CN104276604A - Method for preparing chromate through caustic soda solid oxidization of chromite ore - Google Patents
Method for preparing chromate through caustic soda solid oxidization of chromite ore Download PDFInfo
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- CN104276604A CN104276604A CN201410177745.5A CN201410177745A CN104276604A CN 104276604 A CN104276604 A CN 104276604A CN 201410177745 A CN201410177745 A CN 201410177745A CN 104276604 A CN104276604 A CN 104276604A
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- CN
- China
- Prior art keywords
- caustic soda
- oxygen
- chromite
- ferrochrome
- naoh
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G37/00—Compounds of chromium
- C01G37/14—Chromates; Bichromates
Abstract
The invention discloses a method for preparing sodium chromate or sodium dichromate through directly treating chromite ore (ferrochrome) by using a caustic soda solid roasting method. The method comprises the steps of sufficiently and uniformly mixing a caustic soda solution and chromite ore powder (ferrochrome powder), then, conveying the mixture to the top of a spray drying and granulating tower by using a pump, downwards spraying the mixture in a small drop way, and drying and granulating through countercurrent contact between the mixture and ascending air flow or oxygen-enriched air or oxygen; collecting the dried material at the bottom of the tower, conveying the dried material into a temperature programmed reactor, and continuing to carry out solid oxidization by using air (oxygen-enriched air or oxygen); and then, continuing to treat the obtained material through solid carbonatation, countercurrent extraction, secondary roasting, hot-pressing extraction and the like. The total recovery rate of chromium can be more than 95%, the recovery rate of alkali can be more than 80%, and a brand new process route for preparing sodium chromate or sodium dichromate is formed after a non-calcium roasting method.
Description
Technical field
The present invention relates to chromic salt, particularly the manufacture of Sodium chromate or sodium dichromate 99.
The present invention is supplementing of application for a patent for invention case 201310296637.5 (CN103318960) and expands.
Background technology
From the traditional method of preparing sodium chromate from chromite or sodium dichromate 99, namely use soda ash (Na
2cO
3) chromite is carried out under high temperature to the method for solid phase high-temperature roasting.This method material consumption is high, resource recovery the is low (rate of recovery 70--80%, the Na of chromium
2cO
3utilization ratio only has 30%-40% by production sodium dichromate, counts 60%-80% by production Sodium chromate), energy consumption is high, and sodium dichromate 99 per ton (i.e. sodium dichromate, Na
2cr
2o
72H
2o) product produces 2.5--and 3.0 tons of slags, cause serious pollution of chromium.
Although the calcium-free roasting method improved afterwards, pollution of chromium can be alleviated widely, produce the quantity of slag and only have 0.7-0.8 ton/ton sodium dichromate, Cr in slag
6+(with Na
2cr
2o
72H
2o counts) < 0.2%.But calcium-free roasting method, because of when high-temperature roasting, need add Macrodilution material, so its alkaline consumption is also higher by about 10% than traditional roasting method, energy consumption is also higher than traditional roasting method.
In recent years, people are in liquid-phase oxidation (or claim three-phase oxidation) method of exploration with caustic soda (NaOH), by the method for ferrochrome or preparing sodium chromate from chromite or sodium dichromate 99, oxidizing reaction can be carried out in lesser temps (250--450 DEG C):
4FeO·Cr
2O
3+16NaOH+7O
2＝8Na
2CrO
4+2Fe
2O
3+8H
2O (1)
But because NaOH fusing point only has 318-319 DEG C, the oxidation of the caustic soda of ferrochrome or chromite is difficult to carry out in solid phase, so up to now, the caustic soda oxidation of ferrochrome or chromite all can only be carried out in liquid phase (in the fused salt of caustic soda or caustic soda soln).The CN201110261747.9 (CN102320661) (triphase catalytic oxidation prepares the technique of dissolubility chromate) of such as the people live in plenty in Chongqing Chemical Co., Ltd..
