CN101503203A

CN101503203A - Method for decomposing ammonia sulfate and method for reclaiming sulfuric acid from waste acid and acid wastewater

Info

Publication number: CN101503203A
Application number: CNA200910300912XA
Authority: CN
Inventors: 杨绍泉; 杨峰
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-03-17
Filing date: 2009-03-17
Publication date: 2009-08-12
Anticipated expiration: 2029-03-17
Also published as: CN101503203B

Abstract

The invention belongs to the wastewater treatment field, and relates to a method for treating waste acid and acid wastewater generated during the process of preparing titanium dioxide by using a sulfuric acid method, in particular to a method for decomposing ammonia sulfate and a method for recovering sulfuric acid from waste acid and acid wastewater. In order to effectively recover the sulfuric acid, the method comprises the following steps: sectionally heating by adopting metal oxide (mainly adopt Fe2O3) as a catalyst after the ammonia sulfate is obtained through neutralizing and converting the acid wastewater or the waste acid; decomposing NH3 out at the temperature of 253 DEG C and decomposing SO3 out at the temperature of 480 DEG; and then collecting and absorbing the SO3, and obtaining the sulfuric acid. The waste acid and the acid wastewater are treated by adopting the method; the used raw materials such as the CaCO3, ammonia (or ammonia water) and the Fe2O3 as the catalyst are not consumed theoretically and can be circularly utilized; and in fact, a proper amount of CaCO3, NH3 and Fe2O3 is only required to be supplemented when the raw materials are in use; and the invention provides a novel method for treating the waste acid and the acid wastewater generated during the process of preparing the titanium dioxide.

Description

The method of decomposing ammonia sulfate reaches the method for reclaim(ed) sulfuric acid from spent acid and acid waste water

Technical field

The invention belongs to field of waste water treatment, the spent acid that produces when relating to method for producing gtitanium dioxide with sulphuric acid and the treatment process of acid waste water, the method that is specially decomposing ammonia sulfate reaches the method for reclaim(ed) sulfuric acid from spent acid and acid waste water.

Background technology

Sulfuric acid process is that the ilmenite powder and the vitriol oil are carried out acidolysis reaction generation titanyl sulfate, generates metatitanic acid through hydrolysis, promptly obtains the titanium dioxide product through calcining, pulverizing again.This method can be produced anatase titanium dioxide and Rutile type Titanium Dioxide.Raw material ilmenite concentrate, titanium slag and sulfuric acid in this method are easy to get at a low price, and technology is ripe, and equipment is simple, and anticorrosive easily solves; The titanium dioxide of the various trades mark of anatase titanium dioxide of market demand but the production chlorination process can not be produced.But the defective of sulfuric acid legal system titanium dioxide maximum is to be that refuse and by product are many, and environmental pollution is more serious, and one ton of finished product titanium dioxide of every production will be discharged 6-8 ton spent acid and (be contained H ₂SO ₄About 20-22%, FeSO ₄About 7-10%), (about 60-80 ton contains H to also have a large amount of acid waste water ₂SO ₄About 1-3%, FeSO ₄About 0.4-1.2%), the method of comprehensive utilization of spent acid is more, produce iron pigment and adopt in the ammonia simply effective with spent acid with the method for producing fertilizer, if the sulfuric acid that will reclaim in the spent acid can adopt spissated method that spent acid is concentrated into 60-75%, add 98% vitriol oil again and allocate to 93-95%, but because of containing plurality of impurities such as ferrous sulfate in the spent acid, crystallization blocking pipe in concentrating, equipment operating efficiency is low, the maintenance cost height; Acid waste water is because of wherein sulfuric acid content is low, so generally adopt neutralisation to handle, after the pH value was up to standard, by squeezing, gained water allow compliance with emission standards can be discharged, and by products such as the gypsum of generation generally are that heap is abandoned landfill disposal.

