JPS59230622A - Seed crystal slurry supply method in waste gas desulfurization apparatus due to wet lime gypsum method - Google Patents

Abstract

PURPOSE:To prevent the scale adhesion in a washing apparatus, by constantly controlling the CaSO4-concn. in the washing liquid in a washing apparatus by measuring the flow amount of exhaust gas, the O2-concn. in the gas emitting from an oxidation apparatus, the flow amount of a washing liquid to the oxidation apparatus and the supply amount of a seed crystal slurry to the washing apparatus. CONSTITUTION:An exhaust gas flow amount G measured by a flow meter is inputted to an amplifier 25 and the O2-concn. in the gas emitting from an oxidation apparatus 5 measure by a densitometer 21 is inputted to a function generator 2. The withdrawing flow amount F of a wshing liquid to the oxidation apparatus 5 from a washing apparatus 3 and the flow amount F' of a seed crystal 3 from the oxidation apparatus 5 are inputted to a subtractor 33. The CaSO4-concn. of the washing liquid is calculated by the obtained values and the flow amount of the seed crystal slurry in an arranged pipe 6 is manipulated through a controller 29 by the CaSO4-concn. signal. If the set value of the controller 29 is set to a predetermined amount or more of a CaSO4-concn. generating no scale, scale is not generated under any operational condition.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling a wet flue gas desulfurization device that removes sulfur oxides (hereinafter referred to as SOx) contained in flue gas using carbonate (hereinafter referred to as CaCO).

In the desulfurization method that removes SOx from flue gas using a slurry of Ca(OH) or 1l-iCaCO, the gypsum produced in the flue gas scrubber i'f (hereinafter referred to as scrubber) is removed from the inside of the scrubber. There is a difficult problem of scale build-up, and countermeasures against scale problems are the most important technological factor. As a countermeasure against this scale problem, by adding seed crystal gypsum slurry to the scrubber's liquid (A), the gypsum generated in the scrubber can be removed from the crystal surface of the seed crystal gypsum. -11 has the anti-scaling effect of preventing precipitation inside the scrubber by allowing it to precipitate and grow.
-Always an excellent countermeasure and widely put into practical use)1.

The present invention11. This invention is an invention that provides a method for controlling the cleaning supply, which is an important technical factor for preventing school troubles in the scrubber.

In the method of removing SOX in flue gas using Ca(OH) or CaCO5 slurry, calcium sulfite (hereinafter referred to as Ca503) and calcium sulfate (hereinafter referred to as C) are added to the cleaning solution.
It is a well-known fact that a5O,) is produced, and since both have low solubility, most of them precipitate in the same phase and are suspended in the liquid.

The scale trouble in the conventional example will be explained in more detail below.

Figure 1 illustrates the flow of a conventional method.

For example, gas from a coal-fired boiler is introduced into the scrubber 3 through the exhaust gas inlet duct 1.

At the inlet of scrubber 3, it is cooled by the washing process.

Dust is removed. Of course, there is also a conventionally known method in which the exhaust gas is cooled and dust removed using a separate cooling and dust removal device before entering the scrubber, and the present invention can be applied in the same manner. Due to the cooling of the exhaust gas, some of the water in the washing liquid evaporates, but it is replenished by the make-as-so water 2. Subsequently, the Jdl gas is further cooled and dust removed in the main body of the scrubber 3, and at the same time, the SOx in the waste gas is absorbed into the cleaning liquid.

The reaction when CaC0,f is used for absorption is as follows.

, -1- CaSO, 10 So2+H, O→Ca +2H8O,'
(a) ISO, -44o2 →H→-so,'-(
b) Ca""10So, " -+Ca5O, (c)C
aCO, +H3O, +H'-→Ca5O, →-f(, O
→−CO2(d)S03 tH20→2H1So,”
(e) That is, 1 C generated by the scrubber
aSO3 becomes Ca 2″- and H2O3 in equation (a) with absorbed so, but this H3O3- -rrli N:
It is oxidized by O3 in the 411 gas and becomes H'-1-So, 2-, as shown in formula (b).

father, ISO, and ■] are 411 in the absorbed CaCO3, and as shown in equation (d), Ca5O, and I
(,0 and Ca2, and CO2 is dissipated into the gas.The generated Ca'' and SO1'- are
As shown in formula (C), Ca5O, and Ca5
Like O, it precipitates in the solid phase.

