5 Reasons Why Performance Evaluations are Essential for Your Processing Units
Annual health checks for Sulfur Recovery Units (SRU) and Amine Units have become an industry standard, ensuring operational performance and reliability form ongoing operations and before scheduled turnarounds.
1-Establishing Baseline Performance
Baseline performance data is crucial for assessing the current state of SRUs and Amine Units. This data acts as a reference point, allowing operators to detect deviations from normal operations. Without a baseline, identifying specific issues becomes challenging, leading to extended downtime and increased maintenance costs.
2-Early Detection of Issues
Regular health checks enable early identification of operational inefficiencies, potential corrosion, contamination, fouling, and other issues. Catching these problems early helps prevent them from escalating into costly shutdowns or safety incidents.
3-Optimization Opportunities
By regularly analyzing system performance, SRE’s health checks reveal optimization opportunities. This could involve setting new operating parameters, fine-tuning the amine circulation rates, or adjusting the temperatures within the SRU. These improvements can lead to better recovery rates, lower emissions, and reduced energy consumption.
4-Supporting Turnaround Planning
Comprehensive health checks provide valuable data for planning turnarounds. Knowing the condition of equipment and potential trouble areas allows for precise scheduling and resource allocation, minimizing downtime and optimizing repair efforts.
5-Ensuring Compliance and Safety
In industries dealing with hazardous materials like H2S, safety is paramount. SRE’s rigorous safety protocols, including the use of SCBAs and trained engineers for sample collection, ensure that all health checks comply with the highest safety standards, protecting personnel and the environment.
Sulfur Recovery Engineering (SRE) offers comprehensive health check services that go beyond routine maintenance, establishing baseline performance, pinpointing optimization opportunities, and identifying potential issues early to avoid costly unscheduled and emergency shutdowns.
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From Fuel to Fines: Key Operating Costs in Sulfur Recovery Units
Managing a Sulfur Recovery Unit (SRU) involves more than just initial setup costs; it encompasses a spectrum of ongoing expenses that can significantly impact operational efficiency and regulatory compliance. Let's delve into the breakdown of these costs based on a recent YouTube transcript, categorizing them into three main areas: operating costs, maintenance costs, and emergency costs.
1. Operating Costs
Operating costs are fundamental to day-to-day SRU functionality and include:
Fuel Gas: Used in incinerators, thermal oxidizers, and other processes to convert sulfur compounds into SO2. Costs can vary based on the type and availability of gas.
Hydrogen: Essential for hydrogenation reactors and other units. While using on-site hydrogen can save on procurement costs, it may contain contaminants that reduce catalyst lifespan.
CO2 Emissions: Many jurisdictions impose costs per ton of carbon emitted, impacting overall operational expenses.
2. Maintenance Costs
Maintenance ensures the longevity and efficiency of SRU components:
Catalysts: Crucial for sulfur conversion, with costs varying by type (e.g., Illumina, Titania) and lifespan (typically 4-6 years).
Condenser Tube Sheet Failures: Result from improper thermal management during startups and shutdowns, potentially costing upwards of five figures to repair.
Refractory Damage: Repair costs can escalate dramatically if damaged during a runaway fire.
Plugged Rundown Lines: Costs can arise from unplugging lines, especially if external assistance is required.
Performance Evaluations: Conducted periodically to optimize SRU operations, typically costing around $35,000 per evaluation for comprehensive assessments.
3. Emergency Costs
Emergencies can lead to severe financial repercussions and regulatory penalties:
Regulatory Fines: Non-compliance fines can be substantial, sometimes reaching millions, depending on the severity of emissions violations.
Production Losses: SRU downtime can incur significant daily losses, ranging from $100,000 to over $1 million, highlighting the criticality of swift troubleshooting and repair.
Consent Decrees: Regulatory mandates may require frequent performance evaluations, increasing operational costs.
