Sinter Pot Tests Research Articles

Application of coalbed methane assisted iron ore sintering: Injection effect, pollutant abatement and economic evaluation

Hydrogen-rich gas injection, which has garnered widespread attention from academia and industry, is an effective method for reducing CO2 emissions during the sintering process and for improving sinter quality. Coalbed methane (CBM) is a cost-effective and reliable hydrogen-rich gas resource in China. In this study, we investigated the injection effect of CBM in assisting iron ore sintering. Additionally, we determined the appropriate injection parameters by systematic sintering pot tests and compared it with coke oven gas (COG). The impacts of CBM injection on pollutant abatement and combustion efficiency were analyzed based on the variations in the sintering flue gas composition, and a comprehensive economic evaluation was conducted. The results showed that injecting 0.51 vol% CBM between 5 and 13 min after ignition with 0.3 wt% coke breeze ratio reduction could significantly improve the sintering index and the uniformity of heat distribution within the sinter bed. Excessive injection would affect the bed permeability. CBM took advantage over COG at a gas–solid heat transfer ratio of 1:1.28. The four-stage cascade mode with a gradient of 0.18 vol% and the intermittent mode with an intermittent time of 0.5 min could optimize the injection effect. However, the cascade mode performed better. Besides, injecting CBM increased the emission reduction rates of CO and NOx and improved combustion efficiency by 5.72%, 4.47%, and 1.46%, respectively. Overall, the cost-savings were CNY 2.19 per ton sinter, and the annual production cost could be reduced by approximately CNY 6.71 million for a 265 m2 sintering machine. The profits achieved because of CBM injection can be further improved by increasing the bed permeability and mixed injecting with other gas media. This study provides an effective path for green transformation of sintering production.

A new disposal method for white mud: Replacing limestone in iron ore sintering

The pulp production process generates a CaCO3-rich solid waste known as white mud (WM), and its improper disposal is a cause for global concern. The present study investigates the composition, microstructure, and thermal decomposition characteristics of WM and proposes a strategy for replacing limestone with WM for iron ore sintering. Granulation and sinter pot tests were performed to evaluate the influence of added WM on the granulation and sintering processes. We assess the feasibility of using WM as a flux and discuss the mechanism through which WM affects the mineral phase and strength of the sinter based on metallographic and micropore observations. The results indicate that the sintering rate remains stable after replacing 50% of the limestone with WM via moisture control, and the quality and production indicators of the sinter do not change. Moreover, the mineral phase and microporosity remain similar to the basic case without WM, and the comprehensive index decreased by only 5.5%. Overall, this study demonstrates that it is feasible to replace 50% of limestone with WM in industrial sintering plants, which could significantly increase our WM disposal capacity and bring additional economic benefits.

Recovery of Valuable Materials with the RecoDust Process

The RecoDust process is a pyrometallurgical process for treating steel mill dusts that cannot be recycled internally due to their zinc content, providing numerous benefits compared to conventional processes. State-of-the-art processes often face the problem of recycling only zinc, but not iron, which is frequently landfilled and withdrawn from a closed loop. Furthermore, these processes are also often limited to a specific zinc content in the feedstock. Within the described RecoDust smelting campaigns, basic oxygen converter dust with about 15 wt.% zinc was taken as feedstock. After high-temperature treatment of the input material, the RecoDust slag (RDS) has a zinc content of 0.4 wt.% and the crude zinc oxide (CZO) has a ZnO content of up to 80 wt.%. The RDS is suitable for use in the sinter plant as a secondary raw material. To investigate the influence of adding RDS to a common sintering mixture, sintering pot tests followed by RDI (reduction disintegration indices) tests were carried out. The influence of the admixture of RDS on the RDI values is not detectable. The CZO was fed into a soda extraction system for halogen removal. The halogen removal of this two-stage leaching was highly efficient with over 90% for chlorine.

