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1 Introduction In the wet oxidation desulfurization process, packed towers are still used in the vast majority of cases today. A packed tower is a widely used device for gas-liquid two-phase contact and mass transfer. It is widely used due to its advantages such as simple structure, high operational flexibility, stable operation, and ease of manufacturing. However, when packed towers are used in the wet oxidation method for desulfurization, due to the particularities of the desulfurization reaction, many problems have arisen with these towers in recent years. The most significant issue is the easy clogging of the tower, which leads to high system resistance, high energy consumption, low desulfurization efficiency, and high consumption of process materials. Especially in recent years, due to the significant increase in enterprises’ production capacity, the diameter of desulfurization towers has had to grow larger in order to meet the requirements of the production processes. What is not known is that the larger the tower diameter, the harder it is to achieve a uniform distribution of gas and liquid within the tower, which leads to uneven flow of gas and liquid and subsequent blockage of the tower. Although many companies have carried out extensive technical improvements in the structure of the packing and the distribution of gas and liquid to address issues such as tower blockage in packing desulfurization towers. However, based on the operating conditions of actual industrial plants, many enterprises have still not managed to get rid of the problem of tower blockage fundamentally, which means that this issue has yet to be resolved once and for all. Based on this, our company’s Gas Purification Design and Research Center, taking into account the feedback from numerous users and through simulation experiments, identified the various shortcomings of existing nozzles in the industry. After repeated simulations and modifications, it successfully developed the DSP series of high-efficiency atomizing nozzles suitable for wet flue gas desulfurization. Additionally, a scientific and rational layout for the placement of these nozzles was designed, which not only **improves the efficiency of desulfurization but also helps to prevent blockages in the tower. Working principle and technical characteristics of the 2DSP series high-efficiency atomizing nozzles: Simply put, the working principle of the DSP series high-efficiency atomizing nozzles is that, under a certain pressure, the desulfurization liquid comes into contact with and collides with a continuously shrinking spiral surface, thereby turning into tiny droplets that are ejected to form a mist in a state close to gaseous. Therefore, the quality of its atomization directly determines the efficiency of the desulfurization absorption reaction. The scientifically sound design of the DSP series of high-efficiency atomizing nozzles enables the desulfurization fluid to achieve a maximum flow rate in pipes of given dimensions, thereby ensuring highly efficient atomization of the fluid being sprayed. Thanks to its well-designed flow channels, clogging of the nozzle is minimized to the greatest extent. To prevent corrosion, the material used is stainless steel. Its corrosion resistance, fogging resistance, and clog prevention have been recognized by many users. Based on the flow rate of the medium to be sprayed, the company has designed and manufactured high-efficiency atomizing nozzles in series such as DSP-10, DSP-20, and DSP-30. These nozzles are not only suitable for tower-type desulfurization equipment but also useful for devices used in gas washing, dust removal, and temperature reduction in chemical processing processes. Main technical parameters of the DSP series high-efficiency atomization nozzles: (1) Liquid supply pressure: 0.4–0.5 MPa; (2) Flow rate per nozzle: 5–40 Nm3/h. The technical background for using the DSP series high-efficiency atomization nozzles in tower spray desulfurization: Tower spray technology has been used in the desulfurization process within the fertilizer industry for a long time, but due to issues related to the atomization technology of the nozzles inside the towers as well as the rationality of their design and installation, it was not possible to achieve the desired results, which led to this technology not being further adopted. In many enterprises, spray nozzles used for gas washing and cooling are employed in the pre-desulfurization towers. Due to the poor atomization effect of these nozzles and an unsuitable layout, gas-liquid contact within the tower is inadequate, which prevents the pre-desulfurization towers from functioning effectively. Obviously, to ensure the desulfurization efficiency of spray cooling in empty towers, the atomization performance