Mitsubishi Heavy Industries Technical Review Vol. 49 No. 1 (March 2012)
105

Basic Performance of HBF® (Hybrid Bag Filter) andOperation Reports for Incineration Plants*1

TAKUMI SUZUKIMASATOSHI KATSUKI

*2

*1

*3

KOETSU SHIZUKUISHI TETSUYA SAKUMA*3

TAKUMI MASUDA*3

REIJI TAHARA

Ahead of other competitors, MHI and Mitsubishi Heavy Industries Environmental &Chemical Engineering Co., Ltd. have developed and manufactured a practicable V-Ti
catalyst-supported bag filter, the Hybrid Bag Filter® (HBF), which enables dust removal, De-HCl,
De-SOx, De-NOx, and dioxins reduction (filtration, adsorption, catalytic decomposition)
simultaneously. This paper describes the bench scale test results of the basic performance of HBF
and also reports on the actual achievements of HBF, which prove that both pulse type HBF andreverse type HBF have very stable and favorable performance over long periods.

|1. Introduction
Ahead of other competitors, we have successfully developed and manufactured(1)-(5) apracticable V-Ti catalyst-supported bag filter, the Hybrid Bag Filter® (HBF), which enables dust
removal, De-HCl, De-SOx, De-NOx, and dioxins reduction (filtration, adsorption, catalytic
decomposition) simultaneously, with achievements of practical use at 4 domestic and overseas
incineration plants.
We have both pulse-type HBF, which has a higher filtration rate, and reverse-type HBF,
which has a lower filtration rate.
Bag filters have been so far improved in the direction of lower temperature in order to meet
the trend of tightening regulations for DXNs, Hg emission and in order to use Ca(OH)2 more
efficiently. A lower temperature, however, requires SGH (Steam Gas Heater) to need a lot of steam
when a selective catalytic reactor is installed in later stages, thereby decreasing power generation
efficiency and causing energy loss. It can, therefore, hardly be said that a lower temperature isadvantageous from the viewpoint of the recent emphasis on the effective use of waste heat energy
from municipal incinerators and lower Life Cycle Cost (LCC). It is important in the future to raise
the temperature while maintaining DXNs removal performance.
This paper reports on the results of tests conducted from this viewpoint at MSW Incineration
Plant A to evaluate the DXNs removal performance of a pulse-type HBF at a relatively hightemperature (≧180°C).
Furthermore, examples of actually recorded achievements are also reported on the De-NOx
and De-DXN removal performance under the long-term operation of a reverse-type HBF at MSW
Incineration Plant B and the DXNs removal performance of a pulse-type HBF at MSW
Incineration Plant C.

*1 Yokohama Research & Development Center, Technology & Innovation Headquarters*2 MHI Solution Technologies Co., Ltd.
*3 Mitsubishi Heavy Industries Environment and Chemical Engineering Co., Ltd.

Mitsubishi Heavy Industries Technical Review Vol. 49 No. 1 (March 2012)106|2. Hybrid Bag Filter® (HBF)
HBFs are our original products, the functions of which have been enhanced by coating acatalyst on bag filter fibers with our unique technology to add gaseous dioxins (DXNs), VOC(DXNs precursor), and NOx reduction functions, while maintaining the conventional functions toremove other harmful substances.
That is, the HBF is an integrated flue gas treatment system for which the harmful substanceremoval function, necessary in disposing of exhaust gas from environmental equipment, is entirely
integrated into a bag filter. Figure 1 shows our HBF filter cloth and Figure 2, a conceptual
diagram of the HBF functioning.

Figure 1 View of HBF
filter cloth
Figure 2 Schematic diagram of a catalytic bag filter|3. DXNs removal performance test
In order to investigate the above-mentioned DXNs removal performance of a pulse-type
HBF at a relatively high temperature (≧180°C), the following tests were conducted, with raw gas
branched off.

