CANSOLV SO2 Scrubbing System - 1 Years of Reliable Operation Integration with SRU Tail Gas Incineration NICOLAS EDKINS, NANCY MORETON Cansolv Technologies Inc. (an affiliate of Shell Global Solutions BV) Montreal, Canada In 22 Cansolv was proud to announce the start-up of its second commercial plant at the Lanxess Chemical plant in Belgium. At this particular site the Cansolv process is treating flue gas generated from an incinerator which burns waste tar as well the tail gas from a sulphur recovery unit (SRU or Claus unit). At that time Lanxess was faced with the challenge of meeting new environmental emissions standards in the region. Through a series of piloting campaigns Lanxess evaluated several SO2 capture technologies but Cansolv proved to be the best fit in successfully treating the sites combined waste tar incineration and SRU tail gas. As a result, the Cansolv SO2 Scrubbing System was selected by Lanxess in order to comply with the new environmental regulations and the unit was efficiently integrated into their existing line-up in 21. The maximum SO2 emission limit of 45 mg/nm3 came into effect January 1, 23 and Lanxess have been in compliance ever since. The integration and optimization of a 2 stage SRU and the Cansolv unit has proven to be a reliable and robust operation. Lanxess have successfully been able to control feed ratios at lower H2S flow rates (4 Nm3/hr > 98% H2S) while capturing higher concentrations of SO2 in the incinerator flue gas (1-2%vol SO2) from the 2 stage SRU. With tailgas incineration, the control of the air / H2S ratio to the thermal stage is less demanding, since the Cansolv System can inexpensively scrub the higher SO2 concentrations that may result from off-ratio operation for shorter periods. The SO2 product generated by the Cansolv process is recycled back to the SRU at 6-7 Nm3/hr, expanding its sulfur recovery capacity by reducing the thermal stage combustion air - 351 -
N. Edkins, N. Moreton requirement, while controlling total sulfur emissions to less than 11 mg/nm3 SO2. Operation of the plant has been stable and reliable for 1 years and operators attest to the robustness and trouble-free nature of the Camsolv System. This paper aims to highlight the reliability, on-line availability, performance and general ease of operation that Laxness has achieved with the Cansolv system over the past 1 years. It will also focus on the overall integration and optimization of the Cansolv unit as part of a 2- stage SRU with tail-gas incineration line up and touch on its potential use in other similar applications. This paper highlights the reliability, on-line availability, performance and general ease of operation that Lanxess has achieved with the CANSOLV SO2 Scrubbing System over the past 1 years. The overall integration and optimization of the CANSOLV unit as part of a 2- stage sulfur recovery unit (SRU) with tail-gas incineration line-up has provided a means for Lanxess to optimize their rubber chemicals plant as well as keep emissions within the environmental regulatory limits. INTRODUCTION In 22, the CANSOLV SO2 Scrubbing System was started-up at the Lanxess chemical plant in Belgium. At this particular site, the CANSOLV process treats the flue gas generated from an incinerator which burns waste tar as well the tail gas from a sulfur recovery unit (SRU or Claus unit). At the time of the CANSOLV unit s inception, Lanxess was faced with the challenge of meeting new regional environmental emissions standards. The maximum SO2 emission limit of 45 mg/nm 3 (16 ppmv) would be coming into effect January 1, 23. In addition to meeting the environmental emissions standards, Lanxess was looking for a cost-efficient technology that could easily be integrated in its line-up and would not generate additional turn-downs. Through a series of piloting campaigns, Lanxess evaluated several SO2 capture technologies and Cansolv was proven to be the best fit in successfully treating the site s combined waste tar incineration combustion gas and SRU tail gas. As a result, the CANSOLV SO2 Scrubbing System was selected by Lanxess in order to comply with the new environmental regulations and the unit was efficiently integrated into their existing line-up in 21. PROCESS DESCRIPTION & BENEFITS OF CANSOLV - INTEGRATION INTO SRU Prior to the CANSOLV unit, the SO2-rich flue gas from the incinerator unit is processed through three pre-treatment steps. First, it is treated for NOx removal in the Selective Non-Catalytic Reduction (SNCR) unit, then it is cooled in a waste heat boiler (WHB), and finally, it is quenched in a venturi-type pre-scrubber which also serves to remove the majority of particulates and chlorides. The CANSOLV unit is a typical regenerative amine line-up as shown in the block diagram below (Figure 1B). The recovered SO2 is recycled to the front end of the Claus unit in order to increase the sulfur recovery capacity of the existing SRU. The SO2 removed from the flue gas exiting the incinerator (generated from incineration