The overall project objective is to make available generic coal information on Chinese and Indian coals with regard to their combustion and emission performance, and to establish correlations between basic properties and this performance. Such information is clearly of value to UK industry in view of the export possibilities in these regions.
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This document is a profile for the project titled 'Advanced Materials Modelling And Lifing Technologies For Gas Turbine Components Operating In Coal Gasification Plant'.
Over the next decade all major gas turbine manufacturers will, be aiming to achieve higher efficiencies and lower emissions from turbine technology regardless of the fuel type used. For coal-fired plant the challenges are not only to match the performance of natural gas fired turbines, but also to meet the technical challenge brought about by the use of aggressive fuel gas. By conducting a programme of work in three key technological areas - advanced materials, materials modelling and lifing methodologies - this programme aims:
To improve quantifiably the performance of industrial gas turbines operating in coal-fired power plant.
To provide spin off benefits to gas turbines operating with a wide range of other fuels including biomass, waste and natural gas.
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This document is a report that summarises the findings of the DTI Cleaner Coal Technology R and D Programme Project 217 'Application of CFD Modelling to Mill Classifier Design'.
In order to reduce the carbon in ash (CIA) levels arising from the application of advanced low NOX technologies, it is necessary to improve the quality and consistency of the coal milling process. In many low NOX retrofit applications, mill upgrades, including classifier upgrades, are required to achieve the improved milling performance. Unfortunately, plant space constraints often make it impossible to install classifiers of ideal geometries and the performance of non-ideal geometries is difficult to predict using existing design methods. In addition, low quality coals are increasingly being used, alone or in blends, to reduce plant operating costs. The grinding and classification behaviour of low quality coals and their blends has been found to differ from that of UK and world-traded bituminous coals. Consequently, classifier design rules that have been derived from the extensive experience of milling bituminous coals are less reliable when applied to low quality coals. There is a clear requirement to improve and extend the range of applicability of classifier design methods so that they may be used to design classifiers of non-ideal geometries and for coals outside the conventional range of experience.
This report is divided into the following sections:
Introduction
Classifier Design
Review of E Mill Classifier Process Data and Design Rules
It is generally accepted that improvements in coal particle size distribution are beneficial to carbon burnout, and considerable emphasis is placed on the optimisation and maintenance of coal pulverising equipment at utility power plant. The modelling of carbon burnout has been the subject of a number of recent and ongoing projects, some of which have received the financial support of the DTI, and significant technical advances have been made. However, there is an absence of available plant data to demonstrate the effect of coal particle size distribution on carbon in ash, which would allow the validation of this aspect of CFD and engineering models of burnout. This project seeks to address the shortfall.
The overall aim of the project is to establish good quality plant data to demonstrate the effect of changing coal fineness in a controlled way. Specific objectives are:
To obtain full scale plant data on the impact of coal particle size on carbon in dust and NOx formation
To obtain data on the impact of coal particle size and coal quality on carbon in dust and NOx formation by means of combustion trials on a 1 MWth single burner combustion test facility
To provide coal and flyash samples for detailed laboratory testing and analysis, to establish whether there are differences in the nature of the flyashes arising as a result of the extent of grinding
To analyse the data arising with the engineering model being developed under the auspices of the 'Improvement in Combustion Efficiency in Utility Boilers - DTI Project No. 139' and thereby to validate its ability to predict the effects of coal size distribution
To undertake CFD modelling of the plant tests to establish the validity of this modelling approach (building upon the work undertaken previously in the earlier DTI sponsored project)
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This document is a report for the project titled 'Carbon Burnout Project - Coal Fineness Effects'.
Carbon-in-ash presents an obvious cost to coal-fired generation plant in terms of lost fuel. High levels of carbon-in-ash can also inhibit the efficiency of electrostatic precipitators, which in turn can lead to increased particulate emissions, while the potential for selling fly-ash is dependent upon the level of carbon in the ash and excessive levels can result in additional disposal costs.
The aim of DTI project 226 has been to establish good quality plant and rig data to demonstrate the effect of changing coal fineness on carbon burnout in a controlled manner, which can then be used to support computational fluid dynamics (CFD) and
engineering models of the process. The project was designed to achieve this through:
Full-scale boiler trials.
1MWth combustion test facility (CTF) trials at Powergen's Power Technology Centre.
Laboratory tests of fuel and fly ash samples produced by the plant and rig trials, at Imperial College of Science, Technology and Medicine (ICSTM).
The full scale plant trials were successfully completed at Powergen's Kingsnorth Power Station, establishing plant data that demonstrates the effect of changing coal fineness on carbon burnout in a controlled manner. A full set of tests were also completed on Powergen's CTF, operating with four different fuel grind sizes. During these tests both carbon-in-ash and NOX levels were seen to increase with increasing fuel particle size.
This report is divided into the following sections:
This Briefing Paper focuses on the manufacturing and supply chain aspects of decarbonisation in the UK. Its recommendations contribute to an evolving discussion about the industrial and supply chain aspects of energy transition and implications for the UK.
This document is a report for the project titled 'Particle Impact Erosion and Abrasion Wear - Predictive Methods and Remedial Measures'.
The overall objectives of the project can be listed as follows;
To select a suite of test coals that is representative of the range of ash contents and ash qualities normally encountered in steam coals worldwide, and to subject these coals to a programme of basic characterisation work using both conventional laboratory techniques and Computer Controlled Scanning Electron Microscopic (CCSEM) techniques.
To measure the rate of abrasive wear of coal mill grinding elements associated with the milling of these coals, using the Mini-mill Test Facility operated by Mitsui Babcock in Renfrew.
