Boiler Fuels Research Articles

On the prospect of introduction of plasma ignition in power boilers

One of the most important issues for modern domestic power industry is the creation and further widespread introduction of solid propellant energy units for super-critical steam parameters with high efficiency (43–46%) and improved environmental parameters. This will significantly reduce the use of natural gas.At the same time, one of the major drawbacks of the operation of pulverized coal power units is the need to use a significant amount of fuel oil during start-up and shutdown of boilers to stabilize the burning of the coal torch in the variable boiler operating modes.In this regard, solid fuel TPPs need to be provided with fuel oil facilities, with all the associated problems to ensure the performance (heating of fuel oil in winter), reliability and safety. All of the above problems increase both the TPP capital construction costs, and the electricity generating cost.A practical solution to the above problems at present is the use of a plasma technology for coal torch ignition based on thermochemical preparation of fuel for combustion. The materials of the developments of JSC “NPO CKTI” on application of plasmatrons in boilers of thermal power plants at metallurgical complexes of the Russian Federation are also considered.Plasma ignition systems for solid fuels in boilers were developed by Russian specialists and were introduced at a number of coal-fi red power plants in the Russian Federation, Mongolia, North Korea, and Kazakhstan. Plasma ignition of solid fuels is widely used in China for almost 30% of power boilers.The introduction of plasma-energy technologies will improve the energy efficiency of domestic solid-fuel thermal power plants and can be widely implemented in the modernization of boilers.During the construction of new TPPs, the construction of fuel oil facilities can be abandoned altogether, which will reduce the capital costs of the construction of thermal power plants, reduce the construction footprint, and increase the TPP safety.

Analysis of Combustion of Coal-Water Fuel in Low-Power Hot-Water Boiler via Numerical Modeling and Experiments

The paper presents an experimental and computational study of various regimes of firing coal-water fuel in a low-power hot-water boiler that enable both dry and liquid slag removal. The experimental studies were carried out on a pilot industrial boiler adapted for firing coal-water fuel. The fuel was prepared using flotation products of beneficiation of K grade hard coal. The experiments were accompanied by numerical modeling of combustion processes. The mathematical model includes description of the carrier phase motion (based on the RANS approach with the two-parameter Menter SST k-ω turbulence model), radiation transfer (based on the P1 approximation of the spherical harmonics method for a two-phase two-temperature gray medium), particle motion (based on the Lagrange approach), and gas phase combustion (based on a combination of the kinetic model of combustion of gas components with the vortex break model). The physico-mathematical model was tested on the problem of combustion of coal-water fuel (CWF). One of the goals of the work was verification of a complex mathematical model. A comparative analysis of the results of the numerical modeling and experimental data showed that the model reliably described the process of burning in a combustion chamber. An advanced design of hot-water boiler enabling regimes of both dry and liquid slag removal was investigated. The chamber was shown to provide the necessary conditions for firing CWF in terms of reliability and economy.

Water-In-Oil Emulsion as Boiler Fuel for Reduced NOx Emissions and Improved Energy Saving

An experimental system for observing the drop vaporization and microexplosion characteristics of emulsified droplets in high-temperature environments was conducted to analyze the effects of environmental temperature, droplet size, and water content on droplet behavior. In addition, emulsified low-sulfur heavy fuel oil (HFO) with a 20 vol% water content and pure low-sulfur HFO were used as fuels for burning in an industrial boiler under normal operating conditions. The results showed that by using an emulsified HFO with a 20 vol% water content, the boiler efficiency can be improved by 2%, and that a reduction of 35 ppm in NOx emissions (corresponding to a NOx reduction rate of 18%) can be achieved. These advantages are due to the occurrence of a microexplosion during the combustion of the emulsified droplets. It was observed that when emulsified HFO with a 20 vol% water content was used, the fuel (HFO) consumption rate was 252 l/h. On the other hand, the fuel consumption rate was 271 l/h when pure low-sulfur HFO was used. Therefore, a reduction of 19 l/h in the fuel (HFO) consumption rate was achieved when using the water-in-oil emulsion, corresponding to fuel savings of 7%.

Heteroatom Removal as Pretreatment of Boiler Fuels

Heteroatom removal without the use of hydrogen was investigated for the pretreatment of heavy fuels to produce cleaner burning boiler fuels from petroleum residua and coal. This is relevant for app...