The operation of SRUs involves meticulous cost management across various fronts. From daily operational expenditures to mitigating potential emergencies and regulatory fines, understanding and planning for these costs are critical for maintaining operational reliability and compliance. By proactively addressing these cost factors, refineries and gas plants can optimize their SRU operations and ensure sustainable performance in the face of regulatory scrutiny and operational challenges.
Understanding these nuances not only helps in budgeting effectively but also in strategizing long-term operational excellence and compliance within the dynamic landscape of sulfur recovery management.
Case Study: Troubleshooting Decrease in Recovery Efficiency
Problem Identification
An existing client brought SRE in to troubleshoot an unexplained decrease in recovery efficiency within their Sulfur Recovery Unit (SRU). The plant had three SRU trains and had been experiencing high H2S levels in the product from the downstream degassing operation.
Steps Taken to Address the Problem
1-Initial Compositional Analysis:
SRE performed a compositional analysis of the process gas and found low conversion across Converter 2.
The SRU was generally well-operated, and no significant changes had occurred since the last test period.
2-Simulation and Catalyst Activity:
Simulations reconfirmed that the catalyst activity in the second converter bed was lower than expected.
Despite the catalyst being replaced only six months prior, the sudden reduction in efficiency was puzzling.
3-Inlet Temperature and Sample Testing:
Further analysis revealed that the converter inlet temperature was above the normal recommendation.
SRE installed a sample probe at the inlet, discovering a different gas composition than at the converter one outlet.
4-Identifying a Leak:
The analysis suggested a hole in the multipass condenser, allowing process gas from the first pass to contaminate the second pass.
This leakage explained the reduced conversion efficiency and increased inlet temperature at Converter 2.
5-Degassing Operation Review:
Before the client shut down to repair the condenser leak, SRE evaluated the degassing pits to understand why H2S levels were up to 200 ppm in the liquid sulfur.
Adjustments to the agitator and pump circulation rates were tested. It was found that the circulation rate was too low for adequate degassing.
One of the two sulfur pumps was found to be barely operational and required a complete overhaul.
6-Repair and Validation:
The condenser and pump repairs were scheduled during a planned shutdown.
SRE assisted with the shutdown and subsequent startup, performing tests to verify the effectiveness of the repairs.
Post-repair tests confirmed that recovery efficiency improved to above the license limit of 98%, and H2S levels in the liquid sulfur returned to specification.
Summary of Findings and Benefits
Operational Improvements: Quick identification and repair of the multipass condenser leak and the sulfur pump issues restored the plant's efficiency.
Financial Savings: Early detection and repair prevented further damage to the SRU and avoided substantial costs associated with contaminated product.
Product Quality: Restored liquid sulfur to meet H2S specifications, ensuring high-quality output.
This case study illustrates SRE's proficiency in diagnosing and resolving complex SRU issues efficiently. By identifying and repairing leaks and optimizing degassing operations, SRE restored the client's recovery efficiency and product quality. Other companies can benefit from SRE's thorough approach and expertise in maintaining and improving SRU operations, avoiding potential downtimes and financial losses.
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7 SRU Catalyst Killers: Identifying and Mitigating Contaminants in Sulfur Recovery Units
Catalysts are the heart of the sulfur recovery process, crucial for ensuring high efficiency and low emissions. However, various contaminants can deactive and damage these catalysts, leading to reduced performance and increased operational costs. This article explores the primary contaminants, their mechanisms, and methods for mitigation, alongside the financial impact of catalyst misuse.
Catalysts in sulfur recovery units (SRUs) facilitate the conversion of hydrogen sulfide (H2S) into elemental sulfur. Over time, contaminants can deactive these catalysts, impacting their effectiveness and lifespan. Identifying and understanding these contaminants is critical for maintaining optimal performance.
Major Contaminants and Their Impact
1- BTEX (Benzene, Toluene, Ethylbenzene, Xylene)
Mechanism: BTEX components are not fully destroyed in the reaction furnace (RF) and polymerize on the Claus catalyst.
Deactivation Type: Permanent.
