Ecrodraft

WHY DRAFT CONTROL? Most Solid Fuel Boilers are designed to operate under a negative furnace draft to the extent of -2 to -5 mmWC. This draft is critical both from the maintenance of proper combustion and ensuring safe and efficient operation of the boiler. In Solid Fuel Boilers, it is essential to maintain furnace draft to the minimum possible levels to limit excess air and simultaneously avoid back firing which may be because of improper combustion. Generally, the refractory work in a typical solid fuel boiler develops a lot of leakages and this leads to ingress of unnecessary air into the furnace. This tends to increase the overall draft in the furnace. Such minor variations, if left unattended, can lead to pressurizing of the furnace and can cause backfiring in the unit. A solution for the above problem is to maintain an increased setting of the ID Fan Damper opening. This would result in a carry over of fuel, increased ingress of air into the furnace and therefore reduced operating efficiency of the unit. Proper control of Draft would ensure that the above two situations are avoided by real time monitoring and controlling of the actual draft in the furnace to yield better operating efficiency for the unit. In a typical Solid Fuel Boiler, ID Fan is the largest point of electricity consumption. Control over the ID Fan energy consumption can reduce the overall electrical cost of a Boiler.

Thermax Ltd proposes to achieve the above two purposes by putting an automated Furnace Draft Control System (EcoDraft). A suitable draft measurement sensor shall continuously send readings of the furnace draft to the controller which in turn will govern the VFD operation. Now, VFD shall vary the ID Fan motor speed which is the actual draft measurement.