Plasma Calcination Research Articles

Smarter ways to capture carbon dioxide – exploring alternatives for small to medium-scale carbon capture in Kraft pulp mills

Carbon capture from the calcination process in Kraft pulp mills, also known as sulphate pulp mills, has potential as a part of carbon capture and storage (CCS) infrastructure deployment. Growing concern of climate change is increasing the interest for so-called negative emission technologies (NETs), and large emission points have great potential. However, among other factors, lack of financial incentives, trade-off with investments in existing products, and the necessity of large infrastructure that stretch across country borders, constrain deployment. This study investigates two concepts for carbon capture in combination with lime kilns in Kraft pulp mills: oxyfuel combustion and electric arc plasma calcination. The results from the modelling of six configurations show that carbon capture from the calcination process with these technologies can be made with comparatively low additional energy demand. Sulphate pulp production from Kraft pulp mills, which use lime kilns, is increasing in Europe and in the world. Therefore, there is large potential for capture of CO2 from these alternative calcination technologies, both as a first step towards and as a part of a large-scale deployment of CCS and bioenergy with CCS (BECCS).

Potential for Negative Emissions by Carbon Capture and Storage From a Novel Electric Plasma Calcination Process for Pulp and Paper Mills

The pulp and paper industry has a high potential to contribute to negative emissions through carbon capture and storage (CCS) applied to existing processes. However, there is a need to investigate how CCS solutions also can be combined with implementation of other emerging technologies in pulp and paper mills. This paper investigates the integration of a novel calcination process in two kraft mills and evaluates its potential combination with capture and storage of CO2 from the calcination plant. The alternative calcination process uses electric gas-plasma technology combined with steam slaking and allows replacing the conventional fuel-driven lime kilns with a process driven by electricity. The novel calcination process generates a pure, biogenic, CO2 stream, which provides an opportunity to achieve negative emissions at relatively lower costs. The potential reduction of greenhouse gas emissions when replacing the lime kiln with the plasma calcination concept depends strongly on the emissions intensity of grid electricity, and on whether fossil fuel or biomass was used as a fuel in the lime kiln. If fossil fuel is replaced and electricity is associated with very low emissions, avoided CO2 emissions reach ~50 kt/a for the smaller mill investigated in the paper (ca 400 kt pulp per year) and almost 100 kt/a for the larger mill (ca 700 kt pulp per year). Further emission reductions could then be achieved through CCS from the electrified calcination process, with capture potentials for the two mills of 95 and 164 kt/a, respectively, and capture and storage costs estimated to 36–60 EUR/tCO2.

Highly conductive and transparent electrospun indium tin oxide nanofibers calcined by microwave plasma

In this work, indium tin oxide (ITO) nanofibers have been prepared by electrospinning of polymers and post-growth microwave plasma calcination (MPC). Interestingly, compared to traditional calcination in furnace, MPC can accelerate the degradation of high polar polymers and improve adhesion of ITO nanofibers to the sapphire substrate. Further characterizations reveal that the ITO nanofibers with diameters of 100–150 nm prepared by MPC at 600 °C can reach a low sheet resistance of 269 Ω/sq and a high transmittance of 90.7% at 550 nm simultaneously, which has not been previously reported by others. Our results show that the efficient MPC method has great potential in preparation of metal-oxide nanofibers for electrical and optical applications.

Post-synthesis plasma processing and activation of TiO2 photocatalyst for the removal of synthetic dyes from industrial wastewater

In this study, TiO2 nanopowders were prepared by combining the surfactant assisted sol–gel method with microwave plasma calcination. Plasma calcination was performed just for 20–30 min for reducing the calcination time and ensuring the energy efficient synthesis of photocatalyst. The mixed anatase–rutile phased TiO2 nanoparticles were obtained under these synthesis conditions. The band gap energy of the photocatalyst decreased by 40% on microwave plasma calcination. The surfactants were found to be ineffective on phase transformations of synthesized TiO2. FTIR analysis confirmed the absorption of O–Ti–O band stretching between 415 and 420 cm−1. The hydroxyl bands (OH) were observed to be less stretched after plasma calcination. The conventionally calcined HA–Ti, NA–Ti and MS–Ti samples showed band gap energies of 5.09 eV, 4.88 eV and 5.06 eV, respectively. The band gap energy of plasma calcined MTHA–Ti, MTNNA–Ti and MTMS–Ti samples was calculated about 4.92 eV, 3.11 eV and 4.96 eV, respectively. The combined effect of photocatalyst, plasma reactive species and UV radiations promoted the degradation efficiency of the methylene blue dye. Under DC plasma jet exposure, the maximum degradation efficiency of 95% was achieved after 30 min of plasma exposure time. The catalyst retained about 93–95% degradation efficiency after five cycles of dye degradation.

