Advanced Materials Research Vols. 960-961

Abstract: This paper studies the problem of optimal operation of 300MW boiler. We combine the actual situation of the device and the theory of heat together, and improve the operating efficiency of the boiler through adjustment of device parameters, thus improving the economic benefit of thermal power plants. Firstly, according to coal characteristics and the theory of heat, we establish an improved utility model to calculate the heat loss of exhaust - gas, chemical incomplete combustion heat loss and heat loss of mechanical incomplete combusting. Then, we use fitting and interpolation, which is always applied to problems of Discrete Mathematical Statistics, to analyze discrete form of experiment data record, and give the relationship between 300MW boiler efficiency and excess air coefficient, which leads us to a new way to ascertain optimal excess air coefficient. And then, we use Principal Components Analysis (PCA) and Correlative Analysis (CA) to study the affection of operation parameters on boiler efficiency. Finally, we combine local optimization with global optimization, and establish an optimal operational model.

Abstract: Based on the waste heat characteristics of the coolant and exhaust gas from diesel engine, the Organic Rankine Cycle (ORC) commercial plant had been developed. The working fluid was the R245fa, and the plate type heat exchangers were used as the condenser and evaporator in the ORC systems. The performance of condenser and evaporator had been simulated and developed using the effective-NTU method. Using the engine jacket coolant as the heating media, the coolant absorbs the waste heat from the exhaust gas and engine cylinders. The ORC system and engine can stably run for a long time without frequent control acting. The ORC systems can bring the 14.6 kw electric energy in the stable condition. The efficiency based on the first law of thermodynamics is 7.2%; complete generating efficiency is 6.25%.

Abstract: In order to enhance the economy of steam assisted gravity drainage (SAGD) technology, researches were conducted on the technology for recovering heat from liquid produced from oil wells. In this study, spiral-plate heat exchanger has been chosen after comparison and analysis, which is used to recover the heat from the produced liquid and raise the temperature of the softened water used in steam injection boilers. The procedures are liquid produced from the wellhead enters a metering and transfer station for degasification and then enters a centralized heat exchanger station where its temperature is reduced to 100°C from 170°C and the temperature of softened water used as boiler feed water is increased to 110°C from 70°C. The result shows that the fuel gas consumption will drop by 907200Nm³ for each boiler annually when the liquid heat recovery technology is adopted.

Abstract: At present, there are lots of calculation methods of acid dew point of flue gas; formula of acid dew point in the thermal calculation from the former U.S.S.R has been widely applied in China. But this formula still has some problems, such as the desulphurization ability of different fuels, classification of sulfur content in fuel and the factors of SO2 transferred into SO3.In order to solve these problems,the formula of the acid dew point in the thermal calculation from the former U.S.S.R is adjusted. It was found that the precision of A.G.O kkes formula is the highest by comparing several formulas. So the last will be the compilation of the new formula and A.G.O kkes formula, the former Soviet union formula and the calculation of burning lean coal,bituminous coal and lignite typical instance of 600 MW,it was found that the precision of new formula calculation has improved.

Abstract: As a clean, renewable energy, rational use of biomss can effectively solve the problem of energy shortage and environmental pollution. Co-combustion and Co-gasification of biomass and coal are important ways of biomass utilization. Co-pyrolysis reaction is one of the most important processes in the co-combustion and co-gasification. In order to study the different mix ways of coal and wood chips affections on the co-pyrolysis process, TGA was used to study the co-pyrolysis characters of wood chips and coal mixed by different methods with mass ratio 1:1. it is founded out that there is certain interaction between wood chips and coal by the comparison of TGA curves and calculation curves. There is promoting affection at the high temperature if wood chips and coal had been mixed up. There is inhibiting affection if wood chips and coal are tiering distributed.

Abstract: Thin film evaporation is a kind of high efficiency heat transfer. A thin film evaporator with rectangular micro groove has been designed, constructed and tested. The heat flux, superheat and thermal resistance of the thin film evaporator were investigated under different evaporating temperatures. Compared with the regular evaporator at the same condition, the thin film evaporator with rectangular micro groove has a better heat transfer performance and good temperature uniformity. The experimental investigation presented in this paper can be used as a reference to promote the engineering application and development of the thin film evaporator.

Abstract: The submerged combustion vaporizer (SCV) is a new kind of vaporizer for liquefied natural gas (LNG). In this paper, a numerical study has been carried out to investigate the heat transfer characteristics of supercritical LNG in horizontal tubes. The thermo-physical properties of supercritical LNG were used for this study, and the influence of inlet LNG mass flow rate on heat transfer was investigated. Numerical results showed that the LNG flow in horizontal tubes included two stages. In the first stage, the surface heat transfer coefficients increased significantly with the increase of the fluid bulk temperature and reached a maximum value when the fluid bulk temperature equaled the pseudo-critical point . After the maximum, the surface heat transfer coefficients fell rapidly with the increase of the fluid bulk temperature. With increasing the inlet LNG mass flow rate, the surface heat transfer coefficients increased due to the increased fluid velocity in horizontal tubes.

Abstract: The submerged combustion vaporizer (SCV) is a kind of equipment used for liquefied natural gas (LNG) vaporization. In order to get insights into the heat transfer of supercritical LNG, numerical simulations were carried out in this paper for investigating heat transfer of LNG in horizontal circular tubes under supercritical pressure. Numerical results showed that LNG temperature at the outlet under the design parameters was 276 K which met the demands of application. The velocity of LNG at the outlet was 12 m/s, and the pressure drop along the ducts was 120 kPa.

Abstract: Wood-based materials from Municipal Solid Waste have the potential of covering a significant part of the future demand on gasification capacities. However, their pyrolysis kinetics and gasification behavior has not yet been fully investigated. This paper describes the pyrolysis characteristics of typing paper and Chinese parasol from municipal solid waste applying the non-isothermal thermogravimetric analysis, the apparent activation energy and the pre-exponential factor were obtained by kinetics analysis at the heating rate of 10/20/40 ^oC•min^-1.

Abstract: Power plant will be threatened in the blackout, a tiny carelessness could result in serious damage to the equipment. FCB (FastCutBack) refers to the function that during the normal operation, because of the internal fault or external fault the unit take the moment to get rid of all external power supply instantaneously, and keep the boiler continue running at the lowest load to supply the auxiliary power. In this paper, the new designed FCB control strategy has been applied in a 350MW subcritical coal-fired unit. Through some control logic optimization and debugging, the viable control parameters is obtained, the result of unit FCB function test is excellent and the safety of unit are effectively improved.