Pulverized Coal Injection Rate Research Articles

A Method for Image-Based Interpretation of the Pulverized Coal Cloud in the Blast Furnace Tuyeres

The conditions in the combustion zones, i.e., the raceways, are crucial for the operation of the blast furnace. In recent years, advancements in tuyere cameras and image processing and interpretation techniques have provided a better means by which to obtain information from this region of the furnace. In this study, a comprehensive approach is proposed to visually monitor the status of the pulverized coal cloud at the tuyeres based on a carefully designed processing strategy. Firstly, tuyere images are preprocessed to remove noise and enhance image quality, applying the adaptive Otsu algorithm to detect the edges of the coal cloud, enabling precise delineation of the pulverized coal region. Next, a Swin–Unet model, which combines the strengths of Swin Transformer and U-Net architecture, is employed for accurate segmentation of the coal cloud area. The extracted pulverized coal cloud features are analyzed using RGB super-pixel weighting, which takes into account the variations in color within the cloud region. It is demonstrated that the pulverized coal injection rate shows a correlation with the state of the cloud detected based on the images. The effectiveness of this visual monitoring method is validated using real-world data obtained from a blast furnace of SSAB Europe. The experimental results align with earlier research findings and practical operational experience.

Optimization of pulverized coal injection (PCI) rate in an ironmaking blast furnace by an integrated process model

Pulverized coal injection (PCI) is generally used in modern blast furnace (BFs) ironmaking to reduce coke consumption by burning cheaper coal. This paper presents a numerical study on the effects of PCI on the inner states and overall performance of a 5000-m3 industrial BF. This is based on a recently developed integrated BF model that simulates an entire BF, including the raceway and hearth regions. The model is extended to consider the interaction between the raceway and the remaining BF region, the layered burden structure, and the hydrogen related reactions. After validation, it is used to study the effect of PCI rate and its interaction with oxygen enrichment and top burden distribution. The results are analyzed in detail in terms of raceway combustion characteristics, inner flow and thermochemical behavior, and overall performance. A maximum operable PCI rate is identified under given blast and burden conditions, beyond which relatively low coal-coke replacement ratio, high pressure drop and low hot metal (HM) temperature are observed. The maximum PCI rate is further improved with appropriate oxygen-enriched operation combined with suitable burden distribution. Excessive oxygen enrichment increases the coke rate to compensate for the cooling effect of coal injection. The results suggest that this integrated model can be used as a cost-effective tool to understand, quantify and optimize PCI effects on BF performance under different bottom and top operations.

Optimization of Pulverized Coal Injection (PCI) Rate in an Ironmaking Blast Furnace By an Integrated Process Model

Pulverized coal injection (PCI) is generally used in modern blast furnace (BFs) ironmaking to reduce coke consumption by burning cheaper coal. This paper presents a numerical study on the effects of PCI on the inner states and overall performance of a 5000-m 3 industrial BF. This is based on a recently developed integrated BF model that simulates an entire BF, including the raceway and hearth regions. The model is extended to consider the interaction between the raceway and the remaining BF region, the layered burden structure, and the hydrogen related reactions. After validation, it is used to study the effect of PCI rate and its interaction with oxygen enrichment and top burden distribution. The results are analyzed in detail in terms of raceway combustion characteristics, inner flow and thermochemical behavior, and overall performance. A maximum operable PCI rate is identified under given blast and burden conditions, beyond which relatively low coal-coke replacement ratio, high pressure drop, and low hot metal (HM) temperature are observed. With increasing PCI rate, the indirect reduction rate by CO increases to a maximum and then decreases; however, that by H 2 increases linearly. Consequently, the total indirect reduction rate increases first and then slows down. The maximum PCI rate is further improved with appropriate oxygen-enriched operation combined with suitable burden distribution. Too high oxygen enrichment increases the coke rate to compensate for the cooling effect of coal injection. The results suggest that this integrated model can be used as a cost effective tool to understand, quantify and optimize PCI effects on BF performance under different bottom and top operations.