To measure the rate of erosive wear associated with the impact of pulverised coal particles made from these coals on a carbon steel target, under controlled conditions, using the Erosion Test Rig operated by Mitsui Babcock in Renfrew.
To measure the relative erosion resistance of a range of target materials, including a number of specialist coatings.
To develop correlations between the abrasion and erosion characteristics of the test coals and the ash characteristics of the coals, measured using CCSEM techniques.
This project involved a detailed investigation of the abrasion and erosion characteristics of a suite of pulverised coals, selected to represent the full range of coal quality encountered by boiler plant designers and operators worldwide, and of the relative erosion resistance of a range of materials. The principal objective of the abrasion and erosion work was to develop improved correlations between the abrasion and erosion behaviour of the coals and their basic characteristics, as measured using CCSEM techniques. The CCSEM techniques are relatively novel, and generate quantitative information about the chemical and microstructural characteristics of the pulverised coals, which is not available by any other technique.
The abrasion and erosion testwork and the CCSEM characterisation of the test coals have been very successful, and very good correlations have been developed between the measured abrasion and erosion rates and the volume percent of hard mineral particles above a certain size in the pulverised coals. These correlations are suitable for predictive purposes, and the work has resulted in the development of laboratory procedures suitable for the assessment of the abrasion and erosion behaviour of unfamiliar coals. This represents a very significant step forward in our understanding of the abrasion and erosion behaviour of coal particles.
The project also involved the measurement of the relative erosion resistance of a range of materials and coatings, relevant to the materials of construction of the components of coal milling and combustion equipment and of boiler plant.
This report is divided into the following sections:
Introduction
The Selection and Characterisation of the Test Coals
The Abrasive Wear of the Grinding Elements of Vertical Spindle, Ball and Race, Coal Mills
The Erosion Behaviour of Coal and Ash Particles and the Erosion Resistance of Materials
The SEM and CCSEM Analysis of the Raw and Pulverised Coal Samples
Correlating the CCSEM Pulverised Coal Data with the Abrasion and Erosion Properties of the Coals
A number of the components of cleaner coal energy conversion plants are subject to damage by erosive and abrasive wear - particularly by coal or ash material. This is of concern to equipment suppliers who are required to provide commercial guarantees of the operating lifetimes of components, and to plant operators who need to plan maintenance schedules.
There is a requirement for reliable predictive methods for abrasive and erosive wear rates based on the characteristics of the coals being fired. Recent developments in the application of Computer Controlled Scanning Electron Microscopy (CCSEM) for the quantitative analysis of coals, coal minerals and ash materials provides a new means of obtaining the relevant data on the coal and ash characteristics. This project is intended to make use of these advanced coal characterisation techniques within a programme of experimental work to study the erosiveness and abrasivity of coals and ashes. It is intended that the programme will help:
To provide relevant experimental data on the relationships between the ash characteristics of coals and their abrasivity and erosiveness
To develop predictive methods which will allow the estimation of the abrasion and erosion properties of unfamiliar coals
To identify and test new materials, material combinations and coatings that can provide increased resistance to erosion and abrasion for boiler components
To develop design procedures and design features for coal-fired boiler plants which can minimise the impact of erosive and abrasive wear
In order to achieve the programme objectives a number of activities are planned including selecting and characterising a suite of coal and ash materials - including indigenous coals from India, Southern Africa and China, in addition to British coals and coals traded on the world market - using conventional techniques and advanced CCSEM analysis. The abrasion and erosion resistance of a range of materials will be studied. These will include materials employed for the manufacture of mill grinding elements, pf pipework, burner components and boiler tubes plus a number of specific erosion-resistant coatings.
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To investigate the performance of pulverised fuel meters to measure the relative mass flow rate in two parallel pneumatic conveyors.
To demonstrate, on a small-scale, control of the distribution (split) of pulverised coal between two parallel pneumatic conveyors, fed from a source via a bifurcator, using pulverised fuel meters to measure the mass flow rate The meters providing signals used to actuate a flow control device.
To improve the combustion efficiency of pulverised fuel (p.f.) fired furnaces in electrical power generation, it is desirable to measure, optimise and then, ideally, control the p.f. flow velocity and the solids distribution (split) between pneumatic conveyors leading to burners in the furnace.
On leaving the pulverising mill, the solids-air mixture is split into several different pipes each feeding an individual burner. One mill can feed as many as eight burners. Usually the fuel and air are metered before the mill where the ratio can be accurately set. Differences in routing of the lines injecting p.f. into the furnaces, and phase maldistribution at the splitting points, results in an uneven feed to the burners. Consequently, the combustion stoichiometry at the burners is disturbed. This leads to increased fuel costs, higher levels of carbon in the ash and excessive specific emissions in the flue gas. If the mass flow rate of the fuel can be measured, and the flow splitter controlled, then, in principle, the air-fuel ratio can be accurately set and the combustion stoichiometry optimised.
This experimental project has confirmed that the use of mass pf flowmeters combined with mechanical actuators can be used to control the solids split between two conveyors fed from a bifurcator. It is appreciated that this project was restricted to using 40mm diameter pipes and conditions in 375mm diameter pneumatic conveyors found on large boilers can be expected to be more challenging. However, as a first attempt, the exercise can be judged to have been very successful. Refinements to the flow test rig are planned so that the operation is aligned with industry practice.
This summary provides information on:
Objectives
Summary
Cost
Duration
Contractor
Collaborators
Test Section
ABB PF Meter
Control System
Conclusions
Future Work
Acknowledgements
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