ENK6-2001-00542 Intelligent Process Control System for Biomass Fuelled industrial Power Plants - INTCON

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EESD (Energy, Environment and Sustainable Development) : Electricity : Thermochemical Conversion

Proposal No:	ENK6-2001-00542
Date Prepared:	February 2004
Source:	European Bio-Energy Projects (EUR 20808)

Introduction

Biofuels, both from forest/farmland and from recycling, are in general very inhomogeneous with large, timely variations in moisture content, size distribution, ash content and ash properties. Changes in fuel properties have to be met in a correct way in order to maintain a good economical process.

There is a general trend to increase the emission constrains from combustion plants. Those firing recycled biofuels, like demolitions, would have to comply with the waste combustion directive. All these demands call for the development of a qualified system for controlling the operation of a plant. The system is very complex and includes a multileveled structure including combustion and emission control, minimising mainte-nance and handling overall power and heat demands.

Activities

A general control system suitable for all types of boilers is complex and extensive. As a first step, the objective of the present project is to develop a control system for a grate-fired boiler where the use of inhomogeneous fuel is common, where the aerodynamic problems are the greatest and where the methods for control is the least developed. Alterations for pulverised fuel (PF) and fluidised bed (FB) boilers will be evaluated and the final results will include defined control strategies for these types.

To make INTCON flexible it has a modular structure where certain modules are highly specialised for a particular application, whereas others are of a general nature. The overall structure for the chosen application is presented in the figure below.

The Management Module (MM), where a linguistic fuzzy tool is combined with a knowledge base containing information on the boiler system, will advise on the specific control modules for an optimised and cost effective operation. The learning capability will make the module available for future adaptation to new situations.

A Real-Time Data Base (RTDB) is used for the storage of data, both from the process and from that calculated in the control system. There are several routines for data treatment in the RTDB, and the RTDB and MM modules are general to all INTCON systems.

There is an Overall Boiler Control Module (OBCM), essentially a shell for control modules for the different tasks that have to be performed in the boiler. In this project two general control modules have been developed; a combustion controller (CCM) and a slagging and fouling controller (SFM). There is also a predictive emissions monitoring module (PEMM).

For this application the CCM is divided into two sub-modules, one controlling the grate combustion (CCM:G) and the other the freeboard combustion (CCM:F). This approach simplifies the application of INTCON to other boilers as the primary zone will change but several of the control routines for the freeboard will be the same. The combustion controllers will use the PEMM to find optimal conditions for a reduction of emissions.

The SFM will use selected inputs for predicting and minimising formation of ash deposits in the boiler. To make the INTCON advisory system easily acceptable for the operators, special attention has been given to the development of an attractive human-machine interface (HMI). The system operator can either have full control of the plant or just specific functions.

Progress

The basic layout of most of the modules is ready. By using identification methods process models are developed for both of the combustion controllers. IR-detectors are used to monitor the bed temperature on the grate. The testing and implementation on the target boiler of some of the modules have been initiated during the spring of 2003 and the complete INTCON system will be assembled and testing will commence next heating season.

Impact and exploitation

The main aim of this system is to stabilise the combustion and the behaviour of the boiler in order to maintain, or even increase, boiler and power plant output and efficiency, reduce emissions and achieve higher availability for boilers operated on renewable fuels.

The INTCON-system will need further development to be a general system for controlling all kinds of boilers, and will need even more to control the whole operation of a power/district-heating plant. But as it has a modular structure, several of the modules will be ready for commercialisation at the end of this project.