TWI392655B - Desulfurization seawater treatment method - Google Patents
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本發明係一種脫硫海水的處理方法，尤其是一種對用海水脫除煙氣中的二氧化硫後的脫硫海水處理方法。The invention relates to a method for treating desulfurized seawater, in particular to a method for treating desulfurized seawater after removing sulfur dioxide from flue gas by using seawater.
海水脫硫製程的基本原理主要係利用海水中鹼性成分(碳酸氫根)洗滌並中和煙氣中的酸性物質-二氧化硫。除了完全使用海水的方法外，尚可包括在海水中添加鹼性脫硫劑(如石灰、氫氧化鎂和/或氫氧化鈉等)的方法，以適用於處理高濃度二氧化硫(SO2 )煙氣的情況。而且，與其他濕式脫硫法(如石灰石膏法、氫氧化鎂法等)相比，海水脫硫法可無須使用脫硫藥劑，至少能減少脫硫藥劑的用量，故可節省成本；在煙氣洗滌程序中，各廠家皆使用不同的脫硫裝置，如填充塔、多孔板塔和噴淋塔等皆能達到洗滌煙氣中二氧化硫之目的，而使用這些脫硫裝置則具有製程、設備簡單的優點，故近年廣泛應用於各國。The basic principle of the seawater desulfurization process is mainly to wash and neutralize the acidic substance in the flue gas, sulfur dioxide, by using the alkaline component (bicarbonate) in seawater. In addition to the method of completely using seawater, a method of adding an alkaline desulfurizing agent (such as lime, magnesium hydroxide, and/or sodium hydroxide) to seawater may be included to treat a high concentration of sulfur dioxide (SO 2 ) smoke. The situation of gas. Moreover, compared with other wet desulfurization methods (such as lime gypsum method, magnesium hydroxide method, etc.), the seawater desulfurization method can reduce the amount of desulfurization agent by using no desulfurization agent, thereby saving cost; In the flue gas washing process, each manufacturer uses different desulfurization devices, such as packed towers, perforated trays and spray towers, to achieve the purpose of scrubbing sulfur dioxide in flue gas, and the use of these desulfurization devices has processes and equipment. It has simple advantages and has been widely used in various countries in recent years.
在完全使用海水的方法中，已進行洗滌煙氣中二氧化硫的海水(以下稱「脫硫海水」)會因含有亞硫酸而生成之硫酸，使pH值降低，且因亞硫酸氫根的還原性而導致化學需氧量(COD)值升高，故在排放至大海前必須進行曝氣處理以恢復其pH值和COD值，目前最具有代表性的製程可參考採用先混合後曝氣之方法的Flakt-Hydro法[IChemE Symposium Series No. 131,95-108(1993)]以及揭露於美國專利第5,690,899號中的比肖夫法，其係控制海水之pH值為4~5之間(較佳的是控制在pH值為4.15~4.5)先曝氣後混合的方式。In the method of completely using seawater, seawater which has been subjected to the washing of sulfur dioxide in the flue gas (hereinafter referred to as "desulfurized seawater") is caused by the sulfuric acid formed by the sulfuric acid, which lowers the pH and is reduced by the hydrogensulfite. As a result, the chemical oxygen demand (COD) value increases, so it must be aerated to restore its pH value and COD value before being discharged to the sea. The most representative process can be referred to the method of first mixing and aeration. The Flakt-Hydro method [IChemE Symposium Series No. 131, 95-108 (1993)] and the Bischoff method disclosed in U.S. Patent No. 5,690,899, which controls the pH of seawater between 4 and 5 (more It is better to control the method of mixing after aeration at pH 4.15~4.5).
然而，實際上，以曝氣驅除二氧化碳的動力學反應速率和海水的pH值密切相關，即pH值越高，驅除二氧化碳的速度就越慢，這是因為pH值越高，碳酸根和碳酸氫根的比例就越高，而碳酸的比例越低，導致脫除碳酸更為困難。因此，既有的Flakt-Hydro法採用先混合後曝氣的製程，是在較高的pH值條件下驅除海水中的二氧化碳，即需要大量的空氣曝氣，導致能耗提高。However, in fact, the kinetic reaction rate of carbon dioxide by aeration is closely related to the pH value of seawater, that is, the higher the pH, the slower the rate of carbon dioxide removal, because the higher the pH, the carbonate and hydrogen carbonate. The higher the proportion of roots, the lower the proportion of carbonic acid, which makes it more difficult to remove carbonic acid. Therefore, the existing Flakt-Hydro method adopts a process of first mixing and aeration, which is to remove carbon dioxide in seawater at a relatively high pH value, that is, a large amount of air aeration is required, resulting in an increase in energy consumption.
所以比肖夫法才會將脫硫海水的pH值控制在4~5之間，然而，控制脫硫海水的pH值為4~5雖然可讓脫硫海水中沒有游離態的亞硫酸存在，而恢復其pH值，但此做法為了使脫硫塔(約20~30米高)中的脫硫海水達到pH值為4~5，需要加入大量的海水至脫硫塔，與通常不控制pH值的情況下相比，所需的能耗將會大幅提升；如pH值從2.5改變至4.5，需要增加海水使用量至2.5倍，而從2改變至5，則須增加海水使用量至5.5倍。另外，脫硫海水相同容積的條件下，海水滯留時間(即曝氣時間)將降低為1/2.5或1/5.5，換言之，在同樣的曝氣時間之條件下，所需的水槽容積為既有水槽容積的2.5~5.5倍之大，即建設成本和曝氣成本都會增加。Therefore, the pH of the desulfurized seawater is controlled to be between 4 and 5 by the Schiff method. However, controlling the pH of the desulfurized seawater to 4 to 5 allows the presence of free sulfurous acid in the desulfurized seawater. The pH value is restored, but in order to bring the desulfurized seawater in the desulfurization tower (about 20 to 30 m high) to a pH of 4 to 5, a large amount of seawater needs to be added to the desulfurization tower, and the pH is usually not controlled. In the case of the situation, the required energy consumption will be greatly increased; if the pH value is changed from 2.5 to 4.5, the amount of seawater usage needs to be increased to 2.5 times, and when the value is changed from 2 to 5, the seawater usage must be increased to 5.5 times. . In addition, under the same volume of desulfurized seawater, the seawater retention time (ie, aeration time) will be reduced to 1/2.5 or 1/5.5. In other words, under the same aeration time, the required tank volume is The volume of the sink is 2.5~5.5 times, that is, the construction cost and the aeration cost will increase.