Изменения в ГОСТах на автомобильные и авиационные бензины, дизельные, судовые и котельные топлива

Изменения в ГОСТах на автомобильные и авиационные бензины, дизельные, судовые и котельные топлива

Modification of the Rheological Properties of Heavy Boiler Fuel by Adding Carbon Nanotubes and Dehydrated Carbonate Sludge

The possibilities of reducing the viscosity of heavy fuel oil with an increased proportion of residual fractions through the use of nanomaterials, such as carbon nanotubes (CNTs) and dehydrated carbonate sludge, have been investigated. The results of studying of rheological characteristics of fuel oil and composite fuel containing carbon nanotubes dispersed in an oil-soluble nonionic surfactant (M100 fuel oil + 0.0125 wt % CNT + 0.5 wt % Diproxamine) or dehydrated carbonate sludge (M100 fuel oil + 0.1 wt % carbonate sludge) are presented, as well as their heating value. The existence of a synergistic effect of the combined use of CNTs and carbonate sludge has been established. The possible mechanisms of change in the viscosity of the fuel are considered. It has been shown that carbon nanotubes together with dehydrated carbonate sludge can be most promising for use as heating oil additives, since they reduce fuel viscosity, improve combustion efficiency, and reduce the emission of hazardous gases.

Experimental Study on Online Measurement of Unburned Carbon in Pulverized Fuel Boilers by Thermal Oxidation of Ash

The unburned carbon (UC) in the ash in Indian power plants is presently measured offline by manually collecting the samples and analyzing it by loss on ignition or thermogravimetric analysis methods. The manual collection and offline analysis of samples take 6-8 h. By this time, the existing operating conditions of the boiler may be different from the conditions when the samples were collected. The combustion optimization and corrective maintenance activities can be performed immediately by plant operation and maintenance team if the UC values are available online along with furnace flame intensity and the percentage of CO in flue gases at economizer outlet. The presence of high amounts of the UC in ash decreases the boiler efficiency and reduces the utilization of ash in cement industries. In this paper, 20 ash samples were collected from five Indian thermal power plants of range 150-500 MW. An experimental setup has been developed for the measurement of the UC using the percentages of CO2 and CO obtained by thermal oxidation of ash. The experimental results were compared with the laboratory results. The maximum deviation between experimental and laboratory results was within the range of ± 0.30. The percentages of the UC is more accurate when CO2 and CO both are considered in comparison to the present existing online measurement based on CO2 only.

건물용 연료전지-보일러 복합설치 안전성능 평가에 관한 연구

건물용 연료전지-보일러 복합설치 안전성능 평가에 관한 연구

Methods and Materials of Nanotechnologies for Improving the Boiler Fuel Properties

It was shown that nanotechnology methods and materials can be used to create a composite fuel with improved performance characteristics. To reduce the viscosity of various types of hydrocarbon fuel, small amounts of nanoparticles can be added, leading to an additional structure formation, which may result in a change in the rheological properties due to the transition to layerwise shear flow. The possibilities of using carbon nanotubes and dehydrated carbonate sludge of water treatment were analyzed. The presence of a synergistic effect in the joint application of carbon nanotubes with carbonate sludge has been established. It has been shown that the choice of corresponding nanoparticles and their dispersion medium for a particular type of hydrocarbon fuel can significantly improve its performance characteristics.

Biogas upgrading and liquefaction in an anaerobic digester plant

Thanks to the high energy density and to the extended range it can ensure, LNG is an attractive energy vector especially in heavy-duty transportation. This fuel is even more interesting if produced starting from biogas because of the reduced carbon footprint. Biogas production occurs in anaerobic digestion plants and various production strategies can be pursued to transform biogas into bio-LNG. In this study the anaerobic digester of the municipal wastewater treatment plant of Viareggio has been analyzed. The plant is equipped with a Capstone C600s co-generative micro gas turbine and with a boiler for the sludge heating. Three different bio-LNG production strategies have been considered. In the first strategy (the baseline case), the biogas fueled boiler provides the heat necessary for the sludge heating. The electric energy required for wastewater treatment and for upgrading and liquefaction processes is bought from the electric grid. In the second strategy, the micro gas turbine is operated in thermal following mode and the electric energy required by the plant processes is partly self-produced and partly acquired from the grid. In the third strategy, the micro-turbine is operated in electric following mode, attempting to cover all the electric load necessary to the process and part of the heat necessary to the sludge heating. The plant was analyzed in steady-state conditions by considering the heat requested by the anaerobic digesters, the efficiency curves of the micro gas turbine and the boiler, and the heat exchangers off-design behavior. Results showed that, according to the economic reference scenario, the solution with the high profitability can be that with the boiler of that with the micro gas turbine operated in thermal following mode.