Note that the production ratio of Ca5O and CaSO3 is determined by the amount of So,2- produced by C9 in the exhaust gas.

The cleaning liquid is constantly supplied from the circulation pipe 4 by the circulation pump 18, and the CaC0 and concentration f in the cleaning liquid are kept constant. A portion of the cleaning liquid is sent to the oxidizer 5 through a pipe 9. This amount of extraction is controlled by a level controller 11 and a control valve 12 so as to keep the cleaning liquid level in the scrubber 3 constant. In the oxidizer 5, air or a gas containing oxygen is supplied through a pipe 7, and oxidizes CaSO3 in the cleaning liquid extracted from the scrubber 3 to generate Ca5O. At this time, oxygen in the air or oxygen-containing gas is consumed in proportion to the amount of Ca5O in the extracted slurry. A flow rate adjustment side 19 and a control valve 20 are provided on the open side 1 so that the flow rate of gas containing air or oxygen is constant. Also, used air or gas containing oxygen is taken out from the oxidizer ii 5 through a pipe 10. In the oxidizer 5, Ca5O in the slurry is oxidized and most of the solid phase becomes Ca5O. A part of the slurry is supplied as V1 seed crystal slurry to the scrubber 3 through the pipe 6, and (k and f) in the liquid The production of Ca5O is increasing. Note that the seed crystal slurry flow rate is controlled by a flow rate controller 14 and a control valve 15 so as to be constant. In addition, a novel adjustment valve 116 and a regulating valve 17 are provided so that the cleaning liquid in the oxidizer 5 is kept constant.
The flow rate of the slurry extracted from the piping 8 is completely controlled.

As mentioned earlier, in order to prevent scale buildup in the scrubber, there are 4!1! crystal concentration, i.e. gypsum (CaS
It is necessary to maintain the concentration below a predetermined concentration. Seed crystal slurry is supplied to the scrubber 3 by washing inside the scrubber 3/4)
It has the effect of increasing the concentration of Ca5O in the liquid. However,
In the conventional method, seed crystal slurry flow; There was a danger that once the gas was under the board, scale would adhere.
When the 1 concentration decreases, the amount of so and 2- produced decreases, so the generation of Ca5O, in the scrubber 3 decreases, and conversely, the generation of Ca5O, increases. C in this useless scrubber 3
Since the concentration of a5O becomes smaller, it is possible that the concentration becomes lower than the predetermined concentration. The present invention has been developed with the aim of correcting the above-mentioned drawbacks of the conventional method, and by controlling the concentration of Ca5O in the cleaning liquid in the scrubber to a constant level, the concentration of Ca5O in the cleaning liquid in the scrubber can be maintained at a predetermined concentration under any operating conditions. This can prevent scale E J' 17 in the scrubber.

Hereinafter, the present invention will be explained in more detail at 111 based on the drawings.

FIG. 2 is an illustration of two embodiments of the present invention. The principle of measuring the concentration of Ca5O in the cleaning liquid in the Zuzu scrubber will be explained. Sulfur oxides absorbed from exhaust gas: [;
, becomes (Equation 11).

Δs = G+yso, ・ηso, -(1) However, here ΔS is the amount of sulfur oxide absorbed (kgmo I
/H) G @ Jl [Gas amount (kgmol/H,]
r VBOs is immature*114'Irvine yellow oxide □i in JJ1 gas, ') so2 indicates desulfurization rate [-]. The sulfur compounds supplied to the cleaning device 3 include (1) seed crystal slurry supplied from the pipe 6 in addition to (1) 2; Further, the washing alkaline liquid extracted from the scrubber 3 is only from the pipe 9, and the sulfur compound extracted is t? As mentioned in f+, Ca5
O, and Ca5O.

Therefore, in a static state, from the material balance (27
The relationship of the formula holds true.

ΔS toF' [Ca5O, 1=F((:Ca5O
,]+(CaSO,]) -12-1:Ca5O,)
'=l: Ca5O, ) + [Ca5O,] Song - (2 Dotashi Jinko, F is the extraction flow rate of pipe 9 Cn?/H']
.

[Ca5O,] is 61] Ca5O in purified liquid, molar concentration [
: kgmol/nI′]+[Ca5O,] i,
j a (Ca5O in '4+ liquid, molar concentration 1: kgm
o l/n? ] rF' is the seed crystal slurry flow rate 61/
/H), [:Ca5O,]' seed crystal seed straw Ca5
O, concentration [kgmol/m']? :show. Even if Ca5O is oxidized to Ca5O in the oxidizer 5.