Mitigation: Ensure complete destruction in the RF, maintain correct temperatures, and monitor BTEX levels in the feed.
2-Methanol
Mechanism: Methanol bypasses the RF via an acid gas bypass, leading to polymerization on the catalyst.
Deactivation Type: Permanent.
Mitigation: Properly control bypass systems and monitor methanol concentrations.
3-Soot and Liquid Sulfur Deposition
Mechanism: Incomplete combustion during startup or improper burner stoichiometry leads to soot formation, plugging converter beds.
Deactivation Type: Temporary.
Regeneration: Heat soak.
Mitigation: Optimize startup procedures and maintain burner efficiency.
4-Sulfation
Mechanism: Excessive free oxygen from the RF or reheaters causes sulfation of the catalyst.
Deactivation Type: Permanent.
Mitigation: Control oxygen levels and ensure proper operation of reheaters.
5- Steam (Hydrothermal Aging)
Mechanism: Long-term exposure to excessive water vapor leads to structural damage.
Deactivation Type: Permanent.
Mitigation: Minimize steam introduction and prevent boiler leaks.
6-Thermal Aging
Mechanism: High temperatures during sulfur fires cause catalyst sintering.
Deactivation Type: Permanent.
Mitigation: Avoid thermal excursions and maintain safe operational temperatures.
7-Heavy Hydrocarbons
Mechanism: Heavy hydrocarbons crack and form coke, blocking catalyst pores.
Deactivation Type: Permanent.
Mitigation: Optimize feedstock composition and prevent heavy hydrocarbon carryover
Avoiding Contamination
Preventing catalyst contamination involves maintaining strict operational controls and regular monitoring:
Ensure proper destruction of contaminants in the RF.
Control bypass systems to prevent methanol and heavy hydrocarbons from entering the catalyst beds.
Optimize startup and shutdown procedures to minimize soot formation.
Maintain proper temperatures to avoid sulfur condensation.
Regularly inspect and repair boiler systems to prevent hydrothermal aging.
Avoid thermal excursions by controlling process temperatures and preventing sulfur fires.
Financial Impact of Catalyst Misuse
Catalyst deactivation leads to significant financial burdens due to reduced efficiency, increased maintenance costs, and potential unscheduled shutdowns. Misuse can result in:
Increased operational costs due to frequent catalyst replacements.
Higher energy consumption and lower process efficiency.
Downtime for maintenance and catalyst regeneration or replacement.
How We Can Help: Performance Testing and Optimization
Sulfur Recovery Engineering (SRE) offers comprehensive performance testing and optimization services. Our experts can:
Conduct thorough assessments to identify contamination sources.
Provide tailored solutions to prevent and mitigate catalyst deactivation.
Offer regular monitoring and maintenance programs to ensure long-term efficiency and reliability.
Protect your catalysts and ensure optimal performance of your sulfur recovery units. Contact SRE today to schedule a consultation and learn how we can help you maintain peak efficiency and minimize operational costs.
Overcoming Heat Stable Salts: Enhance Your Amine Treating Process
Introduction
In the operation of amine units, the degradation of the solvent is a common issue caused by contaminants such as oxygen, sulfur dioxide, acids, or acid precursors present in the feed gas. One of the most significant problems arising from this degradation is the formation of Heat Stable Salts (HSS). Understanding the formation, impact, and remediation of HSS is crucial for maintaining the efficiency and longevity of amine treating systems.
Formation of Heat Stable Salts
Heat Stable Salts are formed when acid anions like formate, acetate, thiosulfate, thiocyanate, and chloride react with amine molecules. These salts are termed "heat stable" because they cannot be regenerated by heating. Various sources contribute to HSS formation:
In refineries, gases from the Fluid Catalytic Cracking Unit (FCCU) can contain formic and acetic acids.
Oxygen in refinery gas streams or air leaks in gas gathering systems can lead to the formation of carboxylic acids.
HCN in the feed gas can react with sulfur in the amine solution to form thiocyanate.
