Zhejiang University’s new swirl nozzle technology for multiple fuels generates high-quality superheated steam for the first time

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On August 16, it was learned from the Institute of Thermal Energy Engineering at Zhejiang University that significant progress has been made in China’s water-coal slurry waste boiler gasification technology: a new gasification process using a multi-fuel nozzle cyclone system has been developed by this institute. The biggest feature of this process is the overhead multi-fuel nozzles; the inclination angle of the auxiliary nozzles is adjusted according to the properties of the fuel and the scale of the gasifier in order to optimize the flow field within the gasifier ； It pioneered the production of high-quality superheated steam as a by-product of waste boilers; this new process technology can be applied to newly constructed plants as well as to the retrofitting of existing water-coal slurry systems, offering significant economic benefits. 　　According to Professor Wang Qinhui, head of the R&D team for this new process, from the Institute of Thermal Energy at Zhejiang University, the multi-fuel nozzle swirl gasification process is a new gasification technique developed by that institute and covered by independent intellectual property rights. It is the result of Zhejiang University’s long-term research and development, as well as application of technologies related to coal combustion and gasification; by building upon existing mature coal-water slurry gasification technologies, the university has carried out improvements and innovations, focusing on the development of key technologies such as top-mounted multi-fuel swirl nozzles and superheated steam generated as a by-product of the process. The gasification furnace employs a combined burner system consisting of a main nozzle and a secondary nozzle positioned at the top; the flow field generated by the main jet, along with the swirl produced by the secondary nozzle, helps to create a more uniform flow pattern within the furnace, thereby increasing the carbon conversion rate. At the same time, by taking advantage of multiple nozzles, different raw materials can be gasified, enabling the simultaneous gasification of coal, coke dust, oil residues, solid waste, and biomass – thus meeting the demands of modern coal chemical industry for larger scale operations and a greater diversity of raw materials. 　　It is understood that this new process technology features a combustion gasification chamber equipped with a membrane-type water wall at the upper part of the gasifier, and a quenching chamber with a radiant waste boiler at the lower part; the radiant waste boiler is fitted with a steam generator and a steam superheater. A water-cooled wall gasifier can increase the operating temperature of the combustion chamber, thereby expanding the range of coal types that can be used; it is capable of processing coal with low volatility, high ash content, high ash fusion point, and high sulfur content. Its core components, the radial steam generator and steam superheater, draw on the structural design concepts of liquid slag-discharge cyclone boilers, enabling effective avoidance of the slag blockage and ash accumulation problems associated with similar technologies both domestically and internationally. By recovering the heat from high-temperature syngas, it generates high-quality superheated steam; this steam can be directly integrated into the plant’s overall superheated steam network to serve as power steam for driving compressors and other turbines, or it can be used for superheated steam power generation, thereby creating additional economic benefits for the enterprise. At the same time, the heat efficiency of gasification is significantly improved compared to existing coal-water slurry gasification processes both domestically and internationally, which represents another important advancement in the research, development, and application of large-scale coal gasification technologies. 　　Our country is short of oil and gas, but has relatively abundant coal resources; coal serves as our country’s primary energy source and an important raw material. Against the backdrop of current efforts to reach carbon peak and carbon neutrality, making use of the relatively abundant coal resources to develop a clean coal-based energy and chemical industry driven by advanced coal gasification technologies, in order to achieve direct or indirect substitution for oil and gas, holds great strategic significance for ensuring energy security, realizing sustainable development, and promoting the clean and efficient conversion and utilization of coal. 　　It is said that gasification technology is the core technology for the clean and efficient conversion and utilization of coal, as well as the key technology for the development of the modern coal chemical industry. In the high-temperature and high-pressure fluidized-bed gasification technology, process transfer plays a crucial role during the gasification process. Currently, the heat recovery from the high-temperature syngas produced by coal-water slurry gasifiers is mainly achieved through two methods: the quenching process and the waste boiler process. The quenching process has a simple structure, but it consumes a large amount of water, is inefficient, and suffers from significant heat losses. The waste boiler process has a complex structure and poor operating conditions; existing waste boiler gasification technologies generally feature short operation cycles, tend to get clogged with slag, and produce large amounts of low-quality saturated steam that is difficult to utilize. 　　Wang Qinhui stated that, compared with existing similar technologies at home and abroad, the new multi-fuel nozzle swirl gasification process improves the thermal efficiency of the system while enhancing the versatility of the fuels it can use, thereby providing a better technical solution for the efficient and clean utilization of various carbon-containing materials, including \"high-carbon, high-sulfur, and high-ash\" coals. By leveraging technological innovation to reduce costs and improve efficiency, as well as to save energy and reduce consumption, clean and efficient conversion of coal can be achieved, yielding significant social and economic benefits.