JPS58139725A - Method for controlling basicity in stack gas desulfurization process using basic aluminum sulfate - Google Patents

Abstract

PURPOSE:To reduce an amt. of basic aluminum sulfate to be used remarkably, by digitally grasping data on characteristics of a stack gas and operation states of absorption, oxidation, and neutralization steps, using the data and controlling them, and always maintaining stable operation. CONSTITUTION:An aq. soln. of basic aluminum sulfate (b) is delivered from an absorbing tower 1 through a tank 1' for an intermediate pump to an oxidation tower 2, and during the stay in the tank 1' its basicity is analyzed. This value is used as basicity control data; a digital value of a process state value is thus grasped, and it is fed to each calculation formula corresponding to each step to excute calculation. The results including time lag of control and preestimation of variation of the steps are obtained as set values to control air feed rate to the tower 2 and CaCO3 slurry feed rate to a neutralization vessel 3. In addition, a flow rate F of a stack gas (a) entering the tower 1 and its SOx content S are measured in an operator section 7.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for controlling aluminum sulfate/water/base formation in flue gas desulfurization using basic aluminum sulfate.

Basic aluminum sulfate 9M aqueous solution (hereinafter simply "aluminum liquid")
)? The flue gas desulfurization process to be used will be explained with reference to the diagram 141, where 1 is an absorption tower and 2 is an oxidation tower.

In addition, 3 is neutralization, which refers to flue gas or flue gas from boilers, etc. b)) (absorption process).

Next, this aluminum is fed from the absorption tower 1 through one relay pump tank to the TrR conversion tower 2Kfs, and is oxidized by 9 gas (c) in the oxidation process. , #The majority of the aluminum liquid is returned to the absorption tower 1 from the pipe 1, or is sent to the neutralization tank 3 via the pipe 21 to -S.
A neutralization step is carried out to restore and improve the basicity of the aluminum liquid by neutralizing it with calcium carbonate slurry (hereinafter referred to as "charcoal") supplied separately.

On the other hand, in the above, 1'[4 Al f*( taken out from Hinoki cypress 3)
(b) is separated into six noble molecules in a plaster-fan filter 4, and is returned to the relay tank 1' through five overflow tanks.

Therefore, the conventional aluminum liquid (b) base 1L neutralization tank 3
is created at the exit of
o Because it controls the supply tr.

Take this opportunity to circulate! The neutralization tank, oxidation tower, etc. 11 are large compared to the illumination, and the dead time and first-order delay are significant. Since the base If in (b) changes in a relatively large time cycle, it is difficult to achieve stable πrA node control, and conventional analog control requires 114 @ calculations. , a correction circuit R was required, which was expensive and impractical. (Partial examination of the points in Figure 1) In consideration of this situation, the basicity of Aluminum Q (B) was added to the upper string relay tank 1 in the original 8A. Incorporate measurement f # 傅 n.

In the darkness where 1 tank of aluminum liquid accumulates, the base l
By measuring N1r and using it as data for basicity control as the concentration at the outlet of neutralization tank 1, as described later.

Grasp the process status problem using digital numerical values (data), input it into calculation formulas according to each process characteristic, calculate it, and incorporate control time delays and process variation forecasts. The result is calculated as a set value, and the amount of air supplied to the oxidation tower 2 and the amount of coal carbon slurry supplied to the neutralization tank are controlled.

Hereinafter, the structure of the present invention will be described in more detail according to one embodiment, as shown in FIGS. 2 and 3.

The flow rate (I) of the flue gas entering the absorption tower 1 and its sulfur oxidation removal M ratio (Si, S) are measured in the calculation unit 7, and based on the values, for example, the first-order sequence calculation formulas ■ to ■ Performance I
Perform 4V.

■8iii performance Jt0・a, @= a x s/loo
x Shishi 2.4゜s@: kg-mol/'H', G:
Inlet gas fit (IJH"Al1: Artificial sulfur oxidation force (801 conversion) (container) ■ Moving average...Xo==
←NII, N: Number of samples L: Dead time, T: Time constant
Given that Oa=Charcoal Cal, the calculation results of the above 1■~■ are Al#? 1k (ro)
The distance between the mound if at the exit of the middle 8IOta and the durability setting chest, or the a8 where the coal cal supply is slurry, is determined by actual measurements from the samurai f.
Input the coal cal slurry concentration and the coal cal slurry concentration into the calculation formula for the required coal cal amount in the above V■ for the neutralization tank 3V, calculate the coal cal slurry I) - supply -t + - and then The control valve 94C automatically controls the flow rate 10r based on the actual measured value of the coal slurry supply lid.

Also, the same goes for controlling the amount of air to #other column 2 A:8
x 22.4 x l/2 x 110x efficiency x FX
However, please note that L/L is calculated based on the required air volume and F2 safety factor.

As is already clear from the above results, in the conventional flue gas desulfurization system using base-injected aluminum, control of the basicity of the aluminum liquid has a large effect on the desulfurization effect.
Anap from simple data on basicity around the neutralization tank
In the present invention, the data are digitally controlled including the characteristic values of the flue gas itself and the process condition target values in the absorption, #M conversion, and neutralization processes (characteristic values, state values) Y
Since it can be grasped and controlled, it is possible to constantly rc-stabilize π control, and the aluminum four-wheel assembly is significantly reduced, and the , 1st chapter, 11th chapter, 11th chapter, 1st death, 11 years ago, it is a beneficial invention.

[Brief explanation of the drawing]

Figure 1 shows the conventional base 1f? System diagram in J method rc,
FIG. 2 is a system diagram of the method of the present invention, and FIG. 3 is a block diagram thereof. In Figure 1, 1...Absorption tower, 2...Oxidation tower, 3...Neutralization tank, 4...Ishikano? Ia device, 5... oats (-
Flow tank, 6@... f14m meter, 7... Φ811 calculation unit. 8・Kai Tancal Performance JK Miyako, 9...-Setsube, 10...
) (Rube. Above % allowed - Person Dowa Koei Co., Ltd. Agent Patent attorney Kazuo Ohara

Claims (1)

[Claims] 1. In the flue gas desulfurization method using basic aluminum sulfate, the basic aluminum sulfate aqueous solution absorption step and neutralization step are controlled by V'C-1, flue gas flow rate, and yellow oxide. The sulfur oxide load amount r depending on the content of
Calculation and input are performed, and the signals are used to automatically adjust and manage the supply amount of 9 gas in the oxidation process yt and the calcium carbonate supply in the neutralization process rc. Cardiac basicity control method in the law.