Catalytic co-combustion of biomass and brown coal in a fluidized bed:Economic and environmental benefits

The work is devoted to the study of combustion of brown coal,pine sawdust,and their mixtures in a fluidized bed of catalyst at 600-750℃.It is shown that an increase in the content of sawdust in a mixture with brown coal leads to an increase in the burnout degree of solid fuel from 94.4%to 99.9%,while the emission of greenhouse gases in the form of CO_(2)CO and NOxis reduced(CO_(2)from the biomass is not included in the balance).The high content of alkaline earth metal oxides(CaO and MgO)in the mineral part of brown coal,sawdust,and their mixtures eliminates the emission of sulfur oxides and the slagging of heat-exchange surfaces during the combustion in a fluidized bed of catalyst.The optimal temperature,when the highest burnout degree of the above fuels is achieved in the combustion is 750℃.It is also shown that the increase in temperature and the content of sawdust in the composition of the fuel mixtures has a positive effect on the economic and environmental process indicators.

Considering solid shear stress in MP-PIC simulation of a CFB riser

To enable successful multi-phase particle-in-cell(MP-PIC)simulations of circulating fluidized beds(CFBs),both the interphase drag force and interparticle collisions need to be carefully modeled.Particle collisions are usually represented by the solid stress consisting of the normal and shear components,in which the normal stress was found to have a leading role in the numerical stability of MP-PIC simulations,whereas the impact of the shear stress has seldom been reported.In this work,the effects of the solid shear stress are investigated by using two-dimensional simulations of the moderately dense laboratory-scale CFB riser with in-house MP-PIC code implemented on MFIX open-source platform.Cases including only normal solid stress and those considering both normal and shear solid stresses are simulated.The results of solids flux,axial and radial solids profiles are compared with available experimental data.The results show that the solid shear stress plays a minor role on the accuracy of simulation,and the increase of PPP(number particles per parcel)leads to a lower accuracy of simulation.

Origin of iron-rich minerals,ooids and pisoids in the Jurassic ooidal ironstones of the Labino-Malkin region(Caucasus)

This study investigates the Middle Jurassic rocks of the Labino-Malkin zone(Caucasus),represented by ooidal ironstones,biogenic limestones,and nodular phosphorites.All rocks contain ooids/pisoids.Based on the mineral composition,nine types of ooids and three possible scenarios for their formation have been identified.The mineral composition of ooids indicates the variable conditions of their deposition and repeated changes in physical and chemical conditions of the environment,including fluctuations in theredox regime.The access of oxygen in the bottom environment as a factor of increasing oxic conditions was associated with the regression of the sea and/or the inflow of meteoric waters.The main sources of ooids are the drift of material from the continent and convecting metal-bearing meteoric and/or deep solutions.

A new method for precise optical measurements of the sub-micron height of levitation of droplet clusters

Droplet clusters levitating over the locally heated water surface are considered a very promising phe-nomenon of microfluidics for the potential use of the droplets as unique microreactors for microbio-logical experiments.A new optical method is suggested for precise measurements of the sub-micron levitation height of single droplets.The method is based on the analysis of variable colors of the inter-ference halo around the droplet.For the first time,it is possible to measure the extremely low downward velocity of droplets,which grow due to steam condensation.This velocity was found to be 5-8 nm/s.The height of the levitation of various droplets just before their coalescence with a layer of water was also determined.Such measurements might be used for the verification of sophisticated models for the droplet levitation to be developed for a very thin layer of humid air under the droplet when the Knudsen effect should be taken into account.

Effect of biochar aging in agricultural soil on its wetting properties and surface structure

Biochar wettability and ability to accumulate moisture inside the porous space are crucial for improving soil fertility,regulating soil water balance,and regulating nutrients.However,a long-term interaction of biochar with agricultural soils may drastically alter the wetting properties and,eventually,influence water holding capacity and the structure of soils.In this work,the structure and wetting properties of biochar samples after 6-year long exposure to a sandy loam Spodosol with a crop rotation and mineral fertilizers application were studied.It was found that the elemental composition of the aged biochars was richer and more"soil-like",which is explained by the presence of the mineral crust on the biochar surface.The temporal evolution of biochar in the soil without any mineral fertilizer application resulted in significant improvement of its surface wettability due to the effects of various environmental factors.The lateral surface of biochar after 6-year interaction with the soil changes into a loose porous layer in a form of grooved base filled with adherent mineral soil and clay particles.Contrary,the application of the mineral fertilizer to the soil resulted in decreased wettability of the biochar lateral surfaces due to a decrease in the polar component of surface energy and the crusting of the surface with fine material,which blocks the pore space of the biochar.As a result,water capacity of the biochar from the treatment with the fertilizer decreased compared to the biochar samples collected from the soil without the fertilizer application.The radial biochar surfaces of both types of samples collected from the soil were open vessels filled with soil particles that slow down complete wetting and water absorption.The treatment of the biochar samples with surfactants drastically increased wettability of lateral surface and water absorption capacity of control samples as compared to the samples collected from the soil.The obtained results support the idea that the hydrophilisation of biochar caused by the adhesion of soil particles and treatment of its pore surface with surfactants,can improve the water-holding capacity of the sandy loam Spodosol in the plant-available range of soil water.