3.1

Test method

Tests were conducted in May - June 2010 at MSW Incineration Plant A (stoker-type,
150ton/day×3) as our delivery destination by introducing raw gas into small bag filter test
equipment under normal operation. Figure 3 shows a schematic of the test equipment. To
separately evaluate the DXNs removal performance of the HBF surface sedimentary layer (dustlayer) and the catalyst coated on fiber, a two-staged configuration was also tested. No. 1 is a bag
filter (without any supported catalyst, hereinafter referred to as a normal BF) and No. 2, an HBF.

Figure 3 Schematic of test equipment

The mechanism of DXNs removal by an HBF may be based, as illustrated in Figure 2, on theremoval (adsorption of gaseous DXNs and dust collection of solid-state DXNs) and catalyticoxidative decomposition reaction of gaseous DXNs that passed through the surface sedimentarylayer. Taking the removal efficiency of the former as ηd and of the latter as ηc, HBF’s total
performance ηt is given from the following:t  1 

C2 1  (1   d )  (1－ c )C0Mitsubishi Heavy Industries Technical Review Vol. 49 No. 1 (March 2012)107

In the Figure 3 test equipment, simultaneous measurement of DXN concentrations C0, C1,
and C2 at the entrance of No. 1 normal BF and of No. 2 HBF, and at the exit of No. 2 HBF, enables
direct measurement of the DXNs removal efficiency ηd through the surface sedimentary layer andthe DXNs removal efficiency ηc of the catalyst. Here, it has been confirmed beforehand that there
is no difference in the DXNs removal performance obtained between the 2-stage bag filter(normally BF+HBF) and a 1-stage HBF, both marking 99.9% or more.
Table 1 shows the main specifications for HBF/BF. The amount of gas sucked in was kept
constant by an inverter-controlling IDF (induced draft fan) while an automatic backwash was used
at intervals.

3.2

Test conditions

Tests were conducted under the conditions of Table 2, taking the flue gas treatment
condition at the real plant into consideration. In two-stage bag filter tests, the dust concentration ofgas is of great importance when evaluating the DXNs removal performance of the surface
sedimentary layer. These tests were believed to be performed in near-reality conditions because
constant suction of about 3g/m3N during the test was observed.
The method of analyzing DXNs complied with JIS K 0311. Since the concentration of DXNs
may be variable, sampling was made at one time.
Table 1Main specifications for test
equipment

Amount of gas
Filtration rate
Size of filter cloth
Backwash pressure

3.3

3Table 280-130m N/h
0.6-1.1m/min
164φ×1.2m×6 strips
0.3MPaTest conditions

Temperature
Filtration rate
Dust concentration

180°C-220°C
0.6-1.1m/min≒3g/m3N

Results and discussions

3.3.1 DXNs removal performance
Table 3 shows the test results. Here, values of removal performance ηt，ηd，and ηc were
calculated from actual concentration measurements. Table 3 indicates that, under the conditions
provided (filtration rate of 0.6m/min-1.1m/min, gas temperature of 180°C-220°C), independently
from temperature and filtration rates, a DXNs removal performance of about 98-99% byadsorption/dust collection and of about 95-99% through oxidative decomposition of gaseous DXNs
by the supported filter cloth catalyst, that is, as excellent as 99.9% or more in total, can beachieved.
As seen in Table 3, total HBF performance is less dependent upon gas temperature and thefiltration rate. As mentioned above, the mechanism of DXNs removal with HBF consists of DXNs
removal by adsorption and dust collection at the surface sedimentary layer growing on the filter
cloth surface and oxidative decomposition of gaseous DXNs by the catalyst supported on the filter
cloth. The lower the temperature, the more advantageous is the former, while the higher thetemperature, the more advantageous is the latter. It is considered that, due to the combined effectsof these, a high degree of DXNs removal could be achieved independently from the filtration rate
and temperature.
Table 3 Results of tests on DXNs removal by HBF

Gas
Filtration rate
temperature(m/min)
(°C)

180
200
220

0.60
1.08
0.69
1.06
0.63
1.09

Performanceof removal insurfacesedimentarylayer ηd(-)

Performanceof oxidative
decomposition
by catalyst
ηc(-)

Total HBF
Performance
ηt(-)