In theory, be not consume sulfuric acid in the process of Titanium White Production By Sulfuric Acid Process, sulfuric acid all becomes spent acid or acid waste water leaves the Producing Titanium Dioxide system.If with existing method of enrichment reclaim in the spent acid sulfuric acid or in and vitriolic method in the waste water all can cause the waste of sulfuric acid resource, the invention human desires is by efficient recovery sulfuric acid the spent acid that produces from method for producing gtitanium dioxide with sulphuric acid and the acid waste water.

Summary of the invention

Technical problem solved by the invention provides efficient recovery vitriolic method a kind of spent acid that produces from method for producing gtitanium dioxide with sulphuric acid and the acid waste water.

There is a committed step to be that the ammonium sulfate that intermediate steps is produced is that the catalyzer thermal degradation obtains NH with metal oxides such as ferric oxide in the sulfuric acid in reclaiming spent acid and acid waste water ₃And SO ₃The SO of gained ₃Collect absorption according to ordinary method and promptly get sulfuric acid.

The heating of heating time-division differing temps section is with Fe ₂O ₃As changing agent is example, begins to decomposite NH in the time of 253 ℃ ₃, decomposite SO during 480 ℃ of beginnings ₃In order to reach certain decomposition rate, to satisfy the needs of commercial run, actual decomposition temperature should be higher than decomposition starting temperature, so the contriver is controlled at 253～450 ℃ of temperature sections with temperature and decomposes and obtain NH ₃, obtain SO 480～780 ℃ of temperature sections decomposition ₃, collect respectively.

(NH ₄) ₂SO ₄Promptly pressing following formula at 253 ℃ decomposes:

(NH ₄) ₂SO ₄→NH ₄HSO ₄+NH ₃↑。

If do not add catalyst Fe ₂O ₃, NH ₄HSO ₄Can further decompose according to following formula at 〉=350 ℃:

2NH ₄HSO ₄→(NH ₄) ₂S ₂O ₇+H ₂O；

3(NH ₄) ₂SO ₄→2NH ₃↑+2N ₂↑+6SO ₂↑+9H ₂O。

These two kinds of reactions are not expect the side reaction that occurs.If when having metal oxide to exist, the NH of nascent state ₄HSO ₄Can generate (NH with reactive metal oxide immediately ₄) ₂SO ₄With new vitriol, these new sulphate decomposition temperature all are much higher than (NH ₄) ₂SO ₄Decomposition temperature, utilize this principle can be with (NH ₄) ₂SO ₄Decomposite NH ₃After, improve decomposition temperature again and decomposite SO ₃, so just realized NH ₃And SO ₃Separation.Therefore, all metal oxides can be used as catalyzer in theory, but the decomposition temperature difference of different metal vitriol in fact, as 650 ℃ in copper sulfate, 1000 ℃ of 850 ℃ of lead sulfates of 770 ℃ of manganous sulfates of Tai-Ace S 150,1450 ℃ of fusions of calcium sulfate but do not decompose, the high more material to equipment of industrial decomposition temperature requires also high more, and cost is also big more, and energy-output ratio is also high more.To consider also in addition whether catalyzer is easy to obtain, and whether price is cheap, whether poisonous and can produce environment and pollute etc.Comprehensive these factors, the contriver has selected Fe ₂O ₃Use Fe as catalyzer ₂O ₃Not only decomposition temperature is low, and it is cheap to pass, and is nontoxic again, is optimal decomposition catalyst.After temperature raises, NH ₄HSO ₄With Fe ₂O ₃Reaction generates ferric sulfate, (NH ₄) ₂SO ₄And water, the ferric sulfate of generation resolves into Fe again ₂O ₃And SO ₃, its reaction formula is as follows:

6NH ₄HSO ₄+Fe ₂O ₃→3(NH ₄) ₂SO ₄+Fe ₂(SO ₄) ₃+3H ₂O；

The vitriolic method that reclaims in the spent acid is:

A, spent acid adopt ammoniacal liquor or ammonia adjust pH 3～5.5 to leave standstill more than 2 hours, filter, and remove a little TiO ₂Deng impurity;

B, filtrate add ammoniacal liquor again or ammonia adjust pH 9-11 neutralization reaction obtains (NH ₄) ₂SO ₄, wherein also contain a certain amount of Fe (OH) in the reaction solution ₂

