Cryogenic Tank Pressure Control via Level-Dependent Vaporization
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Solution Overview
Problem
Existing bulk cryogenic liquid storage and dispensing systems face challenges in maintaining consistent supply pressure, leading to inefficiencies and product losses, especially near the bottom of the tank, due to fluctuations in liquid level and vapor pressure, which affects the quality and flow rate of cryogenic liquids in applications like food freezing.
Innovation Solution
A system and method that includes a pressure builder with parallel and series heat exchangers, a programmable logic controller, and sensors to maintain a constant pressure by adjusting the vapor pressure and liquid level, using a baffle for stratification and a vent valve to manage pressure, ensuring consistent cryogenic liquid dispensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a mechanical pressure regulator is used at the top of the bulk tank, then the tank can operate at low liquid levels, but the supply pressure fluctuates and product losses occur near the bottom of the tank
Solution Approach 1:
The invention changes the control parameter from mechanical pressure regulation to electronic control based on liquid level detection. The system uses a level sensor to detect liquid level and a controller to adjust the pressure regulator accordingly, maintaining consistent supply pressure throughout the tank discharge process rather than allowing pressure to fluctuate with liquid level changes
Solution Approach 2:
The system implements feedback control by using a level sensor to continuously monitor liquid level and feed this information to a controller. The controller then adjusts the pressure regulator to maintain consistent supply pressure, creating a closed-loop control system that compensates for liquid level changes and prevents product losses
2Quantity of substance
If the pressure regulator is set to provide enough pressure at low liquid levels, then the tank can be fully utilized, but the supply pressure is higher than necessary when the tank is full
Solution Approach 1:
The system transitions from a static pressure regulator setting to a dynamic control system that adjusts pressure regulation based on real-time liquid level conditions. The controller modifies the pressure regulator settings dynamically as the liquid level changes, optimizing pressure usage throughout the tank discharge cycle and reducing unnecessary energy consumption when the tank is full
Solution Approach 2:
The control parameter (pressure regulation setting) is changed dynamically based on liquid level. Instead of maintaining a constant high pressure setting throughout, the system adjusts the pressure parameter according to the liquid level, reducing pressure when the tank is full and maintaining adequate pressure only when needed at lower levels
3Productivity
If fresh liquid is delivered to restore pressure conditions, then the liquid flow rate is restored, but the tank cannot take a full trailer load and energy is wasted
Solution Approach 1:
The system uses its own level sensor and controller to automatically detect and respond to low liquid level conditions. Instead of requiring external intervention (expedited delivery) to restore proper operating conditions, the system self-monitors and can trigger alerts or automatic refilling operations, eliminating the need for wasteful premature deliveries
Solution Approach 2:
The level sensor provides advance warning before the tank reaches a critical low level. This preliminary detection allows for planned refilling operations rather than emergency deliveries, enabling the tank to be filled to its full capacity and avoiding unnecessary energy waste from premature or partial deliveries
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 maintains a consistent cryogenic liquid flow rate and quality by stabilizing pressure, reducing energy waste and enabling full utilization of the tank capacity, improving snow yield and refrigeration capacity, and allowing for efficient subcooling, thus enhancing production throughput and reducing carbon dioxide consumption.
Implementation Method 1
A first aspect of the present invention provides a system for dispensing a cryogenic liquid... a pressure builder having an inlet in communication with a bottom portion of the interior of the bulk tank and an outlet in communication with a top portion of the interior of the bulk tank
Implementation Method 2
vaporizing liquid from a bottom portion of the bulk tank and directing it to a top portion of the bulk tank
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A system for dispensing cryogenic liquid to a use point includes a bulk tank containing a supply of cryogenic liquid and a pressure builder that is in communication with the tank via a pressure building valve. The pressure builder uses heat exchangers to vaporize a portion of the cryogenic liquid as needed to pressurize the bulk tank. The pressurized cryogenic liquid is dispensed through a dispensing line running from the bottom of the tank. A vent valve also vents vapor from the tank to control pressure. Operation of the vent and pressure building valves is automated by a controller that receives data from sensors. The controller determines the required saturation pressure for the tank and varies the tank pressure to match and provide a generally constant outlet pressure depending on conditions of the cryogenic liquid.