Scheelite Leaching with Mixed Acids and Closed-Circuit Recycling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The tungsten smelting process using alkali decomposition generates hazardous waste and requires high reaction temperatures, leading to equipment corrosion and inefficient acid leaching solution recycling, especially when dealing with fluorine-containing ores.
Innovation Solution
A leaching method involving a mixture of hydrochloric acid, sulfuric acid, and nitric acid at controlled temperatures, with closed-circuit recycling of the acid leaching solution, and using steel-lined tetrafluoro materials to resist corrosion, allowing for efficient scheelite leaching and recovery of tungstate at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hydrochloric acid leaching is used to decompose tungsten concentrate, then the process flow is shortened and production cost is reduced, but high reaction temperature is required which causes equipment corrosion and environmental pollution
Solution Approach 1:
The patent changes the chemical parameters of the leaching system by introducing oxidizing agents (nitric acid, hydrogen peroxide, sodium chlorate, or calcium chlorate) to hydrochloric acid. This parameter change enables the leaching reaction to proceed at lower temperatures (below 100°C) while maintaining high decomposition efficiency, thus resolving the contradiction between production cost and reaction temperature requirements
Solution Approach 2:
The patent creates a composite acid system by combining hydrochloric acid with oxidizing agents (nitric acid, hydrogen peroxide, sodium chlorate, or calcium chlorate). This composite leaching system synergistically enhances the decomposition capability of scheelite at lower temperatures, avoiding the need for high-temperature processing while maintaining cost-effectiveness
2Productivity
If high reaction temperature is used for acid leaching, then decomposition efficiency is improved, but equipment corrosion and acid mist pollution increase
Solution Approach 1:
The patent modifies the temperature parameter from high temperature to low temperature (below 100°C) by introducing oxidizing agents to the hydrochloric acid system. This parameter change maintains high decomposition efficiency through enhanced chemical reactivity while significantly reducing equipment corrosion and acid mist generation associated with high-temperature operations
3Object-generated harmful factors
If acid leaching solution is directly neutralized with lime, then wastewater treatment is achieved, but acid resources are wasted and large amount of sludge is generated
Solution Approach 1:
The patent recovers and reuses the acid leaching solution after tungsten decomposition. Instead of neutralizing with lime, the spent acid solution is regenerated and循环利用 in subsequent leaching operations. This recovery approach eliminates acid resource waste and prevents large-scale sludge generation while still achieving wastewater treatment goals
Solution Approach 2:
The acid leaching solution serves itself by being regenerated and reused in the leaching process. The system creates a closed-loop where the acid solution continuously serves multiple cycles without requiring external neutralization, thereby eliminating resource waste and sludge production
4Reliability
If alkali decomposition process is used for tungsten concentrate, then stable process and high recovery rate are achieved, but hazardous waste is generated and environmental control is strict
Solution Approach 1:
The patent changes the chemical nature of the decomposition process from alkali-based to acid-based (hydrochloric acid with oxidizing agents). This parameter change maintains the stable process characteristics and high tungsten recovery rate while eliminating the generation of hazardous waste associated with alkali decomposition, thereby resolving the environmental control issue
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 increases the tungstate recovery rate to 99.5% or more, reduces equipment requirements, and lowers production costs by minimizing waste and corrosion issues, while maintaining high acid concentration and corrosion resistance.
Implementation Method 1
adding hydrochloric acid according to the liquid-solid ratio of hydrochloric acid to scheelite of 2-4:1 mL/g, and 0.3-1% sulfuric acid or nitric acid by volume of the hydrochloric acid, and then stirring, leaching
Implementation Method 2
adding 0.1-2.5% sulfuric acid by volume of the acid leaching solution to the acid leaching solution for incomplete precipitation of calcium
Implementation Method 3
the inner wall of the reaction kettle is made of steel lined tetrafluoro material... resists the corrosion of HF
Data Source
AI summary
The present disclosure relates to the field of tungsten smelting, and in particular to a leaching method of scheelite, and provides a new technology that scheelite is leached in low temperature with a mixture acid of sulfuric acid and hydrochloric acid or nitric acid and hydrochloric acid, calcium is precipitated incompletely, and then the acid leaching solution is regenerated and closed-circuit recycled is provided. The new technology is able to leach scheelite sufficiently in low temperature so as to improve the recovery rate of tungstate and decrease the requirement of equipment. As well, the inner wall of the reaction kettle, the heating pipe and the temperature measuring device are made of steel lined tetrafluoro material which has high acid corrosion resistance and is able to deal with scheelite with high fluorine, resists the corrosion of HF.