Can domestic sulfur recovery technologies meet **environmental standards

The Klaus and Klaus extension methods certainly cannot meet **the standards; if you want people to give you advice, it’s best to tell them the scale of your sulfur production.

I’m not very familiar with the coal chemical industry; however, the exhaust gases from sulfur recovery units in refineries or natural gas processing plants can meet the required standards.

It is best to install a hydrogen reduction exhaust treatment system (SSR); otherwise, environmental standards will not be met.

The new Crystasulf process can be used; it is simple to implement, has lower investment costs compared to amine washing/Claus process, and reduces hydrogen consumption

Experts in this field have reached a conclusion: when the total sulfur conversion rate is between 98.5% and 99.5%, the sulfur dioxide content in the exhaust gases is generally between 1500 and 8000 mg/m3； Without any exhaust gas treatment equipment, the sulfur dioxide content in the emitted exhaust gases exceeds 15,000 mg/m3 in most cases, failing to meet the requirements of the **new emission standards (30-meter-high chimneys, with levels below 960 mg/m3). I’ve posted Zhang Yiling’s paper below for reference. The Current Status and Development Prospects of Sulfur Recovery in China – Zhang Yiling, Da Jianwen, Research Institute of Sinopec Qilu Branch 【Abstract】 This paper introduces the current status of sulfur recovery and exhaust gas treatment technologies in China, as well as the compliance level of relevant facilities. In light of the development of sulfur recovery technologies both domestically and internationally, and taking into account China’s specific conditions, this paper analyzes the trends in the development of such technologies as well as the application markets for sulfur. It also provides specific recommendations for the construction or expansion of sulfur recovery facilities. 【Keywords】Sulfur recovery, process, catalyst, exhaust gas treatment 1. Introduction With the rapid growth of China’s national economy, its oil processing and natural gas industries have developed at a high pace. Meanwhile, the processing volume of sulfur-containing crude oil and the treatment volume of sulfur-containing natural gas increased accordingly. In 2003, China’s imports of crude oil exceeded 90 million tons, and this figure rose to over 120 million tons in 2004. Most of the imported crude oil was high-sulfur crude. In addition, various processes such as the deep processing of sulfur-containing fuel oils and coal gasification also involve the handling of sulfur compounds. In China, the Shengli Oil Field, the Liaohe Oil Field, and some oil fields in Xinjiang also produce mostly high-sulfur heavy oil, and most of the newly developed natural gas fields are accompanied by large amounts of H2S. GDP growth is expected to remain between 9% and 10% per year, while the elasticity coefficient for the petrochemical industry is around 5%. By 2010, China’s new refining capacity is expected to reach around 100 million tons per year; therefore, it is estimated that China’s sulfur production capacity will reach around 1.5 million tons per year by that time. Economic growth and strict environmental regulations have made related gas desulfurization and sulfur recovery technologies increasingly important. After decades of development, while relying on its own efforts to develop desulfurization, sulfur recovery, and exhaust gas treatment technologies, the large petrochemical complexes in coastal and riverine areas have also introduced advanced foreign technologies in their entirety or in part. At the same time, on this basis, domestic production, design, and research organizations have also developed a set of domestic technologies for large-scale sulfur recovery units through digestion and absorption as well as joint efforts in research. Over the three-year period from 2000 to 2003, the number of sulfur recovery units in the country surged from 62 to over 100. Most of these newly built units were large-scale, highly automated sulfur recovery systems, all equipped with exhaust gas treatment facilities ； Among the newly added devices, those using domestic technology account for about 76%. However, with the construction of large-scale refining complexes along rivers and coasts, there is still a certain gap in the scale of sulfur recovery in China compared to advanced foreign levels. To quickly narrow the gap with advanced foreign technologies, it is essential to seize this opportunity, make strenuous efforts to catch up, and raise our country’s sulfur recovery technology to a new level as soon as possible. 