1294305 (1) 玖、發明說明 【發明所屬之技術領域】 本發明係關於減低燃燒法產生的廢氣流中之NOx濃 度的方法。更特別地，本發明係關於減低廢氣流中之NOx 濃度的方法，其使廢氣流與選自氨和尿素的還原劑接觸。 亞氯酸鈉之後與廢氣流混合，使得亞氯酸鈉將至少一部分 存在於廢氣流中的低階NOx氧化成高階氧化物。 【先前技術】 政府法令對於排放標準日趨嚴格迫使精煉業者發展出 減低燃燒排放物和產製流出物中之氮氧化物（NOx)濃度的 改良技術。已發展出許多減低燃燒和產製流出物之氮氧化 物散逸的方法，例如，Senjo等人的美國專利案第 3,95 7,949號和Vicard等人的美國專利案第6,294，139號（茲 將此二者中所揭示者列入參考）。此外，此技術已經知道 藉注入氨而降低燃燒流出物中之NOx濃度的方法，此請 參考Lyon的美國專利案第3,900,5 54號，茲將其中揭示者 列入參考。Lyon專利案之後，有許多專利案和著作係關 於將氨注入燃燒流中以減低NOx濃度。這樣的專利案包 括Dean等人的美國專利案第4,5 07,269和Tenner等人的 4，1 15,515號，茲將其中揭示者列入參考。揭示使用氨注 射的其他專利案係基於使用動態模型測定注入的氨量。這 樣的專利案包括Dean等人的美國專利案第4,63 6,3 70、 4,624,840和4,6 82,46 8號，茲將其中揭示者列入參考。也 - 5- 1294305 (2) 有許多專利案和著作係關於將尿素注入燃燒流出物中以減 低ΝΟχ濃度。涵蓋此技術的一個這樣的專利案是Arand 等人的美國專利案第4，2 〇 8，3 8 6號，茲亦將其中揭示者列 入參考。Kim 和 Lee( 1 996)印行於 Journal of Chemical Engineering of Japan (茲將其中揭示者列入參考）的硏究 "Kinetics of Nox Reduction by Urea Solution in Pilot Scale Recator’’， Journal of Chemical Engineering of Japan，29(4)，1 99 6，pp· 620-626指出尿素解離成氨和氰尿酸 (HNCO)，此二者於自由基反應的兩個相關環節中皆作爲 NO還原劑。 但來自燃燒單元和產製流的流出物（如：流化催化裂 解單元的再生器廢氣）仍有NOx留在精煉環境中。大多數 的精煉器中，流化催化裂解程序單元配備濕氣體滌氣裝置 以移除磨損的觸媒細粒。這些濕氣體滌氣裝置提供精煉業 者額外之減低NOx散逸至某程度的優點，這是因爲濕氣 體滌氣裝置也會滌除來自流化催化裂解程序單元的濕氣流 中的N02之故。但使用這些滌氣裝置無法完全有效減低 NOx散逸，這是因爲已有之經滌氣和/或飽和氣體系統（ 如：燃燒單元（如：流化催化裂解單元）上的濕氣體滌氣裝 置）中，廢氣基本上含有NO和N02。可藉滌氣移除N02， 但無法滌除NO。NO無法藉滌氣移除的原因在於：這些廢 氣流中所含有的NOx大多是NO。例如，被送至濕氣體滌 氣裝置之流化催化裂解單元的廢氣中的ΝΟχ基本上約90% 是Ν Ο。 -6 - 1294305 (3) 因此，許多精煉業者實驗和實施技巧以將NOx氧化 成高階氧化物，這些技巧符合混合結果。目前所用的大多 數技巧包含須要長反應時間的化學品，此處理單元中製造 出其他問題。這樣的問題包括，如，構築材料腐蝕、處理 單元之廢水的問題’及移除S Ox的問題。例如，此技術已 經知道在濕氣體滌氣液中添加亞氯酸鈉（NaC102)以便將 NOx氧化成高階氧化物（如：1^02和N205，其爲水溶性且 可自處理系統移除，基本分別是硝酸鹽和亞硝酸鹽）。這 些高階氧化物於水中之溶解度述於 J.B.Joshi， V . V . Mahaj ani and V . A . Juvekar ? “Invited Review : Absorption of N O x Gases，” Chemical Engineering Communication，V o 1.3 3 pp 1-92，茲將其中所述者列入參 考。 但在滌氣液體中添加亞氯酸鈉有其缺點。例如，亞氯 酸鈉是昂貴的化學品且會被副反應所消耗，例如，S Ox氧 化成高階硫氧化物（如：S02至S03)。因此，因爲亞氯酸 鈉無法選擇性地將NOx氧化成高階氮氧化物，所以習用 方法於滌氣液體中使用高濃度亞氯酸鈉，達到所欲之減低 N〇x的效果。這些高濃度亞氯酸鈉導致氯化物含量高，此 會導致滌氣裝置構築材料腐蝕。 因此，此技術對於移除廢氣流中之NO,之經濟且有 效的方法仍有需求存在。 【發明內容】 1294305 (4) 根據本發明，提出一種將含有SOx的廢氣流中所含至 少一部分NOx予以氧化的方法，此廢氣流中含有低階和 高階氧化物，此方法包含： a) 形成還原劑（選自氨及尿素）和易氧化的氣體之混合 物，其量爲有效量，會以預定量減低該廢氣流中之NOx 濃度；1294305 (1) Description of the Invention [Technical Field] The present invention relates to a method of reducing the NOx concentration in an exhaust gas stream generated by a combustion method. More particularly, the present invention relates to a method of reducing NOx concentration in an exhaust stream that contacts an exhaust stream with a reducing agent selected from the group consisting of ammonia and urea. The sodium chlorite is then mixed with the exhaust stream such that the sodium chlorite oxidizes at least a portion of the lower order NOx present in the exhaust stream to a higher order oxide. [Prior Art] Government regulations have increasingly tightened emission standards, forcing refiners to develop improved technologies that reduce the concentration of nitrogen oxides (NOx) in combustion emissions and production effluents. A number of methods have been developed to reduce the emission of nitrogen oxides from combustion and production effluents, for example, U.S. Patent No. 3,95,949 to Senjo et al. and U.S. Patent No. 6,294,139 to Vicard et al. The two are disclosed in the reference). In addition, this technique is known to reduce the NOx concentration in the combustion effluent by injecting ammonia, and is described in the U.S. Patent No. 3,900,5, the entire disclosure of which is incorporated herein by reference. After the Lyon patent, there are many patents and writings on injecting ammonia into the combustion stream to reduce NOx concentrations. Such patents include U.S. Patent No. 4,5,07,269 to Dean et al., and No. 4,1,515, the entire disclosure of which is incorporated herein by reference. Other patents that disclose the use of ammonia injection are based on the use of a dynamic model to determine the amount of ammonia injected. Such patents include U.S. Patent Nos. 4,63,3,370, 4,624,840 and 4,6,82,46, the entire disclosure of each of each of each of each of Also - 5- 1294305 (2) There are a number of patents and writings on the injection of urea into combustion effluents to reduce radon concentrations. One such patent case covering this technology is U.S. Patent No. 4,2,8,8,8, to A, et al., the disclosure of which is incorporated herein by reference. Kim and Lee (1 996) published in the Journal of Chemical Engineering of Japan (Kinetics of Nox Reduction by Urea Solution in Pilot Scale Recator'', Journal of Chemical Engineering of Japan , 29(4), 1 99 6, pp· 620-626 indicates that urea dissociates into ammonia and cyanuric acid (HNCO), both of which act as NO reducing agents in both related aspects of the free radical reaction. However, effluent from the combustion unit and the production stream (e.g., regenerator off-gas from the fluid catalytic cracking unit) still leaves NOx in the refining environment. In most refiners, the fluid catalytic cracking program unit is equipped with a wet gas scrubber to remove worn catalyst fines. These wet gas scrubbers provide the refiner with the added benefit of reducing NOx emissions to a certain extent because the wet scrubber also scrubs N02 from the wet gas stream from the fluid catalytic cracker unit. However, the use of these scrubbers is not completely effective in reducing NOx emissions due to existing scrubbed and/or saturated gas systems (eg, wet gas scrubbers on combustion units (eg, fluid catalytic cracking units)) The exhaust gas basically contains NO and N02. N02 can be removed by scrubbing, but NO cannot be removed. The reason why NO cannot be removed by scrubbing gas is that the NOx contained in these waste gas streams is mostly NO. For example, about 90% of the enthalpy in the exhaust