of the nozzles is undoubtedly the most critical factor; secondly, it is the proper layout of the nozzles. The main challenges of this process technology include: the atomization efficiency of the nozzles, the distribution pattern of the nozzles within the tower, the distribution of the gas entering the tower, the issue of mist entrainment in the gas exiting the tower, and nozzle clogging. In response to the above issues, our company’s Gas Purification Research Center conducted numerous experiments and studies, and finally overcame these challenges, enabling the empty tower spray process technology to be successfully applied in wet flue gas desulfurization. Technical features of 4-column spray desulfurization: (1) Low investment; its use in the design of new towers can save approximately 30-50% on the initial investment. (2) The tower blockage problem has been completely resolved. (3) When designing the new tower, its height should be about 10 m lower than that of the packed tower. (4) The gas-liquid contact time is **reduced**, which decreases the impact of CO2 in the gas on desulfurization. (5) It has low tower resistance and strong high-sulfur removal capability, especially showing more significant effects in multi-stage desulfurization. (6) The empty tower spraying technology, when combined organically with the internal components of the pressurized packing-free desulfurization tower QYD, yields particularly significant results. 5 Application of High-Efficiency Atomization Nozzles in Wet Flue Gas Desulfurization Systems 5.1 Application in Atmospheric Pressure Desulfurization Systems 5.1.1 Application in the Pre-desulfurization System of a Company in Guangxi (1) Process Parameters: Treatment capacity of semi-water gas: 125,000 Nm3/h; Composition of semi-water gas: H2S ≤ 7 g/Nm3; H2S level at the outlet of the desulfurization system: 80–100 mg/Nm3 (2) Main Process Flow: Semi-water gas comes from the gas tank, passes through electrostatic precipitators and fans before entering the pre-desulfurization tower; from there it goes into three packed-bed desulfurization towers, and finally enters the subsequent processing stage after passing through wash tanks. (3) Equipment configuration: (4) Application results a. The operating conditions before the modification are shown in the table below (Data table of main components in the semi-deoxidized solution for January–July 2010; Unit: g/L: amount of semi-water gas, inlet H2S concentration, H2S concentration at the outlet of the semi-deoxidization tower, and desulfurization efficiency). b. The operating conditions after the modification are shown in the table below (Data table of main components in the semi-deoxidized solution for July–December 2010; Unit: g/L: amount of semi-water gas, inlet H2S concentration, H2S concentration at the outlet of the semi-deoxidization tower, and desulfurization efficiency). The pre-desulfurization tower is designed to use DSP-type high-efficiency atomizing nozzles for tower spray irrigation, and it operates in series with the existing semi-water gas desulfurization tower, thereby effectively reducing the resistance in the production system (resistance in the pre-desulfurization tower ≤ 50 mm water column). Based on the system operation data, the components in the semi-dissolved solution have decreased significantly, and the desulfurization efficiency has improved markedly. The qualification rate of the semi-removal system’s process parameters was 100%, reducing the impact on subsequent production processes and equipment. 5.1.2 Application in a single-stage desulfurization system at a chemical plant in Inner Mongolia: In September 2008, a chemical manufacturing company in Inner Mongolia modified its desulfurization tower with dimensions of Φ3800 and H34000 into a desulfurization tower that combined a spray section with a packing section. Satisfactory results were achieved after the renovation. Main structural details of the desulfurization tower: The lower section of the tower is the spray tower section, equipped with three layers of nozzles; each layer has 9 DSP-type high-efficiency atomizing nozzles ； The upper section of the tower is the packing section (76×38×2.5 stepped packing, with a total volume of 130 m3 and a height of 5.8 m each). Main equipment configuration: Desulfurization pumps: one with a flow rate of 468 m3/h and a head of 54 m, and two pumps with a flow rate of 162 m3/h each and a head of 50 m; normally, one large pump and one small pump are in operation ； Regeneration pump: Same as desulfurization pump, one large and one small ； Regeneration tank: 6500/7300/8100, equipped with 18 injectors. (1) The operating conditions of the desulfurization tower before the renovation are shown in the table below. (2) The operating conditions of the desulfurization tower after the renovation are shown in the table below. (3) The desulfurization efficiency in the spray section of the empty tower is given in the table below. 