Ultra-optimal Claus process

Super OptiKlaus process? I’ve never heard of it. Please give an introduction

Super Opticlaus is an improved version of Super Claus. The principle is simple; I’ve never been through starting it up either.

A new set of processes cannot do without its most fundamental element, which is Klaus. Could the poster explain how your process differs from conventional Claus processes? Have you worked on sulfur recovery units before? We would like to know that as well.

In the ultra-high Claus stage, the gas coming from the second sulfur cooler is heated again by steam at 3.82 Mpa(g) in a reheater, in order to reach the appropriate temperature (197°C) required for the catalytic reactions in the third (ultra-high Claus) reactor, which contains three different types of catalysts. An alumina catalyst is used at the top layer to promote the conversion of H2S and SO2 into sulfur. In the final super Claus stage, no other components are converted apart from H2S; these components represent recovery losses when they are sent to the super Claus stage. Therefore, the super-claus catalyst used in the second layer is a hydrogenation catalyst, which can reduce SO2 to H2S and sulfur vapor; finally, the titanium oxide catalyst in the bottom layer hydrolyzes the unwanted components (such as COS). The steam going to the third reheater is regulated by a temperature controller at its inlet; the inlet temperature there is lower than that of the other two reactors, which helps to facilitate the efficient conversion of H2S and SO2 into sulfur. The process gas from the third reactor enters the third sulfur cooler for cooling; sulfur is condensed from the process gas and then separated. The liquid sulfur coming out of the third sulfur cooler is sent to the sulfur tank via a sulfur hopper. The outlet of the third sulfur cooler is equipped with a defoamer to recover the sulfur mist entrained in the process gas, after which the process gas enters the fourth reactor (super Claus).

Did you choose the Super OptiKlaus process? Well, the Dutch company Maersk should provide an operation manual. What you mentioned is already part of patented technology; presumably some people are aware of it, but they don’t dare to speak up!

Reply to 6# Mood Snacks: For Klaus’s part, a three-stage reactor was used

Reply to 8# Tongxin Zhiyu: It’s not level 3; it’s level 4. Levels 1 and 2 are the Claus reaction, level 3 is the ultra-Claus process, and level 4 is the super-Claus process.