2. Current Situation 2.1 Scale of Facilities and Compliance Status According to incomplete statistics, by 2003, China had built more than 100 sulfur recovery facilities. By industry, 71 were used in petroleum refining, 12 in natural gas purification, 7 in coking and metallurgy, and 21 in coal gas chemistry. The largest of these facilities had a capacity of 100,000 tons per year, while the smallest had a capacity of 0.03 thousand tons per year. Since 2004, Sinopec’s refineries in Zhenhai, Fujian, and other locations have also built 3 to 4 large-scale sulfur recovery units with a capacity of 100,000 tons per year each, resulting in an overall sulfur recovery capacity of over 1 million tons per year. Among these more than 100 sets of units, those built after 2002 are all equipped with exhaust gas treatment units. Apart from the domestic SSR process and the domestically designed reduction absorption process, the rest are imported processes, most of which can meet **’s environmental protection requirements. However, for the process units such as Sulfreen, Super Claus, MCRC, and Clauspol that were introduced earlier, the overall sulfur conversion rate is between 98.5% and 99.5%, with the SO2 concentration in the exhaust gases being roughly between 1500 and 8000 mg/m³ ； Without exhaust gas treatment devices, the SO2 content in the emitted exhaust gases is mostly above 15,000 mg/m³, and none of them meet the requirements of the **new emission standards. 2.2 Current Status of Sulfur Recovery Technology Since the 1980s, through international technical exchanges and the adoption of advanced foreign technologies and useful experiences, China’s sulfur recovery technology has made significant progress in areas such as plant process design, renovation of individual units, development and use of catalysts, solvent production, as well as corrosion prevention and energy conservation. For example, the Shengli Oil Refining Design Institute of Qilu Petrochemical adopted the SCOT process, and by overcoming its drawbacks such as complex flow processes, high energy consumption, and difficulty in operation, it collaborated with the R&D institute of the Qilu branch to optimize and design a new sulfur recovery and exhaust gas treatment technology called the SSR process. This technology was first put into industrial use at the 86,000 t/year refinery unit in Shengli. This process does not require online heating or related facilities; it features a more compact equipment layout, a simple flow process, and flexible and convenient operation adjustments, making it particularly suitable for the construction of large-scale sulfur recovery units. Furthermore, during this period, our country also introduced, either in its entirety or partially, 18 sets of Claus sulfur recovery and exhaust gas treatment units from abroad, which effectively drove and promoted technological advancements in domestic units. As a result, the sulfur recovery rate and sulfur emissions from China’s main production units quickly reached advanced international levels in a short period of time. The catalysts required for this purpose have also been manufactured domestically, with two representative series: one is the LS series developed by the research institute of the Qilu Branch ； Second, the CT series from Sichuan Natural Gas Research Institute is available. The LS series of catalysts includes various types such as the LS-811 and LS-300 Claus alumina catalysts, the LS-901 TiO2-based catalyst resistant to sulfuric acid oxidation poisoning, the LS-931 Al2O3-based catalyst resistant to sulfation, the LS-951T and LS-951Q hydrogenation catalysts specifically designed for Claus off-gases, and the LS-971 high-activity dual-function catalyst for oxygen removal and protection in the Claus process. These catalysts have been put into industrial use in multiple large-scale sulfur recovery units operated by Sinopec and CNPC, with excellent results ； The CT series of catalysts includes the conventional Al2O3 catalysts CT6-1 and CT6-2, the organic sulfur hydrolysis catalyst CT6-3, the low-temperature Claus catalysts CT6-4 and CT6-4B, the sulfur recovery flue gas hydrogenation catalysts CT6-5 and CT6-5B, the selective oxidation catalyst CT6-6, and the organic sulfur hydrolysis sulfur recovery catalyst CT6-7. The main physical and chemical properties as well as technical specifications of these two series of catalysts are comparable to those of similar foreign products; some of them have reached international advanced levels. They have replaced imported catalysts in newly introduced plants, yielding significant economic and social benefits. At present, the vast majority of sulfur recovery units in China use domestically produced catalysts, and these domestic sulfur recovery catalysts are also exportable. 3. Existing problems: China’s sulfur recovery industry has developed from nothing to something substantial, growing from small scale to larger one. Through the cooperation of research institutions, design firms, and production units, significant progress has been made over the years in areas such as process flows, catalyst development, equipment design, and analysis and control methods, with continuous improvements being made. Some large and medium-sized plants have adopted foreign patented technologies as well as key equipment, instruments, and catalysts, and their technical level has reached that of advanced foreign standards. There are still a series of problems and gaps in aspects such as sulfur recovery rate, exhaust gas treatment, level of automated control, and production management, which need further improvement. 