System and method for low temperature gasification using an ambient air gasifier

Abstract

A gasification system and control method are provided. Liquid refrigerant is provided to a first ambient air gasifier (AAV) unit. When an output superheat vapor temperature is less than a threshold, liquid refrigerant is provided to a second AAV unit. When greater than or equal to the threshold, it is determined whether the second AAV unit has defrosted. When defrosted, liquid refrigerant is provided to the second AAV unit. When not defrosted, it is determined whether ice has formed on the first AAV unit. When not formed, it is again determined whether the superheat vapor temperature is less than the threshold. When formed, it is determined whether current ambient conditions favor defrosting of the second AAV unit. When not favoring defrosting of the second AAV unit, liquid refrigerant is provided to the second set of AAV units. When favoring defrosting of the second AAV unit, it is again determined whether the superheat vapor temperature is less than the threshold.

Description

Technical Field

[0001] This disclosure relates generally to cryogenic vaporization systems, and more specifically to systems for cryogenic vaporization having ambient air vaporizers (AAVs) arranged in parallel. Background Technology

[0002] like Figure 1 As shown, a typical cryogenic regasification system includes a liquid refrigerant storage tank 102, which supplies liquid refrigerant to a heat exchanger (or vaporizer) 106 via a control valve 104. The control valve 104 can be located upstream or downstream of the heat exchanger 106 and controls the flow of liquid refrigerant to the heat exchanger 106. The heat exchanger 106 vaporizes the liquid refrigerant into superheated vapor. The superheated vapor is supplied to the end user via piping. The classification of the heat exchanger 106 depends on the heating medium used for vaporization. For example, ambient air is used as the heating medium for an AAV, and water or a fluid mixture designed to avoid freezing under ambient conditions is used as the heating medium for a water bath vaporizer (WBV).

[0003] If a regasification system is used continuously to supply gasified gas to end users, it is called a continuous supply system. If a regasification system is used only when the equipment is shut down, it is called a standby system. A standby system can also be used for "peak shaving" when end-user demand exceeds the equipment's capacity, supplying gasified gas to the end user for a period of time. Piping within a regasification system is typically made of stainless steel or another suitable material for low temperatures. However, piping to the end user is usually made of carbon steel, which can become brittle at lower temperatures. Therefore, typical piping standards specify a minimum design temperature for carbon steel.

[0004] An AAV (Atmospheric Vaporizer) system comprises one or more vertically positioned tubes or modules, or a group of AAV units. The exterior of the tube is exposed to the ambient atmosphere and has an extended heat transfer surface. Liquid refrigerant flows inside the tube, where it is vaporized and subsequently superheated, sometimes to near ambient atmospheric temperature.

[0005] AAV units offer significant advantages over other heat exchangers, including, for example, low equipment cost, simple and reliable operation, low maintenance, and low operating costs. However, AAV units have several drawbacks, including, for example, a larger size and footprint due to lower heat transfer performance, and a decrease in heat transfer performance due to icing on the tube surfaces. AAV units can be extremely sensitive to environmental conditions. AAV units can also pose certain safety hazards, such as, for example, ice falling and fogging when a "ground air layer" forms under cooler, heavier air and moister, warmer air. The cold air accumulating around the vaporizer can significantly degrade performance to unacceptable levels during prolonged operation.

[0006] As described above, when the AAV units are in operation, frost can occur on the surface of the finned tubes, thereby causing the capacity to decay over time. To defrost the tubes and thus restore the vaporizer capacity, the AAV units can be constructed in parallel, such that one set is operating while the other set is idle for defrosting.

[0007] Figure 2 is a diagram illustrating a typical AAV regasification system. A liquid refrigerant storage tank 202 stores liquid refrigerant and provides liquid refrigerant to first and second parallel lines. On the first line, a first control valve 204 controls the flow of liquid refrigerant to a first set of AAV units 206. On the second line, a second control valve 208 controls the flow of liquid refrigerant to a second set of AAV units 210. At a given time, only one of the first and second parallel lines is operable, thus, when one control valve is open, the other control valve is closed.

[0008] After the first and second lines are re-engaged, a temperature sensor, such as, for example, a resistance temperature detector (RTD) 212, measures the discharge temperature of the superheated vapor output from the working (operating) set of AAV units (e.g., the first set of AAV units 206 or the second set of AAV units 210). A signal X3 indicative of the measured temperature can be sent from the temperature sensor 212 to the processor or controller.

[0009] A timer 214 tracks the run time of the working set of AAV units (e.g., the first set of AAV units 206 or the second set of AAV units 210). A signal Z2 indicative of the run time can be sent from the timer 214 to the processor or controller. Based on one or more of the discharge temperature and the run time, the processor or controller can send a first control signal 228 to the first control valve 204 and can send a second control signal 230 to the second control valve 208 to switch the idle set and the working set of AAV units.