5.2 Application in pressurized desulfurization systems 5.2.1 Application in a 0.9 MPa shift desulfurization tower at a company in Henan (1) Main design parameters: Operating pressure of 0.83 MPa; flow rate of the shifted gas at 65,000 Nm3/h. Dimensions of the shift desulfurization tower: Ø3800×27830; pressure difference across the tower ≤ 30 KPa. Hydrogen sulfide concentration at the inlet ≤ 350 mg/m3, with a requirement that the hydrogen sulfide concentration at the outlet be ≤ 10 mg/m3. (2) Structural design of the Ø3800 shift desulfurization tower: Based on the actual process parameters provided by the company, and considering the high hydrogen sulfide content in the gas entering the tower, this tower was designed as a packing-free tower that combines QYD internal components with spray technology for the empty tower section. Three layers of QYD internals are installed in the upper and middle sections of the tower; each layer’s liquid-holding section is 1 meter high. At the lower part of the tower, there are 20 DSP-type high-efficiency atomizing nozzles, with each nozzle having a liquid flow rate of 10 Nm3/h. (3) Operational performance: Since the system was put into operation in November 2011, satisfactory results have been achieved. The operational data for June 2012 are shown in the table below. As can be seen from these figures, the designed gas processing capacity of this tower is 100,000 Nm3/h, yet the actual gas production volume exceeds 110,000 Nm3/h. Additionally, the desulfurization efficiency is high and the tower’s pressure drop remains stable. 5.2.2 Application in the 2.0 MPa shift gas desulfurization tower in Guangxi (1) Main design parameters: Design pressure – 2.5 MPa; Operating pressure – 1.8 MPa; Shift gas flow rate – 100,000 NM3/h; Diameter of the desulfurization tower – 3200×28374 mm; Pressure difference across the desulfurization tower – ≤30 KPa; Hydrogen sulfide content in the shift gas – ≤350 mg/m3; Hydrogen sulfide content at the outlet – ≤20 mg/m3. (2) Structural format of the 3200-mm-diameter desulfurization tower: Based on the actual values of the process parameters, this desulfurization tower adopts a fillless tower structure that combines the QYD internal component technology with tray spraying technology. Four layers of QYD internals are installed in the upper and middle sections of the tower, while 16 DSP-type high-efficiency atomization nozzles are installed in the lower section of the tower. The liquid flow rate per nozzle is 20 Nm3/h. (3) Operational results: The company started operating the system in June 2011, achieving fairly satisfactory results; the operational performance in July is shown in the table below: 6 Conclusion: The successful use of DSP-series high-efficiency atomizing nozzles in the desulfurization towers of wet flue gas desulfurization systems has fundamentally solved the problematic issue of tower blockage that plagues filler-based desulfurization towers. Due to the significant reduction in the packing inside the tower, coupled with the fact that the spray empty tower also plays a role in cooling and dust removal, it is possible to effectively prevent the packing from causing blockages in the tower. Moreover, the spray empty tower possesses a high desulfurization efficiency; industrial practice has shown that the desulfurization efficiency of this tower alone can reach up to about 60%. Therefore, in atmospheric-pressure desulfurization systems, for enterprises with a single tower configuration, the packing in the lower section of the desulfurization tower can be removed and replaced with a spray section in an empty tower, while the packing in the upper two sections remains unchanged ； For enterprises with a dual-tower or multi-tower configuration, the preceding packed tower can be replaced with a spray tray tower to serve as a pre-desulfurization tower ； For enterprises using high-sulfur coal, the spray air tower technology can be employed in the primary desulfurization process. In pressurized desulfurization systems, the filler-free desulfurization tower technology that combines DSP-series high-efficiency atomizing nozzles with QYD internals offers advantages such as high desulfurization efficiency, low investment costs, low tower resistance, and no risk of tower clogging. In summary, the spray air tower in the wet flue gas desulfurization system uses DSP-series high-efficiency atomizing nozzles, which not only provide a high desulfurization efficiency but also help to cool and remove dust from the process gas. They also reduce the load on the packing section and more effectively prevent tower blockages, thereby enabling the desulfurization system to operate stably over extended periods of time.