1) The SO2 concentration in the exhaust gases emitted by sulfur recovery units does not always meet the specified standards. China’s new comprehensive emission standards for air pollutants, “GB16297—1996”, set the maximum allowable SO2 emission concentration at ≤960 mg/m³ (336 ppmv) for new pollution sources and ≤1200 mg/m³ (420 ppmv) for existing pollution sources; limits are also established for sulfide emissions. This requires the sulfur recovery rate of the unit to be above 99.5%. By 2002, only 29 sulfur recovery units using various SCOT methods and WSA acid production units met the standards; nearly 65% of the units, including those that employed other exhaust gas treatment methods, failed to meet the **emission standards. 2) The production management of some units is inadequate, as evidenced by unstable quality of acidic gases, sometimes high levels of hydrocarbons, delayed analysis and control, and a low sulfur conversion rate. To ensure the long-term stable operation of the device, the quality of the acidic gas feedstock remains crucial. To increase the H2S concentration in acidic gases, the use of selective desulfurization solvents should be further promoted, and the quality of these solvents must be standardized. It is necessary to strengthen the operational management of upstream gas generation units; all desulfurization units are equipped with rich liquid flash tanks, and the hydrocarbon content in the acidic gas must be kept below 2% (v/v), with a maximum limit of 5% (v/v). 3) Automated online analysis and control instruments are not yet fully developed. Except for the introduced units and a few larger-scale units, the control level of most units remains relatively backward. In recent years, some facilities have purchased foreign online analyzers. However, due to the high cost of imported H2S/SO2 analysis and control instruments, there are numerous issues associated with their management and use. Meanwhile, domestic analysis and control instruments have not yet reached a satisfactory level, making it difficult to optimize the operation of these facilities. It is necessary to improve the level of analysis and automated control. 4. Development Prospects 4.1 Process Aspect: Sulfur recovery and exhaust gas treatment technologies have evolved from being mere environmental protection techniques to becoming important process technologies that offer both environmental and economic benefits. As environmental awareness grows among people and environmental regulations become increasingly strict, in recent years various refineries, natural gas plants, coking plants, fertilizer factories, power plants, and coal gasification plants have been building new sulfur recovery units or expanding existing ones. For newly built sulfur recovery units, the reduction absorption process represented by SCOT is predominantly chosen. Although such processes involve high investment and consumption costs, they exhibit strong adaptability to Claus sulfur recovery units, offer high purification efficiency, with a sulfur recovery rate of up to 99.8%. They are currently the exhaust gas purification process with the largest number of installations and the fastest development rate in the world. At present, the SCOT process has undergone numerous improvements, such as low-temperature SCOT process, super SCOT process, low-sulfur SCOT process, and biological SCOT process. It is the technology that has been best integrated and absorbed after being introduced into the country. However, for many small refineries, as well as coking plants and fertilizer plants, the H2S level is low; it is therefore inappropriate and impractical to install large-scale sulfur recovery units. Moreover, some sulfur recovery units, due to their small scale, do not have exhaust gas treatment units, or their exhaust gas treatment processes do not meet the required standards, so improved versions of these existing processes have been developed. As illustrated by the Sulfreen process, Clauspol process, Super Claus process, etc. mentioned earlier, the overall sulfur recovery rate reaches or exceeds 99.5%. For the addition of exhaust gas treatment units, the versatile RAR process and the modular RAR process achieve removal efficiencies of up to 99.7%–99.9%, with low investment and operating costs; they represent a highly promising process for sulfur recovery and exhaust gas treatment. Furthermore, due to various constraints such as site limitations, funding issues, and the level of acidic gases, the sulfur recovery units in some refineries can often only resort to expanding these units in order to address the problem of processing high-sulfur crude oil. The oxygen-enriched sulfur recovery process is one of the most effective processes for expanding plant capacity; it is developing at a rapid pace and currently has the largest number of installations in the world. 4.2 Catalysts: 1) Special catalysts are developed; different processes utilize specific catalysts. 