Ammonium paratungstate calcination tail gas treatment method

Abstract

The invention discloses an ammonium paratungstate calcination tail gas treatment method which comprises the following steps: calcining ammonium paratungstate to obtain tungsten oxide and calcination tail gas containing ammonia and dust; water spraying is conducted on the calcination tail gas, tungsten-containing dust in the calcination tail gas is removed, and pre-purified tail gas and spraying liquid are obtained; and introducing the pre-purified tail gas into a hydrochloric acid solution, and reacting ammonia gas in the pre-purified tail gas with the hydrochloric acid solution to obtain qualified discharged purified tail gas and an ammonium chloride solution. The calcination tail gas is subjected to spraying dust removal and hydrochloric acid absorption, tungsten oxide dust recovery and ammonia gas recycling are achieved, the product loss rate in the ammonium paratungstate calcination process is reduced, the treated tail gas is discharged after reaching the standard, and environmental pollution is reduced. The pre-purified tail gas is directly introduced into the hydrochloric acid solution, the scheme is simple, the manufacturing cost is low, the efficiency is high, and the device is suitable for on-site actual production. The ammonium chloride solution is used for producing ammonium paratungstate after being evaporated and concentrated, and raw materials are fully utilized.

Description

Technical Field

[0001] The invention relates to the technical field of calcination tail gas treatment, and more specifically to a method for treating ammonium paratungstate calcination tail gas. Background Art

[0002] In China, tungsten oxide products are produced by calcining ammonium paratungstate (ATP) in a converter. Ammonium paratungstate contains 5% ammonia, which produces tail gas during calcination and decomposition. The tail gas contains ammonia and tungsten oxide dust. Ammonia is a highly water-soluble, colorless, alkaline, irritating gas. After being discharged, it has a pungent odor, kills trees, and damages people's respiratory system and skin. It not only pollutes the atmosphere, but also causes eutrophication of water bodies and pollutes water sources after forming rainwater, causing serious environmental pollution.

[0003] In the prior art, the acid spraying method is used to absorb ammonia, but the equipment requirements are very high and the cost is expensive. The liquid ammonia consumption per ton of ammonium paratungstate is as high as 180kg, and the ammonia recovery rate is less than 50%. Such a device cannot completely and effectively recover the tungsten oxide dust in the converter calcination process. At the same time, part of the ammonia tail gas is absorbed by the spray liquid and enters the wastewater, causing the ammonia content in the industrial wastewater to exceed the standard, generating new secondary pollution. Since the absorption of ammonia by water is limited, this will cause part of the ammonia in the calcination tail gas to be released into the atmosphere, causing atmospheric pollution.

[0004] Therefore, it is urgent to provide a method for treating tail gas from the calcination of ammonium paratungstate that can effectively absorb ammonia and is relatively inexpensive. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects of the prior art and provide a method for treating tail gas from the calcination of ammonium paratungstate, comprising:

[0006] (1) calcining ammonium paratungstate to obtain tungsten oxide and calcination tail gas containing ammonia and dust;

[0007] (2) spraying the calcination tail gas with water to remove tungsten-containing dust in the calcination tail gas, thereby obtaining pre-purified tail gas and spray liquid;

[0008] (3) The pre-purified tail gas is passed into a hydrochloric acid solution, and the ammonia in the pre-purified tail gas reacts with the hydrochloric acid solution to obtain a purified tail gas and an ammonium chloride solution that are qualified for discharge.

