METHOD FOR PRODUCING MERCURY-FREE ALKALINE-MANGANESE TYPE ELECTROLYZED MANGANESE DIOXIDE

Abstract

Provided is a method for producing mercury-free alkaline-manganese type electrolyzed manganese dioxide, which sequentially comprises: (1) mixing manganese oxide ore and pyrite, continuously feeding the mixture and sulfuric acid into a continuous leaching tank to form a one-stage or multi-stage continuous leaching, removing potassium ions first after leaching, and then removing iron by means of a neutral iron removal method, and adding lime powder at the late stage of iron removal to adjust the pH value of the solution to 6-6.5, so as to obtain a manganese sulfate solution after reaction at 90-95° C. for 3-4 hours; (2) performing purification and impurities removal on the manganese sulfate solution by a two-stage continuous purification process, wherein, during the first stage of the continuous purification on the manganese sulfate solution, calcium polysulfide is added, and during the second stage of the purification, the solution passes through a sluice and calcium and magnesium are dynamically removed, and then the solution is sent to a still tank to stand to deposit and remove impurities such as calcium and magnesium; and (3) subjecting the purified manganese sulfate solution to ultra-fine filtering, heating to 90-100° C. by a plate heat exchanger, and then entering an elevated tank, and at the same time, adding a prepared suspending agent and a prepared foaming agent, and supplying the resulting product to electrolysis baths through pipelines for electrolysis, so as to obtain mercury-free alkaline-manganese type electrolyzed manganese dioxide. The method has the advantages of wide adaptability to manganese oxide ores, short process flow, and low production cost.

Description

The present invention claims the benefit of the priority of the Chinese Application titled “METHOD FOR PRODUCING MERCURY-FREE ALKALINE-MANGANESE TYPE ELECTROLYZED MANGANESE DIOXIDE”, whose Application No. is 201010227988.7 and Application Date is 15, Jul., 2010, and whole of which can be combined into the present invention.

TECHNICAL FIELD

The present invention involves a method for producing mercury-free alkaline-manganese type electrolyzed manganese dioxide; especially involves a method for producing mercury-free alkaline-manganese type electrolyzed manganese dioxide by leaching ultra-low-grade manganese oxide minerals by “two-ores method”.

BACKGROUND

As the high power battery of the lowest cost-performance ratio in battery industry, alkaline-manganese batteries have features such as steady working voltage, continuous discharge of large current, good performance, long storage time (up to 3-5 years), excellent low temperature performance and leak-proof performance and so on, and are popular both home and abroad. The annual consumption of the mercury-free alkaline-manganese type electrolyzed manganese dioxide, which is the main material for producing alkaline-manganese batteries, is more than 300000 tons, and is increasing by more than 10% every year. So it has a bright market prospects.

In the current processes for producing electrolyzed manganese dioxide, the main raw material is manganese carbonate ore or manganese oxide ore. During the smelting process, with domestic manganese carbonate ore as raw material, because the content of the manganese carbonate in the ore is low (below 30%), a large consumption of manganese ore and a high cost of products are resulted. With the manganese oxide ore as raw material, the recently main processes comprise the leaching solution after reducing the manganese oxide ore by roasting and “two-ores method” to produce the electrolyzed manganese dioxide, wherein, the method of the leaching solution after reducing roasting manganese oxide ore by roasting has the shortcomings such as long process flow, high production cost, and easily causing pollution to the surrounding environment of the factory; and the “two-ores method” with high grade manganese oxide as raw material to produce the electrolyzed manganese dioxide, i.e. leaching solution of the manganese dioxide ore and the pyrites which is the reducing agent, when using the low-grade manganese ore, i.e. the grade of it is lower than 25%, has the shortcomings such as low leaching rate, long turnaround time of material among the devices, the increased amount of equipments and low utilization rate because of using intermittent leaching process in the domestic manganese metallurgical industry recently, i.e. directly dissolving the manganese ore into solution in one sole leaching tank The increasingly reducing of the used high-grade manganese ore resources will lead to a difficulty of the method to maintain long-term production. The manganese ore resource in Guangxi Province is rich, but most of which are low-grade manganese ore characterized by low manganese content, high impurity content, so it wasn't adequately exploited for a long time.

