External Boiler Research Articles

Comparison of control strategies for efficient thermal energy storage to decarbonize residential buildings in cold climates: A focus on solar and biomass sources

This work presents novel energy production/storage/usage systems to reduce energy use and environmental effects, in order to address concerns about excessive heating demand/emissions in buildings. This focus is the design, control, and comparison of a biomass-fired model with a novel heater type and a solar-driven system integrated with photovoltaic thermal (PVT) panels and a heat pump. The heater has an external boiler and shell and tube heat exchanger, providing enhanced control over the combustion process and increased efficiency. Another feature of the present work is establishing a rule-based automation framework to manage the energy storage/flow among the components/grid/building. This smart integration reduces the size of the components, eliminates the need for a battery, and allows the system to interact in both directions with the electricity grid. The practicality of both systems is assessed and compared via a code developed in TRNSYS-MATLAB, considering the specific conditions of Toronto, Canada, characterized by high heat demand in winter. According to the results, the proposed solar-based system has an acceptable energy cost (78.9 USD per MWh of heating and electricity) attributable to the developed controllers applied to thermal energy storage. The results show that the PVT-based system integrated with a heat pump is environmentally superior, with a reduction in CO2 emission of 7.2 tonnes over a year. However, the biomass-fired system is an excellent option from the aspect of efficiency, with a relatively high energy efficiency of 69 %. Also, it is observed that the night set-back of the supply temperature can reduce the annual primary energy use and emission up to 60.3 MWh and 21.1 t, respectively. While the system relies more on the heat pump in cold months, the solar energy system supplies the entire demand in summer, demonstrating the significance of PVT and heat pump integration to increase energy reliability throughout the year.

The Influence of Low-Temperature Restorative Heat Treatment on the Structure and Mechanical Properties of Boiler Drum Metal after Long-Term Operation

The drum metal properties of the BKZ-160-100FB and TP-85 boilers installed at the Irkutsk TETs-11 combined heat and power plant were investigated after these boilers had been in operation for 259 000 and 224 000 h, respectively, and after they had been subjected to low-temperature restorative heat treatment, which was carried out with steam produced by an external boiler after replacing all unions installed in the drum’s water volumes. “Plugs” made of grade 22K carbon steel and of grade 16GNM low-alloy steel cut from the drum shell rings were used as research subjects. The samples were subjected to metallographic analysis, tensile tests, impact bending test, and hardness measurement test. The results of tensile tests carried out at room temperature and at the metal operation temperature are presented. The results of drum metal U-notched specimens impact strength tests obtained at room temperature are given. Impact strength tests on V-notched specimens were carried out for samples after their metal had been subjected to low-temperature restorative heat treatment in the temperature range from –10 to +80°C. Based on the results of the V-notched specimens tests, the ductile constituent in the fractures was determined, and the drum metal ductile-to-brittle transition temperature was determined. The microstructure and mechanical properties that the drum metal had after having been in operation and having passed subsequent low-temperature restorative heat treatment were in compliance with the requirements of the relevant regulatory documents. After the boiler drum metal had been subjected to low-temperature restorative heat treatment, the studied steel samples showed a higher proof strength both at room temperature and at the operation temperature. Based on the data obtained from the investigations of boiler drum metal after it had been in operation and then subjected to low-temperature restorative heat treatment, technical diagnostics, and numerical strength analysis, it was recommended to extend the service life of the drums at their design (certificate) parameters.

Discussion of Wort Homogeneity

Constant wort boiling leads to a homogenous wort and is a major quality criterion during beer production. The topic of this article is the determination of wort boiling constancy, and of wort homogeneity, via measurement of dimethyl sulfide (DMS) residue curves. Three states of wort homogeneity are introduced and calculated procedurally in terms of the evaporation of DMS. As an example, evaporation of DMS from water is measured for a falling-film evaporator operating as an external boiler on a technical scale during defined trials. Measurement results are further compared with results of (pre-)calculated states of wort homogeneity. It can be stated that the postulated states were precalculated and simulated within the trials successfully. The current article thus conveys a tool enabling any practitioner to investigate and evaluate wort homogeneity of its particular brewery.

Validation of a Film Evaporator as a Wort Boiling System

The current article's topic is the use of a falling-film evaporator (down-draught vaporizer) as a boiler for flavor compound evaporation from wort. This particular proceeding is recommended because, with the lower temperature in a falling-film evaporator (here 62°C) dimethyl sulfide (DMS) evaporates at a higher volatility, and thus the process is less energy intensive than with the conventional boiling via internal or external boilers (100°C). The boiling process is calculated and validated by trials with both DMS in water and in wort in a pilot-scale plant. As a result, the use of a falling-film evaporator at lower temperatures (here 62°C) is interesting at high pump-around velocities.

