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1. Preface: Shandong Hanhai Chemical Fertilizer Co., Ltd. is a subsidiary controlled by Qinghai Hanhai Group, and is located in the Taocun Town Industrial Park of Qixia City. The company produces 40,000 tons of synthetic ammonia and 60,000 tons of urea per year. In the second half of 2008, in light of the aging condition of the company’s equipment and the need to expand production capacity, and in order to reverse the company’s chronic losses, the board of directors approved a methanol production project as well as an expansion project to increase synthetic ammonia production by 80,000 tons. In line with the company’s development plan, by 2009 the production capacity is set to reach 120,000 tons of synthetic ammonia, 100,000 tons of urea, 100,000 tons of methanol, and 100,000 tons of compound fertilizers. 2. Operation status of the original transformation and dewaxing unit and existing problems: The company originally did not have a transformation and dewaxing unit; when installing such a unit later, considering that production capacity was set to be expanded to 120,000 tons in the near future, a φ3600 transformation and dewaxing unit was installed from the start. Its main equipment includes: a stripping tower with dimensions of φ3600×28000, equipped with three layers of random packing. Desulfurization tower: 150D30×4, flow rate of 150 m3/h, motor power of 90 kW. Regeneration tank: φ3600×5600; Weak liquor tank: φ3600×3900. The device uses the tannin method for desulfurization. Composition of the solution: Total alkalinity: 31.8 g/l; Sodium carbonate: 0; Sodium bicarbonate: 51.4 g/l; Tannin: 0.4 g/l; Sodium aluminate: 0.4 g/l; Suspended sulfur: 1.55 g/l. In actual operation, the sulfur concentration at the inlet of the desulfurization tower is 150–200 mg/m3, while it is 60–80 mg/m3 at the outlet. Not only does the H2S level remain above the specified limits for extended periods after desulfurization, causing a range of problems for subsequent processing stages, but the mismatch between the equipment and its capacity also leads to an overpowered setup, which poses difficulties in production management; electricity consumption is significantly high ； Due to the excessive tower diameter and insufficient spray density, tower plugging becomes relatively severe. Before the annual maintenance in June 2008, tower blockage caused the sulfur level at the outlet to rise above 80 mg/m3, and the tower resistance also increased significantly. To address this issue, and taking into account the excellent operational flexibility of Dongshi Company’s QYD mass transfer internals, it was decided to use these internals in the reactive distillation column during the maintenance work in 2008. 3. Technical advantages of QYD mass transfer internals 3.1 It integrates the four main components of a packed tower – the liquid distribution device, the re-distribution device, the gas distribution device, and the packing – into one unit. These components form 3–5 mass transfer units within the tower; each mass transfer unit consists of a gas distribution device, a bubble re-distribution device, a downcomer, and a liquid holding section made up of the downcomer and partitions, with the liquid holding section serving as the central reaction zone. 3.2 The QYD mass transfer internals completely overcome the drawback of packed towers, which require a high volume of solution circulation. As is well known, for a packed tower, once the tower diameter is determined, in order to maintain a certain flooding density, its solution circulation rate remains fixed. No matter how much the production load decreases, the solution circulation rate cannot be reduced; otherwise, a dry plate phenomenon will occur. The QYD mass transfer internals rely on direct gas-liquid contact to carry out the gas-liquid mass transfer reaction, thereby transforming the traditional gas-liquid mass transfer process that uses packing as a medium into one that involves direct gas-liquid contact without packing. As a result, not only is it not necessary for large amounts of solution to be circulated within these internals, but the amount of solution circulation can also be reduced as needed in response to changes in production load. This not only provides greater operational flexibility but also reduces power consumption. 3.3 This tower makes full use of the desulfurization reaction mechanism—the principle of rapid chemical reaction between H2S and an alkaline solution—to enhance gas-liquid contact, reduce the gas-liquid contact time, further improve the selective absorption of H2S by the alkaline solution, and suppress the influence of CO2 on the absorption reaction. This correspondingly increases the effective components in the solution, raising the sulfur capacity, which is the key to significantly reducing the circulation volume of this internal component solution. 3.4 This reactor features a simple structure, low cost, ease of control and maintenance, easy resolution of corrosion issues, and a wide range of applicable pressures. 4. Operation status after renovation 4.1 High desulfurization efficiency. With a gas flow rate of 22,000–23,000 Nm3/h, a solution circulation rate of 130–150 m3/h, and an inlet sulfur concentration of 150 mg/m3, the outlet sulfur concentration remains stable at 5–8 mg/m3. When the inlet sulfur level is as high as 200 mg/m3, the outlet sulfur level is also below 10 mg/m3. The process qualification rate has reached 100%. 4.2 The solution circulation volume is low, resulting in significant power savings. According to the general design of packed towers, for a tower diameter of φ3600, even when calculating based on the lowest spray density of 40 m3/m2·h, the solution circulation rate should not be less than 400 m3; this requires the operation of three variable displacement pumps. After the modification, one pump in operation is sufficient to meet the requirements. Annual electricity savings: 90×2×24×330×0.35 = 500,000 yuan. 4.3 The consumption of auxiliary materials is significantly reduced. Before the renovation, 250 kg of alkali and 20 kg of tannin were consumed per day, and it was not possible to ensure that the desulfurization standards were met ； After the modification, only 100 kg of alkali and 10 kg of tannin are required per day. Annual savings in auxiliary material consumption: Alkali: (250-100)×330×1500=74,250 yuan; Resin: (20-10)×330×24=79,200 yuan. Just these two items alone result in an annual savings of 150,000 yuan. Furthermore, since the process qualification rate for H2S after desulfurization reached 100%, it became possible to recycle the copper-washing ammonia solution, resulting in an increase in urea production of 30 tons per year, worth over 50,000 yuan. 4.4 The tower plugging issue that has plagued production for many years has been resolved. Generally speaking, for packed towers, tower plugging is absolute, while non-plugging is relative. Especially during the pressurized desulfurization process, the partial pressure of hydrogen sulfide is high, resulting in a strong driving force for absorption and a fast reaction rate; this accelerates the release of sulfur as well. The elemental sulfur that is released has strong adhesiveness and tends to stick to the surface of the packing. Over time, this leads to blockages in the tower. Such blockages start from the lower layers and move upward, until the channels gradually narrow and the resistance increases, forcing the operation to be stopped and the tower to be cleaned. And every stop causes huge losses to businesses, not only in terms of human and material resources as well as financial costs, but also the pressure related to environmental protection is a major concern. This is an experience that many manufacturers have had. The QYD mass transfer internals fundamentally solve the problem of tower blockage in desulfurization towers, while also reducing the likelihood of shutdowns for maintenance due to such blockages, thereby **extending the production operation period**. 4.5 It features simple operation, stable performance, and low system resistance. 5. Conclusion: The use of the composite mass transfer internals in QYD-type desulfurization towers offers advantages over traditional packed towers in terms of initial investment, operating costs, and operational management. Its adoption will undoubtedly bring substantial economic benefits to ammonia fertilizer manufacturers. For enterprises, corporate management and technological progress are always two indispensable wheels for their development. Managing a company effectively is about strengthening its internal capabilities, while paying attention to technological development and progress, investing in technological upgrades, and making use of the most advanced and suitable technologies available in the industry are the key factors that ensure a company’s sustained vitality.