Waste Heat Of Blast Furnace Slag Research Articles

Exploration and optimization on thermoelectric conversion of waste heat of blast furnace slag

The iron and steel industry involves processes that generate abundant waste heat resources. The energy utilization rate can be improved by using thermoelectric conversion technology to directly convert waste heat into electric energy through the Seebeck effect. In this study, a special waste heat recovery device, designed according to the production environment characteristics of blast furnace (BF) slag, is proposed. The heat transfer process between the BF slag and thermoelectric generator (TEG) is analyzed, and the heat source temperature field model is constructed. Based on the temperature distribution, the size of the TEG is determined. The heat transfer behavior of the thermoelectric module (TEM) is optimized using a non-contact heat collection mode and a water-cooling device, which improves the temperature gradient. A thermal conductive silicone grease is introduced as the thermal conductive layer to achieve uniform distribution of the hot end temperature and improve the heat transfer capacity of the collector plate. After design optimization, the temperature gradient of the TEM increased by 15.3 °C and 38 % on average. The experimental results show that a single TEM can generate about 3.084 J of electric energy. Using 70 kg of BF slag with an initial temperature of 600 °C, the TEG per unit installed area can generate about 1.23 kJ of electric energy in 1 h. This study provides an important foundation for research in thermoelectric conversion, utilization of BF slag waste heat and sustainable development of the iron and steel industry.

Experiment study and heat resistance analysis on heat transfer characteristics in staggered tube moving bed heat exchangers

Heat transfer of high temperature granules in the moving bed heat exchanger is an important thermal process in a blast furnace slag waste heat recovery system. Gaining a comprehensive understanding of granular side heat transfer characteristics is crucial. Here, we experimentally investigated the effects of velocity, diameter, diameter distribution, inlet temperature and granule type on granular side heat transfer and the development of heat transfer in the flow direction in a staggered tube array. Furthermore, the experimental results were analysed via the thermal resistance theory. The obtained results indicate that the heat transfer coefficient increases with increasing velocity and inlet temperature and decreases with increasing diameter. Multi-sized granules and blast furnace slag have better heat transfer than mono-sized granules and phosphorus slag, respectively. The heat transfer coefficient tends to increase and then decrease in the flow direction, with the location of the peak, depending on the ratio of the contact and penetration thermal resistance. The semi-empirical formula based on experimental results can provide a theoretical basis required to design.

Combining theory and experiment analysis in molten BFS waste heat recovery integrated with coal gasification

A novel method that a heat recovery system from blast furnace slag integrated with coal gasification reaction to generate syngas was proposed. The motion characteristic and critical velocity of the coal particles in the molten slag were estimated. Meanwhile, the effects of temperature and steam to coal ratio on coal gasification product distribution and gas characterization were discussed. The results showed that the coal particles (~75 μm) would break through the bondage of bubbles and transport into molten slag when the velocity of coal particles were above 4.20 m·s-1 and the diameter of bubbles were less 6 mm. There had higher gasification efficiency, gas yield production and H2 production by this method. The results suggested that the optimal conditions for slag waste heat recovery were achieved at 1623 K and steam to coal ratio of 2.0. Under these conditions, the gas yield and carbon conversion reached 133.48 mol·kg-1 and 97.81%, respectively. The proposed method enhanced the coal gasification efficiency and recovered the high quality of molten blast furnace slag waste heat effectively, and had important guidance for industrial manufacture.

The production of hydrogen-rich gas by wet sludge gasification using waste heat of blast-furnace slag: Mass and energy balance analysis

Sludge gasification for the production of hydrogen-rich gas is a promising technology. In this paper, a pilot study on the hydrogen-rich gas production by sludge gasification using waste heat of blast furnace slag was carried out, and the mass and energy balance of gasification process using waste heat from blast furnace slag were evaluated. The results show that the higher the gasification temperature, the higher the hydrogen content in the gas. When the gasification temperature reaches 880 °C, the hydrogen content in the gas reaches the maximum,35.3%. The technology of sludge gasification combined with waste heat recovery of high furnace slag is feasible. Its efficiency of heat recovery can reach up to 64.35%, and the gasification efficiency and energy consumption ratio can reach to 42.30% and 3.67, respectively.

