Oct-2022

SprayMax FCC feed injection nozzles

Fluid catalytic cracking is a well-established conversion process in the refining industry in which a low-value, heavy hydrocarbon liquid is converted into LPG, light, and middle distillates.

Praveen Kumar Singh AND Pramod Kumar
Hindustan Petroleum Corporation Limited

Article Summary

It is primarily a vapour phase phenomenon where the liquid feed gets vaporised by absorbing heat from the hot catalyst particles and the vapours diffuse through the catalyst pores to get cracked into lighter components. As the residence time is only a few seconds, instantaneous vaporisation of the liquid feed becomes necessary. This requires fine atomisation and efficient mixing of the liquid feed with the catalyst.

The atomisation of FCC feed is achieved through a set of feed injection nozzles. The feed is usually injected into the riser through multiple nozzles installed symmetrically around the riser. A properly designed feed nozzle atomises the liquid feed into fine droplets, which are quickly vaporised on contact with the hot catalyst. The important characteristics that define the performance of a nozzle are droplet size and velocity, spray angle, riser coverage area, and pressure drop across the nozzle, as well as the mechanical integrity to resist erosion.

Conventionally, refiners have relied on FCC technology licensors for the supply of feed nozzles which need to be replaced every 4-5 years. By comparison of prior art on various feed nozzle designs and the understanding of atomisation principles, HPCL envisaged there was scope for enhancing the performance of feed nozzles with the incorporation of proprietary internals. HPCL R&D Centre (HPGRDC) initiated the development of efficient and cost-effective FCC feed nozzles with the objective of improved operational reliability and better performance compared to commercially available nozzles. Extensive in-house research on FCC feed nozzles at HPGRDC resulted in the development of SprayMax feed nozzles. 

SprayMax nozzles were initially installed and commissioned in the FCC unit of a HPCL refinery in June 2016. Comparing test run data of previous nozzles with SprayMax nozzles at identical operating conditions, it was found that conversion increased by 1.2 wt% with an increased yield of naphtha and decreased yield of dry gas and slurry oil. After the success of this project, SprayMax nozzles were commissioned in two more HPCL FCC units, which have improved conversion and operational reliability. 

SprayMax Nozzle Development
At HPGRDC, different prototypes were developed and tested with an air-water system to study the spray pattern, spray angle, and degree of atomisation. The best design was then scaled up and fabricated in a very short time and at a significantly lower cost than commercial nozzles.

This short article appeared in the 2022 Refining India Newspaper, which you can view HERE

Figure 1 shows the spray pattern of two prototype nozzles when tested with an air-water system. It can be observed that the nozzle in Figure 1b has a wider spray of finer droplets compared to the nozzle in Figure 1a.

Feed nozzles have to withstand the harsh riser conditions where hot catalyst (700-750ºC) particles move at high speeds (40-50 m/s), increasing the risk of erosion of the nozzle tip. While the body of the SprayMax nozzle is made of high-grade stainless steel, the tip is made of a highly erosion-resistant alloy with excellent wear resistance.
Figure 2 shows the commercial nozzle taken out during the turnaround of FCC Unit 2 and the new SprayMax nozzles.

Commercialisation of SprayMax nozzles
HPCL refinery FCC Unit 1
One HPCL refinery has a feed capacity of 0.97 MMTPA. During a turnaround in June 2016, the existing commercial nozzles were replaced with SprayMax nozzles with no hardware change in the FCC riser. Figure 3a shows the SprayMax nozzles installed in the unit, while Figure 3b shows the SprayMax nozzle taken out for inspection after three years of operation. Apart from a few minor indentations on the surface of the tip, the nozzle was unaffected, which proved the sound mechanical integrity of the nozzle. 

To evaluate the performance of SprayMax nozzles, test runs were conducted before and after the turnaround at identical operating conditions. Figure 4 shows the comparison of product yield pattern and overall conversion before and after the turnaround of the FCC unit. SprayMax nozzles provided 1.2% higher conversion with 1.5% higher gasoline, 0.3% lower dry gas, and 3.5% lower residue yield than the commercial nozzle. The increase in gasoline yield and decrease in dry gas and resid yield indicate enhanced catalytic cracking due to better atomisation of the feed.

HPCL refinery FCC Unit 2
Another FCC unit at an HPCL refinery has a feed capacity of 1.22 MMTPA. During a turnaround in July-Aug 2016, it was observed that the feed nozzles imported from the licensor were severely eroded, as shown in Figure 2a. It was decided to replace those nozzles with SprayMax nozzles. There was a challenge of no modification in the riser coupled with a short turnaround period. The nozzle design was modified, and nozzles were fabricated within a month and delivered to the refinery in time for installation and unit start-up.  
Figure 5 shows the comparison of product yields and overall conversion before and after the turnaround of the FCC unit. SprayMax nozzles provided around 0.8% higher conversion with an increase of 0.4 wt% in LPG yield, an increase of 0.9 wt% in gasoline yield, and a decrease of 0.6 wt% in dry gas yield than the previous commercial nozzles.

HPCL refinery FCC Unit 3
A third FCC unit at an HPCL refinery has a feed capacity of 0.97 MMTPA. During a turnaround in October 2019, it was observed that the licensor-provided feed nozzles were severely eroded, as shown in Figure 6a. These nozzles were also replaced by SprayMax nozzles during the turnaround without any modifications in the riser or feed circuit.
Figure 7 shows the comparison of product yields and overall conversion before and after the turnaround of FCC Unit 3 under identical operating conditions. SprayMax nozzles provided around 0.5% higher conversion with an increase of 0.9 wt% in LPG yield and a decrease of 0.3 wt% in dry gas yield than the previous commercial nozzles.

Conclusion
HPGRDC has successfully developed and commercialised a cost-effective FCC feed injection nozzle, SprayMax, with improved operational reliability and performance. For the first time in India, FCC feed nozzles were designed entirely in-house, fabricated, and successfully commercialised in HPCL refineries. The improved performance of these nozzles was verified by analysing the data obtained from test runs conducted before and after the installation of SprayMax nozzles. The nozzles have helped increase unit conversion by about 0.5-1.2 wt% with an increase in LPG and gasoline yields and a decrease in dry gas yield in all the units.