A Review of Recent Research and Application Progress in Screw Machines

Screw machines, mainly including single-screw type and twin-screw type, have gone through significant development and improvement during the past decade. This paper reviews the relevant studies available in the open literature for acquiring insight into and to establish the state of the art of the research and application status of screw machines. The related research on different aspects, which would affect the performance and reliability of screw machines includes rotor profile and geometric characteristics, thermodynamic modelling, vibration and noise, lubrication and wear, control of capacity and built-in volume ratio, and liquid injection technology. In the aspect of thermodynamic modelling, the available methods, i.e., empirical or semi-empirical model, lump model, and 3D CFD model, adopted for the performance prediction and optimal design of screw machines are summarized. Then, the review covers the application status of screw machines in the fields of air compression and expansion, refrigeration and heat pump, organic Rankine cycle (ORC), and other popular applications, with an emphasis on the reported performance and progress in technologies of screw machines. Finally, conclusions and perspectives for future research in the area of screw machines are presented. The review provides readers with a good understanding of the research focus and progress in the field of screw machines.

Thermodynamic modelling of roasting of molybdenum sulphide concentrate with calcium hydroxide

This work aims to determine the conditions for the CaMoO4, CaSO4, Ca(ReO4)2 formation during oxidation of MoS2 and ReS2 in the presence of Ca(ОН)2. The concentrate from the Yuzhno-Shameyskoye deposit in the Sverdlovsk region, having 37% wt. Мо and 0.005% wt. Re, was selected as a feedstock for thermodynamic modelling of sweet roasting in the presence of Ca(OH)2. To determine the optimal amount of calcium-containing additives, the thermodynamic modelling was carried out using the following mass ratios: molybdenum concentrate: Ca(OH)2 = 1:0.8, 1:1, 1:1.2 and 1:1.5 in the temperature range of 100–800°С, with a step of 100°С, system pressure of 0.1 MPa in the air (molar ratio: molybdenum concentrate + Ca(OH)2: air = 1:5). The content of all sample components in moles was entered into the HSC 6.1 software package. The main reactions associated with the sweet roasting of molybdenum concentrate in the presence of calcium hydroxide were shown. It was established that the main phases formed as a result of roasting comprise CaSO4, CaSO3, MoO3, CaMoO4, CaMoO3 and CaReO4. The effect of temperature on the formation of the main gaseous products was studied under different mass ratios of molybdenum concentrate and Ca(OH)2. It was found that up to 600°C, with molybdenum concentrate to Ca(OH)2 ratio of 1:1, the concentrations of released sulphurous anhydride are lower than the maximum permissible concentrations. The calculated thermodynamic data was used for modelling the roasting process of molybdenum concentrate with calcium hydroxide. An optimal ratio necessary for the successful process operation was established: molybdenum concentrate: Ca(OH)2 = 1:1 by weight. Thermodynamic modelling showed that, in the temperature range of 100–600°С when using Ca(OH)2, no rhenium and molybdenum loss is observed, the release of sulfur is less than 10 mg/m3.

Genesis of the Eastern Adamello Plutons (Northern Italy): Inferences for the Alpine Geodynamics

The Corno Alto–Monte Ospedale magmatic complex crops out at the eastern border of the Adamello batholith, west of the South Giudicarie Fault (NE Italy). This complex includes tonalites, trondhjemites, granodiorites, granites and diorites exhibiting an unfoliated structure suggesting passive intrusion under extensional-to-transtensional conditions. Major, minor elements, REE and isotopic analyses and geochemical and thermodynamic modelling have been performed to reconstruct the genesis of this complex. Geochemical analyses unravel a marked heterogeneity with a lack of intermediate terms. Samples from different crust sections were considered as possible contaminants of a parental melt, with the European crust of the Serre basement delivering the best fit. The results of the thermodynamic modelling show that crustal melts were produced in the lower crust. Results of the geochemical modelling display how Corno Alto felsic rocks are not reproduced by fractional crystallization nor by partial melting alone: their compositions are intermediate between anatectic melts and melts produced by fractional crystallization. The tectonic scenario which favored the intrusion of this complex was characterized by extensional faults, active in the Southalpine domain during Eocene. This extensional scenario is related to the subduction of the Alpine Tethys in the Eastern Alps starting at Late Cretaceous time.

Thermodynamic modelling of carbonate-silicate rocks from the Sakar unit, Sakar-Strandzha zone, SE Bulgaria

The P-T evolution of carbonate-bearing metasedimentary rocks from the Sakar unit (Sakar-Strandzha Zone, SE Bulgaria) has been obtained using Perple_X modelling and conventional geothermometry. The metamorphic conditions vary from greenschist facies (250–350 °C/2–4 kbar) in the Klokotnitsa village area to amphibolite facies (550–650 °C/4.5–6.5 kbar) in the Topolovgrad town area, confirming a general increase of the metamorphic grade at east-west direction.