refining india 2022
SprayMax FCC feed injection nozzles
Praveen Kumar Singh AND Pramod Kumar Hindustan Petroleum Corporation Limited
Introduction Fluid catalytic cracking is a well-estab- lished conversion process in the refin- ing industry in which a low-value, heavy hydrocarbon liquid is converted into LPG, light, and middle distillates. It is primarily a vapour phase phenomenon where the liq- uid 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 sym- metrically 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 cov- erage 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 princi- ples, HPCL envisaged there was scope for enhancing the performance of feed noz- zles 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 reliabil- ity 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 com- missioned in two more HPCL FCC units, which have improved conversion and oper- ational 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. 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 cata- lyst (700-750 º C) 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 excel- lent 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 noz- zles 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 inspec- tion after three years of operation. Apart from a few minor indentations on the sur- face of the tip, the nozzle was unaffected, which proved the sound mechanical integ- rity of the nozzle. To evaluate the performance of SprayMax nozzles, test runs were con- ducted 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 resi- due 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 atomisa- tion 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 mod- ification in the riser coupled with a short turnaround period. The nozzle design was modified, and nozzles were fabri- DID you know spraymax nozzles have helped increase unit conversion by about 0.5-1.2 wt%?
Figure 1a (left) and Figure 1b (right) Flow pattern obtained during testing of nozzles with air-water system
Figure 2a (left) Damaged feed nozzle (manufactured by licensor) of HPCL refinery FCC Unit 2 2b (right) SprayMax nozzles installed in FCC Unit 2 in Aug 2016
Figure 3a (left) SprayMax nozzles installed in HPCL refinery 1 3b (right) SprayMax nozzle taken out after three years of operation for inspection
70
Commercial n ozzle SprayMax nozzle
60
50
40
30
20
10
0
Dry gas
LPG
Gasoline
LCO
Resid
Coke
Conversion
Figure 4 Comparison of product yield pattern and conversion at HPCL FCC Unit 1
10 15 20 25 30 35 40 45 50 55 65 60
Commercial n ozzle SprayMax nozzle
0 5
ATG
LPG
Gasoline
LCO
CLO
Coke
Conversion
Figure 5 Comparison of product yield pattern and conversion for HPCL FCC Unit 2
14
Powered by FlippingBook