Utilization of the Net Heat Process Tail Gases in the Reactor for the Production of Oil-Furnace Carbon Black

Otpadni procesni plinovi niske donje toplinske vrijednosti koji nastaju kao sporedni proizvod industrijske proizvodnje uljno-pećnih čađa mogu se energetski učinkovito iskoristiti prije konačnog ispuštanja u atmosferu. Osim što se upotrebljavaju za sušenje mokro granulirane uljno-pećne čađe, proizvodnju pare i električne energije te se spaljuju na baklji, učinkovito se mogu iskoristiti i kao zamjena goriva u reaktorima za proizvodnju uljno-pećnih čađa uz povećanje iskorištenja ugljikovodične sirovine. U radu je prikazano tehnološko-tehničko rješenje iskorištenja topline otpadnih procesnih plinova niske donje toplinske vrijednosti u reaktoru za proizvodnju "tvrdih" tipova uljno-pećnih čađa uz povećanje iskorištenja ugljikovodične sirovine. Uvođenje predgrijanih procesnih otpadnih plinova niske donje toplinske vrijednosti u reaktor za proizvodnju "tvrdih" tipova uljno-pećnih čađa ostvareno je serijskim spajanjem četiriju ventilatora. Sustav je izveden pomoću ventilatora predviđenih za pneumatski transport smjese uljno-pećne čađe u prahu i otpadnih procesnih plinova. Navedenom izvedbom osiguran je stabilan tehnološki proces uvođenja otpadnih procesnih plinova niske donje toplinske vrijednosti u reakcijsku zonu sagorijevanja prirodnog plina u predgrijanom zraku. Prilikom proizvodnje uljno-pećne čađe N220 pokazano je da se upotrebom otpadnih procesnih plinova niske donje toplinske vrijednosti u količini Q od 1000 do 2000 m3 h-1 po reaktoru ostvaruje ušteda prirodnog plina od 10 do 20 %,uz istodobno povećanje iskorištenja ugljikovodične sirovine od 7 do 9%.Tail gases of low calorific value, which are the by-product of oil-furnace carbon black industrial production, can be efficiently used as energy before their final release into the atmosphere. Apart from being used mainly for heating dryers, production of steam, electricity, or flared, they can also be used as a substitute for fuel in the reactor for the production of oil-furnace carbon blacks, thus increasing the efficiency of the hydrocarbon raw feedstock. This technical paper represents the technical-technological solution for applying the waste heat of the low calorific tail gases in the reactor for the production of "hard" grade oil-furnace carbon blacks with savings of the hydrocarbon raw feedstock. The introduction of the preheated low calorific tail gases in the reactor for the production of "hard" grade oil-furnace carbon blacks is achieved by serial cascading of four fans. The system consists of fans designed to pneumatically transport the mixture of process tail gases and oil-furnace carbon black dust particles. This ensures a stable technological process for the introduction of the low calorific process tail gases into the reaction zone where the natural gas and preheated air are combusted. In the production of oil-furnace carbon black N220, it is shown that by using low calorific process tail gases in the amount from 1000 to 2000 m3 h–1 per reactor, savings from 10 to 20 % of natural gas and simultaneously 7 to 9 % of the hydrocarbon raw feedstoks were achieved

Optical Evidence for Mixed Phase Behavior in Manganites

Synchrotron infrared measurements were conducted over the range 100 to 8000 cm-1 on a self-doped LaxMnO3-d (x~~0.8) film. From these measurements we determined the conductivity, the effective number of free carriers, and the specific phonon modes as a function of frequency. While the metal-insulator transition temperature (TMI) and the magnetic ordering temperature (TC) approximately coincide, the free carrier density onset occurs at a significantly lower temperature (~~45 K below). This suggests that local distortions exist below TMI and TC which trap the eg conduction electrons. These regions with local distortions constitute an insulating phase which persists for temperatures significantly below TMI and TC. The initial large drop in resistivity is due to the enhanced magnetic ordering while further drops correspond to reductions in the insulating phase which increase the number of free carriers.Comment: 12 pages, 5 figure

Filtration of Oil-furnace Carbon Black Dust Particles from the Tail Gases by Filter Bags With PTFE Membrane

