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PRODUCTS DISPLAY |
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| HNTS boiler ammonia desulfurization deduster |
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| Date: 2008-5-10 Hits: 1610 Print this page Back |
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Working principle
Ammonia desulfuration is a technique to control the discharging of SO2. It not only removes the large amount of SO2 in the flue gas, but also produces ammonium sulfate chemical fertilizer of high added value. This deduster system uses ammonia water of certain thickness as desulfurating agent. The ammonium sulfate serum is transformed to the treating system of chemical fertilizer factory. The quantity of ammonia water that is needed in ammonia desulfuration is controlled automatically by preinstalled PH control valve and measured by flowmeter. Ammonium sulfate crystals are crystallized by saturated ammonium sulfate serum. Floating particles whose weight ratio is 3-5% will be produced. This serum liquid will be taken to the treating area by the second grade pump and be dewatered through two grades. Then it will be taken to the chemical fertilizer factory to be further dewatered, dried, condensed and stored. At the same time of defursurating, considerable byproducts can be produced, so the desulfurating deduster can achieve a certain economic benefit.
Principle and flow of the reaction
1. The reaction equations of the desulfurating deduster
The desulfurating tower is the intermediate equipment of flue gas desulfurating and ammonium sulfate salt production. The SO2 in the flue gas is removed in the desulfurating tower. There is saturated ammonium sulfate, whose PH value is controlled from 5.0 to 5.9, in the desulfurating tower. It reacts with SO2 and produces NH4 HSO4 and NH4 HSO3:
1. SO2+ H2O--H2 SO3
2. H2 SO3+(NH4)2 SO4--NH4 HSO4+ NH4 HSO3
3. H2 SO3+(NH4)2 S O3--2NH4 HSO3
In reaction (1), the flue gas dissolves in the water and produce sulfurous acid. In reaction (2) and (3), sulfurous acid reacts with the soluble ammonium sulfate/sulfite. The ammonia water sprayed to the bottom of the reaction pool reacts with acid contents as follows.
4. H2 SO3+ NH3--NH4 SO3
5. NH4 HSO3+ NH3--NH4 HSO4+ NH4 HSO3
6. H2 SO3+ NH3--(NH4)2 SO4
The oxidized gas, which is sprayed on the bottom of the desulfurating tower, will oxidize sulfite to sulfate as follows:
(NH4)2 SO3+1/2 O2--(NH4)2 SO4
At this time, a large amount of ammonium sulfate is produced in the desulfurating tower. When the ammonium sulfate solution is saturated, ammonium sulfate will be settled in the shape of crystal. Vaporized heat will be supplied by the remnant heat of the flue gas in the following ways.
(NH4)2 SO4(liquid)+Vaporized heat->(NH4)2 SO4(solid)
The salt in the desulfurating tower could dissolve in the solution in the form of ion or be settled in the form of crystal. The product serum would be fully oxidized with crystal ammonium sulfate, which is the main content in the running system.
Ranges of Specific operation flow
The running path of the flue gas: The flue gas goes through the smoke duck system from exiting electrostatic deduster and blower. Then it flows by a 100% axial current pressurizing air blower into the desulfurating tower. After the flue gas enters the desulfurating tower, it contacts with contranatant spray serum containing ammonia serum. The ammonia serum absorbs SO2 in it. At the same time, the serum makes the gas saturated and reduces the temperature from 135centigrade in the entrance to 50centigrade. Then the gas goes through two curved dismisters on top of the desulfuration. Two layers of high efficient demisters are installed on top of the desulfurating tower to remove liquid drips in the flue gas. Gas in the running spray tower leaves the desulfurating tower and goes through the boiler again to heat the gas. With the temperature of 80centigrade, it enters the existing chimney system according to the designed operation conditions.
The path of liquid in the desulfurating tower: The PH value of the serum in the desulfurating tower is kept from 5.0 to 5.9. This PH value improves the demoving efficiency of SO2 and the oxidizing speed of (NH4)2 SO3. Ammonium sulfate is easy to dissolve. In general conditions, the dissolving rate can reach 40%. Under the condition of running desulfurating tower, the rate can reach 48.5%. The overflow serum in the swirler will be taken back to the desulfurating tower. In the bottom of the swirler, the concentrated serum whose thickness rate is 13-17% will be sent into the swirling tank. The concentrated serum is sent to the second-grade dewatering swirler in the chemical fertilizer factory to be further dewatered by a serum pump. A filtrate returning pump sends the watery solution, which is removed by the centrifugal spin-drier in the chemical fertilizer factory, back to the desulfurating tower.
Reactant supplement system: Ammonia water reactant supplement system includes a tank with storage capacity of 7 days and a transforming pump. The ammonia water of thickness rate of 28% mixes with oxidized air and cold water through the oxidation distributor on the bottom of the desulfurating tower. The mixture will be sent to the desulfurating tower of boiler dedusting system. A control valve with presetting PH value controls the flow quantity of the ammonia water.
Application conditions: Ammonia desulfurating deduster not only removes the harmful substances, but also turns harm to benefit. It can produce byproducts that are beneficial to human beings. For example: Acid rain, which is harmful to the soil, can be turned into chemical fertilizer. Ammonia art is similar to the common limestone-gypsum art. But the requirements of producing byproducts are different. Limestone produces byproducts in the form of half-wet and half-dry gypsum. Ammonia method produces byproducts, which come out directly in the form of commodity. They are made into dry and granular carbamide. The drying equipments are complicated. |
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