With the oxidation that caustic soda carries out in liquid phase (solution or fused salt), obtain the mixture of a kind of liquid phase and solid phase, liquid phase is wherein except containing product Sodium chromate, also has NaOH excessive in a large number, and the soluble sodium such as sodium aluminate, water glass salt impurity, the liquid (its viscosity declines with temperature and sharply increases, to the 60-80 DEG C of solid that then congeals into completely) of very thickness; Solid phase is wherein then primarily of iron, magnesium and unreacted chromium, aluminium, silicon and other insoluble impurities etc.This solidliquid mixture, we are called that oxidation completes liquid.Owing to being oxidized the solidliquid mixture that liquid is a kind of very thickness, solid-liquid separation directly being carried out to it, to remove solid impurity very difficult.
The essential defect of caustic soda (NaOH) liquid-phase oxidation (or claiming three-phase oxidation) method, be: normally carry out to make liquid phase reaction, liquid phase oxidation requires that liquid phase > 70%, NaOH consumption is for generating Sodium chromate (Na
2crO
4) theoretical (namely stoichiometrically) 5-8 of measuring doubly, therefore liquid phase is the 70-80% of total material, and after having reacted, amount of liquid phase is more up to 85%-90%.This just gives and completes liquid from oxidation and be separated and prepare Sodium chromate or sodium dichromate 99 brings great difficulty.
Although white liquor phase oxidation (or claiming three-phase oxidation) method after improving, as patent 201110035642.1 (CN102139921), NaOH consumption can be reduced to 3.5-4.5 times that generation Sodium chromate theory (namely stoichiometrically) is measured, but after having reacted, the amount of free NaOH still accounts for about the 30%-50% of the total material of liquid phase, add the soluble sodium such as sodium aluminate, water glass salt impurity, still give and complete liquid from oxidation and be separated and prepare Sodium chromate or sodium dichromate 99 brings great difficulty.
Application for a patent for invention case 201310296637.5 is for above-mentioned white liquor phase oxidation Problems existing, propose by five-step approach, that is: chromite caustic soda solid phase roasting, solid carbon acidifying, counter-current extraction, re-baking and hot pressing leach the technological process that five steps (hereinafter referred to as five-step approach) are formed, white liquor phase oxidation is made to prepare Sodium chromate or sodium dichromate 99 becomes operational path feasible in Technological Economy, and compared with traditional soda ash solid phase roasting and calcium-free roasting method, no matter in material consumption, in the reduction of energy consumption, or on minimizing is chromium slag contaminated, all have a significant improvement.
But application for a patent for invention case 201310296637.5 only relates to: the oxidation that chromite white liquor phase oxidation (or three-phase oxidation) produces is completed to the aftertreatment of liquid, is separated and prepares the method for Sodium chromate or sodium dichromate 99.
Object of the present invention, it is exactly the defect for caustic soda (NaOH) liquid-phase oxidation, the five-step approach proposed in application for a patent for invention case 201310296637.5 is carried out supplementing and expanding, make it the aftertreatment be not limited only to white liquor phase oxidation or three-phase oxidation, and can directly process ferrochrome or chromite, thus the operational path preparing Sodium chromate or sodium dichromate 99 that formation one is after calcium-free roasting method, brand-new, that is: chromite (ferrochrome) caustic soda solid phase roasting method prepares the operational path of Sodium chromate or sodium dichromate 99.
Summary of the invention
The present invention is by the first step in application for a patent for invention case 201310296637.5, i.e. chromite (ferrochrome) caustic soda solid phase roasting step, carry out supplementing and expanding, thus make caustic soda solid phase roasting method also can be used for directly processing chromite (ferrochrome).Add all the other four steps in this patent of invention, that is: solid carbon acidifying, counter-current extraction, re-baking and hot pressing leaching, just define after calcium-free roasting method, brand-new, prepared Sodium chromate or sodium dichromate 99 by chromite (ferrochrome) a operational path.
