1、FIRED HEATER FLOODING PROCEDURE直燃式加熱爐燃料/空氣配比不當的處理方法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 e

2、ach 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. Alternati

3、vely, 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 im

4、pingement, after-burning, and explosions.直燃式加熱爐燃料/空氣配比不當這個術語指的是加熱爐在燃料過剩或者空氣不足的 情況下運行。對于加熱爐的安全、可靠的運行而言，一項基本要求就是向每個燃燒器提供 足夠的空氣，以便確保燃料能夠全部燃燒。如果沒有滿足這項要求，煙道氣中就會含有燃 燒不完全的產物。這種情況是可能發生的，其原因是操作或者控制不當，或者是操作條件 發生波動，此時空氣流量被控制在一個不適當的低流量條件下，盡管實際上存在足夠大的 供風能力。另外一種情況是，在燃料流量很高的情況下，提供的燃燒空氣可能受到限制， 從而不能夠實現合適的空氣/燃料配比。無論是

5、在何種情況下，此時都需要立即采取糾正 措施，使得加熱爐恢復安全、可靠、并且高效的運行狀態。直燃式加熱爐的燃料/空氣配 比不當問題可能會導致火舌舔觸、后期燃燒、以及爆炸等一系列問題。Fired Heater Flooding Detection加熱爐燃料/空氣配比不當的檢測Fired heaters equipped with oxygen and combustibles/CO analyzers provide the best flooding detection. Existing fired heaters should, as a minimum, have an oxygen an

6、alyzer 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 e

7、rroneous oxygen readings.配置了氧含量以及可燃物/CO分析儀的直燃式加熱爐在檢測燃料/空氣配比不當方面 具有最佳的性能。作為最低限度的要求，現有的加熱爐須至少配置一臺氧含量分析儀以及 軟件形式的燃料/空氣配比監測儀，該監測儀須能夠計算燃料提供的熱量，以便和工藝過 程的熱輸入進行比較。此外，具有自動的過剩氧控制器的加熱爐必須具有一臺獨立的可燃 物/CO分析儀作為后備，防止由于錯誤的氧含量讀數而導致加熱爐在不理想的燃料/空氣 配比條件下運行。Indications of flooding noticeable in the control room are:控制室中能夠注意

8、到的燃料/空氣配比不當的跡象：low excess O2 or high combustibles/CO readings低過剩氧或者高可燃物/CO讀數rapid drop in Bridge Wall temperature火墻溫度迅速降低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 redu

9、ced efficiency爐管出口溫度降低，和/或燃燒速率提高(根據燃料氣流量來計算)，此時自動控制系 統會提高燃料流量來盡量補償降低的效率wide, rapid variations in draft爐膛負壓出現寬幅的快速波動Note that measurable oxygen, relatively stable bridgewall temperature and relatively stable coil outlet temperature are not absolute assurances that fired heater flooding is not happeni

10、ng. As such, combustibles or CO monitors and software flooding monitors must also be considered.請注意，可測定的氧含量、相對穩定的火墻溫度以及相對穩定的爐管出口溫度并不能 絕對保證加熱爐的燃料/空氣配比就一定是適當的。因此，還必須考慮使用可燃物或者CO 監測儀以及使用軟件的燃料/空氣配比監測儀。Indications of flooding that may be noticeable to an outside operator are:外勤操作工能夠注意到的燃料/空氣配比不當的跡象：loud r

11、hythmic whoosh sound or vibration很響并且有韻律的“嘶嘶”聲音或者振動flames pulsatingFired Heater Flooding Detection & Mitigation Procedures直燃式加熱爐燃料/空氣配比不當檢測和緩解程序火焰呈現脈動現象 local draft gauge swinging widely就地負壓表讀數寬幅擺動 hazy firebox or smoke from stack (severe bogging)爐膛火焰昏暗或者煙囪冒煙(燃料/空氣配比嚴重失調)Conducting routine checks of

12、 fired heater draft, excess O2 levels, and burner flame patterns may help to provide proactive prevention measures.對加熱爐的負壓、過剩氧含量、以及燃燒器火焰的形狀進行常規檢查，可能有助于事 先采取各種預防措施。Impacts of Flooding燃料/空氣配比不當的影響When flooding occurs, the fired heater will begin to puff or breathe at the burners repeatedly in a rhythm