Prilikom industrijskog procesa proizvodnje uljno-pećnih čađa u zrak se emitiraju otpadni procesni plinovi koji uz plinovite onečišćujuće tvari sadrže i čestice prašine uljno-pećnih čađa. Na postrojenju za proizvodnju uljno-pećne čađe Petrokemije d. d. postoji šest ispusta otpadnih procesnih plinova u zrak. Prije svakog ispusta postavljena je procesna oprema za filtriranje otpadnih procesnih plinova. Učinkovitost filtriranja ponajprije ovisi o konstrukcijskoj izvedbi opreme te odabranoj tehnologiji filtriranja. Blizina naselja, kakvoća zraka kutinskog područja s obzirom na lebdeće čestice PM10 i obveza tvrtke za stalnim unapređenjem stanja okoliša nameću potrebu pronalaženja sve boljih mjera smanjenja emisija čestica prašine uljno-pećnih čađa u zrak. Zbog toga je dizajniran poseban ciklofiltar za filtriranje čestica prašine uljno-pećnih čađa od otpadnih procesnih plinova uz primjenu filtar-vreća s PTFE-membranom (politetrafluoretilen). Posebna konstrukcija ciklofiltra ostvarena je kombinacijom centrifugalnog taložnika i vrećastog filtra "pulse- jet". Kombinacijom dviju tehnika filtriranja čestica prašine uljno-pećnih čađa od otpadnih procesnih plinova osigurava se maksimalna učinkovitost filtriranja od η = 99,9 %. U konstrukcijskom dijelu vrećastog filtra upotrebljavaju se filtar-vreće najnovije generacije s ugrađenim PTFE membranama, koje se naknadno čiste pomoću stlačenog zraka. Tehnologija filtriranja pomoću PTFE-membrana osigurava učinkovitost filtriranja od maksimalno γ = 5 mg m-3 čestica prašine uljno-pećnih čađa u pročišćenim izlaznim otpadnim procesnim plinovima. Učinkovitost filtriranja prati se kontinuiranim mjerenjem emisije čestica prašine uljno-pećnih čađa u pročišćenim izlaznim otpadnim procesnim plinovima putem automatskog neekstraktivnog uređaja. Ostvarena tehnologija filtriranja poslužit će kao osnova za ugradnju filtar-vreća s PTFE-membranom u glavne operacijske filtre, čime će se osigurati poboljšana zaštita zraka grada Kutine s obzirom na lebdeće čestice PM10.During the industrial production of oil furnace carbon black, tail gases containing oil-furnace carbon black dust particles are emitted to the atmosphere. In the carbon black plant, Petrokemija d. d., there are six exhaust stacks for tail gases. Each of them has installed process equipment for cleaning tail gases. Efficiency of cleaning mainly depends on equipment construction and cleaning technology. The vicinity of the town, quality of the air in the region of Kutina, regarding floating particles PM10, and corporate responsibility for further enviromental improvement, imposes development of new methods that will decrease the emmision of oil-furnace carbon black dust particles in the air. Combining centrifugal percipitator and filter, special construction of cyclofilter for filtration of oil-furnace carbon black dust particles from tail gases by using PTFE (polytetrafluoroethylene) membrane filter bags, was designed. Developed filtration technique provides η = 99.9 % efficiency of filtration. Construction part of the filter contains the newest generation of PTFE membrane filter bags with the ability of jet pulse cleaning. Using the PTFE membrane filter bags technology, filtration efficiency for oil-furnace carbon black dust particles in tail gases of maximum γ=5mgm-3 can be achieved. The filtration efficiency was monitored continuously measuring the concentration of the oil-furnace carbon black dust particles in the tail gases with the help of in situ electronic probe. The accomplished filtration technology is the base for the installation of the PTFE membrane filter bags in the main operation filters which will provide better protection of the air in the town of Kutina against floating particles PM10

