Production Of Calcium Carbide Research Articles

Pyrolysis of shenmu coal to prepare blue-coke used as reductant

Blue-coke is a form of granular char prepared by medium-low temperature pyrolysis of low-rank coal. As a reductant, it has been widely used in calcium carbide production, ferroalloy, copper pyro refining, and ferrosilicon production in China due to the abundant reserves of raw coal and its excellent performance. However, there is little research on the pyrolysis process of granular coal to produce blue-coke and its characteristics as a reductant. Thus, the effects of pyrolysis temperature, heating rate, particle size and holding time at the final temperature on blue-coke preparation were investigated in a rotary kiln reactor. The quality index of blue-coke as a reductant and its properties, including the element composition, surface function groups, carbon forms, reactivity and lower heating value under different pyrolysis temperatures, were analyzed in detail. It is demonstrated that the pyrolysis temperature had a more significant impact on the quality of blue-coke compared to other pyrolysis conditions. With the rise of pyrolysis temperature, the blue-coke’s C/O and C/H increased. With the particle size and heating rate increased, the temperature gradients developed within the granular coal during the pyrolysis process led to the volatile release shifting to higher temperature zone and more secondary reaction occurrence. Nevertheless, the secondary reaction was restrained in the rotary kiln with good heat and mass transfer. The indexes of blue-cokes as reductants were met by the chars produced at temperatures from 550 oC to 750 oC with a holding time 60 min at this temperature and a heating rate of 10 oC/min. As the key index of blue-coke, the electrical resistivity decreased with the increase of pyrolysis temperature. It was found to be closely related to the removal of H and O heteroatom at the pyrolysis temperature below 700 °C. While at the higher temperature, the development of graphitized carbon structure took a major role on it. Nonetheless, the crystallite sizes of the blue-coke obtained under this low temperature pyrolysis were small and the carbon forms were turbostratic. These resulted in the blue-coke's high combustion reactivity, which would gradually decline with the rise of pyrolysis temperature.

Sustainable application of calcium carbide residue as a filler for 3D printing materials

Industrial activity results in ton-scale production of calcium carbide and generation of a significant amount of calcium carbide residue (CCR), which is often disposed of in the environment as waste. CCR is an active chemical, and rain washes away alkali from sludge, changing the pH of soils and water and damaging the environment. In this work, we explored new opportunities for the utilization of CCR in view of the coming industrial uptake of digital design and additive technologies. Amazingly, CCR can be successfully used as a filler for the modification of 3D printed materials towards the introduction of hybrid organic/inorganic frameworks. A series of commercially available plastics (PLA, ABS, Nylon, PETG, SBS) were successfully used as matrices for CCR-based composite production with high CCR contents up to 28%. Tensile analyses showed increases in tensile strength and Young’s modulus of 9% and 60%, respectively. Moreover, in comparison with the pure plastics, the CCR-based materials better maintained the digitally designed shape (lower shrinkage). Importantly, CCR-filled materials are 3D printable, making them very promising components in the building sector. Considering the amount of already available CCR stored in the environment, this material is available in large quantities in the near future for hybrid materials, and anticipated opportunities exist in the additive manufacturing sector. The involvement of CCR in practical composite materials is equally important for environmental protection and reuse of already available multiple-ton wastes.

Techno-economic analysis of a liquid air energy storage system combined with calcium carbide production and waste heat recovery

Liquid air energy storage is one of the most promising solutions for the large penetration of renewable energy, but its potential in future industrial scenarios should be explored more. In this regard, a novel energy storage system combined with a calcium carbide production process, a steam Rankine cycle, an organic Rankine cycle, and a hot water unit is proposed in the current study. The thermodynamic and economic performances of the reference system are investigated, and the impacts of the critical parameters on the system performance are reported. The results show that the proposed system has round-trip energy and exergy efficiencies of 45.3 % and 49.0 %, which are 3.1 % and 11.5 % higher than those of stand-alone energy storage systems in the same category of technology. The economic analysis presents attractive and promising results, including a payback period of 1.35 years (which is of course based on special considerations related to the specific case study of the project in China), a total profit of 168.8 million USD, and a levelized cost of storage of 382–888 USD/MWh during the life period of the proposed system. Meanwhile, the calcium carbide production process can save electricity costs by 4.6 % owing to the system integration. The implementation of the proposed system will be of great practical significance for advancing the functionality of energy storage systems, specifically liquid air energy storage units, in industrial processes.