Feed oxygen-containing gas (as air or oxygen etc.) in C, the reaction solution, with Fe (OH) ₂Be oxidized to Fe ₃O ₄, filter, collect Fe ₃O ₄Solid; Fe ₃O ₄Drying, pulverizing can obtain iron black product;

D, filtrate condensing crystal obtain ammonium sulfate, and ammonium sulfate is with Fe ₂O ₃Be the catalyst segments heating: begin to decomposite NH in the time of 253 ℃ ₃, begin to decomposite SO in the time of 480 ℃ ₃In the time of 253～450 ℃, decomposite NH3, decomposite SO when 480～780 ℃ ₃

E, collection absorb SO ₃Promptly get sulfuric acid.

Wherein, among steps A and the B and during spent acid, the H in the spent acid ₂SO ₄And FeSO ₄Generate Fe (OH) with ammoniacal liquor or ammonia gas react ₂(NH ₄) ₂SO ₄, reaction formula is as follows:

With ammonia gas react FeSO ₄+ 2NH ₃+ 2H ₂O → (NH ₄) ₂SO ₄+ Fe (OH) ₂↓;

H ₂SO ₄+2NH ₃→(NH ₄) ₂SO ₄。

With ammoniacal liquor reaction FeSO ₄+ 2NH ₃H ₂O → (NH ₄) ₂SO ₄+ Fe (OH) ₂↓;

H ₂SO ₄+2NH ₃·H ₂O→(NH ₄) ₂SO ₄+2H ₂O。

Fe among the step C (OH) ₂Obtain Fe with oxygen reaction ₃O ₄(iron oxide black), reaction formula is as follows:

4Fe(OH) ₂+O ₂+2H ₂O→4Fe(OH) ₃

Fe(OH) ₂+2Fe(OH) ₃→Fe ₃O ₄+4H ₂O。

Gained Fe ₃O ₄Drying, pulverize iron black product; In order to guarantee the quality of iron black product, need when steps A, not be higher than 60 ℃ by controlled temperature, controlled temperature is 60-80 ℃ when step B.Because the temperature range of step C requires at 60～80 ℃, otherwise can influence iron black quality, and in the steps A and the time emit a large amount of heat, if the temperature of controlled step A is not less than 60 ℃, then during step B temperature easily above 80 ℃, the iron oxide black that enters step C output this moment can be defective in quality, therefore needs controlled step A temperature not to be higher than 60 ℃.If among the step B and the time temperature less than 60 ℃, the color yellowing of the iron oxide black of gained, quality is bad; If be higher than 80 ℃, speed of response is too fast, and iron black product crystal formation is bad, and it is impure to produce color, and energy consumption increases, so needs controlled temperature 60-80 ℃ of the best during step B.

Step D reaction formula is as follows:

6NH ₄HSO ₄+Fe ₂O ₃→3(NH ₄) ₂SO ₄+Fe ₂(SO ₄) ₃+3H ₂O

The SO that reaction produces ₃Preparing the vitriol oil according to the method for conventional sulfuric acid absorption gets final product; The NH that produces ₃Recovery can be used in the steps A and spent acid, does not consume ammonia or ammoniacal liquor in theory, in fact may be overflowed by ammonia because of the pipeline resistance to air loss, and therefore when production application, additional proper ammonia or ammonia can guarantee to react and carry out.

Vitriolic method in the recovered acid wastewater is:

A, employing lime carbonate neutralizing acid wastewater generate CO ₂With calcium sulfate CaSO ₄Because this reaction belongs to solid-liquid phase reaction, thereby the speed of speed of response depends on the size of the specific surface area of solid carbonic acid calcium, and specific surface area is big more, it is thorough more that reaction is carried out, the one way utilization ratio of lime carbonate is high more, the equipment input is also low more, so the big calcium carbonate superfine powder of the preferred specific surface area of the inventive method.

