Search

The iron and steel industry is a high-energy consumption and high-pollution industry. Energy recovery in its process is of great significance. Converter gas is an important by-product in the process of iron and steel production. It is difficult to take effective measures to recover waste heat from converter gas due to its flammability. In this paper, a new technology is proposed based on waste heat recovery by a filled bulb regenerator. The mathematical model of heat transfer and flow in the compound regenerator for converter gas containing dust is established. The effects of the diameter and concentration of dust to heat transfer and flow are discussed. The results show that the temperature of converter gas declined to 132 °C, and recovery efficiency was above 90% using this technology system. Resistance loss increased by 25% due to the dust; with the increase in the diameter and initial concentration of dust, the heat transfer rate in the regenerator was reinforced. At the entrance of the regenerator, dust’s effects are more obvious, and the efficiency of heat transfer is increased by 4.5–8.5%. The results can provide a theoretical basis for a new converter gas waste heat recovery method.

In this work, we studied the kinetics and behavior of wood panel wastes containing ureaformaldehyde resins. For this purpose, we used a TG-FTIR coupled system to analyze the gaseous products of the pyrolysis. With the results, we obtained the models that provide theoretical evidence and data support for the studied reactions. According to our findings, the pyrolysis of the ureaformaldehyde components displayed two stages, and the second stage presented a higher intensity. At a temperature of 900 °C, the gas generation rate for hard UF (UF1) was 32.6% higher than that for soft UF (UF2). When temperature increased from 600 °C to 900 °C, the increase of the gas generation rate was relatively small. In addition, the reaction order was obtained using the CoatsRedfern method, which provided a value for the reaction order of 1.4. The activation energy of UF1 was slightly higher than that of UF2. The FTIR analysis indicated that the main gaseous products of the pyrolysis of the urea-formaldehyde resin samples were CO2, H2O, and other compounds containing the C–H and the N–H bond as well as carbonyl groups. In addition, it was determined that Nitrogen was mainly present in the form of hydronitrogen compounds but not as nitrogen oxides. These last may represent a higher degree of pollution.

The low carbon metallurgy technology based on the high-value utilization of biomass is considered as the key development orientation of green ironmaking. In this paper, a pyrolysis coupling technology of biomass tar and iron ore powder is proposed for the reduction of iron ore. Tar is degraded efficiently due to the synergy effects respectively through oxidation of iron oxides and the catalytic action of reduced iron, and simultaneously the reduction of iron oxide to metallic iron. Representative tar components including vanillin, naphthalene, and catechol were selected as tar model compounds. The various reaction conditions on the reduction degree of iron ores was investigated, which include the type of tar component, the pyrolysis temperature, and the ratio of reactants. According to the results, the optimal relationship between tar degradation and reduction of iron ore was identified. It can be found that under the catalytic effects of iron ore fines, the degradation efficiency of the three model compounds followed the following order: naphthalene > vanillin > catechol. Naphthalene owned the better reduction ability. The highest reduction degree of the product reached to 78.5% at 800 °C for 30 min.

In the present research, TG and FTIR were used to study the effect of chemical activation pretreatment on sludge pyrolysis. The results showed that both acidic and alkaline activation promoted sludge pyrolysis. KOH inhibited the elimination of crystallization water and promoted the release of volatiles. On the other hand, H2SO4 favored the separation of crystallization water and the release of volatiles. Low concentrations of the activator promoted the production of combustible gas and inhibited the generation of CO2. By analyzing the activation energy of the pyrolysis process using the Coats-Redfern method, it was found that both, KOH and H2SO4, were able to reduce the pyrolysis activation energy. When H2SO4 was used, the effect was more significant.

