The invention relates to cleaning of combustion process exhaust gases, especially in the energy sector and all industries in which there is a need for exhaust gas cleaning.

Background Art

Disposal and cleaning of combustion exhaust gases is the subject of numerous technical solutions designed to clean the exhaust gases of particulate matter such as electric filters, sleeve filters, jet filters, cyclones, water filters, etc.

Electric filters - electrostatic separators are systems for separating particulates from gases, essentially electric traps. They are used mainly in large stationary installations such as power plants. The disadvantage of electrostatic filters is their insufficient reliability. In the event of a high voltage failure, such an electric filter suffers from irregular operation, resulting in a release of large quantities of pollutants.

As an alternative to the electric filters, so called sleeve filters are used in industrial applications. These are filters with wire baskets in stabilised rows with vertically suspended filtering sleeves the cylindrical surface of which accumulates dust and forms so called filter cake. Depending on the degree of contamination the filter cake needs to be removed at appropriate times using a variety of technological operations. Dust falling off the filtering sleeves is collected in silos and then added as an ingredient to various materials, such as fuels or cement.

Reverse sleeve filters are also used - in which the exhaust gas being cleaned flows in the direction opposite to that of sleeve filters. Under normal conditions exhaust gases enter into sleeves and pass through the sleeve interior with dust particles contained in the exhaust gasses being deposited at the inner wall of the sleeve. Compared to sleeve filters, reverse sleeve filters have the same space requirements and similar technological cleaning elements, but their maintenance requirements are higher.

Reverse jet sleeves are used in a similar fashion - they use a connected sequential digital timer controlled by a solenoid valve to feed air to the filter pipe. Other facilities used include cyclones and multi-cyclones using cyclone filters in which the exhaust gases are acted upon by the centrifugal force which is used to separate dust particles from the gas stream.

Disadvantages of the described solutions include mainly their high operating costs and underutilization of existing energy potential of the exhaust gas and/or insufficient efficiency.

Disclosure of Invention

It has been discovered that the combustion process exhaust gases can be cleaned of particulate matter and toxic chemicals with high efficiency by an device of the invention the principle of which is that it forms an enclosed space fitted with a cleaning material inlet port, combustion gas inlet port connected to the exhaust of the combustion process and a cleaned exhaust gas outlet port. The device is further equipped with an endless belt conveyor for the cleaning material with a conveyor belt made of air permeable material, located in the area between the exhaust gas inlet and cleaned exhaust gas outlet ports with this endless conveyor being equipped with a variable drive. The enclosed space is also equipped with a used cleaning material outlet port.

The movement of exhaust gases inside the device is ensured by a discharge fan fitted to the exhaust gas inlet port and/or a suction fan fitted to the cleaned exhaust gas outlet port and the endless belt conveyor is preferably fitted with conveyor belt cleaning means enabling entrance of cleaning media for endless belt conveyor cleaning at its undesired fouling, and tensioning means.

The tensioning means may be, for example, rollers, runners, balls, and such like installed in one of the ways well known to those skilled in the art.

The cleaning material is preferably selected from the group of materials including coal, lignite, biomass, sludge from water treatment plants, processed industrial waste and municipal waste or a combination thereof, with this cleaning material being carried on the belt in a single or multiple layers.

It is important that the belt material is air permeable and is preferably selected from a group of materials including metal, plastic, glass, ceramic and/or textile fibres or mixtures thereof, and the belt material itself may be the cleaning material.

The external shape and dimensions of the device of the invention, as well as the shaping of its interior space may be variable depending on the specific conditions of its use. Also for the structural material used the critical factor is only the exhaust gas inlet temperature.

Contaminated combustion exhaust gas containing ΝΟχ, SO _¾ CO, TOC, carbon compounds and PM (particulate matter) are fed into the treatment area and on their way they pass through a cleaning material carried on the belt, resulting in a highly efficient separation of PM and parts of the pollutants. Contingent quality improvement of the cleaning material may enhance the cleaning process and qualitative properties of the cleaned exiting exhaust gas.

The output products include not only cleaned exhaust gas but also modified cleaning material, that might also be dried up and enriched with PM and unburned parts of solids from the exhaust gas.

Before the actual entry of the exhaust gas into the device of the invention the exhaust gas should be preferably cleaned by removing large mechanical impurities and sparks. Technologies and equipment suitable for this purpose are well known to those skilled in the art.

What can be considered one of the most important uses of the device of the invention is the case in which fuel is used as a cleaning material, which gets improved through this process, i.e. demoisturized and enriched with unburned residues of cleaned exhaust gases. This process also enhances its calorific value by the amount of evaporated moisture and it is particularly suitable for feeding into the combustion process or for storage in the combustion device storage tank. At the same time, it is possible during the cleaning process to treat the cleaning material in terms of its ash melting temperature setting in order to achieve optimal combustibility.

If the cleaning material has high moisture content, it can also be used to scrub the exhaust gas being cleaned.

When summarizing the undoubted benefits of the technical advantages and usability of the device of the invention it should be highlighted that it allows cleaning of exhaust gases while at the same time increasing calorific value and/or desirable treatment of the cleaning material depending on its prospective further use.

If fuels such as coal, lignite, biomass or sludge are used as the cleaning material, the device of the invention should preferably be incorporated as a component of the combustion equipment logistic system.