Impact of Heat Stable Salts on Amine Systems
The presence of HSS in amine systems leads to several operational issues:
Reduced Acid Gas Carrying Capacity: HSS bind with amine molecules, decreasing the amount of amine available for acid gas absorption.
Corrosion: High concentrations of HSS can be corrosive, facilitating corrosion reactions and dissolving protective films on metal surfaces.
Foaming: Changes in the surface-active properties and increased viscosity of the solution can lead to foaming, which disrupts operations.
Erosion: The precipitation of salts or corrosion end products can accelerate the erosion of metal components.
Addressing the Problem
Reducing or removing HSS from the amine solution is essential for maintaining system efficiency. The following strategies can be employed:
Monitoring and Prediction: Regular solvent analyses to determine the HSS profile and predict when remedial action is necessary.
Control Strategies: Adjusting operational configurations to reduce the formation of contaminants or improve the removal of contaminants upstream.
Neutralization Technology: Using neutralizers to convert HSS into less corrosive forms, thereby extending the solvent's life.
Solvent Purification: Employing methods such as electrodialysis, ion exchange, or vacuum distillation to remove HSS.
Our experts can help you find the root cause of the problem and provide tailored solutions to maintain your system's efficiency and reliability.
Advantages of Managing Heat Stable Salts
Effective management of HSS offers several benefits:
Reduced Corrosion and Equipment Replacement Costs: Minimizing the corrosive impact of HSS extends the life of equipment.
Optimized System Capacity: Ensuring maximum acid gas removal efficiency prevents unit shutdowns and maintains operational targets.
Lower Maintenance Costs: Reducing the frequency of system cleanings and filter replacements lowers maintenance expenses.
Environmental and Economic Benefits: Avoiding solvent disposal reduces environmental impact and costs associated with solvent replacement.
Conclusion
Managing Heat Stable Salts in amine treating systems is crucial for maintaining system performance and longevity. Regular monitoring, effective neutralization, and advanced purification methods can significantly reduce the negative impacts of HSS. At SRE, we offer comprehensive amine analysis services to identify the exact salts present and determine the root cause of HSS formation. Our detailed analysis capabilities ensure precise solutions to optimize your amine system's performance.
We can help
If you're facing issues with Heat Stable Salts in your amine treating system, contact SRE for a complete amine analysis. Our experts can help you find the root cause of the problem and provide tailored solutions to maintain your system's efficiency and reliability.
Mastering Amine unit Issues 8 Scenarios Where SRE Can Assist
Amine plants play a crucial role in gas sweetening, but they can face numerous operational challenges. Sulfur Recovery Engineering (SRE) offers specialized services to troubleshoot and resolve these issues, ensuring optimal performance and reliability. Here’s a brief description of each problem and how SRE addresses it:
1-Foaming
Problem: Heavy hydrocarbons and contaminants in the inlet feed cause foaming in absorbers, leading to reduced efficiency and potential operational disruptions.
Solution: SRE utilizes advanced Gas Chromatography (GC) technology for rapid identification of contaminants, along with onsite foam testing and evaluation of anti-foam agents to mitigate foaming issues effectively.
2-Corrosion
Problem: Corrosive environments within the amine plant can degrade equipment integrity, leading to increased maintenance costs and safety risks.
Solution: SRE quickly identifies corrosion potential areas through simulation, reviews and refines monitoring programs, and helps minimize corrosion through an online operations and maintenance (O&M) monitoring program.
3-Off-Spec Gas / LPG
Problem: Off-spec gas or LPG indicates deviations from desired product specifications, impacting product quality and compliance.
Solution: SRE conducts rapid onsite testing to diagnose issues, identifies trace sulfur components, and achieves 99% closure of the sulfur balance, ensuring compliance with product specifications.
4-Fouling
Problem: Fouling in amine plants results from contaminants and particulates accumulating in key components, reducing operational efficiency.
Solution: SRE reviews and optimizes filtration programs to prevent fouling, ensuring smooth operation and minimizing maintenance downtime.
