Urea Process Ejector Gas Stream Control
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Solution Overview
Problem
In urea production processes, low availability of liquid ammonia hampers the operation of ejectors, leading to inadequate motive agent for conveying condensate solutions, resulting in suboptimal ammonia-to-carbon dioxide molar ratios and process upsets, especially during reduced capacity operations.
Innovation Solution
Controlling the gas stream leaving the submerged condenser using one or more controlling elements reduces the pressure drop across the ejector, minimizing the need for liquid ammonia as a motive agent, allowing its use for adjusting the ammonia-to-carbon dioxide molar ratio elsewhere in the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If liquid ammonia is used as motive agent for the ejector to transport condensate solution, then the condensate solution can be conveyed from the submerged condenser to the reactor, but the amount of liquid ammonia available for adjusting the ammonia-to-carbon dioxide molar ratio decreases
Solution Approach 1:
The patent extracts the gas stream control function from the ejector system by introducing a separate control valve in the gas line leaving the submerged condenser. This valve independently regulates the gas flow to the stripper, reducing the pressure drop across the ejector and thereby minimizing the liquid ammonia requirement for motive agent while maintaining condensate solution transport capability.
Solution Approach 2:
The patent changes the pressure parameter in the gas stream by introducing a control valve that regulates the gas flow leaving the submerged condenser. By adjusting the pressure drop across the ejector through this valve, the system reduces the motive agent requirement while maintaining effective condensate solution transport to the reactor.
2Quantity of substance
If the process runs at reduced capacity, then ammonia availability for motive agent is improved, but the ammonia-to-carbon dioxide molar ratio control becomes difficult
Solution Approach 1:
The patent separates the gas stream control function from the ejector operation by introducing an independent control valve in the gas line. This extraction of control functions allows independent optimization of both ammonia availability and molar ratio control even during reduced capacity operations.
Solution Approach 2:
The control valve in the gas stream leaving the submerged condenser provides a feedback mechanism that automatically adjusts the gas flow to maintain proper pressure drop across the ejector. This ensures consistent condensate solution transport and stable ammonia-to-carbon dioxide molar ratio control regardless of process capacity variations.
3Reliability
If more liquid ammonia is dosed to the ejector to ensure proper condensate solution transport, then transport reliability is improved, but the ammonia-to-carbon dioxide molar ratio adjustment capability deteriorates
Solution Approach 1:
The patent extracts the gas flow control function from the ejector system by introducing a separate control valve. This separation allows the ejector to operate with minimal liquid ammonia for reliable condensate solution transport, while the control valve independently manages the gas stream to maintain precise ammonia-to-carbon dioxide molar ratio.
Solution Approach 2:
The control valve acts as an intermediary element between the submerged condenser and the stripper gas inlet. It mediates the gas flow to optimize both the ejector performance for condensate transport and the molar ratio control for urea synthesis, eliminating the need for excess liquid ammonia dosing.
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 enables the urea production process to run at lower capacities while maintaining optimal synthesis conditions and ammonia conversion to urea, even with limited ammonia availability.
Implementation Method 1
an ejector, in the line connecting the submerged condenser and the reactor, supporting the transport of the condensate solution from the submerged condenser to the reactor
Implementation Method 2
a submerged condenser, wherein the gas leaving the top of the stripper is, at least partially, condensed to form a condensate solution
Data Source
AI summary
Process for the preparation of urea from ammonia and carbon dioxide in a urea production process comprising, in a high-pressure synthesis section: a. a reactor, wherein ammonia and carbon dioxide react to form a urea-comprising synthesis solution; b. a stripper, wherein the urea-comprising synthesis solution is heated and stripped, optionally in counter-current with a stripping agent; c. a submerged condenser, wherein the gas leaving the top of the stripper is, at least partially, condensed to form a condensate solution and d. an ejector, in the line connecting the submerged condenser and the reactor, supporting the transport of the condensate solution from the submerged condenser to the reactor, wherein a gas stream leaving the top of the submerged condenser is controlled by one or more controlling elements.