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5. Gas Cooling/Quenching Nozzles

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BETE nozzles are used for quenching in commercial and industrial applications around the world. In many processes a gas is raised to temperatures that could easily damage downstream equipment. This can either be by direct combustion, as in the case of flue gas, or by secondary heating. The quickest and most effective way to cool a hot gas is through the evaporation of an injected liquid. Changing the phase of the injected liquid to gas consumes enormous amounts of energy compared to sensible/direct contact cooling. As an example, heating water from 32 °F to 212 °F (0 °C to 100 °C) requires about 180 BTU/lbm (418 kJ/kg). Converting that same water from liquid at 212 °F (100 °C) to steam at 212 °F (100 °C) requires about 1000 BTU/lbm (2320 kJ/kg), or more than 5 times the energy. The energy used to vaporize the gas is taken from the hot gas, thus lowering its temperature.

In evaporative gas cooling, a mist of water is sprayed into the hot gas. In many cases this is flue gas from a combustion process. The water then evaporates, cooling the system rapidly as the energy is used to change the water from liquid to gas. When a volume of water is atomized into smaller droplets, more surface area is exposed, allowing the evaporation rate to increase. The rate of evaporation is often critical as the gas must reach its final temperature before a fixed point downstream. The evaporation rate is dependent on the droplet size, temperature differential, and partial pressure among other variables.

Our applications engineers can confidently assess which nozzle to recommend with the information acquired through the BETE Gas Cooling/Quenching Application Intake Sheet. This data will also allow the engineer to calculate the amount of water, operating pressure, and drop size that is necessary for your application. It is important to note that since spray nozzles produce a droplet size spectrum rather than a single droplet size, expertise is needed to correctly choose between different types of nozzles. BETE engineers perform detailed thermodynamic calculations to determine the ideal nozzle, droplet size, and pressure for each system. For applications with precise requirements and/or complex geometry, BETE offers Computational Fluid Dynamics (CFD) analysis as a contract service to verify the suitability and effectiveness of a proposed quench system.

 

Selecting a Process Gas Cooling Nozzle:

Important factors to consider:

• Initial/final process gas temperatures
• Process gas composition (including initial water content)
• Available residence time for droplet evaporation
• Available and required flow rate
• Available pressure drop (∆P) across the nozzle
  • ∆P = supply pressure at nozzle inlet - process pressure outside nozzle
• Required coverage
  • Ensure complete contact/cooling of gas stream while minimizing potential wall contact
• Required droplet size
  • Achieve complete or partial evaporation to obtain required cooling.
• Required nozzle material
  • Quench nozzles often require special materials to withstand the high temperature and corrosive environments present in these applications.

• Our experienced engineers can help determine which nozzle will perform as required with your design details.

Common Process Gas Cooling Nozzle Uses and Industries: 

• Cooling process gases prior to scrubber/bag-houses
• Cooling combustion exhaust gases
• FGD quench systems
• Emergency quench systems

Also recommended:

SpiralAir high flow air atomizing nozzles