2) Multifunctional composite catalysts. Due to the drawbacks of single alumina catalysts and the high cost of TiO2 catalysts, composite catalysts were developed in order to achieve an appropriate price along with excellent performance – that is, to overcome the defects of alumina catalysts while retaining the good properties of TiO2 catalysts. Furthermore, domestic and international requirements for sulfur recovery catalysts are increasing; they are expected to not only have a long service life, high Claus activity, high sulfur recovery rates, and high organic sulfur hydrolysis rates, but also possess strong protection against \"O2 leakage\". Therefore, the development of multi-functional composite sulfur recovery catalysts has become imperative. 3) Combined use of series of catalysts: There is little difference in terms of performance, brands, and lifespan among sulfur recovery catalysts available domestically and internationally. It is therefore very important to determine how to combine catalysts with different properties so as to achieve cost advantages without any reduction in the overall sulfur recovery rate. Therefore, for different acid gas compositions, using a series of catalyst combinations in a tailored loading scheme can achieve good results at the required minimum conversion rate. 4.3 Market Applications Sulfur is an important chemical raw material; in addition to being used to produce sulfuric acid and directly in the formulation of pesticides, it can also be used to manufacture various high-quality sulfur-based chemicals such as methionine, carbon disulfide, sulfur accelerators, dimethyl sulfoxide, thioethers, methyl mercaptan, and insoluble sulfur. It can also be used to produce plant nutrient sulfur such as sulfur-coated urea and granular sulfur fertilizers, as well as sulfur concrete and sulfur asphalt. Since the 1990s, due to an ongoing surplus supply in the global sulfur market which led to falling prices, imports of sulfur increased sharply, thereby boosting the development of sulfur-based acid production industry in our country. This is also the main reason for the increase in sulfur consumption since the year 2000. It is estimated that China’s sulfur production in 2005 will be around 1 million tons, but this will only account for 12%–15% of the total sulfur consumption; thus, most of the sulfur needed will have to be imported ； By 2007, sulfur-based sulfuric acid production was expected to account for 65% of the total sulfuric acid output, with an average annual growth rate of 3.7% for sulfur-based sulfuric acid production. China’s average annual growth rate was much higher than the world average; therefore, sulfur prices are likely to remain strong over the next 3 to 5 years. As an essential component in the processes of petrochemicals, natural gas chemicals, and coal chemicals, the level of sulfur recovery technology is directly related to the environmental protection standards of the entire chemical industry. With the rapid development of energy-related industries in China, there is an urgent need to develop sulfur recovery technologies with independent intellectual property rights by integrating production, academia, and research, based on the introduction and adaptation of advanced foreign technologies. At the same time, attention should be paid to the development and application of sulfur-based products, in order to create an industry for sulfur recovery and utilization that brings both social and economic benefits. 【References】 1. Zhang Yiling, Li Wenbo et al., “Review of Advances in Sulfur Recovery Technologies,” Petroleum Processing & Chemical Engineering, 2003, 19–12. 2. Thomas K. Chow, J.K. Chen, “Upgrading Sulfur Recovery Units Using Oxygen-Enriched Processes Offers Significant Investment Benefits,” New Millennium Sulfur Recovery Conference, 2000, 10. 3. Chang Honggang et al., “Current Status and Development of Amine-Based Desulfurization and Sulfur Recovery Processes,” Petroleum & Natural Gas Chemistry, 2002, Supplement 33–37. 4. National Sulfuric Acid Industry Information Center, “Sulfur Market Survey,” Issue 8, 2001, 11–20. 5. Yan Tingzhao et al., “Chemical Utilization of Sulfur Resources in Natural Gas,” Petroleum Refining & Chemical Engineering, 2002, 31 (Supplement): 17–24. 6. Zhang Yiling, Tang Zhaozheng et al., “Patent Literature Analysis on Sulfur Recovery and Flue Gas Treatment Technologies,” Gas Desulfurization & Sulfur Recovery, 2001, (2). 7. Mao Weibing, Xu Huijian, “Market Analysis of Sulfur Resources,” Gas Desulfurization & Sulfur Recovery, 2004, (1). 8. Qu Xiaolian et al., “New Processes for Sulfur Recovery and Flue Gas Treatment,” Fertilizer Design, 2003 (03). 9. Chen Gengliang et al., “Advances in SCOT Process for Flue Gas Treatment,” Petroleum Refining & Chemical Engineering, 2003, 34 (10). 10. Kauf, Johannes (Linde AG, Germany), “Sulfur Recovery Technologies,” Hydrocarbon Engineering, 2002, 7(12), 45–46. (English) 【Author Profile】 Zhang Yiling: Engineer. Da Jianwen: Deputy Director, Professor-level Senior Engineer.