Torrefaction of densified mesocarp fibre and palm kernel shell

Abstract Mesocarp fibre and palm kernel shell (PKS) are widely used as fuels for boilers at palm oil mills to generate electricity. In the present study, the PKS and mesocarp fibre were densified under a controlled condition in prior to torrefaction process. Then, the briquettes were torrefied with various temperatures of 250–300 °C, residence time of 40 min and nitrogen flow rate of 1 l/min. In general, the torrefied mesocarp fibre briquettes were successfully produced regardless of torrefaction temperature, whereas the production of torrefied PKS briquettes was only feasible for torrefaction temperature of 250 °C, but the outer surface still remained brittle. The results show that an increase in torrefaction temperature causes a decrease in relaxed density and compressive strength of the torrefied mesocarp fibre briquettes. In terms of combustion properties, an increase in torrefaction temperature causes an increase in gross calorific value, fixed carbon content and ash content while volatile matter decreases. Besides, energy density of the torrefied mesocarp fibre briquettes does not change significantly with respect to the torrefaction temperature. Finally, the gross calorific value and moisture content were found to fulfill the requirements for commercialization as stated by international standards.

Adaptation of hard coal with high sinterability for solid fuel boilers in residential heating systems

Solid fuels boilers with low emission and modern construction, which are used for residential heating, require coal fuel with low sinterability (RI < 15). This paper presents a process for adapting coal with high sinterability for use in small boilers in residential heating systems. This solution allows for the combustion of coals with an RI of 50 without causing negative effects (in terms of combustion stability) in typical burners used in heating devices. The proposed solution involves the delivery of fuel particles coated with an oil film (waste oil and canola oil) to the combustion chamber. Tests were performed using a commercial-scale boiler with a 17–23 kW output, equipped with a retort burner and a dosing device, which applied oil to the coal in the boiler. Tests were performed during the combustion of hard coals characterized by different sinterability, with and without various streams of oils. Emission issues are also analysed. Impregnation of the coal by canola oil caused slightly lower NOx emissions, but higher CO and dust emissions. Analyses of the basic quality parameters (i.e., coal structure after thermal treatment) show that changes in the coal properties also occurred. Based on these studies, a mechanism that explains the beneficial effect of oil presence on high sinterable coal (HSC) combustion is proposed.

Prospects for development of hydrocarbon raw materials resources reproduction

The article presents data on the influence of factors in the field of innovative technology of thermocatalytic depolymerization of solid household wastes (SHW) on the efficiency and prospects for the development of technogenic hydrocarbon raw materials resource reproduction. Process thermodynamics, reactions kinetics, the mechanism of thermolysis of secondary polymers in organic solvents have been studied by means of laboratory experiments. It is shown that different morphological groups of wastes dissolve practically at the same rate at temperatures of 250-310°C. A homogeneous product is formed in the liquid phase; the spread of values for the elements lies in the interval of 1.5-4.5 %; technological requirements of the stages of formation of boiler fuels are satisfied. Using the principles of patent analysis, new techniques of processing household waste components are proposed. The basics of energy-efficient and energy-saving processes of technogenic hydrocarbon raw materials resource reproduction have been laid. The possibility of increasing the production payback and intensification is shown. Ecological and demographic safety for population and technical and economic benefits from SHW processing are achieved.

Study of flame combustion of off-design binary coal blends in steam boilers

Changes in the structure of the fuel consumption by the thermal power stations of Ukraine caused by failure in supplying anthracite from the Donets Basin are analyzed and the major tasks of maintaining the functioning of the coal industry are formulated. The possibility of using, in the near future, the flame combustion of off-design solid fuels in the power boilers of the thermal power plants and combined heat and power plants is studied. The article presents results of expert tests of the TPP-210A and TP-15 boilers under flame combustion of mixtures of anthracites, lean coal, and the coal from the RSA in various combinations. When combusting, such mixtures have higher values of the combustibles yield and the ash fusibility temperature. The existence of the synergetic effect in the flame combustion of binary coal blends with different degrees of metamorphism is discussed. A number of top-priority measures have been worked out that allow for switching over the boilers designed to be fired with anthracite to using blends of coals of different ranks. Zoned thermal analysis of the TP-15 boiler furnace was performed for numerical investigation of the temperature distribution between the furnace chamber zones and exploration of the possibility of the liquid slag disposal and the temperature conditions for realization of this process. A positive result was achieved by combusting anthracite culm (AC), the coal from the RSA, and their mixtures with lean coal within the entire range of the working loads of the boilers in question. The problems of normalization of the liquid slag flow were also successfully solved without closing the slag notch. The results obtained by balance experiments suggest that the characteristics of the flame combustion of a binary blend, i.e., the temperature conditions in the furnace, the support flame values, and the degree of the fuel burnout, are similar to the characteristics of the flame of the coal with a higher reactive capacity, which proves the existence of the synergetic effect in the processes of cocombustion of coals of various grades.

