CN111330427A - Application of a metal sulfide mercury removal agent in washing and removing mercury from flue gas - Google Patents

Abstract

The invention discloses an application of a metal sulfide mercury removal agent in washing and removing mercury in flue gas. The invention uses metal sulfide mercury removing agent as mercury removing medium, and adds the mercury removing agent into flue gas washing device or wet dust removing device to form suspension liquid, which is mixed with elementary mercury (Hg) in flue gas⁰) The mercury is fully contacted with the mercury to be converted into stable mercury sulfide, and the elemental mercury (Hg) in the flue gas is realized⁰) The removal is efficient. The mercury removing agent adopted by the invention has high mercury removing efficiency, simple synthesis method, easily obtained raw materials, lower cost, mechanical property, acid resistance, water resistance and SO resistance₂Good performance, simple technical operation, and no change of production process and existing pollutant control system. The components of the mercury removing agent are similar to those of the smelting raw materials, and the mercury removing agent after mercury recovery can be used as a metallurgical raw material, so that the mercury removing agent has no secondary pollution and has wide market application prospect.

Description

Application of a metal sulfide mercury removal agent in washing and removing mercury from flue gas

technical field

The invention belongs to the technical field of environmental pollution prevention and purification, and in particular relates to the application of a metal sulfide mercury remover in washing and removing mercury from flue gas.

Background technique

Mercury is an environmental pollutant with high toxicity, high corrosiveness, high volatility, bioaccumulation and easy migration and diffusion. The "mercury sources" in nature mainly include natural sources and anthropogenic sources. According to the latest 2018 Global Mercury Pollution Report released by the United Nations Environment Programme (UNEP), the mercury emitted by human activities in the atmosphere exceeds 2,500 tons per year, accounting for It accounts for more than 80% of total mercury emissions in China, which mainly includes mercury emissions from metallurgical industry, fossil fuel combustion, cement production, petrochemical industry, garbage disposal and other industries. In August 2017, the Minamata Convention came into effect in 128 countries around the world, and limiting and reducing anthropogenic mercury emissions has become a broad consensus in the international community.

There are three main forms of mercury, including gaseous elemental mercury (Hg ⁰ ), oxidized mercury (Hg ²⁺ ) and particulate mercury (Hg ^P ), of which particulate mercury (Hg ^p ) can pass through the flue gas purification process. Particle removal equipment removes oxidized mercury (Hg ²⁺ ) by flue gas scrubbers or wet dust removal equipment, while gaseous elemental mercury (Hg ⁰ ) has a low melting point and high volatility, and is almost insoluble in water (with a solubility of about approx. 50 μg/L), it is difficult for existing washing or dust removal equipment to capture Hg ⁰ , so the direct discharge of gaseous elemental mercury (Hg ⁰ ) causes great harm to the environment. Therefore, how to effectively control the emission of Hg ⁰ has become an important problem that needs to be solved urgently.

The mercury removal methods used at home and abroad mainly include activated carbon adsorption method, solution absorption method, low temperature separation method, etc. Activated carbon adsorbent is a relatively mature commercial mercury removal medium, which has been widely used in the field of mercury removal from coal flue gas, but its cost is high, the consumption is large, and the operating cost is high; the mercury adsorption capacity and adsorption rate of commercial activated carbon are small, It is difficult to meet the increasingly stringent mercury emission standards; mercury is mainly physically adsorbed on the surface of activated carbon, and when activated carbon is exposed to the environment, mercury is more likely to be re-released, and it is easy to cause secondary pollution to the environment; the mercury removal efficiency of commercial activated carbon is seriously affected. Restricted by flue gas conditions, acid resistance, water resistance and SO ₂ resistance are poor, and it is not suitable for use in washing equipment or wet dust removal equipment. These shortcomings also limit its use in high SO ₂ flue gas purification process. use. Solution absorption mercury removal methods mainly include Polyton chloride method, potassium iodide method, mercury sulfate method, etc. Although the solution absorption and mercury removal method has a good mercury removal effect, the mercury removal solution is generally corrosive and easily saturated, causing serious environmental pollution, high operating costs, and high equipment requirements; Mercury (Hg ²⁺ ) is easily reduced to gaseous elemental mercury (Hg ⁰ ) under the influence of flue gas components, resulting in the reduction of mercury removal efficiency and secondary pollution of the environment.

SUMMARY OF THE INVENTION

In order to overcome the defects and deficiencies of commercial activated carbon adsorption and mercury removal and solution absorption and mercury removal, the invention provides the application of a metal sulfide mercury removal agent in washing and removing mercury from flue gas. The metal sulfide mercury removing agent of the invention is used for washing and removing mercury in flue gas, and is efficient, economical and environmentally friendly.

