CN115569508A - Preparation method of high-density limestone slurry - Google Patents

Abstract

The invention relates to the technical field of wet desulfurization, and discloses a method for preparing high-density limestone slurry, comprising the following steps: (1) limestone enters a limestone silo through a discharge hopper and a feeder, and then passes through a weighing belt from the limestone silo (2) The water tank of the ball mill supplies water to the ball mill to grind the limestone; (3) The ground limestone enters the cyclone for separation, and the obtained solid material returns to the ball mill to continue grinding, and the liquid material overflows Flow to the limestone slurry tank to obtain high-density limestone slurry. The pass rate of limestone slurry density increased from 31.25% to 95.83%, and the effect is obvious; and after the slurry density is increased, the water content is reduced, the liquid level of the absorption tower is reduced, and the number of flushing of the demister is increased, which reduces the clogging of the demister of the absorption tower probability, improve the stability of desulfurization system operation.

Description

A kind of preparation method of high-density limestone slurry

technical field

The invention relates to the technical field of wet desulfurization, in particular to a preparation method of high-density limestone slurry.

Background technique

In the limestone-gypsum wet desulfurization process, limestone slurry is used as the main absorbent, and the quality of the slurry has a great impact on the stable operation of the desulfurization system. The role of the limestone slurry is to neutralize the acidic components in the absorption tower slurry and increase the pH of the absorption tower slurry value, improve the efficiency of circulating slurry to absorb SO ₂ , thereby increasing the desulfurization efficiency.

If the limestone slurry density is unqualified, it will directly lead to a decrease in the efficiency of absorbing SO ₂ in the absorption tower, a decrease in desulfurization efficiency, and an increase in the risk of SO ₂ exceeding the standard. Increase the supply amount or increase the number of slurry circulation pumps to improve desulfurization efficiency, but increasing the slurry supply will increase the power consumption and wear of the mill system, and increasing the number of slurry circulation pumps will increase the power consumption and wear of the circulation pump. The efficiency of SO ₂ will lead to excessive environmental protection data and seriously endanger the environment. The density of limestone slurry has a great impact on the economy and safety of desulfurization system operation.

Therefore, how to ensure the high density of limestone slurry in the limestone-gypsum wet desulfurization process is an urgent technical problem to be solved by those skilled in the art.

Contents of the invention

In view of this, the present invention provides a method for preparing high-density limestone slurry to solve the problem of the decline in the efficiency of absorbing SO2 in the limestone _- gypsum wet desulfurization process. Conventional methods of increasing desulfurization will seriously increase power consumption, machine loss or pollution environmental problems.

In order to solve the above technical problems, the present invention adopts the following technical solutions:

A preparation method for high-density limestone slurry, comprising the following steps:

(1) The limestone enters the limestone silo through the discharge hopper and the feeder, and then is transported from the limestone silo to the ball mill for grinding through the weighing belt conveyor;

(2) The water tank of the ball mill supplies water to the ball mill and grinds the limestone;

(3) The ground limestone enters the cyclone for separation, the obtained solid material returns to the ball mill to continue grinding, and the liquid material overflows into the limestone slurry tank to obtain high-density limestone slurry.

Preferably, in the above method for preparing high-density limestone slurry, the feed rate of the feeder in step (1) is not less than 80% of the rated output.

Preferably, in the above method for preparing high-density limestone slurry, the total mass of limestone transported to the ball mill by the weighing belt conveyor in step (1) is the same as the total mass of limestone entering the discharge hopper.

Preferably, in the above method for preparing high-density limestone slurry, the water supply of the ball mill water tank to the ball mill in step (2) is 2.85-3.15 times the mass of limestone transported by the weighing belt conveyor to the ball mill.

Preferably, in the preparation method of the above-mentioned high-density limestone slurry, the ball mill is provided with a water flow meter for collecting the pulping water flow rate in the limestone slurry preparation process, and the pulping water flow rate is 1/4 of the process jellyfish pipe flow rate. 97-103%.

