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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...

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.

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

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.

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.

Metallurgical slags, discharged at high temperature range, are produced as by-products in metallurgical processes. In order to reuse waste energy in molten metallurgical slags, the dry granulation and waste heat recovery technology is a popular technology, compared to water quenching granulation. In the study, the solid particle diameter and size distributions of metallurgical slags with different viscosity and surface tension by dry granulation were investigated. The results indicated that the length of molten slag ligament in granulation for ferroalloy slag, with high viscosity, was long. And there was small change in mean diameter of solid particles with an increase in rotating speed for metallurgy slag with low viscosity and surface tension. The semi-empirical relations, based on the experimental data, can be applied to calculate mean diameter of solid particles for different kinds of metallurgical slags. For blast furnace slag and ferroalloy slag granulation, the main mass fraction peak was located in the range of 2.44–3.14 mm. For copper slag granulation, the main mass fraction peak moved to the range of small diameter with an increase in rotating speed.

Waste ion-exchange resin was utilized as precursor to produce activated carbon by KOH chemical activation, on which the effects of different activation temperatures, activation times and impregnation ratios were studied in this paper. The CO2 adsorption of the produced activated carbon was tested by TGA at 30 °C and environment pressure. Furthermore, the effects of preparation parameters on CO2 adsorption were investigated. Experimental results show that the produced activated carbons are microporous carbons, which are suitable for CO2 adsorption. The CO2 adsorption capacity increases firstly and then decreases with the increase of activation temperature, activation time and impregnation rate. The maximum adsorption capacity is 81.24 mg/g under the condition of 30 °C and pure CO2. The results also suggest that waste ion-exchange resin-based activated carbons possess great potential as adsorbents for post-combustion CO2 capture.

Chemical looping air separation (CLAS) is a novel technology to separate oxygen from air. In CLAS process, oxygen carrier releases oxygen in steam atmosphere and the reduced oxygen carrier is regenerated in air atmosphere. The performance of oxygen carrier is essential to CLAS technology. In this study, the feasibility of CuO in steam atmosphere was evaluated by thermodynamics. Steam is not involved in any reaction. The production of oxygen is achieved by the decomposition of CuO to Cu2O and the optional reduction temperatures should be 850–1050 °C. In order to inhibit the agglomeration of copper oxides, oxygen carriers were prepared with 60 wt.% SiO2, TiO2, ZrO2 and MgAl2O4 as support materials. The oxygen release and absorb rates of the four oxygen carriers were determined under reduction temperatures of 950, 975 and 1000 °C and oxidation temperatures of 800, 850, 900 °C in a fixed-bed reactor. Both the reduction and oxidation include quick and slow reaction stages. The reduction rate increases and the oxidation rate decreases with the investigated temperature increasing. The reduction and oxidation macro-kinetic models of the four oxygen carriers were established based on the reactivity data. Binders have great effect on reduction kinetic parameters. The Cu4Mg6 oxygen carrier has the highest reduction and oxidation rates. The stability of Cu4Mg6 was investigated by multi-cycles test. The oxygen release and absorb rates keep stable in each cycle. The chemical and physical characteristics of the oxygen carriers prepared and reacted were also measured. The chemical phases are only copper oxides and binder. The surface area becomes larger after cycles. There is no obvious agglomeration observed after multi-cycles test.

Thermodynamic analysis and experiments of the steam reforming process of 1-methylnaphthalene as the tar model compound from coke oven gas (COG) were performed in this paper. In the thermodynamic analysis, as the temperature and steam/carbon (S/C) ratio rose, the hydrogen yield first increased and then flattened out yet with the compound completely converted and almost no coke deposition formed. In the experiments using a Ni/Mg catalyst with Ca12Al14O33 as a carrier, with the increases of the temperature and S/C ratio and the decrease of the methane-equivalent gas hourly space velocity (GC1HSV), the reforming result for hydrogen production became better gradually. After the temperature and S/C ratio increased to 800 °C and 12:1, respectively, and the GC1HSV decreased to 145 h–1, the hydrogen yield and carbon conversion could reach over 90% and 97%, respectively, even very close to the thermodynamic values. Additionally, the catalytic stability and resistance to coke formation of the used catalyst also impr...

Activated carbons, derived from waste ion-exchange resin by CO2 physical activation, were applied to separate CO2 from flue gas against global warming. The BET specific surface areas of activated carbons at different activation temperatures and times were investigated. The CO2 adsorption capacity was tested under non-isothermal and isothermal conditions. The experimental results show that when keeping the activation temperature constant, the specific surface area increases firstly and then decreases with increasing activation time. For the given activation time, the specific surface area rises firstly and then declines with increasing activation temperature. The adsorption capacity decreases with increasing temperature. The maximum adsorption capacity is 51.46 mg/g under the condition of 298 K and pure CO2. Fractional order kinetic model is the best one to describe the kinetics of CO2 adsorption. The activated carbons show the potential to be an effective adsorbent for the removal of CO2 from flue gas.