Ceramic filters and flue gas cleaning

Polish air is still among the most polluted in Europe due to both industrial and domestic furnace plants. Therefore, any person who decides to buy a heating furnace should be sure that the company that manufactured it is fully aware of and complies with the applicable standards for exhaust emissions and their treatment.

According to the Ordinance of the Minister of Development of January 21, 2016, on the requirements for carrying out the process of thermal waste conversion and how to deal with the waste resulting from this process, the temperature of flue gases in the furnace chamber should not be lower than 850 °C. If the fuel contained more than 1% chlorine, the temperature must be as high as 1100 °C. In a situation where it is not possible to achieve such a value, pre-treatment of the fuel should be carried out. The regulation also says to include in the incinerator, that is, also in the heating furnaces, devices that discharge the flue gases into the air.

Particleboard and wood-based boards - HDF and MDF, which were presented differently in EU directives and differently in Polish regulations - became an issue. According to the directives, biomass is all wood waste except those containing organic-chlorine compounds. The Environment Ministry's November 10, 2015 regulation instead defined it as solid wood, thus excluding HDF and MDF particleboard from combustion.

However, amendments to the January 24, 2016 ordinance introduced a clarification in the form of allowing all wood waste with code ex 03 01 05 (sawdust, shavings, cuttings, wood other than that listed in 03 01 04) from the processing of particleboard to be used as fuel. This means that you can burn slabs in which no hazardous compounds have been used - for example, for impregnation. Their combustion is made possible by UNIWEX biomass furnaces, specifically the COMFORT PREMIUM model with ceramic filters. In turn, the Ordinance of the Minister of the Environment dated on 01.03.2018 specifies the emission standards that filtration equipment should meet throughout the combustion process.

The thermal waste conversion must not be too harmful to the environment. Therefore, heating furnaces should have built-in solutions to take care of the purification of the produced flue gases. Depending on the type and model of the device, these can be:

Among the most essential components are cyclones, ash traps, and filters. They are the ones able to clean exhaust fumes most effectively.

Cyclones, also known as separators, are designed to separate the particulates in the flue gas from the gas, thus cleaning it of dust. Central Heating furnaces UNIWEX most often uses multi cyclones built with several through cyclones. Their operation consists in conducting the combustion gas through the blade elements, where, with the help of centrifugal force, the ash bounces off the wall of the device, getting to the bottom of the tank. Through the exchanger tubes, the dust goes directly to the ash pan. The pipe layout itself is important here. If it is vertical, the ash - thanks to gravitational descent - is only slightly deposited on the exchanger tubes. With a horizontal system, dust settles on the surface of the exchanger channels, thus increasing the resistance to the flow of flue gases.

One of the most reliable solutions designed for flue gas cleaning is ceramic filters, which are used, among others, by UNIWEX (COMFORT PREMIUM) heating furnaces. As with other filters, the ceramic ones are designed to reduce fugitive dust emissions during the combustion process to the required minimum of 10mg/m3. Such filters are distinguished by, among other things, resistance to rapid changes in temperature, uniform flue gas permeability, excellent resistance to erosion and mechanical damage, and non-flammability. In addition, ceramic filters, unlike others offered on the market, have very low power consumption.

It is the ceramic filters that provide a much cleaner flue gas by separating more ash and sludge than can be seen with traditional solutions. They are also responsible for afterburning the dust fraction, leading to easier and less frequent cleaning of the entire plant. Use of ceramic filters in central heating furnaces also ensures more efficient use of less fuel of choice.