of SRU tail gas and waste tars) reduces the inert flow through the SRU acting to debottleneck the unit and increase sulfur production. The integration and optimization of a 2-stage SRU and the CANSOLV unit has proven to be a reliable and robust operation. Lanxess have successfully been able to control feed ratios at lower H2S flow rates (4 Nm 3 /hr > 98% H2S) while capturing higher concentrations of SO2 in the incinerator flue gas (.7-1.5%vol SO2) from the 2-stage SRU. With tail gas incineration, the control of the air / H2S ratio to the thermal stage is less demanding, since the CANSOLV System can inexpensively scrub the higher SO2 concentrations that may result from off-ratio operation for shorter periods. The SO2 product generated by the CANSOLV process is recycled back to the SRU at 6-7 Nm 3 /hr, expanding its sulfur recovery capacity by reducing the thermal stage combustion air requirement, while controlling total sulfur emissions to less than 11 mg/nm 3 SO2 (39 ppmv) which is significantly below the current regulatory requirement of 5 mg/nm 3 SO2 emissions. 352 Sulphur 212 International Conference (Berlin, Germany 28-31 October 212)
CANSOLV SO 2 scrubbing system - 1 years of reliable operation Integration with SRU tail gas incineration Claus Unit and Cansolv Integration Treated Flue Gas Raw Materials S SO 2 DeNOx (SNCR) H 2 S Claus Unit H 2 S Incinerator WHB Cansolv Production SO 2 SO 2 Waste Tar Quench & Chlorides/ Particulates Removal Process Stream organic sulfur compounds Extraction Water Treatment Treated Water Rubber Chemical Fig. 1A: Block diagram of Lanxess plant SO 2 Recycle: Cansolv SO 2 to Treated Flue Gas Sulfur Recovery Lean Cansolv DS Amine Tail GasSO 2 SO 2 -Absorber SO 2 -Stripper Rich Cansolv Amine Fig. 1B: Block diagram of Lanxess s CANSOLV Unit Sulphur 212 International Conference (Berlin, Germany 28-31 October 212) 353
N. Edkins, N. Moreton Fig. 2: CANSOLV SO 2 Scrubbing System at the Lanxess, Belgium plant (September 11, 212) The original 22 design basis used for the Lanxess CANSOLV System Recovery unit is the following: 354 Sulphur 212 International Conference (Berlin, Germany 28-31 October 212)
CANSOLV SO 2 scrubbing system - 1 years of reliable operation Integration with SRU tail gas incineration Table 1 Design basis for Lanxess, Belgium s CANSOLV unit Gas Flow 11, Nm 3 /hr Gas Temperature 65 C Composition Component Vol% (wet) kg/hr N2 61.82 85 O2 3.57 56.7 H2O 27.17 243 CO2 5.94 1283 SO2 1.43 45 SO3.6 2.3 Additional Feedstock Specification HCl.2.35 NOx.24 5.45 H2S.1.2 Organic Compounds 2 mg/nm 3 Dust 5 mg/nm 3 Cations 2 mg/nm 3 Outlet Specifications (cleaned gas) SOx 45 mg/nm 3 EMISSIONS CONTROL As shown in the following graph, despite fluctuations in the SO2 concentration in the inlet gas, the SO2 in the cleaned outlet gas has consistently remained below 36 mg/nm 3 SO2 (125 ppmv SO2). The only rare exceptions are during start-ups and shut-downs when there is insufficient H2S feed to the Claus unit. Since start-up, the unit has successfully met the design and environmental SO2 emissions targets. Figure 3 below is a trend of the inlet SO2 concentration and the outlet concentration in the treated gas (both in ppmv). Day-to-day operating averages are well below emissions targets. Sulphur 212 International Conference (Berlin, Germany 28-31 October 212) 355
N. Edkins, N. Moreton 14 SO 2 Conc. Inlet and Outlet vs. Time (averaged annual values, logorithmic scale) 8 12 7 1 INLET 6 5 SO2 Conc. (ppmv) 8 6 4 3 4 2 2 1 OUTLET 2 1 2 22 24 26 28 21 212 214 SO2 Inlet (ppmv) SO2 Outlet from Cansolv (ppmv) Fig. 3A: Inlet SO 2 vs. Outlet SO 2 (22-212) The CANSOLV process displays a robust ability to handle changes in SO2 inlet concentration while maintaining the desired emissions. As shown in Figure 3A above, since 22 to present-day, the inlet SO2 concentration has almost doubled, however SO2 treated gas concentration has consistently remained well below the design emissions specification of 16 ppmv. In fact, in recent years, the SO2 treated gas concentration has remained below 5 ppmv. The robustness of the CANSOLV unit is further shown in Figure 3B and Figure 4 below. The fluctuations of the SO2 concentration in the inlet gas is mainly attributed to the intermittent operation of the waste tar incineration. The SRU tail gas, on the other hand, is continuously fed through to the CANSOLV unit. Despite the wide fluctuations in SO2 inlet concentration, the emissions are maintained 356 Sulphur 212 International Conference (Berlin, Germany 28-31 October 212)