This post was last edited by qugd on 2011-8-28 08:24. The information below is taken from “Guteng Environmental Protection Network”. The ultra-high-efficiency Claus sulfur recovery process technology and its application prospects: The adoption of high-performance and efficient sulfur recovery technologies holds great practical significance in meeting the increasingly stringent environmental and ecological protection requirements in the future. The current methods for acidic sulfur recovery mainly include wet and dry desulfurization. Dry desulfurization is further divided into the conventional Claus process, sub-dewpoint Claus processes, reduction absorption processes, direct oxidation Claus processes, oxygen-enriched Claus processes, and oxidation absorption Claus processes. The wet processes mainly include Lurgi’s low- and high-temperature condensation processes, as well as Topsoe’s WSA process. Since its industrialization in the 1930s, the Klaus sulfur recovery process has been widely used in various coal, oil, and natural gas processing operations, such as the production of feed gases for ammonia and methanol synthesis, refinery gas processing, and natural gas purification. Recycling sulfur from the H2S-containing gases generated during the desulfurization process not only yields good economic benefits but also addresses the problem of air pollution caused by industrial waste gases. The Claus process is characterized by a simple process flow, flexible operation, high purity of sulfur recovered, low investment costs, as well as significant environmental and scale benefits. The purity of sulfur recovered through this process can reach 99.8%; it can be used as a sulfur source for sulfuric acid production or as a chemical raw material in other industries. It is widely applied in refineries, natural gas purification plants, coking plants, fertilizer factories, methanol plants, power plants, and gasification plants. The EuroClaus process, developed on the basis of the traditional Claus process, offers various advantages in terms of sulfur recovery rate, compliance with environmental standards for exhaust gases, and plant investment costs. Currently, the EuroClaus process has received widespread attention abroad and has been adopted in countries such as Germany, the Netherlands, the United States, Canada, and Japan. In recent years, China has also introduced this process and put it into operational use. 1 Process Principle: The traditional Claus process is a well-established multi-unit treatment technology. Since its invention, it has become the standard process for sulfur recovery in this industry, and it is one of the most widely used sulfur recovery processes today. Depending on the volume percentage of H2S in the process gas, the direct Claus process, the split-flow Claus process, or the direct oxidation Claus process is employed respectively. The process involves burning acidic gases containing H2S in a Claus furnace, which oxidizes part of the H2S to SO2; subsequently, SO2 reacts with the remaining unreacted H2S in the presence of a catalyst to produce sulfur. SuperClaus is an improved version of the Claus process. Building on the principles of sulfur recovery in the Claus process and breaking away from traditional approaches, it combines new technologies developed in recent years to enhance the traditional Claus process. This improvement is aimed at optimizing the thermodynamic balance and boosting sulfur recovery, and it involves the development of new catalysts, oxygen-enriched combustion techniques, cryogenic cooling technologies, etc. A significant modification is made to the Claus process: after the conventional conversion step, a new type of selective oxidation catalyst is used in the final conversion stage, with an additional selective catalytic oxidation reactor (SuperClaus reactor) being added, thus giving rise to the SuperClaus process. At the same time, a layer of hydrogenation reduction catalyst is placed beneath the Claus catalyst in the final Claus catalytic reactor bed, creating a hydrogenation catalytic reduction reactor (SuperClaus reactor). This allows SO2 to be reduced to sulfur and H2S, after which a selective oxidation catalyst is used, thereby increasing the overall sulfur recovery rate. Depending on the amount of acidic gas fed and the number of catalytic reactors, the recovery rate can reach 99.4% or higher. The ultra-high-efficiency Claus process is shown in Figure 1: http://air.chinaep-tech.com/u/201001/298592_1264402680470.jpg. The ultra-high-efficiency Claus unit consists of a high-temperature section and two or three reaction sections. The high-temperature section includes an H2S combustion furnace and a waste heat boiler; in this section, the H2S in the gas is partially oxidized to form SO2 within the Claus combustion furnace. The combustion reaction is H2S + 1.5O2 → SO2 + H2O. Approximately 1/3 of the H2S reacts with air at a temperature of around 1200 °C in the combustion furnace to produce SO2. The remaining unreacted H2S, together with SO2, continues to undergo the Claus reaction in the lower-temperature conversion section with the help of a catalyst, and then reacts with some of the H2S to produce sulfur. The reaction in the Claus reactor is 2H2S + SO2 → 3S + 2H2O. Subsequently, in the hydrogenation catalytic reduction reactor, SO2 is reduced to sulfur and H2S by H2 and CO present in the Claus off-gases through hydrogenation catalytic reduction reactions. The reaction equations are: SO2 + 2 H2 → S + 2 H2O, SO2 + 3 H2 → H2S + 2 H2O, and SO2 + 2 CO → S + 2 CO2. The traditional Claus sulfur recovery flue gas is treated with a selective oxidation catalyst through a selective catalytic oxidation section or a final conversion reactor; under conditions of excess air, the remaining H2S