Precautions for using sulfur catalysts during operation

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This post was last edited by Shandong Huaxing on 2010-8-15 at 20:09. The vast majority of sulfur recovery catalysts do not require activation before use; they can be put into operation after heating to remove the adsorbed water. After the acid gas combustion furnace has been heated up, the flue gases are directed into the converter, causing the catalyst bed to heat up at a rate of 30°C/h. Heat to 120–150°C and maintain the temperature for 2 hours to remove adsorbed water. In principle, raise the temperature of the secondary converter first, and then that of the primary converter, in order to prevent the water removed from the primary converter from condensing in the secondary converter, which could cause difficulties when raising the temperature later on. When the temperatures of the first and second converters reach 300°C and 240°C respectively, maintain the temperature for 2 hours for stable operation, after which acidic gas feed can be introduced for production. When using flue gas to initiate the heating and pre-treatment of the catalyst, care must be taken to prevent carbon deposition in the catalyst bed due to insufficient oxygen and incomplete combustion. Furthermore, during the heating of the catalyst, it is necessary to prevent temperatures from exceeding 450°C as much as possible, in order to avoid damage to the catalyst’s performance. A nitrogen or steam protection line can be installed at the top of the reactor; in case the bed temperature gets out of control, nitrogen or steam can be introduced directly to lower the temperature, provided that conditions permit. It is recommended to use nitrogen first. Before turning on the steam, it is necessary to drain the condensed water accumulated in the pipe lines first. During the operation of the plant, it is necessary to operate as closely as possible in accordance with a ratio of H2S/SO2 of 2:1, as this is key to achieving the highest sulfur recovery efficiency. From the perspective of the reaction mechanism, it is beneficial for the reaction to proceed if the bed temperature is kept relatively low; however, no part of the catalyst bed should drop below the dew point temperature of sulfur. Therefore, the temperature should generally be maintained above 220°C. The operating temperature of the catalytic conversion bed must take into account not only thermodynamic factors but also the dew point of sulfur vapor and the gas composition. The use of multi-stage catalytic conversion along with a process for condensing and recovering sulfur at each stage is intended to reduce the partial pressure of sulfur vapor in the gas phase; this also lowers the sulfur dew point. As a result, the operating temperature of the converter can be reduced, thereby increasing the sulfur conversion rate. The optimal reactor inlet temperature is the value that results in the greatest temperature difference between the reactor inlet and outlet. The operating temperature of the converter should be at least 30°C above the sulfur vapor dew point to prevent sulfur from depositing on the catalyst surface. Generally, primary converters can operate at higher temperatures, such as between 290 and 330°C; this not only increases the reaction rate but also facilitates the hydrolysis of carbon disulfide present in the gas phase into hydrogen sulfide, thereby improving the sulfur conversion rate. The conversion temperature in the later stage can be lower to ensure the final conversion rate; generally, a temperature of 230–260°C is sufficient. In the later stages of catalyst use, the operating temperature can be appropriately increased to compensate for the decline in its activity.