Coal-Fired Boiler Fault Prediction using Artificial Neural Networks

Boiler fault is a critical issue in a coal-fired power plant due to its high temperature and high pressure characteristics. The complexity of boiler design increases the difficulty of fault investigation in a quick moment to avoid long duration shut-down. In this paper, a boiler fault prediction model is proposed using artificial neural network. The key influential parameters analysis is carried out to identify its correlation with the performance of the boiler. The prediction model is developed to achieve the least misclassification rate and mean squared error. Artificial neural network is trained using a set of boiler operational parameters. Subsequenlty, the trained model is used to validate its prediction accuracy against actual fault value from a collected real plant data. With reference to the study and test results, two set of initial weights have been tested to verify the repeatability of the correct prediction. The results show that the artificial neural network implemented is able to provide an average of above 92% prediction rate of accuracy

Using affordable materials from metallurgical industries in Oxygen Carrier Aided Combustion and Chemical-Looping Combustion

Oxygen carriers are solid oxides of transition metals that can be used to convert fuel in the absence of gaseous oxygen in a process called Chemical-Looping Combustion (CLC). The use of oxygen carriers makes it possible to produce undiluted CO2 without expensive gas separation. High-concentration CO2 is a requirement in carbon capture and storage (CCS), which is considered a promising path for climate change mitigation. Oxygen carriers can also be used as bed material in fluidized bed conversion, and in that case provides enhanced oxygen distribution in the furnace. The concept is called Oxygen Carrier Aided Combustion (OCAC), and has been implemented in several existing biomass-, or municipal solid waste-fired boilers with ilmenite as oxygen carrier. This thesis examines utilizing oxygen carriers for the conversion of biomass and waste-derived fuels. Such fuels contain reactive ash species, which cause operational problems in the boiler such as corrosion, bed agglomeration, and slagging. Historically, much of the CLC-research has been on synthetic oxygen carriers with high reactivity. However, since the lifetime is expected to become quite low due to contamination of ash, they are likely not economically viable with these low-grade fuels. Here, the focus instead is on low-cost materials. The situation in Sweden is quite unique, since affordable metal oxide particles are produced in large quantities in our metallurgical industries. Several products and by-products from these industries are potential oxygen carriers. This thesis summarizes and discusses the large-scale utilization of oxygen carriers for OCAC in Sweden. Ilmenite is the most studied oxygen carrier for this purpose, but some other low-cost materials have also been tested in semi-industrial scale. The general findings are that implementing OCAC in already existing fluidized bed boilers is possible and enables a decrease in air-to-fuel ratio. Since biomass and waste fuels have complex and reactive ash compositions, they react with, and affect the lifetime of oxygen carriers. This thesis, therefore, also discusses ash interactions with some low-cost materials. Potassium is considered the most problematic ash element. Potassium is reactive with bed material and causes deposit formation and corrosion on the boiler, among other problems. Fixed bed interaction experiments have been conducted in this work with different potassium salts and oxygen carriers to study the changes in the materials with respect to composition and reactivity. Two by-products from steelmaking (LD-slag and iron mill scale) were studied in fixed bed interactions experiments. Also, as part of the work, a new lab-scale method which allows for improved experiments in a fluidized bed reactor has been developed. The method was used to study the effect of the accumulation of potassium on reactivity and fluidization of oxygen carriers. The study was conducted with ilmenite as oxygen carrier and K2CO3 as ash model compound. The addition of K2CO3 caused defluidization in ilmenite and diffusion of K into the particles