Key of the present invention, is in the roasting of chromite caustic soda (NaOH) solid phase, uses low stoichiometry, or substoichiometric NaOH, and at 200 DEG C-300 DEG C, NaOH is converted into NaCrO very soon
2, Na
2crO
4, NaAlO
2, Na
2siO
2, NaFeO
2deng material, that wherein fusing point is minimum is Na
2crO
4(fusing point is 792 DEG C), as long as control maturing temperature well, whole material just can remain on solid phase.
The chromite caustic soda solid phase roasting method of indication of the present invention directly processes the method for chromite (ferrochrome), by 15-caustic soda (NaOH) solution of 35% and chromite powder (or ferrochrome powder), in molar ratio: the mole number of NaOH: Cr in chromite (ferrochrome)
2o
3mole number=(3.0-4.5): between 1.0 [preferably in (3.8-4.2): 1.0], liquid phase: solid phase=(1.5-3.0): between 1.0 [preferably in (2.0-2.8): 1.0],-150 DEG C (preferably 15-80 DEG C at normal temperature) under stir, after making it fully to mix, by its with pump delivery to a spray drying granulation tower top with droplet form spray under, with 100-315 DEG C, the airflow risen or oxygen-rich air stream or Oxygen Flow (preferably oxygen-rich air) counter current contact carry out drying-granulating, make more than 80%, dried raw meal particle size is 0.05-5.0 millimeters (preferably 0.1-3.0 millimeters) scope.
By dry, granularity 0.05-the range materials in 5.0 millimeters, collect at tower bottom, and send in the reactor (as fluidizing furnace, mechanical stirring kiln or rotary kiln) of a temperature programming, proceed phase oxidative process with air (or oxygen-rich air or oxygen).Heat up gradually, initial temperature controls below 315 DEG C, is then progressively elevated to 700-790 DEG C (being no more than the fusing point of Sodium chromate).
Alkali ratio (NaOH and the Cr of indication in the present invention
2o
3mol ratio) lower, caustic soda phase oxidative carries out more thorough, but in the 4th step thereafter, namely in high-temperature roasting, can be made up; Alkali is than higher, and caustic soda phase oxidative carries out more thorough, can not carry out high-temperature roasting thereafter, just can reach the high conversion of chromium, but also exists in the roasting of caustic soda phase oxidative, produces caking, scabs, thus hinders the risk of normally carrying out of roasting.For siliceous, aluminium, iron etc. (alkali can the be consumed) ore deposit that impurity is higher, higher alkali ratio can be used.
By chromite (ferrochrome) and 15-caustic soda (NaOH) solution of 35% carries out in the process be uniformly mixed, and the concentration of caustic soda soln used should not be too low, otherwise need more greatly, higher drying tower, energy consumption time dry is large too; The concentration of caustic soda (NaOH) also should not be too high, otherwise with chromite, or the mixing of ferrochrome, and conveying afterwards and spray drying granulation are had any problem.
By chromite (ferrochrome) and 15-caustic soda (NaOH) solution of 35% carries out in the process be uniformly mixed, liquid, solid than can not be too low, otherwise the Homogeneous phase mixing of caustic soda soln and chromite (or ferrochrome) can be affected, and conveying afterwards and spray drying granulation; Liquid, solid phase ratio can not be too high, otherwise need more greatly, higher drying tower, energy consumption time dry is large too.
By chromite (ferrochrome) and 15-caustic soda (NaOH) solution of 35% carries out in the process be uniformly mixed, be uniformly mixed carry out at normal temperatures more convenient, certainly also can carry out at relatively high temperatures, but when carrying out at higher than 150 DEG C, generation alkaline solution and other component is had to react, make whole material become thickness, thus affect Homogeneous phase mixing and conveying afterwards and spray drying granulation process.Temperature in drying tower is higher, and rate of drying is higher, but drying temperature can not too close to, more can not higher than the fusing point of NaOH (319 DEG C), otherwise can there is the possibility of luming in material.