Preferably, in the above method for preparing high-density limestone slurry, the limestone slurry tank is also used to receive system additional water, and the amount of system additional water entering the limestone slurry tank does not exceed 10% of the water supply of the ball mill water tank.

Preferably, in the above method for preparing high-density limestone slurry, the current of the ball mill is greater than 80% of the rated current, and the output of the ball mill is greater than 80% of the rated output.

Preferably, in the above method for preparing high-density limestone slurry, the shape of the steel balls in the ball mill is regular, and the ball mill contains steel balls of different types with a diameter of 30-70 mm.

Preferably, in the preparation method of the above-mentioned high-density limestone slurry, the quality of (15-25): (15-25): (20-30): (15-20): (10-20) in the ball mill The score is equipped with steel balls with diameters of 70mm, 60mm, 50mm, 40mm and 30mm.

Preferably, in the above method for preparing high-density limestone slurry, the pressure of the cyclone in step (3) is 200-250KPa. ,

The present invention provides a kind of preparation method of high-density limestone slurry, compared with prior art, its beneficial effect is:

After the limestone slurry is prepared by the inventive method, the power consumption of the mill decreases, the pH value of the slurry in the absorption tower increases significantly, and the slurry absorbs SO _The ability to strengthen; the qualified rate of the limestone slurry density rises to 95.83% from the original 31.25%, The effect is obvious; and after the density of the slurry increases, the water content decreases, the liquid level of the absorption tower decreases, and the number of flushing of the demister increases, which reduces the probability of blockage of the demister of the absorption tower and improves the operation stability of the desulfurization system.

Description of drawings

Fig. 1 is a density histogram of limestone slurry in the first, second and third stages in the embodiment of the present invention;

Fig. 2 is an arrangement diagram of reasons for low density of limestone slurry in an embodiment of the present invention.

detailed description

The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The embodiment of the present invention provides a kind of preparation method of high-density limestone slurry, comprises the following steps:

(1) The limestone enters the limestone silo through the discharge hopper and the feeder, and then is transported from the limestone silo to the ball mill for grinding through the weighing belt conveyor;

(2) The water tank of the ball mill supplies water to the ball mill and grinds the limestone;

(3) The ground limestone enters the cyclone for separation, the obtained solid material returns to the ball mill to continue grinding, and the liquid material overflows into the limestone slurry tank to obtain high-density limestone slurry.

In some of the embodiments, the feeding amount of the feeder in step (1) is not lower than 80% of the rated output.

In some of these embodiments, the total mass of limestone transported by the weighing belt conveyor to the ball mill in step (1) is the same as the total mass of limestone entering the discharge hopper.

In some of the embodiments, the amount of water supplied to the ball mill by the water tank of the ball mill in step (2) is 2.85-3.15 times the mass of limestone transported by the weighing belt conveyor to the ball mill.

In some of the embodiments, the ball mill is provided with a water flow meter for collecting the pulping water flow during the limestone slurry preparation process, and the pulping water flow is 97-103% of the process jellyfish pipe flow.

In some of the embodiments, the limestone slurry tank is also used to receive system additional water, and the amount of system additional water entering the limestone slurry tank does not exceed 10% of the water supply of the ball mill water tank.

In some of the embodiments, the current of the ball mill is greater than 80% of the rated current, and the output of the ball mill is greater than 80% of the rated output.

In some of the embodiments, the shape of the steel balls in the ball mill is regular, and the ball mill contains steel balls of different types with a diameter of 30-70 mm.

In some of these embodiments, the mass ratio of (15-25): (15-25): (20-30): (15-20): (10-20) in the ball mill is allocated with diameters of 70 mm and 60 mm. , 50mm, 40mm, 30mm steel balls.

In some of these embodiments, the pressure of the cyclone in step (3) is 200-250KPa.

