CN103253709A

CN103253709A - Method for producing chromium sesquioxide through hot method

Info

Publication number: CN103253709A
Application number: CN2013102061058A
Authority: CN
Inventors: 韩登仑; 张忠元; 武平; 张宏军
Original assignee: JINSHI CHEMICAL INDUSTRY Co Ltd GANSU
Current assignee: JINSHI CHEMICAL INDUSTRY Co Ltd GANSU
Priority date: 2013-05-29
Filing date: 2013-05-29
Publication date: 2013-08-21
Anticipated expiration: 2033-05-29
Also published as: CN103253709B

Abstract

The invention discloses a method for producing chromium sesquioxide through a hot method, which aims to solve the problem that contained hexavalent chromium and water-soluble salt must be treated through water washing after thermal decomposition in the existing method for making chromium sesquioxide through a chromic acid thermal decomposition continuous method. The method disclosed by the invention comprises the following steps: roasting: putting chromic anhydride into a rotary kiln, and performing thermal decomposition at 1050-1350 DEG C to obtain a solid mixture; and reducing: taking out the solid mixture obtained in the step A from the tail of the rotary kiln, wherein the temperature of the solid mixture taken out is 300-600 DEG C; putting the solid mixture into a roller of a reduction reactor, wherein thiocarbamide accounting for 0.2-3% of the solid mixture in mass is contained in the roller of the reactor in advance; and reacting for 20-60 minutes to obtain chromium sesquioxide. According to the invention, thiocarbamide is directly added into the hot material of chromium sesquioxide which chromic anhydride is decomposed into, thus reducing to obtain chromium sesquioxide of which the hexavalent chromium content is 1ppm or below. The invention has the characteristics of simple treatment process, convenient operation, low investment and the like; and the hexavalent chromium content in the chromium sesquioxide obtained through decomposition of chromic anhydride can be reduced without water washing.

Description

A kind of hot method is produced the method for chromium sesquioxide

Technical field

The present invention relates to a kind of method of producing chromium sesquioxide.

Background technology

The method for making of chromium sesquioxide output maximum is the chromic trioxide decomposition method, 4CrO ₃=2Cr ₂O ₃+ 3O ₂Along with temperature raises, the chromium sesquioxide crystal is able to form gradually in the chromic trioxide liquation and grow up, it is few to have lattice defect, and finished product keeps many excellent properties of chromium sesquioxide monocrystalline, and chromic trioxide is decomposed fully, temperature must be higher than 800 ℃. because the raw material chromic trioxide contains a small amount of sodium salt, alkaline sodium salt can make a small amount of trivalent chromium be oxidized to Sodium chromate in high temperature air, so even heat decomposition temperature up to 1350 ℃, sexavalent chrome that will residual about 100-600ppm.Sexavalent chrome in the chromium sesquioxide not only increases water solubles content in the finished product, and finished color is turned to be yellow, and use exerted an influence, therefore in the customer requirements restriction chromium sesquioxide content of 6-valence Cr ions in 10ppm, if directly wash the chromium sesquioxide that produces in the rotary kiln with water, not only water consumption is big, and the sexavalent chrome in the chromium sesquioxide is difficult to be down to 10ppm.

The method of existing producing dichromium trioxide using chromic acid thermal decomposition continuous method is to add returning charge or its chromic method of additive (boric acid, starch, ammonium chloride, wood chip) thermal decomposition process in chromic trioxide in advance.Process for chromium trioxide by reduction of aminium sulfate is to utilize raw material to be sodium dichromate, must wash with water after the thermolysis and could handle its contained sexavalent chrome and water-soluble salt.

Summary of the invention

The purpose of this invention is to provide the method that a kind of hot method is produced chromium sesquioxide, to solve the method for existing producing dichromium trioxide using chromic acid thermal decomposition continuous method, must wash the problem that to handle its contained sexavalent chrome and water-soluble salt after the thermolysis with water.

Technical solution of the present invention is as follows: a kind of hot method is produced the method for chromium sesquioxide, it is characterized in that it comprises the following steps:

A, roasting: chromic trioxide is put into rotary kiln, the solid mixture that under 1050 ~ 1350 ℃ of temperature, carries out thermolysis;

B, reduction: obtaining solid mixture in the steps A is 300-600 ℃ from the temperature that rotary kiln comes out, and contains the sexavalent chrome of 100-600ppm in the solid mixture.Solid mixture is put into the cylinder of reduction reactor, accommodate the thiocarbamide that accounts for solid mixture quality 0.2-3% in the cylinder of former reactor in advance, the reaction times is 20-60 minute, gets chromium sesquioxide.

As a further improvement on the present invention, the rate of feeding of chromic trioxide is per hour 200 kilograms in the described steps A.

As a further improvement on the present invention, the rotating speed of the cylinder of reduction reactor is 40 ~ 80r/min among the described step B.

Reaction mechanism of the present invention is as follows: in the chromium sesquioxide production process, because containing compositions such as a spot of sodium salt in the starting material chromic trioxide, in roasting process, this part sodium salt can make a small amount of Cr ₂O ₃Be converted into Sodium chromate, thereby make in the chromium sesquioxide finished product content of 6-valence Cr ions higher all the time.But 300-600 ℃ of temperature, in solid mixture, add thiocarbamide [thiocarbamide molecular formula (H ₂N) ₂CS, relative molecular weight 76], its reaction principle be thiocarbamide when temperature is higher, at first decompose to generate reducing gas, utilize raw material self waste heat, with sexavalent chrome reaction content of 6-valence Cr ions is down to below the 1ppm while hot reducing gas.