一般而言，燃燒煙器中二氧化碳的濃度約為14vol%，在傳統的海水脫硫方法中，脫硫塔中海水吸收二氧化硫後，所形成的脫硫海水之pH值會降至2~4之間，從實驗可知，該pH值範圍仍有少量二氧化碳被海水吸收，被吸收的二氧化碳會和水反應生成碳酸，但由於二氧化碳和水的反應速率很慢，所以除了少數分子態碳酸外，絕大部分以二氧化碳水溶液的型態存在於海水中。In general, the concentration of carbon dioxide in the combustion device is about 14 vol%. In the traditional seawater desulfurization method, after the seawater in the desulfurization tower absorbs sulfur dioxide, the pH of the formed desulfurized seawater will drop to 2~4. In the experiment, it is known that a small amount of carbon dioxide is absorbed by seawater in the pH range, and the absorbed carbon dioxide reacts with water to form carbonic acid. However, since the reaction rate of carbon dioxide and water is very slow, it is extremely large except for a few molecular carbonic acids. Part of it is present in seawater in the form of an aqueous solution of carbon dioxide.
在pH值低於4.0時，被吸收的二氧化碳對於脫硫海水的pH值並無貢獻，此可參看第四圖所示，在pH值低於4.0時，分子態碳酸組成佔100%，而碳酸氫根和碳酸根組成為零，溶液吸收二氧化碳之前與之後，碳酸、碳酸氫根和碳酸根相對組成不變，其pH值亦無變動，所以同理可知，在pH值低於4.0時，驅除脫硫海水中二氧化碳之前和之後對於其pH值並無影響。而以傳統曝氣方式驅除二氧化碳的過程中，即在pH值大於4.0的情況下，由於二氧化碳的逸出等同於當量的碳酸被除去，其結果會使pH值升高，而pH值的升高會使殘留的分子態碳酸轉變為二氧化碳的轉變反應難以進行。而傳統混合海水的pH值通常會要求在pH值為5.5~6以上，否則就會如美國專利第5,690,899號所述有臭味產生的問題，然而，若pH值調控在5.5~6以上進行曝氣，則會使驅除二氧化碳的速率下降，而導致曝氣量過大的問題。At pH below 4.0, the absorbed carbon dioxide does not contribute to the pH of the desulfurized seawater. See the fourth figure. At pH below 4.0, the molecular carbonic acid composition accounts for 100%, while carbonic acid. The composition of hydrogen radical and carbonate is zero. Before and after the solution absorbs carbon dioxide, the relative composition of carbonic acid, bicarbonate and carbonate is unchanged, and the pH value does not change. Therefore, it is known that when the pH is lower than 4.0, the repelling is carried out. There is no effect on the pH of the desulfurized seawater before and after the carbon dioxide. In the process of repelling carbon dioxide by conventional aeration, that is, in the case of pH greater than 4.0, since the escape of carbon dioxide is equivalent to the removal of equivalent carbonic acid, the result is an increase in pH and an increase in pH. The conversion reaction that converts residual molecular carbonic acid into carbon dioxide is difficult to carry out. However, the pH of the traditional mixed seawater is usually required to be at a pH of 5.5 to 6. Otherwise, there is a problem of odor as described in U.S. Patent No. 5,690,899. However, if the pH is controlled at 5.5 to 6 or more, the exposure is performed. Gas will cause the rate of carbon dioxide removal to decrease, resulting in an excessive amount of aeration.
再者，海水中的溶氧濃度也是海水的水質指標之一，水中的溶氧濃度除了受溫度的影響之外，鹽類濃度亦有相當大的影響，有文獻指出各溫度下的溶氧濃度和氯量的詳細數據，亦呈現出鹽濃度和氯量的定義關係，即鹽濃度(‰)為1.80655x氯量(‰)(Standard Method for the Examination of Water and Wastewater,4500-O American Public Health Association,19th Edition 1995)。Furthermore, the dissolved oxygen concentration in seawater is also one of the water quality indicators of seawater. In addition to the influence of temperature, the dissolved oxygen concentration in water also has a considerable influence on the concentration of dissolved salt. The detailed data of the amount of chlorine and the amount of chlorine also show the relationship between the salt concentration and the amount of chlorine, that is, the salt concentration (‰) is 1.80065xx (‰) (Standard Method for the Examination of Water and Wastewater, 4500-O American Public Health Association, 19 th Edition 1995).
請參看表1，其係引用於上述文獻，從表1可看出對一般海水(鹽濃度約為35‰。氯量約為20‰)而言，若在30℃時與氯量為0的水相比，溶氧濃度從7.559mg/l降到6.197mg/l。其係意味一般海水與一般淡水相比，海水中溶氧的緩衝能力較低。Please refer to Table 1, which is cited in the above literature. It can be seen from Table 1 that for general seawater (salt concentration is about 35 ‰. chlorine is about 20 ‰), if the amount of chlorine is 0 at 30 ° C Compared with water, the dissolved oxygen concentration decreased from 7.559 mg/l to 6.179 mg/l. It means that the seawater has a lower buffering capacity for dissolved oxygen in seawater than ordinary fresh water.
