CN102275992B

CN102275992B - Two-stage roasting method for chromite

Info

Publication number: CN102275992B
Application number: CN 201110144569
Authority: CN
Inventors: 袁代建; 张金聪; 李小利; 刘清华
Original assignee: Chongqing Minfeng Chemical Co Ltd
Current assignee: Chongqing Minfeng Chemical Co Ltd
Priority date: 2011-05-31
Filing date: 2011-05-31
Publication date: 2013-06-26
Anticipated expiration: 2031-05-31
Also published as: CN102275992A

Abstract

The invention discloses a two-stage roasting method for chromite and particularly relates to a non-calcium two-stage roasting method for chromite. The method comprises the following steps: mixing chromite, sorted return slag and sodium carbonate, transferring into a first kiln, heating the mixture in the first kiln under the condition that oxygen is excluded, transferring the product into a second kiln, ventilating before heating, leaching and washing the obtained solid clinker, returning the sorted chromium slag to the mixing stage, and detoxifying the tailing for comprehensive utilization. Compared with the prior art, the chromite oxidation ratio of the method is high, the reaction rate is higher, and the leaching rate is high; and the utilization of the return slag can save the cost and reduce pollutions. Thus, in the non-calcium roasting field of chromium salt, the method has popularization and application values for environmental protection and enterprise benefit gaining.

Description

The chromite two-section roasting

Technical field

The present invention relates to a kind of calcium-free roasting technique of chromite, particularly a kind of chromite without the calcium two-section roasting.

Background technology

At present, chromite oxidizing roasting method is almost the unique method of chromium salt production, wherein be divided into calcium roasting method and calcium-free roasting method are arranged, its something in common is it is all that chromite and soda ash are carried out roasting under the high temperature oxidation condition, makes the chromium in ore be converted into water miscible Sodium chromate through the subsequent disposal such as leaching acquisition chromic salts product.calcium-free roasting method uses return slag to replace the calcic filler, chromium slag quantity discharged greatly reduces and does not contain high malicious yellow ultramarine, become the main stream approach of chromium salt production, documents 200710017747.8 discloses a kind of by the method for chromite through producing sodium chromate by calcium-free calcination, with chromite, sodium carbonate and return slag mix, carry out oxidizing roasting in rotary kiln, the method is directly carried out oxidizing roasting with mixture, picotite and soda ash and oxygen direct reaction are produced Sodium chromate, because picotite is difficult for reaction, cause whole speed of response to be carried out slowly, so it is not high that chromite fails fully to react leaching rate, there is imagination to improve reaction efficiency by the two-stage roasting of chromite in external related documents, but fail to realize owing to lacking concrete working method.

Summary of the invention

For above-mentioned the deficiencies in the prior art part, the invention provides a kind of chromite two-section roasting that can accelerate chromite calcination speed.

To achieve these goals, the step of chromite two-section roasting employing of the present invention is:

A. batch mixing: with chromite drying, abrasive dust to 200 order by more than 70%, in step D, residue chromium slag passes through more than 70% through the return slag drying after sorting, abrasive dust to 200 order, and soda ash precentagewise 100:70:140 mixing, uniformity coefficient reaches 90～110% and delivers to blending bun by worm conveyor, lift.

B. anaerobic roasting: the batch mixing that obtains in steps A is completely cut off air heating at the first kiln, and calcining temperature is 500 ℃, calcines 1 hour;

C. aerobic roasting: with sending into the second kiln through the batch mixing of heating in step B, pass into air and carry out roasting, 1150 ℃ of high temperature zone temperatures, 500 ℃ of kiln end temperatures were calcined 2～3 hours;

D. leaching: with after the solid clinker cooling that obtains in step C to 200 ℃～300 ℃, send into subsequent processing leaching washing;

E. the processing of chromium slag: in step D, residue chromium slag returns to calcining process after sorting, comprehensive utilization after the tailings detoxifcation.

The technical program adopts two-stage method has been adopted in the roasting of batch mixing, in the first kiln, the isolated air of batch mixing is heated, and picotite is heated to 500 ℃ at oxygen free condition, makes picotite lattice distorted, and potential energy raises, and is easy to reaction, the main and Cr of soda ash ₂O ₃, Al ₂O ₃And Fe ₂O ₃Reaction obtains NaFeO ₂, NaAlO ₂And NaCrO ₂, batch mixing continues to enter the second kiln, passes into air, NaCrO ₂Gas and oxygen reaction obtain Sodium chromate, NaAlO ₂And NaCrO ₂Play the alkalescence effect, adopt such method, fully oxidation of picotite, reaction generates more chromic salts, is conducive to improve leaching rate.

Compared with prior art; this beneficial effect of the invention: the present invention adopts the two-stage method roasting chromite to produce Sodium chromate; the chromite oxidation ratio is high; speed of response is faster; leaching rate is high; and the utilization of return slag has been saved cost and has been reduced pollution, therefore in the chromium salt calcium-free roasting field, all has application value on environment protection or the performance of enterprises.

Embodiment

The present invention is described in further detail below in conjunction with specific embodiment.

Embodiment 1: the invention discloses a kind of chromite two-section roasting, its step is as follows:

One, the mixing of raw material: chromite drying, abrasive dust to 200 order are by more than 70%, return slag drying after sorting, abrasive dust to 200 order are by more than 70%, be 100:70 with per-cent: 140 chromite, return slag and soda ash are sent into biaxial rneader and are mixed, and the compound uniformity coefficient reaches 90% and delivers to blending bun by worm conveyor, lift.

