Solids Volume Measurement in Coal-Fired Power Plants


General Process Information

The coal goes through a moderate grinding process and then is stored in a coal bunker. afterwards the coal is typically delivered to a power plant via rail or conveyor belt.

The coal is transported by conveyor and tripper cars to coal hoppers / silos. These hoppers feed ball mills which is turn fedd the pulverized coal to the boilers. There will be at least one hopper for each boiler. Typically there are two boilers per unit. If a coal hopper were to be completely empty, the boiler would need to be shut down.


Raw Coal

Application: Raw coal is delivered to a coal yard in aggregate pieces of approximately 6" that are later reduced in size by a crusher to approximately 1.5".

Challenges: The raw coal is stored in stock piles in huge yards. Only Rosemount’s 3D Solids Scanner MVL system can accurately and reliably measure the inventory of coal in outside piles or warehouses. This important – and previously unavailable information – can then be integrated into the firm’s ERP systems, greatly improving the end-user’s inventory management, control and reporting capabilities. 

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Coal Storage

Application: Coal Storage / Bunker / Coal Blending Facility - The coal goes through a moderate grinding process and then is stored in a coal bunker.

Challenges:Coal bunkers are large in size, containing dozens of thousands of tons of material. Their size and the extremely dusty conditions created by the coal make it difficult to accurately measure the amount of coal in the bunker or coal blending facility. This also presents considerable safety risks to personnel who must enter these storage areas to "guesstimate" coal inventory levels. Rosemount's 3D Solids Scanner is self-cleaning and essentially maintenance-free. It accurately measures the coal inventory even in these extremely dusty and harsh conditions. In addition, it greatly reduces the time, effort, costs and risks associated with sending maintenance personnel into such hazardous environments.


Coal Silos

Application: Coal Hoppers / Coal Day Vessels / Coal Silos - Coal is transported by conveyor and tripper cars to coal hoppers. These hoppers feed ball mills which in turn feed the pulverized coal to the boilers. There will be at least one hopper for each boiler. Typically there are two boilers per unit.

Challenges:Coal hoppers and silos storing the pre-pulverized coal are large and have very dusty environmental conditions. The silos hold a several hours' supply of coal and can continue to supply coal to the boiler in the event there is a problem downstream in the coal handling system. As coal is critical for the continuous process in coal-fired plants, the end-user seeks to monitor and control the actual volume of coal in the hopper or silo in order to prevent process stoppages. Rosemount's 3D Solids Scanner's sophisticated surface mapping technology delivers accurate real-time volume measurements of the coal remaining in hoppers/silos feeding the boilers, taking into account irregular build-ups of material or other problems that may occur inside the storage facility. 


Electrostatic Precipitators

Application: Fly ash is captured and removed from the flue gas by electrostatic precipitators or fabric bag filters located at the outlet of the furnace and before the induced draft fan. The fly ash is collected in hoppers below the precipitators or bag filters and periodically removed from them.

Challenges: ESP hoppers are continuously filled with hot fly ash. Along with the effects of humidity and high temperature, fly ash tends to stick to the sides of the hopper which can cause material build-ups and clogging of the hopper which can damage the ESP plates.End-users need to continuously monitor the volume of fly ash and its actual distribution inside the hopper so that they can be emptied on time, maintained and cleaned when necessary. This is essential in order to prevent clogging-up and risks of damage to the ESP plates. Damaged plates can create environmental and health concerns as well.


Fly Ash Storage Silos

Application: The contents of the fly ash hopper are pneumatically conveyed to a fly ash storage silo. The silo is emptied on to trucks that then haul the material off for use in other applications.

Challenges:Fly ash derived from burning coal creates a very dusty environment and tends to stick, which over time, can create build-ups inside the silo. Fly ash storage silos are typically very large to allow continuous flow from the hoppers. In addition, the density and dielectric constant of fly ash is low. End-users need to continuously monitor and control the amount of fly ash and its actual distribution inside the silo so that it can be emptied on time, as well as maintained and cleaned when necessary. Rosemount's unique dust-penetrating technology combined with its sophisticated surface mapping approach and 3D visualization tool provide accurate measurements of the volume of the stored fly ash as well as a 3D display of how the fly ash is actually distributed at any time inside the silo. The measurements take into account irregular formations along the material surface, including build-ups and rat holes that may form over time. 

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