Steel converter slag as an oxygen carrier

Thermal conversion of fuels can be used to produce heat and power in addition to chemicals. In order to be aligned with climate targets, it is necessary that such systems do not emit carbon dioxide to the atmosphere. Carbon capture and storage (CCS) can be used together with fuel conversion systems to prevent CO2 from entering the atmosphere. If CCS is used together with biomass-based fuels, it is possible to achieve a net-flow of carbon dioxide out of the atmosphere, so called negative emissions.Chemical looping technologies for combustion (CLC) and gasification (CLG) are technologies which can be used for heat, power and chemical production with no or low penalties for carbon capture. In any chemical looping applications, a functional oxygen carrier is essential. The oxygen carrier is normally a metal oxide based material that can transport oxygen from one reactor to another. However, when fuel is introduced into the system, ash can react with the oxygen carrier and decrease its operational lifespan, especially reactive ash from biomass and low-grade fuels. Therefore, there is growing interest in low-cost oxygen carriers that can contribute to making the process economically feasible. Low-cost oxygen carriers can be obtained from ores or as byproducts of the steel industry. Of particular interest is steel converter slag, which is also known as Linz-Donawitz (LD) slag. LD slag is generated in significant amounts, contains sufficient amount of iron oxide (that can act as an oxygen carrier) and available at a low cost.This work presents a comprehensive overview of the chemistry and behavior of LD slag when it is implemented as an oxygen carrier in chemical-looping applications. The material has been investigated in laboratory reactors, in addition to pilot and semi-industrial units, and LD slags interactions with different fuel components, ash, alkali salts, sulfur and tars have been investigated.It is concluded from this work that LD slag can be viable as material for both CLC and CLG processes with biomass. In contrast to other bed materials, such as silica sand or the commonly investigated iron-based oxygen carrier ilmenite, the slag has limited reactivity with reactive alkali components. This results in more alkali being available in the gas phase, which is beneficial for tar cracking and for the gasification rate of the solid char. The high content of calcium in the LD slag is also favorable in terms of gasification and ash interactions. Calcium oxide catalyzes both the water-gas shift reaction and is catalytic towards tar cracking. A high level of calcium also increases the melting points of both the K-Ca-P and K-Ca-Si matrixes. However, the structural integrity of the material is lower compared to, for example, ilmenite, resulting in more fines being generated during the process. Overall, LD slag is a potential oxygen carrier that is suitable for chemical-looping processes that utilize low-grade fuels

Power generation using modular waste incineration power plant in developing countries

