Method for producing powder form aluminum oxide by low concentration solution seed decomposition
Technical field:
The present invention relates to a kind of alumina-producing method, particularly a kind of method for producing powder form aluminum oxide by low concentration solution seed decomposition.
Background technology:
It is one of important procedure in the bayer's process aluminum oxide production process that seed decomposes, and its task is by control kind of branch condition, and aluminium hydroxide is separated out from oversaturated sodium aluminate solution, decomposes the aluminium hydroxide that obtains and handles for subsequent handling.
Because the bauxite difference that alumina producer is handled, leaching condition is different, and the sodium aluminate solution that obtains is formed also difference.On the whole, the alumina producer of domestic processing diaspore, gibbsite, stripping is generally Na after seminal fluid alkali concn and alumina concentration that the leaf filter obtains are all higher
2O
KConcentration 145~172g/l, Al
2O
3Concentration 160~195g/l, seed decompose employing high density, high seed than producing sandy alumina.
At high-iron gibbsite is easy molten gibbsite type and the low characteristics of aluminum oxide grade, and stripping system and the existing alumina producer taked have very big difference, is the low-temperature atmosphere-pressure stripping, and the circulating mother liquor alkali concn is very low, Na
2O
KConcentration is 140g/l only, and the sodium aluminate solution that obtains is formed with domestic processing higher-grade diaspore and the resulting solution of gibbsite bigger difference; Be the low and α of sodium aluminate solution concentration
KThen higher (seminal fluid α
KBe worth about about 1.85), low helping of concentration decomposes, and α
KHeight then is unfavorable for decomposing.
At the characteristics of this low concentration solution, the existing decomposition technique condition of alumina producer can not satisfy the requirement that this lower concentration decomposes.According to experimental study, a kind of decomposition technique technology is proposed, adopt lower concentration to produce powdery aluminum (being also referred to as common shape aluminum oxide).Why producing powdery aluminum, mainly is to consider that the high-iron gibbsite grade is lower.The high-iron gibbsite of this type is in initial development and industrialization conceptual phase at present, and the initial stage scale of founding the factory should not be too big, and production powdery aluminum output is higher, and technical difficulty is less relatively.
Summary of the invention:
The objective of the invention is to: propose a kind of method of producing powder form aluminum oxide by low concentration solution seed decomposition, to solve the difficult problem of iron scheme decomposition process behind the low-grade high-iron gibbsite elder generation aluminium.
The present invention is achieved in that and adopts to decompose a production powdery aluminum; The seminal fluid of sending here from the sedimentation workshop filters with seed and together adds preceding 2 grooves of decomposing system after the next aluminium hydroxide seed of operation mixes, wherein decomposing first-cell temperature is 58~61 ℃, and last groove temperature is 46~49 ℃, crystal seed coefficient 2.0~2.5,60~62 hours resolving times, seminal concentration is Na
2O
KConcentration 90~100g/l, Al
2O
3Concentration 80~90g/l; Aluminum hydroxide slime part after the decomposition goes finished product to filter operation, and another part goes seed to filter operation (the aluminum hydroxide slime allocation proportion serves as the control foundation to decompose first groove crystal seed coefficient 2.0~2.5); After filtering filter cake of seed and seminal fluid converge, return in preceding 2 decomposers of decomposing system.
In above method, decomposer adopts common flat mechanically agitated precipitator; Best decomposer temperature is: 60 ℃ of first grooves, 47~48 ℃ of last grooves.
Adopt above decomposition technique and process control condition, the seminal fluid rate of decomposition can reach 46~48% scopes, decomposes output capacity 41~45kg/m
3-seminal fluid, the aluminium hydroxide that decomposes output obtains powdery aluminum after roasting, and its chemical ingredients reaches the metallurgical grade first grade specification of quality in the YS/T274-1998 standard of national regulation.
The invention has the beneficial effects as follows: use method of the present invention, can solve the difficult problem of iron scheme decomposition process behind the high-iron gibbsite elder generation aluminium, have favorable economic benefit and social benefit.
Embodiment:
Embodiments of the invention 1: adopt one section to decompose the production powdery aluminum, decomposer adopts common flat mechanically agitated precipitator; The seminal fluid of sending here from the sedimentation workshop filters with seed and together adds preceding 2 grooves of decomposing system after the next aluminium hydroxide seed of operation mixes, each amount of 50% of every groove, wherein decomposing first-cell temperature is 60 ℃, last groove temperature is 48 ℃, crystal seed coefficient 2.0~2.5, seminal concentration are Na
2O
KConcentration 90~100g/l, Al
2O
3Concentration 80~90g/l; Decomposed through 61 hours, rate of decomposition reaches 46%; Aluminum hydroxide slime part after the decomposition goes finished product to filter operation as this process product, another part goes seed to filter operation (the aluminum hydroxide slime allocation proportion serves as the control foundation to decompose first groove crystal seed coefficient 2.0~2.5), after filtering filter cake of seed and seminal fluid converge, return in preceding 2 decomposers of decomposing system.
Embodiments of the invention 2: adopt one section to decompose the production powdery aluminum,, adopted 3000m if the plant produced scale is big
3More than large-scale flat mechanically agitated precipitator, be to guarantee decomposition reaction velocity, can conventional intermediate temperature drop facility be set at 4~No. 8 grooves; Wherein decomposing first-cell temperature is 58 ℃, and last groove temperature is 46 ℃, crystal seed coefficient 2.0, and seminal concentration is Na
2O
KConcentration 90g/l, Al
2O
3Concentration 80g/l; Decomposed through 60 hours, rate of decomposition reaches 46%.