WHAT IS THE RECOVERY BOILER?

Definition Recovery Boiler

Recovery Boiler A boiler is a special unit used to purify the compound - an organic chemical compounds contained in Black Liquor (waste cooking from the digester) and at the same time as high-pressure steam generator (High Pressure Steam).

Heavy Black Liquor (70% solid) containing:

An organic compound with the main content of Na2CO3, Na2SO4, NaOH, Na2S.
Organic compounds derived from wood during cooking in the digester in the form of wood fibers, ligmin
Water
Heat energy contained in the Heavy Black Liquor range 3100 - 3500 kcal / kg dry solid.
Heat energy is partly used to convert the organic compounds and partly used as fuel to generate steam
Heavy Black Liquor Evaporator Vacuum produced by the input to the Mixing Tank, in the mixing tank mixed with combustion ash from ESP (Electrostatic precipitator) and-1 from the economizer, economizer-2, Boiler Bank, then added with salt cake (Na2SO4 powder).
Once mixed in the Mixing Tank, Heavy Black Liquor (HBL) is sprayed into the furnace to burn through the spray gun. Prior to the furnace going process of drying by blowing hot air, then collects in the bottom of the furnace to form charbed and caught fire after reaching the point of combustion.
Combustion air needs exhaled through the Primary, Secondary and Tertiary wind boxes located around the bottom of the furnace wall.

To start combustion in the furnace as well as to stabilize the combustion conditions, use of diesel fuel is sprayed through a burner into the furnace.
During combustion, the following process takes place in the furnace are:
1. The compound - organic compound burning releases heat and partly turned into a gas.
2. Sodium sulphate (Na2SO4) contained in the HBL and the salt cake is reduced to a compound of sodium sulphite (Na2S)
Na2SO4 + 2C + 2 Co2 Ns2S
The speed reduction is calculated:
Reduction Rate: Na2S. X 100%
Na2S + Na2SO4
3. The compound - an organic compound called Smelt melt like lava.
If the conditions of combustion is complete, reduction rate reached> 95%
A melt of organic chemicals (smelt) will accumulate around the side charbed smelt spout and flow out into the dissolving tank, where in the dissolving tank, smelt will be dissolved with WLL (WEAK White Liquor) from RC, the mixture of smelt with the WLL-called Green liquor (GL) which is pumped from the dissolving tank RB to RC section for the Recausticyzing be WL (White Liquor) or cooking liquor
For reuse as raw wood cooking in digester (Pulp Making Section)

Time of air and gases - gases of combustion, called flue gas still contains a high amount of heat Energy.
Flue gas is inhaled / drawn by a device called the Induced Draft Fan (IDF), where the flue gas will pass through the pipe - boiler pipe so that water contained in boiler piping briefly - of land become heated and turned into high-pressure steam will then be used for the propulsion of Turbine Generator to generate electrical energy.
So the production side of the Recovery Boiler is STEAM high pressure (60 bar)

Smelt Reduction Efficiency:
Na2SO4 + 2C + Heat ----- Na2S + 2CO2
SRE = Na2S/Na2S + Na2SO4 x 100%
Recauticizing
--- CaO + H2O Ca (OH) 2
Ca (OH) 2 + Na2CO3 --- 2NaOH + CaCO3
CaCO3 + Heat ----- CaO + CO2

History of Recovery Boiler

Kraft Porridge was first developed in Germany in 1870's, in a strong sense in Germany: kraft pulp fiber slurry to produce hard at a short maturation process.
Addition of Na2SO4 will be accelerated with delignification process without reducing the strength of pulp fibers.
Pulp first made in 1909 in the city Roanake Rapids, North Carolina, kraft pulp growing popularity, in 1930 to found the Recovery Boiler is made more economical kraft pulp.
Today kraft pulp about 70% is produced in America.

Feed Water to Steam Cycle Recovery Boiler 6
Demineralizer water (steam PG) Feed Water Tanks economizer economizer 1 2 Dolezal (to RB & RB-6-12) Steam drum bottom of steam drum to the boiler wall piping, furnaces & Steam Boiler drum bank top to the screen tube Primary Secondary superheater superheater Tertiary superheater steam to the turbine generator.

Park Pressure Recovery Boiler
1. Furnace site of a combustion process HBL
2. Superheater is placed over the furnace, and the screen is protected with a nose tube.

Nose is designed to produce flue gas flow pressure of a strong and directed to the superheater, as well as to protect the superheater from the excess. Then superheater which comes from the furnace to the superheater. This event continues from primary superheater, secondary and tertiary superheater superheater.
3. Screen Tube
To avoid direct heat flue gas coming from the furnace to the superheater and the lower the temperature of the furnace by means used by the screen tube.
4. Boiler Bank
Its location is situated behind the superheater.
5. Economizer
Economizer economizer consists of 1 & 2 is the long stream counter flow between the flow of flue gas and feed water

Factors Supporting Recovery Boiler

1. Soot Blowing System
Aims to bring down the soot blowers or clean ash piping attached to the inside of the boiler (superheater, boiler bank, economizer).
RB-6, has 86 sets Sootblower (43 to the left, 43 top right)
2. Medium Pressure Steam
For Air preheater, start-up burner, smelt spout steam shuttering.
3. Low Pressure Steam
For water preheater
4. Condensate
5. Electrostatic precipitator (ESP)
Each RB must be equipped with ESP which is useful for capturing particles - solid particles contained in the flue gas further solid particles (ash) is returned to the mixing tank to be mixed with HBL
RB-5 Equipped with 2 sets ESP
RB-6 & 12 are equipped with 3 sets ESP
RB-11 is equipped with 4 sets ESP

Recovery Boiler is also equipped with security system

1. Interlock System
This system serves to prevent damage in case of irregularities Boiler operating conditions.
2. Safety Valve
This tool serves to keep the boiler pressure does not exceed the limits specified security pressures.
3. Rappid Drain System.
This system serves to empty the water boiler to a minimum label, if there is a severe leakage in the piping boiler causing water to enter into the furnace.
This system operated at the time of emergency and went so fast for Boilers avoid further damage.

RB Quality Control

1. Demineralizer Water Conductivity pH 6.0 ~ 8.0 <5.0 ms / cm 2. Feed Water Conductivity pH 8.0 ~ 9.5 <5.0 ms / cm SiO2 <40.0 ~ 50.0 ppb 10.0 ppb N2H4 3. Boiler water pH 9.5 ~ 10.5 Conductivity <150.0 mx / cm PO4 2.0 ~ 12.0 ppm SiO2 <3:50 ppm 4. Saturated Steam Conductivity pH 7.5 ~ 9.5 <5.0 ms / cm SiO2 <40.0 ppb 5. Steam superheater Conductivity pH 7.5 ~ 9.5 <5.0 mx / cm SiO2 <40.0 ppb 6. Green Liquor NaOH 12.0 ~ 20.0 g / l Na2S 25.0 ~ 35.0 g / l Na2CO3 70.0 ~ 85.0 g / l TSS <1500 ppm 7. Smelt Reduction rate> 95.0%.see also previous article"How does a power plant boiler work?".