CN1081123A - 烟道气低温脱氮 - Google Patents

烟道气低温脱氮 Download PDF

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CN1081123A
CN1081123A CN93105668A CN93105668A CN1081123A CN 1081123 A CN1081123 A CN 1081123A CN 93105668 A CN93105668 A CN 93105668A CN 93105668 A CN93105668 A CN 93105668A CN 1081123 A CN1081123 A CN 1081123A
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catalyst
low temperatures
flue gas
nitrogen
tetrafluoroethene
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S·布鲁里齐
B·恩格勒
L·昆泽
S·劳苯思坦
E·泼兹素斯
H·姆勒
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    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
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    • B01J23/20—Vanadium, niobium or tantalum
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    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
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    • B01J23/30—Tungsten

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Abstract

本发明的目的是提供一种在低温下从烟道气中 脱氮的催化剂。本身已知的DENOX催化剂在低温 下从烟道气中脱氮的活性可通过赋予它憎水性而得 到改善。

Description

本发明涉及一种用选择性催化还原（SCR）法在低温下从烟道气中脱氮的催化剂，以及一种制备这种催化剂的方法和一种使用该催化剂在低温下脱氮的方法。
如果要取得对不断增长的环境污染斗争的胜利，那么就必需研究每一种可能的途径，以减少排放量。空气污染的主要原因是各种由矿物燃料生产机械能或热能的燃烧过程。氮氧化物是产生酸雨的原因之一，它们属由这些燃烧过程产生的污染物之列。选择性催化还原法（SCR法）已广泛用于从锅炉燃料燃烧装置的烟道气中脱除氮氧化物。该法需要的催化剂已在如DE3740289、DE3841990和DE3906136中，也在US4085193中公开。它们称为DENOX催化剂。
五氧化二钒、各种掺杂的沸石还有铁用作催化活性组分。但要求任何一种催化剂应在特定的操作温度范围内起作用。在高温下由于催化剂老化加速而引起一些问题，而在低温下由于活性中心被例如铵盐或与水相互作用遮蔽而出现失活。这样的失活通常是可逆的，即遮蔽物质可通过加热催化剂而驱出。但是，为此必须安装所需的加热设备，且必须在烟道气净化装置中间歇操作。
所需设备的投资和操作费用是相当高的，以致这一技术仅仅在特殊情况下使用。
废料焚烧装置产生特别不利于DENOX催化剂的条件废气。现在的废料焚烧炉烟道气净化装置的特点是要求实际上完全从废气中脱除所有的有害物质。已证明由各种类型碳过滤器（活性炭/平炉焦）或装有石灰-活性炭混合物的纤维过滤器（悬浮流法）组成的净化段能较好地达到这一目的。这些过滤器一般在80～160℃下操作，优选的是100～140℃。已显现出，采用选择性催化还原法时，这些过滤器脱氮段下游能很有效的操作，因为废气中含有很少量的氧化硫潜含量，因此排除了催化剂被铵盐遮蔽的危险。但是，业已发现，烟道气中的水含量（它一般较高（＞25体积%））可引起活性下降。
