Green ammonia absorption cooling
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Solution Overview
Problem
Conventional ammonia synthesis plants face challenges in maintaining energy efficiency and operational complexity due to fluctuating power supplies from renewable sources, leading to inefficient ammonia cooling at low loads and increased capital expenses from steam turbine limitations.
Innovation Solution
An ammonia cooling system integrating absorption cooling with off-gas cleaning and regeneration, utilizing renewable energy sources for power-driven heating, and reducing the number of equipment units, allowing for better turndown ratios and efficient ammonia recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a multistage ammonia compressor driven by steam turbine is used for ammonia cooling, then energy efficiency is improved at high loads, but device complexity increases and turndown capability is limited
Solution Approach 1:
The system divides the ammonia cooling function into multiple pressure levels (high-pressure and low-pressure circuits) with separate evaporators and condensers, allowing independent operation of each circuit to achieve better load adaptation and turndown capability
Solution Approach 2:
The ammonia compression system is designed to serve multiple functions: ammonia synthesis loop cooling, ammonia evaporator cooling, and off-gas scrubbing, allowing a single system to handle diverse cooling requirements across varying loads
2Use of energy by moving object
If steam turbine is used to drive ammonia refrigeration compressor, then energy utilization is improved, but adaptability to varying loads deteriorates
Solution Approach 1:
The system employs dynamic load distribution between high-pressure and low-pressure ammonia circuits, allowing the steam turbine to operate efficiently at varying loads by adjusting the proportion of steam allocated to each circuit based on instantaneous demand
Solution Approach 2:
The system changes operating parameters (pressure levels, temperature levels, steam flow distribution) between high-pressure and low-pressure circuits to adapt to varying load conditions while maintaining steam turbine efficiency
3Adaptability or versatility
If ammonia cooling circuit operates at low loads, then ammonia production flexibility is improved, but energy efficiency deteriorates
Solution Approach 1:
The system uses partial action by operating only the necessary circuit (high-pressure or low-pressure) based on load requirements, avoiding the energy waste of running both circuits at full capacity during low-load operation
4Ease of operation
If off-gas ammonia stream is released without treatment, then operational simplicity is improved, but environmental harm increases
Solution Approach 1:
The system converts the harmful off-gas ammonia stream into a beneficial resource by using it as a heat source for steam generation in the off-gas scrubbing section, simultaneously eliminating ammonia emissions and producing useful steam for the ammonia synthesis loop
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
The system achieves balanced steam usage across varying loads, reduces equipment complexity, and enhances energy efficiency, enabling efficient ammonia cooling and recovery even at low turndowns, while minimizing ammonia slip and external water requirements.
Implementation Method 1
an ammonia evaporator for evaporating an ammonia liquid stream and generating an ammonia vapor stream
Implementation Method 2
said ammonia evaporator is arranged to receive said ammonia liquid stream and a heat exchanging medium for evaporating said ammonia liquid stream
Implementation Method 3
an off-gas cleaning unit for cleaning said off-gas ammonia stream under the addition of water as a scrubbing agent (absorbing agent), generating a water stream and an ammonia depleted off-gas stream
Implementation Method 4
an absorption cooling unit comprising water for cooling said ammonia vapor stream and collecting a condensed ammonia-water stream
Implementation Method 5
a regeneration unit for generating from said condensed ammonia-water stream: a purified water stream, said ammonia liquid stream, and an overhead ammonia gas stream
Data Source
AI summary
Ammonia synthesis process and plant comprising an ammonia synthesis converter and a downstream ammonia cooling system, wherein the ammonia synthesis converter is arranged to receive an ammonia synthesis gas comprising hydrogen and nitrogen and to produce an ammonia product gas stream and an off-gas ammonia stream; said ammonia cooling system comprising:—an ammonia evaporator for evaporating an ammonia liquid stream and generating an ammonia vapor stream;—an off-gas cleaning unit for cleaning said off-gas ammonia stream under the addition of water as a scrubbing agent, generating a water stream and an ammonia depleted off-gas stream;—an absorption cooling unit comprising water for cooling said ammonia vapor stream and collecting a condensed ammonia-water stream;—a regeneration unit for generating from said condensed ammonia-water stream: a purified water stream, said ammonia liquid stream, and an overhead ammonia gas stream.