Manufacture of urea

Urea is in many ways the most convenient form for fixed nitrogen. It has the highest nitrogen content available in a solid fertilizer (46 %). It is easy to produce as prills or granules and easily transported in bulk or bags with no explosive hazard. It leaves no salt residue after use on crops. Its specific gravity is 1.335, decomposes on boiling and is fairly soluble in water. The principal raw materials required for this purpose are NH3 & CO2.Two reactions are involved in the manufacture of urea. First, ammonium carbamate is formed under pressure by reaction between CO2 & NH3. CO2 + 2NH3 NH2COONH4 H= -37.4 Kcal This highly exothermic reaction is followed by an endothermic decomposition of the ammonium carbamate. NH2COONH4 NH2CONH2 + H2O H= + 6.3 Kcal Various processes for the manufacture of urea are: 1) Snamprogetti ammonia stripping process 2) Stamicarbon CO2 stripping process 3) Once through urea process 4) Mitsui Toatsu total recycle urea process We selected the Snamprogetti ammonia stripping process for the manufacture of urea. In this process ammonia & CO2 are compressed & fed to the reactor. The unconverted carbamate is stripped and recovered from the urea synthesis reactor effluent solution at reactor pressure, condensed to an aqueous solution in a steam producing high pressure condenser & recycled back to the reactor by gravity. Part of the liquid NH3 reactor feed, vapourized in a steam heated exchanger, is used as inert gas to decompose & strip ammonium carbamate in the steam heated high pressure stripper. Energy balance & material balance of the plant is done. The selected capacity of the plant is 4,50,000 tons/year of urea producing 62,500 kg/hr of urea with 98 % purity. Urea reactor & vacuum evaporator are designed. The volume of reactor is calculated & found to be 195 m3. The length & diameter of the reactor are 40 m & 2.5 m respectively. The evaporator used is of climbing-film long- tube type. Snamprogetti ammonia-stripping urea process is selected because it involves a high NH3 to CO2 ratio in the reactor, ensuring the high conversion of carbamate to urea. The highly efficient ammonia stripping operation drastically reduces the recycling of carbamate and the size of equipment in the carbamate decomposition . Snamprogetti technology differs from competitors in being based on the use of excess ammonia to avoid corrosion as well as promote the decomposition of unconverted carbamate into urea. Uses of Urea: • About 56 % of Urea manufactured is used in solid fertilizer. • About 31 % of Urea manufactured is used in liquid fertilizer. • Urea-formaldehyde resins have large use as a plywood adhesive. • Melamine-formaldehyde resins are used as dinnerware & for making extra hard surfaces

Modelling temporal and spatial features of collaboration network

The collaboration network is an example of a social network which has both non-trivial temporal and spatial dependence. Based on the observations of collaborations in Physical Review Letters, a model of collaboration network is proposed which correctly reproduces the time evolution of the link length distributions, clustering coefficients, degree distributions and assortative property of real data to a large extent.Comment: 8 pages, 10 figures; follow up work on arXiv.org/physics/0511181; accepted for publication in IJMP

Forest trees of Odisha, India: An updated checklist

An exhaustive taxonomic inventory of forest trees of Odisha in the Eastern Ghats of India was made during 2015–2020, which revealed the presence of a total of 501 species of wild and naturalised trees belonging to 284 genera under 80 families. The family Euphorbiaceae was the most species-rich represented by 45 species, followed by Rubiaceae (28), Mimosaceae (27), Moraceae (26) and Meliaceae (23). The genus Ficus (Moraceae) had highest number of 21 tree species, followed by Diospyros (10 species), Syzygium (8 species), Albizia (8 species), Senegalia (7 species), Vitex (7 species) and Terminalia (6 species). Nothopodytes nimmoniana, Alphonsea madraspatana, Lasiococca comberi, Siphonodon celastrineus, Searsia paniculata, Syzygium schmidii, Cassipourea ceylanica, Prunus pygeoides, Sonneratia griffithii, Eriolaena hookeriana var. viridis, Dimorphocalyx glabellus, Garcinia xanthochymus and Litsea glutinosa have been identified as regionally threatened species needing conservation intervention. Cocculus laurifolius is reported here as a new distributional record for the state. Field observation on the occurrence and dominance of tree species in different forest types of Odisha has been discussed. A checklist of the tree species of Odisha is presented in this article, along with the correct botanical name, synonym(s), local name, flowering and fruiting time, locality of occurrence and citation of voucher herbarium specimens

Economics of BN Hybrid Grass Production Bundelkhand Region of India: A Case Study

Napier grass is also called as Elephant Grass due to its tallness and vigorous vegetative growth. The plants tiller freely and a single clump may produce more than 60 tillers under favorable climatic and soil conditions. Unfortunately, the grass coarse-textured, the leaf blade sheaths as well as sharply serrated, leaf margins. Therefore, cross was made between Bajra which is more succulent, leafy, fine-textured, palatable, fast growing and drought resistant and Napier to combine these qualities with its high yielding potential. The outcome Hybrid Napier is a perennial grass which can be retained on field for 2-3 years. Hybrid napier grass are mostly grown under assured water supply but cultivating under varying agroclimatic condition is also possible. Low grass production in dry land area is mainly due to the limited availability of soil moisture and plant nutrients. Agrawal et al., (2001) reported NB hybrid is superior to guinea grass or setaria grass. However the economy of production plays an important role in introduction/ adoption of a crop in an area, village or farm. Many earlier studies have been conducted on economics of BN Hybrid production at research farm, or other government farms. But the information on economics of BN hybrid production at farmer’s field and its integration livestock feeding as well rooted slips are limited. Therefore, the present study was conducted with the object to study the economics of BN hybrid at farmer’s field in Bundelkhand

