CN1869685A - Investigating method for lime activity and its analysing system - Google Patents

Abstract

The invention discloses a limestone activity testing method and the analysis system thereof, making limestone pulp directly react with SO2 fume, simulating actual desulfation course, and reflecting limestone activity by measuring SO2 removal ratio, where the higher the SO2 removal ratio is, the better the limestone activity is and vice versa. And the analysis system mainly comprises limestone pulp tank, pulp pump, absorption tower, gas steel cylinder, gas flow controller, limestone pump recover tank and pulp flow controller. And the invention can truly reflect limestone activity and reduce investment and operating cost. And the method is simple, effective and easy to implement, and able to accurately evaluate limestone activity and provides theoretical basis for fume desulfation engineering.

Description

Limestone activity test method and analysis system thereof

Technical Field

The invention relates to a detection technology applied to a flue gas desulfurization process, which is used for guiding the design and optimization of a flue gas desulfurization system. Belongs to the technical field of flue gas desulfurization.

Background

With the rapid and continuous development of economy, the atmosphere is SO-coated₂Severe contamination conditions are becoming more and more pronounced. Such as Chinese SO₂The emission reaches more than 2000 million tons and becomes the world SO₂The first major country of discharge. Flue Gas Desulfurization (FGD) of coal-fired boilers is the only current large-scale SO reduction₂The route of emissions, limestone/gypsum Wet Flue Gas Desulfurization (WFGD) dominates in this technology. In WFGD, limestone slurry is used as SO₂Absorbent of (2) when SO₂At the same concentration, the absorption rate is determined by the dissolution characteristics of the limestone. The activity of the limestone comprehensively reflects the capability of the limestone for absorbing sulfur dioxide, so that the activity of the limestone has important significance on the desulfurization efficiency and the design of a desulfurization system.

In the design of flue gas desulfurization engineering, the pulping capacity of a pulping system is often designed according to the activity of limestone, and if the design capacity is too large, the waste of resources is caused; the design capability is too small to meet the requirement of desulfurization. When the pulping system of each power plant in China is designed at present, the pulping capacity is designed to be large for the sake of insurance due to the facts that the activity of limestone is not deeply solved and the test is inaccurate, and therefore unnecessary investment is caused.

The activity of limestone is an important parameter for evaluating the desulfurization efficiency in the flue gas desulfurization process. At present, tests for limestone activity at home and abroad are almost based on acid drop, a small amount of limestone samples are quickly analyzed in a laboratory, and a system test device is not provided; more mature developments were made by the AEE company as an automatic titrator, which was also built on an acid titration basis. However, the reaction mechanism of acid titration is different from that of the actual desulfurization process, so the test result of the acid titration cannot provide reference for problems in the engineeringoperation process.

At present, no complete and unified limestone activity test standard exists in China, all manufacturers establish test standards and experimental methods according to specific desulfurization equipment and referring to foreign related methods, and the standards are not universal and inconsistent. The existing method for testing the activity of limestone in China is ' standard of the power industry of the people's republic of China ' DL/T943 (the determination of limestone powder reaction rate for wet flue gas desulfurization), which is implemented in the power industry from 6 to 1 of 2005. The method needs to accurately analyze the components of the limestone, considers that the reactivities of calcium carbonate and magnesium carbonate in the limestone and hydrochloric acid are the same, and if the limestone component analysis has errors, the significance of the measurement result is not large, so that the actual application is less. At present, the AEE test method is used mostly at home and abroad. The method has the advantages that the method is simple to operate and rapid to detect; the disadvantage is that the reaction mechanism is different from the actual desulfurization process, and the activity of limestone cannot be correctly reflected. The limestone activity test method and device are key technologies for evaluating the activity of limestone on the desulfurization efficiency and the design of a desulfurization system. Therefore, it is necessary to find a simulation device which is simple, safe and similar to the actual engineering.

Disclosure of Invention

Aiming at the defects of the existing limestone activity titration experimental device, the invention aims to provide a method which can simulate the actual flue gas desulfurization process and can evaluate the limestone activity more accurately.

It is another object of the present invention to provide an analytical system for carrying out the above method.

