Urea Synthesis Density Measurement via Condensed Liquid Phase
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Solution Overview
Problem
Conventional methods for measuring the density of urea synthesis solutions at the outlet of a synthesis reactor face challenges due to gas-liquid two-phase flows, leading to inaccurate measurements and difficulties in grasping the operating conditions, particularly the N/C ratio, in urea manufacturing plants.
Innovation Solution
A method and apparatus that involve a reaction step to produce a urea synthesis solution, a stripping step to separate unreacted gases, a condensing step to obtain a condensed liquid, and a recycling step, with online measurement of the density and temperature of the condensed liquid using a noncontact radiation type density meter to determine the N/C value, allowing for accurate control of the N/C ratio by adjusting the flow rates of ammonia and carbon dioxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If density measurement is performed on urea synthesis solution at the outlet of synthesis reactor, then real-time monitoring of operating conditions is achieved, but measurement accuracy deteriorates due to gas-liquid two-phase flow
Solution Approach 1:
The patent extracts the measurement object from the problematic gas-liquid two-phase flow environment at the reactor outlet and relocates it to the condensed liquid stream after the condenser. By measuring density in the condensed liquid phase where gas-liquid separation has already occurred, the measurement is performed under favorable single-phase conditions that eliminate the accuracy deterioration caused by two-phase flow interference.
Solution Approach 2:
The patent introduces condensed liquid as an intermediary medium for indirect measurement. Instead of directly measuring the problematic synthesis solution at the reactor outlet, the system uses the condensed liquid (which has undergone phase separation) as an intermediary to infer the N/C ratio of the original synthesis solution, thereby avoiding direct measurement in the two-phase flow environment.
2Productivity
If conventional density measurement method is used at synthesis reactor outlet, then real-time monitoring is possible, but operating condition assessment accuracy deteriorates
Solution Approach 1:
The patent extracts the measurement function from the synthesis reactor outlet environment and relocates it to the condenser outlet where condensed liquid flows. This extraction allows real-time monitoring to be maintained while eliminating the source of measurement errors associated with two-phase flow, thereby improving operating condition assessment accuracy.
Solution Approach 2:
The patent changes the measurement parameter location from the high-temperature high-pressure synthesis solution at the reactor outlet to the condensed liquid at the condenser outlet. This parameter change in measurement location transforms the measurement conditions from problematic two-phase flow to favorable single-phase liquid conditions, improving both real-time monitoring capability and assessment accuracy.
3Loss of information
If measurement is performed on synthesis solution at reactor outlet, then direct process monitoring is achieved, but measurement reliability deteriorates due to two-phase flow
Solution Approach 1:
The patent uses condensed liquid as an intermediary to reliably transmit information about the synthesis process conditions. The condensed liquid, being in a stable single-phase state, provides a reliable measurement medium that accurately reflects the N/C ratio of the original synthesis solution without the reliability deterioration caused by two-phase flow variability.
Solution Approach 2:
The patent extracts the measurement from the unreliable two-phase flow environment and places it in the reliable condensed liquid stream. This extraction maintains full information availability about operating conditions (N/C ratio) while dramatically improving measurement reliability by eliminating the instability inherent in two-phase flow measurements.
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 accurate and real-time measurement of the N/C ratio in the synthesis reactor, improving the controllability of the urea synthesis process and stabilizing the operating conditions by avoiding the complexities of gas-liquid two-phase flows and enhancing the measurement accuracy.
Implementation Method 1
a condensing step of obtaining a condensed liquid by condensing the gas mixture in an absorbing medium while cooling the gas mixture
Implementation Method 2
a noncontact type density meter be used to measure the density... the noncontact type density meter be a radiation type density meter
Data Source
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AI summary
In a process and an apparatus for synthesizing urea which synthesize urea from ammonia and carbon dioxide, the operating condition can be grasped easily and with good accuracy. A process for synthesizing urea which includes: a reaction step of obtaining a urea synthesis solution which contains urea, unreacted ammonia, unreacted carbon dioxide and water by causing ammonia and carbon dioxide to react with each other; a stripping step of separating a gas mixture containing the unreacted ammonia and the unreacted carbon dioxide by stripping the urea synthesis solution by using at least a portion of raw material carbon dioxide; a condensing step of obtaining a condensed liquid by condensing the gas mixture in an absorbing medium while cooling the gas mixture; a recycling step of recycling the condensed liquid to the reaction step; and a step of measuring the density of the condensed liquid online. An apparatus for carrying out this process is provided.