Study on In Situ Catalytic Cracking of Coal Tar by Plasma Preparation of the Pyrolysis Coke Catalyst.

A two-stage pyrolysis fixed bed was used, and the vapor-modified pyrolysis coke was used as a carrier. A ZHPC catalyst was prepared by plasma calcination. Gas-phase tar produced by the pyrolysis of raw coal was subjected to in situ catalytic cracking to improve tar and gas yield. The effects of plasma calcination power, calcination time, and ZnO loading on in situ cracked products were studied. The prepared catalyst was characterized by X-ray electron spectroscopy, X-ray diffraction, Brunauer–Emmett–Teller, and scanning electron microscopy. The results showed that (1) compared with traditional catalysts, the catalyst prepared by plasma has better performance; (2) the optimal calcination time of the ZHPC catalyst is 5 min, calcination power is 60 W, and ZnO loading is 10%; (3) compared with raw coal pyrolysis, the optimal ZHPC catalyst on in situ catalytic cracking tar, gas yield increased by 66.16%; the cracking rate of tar increased by 54.46%, and the content of light components increased to 60.7%; (4) in situ catalytic cracking of tar with the optimal PC, the light tar has been greatly improved, in which the light oil, phenol oil, naphthalene oil, and wash oil have increased by 93.04, 126.31, 257.28, and 108.08%, respectively. The anthracene oil and asphalt have decreased by 26.98 and 58.71%; the tar cracking rate has increased.

Performance of transition metal-doped CaCO3 during cyclic CO2 capture-and-release in low-pressure H2O vapour and H2O plasma

The effects of transition metal doping of calcium carbonate on the subsequent performance of the material during CO2 release and recapture have been evaluated for calcination under low-pressure (~0.1 mbar) water vapour and water plasma conditions. The initial samples were prepared by precipitation method from analytical grade carbonate, calcium and transition metal (Fe, Co, Zn, Cu and Ni) containing precursors. The release-recapture properties of the sorbents were monitored over five cycles involving calcination at 1200 K and carbonation at 825 K. The most noteworthy effects were observed for the Zn-doped samples, which exhibited rapid CO2 recapture.Calcination in H2O plasma was tested to evaluate the potential for in-situ material processing as a means to counteract material degradation. The impact of plasma exposure during calcination on the looping performance was mixed and dependent on the specific sample composition. The performance of the Zn-doped CaCO3 was consistently improved by plasma calcination, yielding high uptake and better retention of carrying capacity over the five cycles.All samples exhibited a deterioration in carrying capacity over repeated cycles. The Zn-doped samples also performed best in this respect (least loss of carrying capacity). The beneficial effects of Zn-doping were dependent on the Zn-content of the precursor solutions used for material synthesis.

Highly Dispersed Co Nanoparticles Prepared by an Improved Method for Plasma-Driven NH3 Decomposition to Produce H2

Previous studies reveal that combining non-thermal plasma with cheap metal catalysts achieved a significant synergy of enhancing performance of NH3 decomposition, and this synergy strongly depended on the properties of the catalyst used. In this study, techniques of vacuum-freeze drying and plasma calcination were employed to improve the conventional preparation method of catalyst, aiming to enhance the activity of plasma-catalytic NH3 decomposition. Compared with the activity of the catalyst prepared by a conventional method, the conversion of NH3 significantly increased by 47% when Co/fumed SiO2 was prepared by the improved method, and the energy efficiency of H2 production increased from 2.3 to 5.7 mol(kW·h)−1 as well. So far, the highest energy efficiency of H2 formation of 15.9 mol(kW·h)−1 was achieved on improved prepared Co/fumed SiO2 with 98.0% ammonia conversion at the optimal conditions. The improved preparation method enables cobalt species to be highly dispersed on fumed SiO2 support, which creates more active sites. Besides, interaction of Co with fumed SiO2 and acidity of the catalyst were strengthened according to results of H2-TPR and NH3-probe experiments, respectively. These results demonstrate that employing vacuum-freeze drying and plasma calcination during catalyst preparation is an effective approach to manipulate the properties of catalyst, and enables the catalyst to display high activity towards plasma-catalytic NH3 decomposition to produce H2.

Atmospheric pressure plasma assisted calcination of organometallic fibers

Plasma assisted calcination of composite submicron fibers (Ce(NO3)3/polyvinylpyrrolidone) as a novel method for inorganic submicron fibers preparation was studied. Special type of dielectric barrier discharge, so called Diffuse Coplanar Surface Barrier Discharge (DCSBD) was used for the plasma treatment of composite fibers at atmospheric pressure in ambient air for the purpose of oxidation and removing of organic base polymer by the active species produced in plasma. High decrease of C/Ce ratio and formation of porosity on fibers surface were observed after plasma calcination at exposure time in the order of minutes. Due to the low temperature approach and short treatment time, plasma assisted calcination is a suitable and perspective alternative to the conventional high-temperature calcination.