The device of the invention will be illustrated in more details in the attached schematic drawing.

Brief Description of Drawings

Fig. 1 in the attached drawing shows a schematic cross-section and top view of the device of the invention.

Modes for Carrying Out the Invention

It should be understood that the following examples of the embodiments of the device of the invention are shown only as examples illustrating its technical use and those skilled in the art will recognize possible alternatives of these embodiments and uses, even if they are not explicitly stated. Those skilled in the art will recognize actual dimensioning as well as alternative design and material solutions for the device as such and its individual features.

Example 1

The device of the invention is an enclosed space fitted with a cleaning material inlet port 11, exhaust gas inlet 21 connected to the exhaust from the combustion process, an endless conveyor belt 3 with a layer of the cleaning material spatially separating the exhaust gas inlet 21 from the exhaust gas outlet through the outlet port 22. The endless belt conveyor 3 is equipped with a variable drive (not shown), tensioning means 312 and cleaning means 311 of the belt 31. The outlet through the cleaned exhaust gas outlet port 22 is connected to a suction fan (not shown). The device is connected to the gas exhaust of the biomass burning boiler and it was cleaning exhaust gases in the volume of 250,000 Nm ³ /h, with the content of 2500 mg/m3 PM and the temperature of 150 °C. Biomass chips with 50% moisture content were used as a cleaning material. After the exhaust gases have passed through a layer of biomass wood chips carried on the belt, PM was reduced to 10 mg/m3 and 8 tons of water was evaporated from the wood chips, which ultimately represents about 4% reduction in fuel consumption if the chips are then used in the combustion process.

Example 2

The device of the invention is built into power plant's logistic system and its enclosed space is fitted with a cleaning material inlet port 11, exhaust gas inlet 21 connected to the exhaust from the combustion process, an endless belt conveyor 3 with a layer of the cleaning material spatially separating the exhaust gas inlet 21 from the exhaust gas outlet through the outlet port 22. The endless belt conveyor 3 is equipped with a variable drive (not shown), tensioning means 312 and cleaning means 311 of the belt 31. The exhaust gas flow is driven by a discharge fan at the inlet port 11. The device is connected to the gas exhaust, where the exhaust gases in the volume of 500,000 Nm ³ /h with the content of 3200 mg/m3 PM and the temperature of 185 °C are coming from a coal burning boiler. The cleaning material was coal dust with the moisture content of 26% carried by the conveyor belt 311 of the endless belt conveyor 31. After the exhaust gases have passed through a coal dust layer, the temperature of exhaust gases dropped by 140 degrees and the fuel moisture content was reduced by 20 tons of water per hour. The cleaned exhaust gases were driven by a suction fan (not shown) to the power plant chimney and then released into the atmosphere. In the cleaning process the PM content was reduced to 18 mg/m3.

Example 3

The device was arranged as in Example 1. The device was connected to the gas exhaust, wherein the exhaust gases in the volume of 50,000 Nm ³ /h with the PM content of 3000 mg/m3 and the temperature of 195 °C were brought to the cleaning process from a combustion device. The cleaning material was sludge applied on a biomass backing layer made of wood sawdust. After the exhaust gases have passed through the fuel layer, the temperature of exhaust gases dropped by 145 °C and the cleaning material moisture content was reduced by 1.8 tons of water per hour. Exhaust gases were driven by a suction fan (not shown) to the combustion equipment chimney and then released into the atmosphere. Through the cleaning process the PM content was reduced to 9 mg/m3. Example 4

The device of the invention was arranged as in Example 1. The device was connected to the gas exhaust, where the exhaust gases in the volume of 50,000 Nm ³ /h, with the PM content of 3500 mg/m3 and the temperature of 180 °C were brought from a combustion device. The cleaning material was crushed rape straw placed on a layer of wood chips with the bottom layer formed by pulverized coal. After the exhaust gases have passed through such treated layered cleaning material, the temperature of exhaust gases dropped to 60 °C and the cleaning material moisture content was reduced by 1.7 tons of water per hour. Cleaned exhaust gases were driven by a suction fan to the combustion equipment chimney and then released into the atmosphere. Through the cleaning process the PM content was reduced to 9 mg/m3.

Example 5

The device of the invention was arranged as in Example 1. The device was connected to the gas exhaust, where the exhaust gases in the volume of 50,000 Nm ³ /h, with the PM content of 4200 mg/m3 and the temperature of 180 °C were brought from a combustion device. The cleaning material was cut and crushed straw placed on a layer of wood chips. Such layered cleaning material was in the final stage of the cleaning process enriched with micronized limestone. After the exhaust gases have passed through the cleaning material layer, the temperature of exhaust gases dropped to 70 °C and the cleaning material moisture content was reduced by 1.5 tons of water per hour. Exhaust gases were driven by a suction fan to the combustion equipment chimney and then released into the atmosphere. Through the cleaning process the PM content was reduced to 14 mg/m3. At the same time, through this process the ash melting temperature of the cleaning material was increased by 160 degrees.

Industrial applicability

The device of the invention is intended primarily for power plants, heating plants but also for industrial companies having their own combustion devices. A good example are sugar refineries, pulp producing plants, paper mills and plants for wood processing and particle board manufacture. By using the device an increase of the overall efficiency of the power equipment by 1 to 8%, as an average, can be obtain.