Elucidating elusive quaternary selenide EuCeCuSe3:Synthesis,crystal structure,properties and theoretical studies

We report on the novel heterometallic quaternary selenide EuCeCuSe3,the fabrication of which has been a challenge until this work.The structure of the reported selenide was elucidated from the powder X-ray diffraction data,which revealed the formation of EuCeCuSe3with excellent yield(96.7%)accompanied with a minor fraction of CeSe2(3.3%),and was best solved in orthorhombic space group Pnma with the BaLaCuS3structural type.Thus,the crystal structure of the title compound completes the row of the heterometallic quaternary selenides EuRECuSe3(RE=La,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu,Y),of which the cerium-based derivative exclusively belongs to the BaLaCuS3structural type.The distortion of the CuSe4polyhedron was compared for the whole series of EuRECuSe3compounds using theτ4-descriptor for four coordinated ions,which revealed the highest degree of distortion for the Ce3+-containing selenide,followed by the La3+-based derivative.Furthermore,the crystallographic and geometrical parameters of the reported selenide were discussed in comparison to the Ce3+-based sulfides SrCeCuS3and EuCeCuS3.Ab initio calculations of the crystal structure,a phonon spectrum and elastic constants for the crystal of EuCeCuSe3were also performed.The types and wavenumbers of fundame ntal modes were determined and the involvement of ions participating in the phonon modes was assessed.The experimental IR spectrum of the reported selenide was interpreted and found to be in agreement with the calculated spectrum.The experimental direct band gap of EuCeCuSe3was measured to be 1.36 eV that is consistent with the concept of its origin due to interband transitions between orbitals emerging mainly from 4f(valence band)and 5d(conduction band)levels of the Eu2+cation.The dependence of the Young’s modulus on the direction demonstrates the anisotropy of the elastic properties,while the Vickers hardness for EuCeCuSe3was calculated to be 5.2 GPa.Finally,the title compound is paramagnetic above 4 K.

The Silk Road agenda of the Pan-Eurasian Experiment (PEEX) program

The Silk Road Economic Belt and the 21st-Century Maritime Silk Road(B&R)aims at facilitating the twenty-first Century economic development of China.However,climate change,air quality and related feedbacks are affecting the successful development of the environment and societies in the B&R geographical domain.The most urgent risks related to the atmospheric system,to the land system and to hydrospheric and cryospheric processes are changing climate-air quality interactions,air pollution,changing monsoon dynamics,land degradation,and the melting of Tibetan Plateau glaciers.A framework is needed in which a science and technology-based approach has the critical mass and expertise to identify the main steps toward solutions and is capable to implement this roadmap.The Pan-Eurasian Experiment(PEEX)program,initiated in 2012,aims to resolve science,technology and sustainability questions in the Northern Eurasian region.PEEX is now identifying its science agenda for the B&R region.One fundamental element of the PEEX research agenda is the availability of comprehensive ground-based observations together with Earth observation data.PEEX complements the recently launched international scientific program called Digital Belt and Road(DBAR).PEEX has expertise to coordinate the ground-based observations and initiate new flagship stations,while DBAR provides a big data platform on Earth observation from China and countries along the Belt and Road region.The DBAR and PEEX have joint interests and synergy expertise on monitoring on ecological environment,urbanization,cultural heritages,coastal zones,and arctic cold regions supporting the sustainable development of the Belt and Road region.In this paper we identify the research themes of the PEEX related Silk Road agenda relevant to China and give an overview of the methodological requirements and present the infrastructure requirements needed to carry out large scale research program.

Negative thermal expansion in one-dimension of a new double sulfate AgHo(SO_(4))_(2)with isolated SO_4 tetrahedra

A double holmium-silver sulfate was obtained for the first time.The temperature intervals for the formation and stability of the compound were determined by differential scanning calorimetry.The crystal structure of AgHo(SO_(4))_(2)was determined by Rietveld method.The X-ray diffraction(XRD)analysis showed that the compound crystallizes in the monoclinic syngony,space group P2_1/m,with the unit cell parameters a=4.71751(4)A,b=6.84940(6)A and c=9.89528(9)A,β=95.1466(4)·,V=318.448(5)A^(3),Z=2,R_B=1.55%,T=303 K.Two types of sulfate tetrahedra were found in the structure,which significantly affected the spectral properties in the infrared range.In the temperature range of 143-703 K,a negative thermal expansion along the b direction accompanied by a positive thermal expansion along the a and c directions was observed.It was established that negative thermal expansion is the result of the deformation of sulfate tetrahedra,which is affected by the movement of holmium and silver atoms.The excitation in the blue spectral range(457.9 nm)produces a luminescence in light blue(489 nm),green(545 nm)and red(654 nm)spectral ranges,and the latter two were of comparable intensity that is favorable for WLED sources.The observed luminescent band distribution is ascribed to the specific crystal field at Ho^(3+)ion sites rather than a variation of radiationless probability.