B, by sedimentation, centrifugal with enriching step A gained CaSO ₄, feed ammonia (or ammoniacal liquor) and CO then ₂, transform and obtain lime carbonate and ammonium sulfate, filtering gained filtrate is ammonium sulfate.If steps A gained CaSO ₄Without enrichment, remove part moisture and directly transform, it is low excessively then to transform the gained ammonium sulfate concentrations, cost too high (energy consumption is too high) during condensing crystal and do not have economic worth.In addition, the CaCO that obtains after the conversion reaction ₃Also need to wash, because of CaCO ₃On also attached a lot of ammonium sulfate, therefore wash CaCO ₃Be a critical step, can be with washing CaCO ₃After water lotion add CaSO after the enrichment of steps A gained ₄In, and then can reduce the loss of ammonia and improve H ₂SO ₄The rate of recovery, reduce CaCO ₃Produce the ammonia-nitrogen content in the waste water when recycling, reduce environmental protection pressure.

Wherein, conversion reaction control condition is: prepare burden N by following mol ratio _Gypsum: N _{Carbonic acid gas}: N _Ammonia: N _Water=1.2: 1.0: 2.0: 13.6, gypsum (CaSO wherein ₄) can be excessive, mainly be control CO ₂, ammonia (or ammoniacal liquor) and water proportion relation.50～60 ℃ of temperature of reaction, if be lower than 50 ℃, speed of response is slower, then energy consumption is too high if be higher than this temperature range, is unfavorable for controlling cost about 3 hours of reaction times.The principle of this conversion reaction is based on CaSO ₄And CaCO ₃Dissolved difference in water, CaSO in the time of 25 ℃ ₄Solubility product constant K _SP=7.10 * 10 ^-5, CaCO ₃Solubility product constant K _SP=4.96 * 10 ^-9, thereby can guarantee that reaction is to producing CaCO ₃Direction carry out.

C, step B gained filtrate condensing crystal is obtained ammonium sulfate, ammonium sulfate is the catalyst segments heating with the ferric oxide: decomposite NH in the time of 253 ℃ ₃, decomposite SO in the time of 480 ℃ ₃

D, collection absorb SO ₃Promptly get sulfuric acid.

Wherein, reaction formula is as follows during steps A neutralizing acid wastewater:

CaCO ₃+H ₂SO ₄→CaSO ₄↓+CO ₂↑+H ₂O。

Conversion reaction formula among the step B is:

CaSO ₄+CO ₂+2NH ₃+H ₂O→CaCO ₃+(NH ₄) ₂SO ₄。

The chemical principle of step C, step D is identical with the relative theory of sulfuric acid recovery in the spent acid.

CO used herein ₂And NH ₃The CO that can adopt the steps A reaction to generate ₂And the NH that decomposes gained when handling spent acid and acid waste water at step C ₃, realize recycle.And the CaCO of gained ₃Also can dewater and return steps A after the washing and continue to utilize.

Handle spent acid and acid waste water respectively by above-mentioned two methods, used raw material lime carbonate, ammonia and catalyst Fe ₂O ₃No consumption in theory can recycle, only need replenish The addition of C aCO when in fact using ₃And NH ₃And Fe ₂O ₃Get final product.

The lime carbonate neutral treatment process that also can adopt spent acid reclaims sulfuric acid wherein, but adopts ammoniacal liquor or ammonia neutral method easier, and flow process is shorter, can also obtain the byproduct iron oxide black, thereby preferred ammonia or ammoniacal liquor neutralization when handling spent acid.In addition, as if the sulfuric acid that reclaims with lime carbonate neutral treatment process in the spent acid, the then Fe in the spent acid ²⁺With corresponding SO ₄ ^2-Can not reclaim waste resource, FeSO in the waste water ₄Too highly also can become environmental problem.If adopt ammoniacal liquor or ammonia neutralizing acid wastewater, because sulfuric acid content only be 1-2% in the waste water, steam in the time of can causing the concentrated vitriol ammonium (energy consumption) is too high, thereby preferred lime carbonate neutralizes during treatment of acidic wastewater.Handle spent acid, the disagreeableness waste discharge of the almost unmatchful environment of waste water by this method, reach emission standard, but and effective recycling sulfuric acid and iron black resource wherein also.