Life cycle and economic assessment of multi-stage blast furnace slag waste heat recovery system

Abstract In order to utilize the waste heat of blast furnace slag more effectively, the multi-stage slag waste heat recovery system was proposed. This study employed the life cycle assessment to evaluate the environmental performance of the proposed system. Meanwhile, the economic feasibility of the system was analyzed in terms of capital cost and return analysis. Based on the current status of the environment, CO2 tax was also referred in the net explicit profit and net implicit profit calculation of the system. The energy consumption and resource consumption of the system were 268.84 kg coal-eq/tslag and 1213.60 kg/tslag, respectively. The main environmental impact came from the slag production process. Under the consideration of CO2 tax, the net explicit profit and net implicit profit of the proposed method were 13.40 $/tslag and 135.14 $/tslag when the CO2 tax were 33.00 $ per ton. In this process, the evaluations of the proposed system were done in comparison with the conventional water quenching method-open circuit process and latest dry slag granulation method by the main energy, environmental and economic indicators. As results suggested, the multi-stage slag waste heat recovery system had a good application potential in the aspect of energy conservation and emission reduction for iron and steel industry.

The production of fuel oil and combustible gas by catalytic pyrolysis of waste tire using waste heat of blast-furnace slag

In this study, a novel “waste energy recycling” strategy is presented, i.e., the sensible heat of blast-furnace (BF) slag is utilized for the production of fuel oil and combustible gas from the pyrolysis of waste tire. The effects of various operating parameters including the slag temperature, the mass ratio of BF slag to tire (B/T) and feedstock size on yields and characteristics of pyrolysis products were systematically studied. The results showed that the presence of BF slag greatly improved the production of derived-oil and increased the contents of H2 and CO in pyrolysis gases. This can be explained by the catalytic activity of BF slag and the CaO-MgO complex in BF slag can prevent the formation of stable chemical structures in hydrocarbons, speed up the degradation of hydrocarbons, weaken CC and CH bonds and make them dissociate more easily, and thereby decrease the activation energy of degradation reactions. Increasing BF slag temperature and B/T ratio, and decreasing feedstock (including both BF slag and tire powder) size favored the heat and mass transfer during pyrolysis process and therefore afforded more liquid and gaseous products. In addition, it was observed that the presence of BF slag decreased viscosity, density, H and O content and increased C content, C/H ratio and calorific value of derived-oil relative to pyrolysis oil derived from solely tire powder, thereby resulting in upgradation of oil quality.

Thermodynamic analysis and optimization of an air Brayton cycle for recovering waste heat of blast furnace slag

The efficient utilization of waste heat of blast furnace (BF) slag can reduce energy consumption of iron and steel industry. Based on dry slag granulation (DSG) technology which is a text facility dealing with 1.2 ton molten slag per hour, an air Brayton cycle for recovering waste heat of BF slag is proposed. A finite time thermodynamic (FTT) model of the air Brayton cycle is established and its waste heat recovery performance is analyzed. Moreover, by taking power output as objective, the compressor's pressure ratio and inlet relative pressure drop are optimized. Results show that the maximum power output is 51.46 kW the maximum heat recovery efficiency is 11.98%, and the corresponding thermal efficiency is 20.70% when the compressor pressure ratio is 4.29 and compressor inlet relative pressure drop is 0.023.

