The following devices are successively disposed in the following order from the upstream side to the downstream side in the discharge gas duct of a combustion apparatus: an air preheater which preheats combustion air for use in the apparatus for discharge gas treatment; a heat collector which recovers discharge-gas heat at the outlet of the air preheater; a dust collector which collects soot/dust contained in the discharge gas at the outlet of the heat collector; a wet flue-gas desulfurizer which removes sulfur oxides contained in the discharge gas at the outlet of the dust collector; and a reheater which heats the discharge gas at the outlet of the wet flue-gas desulfurizer. The heat collector and the reheater each has a heat transfer pipe, and a circulation line which connects the heat transfer pipes is disposed. A sulfuric anhydride (SO3) remover is supplied to the upstream side of the heat collector, and the temperature of the discharge gas at the outlet of the heat collector is regulated to or below the dew point of the sulfuric anhydride. As the sulfuric anhydride remover, use is preferably made of at least any one of a sulfuric anhydride adsorbent, sulfuric-anhydride-reducing agent, and sulfuric-anhydride-neutralizing agent. Thus, even when coal having a high sulfur content is used as a fuel, heavy metal(s) contained in the discharge gas can be effectively removed from the discharge gas.

Method and apparatus for treating discharge gas

Disclosed is an exhaust gas treatment device provided with: an exhaust gas treatment unit in which an oxygen combustion boiler (1) using coal as fuel, a denitration device (3), an air preheater (4), a dust-collection device (5), a desulfurization device (6), and a CO2 collection device (8) are arranged in order from the upstream side to the downstream side of an exhaust gas duct on the oxygen combustion boiler (1); an exhaust gas circulation unit that branches off an exhaust gas duct at the exit of the dust-collection device (5) or the desulfurization device (6), preheats the exhaust gas in the air preheater (4), and returns said exhaust gas to the oxygen combustion boiler (1); a heat-recovery heat exchanger (13) that is provided between the air preheater (4) and the dust-collection device (5) and that keeps the gas temperature at the entrance to the dust-collection device (5) less than or equal to the acid dew point of SO3 and greater than or equal to the water dew point thereof; and a reheating heat exchanger (13) that keeps the gas temperature near the branch section of the exhaust gas circulation unit at at least the acid dew point of SO3. By keeping the gas temperature at the entrance to the dust-collection device (5) less than or equal to the acid dew point of SO3, SO3 is condensed and can be removed by the dust-collection device (5), thereby preventing corrosion of pipes in the exhaust gas circulation unit, and in a mill, preventing losses in the ability of pulverized coal in the pipes to flow and combust.

Exhaust gas treatment device for an oxygen combustion system

A thermally efficiency regenerative air preheater (250) extracts more thermal energy from the flue gas exiting a solid fuel fired furnace (26) by employing an alkaline injection system (276). This mitigates acid fouling by selectively injecting different sized alkaline particles (275) into the air preheater (250). Small particles provide nucleation sites for condensation and neutralization of acid vapors. Large particles are injected to contact and selectively adhere to the heat exchange elements (542) and neutralize liquid acid that condenses there. When the deposit accumulation exceeds a threshold, the apparatus generates and utilizes a higher relative percentage of large particles. Similarly, a larger relative percentage of small particles are used in other cases. Mitigation of the fouling conditions permits the redesign of the air preheater (250) to achieve the transfer of more heat from the flue resulting in a lower flue gas outlet temperature without excessive fouling.

Exhaust processing and heat recovery system

A method for improving effectiveness of a steam generator system includes providing air to an air preheater in excess of that required for combustion of fuel and providing the air at a mass flow such that the air preheater has a cold end metal temperature that is no less than a water dew point temperature in the air preheater and such that the cold end metal temperature is less than a sulfuric acid dew point temperature. The method includes mitigating SO 3 in the flue gas which is discharged directly from the air preheater to a particulate removal system and then directly into a flue gas desulfurization system. Flue gas reheat air is fed from the air preheater to heat the flue gas prior to entering a discharge stack to raise the temperature of the flue gas to mitigate visible plume exiting and to mitigate corrosion in the discharge stack.

Method and system for improving boiler effectiveness

The invention discloses a dry-type efficient and energy saving system for cleaning flue gas of multi-pollutants, comprising a pre-denitration device, an air preheater, a pre-deduster, an activated coke gas cleaning device, a waste heat recovery device, a deduster and a flue gas exhaust device which are sequentially communicated. A draught fan is arranged between the deduster and the waste heat recovery device or between the deduster and the flue gas exhaust device. The dry-type efficient and energy saving system for cleaning the flue gas of the multi-pollutants simultaneously has the characteristics of dedusting, desulfuration, denitration, mercury removal and waste heat recovery, and is particularly suitable for cleaning and waste heat recovery of the flue gas of the multi-pollutants generated by burning middle-low sulphur coal; and when all or part of the pre-deduster, the activated coke gas cleaning device, the waste heat recovery device and the deduster are formed in an integral device, structural components of the device are reduced, the cleaning process is shortened, and the system resistance is reduced, so that the whole system occupies a small area, and has small investment and low operation energy consumption.

Dry-type efficient and energy saving system for cleaning flue gas of multi-pollutants

PROBLEM TO BE SOLVED: To reduce the SO3 concn. at the outlet of combustion waste gas to zero and to prevent the generation of blue smoke by equipping an alkali charging device for charging alkali powder at the place at which the temp. of the combustion waste gas is higher than a specified temp. at the upstream side of a desulfurizing device in the treatment of the combustion waste gas containing gaseous SO3. SOLUTION: In the flue gas treating device of a boiler, a denitration device 2, an air preheater 3, a device 5 for recovering heat of a gas heater, an electric dust collector 4, a desulfurizer 6, a reheater 8 of the gas heater and a smoke stack are arranged successively toward the downstream side from a boiler main body 1, and a calcium carbonate charging device 15 is connected to the upstream side of the air preheater 3. The calcium carbonate charging device 15 charges calcium carbonate at the place at which the temp. of the combustion waste gas is higher than 90 deg.C to the combustion waste gas from which nitrogen oxides are removed at the denitration device 2 and neutralizes the SO3 in the combustion waste gas. The contact with the SO3 is promoted and the complete removal is realized by keeping the specific surface area of calcium carbonate particles at >=10 m2/g.

Flue gas treating device

PROBLEM TO BE SOLVED: To lower an operation temp. of an electric dust collector, to reduce an electrical resistance value of a neutralizing agent to prevent the generation of a reverse-ionization phenomenon and to reduce a dust collecting area of the electric dust collector by injecting a neutralizing agent for SO3 on the upstream side of an air preheater and disposing a heat recovering device on the upstream side of the electric dust collector. SOLUTION: Fuel is burned for a boiler main body 1 to generate steam. The nitrogen oxide in the combustion waste gas discharged from the boiler main body 1 is removed at a denitration device 2, and the gas is subjected to heat exchange with the air supplied to the boiler main body 1 by an air preheater 3 and the temp. is lowered by recovering heat by the heat recovering device 5, then ash is captured by the electric dust collector 4 and sulfur oxide is removed by a desulfurizing device 6 and the gas is reheated by a reheater 7 and discharged to the atmosphere from a stack. In such a case, the neutralizing agent for SO3 is injected on the upstream side of the air preheater 3 and the operation temp. of the electric precipitator 4 can be lowered to about 100 deg.C by disposing the heat recovering device 5 on the upstream side of the electric precipitator 4.

裕二難波

Papers

Flue gas treating device

Boiler flue gas treating device

裕二 難波

Papers

Flue gas treating device

Boiler flue gas treating device

裕二難波