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5-Sulfur Plant Feed Quality
Problem: Inaccurate sulfur component levels and impurities in the regenerator overhead impact the efficiency of sulfur recovery processes.
Solution: SRE performs onsite analytical testing to accurately measure sulfur components, identifies mercaptans breakdown, speciates BTEX compounds, and quantifies hydrogen cyanide (HCN) concentrations. We quickly optimize the acid gas circuit to improve overall efficiency and reduce corrosive issues.
6-Hydrocarbon Entrainment
Problem: Ineffective separation equipment allows hydrocarbons to enter the process stream, reducing the purity and efficiency of amine treatment.
Solution: SRE reviews and enhances the performance of inlet separation equipment, quantifying hydrocarbon levels in the process stream to mitigate entrainment issues.
7-Inefficient Energy Usage / High Carbon Intensity
Problem: Excessive energy consumption and high carbon intensity increase operational costs and environmental impact.
Solution: SRE optimizes energy usage through circulation rate adjustments and reboiler duty fine-tuning, recommends alternative amines with lower energy requirements, and assists in transitioning from steam to electric drives for enhanced efficiency.
8-Root Cause Analysis of Common Alarms
Problem: Common alarms such as pressure differentials, analyzer errors, and pH fluctuations indicate underlying operational issues affecting plant reliability.
Solution: SRE conducts detailed root cause analysis on absorber pressure differential (delta P), H2S and total sulfur analyzer errors, fuel gas H2S analyzer errors, sulfur plant tail gas analyzer (ADA) erratic behavior, quench pH, quench cooler fouling, and hydrogen analyzer plugging. Our expert analysis identifies operational inefficiencies and implements targeted solutions to improve overall plant reliability and safety.
SRE’s specialized expertise and innovative solutions address the complex challenges faced by amine plants, ensuring efficient operation, regulatory compliance, and enhanced performance. By partnering with SRE, clients benefit from reduced downtime, lower operational costs, and optimized plant reliability in their gas sweetening operations.
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8 Factors That Affect Sulfur Recovery Efficiency in Gas Plants and Refineries
1. Catalyst Deactivation
Catalyst deactivation in sulfur recovery units (SRUs) occurs due to contamination, poisoning, or thermal degradation. Regular monitoring is essential to maintain optimal efficiency and extend the catalyst's lifespan.
2. Inadequate COS and CS2 Hydrolysis
Effective hydrolysis of carbonyl sulfide (COS) and carbon disulfide (CS2) to hydrogen sulfide (H2S) is essential for optimal sulfur recovery. Inadequate hydrolysis can result in reduced conversion rates and increased emissions. Ensuring the optimal operating temperature of converter bed 1 is crucial for efficient hydrolysis reactions.
3. Excessive Converter Dewpoint Margins
Excessive dewpoint margins in converters can lead to sulfur condensation, causing system blockages and reduced efficiency. Maintaining appropriate temperature margins is essential to prevent these issues and ensure smooth operation.
4. Off-Ratio Control (Tail Gas Analyzer)
Maintaining the precise ratio of hydrogen sulfide (H₂S) to sulfur dioxide (SO₂) is crucial. Deviations from this ratio, often managed by a tail gas analyzer, can result in suboptimal conversion of sulfur compounds. Accurate ratio control is essential to prevent efficiency losses in sulfur recovery.
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5. Inefficient Demister Pad Operation/Sulfur Fog
Demister pads are employed to remove sulfur mist from the gas stream. Inadequate operation or maintenance of these pads can result in sulfur fog and disturbances in operations of the Tail Gas Treatment Unit, thereby reducing overall recovery efficiency. Regular maintenance of demister pads is essential to ensure optimal performance.
6. Elevated Final Condenser Outlet Temperature
The final condenser is crucial for condensing sulfur vapor into liquid sulfur. Elevated outlet temperatures can reduce condensation efficiency, leading to decreased sulfur recovery and increased load on the Tail Gas Treatment Unit. Maintaining optimal condenser temperatures is essential to ensure maximum condensation efficiency.