SUMMARY OF THE INVENTION

The technical problems to be solved by the invention is to provide a method for producing mercury-free alkaline-manganese type electrolyzed manganese dioxide by “two-ores method”, with ultra-low-grade manganese oxide ore as main raw material.

The technical scheme of the invention for solving the technical problems is to provide a method for producing mercury-free alkaline-manganese type electrolyzed manganese dioxide, which comprises the sequential steps: (1) mixing manganese oxide ore and pyrite, continuously feeding the mixture and sulfuric acid into a continuous leaching tank composed of 1-7 stirring leaching tanks to form a one-stage or multi-stage continuous leaching, controlling the reaction temperature at 90-95° C. for about 3 to 4 hours during the process, removing potassium ions first after the leaching, and then removing iron by means of a neutral iron removal method, and adding lime powder at the late stage of iron removal to adjust the pH value of the solution to 6-6.5 at 90-95° C. for 3-4 hours, so as to obtain a manganese sulfate solution; (2) performing purification to remove the impurities from the manganese sulfate solution by a twice-stage continuous purification process, and performing the first stage of the continuous purification of the manganese sulfate solution by adding calcium polysulfide at the controlled temperature of 60° C., and then performing the second stage of the purification to remove the calcium and magnesium by the solution passing through a sluice, and then the solution is sent to a standing tank and left it for 32 hours for ageing the solution and removing the impurities such as calcium and magnesium as precipitate; (3) after an ultrafiltration, subjecting the purified manganese sulfate solution is heated to 90-100° C. by a plate heat exchanger, and then entering an elevated tank, and adding the prepared suspending agent and foaming agent at the same time, and supplying the resulting product to electrolysis baths through pipelines, electrolysis conditions: electrolyte temperature is 100-103° C., the anodic current density is 80-85 A/m², the cell voltage is 2.2-3.5V, electrolytic period is 12-20 days, after electrolysis the mercury-free alkaline-manganese type electrolyzed manganese dioxide is obtained.

In the above-mentioned method for producing mercury-free alkaline-manganese type electrolyzed manganese dioxide, in the step 1, directly feeding the manganese oxide ore and pyrite into the continuous leaching tank by the ratio of 1:0.24, at the same time blending sulfuric acid and waste electrolyte by the ratio of ore to acid of 1:0.47.

In the above-mentioned method for producing mercury-free alkaline-manganese type electrolyzed manganese dioxide, the said waste electrolyte come from the raffinate generated during the electrolysis in the step 3.

In the above method for producing mercury-free alkaline-manganese type electrolyzed manganese dioxide, in the step 3, broking the crude electrolyzed manganese dioxide products obtained from electrolysis on the anode into 6-8 mm particles, entering the particles into a washing rank, using the three-rinsing process which contains washing by water, caustic washing, and washing by water, wherein, the temperature of the alkali liquor for the first and the second caustic washing are both 60-70° C., the temperature of the water for the last washing is 80-90° C., and the rinsing period is 40 hours. The rinsing liquids are heated directly by steam. And then the electrolyzed manganese dioxide with required particle size is obtained through milling.

In the above method for producing mercury-free alkaline-manganese type electrolyzed manganese dioxide, performing homogenization of the milled electrolyzed manganese dioxide by gravity mixing silo, send the manganese dioxide into which by the dense phase conveying method, wherein, the time of mixing is about 16 hours.

Contrast to the existing technology, the present invention has the following beneficial effects: the method for producing mercury-free alkaline-manganese type electrolyzed manganese dioxide provide by the present reduce the grade of the used manganese oxide to its 16% by using the ultra-low-grade manganese oxide ore as main raw material, directly leaching the manganese from the ultra-low-grade manganese oxide ore by “two-ores method”, performing deep purification to remove the impurities from the obtained manganese sulfate solution, and then performing electrolysis to produce mercury-free alkaline-manganese type electrolyzed manganese dioxide. And the process used is not only adaptable for the low-grade and complicated manganese oxide ore, but also adaptable for the high-grade manganese oxide ore, therefore, it has the advantages such as wide adaptability to manganese oxide ores, short process flow, low production cost and so on. It can make full use of the large quantity of low-grade manganese ore in Guangxi Province to produce mercury-free electrolyzed manganese dioxide product, so that it has a very good economic benefits and social benefits to the rational use of manganese ore resources, reduce the production cost.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is the flow diagram of the process of the embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following will further descript the invention referring to the drawing and the embodiments.