gas sent to the fluid catalytic cracking unit of the wet gas scrubber is substantially Ν. -6 - 1294305 (3) Therefore, many refiners experiment and implement techniques to oxidize NOx to higher order oxides. These techniques are consistent with the mixing results. Most of the techniques currently used contain chemicals that require long reaction times, and other problems are created in this processing unit. Such problems include, for example, the problem of constructing material corrosion, treating wastewater from the unit, and removing S Ox. For example, it is known in the art to add sodium chlorite (NaC 102) to a wet gas scrub to oxidize NOx to higher order oxides (eg, 1 02 and N 205, which are water soluble and can be removed from the processing system, The basics are nitrate and nitrite). The solubility of these higher-order oxides in water is described in JBJoshi, V. V. Mahajani and V. A. Juvekar® “Invited Review: Absorption of NO x Gases,” Chemical Engineering Communication, V o 1.3 3 pp 1-92, The above is included in the reference. However, the addition of sodium chlorite to the scrubbing liquid has its drawbacks. For example, sodium chlorite is an expensive chemical and is consumed by side reactions, for example, S Ox is oxidized to higher order sulfur oxides (e.g., S02 to S03). Therefore, since sodium chlorite cannot selectively oxidize NOx into higher-order nitrogen oxides, a conventional method uses a high concentration of sodium chlorite in a scrubbing liquid to achieve a desired effect of reducing N?x. These high concentrations of sodium chlorite result in high chloride levels, which can lead to corrosion of the scrubber construction materials. Therefore, there is still a need for this technology to be economical and efficient in removing NO from the exhaust stream. SUMMARY OF THE INVENTION 1294305 (4) According to the present invention, there is provided a method of oxidizing at least a portion of NOx contained in an exhaust stream containing SOx, the exhaust stream comprising lower order and higher order oxides, the method comprising: a) forming a mixture of a reducing agent (selected from ammonia and urea) and an oxidizable gas in an amount effective to reduce the NOx concentration in the exhaust stream by a predetermined amount;
b) 該混合物於一個點注入該廢氣流中，其中該含有 S Οχ的廢氣流溫度低於1 600 °F Ο移除存在於該廢氣流中之至少一部分SOx ; d)有效量的亞氯酸鈉與該廢氣流於前述步驟c)的下游 處混合，藉此將存在於該廢氣流中之至少一部分低階NOx 氧化成高階氧化物。 本發明的另一實施例中，使用濕氣體滌氣分離滾筒的 噴嘴，使亞氯酸鈉與含S0X的廢氣流混合。 另一實施例中，藉選自鹼溶液吸收、還原溶液吸收、 滌氣、氨注射、催化性轉化和以水吸收的方法，自廢氣流 移除N0X高階氧化物。 本發明的另一實施例中，有效量還原劑和易氧化的氣 體於FCCU的熱回收裝置上游單一位置注入FCC程序單 元已有的再生器塔頂管線中。 本發明的另一實施例中，有效量還原劑和易氧化的氣 體於FCCU的熱回收裝置上游多處同時注入FCC程序單 元已有的再生器塔頂管線中。 本發明的另一實施例中，易氧化的氣體是氫，還原劑 -8- 1294305 (5) 是氨。 實施方式之詳細說明 此處所謂的Ν Ο x或氮氧化物是指可能存在於燃燒廢 氣中之氮的各式各樣氧化物。因此，所謂氮的所有各式各 樣氧化物包括，但不限於，一氧化氮（NO)、二氧化氮 (no2)、過氧化氮（n2o4)、五氧化氮（n2o5)及它們的混合 物。但是因爲NO基本上佔實施所提出之發明的燃燒廢氣 中所存在的氮氧化物的90%以上，所以此亦指一氧化氮 (NO)。因此，所提出的方法特別係關於NO之減少和控制 。同樣地，此處交替使用的煙道氣、濕氣體、燃燒流出物 、燃燒廢氣流出物、廢氣和廢氣流名稱是指相同之經滌氣 和/或飽和的氣流。同樣地，濕氣體滌氣裝置、滌氣裝置 和滌氣器名稱有時也交替使用。亦應注意到，此處所謂的 ”高階氧化物”是指任何NOx，其中”x”是二或以上。 描述還原劑和易氧化的氣體之混合時，所謂的混合爲 廣義定義。因此，混合是指於所欲莫耳比，儘量使還原劑 和易氧化的氣體與廢氣流中的NOx之局部接觸最大。任 何適當的混合技巧可用以達到此目的。這些技巧包括，但 不限於，使用載氣與還原劑和/或易氧化的氣體以有助於 更均勻的混合；將還原劑、易氧化的氣體和載氣之事先混 合的氣流注入廢氣流中；或者，將還原劑與載氣流和易氧 化的氣體與載氣流分別注入廢氣流中。注射之前的適當混 合技巧、方法或方式包括抽取還原劑、易氧化的氣體和載 -9- 1294305 (6) 氣通過獨立管線，進入一個通用槽或進入注射管線至欲處 理的廢氣流，使得兩種物劑和載氣混合並朝向注射點。 本發明提出一種成本有效方式，藉此，精煉業者可自 廢氣流（如··流化催化裂解單元產生的廢氣）移除NOx。 NOx氧化成高階氧化物得以有效地自煙道氣流移除NOx， 這是因爲高階氮氧化物（如：>102和n2o5)比低階氮氧化物 易溶於水中，並更易以硝酸鹽或亞硝酸鹽形式自系統移出 ，高階氧化物（如：no2和n2o5)比低階氧化物較容易移除 。因此，所提出的方法包含形成還原劑和易氧化的氣體之 以預定量有效減低廢氣流中之NOx的量之混合物，移除 至少一部分存在於氣流中的SOx，及添加有效量的亞氯酸 鈉至廢氣流中，藉此將廢氣流中所含一部分NOx氧化成 高階氧化物（如：NO氧化成N02)。之後可藉選自鹼溶液 吸收、還原溶液吸收、滌氣用氨注射、催化性轉化和以水 吸收的方法移除此高階氧化物。 此處所謂的亞氯酸鈉有效量是指將存在於廢氣流中的 至少一部分NOx予以氧化的量，使得至少20體積％，如： 20體積％至80體積％，以40體積。/〇至90體積％爲佳，50體積 °/〇至99體積％更佳，最佳情況是指實質上所有存在於廢氣 流中的低階NOx被氧化成高階氮氧化物。 本發明特別適用於減低流化催化裂解單元（F C C U)程 序流中的N0X濃度。流化催化裂解是一種重要且廣泛應 用的精煉法。催化裂解法基本上將重質油轉化成較輕質產 物（如：汽油）。流化催化裂解（FCC)法中，產生的細粒觸 1294305 (7) 媒連續循環於裂解反應器和觸媒再生器之間。反應器平均 溫度是900- 1 000 °F，進料平均溫度是5 00 - 8 0 0 T。反應器 和再生器一倂構成催化裂解單元的主要構件。FCC程序單 元爲此技術所習知，Swan等人的美國專利案第5,846,403 號（茲將其中所述者列入參考）更詳細地討論這樣的單元。 就觸媒壽命和有效性而言，再生器特別重要，這是因 爲在流化催化裂解期間內，含碳沉積物（焦炭）形成於觸媒 上，其實質上降低其活性。之後，觸媒基本上於再生器中 燒掉至少一部分焦炭地經再生處理以再度恢復其效能。此 基本上藉由將空氣或具可燃量氧的其他氣體以足以使得使 用過的觸媒顆粒流化的速率注入再生器中而達成。觸媒顆 粒上所含的一部分焦炭於再生器中燃燒，得到經再生處理 的觸媒顆粒。典型再生器溫度由約1 05 0 °F至約1 45 0 °F，再 生器廢氣的離開溫度通常由約1200°F至約1 5 00°F。 再生處理之後，觸媒顆粒循環回到反應器。再生器廢 氣通常進入其他程序，如：熱回收裝置、細粒移除裝置、 一氧化碳燃燒/熱回收單元（COHRU ’如前述者’其用以 將CO轉化成C02及回收可資利用的燃料能量）及SOx移除 裝置。 本發明的一個較佳實施例中’初Ν〇χ移除步驟移除 存在於廢氣流中的至少一部分Ν〇χ ’藉此減低將存在於廢 氣流中剩餘Ν Ο X予以氧化所須的亞氯酸鈉量。第一個移 除步驟中，自廢氣流移除的預定量基本上是至少1 〇體積％ ，以超過30體積％爲佳，超過50體積°/°更佳’超過70體積 -11 - 1294305 (8) %最佳’此以程序流中存在的NOx總體積計。 使用有效量還原劑（選自尿素和氨）移除Ν Ο x。以氨爲 佳。有效量還原劑是指還原劑量會以預定量減低ΝΟχ濃 度。還原劑有效量基本上是〇 · 5 -丨2莫耳還原劑/莫耳ν 0, ’以0.5-8莫耳還原劑/莫耳n〇x爲佳。使用1-4莫耳還原 劑/莫耳N〇x最佳。應注意到本發明使用還原劑和易氧 化的氣體。 咸is自由基反應的複雜關係會使得Ν Ο x與本還原劑 和易氧化的氣體進行非催化還原反應。不希望限於理論， 發明者相信總結果以下列兩個競爭反應表示： 式 1 : no + nh3 + o2 — n2 + h2o(還原反應） 式2: NH3 + 02 —Ν0 + Η20(氧化反應） 使用尿素作爲還原劑，將氰尿酸（HNCO)和氨引至方 法中。如Lee和Kim( 1 996)的文獻所示者，氰尿酸作爲 NO的還原劑，亦與式1和2中所示ΝΟ-ΝΗ3·〇2化學交互作 用。雖然未全然瞭解氰尿酸還原法，且不希望限於理論， 本發明者相信一莫耳尿素解離釋出一莫耳氨和一莫耳氰尿 酸。Kim和Lee硏究的實驗數據（1 996)指出氰尿酸以符合 化學計量的方式將NO還原成元素氮和水，其與N0的莫 耳比是1 ·· 1。因此，通常，所用尿素之相對於NO之莫耳 比約是氨之有效莫耳比的一半。 式1的還原反應於1 6 0 0 °F - 2 0 0 0 T進行。高於2 0 0 0 °F， 1294305 (9) 式2的反應佔優勢。因此，實施本發明時，希望操作溫度 低於約2000°F。但使用本發明時，操作溫度低於約1 600 °F 時，式1反應佔優勢。本發明者意外發現到，溫度低於約 1 6 0 0 °F時，只有注入易氧化的氣體（如：氫），式1所示還 原反應才能有效低減低NOx。應注意到，隨著程序流溫度 的降低，驅動還原反應所須的易氧化氣體量提高。但本發 明者測定得知，此處提出之易氧化的氣體的莫耳比可於有 效操作溫度範圍低於約1600°F，甚至低於約1 3 00°F時使用 ，而還原反應有利於式1。此使得本發明特別適用以減低 FCCU再生器廢氣中的NOx濃度，這是因爲再生器廢氣流 溫度通常低，低於約1 600 °F之故。但應瞭解到，本發明亦 可有效地於介於約1 200 °F至約1 600 °F之間的任何溫度範圍 操作。 易氧化的氣體用以驅動>^(^還原反應。有效量的易 氧化氣體是其量能夠使本發明之還原劑以預定量有效減低 ΝΟχ濃度。莫耳比1 : 1至50 : 1莫耳易氧化的氣體/莫耳 還原劑視爲易氧化的氣體的有效量，以高於1 〇 : 1至40 : 1 爲佳，1 1 : 1至40 : 1較佳，15 : 1至30 : 1最佳。