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

Monitoring the waste to energy plant using the latest AI methods and tools

Solid wastes for instance, municipal and industrial wastes present great environmental concerns and challenges all over the world. This has led to development of innovative waste-to-energy process technologies capable of handling different waste materials in a more sustainable and energy efficient manner. However, like in many other complex industrial process operations, waste-to-energy plants would require sophisticated process monitoring systems in order to realize very high overall plant efficiencies. Conventional data-driven statistical methods which include principal component analysis, partial least squares, multivariable linear regression and so forth, are normally applied in process monitoring. But recently, latest artificial intelligence (AI) methods in particular deep learning algorithms have demostrated remarkable performances in several important areas such as machine vision, natural language processing and pattern recognition. The new AI algorithms have gained increasing attention from the process industrial applications for instance in areas such as predictive product quality control and machine health monitoring. Moreover, the availability of big-data processing tools and cloud computing technologies further support the use of deep learning based algorithms for process monitoring. In this work, a process monitoring scheme based on the state-of-the-art artificial intelligence methods and cloud computing platforms is proposed for a waste-to-energy industrial use case. The monitoring scheme supports use of latest AI methods, laveraging big-data processing tools and taking advantage of available cloud computing platforms. Deep learning algorithms are able to describe non-linear, dynamic and high demensionality systems better than most conventional data-based process monitoring methods. Moreover, deep learning based methods are best suited for big-data analytics unlike traditional statistical machine learning methods which are less efficient. Furthermore, the proposed monitoring scheme emphasizes real-time process monitoring in addition to offline data analysis. To achieve this the monitoring scheme proposes use of big-data analytics software frameworks and tools such as Microsoft Azure stream analytics, Apache storm, Apache Spark, Hadoop and many others. The availability of open source in addition to proprietary cloud computing platforms, AI and big-data software tools, all support the realization of the proposed monitoring scheme

The GoBiGas Project - Demonstration of the Production of Biomethane from Biomass via Gasification

In the GoBiGas project, a first-of-its-kind industrial scale biorefinery was built for the purpose of demonstrating and enabling commercial production of biomethane from woody biomass via gasification. This report summarizes the experience, lessons learnt and conclusions from the feasibility study, construction and operation of the GoBiGas plant with the aim of supporting development of commercial production plants for advanced biofuels. The GoBiGas plant, with a production capacity of 20 MW of biomethane gas delivered to the natural gas grid in Sweden, is located in Gothenburg. The plant was built by G\uf6teborg Energi AB with the support of the Swedish Energy Agency and the project was initiated in 2005. This report includes a summary of the main contractors and technology choices made during the project and describes the commissioning of the plant in 2013. The report also describes experience gained from the operation and evaluation of the process until it was decommissioned in 2018. The evaluation of the plant focused on how the technology can be commercialized through construction of a similar stand-alone plant with a production capacity of 100 MW or more. With more than 12,000 hours of operation, the GoBiGas project has demonstrated how the quality of the product gas from a biomass gasifier can be controlled using a range of different feedstocks including bark, wood pellets, wood chips and recovered wood of class A1. Results show that a biomass to biomethane efficiency of up to 70% (based on the lower heating value of the dry ashfree fuel) is possible and that biomethane with a reduction factor for greenhouse gas emissions of over 80% can be produced with this technology. To reach such high efficiency, it is necessary to dry the feedstock and this also benefits the stability of the process. Results also show that gas quality fulfils the European standard for injection into the natural gas grid, thereby showing that large scale production of biomethane delivered by injection to the natural gas grid is possible. The project has demonstrated that this type of process can be applied on a commercial scale with high performance using known technology and that future development should involve improved compatibility between different process steps as well as improved economic feasibility of production. With the current process setup and using forest residues as feedstock, the production cost for a plant with a 200 MW production capacity, estimated based on the economic data from GoBiGas, corresponds to about SEK 600/MWh

Closing the Loop - Utilization of Secondary Resources by Low Temperature Thermal Gasification