Thermal Oxidation of Tail Gases from the Production of Oil-furnace Carbon Black

U radu je prikazana tehnologija proizvodnje uljno-pećne čađe i odabrano tehnološko rješenje u funkciji zaštite zraka. Prilikom industrijskog procesa proizvodnje uljno-pećne čađe osim glavnog proizvoda, kao sporedni proizvodi nastaju i otpadni procesni plinovi. Otpadni procesni plinovi nastali prilikom industrijskog procesa proizvodnje uljno-pećne čađe po kvalitativnom sastavu sastoje se od: ugljikovog (IV) oksida, ugljikovog(II) oksida, vodika, metana, sumporovodika, dušika, kisika i vodene pare. Ovisno o vrsti uljne sirovine za proizvodnju te samom proizvodnom tipu uljno pećne-čađe mijenja se kvantitativan sastav i donja kalorična vrijednost otpadnih procesnih plinova. Donja kalorična vrijednost otpadnih procesnih plinova relativno je mala i nalazi se u području od 1500 do 2300 kJ m–3. U konvencionalnom procesu proizvodnje uljno-pećne čađe pročišćeni otpadni procesni plinovi od čestica čađe ispuštaju se u atmosferu bez ikakve dodatne obrade. Na taj način otpadni procesni plinovi zagađuju atmosferu, jer njihove kvantitativne vrijednosti višestruko premašuju dopuštene granice emisije za sumporovodik i ugljikov(II) oksid, čime se znatno narušava kvaliteta lokalnog zraka grada Kutine. Logično tehnološko rješenje sprječavanja zagađivanja zraka je spaljivanje otpadnih procesnih plinova, odnosno njihova termalna oksidacija. Kao sredstvo za termalnu oksidaciju otpadnih procesnih plinova odabrana je posebno dizajnirana izvedba baklje. Sustav baklje dizajniran je tako da omogućuje termalnu oksidaciju otpadnih procesnih plinova male kalorične vrijednosti s 99%-tnom djelotvornošću uz minimalnu potrošnju prirodnog plina potrebnog za oksidaciju. Na taj način se štetne i zapaljive komponente (sumporovodik, vodik, ugljikov (II) oksid te metan i ostali ugljikovodici u tragovima) prevode u kvalitativno-kvantitativan ekološki prihvatljivij sastav otpadnih procesnih plinova (sumporov(IV) oksid, vodena para, ugljikov (IV) oksid, dušikov(IV) oksid), koji udovoljavaju propisanim graničnim vrijednostima emisije i kakvoće zraka (Uredbe NN 133/2005. i NN 21/2007.) Ispravnim tehnološkim radom sustava baklji u industrijskom postrojenju proizvodnje uljno-pećne čađe ostvareno je rješavanje problema onečišćavanja zraka grada Kutine, posebno prizemnih masenih koncentracija sumporovodika. Usporedo s razvojem sustava baklji uspostavlja se i sustav kontinuiranog praćenja onečišćujućih tvari u zrak (sumporovodik i ugljikov(II) oksid) te njegovo povezivanje s Agencijom za zaštitu okoliša.This paper describes the production technology of oil-furnace carbon black, as well as the selected solution for preventing the emissions of this process from contaminating the environment. The products of industrial oil-furnace carbon black production are different grades of carbon black and process tail gases. The qualitative composition of these tail gases during the production of oil-furnace carbon black are: carbon(IV) oxide, carbon(II) oxide, hydrogen, methane, hydrogen sulfide, nitrogen, oxygen, and water vapor. The quantitative composition and lower caloric value of process tail gases change depending on the type of feedstock used in the production, as well as the type of process. The lower caloric value of process tail gases is relatively small with values ranging between 1500 and 2300 kJ m–3. In the conventional production of oil-furnace carbon black, process tail gases purified from carbon black dust are freely released into the atmosphere untreated. In this manner, the process tail gases pollute the air in the town of Kutina, because their quantitative values are much higher than the prescribed emissions limits for hydrogen sulfide and carbon(II) oxide. A logical solution for the prevention of such air pollution is combustion of the process tail gases, i. e. their thermal oxidation. For this purpose, a specially designed flare system has been developed. Consuming minimum amounts of natural gas needed for oxidation, the flare system is designed to combust low caloric process tail gases with 99 % efficiency. Thus, the toxic and flammable components of the tail gases (hydrogen sulfide, hydrogen, carbon(II) oxide, methane and other trace hydrocarbons) would be transformed into environmentally acceptable components (sulfur(IV) oxide, water, carbon(IV) oxide and nitrogen(IV) oxide), which are in compliance with the emissions limit values prescribed by law. Proper operation of this flare system in the production of oil-furnace carbon black would solve the air pollution problem in the town of Kutina, especially the concentrations of hydrogen sulfide in the troposphere. Together with the development of this flare system, a continuous air-pollutant (hydrogen sulfide and carbon(II) oxide) monitoring system shall be established and linked with the Environmental Protection Agency