Preparation of gangue ceramsite by sintering pot test and potential analysis of waste heat recovery from flue gas

Preparation of gangue ceramsite by sintering pot test and potential analysis of waste heat recovery from flue gas

Strengthening Granulating and Sintering Performance of Refractory Iron Concentrate by Pre-Pelletizing

May Concentrate Iron ore, as a refractory iron concentrate, deteriorates the permeability of the sintered layer during the sintering process due to its fine particle size and poor granulating performance. Therefore, it cannot be widely used in iron ore sintering. In this study, the strengthening granulation of May Concentrate Iron ore using pre-pelletizing to expand its utilization ratio was proposed. The experiments of conventional granulation, pre-pelletizing granulation and sinter pot test were carried out. Increasing May Concentrate Iron ore (a refractory iron concentrate) proportion was detrimental to conventional granulation, reducing the quasi-particle particle size and strength. May Concentrate Iron granulating and sintering performances were improved by pre-pelletizing. The quasi-particle average size at 36% May Concentrate Iron proportion jumped to 4.92 mm of pre-pelletizing granulation from 3.22 mm of conventional granulation. Meanwhile, the permeability index rose to 0.33 from 0.11, while the falling and drying pulverization ratio fell to 7.05% and 6.11% from 22.59% and 15.88%, respectively. The consolidation mode of matrix materials was liquid phase consolidation, while that of May Concentrate Iron pellets was solid phase consolidation, forming the structure of the pellets embedded in the matrix materials. Furthermore, the partial alkalinity of the matrix materials was increased because of the separation of May Concentrate Iron, generating a large amount of acicular calcium ferrite with better consolidation strength than conventional granulation sintering.

Intensive carbon combustion in sintering packed bed via steam spraying: An experimental study on carbon monoxide emission reduction.

Improving the combustion efficiency of solid fuels is important for reducing carbon monoxide emissions in the iron ore sintering process. In this paper, the surface steam spraying technology is introduced in the sintering process based on the auxiliary combustion effect of steam on coke, and its potential to reduce carbon monoxide emissions is demonstrated. Thermogravimetric analysis experiments of coke breeze in air and air-steam mixed atmosphere are carried out, and the results show that the introduction of steam can reduce the concentration of carbon monoxide in the exhaust gas from 183×10-6 to 78×10-6. At the same time, the mechanisms of carbon monoxide emission reduction by surface steam spraying technology are analyzed from the thermodynamic and kinetic perspectives. Then, a series of laboratory-scale sintering pot tests are carried out under no spraying operation, interval spraying operation, and continuous spraying operation. The results indicate that both interval and continuous spraying operations can reduce carbon monoxide emissions. The optimal mode of steam spraying under the present experimental conditions is continuously spraying for 13 min at a volume rate of 0.053 m3/min. Compared with no spraying, the average carbon monoxide concentration in the exhaust gas is reduced from 7565×10-6 to 6231×10-6, and total carbon monoxide emissions for per ton sinter are reduced from 13.46 m3/t to 9.51 m3/t.

Influence of Sinter Parameters on CO Emission in Iron Ore Sintering Process

Carbon monoxide is the major hazardous component in flue gas exhausting from the iron ore sintering. This study aims to reduce the CO emission by changing the sinter parameters by sintering pot tests; specifically, the sinter quality, CO concentration, and total emission in sintering flue gas were analyzed in detail. The sinter strength properties, including the shatter index and the tumble index, are analyzed by the sintering pot test and the sintering flue gas discussion. The results show that the CO emission can be suppressed by modifying the sinter parameters, such as carbon content, coke breeze and coal breeze ratio, water addition, and sintering negative pressure. The good sinter parameters with the lower CO emission are 2.8% carbon content and 7.5% water in the sintering mixture. A higher coke breeze to coal breeze ratio, or only coke breeze fuel in the sinter mixture, is beneficial for the lower CO emission with a negative fan pressure of −12 kPa.

Study on Influencing Factors of High-Temperature Basic Characteristics of Iron Ore Powder and Optimization of Ore Blending.

In order to explore the reasonable ore blending of low-silicon magnetite in sintering, it I necessary to realize the efficient utilization of low-silicon ore, further reduce cost, and increase yield. In this study, based on the high-temperature basic characteristics of iron ore powder used in the experiment, sinter pot tests were carried out with different low-silicon ore ratios, and the microstructure of the sinter was observed by scanning electron microscopy (SEM) and energy spectrum analysis (EDS) to determine the optimal matching law of low-silicon ore. The result showed that SiO2, Al2O3, and burning loss in iron ore powder composition were positively correlated with its assimilation, whereas MgO and basicity R2 were negatively correlated with the assimilation of iron ore powder. When the ratio of low-silicon ore was not more than 35%, increasing the ratio of hematite improved the liquid production and increased the production of acicular calcium ferrite. Therefore, the optimization of ore blending based on assimilation can improve the quality of sinter and strengthen the sintering process. This study has certain reference significance for the industrial production of low-silica sintering.