0.999
0.998
0.993
0.996
0.981
0.977

0.967
0.954
0.978
0.987
0.980
0.990

0.999
0.999
0.999
0.999
0.999
0.999

DXNs concentration at HBF
exit
ActualToxicity
measurement
equivalencyofconcentration
concentration(ngTEQ/m3N)3(ng/m N)
0.011
0.000014
0.032
0.000015
0.027
0.000012
0.014
0.00000081
0.110
0.00057
0.090
0.0004

Mitsubishi Heavy Industries Technical Review Vol. 49 No. 1 (March 2012)108

3.3.2 Pressure drop simulation of HBF
Along with the removal of harmful substances, the stability of the pressure drop is extremely
important for a bag filter while in operation. Hence, the pressure drop of an HBF in operation wasverified.
Figure 4 shows the measurement results of a pressure drop in a 24-hour continuous
operation (backwash interval of 320min., backwash pressure of 0.3Mpa, filtration rate of
1.0m/min.). From these results, it was found that HBF could be used in safety because the pressure
drop was always less than ΔP＝2kPa during continuous operation.
The behavior of the pressure drop at the real plant is, however, a little different from that of
Figure 4 since test equipment was in a one-chamber operation while a multi-chamber is actuallyoperated. Then, pressure drop simulation for a multi-chamber HBF operation was attempted inaccordance with the basic data obtained from these tests.
Bag filter pressure drop ΔP is generally given by the following equation(6):P  Pf  Pd  ( f   d 0  Ld )    u･････････(1)where ΔPf is the pressure drop of the filter itself; ΔPd, the pressure drop of the surface
sedimentary layer; ξf, the resistance coefficient of the filter itself; ξd0, the specific resistance of thesurface sedimentary layer; Ld, the dust loading; μ; the viscosity of flue gas; and u, filtration rate. Ld
increases with time. However, the other parameters are constant if the temperature and filtration
rate are constant.
Next, the pressure drop of a multi-chamber bag filter is examined.
If αi=ξf+ξd0・Ld is taken as No. 1 chamber's total resistance coefficient;from equation (1), the entire pressure drop ΔPf of the bag filter is expressed by equation (2)P   1    u1   2    u 2  ････ 8    u 8

(

1

1



1

2

 ････ 

1

8

－1
）
 (8u m )   R  (8u m )  
R (

1

1



1

2

 ････ ････････(2)
1

8

－1
）

･･･････(3)where um is the symbol of the average filtration rate and R, of the totalized resistancecoefficient. That is, theoretically, if the average filtration rate um, totalized resistance coefficient R,
and gas viscosity μ are known, it is possible to calculate the entire bag filter pressure drop ΔP.
From the data of Figure 4, ξf ＝1.21×109(1/m) and thenξd0 ＝6.28×109(m/kg) can beobtained. Here, dust loading Ld(g/m2) is approximated by:dLd
 Cd  udt････････(4)where Cd is dust concentration (g/m3N).
The use of equations (1)-(4), therefore, permits a simulation of the pressure drop for a
multi-chamber bag filter.
Figure 5 shows the above-based simulation results of a pressure drop for 8 chambers, gas
volume≒62,000m3N/h (≒180t/d). This indicates how the pressure drop tends to stabilize with agrowing surface sedimentary layer. A simulation calculation has found the bag filter pressure drop
to stabilize somewhere around 11kPa. In other words, the finding is that even the HBF of amulti-chamber bag filter can operate stably at a pressure drop of 2kPa or less. But in theabove-mentioned simulation, estimates may have been a little lower than actual performance, nottaking into account the effects of clogging due to long-term operation, etc. At any rate, it is thoughtthat a multi-chamber HBF operates stably at a pressure of 2kPa or less. In fact, no problems
resulting from pressure drop (clogging) have occurred in later-described HBF achievements.
3.3.3 Hg removal
The removal of Hg was checked with this test equipment. The Hg concentration at No. 1
normal BF exit was 0.012mg/m3N, lower than the domestic voluntary regulation value(0.05mg/m3N).

