Classification of Technology:
Cleaner Production Type of Industry:
Electric Subject:
Dry Type Flue Gas Desulfurization - Denitration Technology
( Electron Beam Method )
1. Purpose
This method simultaneously removes sulfur oxides ( SOx ) and nitrogen oxides ( NOx ) contained in flue gas by irradiating electron beam on the gas. This is a dry type desulfurization and denigration technology ( electron beam method ) for recovering valuable by-products ( ammonium sulfate, ammonium nitrate ).
2. History of the Technology Development
12,000 Nm3/h pilot plant test using flue gas from actual equipment was conducted jointly by Chubu Electric power Co., Japan Atomic Energy Research Institute and Ebara Corporation and completed at the end of 1993.
There is no record so far of the introduction of the technology into large scale power plant in Japan.
At present, a plant ( for treating 300,000 Nm3/h of flue gas ) is under construction by Ebara Cooperation in a coal fired power plant in China ( Shisen Province, Seito ).
( Estimated commissioning time - 1997 )
3. Principle and Structure
Process flow and reaction mechanism are as follows.
* Desulfurization rate : Improve with lower reactor outlet temperature or with increase in absorption dose. ( Absorption dose : Energy absorbed by exhaust gas )
* Denigration rate : Improve with lower NOx concentration at inlet or with higher absorption dose.
* Utilization efficiency of energy : Improvement of the utilization efficiency of electron beam is possible by the optimum reactor design considering the beam distribution in the reactor.
* By-product dust collecting performance : Dust collecting performance of over 99% is confirmed by combining an electric dust collector and bag filter. Even without the bag filter, a dust concentration of about 5mg/Nm3 is possible.
* Quality of the by-product : Products that are not inferior to nitrogenous fertilizer on the market can be obtained.
4. Effect and Achievement
Desulfurization rate
Over 94% ( Inlet SOx concentration 800ppm,
outlet SOx concentration under 50ppm )
Denigration rate
Over 80% ( Inlet NOx concentration 225ppm,
outlet NOx concentration under 45ppm )
Dust content at inlet of stack : under 10mg/mN3,
Residual ammonia concentration : under 10ppm.
Features of the electron beam method.
(1) Drain treatment is unnecessary since this is a dry method.
(2) System structure is simple, space required is small and operation is simple.
(3) Expensive catalyst is not required.
(4) By-products ( ammonium sulfate, ammonium nitrate ) can be used effectively as nitrogenous fertilizer.
Although the electron beam method differs depending on the flue gas treating condition, the construction cost is cheaper compared with the wet limestone method and the economy including the operating cost is excellent.
Since it can also cope with high concentration SOx, it is suitable for treating flue gas from the low quality fuel such as residual oil or high sulfur content coal.
5. Situation of Development
In the current test, the continuous operation of about 2,000 hours is being confirmed with a 12,000 mN3/h gas treating equipment.
Implementing company:
Chubu Electric Power Co., Inc.