Efficient double-layer sintering of titanomagnetite concentrate

The traditional titanomagnetite sintering process consumes high fuel and produces weak-strength sinter. In this study, double-layer sintering was used to solve above problems. The theoretical analysis and sintering pot test results showed that sintering of feed bed constituted by two different-basicity layers could improve mineralization and permeability. By using the double layer structure of sintering bed and controlling the basicities of lower and upper layer (2.5 and 1.5, respectively), the yield, productivity, and reduction disintegration index (RDI+3.15) were 67.32%, 1.65 t m2 h−1, 49.68% respectively, which were improved 33.12%, 1.74%, and 9.27%, respectively than those obtained by the traditional sintering process. Meanwhile, 1.69 kg t−1 of solid fuel consumption and nearly 10% of electricity and gas consumption for sintering were saved. It was demonstrated that using different basicities for upper and lower layer of sintering bed would promote formation of silica-ferrite of calcium and aluminum (SFCA) with simultaneous reduction of perovskite, improving the sinter quality.

Numerical simulation of iron ore sintering process with coke oven gas injection and oxygen enrichment

Abstract Oxygen enrichment is believed to improve productivity and reduce fuel consumption, while gas fuel injection is assumed to improve the product yield and quality in iron ore sintering process. It is important to understand the mutual effect of oxygen enrichment and gas fuel injection for combined usage of these two techniques. A mathematical model is developed to simulate the sintering process with coke oven gas (COG) injection and oxygen enrichment, particularly focusing on predicting the quality and yield of sinter production, as well as NO x emission. The model is validated by comparing the model predictions with sintering pot test data, and numerical simulations are carried out to investigate the mutual effect of oxygen enrichment and COG injection. The results show that, compared with the conventional sintering process, with 0.5% COG injection and 30% oxygen enrichment, the mean melt quantity index (MQI) is increased by 4.1% and the mean cooling rate (CR) is decreased by 62.5%, showing that the sinter quality is improved significantly. The sinter yield is increased by 44.5%, whereas the NO x emission is increased by 8.3%. With the increase of oxygen enrichment from 21% to 30%, the sinter yield increases prominently first and then decreases a little, attaining its maximum at 30% of oxygen concentration. In addition, increasing oxygen concentration will increase the conversion rate of coke-N to NO x . Therefore, excessive oxygen enrichment is not only bad for sinter strength and yield, but also increases NO x emission.

Significant influence of self-possessed moisture of limonitic nickel laterite on sintering performance and its action mechanism

In consideration of the abundant moisture of limonitic nickel laterite mined, it is essential to determine whether the self-possessed moisture of limonitic nickel laterite after pre-dried is appropriate for sintering. Thus, based on the characterization of limonitic nickel laterite, the influence of its self-possessed moisture on sintering performance was expounded by sinter pot tests and the relevant mechanism was revealed by the systematical analyses of the granulation properties of sinter mixture, thermodynamic conditions during sintering and mineralogy of product sinter. The results indicate that the self-possessed moisture of limonitic nickel laterite indeed has significant influence on its sintering performance. At the optimum self-possessed moisture of 21 mass%, sinter indices are relatively better with tumble index, productivity and solid fuel rate of 48.87%, 1.04 t m−2 h−1 and 136.52 kg t−1, respectively, due to the superior granulation properties of sinter mixture and thermodynamic conditions during sintering, relatively large amount of silico-ferrite of calcium and alumina and tighter sinter microstructure. However, sintering performance of limonitic nickel laterite is still much poorer than that of ordinary iron ores. It is feasible to strengthen limonitic nickel laterite sintering by inhibiting the over-fast sintering speed and improving the thermodynamic conditions during sintering.

Mathematical modeling of natural gas injection in iron ore sintering process and corresponding environmental assessment of CO2 mitigation

With the objectives of reducing CO2 emissions and applying hydrogen-enriched gas in the iron ore sintering process, a mathematical model was developed to simulate the natural gas (NG) injection in the sintering process. The accuracy of the model was verified via sinter pot tests. Additionally, an environmental assessment of CO2 mitigation was performed. Moreover, the effects of the injection quantity, location, and intensity on the sintering process were examined. Sintering process parameters were adopted to quantitatively assess the NG injection technology. The results indicated that this technology can reduce the CO2 emissions. The CO2 mitigation dosage is 11.75 kg/ton sinters when 15% solid fuel is replaced with NG. The melting zone thickness (MZT) and binding liquid phase amount in the upper sintering bed are gradually improved with NG injection quantity increased gradually, which indicates that the holding time of the high temperature zone in the upper bed is prolonged. Furthermore, the injection locations and intensities affect the sintering process. Earlier injection allows more heat storage and forms more binding liquid phase in the upper bed. Low intensity injection reduces the MZT of the sintering bed and negatively affects the sintering process.