Mitsubishi Heavy Industries Technical Review Vol. 49 No. 1 (March 2012)
109

Figure 4 Pressure drop of an HBF incontinuous operation (test result)
Figure 5 Simulation calculation of amulti-chamber HBF|4. Reverse-type HBF’s achievements in long-term operation
MSW Incineration Plant B is a stoker-type facility to which we delivered equipment in the
1970s. This plant gradually updated its equipment from 2001, replacing electrostatic precipitatorswith HBFs, and now operates all three of its lines with an HBF. The HBF is a reverse-type
integrated flue gas treatment system and is provided not only with de-HCl, de-Sox, and dust
removal capabilities, but also with de-NOx and de-DXN (Table 4). As a reducing agent for
de-NOx, NH3 is supplied from upstream HBF.
Table 5 shows flue gas treatment performance measurement data as of 2009 (about three
years after HBF operation started). This indicates that, even after three years of operation, not only
de-HCl, de-SOx, and dust removal, but also de-NOx and de-DXNs capabilities remain favorable.
With respect to de-NOx in particular, even if NH3 was supplied at the stoichiometric ratio of some
0.6, the reaction efficiency at the HBF was favorable at nearly 100% at that time. Furthermore,
DXNs emission has been significantly reduced by catalytic decomposition to become considerably
lower than the domestic law’s regulatory limits, proving the same effects to those of active carbon
powder supplying.
Table 4Main specifications for MSW
Incineration Plant B HBF

Gas temperature (°C)
Filtration rate (m/min)Type of catalyst

210-230
0.3
V-Ti catalyst

Table 5 MSW Incineration Plant B flue gas
treatment performance measurement results
Item to be analyzed
HBF exit
Dust concentration (g/m3N)
Less than 0.001
HCl concentration (ppm）
1.1
SOx concentration (ppm)Less than 1.0
NOx concentration (ppm)39
NH3 concentration (ppm)Less than 1.6
DXNs (ng-TEQ/m3N)
0.000078*Everything except NH3 is 12% oxygen-equivalent.

|5. Pulse-type HBF achievements
MSW Incineration Plant C is an overseas facility to which we delivered equipment in 2000
and where normal bag filters were upgraded to HBFs in 2003. The flue gas treatment equipment inthis plant is an electrostatic precipitator installed upstream of the HBF.
Table 6 shows the main specifications for HBFs at MSW Incineration Plant C and Table 7,
the results of DXNs removal performance. According to these specifications, a sufficiently highDXNs removal efficiency has been acquired even by pulse-type HBFs for which the filtration rate
is relatively fast (no de-NOx carried out).
Table 7
Table 6Main specifications for HBFs at
MSW Incineration Plant C

Temperature (°C)
Velocity of flowing filtered
fluid (m/min)

180
About 1.1

MSW Incineration Plant C HBF
DXN removal performancemeasurement results

Item to be analyzed
DXN (ng-TEQ/m3N)

HBF exit
0.0054

Mitsubishi Heavy Industries Technical Review Vol. 49 No. 1 (March 2012)110|6. HBF effects of reducing CO2 and LCC
As mentioned above, since the employment of our HBF allows DXNs to be removed more
efficiently – even at relatively high temperatures – than by normal bag filters, it is not necessary tolower the bag filter operating temperature (to about 165°C). That is to say, the amount of steam
used by flue gas heaters (SGHs) can be reduced and excessive steam may be diverted to private
power generators. Hence, this section estimates how much LCC can be improved.
A case where an HBF (200°C) replaced a low-temperature bag filter (165°C) was estimated(Figure 6). Table 8 shows the results of a comparative LCC calculation. As seen from this table,
since an increase in bag filter temperature builds up Ca(OH)2 consumption but activated carbon
need not be used and the temperature width required for reheating treated gas is lessened (ΔT ＝165°C→200°C to ΔT ＝200°C→210°C), steam could also be diverted to power generators. At thesame time, the amount of water injected at the cooling tower can be made smaller by raising the
bag filter temperature for a smaller volume of gas to lessen the loads on the IDF (induced draftfan).
The results showed that the LCC of flue gas treatment equipment and its surroundings as awhole could be lowered by 27.5% (by our comparison).
Furthermore, in this case, a 7.4% decrease in power consumption comes from the reduced
amount of IDF power consumption and the increased power generation. If this is calculated, using
the consumed/generated power-related CO2 conversion factor in the “Manual for Improvement ofEssential Equipment at a Waste Treatment Facility(7),” 7.4% fewer CO2 emissions (by ourcomparison) also occurred.

