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Method for catalytically oxidizing elemental mercury by oxidant controlledly released by porous ceramic membrane

A porous ceramic membrane and controlled release technology, which is applied in the field of environment and chemical industry, can solve the problems of waste, increased removal rate, and low HCl content, and achieve the effect of improving oxidation efficiency and inhibiting a large amount of loss

Inactive Publication Date: 2009-12-02
SHANGHAI JIAO TONG UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

The trace amount of HCl contained in the flue gas itself, under the action of an appropriate catalyst, will react to the Hg 0 It has a certain oxidation ability, but its most prominent problem is: Hg 0 The HCl content of flue gas with high content is often very low, and it is difficult for the catalyst to play a role in this case
Bromine (Br 2 ) as an oxidant loaded on the activated carbon, and then the bromine-loaded activated carbon is sprayed into the flue gas to reduce the Hg 0 Adsorption oxidation, this method can make Hg 0 The removal rate is significantly increased, however, this method still uses activated carbon, which cannot overcome the problems of conventional ACI technology; Cl can also be 2 or Br 2 Spray directly into the flue gas, and use the catalytic effect of fly ash to oxidize Hg 0 , at this time Hg 0 The oxidation of fly ash is mainly based on the catalytic reaction of fly ash. For the flue gas with low dust concentration, the treatment effect of this method is not ideal.
In addition, although Hg 0 The content in the flue gas is low, but in order to ensure the oxidation rate and efficiency, it is necessary to add more oxidants (about 10ppm), but the SO in the flue gas 2 The adsorption competition with the oxidant is obvious, resulting in most of the oxidants not being utilized (utilization rate <0.5%) and being wasted with the loss of flue gas
In addition, the catalytic activity of fly ash in flue gas itself is limited, and it is not ideal to rely solely on the catalytic effect of fly ash

Method used

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  • Method for catalytically oxidizing elemental mercury by oxidant controlledly released by porous ceramic membrane

Examples

Experimental program
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Effect test

Embodiment 1

[0029] Use γ-Al with a micropore diameter of 100nm 2 o 3 The ceramic membrane tube is used as the main body of the membrane module, namely figure 1 For the ceramic membrane diffusion layer (2) shown, the outer diameter of the ceramic membrane tube is 15 mm, and the outer surface is planar; a layer is prepared on the outer surface of the ceramic membrane tube by solution impregnation method figure 1 As shown in the catalyst layer (3), the catalyst layer is made of manganese oxide, and the mass fraction of the manganese load is 1.2%; one such ceramic membrane tube is placed in a glass tube with an inner diameter of 20mm to make a single tube structure Membrane components; figure 1 The oxidizing agent (X (g) ) selects HCl, which is introduced from the top of the ceramic tube, diffused and released from the membrane inner cavity (1) to the outer catalyst layer (3), and is adsorbed and enriched on the outer catalyst layer (3) to form an adsorbed oxidant (X (a) ); the diffusion ...

Embodiment 2

[0034] Adopt the gamma-Al of loading 1.2% manganese oxide used in embodiment 1 2 o 3 The ceramic membrane tube is used as the main body of the membrane module, namely figure 1 Shown ceramic membrane diffusion layer (2), utilizes 5 this ceramic pipes to make tubular ceramic membrane module reactor; Oxidant (X (g) ) choose Cl 2 , Cl 2 It enters from the top of the ceramic tube, and diffuses and releases from the membrane cavity (1) through the ceramic membrane diffusion layer (2) to the catalyst layer (3), so that it is enriched on the catalyst layer on the outer surface of the membrane tube, and Cl 2 The diffusion flux through the ceramic membrane is 1.0mmol / (m 2 h), the Cl diffused into the flue gas 2 The concentration is 0.8ppm.

[0035] Into the reactor into the zero-valent mercury concentration of 126μg / m 3 , gas volume of 200L / h, mercury-containing flue gas at 250°C, other components in the flue gas SO 2 500ppm, NO 50ppm, N 2 80%, CO 2 11%, O 2 7% and 2% water v...

Embodiment 3

[0038] Use γ-Al with a micropore diameter of 200nm 2 o 3 The ceramic flat plate is used as the main body of the membrane module. The ceramic flat plate is 400mm long, 150mm wide, and 16mm thick; a layer of cobalt oxide with a loading of 1.5% is prepared on the outer surface of the ceramic membrane by solution impregnation method as the catalytic active material, and the mass of cobalt Doped with 1% molybdenum as a reference.

[0039] A plate-type ceramic membrane module reactor is made by using 4 pieces of the above-mentioned ceramic plate tubes, and the distance between the plates is 8mm; bromine chloride (BrCl) is selected as the oxidant, and BrCl is passed into the ceramic plate and diffused to the catalyst layer outside the plate. Release, so that It is enriched on the catalyst layer on the outer surface of the plate, Cl 2 The diffusion flux through the ceramic membrane is 1.0mmol / (m 2 h), the BrCl concentration diffused into the flue gas is 0.8ppm.

[0040] The concen...

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Abstract

The invention relates to a method for catalytically oxidizing elemental mercury by an oxidant controlledly released by a porous ceramic membrane in the technical fields of environment and chemical industry. The method comprises the following steps: utilizing the porous ceramic membrane as a main body of a membrane module, of which the shape is tubular or platelike and the outer surface is flat or corrugated; preparing a catalyst layer on the outer surface of the ceramic membrane by one or more of a solution dipping method, a sol-gel method and a coprecipitation method; distributing a plurality of ceramic membrane units in a line mode in a flue or a device for assembling the membrane module, and directly contacting the catalyst layer on the outer surface of the ceramic membrane with flue gas; slowly controllably releasing the gaseous oxidant from the inside of the ceramic membrane to the outside catalyst layer through an air distributing box; and highly effectively oxidizing the elemental mercury through the activation of the catalyst and the enrichment function of the oxidant on the catalyst layer, and removing the elemental mercury by a lower desulfurizing installation or dedusting device. The method realizes catalytic oxidization of the elemental mercury in the flue gas in the condition of not increasing main equipment, can control and save the dosage of the oxidant, and reduces cost.

Description

technical field [0001] The invention relates to a catalytic oxidation method in the technical fields of environment and chemical industry, in particular to a method for catalytic oxidation of zero-valent mercury by controlling the release of oxidants by porous ceramic membranes. Background technique [0002] Coal burning is one of the main causes of mercury pollution, following SO 2 And after NOx, mercury has gradually become an air pollutant that must be controlled. Flue gas mercury removal is the main way to control mercury emissions from coal combustion. Mercury is usually present in flue gas as particulate mercury (Hg P ), gaseous divalent mercury (Hg 2+ ) and gaseous zerovalent mercury (Hg 0 ) in three forms. Among them, Hg 0 It accounts for 20-80% of the total mercury in flue gas, and its content is mainly related to the chlorine content in coal combustion. The first two forms of mercury are relatively easy to control: particulate mercury can be removed by dust ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B01D53/86B01D53/64
Inventor 晏乃强郭永福乔少华瞿赞
Owner SHANGHAI JIAO TONG UNIV
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