厭氧消化是我國解決污泥處理處置的一條重要技術(shù)路線，在污泥消化過程中有機(jī)固體降解的同時，也伴隨產(chǎn)生了沼氣。沼氣是一種混合氣體，一般情況下所含CH4體積分?jǐn)?shù)為60%～70%、CO2為30%～40%，還含有少量的水汽、H2S、NH3等，其中H2S為劇毒物質(zhì)，其危害巨大，當(dāng)空氣中的H2S濃度達(dá)到0.1%時，會使人立即喪失知覺，導(dǎo)致永久性的腦傷害或腦死亡。沼氣中H2S的含量與消化進(jìn)泥中的含硫量直接相關(guān)，我國各地城市污水由于納入工業(yè)廢水的種類及占比差異巨大，在已建成的污泥厭氧消化項(xiàng)目中，沼氣的H2S含量差別很大，但大多在300～9000mg/m?的范圍內(nèi)，也有個別案例由于消化進(jìn)泥包含采用Al(2SO4)3混凝劑的初沉化學(xué)污泥，沼氣中的H2S含量高達(dá)30000mg/m?。

　　Anaerobic digestion is an important technical route for sludge treatment and disposal in China. During the sludge digestion process, organic solids are degraded, and biogas is also generated. Biogas is a mixed gas that generally contains 60% to 70% CH4 and 30% to 40% CO2 by volume. It also contains small amounts of water vapor, H2S, NH3, etc. Among them, H2S is a highly toxic substance with enormous harm. When the concentration of H2S in the air reaches 0.1%, it will immediately cause people to lose consciousness, leading to permanent brain injury or death. The content of H2S in biogas is directly related to the sulfur content digested into the sludge. Due to the significant differences in the types and proportions of industrial wastewater included in urban sewage in various regions of China, the H2S content in biogas varies greatly in completed sludge anaerobic digestion projects, but mostly ranges from 300 to 9000 mg/m? Within the scope, there are also individual cases where the digested sludge contains initial settling chemical sludge using Al (2SO4) 3 coagulant, and the H2S content in the biogas is as high as 30000mg/m?.

　　污泥消化所產(chǎn)沼氣首先用于滿足自身加熱的需求(占沼氣總產(chǎn)量的25%～50%)，然后用于拖動鼓風(fēng)機(jī)、發(fā)電等。但不論是高溫還是中溫厭氧消化，沼氣中均含有飽和水蒸氣，隨著溫度的下降，會形成冷凝液，H2S在這種潮濕的環(huán)境下，對金屬管道、燃燒設(shè)備等具有強(qiáng)烈的腐蝕性;燃燒后產(chǎn)生的SO2，對大氣環(huán)境造成污染，危害人體健康，從而影響沼氣的回收利用。雖然我國尚未有統(tǒng)一完善的沼氣作為能源利用時的氣質(zhì)標(biāo)準(zhǔn)，但《大中型沼氣工程技術(shù)規(guī)范》(GB/T51063—2014)對沼氣利用時的H2S含量已有規(guī)定，即民用集中供氣時H2S≤20mg/m?，發(fā)電時H2S≤200mg/m?。由于常規(guī)污泥消化沼氣中的H2S含量遠(yuǎn)遠(yuǎn)高于這些要求，所以沼氣作為能源利用時，必須進(jìn)行脫硫處理。

　　The biogas produced by sludge digestion is first used to meet its own heating needs (accounting for 25% to 50% of the total biogas production), and then used to drive blowers, generate electricity, etc. However, whether it is high-temperature or medium temperature anaerobic digestion, biogas contains saturated water vapor, which forms condensate as the temperature decreases. H2S has strong corrosiveness to metal pipelines, combustion equipment, etc. in this humid environment; The SO2 produced after combustion causes pollution to the atmospheric environment, endangers human health, and thus affects the recycling and utilization of biogas. Although there is currently no unified and comprehensive gas quality standard for the use of biogas as an energy source in China, the "Technical Specification for Large and Medium sized Biogas Engineering" (GB/T51063-2014) has already stipulated the H2S content during biogas utilization, that is, H2S ≤ 20mg/m during centralized gas supply for civilian use? H2S ≤ 200mg/m during power generation?. Due to the significantly higher H2S content in conventional sludge digested biogas compared to these requirements, desulfurization treatment is necessary when biogas is used as an energy source.

　　1、國內(nèi)污泥消化沼氣脫硫方法及發(fā)展方向主流的沼氣脫硫技術(shù)包括化學(xué)脫硫及生物脫硫兩種。前者作為傳統(tǒng)的脫硫技術(shù)已有百年的歷史，被廣泛用于硫化氫的去除，且積累了豐富的經(jīng)驗(yàn)。根據(jù)反應(yīng)介質(zhì)的固液形態(tài)不同，化學(xué)脫硫分為干法脫硫和濕法脫硫。

　　1. The mainstream methods and development directions for sludge digestion and biogas desulfurization in China include chemical desulfurization and biological desulfurization. The former, as a traditional desulfurization technology with a history of over a hundred years, has been widely used for the removal of hydrogen sulfide and has accumulated rich experience. According to the different solid-liquid forms of the reaction medium, chemical desulfurization can be divided into dry desulfurization and wet desulfurization.