Specifically, the first, second and third phases of Inner Mongolia Shangdu Power Generation Co., Ltd. were taken as the research object. The limestone-gypsum wet desulfurization process was adopted in the first, second and third phases of the plant, and the density requirements of the limestone slurry were also the same. Limestone slurry density for comparison, the results are shown in Table 1:

Table 1 Investigation results of limestone slurry density in the first, second and third phases

According to the density of limestone slurry in the first, second and third phases of Table 1, the histogram shown in Figure 1 is made. It can be seen that the density of limestone slurry in the first and third phases of our factory is normal, and the distribution center of the histogram appears at about 1220kg/m ³ , while the density of the grout in the second stage is biased, and the distribution center appears at 1195kg/m ³ , indicating that the density of the limestone grout is low. The limestone slurry in our factory is required to be controlled between 1200-1300kg/m ³ , and the average value of the slurry density in the first, second and third phases and the passing rate of the slurry density are calculated according to the above diagram, see Table 2:

Table 2 The average value of the slurry density and the pass rate of the slurry density in the first, second and third phases

Phase one Phase II Phase III average density 1223.6kg/m³ 1198.5kg/m³ 1220.3kg/m³ Pass rate 93.75% 31.25% 93.75%

It can be seen from Table 2 that the average density of the limestone slurry in the second stage of desulfurization is 1198.5kg/m ³ , which is lower than the standard value of 1200kg/m ³ , and even lower than the density of the limestone slurry in the first and third stages, and the pass rate is only 31.25%, which is serious unattainable level.

In addition, the present invention also investigates and compares the pulping effect of the ball mill. The second-stage desulfurization limestone pulping system is equipped with two wet ball mills A and B. Taking advantage of the fact that there are few operating units and low load in March-April 2018, the The mill adopts a stand-alone rotation operation mode, and the pulping effect of A and B ball mills is investigated and compared. The comparison results are shown in Table 3:

Table 3 A, B ball mill pulp density investigation results

Calculate and analyze the average value and qualified rate of the pulp density of A and B ball mills respectively, and the analysis results are shown in Table 4:

Table 4A, B ball mill pulp density average and qualified rate

A ball mill B ball mill total average slurry density 1213.1kg/m³ 1183.7kg/m³ 1198.4kg/m³ Serum qualified rate 87.50% 12.50%

It can be seen from Table 4 that the total average pulp density of A and B ball mills is 1198.4kg/m ³ , which is basically the same as the historical data of 1198.5kg/m ³ from September to December 2017, which can be used as an analysis of the low density of limestone slurry in the second period The basis of the results; the pulping effect of the B ball mill is poor, and the average value and pass rate of the slurry density are lower than that of the A ball mill.

Comprehensively analyze the operating conditions and maintenance conditions during the period of investigation and collection of statistical data, and classify and summarize the reasons for the low density of limestone slurry, as shown in Table 5:

Table 5 Reasons for low density of limestone slurry

serial number reason frequency/time frequency/% Cumulative frequency/% 1 B mill pulping effect is poor 12 70.59 70.59 2 Mill blocked, no-load operation 2 11.76 82.35 3 Limestone slurry tank flushing 1 5.88 88.24 4 The three-stage beating fluid for mill withdrawal 1 5.88 94.12 5 Inaccurate measurement of slurry deposition 1 5.88 100 total 17 100

As shown in Figure 2, the reasons for the low density of limestone slurry in Table 5 are arranged and drawn. It can be concluded that the crux of the low pass rate of limestone slurry density in the second-stage desulfurization lies in the low pulping density of the B mill.

Since the passing rate of the limestone slurry density in the first stage and the third stage is both 93.75%, the passing rate of the limestone slurry density in the second stage of desulfurization is at least increased to 93.75% by the method of this embodiment.

