加热炉不完全燃烧的处理办法.doc

Fired Heater Flooding Detection & Mitigation Procedures 直燃式加热炉燃料/空气配比不当检测和缓解程序FIRED HEATER FLOODING PROCEDURE直燃式加热炉燃料/空气配比不当的处理方法Background 背景Fired heater flooding or bogging is a term used to indicate fired heater operation with excess fuel or insufficient air. A fundamental requirement for safe and reliable operation of a fired heater is that sufficient air is supplied to each burner to ensure complete combustion of the fuel. If this is not done, the flue gas contains incomplete combustion products. This condition may occur because of poor operation or control, or upset conditions, where air is held improperly low, even though sufficient air capacity exists. Alternatively, at very high fuel rates, combustion air supply may become limiting and therefore not achieve the proper air to fuel ratio. In either case, immediate corrective action is required to return the fired heater to safe, reliable, and efficient operation. Fired heater flooding can result in flame impingement, after-burning, and explosions. 直燃式加热炉燃料/空气配比不当这个术语指的是加热炉在燃料过剩或者空气不足的情况下运行。对于加热炉的安全、可靠的运行而言，一项基本要求就是向每个燃烧器提供足够的空气，以便确保燃料能够全部燃烧。如果没有满足这项要求，烟道气中就会含有燃烧不完全的产物。这种情况是可能发生的，其原因是操作或者控制不当，或者是操作条件发生波动，此时空气流量被控制在一个不适当的低流量条件下，尽管实际上存在足够大的供风能力。另外一种情况是，在燃料流量很高的情况下，提供的燃烧空气可能受到限制，从而不能够实现合适的空气/燃料配比。无论是在何种情况下，此时都需要立即采取纠正措施，使得加热炉恢复安全、可靠、并且高效的运行状态。直燃式加热炉的燃料/空气配比不当问题可能会导致火舌舔触、后期燃烧、以及爆炸等一系列问题。Fired Heater Flooding Detection 加热炉燃料/空气配比不当的检测 Fired heaters equipped with oxygen and combustibles/CO analyzers provide the best flooding detection. Existing fired heaters should, as a minimum, have an oxygen analyzer and a software flooding monitor that calculates the heat supplied by the fuel for comparison to the process heat input. Additionally, fired heaters with automatic excess oxygen control must have an independent combustibles/CO analyzer as backup to prevent sub-stoichiometric operation due to erroneous oxygen readings.配置了氧含量以及可燃物/CO分析仪的直燃式加热炉在检测燃料/空气配比不当方面具有最佳的性能。作为最低限度的要求，现有的加热炉须至少配置一台氧含量分析仪以及软件形式的燃料/空气配比监测仪，该监测仪须能够计算燃料提供的热量，以便和工艺过程的热输入进行比较。此外，具有自动的过剩氧控制器的加热炉必须具有一台独立的可燃物/CO分析仪作为后备，防止由于错误的氧含量读数而导致加热炉在不理想的燃料/空气配比条件下运行。Indications of flooding noticeable in the control room are: 控制室中能够注意到的燃料/空气配比不当的迹象： low excess O2 or high combustibles/CO readings 低过剩氧或者高可燃物/CO读数 rapid drop in Bridge Wall temperature 火墙温度迅速降低 decrease in coil outlet temperature, and/or increase in firing rate (calculated from fuel gas flow) where the automatic control system increases fuel to try to compensate for reduced efficiency 炉管出口温度降低，和/或燃烧速率提高(根据燃料气流量来计算)，此时自动控制系统会提高燃料流量来尽量补偿降低的效率 wide, rapid variations in draft 炉膛负压出现宽幅的快速波动Note that measurable oxygen, relatively stable bridgewall temperature and relatively stable coil outlet temperature are not absolute assurances that fired heater flooding is not happening. As such, combustibles or CO monitors and software flooding monitors must also be considered.