Microstructural analysis of phase separation in iron chalcogenide superconductors

The interplay between superconductivity, magnetism and crystal structure in iron-based superconductors is a topic of great interest amongst the condensed matter physics community as it is thought to be the key to understanding the mechanisms responsible for high temperature superconductivity. Alkali metal doped iron chalcogenide superconductors exhibit several unique characteristics which are not found in other iron-based superconducting materials such as antiferromagnetic ordering at room temperature, the presence of ordered iron vacancies and high resistivity normal state properties. Detailed microstructural analysis is essential in order to understand the origin of these unusual properties. Here we have used a range of complementary scanning electron microscope based techniques, including high-resolution electron backscatter di raction mapping, to assess local variations in composition and lattice parameter with high precision and sub-micron spatial resolution. Phase separation is observed in the Csx Fe2-ySe2 crystals, with the minor phase distributed in a plate-like morphology throughout the crystal. Our results are consistent with superconductivity occurring only in the minority phase.Comment: Accepted for publication in a special edition of Supercond. Sci. Techno

Evidence for anisotropic polar nanoregions in relaxor PMN: A neutron study of the elastic constants and anomalous TA phonon damping

We use neutron scattering to characterize the acoustic phonons in the relaxor PMN and demonstrate the presence of an anisotropic damping mechanism directly related to short-range, polar correlations. For a large range of temperatures above Tc ~ 210, K, where dynamic polar correlations exist, acoustic phonons propagating along [1\bar{1}0] and polarized along [110] (TA2 phonons) are overdamped and softened across most of the Brillouin zone. By contrast, acoustic phonons propagating along [100] and polarized along [001] (TA1 phonons) are overdamped and softened for only a limited range of wavevectors. The anisotropy and temperature dependence of the acoustic phonon energy linewidth are directly correlated with the elastic diffuse scattering, indicating that polar nanoregions are the cause of the anomalous behavior. The damping and softening vanish for q -> 0, i.e. for long-wavelength acoustic phonons, which supports the notion that the anomalous damping is a result of the coupling between the relaxational component of the diffuse scattering and the harmonic TA phonons. Therefore, these effects are not due to large changes in the elastic constants with temperature because the elastic constants correspond to the long-wavelength limit. We compare the elastic constants we measure to those from Brillouin scattering and to values reported for pure PT. We show that while the values of C44 are quite similar, those for C11 and C12 are significantly less in PMN and result in a softening of (C11-C12) over PT. There is also an increased elastic anisotropy (2C44/(C11-C12)) versus that in PT. These results suggest an instability to TA2 acoustic fluctuations in relaxors. We discuss our results in the context of the debate over the "waterfall" effect and show that they are inconsistent with TA-TO phonon coupling or other models that invoke the presence of a second optic mode.Comment: (21 pages, 16 figures, to be published in Physical Review B

Odnos strukture i aktivnosti u reaktivaciji tabunom fosforilirane ljudske acetilkolinesteraze bispiridinijevim para-aldoksimima