[0010] Figures 3A to 3C is a flow diagram illustrating a conventional control method for an AAV regasification system. As shown in Figure 3A the control method can be time-based and a fixed time period is preset as a setpoint SP1 for switching the sets of AAV units (e.g., a switching period). The working set of AAV units operates or runs until the run time reaches the setpoint SP1. Specifically, at 302, it is determined whether the working set run time is greater than the setpoint SP1. When the working set run time is greater than the setpoint SP1, at 304, a control signal is sent to the control valve to switch the idle set and the working set of AAV units.

[0011] For example, referring back to Figure 2When the signal Z2 indicates that the count of the timer 214 exceeds the setpoint SP1, the processor or controller sends a first control signal 228 to the first control valve 204 and a second control signal 230 to the second control valve 208. When the first line is running and the second line is idle, the first control signal 228 closes the open first control valve 204 and the second control signal 230 opens the closed second control valve 208, thereby causing the second line to run and the first line to idle. When the second line is running and the first line is idle, the first control signal 228 opens the closed first control valve 204 and the second control signal 230 closes the open second control valve 208, thereby causing the first line to run and the second line to idle.

[0012] As Figure 3B illustrated, the conventional control method can be temperature-based and a fixed temperature is preset as the setpoint SP2 for switching the groups of AAV units. The working group of AAV units runs until the discharge temperature of the superheated vapor drops below the setpoint SP2. Specifically, at 306, it is determined whether the discharge temperature of the superheated vapor from the working group of AAV units is less than the setpoint SP2. When the discharge temperature is less than the setpoint SP2, at 308, a control signal is sent to the control valve to switch the idle group and the working group of AAV units.

[0013] For example, referring back to Figure 2 When the temperature indicated by the signal X3 drops below the setpoint SP2, the processor or controller sends a first control signal 228 to the first control valve 204 and a second control signal 230 to the second control valve 208. When the first line is running and the second line is idle, the first control signal 228 closes the open first control valve 204 and the second control signal 230 opens the closed second control valve 208, thereby causing the second line to run and the first line to idle. When the second line is running and the first line is idle, the first control signal 228 opens the closed first control valve 204 and the second control signal 230 closes the open second control valve 208, thereby causing the first line to run and the second line to idle.

[0014] As Figure 3CAs shown, the conventional control method can be based on both time and temperature. At 310, it is determined whether the discharge temperature of the working set of AAV units is less than a setpoint SP2. When the discharge temperature is less than the setpoint SP2, at 312, a control signal is sent to the control valve to switch the idle and working sets of AAV units. When the discharge temperature is greater than or equal to the setpoint SP2, at 314, it is determined whether the run time of the working set of AAV units is greater than a setpoint SP1. When the run time is greater than the setpoint SP1, at 312, a control signal is sent to the control valve to switch the idle and working sets of AAV units. When the run time is less than or equal to the setpoint SP1, at 310, the discharge temperature is compared to the setpoint SP2.

[0015] For example, referring back to Figure 2 When signal X3 indicates that the temperature detected at temperature sensor 212 has dropped below setpoint SP2, the processor or controller sends control signals 228 and 230 to the first and second control valves 204 and 208 to switch the idle and working sets of AAV units. When signal X3 indicates that the temperature detected at RTD 212 is at or above setpoint SP2, the run time of timer 214 is checked. When signal Z2 indicates that the count of timer 214 exceeds setpoint SP1, the processor or controller sends control signals 228 and 230 to the first and second control valves 204 and 208 to switch the idle and working sets of AAV units.

[0016] Thus, the working set continues to run until one of the thresholds SP1 or SP2 is met. However, the switching is controlled by monitoring only the working set of AAVs, regardless of whether the idle set is fully defrosted. If the idle set is not fully defrosted, its gasification capacity is not fully restored and performance is degraded when it is used as the working set in the next cycle. Moreover, this degradation has the potential to become an infinite loop in which the capacity of both sets of AAV units degrades over time and never recovers.

[0017] Additionally, with respect to Figure 2 and Figure 2 The switching of the AAV sets is controlled by monitoring only the run time and / or discharge temperature of the working set, regardless of the frosting and / or icing characteristics of the working set. Thus, while the run time and / or discharge temperature do not indicate that it is time to switch the AAVs, the frosting and / or icing on the working set can make its defrosting process inefficient and slow when it becomes the idle set in the next cycle. Such frosting and / or icing characteristics include, for example, white frost or frost converting to ice, ice bridging across the tube fins, and ice blocking the space between the tube fins.