Example 1

The present embodiment provides a kind of preparation method of high-density limestone slurry, comprises the following steps:

(1) The truck unloads the limestone into the discharge hopper, enters the limestone silo through the vibrating feeder and bucket elevator, and the limestone is transported from the silo to the ball mill for grinding through the weighing belt conveyor;

(2) The water from the water tank of the ball mill and the limestone at the entrance of the ball mill are added to the wet ball mill according to the mass ratio of material to water ratio of 1:3, and the limestone is strongly ground;

(3) The ground limestone enters the cyclone for separation, and the obtained large-grained solid material returns to the ball mill through the recirculation pipe to continue grinding, and the liquid material overflows into the limestone slurry tank to obtain limestone slurry, which is supplied by a slurry pump Hit to the absorption tower;

In step (1), the total mass of limestone delivered by the weighing belt conveyor to the ball mill is the same as the total mass of limestone entering the discharge hopper;

The water supply of the ball mill water tank to the ball mill in step (2) is 3 times of the quality of limestone delivered to the ball mill by the weighing belt conveyor; The water flow is 100% of the process jellyfish tube flow;

In the step (3), the limestone slurry tank is also used for receiving system additional water, and the system additional water entering the limestone slurry tank is 3% of the water supply of the ball mill water tank; the pressure of the cyclone is 220KPa;

And the current of the ball mill is greater than 80% of the rated current, and the output of the ball mill is greater than 80% of the rated output; the shape of the steel balls in the ball mill is regular, and the diameter of the ball mill is 70mm according to the mass ratio of 20:20:25:18:15. , 60mm, 50mm, 40mm, 30mm steel balls.

What is prepared in this embodiment is a limestone slurry with a fineness of 90% passing through a 250-mesh sieve of 63um and a density of 1267kg/m ³ .

Example 2

Embodiment 2 is substantially the same as Embodiment 1, and its difference only lies in the variation of feeding amount.

In this example, the feeding amount of the feeder is used as a variable to study the influence of the feeding amount relative to the rated output on the pulp density of the ball mill. The rated output of the ball mill is 14t/h. The results are shown in Table 6:

Table 6 The effect of the change of feeding amount on the pulp density of the ball mill

It can be seen from Table 6 that when the feeding amount of the feeder to the ball mill is 80% or more of the rated output, the density of the prepared limestone slurry is in the range of 1200-1300kg/m ³ , and when the feeding amount is less than the rated output When the output is 80%, the density of the prepared limestone slurry is less than 12001200-1300kg/m ³ , which will affect the desulfurization efficiency. Therefore, the invention limits the feed rate of the feeder to not be lower than 80% of the rated output.

Example 3

Embodiment 3 is basically the same as Embodiment 1, the only difference being that the material-water ratio changes when the ball mill is running.

In this example, the material-water ratio is used as a variable to study the influence of the material-water ratio change on the pulp density of the ball mill. The results are shown in Table 7:

Table 7 The effect of the change of feeding amount on the pulp density of the ball mill

It can be seen from Table 7 that when the water-material ratio is maintained between 2.85-3.15, the limestone slurry density is maintained at 1200-1300kg/m ³ , which will not affect the pulping effect of the ball mill, and when the water-material ratio exceeds 2.85-3.15, then The density of limestone slurry will be too high or too low, which will affect the pulping effect.

Example 4

Embodiment 4 is basically the same as Embodiment 1, and the only difference is that in step (1), the total mass of limestone transported by the weighing belt conveyor to the ball mill is compared with the change of the total mass of limestone entering the discharge hopper.

In this embodiment, the feeding amount of the weighing belt conveyor and the discharging amount of the discharge hopper are used as variables to study the influence of the accuracy of the feeding amount of the weighing belt conveyor on the pulp density of the ball mill.

The accumulative value of the feeding amount of the weighing belt is consistent with the weighing amount of the limestone hopper (that is, the total mass of limestone entering the discharge hopper). First, a prerequisite should be met: the material levels of the first and last silos in the statistical period should be the same, otherwise the silo material level should be the same. Changes are taken into account. In this embodiment, the material level of the B silo is basically about 6.0 meters (full material), so the cumulative value of the feeding amount of the weighing belt conveyor should be consistent with the weighing of the limestone hopper truck. Continue to carry out the statistics of the limestone material during the period of the separate operation of the B mill, and at the same time carry out statistics on the density of the prepared limestone slurry, the results are shown in Table 8:

