INTEGRATION OF THE CATALYST IN THE WALLS OF LOWER COMBUSTION CHAMBER

Wall catalyst based on MMO/Al2O3-foam: As evident from the Table 2, after the catalyst incorporation, the emissions of CO and VOC (Org.-C)

were reduced by 21% and 42% respectively (in comparison to the refer­ence test). Moreover, the dust emissions were also abated by 55%.

Reduction ofpollutants with the integration of wall catalysts and heat reflecting plate: In order to lower the emissions, the temperature of wall catalysts in the lower combustion chamber was increased by placing a heat reflecting plate (made of vermiculite) in front of the door in the lower combustion chamber (Table 3).

Integration of the MMO/a-Al2O3 catalyst synthesized through Tech­nique 1: After recording positive results concerning emission control by using a suitable catalyst, the active phase of mixed metal oxide (as used in previous experiments) was brought onto the aluminium oxide foam through a novel technique, which is termed here as “Technique 1” (de­scribed in the section 2.2).

As can be seen from the Table 4, the emissions of CO and Org.-C were reduced by 58%, clearly indicating the suitability of both the active phase and the corresponding synthesis route.

Integration of the mixed metal oxide/a-Al2O3 catalyst synthesized through Technique 2: On experimental basis, another technique, “Technique 2” (de­scribed in the section 2.2), has been adopted to observe the suitability of the procedure regarding better oxidation activity of the catalyst.

As evident from the Table 5, the selected synthesis route was not proved to be fruitful, as emission values were higher than using “Tech­nique 1” (Table 6).

Aging behavior of the wall catalyst MMO/a-AfO3: For the determina­tion of the thermal and chemical deactivation of the catalyst, it was aged by fitting into a downdraft stove and subjected to real operating conditions for 630 h (equal to one heating period). The longterm/ aging experiments were planned in such a way that the catalyst was exposed to real operating conditions for three weeks (except the first aging cycle was 6 weeks) and after that immediately tested for its activity. Shortly after, the catalyst was again subjected to a long-term experiment for three weeks before being analyzed again for its stability. The results have indicated that, as shown in Table 7, the catalyst showed initially quite a promising oxidation of pollutants namely, carbon monoxide, volatile organic compounds and dust (particulate matter). This behavior can be attributed to the thermal activa­tion of the catalyst caused by the diffusion of active phase species into the support material, resulting into the synthesis of more active catalytic phase [5]. However, as clear from Table 7, the activity of the catalyst dwindled with the passage of time. This can be possibly due to the poisoning of the active phase on the support material. However, there is so far no evi­dence for the provided assumptions as catalyst characterization (e. g. XRD, XPS) is planned to be done at the end of the aging experiments (after the fifth cycle).

TABLE 4: Reduction in the emissions after integrating the catalyst MMO/a-Al2O3 synthesized through Technique 1.

Experiment Unit Reference* mg/m3 i. N., MMO/a-Al2O3 mg/m3 Reduction %

13 % O2 i. N., 13 % O2

CO

1718

725

58

VOC (Org.-C, FID)

156

65

58

VOC (Org.-C, FTIR)

202

92

54

*The reference experiment was performed again with the new batch of same fuel type

TABLE 5: Emission values after fitting the catalyst (MMO/a-Al2O3) synthesized through Technique 2.

Experiment Unit

Reference mg/m3 i. N., 13 % O2

MMO/a-Al2O3 mg/m3 i. N., 13 % O2

Reduction %

CO

1718

1359

21

VOC (Org.-C, FID)

156

115

26

VOC (Org.-C, FTIR)

202

147

27

Aging behavior of the wall catalyst synthesized through Technique 2: In order to get verification about thermal activation in case of mixed metal oxide catalyst, another long-term/aging experiment was performed with a selected wall catalyst, as tested earlier (see section 3.3.4), where the catalyst was exposed to real conditions in the stove for about 4.5 h. As can be seen from the Table 8, there is quite a substantial amount of reduction in the emissions. The emissions of CO and VOC (Org.-C) were reduced by 62% and 77% respectively. Clearly, there is a thermal activation ef­fect which can be observed in regard to the selected MMO/Al2O3 cata­lyst. However, like pointed out earlier, a catalyst characterization has to be done in order to support this assumption but it is very obvious that there exists quite a high probability of thermal activation, as can be observed from multiple experimental results.

TABLE 6: Comparison between the two selected synthesis routes.

Experiment Unit

Technique 1 mg/m3 i. N., 13 % O2

Technique 2 mg/m3 i. N., 13 % O2

CO

725

1359

VOC (Org.-C, FID)

65

115

VOC (Org.-C, FTIR)

93

147

TABLE 7: Emission values during the course of the aging experiments with MMO/a-Al2O3 catalyst.

Experiment Unit

Reference mg/ m3 i. N., 13

% O2

after cycle-1 mg/m3 i. N., 13

% O2

after cycle-2 mg/ m3 i. N., 13 % O2

after cycle-3 mg/ m3 i. N., 13 % O2

CO

1718

586

222

837

VOC (Org.-C, FID)

156

36

8

64

dust (after rinsing)

37

11

9

16

TABLE 8: Reduction in the emissions after the catalytic treatment during the “normal” and “long-term” experiments.

Experiment Unit

During normal experiment

During long-term experiment

Reduction %

mg/m3 i. N., 13 % O2

mg/m3 i. N., 13 % O2

CO

1359

518

62

VOC (Org.-C, FID)

115

27

77

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