Technology

The HT-L gasifier (航天粉煤加压气化) is a pressurized, entrained-flow, down-flow coal gasifier developed by Tsinghua University and commercialized by Aerospace Long March Chemical Engineering Co., Ltd. (CECO). It uses a water-cooled membrane wall (replacing refractory bricks) and staged oxygen injection for efficient coal-slurry mixing and temperature control.

"HT" stands for "Hangkong Tian" (航天), which means "Aerospace", referencing the technology’s development under the China Aerospace Science and Technology Corporation (CASC). "L" stands for "Liuliu" (流), meaning "flow", which refers to the entrained-flow nature of the gasification process. Therefore, HT-L can be interpreted as "Aerospace Entrained-Flow" gasification technology, highlighting both its aerospace engineering heritage and its process design as an entrained-flow (pressurized, down-flow) coal gasifier.

Figure 1 - HT-L Gasifier (left) | Oxygen Staging (right)

Process History

• Development: Initiated in the early 2000s by Tsinghua University’s Clean Energy Laboratory, leveraging aerospace engine combustion principles.
• Commercialization: CECO was founded in 2007 to specialize in the development, engineering, and industrial deployment of the HT-L gasification process and related technologies.
• Milestones:
  • 2010: First commercial demonstration (750 t/d) at Anhui Linquan Chemical.
  • 2011: World-record continuous operation (140 days) of a 600 t/d water-wall slurry gasifier.
  • 2024: Deployment of 11×4,000 t/d units in Inner Mongolia for the world’s largest green hydrogen-coupled coal-to-olefins project.

Process Summary

• Feedstock: Pulverized coal (dry feed) or coal-water slurry (CWS), adaptable to low-rank/high-ash coals.
• Key Reactions:
  • C + H₂O → CO + H₂ (Water-gas shift reaction, endothermic)
  • C + ½ O₂ → 2 CO (exothermic)
• Reactor Design:
  • Pressurized entrained-flow down-flow reactor with a single burner.
  • Water-cooled membrane wall with SiC-coated tubes, replacing traditional refractory linings. 
  • Adapted from rocket-engine ignition systems, ensuring reliability and repeatability.
• Key Reactor Mechanism and innovations:
  • Oxygen Staging: Optimizes coal-slurry droplet mixing and temperature distribution.
  • Staged Ignition: "Flame-Ignites-Flame", leveraging staged oxygen injection and advanced burner design; a small pilot flame ignites the primary coal-oxygen mixture in a controlled sequence, bypassing gradual preheating.
  • Thermal Efficiency: The water-cooled membrane wall absorbs heat rapidly enabling natural circulation cooling, eliminating refractory "warm-up" delays and refractory maintenance.
  • Rapid Start-Up: Achieves full load in less than 3 hours, compared to 72 hours for refractory-lined gasifiers, reducing downtime during restarts as well as enhancing operational flexibility for intermittent syngas demand.

Technical Parameters and Process Efficiency

Advantages: 

• Oxygen consumption claimed to be 15–20% lower than with Air Products (GE/Texaco) gasifiers
• Handles high-ash coals (ash melting point >1,500°C).
• Capital costs claimed to be 30% lower than Shell/Air Product designs in equivalent coal-to-chemicals applications.
• High reliability due to the water-wall design; minimal refractory maintenance.

Table 1 - HT-L Process Parameters

Table 2 - Dry-Feed vs. CWS Adaptations

Legend: Dry-feed has a minimal water content, resulting in less steam reforming, hence higher CO concentration; With CWS feed, water reacts via endothermic gasification reactions such as the water-gas shift reaction, increasing H₂ yield but diluting CO.

