Ammonia Urea Plant Gas Stream Splitting
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Solution Overview
Problem
Current methods for producing ammonia and urea in integrated plants face challenges such as high energy requirements, inflexibility, and increased costs due to the need for carbon dioxide compression and scrubbing, as well as issues with water input affecting urea formation reactions.
Innovation Solution
Dividing the raw synthesis gas stream into two partial streams, where only one is washed with liquid ammonia, allowing the other to be used for stripping the urea solution, thereby eliminating the need for additional carbon dioxide and reducing equipment requirements, and allowing for separate operation of ammonia and urea plants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If all carbon dioxide is removed from synthesis gas using ammonia scrubbing, then ammonia synthesis purity is improved, but energy consumption increases due to compression requirements
Solution Approach 1:
The patent extracts only the necessary amount of carbon dioxide from the synthesis gas stream through ammonia scrubbing, rather than removing all CO2. The scrubbed synthesis gas is split into two streams: one purified stream for ammonia synthesis and another stream containing CO2 for urea production. This selective extraction maintains synthesis gas purity for ammonia while avoiding the energy-intensive compression of entire CO2 streams.
Solution Approach 2:
The synthesis gas stream is segmented into two separate streams after partial CO2 removal: a purified stream dedicated to ammonia synthesis and a CO2-containing stream for urea production. This segmentation allows each stream to be optimized for its specific purpose without requiring full CO2 removal and compression for both product lines.
2Productivity
If integrated production of ammonia and urea is implemented, then productivity is improved, but device complexity increases due to additional scrubbing and compression equipment
Solution Approach 1:
The ammonia produced in the ammonia synthesis unit serves multiple functions: it acts as a scrubbing agent for CO2 removal and simultaneously serves as a reactant for urea synthesis. This multi-functionality eliminates the need for separate CO2 compression and scrubbing equipment, reducing device complexity while maintaining integrated production benefits.
Solution Approach 2:
The system uses self-generated ammonia from the ammonia synthesis unit to perform the CO2 scrubbing function. The ammonia produced is recycled back to scrub CO2 from the synthesis gas, creating a self-sufficient system that eliminates external scrubbing equipment and reduces overall device complexity.
3Manufacturing precision
If ammonia/water mixture is used for CO2 separation, then CO2 removal efficiency is improved, but water content increases affecting urea formation equilibrium
Solution Approach 1:
The patent uses pure liquid ammonia instead of an ammonia/water mixture for CO2 scrubbing. This eliminates water introduction into the system entirely. The ammonia serves as a temporary scrubbing agent that reacts with CO2 to form ammonium carbamate, which then decomposes to provide CO2 for urea synthesis without contaminating the system with water that would affect urea formation equilibrium.
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 approach reduces energy consumption, capital costs, and avoids additional water input into the urea synthesis, enabling flexible operation and efficient production of ammonia and urea in a common plant complex.
Implementation Method 1
the first synthesis gas stream is washed with liquid ammonia to form a purified synthesis gas stream which is depleted of carbon dioxide and a condensate
Implementation Method 2
When carbon dioxide comes into direct contact with ammonia, ammonium carbamate is predominantly formed; this is also the starting material for urea synthesis
Implementation Method 3
the significantly slower and endothermic subsequent reaction to form urea and water
Data Source
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AI summary
The invention relates to a method for producing ammonia and urea in a common facility or alternatively (according to requirement) only producing ammonia in said facility, in which a raw synthesis gas flow containing at least the gases hydrogen, nitrogen and carbon dioxide is first compressed, then at least one subflow of the raw synthesis gas is washed with ammonia, a pure synthesis gas flow free of carbon dioxide is formed, as well as a condensate, ammonia (11) is synthesised from the pure synthesis gas flow depleted of carbon dioxide, and urea (6) is synthesised from the condensate, forming an aqueous urea composition. According to the invention, during the production of ammonia and urea, the raw synthesis gas flow, following compression (4), is divided into two subflows, specifically a first synthesis gas subflow and a second synthesis gas subflow, only the first synthesis gas subflow being washed with liquid ammonia (5).