Copper slag, an important by-product of the copper smelting process, is mainly composed of 2FeO SiO2, Fe3O4, and SiO2. Due to the sufficient metal oxides, copper slag is regard as a potential oxygen carrier (OC), which can be applied in chemical looping technology. This research proposed to use the granulated copper slag particles as precursor to produce oxygen carrier. Through this method, waste heat of the high-temperature slag can be fully recovered, eliminating the complicated copper slag pretreatment process. In this paper, the reactivity of granulated copper slag after redox calcination was studied by X-ray diffractometer (XRD) and Scanning Electron Microscope (SEM), the highest reactivity occurred at 1,000°C. In addition, the oxygen release and absorption performance of OC were tested in thermal-gravimetric (TG). According to theoretical calculations, the mass loss caused by oxygen release accounts for 70.57% of the total loss and the mass reached by 4.2% at 1,000°C in oxygen absorption experiment. The copper slag modified through calcining in redox condition was proved to be a promising oxygen carrier in chemical looping process. Furthermore, the performance research on OC also provided theoretical references for the operating paraments of OC circulating between air reactor and fuel reactor in practical chemical looping processes.

The C and CO reduction proportional fraction was studied in this work to evaluate consumption of the reducer accurately. Based on two-step reaction mechanism (TSRM) theory, a phase equilibrium calc...

A technology system of copper slag thermal energy recovery and direct reduction (TER-DR) was proposed in this paper. The effects of CaO addition and C/O on the reduction characteristics were discus...

The chromium, iron or zirconium oligomer cations pillared interlayered montmorillonite supported 10 wt% MnOx were synthesized and studied for the flue gas NOx removal in metallurgical sintering pro...

In order to recover the waste heat of aluminum dross and carbon resource in carbon residue, the waste heat recovery process of aluminum dross by coupling of physical and chemical method was propose...

Dry granulation, as a new process for molten blast furnace slag treatment, is an attractive alternative to water quenching. In this study, the performance of dry granulation slag in slag cement blends was investigated. The results demonstrated that the early strength for dry granulation slag cement mortar was too low, which is less than 50% of the strength for the cement clinker. After 28 days, the compressive strength for dry granulation slag cement mortar containing 35 min-milled slag powder was higher than that for cement clinker. With a decrease in cement/slag ratio, the compressive strength for dry granulation slag cement mortar decreased, and then increased, reaching 96.4% of the compressive strength for dry granulation slag cement mortar made with cement/slag ratio of 2:1. Although the content of cement clinker decreased, there was enough Ca(OH)2 to activate dry granulation slag particles to form compact C S H structure when the cement/slag ratio was 1.5:1.

Although, biomass energy is a renewable energy are gradually advocating and studying widely, it is urgent to develop efficient biomass technology and reduce NOx emissions. The combustion mechanism of biogas mixture is unclear, which leads to the lack of basis for the control of operating parameters. Combustion characteristics and reaction path of typical low calorific value biogas with variation of preheating temperature and air equivalence ratio (Φ) are discussed. With the increase of preheating temperature, the final flame temperature moves up. Preheating of biogas can not only improve the flame propagation speed and flame temperature, but also increase the proportion of NO in the product at the end of combustion flame. To some extent, improving combustion efficiency and NOx control are contradictory in operating parameters. The amount of NO formation increases with the increase of flame distance. The maximum value of NO appears when Φ is 1.1. NO formation rate is improved by preheating of the biogas. The paths of N 2 → N 2 O →NO, N 2 → NNH →NO and N 2 →NO) are all enhanced. When the equivalence ratio changes from 1.0 to 0.8, the NO formation rates of the three reaction paths decrease