We investigated interactions of bispyridinium para-aldoximes N,N’-(propano)bis(4-hydroxyiminomethyl) pyridinium bromide (TMB-4), N,N’-(ethano)bis(4-hydroxyiminomethyl)pyridinium methanosulphonate (DMB-4), and N,N’-(methano)bis(4-hydroxyiminomethyl)pyridinium chloride (MMB-4) with human erythrocyte acetylcholinesterase phosphorylated by tabun. We analysed aldoxime conformations to determine the flexibility of aldoxime as an important feature for binding to the acetylcholinesterase active site. Tabun-inhibited human erythrocyte acetylcholinesterase was completely reactivated only by the most flexible bispyridinium aldoxime - TMB-4 with a propylene chain between two rings. Shorter linkers than propylene (methylene or ethylene) as in MMB-4 and DMB-4 did not allow appropriate orientation in the active site, and MMB-4 and DMB-4 were not efficient reactivators of tabun-phosphorylated acetylcholinesterase. Since aldoximes are also reversible inhibitors of native acetylcholinesterase, we determined dissociation constants and their protective index against acetylcholinesterase inactivation by tabun.Proučavali smo interakcije bispiridinijevih para-oksima N,N’-(propano)bis(4-hidroksiiminometil)piridinijeva bromida (TMB-4), N,N’-(etanano)bis(4-hidroksiiminometil)piridinijeva metanosulfonata (DMB-4) i N,N’- (metano)bis(4-hidroksiiminometil)piridinijeva klorida (MMB-4) s ljudskom eritrocitnom acetilkolinesterazom fosforiliranom tabunom. Da bismo odredili fleksibilnosti aldoksima, što je važna osobina kod njihova vezanja u aktivno mjesto acetilkolinesteraze, analizirali smo i konformacijske odlike aldoksima. Ljudska acetilkolinesteraza inhibirana tabunom bila je potpuno reaktivirana samo najfleksibilnijim bispiridinijevim aldoksimom – TMB-4. Aldoksimi MMB-4 i DMB-4 nisu bili efikasni reaktivatori acetilkolinesteraze fosforilirane tabunom jer je kod tih spojeva lanac koji povezuje dva prstena kraći od propilena (metilen u MMB-4 i etilen u DMB-4), što ne dopušta povoljnu orijentaciju tih aldoksima unutar aktivnog mjesta enzima. S obzirom na to da su aldoksimi i reverzibilni inhibitori nativne acetilkolinesteraze, odredili smo njihove disocijacijske konstante, kao i zaštitu acetilkolinesteraze od inhibiranja tabunom reverzibilnim vezanjem aldoksima

Structural heterogeneity and diffuse scattering in morphotropic lead zirconate-titanate single crystals

Complementary diffuse and inelastic synchrotron X-ray scattering measurements of lead zirconate-titanate single crystals with composition near the morphotropic phase boundary (x=0.475) are reported. In the temperature range 293 K < T < 400 K a highly anisotropic quasielastic diffuse scattering is observed. Above 400 K this scattering disappears. Its main features can be reproduced by model of inhomogeneous lattice deformations caused by inclusions of a tetragonal phase into a rhombohedral or monoclinic phase. This observation supports the idea that PZT at its morphotropic phase boundary is essentially structurally inhomogeneous.Comment: 4 pages, 4 figure

Ultrafast photoinduced reflectivity transients in (Nd0.5Sr0.5)MnO3(Nd_{0.5}Sr_{0.5})MnO_3

The temperature dependence of ultrafast photoinduced reflectivity transients is reported in Nd$_{0.5}$Sr$_{0.5}$MnO$_{3}$ thin film. The photoinduced reflectivity shows a complex response with very different temperature dependences on different timescales. The response on the sub-ps timescale appears to be only weakly sensitive to the 270K-metal-insulator phase transition. Below $\sim 160$ K the sub-ps response displays a two component behavior indicating inhomogeneity of the film resulting from the substrate induced strain. On the other hand, the slower response on the 10-100 ps timescale is sensitive only to the metal-insulator phase transition and is in agreement with some previously published results. The difference in the temperature dependences of the responses on nanosecond and $\mu$s timescales indicates that thermal equilibrium between the different degrees of fredom is established relatively slowly - on a nanosecond timescale

Lattice Dynamics of LaFeAsO_{1-x}F_{x} and PrFeAsO_{1-y} via Inelastic X-Ray Scattering and First-Principles Calculation

The lattice dynamics of LaFeAsO_{1-x}F_{x} (x=0, 0.1) and PrFeAsO_{1-y} (y~0.1) are investigated using inelastic x-ray scattering and ab-initio calculation. Measurements of powder samples provide an approximation to the phonon DOS, while dispersion is measured from a single crystal of PrFeAsO_{1-y}. A model that agrees reasonably well with all of the data at room temperature is built from results of ab-initio calculations by softening the strength of the Fe-As bond by 30%.Comment: 4 pages, 4 figures; some changes of the text and a revision of figure