Example 1

Mixing manganese oxide ore powder containing 14.32% manganese and pyrite powder containing 44.54% sulfur by the ratio of the dry weight of 1:0.24, preparing 100 g/L dilute sulfuric acid solution by adding water into a sulfuric acid which concentration is 98%; continuously feeding the mixture of the manganese oxide powder and pyrite powder and the prepared sulfuric acid into a continuous leaching tank by the ratio of 1:0.47, and continuously stirring at the same time. The continuous leaching tank is composed of one leaching tank for one-stage continuous leaching, wherein, the effective volume of the leaching tank is 1 m³, and the temperature of the tank is 95° C. The reaction time of leaching from feeding to out of the leaching tank is 3 hours until the pH values is to 3-3.5 that indicates that the leaching reaction has been completed. Continuously stir during the reaction. The liquid material flowing from the leaching tank enters the neutralization tank in series, the effective volume of which is 1.5 m³. Adding lime powder to continuously perform neutralization reaction, with controlled pH value of 6.0 for 3 hours. After the neutralization, carrying out filtering and the delivering the filter residue to the residue site, and the crude manganese sulfate solution which contains heavy metals such as copper, cobalt, nickel, lead and impurities such as calcium, magnesium is obtained. Using twice-stage continuous purification technology, wherein, during the first stage of continuous purification for the crude manganese sulfate solution calcium polysulfide is added at the controlled temperature of 60° C., the filter residue is sent to residue site, and then performing the second stage of purification, wherein the solution passes through a sluice first so that the calcium and magnesium are dynamically removed, and then the solution is sent to a standing tank and left it for 32 hours to ageing the solution and remove impurities such as calcium and magnesium as precipitate, to obtain refined manganese sulfate solution. The filter residue is sent to residue site, and delivering the filtrate to electrolysis.

Subjecting the qualified refined manganese sulfate solution to ultra filtration, to heat to 90° C. by a plate heat exchanger, and then to suspension electrolysis by entering an elevated tank. And the prepared suspending agent and foaming agent are added at the same time. Wherein, the electrolyte temperature is 100° C., the anodic current density is 81 A/m², the cell voltage is 2.4 V, electrolytic period is 12 days. Stripping the crude products of manganese dioxide on the anode, and broking them to particles of 6-8 mm by crusher, then delivering them into rinse ranks, and the effective volume of each rinse rank is 1 m³. Using the three-stage rinsing process which contains washing by water, caustic washing, and washing by water, wherein, the temperature of the alkali liquor of the first and the second rinsing are both 60° C., and the temperature of the water of the last rinsing is 80° C., and the rinse period is 40 hours. The rinsing liquids are directly heated by steam. Sending the rinsed electrolyzed manganese dioxide into pendulum grinder, to grind and collecting the powder product (particle size is −325 mesh). In order to eliminate difference of the product quality and ensure the uniformity of the product, sending the product into gravity mixing silo by the dense phase conveying method for homogenization mixing for 16 hours, to prepare the qualified mercury-free alkaline-manganese type electrolyzed manganese dioxide product.

Example 2

Mixing manganese oxide ore powder containing 15.56% manganese and pyrite powder containing 40.54% sulfur by the ratio of the dry weight of 1:0.24, preparing 100 g/L dilute sulfuric acid solution by adding water into a sulfuric acid which concentration is 98%; continuously feeding the mixture of the manganese oxide powder and pyrite powder and the prepared sulfuric acid into a continuous leaching tank by the ratio of 1:0.47, and continuously stirring at the same time. The continuous leaching tank is composed of three leaching tanks for three-stage continuous leaching during which material liquid enters the third leaching tank after out of the second leaching tank, wherein, the effective volume of each leaching tank is 1 m³, and the temperature of each tank is 93° C. The reaction time of leaching from feeding to out of the third leaching tank is 3.5 hours. Continuously stir during the reaction. The liquid material flowing from the third leaching tank enters the neutralization tank in series, the effective volume of which is 1.5 m³. Adding lime powder to continuous perform neutralization reaction, with controlled pH value of 6.3 for 3.5 hours. After the neutralization, carrying out filtering and delivering the filter residue to the residue site, and the crude manganese sulfate solution which contains heavy metals such as copper, cobalt, nickel, lead and impurities such as calcium, magnesium is obtained. Using twice-stage continuous purification technology, wherein, during the first stage of continuous purification for the crude manganese sulfate solution calcium polysulfide is added at the controlled temperature of 60° C., the filter residue is sent to residue site, and then performing the second stage of purification, wherein the solution passes through a sluice first so that the calcium and magnesium are dynamically removed, and then the solution is sent to a standing tank and left it for 32 hours to ageing the solution and remove impurities such as calcium and magnesium as precipitate, to obtain refined manganese sulfate solution. The filter residue is sent to residue site, and delivering the filtrate to electrolysis.

