types of vaporizers used for cryogenics

In-Depth Guide to Cryogenic Vaporizers

Cryogenic vaporizers are essential for handling and utilising cryogenic liquids, transforming them into gases for various industrial and commercial applications. These vaporizers use different methods to heat and vaporize cryogenic liquids, each suited to specific operational needs. This overview delves into the various types of vaporizers, including ambient air, electric, steam/water bath vaporizers, forced draft vaporizers, and shell and tube vaporizers. We will explore their unique features, operational principles, and the specific applications for which they best suit.

Components and Function

1. Cryogenic Tank/Dewar
   • Description: Insulated containers designed to store cryogenic liquids at extremely low temperatures, typically below -150°C (-238°F).
2. Vaporizer
   • Heat Exchanger: The primary component transfers heat from the surrounding environment (air, water, steam, etc.) to the cryogenic liquid, causing it to boil and turn into gas.
   • Materials: Typically made from high thermal conductivity materials such as aluminium or stainless steel to efficiently transfer heat.
3. Piping and Valves
   • Supply Line: Connects the cryogenic tank to the vaporizer.
   • Outlet Line: Delivers the gas to the point of use.
   • Safety Valves: Ensure safe operation by relieving excess pressure.
4. Control Systems
   • Thermostats and Sensors: Monitor temperature and pressure to maintain optimal vaporization conditions.
   • Control Valves: Regulate the flow of cryogenic liquid into the vaporizer.

Types of Vaporizers

There are several types of vaporizers used for cryogenic applications.

1. 1. Ambient Air Vaporizers
      • Finned Tube Vaporizers: Feature fins to increase the heat exchange surface area, absorbing heat from the ambient air to vaporize the cryogenic liquid.
        • Principle: Natural convection transfers heat from ambient air to the cryogenic liquid.
        • Design: Typically consists of vertical or horizontal finned tubes with high surface area fins for efficient heat transfer.
        • Advantages: Low operating cost and maintenance.
        • Limitations: Performance can be affected by weather conditions and ambient temperature.
   2. Electric Vaporizers
      • Principle: Electric heaters are employed to provide the heat necessary for vaporization.
        • Design: Contains electric heating elements immersed in or surrounding the heat exchanger.
        • Advantages: Consistent performance regardless of ambient conditions.
        • Limitations: Higher operating costs due to electricity consumption.
   3. Steam/Water Bath Vaporizers
      • Principle: Transfers heat to the cryogenic liquid using hot water or steam.
        • Design: The cryogenic liquid flows through coils immersed in a water bath or steam chamber.
        • Advantages: High efficiency and reliable performance.
        • Limitations: Requires a hot water or steam source, increasing complexity and cost.
        • Application: Suitable for atmospheric gases, LNG, ammonia, and CO2. It is commonly used in pipeline backup, steel plants, ceramic plants, breweries, petrochemical industries, and purging applications.

1. Forced Draft Vaporizers
   • Principle: Uses fans or blowers to enhance airflow over the heat exchanger, improving heat transfer.
     • Design: Similar to ambient air vaporizers but with added mechanical airflow.
     • Advantages: Better performance in environments with low natural convection.
     • Limitations: Additional mechanical components increase maintenance needs.
2. Shell and Tube Vaporizers
   • Design: Consists of a series of tubes within a shell, where the cryogenic liquid flows through the tubes and is heated by a warmer fluid in the shell.
     • Advantages: Efficient heat transfer, commonly used in industrial applications.

Each type of vaporizer offers distinct advantages and is chosen based on the application’s specific requirements, such as the type of cryogenic liquid, desired vaporization rate, and available heat sources.

Applications

1. Industrial
   • Usage: Gaseous nitrogen or oxygen is used in welding and cutting processes, and gaseous argon is provided for metal fabrication and other inert gas applications.
2. Medical
   • Usage: Supplying gaseous oxygen for respiratory therapy; delivering gaseous nitrogen for cryosurgery and medical preservation.
3. Scientific Research
   • Usage: Providing controlled gaseous environments for experiments; supplying gaseous nitrogen or helium for cooling superconducting magnets.
4. Energy
   • Usage: Supplying vaporized LNG for power generation and fuel.

Safety Considerations

1. Pressure Relief Systems: Prevent over-pressurization and potential explosions.
2. Regular Maintenance: Ensures efficient and safe operation of the vaporizer system.
3. Proper Training: Personnel should be trained in handling cryogenic liquids and operating vaporizer systems.

By effectively converting cryogenic liquids to gas, vaporizer systems enable the practical use of cryogenic substances across various industries and applications.