Carbon-calcium composite conversion of calcium carbide-acetylene system: On the imperative roles of carbon capture and solid waste recycling

As an important national basic industry in China, the production of calcium carbide faced with huge pressure on energy conservation and emission reduction because of the CO2 emission and solid waste carbide slag. Therefore, it is necessary to realize the recycling of carbon and calcium in the production process of calcium carbide. A novel system of carbon-calcium compound conversion for calcium carbide-acetylene production was proposed in this work, which combines two-stage carbon capture and calcium carbide waste slag reuse processes to achieve CO2 enrichment and calcium cycle. Based on the simulation data, the proposed system was comprehensively evaluated by material conversion, exergy and exergoeconomic analyses. It was found that the improved process performed better with an effective C, H, Ca atomic conversion rate for carbide furnace of 85.41% and CO2 capture efficiency of 90.35%, compared with the referenced process of 64.51% and 0, respectively. The exergoeconomic analysis results suggested that more focus should be put on carbide furnace, acetylene reactor, re-carbonization furnace, gasifier and calciner since they are the top five of capital investments and exergy destruction. Besides, the carbide furnace, acetylene reactor, re-carbonization furnace and gasifier have relatively lower exergoeconomic factor (fk) values of 1.00%, 0.93%, 2.27% and 3.07%, respectively, indicating that exergy destruction costs of these components can be decreased with the improvement of system thermodynamic and equipment performance. Furthermore, the calcium looping process formed based on the improved oxy-thermal method (OTM) process, using the captured CO2 to mineralize carbide slag to form another calcification cycle for the production of calcium carbide-acetylene, has a higher exergy efficiency of 48.97% than the referenced process of 47.85%, and also achieves the lowest carbon emissions and the obvious reduction in CaO input. Results revealed that the proposed calcium looping system with high-efficiency, low-carbon and clean for calcium carbide-acetylene production, could be a promising process for carbon emission reduction in practical applications.

Comparison of new two-step calcium carbide production process and traditional production process using numerical simulation of heat transfer and chemical reaction

The traditional calcium carbide (CaC2) production process (TCCPP) uses block CaC2 and coke as the main raw materials and produces CaC2 through electrothermal smelting in an arc furnace. The new two-step CaC2 production process (NTCCPP) uses hot pellets of calcium oxide powder and pulverized coal after pelletizing and pyrolysis as raw materials in the arc furnace to replace the block calcium oxide and coke to produce CaC2. In this study, the single-particle heat transfer and reaction models of TCCPP and NTCCPP were established. The reactions of the two processes under the same production conditions were numerically simulated, and the strengthening mechanism of NTCCPP was explored. The result showed that after the same time period, the mass of CaC2 in the traditional CaC2 raw material was lower than that in the pellet raw material of the new process. A higher initial temperature (973 K) can shorten the heating time required for the pellet to reach the reaction temperature and the CaC2 average mass fraction of the pellet with a higher initial temperature was higher than cold pellet in the same reaction time. These findings provide a reference for improving the design and operation of the NTCCPP.

Thermal conductivity prediction of C/CaO packing bed with molecular dynamics corrected effective medium model

High-temperature driven solid–solid reaction at coke (C)/calcium oxide (CaO) interfaces is attractive for industrial-scale production of calcium carbide (CaC2). However, the reaction rate limited by the low thermal conductivity (k) results from a high Kapitza thermal resistance (Rk) at C/CaO interfaces. Identifying various factors including temperature and absorbed moisture on the k of C/CaO pellets is significant for heat transfer enhancement. Here, we developed a modified effective medium assumption model considering the particle-packed configuration to predict the influence of temperature and moisture on the k of C/CaO pellets, in which the Rk is evaluated by the non-equilibrium molecular dynamics. The results show that the k of C/CaO pellets increases from 0.48 to 0.55 W/(m K) when the temperature increases from 300 to 900 K, which is attributed to a 19.7% decrease in the Rk of C/CaO interfaces caused by a rising temperature activated inelastic interfacial phonon scattering. Moreover, it is found that the k of C/CaO pellets decreases from 0.48 to 0.44 W/(m K) after inserting absorption water layers with a thickness of 0.5 nm at C/CaO interfaces. A further 38.4% degeneration in k is harvested when increasing the thickness of the absorption water layers from 0.5 to 1.3 nm. This work provides an overall insight into the interfacial effect on the k of C/CaO porous pellets and guides the heat transfer optimization for particle-packed systems.