Subjecting the qualified refined manganese sulfate solution to ultra filtration, to heat to 95° C. by a plate heat exchanger, and then to suspension electrolysis by entering an elevated tank. And the prepared suspending agent and foaming agent are added at the same time. Wherein, the electrolyte temperature is 102° C., the anodic current density is 83 A/m², the cell voltage is 2.9 V, electrolytic period is 15 days. Stripping the crude products of manganese dioxide on the anode, and broking them to particles of 6-8 mm by crusher, then delivering them into rinse ranks, and the effective volume of each rinse rank is 1 m ³. Using the three-stage rinsing process which contains washing by water, caustic washing, and washing by water, wherein, the temperature of the alkali liquor of the first and the second rinsing are both 65° C., and the temperature of the water of the last rinsing is 85° C., and the rinse period is 40 hours. The rinsing liquids are directly heated by steam. Sending the rinsed electrolyzed manganese dioxide into pendulum grinder, to grind and collecting the powder product (particle size is −325 mesh). In order to eliminate difference of the product quality and ensure the uniformity of the product, sending the product into gravity mixing silo by the dense phase conveying method for homogenization mixing for 16 hours, to prepare the qualified mercury-free alkaline-manganese type electrolyzed manganese dioxide product.

Example 3

Mixing manganese oxide ore powder containing 13.58% manganese and pyrite powder containing 47.44% sulfur by the ratio of the dry weight of 1:0.24, preparing 100 g/L dilute sulfuric acid solution by adding water into a sulfuric acid which concentration is 98%; continuously feeding the mixture of the manganese oxide powder and pyrite powder and the prepared sulfuric acid into a continuous leaching tank by the ratio of 1:0.47, and continuously stirring at the same time. The continuous leaching tank is composed of seven leaching tanks for seven-stage continuous leaching during which material liquid enters the third to the seventh leaching tank after out of the second leaching tank, wherein, the effective volume of each leaching tank is 1 m ³, and the temperature of each tank is 95° C. The reaction time of leaching from feeding to out of the seventh leaching tank is 4 hours. Continuously stir during the reaction. The liquid material flowing from the seventh leaching tank enters the neutralization tank in series, the effective volume of which is 1.5 m³. Adding lime powder to continuously perform neutralization reaction, with controlled pH value of 6.5. After the neutralization, carrying out filtering and the delivering the filter residue to the residue site, and the crude manganese sulfate solution which contains heavy metals such as copper, cobalt, nickel, lead and impurities such as calcium, magnesium is obtained. Using twice-stage continuous purification technology, wherein, during the first stage of continuous purification for the crude manganese sulfate solution calcium polysulfide is added at the controlled temperature of 60° C., the filter residue is sent to residue site, and then performing the second stage of purification, wherein the solution passes through a sluice first so that the calcium and magnesium are dynamically removed, and then the solution is sent to a standing tank and left it for 32 hours to ageing the solution and remove impurities such as calcium and magnesium as precipitate, to obtain refined manganese sulfate solution. The filter residue is sent to residue site, and delivering the filtrate to electrolysis

Subjecting the qualified refined manganese sulfate solution to ultra filtration, to heat to 100° C. by a plate heat exchanger, and then to suspension electrolysis by entering an elevated tank. And the prepared suspending agent and foaming agent are added at the same time. Wherein, the electrolyte temperature is 103° C., the anodic current density is 85 A/m², the cell voltage is 3.5 V, electrolytic period is 20 days. Stripping the crude products of manganese dioxide on the anode, and broking them to particles of 6-8 mm by crusher, then delivering them into rinse ranks, and the effective volume of each rinse rank is 1 m ³. Using the three-stage rinsing process which contains washing by water, caustic washing, and washing by water, wherein, the temperature of the alkali liquor of the first and the second rinsing are both 70° C., and the temperature of the water of the last rinsing is 85° C., and the rinse period is 40 hours. The rinsing liquids are directly heated by steam. Sending the rinsed electrolyzed manganese dioxide into pendulum grinder, to grind and collecting the powder product (particle size is −325 mesh). In order to eliminate difference of the product quality and ensure the uniformity of the product, sending the product into gravity mixing silo by the dense phase conveying method for homogenization mixing for 16 hours, to prepare the qualified mercury-free alkaline-manganese type electrolyzed manganese dioxide product.

