A Pulverized Coal-Fired Boiler Optimized for Oxyfuel Combustion Technology

This paper presents the results of a study on modifying a pulverized coal-fired steam boiler in a 250 MWe power plant for oxygen combustion conditions. The entry point of the study is a boiler that was designed for standard air combustion. It has been proven that simply substituting air by oxygen as an oxidizer is not sufficient for maintaining a satisfactory operating mode, not even with flue gas recycling. Boiler design optimization aggregating modifications to the boiler’s dimensions, heating surfaces and recycled flue gas flow rate, and specification of a flue gas recycling extraction point is therefore necessary in order to achieve suitable conditions for oxygen combustion. Attention is given to reducing boiler leakage, to which external pre-combustion coal drying makes a major contribution. The optimization is carried out with regard to an overall power plant conception for which a decrease in efficiency due to CO2 separation is formulated

CONDENSATION OF WATER VAPOR IN A VERTICAL TUBE CONDENSER

This paper presents an analysis of heat transfer in the process of condensation of water vapor in a vertical shell-and-tube condenser. We analyze the use of the Nusselt model for calculating the condensation heat transfer coefficient (HTC) inside a vertical tube and the Kern, Bell-Delaware and Stream-flow analysis methods for calculating the shell-side HTC from tubes to cooling water. These methods are experimentally verified for a specific condenser of waste process vapor containing air. The operating conditions of the condenser may be different from the assumptions adopted in the basic Nusselt theory. Modifications to the Nusselt condensation model are theoretically analyzed

CONDENSATION OF WATER VAPOR IN A VERTICAL TUBE CONDENSER

This paper presents an analysis of heat transfer in the process of condensation of water vapor in a vertical shell-and-tube condenser. We analyze the use of the Nusselt model for calculating the condensation heat transfer coefficient (HTC) inside a vertical tube and the Kern, Bell-Delaware and Stream-flow analysis methods for calculating the shell-side HTC from tubes to cooling water. These methods are experimentally verified for a specific condenser of waste process vapor containing air. The operating conditions of the condenser may be different from the assumptions adopted in the basic Nusselt theory. Modifications to the Nusselt condensation model are theoretically analyzed.</p

RATIONALIZATION OF THE GEAR MACHINING OPERATIONS AT THE MQ200 TRANSMISSION IN ŠKODA AUTO a.s., MLADÁ BOLESLAV

katedra: KOM; přílohy: 2 výkresy, 2 tabulky, 1 CD ROM; rozsah: 60 s.This bachelor thesis focuses on rationalization of the 1st and 2nd gear machining operations at the MQ 200 transmission in Škoda Auto a.s., Mladá Boleslav. The objective is to propose new layout of productive machines and operators function for individual operations.Bakalářská práce se zabývá racionalizací operací obrábění kol 1. a 2. rychlostního stupně pro převodovku MQ 200 ve firmě Škoda Auto a.s., Mladá Boleslav. Cílem je navrhnout nové uspořádání strojů a obsazení členů obsluhy na jednotlivých operacích

Use of Cold Gas Dynamic Spraying of bi-metallic powder mixtures as alternative to classic powder metallurgy route for producing intermetallic materials

The paper presents cold gas dynamic spraying (or Cold Spray) as a novel surface treatment technology capable not only of surface modifications but also being used as bulk creating technology. This is demonstrated on numerous samples where bi-metallic powder feedstock is deposited into bulk, self-standing pieces of material that does not need the support of substrate. Mixtures from the group of Fe, Al, Ti, Ni, Cu were used for the initial bi-metallic mixtures. The deposited samples were then subjected to annealing at temperatures ranging from 300 to 1100°C in protective atmosphere and resulting morphologies and microstructures were analysed. Generally materials with high proportion of intermetallic phase content were obtained. These are discussed as potential scaffolds for metal or polymer matrix composites or as hi temperature resistive supports for catalysts with filter functions.

