For Steam Rankine Cycle (SRC), Organic Rankine Cycle (ORC) andSteam-Organic Rankine Cycle (S-ORC) power systems, in this paper, mathematical models are developed to explore the feasibility that combines the fluid-low temperature (150-350 C) waste heat steam and low-boiling point organic working fluids for power generation. Using the numerical models, we calculate and compare thermal efficiency, exergy efficiency, operation pressure, generating capacity, etc. of three power systems, namely SRC, ORC and S-ORC under the same heat source conditions. The results show that under the condition of 150-210 C heat source, ORC has the highest thermal efficiency, exergy efficiency and power generation; while at 210-350 C, the performance of the S-ORC has a distinct advantage. Its thermal efficiency and exergy efficiency are higher than those of the SRC and ORC power systems. HIGHLIGHTSSRC, ORC and S-ORC three kinds of power systems are computed and compared under the condition of the same heat source.  For low enthalpy heat, ORC is more efficient than SRC in recovering the latent heat of condensation of steam.  S-ORC power generation system has a better matching of heat source temperature. The ORC is optimal under the condition of 150 C to 210 C, while S-ORC has obvious advantages under the condition of 210 C to 350 C.

To improve the self-ignition capability of oil reservoirs and build a detailed reaction kinetics mechanism of in situ combustion (ISC), ignition and reaction characteristics of light fractions of crude oil (boiling point of <100 °C, 100–125 °C, 125–150 °C, 150–175 °C, 175–200 °C, and 200–225 °C) were investigated on a rapid compression machine at compressed pressures of 20 bar and a compressed temperature range of 660–900 K, with a stoichiometric ratio of 1.0. According to our analysis with a gas chromatography–mass spectrometry instrument (GC-MS), cyclohexane, methyl-cyclohexane, p-xylene, and mesitylene were selected as surrogate fuels and were tested under the same conditions on a rapid compression machine (RCM). The experimental results show that three groups of light fractions, <100 °C, 100–125 °C, and 175–200 °C, display strong reactions at low and high temperatures and negative temperature coefficient (NTC) behavior. These phenomena imply that these reactive components can be used as possible promoters to accelerate the development of an ISC project and to improve the reaction speed of the entire process. Two groups of 125–150 °C and 200–225 °C fractions are difficult to ignite in the low-to-medium temperature range under the compressed pressure of 20 bar, but they can be ignited at relatively higher top dead center (TDC) temperature ranges under the compressed pressure of 30 bar. Moreover, the logarithm of ignition delays and the reciprocal temperature clearly show a linear relationship, meaning that the reactivity of these two groups is poor. The results obtained with these surrogate fuels match well with the experimental results of each light fraction.

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Low pressure economizer is an important equipment to reduce exhaust gas temperature and recover waste heat of flue gas in power plants. In this paper, the welded plate heat exchanger is applied to the field of low pressure economizer. The waste heat of coal slag and flue gas is utilized comprehensively to raise the boiler feed water temperature and reduce coal consumption. The thermal economy of plate economizer and finned tube economizer is analyzed by the equivalent enthalpy drop method. The results show that the plate economizer has obvious advantages under the same pressure drop and heat load. Compared with the finned tube economizer, the heat transfer coefficient the of the plate economizer increases by more than 50%, and the volume decreases by about 2/3. After installing the slag cooler, the heat consumption rate decreases by 119.7 KJ/kWh, and the coal consumption decreases by 4.68 g/kWh.