7. Excessive Turndown
Excessive turndown, or operating the SRU below its designed capacity, can lead to inefficiencies and increased emissions. Operating within the designed capacity range helps maintain optimal recovery efficiency.
8. Routine Operational Upsets
Operational disruptions, such as fluctuations in feed gas composition or unforeseen shutdowns, can significantly impact the sulfur recovery process. Implementing robust control systems and establishing contingency plans are crucial to mitigating the effects of these upsets.
Maximize your sulfur recovery efficiency and ensure operational reliability with Sulfur Recovery Engineering (SRE). Our expert services, including performance evaluation, process optimization, and on-site analysis, are designed to tackle the challenges affecting your sulfur recovery units.
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The Heat Is On! – Why Temperature Plays an Important Role in Sulfur Recovery
The iconic skyline of Alberta’s natural gas sector is marked by labyrinthine tubes and tunnels, pipes and platforms. Atop it all—like candles on the cakes of carbon—are sputters of live flame, alighting the morning sky.
Far more than just a deterrent to low-flying aircrafts (and birds), the powerful heat of the reaction furnace ensures sulfur extraction is maximized, and the purity of outflow is an optimal makeup for cleanliness and machine reliability.
Too Hot to Handle:
Working with sour water means bringing all the good along with the bad. Side reactions inside the reaction furnace will invariably produce unwanted products like CO, H2, COS, and CS2. Luckily, other contaminants such as BTEX, Mercaptans, NH3, HCN, Methanol, and HCs may be destroyed in the reaction furnace with proper calibration and sufficient heat.
While 900℃ (1650℉) is the minimum temperature for flame stability, heats of 1050℃ (1920℉) or above are capable of destroying the unwanted contaminants. Bear in mind the reaction furnace is kinetically limited based on residence time, turbulence, and temperature, as well as burner efficiency.
Through the Fire and Flames:
In our Sulfur Recovery experience, combustion air flow rates are nearly always off by at least 10–20%. While this is standard, we must work to ensure this margin of possible error is not exacerbated. Proper mixture of gasses and the installation of a high-efficiency burner can increase reaction furnace temperatures up to 100℃, which helps to reach the target temperatures mentioned previously.
This is crucial not only for efficiency, but for optimal refinery health. Proper burn-off of ammonia in the reaction furnace is essential, as residuals can carry over to the condensers and converters, bringing with them the risk of forming ammonia salts. These salts will negatively impact heat transfer and recovery efficiency. As with most sulfur recovery unit issues, you won’t know there is a problem until it is too late.
As with any efficient furnace system, management of both inflow and output should be carefully monitored, with changes to procedure made according to the changes in both. Ensure your plant is optimized for the feed it receives. For example, when H2S qualities are low in gas plants, a front side split configuration is often best for ensuring minimal additions of air and nitrogen to the system.
Conclusion:
Sulfur recovery isn’t always easy, but it is undoubtedly important. In the end, you should run your reaction furnace like you would your bathtub: the hotter, the better; the better, the cleaner! Learn more about how we can help you optimize your Sulfur Recovery by contacting us at our website, subscribing to our newsletter, or by giving us a call today.
Ammonia Analysis – SRU Protection
SRE is the only firm in the Oil & Gas industry that can provide timely, on-site results with respect to ‘bulk’ and ‘trace’ ammonia testing. In addition to our standard ‘bulk’ ammonia analysis of refinery-based sour water stripper (SWS) acid gas feed streams, we are capable of measuring the ammonia content (i.e. ppm level) in amine acid gas and the stream exiting your reaction furnace (RF). These specialized services are another example of SRE’s commitment to the efficient and long-term operation of our clients’ SRUs by way of research and development.
