Process intensification on suspension pyrolysis of ultra-fine low-rank pulverized coal via conveyor bed on pilot scale: Distribution and characteristics of products

From the perspective of intensifying the pyrolysis process, suspension pyrolysis characteristics of ultra-fine low-rank coal via conveyor bed (1500 kg/h) were studied. The effects of coal particle size, pyrolysis temperature, and heating rates on the distribution of products were investigated. The relationship between the pyrolysis process and product quality, such as gas, tar, and char, was analyzed. The results showed that suspension pyrolysis enhanced the heat and mass transfer of the upgrading process. When the pyrolysis temperature was between 550 and 650 °C and coal particle size in the range of 0.075 ~ 0.105 mm, the yield of tar reached about 145% of the Gray-King tar yield. The analysis of group composition and four main components of tar showed that each fraction contained a certain amount of chain hydrocarbons or saturated hydrocarbons, which were mainly aromatic hydrocarbon compounds. The effective gas content from pyrolysis was H₂ (19.32 vol%), CH₄ (17.59 vol%), CO (12.53 vol%), and the low calorific value was about 900 kcal/Nm³. With the increase of pyrolysis temperature, the overall yield of pyrolysis gas increased, and the yields of H₂ and CH₄ increased linearly with temperature. The mass fraction of volatiles in char was less than 8%, while the mass content of fixed carbon was more than 80%. With the increase of pyrolysis temperature, the fixed carbon and ash content of the char increased, but the volatile matter decreased. This study provides a fundamental basis for the improvement of the pulverized coal pyrolysis process on large-scale installation.