Standard of living rises and amount of waste generated increases in developing countries. Population and need for energy also grows, creating opportunities for exploit modular waste incineration power plants which are small incinerators and can be located near populated areas. The modular incineration power plant enables an appropriately sized incineration plant by combining incinerator units. Waste incinerated can regionally be collected and generated energy can be recycled back to same region. The object of the thesis is to study balancing of power generation of waste incineration plant and to find out the capital costs and operating and maintenance (O&M) costs of the plant. The aim is also to determine factors affecting balance between electricity generation and consumption in general. Pilot city of the project is Nairobi, the capital of Kenya, and the purpose is to create a model that can also be applied to other developing countries. The study is carried out based on the information from the pilot city and other related material. The literature review at the beginning of this thesis examines common incineration power plant techniques and more specifically the grate incineration technique and project implementation used in the project. The empirical study analyses factors affecting balance between electricity generation and consumption in Nairobi. Cost modelling is based on the Homer optimization program, which uses generation capacity of waste incineration power plants and adapts consumption to generation. As the results of the thesis were obtained methods used to control the production of the waste incineration power plant and a cost model for the capital costs of the study as well as operating and maintenance costs. The cost model is created based on other similar projects and is indicative and changes according to the project implementation. In addition, the result was a study factors contributing to the balance between electricity generation and consumption in Nairobi. The review covered existing energy generation in Kenya, demand side management methods and energy storage technologies.Kehitysmaiden elintaso nousee ja niin myös samalla syntyvän jätteen määräkin kasvaa. Väestö ja energian tarve kasvavat myös, mikä luo mahdollisuuksia hyödyntää modulaarisia jätteenpolttolaitoksia, jotka ovat pieniä polttolaitoksia ja voidaan sijoittaa lähelle asutusta. Modulaarinen polttolaitos mahdollistaa sopivan kokoisen polttolaitoksen yhdistämällä polttolaitosyksiköt. Poltettava jäte voidaan kerätä lähiympäristöstä ja tuotettu energia voidaan kierrättää takaisin samalle alueelle. Diplomityön tavoitteena on tutkia jätteenpolttolaitoksen sähköntuotannon tasapainottamista ja selvittää laitoksen pääomakustannukset sekä käyttö- ja ylläpitokustannukset. Tavoitteena on myös määrittää yleisesti sähkön tuotannon ja kulutuksen väliseen tasapainoon vaikuttavat tekijät. Projektin pilottikaupunki on Kenian pääkaupunki Nairobi, ja tarkoituksena on luoda malli, jota voidaan soveltaa myös muihin kehitysmaihin. Tutkimus toteutetaan pilottikaupungista saatujen tietojen ja muun siihen liittyvän aineiston perusteella. Työn alun kirjallisuuskatsauksessa tarkastellaan yleisiä polttolaitostekniikoita sekä tarkemmin projektissa käytettyä arinapolttotekniikkaa ja projektin toteutusta. Empiirisessä tutkimuksessa analysoidaan tekijöitä, jotka vaikuttavat sähköntuotannon ja kulutuksen väliseen tasapainoon Nairobissa. Kustannusten mallintaminen perustuu Homer optimointiohjelmaan, jossa energian tuotantokapasiteettina käytetään jätteenpolttolaitosten tuotantokapasiteettia ja kulutus sovitetaan tuotantoon. Työn tuloksina saatiin selvitys jätteenpolttolaitoksen tuotannon ohjauksessa käytettävistä menetelmistä sekä kustannusmalli tutkimusprojektin pääomakustannuksista sekä käyttö- ja ylläpitokustannuksista. Kustannusmalli on luotu muiden vastaavien projektien pohjalta ja se on suuntaa antava sekä muuttuu projektin toteutuksen mukaan. Lisäksi tuloksena saatiin selvitys Nairobin sähköntuotannon ja kulutuksen välistä tasapainoa edesauttavista tekijöistä. Tarkasteluun otettiin Kenian olemassa oleva energian tuotanto, kysynnän hallintamenetelmät sekä energian varastoiminen eri tekniikoin

Visualization Measurement of the Flame Temperature in a Power Station Using the Colorimetric Method

AbstractThis paper presents a study on the measurement of the temperature distribution in a power station based on an optical flame/temperature visualization system. This system operates upon the colorimetric principle combining advanced optical sensing and digital image processing techniques. The system was calibrated using a blackbody furnace as standard temperature source. Experimental results are obtained from a 300MW power station boiler. As the measurement height changed, the temperature captured by the system also changed. The maximum temperature occurs on the upper level of the burners. The temperature decreased when the load went down and tended to be stable when the load remained steady. Experimental results also reveal that this system is capable of online measurements of the temperature distribution in a combustion zone. This system can potentially be applied to many areas such as power generation, metallurgy or chemical engineering

Neural Network Based Control of Integrated Recycle Heat Exchanger Superheaters in Circulating Fluidized Bed Boilers

The focus of this thesis is the development and implementation of a neural network model predictive controller to be used for controlling the integrated recycle heat exchanger (Intrex) in a 300MW circulating fluidized bed (CFB) boiler. Discussion of the development of the controller will include data collection and preprocessing, controller design and controller tuning. The controller will be programmed directly into the plant distributed control system (DCS) and does not require the continuous use of any third party software. The intrexes serve as the loop seal in the CFB as well as intermediate and finishing superheaters. Heat is transferred to the steam in the intrex superheaters from the circulating ash which can vary in consistency, quantity and quality. Fuel composition can have a large impact on the ash quality and in turn, on intrex performance. Variations in MW load and airflow settings will also impact intrex performance due to their impact on the quantity of ash circulating in the CFB. Insufficient intrex heat transfer will result in low main steam temperature while excessive heat transfer will result in high superheat attemperator sprays and/or loss of unit efficiency. This controller will automatically adjust to optimize intrex ash flow to compensate for changes in the other ash properties by controlling intrex air flows. The controller will allow the operator to enter a target intrex steam temperature increase which will cause all of the intrex air flows to adjust simultaneously to achieve the target temperature. The result will be stable main steam temperature and in turn stable and reliable operation of the CFB

