CN115324693A - 一种适用于船舶天然气发动机的在线生成氨气的废气脱硝***及控制方法 - Google Patents
一种适用于船舶天然气发动机的在线生成氨气的废气脱硝***及控制方法 Download PDFInfo
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- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims description 97
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- 229910052763 palladium Inorganic materials 0.000 claims description 48
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Abstract
本发明的目的在于提供一种适用于船舶天然气发动机的在线生成氨气的废气脱硝***及控制方法,包括发动机、天然气储罐、燃料重整器、钯基催化器、脱硝反应器,天然气储罐连接发动机的进气管,所述燃料重整器包括第一进气口、第二进气口、第一出气口、第二出气口,第一进气口连接天然气储罐,第二进气口连接发动机的排气管,第一出气口连接发动机的进气管,第二出气口连接钯基催化器,钯基催化器和脱硝反应器沿着排气方向串联导通。本发明不需额外的尿素储罐,低成本、无尿素控制,通过控制不同阀门的开闭实现了被动的生成氨气,降低了NOx的排放。
Description
技术领域
本发明涉及的是一种发动机废气处理***和控制方法,具体地说是船舶天然气发动机废气处理***和控制方法。
背景技术
随着航运业的发展,船舶产生的大量污染物对大气和海洋环境造成了严重的破坏,限制船舶动力装置污染物,尤其是NOx的排放己成为世界共识。世界各国和国际组织(IMO)相继制定了法规来限制污染物的排放,规定在2016年以后,低速柴油机NOx的排放限值在指定排放控制区(ECA)降为3.4g/(kWh)。
目前,控制船舶柴油机排气中NOx排放量的技术主要分机内净化和机外净化两个方面。替代燃料在降低污染物排放方面有很大的潜力,研究表明液化天然气(LNG)具有良好的排放特性,但火焰传播速率慢等缺点。目前在天然气中掺氢是提高火焰传播速率的一个重要方法,同时还可以扩宽稀燃极限,进一步节省燃料,而天然气重整制氢为天然气掺氢以强化燃烧提供了新的解决方案。后处理技术也可以有效的去除氮氧化物,目前选择性催化还原技术(SCR)可以满足IMO Tier III或更严格排放标准。SCR技术是利用尿素热解生成氨气,然后氨气和氮氧化物发生化学反应,然后生成氮气和水。随着排放法规的日益严格,单一的控制措施已很难满足排放要求,新型燃料和后处理技术结合才是减少污染物排放的有效措施。
针对目前的SCR***,主要存在的问题是尿素SCR***需要一个尿素储存罐和一个尿素喷射***,尿素需要定期补充,因此SCR的运行成本较高,除此之外还需要制定合适的尿素喷射策略,以达到利用最少的尿素实现最大的脱硝效率的目的,对于小型船舶来说尿素的储存和喷射控制装置无疑会占据船舶的大部分空间。
发明内容
本发明的目的在于提供不需额外的尿素储罐,低成本、无尿素控制的一种适用于船舶天然气发动机的在线生成氨气的废气脱硝***及控制方法。
本发明的目的是这样实现的:
本发明一种适用于船舶天然气发动机的在线生成氨气的废气脱硝***,其特征是:包括发动机、天然气储罐、燃料重整器、钯基催化器、脱硝反应器,天然气储罐连接发动机的进气管,所述燃料重整器包括第一进气口、第二进气口、第一出气口、第二出气口,第一进气口连接天然气储罐,第二进气口连接发动机的排气管,第一出气口连接发动机的进气管,第二出气口连接钯基催化器,钯基催化器和脱硝反应器沿着排气方向串联导通。
本发明一种适用于船舶天然气发动机的在线生成氨气的废气脱硝***还可以包括:
1、天然气储罐与发动机的进气管之间安装第一阀,天然气储罐与燃料重整器之间安装第二阀,燃料重整器与发动机的排气管之间安装第三阀,燃料重整器与发动机的进气管之间安装第四阀,燃料重整器与钯基催化器之间安装第五阀,钯基催化器入口设有第一NOx传感器,钯基催化器和脱硝反应器之间依次设有氨气传感器和温度传感器,脱硝反应器出口处设有第二NOx传感器;第一阀、第二阀、第三阀、第四阀、第五阀、第一NOx传感器、第二NOx传感器、氨气传感器和温度传感器均连接控制单元。
2、燃料重整器中废气和天然气发生重整反应,所使用的催化剂为镍,工作温度范围在600℃~800℃,发生蒸汽重整反应和干式重整反应,反应所需的初始热量由发动机废气余热提供。
3、钯基催化器所用催化剂为钯,以氧化铝为载体,工作温度范围在300℃~600℃。
4、脱硝反应器所用催化剂为铜沸石,工作温度范围在250℃~450℃。
5、第一NOx传感器测量进入钯基催化器的氮氧化物,氨气传感器测量钯基催化器出口的氨气浓度,温度传感器测量排气温度,第二NOx传感器测量脱硝反应器出口的氮氧化物浓度。
6、控制单元根据各传感器的测量数据来控制各管路中的阀组开闭,进而控制天然气储罐进入燃料重整器以及进入发动机本体的天然气气量;所述控制单元还控制重整器出口的重整气进入发动机本体以及钯基催化器中的重整气气量。
本发明一种适用于船舶天然气发动机的在线生成氨气的废气脱硝***控制方法,其特征是:
(1)天然气发动机正常工作,此时为稀燃工作模式,第一阀、第二阀、第三阀和第四阀同时开启,第五阀关闭,实现天然气燃料的掺氢燃烧,掺氢比由第四阀控制;
(2)发动机由正常的稀燃运行模式切换至化学当量比燃烧,控制单元控制第一阀和第五阀开启,第四阀关闭;
(3)第一NOx传感器检测发动机排气中氮氧化物浓度是否低于设定值C,若是转步骤(4),若否转步骤(5),
(4)根据标定的发动机运行策略调节点火提前角,增加排气中的NOx浓度,使其达到设定值C;
(5)通过氨气传感器测量钯基催化剂出口氨气浓度,判断钯基催化剂出口的氨气浓度和进口NOx浓度比是否为1,若是转步骤(6),若否,转步骤(7);
(6)此时NOx全部转化为氨气,温度传感器测量当前的排气温度,当前温度下脱硝反应器内的催化剂有一个最大储氨值Smax,当储氨值达到最大时关闭第五阀且发动机切换至稀燃运行模式;
(7)控制单元协调第二阀、第三阀和第五阀的开启程度,加大进入钯基催化器的重整气气量,使钯基催化器出口的氨气浓度和进口NOx浓度比值为1;
(8)在稀燃运行模式下,第二NOx传感器检测脱硝反应器出口的NOx浓度,若NOx排放超过设定值D,则再次切换至化学当量比运行模式,重复步骤(1)-(7)。
本发明的优势在于:本发明周期性的将天然气发动机的运行模式由稀燃切换至当量比燃烧,再将天然气重整制取的氢气通入钯基催化器,一氧化氮和氢气在钯催化剂的作用下发生化学反应生成氨气。氨气随排气进入下游的脱硝反应器,储存在催化剂层中,在几种不同的催化剂中,铜沸石的储氨性能较好,储氨量达到最大时再次将发动机切换至稀燃运行模式,排气中的氮氧化物由储存的氨气还原。本发明通过控制不同阀门的开闭实现了被动的生成氨气,降低了NOx的排放。
附图说明
图1为本发明的结构示意图。
具体实施方式
下面结合附图举例对本发明做更详细地描述:
结合图1,本发明包括天然气储罐1、控制单元3、燃料重整器4、进气管7、发动机本体8、排气管9、钯基催化器12和脱硝反应器15。
天然气储罐1与发动机进气管7相连通,管路中设有第一阀2;还和燃料重整器4相连,管路中设有第二阀17;
燃料重整器4有两个进气口和两个出气口,一个进气口和天然气储罐1相连通,另一进气口和发动机排气管9相连通,且管路中设有第三阀6;两个出气口分别与进气管7和钯基催化器12进口管道相连通,管路中分别设有第四阀5和第五阀10;
钯基催化器12和脱硝反应器15沿着所述排气方向串联导通连接;
