Research On Experiment Of Gasification Tar Cracking And Free-Tar Gasification Technology

Coal gasification is one way of clean utilization of coal, but production of coal tar in gasification is the bottle-neck which restricts the high efficient gasification, which can induce pipelines jam, equipment eroding, energy waste and environment pollution, etc. So, it is extremely important to solve the problem of gasification tar for the whole gasification system and even for sub-equipment.This paper gives a review on various factors which affecting tar content, from aspect of factors in gasifier, gasifier configuration and gas purifying respectively. It shows that, factors in gasifier and gasifier configuration can reduce tar content both because, they affect tar cracking reaction and amplify the transmutation ratio of tar. While purifying outside the gasifier which transforms tar from gas state and collects, but the energy in tar is not reclaimed sufficiently, which may arose secondary pollute. So, amplifying tar cracking reaction is a dependable and effective way of reducing tar content in gas.In the experiment on component and property of gasification tar, it shows that, although it contains much hydroxybenzene, has high burning capability, also suit to distillate carbon fiber, because of coal species and technics, gasification tar contains much impurity, which makes its quality low, processing capability not good enough, that means deep processing for gasification tar is much difficult. Otherwise, the cost on collecting, transporting and depositing procedure restricts the scale of gasification tar processing industry. As far as current condition is concerned, gasification tar processing needs time to become mature, to which the better way is being treated in forming tache.It is found in the experiment on tar cracking that, the conversion of tar is enhanced remarkably as temperature and time increasing, which achieves 91.73% under the condition of 1200℃,12s. The component of gas is changed respectively after cracking, which makes its caloric value increased. It shows that, cracking reaction can reduce tar content in gas, but also change its component, improve its quality. The experiment on catalyze cracking shows that, tar conversion reaches 94.75%, the temperature that tar reaches the same conversion needs drops 30% while comparing with no catalyze used condition. Meanwhile, the experiment shows that, the using life and catalyze effect is always reduced by problem of carbon deposit and active attenuation.This paper proposes the conception of tar-free coal gasification; namely, reducing tar content in gas by way of amplifying cracking reaction, which can lighten the load of purifying, avoid problem of tar processing. After comparing all kinds of cracking methods, it shows that, the way of thermal cracking in gasification is much more economic and practical, which is the basic conception for designing gasifier. Optimizing gasifier configuration bases on the down-draft gasifier. Secondary air and throat can enhance temperature; taper deoxidization area and Venturi ejector can postpone the staying time in high temperature area, which are all essential condition for tar cracking.