根據亞硫酸氫根的氧化反應：HSO3 - +1/2O2 →SO2 2- +H+ ，隨著反應的進行，會導致溶氧濃度降低，若沒有及時向脫硫海水補充氧氣，則亞硫酸根的氧化反應將消耗海水中的溶氧量，導致海水溶氧濃度降低。根據上述氧化反應可知，亞硫酸氫根和溶氧濃度間當量關係為81：16，即約為5：1的關係，例如在曝氣池中呈現飽和狀態的30℃海水，若殘留亞硫酸氫根的濃度為8mg/l，則溶氧濃度可能會降至4.6mg/l。According to the oxidation reaction of hydrogen sulfite: HSO 3 - + 1/2 O 2 → SO 2 2- + H + , as the reaction progresses, the concentration of dissolved oxygen will decrease, and if oxygen is not added to the desulfurized seawater in time, The oxidation reaction of sulfite will consume the amount of dissolved oxygen in the seawater, resulting in a decrease in the dissolved oxygen concentration in seawater. According to the above oxidation reaction, the equivalent relationship between the concentration of hydrogen sulfite and dissolved oxygen is 81:16, that is, a relationship of about 5:1, for example, 30 ° C seawater in a saturated state in the aeration tank, if residual hydrogen sulfite When the concentration of the root is 8 mg/l, the dissolved oxygen concentration may drop to 4.6 mg/l.
經實驗可知，在pH值為2~8的海水中，亞硫酸氫根被空氣氧化的反應，對亞硫酸氫根而言為一次反應。請參看第五圖所示，殘留的亞硫酸氫根濃度會隨反應時間呈指數下降，濃度越低則下降速度越慢，而溫度越低則反應時間越長。According to experiments, in the seawater with a pH of 2-8, the reaction of hydrogen sulfite is oxidized by air, and it is a reaction to hydrogen sulfite. Referring to Figure 5, the residual bisulfite concentration decreases exponentially with the reaction time. The lower the concentration, the slower the rate of decline, and the lower the temperature, the longer the reaction time.
再者，目前既有的海水脫硫技術還存在有一個實質的問題，即係環保問題。因為既有海水脫硫技術所使用的海水來源一般是源自於鍋爐冷卻用水，由於該鍋爐冷卻用水經粗濾後加入次亞氯酸鹽殺菌，導致海水中的微生物殘骸以及微細懸浮物質形成浮出液面的浮渣，而通常這些海水會直接排放大海，因此嚴重污染環境且破壞景觀，所以環保議題亦為目前環保意識高漲之時代所需特別注意的環節。Moreover, there is still a substantial problem in the existing seawater desulphurization technology, that is, environmental protection. Because the seawater source used in the seawater desulfurization technology is generally derived from the boiler cooling water, the boiler cooling water is coarsely filtered and then added with hypochlorite to cause microbial residues and fine suspended matter in the seawater to float. The scum of the liquid surface, and usually these seawater will directly discharge into the sea, thus seriously polluting the environment and destroying the landscape. Therefore, environmental protection issues are also the special attention required in the era of high environmental awareness.
本發明人有鑒於既有脫硫海水的技術仍有相當多的問題，包括成本問題、效能問題、環保問題等，故不符合產業的期望，因此經過不斷的研究以及試驗之後，終於發明出此脫硫海水處理方法。The present inventors have invented this in view of the fact that there are still quite a few problems in the technology of desulfurizing seawater, including cost, efficiency, and environmental protection, which do not meet the expectations of the industry. Desulfurization seawater treatment method.
本發明之目的係在於提供一種使用少量的空氣曝氣量達到有效地驅除CO2 (aq)以及有效地氧化亞硫酸氫根，進而在低pH值條件下進行海水的混合及曝氣，以降低設備成本和運作成本，而得到具有經濟效益、高效率且環保的脫硫海水處理方法。The object of the present invention is to provide a method for effectively purging CO 2 (aq) and effectively oxidizing hydrogen sulfite using a small amount of air aeration, thereby performing seawater mixing and aeration under low pH conditions to reduce Equipment cost and operating cost, and a cost-effective, efficient and environmentally friendly method for desulfurization of seawater.
為達上述目的，本發明之脫硫海水處理方法，係包括：使脫硫海水之pH值保持於2~4之間，以向脫硫海水導入曝氣空氣，對海水中的亞硫酸氫根進行氧化處理，並驅除游離態二氧化硫和二氧化碳；用未脫硫之海水對經上述步驟處理後的脫硫海水以二次以上的濃度梯度混合方式進行混合而形成混合海水，同時導入曝氣空氣驅除該混合海水中的二氧化碳以恢復該混合海水的pH值；於上述已恢復pH值的混合海水導入微細空氣泡以維持海水的溶氧濃度，並清除海水中的懸浮物以得到淨化海水。In order to achieve the above object, the method for treating desulfurized seawater according to the present invention comprises: maintaining the pH of the desulfurized seawater between 2 and 4 to introduce aerated air to the desulfurized seawater, and to reduce the hydrogen sulphate in the seawater. Oxidation treatment is carried out, and free sulfur dioxide and carbon dioxide are removed; the desulfurized seawater treated by the above steps is mixed with a concentration gradient of two or more times to form mixed seawater, and an aeration air is introduced to drive out the The carbon dioxide in the seawater is mixed to restore the pH of the mixed seawater; the mixed airwater having the recovered pH value is introduced into the fine air bubbles to maintain the dissolved oxygen concentration of the seawater, and the suspended matter in the seawater is removed to obtain purified seawater.
其中，上述脫硫海水處理方法尚包括將該淨化海水排放至大海。The method for treating the desulfurized seawater further includes discharging the purified seawater to the sea.
