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Limestone FGD New Technology

Abstract: In 2014 limestone desulfurization, denitrification latest technology.

1. limestone slurry preparation system

The limestone (particle size ≤20mm) into the discharge hopper, the feeder, bucket elevator to the inner limestone steel silo, and then by weighing feeder and belt conveyor to the mill made within a wet ball mill slurry, limestone slurry pumped to hydrocyclone after separation, the large size of the material is recycled within a wet ball mill, overflow material stored in the limestone slurry tank, and then pumped through the limestone slurry to the absorber.

The project of two public a desulfurization unit limestone pulping system, limestone slurry to set two wet ball mill system, each wet ball mill output 75 percent by means of two FGD slurry amount required to consider, after grinding limestone product size ≤0.063mm (250 mesh, by 90%).

Limestone silo capacity by two boilers run three days (24 hours a day by the meter) absorbent consumption design BMCR conditions.

Limestone slurry transport provided four slurry pumps, two, two standby. Each is provided a desulfurization unit limestone slurry transfer circuit. For the limestone slurry mixing, to prevent precipitation, fouling, which are installed in the slurry tank slurry agitator.

2. Smoke System

Each boiler flue gas systems provided a whole plant a total of two sets.

From the total flue boiler induced draft fan after the drawn flue gas, after the adoption of the original flue gas inlet damper by means of FGD booster fan booster into the flue gas - flue gas heat exchanger to cool, and then enter in the absorber. sulfur removal in the absorption tower, the removal of the spray mist, but also by the smoke - flue gas heat exchanger warmed to above 80 ℃, access to the main power generation projects through net flue damper FGD flue gas outlet means through the chimney into the atmosphere. bypass damper settings on the main power generation projects flues when the boiler starts and FGD equipment failure outage, close the entrance of the original gas flue damper and net gas flue outlet damper open the bypass damper, flue gas stack emissions from the bypass damper.

Setting flue gas heat exchanger (GGH), utilizing the heat of the original flue heating flue net. At design conditions shall ensure that the chimney flue gas inlet temperature not lower than 80? C. Any low load conditions, should ensure that the chimney inlet flue gas temperature is not lower than 70? C.

It is provided on the inlet and outlet flue FGD double louver baffle seal. Fitted with a single flap sealing air in the bypass flue desulfurization system is set at 100% capacity of flue gas bypass flue, when the desulfurization unit operation, bypass flue damper closed on desulfurization device FGD inlet and outlet damper open, flue gas desulfurization by the desulfurization unit. in the desulfurization equipment failure or maintenance, the FGD inlet and outlet damper Close, bypass flue damper to open the flue gas directly into the chimney flue discharge through the shunt. bypass flue damper has a quick start function to ensure that the device is not in an accident FGD outage or maintenance overhaul affecting the normal operation of generating units.

Rotary regenerative flue gas heat exchanger (GGH) each a desulfurization unit, 100% capacity .GGH a seal gas systems, air purge system and high and low pressure water rinsing system.

Flue gas desulphurization booster fan system using axial flow fans with adjustable vanes, each a desulfurization unit, 100% of capacity.

Flue gas desulfurization system inlet and outlet damper double louvered damper with seal air system, air sealing system settings 2 × 100% capacity turbine seal (a one standby), the fan runs desulfurization unit splitting. the sealing medium is air.

3. SO2 absorption system

Each boiler with a set of SO2 absorption system, since the desulfurization equipment supplier has not been determined, Zanan counterflow spray absorber tower design.

Flue gas upwardly through the vertical spray absorber, the absorber upper part of the spray absorption area, which is arranged nozzle layer of limestone slurry circulation pump, calcium sulfite and gypsum slurry into the mixing nozzle atomization , the slurry is atomised downwardly through the SO2 absorber the absorption zone, then a chemical reaction with the flue gas in countercurrent contact are generated after the absorption column into the lower portion of calcium sulfite pulp circulation tank oxidation slurry to the circulating blower oxidation air bubbling pool the oxidation of calcium sulfite, calcium sulfate gypsum slurry circulating through the gypsum slurry tank bottom discharge pumped to the gypsum hydrocyclone station, from the upper portion of the cyclone overflow was out most of the return to the absorber. after washing sulfur removal wet flue gas flue gas with liquid droplets in the upper section of the absorber outlet is equipped with two mist, wet flue gas through mist eliminator to remove most of the flue gas carried in droplets in the flue gas containing droplets amount lower than 70mg / Nm 3. state emissions.

Absorber circulation pump is a centrifugal slurry pump corrosion, every three tower configuration, circulation pump is a unit system, each corresponding to one layer of spray, no on-site backup, two FGD set up a warehouse spare circulation pump impeller for anti-corrosion, abrasion and fouling, which is made of a special metal impeller, the pump housing with replaceable elastic rubber lining.

Oxidation fan with high performance, high efficiency blower, each FGD apparatus is equipped with two 100% capacity of the oxidation air blower, a one standby to ensure that the calcium sulfite forced oxidation air volume required.

4. gypsum dewatering system

Major equipment gypsum dewatering system has swirl concentrator, vacuum belt dehydrating machine, vacuum pumps, belt conveyors, belt dehydrating feed tank and agitator, gypsum washing pump, filtrate collection box and pump, gypsum warehouses.

