Integrated Formaldehyde-Stabilized Urea Process with CO2 Recycling
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Solution Overview
Problem
The existing processes for producing formaldehyde-stabilized urea face challenges in efficiently co-producing methanol and ammonia, particularly when there is a need for increased methanol and formaldehyde production, as they often require separate facilities and incur high costs due to small-scale demand and insufficient carbon oxides in synthesis gas.
Innovation Solution
An integrated process that generates synthesis gas, subjects it to water-gas shift and carbon dioxide removal, synthesizes methanol, oxidizes it to formaldehyde, and uses the resulting gases to produce ammonia, allowing for the co-production of methanol and ammonia while adjusting the carbon monoxide to carbon dioxide ratio and utilizing a single air compression source for both methanol oxidation and synthesis gas generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If formaldehyde is produced at a separate dedicated facility and transported to the ammonia/urea production facility, then the formaldehyde stabiliser can be supplied, but the capital and operating costs increase due to separate facilities and transportation
Solution Approach 1:
The patent combines the formaldehyde production facility with the ammonia/urea production facility into a single integrated plant. The synthesis gas from the ammonia production process is directly used for methanol synthesis, which is then oxidized to formaldehyde for urea stabilization. This merging eliminates separate facilities and transportation requirements, reducing both capital and operating costs while maintaining continuous production.
Solution Approach 2:
The synthesis gas generation unit serves multiple functions: it provides synthesis gas for ammonia production, and the same synthesis gas (after CO2 removal) is used for methanol synthesis. The methanol is then converted to formaldehyde for urea stabilization. This multi-functionality of the synthesis gas unit eliminates the need for separate dedicated facilities.
2Device complexity
If the synthesis gas from the carbon dioxide removal unit is used directly for methanol synthesis, then the process is simplified, but there is insufficient carbon oxides to generate the required formaldehyde stabiliser
Solution Approach 1:
The patent recovers carbon dioxide from the carbon dioxide removal unit's off-gas stream and feeds it back to the methanol synthesis unit. This recovery and recycling of CO2 ensures sufficient carbon oxides are available for formaldehyde stabiliser production without requiring additional complex process equipment or external CO2 sources.
3Productivity
If more methanol and formaldehyde stabiliser are produced to feed multiple urea plants, then the demand can be met, but the carbon oxides in the synthesis gas outlet are insufficient to generate the required formaldehyde stabiliser
Solution Approach 1:
The patent implements a CO2 recovery and recycling system where carbon dioxide from the carbon dioxide removal unit's off-gas is captured and fed back to the methanol synthesis unit. This circular flow ensures sufficient carbon oxides are available to produce increased amounts of formaldehyde stabiliser for multiple urea plants without requiring additional external CO2 sources.
Solution Approach 2:
The integrated design ensures continuous production and recycling of CO2 within the system. The CO2 removed from synthesis gas is continuously recovered and fed back to methanol synthesis, maintaining a continuous supply of carbon oxides needed for high-volume formaldehyde stabiliser production to meet multiple urea plant demands.
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 integrated process enhances efficiency and flexibility by allowing for the production of formaldehyde-stabilized urea with improved methanol and ammonia synthesis, reducing capital and operating costs, and enabling the reuse of vent gases to augment methanol production, thus addressing the limitations of prior art.
Implementation Method 1
subjecting the synthesis gas to one or more stages of water-gas shift in one or more water-gas shift reactors to form a shifted gas
Implementation Method 2
the carbon dioxide removal unit operates by means of absorption using a liquid absorbent
Implementation Method 3
synthesising methanol from the carbon dioxide-depleted synthesis gas in a methanol synthesis unit
Implementation Method 4
subjecting at least a portion of the recovered methanol to oxidation with air to form formaldehyde in a stabiliser production unit
Implementation Method 5
subjecting the methanol synthesis off-gas to methanation in a methanation reactor containing a methanation catalyst to form an ammonia synthesis gas
Implementation Method 6
synthesising ammonia from the ammonia synthesis gas in an ammonia production unit and recovering the ammonia
Implementation Method 7
reacting a portion of the ammonia and at least a portion of the recovered carbon dioxide stream in a urea production unit to form a urea stream
Data Source
Figure 1
AI summary
A process for the production of formaldehyde-stabilised urea is described comprising the steps of: (a) generating a synthesis gas; (b) subjecting the synthesis gas to one or more stages of water-gas shift in one or more water-gas shift reactors to form a shifted gas; (c) cooling the shifted gas to below the dew point and recovering condensate to form a dried shifted gas; (d) recovering carbon dioxide from the dried shifted gas in a carbon dioxide removal unit to form a carbon dioxide-depleted synthesis gas; (e) synthesising methanol from the carbon dioxide-depleted synthesis gas in a methanol synthesis unit and recovering the methanol and a methanol synthesis off-gas; (f) subjecting at least a portion of the recovered methanol to oxidation with air to form formaldehyde in a stabiliser production unit; (g) subjecting the methanol synthesis off-gas to methanation in a methanation reactor containing a methanation catalyst to form an ammonia synthesis gas; (h) synthesising ammonia from the ammonia synthesis gas in an ammonia production unit and recovering the ammonia; (i) reacting a portion of the ammonia and at least a portion of the recovered carbon dioxide stream in a urea production unit to form a urea stream; and (j) stabilising the urea by mixing the urea stream and a stabiliser prepared using the formaldehyde produced in the stabiliser production unit, wherein the carbon dioxide removal unit operates by means of absorption using a liquid absorbent and comprises an absorbent regeneration unit, wherein the process includes recovering a carbon dioxide-containing gas stream from the absorbent regeneration unit, compressing at least a portion of the recovered carbon dioxide-containing gas stream to form a compressed carbon dioxide-containing gas stream and passing the compressed carbon dioxide-containing gas stream to the methanol synthesis unit.