in the process gas from the final Claus section is selectively oxidized to elemental sulfur: H2S + 0.5O2 → S + H2O. The core of this technology is to reduce the SO2 in Claus off-gases to H2S through catalytic hydrogenation in the catalytic hydrogenation section of the Claus reactor, and then to selectively catalytically oxidize the off-gases containing only H2S into elemental sulfur in the super Claus reactor. Unlike conventional exhaust gas treatment processes, this hydrogenation process does not require a separate reactor; hydrogen is generated by the reaction itself, so no external hydrogen supply is needed. The process gas does not require heating or cooling, and the H2S in the exhaust gas does not need to be absorbed by a solvent. Furthermore, there is no need for solvent absorption and regeneration systems that involve high investment and operational costs. 2 Technical Features 2.1 Flexible and convenient operation: The Ultra-Claus process utilizes excess air, which results in less SO2 production; as a result, strict control over air is not required. There is no need for precise control of the ratio between H2S and SO2, making the operation flexible and convenient. The process is simple, reliable, and has a wide operational range, with the minimum operating level able to reach 15%. The ultra-high-performance Claus catalyst exhibits good thermal stability, chemical stability, and mechanical strength; it produces minimal emissions of harmful substances. Its service life ranges from 8 to 10 years. A high concentration of water in the process gas does not affect the conversion rate of H2S. The unit operates smoothly and reliably, is easy to maintain, with unplanned downtime being less than 1%. 2.2 High sulfur recovery rate: Due to the use of an excess amount of H2S in the upstream Claus process, which reduces the SO2 content in the exhaust gases, the overall sulfur recovery rate of the plant is high. Moreover, it can operate continuously without the need for periodic shutdowns. The selective oxidation reaction is a thermodynamically complete reaction, therefore very high conversion rates can be achieved. Furthermore, the super-Clausius reactor uses a special selective oxidation catalyst that is insensitive to both water and excess oxygen, and no side reactions occur. Furthermore, without any treatment of the exhaust gases, the overall sulfur conversion rate can reach 99% or even 99.5% or higher, meeting environmental emission standards; it thus serves both the purpose of sulfur recovery and exhaust gas treatment. 2.3 The unit has strong adaptability. The ultra-optimal Claus process is suitable for a wide range of acid gas concentrations, with H2S concentrations ranging from 23% to 93%. It can be used in newly built units as well as for the technical upgrading of existing Claus units, and it can also be combined with oxygen-enriched sulfur oxide recovery processes. During operation, the process gas undergoes continuous vapor-phase catalysis; there is no need for condensation and dehydration, and thus no issues related to the treatment of waste gases, wastewater, or solid waste. At the same time, the catalyst promotes selective oxidation only of H2S; other components such as H2 and CO are not oxidized, and no COS or CS2 is formed as a result of side reactions. Even in the presence of oxygen in excess of stoichiometric amounts, very little SO2 is produced. 2.4 Lower investment and operating costs: Due to the absence of complex hydrogenation and amine absorption systems, the investment required for the Ultra-Claus process is only 70% to 50% of that required for a Claus + exhaust gas treatment process of similar scale. For a sulfur recovery unit with an annual production capacity of 20,000 tons, the total investment in the Claus flue gas treatment process is generally over 80 million RMB, whereas the ultra-high-efficiency Claus process requires only around 50 million RMB in total investment. Furthermore, the Klaus exhaust gas treatment process requires MDEA solvent, and the solvent needs to be continuously regenerated, which consumes a large amount of steam. The ultra-optimized Claus process is simple – it requires only a small amount of heating steam, and the entire system generates excess steam; no external hydrogen is needed for hydrogenation. As a result, its overall energy consumption is less than 50% of that of the Claus exhaust gas treatment process. The comparison of relative investment and benefits for Super Urea Process and several other sulfur recovery processes is shown in Table 1. http://air.chinaep-tech.com/u/201001/298592_1264402720157.jpg 3 Domestic Overview: The Ultra-Claus process is a patented technology belonging to the Dutch company Jacobs. It possesses all the advantages of the conventional Claus process; it can be used not only for upgrading existing Claus units but also for constructing new ones. In China’s petrochemical, oil, and gas industries, several units using the Ultra-Claus process are already in operation. Since 2007, several newly built coal chemical plants in China have adopted the ultra-high-efficiency Claus sulfur recovery technology (see Table 2), and most of them are currently under construction. Sulfur recovery technology, one of the five key production technologies in Shaanxi Yulin Natural Gas Chemical Co., Ltd.’s project for the comprehensive utilization of 1.4 million tons per year of coal-based methanol production capacity, utilizes the ultra-optimal Claus technology; commissioning of this system is scheduled for August 1, 2011. In addition, the first phase of the project undertaken by Inner Mongolia Tianhe Chemical Co., Ltd., which has an annual production capacity of 1 million tons of coal-based methanol, also utilizes the ultra-high-efficiency Claus technology for the