At present, in equipment Market, existing polytype equipment, can be used for such spray-drying process.Such as, in Chinese patent medicine manufacture, washing powder manufacture, milk powder manufacture, all this equipment may be used.It is the material that will mix, be ejected into be positioned at drying tower top, on the rotating disk of high speed rotating, form droplet and fall, (or the mode of oxygen-rich air or oxygen stream counter current contact carries out drying-granulating with the warm air risen.
The mode of the rotating speed of the rotating disk of available adjustment high speed rotating, concentration of caustic soda and liquid, solid phase ratio, regulate dry after the granular size of reactant ,-5.0 millimeters (preferably 0.1-3.0 millimeters that make the raw meal particle size of more than 80% 0.05) scope.
Temperature in drying tower controls 100-and 315 DEG C.In the spray drying tower, along with the carrying out of drying, start to create oxidation reaction process between chromite (or ferrochrome) and caustic soda.
By the caustic soda solid phase roasting oxidation method of above-described chromite (or ferrochrome), Cr
2o
3can 80% be reached by the oxidation ratio of (1) formula, then by gained material, by the method described in application for a patent for invention case 201310296637.5, by caustic soda solid phase roasting oxidation gained material, process is continued by steps such as solid carbon acidifying, counter-current extraction, re-baking and hot pressing leachings, the total yield of chromium can reach more than 95%, and alkali recovery can reach more than 80%, defines after calcium-free roasting method, a brand-new operational path preparing Sodium chromate or sodium dichromate 99.
Certainly, if in the caustic soda phase oxidative of the first step, the transformation efficiency of chromium reaches 90%, then can save the step such as re-baking and hot pressing leaching, and with traditional normal temperature causticizing process, namely with CaO or Ca (OH)
2reclaim NaOH with the method for reaction, the rate of recovery also can reach more than 80%.
Embodiment 1
Chromite used is containing Cr
2o
342.31%, Fe
2o
326.51%, MgO12.01%, Al
2o
314.55%, SiO
23.24%, CaO1.30%; NaOH solution used is that hot pressing leaching is reclaimed, the NaOH solution of concentrated about 10-15%, mix with the NaOH solution (>=30%) of supplementing and prepare, concentration is the NaOH solution of 18%.
One ton of chromite powder adds 2.45 tons of 20%NaOH solution, now, and Cr
2o
3mole number (do not comprise hot pressing leaching Ethylene recov in Cr
2o
3): mole number=1 of NaOH: 3.96; Solid phase: liquid phase=1.0: 2.45.
By the mixture of above-mentioned chromite and 20%NaOH solution, stir under normal temperature (about 20 DEG C), with the top of pump delivery to a spray drying granulation tower, be heated to 250 ± 50 DEG C, enter from tower bottom, the mode of carrying out counter current contact containing the oxygen-rich air stream of oxygen 35-40% carries out drying-granulating.
Send into the rotary kiln of a temperature programming from the granular material of the bottom collection of spray drying granulation tower, proceed phase oxidative process with the oxygen-rich air containing oxygen 35-40%: maintain 3 hours at 300 DEG C, be then progressively elevated to 700-790 DEG C, maintain 2 hours.Cr
2o
3oxidation ratio be 81%%.
Embodiment 2
One ton containing Cr
2o
339.31%, Fe
2o
325.01%, MgO14.31%, Al
2o
315.51%, SiO
24.24%, the chromite of CaO1.50%, adds just in 2.45 tons of 17%NaOH solution, now, and Cr
2o
3mole number (do not comprise hot pressing leaching Ethylene recov in Cr
2o
3): mole number=1 of NaOH: 4.03; Solid phase: liquid phase=1.0: 2.45.
By the mixture of above-mentioned chromite powder and 20%NaOH solution, stir under normal temperature (about 20 DEG C), with the top of pump delivery to a spray drying granulation tower, be heated to 250 ± 20 DEG C, enter from tower bottom, the mode of carrying out counter current contact containing the oxygen-rich air stream of oxygen 35-40% carries out drying-granulating.
