Timo Korpela

Continuous Control Issues Concerning Operation Improvement of Small-Scale Biomass Boilers

Abstract To meet the increasing environmental and efficiency requirements, the possibilities to improve the performance of a 25 kWth wood pellet boiler by utilizing PLC and feedback control are investigated. The process is first stabilized by improving the grate sweeping sequence, which originally disturbs the process. Prior to continuous combustion control development, the process is analyzed and identified. After sequential control improvements the combustion behaves well but tends to drift. A PID controller was designed to enable drifting compensation. It is shown that improved grate sweeping sequence and continuous feedback control provide a major improvement for system performance cost effectively.

Online monitoring of flue gas emissions in power plants having multiple fuels

Abstract This paper introduces an online monitoring application for flue gas emission measurements. The monitoring is conducted by analytical redundancy by estimating the monitored measurement variables. The estimated variables are CO 2 , H 2 O, flue gas flow and combustion air flow. Additionally, SO 2 content in the flue gas can be estimated with certain limitations. The monitoring method is based on physical combustion modeling and is therefore boiler structure and fuel independent. The model is valid for multiple fuels as long as the fuel flow measurements, fuel properties and flue gas O 2 measurement are available. The estimates can further be improved by flue gas CO measurement. The monitoring method was successfully tested in an industrial wood, peat, bark and slurry fired power plant. The results verify that the method is able to automatically separate sensor faults and process disturbances.

Modelling of NOx Emissions in Natural Gas Fired Hot Water Boilers

Nitrogen oxides (NOx) are one of the main pollutants produced by combustion processes. New European emission regulations (IED) extent emission monitoring requirements to smaller boilers. Heating grid operators may have a notable number of such boilers and therefore appreciate affordable monitoring solutions. This paper studies several types of regression models for estimating NOx emissions in natural gas fired boilers. The objective is to predict the emissions utilising the existing process measurements for monitoring, without an external NOx analyser. The performance of linear regression is compared with three nonlinear methods: multilayer perceptron, support vector regression and fuzzy inference system. The focus is on generalisation ability. The results on the two boilers in the study suggest that linear regression and multilayer perceptron network outperform the others in predicting with new, unseen data.

EU Emission Trading Related CO2 Monitoring in Power Plants

Abstract European Commission has set new regulations for the third Emission Trading System period (2013-2020) that increased requirements for risk assessment, uncertainty estimation and continuous accuracy surveillance for CO 2 monitoring system. The objective of this paper is to describe and discuss three independent methods to determine CO 2 emissions in power plants that fulfill the new requirements. The presented methods are standard method, direct measurement method and energy balance method. The methods themselves, the required measurements and their properties are discussed. The methods are demonstrated in a 500 MW th pulverized coal fired CHP power plant and the results are discussed.

On-line data reconciliation as a tool to improve the environmental efficiency assessment in power plant environment

Abstract This paper introduces an on-line data reconciliation application that was implemented in Salmisaari coal fired CHP power plant in Helsinki, Finland. The objective of the work was to improve the reliability of measurements for operational and reporting purposes. The developed application calculates on-line reconciled estimates for the measurements which can be used to replace measurements most likely to produce incorrect results. However, quantitative estimates for the reliability of each measurement are required for this purpose. Thus, several parallel methods were developed for estimating the reliability from the process data dynamically. The preliminary results indicate the benefits of such an application.

Control Strategy for Small-Scale Wood Chip Combustion

Abstract The purpose is to control small-scale ( th ) wood chip combustion in an inexpensive and durable way. Therefore, a hierarchical control concept is presented. The main task of the fuel feed control system, which is based on temperature and lambda measurements, is to settle the fuel feed to air feeds and to compensate for the temporary fluctuations in the fuel feed. The task of the air flow control is to set the primary and secondary air flows suitable for the power level and for the fuel moisture content. Test results of a 200 kW commercial system are presented. The process experiments indicate that the high level control system is able to adapt to varying combustion conditions and to maintain low emission levels. The control concept is adaptable also to existing systems.