較佳的是，向脫硫海水導入曝氣空氣的空氣曝氣量，在溫度範圍15～40℃時，每噸海水所需空氣量(Y)[即G(空氣量，Nm3 )/L(海水，噸)]係符合以下關係式：(其中A=0.8、B=2.5、C=0.35、D=50、2<pH<4，而A，B，C和D的單位與上述Y相同)。Preferably, the amount of air aeration of the aerated air introduced into the desulfurized seawater is (Y) per ton of seawater in the temperature range of 15 to 40 ° C [ie, G (air amount, Nm 3 ) / L (Seawater, tons)] is in accordance with the following relationship: (wherein A = 0.8, B = 2.5, C = 0.35, D = 50, 2 < pH < 4, and the units of A, B, C and D are the same as above Y).
較佳的是，該混合海水的pH值為5.2～5.5。Preferably, the mixed seawater has a pH of from 5.2 to 5.5.
較佳的是，最後階段的曝氣該微細空氣泡的的平均直徑為亞毫米(即約為0.35～1毫米)乃至數十微米。Preferably, the average diameter of the aerated air bubbles in the final stage is sub-millimeter (i.e., about 0.35 to 1 mm) or even tens of microns.
本發明在pH值小於4的條件下曝氣，以使得脫硫海水處於酸性環境，即驅除二氧化碳的最佳條件，故能以高效率迅速地直接將未結合態CO2 (aq)自脫硫海水中移除，同時可以完成絕大部份的亞硫酸氫根的氧化以及驅除少量的游離態亞硫酸，以確保後續的混合和曝氣能在較低pH值環境中進行。The invention aerates under the condition of pH value less than 4, so that the desulfurized seawater is in an acidic environment, that is, the optimal condition for repelling carbon dioxide, so that the unbound CO 2 (aq) can be directly desulfurized directly with high efficiency. Removal of seawater allows for the oxidation of most of the bisulfite and the removal of a small amount of free sulfurous acid to ensure subsequent mixing and aeration can be carried out at lower pH.
本發明進一步提出上述脫硫海水處理方法的詳細實做方法，其僅係用於例示之用，以讓於所屬技術領域中具有通常知識者能夠了解並實施本發明，並非欲意限制本發明之範疇。The present invention further provides a detailed method for the above-described desulfurization seawater treatment method, which is for illustrative purposes only, to enable those skilled in the art to understand and practice the present invention, and is not intended to limit the present invention. category.
本發明之脫硫海水處理方法，係包括：The method for treating desulfurized seawater of the present invention comprises:
a.請參看第一圖所示，將含二氧化硫的煙氣以一管線(1)導入具有海水的脫硫塔(2)，該海水係由一管線(4)自該脫硫塔(2)近塔頂處灑下，且經由複數多孔板(25)，讓灑下的海水在該等多孔板(25)上稍作停留，使得海水能與煙氣充分接觸，而處理後的乾淨煙氣沿方向(3)經煙囪排放。將脫硫塔(2)中之脫硫海水的pH值控制在2至4的範圍內，而於該脫硫塔(2)中以一曝氣管(5)向脫硫海水導入曝氣空氣，對海水中的亞硫酸氫根進行氧化處理，並使游離態二氧化硫和二氧化碳驅除出脫硫海水；a. Referring to the first figure, the sulphur dioxide-containing flue gas is introduced into the desulfurization tower (2) with seawater by a line (1) from a desulfurization tower (2) It is sprinkled near the top of the tower, and through the plurality of perforated plates (25), the sprinkled seawater is slightly stopped on the perforated plates (25), so that the seawater can fully contact the flue gas, and the treated clean flue gas Discharged through the chimney in the direction (3). The pH of the desulfurized seawater in the desulfurization tower (2) is controlled to be in the range of 2 to 4, and an aeration air is introduced into the desulfurization seawater by an aeration pipe (5) in the desulfurization tower (2). , oxidizing the hydrogen sulfite in seawater, and driving the free sulfur dioxide and carbon dioxide out of the desulfurized seawater;
b.之後，再以管線(11)將脫硫海水自該脫硫塔(2)中輸出，並以管線(4)運送未脫硫之海水，使管線(11)中的脫硫海水和經一分支管線(41)中未脫硫之海水於一交會處(6)混合，以形成初次混合海水，而該初次混合海水再以管線(71)輸送至一曝氣池(7)中，且該未脫硫之海水又經一分支管線(42)輸入該曝氣池(7)中，以與上述初次混合海水混合，以形成二次混合海水，因此該脫硫海水以及未脫硫海水於本實施例中係總共以二次以上的濃度梯度混合方式進行混合，另外，在該曝氣池(7)之底部設有一曝氣管線(8)，以導入曝氣空氣驅除該混合海水中的二氧化碳，以恢復該混合海水的pH值；b. Thereafter, the desulfurized seawater is output from the desulfurization tower (2) by the pipeline (11), and the undesulfurized seawater is transported by the pipeline (4) to desulfurize the seawater and the desulfurized water in the pipeline (11). The undesulfurized seawater in a branch line (41) is mixed at a junction (6) to form a first mixed seawater, and the primary mixed seawater is then sent to an aeration tank (7) by a line (71), and The undesulfurized seawater is further introduced into the aeration tank (7) via a branch line (42) to be mixed with the first mixed seawater to form a secondary mixed seawater, so the desulfurized seawater and the undesulfurized seawater are In this embodiment, a total of two or more concentration gradient mixing methods are used for mixing, and an aeration line (8) is disposed at the bottom of the aeration tank (7) to introduce the aeration air to drive off the mixed seawater. Carbon dioxide to restore the pH of the mixed seawater;
c.對該混合海水導入以一微細空氣曝氣管線(9)導入微細空氣泡，以恢復和維持海水中的氧氣含量，並同時對海水中的浮游物進行上浮處理，如以各種於所屬技術領域中具有通常知識者可得知的打撈或過濾方法，即可除去浮游物；c. Introducing the fine sea air into a fine air aeration line (9) to recover and maintain the oxygen content in the seawater, and at the same time, floating the floating matter in the seawater, for example, in various technologies In the field, there is a salvage or filtration method known to the general knowledge to remove the float;
d.除去浮游物之海水自該曝氣池(7)之底部溢流方式的溢流管路(10)排放至大海。d. The seawater from which the float is removed is discharged to the sea from the overflow line (10) of the overflow of the aeration tank (7).