Effect of occupational hazard factor type of acetylenogen dust on occupational health risk assessment results

To explore the differences of health hazards between acetylenogen dust as two different occupational hazards of "particles not otherwise regulated" and "calcium carbide". A calcium carbide production enterprise in northwest China was selected. The occupational health survey was used to obtain the spatial distribution and population distribution of calcium carbide dust. Occupational health testing was performed to determine the time-weighted average exposure concentration(C_(TWA)) and excursion limits of calcium carbide dust in the workplace and the main exposure positions. The Singapore semi-quantitative risk matrix was used for occupational risk assessment. The "Classification of Occupational Disease Hazards in the Workplace Part 1: Productive Dust"(GBZ/T 229.1-2010) was used for the operation classification. The calcium carbide dust was regarded as two different occupational hazards: "particles not otherwise regulated" and "calcium carbide", the differences of health hazards between which were compared. PC-TWA of calcium carbide was performed at 2.28 mg/m~3. The heat amount of CaC_2 and CaO released after reacting with water was compared by using Hess' s law, and the reaction rates of the two reactions are compared. The concentrations of calcium carbide dust in the workplace of belt inspection position and the calcium carbide crusher was higher(14.3-15.7 mg/m~3), and the concentrations of the driver in the calcium carbide loader was higher(13.8 mg/m~3). The result of the risk assessment show that the health risks of calcium carbide dust in various positions are basically low risk. Only when the type of damage was "calcium carbide", the risk of the driver of calcium carbide loader increase to medium. The operation classification result show that the hazard classification of calcium carbide dust in each post is basically relatively harmless. Only the type of damage was "calcium carbide", the classification of the driver of the calcium carbide crusher loader increased to moderately hazardous operations. As for the "calcium carbide", the operation classification index of calcium carbide were higher than that of "particles not otherwise regulated". CaC_2 reacting with water released more heat than that of equal amount CaO. In the current production process of calcium carbide dust, except for the crushing section, its occupational health risk was low, but the health risk level of calcium carbide as "calcium carbide" was higher, indicating that the evaluation of calcium carbide dust as "particles not otherwise regulated" may underestimate its occupational hazard.

Investigation on ash fusion temperature and slagging characteristic of Zhundong coal blends, Part 1: The effect of two solid wastes from calcium carbide production

The potential of purified dust (PD) and removed dust (RD) from calcium carbide production as additive to improve the slagging characteristic of Zhundong (ZD) coal blends was studied. Ash fusion tests with varying proportion of two additives (2.5, 5.0 and 7.5 wt%), and ash sample preparation at 1150/1250 °C were conducted. The deposits at different temperatures (1200/1000/800/600 °C) were collected by using an un-cooled probe which was inserted into a drop-tube furnace. The detail characterizations of ash or slag samples were used for analyzing the transformation of mineral phases, and evaluating the effectiveness of additives. The results show that PD and RD have a feature of Ca and C enrichment. The former has a higher Ca content, while the later owns more abundant C element. The addition of PD or RD improves ash fusion temperatures of coal blends, but the effectiveness of 5.0% PD is the best. The addition of 5.0% PD could convert the glassy slags collected at 1200 °C into deposits with low melting fraction, due to the formation of calcium-rich crystal minerals. Controlling the CaO/SiO2 molar ratio at the range of 2.2– 3 would significantly relieve the high temperature melting behavior of ZD coal blends featured by high Ca and low Si.

