Dual Pressure Ammonia Synthesis with Effluent Recycle
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Solution Overview
Problem
Conventional dual pressure ammonia processes face limitations in capacity expansion and temperature control in the first synthesis loop, with the second loop often becoming a bottleneck and equipment downstream facing risks of nitridation due to high inert gas concentrations.
Innovation Solution
A dual pressure process with a first reactive step at pressure P1 and a second reactive step at higher pressure P2, where a portion of the gaseous effluent is recycled back to the first step, either before or after compression, and the make-up gas acts as a motive fluid to enhance reaction efficiency, allowing for increased ammonia production and improved temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional dual pressure process is used with a once-through converter in the first synthesis loop, then the process structure is simple, but the capacity is limited and the second loop becomes a bottleneck
Solution Approach 1:
The invention introduces a feedback mechanism by recycling a portion of the gaseous effluent from the first synthesis loop back to the converter inlet. This recycle stream allows unreacted gases to be reused, increasing overall conversion efficiency and ammonia production capacity without requiring significant structural changes to the process
Solution Approach 2:
The invention changes the operational parameters by operating the first synthesis loop at lower pressure (60-130 bar) and the second loop at higher pressure (150-280 bar), allowing each loop to be optimized for its specific pressure range. This parameter differentiation enables increased capacity in the first loop while maintaining efficiency in the second loop
2Productivity
If the first synthesis loop operates at high pressure with high inert gas concentrations, then the conversion rate decreases, but reducing pressure reduces the overall synthesis efficiency
Solution Approach 1:
The feedback mechanism recycles unreacted gases containing high concentrations of inert components back to the converter inlet. This continuous recycling prevents inert gas accumulation from reaching levels that would significantly reduce conversion rate, while allowing the system to operate at optimized pressure conditions
Solution Approach 2:
By operating the first synthesis loop at lower pressure (60-130 bar) compared to conventional high-pressure operation, the system achieves better conversion rates in the first loop. The pressure is then increased in the second loop (150-280 bar) to maintain overall synthesis efficiency, creating an optimized pressure gradient across the two loops
3Productivity
If the converter outlet temperature is not controlled, then the reaction efficiency decreases, but controlling temperature exposes equipment to nitridation risks
Solution Approach 1:
The invention segments the ammonia synthesis into two separate loops operating at different pressures. The first loop at lower pressure (60-130 bar) handles the initial conversion with better temperature control, while the second loop at higher pressure (150-280 bar) completes the synthesis. This segmentation allows each loop to be optimized for its specific temperature and pressure conditions, reducing nitridation risks
Solution Approach 2:
The invention changes the pressure parameter between the two loops, with the first loop operating at lower pressure to facilitate better temperature control and reduced nitridation risk. The lower pressure conditions in the first loop allow for more effective heat management, while the second loop operates at higher pressure to maintain overall synthesis efficiency
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 increases ammonia production capacity, reduces the burden on the second synthesis loop, and enhances temperature control in the first loop, minimizing the risk of nitridation and optimizing equipment performance.
Implementation Method 1
said process comprises a step of compression of the gaseous effluent of the first reactive step from said first pressure P1 to said second pressure P2
Implementation Method 2
ammonia is synthesized by catalytic conversion of a make-up synthesis gas comprising hydrogen (H2) and nitrogen (N2) at high pressure
Implementation Method 3
the first synthesis loop typically comprises a converter, a cooler-condenser and an ammonia separator
Data Source
AI summary
A dual pressure process for the synthesis of ammonia from a make-up gas, wherein the make-up gas is reacted in two steps in series, the second step operating at a greater pressure than the first step, and wherein a portion of the effluent of the first step is recycled back to the first step, said portion containing unreacted make-up gas.