Reconstruction of the key process stages

1. Coal Preparation & Feed System
   • Pulverized Coal (dry feed) or Coal-Water Slurry (CWS) is pressurized to 2.0–4.0 MPa.
   • Feedstock enters the gasifier via a single top-mounted burner with staged oxygen injection.
2. Gasification Reactor
   • Reactor Type: Pressurized entrained-flow, down-flow gasifier.
   • Operating at a temperature of 1,300–1,600°C and a pressure of 2.0–4.0 MPa.
3. Slag Handling
   • Molten slag flows down the reactor walls into a water quench bath.
   • Solidified slag granules are removed via lock hopper system.
4. Syngas Cooling & Heat Recovery
   • Raw syngas exits the reactor at >1,000°C and enters a radiant syngas cooler (RSC).
   • RSC generates high-pressure steam (used for power or process heat).
   • Syngas is cooled to <300°C for downstream cleaning.
5. Gas Cleaning
   • Cyclones: Remove coarse particulates.
   • Water Scrubbers: Capture fine ash, tars, and water-soluble contaminants (e.g., NH₃, HCl).
   • Acid Gas Removal (AGR): H₂S and CO₂ removed via amine scrubbing or physical absorption.

Table 2 - Key process streams (simplified table)

Applications

HT-L gasification is widely used in: 

• Coal-to-ammonia
• Coal-to-methanol
• Coal-to-olefins
• Coal-to-ethylene glycol
• Coal-to-natural gas (SNG)
• Coal-to-oil
• Coal-to-hydrogen
• IGCC power generation

Commercial Experience and Deployments

A May 2025 news report mentions that t​​he HT-L technology has been successfully applied to 73 projects and 178 furnaces.

In performance terms: 

• As of 2022, Anhui Haoyuan's Phase I project broke the record again, with a long-term continuous operation time of up to 485 days.
• The first ultra-large HT-L furnace in China with a daily coal processing capacity of up to 3,500 tons has been in stable operation for 327 consecutive days since it was put into use as of September 15, 2022. 

CECO’s flagship achievement is the installation of 11 × 4,000 t/d HT-L gasifiers at Baofeng Coal-based New Materials Co., Ltd. in Ordos, Inner Mongolia. Commissioned in March 2025, this facility stands as the world’s largest single-site coal-to-olefins plant.

Intellectual Property and Recognition

• CECO holds over 40 patents related to the HT-L process, including gasifier and burner inventions.
• The technology is listed in national key energy-saving and clean production technology catalogs and is recognized as a “Single Champion Manufacturing Enterprise” in China’s chemical engineering sector.
• The China Petroleum and Chemical Industry Federation has confirmed the HT-L process as internationally advanced, with advantages in operational simplicity, maintenance, coal adaptability, investment and operating costs, and high on-stream rates.

References

1. National Energy Technology Laboratory (NETL) Gasifipedia, HT-L Gasifier, U.S. DOE National Energy Technology Laboratory.
2. Yue Guangxi (Tsinghua University), 2017 Presentation: CFB Combustion and Coal Slurry Gasification.
3. CoalZoom, 2017, Development of Coal Gasification Technology in China.
4. ASIACHEM, 2024, 4000t/d HT-L Gasifiers in Inner Mongolia.
5. Baidu Encyclopedia, 2024, 航天长征化学工程股份有限公司 (Aerospace Long March Chemical Engineering Co., Ltd.).
6. Baidu Encyclopedia, 2023, 航天炉 (Aerospace Furnace).
7. Sina Finance, 16^th Jan 2025, Coal Chemical Industry: Go to Xinjiang, Go Where Industrial Development Is Needed.
8. China Aerospace China & Technology Company, 21^st May 2025, A side note on the aerospace coal chemical technology of the First Academy of Aerospace Science and Technology helping the green upgrade of Hami's energy industry.
9. 犯懒大王康康, 2^nd Mar 2025, The aerospace furnace ran continuously for 485 days, setting a new world record.
10. ASIACHEM, 8th Mar 2024, 4000t/d Grade HT-L Gasifier Installed in Biggest Green H2 Coupled CTO Project.
11. Inner Mongolia Autonomous Region Department of Commerce, 20^th June 2025, Project put into production | The world's largest coal-to-olefins project in a single plant is fully put into production in Ordos City.
12. China Academy of Aerospace Science and Rocket, 19^th Feb 2024, 4,000-ton aerospace furnace helps build the largest coal-to-olefins project.
13. China petroleum and chemical induustry association professional comittee of coal chemical industry (CPCIF), 1^st Nov 2018, New Progress in Aerospace Pulverized Coal Pressurized Gasification Technology.