请注意，可测定的氧含量、相对稳定的火墙温度以及相对稳定的炉管出口温度并不能绝对保证加热炉的燃料/空气配比就一定是适当的。因此，还必须考虑使用可燃物或者CO监测仪以及使用软件的燃料/空气配比监测仪。Indications of flooding that may be noticeable to an outside operator are:外勤操作工能够注意到的燃料/空气配比不当的迹象： loud rhythmic whoosh sound or vibration 很响并且有韵律的“嘶嘶”声音或者振动 flames pulsating 火焰呈现脉动现象 local draft gauge swinging widely 就地负压表读数宽幅摆动 hazy firebox or smoke from stack (severe bogging) 炉膛火焰昏暗或者烟囱冒烟 (燃料/空气配比严重失调)Conducting routine checks of fired heater draft, excess O2 levels, and burner flame patterns may help to provide proactive prevention measures.对加热炉的负压、过剩氧含量、以及燃烧器火焰的形状进行常规检查，可能有助于事先采取各种预防措施。Impacts of Flooding 燃料/空气配比不当的影响When flooding occurs, the fired heater will begin to puff or breathe at the burners repeatedly in a rhythmic pattern. This panting is caused by the changes in the flue gas volume within the firebox. In this situation, the flames become longer and hazy. Flame impingement onto the tubes and tube supports can occur, resulting in coking, hot spots, and/or failure.当发生燃料/空气配比不当的情况时，加热炉就会在燃烧器的位置上以某种韵律方式开始“喘气”或者“呼吸”。这种“喘气”现象是炉膛内的烟道气体积的变化导致的。在这种情况下，火焰就会变得更长、而且昏暗。此时火舌有可能舔触到炉管和炉管支架上，导致炉管结焦、产生热点、和/或损坏等一系列问题。The cycle starts when airflow is reduced to the point where all the fuel is no longer being burned. This causes a significant reduction in the temperature and volume of the flue gas in the radiant section. This volume change causes a momentary increase in airflow, as air is sucked into the firebox. This additional airflow causes more fuel to be combusted, which increases the temperature and volume of the flue gas in the radiant section. This reduces airflow again and the cycle continues.当空气流量降低到一定程度，也就是所有燃料都不再燃烧时，就会触发这种循环。这种情况能够导致辐射段中的烟道气温度和体积大大降低。烟道气的这种体积变化能够导致空气流量的瞬时提高，因为空气是被抽吸到炉膛中的。这种额外的空气流量导致需要燃烧更多的燃料，从而提高辐射段中烟道气的温度和体积。此时这种情况会再次降低空气流量，从而使得这种循环继续延续下去。The puffing can become increasingly violent and burner flames may be partially or totally extinguished. Significant buildup of un-combusted fuel in the firebox that exceeds the explosive limit and is above its auto-ignition temperature can follow. The end result can be a significant explosion should air be introduced either via burner air register, combustion air damper or stack damper changes. Such an explosion can cause damage to equipment and injury to personnel.这种“喘气”现象会变得越来越厉害，可能会导致燃烧器的火焰局部熄灭、甚至全部熄灭。此时炉膛中积聚了大量的没有燃烧的燃料，随后就可能超过爆炸极限和自燃温度。万一空气进入炉膛的话，而无论是通过燃烧器的空气调节器、还是通过燃烧空气挡板或者烟囱挡板的变化进入炉膛，最终结果可能就是猛烈的爆炸。这种爆炸可能导致设备损坏和人员受伤。Fired Heater Flooding Mitigation Procedure 加热炉燃料/空气配比不当问题的减轻方法Caution Points: 注意事项: If a fired heater is puffing or suspected of operating with insufficient air, this situation should be handled remotely. Personnel should stay away from the immediate fired heater area. 如果发现加热炉“喘气”或者怀疑加热炉在空气流量不足的情况下运行，就应当通过远程方式处理这种情况。人员应当远离直燃式加热炉。 Do not automatically trip the fired heater in this situation, as oxygen will not be consumed, which may result in a flammable mixture that could auto-ignite in the firebox. 