　　1.1 干法脫硫干法脫硫包括活性炭系、氧化鐵系及氧化鋅系等，國內(nèi)在早期的污泥消化項(xiàng)目中應(yīng)用較多的是常溫氧化鐵脫硫法。氧化鐵脫硫劑多為條狀多孔結(jié)構(gòu)固體，對H2S能夠進(jìn)行快速不可逆的化學(xué)吸附，數(shù)秒內(nèi)就能將H2S脫除，效率達(dá)到99%以上，工作硫容可達(dá)到40%，強(qiáng)度達(dá)到55N/cm以上。但是對于大型污泥厭氧消化項(xiàng)目，沼氣產(chǎn)量大，H2S含量高，氧化鐵干法脫硫硫容有限，且傳統(tǒng)干法脫硫再生操作易引發(fā)單質(zhì)硫的升華和自燃，安全風(fēng)險高且卸料勞動強(qiáng)度大，因此，針對大型消化項(xiàng)目，氧化鐵干法脫硫不宜作為單級沼氣脫硫處理的選擇。

　　1.1 Dry desulfurization includes activated carbon, iron oxide, and zinc oxide systems. The ambient temperature iron oxide desulfurization method was widely used in early sludge digestion projects in China. Iron oxide desulfurizers are mostly strip-shaped porous solid structures that can rapidly and irreversibly chemically adsorb H2S. They can remove H2S within seconds with an efficiency of over 99%, a working sulfur capacity of up to 40%, and a strength of over 55N/cm. However, for large-scale anaerobic digestion projects of sludge, the biogas production is large, the H2S content is high, the sulfur capacity of iron oxide dry desulfurization is limited, and the traditional dry desulfurization regeneration operation is prone to sublimation and spontaneous combustion of elemental sulfur, with high safety risks and high unloading labor intensity. Therefore, for large-scale digestion projects, iron oxide dry desulfurization is not suitable as the choice for single-stage biogas desulfurization treatment.

　　1.2 濕法脫硫濕法脫硫是利用特定的溶劑與沼氣逆流接觸脫除H2S的工藝，根據(jù)吸收機(jī)理不同，可分為物化吸收和濕式氧化等。該法工藝流程簡單，可連續(xù)運(yùn)行，去除效率較高，適宜處理氣量大、H2S濃度高的氣體。國內(nèi)市政污水廠污泥消化項(xiàng)目一般體量較大，濕法脫硫有較多的應(yīng)用。國內(nèi)消化沼氣濕式脫硫多采用堿液吸收法，以氫氧化鈉作為吸收液。由于沼氣中含有大量的CO2，在堿性溶液中會影響H2S的吸收率，同時受到流速、流量、溫度等因素的影響，H2S并不能全部轉(zhuǎn)移到堿液中。事實(shí)上，在堿耗為3～5kgNaOH/kgH2S的條件下，H2S只能降至150～500mg/m?。為了提高脫硫效率，需要定期外排脫硫循環(huán)液，并對其進(jìn)行處理，既增加了脫硫成本，也常常帶來二次污染。單獨(dú)采用濕法脫硫，很難直接達(dá)到處理要求，同時藥劑消耗巨大，相對干法脫硫能耗高且運(yùn)行管理繁瑣，所以高效、經(jīng)濟(jì)、低能耗、更先進(jìn)的脫硫技術(shù)成為新的探索目標(biāo)，而生物脫硫技術(shù)為該領(lǐng)域的研究和應(yīng)用開辟了新的方向。

　　1.2 Wet flue gas desulfurization is a process that uses specific solvents to remove H2S by countercurrent contact with biogas. Depending on the absorption mechanism, it can be divided into physicochemical absorption and wet oxidation. The process flow of this method is simple, can operate continuously, has high removal efficiency, and is suitable for treating gases with large gas volume and high H2S concentration. Domestic municipal sewage treatment plant sludge digestion projects generally have large volumes, and wet desulfurization has many applications. Wet desulfurization of digested biogas in China often adopts alkaline absorption method, using sodium hydroxide as the absorption solution. Due to the high content of CO2 in biogas, it can affect the absorption rate of H2S in alkaline solutions, and is also affected by factors such as flow rate, flow rate, and temperature. H2S cannot be completely transferred to the alkaline solution. In fact, under the condition of alkali consumption of 3-5 kg NaOH/kgH2S, H2S can only be reduced to 150-500mg/m?. In order to improve desulfurization efficiency, it is necessary to regularly discharge desulfurization circulating liquid and treat it, which not only increases desulfurization costs but also often brings about secondary pollution. It is difficult to directly meet the treatment requirements using wet desulfurization alone, and the consumption of chemicals is huge. Compared with dry desulfurization, it has higher energy consumption and more complicated operation and management. Therefore, efficient, economical, low-energy consumption, and more advanced desulfurization technology has become a new exploration goal. Biological desulfurization technology has opened up new directions for research and application in this field.

　　1.3 生物脫硫生物脫硫是20世紀(jì)80年代興起并逐漸成熟的新工藝，利用微生物自身代謝活動將H2S轉(zhuǎn)化為單質(zhì)硫或硫酸鹽最終達(dá)到去除H2S的目的。該工藝具有無需催化劑、去除效率高、處理成本低、可回收單質(zhì)硫等優(yōu)點(diǎn)，同時能夠滿足大流量、高H2S濃度的場合，是市政污泥厭氧消化項(xiàng)目可以實(shí)現(xiàn)單級解決沼氣脫硫問題的理想選擇。

　　1.3 Biological desulfurization is a new process that emerged and gradually matured in the 1980s. It utilizes the metabolic activity of microorganisms to convert H2S into elemental sulfur or sulfate, ultimately achieving the goal of removing H2S. This process has the advantages of no catalyst required, high removal efficiency, low treatment cost, and recyclability of elemental sulfur. At the same time, it can meet the requirements of high flow rate and high H2S concentration. It is an ideal choice for municipal sludge anaerobic digestion projects to achieve single-stage solution to biogas desulfurization problems.

