{"id":6324,"date":"2011-05-17T17:26:19","date_gmt":"2011-05-17T15:26:19","guid":{"rendered":"http:\/\/inercomunicacion.com\/?p=6324"},"modified":"2018-05-24T10:10:03","modified_gmt":"2018-05-24T08:10:03","slug":"new-loi-monitor-for-maximizing-accuracy-and-reliability-using-calcination-techniques","status":"publish","type":"post","link":"https:\/\/inercomunicacion.com\/en\/new-loi-monitor-for-maximizing-accuracy-and-reliability-using-calcination-techniques\/","title":{"rendered":"New LOI Monitor for Maximizing Accuracy and Reliability Using Calcination Techniques"},"content":{"rendered":"

INTRODUCTION<\/strong><\/h2>\n

The adequate measurement of Loss On Ignition (LOI) in pulverized coal boilers is an issue of the utmost importance for optimizing all-round boiler operation,<\/strong> as this parameter has direct influence on efficiency and marks the limit to establish targeted boiler tunings for NOx minimization. Additional benefits are those related to the surveillance of ash quality for its sale to the cement industry, the proper calculation of CO2 emissions or the continuous monitoring and control of downstream facilities for coal ash separation or postcombustion.<\/p>\n

The benefits associated with the measurement of this parameter also becomes evident by the possibility of providing appropriate monitoring of ash characteristics to assure the revenues coming from its sale, in addition to defining applicable limits for NOx control operative strategies or other combustion optimization tunings.<\/p>\n

Despite its importance, the process of monitoring this parameter is reduced to daily manual ash sampling, generally from the electrofilter hoppers, for laboratory analysis afterwards<\/strong>. It takes a long time to generate measurements from this procedure (in some cases up to a day) making impossible to effectively adjust the combustion conditions on a continuous base.<\/p>\n

In addition, the usual on-line equipment currently used to measure unburnt matter in ash generally demonstrates significant sensitivity to variations in fuel and ash nature, as well as on boiler dynamics. Typical indirect methods (microwaves, infra-red, etc) are normally applied which in some cases cast considerable doubt on the values they provide, resulting in requirements of periodic calibrations when any of the aforementioned parameters is modified.<\/p>\n

This boiler operator demand has been satisfied through the application of the new LOI monitor developed by INERCO<\/strong><\/a> (commercialized as ABACO-Loi<\/em>, patent pending), thanks to years of expertise in designing custom-built equipment for pulverized solids handling and analysis.<\/p>\n

The ABACO-Loi <\/em>monitor, specifically designed to withstand industrial working conditions and minimize maintenance actions, provides accurate measurements by automatically and precisely reproducing the laboratory standard procedure, that is to say, combining appropriate weight and calcination stages. The result is an innovative calibration-free technology producing reliable LOI measurements without affection of typical variations in the physical-chemical properties of coal or fly-ash.<\/p>\n

REFERENCE METHODOLOGY<\/strong><\/h3>\n

The principle behind the ABACO-Loi <\/em>monitor is the determination of the LOI (Loss On Ignition or loss of mass for a sample of particles when it is heated to a constant weight in a kiln at temperatures assuring its total combustion, normally over 750 \u00baC, although calcination temperature is fully configurable).<\/p>\n

Drawing on their vast experience in handling and sampling powdered solids, INERCO<\/strong> <\/a>has developed the automatic ABACO-Loi <\/em>system which, when connected directly with the particle pneumatic transport pipe or even with the ash hoppers, reproduces the laboratory measuring process on an industrial scale. In this way, the ABACO-Loi <\/em>is an on-line monitor, specifically designed to withstand industrial working conditions, providing reliable unburnt matter measurements for the coal ash and whose accuracy in terms of laboratory measurement has been verified by INERCO<\/strong><\/a>, obtaining standard errors as low as 0.15%.<\/p>\n

In addition to assuring accurate analysis of unburnt matter, ABACO-Loi <\/em>pays particular attention to the sampling procedure, in order to guarantee that the ash being analysed is representative of the ash generated by the power station.<\/strong> This aspect is generally not taken into account by other systems and, as a result, usually affects their results to a greater extent than the accuracy of the analysis process itself.<\/p>\n

It should be also considered that in the LOI test method for some kind of ashes the weight loss could not be only related to the presence of unburnt carbon in fly ash, but also to carbonates, and combined water, present in hydrated lime or residual clay mineral. Moreover, the presence of sulphides, sulphur, and some iron minerals will decrease the LOI value due to gain in weight because of oxidation (however, it is accepted that carbon is the substance most responsible for ignition loss).<\/p>\n

In case of managing ashes containing such components that interfere with the LOI determination, INERCO<\/strong><\/a> has developed a specific procedure, implemented in the ABACO-Loi <\/em>system (as an option) based in thermogravimetric analysis of the mass loss. This method is based in calcination under inert\/oxidizing atmospheres permitting one to differentiate between the contribution of hydrated lime and calcium carbonate to the LOI and the contribution of unburnt carbon contents in fly ashes.<\/p>\n

In this case, N2 is needed to be supplied to ABACO-Loi <\/em>to produce the heating of the ashes to be analyzed in an inert atmosphere. During this process, oxidation of carbon by gaseous O2 would be hindered and carbonate content is determined; subsequently, the sample is heated in an oxidizing atmosphere and carbon oxidation takes place.<\/p>\n

Thus, this advanced online monitor is found to be applicable not only for the accurate determination of LOI in conventional coal ashes but in those problematic coal ashes having big interferences when applying the standard method.<\/p>\n

OPTIMIZED CONFIGURATION<\/strong><\/p>\n

The ABACO-Loi <\/em>has been engineered and designed to respond to the main constrains and challenges demanded by plant operators: maximum accuracy, representativeness, repeatability and flexibility, compatible with minimum capital expenditure, operating costs and maintenance needs (that includes no preventive maintenance and no need for calibration, based on the measuring principle used).<\/p>\n

To this end, the LOI monitor is conceived as modular equipment, in order to assure flexible application and easy assembly in small spaces. The system is made up of 3 independent modules (Figure 1), connected together:<\/p>\n