Figure 6

Example of a substituted system with HBF
Table 8Results of comparative calculation

Items for comparison
①
②
③
④
⑤
⑥
⑦

Amount ofactive carbon used (%)
Amount ofslaked lime used (%)
Amount of
special reagent (%)
Filter cloth durability (life)
IDF consumed power (%)
Amount ofpower generated (%)
Flue Gas treatment
equipment-related cost (%)*1*1: Cost for ①-⑥

Low-temperaturebag filter (165°C)

HBF (200°C)

100

0

100

130

100

100

100
100

100
97

100

104

100

72.5

Mitsubishi Heavy Industries Technical Review Vol. 49 No. 1 (March 2012)
111|7. Conclusion
DXNs degradation tests by a HBF were carried out as well as to surveys of performance at an
actual plant and the following results were obtained:(1) Raw gas tests with a small HBF found pulse-type HBFs achieve an extremely high DXNs
removal efficiency (99.9% or more) even under relatively high-temperature operating
conditions (180-220°C, 0.6-1.1m/min). The pressure drop of the equipment in operation was
also found to be stable.
(2) As for reverse-type HBFs, it was found at an actual plant that de-NOx and de-DXNs
performance remained favorable enough even after three years of operation.
(3) Pulse-type HBFs also maintained reasonably high DXNs removal performance at an actual
plant.
(4) Our estimations found that the use of an HBF could improve the the flue gas treatment
equipment by about 27.5% (by our comparison).
(5) Our estimations found the use of an HBF could reduce CO2 emissions from the flue gas
treatment equipment by about 7.4% (by our comparison).
We found that our developed HBF, regardless of whether a reverse- or pulse-type HBF,
could remove harmful substances with high efficiency. It can be said that HBFs are quite excellent
in terms of effective energy utilization and CO2 reduction as well, since they are capable ofremoving enough DXNs to lessen the amount of steam for flue gas reheaters and the quantity ofactive carbon blown in as an anti-DXNs measure.
The future is expected to be more lower-carbon/higher-efficiency power generation-oriented
as well as lower LCC-oriented, moving toward the establishment of a recycling society, and HBFs
may be highly effective technology, not only for newly built incinerators, but also for retrofits.

References
1. Uoya et al., Technology on Flue Gas Treatment of Fine Harmful Compounds from Municipal Incinerators，Mitsubishi Heavy Industries Technical Review Vol. 29 No. 2 (1992).
2. Uoya et al., Reduction of Dioxin from Refuse Incinerator Plant, Mitsubishi Juko Giho Vol. 29 No.4 (1992)
3. Horaguchi et al, Development of Catalytic Bag Filter (part 1), Proceedings of the 2002 Symposium on
Environmental Engineering, The Japan Society of Mechanical Engineers, p. 245 (2002).
4. Uoya et al, Flue Gas Treatment by De-NOx catalytic bag filter, Proceedings of the 14th Annual Conferenceof Japan Waste Management Association, p. 160 (1993).
5. Okada et al, High Removal Efficiency of Dioxins and Hg by Lower Temperature Bag Filter for MSW
Incineration Flue Gas, Proceedings of the 2nd Annual Conference of The Japan Society of Waste
Management Experts, p. 473 (1991).
6. Iinoya Koichi, Shujin Sochi (“Dust Collector” in English) New-edition, Nikkankougyou Shinbunsya(1963).
7. Manual for Improvement of Essential Equipment at a Waste Treatment Facility (Ministry ofEnvironment, 2010) (http://www.env.go.jp/recycle/misc/guideline.html)