Basic Research On Pulverized Coal Injection Mixed With Sludge In Ironmaking Process

Pulverized coal injection is an important technology in metallurgical production,and it has been widely used in many ironmaking processes.With the continuous progress of metallurgical technology,we can predict that the pulverized coal injection will continue to develop.Therefore,the problem of stable coal transportation is still the focus of attention of metallurgical workers.As we know,a lot of sludge is produced in the process of iron and steel production.The majority of sludge is recyclable resource.With the increasing attention to resources and environment problems,it is particularly urgent to strengthen the comprehensive utilization of sludge.As pulverized coal and sludge belong to fine powder,the problem is put forward that mixing pulverized coal and sludge will be used in the ironmaking process,so as to realize the comprehensive utilization of sludge,and provide a new way for the utilization of dusting sludge.Through analyzing the composition and physical properties of pulverized coal and sludge in typical iron and steel enterprises and the basic properties of fluidity,flowability,grindability and ignition point,the feasibility of mixed injection of pulverized coal and sludge was analyzed,and giving the appropriate mixing ratio.The following conclusions:1.Through the physical properties analysis of the powder used in the study,Al has the highest fixed carbon content(77.72%).B has the highest volatile content(30.65%)and the fixed carbon content is the lowest.The sludge content of TFe is relatively high,up to 52.29%,which has a high utilization value.The maximum particle size of-74μm is 79.68%,followed by B with 74.02%and A2 with 73.26%.Compared with pulverized coal,the particle size of the sludge is finer,and the proportion of-74μm reaches 93.19%.Meanwhile,the sludge has larger specific surface area.Reasonable particle size distribution in order to achieve a mixture injection of pulverized coal and sludge lays a good foundation.2.In this paper,we studied the flowability of pulverized coal of typical iron and steel enterprises and found that when the Carr flowability index F(index)is between 45 and 52,the production requirements can still be met.Therefore,the subsequent work also considers this standard as research reference.For mixed pulverized coal,liquidity of binary mixed powder has a certain trend of convergence,the flowability is between two kinds of single powder.By comparing the above criteria that the mixture ratio of A2:B=3:7,it owns the best flowability of pulverized coal,the F(index)is 48.Similarly,the studies have shown that the sludge has the effect of improving the pulverized coal flowability.Based on the above results,and the consideration of pulverized coal flowability and comprehensive utilization of the sludge,it is considered that the suitable mixing ratio is A2:B=7:3+10%of S.3.The results showed that the floodability of sludge was the strongest and the second was B,while the floodability of A1 and A2 were weaker than that of the above two powders,of which A2 was the weakest.The floodability of mixed pulverized coal tends to be neutral,and tends to account for the floodability of larger proportion of pulverized coal.Regardless of single coal,mixed coal,the floodability of the pulverized coal are strong,especially the dust,the Fl(index)up to 77,and Fl(index)requires powder should less than 70.However,the test results of the floodability of pulverized coal in the field show that when the Fl(index)is between 71 and 79,the production requirements are still met.In conclusion,the Fl(index)of A2:B=7:3+10%of S is relatively low at 74.4.The grindability of coal is characterized by HGI.The greater HGI,the better the grindability of the coal.The grindability of the coal is related to its moisture content,ash content and volatile matter content.The higher moisture content may result in a lower HGI.As the ash in the coal increases,its grindability is better.5.Anthracite Al in a single pulverized coal has a maximum ignition point of 393℃,an A2 of 376℃ and a minimum of 300℃ for the bituminous coal B.The ignition point of bituminous coal is generally lower than that of anthracite coal.Because the volatile content of bituminous coal is higher than that of anthracite,the ignition point of coal decreases with the increase of volatile content.The ignition point of mixed pulverized coal has a certain trend of convergence.The ignition point of mixed coal is between the ignition points of two kinds of coal.With the increase of anthracite proportion,the ignition point of mixed coal increases.No matter whether a single kind of pulverized coal and mixed pulverized coal are added with sludge,the ignition temperature of the powder basically increases.Blast furnace requires the ignition point of pulverized injection coal at 350℃～400℃,from the study results,sludge with 10%range,the ignition point to meet the basic requirements of coal injection.Comprehensive study on the composition,basic physical properties,flowability and floodability,grindability and ignition point of pulverized coal and sludge and its mixed powder.According to the research,the most suitable mixing ratio is A2:B=7:3+10%of S.At this time,both the stable output of the powder can be ensured,and a new idea for the comprehensive utilization of the sludge can be provided.