CN104226300A - SCR (Selective Catalytic Reduction) catalyst and preparation method thereof - Google Patents

Abstract

The invention provides an SCR (Selective Catalytic Reduction) catalyst which is prepared from the following raw materials in parts by weight: 85-95 parts of TiO2, 3-5 parts of WO3, 1-3 parts of V2O5, 5-8 parts of glass fibers, 5-10 parts of ammonia water, 8 parts of CMC, 50 parts of ionized water and 6 parts of RP-CHOP functional fibers. The catalyst provided by the invention has the characteristics of high low-temperature activity and high denitration efficiency and also has excellent compressive property and wear resistance. The invention also provides a method for preparing the catalyst.

Description

A kind of SCR catalyst and preparation method thereof

Technical field

The present invention relates to a kind of industrial catalyst, be specifically related to the denitrating catalyst in a kind of SCR, especially vanadium Titanium series catalyst, and preparation method thereof.

Background technology

Nitrogen oxide is one of main atmosphere pollution, and be the main cause causing acid rain, photochemical fog, it also has important function to the aggravation of greenhouse effects and the destruction of ozone layer.Current flue gases purification, namely remove the technology of the nitrogen oxide in flue gas, mainly comprise wet method denitrogenation, catalytic decomposition, solid absorption method, liquid absorption method, plasma activation method, microbial method, SNCR and SCR (SCR) etc.Wherein, SCR is considered to best flue-gas denitrification technology, and its application is also extensive, and reduction of nitrogen oxide mainly, under certain special catalyst existent condition, is optionally become nitrogen and water with reducing agents such as ammonia by this technology.

Core in SCR technology is catalyst, and it is generally made up of base material, carrier and active component.The feature that excellent SCR catalyst should have comprises: high activity, high selectivity, mechanical strength and mar proof that anti-poisoning capability is strong, good, have suitable operation interval, life-span long, cost low etc.The catalyst of current this area extensive use is vanadium Titanium series catalyst (V ₂o ₅/ TiO ₂, V ₂o ₅-WO ₃/ TiO ₂), its active temperature is 250-450 DEG C, but the type catalyst exists problems in the application, and be mainly manifested in catalytic mechanical poor performance, compression strength is low, and causes unnecessary energy waste because active temperature is higher.Therefore be necessary to improve further the low temperature active of SCR catalyst, resistance to compression and the performance such as wear-resisting.

Summary of the invention

Primary and foremost purpose of the present invention is: provide a kind of catalyst for SCR technique, has the advantages that good, the out of stock efficiency of low temperature active is high, has good resistance to compression and anti-wear performance simultaneously.

Another object of the present invention is: the method providing the catalyst described in preparation.

Above-mentioned purpose of the present invention is achieved through the following technical solutions:

First, provide a kind of SCR catalyst, by weight, it is prepared from by following raw material: 85 ~ 95 parts of TiO ₂, 3 ~ 5 parts of WO ₃, 1 ~ 3 part of V ₂o ₅, 5 ~ 8 parts of glass fibres, 5 ~ 10 parts of ammoniacal liquor, 8 parts of CMCs (CMC), 50 parts of ionized waters and 6 parts of RP-CHOP functional fibres.

SCR catalyst of the present invention, by weight, is preferably prepared from by following raw material: 88 ~ 90 parts of TiO ₂, 4 parts of WO ₃, 2 parts of V ₂o ₅, 6 parts of glass fibres, 8 parts of ammoniacal liquor, 8 parts of CMC, 50 parts of ionized waters and 6 parts of RP-CHOP functional fibres.

The present invention also provides the method for the SCR catalyst described in preparation, comprises the following steps:

1) mixed according to described ratio by described raw material, then place under normal temperature, normal pressure and deposit rotten more than 36 hours, until matter homogenizing, moisture is balanced;

2) by step 1) process the material that obtains and carry out pre-extruded and cross leakage, then enter in forming machine shaping;

3) by step 2) shaping product through super-dry until moisture content be placed on 600 ~ 650 DEG C lower than 5% at calcining 8 ~ 12 hours, preferably by step 2) shaping product first through primary drying to moisture be 10%, again through redrying to moisture be 5%, then calcine 8 ~ 2 hours at being placed in 620 DEG C, namely obtain SCR catalyst of the present invention.