所以本发明的目的是提供一种有脱氮活性，甚至当废气的水含量较高时仍维持最大可能的脱氮活性不变的催化剂。本发明的另一目的是说明一种制备该催化剂的方法以及一种用这种催化剂在低温下脱氮的方法。
按照本发明，第一个目的是通过本身已知的DENOX催化剂的憎水性浸渍的方法来实现。用来使催化剂产生憎水性的试剂必须满足特殊的标准。它一定不含催化剂毒物或催化剂多孔结构的阻塞物。而且它应在高达350℃的温度下维持它的作用。已证明四氟乙烯适合作为这种试剂，它能给予憎水性并满足上述这些要求。按照本发明，催化剂用以下步骤制备：用在四氟乙烯悬浮液中一步或多步浸渍的方法，用四氟乙烯浸渍DENOX催化剂;在120℃下干燥，然后在350℃、空气流中人工老化3小时。该催化剂安装在通常用于烟道气净化的过滤器的烟道气下游，以便在低温下从烟道气中脱氮。烟道气仍含有的氮氧化物，加上还原剂（优选氨）在130～350℃下在本发明的催化剂上还原成氮和水。
已变成憎水的催化剂也已从DE3735758中知道。这些催化剂是掺杂有贵金属，并载于活性炭上的催化剂，用于在至多60℃下，在含水介质中（处加氢气）还原氧。在该说明书中给出的实验结果未指出，已变成憎水的催化剂在含水介质中还原氧有任何特别的优点。所以，当DENOX催化剂变成憎水的催化剂时，它们对低温下从烟道气中脱氮有正的影响。这一点对本技术领域熟练的人员来说更是令人吃惊的和意想不到的。与未处理的催化剂相比，已进行憎水处理的催化剂在130～350℃范围内其活性显示出显著的优点。
下面借助一些实施例更详细的说明本发明。其中：
图1为对比催化剂和本发明的催化剂催化的NOX转化率随合成气中水含量的变化。
图2为对比催化剂和本发明催化剂催NOX转化率随中试装置烟道气中水含量的变化。
图3为对比催化剂和本发明的催化剂催化的NOX转化率随中试装置烟道气的温度的变化。
对比实施例1
对比催化剂的制备
按照DE3906136中实施例5给出的制法制备整块蜂窝状的对比催化剂TiO2/WO3/V2O5，成固体催化剂。
实施例1
本发明催化剂的制备
按对比实施例1制备的催化剂用一步浸渍法在5重量%的四氟乙烯粉悬浮液（粒度30微米，30WexDu        Pont）中浸渍。然后催化剂在120℃下干燥，并在350℃、空气流中人工老化3小时。
实施例2
催化剂在合成气试验装置中试验
在合成气试验装置中，通过改变合成气中的水含量（表1），测定对比催化剂和本发明催化剂的NOX转化活性水平。
活性测定结果列入表2，并在图1中图示。对比催化剂的活性曲线表明，一旦水含量超过15%活性就明显下降。水含量为30%时对比催化剂的活性仅保留一半。为了补偿这一活性损失，在烟道气净化装置中必须使用两倍体积的催化剂。另一方面，本发明的催化剂仍保持其活性，而与水含量无关。
实施例3
在不同的烟道气水含量下在中试装置上的活性试验。
在天然气炉下游中试装置上，在现场条件下测试催化剂。烟道气的体积流速为75标米3/小时，对应于空速为16500小时-1。NOX进口浓度在520～560ppm之间变化。取决于操作条件。
开始天然气炉的废气中水的浓度为14体积%，通过注水蒸汽的方法使烟道气中的水含量增加到62体积%。在用NH3/NOX摩尔比为0.78和在160℃下进行的这些实验中，本发明的催化剂的NOX转化率明显高于对比催化剂。这些结果图示在图2中。
实施例4
在不同的烟道气温度下在中试装置上的活性试验。
图3给出在烟道气温度为130～250℃下在中试装置上测定的NOX转化结果。在这些实验中水含量（14%）在最小差范围内，而NH3/NOX摩尔比固定在1.0。尽管水含量较低，仍可观测到催化剂的性能有明显的差别。当烟道气温度低于130℃时，由于它们的活性过低，在这样的温度下使用这些催化剂在经济上不再可行，因为要达到可接受的NOX转化率，必须使用很大体积的催化剂。在250℃以上，按照本发明用四氟乙烯浸渍的催化剂超过对比催化剂的优点变得越来越不明显。四氟乙烯在350℃以上开始熔化，因此使催化剂的活性下降。而且，那样处理来赋予憎水性没有多大意义，因为这些表面在这样的温度下水的吸附实际上停止了。
但是，本发明的催化剂在所要求的温度范围内已给出明显优于先有技术的对比催化剂的性能。
Figure 931056683_IMG2

Claims (4)

