Bicarbonate Facility CO2 Recovery Project Evaluation and Process Design

Project Synopsis

Investigate / troubleshoot significant CO₂ losses, and develop corrective process alternatives for correcting these losses at a sodium bicarbonate production facility in the US.

Project Summary

The client operates a well-established sodium bicarbonate production facility in the US. By observing reagent feed rates, it was found long ago that a significant amount of CO₂ introduced into the plant was escaping unreacted through various locations. To remedy this, two prior third-party CO₂ recovery projects were completed at the facility, but these did not deliver the expected results. Following the two unsuccessful attempts, the client engaged Process Engineering Associates, LLC (PROCESS) for assistance with the remediation efforts.

PROCESS agreed to perform an investigation of the process to help quantify emission sources, to evaluate potential recovery technologies, and to deliver a process design package for any technology expected to perform well for this purpose. The agreed upon tasks and deliverables for this project were as follows:

• Project kickoff meeting and site data collection
• Information review and preliminary design basis development
• Vent system test plan preparation and testing oversight
• Preliminary modeling / mass & energy balance (MEB) development of existing process
• Existing process PFD and process description preparation
• CO₂ recovery technical and economic process alternatives evaluation
• Update of the Design Basis, MEB, and PFD for the modified process
• Modified process utility summary table preparation
• Modified process preliminary P&IDs preparation
• Preliminary red-line of existing P&IDs
• Preliminary major equipment list preparation
• Preliminary general arrangement drawing preparation
• Preliminary installed capital cost estimate preparation, +/- 40%
• Review meetings and teleconference calls.

PROCESS studied the facility documentation and visited the plant to collect additional information of interest. A test plan was developed, and a third-party laboratory was contacted to perform the tests. PROCESS returned to the site to observe testing and to take measurements of other values believed to be impacting the CO₂ movement throughout the plant.

With information obtained, PROCESS developed a model of the process using OLI and Aspen Plus software packages. Using these models and information collected from the plant, the likely CO₂ sources were identified. Tie-in locations for potential recovery systems were found along with acceptable ways of reintroducing the recovered CO₂. PROCESS compared several technologies employed in other industries to capture CO₂, along with some options that the client specifically requested. Most of these were quickly ruled out as being too large to fit the footprint available, too expensive, or requiring new reagents that would not be permitted in the facility because of the food service nature of the product.

Two practical remediation methods were identified. Both involved routing of vent headers to a common point that would then feed the recovery equipment. The two recovery designs are as follows:

• Option 1 would use aqueous sodium carbonate to scrub CO₂ from captured vents by employing a design similar to the reactors used at the facility for sodium bicarbonate production. The reagent flow would be modified to ensure a large excess of soda ash be present in this polishing reactor. Liquids containing the captured CO₂ in the form of carbonates would then be pumped into the plant reactor feed. The remaining vent streams, containing mostly air, would vent to atmosphere.
• Option 2 involved introducing the vents into the bottom of a column where cooled water would continuously circulate through a heat exchanger and a venturi nozzle in the top of the column. This would create a shower to directly cool the vents and remove water vapor. The cooled vents would then be pulled into a liquid ring compressor which would pressurize and inject the vents back into the plant’s existing reactor columns. This would be done in parallel with fresh CO₂

The items completed by PROCESS up to this point, along with the two viable recovery options were presented to the client. After some deliberation, client engineering asked PROCESS to develop a process design package for Option 2.

The equipment design and remaining tasks were completed and included in the process design package presentation. PROCESS was then asked by the client to generate a new proposal that included detailed engineering, start up, and commissioning support for the chosen technology.

Industry Type

Food Grade Chemicals Production

Utilized Skills

• Process investigation / troubleshooting
• Process alternatives evaluation
• Process design package development.