Energy and exergy analysis of a new calcium carbide production process

Energy and exergy analysis is very useful to optimize the design, operation and evaluation of calcium carbide production process. In this paper, a new calcium carbide production process of coal-coke-electricity grading substitution method (GSM) is proposed and evaluated by inter grating the first and second laws of thermodynamics according to the actual operation data from an actual calcium carbide production enterprise. Three typical calcium carbide production processes of GSM, electro thermal method (ETM) and oxygen thermal method (OTM) are compared based on the comprehensive energy and exergy consumption indexes of multiple products. The results show that, for the GSM, the mixed pellet brings into the highest proportion of energy and exergy of 69.36% and 71.85%, while the calcium carbide brings out the highest proportion of energy and exergy of 71.97% and 69.09%. Among the various heat losses, calcium carbide furnace gas takes the most heat, accounting for 15.9% of the total heat output. The power consumption per unit product of GSM is only 2.48 kWh/kg-CaC2, which is 23.93% lower than 3.26 kWh/kg-CaC2 of ETM. According to the energy and exergy analysis, when CaC2 is the only target product, the GSM has the lowest comprehensive energy consumption of 10.22 kWh/kg-CaC2 and the lowest comprehensive exergy consumption of 9.15 kWh/kg-CaC2. Compared with the traditional ETM and OTM, the GSM has obvious advantages.

Thermal treatment of carbon-fibre-reinforced polymers (Part 2: Energy recovery and feedstock recycling).

The use of carbon fibre (CF)-reinforced plastics has grown significantly in recent years, and new areas of application have been and are being developed. As a result, the amount of non-recyclable waste containing CF is also rising. There are currently no treatment methods for this type of waste. Within this project different approaches for the treatment of waste containing CF were investigated. Main subject of the research project were large-scale investigations on treatment possibilities and limits of waste containing CF in high temperature processes, with focus on the investigation of process-specific residues and possible fibre emission. The results showed that the two conventional thermal waste treatment concepts with grate and rotary kiln firing systems are not suitable for a complete oxidation of CFs due to the insufficient process conditions (temperature and dwell time). The CFs were mainly discharged via the bottom ash/slag. Due to the partial decomposition during thermal treatment, World Health Organization (WHO) fibres occurred in low concentrations. The tests run in the cement kiln plant have shown the necessity of comminution for waste containing CF. With respect to the short testing times and moderate quantities of inserted CF, a final evaluation of the suitability of this disposal path was not possible. The use of specially processed waste containing CF (carbon-fibre-reinforced plastic (CFRP) pellets) as a carbon substitute in calcium carbide production led to high carbon conversion rates. In the unburned furnace dust, which is marketed as a by-product of the process, CFs in relevant quantities could be detected.

Experimental Investigation on the Mass Diffusion Behaviors of Calcium Oxide and Carbon in the Solid-State Synthesis of Calcium Carbide by Microwave Heating.

Microwave (MW) heating was proven to efficiently solid-synthesize calcium carbide at 1750 °C, which was about 400 °C lower than electric heating. This study focused on the investigation of the diffusion behaviors of graphite and calcium oxide during the solid-state synthesis of calcium carbide by microwave heating and compared them with these heated by the conventional method. The phase compositions and morphologies of CaO and C pellets before and after heating were carefully characterized by inductively coupled plasma spectrograph (ICP), thermo gravimetric (TG) analyses, X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The experimental results showed that in both thermal fields, Ca and C inter-diffused at a lower temperature, but at a higher temperature, the formed calcium carbide crystals would have a negative effect on Ca diffusion to carbon. The significant enhancement of MW heating on carbon diffusion, thus on the more efficient synthesis of calcium carbide, manifested that MW heating would be a promising way for calcium carbide production, and that a sufficient enough carbon material, instead of CaO, was beneficial for calcium carbide formation in MW reactors.

