فصلنامه فن آوری صنعت آب و برق
سال یکم شماره 3 (1389)

Benzene, toluene and mixture of xylenes (BTX) are major constituents of oil pollutants in environment. These monoaromatic hydrocarbons are volatile, toxic and highly soluble in water. In this study, biodegradability of BTX compounds in synthetically contaminated water was investigated using OxiTop tests, based on the measurement of pressure drop as a result of oxygen consumption in a closed vessel where the carbon dioxide produced was trapped by caustic soda. Data highlighted that monoaromatic compounds were biodegradable by aerobic mixed culture biomass. When concentration of BTX was 60-80 mg/L, results showed the achieved maximum biodegradability was in ranges of 70-80 % (mg BTX /mg ThoD). Experimental works confirmed that the reason of this difference to 100 % solute degradation was connected to oxygen limitation in closed systems and monoaromatic adsorption by rubbers gaskets of OxiTop materials. This work allowed to suggest a versatile, efficient methodology to assess the activity of an aerobic biomass to metabolize volatile organic compounds.

In the current restructured Iran power market, the prediction of load, in different time scales, plays a critical role both in the reliability and optimized behavior of the power system. In spite of all performed researches in this area in the literature, there is still an essential need for more accurate and robust load forecasting methods in Iran electricity market which are based on systematic approaches for predictability analysis of load time series. In this paper, the data analysis and short term load forecasting in Iran electricity market has been considered. The proposed method is a modified singular spectral analysis (SSA) method. SSA decomposes a time series into its principal components i.e. its trend and oscillation components, which are then used for time series forecasting effectively. The employed data are the total required load time series of Iran electricity market in its real size and is long enough to make it possible to take properties such as non-stationarity and annual periodicity of market into account. The obtained results, discussed comprehensively, show that the method has a good ability in characterizing and prediction of the desired load time series.

This paper introduces the drum level and difference pressure control system of the Skoda unit of the Mashhad power station. Slowness of the drum level control system, mechanical trouble of the valves and non linear operation of the actuators of the valves explained. The importance of Priming and hammering phenomena's studied in the system. System transfer function was derived by means of Laplace Transformation method and n4sid algorithm. A new controller for the system that covers the troubles of the system suggested. The controller uses difference of steam flow and feed water flow instead of drum level for solving Priming and Hammering troubles. Two controllers were used to overcome the mechanical trouble of the valves. Pulses with complete amplitude used to solve the non linear operation of the valves and speed control of actuators are done with pulse width modulation. The applicability of controller was tested by means of PLC on the unit 1 Skoda of Mashhad power station.