Effect of coke ratio on pore structure evolution in the high-temperature zone of sintering bed

The high-temperature zone of the sintering bed is the crucial area for material change and structural remodeling, and the heat is provided by coke combustion. Understanding how fuel combustion affects bed structure is of great significance to optimize sintering parameters and sintering quality. In this study, sintering pot tests were carried out under three coke ratios of 4.5%, 5.0% and 5.5%, and liquid nitrogen was used to quench the high-temperature zone sintering. The clear internal structure of the high-temperature zone sinter was obtained using X-ray computed tomography (XCT). Results show that with the increase of coke ratio, the porosity in the high-temperature zone decreases from 54.29% to 51.04% and 48.07%, and the number of terminal nodes, branch nodes and segments of the pore skeleton decreases by 51.6%, 55.2% and 53.1% respectively. The pores in the high-temperature zone are fully fused and developed.

Experimental investigation on the effect of granulation moisture on the flame front propagation and pore structure in the high-temperature zone of the sinter bed

The pore structure in the high-temperature zone plays a leading role in the permeability of the sinter bed. However, few studies on the bed structure in the high-temperature zone of sintering are due to the difficulty of sampling. Pilot-scale sinter pot tests were conducted to investigate the flame front propagation properties and pore evolution characteristics under different granulation moisture in this paper. Liquid nitrogen was injected to quench the sintering bed. We use X-ray computed tomography to reconstruct the high-temperature zone sinter structures. Results show that the higher porosity of green bed under higher granulation moisture results in faster flame front and more likely channels formation. The porosity of the high-temperature zone increases from 48.40% to 51.50% and 55.68% with moisture increasing from 5.30% to 6.35% and 6.91%. However, the mean length of pores decreases from 1.60 mm to 1.38 mm caused by inadequate coalesce under high moisture conditions.

Effect of TiO2 on the Sintering Behavior of Low-Grade Vanadiferous Titanomagnetite Ore.

Low-grade vanadiferous titanomagnetite ore (LVTM) is as an important mineral resource for sintering ore manufacturing. Furthermore, TiO2 has a significant effect on the sintering process of iron ore fines. The effects of TiO2 on the metallurgical properties, microstructure, and mineral composition of LVTM sinter were investigated by sintering pot tests, X-ray diffraction (XRD), scanning electron microscopy (SEM), and mineral phase microanalysis. The results were as follows: as the TiO2 content increased from 1.75% to 4.55%, the flame front speed and productivity decreased, while the reduction degradation index (RDI) and softening properties deteriorated. In addition, the tumbler index (TI) values reached a maximum at TiO2 = 1.75%. In addition, with increasing TiO2 content, an increase in the magnetite and perovskite phase, and a decrease in calcium ferrite and hematite were found with an increase in TiO2 content. Thus, the lower the TiO2 content, the better the quality of the sinter.

Study of Humidity on Moisture Transfer Characteristics in Iron Ore Sintering

The cold permeability of a sinter bed is a complex function of the granules’ effective mean diameter and bed moisture. The binding force provided by moisture before fusion commences crucial in determining the strength of a sinter. However, excess moisture is detrimental to the propagation of the heat front, because it reduces the bed’s permeability. The source of moisture can be either the inherent moisture in the bed or from the incoming gases due to suction in the bottom of the bed. An unsteady-state mathematical model was developed in the current study to describe the moisture transport phenomena during the iron ore sintering. The model was then validated using experimental data from laboratory sintering pot tests. Using the help of the model, the effect of humidity on the moisture characteristics was then investigated. The temperature profiles revealed that the change in the solid temperatures was less than 5% with increasing humid conditions.