Since the total as a sulfur compound does not change, it can be seen that the formula =' holds true.

Next, the pipe 1o of the oxidizer 5 is filled with air or oxygen-containing gas after use. The following relationship exists between the concentration and the molar concentration of Ca5Os in the cleaning solution. The explanation will be given assuming that the oxidizing gas in the oxidizing device ξ5 is air. The amount Z (kgmol/H) of Ca5O in the slurry flowing into the oxidizer 5 through the pipe 9 is oxidized to become Ca5O in the molar ratio 5.

Since half of the amount of oxidized Ca5O is sufficient, equation (4) is obtained.

Z'=42=-i"y"F"(CaSO,)'-'+4
1 On the other hand, the air flow i3 supplied to the oxidizer 5 from the pipe 7
．． Fair (kgmol/H) + oxygen concentration χ1 (
−), the amount of oxygen supplied A (kgmol/H)
is (5-inch type).

A=Fair・χ, −・・−(5)(4
1. From equation (5), the amount of oxygen coming out of the pipe 10 A'(k
grno l/H) is expressed as equation (6).

1, + A'=A-Z'=Fair・χ1-7aF・[CaSO
3] (6) The oxidizer 5 consumes only oxygen and does not extinguish other gases by 1ψ, so the i-, t-c (kgmol/H) of the other gases other than oxygen are determined by the pipe 7. The amount is the same for piping 10.

(:=Fair(]−χ, )
-=171 O26n IWχ2(-) at pipe 10 is (
8) becomes the equation χ・−8・+c゛°゛(8) (6) , ('If 71 people are combined, the equation (9) becomes.

Transforming equation (9) into the equation for calculating [Ca5O,], (
l[0. The relationship between the concentration and the concentration of Ca5O in the cleaning solution is interesting.

(1) (2) Ca5 in the cleaning solution from the t2J”00 formula
O, 21 degrees is determined by formula 00.

In formula 09, when the sulfur content in the fuel of the boiler that generates exhaust gas is constant, so, p degree yso, in the exhaust gas are almost constant, 1 Normal desulfurization rate ηso, i is operated so as to be constant. It can be considered constant. Furthermore, since the air flow rate of the pipe 7 is controlled, it is assumed to be constant, and the 1 yen conversion rate α is also constant. air o
2 concentration χ1 is fairly constant. From the above, the QlJ formula including all two constant parts becomes the 02 formula.

However, K,=yso−ηs O2”””α32°
1゛°""・-7' ...... 斡f(χ,)=α 1-χ2 (~According to formula 03, the exhaust gas flow rate G, the 0.IA suction of the used air in the pipe 10, χ7. By measuring the extraction cleaning liquid flow ii, F in the pipe 9 and the seed crystal slurry flow rate F' in the pipe 6, it can be seen that the (:aSO, concentration) of the cleaning liquid in the scrubber is determined. The flow rate of the seed crystal slurry can be adjusted to adjust the flow rate of the seed crystal slurry.

This will be explained in detail with reference to FIG.

The flow rate side 24 is installed in the exhaust gas artificial duct 1, and the waste flow is
The gas flow rate signal is input to the amplifier 25 and amplified seven times. In addition, the valence shown in formula 03 is set.

An O2 concentration filter 21 is installed in the pipe 10, and the O2 concentration level is set to 0. The concentration χ2 is sub>il l-, and this 02'IA degree signal is manually inputted to the number generator 22.
All the functions that occur in f(χ,) shown in the Φ equation are embedded and sheared. Install flow 1ii3127 in pipe 9 and extract flow rate F
A flowmeter 32 is installed in the cut pipe 6 to measure the seed crystal slurry flow rate F'. Subtractor ■3 for these two flow rate signals
3, and input the output signal of the amplifier 25 and the output signal of the MiJ subtracter 33 to the II circuit 34. moreover,
The output signal of the function generator 22 and the flow rate signal of the flow meter 27 are input to a divider 28. The output signal of the divider 34 and the output signal of the divider 28 are input to the total reducer 26.

