CN114671421A - A method and system for preparing iron phosphate by utilizing iron-containing hydrochloric acid pickling waste liquid as resources - Google Patents

Abstract

The invention relates to a method and a system for preparing iron phosphate by recycling iron-containing hydrochloric acid pickling waste liquid. Hydrogen chloride generated in the synthesis reaction process at 130-200 ℃ is recycled to obtain regenerated hydrochloric acid with the concentration of 18-21 wt% and suitable for cold rolling and pickling; the aging mother liquor and the washing water formed in the process can be recycled; the invention also provides a system for realizing the method, which comprises an oxidation unit, a synthesis unit, a hydrochloric acid recovery unit, an aging separation unit, a chemical pulp washing unit and a drying discharge unit; the application of the invention can realize the resource utilization of the hydrochloric acid waste liquid, prepare the new energy material ferric phosphate, obviously improve the value and the quality, realize the regeneration cycle of the hydrochloric acid, and has no three wastes discharge and no environmental pollution.

Description

A method and system for preparing iron phosphate by utilizing iron-containing hydrochloric acid pickling waste liquid as resources

technical field

The invention belongs to the field of waste liquid resource utilization and new energy material preparation, and relates to a method and a system for preparing iron phosphate by utilizing iron-containing hydrochloric acid pickling waste liquid for recycling.

Background technique

my country has a large number of production lines for cold-rolled strip, pickling strip, steel pipe and steel wire. These products need to be pickled on the surface during the deep processing process to remove the iron oxide scale on the surface. Among them, the most commonly used pickling solution It is hydrochloric acid, so a large amount of hydrochloric acid pickling waste liquid will be produced. The hydrochloric acid pickling waste liquid contains a small amount of free acid, ferric iron and a large amount of ferrous iron. Due to its serious corrosivity, it has been included in the "National Hazardous Waste List". At present, the methods for the treatment of steel pickling waste liquid at home and abroad mainly include direct roasting method, evaporation concentration crystallization method and membrane method, etc. Among them, the direct roasting method is undoubtedly the most thorough method to solve the problem of waste acid, which can realize the maximum reuse of hydrochloric acid. However, the direct roasting method has a high threshold and large investment in equipment, which is generally unbearable for small enterprises, thus restricting the development of enterprises in this area; while the product market capacity of the evaporation concentration crystallization method is small, and the product quality is difficult to guarantee; and the membrane method It can only deal with relatively dilute waste liquid, but cannot deal with high concentration, and this method only produces the effect of weight reduction, and cannot completely solve the problem of large-scale and effective utilization of hydrochloric acid pickling waste liquid.

Ferric phosphate has been well used in agriculture, ceramic glass, steel and surface passivation. Due to its unique catalytic properties, ion exchange capacity and electrochemical performance, it has attracted widespread attention in recent years, resulting in more and more important applications in the fields of catalysis and lithium battery electrode materials. For example, lithium iron phosphate is an important It is widely used in new energy vehicles, and iron phosphate is an important precursor for the synthesis of lithium iron phosphate. At present, the preparation method of iron phosphate is mainly precipitation method, including using ferrous sulfate as iron source and phosphoric acid. Ammonium dihydrogen is used as the phosphorus source for the reaction, or ferric chloride is used as the iron source and phosphoric acid is used as the phosphorus source to synthesize. The former will produce a large amount of iron-containing ammonium sulfate by-products, while the latter requires a larger phosphorus-iron ratio.

CN112661129A discloses a preparation method of ferric phosphate, ferrous sulfate solution is used as raw material, and phosphorus is firstly formed into ferrous phosphate, and then impurities are removed by complex oxidation to obtain ferric phosphate dihydrate, and finally calcined at high temperature to obtain ferric phosphate anhydrous; this method requires more The phosphorus source is added for the second time, and the process flow is longer.

CN112479174A discloses a method for synthesizing iron phosphate by utilizing titanium dioxide by-product ferrous sulfate, using titanium dioxide by-product ferrous sulfate as raw material to prepare finished iron phosphate, the method utilizes inorganic acids such as sulfuric acid or hydrogen chloride to partially replace phosphoric acid as acidification The liquid method can effectively reduce the content of impurity Mn, Mg and S elements, but due to the introduction of strong acid, it has strict requirements on equipment and is easy to cause pollution.

CN113955732A discloses a method for preparing ferric phosphate by using ferric chloride as a catalyst. The method prepares ferric phosphate by cyclically dissolving iron sources with ferric chloride and reacting with phosphoric acid, which requires nitric acid as a catalyst, requires high equipment, and is easy to produce Nitrogenous wastewater.

It can be seen from the above that a new technology method that can not only utilize hydrochloric acid pickling waste liquid on a large scale to solve the problem of its resource utilization, but also realize the preparation of iron phosphate in a low-cost and short process, and the medium can be recycled is very necessary.

SUMMARY OF THE INVENTION

In view of the problems existing in the prior art, the object of the present invention is to provide a method and system for preparing iron phosphate by utilizing iron-containing hydrochloric acid pickling waste liquid for recycling, the method uses iron-containing hydrochloric acid pickling waste liquid as a raw material, and sequentially The processes of oxidation, reaction with phosphoric acid at 130-200° C., homogeneous aging, slurry washing and drying and discharging are carried out to obtain iron phosphate. The hydrogen chloride generated by the synthesis reaction carried out at high temperature can be recovered to obtain regenerated hydrochloric acid suitable for cold rolling and pickling; the aging mother liquor and washing water formed in the process can also be recycled; The system can make the recovery rate of hydrochloric acid in the iron-containing hydrochloric acid pickling waste liquid reach more than 95%, the recovery rate of iron element can reach more than 95%, and can obtain iron phosphate with a purity of 99.5% to 99.9%; therefore, the present invention can not only achieve The utilization of hydrochloric acid pickling waste liquid as a resource can produce iron phosphate as a new energy material, and the value and quality can be significantly improved, and the regeneration cycle of hydrochloric acid can also be realized, and no three wastes are discharged, and no environmental pollution is generated.

For this purpose, the present invention adopts the following technical solutions:

In the first aspect, the present invention provides a method for preparing iron phosphate by utilizing iron-containing hydrochloric acid pickling waste liquid for recycling, and the method comprises the following steps:

(1) oxidizing agent is added in iron-containing hydrochloric acid pickling waste liquid to carry out oxidation treatment to obtain ferric acid solution;

(2) adding phosphoric acid to the ferric acid solution described in step (1), and carrying out a synthesis reaction at 130-200° C. to obtain crude iron phosphate slurry and gaseous hydrogen chloride;

(3) use an absorbent to absorb and purify the gaseous hydrogen chloride described in step (2) to obtain regenerated hydrochloric acid;

(4) adding water to the crude iron phosphate slurry described in step (2) for homogeneous ageing, and then performing solid-liquid separation to obtain the first filter cake and ageing mother liquor; wherein, the ageing mother liquor returns Step (2) and join in the described ferric acid solution;

(5) using water to carry out slurry washing and filtering of the first filter cake described in step (4) to obtain a second filter cake and washing water; wherein, the washing water is returned to step (4) and added to the crude In iron phosphate slurry;

(6) drying and dehydrating the second filter cake described in step (5) to obtain iron phosphate;

Wherein, step (3) is performed simultaneously in the process of performing steps (4)-(6).

The iron-containing hydrochloric acid pickling waste liquid of the present invention is derived from the waste liquid of cold rolling and pickling in the iron and steel industry. Using the method of the present invention, the new energy material iron phosphate can be prepared from the waste liquid, and hydrogen chloride can be recovered to generate regeneration The hydrochloric acid can be reused in the cold rolling and pickling process, and the formed pickling waste liquid can be re-entered into the present invention for recycling; in the process of recovering the hydrochloric acid, the remaining tail gas is purified and discharged up to the standard, no three wastes are discharged in the whole process, and the resource utilization rate is high , the added value of the product is greatly improved, and the organic coupling of the two fields of waste liquid recycling and new energy material preparation can be realized.

In step (2) of the method of the present invention, the synthesis reaction refers to the reaction between ferric chloride and phosphoric acid to generate ferric phosphate and gaseous hydrogen chloride. In the present invention, the synthesis reaction is performed at a high temperature of 130-200° C., which can promote the volatilization of hydrogen chloride from the solution. come out, and bring it into the absorbent for recovery of hydrochloric acid through the evaporated water vapor. After a large amount of hydrogen chloride is taken away, the reverse reaction of iron phosphate synthesis can be weakened, and the precipitation rate of iron phosphate can be improved. Due to the evaporation of a large amount of water, the final obtained The product is a slurry containing crude iron phosphate and having a larger viscosity; therefore, the present invention needs to carry out a subsequent water-adding ageing process, so that the iron phosphate crystal is re-homogeneously ageing in a liquid phase with a larger mass transfer coefficient, Control and optimize the particle size and morphology of iron phosphate crystals, reduce the adsorption of impurities to a certain extent, and obtain iron phosphate dihydrate products; then remove excess impurities through slurry washing, improve product purity, and dry the iron phosphate products. The crystals remove free water to obtain iron phosphate products.

It should be noted that in step (1) of the method of the present invention, the synthesis reaction is performed at 130-200°C, for example, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C , 170°C, 175°C, 180°C, 185°C, 190°C, 195°C or 200°C, etc., but are not limited to the listed values, and other non-recited values within the above numerical range are also applicable.

The following is a preferred technical solution of the present invention, but is not a limitation of the technical solution provided by the present invention. Through the following technical solutions, the technical purpose and beneficial effects of the present invention can be better achieved and realized.

As a preferred technical solution of the present invention, the oxidant in step (1) includes hydrogen peroxide and/or oxygen.

Preferably, the dosage of the oxidant is 1.02 to 1.1 times the molar amount of divalent iron ions in the iron-containing hydrochloric acid pickling waste liquid, such as 1.02 times, 1.03 times, 1.04 times, 1.05 times, 1.06 times, 1.07 times, 1.08 times, 1.09 times, 1.1 times, etc., but not limited to the listed values, and other unlisted values within the above-mentioned numerical range are also applicable.

The iron-containing hydrochloric acid pickling waste liquid of the present invention contains a large amount of iron elements, but most of them exist in the solution in the form of divalent iron ions, and the amount of oxidant in the present invention can be calculated according to the molar amount of divalent iron ions in the solution. , and the amount of oxidant should ensure that all ferrous ions are oxidized to ferric ions.

Preferably, the oxidation treatment in step (1) is carried out under stirring.

As a preferred technical solution of the present invention, the amount of phosphoric acid used in step (2) is 1 to 1.2 times the molar amount of iron in the ferric acid solution, such as 1 time, 1.02 times, 1.04 times, 1.06 times, 1.08 times , 1.1 times, 1.12 times, 1.14 times, 1.16 times, 1.18 times or 1.2 times, etc., but are not limited to the listed values, and other unlisted values within the above numerical range are also applicable.

Preferably, the synthesis reaction of step (2) is carried out under stirring.

Preferably, the time of the synthesis reaction in step (2) is 3-7h, such as 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h or 7h, etc., but not limited to the listed values , and other non-recited values within the above-mentioned numerical range are also applicable.

In the step (2) of the present invention, the temperature of the synthesis reaction is related to the time. When the temperature of the synthesis reaction used in the range is higher, the reaction time can be appropriately reduced within the range, but the reaction time cannot be too short, otherwise it will affect The volatilization amount of hydrogen chloride, and the reaction time is too long will lead to excessive evaporation of water, and the obtained crude iron phosphate slurry is too dry and has poor fluidity, which is not conducive to the subsequent process.

As a preferred technical solution of the present invention, the absorbent forms an internal circulation in the absorption and the exhaust gas purification, respectively.

Preferably, the absorbent in step (3) includes water.

Preferably, the internal circulation of the exhaust gas purification generates hydrochloric acid with a concentration of less than 5wt%, and directly returns to the absorption as an absorbent, such as 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt% , 3.5 wt %, 4 wt %, 4.5 wt % or 4.9 wt %, etc., but are not limited to the listed values, and other unlisted values within the above numerical range are also applicable.

Preferably, the inner circulation of the absorption produces the regenerated hydrochloric acid at a concentration of 18-21 wt%, such as 18 wt%, 18.5 wt%, 19 wt%, 19.5 wt%, 20 wt%, 20.5 wt% or 21 wt%, etc., but not Not limited to the recited numerical values, other non-recited numerical values within the above numerical ranges are equally applicable.

At the beginning of the absorption and tail gas purification of the present invention, the present invention preferably adds pure water as an absorbent, first absorbs the hydrogen chloride gas with pure water, and then uses pure water to further absorb the remaining gas to realize the purification of tail gas After the internal circulation of exhaust gas purification, pure water absorbs hydrogen chloride to generate hydrochloric acid with a concentration of less than 5wt%, and this hydrochloric acid is used as an absorbent to directly return to the absorption. 21wt% of regenerated hydrochloric acid, this regenerated hydrochloric acid can be directly used for cold rolling; it should be emphasized that the present invention needs to reuse the low-concentration hydrochloric acid produced by the purification of the tail gas to the absorption process, and only through the internal circulation of the absorption can the obtained regeneration be made The concentration of hydrochloric acid meets the requirements to ensure that the hydrogen chloride has a high recovery rate, and the internal circulation of the exhaust gas purification is also conducive to realizing the discharge of the exhaust gas up to the standard. Difficult to achieve.

As a preferred technical solution of the present invention, the amount of the water in step (4) is 3 to 5 times the mass of the iron phosphate in the crude iron phosphate slurry, such as 1 time, 1.5 times, 2 times, 2.5 times, 3 times, 3.5 times, 4 times, 4.5 times or 5 times, etc., but not limited to the listed numerical values, other unlisted numerical values within the above-mentioned numerical range are also applicable; and it should be noted that in the crude iron phosphate slurry The quality of ferric phosphate is the theoretical yield of ferric phosphate, which is calculated according to the molar amount of iron in the ferric acid solution obtained in step (3) at a conversion yield of 100%.

Preferably, the homogeneous aging in step (4) is performed under stirring.

Preferably, the time for the homogeneous aging in step (4) is 2-6h, for example, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h or 6h, etc., but not limited to those listed The numerical value of the above-mentioned numerical value range is also applicable to other non-recited numerical values.

The aging time of the present invention is related to the synthesis reaction carried out in step (2), and when the synthesis reaction is carried out at a higher temperature, the required aging time should be appropriately extended within the range, so that the iron phosphate crystals are fully obtained. aging effect.

As a preferred technical solution of the present invention, the amount of water used in step (5) is 3 to 5 times the mass of the first filter cake, such as 1 time, 1.5 times, 2 times, 2.5 times, 3 times, and 3.5 times. , 4 times, 4.5 times, or 5 times, etc., but are not limited to the listed numerical values, and other unlisted numerical values within the above numerical range are also applicable.

Preferably, the slurry washing in step (5) is carried out under stirring.

Preferably, the temperature of the drying and dehydration in step (6) is 80 to 90°C, such as 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C or 90°C, etc., but not limited to the listed numerical values, and other unlisted numerical values within the above numerical range are also applicable.

Preferably, the drying and dehydration time in step (6) is 1-3h, for example, 1h, 1.2h, 1.4h, 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.6h, 2.8h or 3h, etc., However, it is not limited to the recited numerical values, and other non-recited numerical values within the above-mentioned numerical range are equally applicable.

In order to obtain the iron phosphate dihydrate product in the present invention, the drying and dehydration time is set to 1 to 3 hours. Longer drying time or increasing the subsequent heat treatment process will lead to the reduction of crystal water in the iron phosphate, but those skilled in the art can Selection and adjustment are actually required.

As the preferred technical solution of the present invention, the method comprises the following steps:

(1) hydrogen peroxide and/or oxygen are added to the iron-containing hydrochloric acid pickling waste liquid as an oxidant, and the usage amount of the oxidant is 1.02～1.02～1.02～2.0% of the molar weight of divalent iron ions in the iron-containing hydrochloric acid pickling waste liquid 1.1 times, and then carry out oxidation treatment under stirring to obtain ferric acid solution;

(2) adding phosphoric acid to the ferric acid solution described in step (1), and performing a synthesis reaction at 130-200° C. for 3-7 hours under stirring. The amount of phosphoric acid used is the iron element in the ferric acid solution. 1 to 1.2 times the molar amount to obtain crude iron phosphate slurry and gaseous hydrogen chloride;

(3) using water as an absorbent to absorb and purify the gaseous hydrogen chloride described in step (2); the absorbent forms an internal circulation in the absorption and the purification of the exhaust gas respectively; the internal circulation of the purification of the exhaust gas Hydrochloric acid with a concentration of less than 5wt% is generated and directly returned to the absorption as an absorbent; the inner circulation of the absorption generates regenerated hydrochloric acid with a concentration of 18-21wt%;

(4) adding water to the crude iron phosphate slurry described in step (2), and performing homogeneous aging for 2 to 6 hours under stirring, the amount of the water being the iron phosphate in the crude iron phosphate slurry 3 to 5 times of the quality of the first filter cake, and then carry out solid-liquid separation to obtain a first filter cake and an aging mother liquor; wherein, the aging mother liquor is returned to step (2) and added to the ferric acid solution;

(5) under stirring state, the first filter cake described in step (4) is subjected to slurry washing and filtration with water, and the consumption of the water is 3 to 5 times of the quality of the first filter cake to obtain the second filter cake. filter cake and washing water; wherein, the washing water is returned to step (4) and added to the crude iron phosphate slurry;

(6) drying and dehydrating the second filter cake in step (5) at 80-90° C. for 1-3 h to obtain iron phosphate;

Wherein, step (3) is performed simultaneously in the process of performing steps (4)-(6).

In the second aspect, the present invention provides a system for preparing iron phosphate by utilizing iron-containing hydrochloric acid pickling waste liquid for recycling. The system includes an oxidation unit, a synthesis unit, an aging separation unit, a The pulp washing unit and the drying and discharging unit also include a hydrochloric acid recovery unit connected to the gas outlet of the synthesis unit; wherein, the liquid outlet of the aging separation unit is connected to the inlet of the synthesis unit; the slurry washing unit The liquid outlet is connected to the inlet of the aging separation unit; the hydrochloric acid recovery unit includes a hydrochloric acid absorption tower and a tail gas purification tower connected in sequence along the gas flow direction.

As a preferred technical solution of the present invention, the oxidation unit includes an oxidation tank.

Preferably, an oxidation tank discharge pump is arranged between the oxidation unit and the synthesis unit; the inlet of the oxidation tank discharge pump is connected to the outlet of the oxidation unit, and the outlet of the oxidation tank discharge pump is connected to the entry to the synthesis unit.

Preferably, the synthesis unit includes a synthesis kettle; the synthesis kettle is provided with a material outlet and a gas outlet, and the gas outlet serves as the gas outlet of the synthesis unit.

Preferably, a synthesis kettle discharge pump is arranged between the synthesis unit and the aging separation unit; the inlet of the synthesis kettle discharge pump is connected to the material outlet of the synthesis unit, and the synthesis kettle discharge device has an outlet. The outlet is connected to the inlet of the aging separation unit.

Preferably, the ageing separation unit comprises a homogeneous ageing tank and an ageing filter press connected in sequence; wherein the ageing filter press is provided with a material outlet and a liquid outlet, and the liquid outlet serves as the ageing filter. Liquid outlet of the separation unit.

Preferably, an aging tank discharge pump is provided between the homogeneous aging tank and the aging filter press; the inlet of the aging tank discharge pump is connected to the outlet of the homogeneous aging tank, The outlet of the discharging pump of the aging tank is connected to the inlet of the aging filter press.

Preferably, a screw conveyor is arranged between the aging separation unit and the pulp washing unit; the inlet of the screw conveyor is connected to the material outlet of the aging separation unit, and the outlet of the screw conveyor is connected to the The inlet of the slurry washing unit.

Preferably, the slurry washing unit includes a slurry tank and a washing filter press connected in sequence; wherein, the washing filter press is provided with a material outlet and a liquid outlet, and the liquid outlet is used as the outlet of the slurry washing unit. Liquid outlet.

Preferably, a slurry tank discharge pump is provided between the slurry tank and the washing filter press; the inlet of the slurry tank discharge pump is connected to the outlet of the slurry tank, and the slurry tank is connected to the outlet of the slurry tank. The outlet of the discharge pump is connected to the inlet of the dry discharge unit.

Preferably, a belt conveyor is arranged between the slurry washing unit and the drying and discharging unit; the inlet of the belt conveyor is connected to the material outlet of the slurry washing unit, and the outlet of the belt conveyor is connected to the The inlet of the dry discharge unit.

Preferably, the drying and discharging unit includes a dryer.

Preferably, the oxidation tank, the synthesis kettle, the homogeneous aging tank and the slurry tank are all acid-resistant and oxidation-resistant equipment with a stirring module.

Since the reaction process of the present invention is in a strongly acidic environment, the oxidation tank, the synthesis kettle, the homogeneous aging tank and the slurry tank are required to be acid-resistant and oxidation-resistant equipment. For example, the materials of the oxidation tank and the slurry tank are steel-lined tetrafluoroethylene. The lining material of the synthesis kettle is graphite; it should also be noted that the heating method of the synthesis kettle of the present invention is indirect heating, for example, the synthesis kettle is provided with a jacket, and low-pressure hot steam is introduced into the jacket as a The heating source is not limited to this heating method, and other indirect heating methods are also applicable to the present invention, and those skilled in the art can choose according to the actual situation.

As a preferred technical solution of the present invention, the bottom liquid outlet of the hydrochloric acid absorption tower is respectively connected to the inlet of the regenerated hydrochloric acid storage device and the tower top liquid inlet of the hydrochloric acid absorption tower; the tower bottom liquid outlet of the tail gas purification tower is respectively connected to The top liquid inlet of the hydrochloric acid absorption tower and the top liquid inlet of the tail gas purification tower; the top liquid inlet of the tail gas purification tower is connected with a water inlet pipe; the top of the tail gas purification tower is provided with a tail gas discharge port.

The top liquid inlet of the tail gas purification tower of the present invention is connected to a water inlet pipe, and the present invention adds water to the hydrochloric acid recovery unit through the water inlet pipe as an absorbent; initially, before the hydrogen chloride gas enters the hydrochloric acid recovery unit, it needs to pass through the inlet pipe. Pure water is added to the water pipe, so that the hydrochloric acid absorption tower and the tail gas purification tower can reach the working state of absorption treatment, and then the hydrogen chloride gas enters the hydrochloric acid recovery unit for absorption.

When the hydrogen chloride gas enters the hydrochloric acid absorption tower, the pure water in the tower absorbs the gas, and then it is divided into two channels for output through the liquid outlet at the bottom of the tower. To increase the concentration of regenerated hydrochloric acid; another way to output the regenerated hydrochloric acid product with the required concentration or to store it; after the unabsorbed gas in the hydrochloric acid absorption tower enters the tail gas purification tower, the pure water in the tower purifies and absorbs the gas, and the remaining tail gas The low-concentration regenerated hydrochloric acid is discharged from the tail gas outlet at the top of the tower up to the standard, and the obtained low-concentration regenerated hydrochloric acid is output in two ways from the liquid outlet at the bottom of the tower. , the hydrochloric acid with a concentration of less than 5wt% can be obtained in this internal circulation; the other way, the hydrochloric acid with a concentration less than 5wt% is input into the hydrochloric acid absorption tower as an absorbent through the top liquid inlet of the hydrochloric acid absorption tower; it should be noted that, for the above-mentioned The flow proportional relationship between the branches can be adjusted by those skilled in the art according to the actual situation.

The present invention realizes the stepwise absorption of hydrogen chloride through the above-mentioned process, that is, pure water is added to the tail gas purification tower and the concentration is increased after repeated cycles in the tower to obtain low-concentration hydrochloric acid (hydrogen chloride concentration<5%), and then the low-concentration hydrochloric acid is obtained. After the regenerated hydrochloric acid is transported into the hydrochloric acid absorption tower as an absorbent and circulated for many times, high-concentration regenerated hydrochloric acid (hydrogen chloride concentration 18-21 wt%) is finally obtained to realize the regeneration and recycling of hydrochloric acid; it should be noted that when the output of the hydrochloric acid absorption tower is After a part of the regenerated hydrochloric acid products meet the requirements, the tail gas purification tower should transport low-concentration hydrochloric acid to the hydrochloric acid absorption tower in time as an absorbent for supplementation, and then pure water should be added to the tail gas purification tower through the water inlet pipe to maintain dynamic balance throughout the process. It should also be noted that, at the initial stage of the present invention, pure water is preferably added as the absorbent. If the hydrochloric acid with a concentration of less than 5wt% is selected to be added directly from the water inlet pipe as the absorbent, it is also necessary to use the tail gas purification tower of the present invention. Further increase the basic exhaust gas treatment device to solve the initial exhaust gas problem.

Preferably, an acid-resistant tail gas fan is arranged between the hydrochloric acid absorption tower and the tail gas purification tower; the inlet of the acid-resistant tail gas fan is connected to the gas outlet of the hydrochloric acid absorption tower, and the outlet of the acid-resistant tail gas fan is connected to the tail gas The gas inlet of the purification tower.

Preferably, the bottom liquid outlet of the hydrochloric acid absorption tower is connected with an absorption tower circulating pump, the outlet of the absorption tower circulating pump is divided into two branches, and the first branch is connected to the inlet of the regenerated hydrochloric acid storage device, The second branch is connected to the top liquid inlet of the hydrochloric acid absorption tower.

Preferably, the bottom liquid outlet of the tail gas purification tower is connected with a purification tower circulation pump, the outlet of the purification tower circulation pump is divided into two paths, and the first branch is connected to the tower top liquid of the hydrochloric acid absorption tower The inlet, the second branch is connected to the top liquid inlet of the tail gas purification tower.

Compared with the prior art solutions, the present invention at least has the following beneficial effects:

(1) the present invention takes the iron-containing hydrochloric acid pickling waste liquid of iron and steel cold rolling as iron source, realizes the separation and recovery of iron and chlorine, iron becomes iron phosphate, and chlorine becomes hydrochloric acid and can be recycled, and realizes containing Resource utilization of ferric hydrochloric acid pickling waste liquor;

(2) The present invention prepares new energy material iron phosphate with cheap iron-containing hydrochloric acid pickling waste liquid, realizes the upgrading of product value and quality, and organically couples waste liquid recycling and new energy material preparation;

(3) The process of the present invention adopts cascade absorption and recovery of hydrochloric acid, and there is no discharge of three wastes and no environmental hidden danger.

Description of drawings

Fig. 1 is the schematic flow sheet of the method for utilizing iron-containing hydrochloric acid pickling waste liquor to be recycled to prepare iron phosphate according to the present invention;

Fig. 2 is the schematic diagram of the system that utilizes iron-containing hydrochloric acid pickling waste liquor to be used in the embodiment of the present invention to prepare iron phosphate;

In the picture: 1-oxidation tank, 2-oxidation tank discharge pump, 3-synthesis kettle, 4-hydrochloric acid absorption tower, 5-absorption tower circulating pump, 6-acid-resistant tail gas fan, 7- tail gas purification tower, 8-purification tower Circulating pump, 9- Synthetic kettle discharge pump, 10- Homogeneous ageing tank, 11- Ageing tank discharge pump, 12- Ageing filter press, 13- Screw conveyor, 14- Slurry tank, 15- Slurry tank discharge pump, 16-washing filter press, 17-belt conveyor, 18-dryer.

Detailed ways

The technical solutions of the present invention are further described below through specific embodiments. It should be understood by those skilled in the art that the embodiments are only for helping the understanding of the present invention, and should not be regarded as a specific limitation of the present invention.

The schematic flow chart of the method for utilizing iron-containing hydrochloric acid waste liquid to recycle and prepare iron phosphate according to the present invention is shown in Figure 1, and it can be seen from the figure that the method comprises the following steps:

(1) hydrogen peroxide and/or oxygen are added to the iron-containing hydrochloric acid pickling waste liquid as an oxidant, and the usage amount of the oxidant is 1.02～1.02～1.02～2.0% of the molar weight of divalent iron ions in the iron-containing hydrochloric acid pickling waste liquid 1.1 times, then carry out oxidation treatment under stirring, and obtain ferric acid solution;

(2) adding phosphoric acid to the ferric acid solution described in step (1), and performing a synthesis reaction at 130-200° C. for 3-7 hours under stirring. The amount of phosphoric acid used is the iron element in the ferric acid solution. 1 to 1.2 times the molar amount to obtain crude iron phosphate slurry and gaseous hydrogen chloride;

(3) using water as an absorbent to absorb and purify the gaseous hydrogen chloride described in step (2); the absorbent forms an internal circulation in the absorption and the purification of the exhaust gas respectively; the internal circulation of the purification of the exhaust gas Hydrochloric acid with a concentration of less than 5wt% is generated and directly returned to the absorption as an absorbent; the inner circulation of the absorption generates regenerated hydrochloric acid with a concentration of 18-21wt%;

(4) adding water to the crude iron phosphate slurry described in step (2), and performing homogeneous aging for 2 to 6 hours under stirring, the amount of the water being the iron phosphate in the crude iron phosphate slurry 3 to 5 times of the quality of the first filter cake, and then carry out solid-liquid separation to obtain a first filter cake and an aging mother liquor; wherein, the aging mother liquor is returned to step (2) and added to the ferric acid solution;

(5) under stirring state, the first filter cake described in step (4) is subjected to slurry washing and filtration with water, and the consumption of the water is 3 to 5 times of the quality of the first filter cake to obtain the second filter cake. filter cake and washing water; wherein, the washing water is returned to step (4) and added to the crude iron phosphate slurry;

(6) drying and dehydrating the second filter cake in step (5) at 80-90° C. for 1-3 h to obtain iron phosphate;

Wherein, step (3) is performed simultaneously in the process of performing steps (4)-(6).

The schematic diagram of the system for preparing iron phosphate by utilizing iron-containing hydrochloric acid waste liquid for recycling adopted in the embodiments and comparative examples of the present invention is shown in FIG. 2 . As can be seen from FIG. 2 , the system includes an oxidation tank 1 and an oxidation tank discharge. Pump 2; synthesis kettle 3; hydrochloric acid absorption tower 4, absorption tower circulation pump 5, acid-resistant tail gas fan 6, tail gas purification tower 7, purification tower circulation pump 8; synthesis kettle discharge pump 9; homogeneous aging tank 10, aging Tank discharge pump 11, ageing filter press 12, screw conveyor 13; slurry tank 14, slurry tank discharge pump 15, washing filter press 16, belt conveyor 17 and dryer 18; among them, the oxidation tank The outlet of 1 is connected with the inlet of the oxidation tank discharge pump 2, and the outlet of the oxidation tank discharge pump 2 is connected with the entrance of the synthesis kettle 3; the gas outlet of the synthesis kettle 3 is connected with the gas inlet of the hydrochloric acid absorption tower 4, and the hydrochloric acid absorption tower 4 The gas outlet is connected with the inlet of the acid-resistant tail gas fan 6, and the outlet of the hydrochloric acid tail gas fan 6 is connected with the gas inlet of the tail gas purification tower 7; the top liquid inlet of the tail gas purification tower is provided with a water inlet pipe, and the top of the tail gas purification tower is provided with tail gas Discharge outlet; The bottom liquid outlet of the hydrochloric acid absorption tower 4 is connected with the inlet of the absorption tower circulating pump 5, and the outlet of the absorption tower circulating pump 5 is respectively connected with the tower top liquid inlet of the hydrochloric acid absorption tower 4 and the regeneration hydrochloric acid storage device or the regeneration hydrochloric acid will be connected. It is directly used for cold rolling and pickling; the liquid outlet at the bottom of the tail gas purification tower 7 is connected with the inlet of the purification tower circulating pump 8, and the outlet of the purification tower circulating pump 8 is respectively connected with the tower top liquid inlet of the tail gas purification tower 7 and the hydrochloric acid absorption tower 4 The inlet of the tower top liquid is connected; the material outlet of the synthesis kettle 3 is connected with the inlet of the synthesis kettle discharge pump 9, and the outlet of the synthesis kettle discharge pump 9 is connected with the inlet of the homogeneous aging tank 10; The outlet is connected with the inlet of the ageing tank discharge pump 11, the outlet of the ageing tank discharge pump 11 is connected with the inlet of the ageing filter press 12; the liquid outlet of the ageing filter press 12 is connected with the inlet of the synthesis kettle 3, The material outlet of the aging filter press 12 is connected with the inlet of the screw conveyor 13, the outlet of the screw conveyor 13 is connected with the inlet of the slurry tank 14; the outlet of the slurry tank 14 is connected with the inlet of the slurry tank discharge pump 15 , the outlet of the slurry tank discharge pump 15 is connected to the inlet of the washing filter press 16; the liquid outlet of the washing filter press 16 is connected to the inlet of the homogeneous ageing tank 10, and the material outlet of the washing filter press 16 is connected with the belt conveyor The inlet of the dryer 17 is connected, and the outlet of the belt conveyor 17 is connected to the inlet of the dryer 18 .

The iron-containing hydrochloric acid pickling waste liquid used in the embodiment of the present invention and the comparative example is from the cold-rolling and pickling workshop of a domestic iron and steel enterprise, and the content of the main components in the waste liquid is shown in Table 1.

Table 1

Example 1

The present embodiment provides a method for preparing iron phosphate by utilizing iron-containing hydrochloric acid waste liquid for recycling, and the method comprises the following steps:

(1) adding iron-containing hydrochloric acid pickling waste liquid into oxidation tank, then adding hydrogen peroxide as oxidant, the usage amount of described oxidizing agent is the ferrous ion molar weight in the iron-containing hydrochloric acid pickling waste liquid 1.05 times, and then carry out oxidation treatment under stirring to obtain ferric acid solution;

(2) The ferric acid solution flows into the synthesis kettle through the discharge pump of the oxidation tank, and phosphoric acid is added to it, and the synthesis reaction is carried out at 130 ° C under stirring for 7 hours. The consumption of the phosphoric acid is the iron element in the ferric iron solution. 1.1 times the molar amount to generate crude iron phosphate slurry and gaseous hydrogen chloride;

(3) pure water is added as absorbent through the inlet pipe connected to the top liquid inlet of the tail gas purification tower, so that the hydrochloric acid purification tower and the tail gas purification tower reach the absorption treatment state, gaseous hydrogen chloride is passed into the hydrochloric acid absorption tower, and in the absorption tower It is absorbed by the absorbent to form the first-stage regenerated hydrochloric acid. The unabsorbed hydrogen chloride gas enters the tail gas purification tower through the acid-resistant tail gas fan, and is purified and absorbed to obtain the second-stage regeneration hydrochloric acid. The remaining tail gas after purification passes through the tail gas exhaust port of the tail gas purification tower Discharge; at this time, a part of the secondary regenerated hydrochloric acid is circulated in the tail gas purification tower by the purification tower circulating pump, and the other part is transported to the hydrochloric acid absorption tower by the purification tower circulating pump for further absorption as an absorbent; at this time, the hydrochloric acid is A part of the first-stage regenerated hydrochloric acid obtained in the absorption tower is circulated in the hydrochloric acid absorption tower through the absorption tower circulating pump, and the other part is outputted through the outlet of the absorption tower circulating pump to output the regenerated hydrochloric acid product, which is directly used for cold-rolling and pickling, and the iron-containing hydrochloric acid is formed. The pickling waste liquid is reused in the present invention;

(4) the crude iron phosphate slurry described in step (2) is transported to the homogeneous ageing tank by the synthesis kettle discharge pump, and water is added to the homogeneous ageing tank and the homogeneous ageing is carried out under stirring for 2h, The consumption of the water is 3 times the quality of the iron phosphate in the crude iron phosphate slurry, and then the obtained system is transported to the aging filter press through the aging tank discharge pump for solid-liquid separation to obtain the first Filter cake and ageing mother liquor; wherein, described ageing mother liquor returns to the synthesis kettle of step (2) and joins in described ferric acid solution;

(5) The first filter cake in step (4) enters the slurry tank through a screw conveyor, and under stirring, water is added to the first filter cake for slurry washing, and the amount of water used is the amount of the first filter cake. 3 times the quality of the cake; then the obtained system is sent to the washing filter press through the slurry tank discharge pump for filtration to obtain the second filter cake and washing water; wherein, the washing water returns to the homogenization of step (4) The aging tank is added to the crude iron phosphate slurry;

(6) The second filter cake described in step (5) enters the dryer through a belt conveyor, and is dried and dehydrated at 80° C. for 3 hours to obtain iron phosphate;

Wherein, step (3) is performed simultaneously in the process of performing steps (4)-(6).

Example 2

The present embodiment provides a method for preparing iron phosphate by utilizing iron-containing hydrochloric acid waste liquid for recycling, and the method comprises the following steps:

(1) join iron-containing hydrochloric acid pickling waste liquid in oxidation tank, then feed into oxygen as oxidant, the usage amount of described oxidant is 1.04% of ferrous ion molar weight in described iron-containing hydrochloric acid pickling waste liquid times, and then carry out oxidation treatment under stirring to obtain ferric acid solution;

(2) The ferric acid solution flows into the synthesis kettle through the discharge pump of the oxidation tank, and phosphoric acid is added to it, and the synthesis reaction is carried out at 150 ° C under stirring for 6 hours. The consumption of the phosphoric acid is the iron element in the ferric iron solution. 1 times the molar amount to generate crude iron phosphate slurry and gaseous hydrogen chloride;

(3) pure water is added as absorbent through the inlet pipe connected to the top liquid inlet of the tail gas purification tower, so that the hydrochloric acid purification tower and the tail gas purification tower reach the absorption treatment state, gaseous hydrogen chloride is passed into the hydrochloric acid absorption tower, and in the absorption tower It is absorbed by the absorbent to form the first-stage regenerated hydrochloric acid. The unabsorbed hydrogen chloride gas enters the tail gas purification tower through the acid-resistant tail gas fan, and is purified and absorbed to obtain the second-stage regeneration hydrochloric acid. The remaining tail gas after purification passes through the tail gas exhaust port of the tail gas purification tower Discharge; at this time, a part of the secondary regenerated hydrochloric acid is circulated in the tail gas purification tower by the purification tower circulating pump, and the other part is transported to the hydrochloric acid absorption tower by the purification tower circulating pump for further absorption as an absorbent; at this time, the hydrochloric acid is A part of the first-stage regenerated hydrochloric acid obtained in the absorption tower is circulated in the hydrochloric acid absorption tower through the absorption tower circulating pump, and the other part is outputted through the outlet of the absorption tower circulating pump to output the regenerated hydrochloric acid product, which is directly used for cold-rolling and pickling, and the iron-containing hydrochloric acid is formed. The pickling waste liquid is reused in the present invention;

(4) the crude iron phosphate slurry described in step (2) is transported to the homogeneous ageing tank by the synthesis kettle discharge pump, and water is added to the homogeneous ageing tank and the homogeneous ageing is carried out under stirring for 3h, The consumption of the water is 4 times of the quality of the iron phosphate in the crude iron phosphate slurry, and then the obtained system is transported to the aging filter press through the aging tank discharge pump for solid-liquid separation to obtain the first Filter cake and ageing mother liquor; wherein, described ageing mother liquor returns to the synthesis kettle of step (2) and joins in described ferric acid solution;

(5) The first filter cake in step (4) enters the slurry tank through a screw conveyor, and under stirring, water is added to the first filter cake for slurry washing, and the amount of water used is the amount of the first filter cake. 4 times of the quality of the cake; then the obtained system is sent to the washing filter press through the slurry tank discharge pump for filtration to obtain the second filter cake and washing water; wherein, the washing water returns to the homogenization of step (4) The aging tank is added to the crude iron phosphate slurry;

(6) The second filter cake described in step (5) enters the dryer through a belt conveyor, and is dried and dehydrated at 85° C. for 2 hours to obtain iron phosphate;

Wherein, step (3) is performed simultaneously in the process of performing steps (4)-(6).

Example 3

The present embodiment provides a method for preparing iron phosphate by utilizing iron-containing hydrochloric acid waste liquid for recycling, and the method comprises the following steps:

(1) join iron-containing hydrochloric acid pickling waste liquid in oxidation tank, then add oxygen as oxidant, the usage amount of described oxidant is 1.02 times of ferrous ion molar weight in described iron-containing hydrochloric acid pickling waste liquid , and then carry out oxidation treatment under stirring to obtain ferric acid solution;

(2) The ferric acid solution flows into the synthesis kettle through the discharge pump of the oxidation tank, and phosphoric acid is added to it, and the synthesis reaction is carried out at 170 ° C under stirring for 4 hours. The amount of the phosphoric acid is the iron element in the ferric iron solution. 1.2 times the molar amount to generate crude iron phosphate slurry and gaseous hydrogen chloride;

(3) pure water is added as absorbent through the inlet pipe connected to the top liquid inlet of the tail gas purification tower, so that the hydrochloric acid purification tower and the tail gas purification tower reach the absorption treatment state, gaseous hydrogen chloride is passed into the hydrochloric acid absorption tower, and in the absorption tower It is absorbed by the absorbent to form the first-stage regenerated hydrochloric acid. The unabsorbed hydrogen chloride gas enters the tail gas purification tower through the acid-resistant tail gas fan, and is purified and absorbed to obtain the second-stage regeneration hydrochloric acid. The remaining tail gas after purification passes through the tail gas exhaust port of the tail gas purification tower Discharge; at this time, a part of the secondary regenerated hydrochloric acid is circulated in the tail gas purification tower by the purification tower circulating pump, and the other part is transported to the hydrochloric acid absorption tower by the purification tower circulating pump for further absorption as an absorbent; at this time, the hydrochloric acid is A part of the first-stage regenerated hydrochloric acid obtained in the absorption tower is circulated in the hydrochloric acid absorption tower through the absorption tower circulating pump, and the other part is outputted through the outlet of the absorption tower circulating pump to output the regenerated hydrochloric acid product, which is directly used for cold-rolling and pickling, and the iron-containing hydrochloric acid is formed. The pickling waste liquid is reused in the present invention;

(4) the crude iron phosphate slurry described in step (2) is transported to the homogeneous ageing tank by the synthesis kettle discharge pump, and water is added to the homogeneous ageing tank and the homogeneous ageing is carried out under stirring for 4h, The consumption of the water is 5 times of the quality of the iron phosphate in the crude iron phosphate slurry, and then the obtained system is transported to the aging filter press through the aging tank discharge pump for solid-liquid separation to obtain the first Filter cake and ageing mother liquor; wherein, described ageing mother liquor returns to the synthesis kettle of step (2) and joins in described ferric acid solution;

(5) The first filter cake in step (4) enters the slurry tank through a screw conveyor, and under stirring, water is added to the first filter cake for slurry washing, and the amount of water used is the amount of the first filter cake. 5 times the quality of the cake; then the obtained system is sent to the washing filter press through the slurry tank discharge pump for filtration to obtain the second filter cake and washing water; wherein, the washing water returns to the homogenization of step (4) The aging tank is added to the crude iron phosphate slurry;

(6) The second filter cake described in step (5) enters the dryer through a belt conveyor, and is dried and removed at 90° C. for 1 h to obtain iron phosphate;

Wherein, step (3) is performed simultaneously in the process of performing steps (4)-(6).

Example 4

The present embodiment provides a method for preparing iron phosphate by utilizing iron-containing hydrochloric acid waste liquid for recycling, and the method comprises the following steps:

(1) adding iron-containing hydrochloric acid pickling waste liquid into oxidation tank, then adding hydrogen peroxide as oxidant, the usage amount of described oxidizing agent is the ferrous ion molar weight in the iron-containing hydrochloric acid pickling waste liquid 1.08 times, and then carry out oxidation treatment under stirring to obtain ferric acid solution;

(2) The ferric acid solution flows into the synthesis kettle through the discharge pump of the oxidation tank, and phosphoric acid is added to it, and the synthesis reaction is carried out at 190° C. under stirring for 3 hours. The consumption of the phosphoric acid is the iron element in the ferric iron solution. 1.1 times the molar amount to generate crude iron phosphate slurry and gaseous hydrogen chloride;

(3) pure water is added as absorbent through the inlet pipe connected to the top liquid inlet of the tail gas purification tower, so that the hydrochloric acid purification tower and the tail gas purification tower reach the absorption treatment state, gaseous hydrogen chloride is passed into the hydrochloric acid absorption tower, and in the absorption tower It is absorbed by the absorbent to form the first-level regenerated hydrochloric acid. The unabsorbed hydrogen chloride gas enters the tail gas purification tower through the acid-resistant tail gas fan, and is purified and absorbed to obtain the second-stage regeneration hydrochloric acid. Discharge; at this time, a part of the secondary regenerated hydrochloric acid is circulated in the tail gas purification tower by the purification tower circulating pump, and the other part is transported to the hydrochloric acid absorption tower by the purification tower circulating pump for further absorption as an absorbent; at this time, the hydrochloric acid is A part of the first-stage regenerated hydrochloric acid obtained in the absorption tower is circulated in the hydrochloric acid absorption tower through the absorption tower circulating pump, and the other part is outputted through the outlet of the absorption tower circulating pump to output the regenerated hydrochloric acid product, which is directly used for cold-rolling and pickling, and the iron-containing hydrochloric acid is formed. The pickling waste liquid is reused in the present invention;

(4) the crude iron phosphate slurry described in step (2) is transported to the homogeneous ageing tank by the synthesis kettle discharge pump, and water is added to the homogeneous ageing tank and the homogeneous ageing is carried out under stirring for 5h, The consumption of the water is 5 times of the quality of the iron phosphate in the crude iron phosphate slurry, and then the obtained system is transported to the aging filter press through the aging tank discharge pump for solid-liquid separation to obtain the first Filter cake and ageing mother liquor; wherein, described ageing mother liquor returns to the synthesis kettle of step (2) and joins in described ferric acid solution;

(5) The first filter cake in step (4) enters the slurry tank through a screw conveyor, and under stirring, water is added to the first filter cake for slurry washing, and the amount of water used is the amount of the first filter cake. 5 times the quality of the cake; then the obtained system is sent to the washing filter press through the slurry tank discharge pump for filtration to obtain the second filter cake and washing water; wherein, the washing water returns to the homogenization of step (4) The aging tank is added to the crude iron phosphate slurry;

(6) The second filter cake described in step (5) enters the dryer through a belt conveyor, and is dried and dehydrated at 80° C. for 3 hours to obtain iron phosphate;

Wherein, step (3) is performed simultaneously in the process of performing steps (4)-(6).

Example 5

The present embodiment provides a method for utilizing iron-containing hydrochloric acid waste liquid to recycle and prepare iron phosphate, and the method comprises the following steps:

(1) adding iron-containing hydrochloric acid pickling waste liquid into oxidation tank, then adding hydrogen peroxide as oxidant, the usage amount of described oxidizing agent is the ferrous ion molar weight in the iron-containing hydrochloric acid pickling waste liquid 1.1 times, and then carry out oxidation treatment under stirring to obtain ferric acid solution;

(2) The ferric acid solution flows into the synthesis kettle through the discharge pump of the oxidation tank, and phosphoric acid is added to it, and the synthesis reaction is carried out at 200 ° C under stirring for 3 hours. The consumption of the phosphoric acid is the iron element in the ferric iron solution. 1.1 times the molar amount to generate crude iron phosphate slurry and gaseous hydrogen chloride;

(3) pure water is added as absorbent through the inlet pipe connected to the top liquid inlet of the tail gas purification tower, so that the hydrochloric acid purification tower and the tail gas purification tower reach the absorption treatment state, gaseous hydrogen chloride is passed into the hydrochloric acid absorption tower, and in the absorption tower It is absorbed by the absorbent to form the first-level regenerated hydrochloric acid. The unabsorbed hydrogen chloride gas enters the tail gas purification tower through the acid-resistant tail gas fan, and is purified and absorbed to obtain the second-stage regeneration hydrochloric acid. Discharge; at this time, a part of the secondary regenerated hydrochloric acid is circulated in the tail gas purification tower by the purification tower circulating pump, and the other part is transported to the hydrochloric acid absorption tower by the purification tower circulating pump for further absorption as an absorbent; at this time, the hydrochloric acid is A part of the first-stage regenerated hydrochloric acid obtained in the absorption tower is circulated in the hydrochloric acid absorption tower through the absorption tower circulating pump, and the other part is outputted through the outlet of the absorption tower circulating pump to output the regenerated hydrochloric acid product, which is directly used for cold-rolling and pickling, and the iron-containing hydrochloric acid is formed. The pickling waste liquid is reused in the present invention;

(4) the crude iron phosphate slurry described in step (2) is transported to the homogeneous ageing tank by the synthesis kettle discharge pump, and water is added to the homogeneous ageing tank and the homogeneous ageing is carried out under stirring for 6h, The consumption of the water is 4 times of the quality of the iron phosphate in the crude iron phosphate slurry, and then the obtained system is transported to the aging filter press through the aging tank discharge pump for solid-liquid separation to obtain the first Filter cake and ageing mother liquor; wherein, described ageing mother liquor returns to the synthesis kettle of step (2) and joins in described ferric acid solution;

(5) The first filter cake in step (4) enters the slurry tank through a screw conveyor, and under stirring, water is added to the first filter cake for slurry washing, and the amount of water used is the amount of the first filter cake. 4 times of the quality of the cake; then the obtained system is sent to the washing filter press through the slurry tank discharge pump for filtration to obtain the second filter cake and washing water; wherein, the washing water returns to the homogenization of step (4) The aging tank is added to the crude iron phosphate slurry;

(6) The second filter cake described in step (5) enters the dryer through a belt conveyor, and is dried and dehydrated at 85° C. for 2 hours to obtain iron phosphate;

Wherein, step (3) is performed simultaneously in the process of performing steps (4)-(6).

Example 6

The present embodiment provides a method for preparing iron phosphate by utilizing iron-containing hydrochloric acid waste liquid as a resource. In the method, except that in step (2), the synthesis reaction time is adjusted from 3h to 1h, other conditions are completely the same as those in Example 5. same.

Example 7

The present embodiment provides a method for preparing iron phosphate by utilizing iron-containing hydrochloric acid waste liquid as a resource. In the method, except that in step (2), the time of the synthesis reaction is adjusted from 7h to 9h, other conditions are completely the same as those in Example 1. same.

Example 8

The present embodiment provides a method for preparing iron phosphate by utilizing iron-containing hydrochloric acid waste liquid as a resource. In the method, except that in step (4), the time of homogenizing aging is adjusted from 2h to 1h, other conditions and examples 1 is exactly the same.

Example 9

The present embodiment provides a method for preparing iron phosphate by utilizing iron-containing hydrochloric acid waste liquid as a resource. In the method, except that in step (4), the time for homogenizing aging is adjusted from 6h to 7h, other conditions and examples 5 is exactly the same.

Comparative Example 1

This comparative example provides a method for preparing iron phosphate by utilizing iron-containing hydrochloric acid waste liquid as resources, and the method does not perform homogeneous aging, that is, step (4) of the method is: the step (2) described The crude iron phosphate slurry is transported to the homogeneous aging tank by the discharge pump of the synthesis kettle, and then transported to the aging filter press through the discharge pump of the aging tank for solid-liquid separation to obtain the first filter cake and aging Mother liquor; wherein, the aging mother liquor is returned to the synthesis kettle of step (2) and added to the ferric acid solution; other than this step, other conditions are exactly the same as in Example 5.

Comparative Example 2

This comparative example provides a method for preparing iron phosphate by utilizing iron-containing hydrochloric acid waste liquid as resources. In the method, except that the temperature of the synthesis reaction is adjusted from 130°C to 100°C in step (2), other conditions and examples 1 is exactly the same.

Comparative Example 3

This comparative example provides a method for preparing iron phosphate by utilizing iron-containing hydrochloric acid waste liquid as resources. In the method, except that in step (2), the temperature of the synthesis reaction is adjusted from 200°C to 220°C, other conditions and examples 5 is exactly the same.

According to the analytical method of "GB/T 622-2006 Chemical Reagent Hydrochloric Acid", the concentration of the regenerated hydrochloric acid obtained in the Examples and Comparative Examples was tested, and the "GB/T 3051-2000 General Method for Determination of Chloride Content in Inorganic Chemical Products" Mercury Measurement " and Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) were used to test the recovery rates of Cl and Fe elements in the iron-containing hydrochloric acid pickling waste liquid, and also used "HG/T4701-2014 Phosphoric Acid for Batteries" Iron" tested the purity of the obtained iron phosphate product, and the results obtained above are listed in Table 2.

Table 2

project Regenerated hydrochloric acid concentration Cl recovery rate in waste liquid Fe recovery rate in waste liquid Ferric Phosphate Purity Example 1 18wt% 96.6wt% 98.9wt% 99.77wt% Example 2 19wt% 95.5wt% 98.3wt% 99.76wt% Example 3 20wt% 98.3wt% 99.7wt% 99.84wt% Example 4 21wt% 98.1wt% 99.3wt% 99.85wt% Example 5 21wt% 98.0wt% 99.2wt% 99.83wt% Example 6 19wt% 95.7wt% 97.9wt% 99.81wt% Example 7 18wt% 97.2wt% 99.1wt% 99.46wt% Example 8 18wt% 96.6wt% 97.1wt% 99.45wt% Example 9 21wt% 98.1wt% 99.3wt% 99.85wt% Comparative Example 1 21wt% 98.1wt% 76wt% 99.88wt% Comparative Example 2 3wt% 10wt% 0wt% / Comparative Example 3 21wt% 98.5wt% 96.6wt% 97.91wt%

It can be seen from Table 2 that:

(1) Compared with Example 1, in the step (2) of Example 7, the time of the synthesis reaction was adjusted from 7h to 9h, which was 3-7h higher than the preferred range; compared with Example 5, the step (2) of Example 6 In ), the time of the synthesis reaction is adjusted from 3h to 1h, which is lower than the preferred range of 3～7h; the length of the synthesis reaction time is related to the reaction temperature, and the reaction temperature is high, and the required synthesis time is short, otherwise it is long; and the longer the synthesis time is. long, the yields of Cl and Fe will not deteriorate, but the production efficiency will decrease and the energy consumption will increase; and when the synthesis time is too short, it is easy to cause the hydrogen chloride gas to not completely escape and volatilize from the slurry, resulting in Cl and Fe The yield is relatively low;

(2) Compared with Example 1, in Example 8, the time of homogeneous aging in step (4) was adjusted from 2h to 1h, which was lower than the preferred range of 2-6h; In step (4), the time of homogeneous ageing is adjusted from 6h to 7h, which is higher than the preferred range of 2～6h; the ageing reaction is a key step for preparing the yield and crystal size of iron phosphate, and the longer the ageing reaction time, the greater the effect on phosphorus. , The yield of iron has a promoting effect, which can improve the yield of iron phosphate, but it will also agglomerate the iron phosphate grains, make the crystal grain size larger, and have a certain impact on the purity, which is not conducive to impurity removal, and then affects the product. performance; and too short aging reaction time, can cause iron phosphate crystal grains to be too late to form or to be transported to the next stage, so the yield of the product will be affected; and the Fe yield obtained in Example 5 Compared with (99.2wt%), Comparative Example 1 is not aged, so the yield of Fe is seriously reduced, only 76wt%, therefore, for improving the yield of phosphoric acid product, it is very necessary to set homogeneous aging;

(3) Compared with Example 1, in Comparative Example 2, the temperature of the synthesis reaction in step (2) was adjusted from 130°C to 100°C, which was lower than the preferred range of 120-200°C; compared with Example 5, Comparative Example 3 The temperature of the synthesis reaction in the step (2) is adjusted from 200 ° C to 220 ° C, which is higher than the preferred range of 120 to 200 ° C; an excessively low synthesis reaction temperature will cause the slurry in the synthesis system to fail to reach the boiling point of boiling, so hydrogen chloride gas The volatilization rate of ferric acid is seriously affected, and even the volatilization does not escape from the slurry, the reaction cannot proceed, ferric phosphate cannot be obtained, and high-concentration regenerated hydrochloric acid cannot be recovered; and the use of an excessively high synthesis reaction temperature will cause the synthesis reaction to occur. The side reaction generates ferric pyrophosphate and ferric hydroxychloride, etc., which reduces the purity of the ferric phosphate product. For example, the purity of the ferric phosphate obtained in Comparative Example 3 is only 97.91 wt%. In addition, the volatilization of hydrogen chloride gas may carry phosphoric acid, thereby reducing the product. yield.

(4) as can be seen from the above analysis and comparison, the method for preparing iron phosphate by utilizing iron-containing hydrochloric acid pickling waste liquid for recycling can be separated from iron and chlorine in the hydrochloric acid pickling waste liquid, thereby realizing the recovery of iron phosphate. Preparation and recycling and recycling of hydrochloric acid, the present invention utilizes low-cost iron sources to prepare high-value iron phosphate, which not only realizes the improvement of value and quality, but also organically couples the resource utilization of waste liquid with the preparation of new energy materials. There are no three wastes in the process, and no environmental hidden dangers.

The present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of the selected components of the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

The preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the specific details of the above-mentioned embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention. These simple modifications All belong to the protection scope of the present invention.

In addition, it should be noted that the specific technical features described in the above-mentioned specific embodiments can be combined in any suitable manner under the condition of no contradiction. In order to avoid unnecessary repetition, the present invention has The combination method will not be specified otherwise.

In addition, the various embodiments of the present invention can also be combined arbitrarily, as long as they do not violate the spirit of the present invention, they should also be regarded as the contents disclosed in the present invention.

Claims (10)

1. A method for preparing iron phosphate by utilizing a resource of iron-containing hydrochloric acid pickling waste liquid is characterized by comprising the following steps:

(1) adding an oxidant into the iron-containing hydrochloric acid pickling waste liquid for oxidation treatment to obtain ferric acid liquid;

(2) adding phosphoric acid into the ferric acid solution obtained in the step (1), and performing a synthesis reaction at 130-200 ℃ to obtain a rough ferric phosphate slurry and gaseous hydrogen chloride;

(3) absorbing the gaseous hydrogen chloride obtained in the step (2) by using an absorbent and purifying tail gas to obtain regenerated hydrochloric acid;

(4) adding water into the rough ferric phosphate slurry obtained in the step (2) for homogenizing and aging, and then carrying out solid-liquid separation to obtain a first filter cake and an aging mother liquor; wherein the aging mother liquor returns to the step (2) and is added into the ferric acid liquor;

(5) using water to carry out slurry washing on the first filter cake obtained in the step (4) and filtering to obtain a second filter cake and washing water; wherein the wash water is returned to step (4) and added to the crude iron phosphate slurry;

(6) drying and dehydrating the second filter cake obtained in the step (5) to obtain iron phosphate;

wherein, the step (3) is simultaneously carried out in the processes of the steps (4) to (6).

2. The method of claim 1, wherein the oxidizing agent of step (1) comprises hydrogen peroxide and/or oxygen;

preferably, the dosage of the oxidant is 1.02-1.1 times of the molar weight of ferrous ions in the iron-containing hydrochloric acid pickling waste liquid;

preferably, the oxidation treatment of step (1) is carried out under stirring.