The main indexes of the manganese dioxide products in the three examples are: MnO₂≧91.0%, Fe≦60 ppm, Cu≦5 ppm, Pb≦5 ppm, Ni≦5 ppm, Co≦5 ppm, Mo≦0.5 ppm, As≦0.5 ppm, Sb≦0.5 ppm, K≦200 ppm.

While the present invention has been revealed by the above preferred embodiments, but its not to limit the invention; and any technical personnel of the areas, within the spirit and scope of the invention, can make some modifications and improvements, so that the protection scope of the invention subject to the defined by the claims.

Claims

1. A method for producing mercury-free alkaline-manganese type electrolyzed manganese dioxide, comprising the following sequential steps:

(1) mixing manganese oxide ore and pyrite, continuously feeding the mixture and sulfuric acid into a continuous leaching tank composed of 1-7 stirring leaching tanks to form a one-stage or multi-stage continuous leaching, controlling the reaction temperature at 90-95° C. for about 3 to 4 hours during the process, removing potassium ions first after leaching, and then removing iron by means of a iron removal-method by neutralization, and adding lime powder at the late stage of iron removal to adjust the value of the solution to 6-6.5 at 90-95° C. for 3-4 hours, so as to obtain a manganese sulfate solution;

(2) performing purification and impurities removal from the manganese sulfate solution by a twice-stage continuous purification process, wherein, during the first stage of the continuous purification of the manganese sulfate solution, calcium polysulfide is added, at the controlled temperature of 60° C., and then performing the second stage of the purification, during which the solution passes through a sluice and the calcium and magnesium are dynamically removed, and then the solution is sent to a stand tank to left for 32 hours to ageing and remove impurities such as calcium and magnesium as precipitate;

(3) subjecting the purified manganese sulfate solution to ultrafiltration, heating the solution to 90-100° C. by a plate heat exchanger, and then entering it into an elevated tank, and adding the prepared suspending agent and foaming agent at the same time, and supplying the resulting product to electrolysis baths through pipelines, electrolysis conditions: electrolyte temperature is 100-103° C., the anodic current density is 80-85 A/m2, the cell voltage is 2.2-3.5V, electrolytic period is 12-20 days, after electrolysis the mercury-free alkaline-manganese type electrolyzed manganese dioxide is obtained.

2. The method for producing mercury-free alkaline-manganese type electrolyzed manganese dioxide according to claim 1, wherein the step 1 further comprises; directly feeding the manganese oxide ore and pyrite into the continuous leaching tank by the ratio of 1:0.24, at the same time blending sulfuric acid and waste electrolyte the ratio of 1:0.47.

3. The method for producing mercury-free alkaline-manganese type electrolyzed manganese dioxide according to claim 2, wherein said waste electrolyte come from the raffinate liquid generated during the electrolysis in the step 3.

4. The method for producing mercury-free alkaline-manganese type electrolyzed manganese dioxide according to claim 1, wherein the step 3 further comprises broking the crude electrolyzed manganese dioxide products obtained during the electrolysis on the anode into particles of 6-8 mm, sending the particles into rinse ranks; using the three-stage rinsing process consisted of washing by water-caustic washing-washing by water, wherein, the temperature of the alkali liquor of the first and the second rinsing are both 60-70° C., the temperature of the water of the last washing is 80-90° C., the rinsing period is about 40 hours, and the rinsing liquids are directly heated by steam, and then obtaining the electrolyzed manganese dioxide with required particle size through milling.

5. The method for producing mercury-free alkaline-manganese type electrolyzed manganese dioxide according to claim 4, further comprising sending the milled electrolyzed manganese dioxide into gravity mixing silos by the dense phase conveying mode to homogenization mixing, and the time of mixing is about 16 hours.