Closed-Loop Recirculation Heating for Variable-Load Ammonia Synthesis
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Solution Overview
Problem
Ammonia synthesis plants face challenges in compensating for fluctuations in the provision of reactants, particularly hydrogen, due to intermittent renewable energy sources, leading to inefficiencies and the need for large energy and hydrogen storage means.
Innovation Solution
Incorporating a heating element in the recirculation circuit to maintain converter temperature through closed-loop control, bypassing heat exchangers and ammonia separators at low loads, and adjusting heating output based on reactant flow rates to minimize energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the ammonia synthesis plant operates with intermittent renewable energy sources, then sustainability is improved, but the plant cannot maintain continuous operation due to diurnal cycles and energy fluctuations
Solution Approach 1:
The plant performs preliminary action by maintaining the converter at operating temperature through continuous circulation of reactant gases even when hydrogen production is temporarily suspended. This allows the plant to resume operation quickly when energy becomes available again, rather than shutting down completely and requiring lengthy restart procedures
Solution Approach 2:
The recirculation circuit enables continuous circulation of nitrogen and inert gases through the converter, maintaining thermal conditions and catalyst activity continuously. This continuous useful action preserves the plant's readiness to produce ammonia as soon as hydrogen is available, despite intermittent energy supply
2Reliability
If large energy storage means and hydrogen storage means are used to compensate for fluctuations, then operation stability is improved, but device complexity and cost increase
Solution Approach 1:
The plant uses its own recirculation circuit and existing thermal mass to maintain operation during fluctuations, rather than relying on external storage systems. The system serves itself by continuously circulating gases and maintaining temperature through internal heat exchange, eliminating the need for separate large-scale storage infrastructure
Solution Approach 2:
The control system dynamically adjusts operating parameters such as circulation flow rates, heating element output, and reactor temperature based on real-time hydrogen availability. By changing these parameters adaptively, the plant maintains stability without requiring oversized storage means to buffer all fluctuations
3Productivity
If the converter temperature is maintained at least 350°C for reaction to occur, then ammonia synthesis efficiency is improved, but energy consumption increases during low load operation
Solution Approach 1:
The heating element is positioned locally within the recirculation circuit to provide targeted heating only when and where needed. The control system activates heating locally during low-load periods to maintain converter temperature, rather than heating the entire system uniformly, thus minimizing energy consumption while preserving synthesis efficiency
Solution Approach 2:
The heating element operates periodically rather than continuously, activating only when temperature drops below the required 350°C threshold during low-load operation. This periodic heating maintains the necessary thermal conditions for efficient ammonia synthesis while significantly reducing overall energy consumption compared to continuous heating
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
Enables continuous operation of ammonia synthesis plants at varying loads without significant energy storage, effectively managing fluctuations in renewable energy supply and reactant availability.
Implementation Method 1
the recirculation circuit has a heating element (70)... heating output of the heating element is under closed-loop control
Implementation Method 2
The mixture exiting from the converter is guided through the first heat exchanger, where it releases the heat formed by the reaction to a heat carrier medium
Implementation Method 3
the gas mixture is conducted through the second heat exchanger and cooled down (while in return heating the stream flowing toward the converter)
Implementation Method 4
hydrogen is first produced from natural gas, and this is reacted with nitrogen under high pressure and at high temperature over a catalyst
Data Source
AI summary
The present disclosure relates to a process for operating an ammonia synthesis plant, wherein the ammonia synthesis plant has a recirculation circuit, wherein the recirculation circuit comprises a converter, a first heat exchanger, a second heat exchanger, an ammonia separator, a compressor and a reactant feed, characterized in that the recirculation circuit comprises a heating element, wherein in case of partial plant utilization the heating power of the heating element is subjected to closed-loop control according to the reactant gas amount supplied via the reactant feed.