13、ic 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.當發生燃料/空氣配比不當的情況時，加熱爐就會在燃燒器的位置上以某種韻律方式 開始“喘氣”

14、或者“呼吸”。這種“喘氣”現象是爐膛內的煙道氣體積的變化導致的。在 這種情況下，火焰就會變得更長、而且昏暗。此時火舌有可能舔觸到爐管和爐管支架上， 導致爐管結焦、產生熱點、和/或損壞等一系列問題。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 secti

15、on. 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.當空氣流量降低到一定

16、程度，也就是所有燃料都不再燃燒時，就會觸發這種循環。這 種情況能夠導致輻射段中的煙道氣溫度和體積大大降低。煙道氣的這種體積變化能夠導致 空氣流量的瞬時提高，因為空氣是被抽吸到爐膛中的。這種額外的空氣流量導致需要燃燒 更多的燃料，從而提高輻射段中煙道氣的溫度和體積。此時這種情況會再次降低空氣流 量，從而使得這種循環繼續延續下去。The puffing can become increasingly violent and burner flames may be partially or totally extinguished. Significant buildup of un-combus

17、ted 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

18、equipment and injury to personnel.這種“喘氣”現象會變得越來越厲害，可能會導致燃燒器的火焰局部熄滅、甚至全部 熄滅。此時爐膛中積聚了大量的沒有燃燒的燃料，隨后就可能超過爆炸極限和自燃溫度。 萬一空氣進入爐膛的話，而無論是通過燃燒器的空氣調節器、還是通過燃燒空氣擋板或者 煙囪擋板的變化進入爐膛，最終結果可能就是猛烈的爆炸。這種爆炸可能導致設備損壞和 人員受傷。Fired Heater Flooding Mitigation Procedure加熱爐燃料/空氣配比不當問題的減輕方法Caution Points:注意事項：If a fired heater is p

19、uffing or suspected of operating with insufficient air, this situation should be handled remotely. Personnel should stay away from the immediate fired heater area.如果發現加熱爐“喘氣”或者懷疑加熱爐在空氣流量不足的情況下運行，就應當通過 遠程方式處理這種情況。人員應當遠離直燃式加熱爐。Do not automatically trip the fired heater in this situation, as oxygen wil

20、l not be consumed, which may result in a flammable mixture that could auto-ignite in the firebox.在這種情況下不得自動觸發加熱爐跳閘，因為氧氣沒有被消耗掉，從而可能導致產生 某種可燃性混合物而導致爐膛中自動燃爆。 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 f

21、uel/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.此時需要注意的問題是，爐膛中可能充滿了高于其爆炸極限的烴類物質。如果燃料 氣跳閘，燃料/空氣配比就會降低到爆炸上極限和下極限之間的某個數值上，當存 在足夠的熱量或者某種點火源時，周圍就可能發生燃燒或者爆炸。 Duri

22、ng 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

23、be taken as described in the following steps.在燃料/空氣配比不當的條件下，控制室的操作工通常是首先看到氧含量分析儀上的讀 數低，而可燃物分析儀或者CO分析儀(如果有的話)上的讀數高。如果發現這些跡象， 就應當按照以下步驟中所述立即采取應對行動。Basic Steps:基本步驟：Immediately place fuel and air controllers in manual and reduce the fuel to the burners. Normally 10 to 25% fuel reduction is sufficient.立

24、即將燃料控制器和空氣控制器置于手動控制，并且降低去燃燒器的燃料流量。通常 將燃料流量降低10-25%就足夠了。Do 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.不要開啟燃燒空氣擋板、或者煙囪擋板、或者燃燒器空氣調節器，因為此類行 動會大大提高加熱爐“喘氣”的劇烈程度，從而可能導致爆炸。Redu

25、ce fuel to change the air/fuel ratio. Do not increase air during this first correction.降低燃料流量，從而改變空氣/燃料配比。在采取這種最初的糾正行動時，不 得提高空氣流量。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 c

26、ompletely 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/空氣配比嚴重不當，而過程儀表指示出燃燒器有可能已經全部熄火、 并且爐膛有可能充滿了燃料氣，此時就應當立即準備停掉加熱爐。例如，100-300 C范 圍內的爐管出

27、口溫度或者火墻溫度突然急劇降低，就可能表示所有燃燒器都已經熄 火。Ensure all outside operators have moved to a safe location away from the heater.Fired Heater Flooding Detection & Mitigation Procedures直燃式加熱爐燃料/空氣配比不當檢測和緩解程序確保所有外勤操作工都轉移到一個遠離加熱爐的安全位置上。Proceed immediately to Step 2 of this procedure.立即執行本操作規程的步驟2If fuel reduction does

