The spraying of reagents into a gas to remove contaminants, or to change the make up of the gas, is common in many chemical processes.
Modern emissions legislation in many countries mean there are strict controls on the levels of pollutant gases that can be emitted from industrial, chemical or power plants. Bete produce a variety of nozzles that operate in these often very harsh conditions.
Not all scrubbing applications are lead by environmental issues. Scrubbing and cooling gases is commonly performed to remove heat or contaminant to extend the life of linings and equipment further down stream in the process.
Engineering Considerations for gas scrubber nozzles
Different designs of scrubber will require different types of nozzles and spray properties to operate effectively. The key engineering considerations to be made when selecting nozzles for gas scrubbing applications are listed in the blue menu to the right hand side of this page. Below this, through the grey menu, details on the different designs of suitable gas scrubbing nozzle are accessible.
The information contained in both the engineering considerations pages and the nozzle designs pages is summarised in the “Gas scrubbing nozzle cheat sheet” which is accessed by the orange button also to the right hand side of this page.
A variety of nozzles are suitable for gas scrubbing applications. For packed bed scrubbers TF spiral nozzles can give very wide distribution patterns with up to 170 degree spray angles. TF nozzles are also useful in absorber spray scrubbers as they produce sprays with good levels of atomisation.
GAS COOLING NOZZLES
The cooling of gas flows by injecting water or other coolants is a very common application for our spray nozzles. Correct nozzle selection is of critical importance in many spray cooling applications as the properties of the spray will determine how quickly heat is absorbed and where the spray will reach within a given gas flow.
When spraying into a hot gas flow above the boiling point of the coolant most of the cooling is caused by taking heat from the gas to evaporate the fluid. The rate of evaporation will depend on the average droplet size of the spray. Sprays consisting of smaller droplets will evaporate far more rapidly that sprays containing larger droplets. In fast moving gas flows this can be very important as often cooling needs to be achieved before the gas reaches another point in the process. Correct nozzle selection can thus reduce the need for long quench chambers.
Not just droplet size
Whilst sprays consisting of very small droplets will absorb heat faster they will also become entrained within gas flows more easily. This means that if a spray is too fine it may only cool a channel within a gas flow rather than the whole gas volume. So there is often a balancing act to be performed between getting sufficiently small droplets to achieve rapid heat transfer and have enough larger droplets to carry the spray into a gas stream and distribute it evenly.
Variable gas flows
In many applications the amount of gas that needs to be cooled can vary depending on operating conditions. For example the pre-quenching of hot flue gasses before they enter a scrubber may vary dramatically depending on what is happening further up the process line to produce the gases. Variable cooling loads present problems for spray cooling because lowering the amount of coolant spray will typically mean lowering fluid pressure which will increase the droplet size and thus increase evaporation time. This means that in lower gas flow scenarios cooling may not be achieved in time, or may necessitate a deliberately larger quench chamber.
There are a number of ways in which good nozzle selection can help overcome variable gas flow cooling problems. The use of spillback nozzle systems means that droplet size can be kept relatively stead even if the pressure and flow rate are reduced. Alternatively air atomising systems with variable air and fluid pressures can be used to maintain smaller droplets at reduced flows. Finally multi nozzles arrays can be deployed to given variable flows at stable droplet sizes.
Gas cooling nozzle selection will vary greatly depending on the application. For many cooling applications our spiral TF nozzles produce an excellent combination of small droplets mixed with some larger droplets to give penetration into rapidly moving gasses. For variable gas flows our spillback lances can provide optimum cooling even under highly changeable process loads. Our Spriral Air (SA) nozzles give a robust air atomising system suitable for use in hot gas flows that require finely atomised sprays for rapid quenching.
As gas cooling is a wide and highly varied application other nozzle types may well be recommended depending on the situation.
FLUE GAS DESULFURIZATION (FGD): OVERVIEW
BETE provides a wide variety of high-performance nozzles for all aspects of the flue gas desulfurization (FGD) process. FGD specifically targets the removal of sulfur oxides, commonly referred to as SOx, from an exhaust gas using an alkali reagent, such as a wet limestone slurry.
FGD inquiry worksheet (PDF – 87 KB)
BETE FGD Technical Manual (PDF – 1 MB)
FGD requires precise calculations and nozzle fitting to ensure continual proper functioning of the system. BETE engineers have decades of experience in helping customers around the world find the best FGD solution for their custom application.
Types of FGD Nozzles:
- FGD Absorber Nozzles
- FGD Mist Eliminator Nozzles
- FGD Emergency Quenching Nozzles
Selecting a FGD Nozzle:
To learn more about which nozzle would be right for your application, please explore the specific categories listed above, or contact our experienced engineers.
Common FGD Nozzle Uses, Applications, and Industries:
- Coal and other fossil fuel power plants
- Petroleum refineries
- Municipal Waste Incinerators
- Cement kilns and metal smelters
GAS COOLING SPRAT NOZZLES
Evaporatively quench hot gases
Hot gas can be cooled to a lower temperature by evaporating a liquid into the gas stream. Smaller droplets lead to faster evaporation times and a shorter distance required for the gas temperature to reduce to the desired level.
Nozzle Selection Guidelines
A number of thermodynamic calculations need to be made to select the correct nozzle for a given situation and are based on a variety of factors. The information required to make these calculations is detailed in the BETE Gas Cooling/Quenching Application Data Sheet (PDF – 229 KB). With this information, BETE Application Engineers can perform the calculations and combine the results with their knowledge of nozzle performance and help select the nozzle that fits your needs.
Typical operating conditions for this application are listed for each nozzle
GAS QUENCHING NOZZLES
Evaporatively quench hot gases
Typical operating conditions for this application are lister for each nozzle
SWIRL AIR NOZZLES
GAS FUME SCRUBBING
PNR 120° SPIRAL SPRAY NOZZLE IN GAS FUME SCRUBBING PROCESS (AFTER THE WASTE FOOD DIGESTION PROCESS)
There are numerous fume scrubbing plant requirements used in industries today. Mainly full and hollow cone nozzle types are used and many are tailored to suit engineer’s designs. One of the most common types is the spiral full cone which can cope with dirty processed water without blocking and at the same time provides the efficiency needed.