Development on cyclone-finger roller two-stage purification device of pyrolysis gas from straw carbonization

Carbonization is one of the effective measures for utilization of straw. However, the tar and dust produced by carbonization are mixed in the pyrolysis gas, which will hinder the extraction and subsequent utilization of the flammable gases in the gas, and the tar may stick onto the inner wall of the device if the gas was not purified. And the air may be seriously polluted if it is vented into the air without purification. A two-stage purification device which consisted of a cyclone and a finger roller in its exhaust tunnel was designed in this study to improve the purification rate of carbonized flue gas, the structural parameters of the device were determined and the finger rod was designed. To get an efficient purification of the gas, the cyclone is the first stage which separates large particles in the gas by centrifugal force, and finger roller is the second stage which collides and gathers small particles into large particles and separates the particles along the taper finger by centrifugal force. The quadratic regression experiment with general rotary design method was carried out, with factors of the finger roller speed, the flue gas inlet speed and the core tube insert distance and with indicators of the flue gas purification rate and the pressure loss, the variance analysis and surface response analysis of the data were conducted with software Design-Expert8.0.6, and the mathematic models between the indicators and factors were established. The results showed that the three factors had significant effect on the purification rate and pressure loss of flue gas (P<0.01); The impact order of factors on pressure loss was as follows: finger roller speed > inlet gas speed >core tube insert distance, and the order of factors on purification rate was as follows: finger roller speed >inlet gas speed >core tube insert distance. As for effect of interaction of factors, the interactions of finger roller speed and inlet gas speed, inlet gas speed and core tube insert distance had significant effect on the pressure loss (P<0.01); the interaction of finger roller speed and inlet gas speed was extremely significant on purification rate (P<0.01). The optimal combinations of factors and levels were determined with optimization of multiple indices and verified through experiment. The optimal parameters were finger roller speed of 3 030 r/min, inlet gas speed of 19.5 m/s, insert tube distance of 210 mm, under the conditions, the pyrolysis gas pressure loss was 1 971.73 Pa, the purification rate was 84.2%. It can meet the requirements of pyrolysis gas purification of straw carbonization. This study may provide a reference for the development of pyrolysis gas purification device.