　　1.4 脫硫技術(shù)發(fā)展方向我國沼氣科研和應(yīng)用雖然有了一定的基礎(chǔ)，但是發(fā)展緩慢，無論是基礎(chǔ)研究，還是具體工藝技術(shù)、裝備化程度以及標(biāo)準(zhǔn)化、產(chǎn)業(yè)化，與發(fā)達(dá)國家相比都還有相當(dāng)?shù)牟罹?。為了解決沼氣脫硫問題，需大力開發(fā)和應(yīng)用新技術(shù)新工藝，同時對某些方面具有優(yōu)勢的傳統(tǒng)工藝進(jìn)行加強(qiáng)改良。干法脫硫反應(yīng)快、去除率高、投資少，目前的短板在于其再生環(huán)節(jié)，通過自控系統(tǒng)可實(shí)現(xiàn)連續(xù)定量投加空氣再生，揚(yáng)長避短，作為二級處理，充分發(fā)揮其精細(xì)脫硫的特點(diǎn)，也是一級脫硫系統(tǒng)故障時的應(yīng)急保證。因此，在大體量市政污泥消化沼氣脫硫處理中，以生物脫硫替代傳統(tǒng)濕法脫硫，外加同步再生干法脫硫，做到新技術(shù)與改良傳統(tǒng)技術(shù)的新老結(jié)合，充分發(fā)揮各自優(yōu)點(diǎn)，成為一個可行的解決方案。

　　1.4 Development direction of desulfurization technology Although China has a certain foundation for biogas research and application, its development is slow. Whether it is basic research, specific process technology, equipment level, standardization, or industrialization, there is still a considerable gap compared to developed countries. In order to solve the problem of biogas desulfurization, it is necessary to vigorously develop and apply new technologies and processes, while strengthening and improving traditional processes that have advantages in certain aspects. Dry desulfurization has the advantages of fast reaction, high removal rate, and low investment. The current weakness lies in its regeneration process. Through the automatic control system, continuous and quantitative air regeneration can be achieved, highlighting its strengths and avoiding its weaknesses. As a secondary treatment, it fully utilizes its fine desulfurization characteristics and is also an emergency guarantee in case of a failure in the primary desulfurization system. Therefore, in the large-scale municipal sludge digestion and biogas desulfurization treatment, replacing traditional wet desulfurization with biological desulfurization and adding synchronous regeneration dry desulfurization can achieve a combination of new and improved traditional technologies, fully leveraging their respective advantages and becoming a feasible solution.

　　2、生物脫硫工藝在生物脫硫過程中，起主要作用的是脫硫細(xì)菌。按其性狀大致可以分為2類，即：有色硫細(xì)菌和無色硫細(xì)菌。有色硫細(xì)菌因?yàn)楹泄夂仙囟軌蜻M(jìn)行光合作用，主要為光能自養(yǎng)型脫硫菌。光能自養(yǎng)型微生物脫硫效率高，在脫除H2S的同時，還能脫除一定量的CO2，用于沼氣脫硫很有優(yōu)勢，但是還沒有工程應(yīng)用方面的報道。原因是光能細(xì)菌在轉(zhuǎn)化硫化物的過程中需要大量的輻射能，在經(jīng)濟(jì)和技術(shù)上都難以實(shí)現(xiàn)，同時生成單質(zhì)硫顆粒后，反應(yīng)器介質(zhì)變得混濁，透光率大大降低，影響了脫硫效率。無色硫細(xì)菌體內(nèi)不含光合色素，不能進(jìn)行光合作用，主要為化能自養(yǎng)型脫硫菌，但也有異養(yǎng)脫硫菌的報道?；茏责B(yǎng)型脫硫菌中的硫桿菌屬是目前生物脫硫工藝中應(yīng)用最廣泛的一個菌屬，代表性菌種包括氧化亞鐵硫桿菌、氧化硫硫桿菌、排硫硫桿菌和脫氮硫桿菌等，其中脫氮硫桿菌因其具有較好的選擇性和環(huán)境適應(yīng)性，應(yīng)用最多?；苄兔摿蚬に嚹壳伴_發(fā)得較為成熟，主要包括生物洗滌器、生物濾池和生物滴濾池3種。其中生物濾池主要用來處理氣量大、濃度低的含硫臭氣，對于沼氣生物脫硫的應(yīng)用則主要集中在生物滴濾池(見圖1)和生物洗滌器反應(yīng)器(見圖2)上。生物滴濾池的系統(tǒng)造價和運(yùn)行成本相對較低，但是為了避免單質(zhì)硫堵塞填料，需要注入過量空氣，將H2S氧化成硫酸根，同時空氣中的惰性成分包括過量的氧都會進(jìn)入沼氣，降低其熱值，且排放的廢液中含有pH較低的稀硫酸，會對環(huán)境造成二次污染。考慮到凈化沼氣的再利用，堿再生生物洗滌沼氣脫硫系統(tǒng)還能夠?qū)崿F(xiàn)單質(zhì)硫回收的資源化利用。因此在消化沼氣生物脫硫工藝選擇時，優(yōu)先推薦堿再生生物洗滌。不同沼氣生物脫硫工藝比較見表1。

