Feature
Sulfur gun advancements In production of sulfuric acid from molten sulfur, it is critical that the sulfur is atomized into droplets so that combustion occurs efficiently. The spray nozzle converts bulk sulfur into a predictable droplet size distribution, spray angle, and coverage. The most widely used nozzle in sulfuric acid production today is the BA WhirlJet® nozzle. These nozzles provide superior performance during normal operation, but when flow is decreased or turned off, the nozzles may plug. This happens because the nozzles protrude beyond the steam jacket of the sulfur gun. Without the cooling provided by the steam jacket, the sulfur flowing inside the nozzle heats up beyond the normal working temperature. This causes the sulfur viscosity to increase and plugging may occur. Operators have been compensating for this by purging the nozzles or removing the guns at the end of operation. However, if one of these actions doesn’t occur quite quickly, pluggage is likely. Flexibility in production rates is required to optimize sulfuric acid production. Sulfur guns are either turned on and off, or flow rate is increased or decreased. To meet this requirement and minimize pluggage, a new sulfur nozzle and gun have been introduced. The CBA SulfurJet™ nozzle has the same superior performance as the BA WhirlJet nozzle. The CBA SulfurJet gun features a steam jacket that fully protects the nozzle to minimize or eliminate plugging. As sulfur passes through the CBA SulfurJet nozzle, sulfur temperature is maintained in the optimal range as production rates change.
Fig. 1
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Fig. 3
In production of sulfuric acid from molten sulfur, it is critical that the sulfur is atomized into droplets so that combustion occurs efficiently. (3,847 lbs/hr) sulfur at 5 psig ΔP (0.35 bar). The feed sulfur temperature was set at 284°F (140°C) and steam in the steam jacket pipe was at 293°F (145°C) and 60 psig (4.1 bar). At full flow conditions for both spray nozzles, the sulfur temperature was maintained until it exited the spray nozzles. The temperature change in the BA WhirlJet nozzle was validated
CBA SulfurJet nozzle and CBA SulfurJet gun validation research
Computational Fluid Dynamics (CFD) was used to model heat transfer in a sulfur gun with BA WhirlJet nozzles and a gun equipped with CBA SulfurJet nozzles. A full flow rate condition of 9,410 kg/hr (20,745 lbs/hr) sulfur at 150 psig ΔP (10 bar) was compared to a reduced flow condition of 1,745 kg/hr
By: Chuck Munro, Refinery Application Specialist, Spraying Systems Co.
Fig. 2
when the reduced flow conditions were used. Fig. 1 shows the BA WhirlJet nozzle at the reduced flow conditions. The sulfur polymerizes inside the nozzle as the temperature rises above 305.6°F (152°C) and starts to form a skin. Over time, the skin grows thicker and reaches the point where the sulfur can no longer pass through the nozzle. The CBA SulfurJet nozzle
is shown in Fig. 2. At the same reduced flow condition, the sulfur temperature remains at 289.4°F (143°C) as it passes through the nozzle. Polymerization does not occur. Due to the hydraulic atomization design, the pressure to the gun is decreased as the flow rate is reduced. As a result, velocity through the internal cavity is decreased. Velocity for the BA
WhirlJet nozzle at the exit is reduced from approximately 32 m/s (105 ft/sec) at full flow rate to approximately 8 m/s (26.2 ft/ sec) at reduced flow rate as shown in Fig. 3. Since the fluid moves more slowly through the gun, the temperature near the walls of the sulfur cavity increases to 635°F (335°C). This causes the sulfur to polymerize at 318.2°F (159°C) and eventually build a skin inside the nozzle. The velocity decrease in the CBA SulfurJet has a smaller impact temperature of 442.4°F (228°C) and pluggage is avoided.
Summary
The new CBA SulfurJet nozzle and CBA SulfurJet gun deliver the flexible performance required by producers. The new nozzle provides superior atomization of bulk sulfur so producers can achieve the same or better performance than the BA WhirlJet spray nozzles currently in use. In addition, the new gun design allows production rates to be adjusted with reduced risk of pluggage. Producers will be able to maximize production time, reduce maintenance time, and extend gun life. Chuck Munro has more than 20 years of experience in spray technology with Spraying Systems Co. He is a specialist in the petrochemical and chemical industries and is active in several industry committees. For more information, visit www.spray.com. q
Sulfuric Acid Today • Spring/Summer 2020