3. The method according to claim 1 or 2, wherein the phosphoric acid in the step (2) is used in an amount of 1 to 1.2 times the molar amount of the iron element in the ferric ferrite solution;

preferably, the synthesis reaction of step (2) is carried out under stirring;

preferably, the time of the synthesis reaction in the step (2) is 3-7 h.

4. The method according to any one of claims 1 to 3, wherein the absorbent of step (3) forms an internal circulation in the absorption and the tail gas purification, respectively;

preferably, the absorbent of step (3) comprises water;

preferably, the internal recycle of tail gas cleanup produces hydrochloric acid at a concentration of less than 5 wt% and is returned directly to the absorption as absorbent;

preferably, the internal circulation of absorption generates the regenerated hydrochloric acid with the concentration of 18-21 wt%.

5. The method according to any one of claims 1 to 4, wherein the amount of water used in step (4) is 3 to 5 times the mass of the iron phosphate in the crude iron phosphate slurry;

preferably, the homogeneous aging of step (4) is performed under stirring;

preferably, the time for homogenizing and aging in the step (4) is 2-6 h.

6. The method according to any one of claims 1 to 5, wherein the amount of water used in step (5) is 3 to 5 times the mass of the first filter cake;

preferably, the slurry washing in the step (5) is carried out under stirring;

preferably, the temperature for drying and dehydrating in the step (6) is 80-90 ℃;

preferably, the drying and dehydrating time in the step (6) is 1-3 h.

7. The method according to any one of claims 1 to 6, characterized in that it comprises the steps of:

(1) adding hydrogen peroxide and/or oxygen as an oxidizing agent into the iron-containing hydrochloric acid pickling waste liquid, wherein the using amount of the oxidizing agent is 1.02-1.1 times of the molar amount of ferrous ions in the iron-containing hydrochloric acid pickling waste liquid, and then performing oxidation treatment under stirring to obtain a ferric acid liquid;

(2) adding phosphoric acid into the ferric acid solution obtained in the step (1), and carrying out synthetic reaction for 3-7 h at 130-200 ℃ under stirring, wherein the use amount of the phosphoric acid is 1-1.2 times of the molar amount of the iron element in the ferric acid solution, so as to obtain rough ferric phosphate slurry and gaseous hydrogen chloride;

(3) using water as an absorbent to absorb the gaseous hydrogen chloride in the step (2) and purify tail gas; the absorbent forms internal circulation in the absorption and the tail gas purification respectively; hydrochloric acid with the concentration of less than 5 wt% is generated by the internal circulation of tail gas purification and directly flows back to the absorption as an absorbent; the absorbed internal circulation generates regenerated hydrochloric acid with the concentration of 18-21 wt%;

(4) adding water into the rough ferric phosphate slurry obtained in the step (2), performing homogeneous aging for 2-6 hours under stirring, wherein the amount of the water is 3-5 times of the mass of ferric phosphate in the rough ferric phosphate slurry, and performing solid-liquid separation to obtain a first filter cake and an aging mother liquor; wherein the aging mother liquor returns to the step (2) and is added into the ferric acid liquor;

(5) under the stirring state, carrying out slurry washing and filtering on the first filter cake obtained in the step (4) by using water, wherein the using amount of the water is 3-5 times of the mass of the first filter cake, and obtaining a second filter cake and washing water; wherein the wash water is returned to step (4) and added to the crude iron phosphate slurry;

(6) drying and dehydrating the second filter cake obtained in the step (5) at the temperature of 80-90 ℃ for 1-3 h to obtain iron phosphate;

wherein, the step (3) is simultaneously carried out in the process of carrying out the steps (4) to (6).

8. The system for preparing the iron phosphate by utilizing the recycling of the iron-containing hydrochloric acid pickling waste liquid is characterized by comprising an oxidation unit, a synthesis unit, an aging separation unit, a chemical pulp washing unit, a drying and discharging unit and a hydrochloric acid recovery unit, wherein the oxidation unit, the synthesis unit, the aging separation unit, the chemical pulp washing unit and the drying and discharging unit are sequentially connected along the material flowing direction; wherein the liquid outlet of the aging separation unit is connected to the inlet of the synthesis unit; the liquid outlet of the slurry washing unit is connected with the inlet of the aging separation unit; the hydrochloric acid recovery unit comprises a hydrochloric acid absorption tower and a tail gas purification tower which are sequentially connected along the gas flow direction.

9. The system of claim 8, wherein the oxidation unit comprises an oxidation tank;

preferably, an oxidation tank discharge pump is arranged between the oxidation unit and the synthesis unit; an inlet of the oxidation tank discharging pump is connected with an outlet of the oxidation unit, and an outlet of the oxidation tank discharging pump is connected with an inlet of the synthesis unit;

preferably, the synthesis unit comprises a synthesis kettle; the synthesis kettle is provided with a material outlet and a gas outlet, and the gas outlet is used as a gas outlet of the synthesis unit;

preferably, a synthesis kettle discharge pump is arranged between the synthesis unit and the aging separation unit; an inlet of the synthesis kettle discharging pump is connected with a material outlet of the synthesis unit, and an outlet of the synthesis kettle discharging device is connected with an inlet of the aging separation unit;

preferably, the aging separation unit comprises a homogenizing aging tank and an aging filter press which are connected in sequence; the aging separation unit is provided with a material outlet and a liquid outlet, wherein the material outlet and the liquid outlet are arranged on the aging filter press;

preferably, an ageing tank discharge pump is arranged between the homogenizing ageing tank and the ageing filter press; an inlet of the ageing tank discharge pump is connected with an outlet of the homogenizing ageing tank, and an outlet of the ageing tank discharge pump is connected with an inlet of the ageing filter press;

preferably, a screw conveyor is arranged between the aging separation unit and the chemical pulp washing unit; the inlet of the screw conveyer is connected with the material outlet of the aging separation unit, and the outlet of the screw conveyer is connected with the inlet of the slurry washing unit;

preferably, the slurry dissolving and washing unit comprises a slurry dissolving tank and a washing filter press which are connected in sequence; the washing filter press is provided with a material outlet and a liquid outlet, and the liquid outlet is used as a liquid outlet of the chemical pulp washing unit;

preferably, a slurry melting tank discharge pump is arranged between the slurry melting tank and the washing filter press; an inlet of the slurry melting tank discharging pump is connected with an outlet of the slurry melting tank, and an outlet of the slurry melting tank discharging pump is connected with an inlet of the drying discharging unit;

preferably, a belt conveyor is arranged between the slurry washing unit and the drying and discharging unit; the inlet of the belt conveyor is connected with the material outlet of the slurry washing unit, and the outlet of the belt conveyor is connected with the inlet of the drying and discharging unit;

preferably, the dry discharge unit comprises a dryer;

preferably, the oxidation tank, the synthesis kettle, the homogenizing aging tank and the slurry tank are acid-resistant and oxidation-resistant equipment with stirring modules.

10. The system according to claim 8 or 9, wherein the bottom liquid outlet of the hydrochloric acid absorption column is connected to an inlet of the regenerated hydrochloric acid storage device and an overhead liquid inlet of the hydrochloric acid absorption column, respectively; the tower bottom liquid outlet of the tail gas purification tower is respectively connected with the tower top liquid inlet of the hydrochloric acid absorption tower and the tower top liquid inlet of the tail gas purification tower; a liquid inlet at the top of the tail gas purification tower is connected with a water inlet pipe; a tail gas outlet is formed in the tower top of the tail gas purification tower;

preferably, an acid-resistant tail gas fan is arranged between the hydrochloric acid absorption tower and the tail gas purification tower; an inlet of the acid-proof tail gas fan is connected with a gas outlet of the hydrochloric acid absorption tower, and an outlet of the acid-proof tail gas fan is connected with a gas inlet of the tail gas purification tower;

preferably, an outlet of the tower bottom liquid of the hydrochloric acid absorption tower is connected with an absorption tower circulating pump, an outlet of the absorption tower circulating pump is divided into two branches, a first branch is connected with an inlet of the regenerated hydrochloric acid storage device, and a second branch is connected with an inlet of the tower top liquid of the hydrochloric acid absorption tower;

preferably, a tower bottom liquid outlet of the tail gas purification tower is connected with a purification tower circulating pump, an outlet of the purification tower circulating pump is divided into two paths, a first path is connected to a tower top liquid inlet of the hydrochloric acid absorption tower, and a second path is connected to the tower top liquid inlet of the tail gas purification tower.

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