In the current energy crisis and considering the accelerated increase in the cost of energy and other materials, it has become very important to search for strategies and methodologies that help operations and equipment to be more efficient in the use of energy and in adopting state-of-the-art equipment to maintain the necessary competitive advantage in the market.
In the last decade, companies in the cement industry have sought to improve production as such and have managed to reduce energy consumption, contributing to the reduction of the carbon footprint. As part of this, many investigations have concluded that false air is one of the factors that lead to higher energy consumption and additionally, it can be concluded that with the reduction of false air, the level of production and energy consumption can be improved.
False air is any unwanted air that enters the process system. The exact amount of false air is difficult to measure. However, an indicator of false air can be the increase in % of oxygen between two points. This unwanted air increases energy consumption and decreases the temperature of the system. As a result, increased fuel consumption is required to maintain the temperature.
In the cement industry, false air intake happens usually into the kiln section through the kiln outlet, inlet seal, sliding gate, inspection doors and flap box. Similarly, in the mill section, false intake happens through the rotary feeder at the mill inlet, mill body, mill door, gates, expansion joints, duct holes and tie bar entry point.
To measure false air, it is important to know that atmospheric air normally has a content of zero percent CO and 20.99 percent O2. To measure false air in the preheater and mill: Based on the oxygen content and flow measurement at a particular location, the amount of false air in the preheater and mill circuit can be measured. For this purpose, the % O2 is measured at different locations, i.e., preheater inlet and outlet, cyclone inlet and outlet, mill inlet and outlet, mill outlet to fan inlet, in the baghouse or ESP.
One option for detecting false air intake is the ultrasonic leak detector. These detectors are specially designed to find small leaks. Since they look for leak sounds rather than escaping gases, they can detect leaks of any type of gas. Although the device cannot measure gas concentration, it can determine the leak rate of an escaping gas because the ultrasonic sound level depends on the gas pressure and the size of the leak.
When gas escapes from a pressurized line, it generates a sound in the range of 25 kHz to 10 MHz, well above the frequencies to which the human ear is sensitive, but in a range easily identifiable to ultrasonic sensors. When the detector detects ultrasonic frequencies, they are isolated from the normal background noise, amplified, and converted into a frequency audible to humans.
Normally, cement plants use conventional methods to stop false air, but these conventional methods are not reliable or permanent. In fact, they work more like a silencer and after a few days, they get damaged. One of the solutions that greatly help to reduce false air intake into the kiln is the installation of a quality and efficient kiln seal between the rotating part and the fixed part at the inlet and outlet.
There is great potential to improve energy efficiency in the cement industry in general and in individual plants. Constant efforts are increasingly being made to improve energy efficiency and reduce the cost of energy so that the industry can survive and grow. There are several alternatives in the market that can contribute to the cost reduction of cement manufacturing and improving energy efficiency.
Source: https://indiancementreview.com/