燃料重整器4所使用的催化剂为镍(Ni),工作温度范围在600℃~800℃,反应所需的初始热量由发动机废气余热提供,重整器内主要发生蒸汽重整反应、部分氧化重整反应和自热重整反应等化学反应,化学反应主要有以下几种:
钯基催化器12所用催化剂为钯(Pd),以氧化铝(Al2O3)为载体,工作温度范围在300℃~600℃,在其中会发生氨气的生成反应,以及甲烷、氢气和一氧化碳的氧化反应,具体反应如下:
2CO+O2→2CO2
2H2+O2→2H2O
CH4+2O2→CO2+2H2O
5H2+2NO→2NH3+2H2O
所述脱硝反应器15所用催化剂为铜沸石催化剂,工作温度范围在250℃~450℃,在其中主要发生氮氧化物的还原反应以及氨气的氧化反应,具体化学反应如下:
4NH3+4NO+O2→4N2+6H2O
2NH3+NO2+NO→2N2+3H2O
4NH3+3O2→2N2+6H2O
在钯基催化器12入口设有第一NOx传感器11,钯基催化器12和脱硝反应器15之间依次设有氨气传感器13和温度传感器14,脱硝反应器15出口处设有第二NOx传感器16;第一NOx传感器11测量进入钯基催化器的氮氧化物,氨气传感器13测量钯基催化器出口的氨气浓度,温度传感器14测量排气温度,第二NOx传感器15测量脱硝反应器出口的氮氧化物浓度。
第一阀、第二阀、第三阀、第四阀、第五阀、第一NOx传感器、温度传感器、氨气传感器和第二NOx传感器均与控制单元相连接。传感器的测量值会反馈给控制单元2,进而控制单元2控制第一阀至第五阀的开闭
本发明的实现结合了发动机的运行模式,发动机正常运行在稀燃模式(λ>1)下会产生较多的NOx,为了去除过量的NOx,将发动机切换至化学当量比燃烧模式(λ≈1),此时将燃料重整器4中产生的氢气通入排气管9。发动机排气和重整气混合后在钯基催化器12内就会发生氨气生成反应,生成的氨气随排气进入下游的脱硝反应器15后储存在催化剂中,当储氨量达到最大值时再次将发动机8切换至正常运行模式。此时储存的氨气就可以将排气中过量的NOx还原,实现了无氨喷射的被动式选择性催化还原。
本发明的另一方面是提供了一种在线生产氨气的废气脱硝***的控制方法,通过控制方法可以实现氨气生成的最大化以及脱硝效率的最大化,具体包括以下步骤:
S1:天然气发动机8正常工作,此时为稀燃工作模式,第一阀2、第二阀17、第三阀6和同时开启,第五阀10关闭,实现天然气燃料的掺氢燃烧,掺氢比由第四阀5控制,此时NOx排放较高;
S2:发动机8由正常的稀燃运行模式切换至化学当量比燃烧,控制单元3控制第一阀2和第五阀10开启,第四阀5关闭;
S3:第一NOx传感器11检测发动机排气中氮氧化物浓度是否低于设定值C,若是转步骤S4,若否转步骤S5,
S4:根据标定的发动机运行策略调节点火提前角等参数增加排气中的NOx浓度,使其达到设定值C;
S5:通过氨气传感器13测量钯基催化剂12出口氨气浓度,判断钯基催化剂12出口的氨气浓度和进口NOx浓度比是否为1,若是转步骤S6,若否,转步骤S7;
S6:此时表示NOx全部转化为氨气,温度传感器13测量当前的排气温度,当前温度下脱硝反应器15内的催化剂有一个最大储氨值Smax,当储氨值达到最大时关闭第五阀10且发动机切换至稀燃运行模式;
S7:控制单元3协调第二阀17、第三阀6和第五阀10的开启程度,加大进入钯基催化器12的重整气气量,使钯基催化器12出口的氨气浓度和进口NOx浓度比值为1,cNH3/cNOx=1;
S8:在稀燃运行模式下,第二NOx传感器16检测脱硝反应器15出口的NOx浓度,若NOx排放超过设定值D,则再次切换至化学当量比运行模式,重复步骤S1~S7。
本发明提出的***通过改变发动机运行模式来产生不同的废气成分,在催化剂的作用下在线生成的氨气。废气组分中的氢气量对氨气生成影响很大,容易因氢气量不足而不产生氨气,通过燃料重整可以将重整后的富氢气体通入钯基催化器,保证了可以生成足量的氨气。燃料重整过程中利用了废气余热,提高重整器的初始反应温度,后续反应的进行由反应自身放热来维持。控制单元根据传感器的测量值来控制各个管路中阀门的开闭,制定合适的控制策略可以实现脱硝效率的最大化。