Measurement study of preheated pulverized coal injection on combustion in a blast furnace raceway by visual detection

Pulverized coal injection (PCI) is a special process used in blast furnaces in which pulverized coal is preheated. However, there are few studies on the application of this technology in industry. In this paper, the combustion of pulverized coal in the tuyere of a blast furnace with different preheating temperatures and PCI rates is observed by a digital imaging detection system. The effects of the preheating temperature and coal injection rates on pulverized coal combustion in the raceway are obtained. The projected temperature field of the tuyere raceway of the blast furnace is obtained by image processing and the two-color method. The results show an increase in the preheating temperature will increase the average projected temperature of the raceway when the PCI rate is fixed. In addition, the influences of the preheating temperature and PCI rates on unburned pulverized coal are also studied. With the increase in the PCI rates, the area growth rate of the coal plume after preheating is smaller than that before preheating.

Technological advancements in evaluating the performance of the pulverized coal injection through tuyeres in blast furnace

The pulverized coal injection (PCI) is pursued to reduce the hot metal production cost by replacing the expensive metallurgical coke with the non-coking coal. Increasing the PCI rate causes various difficulties in the blast furnace (BF) operation. In the present work, an attempt is made to review the various aspects of PC injection in BF such as the challenges with increasing the PCI rate and modifications in the injection system to circumvent the concerns related to higher PCI rate. Various methods for detecting the tuyere blockage and failure caused due to the high PCI rate are elaborated. The factors influencing the combustion of coal in front of tuyeres have been discussed and their impact in the replacement ratio has been discussed. Further, recommendations are made to improve the coal combustibility in front of tuyeres.

Measurement study of the PCI process on the temperature distribution in raceway zone of blast furnace by using digital imaging techniques

Abstract The combustion process in blast furnace (BF) has play a significant role in providing heat resources, reducing agent and primary gas flow distribution. Accordingly, large proportion energy was also consumed and discharging massive amount CO2, the most effective way to reduce that is to increase the pulverized coal injection (PCI) rate to substitute the coke and maintaining stability state of BF. But the relationship of PCI rate and raceway temperature is still unknown. In this paper, the temperature detection system based on digital imaging techniques (DIT) has been firstly applied to study the tuyere temperature regularity on various conditions in 2500 m3 BF, such as different PCI rates, PCI cease and none PCI processes. And the colorimetric method was used to calculate the temperature distributions of tuyere images in raceway zone of BF. Moreover, the calibration, denoising and edge detection were firstly used to improve the accuracy of temperature detection. At last the influence regularity of PCI rate on the tuyere temperature was obtained. The studies not only could contribute to qualify the effect of the PCI rate on the temperature distribution in raceway zone, but also could useful to understand the pulverized coal combustion mechanism in BF raceway zone.

A reduced order mathematical model of the blast furnace raceway with and without pulverized coal injection for real time plant application

Pulverized coal is injected into blast furnace tuyeres to reduce coke consumption as well as to reduce hot metal production cost. Knowledge of the combustion behavior of pulverized coal in the blast furnace raceway zone and accumulation of unburnt char are of paramount importance. To alleviate the problem of high computational time of a multidimensional model, a reduced order raceway model of the blast furnace has been proposed for real time plant application. The model is capable of predicting radial temperature and gas composition profiles in the raceway zone with and without pulverized coal injection (PCI). Influence of all the key operating process parameters such as PCI rate, blast temperature, blast volume, oxygen enrichment and steam addition on the raceway combustion behavior, temperature and gas composition profiles as well as raceway depth have been investigated and validated with literature and plant database, wherever possible. It has been observed that with increasing PCI rate on a fixed fuel rate basis, the peak gas temperature (PGT) decreases and the location of PGT tends to shift toward tuyere nose. The present model is an efficient computational tool to predict the raceway process variables for online application, in synchronization with plant operation.

Numerical simulation and optimization of pulverized coal injection with enriched oxygen into blast furnace

The combustion characteristics of pulverized coal in the blast furnace raceway is an important factor which determines the performance of injection of pulverized coal with enriched oxygen as well as the energy consumption of blast furnace. Research was carried out to investigate processes including the gas and solid flow, particle movement, drying and pyrolysis of pulverized coal and combustion of carbon residue and coke in a blast furnace with standard k–ɛ model, discrete phase model, evaporation and diffusion model, dual parallel competition model and diffusion-kinetic combustion model respectively in Fluent 6.3. The accuracy and reliability of the numerical model was verified with a semi-industrial experiment. Moreover, 7 parameters were optimized by the orthogonal experiments, taking the burnout rate as the evaluation indicator. Results show that the burnout rate under the optimal condition can be increased by 110.8% comparing to that under the standard condition. The importance of parameters influencing the evaluation indicator is found in the order which is the type of the pulverized coal, the pulverized coal injection rate, the oxygen enrichment rate, the blast temperature, the spraying gun type, the blast volume and the angle.