[0018] Moreover, with respect to Figures 3A to 3C and Figure 2by monitoring only the vaporizer performance without considering the dynamic changes in the environmental conditions under which the system is operating. The run time and discharge temperature set points that are suitable for one environmental condition can not be suitable for another environmental condition. For example, warm and / or humid environmental conditions can result in faster defrosting and require shorter switching cycles, while cold and / or dry environmental conditions can result in slower defrosting and require longer switching cycles. SUMMARY

[0019] According to one embodiment, a method for controlling a cryogenic vaporization system is provided. Liquid refrigerant is provided to a first set of AAV units via at least one control valve of the cryogenic vaporization system. Superheated vapor is output from the first set of AAV units. A controller of the cryogenic vaporization system determines whether a temperature of the output superheated vapor is less than a temperature threshold. When the temperature of the output superheated vapor is less than the temperature threshold, the at least one control valve switches the supply of liquid refrigerant to a second set of AAV units. The second set of AAV units is connected in parallel with the first set of AAV units. When the temperature of the output superheated vapor is greater than or equal to the temperature threshold, the controller determines whether the second set of AAV units has defrosted. When the second set of AAV units has defrosted, the at least one control valve switches the supply of liquid refrigerant to the second set of AAV units.

[0020] According to one embodiment, a cryogenic vaporization system is provided. The system includes a first set of AAV units and a second set of AAV units, the first set of AAV units being configured to receive liquid refrigerant and output superheated vapor, and the second set of AAV units being configured to receive liquid refrigerant and output superheated vapor. The second set of AAV units is connected in parallel with the first set of AAV units. The system further includes at least one control valve to provide liquid refrigerant to one of the first set of AAV units and the second set of AAV units, and a sensor to detect a temperature of the superheated vapor output from the first set of AAV units and the second set of AAV units. The system further includes a first plurality of sensors to measure a surface temperature at the second set of AAV units. Additionally, the system includes a controller configured to determine, via the sensor, whether the temperature of the superheated vapor is less than a temperature threshold. The controller is further configured to control the at least one control valve to switch the supply of liquid refrigerant to the second set of AAV units when the temperature of the output superheated vapor is less than the temperature threshold. The controller is further configured to determine, based on the first plurality of sensors, whether the second set of AAV units has defrosted when the temperature of the output superheated vapor is greater than or equal to the temperature threshold. Additionally, the controller is configured to control the at least one control valve to switch the supply of liquid refrigerant to the second set of AAV units when the second set of AAV units has defrosted. BRIEF DESCRIPTION OF DRAWINGS

[0021] The above and other aspects, features, and advantages of certain embodiments of the present disclosure will be more apparent from the following detailed description, taken in conjunction with the accompanying drawings, in which:

[0022] Figures 3A to 3C is a diagram illustrating a typical low temperature regasification system;

[0023] Figure 1 is a diagram illustrating a typical AAV regasification system;

[0024] Figure 2 is a flowchart illustrating a conventional control method for an AAV regasification system;

[0025] Figures 3A to 3C is a diagram illustrating an AAV regasification system according to an embodiment of the present disclosure;

[0026] Figure 4 is a flowchart illustrating a control method for an AAV regasification system according to an embodiment of the present disclosure;

[0027] Figure 5 is a block diagram illustrating a controller for controlling an AAV regasification system according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0028] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. It should be noted that the same elements will be designated by the same reference numerals, although they are illustrated in different drawings. In the following description, specific details such as detailed configuration and components are provided in order to assist in a general understanding of the embodiments of the present disclosure. Therefore, it will be apparent to those skilled in the art that various changes in the embodiments described herein can be made without departing from the scope of the present disclosure. In addition, descriptions of well-known functions and configurations are omitted for clarity and conciseness. The terms described below are terms defined in consideration of functions in the present disclosure, and can differ according to users, user's intentions, or habits. Therefore, the definition of the terms should be determined based on the contents of the entire specification.

[0029] The present disclosure can have various modifications and various embodiments, and embodiments thereof are described in detail below with reference to the accompanying drawings. However, it should be understood that the present disclosure is not limited to these embodiments but includes all modifications, equivalents, and alternatives within the scope of the present disclosure.

[0030] Although terms including ordinal numbers such as first, second, etc., may be used to describe various elements, structural elements are not limited by these terms. These terms are used only to distinguish one element from another. For example, a first structural element may be referred to as a second structural element without departing from the scope of this disclosure. Similarly, a second structural element may also be referred to as a first structural element. As used herein, the term "and / or" includes any and all combinations of one or more related items.

[0031] The terminology used herein is for the purpose of describing various embodiments of this disclosure only and is not intended to limit this disclosure. The singular form is intended to include the plural form unless the context clearly indicates otherwise. In this disclosure, it should be understood that the terms “comprising” or “having” indicate the presence of a feature, quantity, step, operation, structural element, component, or combination thereof, and do not preclude the possibility of the presence or addition of one or more other features, quantities, steps, operations, structural elements, components, or combinations thereof.