Based on 20+ years of field-testing experience, SRE strongly recommends ammonia breakthrough from the RF is kept below 150 ppm. The prevention of ammonia salt formation in downstream condensers will ensure optimal sulfur recoveries are realized without capacity reduction, all while preventing costly shutdowns to unplug or replace condenser tubes. While on-site, SRE Engineers will work with operations to maximize ammonia destruction by way of optimizing your front-side split parameters and, if applicable, adjusting the fuel gas co-firing strategy.
The combination of an SRU performance test and ammonia destruction study will minimize the potential risk of downstream ammonia salt formation in your SRU. SRE’s specialized services are designed to protect your facilities, personnel, and bottom line.
Breakdown: Claus Processing Units
Today we will be breaking down the different components of Claus Processing Units. Let’s take a look at each component and some best practices to guide you as you consider your own operations.
Reaction Furnace
This is the first unit in the Sulfur Recovery Unit (SRU) process where feed enters and where thermal combustion happens. Most of the heat is produced in this section due to the highly exothermic reaction (H2S is burned using oxygen to produce desired amount of SO2). The inner walls of the reaction furnace are lined with refractory bricks to protect the shell of the vessel from the extreme heat.
Wasteheat Boilers
The wasteheat boiler is attached to the back of the reaction furnace. This is where most of the heat removal takes place. These boilers are available in either a one-pass or two-pass design. A two-pass is used when there is a hot gas bypass already in place. By sending hot, processed gas to the first converter, the tube sheet is protected from high temperatures and sulphite attacks. When it comes to removing heat, the waste heat boiler is your friend— just let that hot steam rise to the top!
Claus Process Condenser
The Claus process condenser is an excellent shell and tube heat exchanger. Its function is to remove sulfur and heat. It separates gas and the liquid leads into your liquid-sulfur run downs. It maintains an outwards temperature in the range of 150°C to 165°C to minimize the sulfur vapour carry-over to the incinerator. Any higher than that and things might get frenetic! Keep in mind that condensers achieve low pressure steam production — 50 psig. Use this steam in heat tracing, as desired. That steam is produced on the shell side, with sulfur product on the tube side.
Reheater
Reheaters play a crucial role in maintaining sulfur temperature and avoiding condensation in the converters. Remember that processed gas leaves the condenser at the sulfur dew point temperature. This temperature must be increased. This increase provides optimal temperature for the Claus reaction in the gas phase and on to the converters.
Although two reheating methods exist, one is clearly superior. The direct reheating method is less desirable, as it adds additional sulfur bearing compounds to the process; this immediately lowers the overall practicable efficiency of the SRU. Moreover, between 0.1-0.5 % loss of sulfur can occur through this method.
Indirect heating is preferred for this reason. Harnessing the mighty power of steam, no added compounds can crawl through the pipes and into your end product. Simple to control and with no effect on overall practicable efficiency, indirect heating is the industry gold standard. Cost issues may arise, however, as some refineries see steam costing up to $5 per ton. The key point here is to focus on maintaining a 2:1 H2S to SO2 ratio.
Whatever the method, once converted and reheated the sulfur moves to the catalytic converter stage and incineration stage.
Catalytic Converter , Thermal Incinerators and Instrumentation
The catalytic reaction occurs at this stage. Through an exothermic reaction, heat is released, and the temperature begins to rise in the catalyst bed. Temperature control, as always, remains critical. Here, Claus reaction is favoured at lower temperatures. We want the processed gas to be in the gas phase.
Once catalyzed the thermal incinerator comes into play by converting the remaining off gas into SO2. The temperature of your incinerator should not exceed 650°C. Keep in mind that this is controlled by the amount of fuel gas and air being burned. Be sure to monitor SO2 concentrations at ground level for proper plume dispersion. Instrumentation can help monitor oxygen levels within a 2-4% range, but they are not always accurate. Make sure you understand the normal base conditions to avoid excess temperatures and any accidents.
We hope this blog was informative to you and your Claus Processing Unit aspirations. Follow our blog for more pertinent and useful updates in the field of sulfur recovery.