Technological Status and Tendency of Modern Blast Furnace

In this paper, the present status and challenges of blast furnace (BF) ironmaking technology are analyzed, and the developing tendencies of the modern BF ironmaking technology are mentioned. The significance and function of high blast temperature and oxygen enriched-pulverized coal injection for BF ironmaking are described. The key technologies of high blast temperature, oxygen enriched, and pulverized coal injection (PCI) are discussed and evaluated emphatically. Promoting blast temperature and improving oxygen enrichment ratio, as well as enhancing PCI rate which are important guarantee for saving fuel consumption, reducing operation cost, and realizing sustainable development. There are broad developing prospects of modern BF process under the condition of high blast temperature and low fuel ratio ironmaking technologies are applied.

Off-gas Dust in an Experimental Blast Furnace

In blast furnace (BF) ironmaking, efforts are made to decrease coke consumption, which can be done by increasing the pulverized coal injection rate (PCR). This will cause changes in in-furnace reduction conditions, burden distribution, demands on raw material strength, etc. In order to maintain stable operation, but also to obtain low amounts of material losses through the off-gas, it is important to understand fines generation and behaviour in the BF. Off-gas dust and shaft fines generated in the LKAB Experimental Blast Furnace (EBF) were sampled during operation with olivine pellets and mixtures of acid pellets and sinter as iron-bearing materials. Characterization using XRD, SEM and LOM was focused on fines from iron-bearing materials, coke and slag formers. The results showed that flue dust, mainly 0.5 mm, was mechanically formed and created in the same manner for all investigated samples. Carbon-containing particles dominated in the fractions 0.075 mm and consisted mainly of coke particles from the shaft. Fe-containing particles, as Fe2O3 from the top of the shaft, formed the major part of flue dust fractions 0.063 mm. Particles from slag formers such as quartzite and limestone were observed in flue dust when slag formers were utilized in the feed. Sludge consisted mainly of chemically formed spherical particles 1 mm precipitated from the ascending gas as the temperature decreased.

Effect of Different PCI Practice on the Texture Obtained during Reduction of Iron Oxide Pellets

In modern blast furnace ironmaking, producers continuously strive to reduce coke consumption by replacing coke with e.g., an increased amount of injected pulverized coal. A change in pulverized coal injection rate (PCR) and injection coal type will influence the in-furnace conditions and thus the reduction of iron oxides. In the present study, the reduction behaviour of olivine pellets and textures formed were investigated in the LKAB Experimental Blast Furnace (EBF) and in laboratory scale. In the EBF, effects of injection of an low-volatile (LV) and an high-volatile (HV) coal type at different PCR while two types of oxygen supply methods were employed were investigated. The choice of injection coal type was conclusive for the Femet texture formed during reduction, extent of Femet carburization and K distribution in the pellets. The amount of volatile matters in the coal type had a greater effect on the reduction properties than the PCR and oxygen supply method. Laboratory experiments simulating PCR, based on measurements in the EBF, showed that the initial reduction conditions, in terms of temperature level and reduction gas composition, determined the pellet texture up to a reduction degree of at least 60%. The tests carried out in the EBF showed that the pellets were well suited for blast furnace reduction under all the investigated process conditions. The laboratory tests supported this conclusion.

Numerical Analysis of Static Holdup of Fine Particles in Blast Furnace

With increased in pulverized coal injection rate into blast furnace, the importance of understanding flow characteristics of powders within packed bed increases because more unburned char and coke fragments would be generated, it would be deteriorate permeability in the blast furnace. Although flow characteristics of dynamic or total holdup of powders in packed beds is found in several reports, 3-6) behavior of powders in blast furnace using separate treatment of dynamic and static holdup has yet to be reported. In this study the behavior of static powders was examined through numerical simulation using the “four fluid model”, 3) which included the formulation of static powders behavior. The model results were compared with two dimensional temperature distributions measured in the furnace for three different pulverized coal injections (PCI) rates (100, 200 and 250 kg/thm) for validated. The model was applied to quantitative analysis of static powders holdup in the blast furnace operation with high-rate pulverized coal injection. The higher amount of static powders holdup was found mostly in the center lower deadman, above and below the tuyere level, and in upper shaft, for PCI rate 100 kg/thm, 150 kg/thm, 200 kg/thm and 225 kg/thm respectively. The lower amount of static powders holdup was found in the raceway region throughout the surface of deadman.