In catalyst raw material of the present invention, RP-CHOP functional fibre belongs to existing commercially available prod, can be buied by Zhong Ding economic development Co., Ltd of Wuhan City.

SCR catalyst of the present invention belongs to the vanadium Titanium series catalyst (V of improvement ₂o ₅/ TiO ₂catalyst), in its raw material, TiO ₂carrier components, V ₂o ₅form activated centre, WO ₃as auxiliary element, glass fibre serves the effect improving product mechanical performance, and CMC can play good dispersion, thickening and stable effect, and RP-CHOP functional fibre can play bonding effect, thus improves product mechanical performance.Described raw material components is prepared into SCR catalyst according to special ratios by the present invention, through experimental verification, obtains excellent low temperature active and resistance to compression and anti-wear performance, for obtaining the out of stock efficiency of more than 95% in SCR technique.

Compared with prior art, catalyst of the present invention has excellent low-temperature catalytic activity, scuff resistance, compression strength, denitration efficiency simultaneously.

Accompanying drawing explanation

Fig. 1 tests sample activity, SO in effect experimental examples ₂/ SO ₃the experimental bench structural representation that conversion ratio, resistance, cell cube denitration rate and the escaping of ammonia are used.

Fig. 2 tests sample tear strength test platform structure schematic diagram used in effect experimental examples.

Detailed description of the invention

The present invention is further described below by way of specific embodiment.

Embodiment 1

A kind of SCR catalyst, by weight, it is prepared from by following raw material: 90 parts of TiO ₂, 4 parts of WO ₃, 2 parts of V ₂o ₅, 6 parts of glass fibres, 8 parts of ammoniacal liquor, 8 parts of CMC, 50 parts of ionized waters and 6 parts of RP-CHOP functional fibres.

Concrete preparation method is as follows:

1) described raw material is mixed according to described ratio, then deposit rotten 40 hours;

2) by step 1) deposit rotten good material and carry out pre-extruded and cross leakage, then enter in forming machine shaping;

3) by shaping product through primary drying and redrying, until moisture content reaches 5%, then enter kiln be built in 620 DEG C at calcining 12 hours;

4) by step 3) burned product carries out cutting and then classification packing puts in storage.

The catalyst elements body of the honeycomb fashion that the present embodiment prepares, through calculating: length 801mm, inner wall thickness 1.05mm, outer wall thickness 2.24mm, aperture 5.56mm, percent opening 66.4%, geometric proportion surface area 478.0m ²/ m ³.

Embodiment 2

A kind of SCR catalyst, by weight, it is prepared from by following raw material: 85 parts of TiO ₂, 5 parts of WO ₃, 1 part of V ₂o ₅, 8 parts of glass fibres, 5 parts of ammoniacal liquor, 8 parts of CMC, 50 parts of ionized waters and 6 parts of RP-CHOP functional fibres.

Concrete preparation method is as follows:

1) described raw material is mixed according to described ratio, then deposit rotten 50 hours;

2) by step 1) deposit rotten good material and carry out pre-extruded and cross leakage, then enter in forming machine shaping;

3) by shaping product through primary drying and redrying, until moisture content reaches 5%, then enter kiln be built in 620 DEG C at calcining 12 hours;

4) by step 3) burned product carries out cutting and then classification packing puts in storage.

Embodiment 3

A kind of SCR catalyst, by weight, it is prepared from by following raw material: 95 parts of TiO ₂, 3 parts of WO ₃, 3 parts of V ₂o ₅, 5 parts of glass fibres, 10 parts of ammoniacal liquor, 8 parts of CMC, 50 parts of ionized waters and 6 parts of RP-CHOP functional fibres.

Concrete preparation method is as follows:

1) described raw material is mixed according to described ratio, then deposit rotten 50 hours;

2) by step 1) deposit rotten good material and carry out pre-extruded and cross leakage, then enter in forming machine shaping;

3) by shaping product through primary drying and redrying, until moisture content reaches 5%, then enter kiln be built in 620 DEG C at calcining 12 hours;

4) by step 3) burned product carries out cutting and then classification packing puts in storage.

Effect experimental examples

Activity, SO is carried out as test sample using catalyst prepared by the embodiment of the present invention ₂/ SO ₃the detection of conversion ratio, resistance, and the detection of cell cube denitration rate and the escaping of ammonia, all carry out on the experimental bench shown in Fig. 1.

This experimental bench is made up of gas generation, distribution mixing, gas-heated, reactor and transfer valve group, control and the unit block such as detection, vent gas treatment.Experimental bench can complete, simulate the flue gas condition of catalyst in true SCR denitration equipment exactly, that is: air speed, temperature, NO, SO ₂, SO ₃, NH ₃, humidity, oxygen amount etc.Experimental bench test samples is full-scale, i.e. the actual catalyst elements body used.Experimental bench can meet the needs of SCR reactor " 3+1 " layer catalyst arrangement pattern, can detect at most 4 catalyst elements bodies of different layers in a reactor simultaneously.Experimental bench simulation air speed can meet the demand of 100MW grade unit exhaust gas volumn.Experimental bench is equipped with gas mass and flow control device, can accuracy controlling simulated flue gas flow, and the concentration of wherein each kind of component gas.Shell of reactor and connecting line lay electric with worm line, maintains reactor and work under temperature constant state.Experimental bench is equipped with special steam generator, for simulated flue gas provides quantitative water vapour.

Before entering formal detection (data acquisition), original catalyst sample logical flue gas in reactor carries out " aging " process for 36 hours.In addition, when flue gas condition changes, at least stablize after one hour and carry out image data.Data acquisition is carried out at reactor import and export, and the cycle is 2 ~ 3 hours.

This main design parameters detecting sample sees the following form 1:

Table 1 detection design parameter

It is as shown in table 2 that this detects operating mode.

Operating mode surveyed by table 2

In table: Ugs: void tower mobility, flue gas flow (m ³/ h) and catalyst sectional area (m ²) ratio;

¹: SO ₂=3132.9mg/m ³(butt, 6%O ₂);

²: NOx=299.4mg/m ³(butt, 6%O ₂)

Specific analytical method is as follows:

1.NO and O ₂analyze

Adopt 42i and the 43i model flue gas analyzer of U.S. Thermo, NO is measured as non-dispersive infrared method, O ₂be measured as paramagnetic method.The range of NO analyzer is 0 ~ 1000 μ L/L, precision≤± 1%.Before flue gas enters analyzer, through filtrating smoke dust and dehumidification treatments.

NOx concentration computational methods:

${\mathrm{NO}}_x\left({\mathrm{mg}/m}^3\right)=\frac{\mathrm{NO}(\mathrm{\μL}/L)}{0.95}\×2.05\×\frac{21-6}{{21-O}_2}$

In formula:

NOx: standard state, NOx concentration under 6% oxygen amount, dry flue gas, m _g/ m ³;

NO: NO volume content in actual measurement dry flue gas, μ L/L;

O ₂: oxygen content in actual measurement dry flue gas, %;

0.95: (in NOx, NO accounts for 95%, NO to empirical data ₂account for 5%);

2.05:NO ₂by volume content μ L/L to mass content mg/m ³conversion coefficient.

2.SO ₂analyze

SO ₂employing chemical method is measured, and smoke sampling follows Environmental Protection Agency (EPA) Method-6.Adopt hydrogen peroxide absorption process to carry out smoke sampling, simultaneously metering sampling flue gas flow and time, sample point is at reactor inlet.Use SO in ion chromatograph (ThermoFisher ICS1100) analytical sample ₂content, and calculate SO in flue gas according to flue gas flow ₂concentration.Whole detection-phase repeatedly sampling and measuring, results averaged.

3.SO ₃analyze

SO ₃employing chemical method is measured.With reference to ASTM D-3226-73T, SO ₃sampling adopts temperature control coagulation, by SO within the scope of 65 ~ 100 DEG C ₃be separated from flue gas stream and sample, simultaneously metering sampling flue gas flow and time, sample point is located at import and the outlet of catalyst elements body.Use SO in ion chromatograph (ThermoFisher ICS1100) analytical sample ₃content, and calculate SO in flue gas according to flue gas flow ₃concentration.Whole detection-phase repeatedly sampling and measuring, results averaged.

4.H ₂o analyzes

H ₂o adopts condensation method to measure.H ₂o sampling adopts temperature control coagulation, at ice-water bath by H ₂o is separated and samples from flue gas stream, and simultaneously metering sampling flue gas flow and time, sample point is located at Reactor inlet and outlet.

Denitration efficiency calculates:

$\mathrm{\η}=\frac{C_1-C_2}{C_1}$

In formula:

η: the denitration efficiency of catalyst elements body, %;

C ₁: reactor inlet NOx concentration, gaseous volume ratio, butt, 6%O ₂, mg/m ³;

C ₂: reactor outlet NOx concentration, gaseous volume ratio, butt, 6%O2, mg/m ³.

SO ₂/ SO ₃conversion ratio calculates:

$X=\frac{S_{3o}-S_{3i}}{S_{2i}}\×100$

In formula:

X: the SO of catalyst elements body ₂/ SO ₃conversion ratio, %;

S ₃o: reactor outlet SO ₃concentration, gaseous volume ratio, butt, μ L/L;

S ₃i: Reactor inlet SO ₃concentration, gaseous volume ratio, butt, μ L/L;

S ₂i: Reactor inlet SO ₂concentration, gaseous volume ratio, butt, μ L/L.

This tests SO ₂/ SO ₃conversion ratio results of measuring is as shown in table 3 below:

Table 3

Active calculating:

According to the ammonia nitrogen mol ratio (MR) of surveying, denitration efficiency (η) and face velocity (AV), calculated the catalyst activity K detected under flue gas condition by following formula.

$K=0.5\×\mathrm{AV}\×\ln \frac{\mathrm{MR}}{(\mathrm{MR}-\mathrm{\η})\×(1-\mathrm{\η})}$

In formula:

K: the activity of catalyst elements body, m/h;

AV: face velocity, the ratio of flue gas flow and total geometrical surface of catalyst elements body, m/h;

MR: ammonia nitrogen mol ratio.

The active results of measuring of this detecting catalyst is as shown in table 4 below:

Table 4

5.NH ₃analyze

NH ₃employing chemical method is measured.Adopt H ₂sO ₄for absorbent solution gathers sample, simultaneously metering sampling flue gas flow and time, sample point is located at reactor outlet.Ion chromatograph (DIONEX ICS1100) is used to analyze NH ₃content, and calculate NH in flue gas according to flue gas flow ₃concentration.Whole detection-phase repeatedly sampling and measuring, results averaged.

The escaping of ammonia is converted:

The escaping of ammonia following formula converts benchmark oxygen content (6%O by actual oxygen amount ₂).

$C_{{\mathrm{NH}}_3}={C^{\′}}_{{\mathrm{NH}}_3}\×\frac{21-6}{21-{O^{\′}}_2}$

In formula:

C _nH3: conversion is to benchmark oxygen content (6%O ₂) under the escaping of ammonia, μ L/L;

C' _nH3: the escaping of ammonia of actual measurement, μ L/L;

O' ₂: the oxygen amount of actual measurement, %.

Out of stock efficiency, the escaping of ammonia results of measuring of this detecting catalyst are as shown in table 5 below:

Table 5

6. resistance

Before and after SCR reactor import and export, all pressure-measuring-point is housed, carry out catalyst drag measurement by differential manometer, result is as shown in table 6 below:

Table 6

7. compression strength

Compression strength detects and adopts microcomputer controlled electronic pressure testing machine, and INSTRUMENT MODEL is CDT1305.