Life cycle assessment of HFC-134a production by calcium carbide acetylene route in China

HFC-134a is a widely used environment-friendly refrigerant. At present, China is the largest producer of HFC-134a in the world. The production of HFC-134a in China mainly adopts the calcium carbide acetylene route. However, the production route has high resource and energy consumption and large waste emission, and few of the studies addressed on the environmental performance of its production process. This study quantified the environmental performance of HFC-134a production by calcium carbide route via carrying out a life cycle assessment (LCA) using the CML 2001 method. And uncertainty analysis by Monte-Carlo simulation was also carried out. The results showed that electricity had the most impact on the environment, followed by steam, hydrogen fluoride and chlorine, and the impact of direct CO 2 emissions in calcium carbide production stage on the global warming effect also could not be ignored. Therefore, the clean energy ( e . g ., wind, solar, biomass, and natural gas) was used to replace coal-based electricity and coal-fired steam in this study, showing considerable environmental benefits. At the same time, the use of advanced production technologies could also improve environmental benefits, and the environmental impact of the global warming category could be reduced by 4.1% via using CO 2 capture and purification technology. The Chinese database of HFC-134a production established in this study provides convenience for the relevant study of scholars. For the production of HFC-134a, this study helps to better identify the specific environmental hotspots and proposes useful ways to improve the environmental benefits.

The single-particle model of calcium carbide production and strengthening mechanism of the novel pelletizing process

The single-particle model of calcium carbide production and strengthening mechanism of the novel pelletizing process

Development of calcium coke for CaC2 production using calcium carbide slag and coking coal

A type of calcium coke was developed for use in the oxy-thermal process of calcium carbide production. The calcium coke was prepared by the co-pyrolysis of coking coal and calcium carbide slag, which is a solid waste generated from the chlor-alkali industry. The characteristics of the calcium cokes under different conditions were analyzed experimentally and theoretically. The results show that the thermal strength of calcium coke increased with the increase in the coking coal proportion, and the waterproof property of calcium coke also increased with increased carbonation time. The calcium coke can increase the contact area of calcium and carbon in the calcium carbide production process. Furthermore, the pore structure of the calcium coke can enhance the diffusion of gas inside the furnace, thus improving the efficiency of the oxy-thermal technology.

Analysis and optimization about electromagnetics-temperature-component distribution in calcium carbide electric furnace

It is of particular value to optimize the electromagnetics-temperature-component multi-physical field in electric furnace in improving productivity and reducing energy consumption. In this paper, the effects of three-phase alternating current and electrode immersion ratio on multi-physical field in calcium carbide electric furnace were studied. Meanwhile, a new criterion called benefit evaluation factor was proposed. Benefit evaluation factor is used to comprehensively evaluate the consumption of electric energy and calcium carbide production in electric furnace. Additionally, to improve the physical field distribution in the equipment, an innovative multi-layer electrode furnace was proposed. The results show that the energy consumption and calcium carbide production decrease with the increase of electrode immersion ratio or the decrease of current. Considering benefit evaluation factor and operate temperature, the recommended electrode immersion ratio range is 0.25–0.48. More importantly, the application of multi-layer electrode has a beneficial effect on smelting performance of electric furnace. The average benefit evaluation factor of two-layer-electrode furnace is 7.5% higher than that of traditional calcium carbide electric furnace when electrode immersion ratio equals to 0.25. In this paper, the newly proposed index contributes to the calcium carbide electric furnace smelting performance evaluation, and the multi-layer electrode furnace proposal opens up novel ideas in new furnace design.

Numerical simulation of heat transfer and chemical reaction of CaO-C porous pellets in the reaction layer of calcium carbide furnace

In this paper, a three-dimensional multi-physical model is established to analyze the heat transfer and chemical reaction processes during the production of calcium carbide from CaO-C porous pellets. The model considers simultaneously radiant heat transfer, convective heat transfer, heat conduction and chemical reaction process in the pellet bed. The multi-physical fields are solved by finite element method, and the numerical modeling method is verified based on literature data. The results show that the temperature field and the reaction region are strongly coupled and inhomogeneous in the reaction layer. The reaction diffuses from the surface of the pellet to the inside, and the center of the reaction region gradually shifts to the low temperature side. In the case of three-layer pellets, when heat is transferred from one layer to the upper layer, the time required is about 80% of the total reaction time of the current layer. In addition, the orthogonal test was carried out in the present study, and the result shows that the radius of the particles, velocity of the gas and the surface emissivity of the pellets have influence on the reaction process, and the degree of influence gradually decreases. When these three parameters changed from 1 mm to 0.71 mm, 0.01 m/s to 0.1 m/s and 0.7 to 0.9, the output of calcium carbide increased by 8.74%, 3.52% and 1.3% respectively in the same reaction time.