The invention uses metal sulfide as a mercury removal medium. During the flue gas scrubbing process, the metal sulfide mercury removal agent is added to the flue gas scrubbing device or the wet dust removal device to form a suspension, and the metal sulfide mercury removal agent can be used in the gas, It can efficiently combine with mercury in liquid and two phases, convert mercury into stable mercury sulfide, and realize efficient removal of Hg ⁰ in flue gas.

The technical scheme of the present invention is specifically introduced as follows:

The invention provides the application of a metal sulfide mercury removing agent in washing and removing mercury from flue gas.

Preferably, the application method is as follows: the metal sulfide mercury removal agent is formed into a suspension in a washing device or a wet dust removal device, and the Hg ⁰ in the flue gas is converted into stable mercury sulfide to realize the washing and removal of Hg ⁰ .

Preferably, the metal sulfide mercury removal agent is selected from metal sulfides or their combinations, and the metal sulfides are monometallic metal sulfides such as copper sulfide, molybdenum sulfide, zinc sulfide, lead sulfide, manganese sulfide, etc., and iron sulfide, copper sulfide, etc. can also be used. Binary or multi-component metal sulfides.

Preferably, the metal sulfide mercury removal agent is obtained by modifying natural sulfur-containing minerals.

Preferably, the metal sulfide mercury removal agent is obtained by artificial synthesis by adding a surfactant; the surfactant is dodecyl trimethyl ammonium bromide, octadecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium One or a combination of alkyl trimethyl ammonium bromide, dodecyl dimethyl benzyl ammonium bromide, potassium monododecyl phosphate, octadecyl amide methyl pyridine chloride or hydrazine.

Preferably, the metal sulfide mercury removal agent can be obtained by supporting metal sulfide on a carrier; the carrier is Fe ₂ O ₃ , Fe ₃ O ₄ , Al ₂ O ₃ , molecular sieve, silica, silicate, One or a combination of fly ash, zeolite, activated carbon or red mud.

Preferably, the metal sulfide demercuring agent is sprayed in front of the flue gas scrubbing device or wet dedusting device, or directly added to the circulating washing liquid of the flue gas scrubbing or wet dedusting device. After the metal sulfide demercuring agent is added Suspended in water to form a homogeneous suspension.

Preferably, the flue gas scrubbing device or wet dedusting device is selected from scrubbing mercury removal towers, dynamic wave high-efficiency scrubbers, packed tower scrubbers, venturi scrubbers, spray scrubbers, cyclone atomization chambers, water film dedusting One or a combination of devices such as filter, foam dust collector, orifice scrubber, impingement scrubber, packed bed scrubber, air cooling tower, etc.

Preferably, the temperature of the washing liquid or the dust removal liquid in the flue gas scrubbing device or the wet dust removal device is 20-95°C, the ratio of the amount of metal sulfide added to the volume of the washing liquid or the dust removal liquid is 0.1-100 kg/m ³ , and the washing liquid Or the dust removal liquid is acidic and neutral, and the acidity range is c(H ⁺ )=10 ^-7 -15mol/L.

In the present invention, a gas-liquid interface is generated in the flue gas scrubbing device or the wet dust removal device, and the flue gas is fully contacted with the suspension of the metal sulfide demercuring agent, thereby causing at least one of the following:

①The gaseous elemental mercury (Hg ⁰ ) or oxidized mercury (Hg ²⁺ ) in the flue gas is adsorbed by the metal sulfide in the suspension

on the surface of the mercury remover;

②The oxidized mercury (Hg ²⁺ ) or particulate mercury (Hg ^P ) in the flue gas enters the washing liquid or the dust removal liquid.

The metal sulfide ^{mercury remover} has good mechanical properties, good water resistance, and strong hydrophobicity. The influence is small, and the gaseous elemental mercury (Hg ⁰ ) or oxidized mercury (Hg ²⁺ ) can fully contact the surface of the metal sulfide adsorbent, and finally be captured by the metal sulfide adsorbent. On the one hand, according to the gas absorption double-film theory, the absorption resistance is mainly in the liquid film, the oxidized mercury (Hg ²⁺ ) in the solution is captured by the adsorbent, the Hg ²⁺ concentration in the liquid phase is significantly reduced, and the Hg ²⁺ in the liquid film Increasing the concentration gradient will enhance the uptake of Hg ⁰ by the solution. On the other hand, the solubility product constant of HgS is much smaller than that of metal sulfides. Metal sulfides can exchange ions with Hg ²⁺ in solution to generate incompatible HgS, which reduces the Hg ^{2 +} concentration, promote the absorption of Hg ⁰ by the solution, increase the contact probability of gaseous elemental mercury (Hg ⁰ ) with the surface of the metal sulfide mercury remover, and further improve the removal efficiency of mercury, gaseous elemental mercury (Hg ⁰ ) or oxidized mercury ( Hg ²⁺ ) was synergistically removed by metal sulfide mercury removers.

