hydrogen) to convert arsenic into volatile forms that can be removed at lower temperatures. This transforms the approach from energy-intensive high-temperature oxidation to energy-efficient low-temperature reduction, making the process more economical while achieving the same purification goal
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 effectively removes arsenic from pyrite-free materials as volatile compounds, avoiding sulphuric acid-related waste issues and enabling the production of arsenic-free calcium borate suitable for further processing into boric acid.
Implementation Method 1
roasting pyrite-free materials in reducing conditions at temperatures below 900°C, using preheated hydrogen or gases from natural gas combustion
Implementation Method 2
convert arsenic into volatile forms that can be purified and removed
Implementation Method 3
in a fluidized bed reactor
Implementation Method 4
roasting at temperatures below 900°C
Implementation Method 5
using preheated hydrogen or gases from natural gas combustion
Data Source
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Figure 3~4
AI summary
The invention relates to a method and an arrangement for removing arsenic from pyrite-free minerals, such as cole- manite and howlite. The method comprises roasting the pyrite-free material at a temperature of less than 900°C in reducing conditions. The method is typically performed in a fluidized bed reactor by using a reducing gas, such as hydrogen, as the fluidization gas.