在脫硫海水pH值為2<pH<4範圍內曝氣，這一酸鹼值的調控係利用所屬技術領域中具有通常知識者所能得知的方法進行，因此無需繁雜的pH值調整技術或設置相應的設備。由於pH值較低即脫硫海水水量較少，在同等的脫硫海水水槽的條件下能實現較長的曝氣時間即氧化時間，達到更好的氧化效果。確實如比肖夫法所指，在pH<4時，游離態二氧化硫會被空氣攜帶出海水，然而從氧化的觀點看，這正是氧化所要期待的結果，即降低海水中的亞硫酸氫根濃度，相當於提高了氧化效率。同時在這一pH值範圍，幾乎所有的二氧化碳以CO2 (aq)的形態存在，與較高pH值的條件相比，不再經過碳酸根，亦即碳酸氫根以及碳酸分子轉變為CO2 的反應速度很慢的構型轉變反應，所以很容易被空氣驅除出脫硫海水。Aeration in the range of pH 2 < pH < 4 of the desulfurized seawater, this pH adjustment is carried out by methods known to those of ordinary skill in the art, so that no complicated pH adjustment technique is required. Or set the appropriate device. Since the pH value is low, that is, the amount of desulfurized seawater is small, a longer aeration time, that is, an oxidation time, can be achieved under the same conditions of desulfurization seawater tank, thereby achieving a better oxidation effect. Indeed, as far as the Schiff method is concerned, at pH < 4, free sulfur dioxide is carried by the air, but from the oxidation point of view, this is the result of oxidation, which is to reduce the concentration of bisulfite in seawater. It is equivalent to an increase in oxidation efficiency. At the same time, in this pH range, almost all carbon dioxide exists in the form of CO 2 (aq), which is no longer converted to CO 2 , ie, bicarbonate and carbonic acid molecules, compared to the conditions of higher pH. The reaction rate of the reaction is very slow, so it is easy to be driven out of the desulfurized seawater by air.
由於氧化亞硫酸氫根的速度隨海水溫度降低而變慢，較低的溫度條件意味著需要更多的曝氣量。另外，pH值越低意味著吸收的二氧化硫越多，也需要更多的曝氣空氣量。Since the rate of oxysulfite slows as the seawater temperature decreases, lower temperature conditions mean more aeration is required. In addition, a lower pH means more sulphur dioxide is absorbed and more aeration air is required.
請參看第二圖所示，其係顯示步驟a中，需考慮到溫度和pH值的影響以確定了適宜的空氣曝氣量，在溫度範圍15～40℃時，所需空氣量(Y)[即G(空氣量，Nm3 )/L(海水，噸)]的選擇範圍如圖所示，其係根據以下關係所定：Please refer to the second figure, which shows that in step a, the influence of temperature and pH should be taken into consideration to determine the appropriate air aeration. The required air volume (Y) in the temperature range of 15 to 40 °C. [The choice range of G (air quantity, Nm 3 ) / L (sea water, tons)] is shown in the figure, which is based on the following relationship:
(其中A=0.8、B=2.5、C=0.35、D=50、2<pH<4，而A，B，C和D的單位與上述Y的單位相同)。 (wherein A = 0.8, B = 2.5, C = 0.35, D = 50, 2 < pH < 4, and the units of A, B, C and D are the same as the units of Y above).
其中，恢復該混合海水的pH值至6.8~7.8之間。Among them, the pH of the mixed seawater is restored to between 6.8 and 7.8.
其中，該海水的溶氧濃度為飽和濃度的90%以上。源於亞硫酸根的COD值為1mg/L以下。The dissolved oxygen concentration of the seawater is 90% or more of the saturated concentration. The COD value derived from sulfite is 1 mg/L or less.
從實驗中得知，在脫硫過程中，劇烈的氣液接觸會使海水中的亞硫酸氫根與煙氣中的氧氣發生氧化反應，一部分亞硫酸氫根被氧化成硫酸根。It is known from experiments that during the desulfurization process, intense gas-liquid contact causes oxidation of bisulfite in seawater with oxygen in the flue gas, and a portion of bisulfite is oxidized to sulfate.