As a new reducer, biomass was tested as an alternative to coal in copper slag pelleting process by cold pressed preparation method. As two kinds of reducer, biomass and lignite were used in this paper. Without binder addition, the compressive strength of lignite pellets remained in the range of 44 N–75 N under experimental conditions. Compared with lignite, biomass provided higher reduction ratio and higher compressive strength. Fiber structure of biomass increased surface area and strengthened adhesive force of composite pellets. Compressive strength of biomass composite pellet was much higher than lignite composite pellets and remained steady between 2093N and 2246 N with the variation of pressure and CaO addition ratio when C/O was 1.0. Using biomass as reducer, reduction mechanism of copper slag was established. The reduction experiments showed that in the reduction reaction process, metallic iron outflowed from cracks in pellet and it was in the formation of sphere under the effect of surface tension. And the ‘sweating metallic iron’ reduced by biomass distributed more homogeneously than by lignite. When the temperature was above 1423 K, reduction ratio of copper slag was higher than 0.9. And reduction ratio reached a peak when CaO addition ratio was 0.3.

To make a comparison between coal gasification in molten blast furnace slag (MBFS) in different ambience and choose an appropriate agent to recover BF slag’s waste heat entirely, coal gasification with steam and CO2 in molten blast furnace slags was studied by isothermal thermo-gravimetric analysis. The effects of temperature and addition of MBFS were studied. Carbon conversion and reaction rate increased with increasing temperature and MBFS. Volumetric model (VM), shrinking core model (SCM), and diffusion model (DM) were applied to describe the coal gasification behavior of FX coal. The most appropriate model describing the coal gasification was SCM in steam ambience and VM in CO2 ambience, respectively. The reaction rate constant k(T) in CO2 ambience is greater than that in steam ambience, which means the gasification reactivity of coal in CO2 ambience is better than that in steam ambience. BF slag can effectively reduce the activation energy EA of coal gasification reaction in different ambiences. But, the difference of activation energies is not large in different ambiences. Based on the results of kinetic analysis including k(T) and EA calculated by the established model, CO2 was chosen to be the most appropriate agent.

Thermal energy recovery of pyrometallurgy slags is a worldwide problem that is widely concerned for decades. As chemical recovery method, molten slag cascade recovery method (MS-WHCR) is proposed in this work. As typical endothermic chemical reactions, pyrolysis, gasification, calcination and reforming reactions are applied in this method. Gasification–pyrolysis system, calcination–pyrolysis system, enhanced pyrolysis system (R-SEP) and fixed carbon gasification and sorption-enhanced pyrolysis system (CG–SEP) systems of MS-WHCR method are designed. Based on the first law of thermodynamics and second law of thermodynamics, enthalpy–exergy compass analysis method is applied to analyze the exergy efficiency, consumption of reactants and products of designed MS-WHCR method, compared with traditional water quenched (WQ) method and gravity bed waste heat recovery (GWHR) method. As calculation example, 1000kg copper slag is used in this paper. The results showed that the exergy efficiency and exergy loss of WQ method are 20.7% and −947 MJ respectively. By WQ method, energy quality of molten copper slag is discounted. Copper slag particles should be fast cooled during granulation process. Thus, lots of air is blown in to make enough heat transfer with copper slag particles, which generate some exergy loss. And exergy efficiency of GWHR method is 76.9%. Using chemical endothermic reactions, MS-WHCR method improves the exergy efficiency of molten slag waste heat recovery. There is a slight fluctuation of exergy efficiency by MS-WHCR method for four kinds of systems from 66.6 to 70.1%. Fixed carbon and combustible syngas are acquired by MS-WHCR. And enhanced pyrolysis process in proposed R-SEP and CG–SEP systems improves hydrogen contents in syngas.

Copper slag is a good valuable material resource with high iron content in the form of fayalite. Biomass as reduction reducer was proposed in this paper. For the basic research of the reduction in biomass, the biomass reducer was simplified as molding compound C, CO, H2 and CH4. The reactions of 2FeO·SiO2 with C, CO, H2 and CH4 could proceed spontaneously with the addition of CaO. The Gibbs free energy is decreased significantly by addition of CaO. The equilibrium compositions of products were calculated and analyzed combing with 19 basic reactions. Beginning temperature of C, CO, H2 and CH4 is 900, 623, 567 and 511 K, respectively The reduction degree of C, CH4, H2 and CO is 1, 0.851, 0.695 and 0.452, respectively, at 1773 K when the reducer addition ratio is 1.0 calculated by phase equilibrium calculating model. Direct reduction reaction of copper slag dominates at higher temperature, and temperature region of 700–1173 K is the transformational zone. Indirect reduction index curves are in the shape of reverse ‘S,’ and the higher temperature is in favor of indirect reduction in copper slag. There is a steady increase in reduction degree with the increase in reducer. Reduction reaction path of copper slag by C, CO, H2 and CH4 is established.