Adopt in ammonia or the ammoniacal liquor and during spent acid, to reclaim 1 ton of 98% H ₂SO ₄Meter: about 160 degree of power consumption, about 1.55 tons of steam, the about 280kg of coal (decomposing ammonia sulfate is used), the vitriolic rate of recovery can reach 96%, FeSO ₄In SO ₄ ^2-Conversion is H ₂SO ₄The time the rate of recovery can reach 94%.

When adopting lime carbonate neutralizing acid wastewater, to reclaim 1 ton of 98% H ₂SO ₄Meter: about 210 degree of power consumption, about 1.65 tons of steam, the about 280kg of coal (decomposing ammonia sulfate is used), the vitriolic rate of recovery can reach 92%.

Description of drawings

Fig. 1 has sulfuric acid legal system titanium dioxide process flow sheet now.

Fig. 2 is with in ammoniacal liquor or the ammonia and reclaim vitriolic process flow sheet in spent acid or the acid waste water.

Fig. 3 is with in the lime carbonate and reclaim vitriolic process flow sheet in spent acid or the acid waste water.

Embodiment

Below by specific description of embodiments of the present invention the explanation but do not limit the present invention.

Embodiment 1

The contriver uses the sulfuric acid in the following method recovery spent acid, contains H in the spent acid ₂SO ₄About 20-22%, FeSO ₄About 7-10%.Flow process is referring to Fig. 2.

A, spent acid adopt the ammonia neutralization, and adjusting the pH value is 4.5～5.5, and (temperature is not higher than 60 ℃) left standstill more than 2 hours, filter and go out a little TiO ₂Deng impurity;

B, adjust pH 9-11, temperature of reaction is 60-80 ℃;

C, aerating oxygen, oxidation obtains Z 250, filters, and removes Z 250;

D, filtrate condensing crystal obtain ammonium sulfate, and ammonium sulfate is the catalyst segments heating with the ferric oxide: decomposite NH in the time of 253 ℃ ₃, decomposite SO in the time of 480 ℃ ₃

D, collection absorb SO ₃Promptly get sulfuric acid.The NH that produces ₃Recovery is used for steps A and spent acid, realizes recycle.

Mainly consume (to reclaim 1 ton of 98%H ₂SO ₄Meter):

Electricity 160 degree, 1.55 tons of steam, coal (decomposing ammonia sulfate is used) 280Kg.Wherein the vitriolic rate of recovery is 96%, FeSO ₄In SO ₄ ^2-Conversion is H ₂SO ₄The time the rate of recovery be 94%.

Embodiment 2

The sulfuric acid spent acid that the contriver uses in the following method recovery spent acid contains H ₂SO ₄About H ₂SO ₄About 20-22%, FeSO ₄About 7-10%.Flow process is referring to Fig. 3.

A, spent acid adopt the calcium carbonate superfine powder neutralization, generate CO ₂With calcium sulfate CaSO ₄

B, sedimentation enriching step A gained CaSO ₄, the dehydration back feeds ammonia and CO ₂, transform and obtain lime carbonate and ammonium sulfate, filter and promptly get ammonium sulfate;

D, collection absorb SO ₃Promptly get sulfuric acid.

The vitriolic energy consumption that reclaims spent acid is following (to reclaim 1 ton of 98%H ₂SO ₄Meter): electricity 210 degree, 1.65 tons of steam, coal (decompose and use) 280Kg.

Embodiment 3

The contriver uses the sulfuric acid in the following method recovered acid wastewater, contains H in the acid waste water ₂SO ₄About 1-3%, FeSO ₄About 0.4-1.2%.Flow process is referring to Fig. 3.

A, acid waste water adopt the calcium carbonate superfine powder neutralization, generate CO ₂With calcium sulfate CaSO ₄

B, sedimentation enriching step A gained CaSO ₄, dewatering and joining the slurry back feeds ammonia and CO ₂, transform and obtain lime carbonate and ammonium sulfate, filtering gained filtrate is ammonium sulfate;

C, step B gained filtrate condensing crystal is obtained ammonium sulfate, ammonium sulfate is the catalyst segments heating with the ferric oxide: decomposite NH in the time of 253 ℃ ₃, decomposite SO in the time of 580 ℃ ₃

D, collection absorb SO ₃Promptly get sulfuric acid.

