(210c) Demonstration of a Commercial Scale Circulating Fluidized Bed Gasifier for Industrial Fuel Gas

Coal is the main energy resource of China and will continue to be predominant in the next few decades. Coal gasification has attracted worldwide interest due to its high efficiency and low pollution emissions. With the steadily rising demand in clean fuel gas, circulating fluidized bed (CFB) gasification has become one of the most popular gasification technologies in Chinese market. Some advantages of CFB gasification are that it can use low-cost pulverized coal, has satisfied adaptability of a wide range of solid fuels, can use poor quality coals and emits lower amounts of pollutants.

In 2015, Institute of Engineering Thermophysics (IET) had designed and built up 5 sites of CFB gasification system in Guangxi province. The designed fuel gas production capacity is about 40000 Nm³/h for one site. The produced clean fuel gas is used to provide heat for alumina calcination. Novel key technologies were developed and carried out in this system, including counterflow air cap, air preheating technology and direct slag disposal technology.

In 2016, different types of low rank coals were used as feedstocks to study their gasification performances and operation stability of the CFB gasifiers. More than 320 days of long-term and stable operation has achieved, and significant experimental results are obtained to improve gasifier design and operation. For example, Shenhua lignite coal, and blended coal of Shenhua with Baikuang coal were investigated during industrial trials. The system temperature and pressure are stable, and no slagging phenomena occur. When shenhua coal is used as feedstock, the cold gas efficiency, the carbon conversion and the gas heat value of Shenhua coal gasification are 71.96%, 86.90% and 5.59 MJ/Nm³. With the same air flow rate (about 18700 Nm³/h), the cold gas efficiency, the carbon conversion and the gas heat value of blended coal gasification are 63.91%, 81.24% and 5.35 MJ/Nm³. Mainly due to the poor gasification reactivity of Baikuang coal, the gasification performances of blended coal are lower than shenhua coal, but the produced fuel gas could satisfy the production of the alumina calcination. When Baikuang coal is added to Shenhua coal, the ash fusibility characteristics of Shenhua coal could be improved, which is helpful to achieve the long-term operation of industrial gasifier. The results indicate that CFB gasification is an efficient and clean coal conversion technology with low cost and high social recognition.