Thermo-chemical conversion method can transform sewage sludge (abbreviated as SS) to bio-char with hydrogen-rich gas and has good prospects for development. In this research, copper slag was used as heat carrier and provide energy for conversion process of SS. A method of carbonization-activation waste heat cascade recovery technology system was designed. In this technology process, multi-stage endothermic chemical reactions absorb sensible heat from hot copper slag particles. Syngas, activated carbon (abbreviated as AC) and char are produced from SS. Mass and energy balance of this system were evaluated. The results showed that waste heat recovery efficiency and byproducts' additional value were improved by this method comparing with traditional water quenched method. Increasing heat quantity of carbonization process can improve system's energy recovery ratio. In theory, under the optimal condition (T2 = 700 °C, T3 = 200 °C), waste heat recovery ratio and exergy recovery ratio reach 90.8% and 94.9%, respectively.

Massive computations of three-dimensional (3D) flow in subcritical flow state are carried out to investigate the transition from 3D steady flow to time-periodic oscillatory flow via Hopf bifurcation in a cube. Previous prediction of the steady-oscillatory transition in published works has been summarized. The transition point in lid-driven cavity has yet to come to consensus as the critical parameters are predicted in a wide range of values. The 3D unsteady governing equations are solved numerically using the spectral collocation method (SCM) in combination with the artificial compressibility method (ACM), SCM-ACM, a combined method with high accuracy that we developed. The temporal velocity evolution, amplitude evolution and dimensionless angular frequency are investigated. The accurate critical Reynolds number R e c r is predicted by Richardson extrapolation. Results show that the initial conditions have significant effect to obtain the velocity which gradually approaches to steady state in the subcritical flow state, and appropriate initial conditions are given to efficiently obtain stable results by gradually increasing R e . Exponential decay of velocity amplitude becomes weaker with the increase of R e , and the decay rate is strictly linear against R e , while the dimensionless angular frequency remains constant. The R e c r is affected by the number of nodes, which has also been observed by Feldman and Gelfgat [1] and Kuhlmann and Albensoeder [2] , while the critical frequency is unaffected by the number of nodes in the present results. It also indicates that the R e c r and the constant dimensionless angular frequency can be innovatively predicted with more accuracy and much fewer nodes. The improved point of steady-oscillatory transition in 3D lid-driven cube is R e c r = 1916.6 via Hopf bifurcation by Richardson extrapolation with dimensionless angular frequency ω = 0.5752 .

This paper is first to investigate the kinetics of CO 2 adsorption and desorption on waste ion-exchange resin-based activated carbons by the isothermal thermal analysis method. Not only the application of isothermal thermal analysis is expanded, but also a new method for study the kinetics of CO 2 adsorption and desorption is provided in this paper. CO 2 adsorption kinetics following Avrami-Erofeev model is A3/2 on chemically activated carbon (CA) and physically activated carbon (PA). The values of activation energy ( E ) of CA and PA are negative, and the absolute values of activation energy ( E ) reduce with the increase of CO 2 concentration. Desorption kinetics also follow Avrami-Erofeev model, and CA is A3/2 while PA is A1. The values of activation energy are positive, which is opposite to adsorption. CO 2 adsorption and desorption processes are similar to the nucleation and growth of the crystal, which starts from a point, then spreads to the surrounding.

