Carbon in ash monitor

Overview

 

For a coal fired power station, unburned carbon in fly ash is an indication of inefficient fuel utilization, which means more fuel will be burned to obtain desired boiler load. Now power generation units grow towards higher capacity, it is of more significance to analyze unburned carbon in time. Carbon in ash monitor is measurement system designed to perform online analysis of unburned carbon content in fly ash. With it, boiler operators can make reasonable adjustment during staged combustion. Better boiler control will lead to lower production cost. Fly ash, as profitable by-product, will be of higher quality to cement industry.

 

There are different ways to determine carbon in ash online, directly or indirectly, including infrared, microwave, loss on ignition, etc. Now measurement of unburned carbon is mostly done via microwave method or LOI method.

 

Carbon in ash analysis by microwave method

 

As an indirect way, microwave method has been historically used for determination of carbon content. It performs analysis by monitoring on microwave absorption by UBC or cavity resonator parameter changes due to UBC. Only accuracy is not so reliable due to drift on result. Calibration must be done with results from laboratory analysis based on loss on ignition method. When coal or ash parameters change, considerable drift in measurement will require re-calibration. This method is sensitive to variation in coal and ash composition, as well as boiler dynamics. It is not suggested when coal source is not stable.

 

Carbon in ash analysis by loss on ignition

 

Carbon in ash monitor by LOI method is actually reproduced process of laboratory measurement on industrial scale. The system could work out unburned carbon content by weight loss before and after calcination in kiln. On the market, LOI method is more popular due to independence of coal source and particle size.

 

Features of LOI monitor

 

• Unaffected by coal quality or coal fineness. No need for calibration with lab test.
• Wearing resistant material allows sampling tube to serve more than 5 years.
• Advanced design like heat tracing, compressed air purging, anti-clogging structure can prevent fly ash buildup and minimize maintenance work.
• Multi-point samplers guarantees extraction and collection of representative fly ash samples.
• Intelligent quantitative ash collection. Fly ash content in flue gas varies when boiler thermal load changes. Our system can ensure sample of fixed amount is collected in each time to make analysis results more comparable.
• Precise sample weighing by sensitive scale with accuracy to mg level.

 

Unburned carbon level is influenced by factors like boiler load, coal quality, coal fineness, excess oxygen, etc. Carbon in ash monitors make it possible to follow up on changes of UBC online. As an assistance for boiler combustion optimization, it helps boiler operator to make responsive control of burner, pulverizer, air classifier, damper, etc.