The purpose of the invention is realized as follows: the limestone activity test method is characterized by comprising the following steps: mixing limestone slurry with SO₂The flue gas directly reacts to simulate the actual desulfurization process and measure SO₂The removal rate of (A) reflects the activity of limestone, SO₂The higher the removal rate, the better the limestone activity; SO (SO)₂The lower the removal rate, the poorer the limestone activity.

The method comprises the following specific steps:

A. test preparation

(1) Grinding limestone to be analyzed into 250-mesh powder;

(2) preparing limestone slurry with the slurry proportion of 5% (weight to volume);

B. test procedure

(1) Simulating flue gas and flow control, and regulating N by pressure reducing valve₂，CO₂，O₂And SO₂The gas flow rate;

(2) starting a temperature controller, and setting the temperature of the flue gas to be about 135 ℃;

(3) placing the prepared limestone slurry into a slurry pool, maintaining the temperature of the limestone slurry at about 50 ℃, and keeping stirring to prevent limestone particles in the limestone slurry from settling;

(4) starting a slurry pump, controlling the flow to be 20L/h, starting a pH controller, and adjusting the pH value in the slurry tank; when the pH is not adjusted, the pH can be saved; and recording SO in the absorbed tail gas₂And (4) and finally analyzing.

The limestone activity test analysis system for realizing the method comprises a limestone slurry pool, a slurry pump, an absorption tower, a gas steel cylinder, a gas flow controller, a limestone slurry recovery pool and a slurry flow controller; the slurry tank is communicated with a main pipe inlet at the top of the absorption tower through a pipeline, a slurry pump and a slurry flow controller, the main pipe is provided with the slurry flow controller which is communicated with the absorption tower, and an outlet at the bottom of the absorption tower is communicated with a limestone slurry recovery tank; the downstream absorption end part of the absorption tower is connected with a flue gas temperature controller; the countercurrent absorption end part of the absorption tower is connected with a gas analyzer through a data measurement port; the simulated flue gas of the gas steel cylinder is introduced into a flue gas temperature controller through a gas flow controller; and the limestone slurry pool and the limestone slurry recovery pool are internally provided with a stirring device and a constant temperature device.

Furthermore, a pH controller is arranged between the limestone slurry pool and the limestone slurry recovery pool.

The method of the invention is mainly characterized in the following aspects:

(1) comprehensively considers the properties of various aspects such as the components, impurities, structures and the like of the limestone to the SO₂The effect of absorption;

(2) the absorption reaction conditions are very close to the actual industrial process, and the activity of limestone is truly reflected;

(3) the method is adopted to analyze the activity of the limestone, which is not only beneficial to selecting proper absorbent in the design stage of the WFGD system, but also can determine the optimal operation parameters in the operation stage, thereby reducing the investment and operation;

(4) the test system can simulate the actual industrial process and research the absorption condition of the limestone slurry on the sulfur dioxide;

(5) the determination method is simple, effective and easy to realize, can correctly evaluate the activity of limestone, and provides a theoretical basis for the design of flue gas desulfurization engineering;

(6) the simulation system of the invention is close to industrial practice, simple in structure and easy to control.

Drawings

FIG. 1 is a schematic flow chart of a test analysis system according to the present invention.

Detailed Description

Limestone activity test method, limestone slurry and SO₂The flue gas directly reacts to simulate the actual desulfurization process and measure SO₂The removal rate of (A) reflects the activity of limestone, SO₂The higher the removal rate, the better the limestone activity; SO (SO)₂The lower the removal rate, the poorer the limestone activity. The method comprises the following specific steps:

A. test preparation

(1) Grinding limestone to be analyzed into 250-mesh powder;

(2) preparing limestone slurry with a slurry ratio of 5% (e.g. 50 g: 1L) limestone and water;

B. test procedure

(1) Simulating flue gas and flow control, and regulating N by pressure reducing valve₂，CO₂，O₂And SO₂The gas flow rate; the four gas flows are respectively as follows: n is a radical of₂＝1.64m³/h，CO₂＝0.24m³/h，O₂＝0.12m³/h，SO₂＝120mL/min；

(2) Starting a temperature controller, and setting the temperature of the flue gas to be 135 ℃;

(3) placing the prepared limestone slurry into a slurry pool, maintaining the temperature of the limestone slurry at about 50 ℃, and keeping stirring to prevent limestone particles in the limestone slurry from settling;

(4) starting a slurry pump, controlling the flow to be 20L/h, starting a pH controller, and adjusting the pH value in the slurry tank; when the pH is not adjusted, the pH can be saved; and recording SO in the absorbed tail gas₂And (4) and finally analyzing.