Send into the rotary kiln of a temperature programming from the granular material of the bottom collection of spray drying granulation tower, proceed phase oxidative process with the oxygen-rich air containing oxygen 35-40%: maintain 3 hours at 300 DEG C, be then progressively elevated to 700-790 DEG C, maintain 2 hours.Cr
2o
3oxidation ratio be 82%.
Claims (1)
1. directly process by caustic soda solid phase roasting method the method that chromite (ferrochrome) prepares Sodium chromate or sodium dichromate 99, it is characterized by:
(1), one caustic soda solid phase roasting method directly processes the process that chromite (ferrochrome) prepares Sodium chromate or sodium dichromate 99, by 15-caustic soda (NaOH) solution of 35% and chromite powder (or ferrochrome powder), in molar ratio: the mole number of NaOH: Cr in chromite (ferrochrome)
2o
3mole number=(3.0-4.5): between 1.0 [preferably in (3.8-4.2): 1.0]; Liquid phase: solid phase=(1.5-3.0): between 1.0 [preferably in (2.0-2.8): 1.0], at normal temperature-150 DEG C (preferably 15-80 DEG C) under stir.Then, by this mixture, with the top of pump delivery to a spray drying granulation tower, with be heated to 100-315 DEG C, the air that rises (or the mode of oxygen-rich air or oxygen stream counter current contact carries out drying-granulating, make more than 80%, dried raw meal particle size is 0.05-5.0 millimeters (preferably 0.1-3.0 millimeters) scope.
By dry, granularity 0.05-the range materials in 5.0 millimeters, collect at tower bottom, and send in the reactor (as fluidizing furnace, mechanical stirring kiln or rotary kiln) of a temperature programming, proceed phase oxidative process with air (or oxygen-rich air or oxygen).Heat up gradually, initial temperature controls below 315 DEG C, is then progressively elevated to 700-790 DEG C (fusing point lower than Sodium chromate).
(2), in claim (1) said caustic soda solid phase roasting method directly processes the method that chromite (ferrochrome) prepares Sodium chromate or sodium dichromate 99, also comprises solid carbon acidifying, counter-current extraction, re-baking and hot pressing and leaches four steps.
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|---|---|---|---|
| CN201410177745.5A CN104276604A (en) | 2014-04-29 | 2014-04-29 | Method for preparing chromate through caustic soda solid oxidization of chromite ore |
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|---|---|---|---|
| CN201410177745.5A CN104276604A (en) | 2014-04-29 | 2014-04-29 | Method for preparing chromate through caustic soda solid oxidization of chromite ore |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SU1142448A1 (en) * | 1979-07-10 | 1985-02-28 | Предприятие П/Я А-7125 | Method of obtaining sodium chromate |
| CN102320661A (en) * | 2011-09-06 | 2012-01-18 | 重庆民丰化工有限责任公司 | Three-phase catalytic oxidation preparation technology of soluble chromate |
| CN102432068A (en) * | 2011-09-28 | 2012-05-02 | 北京科技大学 | Process for producing sodium chromate |
| CN103318960A (en) * | 2013-07-04 | 2013-09-25 | 余华强 | Separation method for completion liquid of caustic soda liquid-phase oxidation of chromite |
-
2014
- 2014-04-29 CN CN201410177745.5A patent/CN104276604A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SU1142448A1 (en) * | 1979-07-10 | 1985-02-28 | Предприятие П/Я А-7125 | Method of obtaining sodium chromate |
| CN102320661A (en) * | 2011-09-06 | 2012-01-18 | 重庆民丰化工有限责任公司 | Three-phase catalytic oxidation preparation technology of soluble chromate |
| CN102432068A (en) * | 2011-09-28 | 2012-05-02 | 北京科技大学 | Process for producing sodium chromate |
| CN103318960A (en) * | 2013-07-04 | 2013-09-25 | 余华强 | Separation method for completion liquid of caustic soda liquid-phase oxidation of chromite |
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Application publication date: 20150114 |