Reaction equation is as follows:

3(H ₂N) ₂CS+2CrO ₃=Cr ₂O ₃+3S+3(NH ₂) ₂CO

3(H ₂N) ₂CS+8CrO ₃=4Cr ₂O ₃+3S+?3N ₂+3CO ₂+6H ₂O

The present invention utilizes and directly sneaks into the thiocarbamide reduction in the heat material after chromic trioxide is decomposed into chromium sesquioxide and obtain the chromium sesquioxide of a kind of sexavalent chrome below 1ppm, it is simple that the present invention has a treatment process, characteristics such as easy to operate, less investment need not to wash and just can reduce chromic trioxide and decompose sexavalent chrome in the gained chromium sesquioxide.

Contrast: handle chromium sesquioxide (per 100 parts of Cr with urea ₂O ₃Add 1.5-2.5 part), reaction formula (NH ₂) ₂CO+ 2CrO ₃=Cr ₂O ₃+ N ₂+ CO ₂+ 2H ₂O through checking repeatedly, can only obtain the product of 10-20ppm, does not reach customer requirements.And gained chromium sesquioxide content of the present invention can reach 99.4-99.6%.Than remarkable with chromic effect in the urea processing chromium sesquioxide.

Embodiment

The following examples can further specify the present invention, but do not limit the present invention in any way.

Embodiment 1

A, roasting: on average chromic trioxide is evenly dropped in the rotary kiln solid mixture that under 1050 ℃ of temperature, carries out thermolysis with 200 kilograms speed per hour;

B, reduction: obtaining the temperature that solid mixture comes out from rotary kiln in the steps A is 300 ℃, contain the sexavalent chrome of 100-600ppm this moment in the solid mixture, when solid mixture when rotary kiln is focused to double centner, solid mixture is put into the cylinder of reduction reactor, accommodate 0.2 kilogram of thiocarbamide in the cylinder of former reactor in advance, after filling material in the cylinder, locking charging opening lid, open ventilating pit, rotating speed swing roller with 40r/min, rotate after 40 minutes, emit material, get chromium sesquioxide; Make after testing that sexavalent chrome is 0.62ppm in the chromium sesquioxide, chromium sesquioxide content can reach 99.6%.

Embodiment 2

A, roasting: on average chromic trioxide is evenly dropped in the rotary kiln solid mixture that under 1200 ℃ of temperature, carries out thermolysis with 200 kilograms speed per hour;

B, reduction: obtaining the temperature that solid mixture comes out from rotary kiln in the steps A is 400 ℃, contain the sexavalent chrome of 100-600ppm this moment in the solid mixture, when solid mixture when rotary kiln is focused to double centner, solid mixture is put into the cylinder of reduction reactor, accommodate the thiocarbamide that accounts for 1 kilogram of solid mixture quality in the cylinder of former reactor in advance, after filling material in the cylinder, locking charging opening lid, open ventilating pit, with the rotating speed swing roller of 60r/min, rotate after 50 minutes, emit material, chromium sesquioxide, make after testing that sexavalent chrome is 0.12ppm in the chromium sesquioxide, chromium sesquioxide content can reach 99.5%.

Embodiment 3

A, roasting: on average chromic trioxide is evenly dropped in the rotary kiln solid mixture that under 1350 ℃ of temperature, carries out thermolysis with 200 kilograms speed per hour;

B, reduction: obtaining the temperature that solid mixture comes out from rotary kiln in the steps A is 600 ℃, contain the sexavalent chrome of 100-600ppm this moment in the solid mixture, when solid mixture when rotary kiln is focused to double centner, solid mixture is put into the cylinder of reduction reactor, accommodate 3 kilograms thiocarbamide in the cylinder of former reactor in advance, after filling material in the cylinder, locking charging opening lid, open ventilating pit, with the rotating speed swing roller of 80r/min, rotate after 60 minutes, emit material, chromium sesquioxide, make after testing that sexavalent chrome is 0ppm in the chromium sesquioxide, chromium sesquioxide content can reach 99.4%.

Claims

1. the method that hot method is produced chromium sesquioxide is characterized in that it comprises the following steps:

A, roasting: chromic trioxide is put into rotary kiln, the solid mixture that under 1050-1350 ℃ of temperature, carries out thermolysis;

B, reduction: obtaining the temperature that solid mixture comes out from rotary kiln in the steps A is 300-600 ℃, solid mixture is put into the cylinder of reduction reactor, accommodate the thiocarbamide that accounts for solid mixture quality 0.2-3% in the cylinder of former reactor in advance, reaction times is 20-60 minute, gets chromium sesquioxide.

2. a kind of hot method according to claim 1 method of producing chromium sesquioxide, it is characterized in that: the rate of feeding of chromic trioxide is per hour 200 kilograms in the described steps A.

3. a kind of hot method according to claim 1 and 2 method of producing chromium sesquioxide, it is characterized in that: the rotating speed of the cylinder of reduction reactor is 40-80r/min among the described step B.