This study addresses certain issues related to unsustainable management of secondary resources like organic waste, sewage sludge and residues from agriculture and industry with a focus on losses of nonfossil energy potential and valuable elements. In this context it is investigated how suitable application of low temperature thermal gasification could be applied to reduce the environmental impact of such management systems and increase the value and positive awareness of the resources in question.In the first part of this study, the Low Temperature Circulating Fluidized Bed (LT‐CFB gasifier) is described.The LT‐CFB gasifier is a technology originally developed for pre‐processing of biomass fuels like cereal straw. In popular terms, the LT‐CFB gasification process separates the inorganic and organic fractions of the straw. The majority of the inorganic material is extracted in one or several different ash fractions and the organic material is converted into a hot combustible gas product, which is subsequently combusted in an adjacent boiler. This substantially reduces the influence of the fuels inorganic composition on thecombustion properties. When combining LT‐CFB gasification with existing dust‐fired coal boilers, fossil fuels can be directly substituted with renewable fuels while reusing existing energy infrastructure. Currently, two operational LT‐CFB gasifiers exist: A pilot scale facility with a thermal capacity (TH) of 100 kW and a demonstration unit of 6 MWTH. Both units are involved in the present study. Many different fuels have previously been tested in LT‐CFB gasifiers and previous results from these experiments are described and evaluated with focus on the energy efficiency of the process and the quality of LT‐CFB ashes for use as fertilizers. The general benefits and drawbacks of low temperature gasification compared to anaerobic digestion and incineration are briefly discussed in this regard.Development and implementation of a method to screen for new fuel candidates for LT‐CFB gasification is conducted, and 22 new potential fuel candidates are characterized and compared to 4 previously proven LT‐CFB fuels. The investigated fuel candidates are categorized by their apparent suitability as LT‐CFB fuels and various positive characteristics as well as potentially problematic issues are discussed. The overall conclusion from the fuel screening is that in a Danish context it is highly relevant to consider low temperature gasification of especially sewage sludge and manure fibers while the international perspective includes especially sugarcane bagasse, various residues from olive oil production and rice husks. Only five fuel candidates are considered as potentially very problematic for single fuel LT‐CFB gasification: Fat separated from wastewater treatment, palm kernel shell residues, two animal meat and bone meal samples and wood pruning from Italian vineyards. The problems mainly relate to the proximate composition, ash sintering, char deposit formation and corrosion of steel surfaces during thermal tests. The fuel screening also includes a screening of P fertilizer quality of ashes and chars produced from thermal treatment of the different fuels, and significant differences were identified between the P fertilizer quality of ashes and chars. The fuel screening also involves an investigation of how analytically determined characteristics of three fuel mixes differ from the expected linear sum of the involved fuels’ individual characteristics. The results indicate profound possibilities for optimizing fuel and ash characteristics by fuel mixing with regard to ash deposit formation and sintering as well as ash and char P fertilizer quality.Of the 5 best candidates identified in the fuel screening, sewage sludge is found to be one of the most interesting as it is a locally as well as globally available resource with a large potential for optimized management compared to several of the currently applied management options. Proper management of sewage sludge holds a substantial potential for recovery of highly concentrated phosphorus (P) with good plant availability in ashes and chars from the thermal conversion. It is therefore decided to progress with sewage sludge in a series of experimental campaigns to provide a detailed investigation of potential benefits and problematic issues related to sewage sludge management by LT‐CFB gasification. Four experimental campaigns with gasification and co‐gasification of sewage sludge in LT‐CFB gasifiers are conducted and the results on process performance and the quality of the gas product are compared to results from other studies on thermal gasification of sludge. The overall conclusion is that many different gasifier designs have been proven successfully on sewage sludge fuels and LT‐CFB gasification is very well suited for gasification of sewage sludge as well as co‐gasification of sewage sludge and cereal straw. The LTCFB gasifier is found to yield the highest hot gas efficiency, carbon conversion rate and total system electrical efficiency of the assessed systems.Examination of the fertilizer quality of ash substrates from thermal conversion of sewage sludge is a central part of this study. Fertilizer quality is addressed by comparing the elemental composition, PAH content and P plant availability of LT‐CFB ashes from different gasification and co‐gasification campaigns to ash and char samples from incineration and pyrolysis of sewage sludge as well as to their respective untreated sludge samples and a mineral P reference. In addition to the conventional thermal platforms, a process for postoxidation of pyrolysis chars and gasification ashes has been developed and the oxidized substrates are also included in the investigation. From the investigation of ash fertilizer quality it is concluded that all of the investigated thermal platforms are applicable for production of P fertilizers by conversion of sewage sludge with the proper design and operational settings. Post‐oxidation of pyrolysis chars and gasification ashes is found to have a remarkable effect on P fertilizer quality while co‐gasification of sludge and straw in LT‐CFB gasifiers in general seem to provide a better ash fertilizer than mono‐sludge gasification. Assessment of the influence of the thermal process on the fertilizer quality of the ashes is studied with chemical sequential extraction and scanning electron microscopy to identify changes in P association induced by different thermal treatments. Changes in P fertilizer quality as function of incubation time and as function of changes in the particle size distribution of the ash substrate is also discussed.In the last part of the study, the results from the previous chapters are combined in an assessment of the possibilities to produce controlled release fertilizers and context‐specific designer fertilizers in systems encompassing thermal conversion of secondary resources. A discussion about burden shifting in such management systems is also introduced and results are analyzed from two life cycle assessment case studies comparing sewage sludge gasification in centralized LT‐CFB gasifiers with the current practice of direct application of sludge on farm soil. The results indicate a substantial improvement of the LT‐CFB scenario compared to the reference case with regard to a reduced impact on climate change and reduced toxicity of the P fertilizer.Based on this work it is concluded that there is a profound potential for optimizing the management of sewage sludge – and most likely also many other secondary resources, by applying the proper thermal processes. With a good match between fuel characteristics, process design and end use of the produce dash and gas products, such a system can be setup to encompass full utilization of the energy potential in the resource and simultaneously produce high quality fertilizers. LT‐CFB gasification is in many respects a very promising platform for this purpose combining flexibility in fuels and products and high energy efficiency. Co‐gasification of sewage sludge and cereal straw is found to produce very high quality thermally purified P fertilizers, and the potential benefits of fuel mixing needs to be further examined

