Chemical looping gasification (CLG) is one of the advanced technologies producing high quality syngas with dual fluidized bed system. It decouples the coal gasification and char combustion respectively in a gasifier and a combustor, between which inexpensive looping particles such as limestone and iron ore is cycled for CO2 in-situ separation and heat transfer. In the gasifier, coal is gasified with steam and sensible heat carried by the looping particle. The looping particle can enhance water gas shift reaction and enrich the hydrogen content of the syngas. All the volatile and most of the char content in coal are converted to hydrogen-rich syngas. In the combustor, residual char is burned with air to supply the necessary heat for the regeneration of the looping particle. The regenerated particles are separated from the flue gas in a cyclone, and then return to the gasifier for completing the cycle.
There are many advantages of the CLG process. First, the gasification process efficiency can be optimized by adjusting the carbon conversion between the two reactors. Second, the char which is hard to be gasified is burned in the combustor, thus improving the overall carbon conversion and reducing the gasifier size at the same time. Third, the combustor uses air instead of high purity oxygen, therefore the air separation unit is avoided and the capital investment is significantly reduced. Last but not least, the looping particles can be used to in-situ separate CO2 and directly adjust the ratio of H2/CO which is beneficial for the downstream application with reduced costs.
ENN has developed the CLG process for clean and efficient coal conversion since 2016. A 1 MW CLG pilot unit has been designed and constructed based on process simulation, lab scale tests and cold flow model study. The reactors adopt bubbling fluidized bed design for controlling solid residence time and reaction temperature. Non-mechanical valves have been investigated and applied for the high temperature solid looping system. The construction of the pilot unit has been completed and a series of tests have been conducted including instrumentation and control system commissioning, shakedown tests and cold flow studies. The startup, shutdown and emergency shutdown procedures have been discussed and documented. Experimental data from the design, construction, and testing will be used to identify and address technical issues, and evaluate the techno-economic feasibility of the CLG process.
CLG pilot plant in ENN Industrial Park, Langfang