[0032] Unless otherwise defined, all terms used herein have the same meaning as understood by one of ordinary skill in the art to which this disclosure pertains. Terms such as those defined in commonly used dictionaries are to be interpreted as having the same meaning as in the context of the relevant technical field and are not to be interpreted as having an ideal or overly formal meaning unless clearly defined in this disclosure.

[0033] Now for reference Figure 6 The figure illustrates an AAV regasification system according to an embodiment of the present disclosure. A liquid refrigerant storage tank 402 stores liquid refrigerant and supplies it to first and second parallel lines. On the first line, a first control valve 404 controls the flow of liquid refrigerant to a first group of AAV units 406. On the second line, a second control valve 408 controls the flow of liquid refrigerant to a second group of AAV units 410. At any given time, only one of the first and second parallel lines is operational; therefore, when one control valve is open, the other control valve is closed. Alternative embodiments may include one or more additional parallel lines to the AAV units, and a different number of control valves and groups on each line.

[0034] After the liquid refrigerant is re-gasified and the first and second lines are re-engaged, a first temperature sensor, such as, for example, RTD 412, measures the discharge temperature of the superheated vapor output from the working set (e.g., the first set of AAV units 406 or the second set of AAV units 410) of AAV units. A signal X3 can be sent from the first temperature sensor 412 to the controller or processor for use by the controller or processor to determine whether to switch the idle and working sets of AAV units via control of the first and second control valves 404, 408. In alternative embodiments, the controller or processor can be embodied as a model predictive controller (MPC) 426.

[0035] A second temperature sensor 416 is disposed on the first set of AAV units 406 that measures the temperature at a disposed location on the first set of AAV units 406. The second temperature sensor can be embodied as a thermocouple or an RTD. In alternative embodiments, multiple temperature sensors are disposed at multiple locations on the first set of AAV units 406. In particular, the second temperature sensor 416 is placed on the finned tubes of the first set of AAV units 406. Alternative embodiments can utilize other temperature measurement devices without departing from the scope of the present disclosure. A signal X1 with temperature information can be sent from the second temperature sensor 416 to the controller or processor (or MPC 426) for use by the controller or processor in conjunction with other received signals to determine whether to switch the idle and working sets of AAV units via control of the first and second control valves 404, 408.

[0036] A third temperature sensor 418 is disposed on the second set of AAV units 410 that measures the temperature at a disposed location on the second set of AAV units 410. The third temperature sensor can be embodied as a thermocouple or an RTD. In alternative embodiments, multiple temperature sensors are disposed at multiple locations on the second set of AAV units 410. In particular, the third temperature sensor 418 is placed on the finned tubes of the second set of AAV units 410. Alternative embodiments can utilize other temperature measurement devices without departing from the scope of the present disclosure. A signal X2 with temperature information can be sent from the third temperature sensor 418 to the controller or processor (or MPC 426) for use by the controller or processor in conjunction with other received signals to determine whether to switch the idle and working sets of AAV units via control of the first and second control valves 404, 408.

[0037] A first infrared (IR) camera unit 420 is disposed within the field of view of the first set of AAV units 406 that captures thermal imaging of the finned tubes of the first set of AAV units 406 using infrared radiation. In alternative embodiments, multiple IR camera units are disposed within the field of view of the first set of AAV units 406. Alternative embodiments can also utilize other thermal imaging devices without departing from the scope of the disclosure. The signal Y1 of the thermal imaging can be sent from the first IR camera unit 420 to the controller or processor (or MPC 426) for analysis to determine the profile and behavior of frost and ice on the finned tubes of the first set of AAV units 406. The profile and behavior of frost and ice are used by the controller or processor in conjunction with other received signals to determine whether to switch the idle and working sets of AAV units via control of the first control valve 404 and the second control valve 408.

[0038] A second IR camera unit 422 is disposed within the field of view of the second set of AAV units 410 that captures thermal imaging of the finned tubes of the second set of AAV units 410 using infrared radiation. In alternative embodiments, multiple IR camera units are disposed within the field of view of the second set of AAV units 410. Alternative embodiments can also utilize other thermal imaging devices without departing from the scope of the disclosure. The signal Y2 of the thermal imaging can be sent from the second IR camera unit 422 to the controller or processor (or MPC 426) for analysis to determine the profile and behavior of frost and ice on the finned tubes of the second set of AAV units 410. The profile and behavior of frost and ice are used by the controller or processor in conjunction with other received signals to determine whether to switch the idle and working sets of AAV units via control of the first control valve 404 and the second control valve 408.

[0039] A weather station 424 is installed and used to monitor changes in environmental weather conditions, including, for example, ambient temperature, humidity, wind, and precipitation. The weather station 424 is in communication with the MPC 426, and the monitored changes in environmental weather conditions are sent from the weather station 424 to the MPC 426.