CANSOLV SO 2 scrubbing system - 1 years of reliable operation Integration with SRU tail gas incineration 18 SO 2 in and SO 2 out (ppm) vs. Time - 211/212 monthly average 5 16 14 INLET 45 4 12 35 SO2 Conc. (ppmv) 1 8 3 25 2 6 15 4 1 2 OUTLET 1 5 Nov-1 Feb-11 Jun-11 Sep-11 Dec-11 Apr-12 Jul-12 Oct-12 SO2 In (ppm) SO2 In Treated Gas (ppm) Fig. 3B: Inlet SO 2 vs. Outlet SO 2 (211-212) 14 Inlet/Outlet SO 2 Conc. and Flue Gas Flow vs. Time (averaged annual values) 8. 12 7. Flue Gas Flow (Nm3/hr) and SO2 Inlet and Outlet Conc. (ppmv) 1 8 6 4 2 1 6. 5. 4. 3. 2. 1.. 2 22 24 26 28 21 212 214 SO2 Inlet (ppmv) Throughput (Nm3/hr) SO2 Outlet (ppmv) Fig. 4: Flue gas flow rate and SO 2 inlet concentration (22-212) In 27, Lanxess added a Waste Heat Boiler (WHB) into the line-up to recover energy and generate steam for use in other locations around the facility (see block diagram in Figure 1A). This resulted in a reduction of the flue gas temperature entering the CANSOLV absorber of ~1-15 C (45-6 C pre-whb, 3-45 C Sulphur 212 International Conference (Berlin, Germany 28-31 October 212) 357
N. Edkins, N. Moreton post- WHB). This trend can be seen in Figure 5 below. The CANSOLV process benefits from lower operating conditions in the absorber and as a result SO2 capture is improved. 6 Flue Gas Inlet Temperature and SO 2 Outlet vs. Time (averaged annual values) 4 5 Installed WHB in late 26 35 3 Flue Gs inlet Temperature (C) 4 3 2 25 2 15 SO2 in Treated Gas (ppmv) 1 1 5 2 22 24 26 28 21 212 214 Flue Gas Inlet Temperature (C) SO2 in Treated Gas (ppmv) Fig. 5: Flue gas inlet temperature ( C) and SO 2 outlet concentration (ppmv) Also, by sending excess steam to the stripper, even lower emissions were attained. The flexibility provided by increasing steam above original values has allowed the site to increase throughput of sulfur as well as reduce emissions. RELIABILITY AND EASE OF OPERATION The CANSOLV unit has required essentially no maintenance over the past 1 years. The CANSOLV unit is off-line once a year when the SRU Claus unit is shut down for maintenance reasons. The plant has never shutdown due to unavailability of the CANSOLV unit. Regarding its ease of operation, the CANSOLV unit is essentially self-sufficient and does not require a full-time operator. One operator runs the entire Claus unit, which includes the CANSOLV unit. The overall yearly operating expense of the CANSOLV unit is low. The required utilities are cooling water for the regenerator condenser and lean amine cooler, steam for the stripper, and demineralized water and caustic for the amine purification unit. Amine losses are also kept very low, at approximately 5-8% make-up per year. For Lanxess, this translates to 2-3 drums of amine per year. The source of the losses are mainly mechanical and as a result of solvent degradation. When the CANSOLV system was starting in 22, an electro-dialysis unit (EDU) was provided to control heat stable salt (HSS) level in the amine inventory. After overcoming several challenges related to deploying the EDU technology, it was successfully integrated and used to manage HSS levels until 25. In 25, Lanxess opted to switch to a skidded ion exchange (IX) technology in favor of lower operating and maintenance expenses. This technology is currently still in use at the site and has proven to be a low maintenance, cost-effective method of managing HSS levels in the CANSOLV amine. 358 Sulphur 212 International Conference (Berlin, Germany 28-31 October 212)
CANSOLV SO 2 scrubbing system - 1 years of reliable operation Integration with SRU tail gas incineration CLOSING SUMMARY After 1 years of trouble-free operation, the Lanxess rubber plant in Belgium attests to the reliability, the cost-effectiveness and the ease of maintenance of the CANSOLV SO2 Scrubbing System. The level of emissions has been kept below the imposed regulatory limits, whilst the SO2 recycled back to the SRU unit has optimized its operations and lowered its operating costs. In addition, the flexibility of the CANSOLV SO2 Scrubbing System proved useful to surpass the environmental regulations and optimize the unit. Simply by cooling the feed gas to the unit and by increasing the steam feed to the stripper, the emissions were reduced by a factor of 2 and sulfur recovery was further increased. From an emerging technology in the late 9s, the CANSOLV SO2 Scrubbing System has proven to be a mature cost-efficient technology, adopted by numerous plants around the world. CANSOLV PRESENTATION Cansolv Technologies Incorporated (CTI) is an innovative, technology-centered company that offers its clients high efficiency air pollution and capture solutions for the removal of SO2 and CO2 from gas streams in various industrial applications. Our commitment is to provide custom designed economic solutions to our clients' environmental problems. Cansolv Technologies Incorporated was formed in 1997 to commercialize the CANSOLV SO2 Scrubbing System. On November 3th of 28, Shell Global Solutions International B.V (SGSI) purchased 1% of the shares of CTI. The company now operates as a wholly owned subsidiary of SGSI. CTI has maintained a strong Research and Development program focused on continuously improving the CANSOLV SO2 process, developing a CO2 Capture process, and integrating advanced amine purification systems. Sulphur 212 International Conference (Berlin, Germany 28-31 October 212) 359
N. Edkins, N. Moreton 36 Sulphur 212 International Conference (Berlin, Germany 28-31 October 212)