production of 600,000 tons of methanol per year. http://air.chinaep-tech.com/u/201001/298592_1264402750220.jpg Shaanxi Xianyang Chemical Industry Co., Ltd. is building a project with an annual production capacity of 600,000 tons of methanol in the Chemical Industry Park on the eastern outskirts of Xianyang City, Shaanxi Province. Since the site of this project is located between Xi’an and Xianyang cities, with a high population density, the requirements regarding environmental protection are very strict. The Ultra-Claus process can fully meet the project’s emission requirements. Acidic gases containing H2S enter the sulfur recovery unit’s area; after treatment, the acidic exhaust gases are discharged outside the unit in compliance with regulations, while liquid sulfur products are produced. The project is expected to begin trial operation in October 2009. Huating Zhongxu Coal Chemical Co., Ltd. has adopted the Ultra-Claus technology for sulfur recovery in its project with an annual production capacity of 600,000 tons of methanol. The acidic gas used as feed for sulfur recovery in this project comes from the methanol washing unit; COS and H2S in this acidic gas are removed and recovered using the ultra-supercritical Claus technology, and the SO2 concentration in the exhaust gas meets the emission requirement of being less than 550 mg/m3. The Shaanxi Yanchang Petroleum Group’s project with an annual production capacity of 200,000 tons of acetic acid and related facilities uses coal as raw material, employs Texaco’s gasification technology from the United States, and adopts the low-pressure carbonylation method using methanol to produce acetic acid. The purification of syngas is carried out using the low-temperature methanol washing process; the H2S-containing acidic gases from the methanol washing unit are sent to an ultra-efficient Claus sulfur recovery unit for treatment, ensuring that the SO2 concentration in the exhaust gases remains below the **emission requirements. The construction period for this project is 3 years, with commissioning expected in June 2009. Anhui Huaihua Group is the largest coal chemical production base in Anhui Province. In the project with an annual production capacity of 300,000 tons of synthetic ammonia, the purification of syngas is carried out using the low-temperature methanol washing process. The acidic gas components exiting the low-temperature methanol washing unit are as follows: H2S at 19.98%, CO2 at 75.926%, COS at 1.997%, N2 at 1.993%, and CH2OH at 0.104%. By measures such as reducing the methanol circulation volume, using a lower regeneration pressure, and increasing the regeneration temperature, the H2S content in the acidic gases is increased to over 23%, thereby meeting the requirements of the ultra-optimal Claus process regarding the H2S content in the feed gas. The gas then enters the ultra-optimal Claus sulfur recovery unit for further treatment; this unit has an operating range of 20% to 145%, and the exhaust gas after treatment meets the specified emission standards. The project is expected to be completed by the end of 2008, and to come online in mid-2009. 4 Application Prospects: The new environmental protection regulations issued in China in 1996, namely the \"Comprehensive Emission Standards for Air Pollutants\" (GB16279-1996), stipulate that the maximum allowable concentration of SO2 in the flue gases emitted by acid gas treatment devices is ≤960 mg/m3 (i.e., ≤0.0336%). Although secondary and tertiary Claus technologies are now available in China, they fail to meet environmental protection requirements. The overall sulfur recovery rate for Class 3 Claus units in China is generally between 94% and 96%, with a maximum of 98%. Based on a recovery rate of 98%, the SO2 emission concentration will reach 0.29%, which is far above the environmental standard of 0.0336%. Since the ultra-optimal Claus sulfur recovery process can be implemented by modifying existing Claus units with minimal additional investment, it enables a sulfur recovery rate of 99.2%–99.5%, an SO2 emission concentration of less than 550 mg/m3. It also helps to increase the sulfur recovery rate, reduce investment costs and operating expenses, while ensuring that the exhaust gases meet emission standards. The acidic gases in coal chemical industries have a complex composition; in addition to the hydrocarbons, ammonia, and organic sulfur compounds commonly found in refineries and natural gas processing plants, they also contain impurities such as COS, HCN, NH3, CHOH, and CH3OH. Furthermore, unlike in refineries and natural gas processing plants where acidic gases originate from alcohol amine absorption processes such as MDEA, acidic gases in coal chemical plants generally come directly from syngas purification processes such as low-temperature methanol washing; as a result, the H2S concentration is relatively low, typically only 20%–30%. Given the characteristics of coal chemical industries, a sulfur recovery process that is suitable for low concentrations of acidic gases, operates within a wide range of elasticities, and can handle complex gas mixtures should be selected, while also striving to keep the investment and operating costs as low as possible. As domestic production facilities for synthetic ammonia and methanol using coal as a raw material continue to increase, it is expected that such facilities will keep growing in number and scale over the coming years. Traditional Claus processes or other outdated treatment methods designed for small-scale facilities can no longer meet environmental requirements, and the increasingly stringent environmental regulations also impose new demands on China’s facilities for producing synthetic ammonia and methanol from coal. Due to the particularities of the coal chemical