The output signal υ of the subtracter 26 represents the value on the right side of the O2 equation. Therefore +! j'Jki decrease vessel ■26
The output signal is equivalent to the Ca5O concentration of the cleaning solution. Output signal of the music reduction device 26 “i k adjustment word 129”
The seed crystal slurry view in the pipe 6 is controlled by the output signal of the adjustment 129. When operating the seed crystal slurry flow rate, the flow rate controller 14 and the control valve 15 fully control the seed crystal slurry flow as shown in Fig. Either a cascade coupling method in which the change is made by the output signal of the controller 29, or a method in which the control valve 15 is not operated by the output signal of the controller 28 may be used. Said adjustment side 2
If the setting value of 9 is set to a certain predetermined amount or more at which scale does not occur, Ca50.1jkD3- is set.

Under any operating conditions, the cleaning concentration is maintained at a predetermined level or higher, and scale does not occur.

Hereinafter, the present invention has been specifically explained based on one embodiment. However, the present invention is not limited to this embodiment, and the point is that the exhaust gas flow rate and the air or oxygen discharged from the oxidizer are Measure four items: the O1 concentration in the gas contained, the flow rate of the cleaning liquid extracted from the cleaning device and introduced into the oxidation device, and the flow rate of the seed crystal slurry supplied from the oxidation device to the cleaning device, perform the calculation shown in formula 04, and calculate the multiplication result. Any method may be used as long as the flow rate of the seed crystal slurry supplied from the oxidizing device to the cleaning device is controlled to be constant. For example, the calculation shown in equation 02 may be performed by an electronic computer. Great, the seed crystal slurry flowmeter 32 is the seed crystal slurry flow 1! +, Separate from the controller 14, there is a type 1 crystal slurry flow rate adjustment J meter 14 swords/ra'! Il [additional 1g
The seed crystal slurry flowmeter 32 may be omitted if the structure is such that the number can be outputted.

From this more structured VC, the present invention has the advantage of being able to control Ca5O, a1 & k in the cleaning liquid inside the scrubber to a constant level, and completely preventing the accumulation of scale inside the scrubber. do.

[Brief explanation of drawings]

FIG. 1 is an illustrative diagram of an example of a conventional flue gas desulfurization device;
FIG. 2 is an illustrative diagram of an example of an embodiment of j that emits zero. 1... Exhaust gas inlet duct, 2... Make-up water. 3...Scrubber, 4...Circulation piping, 5...Oxidizer. 6, 7, 3.9.10...Piping, 11.16...Level adjustment needle. 1 2, 1. 5. 1 7. 2 0
... g4 section square, 14.19 ... @
W2 ta meter, 18...circulation pump, 13...e
, collected supply line, 21... O1 concentration meter, 22...
Function generator. 24...Gas flow meter, 25...Amplifier, 33.26
... Subtractor, 28.34 ... Divider, 29 ... Adjustment fj'r +27.32 ... Express the fluid force ゛1゜ Fig. 1

Claims (1)

[Claims] A wet flue gas treatment device that cleans flue gas and removes sulfur oxides from the flue gas using a slurry containing all of cal/rum hydroxide and/or caloonium carbonate. Part or all of the cleaning liquid is extracted and introduced into an oxidizer that supplies air or oxygen-containing gas to oxidize it, and removes it from the exhaust gas:
, a method in which after oxidizing the sulfur oxides absorbed in the acid solution, a part of the gypsum slurry is again supplied to the cleaning device as a seed crystal slurry, in which the sulfur gas is r, -iI+
2. Measure the gas flow rate signal and input it to the amplifier. −
Measure the amount of oxygen in the spent air or gas containing spent oxygen coming out of the oxidizer. The oxygen concentration signal is inputted to a function generator that generates a preset function, and the flow rate of the cleaning liquid extracted from the cleaning device and introduced into the oxidation device and the seed crystal slurry supplied from the oxidation device to the cleaning device are The cleaning liquid flow rate signal and the seed crystal slurry flow rate signal are input to a subtracter, the amplifier output signal and the output signal of the subtracter (2) are input to a divider (2), and the output of the function generator is The signal and the cleaning liquid flow rate signal are input to the divider (2), the output signal of the divider (2) and the output signal of the divider (2) are input to the subtracter (2), the output signal of the subtractor (2) is taken as the control amount, and the A method for supplying seed crystal slurry in a wet lime-gypsum flue gas desulfurization system, characterized in that the flow rate of seed crystal slurry supplied from the oxidizing device to the cleaning device is used as a manipulated variable to control the output signal value of the subtractor (1) to a constant value.