28、 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徹底解決加熱爐的燃料/空氣配比不當問題，則可以采用以下步 驟來準備停掉加熱爐，但是不要立即使得燃料系統跳閘。If snuffing steam is available, and can be lined up from a safe distance, purge the firebox with st

29、eam prior to shutting down the fuel flow to all burners. This step helps to disperse un-burnt fuel.如果能夠提供滅火蒸汽，并且能夠從一個安全的距離上轉好流程，就用滅火蒸 汽對爐膛進行吹掃，然后再切斷去所有燃燒器的燃料流量。這個步驟有助于驅 散尚未燃燒的燃料。If snuffing steam is not available/accessible, shut off pilot gas from a remote location and then continue to slowly cut f

30、uel to the main burners.如果不能提供滅火蒸汽或者使用起來不方便，就從一個遠程位置上切斷引火氣 體，然后繼續緩慢切斷去主燃燒器的燃料。When fuel is completely shut-off, initiate a heater trip and allow the draft to purge any excess fuel prior to personnel approaching the heater.當燃料被徹底切斷時，觸發加熱爐的跳閘動作，允許通過抽風系統來將任何過 剩的燃料吹掃出去，然后才允許人員靠近加熱爐。Ensure that the fireb

31、ox is sufficiently purged with steam or draft before restarting via normal startup procedures.在通過正常的開工程序對加熱爐重新開工之前，確保利用滅火蒸汽或者通過抽 風系統對爐膛進行充分的吹掃。If fuel reduction is effective, then once the puffing has stopped, the console operator should perform the following steps to determine whether the fired hea

32、ter is operating in a stable regime:如果減少燃料是有效的，則一旦加熱爐停止“喘氣”，控制室操作工就應當執行以下 步驟來確定加熱爐是否處于安全穩定的運行狀態：Verify 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.確認去加熱爐的燃料流量和工藝過

33、程的熱輸入是保持一致的(即爐管出口溫度 是能夠接受的，燃料流量也是足夠的)，并且軟件形式的燃料/空氣配比報警器 指示加熱爐處于穩定的運行狀態。Verify that the excess O2indicator is operating in a stable and safe mode.確認過剩氧分析儀在穩定和安全的模式下運行。Verify that the combustible or CO analyzer (if available) indicates that all of the fuel is being completely combusted in the firebox.

34、確認可燃物分析儀或者CO分析儀(如果有的話)指示出所有的燃料都在爐膛中 完全燃燒。After 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.在經過一段時間長度合理的穩定運行階段之后，指示外勤操作工去檢查燃燒器

35、的狀態。加熱爐的“喘氣”現象表示部分燃燒器或者全部燃燒器可能存在熄火 的趨勢，所以這種檢查非常重要。If 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 procedu

36、res), or shutdown the heater entirely.如果發現某些燃燒器已經熄滅，則操作人員須根據加熱爐的穩定性情 況，決定是否切斷去所有尚未重新點燃的獨立燃燒器(隨后采用以下 的標準操作規程重新點燃)的燃料，還是將整個加熱爐停掉。*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 completel

37、y heated up, then it is recommended to shutdown the heater if any burners have been extinguished.*注意：一般來說，在爐膛仍然處于高溫的情況下，燃燒器能夠借助 高溫的爐膛耐火材料自行重新點火。如果加熱爐處于開工階段，則爐 膛可能尚未完全升溫，則此時建議停掉加熱爐，如果發現任何燃燒器 已經熄滅的話。If the outside operator verifies that all burners and pilots are operating properly, slowly increase ai

38、r 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.如果外勤操作工確認所有燃燒器和引火燒嘴的工作都是正常的，即可 緩慢提高空氣流量，方法是逐漸開啟煙囪擋板或者空氣擋板(風門)。 這樣能夠讓氧氣逐漸進入爐膛，并且被燃燒器火焰消耗掉。Once all burners are stable, slowly increase the fuel to regain firing rate, monitoring closely for the return of bogging conditions.一旦所有燃燒器都穩定下來，緩慢提高燃料流量，以便恢復燃燒速率，同時密 切監視燃料/空氣配比不當的情況是否再次發生。Check draft and excess oxygen t