This specimen size is 150mm × 150mm × 150mm.Be that the catalyst sample of 150mm is fixed on testing machine by length, the axis and radial section of sample apply pressure, the compression strength of calculation of pressure sample during by detecting sample burst.Testing machine utilizes oil cylinder piston to be elevated, and piston movement drives monitor station to exert a force to sample, thus realizes the compression to sample.The closed loop servo-control system be jointly made up of electric controller, load sensor, computer, automatically and accurately Control experiment process, and automatic detection record test parameters.

The compressive strength determination result of this detecting catalyst is as shown in table 7 below:

Table 7

8. tear strength

Tear strength detects and adopts the testing stand shown in Fig. 2.Be 60 ~ 80mm from same cell cube intercepted length and width, be highly two pieces of samples of 100 ± 2mm, respectively as test sample and comparative sample, be placed in the dry 2h of constant temperature oven of 105 DEG C ± 2 DEG C, take out and weigh after naturally cooling to room temperature, sample loads bypass sample pipe on testing stand and test sample pipe.After the sealing of sample surrounding, pass into the air-flow of same flow velocity in two pipelines, wherein contain the wearing and tearing agent of certain particle size and concentration in testing conduit air-flow, without wearing and tearing agent in bypass duct, duration of test runs is 2 hours.After being completed, taking out two samples and again weigh, collect the abrasive material by sample simultaneously and weigh.

Testing conditions is as follows:

Sample size: 10 × 10 holes

Air velocity: 15.0m/s

Abrasive concentration in air-flow: 50 ± 5g/m ³

Average grain diameter: 40-50 order

Wearing and tearing agent: quartz sand

Tear strength calculates:

${\mathrm{\ξ}}_h=\frac{[1-\frac{W_2}{W_1}\×\frac{W_3}{W_4}]}{W}\×100$

Wherein:

ξ _h: the tear strength of cellular catalyst, %/kg;

W ₁: quality (g) before test sample test;

W ₂: weight (g) after test sample test;

W ₃: quality (g) before comparative sample test;

W ₄: quality (g) after comparative sample test;

W: wearing and tearing agent quality (kg).

The tear strength that above-mentioned computational methods obtain reflects the wear rate of the catalyst sample caused by the abrasive material of unit mass.This index reflects the relative wear intensity of catalyst, and the numerical value of tear strength shows that more greatly the wearability of catalyst is poorer.

The tear strength measurement result of this detecting catalyst is as shown in table 8 below:

Table 8

Claims (4)

1. a SCR catalyst, is characterized in that, by weight, it is prepared from by following raw material: 85 ~ 95 parts of TiO ₂, 3 ~ 5 parts of WO ₃, 1 ~ 3 part of V ₂o ₅, 5 ~ 8 parts of glass fibres, 5 ~ 10 parts of ammoniacal liquor, 8 parts of CMC, 50 parts of ionized waters and 6 parts of RP-CHOP functional fibres.

2. SCR catalyst according to claim 1, is characterized in that, by weight, is prepared from by following raw material: 88 ~ 90 parts of TiO ₂, 4 parts of WO ₃, 2 parts of V ₂o ₅, 6 parts of glass fibres, 8 parts of ammoniacal liquor, 8 parts of CMC, 50 parts of ionized waters and 6 parts of RP-CHOP functional fibres.

3. prepare the method for SCR catalyst according to claim 1, comprise the following steps:

1) mixed according to described ratio by described raw material, then place under normal temperature, normal pressure and deposit rotten more than 36 hours, until matter homogenizing, moisture is balanced;

2) by step 1) deposit rotten good material and carry out pre-extruded and cross leakage, then enter in forming machine shaping;

3) by step 2) shaping product until moisture content calcines 8-12 hour at being placed on 600 ~ 650 DEG C lower than 5%, namely obtains described SCR catalyst through super-dry.

4. method according to claim 3, is characterized in that: described step 3) be by step 2) shaping product is first 10% through primary drying to moisture, then is 5% through redrying to moisture, calcine 8 ~ 2 hours at being then placed in 620 DEG C.