Results are given on cleaning diesel exhaust gases by means of a system containing ceramic filters, which show that high-temperature filtration provides effective cleaning.Much attention is being given to ecological cleanliness of diesel engines, as the exhausts from diesel engines contain soot, CO 2 , CO, NO x , SO x , hydrocarbons, aldehydes, acids, benzpyrene, and so on [1]. To reduce the ecological risks from diesel engines, various processes have been introduced: additives in the hydrocarbon fuel, liquid and plasma neutralization of exhaust components, catalytic aftercombustion, filtration, electrofiltration, and so on [2]. However, such cleaning systems cannot be used for maintaining backup diesels, which are usually installed mainly in underground rooms.It has been proposed to treat engine gases by high-temperature filtration with ceramic components developed by the Keramikfil'tr Company (patent RF No. 2164444).A ceramic filter element (CFE) is a close-packed bundle of tubes, whose ends are open on one side and closed on the other. The gases enter the open end, filter through the walls, and pass into the space between the tubes.These CFE tubes are fitted with membranes and are made from ceramic mass based on classified electrocorundum powders. The material also includes refractory bentonite clay, carboxymethylcellulose, and water. It is prepared in a mixer with Z-shaped blades and extruded in a vacuum press into tubes with the required outside and inside diameters, and is then dried and fired at about 1300°C. The total open porosity, no matter what the grain size of the electrocorundum, is ε = 0.38-0.42 m 2 /m 2 , which is close to theoretical close packing of spheres (α = 1 -ε).The CFE are used under the following conditions: gas temperature not more than 500°C, gas pressure not more than 1.0 MPa, and pH 1-12.The CFE may be chemically regenerated by alternating acid-alkali treatment; one cycle of alkali treatment lasts not more than 10-15 min at a temperature of not more than 80°C and an alkali concentration of not more than 0.08 mass %.We tested an experimental specimen of a filter containing CFE as developed by the Keramikfil'tr Company on a 6Ch12/14 diesel of nominal power 50 kW (exhaust output not more than 500 m 3 /h, exhaust gas temperature up to 500°C).The soot concentration (smoke) in the exhaust was determined by the methods described by the NAMI organization [3] and the NIIOGAZ Company [4], which before the apparatus containing the CFE constituted respectively 0.15 g/m 3 and 0.114-0.148 g/m 3 for a maximum permissible concentration of soot in air 0.115 mg/m 3 .

Results are given from three test series on a ceramic filter for diesel exhausts. In the first and second series, use was made of diesel fuel (in the summer), while in the third series, we used the Standard Euro-4 fuel. A grain-size analysis is given for the dust. The filtration performance (with hot gases) is compared with experiments on filters made of ceramic materials.Test results have been reported [1] for a ceramic filter used with diesel exhausts for plant in underground locations. In 2007, three new test series were performed that included certification ones with a ceramic filter for handling exhaust from a diesel of type 6Ch 12/14 (without turbocharge) with nominal power of 50 kW [2].Filter parameters: total area of filter surface 7.8 m 2 ; porosity of filter material ε = 0.38 m 3 /m 3 ; thickness of filter h = 1.25 mm; and diameter of the grains used in making the filter components d gr = 22 µm.The exhaust gas flow under normal conditions was about 450 m 3 /h; as in the previous tests, we determined the dust concentration at the inlet to the filter and at the outlet from it by a gravimetric method and based on filters type AFA in accordance with GOST R 50820-95.In the first and second series, we used diesel fuel in accordance with GOST 305-82 (summer). The idling speed of the diesel was 1000 rpm, while in the working state it was 1500 rpm. The current load in the working state in the first series was 30 A, and in the second it was 58 A.The third (certification) series was performed with the Standard Euro-4 fuel. The shaft speeds in the idling and working states were as in the first and second series. The load current in the working state was 70 A (maximum permissible value 90 A). Table 1 gives the results from the three series. During the tests with a jet impactor [3], the dust was examined for grain size at the inlet to the filter with the diesel working on both forms of fuel (second and third series). The dust dispersion analyses (Fig. 1) are of significance because the fractional composition of the diesel fuel determines the unburned residue, i.e., the parameters of the suspended particles formed in combustion [4].When we used diesel fuel (summer), we obtained the following results from the grain size analysis: median particle size d m = 2.0 µm; and mean logarithmic deviation of the distribution in size with log σ p = 0.688.When we used the Standard Euro-4 fuel, the suspended particles were larger: d m = 3.1 µm and log σ p = 0.41. These larger particles were confirmed also by the data on the trapping performance: the mean performance in working states in the second series was 0.922, while in the third series it was 0.951.The grain-size data allowed us to compare the performance results with the ceramic filter with those for ceramic filter baffles [5]. In the comparisons, we used the averaged data from the experiments in each series (Table 1).