[0009] Implementing the embodiments of the present invention will have the following beneficial effects:

[0010] The present invention provides a method for treating tail gas from calcination of ammonium paratungstate, comprising: calcining ammonium paratungstate to obtain tungsten oxide and calcination tail gas containing ammonia and dust; spraying the calcination tail gas with water to remove tungsten dust in the calcination tail gas to obtain pre-purified tail gas and spraying liquid; passing the pre-purified tail gas into a hydrochloric acid solution, reacting ammonia in the pre-purified tail gas with the hydrochloric acid solution to obtain purified tail gas and ammonium chloride solution with qualified discharge. In the present invention, the calcination tail gas is subjected to spray dust removal and hydrochloric acid absorption respectively, so as to realize the recovery of tungsten oxide dust and the recovery and reuse of ammonia, reduce the product loss rate in the calcination process of ammonium paratungstate, and discharge the treated tail gas after meeting the standard, thereby reducing environmental pollution. The pre-purified tail gas is directly passed into the hydrochloric acid solution, the scheme is simple, the cost is relatively cheap, the efficiency is high, and it is suitable for actual production on site. The ammonium chloride solution is evaporated and concentrated to obtain a high-concentration ammonium chloride solution, and the high-concentration ammonium chloride solution is used to produce ammonium paratungstate, making full use of raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0012] in:

[0013] Figure 1 The present invention provides a flow chart of a method for treating tail gas from the calcination of ammonium paratungstate. DETAILED DESCRIPTION

[0014] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0015] Reference Figure 1 The present invention provides a method for treating tail gas from the calcination of ammonium paratungstate, comprising:

[0016] (1) calcining ammonium paratungstate (APT) to obtain tungsten oxide and calcination tail gas containing ammonia and dust;

[0017] (2) spraying the calcination tail gas with water to remove tungsten-containing dust in the calcination tail gas, thereby obtaining pre-purified tail gas and spray liquid;

[0018] (3) The pre-purified tail gas is passed into a hydrochloric acid solution, and the ammonia in the pre-purified tail gas reacts with the hydrochloric acid solution to obtain a purified tail gas and an ammonium chloride solution that are qualified for discharge.

[0019] It should be noted that the calcination temperature of ammonium paratungstate is 500°C to 600°C to obtain tungsten oxide and calcination tail gas. The tungsten oxide includes one or more of blue tungsten, purple tungsten and yellow tungsten. The calcination tail gas includes NH3, H2O, O2, N2 and tungsten-containing dust.

[0020] The calcined tail gas is sprayed with water, and the tungsten-containing dust is washed down, reducing the product loss during the calcination of ammonium paratungstate. Since ammonia is an alkaline gas and can react with hydrochloric acid, the pre-purified tail gas sprayed with water is introduced into the hydrochloric acid solution to fully react with the hydrochloric acid solution, thereby reducing the ammonia content in the exhaust gas and improving the recovery rate of ammonia. At the same time, the ammonium chloride generated by the reaction of ammonia and hydrochloric acid can be used as a raw material in the production process of ammonium paratungstate.

[0021] It is understandable that the calcined tail gas can realize the recovery of tungsten oxide dust and the recycling of ammonia by spraying dust removal and hydrochloric acid absorption, reduce the product loss rate during the calcination of ammonium paratungstate, and discharge the treated tail gas after it reaches the standard, thereby reducing environmental pollution. In this embodiment, the pre-purified tail gas is directly introduced into the hydrochloric acid solution, the scheme is simple, the cost is low, the efficiency is high, and it is suitable for actual production on site. The ammonium chloride solution is used to produce ammonium paratungstate after evaporation and concentration, making full use of the raw materials.

[0022] In a specific embodiment, the ammonium chloride solution is concentrated by evaporation to obtain a high-concentration ammonium chloride solution and condensed water. The high-concentration ammonium chloride solution is used to produce ammonium paratungstate, and the condensed water is used to prepare a hydrochloric acid solution.

