Study On Caking And Coking Properties Of Coal Group Components And Its Application In Coal Blending For Coking

Taking coking coals as the research objects,pyrolysis properties of coal group components were investigated and the relationship between structural features of functional groups and swelling of loose medium component was analyzed quantificationally.Effects of coal group components on rheological properties(swelling and fluidity)of raw coal and its mechanism were studied.Coal coking process was discussed based on pyrolysis properties of coal group components.Two methods were used to establish prediction models.The results are as follows:During pyrolysis process,all group components show distinct morphological changes.The pyrolysis of dense medium component is mainly characterized by its strong fluidity.During coking process,dense medium component could form liquid phase,fill the gaps between coal particles,and finally form coke with certain strength.The pyrolysis of loose medium component is mainly characterized by its strong swelling which plays an important role in pore-forming and provides certain swelling pressure to promote adhesion between solid particles.Heavy component is an inert substance in coal coking process and basically keeps shape unchanged during the pyrolysis process.Most light component decomposes into gas during the pyrolysis process and it has little effect on coal coking process.The ratio of lipid hydrogen and aromatic hydrogen is the primary factor which affects the swelling of loose medium component while the length and branching degree of fat chain is the secondary factor.Both of them are key factors to determine the swelling of loose medium component.In loose medium component,the content of a specific form of hydrogen bond—hydroxyl tetramer,plays a complementary role on above-mentioned factors.In the coking process,heavy component serves as skeleton and hinders the flow of liquid phase.The content of heavy component is the main factor affecting the fluidity of coal.Dense medium component which generates liquid phase and causes fluidity,plays an auxiliary role on the fluidity of raw coal.Light component and loose medium component have no significant influence on the fluidity of coal.The main contribution of loose medium component is to provide the swelling of coal which is mainly determined by the swelling of loose medium component while the content of loose medium component has little effect on the swelling of coal.Based on the caking and coking properties of group components and their different functions in coal coking process,the coking mechanism was established.The coking process of coal is divided into 6 stages:(1)room temperature-200 ?,the drying stage of coal;(2)200-340 ?,the softening stage of dense medium component;(3)340-440 ?,the flowing stage of dense medium component;(4)440-500 ? the swelling stage of loose medium component which can be divided into swelling rapidly stage(440-460 ?)and swelling slowly stage(460-500 ?);(5)500-540 ?,the stage of curing to semi-coke;(6)540-1000 ?,the semi-coke shrinkage stage for coke.Coke quality prediction models were constructed by the methods of multiple regression and support vector machine(SVM)respectively.The average relative errors of multiple regression models for MSI,PRI,and PSR are 3.88%,2.53%,and 17.92% respectively while the average relative errors of SVM models for MSI,PRI,and PSR are 1.78%,0.90%,and 10.32% respectively.SVM models have higher consistency between predicted values and measured values for MSI,PRI,and PSR.