The reactions of the mercury removal process are as follows:

In the present invention, the mercury removal agent is collected by filter press in the bottom flow of the circulating tank of the washing device or the wet dust removal device, and the mercury in the mercury removal agent is recovered by heat treatment. The composition of the mercury removal agent is similar to that of the smelting raw materials. Mercury agent can be used as metallurgical raw material into the smelting process, with high economic and environmental benefits.

Compared with the prior art, the present invention has the following advantages:

(1) The metal sulfide mercury removal agent has high mercury removal efficiency, good mechanical properties, stable chemical properties, low solubility, and simple operation.

Single, easy to obtain raw materials, low cost.

(2) The metal sulfide mercury remover is less affected by moisture and flue gas components, and has excellent acid resistance, water resistance and SO ₂ resistance. It can be used in washing equipment or wet dust removal equipment, and is suitable for high SO ₂ smelting The flue gas purification system can be used in multiple parts of flue gas treatment. It has a wide range of applications in flue gas mercury removal systems. It can use existing flue gas purification equipment without changing the production process and existing pollutant control system. Investment costs are low.

(3) The metal sulfide mercury removal agent can be efficiently combined with mercury in the gas and liquid phases to achieve efficient removal of Hg ⁰ and simplify the flue gas mercury removal system.

(4) The extremely stable compound (mercury sulfide, HgS) formed by the metal sulfide mercury remover and mercury can achieve high selective fixation of mercury and avoid the re-release of mercury.

(5) The present invention can recover the mercury in the mercury remover by heat treatment. Since the composition of the mercury remover is similar to the smelting raw material, the mercury remover after the mercury recovery can be used as a metallurgical raw material, with high economic and environmental benefits.

Detailed ways

The technical solutions of the present invention will be further described below through specific embodiments. The examples are not intended to limit the scope of protection.

Example 1

Using equimolar amounts of ammonium sulfide and cupric chloride as reactants, in the presence of cetyltrimethylammonium bromide, metal sulfide mercury removal agent 1 was prepared by hydrothermal method, and the specific surface area of mercury removal agent 1 was 34.3m ² /g. The metal sulfide demercuring agent was added to the simulated flue gas scrubbing device, the set temperature of the scrubbing liquid was 25 °C, the ratio of the amount of the metal sulfide demercuring agent to the scrubbing liquid was 1kg/m ³ , and the simulated scrubbing liquid was pH=2. The VM-3000 mercury measuring instrument was used to measure the mercury concentration in real time. The mass flowmeter accurately controlled the gas flow of each component to simulate the composition of the flue gas. The total gas flow was 1L/min, and the initial Hg ⁰ concentration was 100±1μg/m ³ . Under pure _N2 atmosphere, the removal efficiency of ^Hg0 by metal sulfide mercury remover was 99.2% within 10h.

Example 2

Using ammonium sulfide, ferric chloride and cupric chloride in molar ratio of 2:1:1 as reactants, metal sulfide mercury removal agent was prepared by simple precipitation method in the presence of dodecyldimethylbenzylammonium bromide 2. The specific surface area of mercury remover 2 is 20.3 m ² /g. The metal sulfide demercuring agent was added to the simulated flue gas scrubbing device, the set temperature of the scrubbing liquid was 25 °C, the ratio of the amount of the metal sulfide demercuring agent to the scrubbing liquid was 1kg/m ³ , and the simulated scrubbing liquid was pH=7. The VM-3000 mercury measuring instrument is used to measure the mercury concentration in real time. The mass flow meter accurately controls the gas flow of each component to simulate the composition of the flue gas. The total gas flow is 1L/min, and the initial Hg ⁰ concentration is 100±1μg/m3. Under pure N ₂ atmosphere, the removal efficiency of Hg ⁰ by metal sulfide mercury remover was 95.7% within 10h.