Preparation of Copper-Cobalt Catalyst by Glow Discharge Plasma for Lower Alcohols Synthesis

CuCo/ZrO2 catalysts for lower-alcohol synthesis from syngas were prepared by glow discharge plasma and conventional calcination method. The effects of plasma atmosphere(N2, H2 or first N2 then H2) on the catalyst structure and performance were investigated. These catalysts were characterized using BET, XPS, XRD, TG, and TPR techniques. The experimental results indicated that plasma treatment restrained effectively the production of hydrocarbon and enhanced the selectivity to total alcohols. Compared with the calcined sample, the plasma treated catalyst had higher activity and space time yield (STY). Characterization results showed that the catalyst precursor with plasma treatment was decomposed to active phase under low temperature and the specific surface area of catalyst was significantly improved. Meanwhile, the plasma treatment promoted the grain refining, dispersion of the active component and enrichment of copper on the catalyst surface.

Functionalized mesoporous silica films for gas sensing applications

Mesoporous silica films prepared by sol gel process and argon plasma calcination have been used to form hybrids for gas sensing applications by entrapping sensitive materials in the porous network. Plasma calcination, a low temperature process, is employed to gel the sol instead of conventional thermal calcination. Polymers and surfactants are used as templates for generating the mesoporous structure upon removal by the plasma calcination. TEM, EDX and FT-IR are used to characterize the obtained films. To demonstrate the gas sensing property of the functionalized silica films, 10 MHz Quartz Crystal Microbalance (QCM) coated with β-cyclodextrin (β-CD) functionalized silica film is tested as a sensor for benzene vapor detection. The higher surface area of the mesoporous silica films could accommodate more receptor molecules (β-CD molecules) and subsequently more target analytes that enhance the QCM response. The sensitivity of the QCM is enhanced by depositing plasma calcined mesoporous sensing films on the electrodes.

Surface-enhanced Raman spectroscopy of the growth of ultra-thin organosilicon plasma polymers on nanoporous Ag/SiO2-bilayer films

A new method for the synthesis of thin bilayer films as surface-enhanced Raman spectroscopy (SERS) active substrates was developed which is based on the combination of plasma polymerization, plasma calcination and Ag-film deposition by means of physical vapor deposition. The surface morphology of prepared substrates was characterized by field emission scanning electron microscopy, atomic force microscopy and electrochemical impedance spectroscopy. These substrates lead to high surface enhancement factors proven by the spectroscopic analysis of adsorbed Trans-1,2 bis-(4-pyridyl) ethylene molecules. By this preparation technique, SERS-active films can be deposited on any substrate. The new SERS substrates were successfully applied to study the growth of ultra-thin hexamethyldisiloxane plasma polymer films. The Raman intensity of the CH-stretching vibration was studied as a function of the film thickness. The surface enhancement decreased sharply at about 20 nm. The resulting increase in the intensity of Raman peaks for thin adsorbed plasma polymer films was observed to be a combination of the electromagnetic enhancement mechanism and the high surface area increase of the rough Ag-surface.

Cyclodextrin functionalized mesoporous silica films on quartz crystal microbalance for enhanced gas sensing

We have attempted to enhance the detection sensitivity of frequency domain sensors such as quartz crystal microbalance (QCM) by depositing a mesoporous silica film on their flat electrode surface. The mesoporous silica film is prepared by using a sol–gel process in combination with plasma calcination. To demonstrate the effect of the mesoporous silica film on the sensitivity of QCM, β-cyclodextrin (β-CD) is trapped in the mesoporous network to detect benzene and ethanol vapors. To ensure a covalent immobilization, the β-CD molecules are modified through alkenylation of the hydroxyl groups and then immobilized on a thiolated silica film by using the anti-Markovnikov reaction. A field emission scanning electron microscopy (FESEM) and nitrogen adsorption analysis are used to characterize the mesoporous structure of the silica film. NMR and time-of-flight secondary ion mass spectroscopy (ToFSIMS) are used to confirm the alkenylation of β-CD and the presence of β-CD in the silica network, respectively. The sensing performance of the β-CD/silica hybrid coatings are tested to benzene and ethanol vapors. The results show that the responses of the QCM to benzene and ethanol vapors are enhanced by the introduction of the mesoporous sensing film on the electrodes. Through sufficient control experiments, i.e. sensing response of non-β-CD modified silica-QCM and β-CD modified planar QCM without a silica film to the target chemical vapors, we confirm that the total surface area of the silica controls the sensitivity and the chemical property of the β-CD controls the selectivity of the sensing system.