As shown in fig. 1, the limestone activity test analysis system comprises a limestone slurry pool 11, a slurry pump 12, an absorption tower 13, a gas cylinder 14, gas flow controllers J-N, a limestone slurry recovery pool 15 and slurry flow controllers a-I; the slurry tank 11 is communicated with an inlet of a main pipe 16 at the top of the absorption tower 13 through a pipeline, a slurry pump 12 and a slurry flow controller I, the main pipe 16 is provided with slurry flow controllers A-F which are communicated with the absorption tower 13, and an outlet arranged at the bottom of the absorption tower 13 is introduced into a limestone slurry recovery tank 15; the downstream absorption end of the absorption tower 13 is connected with a flue gas temperature controller R; the countercurrent absorption end part of the absorption tower 13 is connected with a gas analyzer through a data measurement port 1-5; the gas steel cylinder 14 simulates flue gas and leads the flue gas into a flue gas temperature controller R through a gas flow controller J-N; a stirring device P, O and aconstant temperature device are arranged in the limestone slurry pool 11 and the limestone slurry recovery pool 15; the gas analyzer is prepared by adopting the existing mature product.

Referring to fig. 1, a PH controller Q is provided between the limestone slurry tank 11 and the limestone slurry recovery tank 15, and the flow direction of the limestone slurry is determined by the selection of the on-off valve G, H.

The test results of the invention are as follows:

the testing technology is in accordance with the engineering practice, the activity of limestone can be accurately measured, the method can simulate the flue gas desulfurization practical process, and the accuracy is high. The limestone activity parameter obtained by the method can be used for flue gas desulfurization design, and the limestone activity testing technology belongs to an advanced level at home and abroad.

Activity evaluation

The method and the system can simulate the actual industrial process and research the absorption condition of the limestone slurry on the sulfur dioxide. The technological parameters of the absorption process are close to the actual conditions, and the activity of the limestone adopts SO₂The average rate of dissolution was measured. The main reaction of the sulfur dioxide-containing flue gas and the limestone slurry is as follows:

the instantaneous rate of limestone at time t is:

${A_{2,i}}^{\′}=\frac{c_{i-1}-c_i}{{\mathrm{\Δt}}_i},i=\mathrm{1,2,3}\·\·\·\·\·\·n$

$A_2^{\′}=\frac{\underset{1}{\overset{n}{\mathrm{\Σ}}}{A_{2,i}}^{\′}}{n}$

in the formula, c_iOutlet SO at time i₂Concentration, ppm;

c_i-1outlet SO at time i-1₂Concentration, ppm;

Δt_i-the time interval between time i and time i-1, s;

A_2i′-SO₂at Δ t_iAverage dissolution rate over time;

A₂′-SO₂the average dissolution rate of (a) is the activity of limestone.

n-SO₂N is not less than 100

By SO₂Average rate of dissolution the activity of limestone was evaluated. SO (SO)₂The greater the average rate of dissolution, the greater the limestone activity; SO (SO)₂The smaller the average rate of dissolution, the less active the limestone.

The invention develops a simulation device which is similar to the actual engineering aiming at the actual operation condition, obtains a more accurate limestone activity value through the simulation of the actual desulfurization process, provides a basis for engineering design, and thus reduces the investment cost of flue gas desulfurization.

The invention uses a steel cylinder as a gas source, uses a flowmeter to regulate the gas components and flow, and obtains flue gas simulating the industrial actual condition after electric heating. The temperature, stirring intensity and oxygenation intensity of the reaction tank are set at certain values, and the addition of limestone slurry is controlled by a pH meter to maintain the pH value unchanged. The activity of limestone is SO₂The average rate of dissolution was measured.