[0040] A timer 414 tracks the run time of the working set of AAV units (e.g., the first set of AAV units 406 or the second set of AAV units 410) based on a preset switching period of the first and second AAV units. This switching period is initially preset by the MPC 426 based on the environmental weather conditions received from the weather station 424. The remaining run time of the working set of AAV units relative to the switching period is provided by the timer 414 to the MPC 426.

[0041] The monitored weather changes and remaining run times are used in combination by the MPC 426 to generate a signal Z1 that indicates whether favorable environmental conditions exist for defrosting the idle set of AAV units. The signal Z1 is sent to a processor or controller (or still present in the MPC 426) and combined with other received signals to determine whether to switch the idle and working sets of AAV units via control of the first and second control valves 404, 408.

[0042] When the signals X1, X2, X3, Y1, Y2, and Z1 are received, the processor or controller (or MPC 426) determines whether to switch the idle and working sets of AAV units. When it is determined to switch the idle and working sets of AAV units, the processor or controller (or MPC 426) sends a first control signal 428 to the first control valve 404 and a second control signal 430 to the second control valve 408. One of the first and second control signals 428, 430 is a signal to open the closed control valve and the other of the first and second control signals 428, 430 is a signal to close the open control valve, thereby enabling switching of the idle and working sets of AAV units.

[0043] Figure 4 is a flowchart illustrating a method for controlling an AAV regasification system according to embodiments of the present disclosure. As described above with respect to Figure 5 the additional conditions are obtained and utilized to determine whether to switch the idle and working sets of AAV units via control valves.

[0044] Initially, at 502, the MPC 426 calculates a switching period for the first and second AAV units based on environmental conditions. The environmental conditions are provided to the MPC 426 from the weather station 424 and the switching period is provided to the timer 414 from the MPC 426 as a switching period or setpoint SP1. The setpoint SP1 can be dynamically calculated as the environmental conditions dynamically change. The switching period can be in the range of 1 hour to 8 hours.

[0045] At 504, it is determined whether the discharge temperature of the superheated vapor from the working set of AAV units is less than a setpoint SP2. When the discharge temperature is less than the setpoint SP2, at 506, the control valves switch the idle and working sets of AAV units. According to one embodiment, SP2 can be set to about -20°F.

[0046] For example, referring back to Figure 4When signal X3 indicates that the temperature detected at the first temperature sensor 412 has dropped below the setpoint SP2, the processor or controller (or MPC 426) sends control signals to the first control valve 404 and the second control valve 408. When the first pipeline is running and the second pipeline is idle upon receiving signal X3, the first control signal 428 closes the first control valve 404 and the second control signal 430 opens the second control valve 408, thereby running the second pipeline and idling the first pipeline. When the second pipeline is running and the first pipeline is idle upon receiving signal X3, the second control signal 430 closes the second control valve 408 and the first control signal 428 opens the first control valve 404, thereby running the first pipeline and idling the second pipeline.

[0047] When the discharge temperature is greater than or equal to setpoint SP2, at 508, it is determined whether the idle group of the AAV unit has been defrosted. This determination is made by the processor or controller (or MPC 426) based on a signal (X1 or X2) indicating the temperature and transmitted from a temperature sensor located on the finned tube of the idle group of the AAV unit. Figure 4 The signal is received from the 416 or 418. This determination is also made by the processor or controller based on the thermal imaging signal (Y1 or Y2) of the finned tubes of the idle group of the AAV unit, which is received from the IR camera unit pointing to the idle group of the AAV unit. Figure 4 The thermal image (420 or 422) is received. The processor or controller (or MPC 426) analyzes the thermal image to determine the profile and behavior of frost and ice on the finned tubes of the idle group of the AAV unit. Therefore, based on the received temperature information and the determined profile and behavior of frost and ice, it is determined whether the idle group of the AAV unit has been defrosted. For example, if the surface temperature of the finned tube has reached the minimum of the ambient temperature and 0°C, the idle group can be considered defrosted. Alternatively, if the thermal image indicates that no frost or ice remains on the surface of the finned tube, the idle group can be considered defrosted.

[0048] When it is determined that the idle group of the AAV unit has been defrosted, at point 506, the control valve switches the idle group and the working group of the AAV unit. For example, re-referencing Figure 4 The processor or controller (or MPC 426) sends a first control signal 428 and a second control signal 430 to a first control valve 404 and a second control valve 408, thereby switching the idle group and the working group of the AAV unit as described above. When the idle group of the AAV unit has been fully defrosted, this prevents any additional buildup of frost or ice on the working group of the AAV unit, thus preventing unnecessary additional defrosting in subsequent cycles and improving the efficiency of the regasification system.