不言而喻，等同步驟a中被空氣攜帶出來的二氧化硫進行處理的方式除了第一圖所示在脫硫塔(2)內直接曝氣以外，還可以有如下兩種，其中一方式，如第六圖所示，在密閉曝氣槽(21)中藉由曝氣管(51)曝氣，從脫硫海水驅除出來的二氧化硫和空氣，再將含有二氧化硫的酸性氣體藉由酸性氣體輸送管線(22)一起送回脫硫塔(2)中與煙氣合流，以使得二氧化硫在脫硫塔(2)內再次被塔頂流下的海水吸收，並隨下流海水一起與煙氣中的氧氣(一般煙氣含有約為5vol%O2 )發生激烈氣液接觸，並部分反應生成硫酸氫根或硫酸根。經密閉曝氣處理後的海水與未脫硫海水在交會點(6)混合進入曝氣池，以後的流程同第一圖。該方式適用於脫硫塔內不曝氣的情況，可以節省脫硫塔水槽容積。另一方式，如第七圖所示，在密閉曝氣槽(21)中經曝氣管(51)曝氣，從脫硫海水驅除出含有二氧化硫的酸性氣體，再將該酸性氣體經由酸性氣體輸送管線(22)在一水槽(23)底部，即密閉條件下與未脫硫海水的一部分(43)進行接觸洗滌，讓二氧化硫在與未脫硫之海水發生氣液接觸而被海水吸收，該吸收酸性氣體的海水(24)之後與脫硫海水在交會處(61)混合，其中的亞硫酸氫根將會在後續的步驟中完成氧化處理，而洗滌後乾淨氣體則排放大氣。It goes without saying that the method of treating the sulfur dioxide carried by the air in the same step a is directly aerated in the desulfurization tower (2) as shown in the first figure, and there are two types, one of which is As shown in the sixth figure, in the closed aeration tank (21), the aeration gas (51) is aerated, the sulfur dioxide and air are removed from the desulfurized seawater, and the acid gas containing sulfur dioxide is passed through the acid gas delivery pipeline. (22) Returning together to the flue gas in the desulfurization tower (2), so that the sulfur dioxide is again absorbed by the seawater flowing down the top of the tower in the desulfurization tower (2), and together with the downstream seawater and the oxygen in the flue gas ( Generally, the flue gas contains about 5 vol% O 2 ), intense gas-liquid contact occurs, and partial reaction produces hydrogen sulfate or sulfate. The seawater after the closed aeration treatment is mixed with the undesulfurized seawater at the intersection point (6) into the aeration tank, and the subsequent flow is the same as the first diagram. This method is suitable for the case where the desulfurization tower is not aerated, and the volume of the desulfurization tower sink can be saved. Alternatively, as shown in the seventh figure, the aeration tube (51) is aerated in the closed aeration tank (21), the acid gas containing sulfur dioxide is removed from the desulfurized seawater, and the acid gas is passed through the acid gas. The transfer line (22) is contact-washed with a portion (43) of the undesulfurized seawater at the bottom of the water tank (23), that is, under closed conditions, so that the sulfur dioxide is absorbed by the seawater in gas-liquid contact with the undesulfurized seawater. The seawater (24) that absorbs the acid gas is then mixed with the desulfurized seawater at the intersection (61), wherein the hydrogen sulfite will be oxidized in a subsequent step, and the clean gas will be vented to the atmosphere after washing.
在以上兩種情況下，一旦被攜帶出的亞硫酸氣體都不會進入大氣造成二次污染。因此採用本發明的方法，讓被空氣攜帶出的亞硫酸再次與海水接觸，它將被吸收和部分氧化，經實驗證明本發明有效地降低了脫硫海水中的亞硫酸氫根，而對脫硫系統則沒有任何影響。本發明極力降低脫硫海水中的亞硫酸氫根，以為後續的梯度混合和弱酸性條件曝氣提供了更為有利的前提條件。In the above two cases, once the sulfite gas that is carried out does not enter the atmosphere, it causes secondary pollution. Therefore, by using the method of the invention, the sulfuric acid carried by the air is again brought into contact with seawater, and it will be absorbed and partially oxidized, and the invention proves that the invention effectively reduces the hydrogensulfite in the desulfurized seawater, and The sulfur system has no effect. The present invention minimizes the reduction of bisulfite in the desulfurized seawater to provide a more favorable precondition for subsequent gradient mixing and weakly acidic aeration.
在步驟b中，用未脫硫海水對經步驟a處理後的海水進行梯度混合，可提供最為經濟的處理方式，在較低pH值中驅除碳酸。其理由在於傳統的先混合後曝氣的脫硫海水處理方法中皆係以一次性混合，讓海水的pH值達到最大值，也就是說，曝氣係從較高的pH值開始，與較低pH值情況相比，驅除同樣量的二氧化碳需要較大的空氣曝氣量。而本發明係以梯度混合的方式進行，每次混合只使用一部分未脫硫之海水，使混合海水處於較低pH值的範圍，從而能得到較高的二氧化碳驅除速度，可以節約曝氣空氣量。當然，最初的混合點，可以選擇在曝氣池內進行，也可以選擇在曝氣池前的密閉管道內進行。In step b, the stepwise mixing of the seawater treated in step a with undesulfurized seawater provides the most economical treatment to drive off the carbonic acid at lower pH values. The reason is that the traditional pre-mixed aerated desulfurized seawater treatment method is a one-time mixing, so that the pH value of seawater reaches a maximum value, that is, the aeration system starts from a higher pH value, and A lower air aeration is required to drive off the same amount of carbon dioxide compared to the low pH. The present invention is carried out in a gradient mixing manner, using only a part of undesulfurized seawater for each mixing, so that the mixed seawater is in a lower pH range, thereby obtaining a higher carbon dioxide repelling speed and saving the amount of aeration air. . Of course, the initial mixing point can be selected in the aeration tank or in a closed pipeline in front of the aeration tank.