在这种情况下不得自动触发加热炉跳闸，因为氧气没有被消耗掉，从而可能导致产生某种可燃性混合物而导致炉膛中自动燃爆。 The concern here is that the firebox could be filled with hydrocarbon that is above its higher explosive limit. If the fuel gas is tripped, the fuel/air ratio will decrease to a value between the higher and lower explosive limits, the boundaries where combustion or explosions occur when sufficient heat or an ignition source is present. 此时需要注意的问题是，炉膛中可能充满了高于其爆炸极限的烃类物质。如果燃料气跳闸，燃料/空气配比就会降低到爆炸上极限和下极限之间的某个数值上，当存在足够的热量或者某种点火源时，周围就可能发生燃烧或者爆炸。 During bogging conditions, console operators will typically see low O2 analyzer readings and high combustibles or CO analyzer (if available) readings. Flooding monitors/alarms will indicate an imbalance in fuel flow vs. process temperatures or heat input. With these indications, immediate action should be taken as described in the following steps. 在燃料/空气配比不当的条件下，控制室的操作工通常是首先看到氧含量分析仪上的读数低，而可燃物分析仪或者CO分析仪(如果有的话)上的读数高。如果发现这些迹象，就应当按照以下步骤中所述立即采取应对行动。Basic Steps: 基本步骤:1. Immediately place fuel and air controllers in manual and reduce the fuel to the burners. Normally 10 to 25% fuel reduction is sufficient.立即将燃料控制器和空气控制器置于手动控制，并且降低去燃烧器的燃料流量。通常将燃料流量降低10-25%就足够了。1.1Do not open the combustion air or stack dampers or burner air registers because such action will greatly increase the violence of the puffing and possibly result in an explosion.不要开启燃烧空气挡板、或者烟囱挡板、或者燃烧器空气调节器，因为此类行动会大大提高加热炉“喘气”的剧烈程度，从而可能导致爆炸。 1.2 Reduce fuel to change the air/fuel ratio. Do not increase air during this first correction.降低燃料流量，从而改变空气/燃料配比。在采取这种最初的纠正行动时，不得提高空气流量。Note: If bogging has become so severe that process instrumentation indicates the possibility that all burners have been extinguished and that the firebox is potentially completely full of fuel gas, immediately prepare to shutdown the heater. For example, a sudden sharp drop in COTs or Bridge Wall temperatures in the range of 100-300 o C could be indicative of loss of all burners.注意：如果燃料/空气配比严重不当，而过程仪表指示出燃烧器有可能已经全部熄火、并且炉膛有可能充满了燃料气，此时就应当立即准备停掉加热炉。例如，100-300范围内的炉管出口温度或者火墙温度突然急剧降低，就可能表示所有燃烧器都已经熄火。1.3Ensure all outside operators have moved to a safe location away from the heater.确保所有外勤操作工都转移到一个远离加热炉的安全位置上。1.4Proceed immediately to Step 2 of this procedure.立即执行本操作规程的步骤22.If fuel reduction does not eliminate all signs of bogging, prepare to shutdown the heater using the following steps, however, do not immediately trip the fuel.如果降低燃料流量不能彻底解决加热炉的燃料/空气配比不当问题，则可以采用以下步骤来准备停掉加热炉，但是不要立即使得燃料系统跳闸。2.1If snuffing steam is available, and can be lined up from a safe distance, purge the firebox with steam prior to shutting down the fuel flow to all burners. This step helps to disperse un-burnt fuel.如果能够提供灭火蒸汽，并且能够从一个安全的距离上转好流程，就用灭火蒸汽对炉膛进行吹扫，然后再切断去所有燃烧器的燃料流量。这个步骤有助于驱散尚未燃烧的燃料。2.2If snuffing steam is not available/accessible, shut off pilot gas from a remote location and then continue to slowly cut fuel to the main burners.