Table 8 The influence of the feeding amount of the weighing belt conveyor on the slurry density

It can be seen from Table 8 that due to the high deviation between the displayed value of the feeding amount of the weighing belt conveyor and the actual discharge amount, the density of the finally prepared limestone slurry is quite different from the standard limestone slurry density of 1200-1300kg/m ³ , so it is called The accuracy of the display value of the feeding amount of the heavy belt conveyor has an important influence on the density of the limestone slurry. During operation, it is necessary to ensure that the total mass of limestone transported by the weighing belt conveyor to the ball mill is basically consistent with the total mass of limestone entering the discharge hopper.

Example 5

Embodiment 5 is basically the same as Embodiment 1, the only difference being the change in the accuracy of the pulping water flowmeter.

In this embodiment, the display value of the pulping water flow meter is used as a variable to study the influence of the pulping water flow rate on the pulp density of the ball mill compared with the process water flow rate. The results are shown in Table 9:

Table 9 The influence of pulping water flow rate on pulping density

It can be seen from Table 9 that as long as the ball mill slurry water flow rate is basically consistent with the process jellyfish tube flow rate, and the deviation is no more than 3%, the density of the limestone slurry will not be affected.

Example 6

Embodiment 6 is basically the same as Embodiment 1, the only difference is that the additional water volume of the system changes, the additional water volume of the system is composed of mill cooling water, mill sewage pipe flushing water, mill slurry recirculation pump cooling water, slurry supply pump Composition of cooling water etc. The additional water flows to the pit of the ball mill, is pumped from the pit to the slurry tank of the ball mill, and finally flows to the slurry tank of the limestone, which affects the density of the limestone slurry.

In this embodiment, the additional water volume of the system is used as a variable to study the influence of the additional water volume of the system on the pulp density of the ball mill. Specifically, when a single ball mill is running, the rise of the ball mill pit liquid level is investigated and counted, and the additional water volume of the ball mill system is calculated. . After measurement, the size of the ball mill pit is 3.5m long and 2.9m wide; the cross-sectional area is 3.5×2.9=10.15m ² . The impact of additional water in the system on the pulp density of the ball mill is shown in Table 10:

Table 10 The effect of additional water in the system on the pulp density of the ball mill

It can be seen from Table 10 that the water-material ratio will increase due to the additional water in the system, which will affect the pulping density. However, as long as the additional water does not exceed 10% of the original water supply, it will not have a great impact on the pulping density.

Example 7

Embodiment 7 is basically the same as Embodiment 1, the only difference being the change of the current of the ball mill.

In this embodiment, the current of the ball mill is used as a variable to study the influence of the current of the ball mill on the pulp density of the ball mill. In this embodiment, the rated current of the ball mill is 160.4A, and the rated output is 14.0t/h. Wear and tear, the current of the ball mill drops gradually. When it drops to a certain level, add steel balls. See Table 11 for the results:

Table 11 Effect of ball mill current on pulping density

It can be seen from Table 11 that when the weight of the steel balls in the ball mill loses to a certain extent, the current of the ball mill will be affected, and then the density of the limestone slurry will be affected. The current of the ball mill should not be lower than 80% of the rated current.

Example 8

Embodiment 8 is basically the same as Embodiment 1, the only difference being the change of the proportion of steel balls in the ball mill.

In this example, the ratio of steel balls in the ball mill was used as a variable to study the influence of the ratio of steel balls on the pulp density of the ball mill. For details, see Table 12:

Table 12 Effect of steel ball ratio on pulping density

It can be seen from Table 12 that the proportion of steel balls in the mill does not meet the requirements, which affects the grinding process and eventually leads to low density of limestone slurry produced by the mill.

Example 9

Embodiment 9 is basically the same as Embodiment 1, the only difference being that the pressure of the ball mill cyclone changes.