[0049] When it is determined that the idle group of the AAV unit has not been defrosted, at 510, it is determined whether the working group of the AAV unit shows signs of frost turning into ice or ice bridging or blockage on the finned tubes. This determination is made by the processor or controller (or MPC 426) based on a signal (X1 or X2) indicating the temperature and transmitted from a temperature sensor located on the finned tubes of the working group of the AAV unit. Figure 4 The received temperature information (416 or 418) is used to determine whether the frost or ice on the finned tubes of the AAV unit is bridging the airflow. This determination is also made by the processor or controller (or MPC 426) based on the thermal imaging signal (Y1 or Y2) of the working group of the AAV unit. The processor or controller (or MPC 426) analyzes the thermal imaging to determine the profile and behavior of frost and ice on the finned tubes of the working group of the AAV unit. Therefore, based on the received temperature information and the determined profile and behavior of frost and ice, it is determined whether the working group of the AAV unit shows signs of frost turning into ice or of ice bridging or ice blockage.

[0050] For example, if the surface temperature of a finned tube has dropped to a threshold or range, it indicates that frost has turned into ice. However, this threshold or range depends on specific environmental conditions (e.g., temperature, humidity, and wind) and specific process conditions (e.g., fluid type, inlet temperature and pressure, and flow rate). Thermal imaging can display the temperature field and the profile of frost and / or ice, indicating whether ice bridging or ice blockage has occurred.

[0051] When it is determined that the working group of the AAV unit does not show any signs of frost turning into ice on the finned tubes, or of ice bridging or blockage, the superheated steam discharge temperature at 504 is rechecked and compared with the setpoint SP2. Therefore, the working group of the AAV unit is allowed to continue operating, while the idle group of the AAV unit continues defrosting.

[0052] When it is determined that the working group of AAV units exhibits signs of frost turning into ice on the finned tubes, or the presence of ice bridges or ice blockages, at point 512, it is determined whether the idle group of AAV units is under environmental conditions favorable for defrosting. This determination is made by the processor or controller (or MPC 426) based on signals received from weather station 424, which monitors environmental weather conditions including, for example, changes in ambient temperature, humidity, wind, and precipitation. This determination is also made by the processor or controller (or MPC 426) based on the amount of remaining operating time of the working group of AAV units, which is based on a preset switching cycle and a setpoint SP1 at timer 414. MPC 426 generates signal Z1 based on the environmental weather conditions and the remaining operating time in the switching cycle of the AAV unit group.

[0053] is also determined by the processor or controller (or MPC 426) based on a signal (XI or X2) indicative of temperature and received from a temperature sensor (416 or 418) disposed on the finned tubes of the idle group of AAV units, which signal is indicative of the ambient weather conditions. The determination is also made by the processor or controller based on a signal (Yl or Y2) of thermal imaging of the finned tubes of the idle group of AAV units, which signal is received from an IR camera unit (420 or 422) directed at the idle group of AAV units. The processor or controller (or MPC 426) analyzes the thermal imaging to determine the profile and behavior of frost and ice on the finned tubes of the idle group of AAV units. Figure 4 Figure 4 is also determined by the processor or controller (or MPC 426) based on a signal (XI or X2) indicative of temperature and received from a temperature sensor (416 or 418) disposed on the finned tubes of the idle group of AAV units, which signal is indicative of the ambient weather conditions. The determination is also made by the processor or controller based on a signal (Yl or Y2) of thermal imaging of the finned tubes of the idle group of AAV units, which signal is received from an IR camera unit (420 or 422) directed at the idle group of AAV units. The processor or controller (or MPC 426) analyzes the thermal imaging to determine the profile and behavior of frost and ice on the finned tubes of the idle group of AAV units.

[0054] is also determined by the processor or controller (or MPC 426) based on a signal (XI or X2) indicative of temperature and received from a temperature sensor (416 or 418) disposed on the finned tubes of the idle group of AAV units, which signal is indicative of the ambient weather conditions. The determination is also made by the processor or controller based on a signal (Yl or Y2) of thermal imaging of the finned tubes of the idle group of AAV units, which signal is received from an IR camera unit (420 or 422) directed at the idle group of AAV units. The processor or controller (or MPC 426) analyzes the thermal imaging to determine the profile and behavior of frost and ice on the finned tubes of the idle group of AAV units.

[0055] is also determined by the processor or controller (or MPC 426) based on a signal (XI or X2) indicative of temperature and received from a temperature sensor (416 or 418) disposed on the finned tubes of the idle group of AAV units, which signal is indicative of the ambient weather conditions. The determination is also made by the processor or controller based on a signal (Yl or Y2) of thermal imaging of the finned tubes of the idle group of AAV units, which signal is received from an IR camera unit (420 or 422) directed at the idle group of AAV units. The processor or controller (or MPC 426) analyzes the thermal imaging to determine the profile and behavior of frost and ice on the finned tubes of the idle group of AAV units.

