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.