　　2. The desulfurization bacteria play a major role in the biological desulfurization process. According to their characteristics, they can be roughly divided into two categories: colored sulfur bacteria and colorless sulfur bacteria. Colored sulfur bacteria can carry out photosynthesis due to the presence of photosynthetic pigments, mainly being photoautotrophic desulfurization bacteria. Light autotrophic microorganisms have high desulfurization efficiency, and can remove a certain amount of CO2 while removing H2S, which is very advantageous for biogas desulfurization. However, there are no reports on engineering applications yet. The reason is that photobacteria require a large amount of radiation energy in the process of converting sulfides, which is difficult to achieve economically and technically. At the same time, after generating elemental sulfur particles, the reactor medium becomes turbid, and the light transmittance is greatly reduced, which affects the desulfurization efficiency. Colorless sulfur bacteria do not contain photosynthetic pigments in their bodies and cannot carry out photosynthesis. They are mainly chemoautotrophic desulfurization bacteria, but there are also reports of heterotrophic desulfurization bacteria. The genus Thiobacillus in chemoautotrophic desulfurization bacteria is currently the most widely used in biological desulfurization processes, with representative strains including Thiobacillus ferrooxidans, Thiobacillus thiooxidans, Thiobacillus thiooxidans, and Desulfobacterium denitrifying. Among them, Desulfobacterium denitrifying is the most widely used due to its good selectivity and environmental adaptability. The development of chemical energy desulfurization technology is currently relatively mature, mainly including three types: biological scrubbers, biological filters, and biological drip filters. The biological filter is mainly used to treat sulfur-containing odors with high gas volume and low concentration, while the application of biogas biological desulfurization is mainly focused on the biological drip filter (see Figure 1) and the biological scrubber reactor (see Figure 2). The system cost and operating cost of the biological drip filter are relatively low, but in order to avoid clogging of the packing with elemental sulfur, excessive air injection is required to oxidize H2S into sulfate ions. At the same time, inert components in the air, including excess oxygen, will enter the biogas, reducing its calorific value. The discharged waste liquid also contains dilute sulfuric acid with low pH, which will cause secondary pollution to the environment. Considering the reuse of purified biogas, the alkaline regeneration biological washing biogas desulfurization system can also achieve the resource utilization of elemental sulfur recovery. Therefore, when selecting the process of digesting biogas for biological desulfurization, alkaline regeneration biological washing is preferred. The comparison of different biogas biological desulfurization processes is shown in Table 1.

　　3、同步再生干法脫硫傳統(tǒng)干法脫硫主要是利用水合氧化鐵與沼氣中的硫化氫反應(yīng)，從而達(dá)到脫硫的目的。

　　3. Synchronous regeneration dry desulfurization. Traditional dry desulfurization mainly utilizes the reaction between hydrated iron oxide and hydrogen sulfide in biogas to achieve desulfurization.

　　這種干法脫硫會出現(xiàn)以下幾個問題：①硫化鐵塔內(nèi)再生操作困難，脫硫劑難以被完全利用;②脫硫劑卸出塔體再生會占用較大的場地，且過程不易控制;③脫硫劑的裝卸過程無法避免氧氣進(jìn)入塔體，可能造成塔內(nèi)脫硫劑自燃;④塔內(nèi)脫硫劑容易板結(jié)，甚至無法排出。同步再生脫硫是對傳統(tǒng)干法脫硫的改進(jìn)，在H2S脫除的同時，對脫硫劑進(jìn)行連續(xù)再生，以充分利用脫硫劑的硫容。氧化鐵脫硫及再生原理見式(1)、(2)，兩者綜合得到如式(3)所示的沼氣脫硫反應(yīng)式。由此可知，去除1mol的H2S理論上需要0.5mol的O2，但是實(shí)際工程中由于反應(yīng)介質(zhì)接觸不夠充分，再生空氣投加的富余系數(shù)為1.2～1.8，空氣量隨H2S濃度及沼氣流量變化的曲線如圖3所示?？梢?，H2S含量越大，空氣投加比例越高，但工程上一般控制空氣投加比最大不超過4%。要實(shí)現(xiàn)脫硫劑的同步再生，關(guān)鍵要實(shí)現(xiàn)空氣量根據(jù)H2S濃度和沼氣流量進(jìn)行自動投加，由于前者在一定時段內(nèi)相對穩(wěn)定，所以工程上根據(jù)沼氣流量的動態(tài)變化，以預(yù)設(shè)比例投加空氣，空壓機(jī)變頻可調(diào)，其控制原理見圖4同步再生脫硫塔對脫硫劑的裝卸采用了隔離倉的概念(見圖5)，控制裝卸過程可能進(jìn)入塔體的空氣量。隔離倉由上下兩個閥門和一個緩沖倉構(gòu)成。相關(guān)閥門需要通過消防耐火測試，并且取得認(rèn)證。卸料時，先開啟靠近塔體的卸料閥1，脫硫劑卸入緩存?zhèn)}，然后關(guān)閉該閥。再開啟卸料閥2，將倉中脫硫劑卸出，最后關(guān)閉卸料閥2。通過該方式，盡可能地避免空氣帶入塔體。該技術(shù)還采用獨(dú)特的進(jìn)氣和加熱措施(見圖6)，防止塔體內(nèi)部溫度過低，出現(xiàn)水汽冷凝，造成脫硫劑板結(jié)。塔體外部配置加熱裝置，形式為伴熱帶或熱水盤管，同時設(shè)有保溫層，通過塔內(nèi)溫度反饋，自動調(diào)節(jié)熱水量或伴熱功率，以保證塔內(nèi)溫度比進(jìn)氣的露點(diǎn)溫度高10~20℃。如圖6所示，飽和沼氣從塔中下部分進(jìn)入塔體，沿著漸擴(kuò)管向下，在漸擴(kuò)管管口，氣流折返向上經(jīng)過脫硫劑層，之后從頂部流出塔體。進(jìn)氣在接觸到脫硫劑之前經(jīng)過預(yù)熱，水汽凝出的可能性降低，同時經(jīng)過二次分配，也增加了布?xì)獾木鶆蛐浴?/p>