[0023] It should be noted that the production process of ammonium paratungstate is complex and delicate, including starting from molybdenum tungstate ore, and preparing crude sodium tungstate solution through a series of processes such as crushing and decomposition. Subsequently, the crude sodium tungstate undergoes a series of treatments, such as purification and impurity removal, extraction, transformation, crystallization, etc., to prepare ammonium paratungstate. In this process, ammonium chloride solution is used as a raw material for preparing ammonium paratungstate. The ammonia produced by ammonium paratungstate during the calcination process reacts with hydrochloric acid to form ammonium chloride solution. After evaporation and concentration, the ammonium chloride solution is concentrated to obtain a high-concentration ammonium chloride solution and condensed water. The high-concentration ammonium chloride solution is used to produce ammonium paratungstate, and the condensed water is used to prepare the hydrochloric acid solution, making full use of the raw materials.

[0024] In a specific embodiment, the spray liquid is filtered to obtain a filtrate and a filter residue. The filtrate is used to prepare a hydrochloric acid solution. The filter residue is added to a calcination process after being washed and dried. The filter residue is tungsten-containing dust, which is further added to the calcination process to fully utilize the raw materials.

[0025] Furthermore, the washing liquid for cleaning the filter residue is used in the water spraying process, thereby making full use of the raw materials.

[0026] In a specific embodiment, the calcination tail gas is sprayed with water through a Venturi spray dust removal device. The Venturi spray dust removal device uses the Venturi principle. When the spray liquid fluid passes through the variable diameter pipe and flows through the narrow inlet section, the flow rate will increase. At the same time, negative pressure is generated after the inlet section to suck in the dust. The dust is sprayed by the liquid, and fine tungsten-containing dust can be recovered. The recovery rate of tungsten-containing dust reaches 99%.

[0027] In a specific embodiment, the pH value of the hydrochloric acid solution is monitored, and an automatic liquid replenishing device is provided, and the automatic liquid replenishing device replenishes the hydrochloric acid solution according to the pH value of the hydrochloric acid solution.

[0028] Furthermore, when the pH of the hydrochloric acid solution is greater than 6, the automatic liquid replenishing device automatically replenishes the hydrochloric acid solution until the pH of the hydrochloric acid solution is 1.

[0029] It is understandable that the acidity of the hydrochloric acid solution is adjusted by the automatic liquid replenishing device so that the pH of the solution is maintained at 1-6 to ensure sufficient absorption of ammonia gas, and the automatic liquid replenishing device automatically replenishes the liquid to reduce labor costs.

[0030] The following are specific embodiments.

[0031] Example 1

[0032] The calcination temperature of ammonium paratungstate is 500℃, the calcination amount is 6800, the calcination product is tungsten oxide, the tungsten-containing particles in the tail gas are about 3.4Kg per day, and the total amount of calcination tail gas produced per day is about 0.6t.

[0033] The calcined tail gas is passed through a Venturi spray dust removal device to remove tungsten-containing dust in the calcined tail gas, thereby obtaining tungsten-containing dust and pre-purified tail gas. The Venturi spray dust removal device absorbs 99% of the tungsten-containing dust. Most of the gases in the tail gas passing through the device are NH3, O2, and N2, and contain very little water.

[0034] Ammonia water and pre-purified tail gas are introduced into the absorption device. The concentration of hydrochloric acid solution in the absorption device is 36.5g / L. The volume of the tank is 400m 3 , 2.9t of concentrated hydrochloric acid is needed to absorb all the ammonia in the pre-purified tail gas, and the final concentration of the ammonium chloride solution is about 50g / L. By evaporation and concentration, a high-concentration ammonium chloride solution of 262.5g / L is obtained, and the weight of the recovered high-purity ammonium chloride solution is about 8.9t.

[0035] The recovery rate of ammonia in the calcination tail gas reaches 99%, and the recovery rate of tungsten oxide is close to 100%, which can reduce the purchase and use of ammonium chloride by 50% in the production process of ammonium paratungstate.

[0036] Example 2

[0037] The calcination temperature of ammonium paratungstate is 600℃, the calcination amount is 7800kg / day, the calcination product is tungsten oxide, the tungsten particles in the tail gas are about 3.9Kg per day, and the total amount of calcination tail gas produced per day is about 0.7t.

