On-line determination of the caloric value of solid fuels

In thermal processes with highly inhomogeneous fuels it is desirable to know real time fuel characteristics. In the case of municipal solid waste combustion (MSWC) it was up till now not possible to determine the calorific value of the waste on-line with a high accuracy. In this paper, a new method is presented where the calorific value is determined by means of an observer. A model based upon the mass balance is used together with concentration measurements in the flue gas to calculate on-line the calorific value of the waste. The background of this observer based sensor is discussed in detail, including a sensitivity analysis. Results from tests in different full-scale MSWC plants are presented as well as a comparison with other known off-line methods. It will be shown that the sensor works well and is more accurate than the present off-line methods. Furthermore, some applications of the calorific value sensor will be shortly discussed

The effect of air preheating on the combustion of solid fuels on a grate

Combustion of solid fuels on a grate is widely used. Mostly, the combustion behaviour is explained by the classical theory of Rogers. However, that theory cannot explain the combustion process when primary air preheating is applied. Solid fuel grate combustion is studied by experiments in a pot furnace. Experiments with and without primary air heating are described. These are compared with conclusions learnt from real plant experiments. It was found that the pot furnace experiments have a limited value in explaining the combustion behaviour of solid fuels on a grate. In order to be able to explain the results from practice an quantitative extension of Rogers' theory for the case with air preheating is presented

Improved economic operation of MSWC plants with a new model based PID control strategy

\u3cp\u3eMunicipal solid waste combustion (MSWC) plant operators are currently under an increasing pressure to optimize the economic performance of their plants. A route with high potential for optimizing this performance is by improving the performance of the MSWC plant combustion control system, which typically is of the PID-type. In this paper, motivated by the industrial need to improve the overall economic MSWC plant performance, a model based approach is taken to optimize this control system, using recently derived black and white box MSWC plant models. More specific, from a closer analysis of the dynamics of these models a new PID-type of MSWC plant combustion control strategy is derived. It is shown that this new control strategy has improved setpoint tracking properties compared to PID-type of combustion control strategies typically encountered in the industry. As a result, a significant improvement of the economic performance of an MSWC plant will be obtained when replacing such a control strategy for the new one. However, no improvement of the disturbance rejection properties of existing PID-type of combustion control strategies has been observed with the new control strategy, which would also lead to a significant improvement of the economic performance of an MSWC plant, indicating that other, non-PID, types of combustion control strategies are required for that.\u3c/p\u3