Two, roasting: be divided into aerobic stage and anaerobic stage, batch mixing passes through aerobic stage and anaerobic stage successively;

The main reaction that in roasting, chromite and soda ash and oxygen occur is:

Cr ₂O ₃+ 2Na ₂CO ₃+ 1.5O ₂＝2Na ₂CrO ₄+2 CO ₂+ Q ①

1, the anaerobic stage: weighing belt is sent the batch mixing spiral into the first kiln, and the mixture of chromite and soda ash was calcined 1 hour under the condition of starvation, 500 ℃ of kiln temperatures, and when picotite is heated to 500 ℃, Fe ²⁺At first be oxidized to Fe ³⁺Thereby, making spinel lattice distorted, potential energy raises, and is easy to reaction.

Soda ash is same R first ₂O ₃Reaction generates NaRO ₃, i.e. chromous acid sodium (NaCrO ₂), sodium aluminate (NaAlO ₂) and sodium ferrite (NaFeO ₂), described reaction formula is:

Cr ₂O ₃+Na ₂CO ₃＝2NaCrO ₂+ CO ₂ ②

Al ₂O ₃+ Na ₂CO ₃＝2NaAlO ₂+ CO ₂ ③

Fe ₂O ₃+ Na ₂CO ₃＝2NaFeO ₂+ CO ₂ ④

2, the aerobic stage: enter the second kiln from anaerobic stage batch mixing out, pass into air roasting, in kiln, high temperature zone temperature is 1150 ℃, and 500 ℃ of kiln end temperatures were calcined 3 hours; In high-temperature oxidation environment, chromous acid sodium (NaCrO ₂) continue reaction generation Na with oxygen and soda ash immediately ₂CrO ₄Sodium aluminate (NaAlO ₂) and sodium ferrite (NaFeO ₂) also play the alkalescence effect, make NaCrO ₂Be oxidized to Na ₂CrO ₄

2NaCrO ₂+ Na ₂CO ₃+ 1.5O ₂＝2Na ₂CrO ₄+ CO ₂+ Q ⑤

2NaCrO ₂+ 2NaAlO ₂+ 1.5O ₂＝2Na ₂CrO ₄+ Al ₂O ₃+ Q ⑥

2NaCrO ₂+ NaFeO ₂+ 1.5O ₂＝2Na ₂CrO ₄+ Fe ₂O ₃+ Q ⑦

Wherein, the side reaction that occurs in roasting is: Na ₂CO ₃Except occur 3. with chromite, 4., 1. reaction generates NaRO ₂And Na ₂CrO ₄Outward, also with impurity SiO in the ore deposit ₂, V ₂O ₅Reaction generates the lower product (Na of molten point ₂SiO ₃, NaVO ₃); N ₂SiO ₃And NaAlO ₂Not only can provide sodium ion, make that 6. trivalent chromium occurs, reaction 9. changes Sodium chromate into, and both also generate aluminum magnesium silicate sodium (Na with magnesium oxide generation complex reaction ₄MgAl ₂Si ₃O ₁₂).

Si＋Na ₂CO ₃＝Na ₂SiO ₃＋CO ₂ ⑧

V ₂O ₅＋Na ₂CO ₃ ＝2NaVO ₃＋CO ₂ ⑨

Na ₂SiO ₃＋2NaCrO ₂＋1.5O ₂＝2 Na ₂CrO ₄＋SiO ₂ ⑩

Na ₂SiO ₃＋2NaAlO ₂＋MgO＋2SiO ₂＝Na ₄MgAl ₂Si ₃O

Figure 2011101445691100002DEST_PATH_IMAGE001

The Na that 8., 9. formula generates ₂SiO ₃And NaAlO ₂Make grog containing water-soluble silicon, aluminium, and its back-pushed-type Further reaction is transformed into the water-fast aluminum magnesium silicate sodium of Sodium chromate generation, can reduce water-soluble silicon, aluminium.

The stack gas that roasting produces after settling pocket, waste heat boiler and electrostatic precipitator gas through smoke stack emission to atmosphere, the powder that in fly-ash separator, dedusting is got off submits to the kiln ash silo through the spiral bucket, and use in the process of batching, the steam that waste heat boiler produces is delivered to steam pipe system, for full factory.

Three, leaching and washing

Batch mixing becomes through after roasting the solid grog that contains Sodium chromate, and the solid grog is cooled to 200 ℃ through cooler, enters the leaching car and leaches and wash.

Four, the processing of chromium slag

Part chromium slag is used for roasting after super-dry, part chromium slag is used for calcining process as return slag through rod milling, wet concentration after thick slag process band filter, drying;

Thin slag fully utilizes after detoxifcation through after box filter, for example: ironmaking, production cement, brickmaking and glass colorant etc.

The above only is the detailed description of preferred embodiment of the present invention, is not to limit the present invention, and the embodiment of all similar variations of doing according to creation spirit of the present invention all should be contained among the present invention.

Claims

1. chromite two-section roasting is characterized in that it comprises the following steps:

A, batch mixing: chromite drying, abrasive dust to 200 order are by more than 70%, return slag drying after sorting, abrasive dust to 200 order are by more than 70%, be 100:70 with per-cent: 140 chromite, return slag and soda ash mix, and the compound uniformity coefficient reaches 90% and delivers to blending bun by worm conveyor, lift;

B, anaerobic roasting: the batch mixing that obtains in steps A is completely cut off air heating at the first kiln, and calcining temperature is 500 ℃, calcines 1 hour;

C, aerobic roasting: with sending into the second kiln through the batch mixing of heating in step B, pass into air and carry out roasting, 1150 ℃ of high temperature zone temperatures, 500 ℃ of kiln end temperatures were calcined 2～3 hours;

D, leaching: with after the solid clinker cooling that obtains in step C to 200 ℃～300 ℃, leach and wash;

The processing of E, chromium slag: residue chromium slag in step D is returned to calcining process, comprehensive utilization after the tailings detoxifcation after sorting.