Improvement of production and high temperature properties of low SiO2 sinter

It is very important both to use low price ore for the sinter plant and to improve the sinter high temperature properties in view of high PCI rate. At the Kokura sinter plant, the granulation of the sinter mixture has been improved by introducing a high agitating mixer. The sintering operation using low price ore is now carried out successfully. The high temperature behaviour is improved by reducing the SiO2 content in the sinter, and a pulverized coal injection rate up to 180 kg/thm has been achieved at the Kokura blast furnace.

Raceway behaviors in blast furnace with pulverized coal injection

The blast furnace raceway shows different characteristics with PCR (pulverized coal injection rate). It was found in this study that with the increase of PCR the raceway depth decreases, and the size of birds nest and sometimes with liquid holdup, increases. Oxygen enrichment with co-axial lances was known to be very effective on the extension of raceway depth and size reduction of birds nest. It was also found that there are various factors which affect the coke properties at tuyere level of the blast furnace. Coke traveling time was calculated to be extended with PCR and it had a close relationship with the coke size in bosh. Coke mean size decreased with the increase of coke traveling time, that is, with the increase of PCR. Both DI (the strength of coke in cold) and CSR (the strength of coke after reaction) were also decreased with PCR. RAFT (Raceway Adiabatic Flame Temperature) had a tendency to be decreased with the increase of PCR, which is obtained by the estimation of coke temperature via XRD analysis. From the analysis of alkali contents in coke sampled along the radius of the blast furnace, it was understood that no difference in alkali contents betweenmore » fine and lump coke represents that coke fines generated from upper burden might appear at tuyere level.« less

Operational results for high pulverized coal injection rate at Kimitsu No. 3 blast furnace

In order to further develop the technology for high-rate pulverized coal injection (PCI), namely over 200 kg/t-pig, Nippon Steel performed a high injection rate test at the Kimitsu No. 3 blast furnace in November, 1993. The paper describes PCI equipment; the operational design of the test, including blast conditions, reducibility of sinter, coke strength and burden distribution; and test results. These results include a discussion of the transition of operation, burden distribution control, replacement ratio of coke, permeability at upper and lower parts of the furnace, reducibility at lower part of the furnace, accumulation of fines in the deadman, and generation and accumulation of unburnt char. Stable operation was achieved at a PCI rate of 190 kg/t-pig. With injection rates between 200--300 kg/t-pig, the problem becomes how to improve the reduction-meltdown behavior in the lower part of the furnace.

Operation of Kakogawa No. 1 blast furnace with high pulverized coal injection rate

Kakogawa No. 1 blast furnace has increased its pulverized coal (PC) injection rate from 100 kg/thm, after the enlargement of the PC injection system which was completed in October 1992. And the PC injection rate reached more than 180 kg/thm in October 1993 and this stable operation is being maintained.

高炉レースウェイ周辺部の圧力,温度および炭材粉率におよぼす微粉炭吹込みの影響

Pulverized Coal Injection (PCI) tests were carried out by using a coke-filled test furnace to clear the combustion behaviour of Pulverized Coal (PC) in a blast furnace and its effects on the furnace phenomena.Effects of Pulverized Coal Injection Rate (PCR) and charged sinter on pressure drop, temperature and fine particle fraction distribution in the test furnace were studied. On the basis of these experimental results, carbon solution loss reaction rates of unburnt PC and fine coke was measured with "in-situ" analysis of high temperature gas. The results obtained are as follows.(1) Increase in blast pressure with PCI is much dependent on the increase in blast velocity by PC combustion in the blow pipe.(2) As unburnt PC accumulated in the furnace is gasified with CO2 much faster than fine coke, it has no harmful influence on the pressure drop in the furnace.(3)As descending velocity of solid at the peripheral part in blast furnace bosh decreases with increase in PCR, furnace heat loss increases.