　　This dry desulfurization method may encounter the following problems: ① difficult regeneration operation inside the sulfide iron tower, and difficulty in fully utilizing the desulfurizer; ② Unloading desulfurizer from the tower for regeneration will occupy a large area and the process is difficult to control; ③ The loading and unloading process of desulfurizer cannot avoid oxygen entering the tower body, which may cause spontaneous combustion of desulfurizer inside the tower; ④ The desulfurizer inside the tower is prone to caking and may even be unable to be discharged. Synchronous regeneration desulfurization is an improvement on traditional dry desulfurization, which continuously regenerates the desulfurizer while removing H2S, in order to fully utilize the sulfur capacity of the desulfurizer. The principle of iron oxide desulfurization and regeneration is shown in equations (1) and (2), and the two are combined to obtain the biogas desulfurization reaction equation shown in equation (3). From this, it can be seen that theoretically, removing 1mol of H2S requires 0.5mol of O2. However, in practical engineering, due to insufficient contact with the reaction medium, the excess coefficient of regenerated air is 1.2-1.8. The curve of air volume changing with H2S concentration and biogas flow rate is shown in Figure 3. It can be seen that the higher the H2S content, the higher the air addition ratio, but in engineering, the maximum air addition ratio is generally controlled to not exceed 4%. To achieve synchronous regeneration of desulfurizer, the key is to automatically add air based on H2S concentration and biogas flow rate. As the former is relatively stable for a certain period of time, air is added in a preset proportion according to the dynamic changes of biogas flow rate in the project. The frequency conversion of the air compressor is adjustable, and its control principle is shown in Figure 4. The synchronous regeneration desulfurization tower adopts the concept of an isolation compartment for the loading and unloading of desulfurizer (see Figure 5) to control the amount of air that may enter the tower during the loading and unloading process. The isolation chamber consists of two upper and lower valves and a buffer chamber. The relevant valves need to pass fire resistance testing and obtain certification. When unloading, first open the unloading valve 1 near the tower body, unload the desulfurizer into the buffer bin, and then close the valve. Open discharge valve 2 again to discharge the desulfurizer from the warehouse, and finally close discharge valve 2. Through this method, try to avoid air entering the tower as much as possible. This technology also adopts unique intake and heating measures (see Figure 6) to prevent the internal temperature of the tower from being too low, resulting in water vapor condensation and causing the desulfurizer to plate. A heating device is installed outside the tower, in the form of a heat tracing or hot water coil, with an insulation layer. Through temperature feedback inside the tower, the amount of hot water or heat tracing power is automatically adjusted to ensure that the temperature inside the tower is 10-20 ℃ higher than the dew point temperature of the inlet air. As shown in Figure 6, saturated biogas enters the tower body from the lower part of the tower, flows downwards along the expanding pipe, and at the mouth of the expanding pipe, the airflow returns upwards through the desulfurizer layer before flowing out of the tower body from the top. The intake is preheated before coming into contact with the desulfurizer, reducing the possibility of water vapor condensation. At the same time, it undergoes secondary distribution, which also increases the uniformity of gas distribution.

　　4、生物+同步再生干法脫硫工程應(yīng)用案例4.1 脫硫系統(tǒng)主要工藝參數(shù)華東某大型市政污泥厭氧消化項(xiàng)目脫硫系統(tǒng)采用堿再生生物洗滌+同步再生干法脫硫工藝，主要工藝參數(shù)如表2所示。

　　4. Application case of biological+synchronous regeneration dry desulfurization project 4.1 Main process parameters of desulfurization system. The desulfurization system of a large municipal sludge anaerobic digestion project in East China adopts alkaline regeneration biological washing+synchronous regeneration dry desulfurization process. The main process parameters are shown in Table 2.

