CO2 Purification via Three-Stage Scrubbing
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Solution Overview
Problem
The existing methods for purifying CO2 offgas streams from methionine production processes are inefficient, as they result in the loss of CO2 and generate odorous and toxic waste streams due to the presence of methyl mercaptan, which cannot be recycled effectively, leading to increased costs and process disruptions.
Innovation Solution
A three-stage scrubbing process using water, methylmercaptopropionaldehyde (MMP), and subsequent water scrubbing to remove methyl mercaptan from CO2 offgas streams, allowing for the recycling of purified CO2 back into the production process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the offgas is incinerated to remove methyl mercaptan, then the harmful substances are destroyed, but CO2 is lost and considerable combustion costs arise
Solution Approach 1:
The offgas treatment is divided into multiple sequential scrubbing stages, each targeting specific components: first stage removes methyl mercaptan using ammonium carbonate, second stage removes HCN using water, third stage removes remaining ammonia using MMP. This segmented approach allows selective removal of harmful substances while preserving CO2 for recycling.
Solution Approach 2:
The process recovers CO2 from the offgas stream by removing only the harmful contaminants (methyl mercaptan, HCN, ammonia) through selective scrubbing. The purified CO2 is then recovered and recycled back into the hydantoin formation process, eliminating the need for incineration and associated CO2 losses.
2Object-affected harmful factors
If multistage scrubbing is used to recover HCN and methyl mercaptan, then these substances are removed, but CO2 escapes unutilized and additional waste streams are formed
Solution Approach 1:
The process optimizes the sequence and conditions of scrubbing stages to achieve selective removal of contaminants while preserving CO2. By adjusting the order of scrubbing (ammonium carbonate first, then water, then MMP) and controlling pH conditions, the process enables CO2 to remain in the gas phase for recycling while contaminants are transferred to liquid phases for disposal or further treatment.
3Object-affected harmful factors
If the offgas is scrubbed with water to remove ammonia, then ammonia is removed, but methyl mercaptan and CO2 are lost in the waste stream
Solution Approach 1:
The scrubbing process is arranged in a specific sequence where methyl mercaptan is removed first using ammonium carbonate, then HCN is removed using water, and finally ammonia is removed using MMP. This preliminary removal of more problematic substances before final ammonia scrubbing prevents them from contaminating the wastewater stream and eliminates the need for additional waste treatment.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This process achieves a CO2 purity of >98% by weight, eliminating the need for CO2 loss and unwanted waste streams, thereby optimizing the methionine production process without additional offgas or wastewater generation.
Implementation Method 1
the gas is scrubbed a) with water or with water in which methylmercaptopropionaldehyde (MMP) is present dissolved up to a maximum of the solubility limit, b) subsequently with MMP
Data Source
AI summary
A process for purifying CO2 offgas streams to free them of chemical compounds, and to the recycling of the purified gas streams into the production process.