Piggery slurry - Aerobic treatment with heat recovery

The objectives of the study were to evaluate a mathematical model, derived from empirical data obtained from laboratory experiments, for the prediction of the characteristics of aerobically-treated piggery slurry in a large-scale reactor operating under practical conditions. This model was extrapolated for use in the prediction of extractable heat and heat losses from the process and written as a computer program "Farm Waste Management". Predicted heat values from this program were then compared with observed experimental data. The 23m3 reactor, insulated for heat conservation, was built together with a commercial piggery for fattening and weaning pigs. The reactor was fitted with an aerator and a water to water heat exchanger. Energy recovered from the reactor was measured and used in the weaner house. The slurry collected from the piggery varied in composition and the total solids concentration ranged from 25.2g/l to 101.8g/l. Several of the major analytical values were correlated to enable, in the future, the calculation of a whole complex of analyses from the results of a few relatively simple analyses within the range of total solids experienced. Aeration of slurry and operation of the treatment plant met with some technical difficulties in the early stages, but after four months the plant was commissioned and an experimental program initiated. The effects of treatment time, temperature and dissolved oxygen concentration on the quality of the treated slurry were determined and the characteristics of the treated slurries were compared with the predicted values from the model and computer program. Differences between the observed experimental results and the predicted values are discussed and possible explanations offered. Some changes in the model would improve the accuracy of the predictions although variations in some of the experimental data may be due to the inability to control operating conditions in the large scale reactor. Incomplete mixing in particular caused sedimentation, with resultant anoxic or anaerobic zones. The highest quality effluent slurry in terms of pollution potential was produced by treatment at mesophilic temperatures during which nitrification occurred. In general, the performance equalled or exceeded that predicted by the model except for the BOD5 of the supernatant effluent. Shorter treatment times and low dissolved oxygen concentrations prevented nitrification and the results of treatment were similar to those predicted except again for the BOD5 of the supernatant. Thermophilic treatments at 5

Preliminary design of the COMPASS upgrade tokamak

COMPASS Upgrade is a new medium size, high magnetic field tokamak (R = 0.9 m, Bt = 5 T, Ip = 2 MA) currently under design in the Czech Republic. It will provide unique capabilities for addressing some of the key challenges in plasma exhaust physics, advanced confinement modes and advanced plasma configurations as well as testing new plasma facing materials and liquid metal divertor concepts. This paper contains an overview of the preliminary engineering design of the main systems of the COMPASS Upgrade tokamak (vacuum vessel, central solenoid and poloidal field coils, toroidal field coils, support structure, cryostat, cryogenic system, power supply system and machine monitoring and protection system). The description of foreseen auxiliary plasma heating systems and plasma diagnostics is also provided as well as a summary of expected plasma performance and available plasma configurations

Recent progress in L-H transition studies at JET: Tritium, Helium, Hydrogen and Deuterium

We present an overview of results from a series of L-II transition experiments undertaken at JET since the installation of the ITER-like-wall (JET-ILW), with beryllium wall tiles and a tungsten divertor. Tritium, helium and deuterium plasmas have been investigated. Initial results in tritium show ohmic L-H transitions at low density and the power threshold for the L-H transition (P-LH) is lower in tritium plasmas than in deuterium ones at low densities, while we still lack contrasted data to provide a scaling at high densities. In helium plasmas there is a notable shift of the density at which the power threshold is minimum ((n) over bar (e,min)) to higher values relative to deuterium and hydrogen references. Above (n) over bar (e,min) (He) the L-H power threshold at high densities is similar for D and He plasmas. Transport modelling in slab geometry shows that in helium neoclassical transport competes with interchange-driven transport, unlike in hydrogen isotopes. Measurements of the radial electric field in deuterium plasmas show that E-r shear is not a good indicator of proximity to the L-H transition. Transport analysis of ion heat flux in deuterium plasmas show a non-linearity as density is decreased below (n) over bar (e,min). Lastly, a regression of the JET-ILW deuterium data is compared to the 2008 ITPA scaling law