In this example, the cyclone pressure was used as a variable to study the influence of the cyclone pressure on the pulp density of the ball mill. The results are shown in Table 13:

Table 13 Effect of cyclone pressure on pulping density

It can be seen from Table 13 that if the pressure of the cyclone is lower than 200KPa, the density of the limestone slurry cannot meet the standard. In order to ensure the swirling effect of the cyclone, the pressure of the cyclone should not be lower than 200KPa; if the pressure of the cyclone is higher than 250KPa , although it will not reduce the density of limestone slurry, but the excessive pressure of the cyclone station will affect the service life of the equipment, so the pressure of the cyclone station should not be higher than 250KPa.

And through the data before and after the repair of the ball mill in the factory, it can be found that in the process of preparing limestone slurry through the method of the present invention, the power consumption of the mill can be reduced from the highest 507291kW·h/month to 407934kW·h/month; and the preparation of limestone through the method of the present invention Slurry, the rise rate of the pH value of the slurry in the absorption tower is significantly increased, and the ability of the slurry to absorb SO2 is enhanced; more importantly, the pass rate of the limestone slurry density has increased from 31.25% to 95.83%, exceeding the 93.75% of the first and third phases. The effect is obvious; and after the density of the slurry is increased, the water content is reduced, the liquid level of the absorption tower is reduced, and the number of flushing of the demister is increased, which reduces the probability of clogging of the demister of the absorption tower and improves the operation stability of the desulfurization system.

Each embodiment in this specification is described in a progressive manner, each embodiment focuses on the difference from other embodiments, and the same and similar parts of each embodiment can be referred to each other. As for the solutions disclosed in the examples, since they correspond to the methods disclosed in the examples, the description is relatively simple, and for the relevant details, please refer to the description of the method section.

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. a preparation method of high-density limestone slurry, is characterized in that, comprises the following steps: (1) The limestone enters the limestone silo through the discharge hopper and the feeder, and then is transported from the limestone silo to the ball mill for grinding through the weighing belt conveyor; (2) The water tank of the ball mill supplies water to the ball mill and grinds the limestone; (3) The ground limestone enters the cyclone for separation, the obtained solid material returns to the ball mill to continue grinding, and the liquid material overflows into the limestone slurry tank to obtain high-density limestone slurry. 2. The preparation method of high-density limestone slurry according to claim 1, characterized in that, the feed rate of the feeder described in step (1) is not less than 80% of the rated output. 3. the preparation method of high-density limestone slurry according to claim 1 is characterized in that, the total mass of limestone that is transported to described ball mill by weighing belt conveyor in step (1) and the total mass of limestone that enters described discharge hopper Same quality. 4. The preparation method of high-density limestone slurry according to claim 1, characterized in that, the water supply of the ball mill water tank to the ball mill in the step (2) is 2.85-2.85% of the quality of limestone transported by the weighing belt conveyor to the ball mill. 3.15 times. 5. the preparation method of high-density limestone slurry according to claim 1, is characterized in that, described ball mill is provided with water flowmeter, is used for collecting the pulping water flow rate in limestone slurry preparation process, and described pulping water The flow rate is 97-103% of the flow rate of the process jellyfish tube. 6. The preparation method of high-density limestone slurry according to claim 1, characterized in that, the limestone slurry tank is also used to receive system additional water, and the amount of system additional water entering the limestone slurry tank does not exceed the ball mill 10% of the tank water supply. 7. The method for preparing high-density limestone slurry according to claim 1, characterized in that the current of the ball mill is greater than 80% of the rated current, and the output of the ball mill is greater than 80% of the rated output. 8. The method for preparing high-density limestone slurry according to claim 1, characterized in that the shape of the steel balls in the ball mill is regular, and the ball mill contains steel balls of different types with a diameter of 30-70mm. 9. The method for preparing high-density limestone slurry according to claim 8, characterized in that, in the ball mill according to (15-25): (15-25): (20-30): (15-20): (10-20) The mass ratio is equipped with steel balls with diameters of 70mm, 60mm, 50mm, 40mm, and 30mm. 10. The method for preparing high-density limestone slurry according to claim 1, characterized in that the pressure of the cyclone in step (3) is 200-250KPa.

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