所用的確 實莫耳比視廢氣流溫度、廢氣流組成、用以使易氧化的氣 體與載氣、還原劑和帶有NOx的氣流混合的注射裝置效 能及所用還原劑而定。因此，就選定程序流而言，最有效 之易氧化的氣體與還原劑莫耳比在1 : 1至5 0 ·· 1範圍內。 易氧化的氣體的注入速率使得易氧化的氣體與還原劑的莫 耳比大於1 0 : 1，此一部分由廢氣流（如：再生器廢氣）中 -13- 1294305 (10) 的低氧濃度構成。例如，這樣的流體基本上含有低於約 1.5 體積 ％02。 還原劑和易氧化的氣體於至少一部分存在於廢氣流中 的SOx被移除之處之前引至廢氣流中。此處，廢氣流自再 生器流至下一個處理設備（基本上是COHRU)，必須具有 以廢氣流體積計之高於0.1體積％氧。程序氣流含有至少 〇 . 4體積％爲佳，以0.4至1 . 5體積％更佳。因此，方法的此 階段特別適用以處理流化催化裂解單元的再生器廢氣。較 佳情況中，還原劑和易氧化的氣體注入與FCCU有關的一 氧化碳燃燒/熱回收單元之後，直接注入流化催化裂解單 元（"FCCU”）再生器頂餾管線。更佳情況中，還原劑和易氧 化的氣體儘可能接近再生器出口處地直接引至再生器頂餾 管線。此實施例中，還原劑和易氧化的氣體可以同時自沿 著再生器頂餾管線的多個點引至再生器頂餾管線中。 因爲易氧化的氣體和還原劑用量相對於再生器廢氣流 基本上是小百分比，基本上低於0.5體積％(以流體體積計） ，以僅使用有效量的易取得和相對價廉的載體材料爲佳。 載體材料的非限制例包括空氣和水蒸汽；但可以使用對於 Ν Ο x減低無不利影響或者其本身所助於抑制所不欲發散的 任何載體材料。因此，混合有效量的還原劑和/或易氧化 的氣體’之後與載體材料混合，或者於含有載體材料的管 線中混合。較佳情況中’還原劑/易氧化的氣體混合物注 入導引載體材料的管線中。 所謂的有效量載體材料是指載體材料量使還原劑和易 -14- 1294305 (11) 氧化的氣體及程序流的混合程度足夠，即，使兩種物劑與 欲減低的NOx之接觸最大化。 再生器廢氣基本上亦含有觸媒細粒。藉此技術中已知 的任何適當方式，可自再生器廢氣移除這些觸媒顆粒。但 咸信再生器廢氣中存在的觸媒細粒有助於NOx還原反應 。因此，以有一些觸媒細粒存在（雖非實施本發明必要者） 爲佳，以有助於NOx還原反應及減低易氧化的氣體需求 量。 本發明的一個較佳實施例中，有效量的還原劑和易氧 化的氣體（以與有效量載體材料爲佳）直接注入再生器出口 頂餾管線中。因此，存在的頂餾管線作爲Ν Ο x還原反應 的反應區，藉此免除增添昂貴的處理設備以進行此方法的 必要性。注射混合物以於儘可能介於COHRU和再生器之 間注入爲佳，注射點以儘可能接近再生器廢氣出口處爲佳 ，以使得接近再生器出口處的較高溫度得以被利用，藉此 降低達到所欲NOx減低程度的易氧化的氣體所須用量。 亦有利的情況是，儘量提高還原劑和易氧化的氣體於NOx 還原反應的停留時間。 另一實施例中，使用沿著再生器頂餾管線的至少二個 (以多個爲佳）注射點。有效量的還原劑和易氧化的氣體（ 以亦與有效量的載體材料爲佳）注入這些多個注射點，這 些注射點基本上介於COHRU和再生器之間。較佳情況中 ，所有的注射同時進行。因此，存在的再生器餾頂管線再 度作爲NOx還原反應的反應區，藉此消除增添昂貴處理 1294305 (12) 設備以實施本發明的必要性。較佳情況中，同時注射發生 於儘可能接近再生益廢热出口處。但多個注射點亦以有間 隔爲佳，以使得在注射點之間有適當的停留時間，以獲致 使用多重注射點所能達到的效果。如前述者，儘量提高還 原劑和易氧化的氣體在頂餾管線中的停留時間，以完成此 反應。 如前所討論者，此技術已經知道將亞氯酸鈉添加至滌 氣液中，此述於美國專利案第6,2 94,1 3 9號，已將其中所 揭示者列入參考。亞氯酸鈉添加至滌氣液的缺點在於：亞 氯酸鈉也會將S Ox氧化成高階硫氧化物。此非所欲氧化反 應迫使精煉業者將相當高量的亞氯酸鈉注Λ廢氣流中，以 自廢氣流移除令人滿意量之存在於廢氣流中的ΝΟχ。如前 所討論者，這些高量亞氯酸鈉具有引發滌氣裝置硬體腐蝕 的所不欲效應，引發與廢水處理有關的問題，也會提高物 劑成本。此外，使用二氧化氯將ΝΟχ氧化成高階氮氧化 物，並以亞氯酸鈉吸收以移除高階氮氧化物有著成本較高 的額外缺點。 藉由使經滌氣和/飽和的氣體直接與亞氯酸鈉 (NaC102)於SOx移除步驟下游接觸，所提出的本發明解決 這些和其他問題。所用SOx移除法非本發明之基礎，可以 是任何有效方法。但實施所提出本發明之方法應在亞氯酸 鈉與廢氣流混合之前，將廢氣流中的 SOx量降至低於 lOOppm，以低於50ppm爲佳，低於l〇ppm更佳。最佳情況 是在亞氯酸鈉與廢氣流混合之前，移除實質上所有存在於 -16- 1294305 (13) 廢氣流中的sox。適用於此處之sox移除法的非限制例包 括濕脫硫法（$[]:水滌氣、鹼滌氣、氧化鎂滌氣和氨滌氣） 及乾脫硫法（如：使用氧化錳或活性碳）。sox藉濕脫硫法 移除爲佳，使用濕氣體滌氣裝置最佳。 濕氣體滌氣裝置移除，如：磨損的觸媒細粒和S 0 x。 因此，藉由使煙道氣與亞氯酸鈉於滌氣裝置之後接觸，於 與亞氯酸鈉混合處，廢氣流中的sox含量低。因此，較少 量的亞氯酸鈉便能達到所欲NOx減低結果。此外，此亞 氯酸鈉的使用比例較低也會緩和前述問題，如··硬體腐蝕 和廢水處理。 亞氯酸鈉將低階ΝΟχ氧化成高階氧化物的機構複雜 。實施所提出的方法時，亞氯酸鈉可直接與ΝΟχ反應， 或者於酸性條件（此處以pH低於6爲佳）下形成二氧化氯。 不希望限於任何理論或模式，嫻信在這樣的酸性條件下， 亞氯酸鈉化合物不對稱成爲鈉離子和二氧化氯。藉此形成 的二氧化氯氣體將低階NOx氧化成高階氧化物。不希望 受限的同時，本發明者相信二氧化氯氧將NOx予以氧化 的一般氧化反應可以下列式表示： 式 1 ·· 5N0 + 3C102 + 4H20 —5HN03 + 3HC1 因此，在酸性環境（以pH低於6爲佳）中使用亞氯酸鈉 時，必須將至少一部分低階Ν Ο X氧化成高階氧化物所須 的二氧化氯量列入考慮，以確保有足量的亞氯酸鈉存在， -17- 1294305 (14) 據此，亞氯酸鈉進行不對稱反應時，有足量二氧化氯濃度 存在以將低階NOx氧化成高階氧化物。通常，二氧化氯 於酸性環境中的用量由3至8莫耳c 1 0 2 / 5莫耳n 0。精煉 業者可藉由使用4至7莫耳Cl〇2/ 5莫耳NO地實施本發明 。較佳情況是在亞氯酸鈉不對稱反應之後，使用略高於亞 氣酸納化學計量’如：3至4旲耳CIO〗 / 5莫耳NO。 如所討論者，亞氯酸鈉亦可直接將Ν Ο x予以氧化。 此氧化反應可以於略酸性環境（如：p Η 6至7 )、中性環境 (ΡΗ7)或鹼性環境（pH高於7)條件下發生。但隨著ρΗ提高 至1 0，Ν Ο x的吸收降低。不希望受限的同時，咸信亞氯酸 鈉與NOx直接反應的機構可以下面的式2表示。 式2: NO + 3NaC102 + 2H2〇 — 4HN03 + 3NaCl 亞氯酸鈉直接將NOx予以氧化時，亞氯酸鈉用量是 將至少一部分低階氮氧化物氧化成高階氮氧化物所須之亞 氯酸鈉化學計量的3至10倍，以減少NOx，以2-8倍化學計 量爲佳，略高於亞氯酸鈉化學計量最佳，如：1.1至2.5倍 化學計量。 至少一部分可氧化的Ν Ο X被氧化成高階氮氧化物之 後，本發明的另一實施例包含移除至少一部分高階氮氧化 物。高階氮氧化物之移除可藉任何有效方法達成。這樣的 方法包括，但不限於，使用鹼性溶液（如：苛性鈉水溶液） 或還原溶液（如··硫代硫酸鈉水溶液）、亞氯酸鈉吸收、催 -18- 1294305 (15) 化性轉化及氨和氫注射，此如美國專利案第3，9 0 0，5 5 4號 中所描述者，茲將其中所述者列入參考。最佳情況中，經 · 氧化的NOx化合物藉以水滌氣而移除，這是因爲高階氧 化物（如：1^02和N20 5 )比低階氧化物易溶於水之故。實施 所提出的本發明之時，氧化反應之後移除20體積％至100 體積％高階氧化物爲佳，氧化反應之後移除40體積％至80 體積％高階氧化物較佳，氧化反應之後移除6 0體積％至9 0 體積％ NOx的高階氧化物最佳。 φ 如所討論者，本發明範圍中，藉濕氣體滌氣移除廢氣 流中的至少一部分S Ox。因此，本發明的一個實施例中， 亞氯酸鈉與廢氣流於與濕氣體滌氣器連接之已有的分離滾 筒中混合。分離滾筒基本上含有硬體（如：噴嘴）位於分離 滾筒內。此實施例中，亞氯酸鈉由噴嘴噴灑，被污染的煙 道氣流被導至分離滾筒，其先與亞氯酸鈉接觸。此亞氯酸 鈉可以先與水（以去離水爲佳）混合，水作爲承載流體以使 亞氯酸鈉達較佳分散狀態。同樣地，此實施例中，額外量 馨 的去離子水可由噴嘴噴灑。所謂額外量的去離水是指去離 子水的量足以吸收至少一部分高階氮氧化物。 所提出的本發明的另一實施例中，在SOx移除步驟之 後，以將存在於廢氣流中之一部分NOx予以氧化所須量 來得多的亞氯酸鈉與廢氣流混合。此額外量的亞氯酸鈉將 至少一部分在S Ox移除步驟之後仍留在廢氣流中的任何 SOx氧化成高階硫氧化物。這些SOx高階氧化物可藉此技 術中已知的任何方法移除。 -19- 1294305 (16) 前述描述針對實施本發明的一個較佳方式。嫻於此技 術者瞭解其他方式亦能有效地達成本發明之精神。 實例 下列實例說明本方法的有效性，但不欲限制本發明。 實例1 在實驗室規模環境中測試亞氯酸鈉於廢氣流中之添加 。在開始實驗之前，測定廢氣流和模擬滌氣液體中的sox 和NOx濃度，其數據示於下面的附表1。使用熱偶裝置測 知流體初溫爲68°F知廢氣流中的氧初濃度是3.0體積％〇2。 使此廢氣流通過5公分實驗室規模的細腰滌氣器，亞 氯酸鈉自滌氣器下游加至此廢氣流中。亦偵測系統的pH 和亞氯酸鈉濃度及輸出的S Ο x和Ν Ο x濃度。此實驗移除 原存在於廢氣流中之超過95%SOx和超過90%NOX。所有參 數及此實驗結果列於下面的附表1。 -20- 1294305 (17) 附表1 NOx輸出 50-60ppmv S 〇 X輸出 50-500ppmv 廢氣溫度 6 8〇F 〇2體積％ 3 滌氣液 模擬 NaC102濃度 0.01-0.1 Μ 系統pH 4.05-9.10 NOx輸出（移除。 >90% SOx輸出（移除。 >95% 實例2 在全規格操作流化催化裂解程序單元上，測試本發明 的第二部分，如·· S〇x移除步驟之後添加亞氯酸鈉。以未 修飾之已有的與流化催化裂解程序單元的濕氣體滌氣裝置 連通之分離滾筒地進行實驗。 此實驗中，流化催化裂解程序單元的濕氣體滌氣裝置 的噴嘴用以使亞氯酸鈉與廢氣流混合。因此，亞氯酸鈉與 去離子水混合並使用噴嘴噴入分離滾筒中。此實驗使用額 外量的去離子水以藉水吸收而移除一部分高階氧化物。 此實驗以流化催化裂解程序單元進行，以於S Ox步驟 之後，僅添加亞氯酸鈉三天，於此期間內，偵測和記錄 NO氧化反應、NOx總移除、亞氯酸鈉流率和去離子水流 率。N 0氧化反應和N 0 X移除以％表示，其定義爲[(輸入 1294305 (18) 濃度-輸出濃度）/輸入濃度]x 100。此數據列於下面的附 表2。b) the mixture is injected into the exhaust stream at a point wherein the temperature of the exhaust stream containing S 低于 is less than 1 600 °F Ο removing at least a portion of the SOx present in the exhaust stream; d) an effective amount of chlorous acid Sodium is mixed with the off-gas stream downstream of the aforementioned step c) whereby at least a portion of the lower order NOx present in the exhaust stream is oxidized to a higher order oxide. In another embodiment of the invention, the nozzle of the wet gas scrubber is used to mix sodium chlorite with the SOX-containing exhaust stream. In another embodiment, the NOX higher order oxide is removed from the exhaust stream by a method selected from the group consisting of alkali solution absorption, reduction solution absorption, scrubbing, ammonia injection, catalytic conversion, and water absorption. In another embodiment of the invention, the effective amount of reducing agent and oxidizable gas are injected into the existing regenerator overhead line of the FCC program unit at a single location upstream of the FCCU heat recovery unit. In another embodiment of the invention, an effective amount of reducing agent and oxidizable gas are simultaneously injected into the existing regenerator overhead line of the FCC program unit at multiple locations upstream of the FCCU heat recovery unit. In another embodiment of the invention, the oxidizable gas is hydrogen and the reducing agent -8- 1294305 (5) is ammonia. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The term "xenon x" or "nitrogen oxide" as used herein refers to a wide variety of oxides which may be present in the combustion exhaust gas. Thus, all of the various oxides of nitrogen include, but are not limited to, nitric oxide (NO), nitrogen dioxide (no2), nitrogen peroxide (n2o4), nitrogen pentoxide (n2o5), and mixtures thereof. However, since NO substantially accounts for more than 90% of the nitrogen oxides present in the combustion exhaust gas of the invention of the present invention, it also refers to nitrogen monoxide (NO). Therefore, the proposed method is particularly concerned with the reduction and control of NO. Similarly, the flue gas, wet gas, combustion effluent, combustion exhaust effluent, exhaust gas, and exhaust stream names used interchangeably herein refer to the same scrubbed and/or saturated gas stream. Similarly, the names of wet gas scrubbers, scrubbers, and scrubbers are sometimes used interchangeably. It should also be noted that the term "higher order oxide" as used herein refers to any NOx wherein "x" is two or more. When describing the mixing of a reducing agent and an easily oxidizable gas, the so-called mixing is broadly defined. Therefore, mixing means maximizing the local contact of the reducing agent and the oxidizable gas with the NOx in the exhaust gas stream as much as possible at the desired molar ratio. Any suitable mixing technique can be used to achieve this. These techniques include, but are not limited to, the use of a carrier gas with a reducing agent and/or an oxidizable gas to facilitate more uniform mixing; a premixed gas stream of reducing agent, oxidizable gas, and carrier gas is injected into the exhaust stream. Alternatively, the reducing agent and the carrier gas stream and the easily oxidizable gas and the carrier gas stream are separately injected into the exhaust gas stream. Suitable mixing techniques, methods or means prior to injection include the extraction of a reducing agent, an oxidizable gas, and the loading of -9- 1294305 (6) gas through a separate line into a universal tank or into the injection line to the exhaust stream to be treated, such that The seed and the carrier gas are mixed and directed toward the injection point. The present invention proposes a cost effective way whereby the refiner can remove NOx from the exhaust stream (e.g., the exhaust gas produced by the fluid catalytic cracking unit). Oxidation of NOx into higher-order oxides effectively removes NOx from the flue gas stream because higher-order nitrogen oxides (eg, >102 and n2o5) are more soluble in water than lower-order nitrogen oxides and are more readily nitrated or The nitrite form is removed from the system and higher order oxides (eg, no2 and n2o5) are easier to remove than lower order oxides. Accordingly, the proposed method comprises forming a mixture of a reducing agent and an oxidizable gas in a predetermined amount to effectively reduce the amount of NOx in the exhaust stream, removing at least a portion of the SOx present in the gas stream, and adding an effective amount of chlorous acid. Sodium is introduced into the exhaust stream whereby a portion of the NOx contained in the exhaust stream is oxidized to a higher order oxide (e.g., NO is oxidized to N02). This higher order oxide can then be removed by absorption from an alkali solution, absorption by a reducing solution, ammonia injection by a scrubber, catalytic conversion, and absorption by water. By effective sodium chlorite herein is meant an amount which oxidizes at least a portion of the NOx present in the exhaust stream such that it is at least 20% by volume, such as from 20% to 80% by volume, in 40 volumes. More preferably, 90% by volume, more preferably 50% by volume/〇 to 99% by volume, and most preferably means that substantially all of the lower-order NOx present in the exhaust gas stream is oxidized to higher-order nitrogen oxides. The invention is particularly useful for reducing the concentration of NOx in a fluid catalytic cracking unit (F C C U) process stream. Fluid catalytic cracking is an important and widely used refining process. Catalytic cracking essentially converts heavy oil into lighter products (eg, gasoline). In the fluid catalytic cracking (FCC) process, the fine particle contact 1294305 (7) is continuously circulated between the cleavage reactor and the catalyst regenerator. The average reactor temperature is 900-1 000 °F and the average feed temperature is 500-800 °T. The reactor and regenerator together form the main building block of the catalytic cracking unit. The FCC program unit is known in the art, and such a unit is discussed in more detail in U.S. Patent No. 5,846,403, the disclosure of which is incorporated herein by reference. Regenerators are particularly important in terms of catalyst life and effectiveness because carbonaceous deposits (coke) are formed on the catalyst during fluid catalytic cracking, which substantially reduces its activity. Thereafter, the catalyst is substantially regenerated by burning at least a portion of the coke in the regenerator to restore its performance again. This is basically achieved by injecting air or