Simulating a smoke part: main component N in smoke₂、O₂And CO₂，SO₂For the key control object, various gases are bottled with pure gas.

An absorption tower part: the simulation was performed using a liquid curtain absorption tower. The residence time of the simulated flue gas in the tower must be long enough to ensure adequate absorption of the sulphur dioxide.

The operation procedures of the invention are as follows: in the actual engineering, the slurry entering the absorption tower is strictly controlled by pH, but in the limestone activity test of the project, only the flue gas absorption of the upper half part of the absorption tower needs to be considered, the oxidation process of the lower half part does not need to be considered, and the operation for controlling the pH value is relatively complex, so most of simulated flue gas in the invention can not be subjected to pH adjustment. In fact, whether the pH value of the sprayed slurry is adjusted or not does not affect the activity sequence of several limestone, and when the original limestone slurry is directly sprayed without pH adjustment, the activity of several limestone is simultaneously increased due to the higher pH value; while the pH adjustment, which is carried out, lowers the pH of the sprayed circulating slurry, so that the activity of several limestone types decreases simultaneously, the trend of the change should be the same and the order of the activity magnitude should not change, and the results obtained from the test observation also confirm this conclusion.

The AEE determination method adopts acid to titrate limestone, and because the limestone consumption is low during analysis, component segregation is easily caused by limestone sampling, and finally, the activity result is inaccurate, and the reaction mechanism of acid titration is greatly different from the actual desulfurization process.

Claims (4)

1. The limestone activity test method is characterized by comprising the following steps: mixing limestone slurry with SO₂The flue gas directly reacts to simulate the actual desulfurization process and measure SO₂The removal rate of (A) reflects the activity of limestone, SO₂The higher the removal rate, the better the limestone activity; SO (SO)₂The lower the removal rate, the poorer the limestone activity.

2. The method according to claim 1, characterized by the steps of:

A. test preparation

(1) Grinding limestone to be analyzed into 250-mesh powder;

(2) preparing limestone slurry with the slurry ratio of 5%;

B. test procedure

(1) Simulating flue gas and flow control, and regulating N by pressure reducing valve₂，CO₂，O₂And SO₂The gas flow rate;

(2) starting a temperature controller, and setting the temperature of the flue gas to be 135 ℃;

(3) placing the prepared limestone slurry into a slurry tank, maintaining the temperature of the slurry tank at 50 ℃, and keeping stirring to prevent limestone particles in the slurry from settling;

(4) starting a slurry pump, controlling the flow to be 20L/h, starting a pH controller, and adjusting the pH value in the slurry tank; when the pH is not adjusted, the pH can be saved; and recording SO in the absorbed tail gas₂And (4) and finally analyzing.

3. The limestone activity test analysis system is characterized by comprising a limestone slurry pool (11), a slurry pump (12), an absorption tower (13), a gas steel cylinder (14), a gas flow controller (J-N), a limestone slurry recovery pool (15) and a slurry flow controller (A-I); the slurry pool (11) is communicated with the inlet of a main pipe (16) at the top of the absorption tower (13) through a pipeline, a slurry pump (12) and a slurry flow controller (I), the main pipe (16) is provided with slurry flow controllers (A-F) which are communicated with the absorption tower (13), and the bottom of the absorption tower (13) is provided with an outlet which is communicated with a limestone slurry recovery pool (15); the downstream absorption end of the absorption tower (13) is connected with a flue gas temperature controller (R); the countercurrent absorption end part of the absorption tower (13) is connected with a gas analyzer through a data measurement port (1-5); the simulated flue gas of the gas steel cylinder (14) is introduced into a flue gas temperature controller (R) through a gas flow controller (J-N); a stirring device (P, O) and a constant temperature device are arranged in the limestone slurry pool (11) and the limestone slurry recovery pool (15).

4. The limestone activity test and analysis system according to claim 3, characterized in that a pH controller (Q) is arranged between the limestone slurry tank (11) and the limestone slurry recovery tank (15).