1、一种在低温下从烟道气中脱氮的催化剂，它含有本身已知的DENOX催化剂，其特征在于，该催化剂赋有憎水性涂料。
2、按照权利要求1的催化剂，其特征在于，该催化剂用四氟乙烯涂覆。
3、一种制备权利要求1的催化剂的方法，其特征在于，本身已知的DENOX催化剂通过在四氟乙烯悬浮液中一步或多步浸渍的方法用四氟乙烯浸渍，在130℃下干燥，然后在350℃、空气流中人工老化3小时。
4、一种在低温下从烟道气中脱氮的方法，其特征在于，要处理的烟道气用碳或纤维过滤器净化，然后外加还原剂（优选的是氨），仍含有的氮氧化物在130～350℃下，在权利要求1的催化剂上还原成氮气和水。
CN93105668A 1992-05-12 1993-05-11 烟道气低温脱氮 Pending CN1081123A (zh)

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DEP4215582.7 1992-05-12
DE4215582A DE4215582C1 (de) 1992-05-12 1992-05-12 DENOX - Katalysator für die Tieftemperatur-Entstickung von Rauchgasen

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Cited By (2)

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CN109225248A (zh) * 2018-08-09 2019-01-18 江苏龙净科杰环保技术有限公司 蜂窝式低温脱硝催化剂及其制备工艺
CN112789106A (zh) * 2018-10-02 2021-05-11 巴斯夫欧洲公司 在包含催化剂颗粒的膜存在下在流体相中进行化学反应的方法

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AT399829B (de) * 1994-03-11 1995-07-25 Austrian Energy & Environment Verfahren zur abscheidung von schwefeltrioxid und zum betreiben einer katalytischen entstickungsanlage
US5620669A (en) * 1995-08-15 1997-04-15 W. L. Gore & Associates, Inc. Catalytic filter material and method of making same
TWI242464B (en) * 1997-07-09 2005-11-01 Babcock Hitachi Kk Denitration catalyst, process for preparing the same, and exhaust gas purification method
JP2003220317A (ja) * 2002-01-30 2003-08-05 Mitsubishi Heavy Ind Ltd 燃焼排ガスの処理方法およびそのシステム
US11541380B2 (en) 2020-09-23 2023-01-03 Southwest Research Institute Superhydrophobic coatings for deposit reduction in selective catalytic reductant systems
WO2024196637A1 (en) * 2023-03-17 2024-09-26 W. L. Gore & Associates, Inc. In-situ regeneration of filter medium for improving catalytic efficiency

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CA1200540A (en) * 1983-10-24 1986-02-11 Atomic Energy Of Canada Limited - Energie Atomique Du Canada, Limitee Method of manufacturing a crystalline silica/platinum catalyst structure
DE3544320A1 (de) * 1985-12-14 1987-08-27 Rennebeck Klaus Kaskaden-sequenzkatalysation mit katalysator-serienschaltung in abhaengigkeit zur reaktionstemperatur
DE3713169A1 (de) * 1987-04-17 1988-11-03 Bayer Ag Verfahren und vorrichtung zur reduktion von stickoxiden
CA1301400C (en) * 1987-11-09 1992-05-19 Sellathurai Suppiah Porous composite materials and methods for preparing them
DE3735758A1 (de) * 1987-10-22 1989-05-03 Degussa Verfahren zur katalytischen reduktion von sauerstoff in waessrigen medien
CA1295813C (en) * 1988-12-14 1992-02-18 Karl T. Chuang Reduction of nitrogen oxides

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Publication number Priority date Publication date Assignee Title
CN109225248A (zh) * 2018-08-09 2019-01-18 江苏龙净科杰环保技术有限公司 蜂窝式低温脱硝催化剂及其制备工艺
CN109225248B (zh) * 2018-08-09 2021-03-16 江苏龙净科杰环保技术有限公司 蜂窝式低温脱硝催化剂及其制备工艺
CN112789106A (zh) * 2018-10-02 2021-05-11 巴斯夫欧洲公司 在包含催化剂颗粒的膜存在下在流体相中进行化学反应的方法

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