THE CONDENSATION OF WATER VAPOUR IN A MIXTURE CONTAINING A HIGH CONCENTRATION OF NON-CONDENSABLE GAS IN A VERTICAL TUBE

This paper deals with the condensation of water vapour possessing a content of noncondensable gas in vertical tubes. The condensation of pure steam on a vertical surface is introduced by the Nusselt condensation model. However, the condensation of water vapour in a mixture with non-condensable gas differs from pure vapour condensation and is a much more complex process. The differences for the condensation of water vapour in a mixture containing a high concentration were theoretically analysed and evaluated. In order to investigate these effects, an experimental stand was built. Experiments were carried out in regards to the case of pure steam condensation and the condensation of water vapour with a non-condensable gas mixture to evaluate the influence of the variable non-condensable gas content during the process. A non-condensable gas in a mixture with steam decreases the intensity of the condensation and the condensation heat transfer coefficient. A gradual reduction of the volume and partial pressure of steam in the mixture causes a decrease in the condensation temperature of steam, and the temperature difference between steam and cooling water. The increasing non-condensable gas concentration restrains the transportation of steam towards the tube wall and this has a significant effect on the decrease in the condensation rate

THE EFFECT OF THE FILLING RATIO ON THE OPERATING CHARACTERISTICS OF AN INDIRECT DRUM DRYER

This article investigates the effect of the filling ratio of the indirect rotary dryers on their operating characteristics. For moist biomass drying before combustion, the use of indirect drum dryers heated by a low pressure steam has proven to be highly suitable. Regarding the design of new dryers, it is necessary to experimentally verify the operating characteristics for specific materials and drying conditions. For this purpose, a set of experiments on a steam heated rotary drum dryer were carried out with green wood chips containing 60 to 66 wt% of moisture. The following operational characteristics of the dryer were experimentally determined: drying curves describing the process, square and volumetric evaporation capacities and drying heat consumptions. Based on the experimental results, the effect of various drum filling by dried material on the mentioned operating characteristics was analysed. On the one hand, higher drum filling ratio increases the drying time, on the other hand, the evaporation capacity also increases, while the specific energy consumption does not significantly alter. The maximum value of the evaporation capacity was reached when the drum was filled to 20 wt%. When the filling ratio was increased to 25 wt%, the evaporation capacity experienced almost no change

Improving the efficiency of a steam power plant cycle by integrating a rotary indirect dryer

This article deals with the integration of a rotary indirect dryer, heated by low pressure extraction steam, into the Rankine cycle. The article evaluates the power generation efficiency of a steam power plant, with an integrated indirect dryer, which combusts waste biomass with a high moisture content and is further compared to the same plant without the dryer. The benefits of the dryer’s integration are analysed in respect to various moisture contents of biomass before and after the drying. The evaluation of the power generation efficiency is based on parameters evaluated from experiments carried out on the steam-heated rotary indirect dryer, such as specific energy consumption and evaporation capacity. The dryer’s integration improves the efficiency of the cycle in comparison to a cycle without a dryer, where moist biomass is directly combusted. This improvement increases along with the difference between the moisture content before and after the drying. For the reference state, a fuel with a moisture content of 50% was dried to 20% and the efficiency rised by 4.38 %. When the fuel with a moisture content of 60% is dried to 10 %, the power generation efficiency increases by a further 10.1 %. However, the required dryer surface for drying the fuel with a moisture content of 60% to 10% is 1.9 times greater as compared to the reference state. The results of the work can be used both for the prediction of the power generation efficiency in a power plant with this type of dryer based on the moisture content in the fuel and the biomass indirect dryer design

Use of Cold Gas Dynamic Spraying of bi-metallic powder mixtures as alternative to classic powder metallurgy route for producing intermetallic materials

The paper presents cold gas dynamic spraying (or Cold Spray) as a novel surface treatment technology capable not only of surface modifications but also being used as bulk creating technology. This is demonstrated on numerous samples where bi-metallic powder feedstock is deposited into bulk, self-standing pieces of material that does not need the support of substrate. Mixtures from the group of Fe, Al, Ti, Ni, Cu were used for the initial bi-metallic mixtures. The deposited samples were then subjected to annealing at temperatures ranging from 300 to 1100°C in protective atmosphere and resulting morphologies and microstructures were analysed. Generally materials with high proportion of intermetallic phase content were obtained. These are discussed as potential scaffolds for metal or polymer matrix composites or as hi temperature resistive supports for catalysts with filter functions.

EVALUATION OF MOIST BIOMASS

Biomass as a fuel for the direct processing of energy is accessible in many forms of variable quality. Therefore, determining the price is problematic. This paper deals with the price determination of biomass depending on its moisture. Fuel moisture influences the amount of heat it is possible to gain from the combustion process, as well as the production costs of the heat. These factors are analyzed for variable fuel moisture. Evaluation of the biomass is carried out according to computed dependencies and the dependence of biomass price on its moisture is proposed