industry, there are usually no SCOT flue gas treatment units downstream of the Claus unit. In such cases, while the traditional Claus+SCOT process can meet environmental requirements, it has a relatively complex process flow, stringent operating conditions, and high capital costs for the installation. Therefore, it is not a good choice either for the coal chemical industry, which lacks solvent absorption systems. In recent years, gas purification in newly built ammonia and methanol plants in China has mostly relied on the low-temperature methanol washing technology developed by German company Lurgi, as well as the NHD gas purification technology developed domestically. Regardless of the technology used, the H2S concentration in the acidic gas after solvent regeneration is generally between 25% and 30%, and the volume of gas involved is not large. Due to the low concentration of acidic gases and small gas flow rate, the temperature in the combustion section is low, which results in incomplete combustion of other impurities. Secondly, due to the limitations of the traditional Claus process itself, the theoretical recovery rate for higher concentrations of acidic gases is usually 96%–98%, while the actual recovery rate generally only reaches 94%–97%. Therefore, at present, most ammonia and methanol plants that use the conventional single Claus process face the problem of excessive emissions of Claus off-gases. Existing or some newly built methanol plants and ammonia synthesis plants in the country typically use the conventional single Claus process, which means there is no gas absorption section upstream of the Claus unit; as a result, acidic gases cannot be concentrated. Similarly, there is no SCOT exhaust treatment device downstream of the Claus unit either; as a result, it is absolutely impossible to meet the emission standards specified in GB1679-1996 \"Comprehensive Emission Standards for Air Pollutants\", which require that the S02 emission concentration for existing units be less than 0.042%, and that it be less than 0.0336% for newly built units. Faced with such circumstances, existing Claus sulfur recovery units are no longer suitable for the purification of acidic gases with low H2S concentrations. The ultra-Claus process utilizes oxygen-enriched combustion technology and selective oxidation reactions to ensure complete combustion and reaction of the process gases. Additionally, cryogenic coolers are used to cool the process gases to the freezing point of sulfur, around 114.5°C, thereby minimizing sulfur vapor losses – typically by nearly 0.06%. This reduces the SO2 content in the exhaust gases, allowing compliance with increasingly strict environmental regulations without the need for exhaust gas treatment. It is thus the best choice for installing new sulfur recovery units for coal-based ammonia and methanol production, as well as for upgrading existing Claus units. In summary, when choosing a sulfur recovery process, economic considerations, technical aspects, and the need to meet **existing and future environmental standards should be taken into account. Therefore, adopting the ultra-supercritical Claus sulfur recovery process in the acid gas treatment units for producing synthetic ammonia and methanol from coal is the best choice. Compared with Claus units equipped with the SCOT process, although they lack exhaust gas treatment systems, ultra-optimal Claus units can still achieve a high sulfur recovery rate of over 99.0%, with lower investment costs. Compared with traditional Claus sulfur recovery units, its main advantage is that the investment is comparable, but the sulfur recovery rate is significantly higher, and the exhaust gases meet environmental emission standards. China currently has 77 Claus sulfur recovery units. In many small refineries, coking plants, fertilizer factories, etc., the H2S concentration is low, making it inappropriate and impractical to install large-scale sulfur recovery units. There are also some sulfur recovery units that, due to their small scale, do not have exhaust gas treatment systems or have exhaust gas treatment that does not meet standards. It is expected that the ultra-efficient Claus process will hold certain value in terms of technological upgrading of existing Claus units in China as well as in the installation of new sulfur recovery units in the future. References: Xiao Qiutao, Chen Ming, Liu Jiahong. Engineering practice and preliminary analysis of the SuperClaus process. Natural Gas & Petroleum, 2005, 23(3): 55–58. Hu Wenbin, Zhang Yiling. Selection of the Claus sulfur recovery process. http://www.zshg.com/wenzhang/jishujiaoliu/klsl-1.htm. Accessed on 2005.10.8. Chen Gengliang. Technical progress in the Claus sulfur recovery process. Petroleum Refining & Chemical Engineering, 2007, 38(9): 32–37. Zheng Yanbin, Xie Ying, Wang Wei. Application of SUPERCLAUS® and EUROCLAUS® sulfur recovery processes in coal gasification for methanol and ammonia production. http://www.hofung-technology.com/downloads. Accessed on 2007.3.6. Chen Jinchang. Application of the SuperClaus-99 sulfur recovery process. Environmental Protection in Petrochemical Industry, 2004, 27(1): 29–32. Liu Gongnian. Selection of sulfur recovery technologies for 300 kt/a ammonia production plants. Nitrogen Fertilizer Technology, 2008, 29(3): 14–17. Wang Wei. Selection of sulfur recovery units in the coal chemical industry. http://www.ureanet.cn. Accessed on 2008.6.26. Zhang Yiling, Da Jianwen. Current status and development prospects of sulfur recovery in China. http://www.chinanpk.com/ztbd/da*nghua/zhonghe. Accessed on 2007.3.6. Zhao Qi. Application of the SuperClaus process in natural gas sulfur recovery units. Fertilizer Design, 2004, 42(1): 24–26

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