ASPEN Plus simulation of coal integrated gasification combined blast furnace slag waste heat recovery system

This article presented a model for the system of coal gasification with steam and blast furnace slag waste heat recovery by using the ASPEN Plus as the simulating and modeling tool. Constrained by mass and energy balance for the entire system, the model included the gasifier used to product syngas at the chemical equilibrium based on the Gibbs free energy minimization approach and the boiler used to recover the heat of the blast furnace slag (BF slag) and syngas. Two parameters of temperature and steam to coal ratio (S/C) were considered to account for their impacts on the Datong coal (DT coal) gasification process. The carbon gasification efficiency (CE), cold gasification efficiency (CGE), syngas product efficiency (PE) and the heating value of syngas produced by 1kg pulverized coal (HV) were adopted as the indicators to examine the gasification performance. The optimal operating temperature and S/C were 800°C and 1.5, respectively. At this condition, CE reached above 90% and the maximum values of the CGE, PE and HV were all obtained. Under the optimal operating conditions, 1000kg/min BF slag, about 40.41kg/min DT pulverized coal and 77.94kg/min steam were fed into the gasifier and approximate 6.64kmol/min syngas could be generated. Overall, the coal was converted to clean syngas by gasification reaction and the BF slag waste heat was also recovered effectively (reached up to 83.08%) in this system, achieving the objective of energy saving and emission reduction.

Thermodynamic Analysis of Blast Furnace Slag Waste Heat-Recovery System Integrated with Coal Gasification

The blast furnace (BF) slag waste heat was recovered by an integrated system stage by stage, which combined a physical and chemical method. The water and coal gasification reactions were used to recover the heat in the system. Based on the first and second law of thermodynamics, the thermodynamic analysis of the system was carried out by the enthalpy–exergy diagram. The results showed that the concept of the “recovery-temperature countercurrent, energy cascade utilization” was realized by this system to recover and use the high-quality BF slag waste heat. In this system, the high-temperature waste heat was recovered by coal gasification and the relatively low-temperature waste heat was used to produce steam. The system’s exergy and thermal recycling efficiency were 52.6% and 75.4%, respectively. The exergy loss of the integrated system was only 620.0 MJ/tslag. Compared with the traditional physical recycling method producing steam, the exergy and thermal efficiencies of the integrated system were improved significantly. Meanwhile, approximately 182.0 m3/tslag syngas was produced by coal gasification. The BF slag waste heat will be used integrally and efficiently by the integrated system. The results provide the theoretical reference for recycling and using the BF slag waste heat.

Thermodynamic analysis of hydrogen-rich gas generation from coal/steam gasification using blast furnace slag as heat carrier

Abstract Thermodynamic analysis with Gibbs free energy minimization through Lagrange multiplier method was performed for coal gasification with steam using blast furnace (BF) slag as heat carrier and recycling its waste heat to produce hydrogen-rich gas (HRG). Simulations were carried out to study the operation temperature, pressure, S/C and BF slag basicity based on chemical equilibrium calculations. The optimal thermodynamic conditions were determined to improve hydrogen concentration and total syngas production as high as possible. The results suggested that the preferential conditions for HRG from Datong coal were achieved at 775 °C, atmospheric pressure and S/C of 2.0–3.0. Under these conditions, hydrogen concentration reached to 62.36% and the total gas production was 2.45 mol per mole of carbon in the coal. What's more, not only was the quality of HRG improved significantly, but also the BF slag waste heat was recycled effectively when using BF slag as heat carrier. The effect of BF slag basicity upon the gasification characteristics was also investigated, and the production of hydrogen increased significantly when basicity was 1.3.

The Experimental Study of Molten Blast Slag Dry Granulation

Based on the comprehensive experimental test-bed of blast furnace slag waste heat recovery, we study the impacts which are caused by the changes of the key parameters, such as blast furnace slag discharged temperature, the speed of the granulation device, on the particle diameter distribution and sphericity, so as to master the best operating parameters of the blast furnace slag dry granulation, and provide experimental basic materials for blast furnace slag waste heat recovery. The results show that: when the discharged temperature of the blast furnace slag is controlled in 1400°C～1450°C, and the speed of the granulation device is controlled above 2000r/min, the sphericity is better, and 80% of the particle’s diameter will be 2～5mm.