Analysis of Flue Gas Emission Data from Fluidized Bed Combustion Using Self-Organizing Maps

Efficient combustion of fuels with lower emissions levels has become a demanding task in modern power plants, and new tools are needed to diagnose their energy production. The goals of the study were to find dependencies between process variables and the concentrations of gaseous emission components and to create multivariate nonlinear models describing their formation in the process. First, a generic process model was created by using a self-organizing map, which was clustered with the k-means algorithm to create subsets representing the different states of the process. Characteristically, these process states may include high- and low- load situations and transition states where the load is increased or decreased. Then emission models were constructed for both the entire process and for the process state of high boiler load. The main conclusion is that the methodology used is able to reveal such phenomena that occur within the process states and that could otherwise be difficult to observe

Kustannusoptimoinnin menetelmät leijukerroskattiloille

In this Master of Science thesis, the operational cost structure and a method to optimize this structure are studied. The whole operational cost structure and different basis for optimization are presented. Optimization of the soot-blowing cycle was chosen as the studied method as it is a feasible target for optimization from technical point of view and it is linked to the cost structure in a straightforward manner. This thesis of focused on the most common form of fluidized bed boilers, circulating fluidized bed boilers, but the theory and studied method are for the most parts also applicable to bubbling fluidized bed boilers. Research targets of this thesis were to identify factors that form the operational cost structure of a circulating fluidized bed boiler, to identify the most critical Key Performance Indicators from cost point of view and to study the feasibility of soot-blowing optimization as a cost optimization method. This thesis is divided into theoretical and computational parts. In the theoretical part the techno-economic background of circulating fluidized bed boiler technology is introduced, including the operational cost structure of circulating fluidized bed boilers. Theory of Key Performance Indicators and state of the art references regarding soot-blowing optimization are presented in their own Sections. In the computational part the developed method for soot-blowing optimization is presented. This method was applied to six different power plants and the most cost optimal soot-blowing cycles for these power plants were calculated from history data based on the behavior of flue gas losses between soot-blowing cycles. The results clearly indicate, that power plant operators initiate soot-blowing cycles too often as in all inspected cases the calculated optimal cycles were longer than the cycles that were used on average. The calculated potential savings on a yearly level varied from 200 to 12 800 tons of fuel. These results clearly indicate, that soot-blowing optimization is a feasible cost optimization method in fluidized bed boilers

Dynamic model of circulating fluidized bed

Circulating fluidized beds (CFBs) are used in many processes in the chemical industry to reduce pollution and increase efficiency. Optimization and control of CFBs are very important and require an accurate, real time, dynamic model to describe and quantify the process.;The present work focuses on modeling the transient behavior of large CFB units, whose flow characteristics were shown to yield C-shaped voidage profiles using cork as the fluidized material and air at ambient conditions.;The riser is modeled in two ways: (1) as a set of well-mixed tanks connected in series; (2) as a 1-D axisymetric cluster flow. The tanks-in-series model visualizes the riser as consisting of a series of well-mixed vessels. Using this method, the dynamic response time at different locations along the riser was estimated successfully. The cluster flow model assumes that gas and solids flows are unidirectional with no mixing in the axial direction, and the solids move upward in the riser as clusters. This model can be used to predict the smooth changes in voidage profiles for transient processes. The influence of exit is also considered and a modified cluster model can be extended to the entire riser which includes an acceleration region, developed flow region and exit region. It can also be applied to a reacting system.;A model based on the Ergun equation is developed to predict the solids flow rate and voidage in the dense phase of the standpipe. The profile of solids flow rate under unsteady state is also presented. Using this method, the dynamic response time at different locations along the standpipe is estimated successfully.;Using the pressure balance analysis, the above models are combined into an integrated CFB model. It can be applied to CFB real-time simulation under transient conditions