Pulverized fuel sampler

For pulverized coal-fired boiler, primary air carries pulverized fuel to individual burners in furnace wall. While mill is in service, coal samples are collected for fineness analysis. This procedure is to determine mill & classifier performance, then optimize combustion efficiency. Measurement of particle size distribution is an important work that can bring operation to next level.

For a central system (or bin and feeder system), it is easy to get coal samples from storage hopper. For direct firing system, pressure inside fuel line is positive. An easy-to-use pulverized fuel sampler is an aid to collect representative samplers from primary air flow.

Isokinetic pulverized coal sampling unit

In boiler operation, coal fineness will vary and affect combustion efficiency because of mill parts wearing, changes of coal types & sizes. Regular coal sampling is necessary. Analysis data like coal property, particle size, moisture can provide guidance for operators. Pulverized fuel sampler is designed for sampling from fuel line, the coal pipes that convey coal/air mix between mills and burners.

Our pulverized fuel sampler separates particles from coal/air mix based on the principle of negative pressure suction and cyclone separation. When compressed air passes through venturi ejector, air jet will build negative pressure inside sample bottle, sample lance, cyclone separator. When airflow is seduced into sample lance, cyclone separates coal particles into sample bottle, while air is turned back into fuel line. There is no pollution to neighbor environment.

Compressed air pressure can be regulated to adjust extraction velocity. That is to match with true particle velocity inside coal pipes and achieve isokinetic sampling.

Installation

To get representative samples, pulverized fuel sampler is installed on vertical pipes and must keep reasonable distance from classifier, fuel distributor, bends. Or, stratification will occur when mixture flows through bends or horizontal pipes. Dense phase will form at outside corner of bend and bottom of horizontal pipe.

Anti-clogging

Compressed air not only drives the system to collect samples. Self cleaning by compressed air purging can make the system work a longer period while minimum maintenance is required.

Anti-wearing

Sample lance of pulverized fuel sampler is turnable. When sampling is not required, sample lance will hide in the enclosure out of fuel line. When it needs to work, sample lance will rotate into airflow to collect samples. This design avoids abrasion of coal particles and extends service life.

Multi-point sampling

Larger particles of coal have a greater tendency to rope (rather than mix with the air) through coal pipes. The distribution is not even on the cross section. Multi-point sampling ensures reasonable collection of coal samples.

Also, we can design and fabricate screw sampler, retractable sampler, stationary sampler according to client requirement.

Among many different types, pulverized fuel sampler that takes samples from equal area of traverse is worth of a special mention. During pneumatic convey, two phase flow “roping” in coal pipes is a common phenomenon. Coal distribution on the cross section is not even. To get reliable result, cross section is divided into 4 zones with equal area (shown as below). Driven by motor, sample lance with 4 nozzles rotate inside coal pipe. Every nozzle is to collect sample from each zone continuously. This design guarantees any unmixed stream passing that location can be collected.