由於步驟a的操作能使脫硫海水中的亞硫酸氫根降低至極低濃度，從而確保在後續曝氣階段，即使在弱酸性的低pH值時，仍可將亞硫酸氣體控制在可以感知的所謂臭氣發生的臨界值0.3ppm之下，因此比如在pH<5.5之pH範圍也能曝氣驅除二氧化碳而不會造成二次污染的高效曝氣技術。請參看第三圖所示，其係在溫度35℃下，對混合前脫硫海水進行氧化處理和無氧化處理兩種情況，脫硫海水的pH值和與之平衡的氣相中SO2 濃度的關係。該圖清楚顯示經氧化前處理後的海水與沒有氧化前處理相比，在同一pH值下的氣相中SO2 濃度降低很多，即使海水酸度降到pH=5，其SO2 濃度沒有檢出，更遠低於感知臭氧的臨界值。故可得知亞硫酸濃度較低時，即使在較低pH值的環境中曝氣也不會產生所謂臭氣的問題。Since the operation of step a can reduce the amount of bisulfite in the desulfurized seawater to a very low concentration, it is ensured that the sulfurous acid gas can be controlled to be perceptible in the subsequent aeration stage even at a low pH of weak acidity. The so-called odor generation threshold value is below 0.3 ppm, so for example, in the pH range of pH < 5.5, it can also aerate to remove carbon dioxide without causing secondary pollution. Please refer to the third figure, which is the oxidation treatment and non-oxidation treatment of the desulfurized seawater before mixing at a temperature of 35 ° C. The pH of the desulfurized seawater and the concentration of SO 2 in the gas phase in equilibrium with it. Relationship. The figure clearly shows that the seawater after pre-oxidation treatment has a much lower SO 2 concentration in the gas phase at the same pH value than the pre-oxidation treatment. Even if the acidity of the seawater drops to pH=5, the SO 2 concentration is not detected. , farther below the threshold for perceived ozone. Therefore, it can be known that when the concentration of sulfurous acid is low, the problem of so-called odor is not generated even if it is aerated in a lower pH environment.
而本發明對脫硫海水藉由步驟a的處理後，再與未脫硫海水梯度混合而將pH值調整到pH=5.2～5.5之範圍，然後同時導入空氣驅除海水中的二氧化碳以恢復海水的pH值，可以得到既沒有二氧化硫之臭氣產生，又能達到高效脫除二氧化碳的效果。而其後的梯度混合則在沿曝氣池(7)之徑向方向0～1/2的區間內進行，將剩餘的海水導入曝氣池進行混合。採用這種方式進行梯度混合既可控制第一次混合後的海水量為少量，使得在同樣曝氣量的條件下能夠取得較長的曝氣時間和曝氣效果，又能保證所有海水在排放前都能恢復溶氧量。However, the present invention treats the desulfurized seawater by the step a, and then mixes with the undesulfurized seawater gradient to adjust the pH to a range of pH=5.2-5.5, and then simultaneously introduces air to drive off the carbon dioxide in the seawater to recover the seawater. The pH value can be obtained without the generation of odor of sulfur dioxide and the effect of efficiently removing carbon dioxide. The subsequent gradient mixing is carried out in the interval of 0 to 1/2 in the radial direction of the aeration tank (7), and the remaining seawater is introduced into the aeration tank for mixing. Gradient mixing in this way can control the amount of seawater after the first mixing to a small amount, so that a longer aeration time and aeration effect can be obtained under the same aeration conditions, and all seawater can be discharged. The amount of dissolved oxygen can be restored before.
另外考慮到亞硫酸氫根的氧化反應為一次反應，在較低濃度範圍內需要較多時間才能完成反應。並且實際情況顯示，一般脫硫海水從曝氣池到匯入大海還有數分鐘的距離，在此期間，由於殘留有亞硫酸氫根的緣故，最終排放海水的溶氧濃度勢必有所減低。而在一般曝氣裝置中氣泡直徑大小約為數毫米～數百毫米，在水中上升速度約為25cm/sec以上，流出曝氣池後，以放水路水深為2米計，氣泡將在8秒後全部逸出水體。而如果採用微細氣泡發生器，氣泡直徑大小約為亞毫米(即約為0.35～1毫米)乃至數十微米，在水中的停留時間可以長達數分鐘乃至更久。這樣可以有效的補償由於殘留亞硫酸氫根的氧化而降低的溶氧濃度，長時間維持海水的飽和溶氧濃度。In addition, considering that the oxidation reaction of hydrogen sulfite is a single reaction, it takes more time to complete the reaction in a lower concentration range. And the actual situation shows that the desulfurized seawater generally has a distance of several minutes from the aeration tank to the sea. During this period, due to the residual of bisulfite, the dissolved oxygen concentration of the final seawater is bound to decrease. In the general aeration device, the diameter of the bubble is about several millimeters to several hundreds of millimeters, and the rising speed in the water is about 25 cm/sec or more. After flowing out of the aeration tank, the water depth of the water discharge channel is 2 meters, and the bubble will be after 8 seconds. All escaped from the water body. However, if a microbubble generator is used, the bubble diameter is about a sub-millimeter (i.e., about 0.35 to 1 mm) or even tens of micrometers, and the residence time in water can be as long as several minutes or longer. This can effectively compensate for the dissolved oxygen concentration which is lowered by the oxidation of residual hydrogen sulfite, and maintain the saturated dissolved oxygen concentration of seawater for a long time.
在步驟c中，對經步驟b處理後的混合海水導入微細空氣泡恢復海水溶解氧，並同時對海水中的浮游物質進行上浮處理，處理後海水經底部溢流後排放大海。當然，上浮物質會被定期清除處理。如此，既能維持海水中的溶氧濃度，又能除去海水中浮游物質，使回歸海洋的海水水質更好，能充分滿足當地環境保護標準。In the step c, the mixed airwater treated in the step b is introduced into the fine air bubbles to recover the seawater dissolved oxygen, and at the same time, the floating matter in the seawater is floated, and the treated seawater is discharged to the sea after overflowing through the bottom. Of course, the floating material will be removed regularly. In this way, both the dissolved oxygen concentration in the seawater and the floating matter in the seawater can be removed, and the seawater quality returning to the ocean can be better, and the local environmental protection standard can be fully satisfied.