[0056] is also determined by the processor or controller (or MPC 426) based on a signal (XI or X2) indicative of temperature and received from a temperature sensor (416 or 418) disposed on the finned tubes of the idle group of AAV units, which signal is indicative of the ambient weather conditions. The determination is also made by the processor or controller based on a signal (Yl or Y2) of thermal imaging of the finned tubes of the idle group of AAV units, which signal is received from an IR camera unit (420 or 422) directed at the idle group of AAV units. The processor or controller (or MPC 426) analyzes the thermal imaging to determine the profile and behavior of frost and ice on the finned tubes of the idle group of AAV units.

[0057] is also determined by the processor or controller (or MPC 426) based on a signal (XI or X2) indicative of temperature and received from a temperature sensor (416 or 418) disposed on the finned tubes of the idle group of AAV units, which signal is indicative of the ambient weather conditions. The determination is also made by the processor or controller based on a signal (Yl or Y2) of thermal imaging of the finned tubes of the idle group of AAV units, which signal is received from an IR camera unit (420 or 422) directed at the idle group of AAV units. The processor or controller (or MPC 426) analyzes the thermal imaging to determine the profile and behavior of frost and ice on the finned tubes of the idle group of AAV units. Figure 6 is also determined by the processor or controller (or MPC 426) based on a signal (XI or X2) indicative of temperature and received from a temperature sensor (416 or 418) disposed on the finned tubes of the idle group of AAV units, which signal is indicative of the ambient weather conditions. The determination is also made by the processor or controller based on a signal (Yl or Y2) of thermal imaging of the finned tubes of the idle group of AAV units, which signal is received from an IR camera unit (420 or 422) directed at the idle group of AAV units. The processor or controller (or MPC 426) analyzes the thermal imaging to determine the profile and behavior of frost and ice on the finned tubes of the idle group of AAV units. ​

[0058] After switching the idle group and the working group of AAV units at 506, at 502, the controller or processor (or MPC 426) recalculates the switching period for the first AAV unit and the second AAV unit based on the environmental conditions. Alternatively, at 504, the discharge temperature of the superheated vapor can be rechecked and compared to the setpoint SP2 without recalculating the switching period.

[0059] The reliability, efficiency, and flexibility of the AAV regasification system described above is improved by monitoring not only the working group performance but also the defrosting of the idle group, the frost / ice characteristics of the working group, and the dynamic changes in the environmental conditions under which the system is operating.

[0060] Potential capital savings can be realized by designing the AAV regasification system for typical, but not necessarily the worst, environmental conditions in the geographic location. Embodiments of the present disclosure can help to effectively operate the AAV regasification system under adverse environmental conditions.

[0061] ​ is a block diagram illustrating a controller for controlling an AAV regasification system according to one embodiment. The processor or controller can be embodied as an MPC and can include at least one user input device 602 and a memory 604. The memory 604 can include instructions that allow the processor 606 to analyze thermal imaging and determine when to switch the idle group and the working group of AAV units.

[0062] The apparatus also includes a processor 606 for determining when to switch between the parallel paths of groups of AAV units. For example, the processor 606 can accept inputs from the first temperature sensor 412, the second temperature sensor 416, the third temperature sensor 418, the first IR camera unit 420, the second IR camera unit 422, the weather station 424, and the timer 414 and utilize such inputs to determine when to switch between groups of AAV units. The processor can also control the first control valve 404 and the second control valve 408 to effect the switch. In addition, the processor can analyze thermal imaging from the first IR camera unit 420 and the second IR camera unit 422 and determine the run time of the timer 414 based on inputs from the weather station 424. Further, the apparatus can include a communication interface 608 that receives signals such as, for example, X1, X2, X3, Y1, Y2, and Z1 and transmits signals such as, for example, the first control signal 428 and the second control signal 430.

[0063] While certain embodiments of the present disclosure have been described in the detailed description of the disclosure, the disclosure can be modified in various forms without departing from the scope of the disclosure. Accordingly, the scope of the disclosure should not be determined solely based on the described embodiments, but based on the claims and their equivalents.

Claims

1. A method for controlling a cryogenic gasification system, the method comprising: providing liquid refrigerant to a first set of ambient air gasification units via at least one control valve of the cryogenic gasification system; outputting superheated vapor from the first set of ambient air gasification units; determining, by a controller of the cryogenic gasification system, whether a temperature of the output superheated vapor is less than a temperature threshold; when the temperature of the output superheated vapor is less than the temperature threshold, switching the supply of the liquid refrigerant to a second set of ambient air gasification units via the at least one control valve, wherein the second set of ambient air gasification units are connected in parallel with the first set of ambient air gasification units; monitoring defrosting of the second set of ambient air gasification units using at least one of an infrared camera and a temperature sensor associated with the second set of ambient air gasification units; when the temperature of the output superheated vapor is greater than or equal to the temperature threshold, determining, by the controller, whether the second set of ambient air gasification units have defrosted; when the second set of ambient air gasification units have defrosted, switching the supply of the liquid refrigerant to the second set of ambient air gasification units via the at least one control valve.