Activated carbons were produced using waste ion-exchange resin, and the effects of different activation temperatures were researched in this article. The experimental results indicate that the activated carbons are microporous carbons. The BET specific surface area and total volume increase at first and then decrease as the activation temperature increases. The maximum adsorption capacity is 81.24 mg/g at 30°C. A higher adsorption temperature and lower CO2 partial pressure resulted in a lower CO2 adsorption capacity. After 20 adsorption–desorption cycles, the CO2 adsorption capacity decreases slightly, and the regeneration degree is always at a high level, which indicates that the activated carbons can be used for a long time. The results in this work suggest that waste ion-exchange resin-based activated carbons show great potential as adsorbents for postcombustion CO2 capture. © 2017 American Institute of Chemical Engineers Environ Prog, 2017

At present, air cooling and water quenching are traditional treatment methods for molten copper slag. However, the waste heat and valuable metals cannot be recovered efficiently by these methods. Exergy efficiency (EE) of this method is only 21.0%. This paper describes a feasibility of waste heat recovery and direct reduction of copper slag. To investigate the feasibility of this new thermal energy recovery and direct reduction system (TER-DR), thermodynamic compass method was applied. Based on physical and chemical recovery methods, TER-DR1 and TER-DR2 systems are put forward. TER-DR1 system decreases the exergy loss (EXL) and improves the EE to 57.3%, and 0.489 t DRI is acquired for every ton of copper slag. Exergy of six kinds of typical endothermic chemical reactions was analyzed. The exergy of reforming reaction of CH4 by CO2 is the highest and suitable for TER-DR system. Combined with chemical method, TER-DR2 system decreases EXL further and improves the EE to 61.3%. Steam, synthesis gas and DRI are produced by this method. By TER-DR2, for every ton of copper slag, 0.489 t DRI, 67.3 m3 CO and 67.3 m3 H2 are acquired.

The CO2 desorption kinetics of waste ion-exchange resin-based activated carbons was analyzed by model-fitting and model-free approaches using thermogravimetric analysis. A non-isothermal method was applied in the temperature range of 303–393 K with different heating rates. The experiments were performed under two different inlet CO2 concentrations. The experimental results showed that the extent of conversion of desorption is independent of inlet CO2 concentration during the adsorption process. At the range of 0.2 ≤ α ≤ 0.7, CO2 desorption on chemically activated carbon is complex, while physically activated carbon is simple. The kinetic models comply with Avrami-Erofeev models. The obtained artificial isokinetic temperatures lie in the region of the experimental temperatures, indicating that the reaction model for conversion 0.2 ≤ α ≤ 0.7 remains a proper choice. On the basis of the experimental results, the thermal analysis method can be used successfully in projecting CO2 desorption.

Thermo gravimetric analysis experiments were carried out on pyrolysis of three kinds of biomasses by temperature programming method. Employed by thermogravimetric analyzer, the effects of the type of biomass and the ratio of copper slag addition on pyrolysis were studied. Biomass pyrolysis process can be divided into four stages, dehydration, pre-pyrolysis, pyrolysis and carbonization. The experimental yields in this paper were modeled by CH4, C2H6, C3H8, C2H4 and C3H6, considering first-order primary reaction and reactions of alkanes and alkenes. Copper slag is beneficial for biomass pyrolysis. With Coats–Redfern method, nonlinear regression of biomass catalytic pyrolysis showed that reaction mechanism of pyrolysis process confirms well with shrinking core model (A3). The kinetic parameters and equations were also calculated. Copper slag promotes both the primary reactions of biomass pyrolysis and the Cracking reactions of alkanes and alkenes, but it cannot decrease the activation energy effectively.