　　4.2 脫硫系統(tǒng)組成及主要設(shè)備參數(shù)4.2.1 生物脫硫部分生物脫硫單元采用堿再生生物洗滌工藝，共分A、B兩條線，主要設(shè)備包括生物洗滌塔、生物反應(yīng)器和硫沉淀器等，總裝機(jī)功率148kW，實(shí)際運(yùn)行功率107kW。①生物洗滌塔含H2S沼氣進(jìn)入生物洗滌塔，與洗滌液在塔內(nèi)逆流接觸，H2S被洗滌液吸收。洗滌塔內(nèi)裝有填料，目的是增加氣液接觸的面積。洗滌液由循環(huán)泵從生物反應(yīng)器的脫氣區(qū)泵入洗滌塔，洗滌水在塔底收集后流向生物反應(yīng)器。脫硫后的氣體從洗滌塔頂部排出。洗滌塔共4臺，單臺過氣量1000m?/h，尺寸D1.2m×H15.8m，HDPE材質(zhì)，填料高度6m，頂部設(shè)有除沫器，用來去除沼氣出氣中夾帶的液滴;循環(huán)泵4用2備，離心泵，流量84m?/h，揚(yáng)程210kPa，電機(jī)功率11kW。②生物反應(yīng)器含有硫化物的洗滌液重力流入生物反應(yīng)器。生物反應(yīng)器液相中含有硫桿菌，通過控制DO水平將硫化物生物氧化，使之主要生成單質(zhì)硫，同時再生形成吸收H2S所需的堿。反應(yīng)器中無固定微生物的載體，生物硫本身充當(dāng)了載體的角色。生物反應(yīng)器2臺，單臺尺寸D2.9m×H6.0m，HDPE材質(zhì);配套曝氣鼓風(fēng)機(jī)4用2備，180m?/h，60kPa，5.5kW，變頻控制;營養(yǎng)鹽投加泵2臺，電磁驅(qū)動隔膜計量泵，1.6L/h，0.76MPa，0.012kW，手動沖程調(diào)節(jié);NaOH投加泵2用1備，電磁隔膜計量泵，90L/h，0.7MPa，0.25kW，手動沖程調(diào)節(jié);測量循環(huán)泵2臺，25m?/h，150kPa，2.2kW。③硫沉淀器反應(yīng)液由生物反應(yīng)器連續(xù)泵向硫沉淀器，在此產(chǎn)物硫與洗滌液分離，沉淀器的上清液回流到生物反應(yīng)器，單質(zhì)硫泵入硫貯槽。硫貯槽的硫污泥經(jīng)攪拌器混勻后泵入儲泥罐，并定期外運(yùn)。硫沉淀器2臺，單臺尺寸D1.0m×H6.0m，HDPE材質(zhì);硫貯槽1臺，尺寸D2.0m×H3.5m，HDPE材質(zhì);硫污泥泵1臺，用于將硫污泥自沉淀器泵送至硫貯槽，軟管泵，200L/h，0.5MPa，0.75kW;硫外送泵1臺，軟管泵，500L/h，0.5MPa，0.75kW。④輔助單元為維持生物反應(yīng)最適宜的溫度，配套循環(huán)冷卻單元1套，包括板式換熱器2臺，45kW;冷卻水泵1用1備，立式離心泵，20m?/h，330kPa，5.5kW。4.2.2 同步再生干法脫硫部分沼氣經(jīng)過生物脫硫后，H2S含量大幅降低，然后進(jìn)入干法脫硫單元精脫硫，使H2S含量進(jìn)一步下降，確保滿足設(shè)計要求。H2S的脫除與脫硫劑的氧化再生在脫硫塔中同時進(jìn)行，大大提高了傳統(tǒng)干法脫硫再生環(huán)節(jié)的效率。沼氣系統(tǒng)正常運(yùn)行時，生物脫硫出口H2S濃度在100mg/m?以下，同步再生脫硫塔可將之進(jìn)一步處理到1mg/m?以下。如遇到生物脫硫故障，僅依靠堿洗脫硫，在干式脫硫塔進(jìn)口H2S濃度可能增加至300～500mg/m?甚至更高時，同步再生干法脫硫塔亦可保證出口H2S含量小于20mg/m?，只是脫硫劑的消耗量會相應(yīng)增加。但作為沼氣脫硫系統(tǒng)故障時的短期應(yīng)用，事實(shí)上也起到了應(yīng)急保障的作用。脫硫塔共計2臺，單臺最大過氣量2000m?/h，停留時間1.8min，空塔濾速0.1m/s。脫硫塔尺寸D2.8m×H14.2m，單臺有效容積60m?，316L不銹鋼材質(zhì)，熱水盤管加熱方式，外殼配巖棉保溫層;氣環(huán)式壓縮機(jī)2臺，20m?/h，變頻可調(diào);伴熱泵2臺，立式離心泵，2m?/h，100kPa，0.37kW;氧化鐵脫硫劑，硫容40%，約0.7t/m?，孔隙率50%，直徑1cm，長2~3cm，強(qiáng)度50N/cm，總裝填量約84t。