2. The method of claim 1, further comprising detecting the temperature of the output superheated vapor via a sensor.

3. The method of claim 1, further comprising: when the second set of ambient air gasification units have not defrosted, determining, by the controller, whether icing has occurred on the first set of ambient air gasification units; when icing has not occurred on the first set of ambient air gasification units, repeating the step of determining whether a temperature of the output superheated vapor is less than the temperature threshold.

4. The method of claim 3, further comprising monitoring icing on the first set of ambient air gasification units using at least one of an infrared camera and a temperature sensor associated with the first set of ambient air gasification units.

5. The method of claim 3, further comprising: when icing has occurred on the first set of ambient air gasification units, determining, by the controller, whether current environmental conditions are conducive to defrosting the second set of ambient air gasification units; when the current environmental conditions are not conducive to defrosting the second set of ambient air gasification units, switching the supply of the liquid refrigerant to the second set of ambient air gasification units via the at least one control valve; and when the current environmental conditions are conducive to defrosting the second set of ambient air gasification units, repeating the step of determining whether a temperature of the output superheated vapor is less than the temperature threshold.

6. The method of claim 5, further comprising determining the current environmental conditions based on at least one of: current ambient weather monitored at a weather station coupled to the controller, a remaining run time of the first set of ambient air gasification units, a temperature of the second set of ambient air gasification units, and a profile and behavior of frost and ice at the second set of ambient air gasification units.

7. A cryogenic gasification system, the system comprising: ​ a first set of ambient air gasification units configured to receive a liquid refrigerant and output a superheated vapor; a second set of ambient air gasification units configured to receive the liquid refrigerant and output the superheated vapor, the second set of ambient air gasification units connected in parallel with the first set of ambient air gasification units; at least one control valve providing liquid refrigerant to one of the first set of ambient air gasification units and the second set of ambient air gasification units; a sensor detecting a temperature of the superheated vapor output from the first set of ambient air gasification units and the second set of ambient air gasification units; a first plurality of sensors measuring a surface temperature at the second set of ambient air gasification units, the first plurality of sensors including at least one of an infrared camera and a temperature sensor; a controller configured to: determine, via the sensor, whether the temperature of the superheated vapor is less than a temperature threshold; when the temperature of the output superheated vapor is less than the temperature threshold, control the at least one control valve to switch supply of the liquid refrigerant to the second set of ambient air gasification units; when the temperature of the output superheated vapor is greater than or equal to the temperature threshold, determine, based on the first plurality of sensors, whether the second set of ambient air gasification units has defrosted; and when the second set of ambient air gasification units has defrosted, control the at least one control valve to switch supply of the liquid refrigerant to the second set of ambient air gasification units.

8. The cryogenic gasification system of claim 7, further comprising a second plurality of sensors measuring a surface temperature at the first set of ambient air gasification units, wherein the controller is further configured to: when the second set of ambient air gasification units has not defrosted, determine, based on the second plurality of sensors, whether ice has formed on the first set of ambient air gasification units; and when ice has not formed on the first set of ambient air gasification units, repeat the step of determining whether the temperature of the output superheated vapor is less than the temperature threshold.

9. The cryogenic gasification system of claim 8, wherein the second plurality of sensors includes at least one of an infrared camera and a temperature sensor associated with the first set of ambient air gasification units.

10. The cryogenic gasification system of claim 8, further comprising a weather station coupled to the controller and monitoring current ambient weather conditions, wherein the controller is further configured to: when ice has formed on the first set of ambient air gasification units, determine, based on the weather station, whether current ambient conditions are conducive to defrosting the second set of ambient air gasification units; when the current ambient conditions are not conducive to defrosting the second set of ambient air gasification units, control the at least one control valve to switch supply of the liquid refrigerant to the second set of ambient air gasification units; and repeating the step of determining whether the temperature of the output superheated vapor is less than the temperature threshold, beginning when the current environmental conditions are favorable for defrosting the second set of ambient air gasification units.

11. The cryogenic gasification system of claim 10, wherein the controller is further configured to: determine the current environmental conditions based on at least one of: the current environmental weather conditions, a remaining run time of the first set of ambient air gasification units, a temperature at the second set of ambient air gasification units, and a profile and behavior of frost and ice at the second set of ambient air gasification units.

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