Pump Start Process for Urea Solution Temperature Control
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Solution Overview
Problem
Existing systems for starting pumps that handle aqueous urea solutions, used in SCR processes for reducing NOx emissions, face challenges in determining optimal actuation time, leading to potential pump damage or suboptimal pollution control due to under or overestimation of starting time, especially in varying temperature conditions.
Innovation Solution
A process that determines the temperature of the liquid in the tank and compares it to a setpoint temperature, heating the tank if necessary, and then actuates the pump to maintain a stable outlet pressure, using a controller and heating elements to ensure safe and efficient operation, particularly for eutectic water/urea solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pump actuation time is underestimated to enable faster operation, then productivity is improved, but the pump may be damaged due to insufficient melting time
Solution Approach 1:
The system performs preliminary heating of the urea solution tank before pump actuation. The control unit activates heating elements to raise the solution temperature above its freezing point, ensuring the solution is in liquid state before the pump starts operating, thus preventing damage from pumping crystallized material.
Solution Approach 2:
The system uses temperature sensors to continuously monitor the urea solution temperature and provides feedback to the control unit. Based on this feedback, the control unit adjusts the heating duration and intensity, and determines the optimal pump start time, creating a closed-loop control system that adapts to actual thermal conditions.
2Reliability
If the pump actuation time is overestimated to ensure safe operation, then reliability is improved, but the system performance deteriorates due to delayed operation
Solution Approach 1:
The system dynamically adjusts the pump actuation timing based on real-time temperature measurements and thermal model calculations. Rather than using fixed conservative delays, the control unit computes the precise moment when sufficient liquid has melted, allowing the pump to start as early as safely possible, optimizing both reliability and productivity.
Solution Approach 2:
The system changes the operational parameters (heating power, heating duration, pump start time) based on the measured initial temperature of the urea solution. The control unit uses thermal data to calculate required heating time and adjusts the actuation schedule dynamically, allowing faster operation when temperatures are already favorable while maintaining safety margins.
3Measurement precision
If experimental data from cold room tests is used to determine actuation time, then measurement precision is improved, but the results do not account for practical variability such as wind and vibrations
Solution Approach 1:
The system incorporates safety margins and robustness factors into the thermal model predictions. The control unit adds time buffers and temperature thresholds that account for unexpected variations in real-world conditions (wind, vibrations, thermal losses), cushioning against the differences between controlled test environments and actual operating conditions.
Solution Approach 2:
The system uses its own operational sensors and control mechanisms to adapt to real conditions during actual use. Rather than relying solely on pre-characterized experimental data, the system continuously monitors actual thermal response and adjusts future actuation decisions based on observed performance, allowing it to self-calibrate to its specific installation environment.
4Device complexity
If thermodynamic and thermal data calculations are used to determine actuation time, then device complexity is reduced, but the results do not account for practical parameters of variability
Solution Approach 1:
The system introduces an empirical thermal model as an intermediary between simple thermodynamic calculations and complex real-world behavior. This model incorporates experimentally determined heat transfer coefficients and thermal capacitances that capture practical effects (convection, radiation, conduction variations) without requiring full computational complexity, bridging the gap between theory and practice.
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 process optimizes the pump starting time, preventing damage and ensuring optimal system performance by maintaining stable pressure within acceptable margins, even in low-temperature conditions, thereby enhancing the reliability and efficiency of the SCR system.
Implementation Method 1
a heating device to liquefy the solution... the tank is heated for a time t1
Implementation Method 2
the pump is actuated for a time t2 during which the pump outlet pressure is measured
Implementation Method 3
injected into the exhaust gas stream where it is hydrolysed before converting the nitrogen oxide (NOx) to nitrogen (N2) and water (H2O)
Data Source
Figure 1
Figure 2
AI summary
Process for starting a pump intended to pump a liquid contained in a tank and to produce a substantially constant outlet pressure (setpoint pressure), according to which: 1. the temperature (T1) of the liquid held in the tank is determined and compared to a setpoint temperature (T0); 2. if the temperature (T1) is greater than the setpoint temperature (T0), the pump is actuated; 3. if the temperature (T1) is less than or equal to the setpoint temperature (T0), the tank is heated for a time tl; then 4. the pump is actuated for a time t2 during which the pump outlet pressure is measured; 5. if this pressure is stable and in an acceptable margin of the setpoint pressure, the pump is kept going; 6. if this pressure is not stable and/or is not in the acceptable margin of the setpoint pressure, the pump is stopped and the tank is heated for a time t3, at the end of which steps 4 to 6 are repeated.