other gas having a combustible amount of oxygen into the regenerator at a rate sufficient to fluidize the used catalyst particles. A part of the coke contained in the catalyst particles is burned in a regenerator to obtain regenerated catalyst particles. Typical regenerator temperatures range from about 10.05 ° C to about 1 45 0 ° F, and the exit temperature of the regenerator exhaust gas typically ranges from about 1200 °F to about 1 500 °F. After the regeneration treatment, the catalyst particles are recycled back to the reactor. Regenerator off-gas typically enters other processes such as: heat recovery unit, fines removal unit, carbon monoxide combustion/heat recovery unit (COHRU 'as described above' for converting CO to CO 2 and recovering available fuel energy) And SOx removal device. In a preferred embodiment of the invention, the 'primary removal step removes at least a portion of the enthalpy present in the exhaust stream' thereby reducing the need to oxidize the remaining Ν Ο X present in the exhaust stream. The amount of sodium chlorate. In the first removal step, the predetermined amount removed from the exhaust stream is substantially at least 1% by volume, preferably more than 30% by volume, more than 50% by volume/° more preferably 'more than 70 volumes -11 - 1294305 ( 8) % Best' This is based on the total volume of NOx present in the program stream. Use an effective amount of reducing agent (selected from urea and ammonia) to remove Ν Ο x. Ammonia is preferred. An effective amount of a reducing agent means that the reducing dose reduces the concentration of hydrazine by a predetermined amount. The effective amount of reducing agent is substantially 〇 5 - 丨 2 molar reducing agent / mol ν 0, ' preferably 0.5-8 mole reducing agent / mol n 〇 x. It is best to use 1-4 moles of reducing agent/mole N〇x. It should be noted that the present invention uses a reducing agent and an oxidizing gas. The complex relationship of the salty is radical reaction causes the non-catalytic reduction reaction of Ν Ο x with the present reducing agent and the oxidizable gas. Without wishing to be bound by theory, the inventors believe that the total results are expressed in two competitive reactions: Equation 1: no + nh3 + o2 - n2 + h2o (reduction reaction) Formula 2: NH3 + 02 - Ν0 + Η20 (oxidation reaction) Using urea As a reducing agent, cyanuric acid (HNCO) and ammonia are introduced into the process. As shown by the literature of Lee and Kim (1 996), cyanuric acid acts as a reducing agent for NO and also chemically interacts with ΝΟ-ΝΗ3·〇2 as shown in Formulas 1 and 2. Although the cyanuric acid reduction process is not fully understood and is not intended to be limited to theory, the inventors believe that one mole of urea dissociates to release one mole of ammonia and one mole of cyanuric acid. Kim and Lee's experimental data (1 996) indicate that cyanuric acid reduces NO to elemental nitrogen and water in a stoichiometric manner, and its molar ratio to N0 is 1··1. Therefore, in general, the molar ratio of urea used to NO is about half that of ammonia. The reduction reaction of Formula 1 is carried out at 1 60 °F - 2 0 0 T. Above 2000°F, 1294305 (9) The reaction of Equation 2 predominates. Thus, in practicing the present invention, it is desirable to have an operating temperature below about 2000 °F. However, when using the present invention, the reaction of Formula 1 predominates when the operating temperature is below about 1 600 °F. The inventors have unexpectedly discovered that when the temperature is lower than about 1600 °F, only a gas which is easily oxidized (e.g., hydrogen) is injected, and the reduction reaction shown in Formula 1 can effectively reduce NOx. It should be noted that as the temperature of the program stream decreases, the amount of oxidizable gas required to drive the reduction reaction increases. However, the inventors have determined that the moiré ratio of the oxidizable gas proposed herein can be used at an effective operating temperature range of less than about 1600 °F, or even less than about 1300 °F, and the reduction reaction is advantageous. Formula 1. This makes the invention particularly useful for reducing the NOx concentration in the FCCU regenerator exhaust since the regenerator exhaust stream temperature is typically low, below about 1 600 °F. It should be understood, however, that the present invention is also effective to operate at any temperature range between about 1 200 °F and about 1 600 °F. The oxidizable gas is used to drive the reduction reaction. An effective amount of the oxidizable gas is such an amount that the reducing agent of the present invention can effectively reduce the cerium concentration by a predetermined amount. Mohr ratio 1: 1 to 50: 1 Mo The oxidative gas of the ear/mole reducing agent is considered to be an effective amount of the oxidizable gas, preferably higher than 1 〇: 1 to 40:1, preferably 1 1 : 1 to 40 : 1 , 15 : 1 to 30 : 1 Optimum. The exact molar ratio used depends on the temperature of the exhaust gas stream, the composition of the exhaust gas stream, the efficiency of the injection device used to mix the oxidizable gas with the carrier gas, the reducing agent and the NOx-laden gas stream, and the reducing agent used. Therefore, in terms of the selected program flow, the most effective oxidizable gas and reducing agent molar ratio is in the range of 1:1 to 5 0 ··1. The rate of injection of easily oxidizable gas makes the easily oxidizable gas and reduction The molar ratio of the agent is greater than 10: 1. This portion is composed of a low oxygen concentration of -13294525 (10) in the exhaust gas stream (eg, regenerator off-gas). For