With only the Claus desulfurization process in use, it is difficult for the exhaust gases to meet the standards; therefore, an SCOT exhaust gas recovery unit needs to be added. By using domestic technology (SCOT), the SO2 content in the flue gas can also meet the standards. Our company’s 30,000 tons per year sulfur production facility uses two-stage CLAUS and SCOT processes; the SO2 content in the flue gas is typically less than 100 mg/m3 (as determined by online monitors as well as regular sampling and analysis).

If you have any other questions, feel free to ask so we can exchange ideas and improve together.

Environmental regulations will become increasingly strict in the future; I wonder what other processes can be developed, or what areas merit improvement

In general, in oil refining and natural gas processing, the hydrogen sulfide concentration is high, the volume of gas is large, sulfur production is high as well, and the profitability is relatively good. Sulfur recovery systems always include exhaust gas treatment; processes such as SCOT are quite mature, but the investment required for such installations is high. In coal chemical industries, the volume and concentration of hydrogen sulfide are low, resulting in minimal benefits; therefore, processes such as SCOT, which require substantial investment, are generally not used. The various processes currently used for sulfur recovery in the coal chemical industry, which rely solely on increasing conversion rates, generally fail to meet the required standards ； The various small exhaust treatment devices that have emerged in recent years have seen few put into operation, and most of those that are in use are not functioning properly. Therefore, the exhaust gas treatment technology for small-scale sulfur recovery units still needs further improvement.

Small-scale devices are used mainly because the sulfur content in the raw materials is too low; most of these materials have a high amine content, and the amine-burning method cannot be applied due to insufficient temperature

Many local refineries, due to low operational load and lack of economic viability, only operate the sulfur production unit and the incinerator; all other units remain shut down. In addition, they have to deal with sulfur-containing wastewater, and the acid gas contains high levels of ammonia. Moreover, the temperature in the sulfur production furnace is not sufficient for burning ammonia, so environmental standards cannot be met. Even running it in this way is harmful to the equipment and further damages our living environment. We urge the environmental protection authorities to strengthen oversight, so that we can preserve clear waters and blue skies for our future and for future generations! ! ! This post was last edited by adsl121 on 2009-4-19 17:01]

The SSR process can meet the current requirements for SO2 emission concentrations

If the temperature is not sufficient, more oxygen and gas can be added; at the same time, the acidic gases should be preheated before entering the combustion chamber, as well as the air. This can increase the temperature inside the combustion chamber.

The Claus desulfurization process used in our facility allows for a theoretical sulfur treatment efficiency of 95%; with the addition of a RAR unit, proper operation can ensure compliance with environmental regulations

It is generally for environmental protection projects; it is difficult to meet the environmental requirements at low load levels.