Modern approaches to control of a multiple hearth furnace in kaolin production

The aim of this thesis is to improve the overall efficiency of the multiple hearth furnace (MHF) in kaolin calcination by developing control strategies which incorporate machine learning based soft sensors to estimate mineralogy related constraints in the control strategy. The objective of the control strategy is to maximize the capacity of the furnace and minimize energy consumption while maintaining the product quality of the calcined kaolin. First, the description of the process of interest is given, highlighting the control strategy currently implemented at the calciner studied in this work. Next, the state of the art on control of calcination furnaces is presented and discussed. Then, the description of the mechanistic model of the MHF, which plays a key role in the testing environment, is provided and an analysis of the MHF dynamic behavior based on the industrial and simulated data is presented. The design of the mineralogy-driven control strategy for the multiple hearth furnace and its implementation in the simulation environment are also outlined. The analysis of the results is then presented. Furthermore, the extensive sampling campaign for testing the soft sensors and the control strategy logic of the industrial MHF is reported, and the results are analyzed and discussed. Finally, an introduction to Model Predictive Control (MPC) is presented, the design of the Linear MPC framework for the MHF in kaolin calcination is described and discussed, and future research is outlined

Energy from municipal solid waste in Chennai, India : a feasibility study

Solid waste management is one of the most essential functions in a country to achieve a sustainable development. In India, it has been one of the least prioritized functions during the last decades. The most common ways to treat waste in India today are open dumping and uncontrolled burning. These methods are causing severe environmental pollution and health problems. India is one of the world’s largest emitter of methane gas from waste disposal. Since methane is a strong greenhouse gas, even small emissions have large impact on the climate. Improper treatment of waste will also affect peoples’ health, first of all by the spreading of toxic compounds from uncontrolled burning and secondly by leakage of sewage from the dumping grounds into the groundwater. When waste is incinerated in an incineration plant there are many environmental benefits. First of all, the possibility of using flue gas treatment prevents emissions of toxic compounds to emit to the air compared to if waste is burnt uncontrolled. Secondly, the amount of waste going to the dumpsite will decrease, resulting in a reduction of methane formation and less leakage of sewage from the dumpsite to the groundwater. Chennai is the fourth largest city in India with a population of 4.3 million (2001 census). It is the Corporation of Chennai, CoC, which has the overall responsibility for solid waste management in the city. With street sweepers, tricycles and compactors they collect and transport the waste to one of the two dumpsites in the city; Perungudi in the north or Kodungaiyur in the south. Like most municipalities in India, CoC has experienced difficulties keeping in pace with last decades’ industrialization, resulting in insufficient collection of municipal solid waste and over burdened dumpsites. Another consequence of the rapid industrialization is the increased demand for electricity. Today there is not enough installed capacity of power stations in Chennai to meet this demand, leading to daily power cuts. If the waste on the two dumpsites will be left untreated, the dumpsites are only expected to be useful until the year 2015. To prolong the lifespan of the dumpsites CoC has signed a contract with the company Hydroair Tectonics, who shall minimize the waste on Perungudi. There is a chance that there will be a similar contract on Kodungaiyur as well. This company will build a processing plant that will segregate the waste into recyclable, inert, organic and burnable material. The inert and organic waste will be processed further into bricks and compost, which will be sold on the open market. The burnable material will be processed into a fluffy fraction called RDF-fluff. In the initial stage the RDF-fluff will be sold to coal-fired industries as "green coal". In the future Hydroair Tectonics plans to build a combustion unit for burning RDF and generate electricity, which will be sold to the grid. This report will give an overview of the current waste and electricity situation in Chennai and analyze whether Hydroair Tectonics should build this combustion unit or if they should sell the generated RDF to industries. The result will be presented in a case study