綜上所述，本發明採用在脫硫海水pH值為2<pH<4範圍內直接曝氣的手法，實現了高效的處理海水中的亞硫酸氫根和驅除少量的游離態二氧化硫和二氧化碳的效果，並採用梯度混合的手法，保證了在較低pH值範圍導入空氣有效的驅除海水中的二氧化碳以快速恢復海水的pH值，並在曝氣後，對海水導入微細空氣泡以最大限度維持海水溶氧濃度的同時對海水中的浮游物進行上浮處理達到高質量的水質標準，從而開發了一種經濟的、高效的脫硫海水的處理方法。In summary, the invention adopts the method of directly aerating in the range of pH value of the desulfurized seawater of 2<pH<4, and realizes the effect of efficiently treating the hydrogensulfite in the seawater and repelling a small amount of free sulfur dioxide and carbon dioxide. The use of gradient mixing method ensures that the introduction of air at a lower pH range effectively removes carbon dioxide from seawater to quickly restore the pH of the seawater, and after aeration, introduces fine air bubbles into the seawater to maximize the sea. The water-soluble oxygen concentration simultaneously floats the floats in the seawater to achieve high-quality water quality standards, thus developing an economical and efficient treatment method for desulfurized seawater.
(1)．．．管線(1). . . Pipeline
(11)．．．管線(11). . . Pipeline
(2)．．．脫硫塔(2). . . Desulfurization tower
(21)．．．密閉曝氣槽(twenty one). . . Closed aeration tank
(22)．．．酸性氣體輸送管線(twenty two). . . Acid gas transfer line
(23)．．．水槽(twenty three). . . sink
(24)．．．管線(twenty four). . . Pipeline
(25)．．．多孔板(25). . . Multiwell plate
(3)．．．方向(3). . . direction
(4)．．．管線(4). . . Pipeline
(41)(42)(43)．．．分支管線(41)(42)(43). . . Branch pipeline
(5)．．．曝氣管(5). . . Aeration tube
(51)．．．曝氣管(51). . . Aeration tube
(6)．．．交會處(6). . . Meeting place
(61)．．．交會處(61). . . Meeting place
(7)．．．曝氣池(7). . . Aeration tank
(71)．．．管線(71). . . Pipeline
(8)．．．曝氣管線(8). . . Aeration pipeline
(9)．．．微細空氣曝氣管線(9). . . Micro air aeration pipeline
(10)．．．溢流管線(10). . . Overflow pipeline
第一圖係本發明脫硫海水處理方法的流程管線圖。The first figure is a flow diagram of the process of the desulfurized seawater treatment method of the present invention.
第二圖係本發明曝氣空氣量Y的選擇範圍。The second figure is the selection range of the amount of aeration air Y of the present invention.
第三圖係溶液中溶液中在不同亞硫酸濃度下氣相中SO2 濃度和pH值的關係。The third graph is the relationship between SO 2 concentration and pH in the gas phase at different concentrations of sulfite in the solution.
第四圖係海水中碳酸系統各組份的組成和pH值的關係。The fourth graph is the relationship between the composition of each component of the carbonation system in seawater and the pH value.
第五圖係各溫度下曝氣時海水中亞硫酸氫根濃度隨時間變化的關係。The fifth graph shows the relationship between the concentration of bisulfite in seawater as a function of time at various temperatures.
第六圖係在密閉曝氣槽中對脫硫海水曝氣處理後酸性氣體返回脫硫塔的部分流程管線圖。The sixth figure is a partial process pipeline diagram of the acid gas returning to the desulfurization tower after the aerated seawater aeration treatment in the closed aeration tank.
第七圖係在曝氣槽中脫硫海水曝氣處理後酸性氣體經洗滌後排放大氣的流程管線圖。The seventh figure is a flow diagram of the process of discharging the atmosphere after the acid gas is washed after desulfurization seawater aeration treatment in the aeration tank.
(1)．．．管線(1). . . Pipeline
(11)．．．管線(11). . . Pipeline
(2)．．．脫硫塔(2). . . Desulfurization tower
(25)．．．多孔板(25). . . Multiwell plate
(3)．．．方向(3). . . direction
(4)．．．管線(4). . . Pipeline
(41)(42)．．．分支管線(41) (42). . . Branch pipeline
(5)．．．曝氣管(5). . . Aeration tube
(6)．．．交會處(6). . . Meeting place
(7)．．．曝氣池(7). . . Aeration tank
(71)．．．管線(71). . . Pipeline
(8)．．．曝氣管線(8). . . Aeration pipeline
(9)．．．微細空氣曝氣管線(9). . . Micro air aeration pipeline
(10)．．．溢流管線(10). . . Overflow pipeline
Claims (7)
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| TW097141507A TWI392655B (en) | 2008-10-29 | 2008-10-29 | Desulfurization seawater treatment method |
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| TW097141507A TWI392655B (en) | 2008-10-29 | 2008-10-29 | Desulfurization seawater treatment method |
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| JP5535817B2 (en) * | 2010-08-06 | 2014-07-02 | 三菱重工業株式会社 | Aeration apparatus, seawater flue gas desulfurization apparatus equipped with the aeration apparatus, and humidification method of aeration apparatus |
| CN102557194B (en) * | 2011-12-31 | 2013-07-10 | 国家***天津海水淡化与综合利用研究所 | Film method aeration industrial flue gas desulfurization seawater recovery process |
| US9630864B2 (en) | 2015-06-17 | 2017-04-25 | General Electric Technology Gmbh | Seawater plant with inclined aeration and mixed auto recovery |
| CN108128882A (en) * | 2018-02-05 | 2018-06-08 | 北京龙源环保工程有限公司 | Sea water desulfuration recovery system Simulation experimental method and device |
| CN108218050A (en) * | 2018-03-23 | 2018-06-29 | 东方电气集团东方锅炉股份有限公司 | The quality recovery device and restoration methods of acid seawater after a kind of flue gas desulfurization with seawater |
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| TW364859B (en) * | 1995-09-23 | 1999-07-21 | Lentjes Bischoff Gmbh | Process for removing sulfur dioxide from flue gas |
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| TW364859B (en) * | 1995-09-23 | 1999-07-21 | Lentjes Bischoff Gmbh | Process for removing sulfur dioxide from flue gas |
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