Rejuvenation of Wild Ber (\u3cem\u3eZizyphus\u3c/em\u3e Species) through Budding at Farmer’s Field

Ber is mainly cultivated for its fresh fruits, which are rich in vitamins C, A and B complex. Due to its nutritional qualities it is called poor man’s apple (Gajbhiya et al., 2003). A large number of wild ber shrubs (Zizyphus mauritiana, Z. rotundifolia and Z. nummularia) were seen growing on the neglected lands, uncultivated lands, roadsides and farm boundaries in Kadesara Kala Village in Lalitpur district of Uttar Pradesh (India). Production potential of this species is very low because of poor upkeep and inferior genetic makeup. But they have extensive root system which can withstand prolonged drought and has capability to regenerate even if the shoot system is damaged completely (Batahr, 1990). They are also responsibly resistant to common insect and pest. Therefore, these species offer an excellent production potential from the degraded lands of Bundelkhand region of India (Sharma and Tiwari, 1994; Tiwari and Sharma, 1993) after in-situ budding with improved cultivars. It also provides sufficient leaf biomass (pala) which can be utilized as fodder in lean period and also suitable for hay and silage for goat as it contains 11-13 percent crude protein (Tewatia and Khirwar, 2002). Pruned twigs/stems of ber also meet, to some extent, the fuel wood requirement in rural areas (Kumar et al., 2004)

Inter-Landau-level Andreev Reflection at the Dirac Point in a Graphene Quantum Hall State Coupled to a NbSe2 Superconductor

Superconductivity and quantum Hall effect are distinct states of matter occurring in apparently incompatible physical conditions. Recent theoretical developments suggest that the coupling of quantum Hall effect with a superconductor can provide a fertile ground for realizing exotic topological excitations such as non-abelian Majorana fermions or Fibonacci particles. As a step toward that goal, we report observation of Andreev reflection at the junction of a quantum Hall edge state in a single layer graphene and a quasi-two dimensional niobium diselenide (NbSe2) superconductor. Our principal finding is the observation of an anomalous finite-temperature conductance peak located precisely at the Dirac point, providing a definitive evidence for inter-Landau level Andreev reflection in a quantum Hall system. Our observations are well supported by detailed numerical simulations, which offer additional insight into the role of the edge states in Andreev physics. This study paves the way for investigating analogous Andreev reflection in a fractional quantum Hall system coupled to a superconductor to realize exotic quasiparticles.Comment: published verio

Quantum phase transition in few-layer NbSe2_2 probed through quantized conductance fluctuations

We present the first observation of dynamically modulated quantum phase transition (QPT) between two distinct charge density wave (CDW) phases in 2-dimensional 2H-NbSe$_2$. There is recent spectroscopic evidence for the presence of these two quantum phases, but its evidence in bulk measurements remained elusive. We studied suspended, ultra-thin \nbse devices fabricated on piezoelectric substrates - with tunable flakes thickness, disorder level and strain. We find a surprising evolution of the conductance fluctuation spectra across the CDW temperature: the conductance fluctuates between two precise values, separated by a quantum of conductance. These quantized fluctuations disappear for disordered and on-substrate devices. With the help of mean-field calculations, these observations can be explained as to arise from dynamical phase transition between the two CDW states. To affirm this idea, we vary the lateral strain across the device via piezoelectric medium and map out the phase diagram near the quantum critical point (QCP). The results resolve a long-standing mystery of the anomalously large spectroscopic gap in NbSe$_2$

Constraints for Grassland Development in Kadesara Kala Village, Lalitpur, Bundelkhand: A Case Study

India is maintaining a livestock population of over 500 million and has a grim situation of forage and feed deficit to the tune of 35.6% green fodder, 10.95% crop residues and 44% concentrate. In term of nutrients, the deficit is expected to the tune of 24.6 and 19.9% respectively by the year 2020. The gap is to be bridged up through development as well as extension of appropriate fodder production technologies suitable for different farming situation strategies. Fifty-eight % of the available fodder comes from grazing land and 42% from stall feeding with crop residues (30%) and leaf fodder (12%). Grasses constitute the majority (88%) of fodder available in Uttar Pradesh (GOUP, 1994). However, the role of grasslands cannot be under judged, as the large animal populations owned by small, marginal and landless farm family strive upon these. The livestock sector achieved an average growth rate of 4.8 per cent during the Eleventh Five Year Plan (Economic Survey, 2012-13) and it contributed 3.6 percent of national GDP during the Eleventh Plan. In the same tune, the contribution from this sector is expected to improve because increasing purchasing power is favoring the proportion of protein from animal source in the human diets. Further, The Indian livestock sector is becoming more competitive participant in the world market. All this largely depends, however, on improvement and sufficiency in the production of feeds and forages. Notwithstanding the above, the grasslands and pastureland in the country are continuously shrinking. The paper addresses important issues limiting the development of new grasslands in semiarid Bundelkhand region of Uttar Pradesh particularly the Lalitpur district