Preparation of mesoporous silica films using sol–gel process and argon plasma treatment

This Letter demonstrates the first attempt of using sol–gel technique in combination with argon plasma calcination for the preparation of mesoporous silica films. CTAB is used as an organic template to generate the porous structure upon removal by the argon plasma treatment. Field emission scanning electron microscope, Fourier transform infrared spectroscopy, small angle X-ray scattering, N 2-sorption experiment and nanoindentation technique are used for characterization. Results show that the obtained films have identical chemical structure and comparable mechanical properties with those prepared using thermal calcination. The plasma parameters have distinct influences on the thickness and mesoporous property of the films.

Remarkable Enhancement in the Dispersion and Low-Temperature Activity of Catalysts Prepared via Novel Plasma Reduction-Calcination Method

A novel plasma reduction and calcination (PR&C) method has been recently developed. Upon the experimental investigations on methane conversions, including partial oxidation, methane combustion, NO reduction by methane and CO2 reforming, the catalysts prepared by this PR&C method exhibit a remarkable enhancement in the dispersion, low-temperature activity and stability. A plasma-enhanced acidity has also been addressed, which would play an important role in the improved dispersion. The PR&C method is leading to a better preparation of supported catalysts, esp., those for methane conversion.

Synthesis of Actinide-Doped Zirconia by Plasma Calcination

ABSTRACTZirconia containing actinides in solid solution, (Zr, An)Ox, where An = U, Pu, Am, Np, Cm is considered as a starting material for the synthesis of two durable crystalline host-phases for actinide immobilization: zircon (Zr, An)SiO4 and cubic zirconia (Zr,An)O2. The use of this starting material is necessary in order to provide for total actinide incorporation into the structures of the final phases, zircon and cubic zirconia, while avoiding the presence of unincorporated actinides. Difficulties arise when the chemically inert pure oxides, ZrO2 and AnOx are used as precursor materials. Melting techniques, which are commonly used to provide solid solution of inert oxides are not acceptable for ceramic preparation, particularly the synthesis of ceramic Pufuels. This paper presents a new approach utilizing plasma calcination. Solids containing both zirconium and actinides are calcined in a plasma. This allows the use of intermediate, stabilized actinide forms, for example, co-precipitated actinide-zirconium oxalates which have a low solubility level or a solid sol-gel precursor, such as (Zr, An)SiOx.Calcination was completed using an induction plasma in an argon gas mredium. Two types of material were used: co-precipitated oxalates of Zr and Ce with 10 wt.% Ce and a solidified sol-gel (Zr, Ce)SiOx with 10 wt.% Ce. Weakly milled material with a particle size of 0.34 mm was dropped through the plasma at a speed of 40-60 grams per hour. The final product was examined by high resolution transmission electron microscopy (HRTEM). The calcined oxalate material consisted of aggregates of globular particles (tens to hundreds of nm) of monoclinic and tetragonal (Zr,Ce)O2. The calcined sol-gel consisted of globular particles (50 to 100s nm) of monoclinic and tetragonal (or pseudo-cubic) (Zr, Ce)O2 in an amorphous silica matrix. This paper discusses the application of plasma calcination to the immobilization of excess weapons Pu and other actinides. The plasma calcination of solid materials would be used for ceramic Pu-fuel fabrication, as well as for the final disposal in geological formations.

Template removal from molecular sieves by low-temperature plasma calcination

The oxidative removal of templates from crystals of MFI- and TON-type zeolites using low-temperature oxygen plasma at 370 K has been investigated. This treatment removes tetrapropylammonium inside 5 µm lengths of channels in the completely siliceous MFI structure (silicalite), and diethylamine to a depth of at least 70 µm in the channels of the completely siliceous TON structure. Substitution of B, Al or Fe into the framework of silicalite significantly obstructs the removal of tetrapropylammonium, but complete decomposition of the template can be accomplished in small samples of [Si, B]-MFI. A comparison of plasma calcination with thermal calcination in air indicates that the release of boron into extra-framework positions upon either treatment is caused by the slow desorption of water at the calcination temperature.

Low-temperature Plasma Calcination of Zeolite NH 4, Na-Y

70% Ammonium-exchanged zeolite NH 4, Na-Y is completely deammoniated by low-temperature plasma calcination, while the crystallinity of the samples is not impaired. Neither the plasma calcined nor shallow bed treated material is “pure H-Y” zeolite, and 27Al MAS NMR indicates a slight dealumination of the zeolitic framework in each case. Hydronium ion exchange to product H,Na-Y from Na-Y using highly dilute acidic medium also resulted in partial dealumination of the sample. Plasma calcination of 87% ammonium-exchanged NH 4, Na-Y caused a severe loss of crystallinity, possibly because of mineral acid formation at inaccessible sites. Low-temperature plasma calcination is a mild technique for the oxidative removal of ammonia as long as oxidation products can easily leave the crystallite.