Preparation of CaO-rich briquette from powdered semi-cokes by cold-pressing

ABSTRACT In this work, CaO-rich briquette coke was prepared by carbonizing the cold pressing briquette composed of powdered char, CaO, and binders. The influences of binder type, binder content in briquette, the CaO/char ratio, and carbonization condition on compressive strength, resistivity, and porosity of the briquette were investigated. Subsequently, the optimum preparation conditions for producing CaO-rich briquetting coke were determined. The obtained results can promote development and optimization of in-situ production of calcium carbide and acetylene from CaO-rich briquetting coke.

Roles of impurities on sintering structure and thermal strength of CaO-containing carbon pellet and the CaO sintering kinetic analysis

CaO containing carbon pellet (CCCP) for calcium carbide production was proposed in this work. The occurrence of impurities in both pulverized char and carbide slag is normally inevitable. This study is to examine the effects of the inorganic oxides on the microstructure and thermal strength of CCCP. Three different CCCPs of Ca(OH)2 + raw char (CRC), carbide slag + raw char (CSRC) and Ca(OH)2 + demineralized char with various impurities were prepared for the purpose of comparison. The results showed that the order of thermal strength of three kinds of CCCPs was as follows: Ca(OH)2 + raw char (CRC) > carbide slag + raw char (CSRC) > Ca(OH)2 + demineralized char (CDC). Four kinds of oxides (i.e. SiO2, Al2O3, Fe2O3 and MgO) as impurities could all possibly react with CaO to form low-melting eutectic matters to different extents, thus resulting in the decrease in the stability of CaO pellet. The presence of CaF2 in the demineralized char has caused over-sintered CaO grains and reduced the thermal strength of CDC. Meantime, the isothermal and non-isothermal experiments have revealed that the CaO grain sintering process could be well expressed by the model of “porous body sintering”.

Taguchi Metodu ile Kalsiyum Karpit Cürufundan Kalıplama ve Kalsinasyon Yöntemleri Uygulanarak Kalsiyum Oksit Briketlerinin Hazırlanması

As the disposal of calcium carbide slag (CCS) obtained a by-product during an acetylene gas process creates an environmental problem, this study aimed to use of CCS to prepare calcium oxide (CaO) briquettes for re-use in the production of calcium carbide (CaC2). The influence of binder types (phosphoric acid (H3PO4), molasses, and corn syrup), binder amount (1, 3, and 5%), briquetting pressure (20, 28, and 36 MPa), calcination temperature (800, 900, and 1000 oC), and calcination time (30, 45, and 60 min) on the strength value of CaO briquettes was investigated using the Taguchi approach. The highest compressive strength value of CaO briquettes was found to be 4.05 MPa. The stability and friability values of the final product were 92% and 8%, respectively. ANOVA analysis revealed that the contribution rate of production parameters on the strength value of CaO briquettes were as follows: (i) binder amount, (ii) binder type, (iii) briquetting pressure, (iv) calcination temperature, and (v) calcination time. The optimal production conditions were determined as follows: the amount of binder: 5%, briquetting pressure: 28 MPa, calcination temperature: 900 oC, and calcination time: 60 min. The obtained CaO briquettes provide a required strength value for re-use in the production of CaC2.

Multiperiod Planning of a PVC Plant for the Optimization of Process Operation and Energy Consumption: An MINLP Approach

This work addresses the integrated optimization of both the plant-wide material processing system and the utility system for a polyvinyl chloride (PVC) plant. In the plant-wide material processing system, vinyl chloride monomer (VCM) production process and VCM polymerization process are optimized to determine production allocation and switching operation of parallel equipment as well as raw material supply arrangement. In the utility system, power generation/supply plan is determined by combined heat and power (CHP) units and the state grid. The nonlinear electricity consuming characteristics of calcium carbide production process, CHP process, and electrolysis process are modeled based on the industrial data. A multiperiod mixed-integer nonlinear programming (MINLP) model of a PVC plant by calcium carbide method is proposed with the intent to enhance the profit and reduce the energy consumption. The proposed MINLP model is successfully applied to two cases originated from a real-world industrial plant in ...