REVISITING THE ICONIC: THE EXCAVATION OF THE REELFITZ PIT ENGINE AND THE NEWCOMEN STEAM ENGINE IN CUMBERLAND, UK

Examples of excavated 18th-century stationary steam engine sites are very rare in Britain. This article records the rescue excavations ahead of road-building works of one such site in 1974–5 at Reelfitz Pit in Little Clifton, Cumberland. The Reelfitz Pit pumping engine was built around 1780 and abandoned in 1781. The remains uncovered show that the site had two external boilers and a narrow engine house with a cylinder on the ground floor. The excavation uncovered three engine parts from within the engine house: the piston flange from the cylinder, the connecting link from the piston rod to the beam and one of the chain links which fitted into the piston head. The current work discusses the site in terms of the development of the West Cumberland coalfield and in the context of the surviving 18th-century Newcomen engines.

Low-temperature organic Rankine cycle engine with isothermal expansion for use in desalination

Groundwater salinity is a widespread problem that contributes to the freshwater deficit of humanity. Consequently, where conventional energy supply is also lacking, organic Rankine cycle (ORC) engines are being considered as a feasible option to harness readily available low-grade heat (<180°C) to drive the desalination of the saline water via reverse osmosis (RO). However, this application is still not very well developed, and has significantly high specific energy consumption (SEC). Hence, this study explores the isothermal expansion of the ORC working fluid to achieve improved efficiency for driving a batch-RO desalination process, “DesaLink”. Here, the working fluid is directly vaporized in the expansion cylinder which is heated externally by heat transfer fluid, thus obviating the need for a separate external boiler and high-pressure piping. Experimental investigations with R245fa have shown cycle efficiency of 8.8%. And it is predicted that the engine could drive DesaLink to produce 256 L of freshwater per 8 h per day, from 4000 ppm saline water, with a thermal and mechanical SEC of 2.5 and 0.36 kWh/m3, respectively, representing a significant improvement on previously reported or predicted SEC values.

A high-efficiency solar Rankine engine with isothermal expansion

Though the principle of the solar Rankine cycle is well known, with several examples reported in the literature, there is yet a scarcity of engines that could be efficiently applied in small-scale (<100 KW) applications. Hence, this paper presents a variant of the engine that uses an isothermal expansion to achieve a theoretical efficiency close to the Carnot limit. Generation of steam inside the power cylinder obviates the need for an external boiler. The device is suitable for slow-moving applications and is of particular interest for driving a batch-desalination process. Preliminary experiments have shown cycle efficiency of 16%, and a high work ratio of 0.997. ©The Author 2013. Published by Oxford University Press. All rights reserved.

Environmental Life Cycle Assessment of a Swedish Dissolving Pulp Mill Integrated Biorefinery

The pulp industry plays an important role in the structure of the European economy and society. The production of pulp has been traditionally considered an important source of pollution due to the use of large amounts of chemicals, fuels, and water and its intensive energy consumption. Currently, this situation is changing due to the potential use of biomass to produce value-added products, which minimizes environmental impacts and increases sustainability. This article uses life cycle assessment (LCA) to identify and quantify the environmental impacts associated with a Swedish softwood-based biorefinery where total chlorine-free (TCF) dissolving cellulose is produced together with ethanol and lignosulfonates. The system was defined according to a cradle-to-gate perspective—that is to say, from forest activities to the output of the biorefinery mill. According to the results, forest activities associated with the production of soft roundwood play a minor role in all the environmental impact categories under study. In contrast, the production of chemicals consumed in the cooking and bleaching stages, the sludge treatment generated in the wastewater treatment plant, and the on-site energy production system were identified as the elements that negatively contribute the most to all impact categories. The production of steam from biorefinery wastes, biogas, and methanol in external boilers reduces the environmental impact in all categories. Specific actions associated with the reuse of wastes and improved gas treatment systems would improve the environmental profile of this production activity.

Experimental observation of the droplet size change across a wet grid spacer in a 6 × 6 rod bundle

During the reflood phase of a postulated loss of coolant accident in a nuclear reactor, entrainment of liquid droplets can occur at a quench front of reflooding water. It is widely recognized that the behavior of the entrained droplets crucially affects the reflood heat transfer phenomena by decreasing the superheated steam temperature and interacting with a rod bundle and spacer grids. For this reason, various experimental and numerical studies have been performed to examine droplet behavior such as the droplet size, velocity and droplet fraction inside a rod array. In this study, an experiment on the droplet behavior inside a heated rod bundle has been performed. The experiment was focused on the change of droplet size induced by a spacer grid in a rod bundle geometry, which results in the change of the interfacial heat transfer between droplets and superheated steam. A 6 × 6 rod bundle test facility in Korea Atomic Energy Research Institute was used for the experiment. Steam was supplied by an external boiler into the bottom of the test channel, and a droplet injection nozzle was equipped instead of simulating a quench front of reflooding water. The major measuring parameters of the experiment were the droplet size and velocity, which were measured by a high-speed camera and a digital image processing technique. A series of experiments were conducted with various flow conditions of a steam injection velocity, heater temperature, droplet size, and droplet flow rate. The experiments provided the data on the change of the Sauter mean diameter of droplets after collision with a wet grid spacer depending on flow conditions.