Claims (8)
1.一种适用于船舶天然气发动机的在线生成氨气的废气脱硝***,其特征是:包括发动机、天然气储罐、燃料重整器、钯基催化器、脱硝反应器,天然气储罐连接发动机的进气管,所述燃料重整器包括第一进气口、第二进气口、第一出气口、第二出气口,第一进气口连接天然气储罐,第二进气口连接发动机的排气管,第一出气口连接发动机的进气管,第二出气口连接钯基催化器,钯基催化器和脱硝反应器沿着排气方向串联导通。
2.根据权利要求1所述的一种适用于船舶天然气发动机的在线生成氨气的废气脱硝***,其特征是:天然气储罐与发动机的进气管之间安装第一阀,天然气储罐与燃料重整器之间安装第二阀,燃料重整器与发动机的排气管之间安装第三阀,燃料重整器与发动机的进气管之间安装第四阀,燃料重整器与钯基催化器之间安装第五阀,钯基催化器入口设有第一NOx传感器,钯基催化器和脱硝反应器之间依次设有氨气传感器和温度传感器,脱硝反应器出口处设有第二NOx传感器;第一阀、第二阀、第三阀、第四阀、第五阀、第一NOx传感器、第二NOx传感器、氨气传感器和温度传感器均连接控制单元。
3.根据权利要求1所述的一种适用于船舶天然气发动机的在线生成氨气的废气脱硝***,其特征是:燃料重整器中废气和天然气发生重整反应,所使用的催化剂为镍,工作温度范围在600℃~800℃,发生蒸汽重整反应和干式重整反应,反应所需的初始热量由发动机废气余热提供。
4.根据权利要求1所述的一种适用于船舶天然气发动机的在线生成氨气的废气脱硝***,其特征是:钯基催化器所用催化剂为钯,以氧化铝为载体,工作温度范围在300℃~600℃。
5.根据权利要求1所述的一种适用于船舶天然气发动机的在线生成氨气的废气脱硝***,其特征是:脱硝反应器所用催化剂为铜沸石,工作温度范围在250℃~450℃。
6.根据权利要求2所述的一种适用于船舶天然气发动机的在线生成氨气的废气脱硝***,其特征是:第一NOx传感器测量进入钯基催化器的氮氧化物,氨气传感器测量钯基催化器出口的氨气浓度,温度传感器测量排气温度,第二NOx传感器测量脱硝反应器出口的氮氧化物浓度。
7.根据权利要求2所述的一种适用于船舶天然气发动机的在线生成氨气的废气脱硝***,其特征是:控制单元根据各传感器的测量数据来控制各管路中的阀组开闭,进而控制天然气储罐进入燃料重整器以及进入发动机本体的天然气气量;所述控制单元还控制重整器出口的重整气进入发动机本体以及钯基催化器中的重整气气量。
8.一种适用于船舶天然气发动机的在线生成氨气的废气脱硝***控制方法,其特征是:
(1)天然气发动机正常工作,此时为稀燃工作模式,第一阀、第二阀、第三阀和第四阀同时开启,第五阀关闭,实现天然气燃料的掺氢燃烧,掺氢比由第四阀控制;
(2)发动机由正常的稀燃运行模式切换至化学当量比燃烧,控制单元控制第一阀和第五阀开启,第四阀关闭;
(3)第一NOx传感器检测发动机排气中氮氧化物浓度是否低于设定值C,若是转步骤(4),若否转步骤(5),
(4)根据标定的发动机运行策略调节点火提前角,增加排气中的NOx浓度,使其达到设定值C;
(5)通过氨气传感器测量钯基催化剂出口氨气浓度,判断钯基催化剂出口的氨气浓度和进口NOx浓度比是否为1,若是转步骤(6),若否,转步骤(7);
(6)此时NOx全部转化为氨气,温度传感器测量当前的排气温度,当前温度下脱硝反应器内的催化剂有一个最大储氨值Smax,当储氨值达到最大时关闭第五阀且发动机切换至稀燃运行模式;
(7)控制单元协调第二阀、第三阀和第五阀的开启程度,加大进入钯基催化器的重整气气量,使钯基催化器出口的氨气浓度和进口NOx浓度比值为1;
(8)在稀燃运行模式下,第二NOx传感器检测脱硝反应器出口的NOx浓度,若NOx排放超过设定值D,则再次切换至化学当量比运行模式,重复步骤(1)-(7)。
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