　　4.2 Composition and main equipment parameters of desulfurization system 4.2.1 Biological desulfurization section The biological desulfurization unit adopts alkaline regeneration biological washing process, which is divided into two lines A and B. The main equipment includes biological washing tower, bioreactor, and sulfur precipitant, with a total installed power of 148kW and an actual operating power of 107kW. ① The biogas containing H2S enters the biological washing tower and comes into contact with the washing solution in reverse flow inside the tower, and H2S is absorbed by the washing solution. The washing tower is equipped with packing to increase the area of gas-liquid contact. The washing solution is pumped from the deaeration zone of the bioreactor into the washing tower by a circulation pump, and the washing water is collected at the bottom of the tower and flows towards the bioreactor. The desulfurized gas is discharged from the top of the scrubbing tower. There are a total of 4 washing towers, each with a gas flow rate of 1000m ?/h, dimensions of D1.2m × H15.8m, made of HDPE material, and a packing height of 6m. The top is equipped with a demister to remove liquid droplets carried in the biogas exhaust; Circulating pump 4 in use and 2 as backup, centrifugal pump, flow rate 84m?/h, head 210kPa, motor power 11kW. ② The washing solution containing sulfides flows into the bioreactor by gravity. The liquid phase of the bioreactor contains sulfur bacteria. By controlling the DO level, sulfides are biologically oxidized to mainly produce elemental sulfur, while regenerating to form the alkali required for H2S absorption. There is no fixed microbial carrier in the reactor, and biological sulfur itself acts as a carrier. Two bioreactors, each measuring D2.9m × H6.0m and made of HDPE material; Equipped with 4 aeration blowers for use and 2 backup, 180m ?/h, 60kPa, 5.5kW, frequency conversion control; 2 nutrient dosing pumps, electromagnetic driven diaphragm metering pump, 1.6L/h, 0.76MPa, 0.012kW, manual stroke adjustment; NaOH dosing pump 2 in use and 1 backup, electromagnetic diaphragm metering pump, 90L/h, 0.7MPa, 0.25kW, manual stroke adjustment; Measure 2 circulating pumps, 25m?/h, 150kPa, 2.2kW. ③ The reaction solution of the sulfur precipitator is continuously pumped from the bioreactor to the sulfur precipitator, where the product sulfur is separated from the washing solution. The supernatant of the precipitator flows back to the bioreactor, and elemental sulfur is pumped into the sulfur storage tank. The sulfur sludge in the sulfur storage tank is mixed by a mixer and pumped into the storage tank, and is regularly transported outside. Two sulfur precipitators, each measuring D1.0m × H6.0m, made of HDPE material; One sulfur storage tank, size D2.0m × H3.5m, made of HDPE material; One sulfur sludge pump, used to pump sulfur sludge from the sedimentation tank to the sulfur storage tank, hose pump, 200L/h, 0.5MPa, 0.75kW; One sulfur export pump, hose pump, 500L/h, 0.5MPa, 0.75kW. ④ To maintain the most suitable temperature for biological reactions, the auxiliary unit is equipped with one set of circulating cooling unit, including two plate heat exchangers with a power of 45kW; one cooling water pump is in use and one backup, a vertical centrifugal pump with a capacity of 20m ?/h, 330kPa, and 5.5kW. 4.2.2 Synchronous regeneration of dry flue gas. After biological desulfurization, the H2S content is significantly reduced, and then it enters the dry flue gas desulfurization unit for fine desulfurization, further reducing the H2S content to ensure compliance with design requirements. The removal of H2S and the oxidation regeneration of desulfurizer are carried out simultaneously in the desulfurization tower, greatly improving the efficiency of the traditional dry desulfurization regeneration process. When the biogas system is operating normally, is the H2S concentration at the outlet of the biological desulfurization system 100mg/m? Can the synchronous regeneration desulfurization tower further process it to 1mg/m? following. If encountering a biological desulfurization failure, relying solely on alkaline washing desulfurization may increase the H2S concentration at the inlet of the dry desulfurization tower to 300-500mg/m? Even higher, can the synchronous regeneration dry desulfurization tower ensure that the H2S content at the outlet is less than 20mg/m? However, the consumption of desulfurizer will increase accordingly. But as a short-term application in the event of a malfunction in the biogas desulfurization system, it actually plays a role in emergency support. There are a total of 2 desulfurization towers, with a maximum gas flow rate of 2000m?/h per unit, a residence time of 1.8min, and an empty tower filtration rate of 0.1m/s. The size of the desulfurization tower is D2.8m × H14.2m, with an effective capacity of 60m ? per unit. It is made of 316L stainless steel and heated by a hot water coil. The outer shell is equipped with a rock wool insulation layer; Two gas ring compressors, 20m ?/h, with adjustable frequency conversion; Two companion heat pumps, vertical centrifugal pumps, 2m ?/h, 100kPa, 0.37kW; Iron oxide desulfurizer with a sulfur capacity of 40%, approximately 0.7t/m? The porosity is 50%, the diameter is 1cm, the length is 2-3cm, the strength is 50N/cm, and the total filling amount is about 84t.