example, such a fluid contains substantially less than about 1.5 volumes. %02. The reducing agent and the oxidizable gas are at least a part of the SOx present in the exhaust gas stream The removal is directed to the exhaust stream. Here, the exhaust stream flows from the regenerator to the next processing unit (essentially COHRU) and must have more than 0.1% by volume of oxygen based on the volume of the exhaust stream. At least 4 4 vol% is preferred, preferably from 0.4 to 1.5 vol%. Therefore, this stage of the process is particularly suitable for treating the regenerator off-gas of the fluid catalytic cracking unit. Preferably, the reducing agent and the oxidizing agent are preferred. After the gas is injected into the carbon monoxide combustion/heat recovery unit associated with the FCCU, it is directly injected into the fluid catalytic cracking unit ("FCCU" regenerator overhead line. In a better case, the reducing agent and the oxidizable gas are as close as possible to regeneration. The outlet of the device is directly led to the regenerator overhead line. In this embodiment, the reducing agent and the easily oxidizable gas can be simultaneously introduced from the plurality of points along the regenerator overhead line to the regenerator overhead line. The amount of oxidizing gas and reducing agent is substantially a small percentage relative to the regenerator off-gas stream, substantially less than 0.5% by volume (based on fluid volume) to use only an effective amount of readily available A relatively inexpensive carrier material is preferred. Non-limiting examples of carrier materials include air and water vapor; however, any carrier material which does not adversely affect the reduction of Ν x or which itself contributes to suppress unwanted divergence may be used. Mixing an effective amount of reducing agent and/or oxidizable gas' is then mixed with the carrier material or mixed in a line containing the carrier material. Preferably, the reducing agent/oxidizable gas mixture is injected into the line of the guiding carrier material. The so-called effective amount of carrier material means that the amount of carrier material is sufficient to mix the reducing agent and the gas and process stream oxidized by Yi-14-1294305 (11), that is, to bring the two agents into contact with the NOx to be reduced. maximize. The regenerator off-gas also contains catalytic fines. These catalyst particles can be removed from the regenerator offgas in any suitable manner known in the art. However, the catalyst fine particles present in the exhaust gas of the Xianxin regenerator contribute to the NOx reduction reaction. Therefore, it is preferred to have some catalyst fine particles (although not necessary for carrying out the invention) to contribute to the NOx reduction reaction and to reduce the gas demand for oxidation. In a preferred embodiment of the invention, an effective amount of a reducing agent and an oxidizing gas (preferably with an effective amount of carrier material) are injected directly into the regenerator outlet overhead line. Therefore, the overhead line present exists as a reaction zone for the reduction reaction of Ν Ο x, thereby eliminating the need to add expensive processing equipment to carry out the process. It is preferred to inject the mixture as much as possible between the COHRU and the regenerator, with the injection point being as close as possible to the regenerator off-gas outlet so that higher temperatures near the regenerator outlet are utilized, thereby reducing The amount of oxidizable gas required to achieve the desired reduction in NOx. It is also advantageous to increase the residence time of the reducing agent and the oxidizable gas in the NOx reduction reaction as much as possible. In another embodiment, at least two (preferably multiple) injection points along the regenerator overhead line are used. An effective amount of reducing agent and oxidizable gas (preferably also with an effective amount of carrier material) are injected into the plurality of injection points, which are substantially between the COHRU and the regenerator. Preferably, all injections are performed simultaneously. Thus, the regenerator head line present is again used as a reaction zone for the NOx reduction reaction, thereby eliminating the need to add expensive processing 1294305 (12) equipment to practice the invention. Preferably, the simultaneous injection occurs as close as possible to the regenerative waste heat outlet. However, multiple injection points are also preferably spaced so that there is an appropriate residence time between injection points to achieve the effect of using multiple injection points. As described above, the residence time of the reducing agent and the oxidizable gas in the overhead line is increased as much as possible to complete the reaction. As previously discussed, it is known in the art to add sodium chlorite to a scrubbing liquid as described in U.S. Patent No. 6,2,94,1,9, the disclosure of which is incorporated herein by reference. A disadvantage of the addition of sodium chlorite to the scrubbing liquid is that sodium chlorite also oxidizes S Ox to higher order sulfur oxides. This undesired oxidation reaction forces the refiner to inject a relatively high amount of sodium chlorite into the exhaust stream to remove a satisfactory amount of helium present in the exhaust stream from the exhaust stream. As discussed above, these high amounts of sodium chlorite have the undesirable effect of causing hard corrosion of the scrubber unit, causing problems associated with wastewater treatment and increasing the cost of the agent. In addition, the use of chlorine