如果不能提供灭火蒸汽或者使用起来不方便，就从一个远程位置上切断引火气体，然后继续缓慢切断去主燃烧器的燃料。2.3When fuel is completely shut-off, initiate a heater trip and allow the draft to purge any excess fuel prior to personnel approaching the heater.当燃料被彻底切断时，触发加热炉的跳闸动作，允许通过抽风系统来将任何过剩的燃料吹扫出去，然后才允许人员靠近加热炉。2.4Ensure that the firebox is sufficiently purged with steam or draft before restarting via normal startup procedures.在通过正常的开工程序对加热炉重新开工之前，确保利用灭火蒸汽或者通过抽风系统对炉膛进行充分的吹扫。3.If fuel reduction is effective, then once the puffing has stopped, the console operator should perform the following steps to determine whether the fired heater is operating in a stable regime:如果减少燃料是有效的，则一旦加热炉停止“喘气”，控制室操作工就应当执行以下步骤来确定加热炉是否处于安全稳定的运行状态：3.1Verify that fuel flow to the fired heater is consistent with process heat input (i.e. COTs are acceptable, fuel flow is adequate) and the software flooding alarm indicates stable operation.确认去加热炉的燃料流量和工艺过程的热输入是保持一致的(即炉管出口温度是能够接受的，燃料流量也是足够的)，并且软件形式的燃料/空气配比报警器指示加热炉处于稳定的运行状态。3.2Verify that the excess O2 indicator is operating in a stable and safe mode.确认过剩氧分析仪在稳定和安全的模式下运行。3.3Verify that the combustible or CO analyzer (if available) indicates that all of the fuel is being completely combusted in the firebox.确认可燃物分析仪或者CO分析仪(如果有的话)指示出所有的燃料都在炉膛中完全燃烧。3.4After a reasonable amount of time in stable operation, have the outside operator check the status of the burners. Puffing has a tendency to extinguish some or possibly all of the burners and therefore this check is critical.在经过一段时间长度合理的稳定运行阶段之后，指示外勤操作工去检查燃烧器的状态。加热炉的“喘气”现象表示部分燃烧器或者全部燃烧器可能存在熄火的趋势，所以这种检查非常重要。3.4.1If some burners are found to have been extinguished, operations personnel shall decide, based on the stability of the heater, to either block in fuel to all the individual burners that are not re-lit (and then re-light them following standard procedures), or shutdown the heater entirely.如果发现某些燃烧器已经熄灭，则操作人员须根据加热炉的稳定性情况，决定是否切断去所有尚未重新点燃的独立燃烧器(随后采用以下的标准操作规程重新点燃)的燃料，还是将整个加热炉停掉。3.4.2*Note: Typically, with a hot firebox, a burner will re-light itself off of the hot refractory. If the fired heater is in a start-up mode and the firebox may not be completely heated up, then it is recommended to shutdown the heater if any burners have been extinguished.* 注意：一般来说，在炉膛仍然处于高温的情况下，燃烧器能够借助高温的炉膛耐火材料自行重新点火。如果加热炉处于开工阶段，则炉膛可能尚未完全升温，则此时建议停掉加热炉，如果发现任何燃烧器已经熄灭的话。3.4.3If the outside operator verifies that all burners and pilots are operating properly, slowly increase air by gradually opening the stack damper or air damper(s). This allows oxygen to gradually enter the firebox and be consumed by the burner flames.如果外勤操作工确认所有燃烧器和引火烧嘴的工作都是正常的，即可缓慢提高空气流量，方法是逐渐开启烟囱挡板或者空气挡板(风门)。这样能够让氧气逐渐进入炉膛，并且被燃烧器火焰消耗掉。3.5 Once all burners are stable, slowly increase the fuel to regain firing rate, monitoring closely for the return of bogging conditions.一旦所有燃烧器都稳定下来，缓慢提高燃料流量，以便恢复燃烧速率，同时密切监视燃料/空气配比不当的情况是否再次发生。3.5.1Check draft and excess oxygen to ensure that they are at adequ