Laser Based Gas Analysis for Process Control In Waste Incineration Applications

摘要

The commercial gas analyzer LDS3000, based on tunable diode laser spectroscopy, has successfully been applied to control and monitoring applications in the waste incineration industry. The analyzer is optimized for process control in the industrial environment and is able to provide real time signals for the combustion control as well as for the gas cleaning system in a waste incinerator, Signals from in-situ measurements of H{sub}2O, O{sub}2 and temperature in the combustion zone can be fed to the control system to reduce the amount of excess air substantially and thereby obtain more stable conditions than by conventional control schemes. The analyzer also provides an important control signal for the reduction of NO{sub}x by measuring ammonia, which is the typical reactant added in non-catalytic (SNCR) as well as catalytic (SCR) reduction. The process is controlled to minimize the ammonia slip, thus keeping the total nitrogen emission low from the plant, avoiding ammonium salt formation, and minimizing ammonia consumption. A further application in the gas cleaning process is the filter control where, for example, HCl can be measured before as well as behind the filter, providing the necessary signals for optimizing the filter performance and thereby reducing the lime consumption and avoiding corrosion. The gas analyzer used in these applications comprises a central unit that contains all the sensitive electronic and electro-optic parts, including a tunable diode laser. One central unit can support up to three measurement points that are connected to this unit via fiber optics. This concept is very well suited for combustion applications since it allows the central unit to be placed in a control room while the sensors, designed for extremely harsh industrial environments, can be situated at measurement points at far distance from the central unit.