dioxide to oxidize ruthenium to higher order oxynitrides and absorption with sodium chlorite to remove higher order NOx has additional cost disadvantages. The present invention addresses these and other problems by bringing the scrubbed and/or saturated gas directly into contact with the sodium chlorite (NaC 102) downstream of the SOx removal step. The SOx removal method used is not the basis of the present invention and can be any effective method. However, the method of the present invention is practiced to reduce the amount of SOx in the exhaust stream to less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm, prior to mixing the sodium chlorite with the exhaust stream. The best case is to remove substantially all of the sox present in the -16- 1294305 (13) exhaust stream before the sodium chlorite is mixed with the exhaust stream. Non-limiting examples of sox removal methods suitable for use herein include wet desulfurization ($[]: water scrubbing, alkali scrubbing, magnesia scrubbing, and ammonia scrubbing) and dry desulfurization (eg, oxidation) Manganese or activated carbon). It is better to remove the sox by wet desulfurization, and it is best to use a wet gas scrubber. The wet gas scrubber is removed, such as: worn catalyst fines and S 0 x. Therefore, by bringing the flue gas into contact with the sodium chlorite after the scrubber, the sox content in the exhaust gas stream is low at the point where it is mixed with the sodium chlorite. Therefore, a smaller amount of sodium chlorite can achieve the desired NOx reduction. In addition, the lower use ratio of this sodium chlorite will also alleviate the aforementioned problems, such as hard corrosion and wastewater treatment. The mechanism by which sodium chlorite oxidizes low-order bismuth into higher-order oxides is complicated. When the proposed method is carried out, sodium chlorite can be directly reacted with hydrazine or under acidic conditions (here preferably below pH 6) to form chlorine dioxide. Without wishing to be bound by any theory or mode, it is believed that under such acidic conditions, the sodium chlorite compound is asymmetrical to sodium ions and chlorine dioxide. The chlorine dioxide gas thus formed oxidizes the low-order NOx into a higher-order oxide. While not wishing to be limited, the inventors believe that the general oxidation reaction in which chlorine dioxide oxidizes NOx can be expressed by the following formula: Formula 1 ··· 5N0 + 3C102 + 4H20 —5HN03 + 3HC1 Therefore, in an acidic environment (low pH) When sodium chlorite is used in 6 is preferred, the amount of chlorine dioxide required to oxidize at least a portion of the lower-order Ν Ο X to higher-order oxides must be considered to ensure that sufficient sodium chlorite is present. -17- 1294305 (14) Accordingly, when sodium chlorite is subjected to an asymmetric reaction, a sufficient amount of chlorine dioxide is present to oxidize low-order NOx to a higher-order oxide. Typically, the amount of chlorine dioxide used in an acidic environment is from 3 to 8 moles c 1 0 2 / 5 moles n 0 . The refiner can implement the invention by using 4 to 7 moles Cl 〇 2 / 5 moles NO. Preferably, after the asymmetric reaction of sodium chlorite, a stoichiometric amount slightly higher than that of the sub-nano acid is used, e.g., 3 to 4 旲 CIO / 5 mol NO. As discussed, sodium chlorite can also oxidize Ν Ο x directly. This oxidation reaction can take place in a slightly acidic environment (e.g., p Η 6 to 7), a neutral environment (ΡΗ7), or an alkaline environment (pH higher than 7). However, as ρΗ increases to 10, the absorption of Ν Ο x decreases. While not wishing to be limited, the mechanism for the direct reaction of sodium chlorite with NOx can be expressed by the following formula 2. Formula 2: NO + 3NaC102 + 2H2〇— 4HN03 + 3NaCl Sodium chlorite directly oxidizes NOx. The amount of sodium chlorite is the chlorite required to oxidize at least a portion of the lower-order nitrogen oxides to higher-order nitrogen oxides. Sodium stoichiometry is 3 to 10 times to reduce NOx, preferably 2-8 times stoichiometric, slightly better than sodium chlorite stoichiometry, such as: 1.1 to 2.5 times stoichiometry. After at least a portion of the oxidizable ΝX is oxidized to a higher order oxynitride, another embodiment of the invention includes removing at least a portion of the higher order oxynitride. The removal of higher order nitrogen oxides can be achieved by any effective method. Such methods include, but are not limited to, the use of an alkaline solution (such as: aqueous caustic soda) or a reducing solution (such as sodium thiosulfate aqueous solution), sodium chlorite absorption, reminder -18-1294305 (15) Conversion and injection of ammonia and hydrogen, as described in U.S. Patent No. 3,900,515, the disclosure of which is incorporated herein by reference. In the best case, the oxidized NOx compound is removed by water scrubbing because higher order oxides (e.g., 1^02 and N20 5 ) are more soluble in water than lower order oxides. When carrying out the proposed invention, it is preferred to remove 20% by volume to 100% by volume of the higher-order oxide after the oxidation reaction, and it is preferred to remove 40% by volume to 80% by volume of the higher-order oxide after the oxidation reaction, and remove after the oxidation reaction. The high-order oxide of 60% by volume to 90% by volume of NOx is optimal. φ As discussed, in the context of the present invention, at least a portion of the S Ox in the exhaust stream is removed by the scrubbing of the wet gas. Thus, in one embodiment of the invention, the sodium chlorite is mixed with the exhaust stream in an existing separation drum