Blast furnace slag obtained from water quenching is generally used for cement production. However, harmful waste, such as SO 2 , H 2 S and heavy metals, is discharged into the surrounding environment after water quenching. Dry granulation is an environmentally-friendly treatment, and the performance of dry granulation slag cement is investigated in the study. The results demonstrated that the particle size distribution and XRD pattern of dry granulation slag were similar to those of slag obtained from water quenching. The early strength of cement mortar made from dry granulation slag was very low, less than 50% of the cement clinker strength. Due to the weak reaction with the slag, the content of the CH phase was high. Next the CH phase was consumed in a reaction with dry granulation slag after 28 days. Crystalline and amorphous C S H were formed in the hydration of the slag cement paste system from dry granulation, and were measured by XRD and FTIR. The compressive strength data, including SEM study, indicate that dry granulation slag can accelerate the hydration of slag cement in the next stage.

The effective utilization of waste plastics is the key technology for environmental protection. Waste plastic char was proposed as a reductant for recovering valuable metals from copper slag. Reaction reactivity, mass-loss behavior and thermokinetics of copper slag were studied by FTIR and thermogravimetric analyzer. The main functional groups of waste plastic char are benzene ring, C-O and –OH. Mass-loss behavior evaluation method was proposed based on calculating and detection of sample’s total mass-loss and reductant mass-loss. With temperature increasing, reaction mechanism transformed. Three-dimension diffusion and interface’s chemical reaction rate are restrictive steps for the first and the second reaction regime, respectively. For waste plastic char, activation energy of the first regime and second regime are about 289.5 ~ 276.2 kJ/mol and 584.5 ~ 709.9 kJ/mol, respectively. CaO changed the second regime’s activation energy. When CaO added, activation energy of waste plastic char and coal decreased by 119.8 ~ 121.5 kJ/mol and 100.0 ~ 113.6 kJ/mol respectively. Waste plastic char presents better reduction reactivity in the second reduction regime than coal. This research makes it possible for recycling of municipal organic wastes and iron containing slags.

The catalytic activities of the Ni-based catalysts with Ca12Al14O33 as carrier for the steam reforming of tar from coke oven gas were studied. The carriers were prepared with three methods, high temperature roasting (HTR), coprecipitation (CP) and sol−gel (SG), respectively. Compared to the catalyst with CP, the catalyst with HTR showed stronger peaks of NiO as well as Ca12Al14O33, similar to the one with SG, and had obviously higher catalytic activity than those with CP and especially with Al2O3 as carrier, just slightly lower than that with SG. When the calcination temperature was 1350°C (HTR-1350), the prepared catalyst showed the strongest peaks of Ca12Al14O33 and NiO and the highest surface area, resulting in the excellent performance for tar reforming. For Ni/Mg−Ca12Al14O33 catalyst with HTR-1350, the catalytic activity and stability were improved as the reforming temperature and the steam/carbon ratio (S/C) rose, and especially at 850°C and the S/C ratio of 12:1, the hydrogen yield can reach 93.16%, with the carbon conversion reaching 97.14%. © 2016 American Institute of Chemical Engineers Environ Prog, 2016

The steam reforming processes of raw coke oven gas (RCOG) for hydrogen production without and with CO2 adsorption were studied via the thermodynamic analysis. Ordinary pressure (1 bar) was found as the best reaction pressure for RCOG steam reforming. The hydrogen yield increased with the increases in temperature and S/RCOG ratio and then flatted out around 160 mol per 100 mol RCOG at the temperature above 700 °C and S/RCOG ratio above 0.8, yet with hydrogen concentration of just about 70 %. After the addition of CaO as CO2 sorbent, the hydrogen yields increased on the whole as the CaO/C ratio and S/RCOG ratio rose, and the temperature range with the hydrogen yield around 160 mol and even higher was widened and moved to low temperature. The optimal conditions of sorption-enhanced RCOG steam reforming for hydrogen production were S/RCOG ratio above 0.8, CaO/C ratio above 2.0 and the temperature from 550 to 700 °C, with the hydrogen yield and concentration reaching around 160 mol and over 90 %, respectively.