Gypsum slurry from the absorber reaction tank discharge concentration of only 15 ~ 20% (wt), by absorption tower pump discharge into the cyclone concentrator, a cyclone concentrator column a. Through cyclone concentrator the concentrated the slurry concentration of 45 ~ 55% (wt), into the vacuum belt dehydrating apparatus, after the vacuum belt dehydrating machine dehydrated gypsum containing less than 10% (wt), after dehydration of gypsum plaster by belt conveyor to the stacking cage gypsum gypsum warehouse forklift loading from the plaster after car Sinotrans for comprehensive utilization. hydrocyclone separated the flooding most of the returns absorber recycling. to control ingredient FGD gypsum Cl-, to ensure gypsum quality gypsum dewatering process required for process water and filter cloth rinse plaster gypsum filtered water is collected in the filtrate tank, the filtrate from the limestone slurry is pumped back to the absorber system or return.

This issue of preparing gypsum desulfurization apparatus according to the two sets of desulfurization equipment public a system design set up two vacuum belt dehydrating machine, each run by two dewatering device FGD gypsum discharge amount of 75% design. Each one dewatering machine configuration water ring vacuum pump, a total of two.

Each absorber setting a plaster cyclone concentrator.

Two public a vacuum belt dryer filter cloth washing water tank and flushing water pump systems and filtrate tanks and filtrate pump system.

Two whole plant desulfurization gypsum a public warehouse, the effective volume of gypsum warehouse to meet boiler BMCR conditions yield two gypsum FGD 3 days.

5. process water supply system

Connection of water from the water supply system to the desulfurization Island has two, all the way to industrial water, the other way is the main circulating water industrial water users: mist of water, gypsum is washed with water circulating water main users: the limestone slurry preparation water , flue gas heat exchanger flushing water, water ring vacuum pumps, vacuum belt dehydrating machine, and all the wash water slurry transportation equipment, transmission lines, storage tanks, cooling water booster fan oxide, fans and other equipment and seal water.

Process water supply system is provided a process tank volume of 110m3, two process pumps, an operation of a device. Water is recycled water.

Demister flushing the water system provided a flush tank volume of 60m3, four demister flushing water pump, two, two standby. Water for industrial water.

6. Slurry evacuation and recovery system

The slurry evacuation and recovery system including sump, pump, irrigation system and slurry tank accident.

When the absorber slurry tank maintenance needs emptying the slurry into the tower through the discharge pump slurry tank accident before the absorber is restarted by accident slurry pump slurry tank pumped back to the absorber; a two absorber settings public slurry tank capacity of 1500m3 of accident. when empty the absorber failure or maintenance, temporary storage of gypsum slurry absorber slurry tank accident before the absorber is started again with the return pump into the absorber, the absorber is started again as gypsum seed.

In the area of limestone slurry preparation, absorption regions are provided with a sump shall flush the slurry pipe and FGD slurry pump outage during normal operation, the flushing water collected in the respective sump by pumping to dive accident Back absorber slurry tank or slurry pond.

Limestone slurry sump area provided a total of one.

Each absorber absorber sump provided a total of two.

Desulfurization equipment for sewage discharged into the sewage sewer plant to centralize the sewage treatment station.

Desulfurization unit each bearing cooling water discharged into the island desulfurization process pool, recycling, and not discharged.

7. Wastewater treatment

Wet limestone - gypsum desulfurization process for an external system to emit a certain amount of waste water to reduce the concentration of soluble ions absorb the slurry (such as Cl-, Mg2 +, etc.).

The project wet desulfurization system, a total of two units of automatic control of the integrated waste water treatment system. Wastewater system consists of waste water collection tank, PH adjustment tank, reaction tank, condensation tank, clarified concentrated boxes and other components, integrated processing capacity to 30m3 / h. gypsum dewatering plant for waste water through a pipe to the desulfurization wastewater collection tank, and then sent to PH adjustment tank by a wastewater collection tank, and adding lime therein wastewater PH adjusted to 9 to 10, and then by gravity into the reaction tank, filling or Na2S organic sulfur in the reaction chamber, heavy metal and sulfide ions state chemical reaction to produce small complex, and then condensed into the gravity tank, adding coagulant in the coagulation tank, so small complexes grow into larger floc, and then condensed in the outlet box coagulant is added to generate a larger floc, and finally into the box clarified concentrated in clarified concentrated floc tank by gravity and water separated denser slurry settled at the bottom of the tank to become clarified concentrated concentrated sludge, most of the low density clarified water through the overflow tank back to the net, by acid treatment, the PH value is adjusted to 6 to 9 rows the main power generation system drainage system, while a small portion is returned through the thick paste pumped to PH adjustment tank, as the next batch of "seed."

Desulfurization equipment sewage discharged into domestic sewage treatment plant for centralized treatment.

Each bearing desulfurization plant cooling water into the cooling water return pipe, and not discharged.

Desulfurization venue flushing water and a variety of miscellaneous water drainage into the waste water treatment system.

8. Instrument / Utility Air System

Power compressor system does not provide high-quality instrument desulfurization island with compressed air, the island desulfurization set up a separate compressor stations, oil-free to the desulfurization apparatus pneumatic instruments, valves, control equipment and maintenance, and other thermal instrumentation , clean, dry compressed air.

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