Technology

The HQC Ethylene Steam Cracking Technology is a complete indigenous ethylene production system developed by China Huanqiu Engineering Co., Ltd. (HQC/寰球), a subsidiary of CNPC/PetroChina. Development began in 2007 with the "Large Ethylene Phase I" project and continued through "Large Ethylene Phase II" (2017-2023), making China the fourth country globally to master complete large-scale ethylene production technology.

Cracking Furnace Technology

The cracking furnace is the "heart" of the ethylene plant. HQC developed proprietary furnace designs with the following characteristics:​

• Radiant section geometry – Typical dimensions of approximately 20m length, over 10m height, and about 3m width​
• Tube arrangement – Radiant coils suspended in the center of the firebox, with two-pass configuration: inlet tubes enter from the crossover section at the top, descend to near the furnace bottom where they pass through an S-bend splitting to both sides, then through a U-bend before returning upward as outlet tubes​
• Burner configuration – Bottom burners and/or side-wall burners on both sides of the firebox; for bottom-fired designs, fuel gas inlets are arranged in two stages with primary burners at the inner edge of the air inlet and secondary burners on the outer side​
• Multi-pass radiant coil configurations – Optimized tube arrangements for different feedstocks, including 2-1-1-1 bottom bend structures for ethane cracking
• Enhanced heat transfer tubes – Proprietary technology in the radiant section reduces the tendency of coking on the inner surface of the furnace tubes, extending decoking cycles by 30-50% and reducing tube wall temperatures by 10-15°C​
• High steam production process – Adapted for liquid feedstock operations, the cracking furnace employs a high steam production configuration
• Secondary quench cooling – After cracking gas is cooled by the traditional primary transfer line exchanger (TLE), it is further cooled by boiler feed water for additional temperature reduction
• High thermal efficiency – Furnaces achieve 94-96% thermal efficiency, listed in China's National Industrial Energy-Saving Technology Recommended Directory​
• Feedstock flexibility – Capable of processing ethane, LPG, naphtha, coal-based naphtha, hydrogenated tail oil, and light crude oil​
• Extended run lengths – Ethane cracking furnaces achieve operating cycles up to 150 days​
• High selectivity – Ethylene comprehensive yield reaches 83% for ethane feedstock​
• Largest domestic liquid cracking furnace – HQC has designed and built the single liquid cracking furnace with the largest production capacity in China

Process Flow

The feedstock cracking process follows this sequence:​

• Convection section preheat – Feedstock enters the convection section for initial preheating
• Dilution steam mixing – Preheated feedstock mixes with dilution steam
• Final preheat and vaporization – Mixed feed is reheated to complete vaporization and raised to cracking temperature
• Radiant section cracking – Feed enters radiant coils where pyrolysis occurs, producing ethylene, propylene, butadiene and other products
• Rapid quench – Cracked gas immediately enters the transfer line exchanger (waste heat boiler) upon leaving the radiant section to minimize secondary reactions and preserve ethylene yield
• Heat recovery – Hot flue gas from combustion passes through the convection section to preheat feedstock and generate superheated steam from boiler feed water

Furnace Design and Simulation Technology

HQC has developed a sophisticated coupled modeling methodology for furnace design verification and optimization:​

• Firebox modeling – Computational Fluid Dynamics (CFD) with detailed 3D geometry of burners and tubes, using standard k-ε turbulence model, probability density function (PDF) model for non-premixed combustion, and discrete ordinates (DO) radiation model with weighted-sum-of-gray-gases (WSGGM) for absorption coefficients
• Tube-side modeling – One-dimensional plug flow reactor model with free radical reaction kinetics; feedstock composition characterized using neural network methods based on PONA values and distillation properties
• Coupled iteration – Firebox and tube models are iteratively solved using tube wall temperature and heat flux as boundary conditions until convergence (temperature maximum difference <1°C)

This modeling capability enables prediction of:​

• Cracked gas velocity, temperature, pressure, and product yields along tube length
• Tube outer wall temperature and heat flux distribution
• Firebox flue gas temperature, concentration distribution, and flame shape/height

Reaction Kinetics

The tube-side cracking reactions are modeled using detailed free radical reaction mechanisms:​

• Chain initiation – Carbon-carbon and carbon-hydrogen bond cleavage
• Hydrogen abstraction – Intramolecular and intermolecular H-transfer reactions
• Radical addition/β-scission – Addition reactions and reverse β-scission

Free radicals are classified into three categories for network simplification:

• β radicals – Small radicals (H- , CH₃- ) participating only in bimolecular reactions
• μ radicals – Larger radicals (>C5) where bimolecular reactions are negligible
• βμ radicals – Intermediate radicals (e.g., C₂H₅- ) exhibiting β behavior at low temperature and μ behavior at high temperature

Kinetic parameters are calculated using group contribution methods.

