Ammonia, a primary raw material for the fertilizer and organic chemical industries, is also a significant source of environmental pollution during its production. In China, approximately 40% of nitrogen fertilizer capacity (20 million tons/year) still relies on atmospheric intermittent fixed-bed coal gasification, generating substantial "three wastes" (waste gas, wastewater, and residue). In 2021, Carbon Peaking and Carbon Neutrality (the "Dual Carbon" goals) were formally included in China’s Government Work Report, with an emphasis on “striving to peak carbon emissions by 2030 and achieve carbon neutrality by 2060”. As the transition toward carbon neutrality gains momentum, environmental upgrades in the synthetic ammonia industry have become a critical focus for enterprises.
Yu Kuangshi, General Manager of ZHGAS, Delivers Keynote Speech at the 2021 China Nitrogen Fertilizer and Methanol Technology Conference
At the 2021 China Nitrogen Fertilizer & Methanol Technology Conference (July 21),CAS Hefei Gasification Technology Co., Ltd.(hereinafter referred to as ZHGAS) proposed a closed-loop environmental solution for synthetic ammonia gasification, integrating:
CGAS Circulating Fluidized Bed Coal Gasification for syngas production.
Gasification fine slag resource utilization.
Fixed-bed indirect cooling retrofits.
This comprehensive approach addresses pollution from gasification processes to slag disposal, creating a full-chain eco-friendly system.
CGAS Technology: Tackling Emissions at the Source
Clean and efficient coal utilization is key to reducing carbon emissions. Current gasification technologies in synthetic ammonia include fixed-bed, fluidized-bed, and entrained Flow. While fixed-bed (requiring costly lump coal) and entrained-flow (high capital/long cycles) face limitations, CGAS offers:
Broad coal adaptability(low-/high-rank coals).
Low operating costs and short construction cycles.
Zero shutdowns during retrofits.
Superior environmental performance.
Yu Kuangshi, General Manager of ZHGAS
Developed under China’s "863 Program" by the Institute of Engineering Thermophysics, CAS, CGAS was industrialized via ZHGAS in 2016. General Manager Yu Kuangshi emphasized:"CGAS matches entrained-flow in efficiency post-slag treatment but cuts project costs by 50%, offering SMEs a revolutionary gasification pathway."
Xinjiang Yihua Coal Gasification Facility Site
In 2020, ZHGAS completed:
Xinjiang Yihua CGAS-CFB Project: Utilizing high-alkali coal, it reduced ton-ammonia costs by over ￥200 while resolving challenges like slagging and ash variability. Guizhou Hongsheng Retrofit: Replaced 10 fixed-bed gasifiers with 1×CGAS unit, enabling clean gasification of low-reactivity anthracite. This project was listed among CAS’s 2020 Top Tech Transfer Achievements.
To date, CGAS has been deployed in 70+ industrial systems across alumina, magnesium, and foundry sectors.
Gasification Fine Slag: Turning Waste into Profit
The rise of CFB/entrained-flow technologies has intensified challenges in fine slag disposal (typically landfilled or used in low-value bricks). ZHGAS addresses this via:
Preheating Melting Gasification: Converts slag into syngas, overcoming hurdles like low reactivity and high ignition temperatures. It also immobilizes heavy metals in glassy slag.
Residual Carbon Combustion: Generates ultra-high-temperature steam via CFB combustion, enabling cascaded coal utilization.
Indirect Cooling Retrofit Technology Extends Service Life of Fixed-Bed Systems
As national environmental regulations tighten year by year, fixed-bed gasification technology is gradually being phased out. However, for small and medium-sized synthetic ammonia enterprises with limited financial capacity, the complete exit from fixed-bed systems remains prohibitively costly and time-consuming.
Faced with urgent environmental challenges, how can these enterprises proceed? Retrofitting heavily polluting processes has emerged as a viable path. Regulatory policies explicitly mandate this shift. The Industrial Furnace Atmospheric Pollution Control Plan and Comprehensive VOC Treatment Plan for Key Industries (Draft) state:
"For nitrogen fertilizer and other industries using intermittent fixed-bed gasifiers, accelerate the transition from direct water washing to indirect cooling for gas cooling."
Yu Kuangshi explains that during gas purification and cooling, direct water washing allows harmful substances like tar and cyanide to contact water directly, generating toxic wastewater. In contrast, indirect cooling employs indirect heat exchangers to prevent pollutant-water contact, enabling dry and wet separation for independent treatment. This approach slashes wastewater complexity and boosts environmental performance.
Site Visit to Shanxi Jinfeng Fixed-Bed Gasification Indirect Cooling Upgrade Project
Notably, this indirect cooling and dry dust removal system builds on purification and cooling technologies already proven in circulating fluidized bed coal gasification systems over years of operation. Leveraging this foundation, ZHGAS innovatively developed an indirect cooling technology tailored for intermittent fixed-bed retrofits, integrating extensively validated components:
Water-cooled cyclone pre-dust removal
Dry dust removal
Indirect cooling
This unified process achieves integrated gas purification and indirect cooling, addressing high-pollution issues from direct cooling wastewater while recovering coal dust. Key features include:
Pneumatic ash conveying to silos for collected dust.
Ammonia recovery from condensate via ammonia stripping systems, repurposing it as aqueous ammonia.
Site Visit to Shanxi Jinfeng Fixed-Bed Gasification Indirect Cooling Upgrade Project
This technology has been implemented in the fixed-bed indirect cooling retrofit projects at three subsidiaries of Jinneng Holding Group: Tianyuan, Jinxiang, and Jinfeng. At the Jinfeng project site, dry dust is transported via sealed pneumatic pumps to silos and then loaded onto trucks using bulk loaders. Despite handling dry dust, the entire process is dust-free and fully automated. Additionally, the treated condensate has been restored to transparency.
Water Quality Comparison Before and After Indirect Cooling Retrofit
Chen Zhiyun, Assistant General Manager of the Regional Company under Jinneng Holding Equipment Manufacturing Group, stated that since its commissioning in January 2021, the indirect cooling system at Tianyuan Company has maintained a dust concentration of <10 mg/Nm3 at the bag filter outlet, resolving a widespread environmental challenge for coal chemical enterprises. As a result, Jinneng Tianyuan was designated as the only “Grade B Environmental Protection Enterprise in Jincheng City”, granting it exemption from production halts during pollution alerts.