Combined Cycles With CO2 Capture: Two Alternatives for System Integration

As carbon capture and storage technology has grown as a promising option to significantly reduce CO2 emissions, system integration and optimization claim an important and crucial role. This paper presents a comparative study of a gas turbine cycle with postcombustion CO2 separation using an amine-based absorption process with monoethanolamine. The study has been made for a triple pressure reheated 400 MWe natural gas-fuelled combined cycle with exhaust gas recirculation (EGR) to improve capture efficiency. Two different options for the energy supply to the solvent regeneration have been evaluated and compared concerning plant performance. In the first alternative heat is provided by steam extracted internally from the bottoming steam cycle, while in the second option an external biomass-fuelled boiler was utilized to generate the required heat. With this novel configuration the amount of CO2 captured can be even more than 100% if the exhaust gas from the biofuelled boiler is mixed and cleaned together with the main exhaust gas flow from the combined cycle. In order to make an unprejudiced comparison between the two alternatives, the reduced steam turbine efficiency has been taken into consideration and estimated, for the alternative with internal steam extraction. The cycles have been modeled in the commercial heat and mass balance program IPSEPRO™ using detailed component models. Utilizing EGR can double the CO2 content of the exhaust gases and reduce the energy need for the separation process by approximately 2% points. Using an external biomass-fuelled boiler as heat source for amine regeneration turns out to be an interesting option due to high CO2 capture effectiveness. However the electrical efficiency of the power plant is reduced compared with the option with internal steam extraction. Another drawback with the external boiler is the higher investment costs but nevertheless, it is flexibility due to the independency from the rest of the power generation system represents a major operational advantage.

Solid waste trial for coal-burning process

Battelle Columbus Laboratories is studying the combustion of municipal solid waste and sewage sludge in its multisolid fluidized-bed process developed for burning coal. If successful, low-pressure steam would be generated for municipal wastewater treatment facilities. In operation, wastes are burned with sand while the mixture is fluidized with air. After leaving the combustor, hot sand is separated and recirculated into an external boiler. There it dries the sludge and vaporizes water to produce steam.

Liquid Metal Breeder Reactor (LIMB) Nuclear Evaluation

The Liquid Metal Breeder (LIMB) reactor is an internally-cooled fluid fuel reactor based upon a Th232-U233 thermal breeder cycle. It employs a molten lead coolant, a uranium-bismuth solution fuel, a thorium bismuthide dispersion in lead-bismuth blanket fluid and a graphite moderator. Heat from the fuel is transferred through a graphite fuel element to the coolant which transports the heat to an external boiler and pump. This arrangement overcomes the major disadvantages found in previous “externally-cooled” liquid-metal-fuel reactors.Equilibrium concentrations of uranium isotopes heavier than U233 and other reasonable assumptions were derived from existing information and then used to develop a broad survey of LIMB reactor sizes. Two sizes, 200 and 1000 MW(th), were chosen for more detailed evaluation. The 200 MW(th) has a potential breeding ratio of 1.08 and an 8 year doubling time. The 1000 MW(th) reactor has a breeding ratio of 1.05 and a 12 year doubling time. Using the most pessimistic estimates on processing could reduce the breeding ratio, while improvements in design and the utilization of low-cross-section coolants can counteract these losses.LIMB reactor technology can lead to an efficient breeder, even in large power sources, and warrants further engineering evaluations.

The analysis of external deposits from boilers. part III. Methods in use at British coal utilisation research association for the analysis of the water‐soluble fraction of external boiler deposits

AbstractMethods in use at. B.C.U.R.A. for the analysis of the water‐soluble fraction of boiler deposits arc described. A method is given for the extraction of the water‐soluble fraction of an external boiler deposit. The scheme of analysis outlined separates the solution of the water‐soluble fraction into three parts for determinations of (1) acidity, (2) sulphate and alkalis and (3) silica, mixed oxides, lime and magnesia, methods for which are described.

The analysis of external deposits from boilers. part II. Method in use at british coal utilisation research association for the analysis of external boiler deposits rich in phosphates

AbstractThe methods in use at B.C.U.R.A. for the analysis of external boiler deposits rich in phosphates are described. A special procedure is recommended where the phosphate concentration (as P2O2) exceeds 6%, sulphates also being present. It is recommended that a known excess of ferric sulphate be added for the removal of phosphate to the solution prepared for the precipitation of mixed oxides. Methods for the determination of phosphate, sulphate and alkalis are also included.

The analysis of external deposits from boilers part I. General remarks on the nature of boiler deposits and their examination

AbstractA description is given of the nature of external boiler deposits and of the methods used for examination. Special considerations attach to the collection of deposits from boilers if a maximum of information regarding their formation is to be obtained. The analytical difficulties arising from the presence of such radicals and elements as sulphate, phosphate, arsenic and boron (which may interfere with the normal procedure) are discussed, and methods for avoiding these difficulties are suggested. A rapid method is given for the determination, us mixed sulphates, of sodium and potassium in the water soluble fraction of a deposit.