[0038] The calcined tail gas is passed through a Venturi spray dust removal device to remove tungsten-containing dust in the calcined tail gas, thereby obtaining tungsten-containing dust and pre-purified tail gas. The Venturi spray dust removal device absorbs 99% of the tungsten-containing dust. Most of the gases in the tail gas passing through the device are NH3, O2, and N2, and contain very little water.

[0039] Ammonia water and pre-purified tail gas are introduced into the absorption device. The concentration of hydrochloric acid solution in the absorption device is 36.5g / L. The volume of the tank is 400m 3 , 3.4t of concentrated hydrochloric acid is needed to absorb all the ammonia in the pre-purified tail gas, and the final concentration of the ammonium chloride solution is about 50g / L. By evaporation and concentration, a high-concentration ammonium chloride solution of 262.5g / L is obtained, and the weight of the recovered high-purity ammonium chloride solution is about 10.4t.

[0040] The recovery rate of ammonia in the calcination tail gas reaches 99%, and the recovery rate of tungsten oxide is close to 100%, which can reduce the purchase and use of ammonium chloride by 50% in the production process of ammonium paratungstate.

[0041] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for treating tail gas from the calcination of ammonium paratungstate, characterized in that: include: (1) calcining ammonium paratungstate to obtain tungsten oxide and calcination tail gas containing ammonia and dust; (2) spraying the calcination tail gas with water to remove tungsten-containing dust in the calcination tail gas, thereby obtaining pre-purified tail gas and spray liquid; (3) The pre-purified tail gas is passed into a hydrochloric acid solution, and the ammonia in the pre-purified tail gas reacts with the hydrochloric acid solution to obtain a purified tail gas and an ammonium chloride solution that are qualified for discharge.

2. The method for treating tail gas from calcination of ammonium paratungstate according to claim 1, characterized in that: The ammonium chloride solution is concentrated by evaporation to obtain a high-concentration ammonium chloride solution and condensed water. The high-concentration ammonium chloride solution is used to produce the ammonium paratungstate, and the condensed water is used to prepare the hydrochloric acid solution.

3. The method for treating tail gas from calcination of ammonium paratungstate according to claim 1, characterized in that: The spray liquid is filtered to obtain a filtrate and a filter residue, wherein the filtrate is used to prepare the hydrochloric acid solution, and the filter residue is added to the calcination process after being washed and dried.

4. The method for treating tail gas from calcination of ammonium paratungstate according to claim 3, characterized in that: The washing liquid for cleaning the filter residue is used in the water spraying process.

5. The method for treating tail gas from calcination of ammonium paratungstate according to claim 1, characterized in that: The pH value of the hydrochloric acid solution is monitored, and an automatic liquid replenishing device is provided, wherein the automatic liquid replenishing device replenishes the hydrochloric acid solution according to the pH value of the hydrochloric acid solution.

6. The method for treating tail gas from calcination of ammonium paratungstate according to claim 5, characterized in that: When the pH of the hydrochloric acid solution is greater than 6, the automatic liquid replenishing device automatically replenishes the hydrochloric acid solution until the pH of the hydrochloric acid solution is 1.

7. The method for treating tail gas from calcination of ammonium paratungstate according to claim 1, characterized in that: The calcination tail gas is sprayed with water through a Venturi spray dust removal device.

8. The method for treating tail gas from calcination of ammonium paratungstate according to claim 1, characterized in that: The tungsten oxide includes one or more of blue tungsten, purple tungsten and yellow tungsten.

9. The method for treating tail gas from calcination of ammonium paratungstate according to claim 1, characterized in that: The calcination tail gas includes NH3, H2O, O2, N2 and tungsten-containing dust.

10. The method for treating tail gas from calcination of ammonium paratungstate according to claim 1, characterized in that: The ammonium paratungstate is calcined at a temperature of 500°C to 600°C.

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