Load Control for Rotary Kilns in Cement and Lime plants
Why control the load of a rotary furnace?
Controlling a rotary furnace is a complex and important job for process efficiency. The most important challenges are:
The efficient use of Natural Gas (NG).
The most important basis for achieving this goal is the mixture between NG and air. If we manage to measure the oxygen at the outlet of the furnace at a temperature of 1000?C to 1400?C and put it in relation to the ratio of NG flow and air we achieve a perfect combustion with in important saving effect. We have the solution at your disposal.
The control of the exterior and interior temperature of the furnace to avoid damage to the refractory and optimize the melting.
External control through a solution with thermal imaging cameras helps us detect hotspots and plan the next stoppage. The internal control by means of a thermographic image allows the control of the flow of the material inside the furnace and detect clogs in the output. This was one of my last projects at Zinc plant in Monterrey.
Furnace load control.
This part of the control is also very challenging because of the high temperatures that rise from the furnace to the feed ducts.
Solutions for this measurement
There are several solutions on the market for solids flow measurement:
1. MassFlow on conveyor belt. Good solution if the plant infrastructure allows the assembly of such a measurement system. The installation of a weighing system can be quite expensive by adapting the scale to the width of the belt. I got good experiences with these systems especially their behavior at longer times. Even calibrations convert after the first experience to an easy-to-master process.
Impact plate: This system consists of a plate with a defined angle where the material falls from a defined distance. The impact force causes a horizontal movement of the plate. This horizontal movement is realized with a highly sensitive load cell or, in some other equipment, through capacitive systems. As the plate is a weighing system that requires movement and as the solids normally create lots of dusts, the biggest problem these systems have is the cost of ongoing maintenance. In addition, as factories are always exposed to a certain vibration, these accelerations also cause certain peaks in the measurement and impact on the accuracy of the system.
Non-contact electrodynamic systems: These solid flow measurement systems are non-contact systems. The sensor creates a microwave field inside the tube and the impact of the solids crossing this field allows the measurement of the solids mass flow. These systems work in freefall tubes and pneumatic transports. The assembly of such a system is easy and as the ceramic sensors are almost not in contact with the solids the problem of abrasion does not exist.
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ENVEA Solutions
Envea Solidflow 2.0
Where and how to apply the sensors:
1. Pneumatic transport:
After a screw conveying system
Envea : MaxxFlow HTC
The MaxxFlow HTC is specially developed for the measurement of the flow of dry solids in bulk without any restriction. Due to its independence from the pipe angle and its low installation height, the MaxxFlow HTC is especially suitable in situations where previously it was only possible to use complicated or expensive mechanical solutions. The installation of the MaxxFlow HTC is carried out independently of the orientation of the tube (vertical / inclined), but always after an mechanical conveyor, e.g. rotary valves, screw conveyers, slides or chain conveyors.
Where to apply: