Technology in Action
production rates until the critical fired equipment could be replaced, suspending the flow of millions of dollars in poten - tial revenue for the company. Challenge The Hengli refinery not only needed to replace two large sets of eight duct burners each in the PDH air heater sys- tem, but the facility also required the new burners to be more robust to prevent future failures. The original air heater burner supplier informed the refinery that, under normal circumstances, a project of this magnitude would require at least six months to deliver a complete replace - ment to the site. Additionally, the COVID-19 pandemic introduced many unique challenges to the situation. Beyond the obstacles of global travel restrictions, many vendors around the world closed, suspended operations, or operated at reduced capacity, which made procurement and delivery of materials and equipment substantially more difficult. Solution To avoid a complete shutdown, operators at the refinery called on Zeeco China. Applications engineers at Zeeco immediately assembled a multidisciplinary team from China and the US to assess the situation. On April 8, 2020, Zeeco’s
The propane dehydrogenation (PDH) process generates propylene from a propane feedstock through the cata- lytic conversion of propane into propylene and hydrogen. The process, as developed by Lummus, uses fixed-bed reactors and a chromium-based catalyst and is carried out in two main areas: reaction/regeneration and product recovery. Large single train capacities for these process units require extremely high heat release from the air heater for continu - ous regeneration of the offline reactor beds. Lummus’ main requirements for PDH air heater applica- tions are the following: • Maximum recommended temperature difference between any two transverse points in the air stream from the heater should be less than 15°C • Maximum allowed pressure drop through the air heater is 0.007 MPa • Minimisation of NOx generation in the heater design. Although the regeneration cycle is a relatively small por- tion of the overall process equipment train, the cycle is a critical component, and the air heater must run until a scheduled shutdown. Situation Hengli Group, one of China’s foremost suppliers of petro- chemicals, started up the world’s largest dehydrogenation plant using CATOFIN technology in August 2019. In early April 2020, the duct burners of the two PDH air heaters failed. Without a duct burner system to provide supplemen- tary firing for the reactors, the facility was forced to reduce Zeeco delivers robust duct burner system for PDH air heaters
Composition
Process CCR PSA Refinery fuel gas tailgas fuel gas
Hydrogen, mol% Nitrogen, mol%
33.02
35.83
19.71
0.06 0.34
1.19 0.90 0.49
CO, mol% CO₂, mol%
Methane, mol% Acetylene, mol% Ethylene, mol% Ethane, mol% Propylene, mol% Propane, mol% Iso-Butane, mol% n-Butane, mol%
20.94
21 .72
33.53
LTRU o ff-gas
Composition
0.05 1.28
SOR
EOR
0.16
34.49
31.52
25.20
Hydrogen, mol% Nitrogen, mol%
90.96
86.94
0.12 6.21 0.80 0.61 0.14 0,07 0.33 0.26 0.20 0.07 1.00
0.20 8.31 2.99 2.21 0.04 2.50 1.92 0.12 0.12 0.04 0.37
0.81 2.69 0.12 4.44 0.19 0.40
1.77 3.36 0.30 6.28 0.39 0.59
7.18 0.93 0.70 0.16 0.08 0.39 0.31 0.24 0.08 0.87
CO, mol% CO₂, mol%
Methane, mol% Ethylene, mol% Ethane, mol% MAPD, mol% Propylene, mol% Propane, mol% Iso-Butane, mol% n-Butane, mol% H₂O, mol% TOTAL, mol%
Butene, mol%
lso-Pentane, mol% n-Pentane, mol%
Hexane, mol% Benzene, mol% Toluene, mol%
0.22 0.16
0.20 0.16
C₈+, mol% H₂O, mol%
TOTAL, mol%
100.00
100.00
100.00
100.00
100.00
Sulphur content (as H₂S), ppmw
50
By DEC By DEC
Sulphur content (as H₂S), ppmw 35
35
Molecular weight Pressure, MPa(g) Temperature, ºC
19.6 0.30
19.0 0.30
24.5 0.30
Molecular weight Pressure, MPa(g) Temperature, ºC
3.92 0.30
4.77 0.30
102.0
102.0
102.0
102.0
102.0
Lower heating value, kJ/kg
49,062
49,581
46,829
Lower heating value, kJ/kg
71,192
60,939
Table 1 Normal fuel
Table 2 High hydrogen fuel
101
PTQ Q42022
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