that is coupled to the wet gas scrubber. The separation drum basically contains a hard body (e.g., a nozzle) located in the separation drum. In this embodiment, sodium chlorite is sprayed by a nozzle and the contaminated flue gas stream is directed to a separation drum which is first contacted with sodium chlorite. The sodium chlorite may be first mixed with water (preferably as deionized water) and the water acts as a carrier fluid to achieve a better dispersion of sodium chlorite. Similarly, in this embodiment, an additional amount of deionized water can be sprayed by the nozzle. By extra volume of deionized water is meant that the amount of deionized water is sufficient to absorb at least a portion of the higher order nitrogen oxides. In another embodiment of the present invention, after the SOx removal step, sodium chlorite is mixed with the exhaust stream at a much greater amount required to oxidize a portion of the NOx present in the exhaust stream. This additional amount of sodium chlorite will oxidize at least a portion of any SOx remaining in the exhaust stream after the S Ox removal step to a higher order sulfur oxide. These SOx higher order oxides can be removed by any method known in the art. -19- 1294305 (16) The foregoing description is directed to a preferred embodiment of the invention. The spirit of the present invention can be effectively achieved by other skilled artisans. EXAMPLES The following examples illustrate the effectiveness of the method, but are not intended to limit the invention. Example 1 The addition of sodium chlorite to the exhaust stream was tested in a laboratory scale environment. The sox and NOx concentrations in the exhaust gas stream and the simulated scrubbing liquid were determined prior to the start of the experiment and the data is shown in Table 1 below. Using a thermocouple device, it was determined that the initial temperature of the fluid was 68 °F and the initial oxygen concentration in the exhaust gas stream was 3.0% by volume 〇2. This exhaust stream was passed through a 5 cm laboratory scale fine waist scrubber, and sodium chlorite was added to the exhaust stream from the downstream of the scrubber. The pH and sodium chlorite concentration of the system and the S Ο x and Ν Ο x concentrations of the output are also detected. This experiment removes more than 95% SOx and more than 90% NOx originally present in the exhaust stream. All parameters and the results of this experiment are listed in Schedule 1 below. -20- 1294305 (17) Schedule 1 NOx output 50-60ppmv S 〇X output 50-500ppmv Exhaust gas temperature 6 8〇F 〇2% by volume 3 Detergent simulation NaC102 concentration 0.01-0.1 Μ System pH 4.05-9.10 NOx output (Remove. > 90% SOx Output (Remove. > 95% Example 2) Test the second part of the invention on a full-scale operational fluid catalytic cracker program unit, such as after the S〇x removal step Adding sodium chlorite. The experiment was carried out with an unmodified existing separation drum connected to the wet gas scrubber unit of the fluid catalytic cracking program unit. In this experiment, the wet gas scrubber of the fluid catalytic cracking program unit was used. The nozzle is used to mix sodium chlorite with the exhaust stream. Therefore, sodium chlorite is mixed with deionized water and sprayed into the separation drum using a nozzle. This experiment uses an additional amount of deionized water to remove it by water absorption. Part of the high-order oxide. This experiment was carried out in a fluid catalytic cracking program unit to add only sodium chlorite for three days after the S Ox step. During this period, NO oxidation reaction, total NOx removal, and NOx were detected and recorded. Sodium chlorite flow rate and go Ion water flow rate. N 0 oxidation reaction and N 0 X removal are expressed in % and are defined as [(input 1294305 (18) concentration - output concentration) / input concentration] x 100. This data is listed in Table 2 below.
-22- 1294305 (19) 附表2 天 水流 (gpm) NaC102 流（gpm) NO 氧化反應％ NOx 移除％ 1 0 0 0 0 80-90 0 0 0 90 1 42 15 200 2.3 94 49 300 2.3 99 57 465 2 99 55 2 465 2 99 46 465 8 99 44 465 1.5 99 42 465 1.25 99 40 465 1 . 1 99 39 465 0.7 93 39 465 0 0 0 3 1 70 1 5 1 9 170 1.8 63 13 170 2 67 13 170 2.3 76 15 350 2.3 98 32 465 2.2 97 45 350 1.8 99 44 350 1 97 38-22- 1294305 (19) Schedule 2 Water flow (gpm) NaC102 flow (gpm) NO oxidation reaction % NOx removal % 1 0 0 0 0 80-90 0 0 0 90 1 42 15 200 2.3 94 49 300 2.3 99 57 465 2 99 55 2 465 2 99 46 465 8 99 44 465 1.5 99 42 465 1.25 99 40 465 1 . 1 99 39 465 0.7 93 39 465 0 0 0 3 1 70 1 5 1 9 170 1.8 63 13 170 2 67 13 170 2.3 76 15 350 2.3 98 32 465 2.2 97 45 350 1.8 99 44 350 1 97 38
-23- 1294305 (20) 應注意，與分離滾筒之噴嘴相關的最大水流率是 4 6 5 g p m。因此，由收集的數據相信，使用流率能力較高 的噴嘴或修飾此處所用的噴嘴而使得它們的流率能力提高 ，會提高NOx的移除速率。 同樣的，本發明者也相信，提高氣/液接觸面積， NOx移除率也會提高。此實驗中使用塡充材料，其限於5 英呎分離滾筒。可以藉，如，提高塡充材料體積或使用能 夠提高氣/液接觸面積的塡充材料，而有利地提高氣/液 接觸面積。-23- 1294305 (20) It should be noted that the maximum water flow rate associated with the nozzle of the separation drum is 4 6 5 g p m. Therefore, from the collected data, it is believed that the use of nozzles having higher flow rate capabilities or modifying the nozzles used herein increases their flow rate capability, which increases the rate of NOx removal. Similarly, the inventors believe that the gas/liquid contact area is increased and the NOx removal rate is also increased. A charge material was used in this experiment, which was limited to a 5 inch separation drum. The gas/liquid contact area can be advantageously increased by, for example, increasing the volume of the charge material or using a charge material capable of increasing the gas/liquid contact area.
-24--twenty four-