Compression Section

The technology incorporates China's highest-power domestically manufactured cracking gas compressor, marking a breakthrough in localization of critical rotating equipment for large-scale ethylene plants.​

Separation Technology

HQC developed three main separation process configurations:​

For ethane cracking, HQC's front-end deethanization with front-end hydrogenation process reduces equipment count by more than 20%. The technology includes a two-stage tail gas expansion refrigeration system that is claimed to reduce ethylene losses by 60% compared to international benchmarks.​

Product Slate

The ethylene plant produces the following products:​

• Primary products: Ethylene, propylene
• By-products: Hydrogen, methane-rich gas, cracked C₄, cracked gasoline (pygas), fuel oil

Environmental Technologies

The technology incorporates advanced environmental control systems:​

• Ammonia-based SCR denitration – Multi-branch staged ammonia injection with pre-mixing technology reduces NOx emissions by 70%
• Process water treatment – "Coke capture + flotation + coalescence" cascade purification reduces coke/oil impurities to below 100 ppm
• Waste caustic treatment – Oxidation-salt crystallization technology enables "near-zero discharge" of sulfide-containing waste streams

Scale and Capacity

HQC technology supports single-train capacities from 600 ktpa to 1,500 ktpa:​

• 600 ktpa
  • Petrochina Daqing Petrochemical naphtha cracker (2012) 
  • Dushanzi Petrochemical Tarim ethane cracker (2021)
• 800 ktpa
  • Lanzhou Petrochemical Changqing ethane cracker (2021)
• 1,200 ktpa
  • Guangdong Petrochemical mixed feed cracker (2023)
  • Guangxi Petrochemical mixed feed cracker (2025)
  • Dushanzi Tarim Phase II mixed feed cracker (Sep 2026 prospective commissioning) 
  • Hohhot Petrochemical ethane cracker with CCUS in Ordos (project construction timeline Jun 2025-Jun 2028)
• 1,500 ktpa
  • Super-large scale technology validated​ (2024)

The Daqing Petrochemical 600 ktpa plant (2012) was the pilot project that validated HQC's indigenous ethylene technology before deployment at subsequent larger-scale projects.

Intellectual Property

The technology portfolio includes 64 patents, 27 trade secrets, 1 software copyright, and 44 individual technology achievements across four series. The ethane-to-ethylene complete technology package received the 2024 First Prize for Science and Technology Progress from the China Petroleum and Chemical Industry Federation.

References

English-language sources:

1. Ye Dan. Aug or Sep 2017 (estimated publication date). Daqing Petrochemical Fine Chemicals Advanced to High-End. 3E Chemical
2. Archana Rani. Sep 1, 2021. PetroChina commissions $1.2bn ethane-to-ethylene project. Offshore Technology
3. Sep 1, 2021. 600,000 tons! Another ethane to ethylene project started successfully. ECHEMI
4. Mar 31, 2022. Guangdong Petrochemical ethylene plant process details. ECHEMI 
5. Jul 4, 2022. The ethylene plant was built and handed over. Liaoyang Petrochemical
6. Oct 16, 2023. PetroChina to Add CCUS to New Ethane Cracker. Industrial Info Resources

Chinese-language sources:

1. Li Xinzhe. Sep 25, 2025. [Smart Manufacturing Future] Petrochemical Deconstruction and Ethylene Rebirth—Large Ethylene Technology. Guangming Science Popularization Cloud
2. Xu Yan. March 1, 2023. Has PetroChina's Ethylene Technology Entered the 2.0 Era? . Petrochemical Economic and Technical Information
3. Huang Yang, He Ling, Lei Zhenyou. Feb 7, 2025. Record of the First Prize Science and Technology Progress Project: Development and Industrial Application of Complete Ethane Cracking to Ethylene Technology
4. Huanqiu Ethane Cracking to Ethylene Complete Technology. VIP Journal
5. Yang Xiufeng. Jun 7, 2018. Daqing Petrochemical Company's "Large Ethylene" Supports "Oil Head, Chemical Tail" Upgrade and Transformation. China Economic Net
6. Dec 15, 2020. Daqing Petrochemical's "Large Ethylene" Dream. Petroleum and Equipment
7. Apr 4, 2024. Chronicle of Major Events for Large Ethylene Plants. China Science Popularization Net
8. Oct 27, 2025. PetroChina Guangxi Petrochemical 1.2 Million Tons/Year Ethylene Plant Successfully Starts Up on First Attempt. Guangxi Qinzhou Bonded Port Area
9. Hu Jing. Sep 10, 2023. Total investment of RMB 24.332 billion: Latest progress on Hohhot Petrochemical's 1.2 million tonnes per annum ethane-to-ethylene project. Sohu
10. Nov 4, 2024. The Light of Technology Illuminates the Dream of Ethylene Superpower Status —A Profile of the Large-Scale Ethylene Turnkey Technology Development and Innovation Team at PetroChina Global. China Huanqiu Contracting & Engineering Co., Ltd.
11. Xie Yun. Mar 4, 2023. Pioneer of Domestic Large-Scale Ethylene Turnkey Technology. Guangmin
12. Oct 30, 2024. China's Petroleum Refining and Chemical Enterprises: Writing a New Chapter in Energy Saving and Consumption Reduction. PetroChina News Center
13. Li Zheng. Sep 10, 2023. The Guangxi Petrochemical Refining and Chemical Integration Transformation and Upgrading Project held a trade union meeting. Process Industry

Patents:

1. China Huanqiu Contracting & Engineering Corp. (2011). Ethylene cracking furnace. U.S. Patent No. 9,205,400 B2.
2. China Huanqiu Contracting & Engineering Corp. (2013). Ethylene Cracking Furnace. U.S. Patent Application No. 2014/0199214.
3. China Huanqiu Contracting & Engineering Corp. (2014). Ethylene Cracking Furnace With Multi-Pass Radiant Coil. U.S. Patent Application No. 2012/0219466.
4. China Huanqiu Contracting & Engineering Corp. (2013). Coupled modeling method for design verification and optimization of industrial ethylene steam cracking furnaces. Chinese Patent Application No. CN103310123A.