Mapping Urban Heat Demand with the Use of GIS-Based Tools

This article presents a bottom-up approach for calculation of the useful heat demand for space heating and hot water preparation using geo-referenced datasets for buildings at the city level. This geographic information system (GIS) based approach was applied in the case study for the city of Krakow, where on the one hand the district heat network is well developed, while on the other hand there are still substantial number of buildings burning solid fuels in individual boilers and stoves, causing air pollution. The calculated heat demand was aggregated in the grid with 100 m × 100 m spatial resolution to deliver the heat map depicting the current situation for 21 buildings types. The results show that the residential buildings, in particular one- and multi-family buildings, have the highest share in overall demand for heat. By combining the results with location of the district heat (DH) network, the potential areas in its close vicinity that have sufficient heat demand density for developing the net were pointed out. Future evolution in heat demand for space heating in one-family houses was evaluated with the use of deterministic method employing building stock model. The study lays a foundation for planning the development of the heating system at the city level.

The Characteristics of Oxycombustion of Liquid Fuel in a Typical Water-Tube Boiler

Among the various carbon capture technologies, oxyfuel combustion provides an effective way to reduce CO2 emissions, because of similar flame characteristics, relative to those of air combustion, and its ability to be retrofitted in the existing plants. In this work, combustion of liquid fuel in O2/CO2 environment inside a water-tube boiler has been modeled numerically, and the results were compared with that of the air combustion case. Two cases of oxycombustion were studied: (i) OF21 (21% oxygen (by volume) and 79% CO2 (by volume)) and (ii) OF29 (29% oxygen (by volume) and 71% CO2 (by volume)). The model was extended to study the effects of droplet size and swirl number on the combustion characteristics of the liquid fuel. Probability density function (PDF) was applied to solve the turbulence–chemistry interaction. It was found that the replacement of N2 from air with carbon dioxide significantly reduces the temperature level. It was also found that reducing the CO2 concentration results in an increase ...

Numerical Study of Co-firing Biomass with Lean Coal under Air–Fuel and Oxy-fuel Conditions in a Wall-Fired Utility Boiler

Co-firing biomass under oxy-fuel condition is one of the most attractive methods which is conducive to mitigating CO2 emissions by combining the advantages of these two respective technologies. The combustion characteristics of a wall-fired utility boiler operating in this mode have been seldom investigated. The burnout behavior of the blended fuel is still controversial. By using the newly proposed combustion mechanisms, a numerical study was carried out in a 600 MW wall-fired boiler to evaluate the influences of oxy-fuel working condition and biomass share on flow, temperature, O2 distributions, and burnout behavior in this combustion mode. Besides, the effect of biomass injection position was also explored, which has yet to be fully understood. The simulation results show that oxy-fuel working condition affected the combustion characteristics to some extent. The introduction of biomass led to a lower temperature but a better burnout within the furnace. O2 distribution was also correlated to the biomass...

3-4-1 木質バイオマスボイラ用燃料の地域供給システムにおけるベストミックス

3-4-1 木質バイオマスボイラ用燃料の地域供給システムにおけるベストミックス

DESIGN SOLUTIONS ON THE LOW TEMPERATURE CORROSION PROBLEM FOR HEATING SURFACES OF HEAT EXCHANGERS AT GAS TURBINE CHP

The article is devoted to the problem of low temperature corrosion of heating surfaces occurring in the non-heating season in heat exchangers of gas turbine cogeneration power plant when working on 150/70 heating system temperature chart. An overview is presented of the existing methods of eliminating such corrosion, including the analysis of their drawbacks. A new approach to ensuring the required temperature level of water in the heat exchangers is proposed. Based on the proposed approach, design solutions are developed and proposed aimed at eliminating the problem of low temperature corrosion of the heating surfaces during the non-heating season. The developed solutions are based on the arrangement of loop pre-heating of the network water where the reverse network water is heated to the minimum allowable temperature at the inlet to the gas-water heat exchanger (GWHE). Two options of thermal circuits with a closed circuit coolant circulation are proposed. The circuits differ in the method of heating the heating medium flowing in WTO: the first one operates by burning fuels in boilers, and the second one by using the heat of the exhaust gas entering the dedicated heating surface of GWHE. The advantage of the first option is the ability to disable the loop pre-heating at low outdoor temperatures when the temperature of the water at the inlet to GWHE exceeds the allowed minimum which reduces the annual cost of electricity for own needs. The advantage of the second option of the thermal circuit is a reduction in energy costs of the circulation pump operation by reducing the flow of coolant circulating in a closed circuit. The calculations of the proposed thermal schemes allowed to conclude that the proposed methods of closed loop pre-heating of the network water provide acceptable water temperature in GWHE with consideration of CHP operation modes throughout the year and help to prevent low-temperature corrosion of heat exchangers heating surfaces.

From Biogas to Boiler Fuel - Cleaning Up Digester Gas Biologically at a Large Scale

From Biogas to Boiler Fuel - Cleaning Up Digester Gas Biologically at a Large Scale