Low-Level Oxygen Enrichment
Low-level oxygen enrichment is implemented by injecting oxygen into the SRU combustion air line through a custom designed diffuser that promotes good mixing. This technology typically allows for maximum enrichment levels of 28% due to limitations relating to oxygen compatibility and cleanliness of the combustion air piping. This technology requires minimal capital investment and process modification and typically offers an SRU capacity increase of 15% to 25%.
The equipment required for low level oxygen enrichment is a custom designed diffuser that injects oxygen into the combustion air header and an oxygen supply skid. Normal installation time is a few days and does not require a shutdown of the SRU. The diffuser may be hot-tapped into the combustion air header through a packing gland while the air blower and the sulfur plant are in operation.
COPE Phase I: Mid-Level Oxygen Enrichment
Oxygen enrichment levels exceeding 28% require the use of a special burner with discrete oxygen port(s) to safely handle oxygen. The COPE burner is a high-intensity burner that can safely handle the multiple incoming gas streams and has excellent ammonia destruction capability. COPE Phase I provides SRU capacity increases of up to 60% at oxygen enrichment levels of up to 45% for typical refinery acid gas streams. The upper oxygen enrichment limit of this technology is set by the maximum allowable furnace refractory temperature.
The COPE Phase I process requires the addition of a patented, special high-intensity COPE burner designed for multiple gas streams, safe oxygen handling and effective ammonia destruction.
COPE Phase II: High-Level Oxygen Enrichment
The high reaction furnace temperatures typically encountered when oxygen enrichment exceeds 40% to 45% for rich acid gas streams require the implementation of special temperature moderation technology to attain further capacity gains. COPE Phase II is a patented technology in which a portion of the cooled gas from downstream of the first sulfur condenser is recycled back to the reaction furnace to achieve temperature moderation. This technology can be deployed at oxygen enrichment levels up to 100% to more than double the capacity of an existing SRU. The COPE technology allows an SRU to operate over the entire range of oxygen enrichment levels, from an air-based mode to 100% oxygen, for the greatest possible operational flexibility.
The COPE Phase II process requires the addition of equipment: the COPE burner, a recycle compressor, and acid gas pre-heater(s
NH3 Destruction System
To recover elemental sulfur from acid gas containing NH3 in addition to H2S and CO2 using the Claus process. In Jacobs Comprimo's ammonia destruction system, all gases containing H2S and NH3 are burned in one burner, offering the following advantages:
Complete destruction of NH3.
No deposits of ammonia salts.
No NOx formation due to reducing flame conditions.
Simple operation and control.
Since 1969 this Jacobs Comprimo® system has been installed in more than 150 Claus plants.
Heavy Hydrocarbon Destruction System
Some feed gas streams may contain small amounts of heavy hydrocarbons and aromatics (e.g. BTX). In Jacobs Comprimo's HHC Destruction System, these components are completely burned, preventing soot formation and assuring the production of on-spec sulfur.
ABC Advanced Burner Control
To control the air to acid gas ratio to the SRU, the ABC system has to be developed for assuring the correct H2S content in the gas to the SUPERCLAUS® reactor stage. The ABC system can also be applied to control the H2S/SO2 ratio in a conventional Claus plant.
To cope with the flow rate variations, both the conventional control system and the Advanced Control System (ABC) use a feed-forward (ratio) control scheme. The conventional control system controls the air through the main air valve in ratio to the acid gas flow. It has the disadvantage that the main air valve is big and therefore slow. A step change in acid gas flow or composition does not result in a step change in the main air flow, and leads to an incorrect ratio during the (long) response time of the main air valve. The ABC system reacts faster to changes in the acid gas flow rate and provides superior process control and system performance.
The (total) flow controller (FC) manipulates the small (and thus quick) trim air valve, which operates parallel to the big main air valve. To prevent system upsets during a large flow rate disturbance, a trim valve position controller re-adjusts the trim air valve position to neutral by manipulating the main air valve.
The second type is a disturbance in the composition of the sour gas. A composition change of the sour gas results in a change in air demand. Both the conventional control scheme and ABC control schemes use a feedback system to compensate for acid gas composition changes. The conventional control scheme, however, is not able to react precisely to changes in flow rate and gas composition at the same time. The ABC system automatically adjusts the design air to acid gas ratio. A change in acid gas flow rate now results (through the adapted ratio) in the correct air demand, without any further re-adjustment from the quality controller.
ABC Advanced Burner Control +
To control the air to acid gas ratio to the SRU with feed forward control based on continuous measurement of feed gas composition.
Although ABC is an important improvement over conventional controls, it cannot react to rapid and frequent changes in acid gas composition. In these cases the ABC+ system addresses the problem by adding a feed gas analyzer and related calculating functions. This revolutionary development changes the air to feed gas ratio dynamically to precisely deliver the proper air volume. The combustion air to the main burner is adapted continuously based on the feed gas composition prior to entering the main burner. This results in a more accurate air to feed gas control and improved SRU control robustness.
ABC+ analyzes the feed gas and calculates the correct air demand as feed-forward control in combination with the standard ABC functions. In many cases measurement of H2S, CO2, H2O and total hydrocarbons gives sufficient information.
In refinery applications where sour water stripper (SWS) acid gas containing NH3 is processed, a dedicated analyzer can be set up to also analyze H2S, NH3, H2O and total hydrocarbons in the SWS gas.
Once the composition of the feed gas is known, the total air demand is calculated using proprietary Comprimo® algorithms. From the analyzer output also the actual molecular weight of the feed gas is calculated and used for molecular weight compensation of the feed gas flow This further improves the accuracy of ABC+.