Feasibility Study of Using Carbide Slag as In-Bed Desulfurizer in Circulating Fluidized Bed Boiler

Abstract

Carbide slag is a waste residue during the production of acetylene. Due to its high content of Ca(OH)2, carbide slag becomes a potential alternative to limestone as the in-bed desulfurizer of circulating fluidized bed (CFB) boilers. In this study, the calcination and sulfation characteristics of carbide slag were investigated by three different facilities, thermogravimetric analyzer (TGA), 1 MWth pilot CFB boiler, and 690 t·h−1 CFB boiler. Pore structures and sulfation behaviors of carbide slag and limestone were investigated for the sake of comparison. The results showed that carbide slag has a lower calcination temperature than limestone. Its calcined product has a better pore structure and desulfurization activity. The carbide slag exhibited a higher desulfurization efficiency than the limestone in the pilot tests. The SO2 emission concentration showed a downward trend with the increase of molar fraction of carbide slag in the desulfurizer. Meanwhile, carbide slag had a better sintering-resistance property, which makes it possible to effectively reduce SO2 emissions even at high combustion temperatures (>910 °C). While the field test results were similar to that of the pilot tests, the desulfurization efficiency of carbide slag with the same Ca/S mole ratio was higher than that of limestone. The fine size of carbide slag particles and the lower separation efficiency of the cyclone on the 690 t·h−1 boiler left the carbide slag with insufficient residence time in the furnace. Therefore, it is necessary to ensure a high separation efficiency of the cyclone if the carbide slag is used as an alternative desulfurizer in furnace.

Desulfurization Characteristics of Carbide Slag during Circulating Fluidized Bed Coal Combustion

“…A temperature increasing from 800 to 920 °C caused a decrease in the desulfurization efficiency from 66.7 to 60.5% when the Ca/S molar ratio was 2. This finding aligns with a previous study conducted in a 690 t/h CFB boiler using carbide slag as a desulfurizer, which demonstrated that the desulfurization effectiveness decreased as the bed temperature rose from 870 to 940 °C …”

“…The use of carbide slag as a CFB desulfurizer can be classified as this category. The desulfurization performance of carbide slag during coal combustion was evaluated in previous research studies. − Cheng et al and Zhen and Lu compared the desulfurization property of carbide slag and limestone during coal combustion in a fixed-bed reactor and found that the desulfurization efficiency of carbide slag was higher than that of limestone at 1000–1100 °C. Zhen and Ji found that the sulfur capture ability of carbide slag during coal combustion could be improved at 900 °C when the salt slurry was added with the mixing ratio of 2:8.…”

“…Zhen and Ji found that the sulfur capture ability of carbide slag during coal combustion could be improved at 900 °C when the salt slurry was added with the mixing ratio of 2:8. Huang et al conducted an experimental study on the feasibility of using carbide slag as a desulfurizer in a 1 MW pilot CFB boiler and 690 t/h CFB boiler. The bed temperature was in the range of 870–940 °C during the experiment.…”

What are the resource benefits of circulating fluidized bed power generation technology? Take some key thermal power units in China as an example

“…Compared to the other main boiler types of coal-fired power plants, the CFB boiler has many advantages, such as wide fuel adaptability, low-cost in-bed desulfurization. 2 At present, there are few analyses and measurement studies on CFB technology resource benefits in China. There are few studies on CFB technology for recycling of low calorific value coal and sustainable development of coal resources.…”

“…Compared to the other main boiler types of coal‐fired power plants, the CFB boiler has many advantages, such as wide fuel adaptability, low‐cost in‐bed desulfurization …”