Ceramic Honeycomb Regenerators
Lately due to increasing competition in the industry all companies have had to reduce production costs. This drives manufacturers to exert pressure on technology suppliers to reduce fuel consumption and energy costs. Additionally, the newest, very restrictive emission limits of pollutant gases (for example: NOx, CO2, CO) and a continuous increase in ecological consciousness result in great interest of the industry in applying the newest combustion technology.
All the conditions and targets which were listed above can be reached by using the HiTAC (High Temperature Air Combustion) technology combined with the High-cycle Regenerative System (HRS) technology, where the regenerative heat exchanger is used.
The regenerative heat exchanger used in the HRS burners is made from ceramic honeycombs. A typical honeycomb used as a regenerative medium has 100 cells per square inch. This great number of cells per square inch ensures the following features of the regenerative heat exchanger:
- high specific surface area equal to 1307 m2/m3, about 7 times bigger than in the case of the ball type (a ball diameter – 20 mm)
- high equivalent heat transfer rate per volume equal to 165 kW/mK, about 5 times bigger than in the case of the ball type,
- low unit weight – about 3 times less that in the case of the ball type,
- low unit volume – about 5 times less that in the case of the ball type. This factor causes that burners are compact and easy to install, especially during furnace revamping.
- short optimum switching time equal to 30 s – the time where the highest regenerative efficiency is obtained. It is about 2 to 4 times lower compared to the ball type. Short switching time results in small fluctuation of the preheated air temperature.
- low pressure drop, about 3 to 4 times lower than in the case of the ball type,
- no problems with plugging due to the construction of the honeycombs (lack of flow dead zone)
Square and round type of ceramic “honeycomb” regenerative heat exchangers
Besides the typical honeycomb with 100 cells per square inch in the square type, there are round type honeycombs too. There are also honeycombs with lower cells number per inch, like for example 54 cells per square inch. The honeycombs are made out of the two material, first one is almost pure alumina, second one is the Cordierite.
The natural area of the applications of the honeycomb regenerative heat exchangers for example incorporate in the HRS systems, are as follow:
- the steel industry, the different types of the furnaces,
- the systems so-called the Regenerative Thermal Oxidisers used for the high thermal efficiency combustion utilization of the contaminated gases of hydrocarbons.