Example 3

Using ammonium sulfide and cupric chloride with a molar ratio of 1:1 as reactants, metal sulfide mercury removal agent 3 was prepared by titration method. The specific surface area of mercury removal agent 3 was 5.77m ² /g. The metal sulfide demercuring agent was added to the simulated flue gas scrubbing device, the set temperature of the scrubbing liquid was 25 °C, the ratio of the addition amount of the metal sulfide demercuring agent to the scrubbing liquid was 5kg/m ³ , and the simulated scrubbing liquid was 5 kg/m 3 . pH=2. The VM-3000 mercury measuring instrument was used to measure the mercury concentration in real time. The mass flowmeter accurately controlled the gas flow of each component to simulate the composition of the flue gas. The total gas flow was 1L/min, and the initial Hg ⁰ concentration was 100±1μg/m ³ . Under pure N ₂ atmosphere, the removal efficiency of Hg ⁰ by metal sulfide mercury remover was 85.2% within 10 h.

Example 4

Add the metal sulfide demercuring agent 1 to the simulated flue gas scrubbing device, the set temperature of the scrubbing liquid is 50°C, and the ratio of the addition amount of the metallic sulfide demercuring agent to the scrubbing liquid is 3kg/m ³ , simulating the scrubbing liquid where c(H ⁺ )=15mol/L. The VM-3000 mercury measuring instrument was used to measure the mercury concentration in real time. The mass flowmeter accurately controlled the gas flow of each component to simulate the composition of the flue gas. The total gas flow was 1L/min, and the initial Hg ⁰ concentration was 2000±10μg/m ³ . Under the pure N ₂ atmosphere, the removal efficiency of Hg ⁰ by the metal sulfide mercury remover was 82.2% within 4h. When the simulated flue gas atmosphere was 2000ppm SO ₂ and ₅ %O ₂ and the carrier gas was N The average removal efficiency of Hg ⁰ by the metal sulfide adsorbent was 81.3%.

Example 5

The metal sulfide mercury removal agent 1 was added to the simulated flue gas scrubbing device, the set temperature of the cleaning solution was 25°C, the ratio of the addition amount of the metal sulfide mercury removal agent to the cleaning solution was 5kg/m ³ , and the cleaning solution used The actual smelting flue gas scrubbing liquid, the scrubbing liquid pH=1.7. The VM-3000 mercury measuring instrument was used to measure the mercury concentration in real time. The mass flowmeter accurately controlled the gas flow of each component to simulate the composition of the flue gas. The total gas flow was 1L/min, and the initial Hg ⁰ concentration was 1000±5μg/m ³ . Under pure _N2 atmosphere, the removal efficiency of Hg0 by metal sulfide mercury remover was 94.3% after ¹⁰ h. When the simulated flue gas atmosphere is 2000ppm SO ₂ , 5% O ₂ and the carrier gas is N ₂ , the average mercury removal efficiency of metal sulfide adsorbent for Hg ⁰ is 92.3% within 4h.

Example 6

Select a small amount of natural copper sulfide concentrate, vacuum dry at 120 °C for 12 hours, crush and screen the dried concentrate, and carry out selenization modification treatment by anion exchange method to obtain modified copper sulfide concentrate. The modified copper sulfide concentrate powder was tested. The modified copper sulfide concentrate powder was added to the simulated flue gas scrubbing device, the set temperature of the scrubbing solution was 25°C, and the ratio of the modified copper sulfide concentrate to the scrubbing solution was 2kg/m ³ , simulating scrubbing. The pH of the solution is 7. The VM-3000 mercury measuring instrument is used to measure the mercury concentration in real time. The mass flow meter accurately controls the gas flow of each component to simulate the composition of the flue gas. The total gas flow is 1L/min, and the initial Hg ⁰ concentration is 100±1μg/m3. Under pure N ₂ atmosphere, the removal efficiency of Hg ⁰ by metal sulfide mercury remover was higher than 93.8% within 10h.

Comparative Example 1

Select a small amount of natural copper sulfide concentrate, vacuum dry at 120 °C for 12 hours, crush and screen the dried concentrate, and take a certain amount of natural copper sulfide concentrate powder for experiment. The natural copper sulfide concentrate ore powder was added to the simulated flue gas scrubbing device, the set temperature of the scrubbing solution was 25 °C, the ratio of the added amount of natural copper sulfide concentrate to the scrubbing solution was 2kg/m ³ , and the simulated scrubbing solution was pH=7. The VM-3000 mercury measuring instrument was used to measure the mercury concentration in real time. The mass flowmeter accurately controlled the gas flow of each component to simulate the composition of the flue gas. The total gas flow was 1L/min, and the initial Hg ⁰ concentration was 100±1μg/m ³ . Under pure N ₂ atmosphere, the removal efficiency of Hg ⁰ by metal sulfide mercury remover was higher than 32.3% within 10 h.

