Part 2 CCT Overview
Environmental Protection Technologies (Flue Gas Treatment and Gas Cleaning Technologies)

5B3. Simultaneous De-SOx and De-NOx Technology
Technology overview

1. Background
The technology behind the wet desulfurization process has also

expensive DeNOx catalysts but also measures to prevent

matured but requires a significant amount of service water as wellammonia leaks. Development efforts are, therefore, underway for

as advanced wastewater treatment measures. Meanwhile, an

a dry combined desulfurization DeNOx method to remove NOx

already commercialized ammonia-based selective catalyticand SOx simultaneously without requiring any service water,reduction (SCR) process requires not only long-term control ofwastewater treatment, or a DeNOx catalyst.

2. Technology(1) Active carbon adsorption method

Research and development: J-POWER; Sumitomo Heavy Industries, Ltd.; Mitsui Mining Co., Ltd.
Project type: Voluntary support project for coal utilization promotion
Overview
The active carbon adsorption method causes a reaction between

technology, verified after being up-scaled to a capacity of

SO2 in exhaust gas and injected NH3 on active carbon at 120-150Km3N/h, was introduced in 1995 to the DeNOx unit of the No.

o150 C, thereby converting SO2 into ammonium hydrogen sulfate

2 unit of the Takehara coal thermal power plant’s normal-(NH 4HSO 4)

forpressure fluidized-bed boiler (350MW), and is currently inadsorption/removal while decomposing NOx into nitrogen andoperation. This technology was also installed as a desulfurizer inwater as does the SCR process. Figure 1 shows the process. The

2002 at J-POWER’s Isogo thermal power plant’s No. 1 new unit

moving-bed adsorption tower (desulfurization tower) removes(600MW) (Photo 1). Although this technology is currently in

SO2 in the first-stage and, in the second stage (denitration

operation, there are no cases of it being used as a combinedtower), NOx is decomposed. This method first removes SOx anddesulfurization-denitration system.

andammoniumsulfate((NH 4) 2SO 4)

then NOx since, as shown in the figure, the presence of highconcentration SO2 tends to decrease the effectiveness of NOx

Active carbon

removal.

Exhaustgas

regenerated. SO2 can be adsorbed and removed in the form of
sulfuric acid (H2SO4) even if NH3 is not injected in thedesulfurization tower. However, since the following reaction withHotairDesorption tower

decomposing it into NH3 and SO2, while the active carbon isDenitration towerhigher in the desorption tower to desorb NH4HSO4 after

Desulfurization tower

Active carbon that has absorbed NH4HSO4 is heated to 350oC orcarbon occurs during desorption, consuming active carbon, NH3is added at the time of desulfurization to prevent such activeFig. 1 Active carbon method desulfurization processcarbon consumption.
H2SO4SO3+H2OSO3+0.5CSO2+CO2

Coal is used to reduce desorbed SO2 into elemental sulfur at900oC for recovery. There is another method that oxidizes SO2
into SO3 to recover it as sulfuric acid.
During the development of this technology, carried out at JPOWER’s Matsushima thermal power plant, first, an activecarbon desulfurization method (with an adsorption tower) that cantreat 300Km3N/h (90MW-equivalent) of gas was subjected toverification tests (1983-1986), obtaining removal efficiency of
98% for SOx and 30% for NOx. To improve the DeNOx removal
efficiency, a combined desulfurization DeNOx pilot plant that cantreat 3,000m3N/h of gas with two towers was tested (1984-1986).
SOx was almost completely removed by the desulfurization tower

Photo 1 Active carbon method desulfurizerin the first stage, while 80% of NOx was removed. This89

Hot
airDesorbed gas

Clean Coal Technologies in Japan(2) Electron beam process

Research and development: Ebara Corporation; Chubu Electric Power Co., Inc.; Japan Atomic Energy Research Institute; others
Project type: Voluntary
Overview
The electron beam process, as shown in Figure 2, involves using

For this process, technology development was undertaken byan electron beam to irradiate SOx/NOx in exhaust gas andEbara Corporation and U.S. partners, including DOE, which madeinjected NH3 to cause a reaction for their recovery as ammonium

joint contributions from 1981-1987. In Japan, based on thesulfate ((NH4)2SO4) or ammonium nitrate (NH4NO3) in thedevelopment results, a pilot plant that can treat 12,000m3N/h ofdownstream precipitator. Byproducts: ammonium sulfate andgas was built at Chubu Electric Power’s Shin-Nagoya power plant,

ammonium nitrate, which are used as fertilizers. Removal

where the technology was verified from 1991-1994.

efficiencies of 98% or more for SOx and 80% for NOx, at anRegarding this technology, a plant that can treat

o300Km3N/hNH3/NO molar ratio of 1, is obtained at 70-120 C. The NOx(90MW) of gas (Photo 2) was built at Chengdu Heat-Electricity

removal efficiency also characteristically increases with higher

Factory, a co-generation power plant in Sichuan Province, China.

SO2 concentrations, though SOx removal efficiency does not

It is currently being operated for demonstration and is obtaining aaffect the concentration of SO2 at the inlet.

NOx removal efficiency of 80%.

ExistingboilerAir
Dry electrostatic
preheater
precipitator

SmokestackAir

Cooling waterElectron beam generator
Dry electrostatic
precipitator

ReactorCoolingtower

Granulator

Ammonia equipment

Nitrogen fertilizer(ammonium sulfate/ammonium nitrate)

Fig. 2 Process flow for electron beam desulfurization process

Photo 2 Electron beam desulfurizer

References

1) Hanada et al., "Dry Desulfurization-Denitration-Technology Dry Active Carbon-Method Sulfur Recovery Formula at Coal Thermal Power Plant"
Thermal/Electronic Power Generation, Vol. 40, No. 3, 1989.
2) "Renewing Isogo Thermal Power Plant" pamphlet, J-POWER.
3) Aoki, "Electronic Beam Flue Gas Treatment Technology," Fuel Association Journal, Vol. 69, No. 3, 1990.
4) S. Hirono et al., "Ebara Electro-Beam Simultaneous SOx/NOx Removal," proc 25th Int Tech Conf Util Sys, 2000.

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