Mainly consume (to reclaim 1 ton of 98%H ₂SO ₄Meter): electricity 210 degree, 1.65 tons of steam, coal (decomposing ammonia sulfate is used) 280Kg, wherein the vitriolic rate of recovery can reach 90%.

The inventive method is simple, and on-the-spot transformation process is convenient, and workable, application prospect is wide.

Claims

The method of [claim 1] decomposing ammonia sulfate is characterized in that: obtain NH with the metal oxide for the catalyzer thermal degradation during decomposing ammonia sulfate ₃And SO ₃
The method of [claim 2] decomposing ammonia sulfate according to claim 1 is characterized in that: described metal oxide is a ferric oxide.
The method of [claim 3] decomposing ammonia sulfate according to claim 2 is characterized in that: the heating of heating time-division differing temps section begins to decomposite NH in the time of 253 ℃ ₃, decomposite SO during 480 ℃ of beginnings ₃, collect respectively.
[claim 4] is characterized in that according to the method for claim 2 or 3 described decomposing ammonia sulfates: the heating of heating time-division differing temps section, 253～450 ℃ of decomposition obtain NH ₃, 480～780 ℃ of decomposition obtain SO ₃, collect respectively
[claim 5] reclaims the vitriolic method in spent acid or the acid waste water, and it is characterized in that: with the sulfuric acid conversion in spent acid or the acid waste water is ammonium sulfate, and thickening obtains solid ammonium sulfate then, obtains NH with the ferric oxide for the catalyzer thermal degradation ₃And SO ₃, collect absorption SO ₃Promptly get sulfuric acid;

Wherein, ammonium sulfate is the catalyst segments heating with the ferric oxide: begin to decomposite NH in the time of 253 ℃ ₃, begin to decomposite SO in the time of 480 ℃ ₃
Vitriolic method in [claim 6] recovery spent acid according to claim 5 or the acid waste water is characterized in that, when ammonium sulfate with the ferric oxide is the catalyst segments heating, controls 253～450 ℃ of decomposition and obtains NH ₃, 480～780 ℃ of decomposition obtain SO ₃, collect respectively.
[claim 7] is characterized in that with the sulfuric acid conversion in the spent acid being that ammonium sulfate comprises the steps: according to the vitriolic method in claim 5 or 6 described recovery spent acid or the acid waste water

A, spent acid adopt ammoniacal liquor or ammonia adjust pH 3～5.5 to leave standstill, and filter;

B, filtrate add ammoniacal liquor or ammonia adjust pH 9-11 neutralization reaction again;

Feed oxygen-containing gas in C, the reaction solution, filter;

D, filtrate condensing crystal promptly get ammonium sulfate.
Vitriolic method in [claim 8] recovery spent acid according to claim 7 or the acid waste water is characterized in that the steps A controlled temperature is not higher than 60 ℃; Step B controlled temperature is 60-80 ℃.
[claim 9] is characterized in that with the sulfuric acid conversion in the acid waste water being that ammonium sulfate comprises the steps: according to the vitriolic method in claim 5 or 6 described recovery spent acid or the acid waste water

A, acid waste water adopt the lime carbonate neutralization, generate CO ₂With calcium sulfate CaSO ₄

B, by sedimentation, centrifugal with enriching step A gained CaSO ₄, feed ammonia or ammoniacal liquor and CO then ₂Carry out conversion reaction, filtering gained filtrate is ammoniumsulphate soln;

C, step B gained ammoniumsulphate soln condensing crystal is obtained ammonium sulfate.
Vitriolic method in [claim 10] recovery spent acid according to claim 9 or the acid waste water is characterized in that the control material molar ratio is in the step B conversion reaction

N _{Lime carbonate}: N _{Carbonic acid gas}: N _Ammonia: N _Water=1.2: 1.0: 2.0: 13.6.