Effect of alumina occurrence on sintering performance of iron ores and its action mechanism

Iron ores always contain several forms of alumina, which may have different effect on sintering performance. In this paper, sinter pot tests were systematically conducted with various alumina types and contents by means of alumina additives substituting for the corresponding types of alumina, and the relevant action mechanism on sintering performance was clarified by the mineralogy of product sinter. The results show that kaolinite is beneficial to the granulation process rather than other three alumina types. In addition, it contributes to relatively better sintering performance while aluminous goethite ranks the only next, followed by gibbsite and free alumina. Mechanism analysis indicates that kaolinite and aluminous goethite are preferable to achieve relatively lower sinter porosity and higher amount of silico-ferrite of calcium and alumina (SFCA) compared with gibbsite and free alumina. Besides, the former two alumina types are apt to promote the formation of higher strength SFCA such as dendritic and acicular SFCA. Furthermore, much tighter interlocking texture in product sinter is formed as alumina occurs in kaolinite or aluminous goethite. Kaolinite and aluminous goethite are the preferably desirable alumina types for sintering rather than free alumina and gibbsite.

Effect of coating structure of granulated quasi‐fuel particles in iron ore sintering

AbstractTo reduce greenhouse gas emissions, biomass fuels are used to gradually replace fossil fuels in the sintering process. Unfortunately, the sinter quality will deteriorate sharply due to too fast combustion rate when using biomass fuels. To address this problem, pregranulation proved to be an effective method. In this study, the pilot‐scale sinter pot tests were carried out to study the effect of coating structure of granulated quasi‐fuel particles on the granulation properties, flame front propagation in sintering, sinter indexes, sinter mineralogy, and pore structure. The experimental results show that when substituting coke with biomass char, the average size of the granules decreased whereas bed voidage increased due to the irregular shape and lower apparent density of granules. Pregranulation can reduce the flame front speed and increase the maximum bed temperature, thereby alleviating the deterioration of sinter quality and sinter yield. By pregranulating biomass char and 2% magnetite concentrate, the tumbler strength, sinter yield, and productivity can be increased from 44.9% to 55.0%, from 41.9% to 49.3%, and from 28.54 to 31.10 t/m2/d, respectively. The microscopic observation results show that substituting coke with biomass char for sintering decreased the content of calcium ferrite in sinter and increased sinter porosity. On the contrary, pregranulating increased calcium ferrite content in sinter and decreased sinter porosity, and thus sinter quality was improved.

Rate-Limiting Mechanism in Iron Ore Sintering Process with Waste Gas Recycling

Recycling waste gas through the sinter bed has an advantage of saving solid fuel. Depending upon the amount of waste gas recycled and its CO content, an equivalent quantity of solid fuel is saved. FeO is one of the key indicators of fuel needed for sintering; its optimization is critical to the consistency in sinter quality. Sinter pot tests were conducted to identify the effect of varying amounts of waste gas recycled. FeO and Tumbler Index increased with increasing waste gas up to 30%. Beyond 40% waste gas recycled, Tumbler Index decreased and the disintegration of the sinter was noticed. Incidental variation in the rate of solid fuel in an industrial scale Sinter Plant with waste gas recycling arrangement has resulted in a large variation in FeO than expected. Above 20%, productivity got adversely affected and Tumbler Index dropped as oxygen in the recycled gas started dropping below 19%. The rate-limiting mechanism has been identified as the underlying reason for low FeO. The deficiency of oxygen has affected the combustion efficiency of solid fuel, and hence, fresh airflow has been optimized to maintain the productivity and quality parameters. The variation in the carbon rate was restricted to 0.77 ± 0.5 kg/t, and oxygen was maintained above 19% to achieve consistent performance.

Effect of high MgO/Al2O3ratio (1.2 to 2.2) on sintering behavior and metallurgical properties

The sintering pot test was used to investigate the effect of MgO/Al2O3 ratio in the range of 1.2 to 2.2 on the sintering behavior of iron ore. The main characterization methods of X-ray diffraction (XRD) and scanning electron microscopyenergy disperse spectroscopy (SEM-EDS) were employed. The results showed that the strength, yield, and reducibility of sinter initially increased and then decreased with increasing MgO/Al2O3 ratio from 1.2 to 2.2. The index would reach the peak value with the strength of 70.6% and the yield of 83.81%, respectively, when MgO/Al2O3 ratio was 1.8. The reduction index would reach the peak value of 88.54% with MgO/Al2O3 ratio of 1.6. The FeO content, solid fuel consumption, and the RDI+3.15 of sinter increased dramatically with increasing MgO/Al2O3 ratio. When MgO/Al2O3 ratio was up to 2.2, the solid fuel consumption and RDI+3.15 reached a maximum value of 61.93 kg/t and 96.1%, respectively. The form of SFCA was acicular when MgO/Al2O3 ratio was less than 1.6 and then transformed to plate-like which content also reduced. The magnetite increased while hematite decreased with enhancing MgO/Al2O3 ratio.