　　4.3 運(yùn)行結(jié)果經(jīng)過調(diào)試、試運(yùn)行，裝置達(dá)到穩(wěn)定運(yùn)行狀態(tài)，為檢驗(yàn)脫硫系統(tǒng)的綜合處理能力，進(jìn)行了性能測試。檢測表明，沼氣的平均處理量達(dá)到了48166m?/d(見圖7)，較設(shè)計值(44512m?/d)略高。沼氣的進(jìn)氣H2S濃度為4125～7425mg/m?，波動范圍較大，但堿再生生物脫硫系統(tǒng)表現(xiàn)出優(yōu)異的耐沖擊及H2S高效去除能力，A、B兩套裝置出氣H2S均小于27mg/m?，平均11.72mg/m?，去除效率均大于99%。生物脫硫雖然沒有全部直接達(dá)到設(shè)計要求的20mg/m?，但經(jīng)過同步再生干法脫硫后，所有出氣均未檢出H2S(見圖8)，證明本項(xiàng)目生物+同步再生干法脫硫工藝是一個成功的選擇。另外，堿再生生物洗滌脫硫單元的堿耗平均為0.63kgNaOH/kgH2S(見圖9)，遠(yuǎn)遠(yuǎn)低于傳統(tǒng)堿吸收濕法脫硫的堿耗(3～5kgNaOH/kgH2S)，也證明了系統(tǒng)通過自身運(yùn)行實(shí)現(xiàn)了堿再生的目的，藥耗減少，運(yùn)行成本降低。從以上運(yùn)行效果看，生物脫硫系統(tǒng)能夠滿足實(shí)際要求，干式脫硫系統(tǒng)起到了雙保險作用。以生物脫硫出氣H2S平均濃度為11.72mg/m?計，日脫硫劑消耗量約為1~2kg/d，脫硫劑更換時間長達(dá)若干年。如果生物脫硫出現(xiàn)故障或效能下降，脫硫塔在保證處理效果的前提下，脫硫劑更換時間將大幅縮短。以上述沼氣進(jìn)氣平均流量為48166m?/d、H2S濃度區(qū)間上限為7500mg/m?計，在不同生物脫硫效果下脫硫劑消耗情況見圖10。由圖10可見，在生物脫硫?qū)2S的去除率僅有60%時，每日脫硫劑耗量達(dá)到近600kg/d，脫硫劑更換時間長達(dá)140d以上，因此在生物脫硫短時故障、脫硫效果有所降低的情況下，同步再生干式脫硫塔仍能保證沼氣系統(tǒng)穩(wěn)定運(yùn)行。

　　4.3 After debugging and trial operation, the device reached a stable operating state. To test the comprehensive processing capability of the desulfurization system, performance tests were conducted. Tests have shown that the average processing capacity of biogas has reached 48166m?/d (see Figure 7), slightly higher than the design value (44512m?/d). The H2S concentration in the intake of biogas is 4125-7425mg/m? The fluctuation range is relatively large, but the alkaline regeneration biological desulfurization system exhibits excellent shock resistance and efficient H2S removal ability. Both sets of devices A and B have H2S emissions of less than 27mg/m? On average, 11.72mg/m? The removal efficiency is all greater than 99%. Although not all biological desulfurization directly meets the design requirement of 20mg/m? However, after synchronous regeneration dry desulfurization, no H2S was detected in all the exhaust gases (see Figure 8), proving that the biological+synchronous regeneration dry desulfurization process in this project is a successful choice. In addition, the average alkali consumption of the alkaline regeneration biological washing desulfurization unit is 0.63kgNaOH/kgH2S (see Figure 9), which is much lower than the alkali consumption of traditional alkaline absorption wet desulfurization (3-5kgNaOH/kgH2S). This also proves that the system achieves the purpose of alkaline regeneration through its own operation, reduces drug consumption, and lowers operating costs. From the above operational effects, it can be seen that the biological desulfurization system can meet practical requirements, and the dry desulfurization system plays a dual insurance role. The average concentration of H2S in the gas produced by biological desulfurization is 11.72mg/m? The daily consumption of desulfurizer is about 1-2kg/d, and the replacement time of desulfurizer can last for several years. If there is a malfunction or a decrease in the efficiency of biological desulfurization, the replacement time of desulfurizer in the desulfurization tower will be significantly shortened while ensuring the treatment effect. Based on the above average flow rate of 48166m?/d for biogas intake and an upper limit of 7500mg/m for H2S concentration range? The consumption of desulfurizer under different biological desulfurization effects is shown in Figure 10. As shown in Figure 10, when the removal rate of H2S by biological desulfurization is only 60%, the daily consumption of desulfurizer reaches nearly 600kg/d, and the replacement time of desulfurizer is over 140d. Therefore, even in the case of short-term failure and reduced desulfurization effect of biological desulfurization, the synchronous regeneration dry desulfurization tower can still ensure the stable operation of the biogas system.

　　4.4 經(jīng)濟(jì)效益評價案例項(xiàng)目脫硫系統(tǒng)設(shè)備總投資約700萬元，占地面積600m?，經(jīng)性能測試核算處理成本約為0.101元/m?沼氣，分別由電費(fèi)、水費(fèi)、NaOH藥劑費(fèi)、營養(yǎng)鹽費(fèi)、干式脫硫劑費(fèi)、人工費(fèi)、設(shè)備折舊費(fèi)、運(yùn)行維護(hù)費(fèi)和其他費(fèi)用等組成，各部分比例如圖11所示。如果只計前五項(xiàng)直接運(yùn)行成本，則折合0.039元/m?沼氣，顯著低于傳統(tǒng)濕法脫硫，且用電成本占比最大，電耗約為0.029kW·h/m?沼氣。

　　4.4 Economic Benefit Evaluation Case: The total investment of the desulfurization system equipment in the project is about 7 million yuan, covering an area of 600m ?. After performance testing, the processing cost is calculated to be about 0.101 yuan/m ? for biogas, which is composed of electricity, water, NaOH reagent, nutrient salt, dry desulfurizer, labor, equipment depreciation, operation and maintenance, and other expenses. The proportion of each part is shown in Figure 11. If only the first five direct operating costs are included, it is equivalent to 0.039 yuan/m ? of biogas, which is significantly lower than traditional wet desulfurization, and the proportion of electricity cost is the largest, with an electricity consumption of about 0.029 kW · h/m ?? Biogas.

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