Example 8

Using 3-5mm alumina pellets and sodium X-type zeolite as carriers, copper sulfate, ammonium sulfide, etc. as raw materials, a carrier-supported metal sulfide mercury removal agent was prepared by adding a carrier, impregnating, ultrasonicating, filtering, and drying. . The metal sulfide-loaded mercury remover was added to the simulated flue gas scrubbing device, the setting temperature of the washing liquid was 95 °C, and the ratio of the addition amount of the metal sulfide-loaded mercury remover to the washing liquid was 10kg/m ³ , simulating washing The pH of the solution is 7. The VM-3000 mercury measuring instrument was used to measure the mercury concentration in real time. The mass flowmeter accurately controlled the gas flow of each component to simulate the composition of the flue gas. The total gas flow was 1L/min, and the initial Hg ⁰ concentration was 200±2μg/m ³ . Under pure _N2 atmosphere, after 4 h, the removal efficiency of Hg ⁰ by alumina-type metal sulfide-supported mercury remover was 95.2%, and the removal efficiency of zeolite-type metal sulfide-supported mercury remover was 93.2 ^% .

Example 9

Using metal sulfide ^demercuring agent ¹ , an experiment was carried out in a small zinc smelting plant where the zinc smelting process was carried out. The discharge amount is 3.5mg/m ³ , the metal sulfide mercury removal agent is injected into the two-stage flue gas scrubber (dynamic wave scrubber), and the addition amount of the metal sulfide mercury removal agent is 15kg/m ³ , Hg ⁰ The removal efficiency is 99.9%.

The above embodiments are illustrative of the present invention, not limitations of the present invention. Any scheme after simple modification of the present invention belongs to the protection scope of the present invention.

Claims (9)

1. An application of metal sulfide mercury removing agent in washing and removing mercury in flue gas.

2. The application according to claim 1, characterized in that the application method is as follows: forming metal sulfide mercury removing agent into suspension in a washing device or a wet dust removal device, and removing Hg in flue gas⁰Conversion to stabilized mercury sulfide to realize Hg⁰And (4) washing and removing.

3. Use according to claim 2, characterized in that the metal sulphide mercury removing agent is selected from the group consisting of copper sulphide, molybdenum sulphide, sulphur

One or more of zinc sulfide, lead sulfide, manganese sulfide or iron copper sulfide.

4. Use according to claim 1, characterized in that the metal sulphide mercury removing agent is obtained by modification treatment of a natural sulphur-containing mineral.

5. The use according to claim 1, characterized in that the metal sulfide mercury removal agent is obtained by artificial synthesis by means of adding a surfactant; the surfactant is one or a combination of dodecyl trimethyl ammonium bromide, octadecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium bromide, dodecyl dimethyl benzyl ammonium bromide, potassium monododecyl phosphate, octadecyl amide methyl pyridine chloride or hydrazine.

6. Use according to claim 1, characterized in that the metal sulphide mercury removing agent is obtained by loading a metal sulphide on a support; the carrier is Fe₂O₃、Fe₃O₄、Al₂O₃One or a combination of molecular sieve, silicon dioxide, silicate, fly ash, zeolite, activated carbon or red mud.

7. The use according to claim 1, wherein the metal sulfide mercury removing agent is sprayed in a spraying manner before the flue gas scrubbing device or the wet dust removal device, or is directly added into the circulating scrubbing liquid of the flue gas scrubbing device or the wet dust removal device, and the metal sulfide mercury removing agent is suspended in water after being added to form a uniform suspension.

8. The use according to claim 7, wherein the flue gas scrubbing device or wet dust removal device is selected from one or a combination of a scrubber demercuration tower, a dynamic wave high efficiency scrubber, a packed tower scrubber, a venturi scrubber, a spray scrubber, a cyclone atomization chamber, a water film dust scrubber, a foam dust scrubber, an orifice scrubber, an impingement scrubber, a packed bed scrubber, an air cooling tower device.

9. The use according to claim 8, wherein the temperature of the scrubbing or dedusting liquid in the flue gas scrubbing or wet dedusting apparatus is 20-95 ℃, and the ratio of the addition amount of the metal sulfide mercury removal agent to the volume of the scrubbing or dedusting liquid is 0.1-100g/m³The washing liquid or dedusting liquid is acidic and neutral, wherein the acidity range is c (H)⁺)=10^-7-15mol/L。