A limestone slurry preparation system and slurry preparation method

Abstract

The invention discloses a limestone slurry preparation system, comprising a primary wet ball mill, wherein the outlet of the primary wet ball mill is connected to a recirculation box; the recirculation box is connected to a limestone slurry cyclone through a slurry circulation pump, the underflow port of the limestone slurry cyclone is connected to the inlet of the primary wet ball mill, the overflow port of the limestone slurry cyclone is connected to a distributor, the distributor is connected to the inlet of a secondary separator, the underflow port of the secondary separator is connected to the inlet of the secondary wet ball mill, the overflow port of the secondary separator is connected to a limestone slurry box, and the limestone slurry box is connected to an absorption tower slurry pool through an absorption tower slurry supply pump. The invention also discloses a slurry preparation method for limestone slurry, wherein more than 90% of the particles in the finished limestone slurry are less than 40 μm. The limestone slurry preparation system avoids the transportation of unqualified limestone slurry to the absorption tower slurry pool, delays the equipment wear of the slurry circulation system, and reduces the calcium-sulfur ratio of the desulfurization system.

Description

Technical Field

[0001] The invention belongs to the technical field of limestone-gypsum wet desulfurization equipment, and in particular relates to a limestone slurry preparation system and a slurry preparation method thereof. Technical Background

[0002] The limestone-gypsum wet flue gas desulfurization system generally has the phenomenon of sediment accumulation at the bottom of the absorption tower. Most of the sediment particles are limestone particles that do not meet the grinding requirements, and a small part are silica crystals that are difficult to grind mixed in the limestone ore. A large amount of sediment accumulates at the bottom of the absorption tower. On the one hand, during the operation of the desulfurization system, the sediment particles are repeatedly sprayed and circulated with the slurry circulation pump, causing wear of the lining and impeller of the slurry circulation pump, the spray layer pipeline and the nozzle, thereby affecting the output of the slurry circulation pump and the atomization effect of the spray layer. On the other hand, due to the continuous deposition of large solid particles, the slurry pool volume of the absorption tower is reduced, which brings certain risks to the stable operation of the desulfurization system. On the other hand, during the shutdown and maintenance process of the unit, the sediment at the bottom of the absorption tower needs to be manually cleaned, which greatly increases the workload of the unit maintenance and prolongs the maintenance cycle.

[0003] There are two main types of limestone slurry preparation systems: limestone powder slurry making process and wet ball mill process. The powder slurry making process includes limestone powder silo, limestone slurry tank, limestone slurry tank agitator, fluidizing fan, fluidizing air heater, and silo top dust collector. The limestone powder purchased from outside the factory (325 mesh pass rate 90%) is transported to the limestone powder silo by the pneumatic conveying pump carried by the limestone powder tank truck. The limestone powder is evenly fed into the limestone slurry tank by the limestone powder feeder, and then the filtrate water or spare water source process water is fed in proportion to make a density of 1200-1240kg / m 3 The limestone slurry is then pumped to the absorption tower by the limestone slurry pump. The wet ball mill process route is: the purchased limestone blocks with a particle size of ≤20mm are transported to the factory by dump trucks and unloaded into the discharge hopper. The feeder sends the limestone in the discharge hopper to the vibrating conveyor with a metal separator, and then the limestone is sent to the limestone silo through the bucket elevator through the buried scraper conveyor. A steel grid is used on the top of the discharge hopper to prevent large-sized limestone from entering. A shut-off door and a weighing feeder are set at the bottom outlet of the limestone silo. The limestone is weighed and mixed with water in a certain weight ratio (3:1) and sent to the wet ball mill system to grind the limestone slurry. The slurry at the ball mill outlet flows downstream to the circulating slurry box (each box is equipped with a stirrer). The mill slurry circulation pump sends the limestone slurry to the cyclone station. After being sorted by the cyclone, the qualified overflow product directly enters the limestone slurry box, and the unqualified bottom flow enters the wet mill for further grinding. Qualified limestone slurry is stored in the slurry tank and pumped to the absorption tower by the limestone slurry pump.

[0004] The sediment in the limestone slurry is not selective in which box it is deposited in. There will also be sediment accumulation at the bottom of the limestone slurry box supporting the desulfurization system, but the amount of sediment accumulation is mainly determined by the elevation of the inlet pipe of the limestone slurry pump. When the sediment accumulation at the bottom of the limestone slurry box reaches the upper limit, the sediment particles will accumulate at the bottom of the absorption tower. The amount of sediment accumulation in the absorption tower mainly depends on the amount of limestone used and the fineness of the limestone powder. For the same standard of limestone powder per unit time, the greater the amount of sediment accumulation, the greater the amount of limestone used. For the same amount of limestone used per unit time, the worse the fineness of the limestone powder, the greater the sediment measurement. At the same time, the elevation of the gypsum slurry discharge pump also has a certain influence, but due to the large cross-section of the absorption tower, the sediment deposition height and shape at the bottom of the absorption tower are related to the installation position of the slurry circulation pump inlet and the output of the absorption tower agitator. Summary of the invention

[0005] The purpose of the present invention is to provide a limestone slurry preparation system to avoid conveying limestone slurry with unqualified fineness to the absorption tower slurry pool, delay equipment wear of the slurry circulation system, and reduce the calcium-sulfur ratio of the desulfurization system.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned limestone slurry.

[0007] The technical solution adopted by the present invention is a limestone slurry preparation system, which includes a primary wet ball mill, wherein the outlet of the primary wet ball mill is connected to a recycling box; the recycling box is connected to a limestone slurry cyclone through a slurry circulation pump, the bottom flow port of the limestone slurry cyclone is connected to an inlet of the primary wet ball mill, the overflow port of the limestone slurry cyclone is connected to a distributor, the distributor is connected to an inlet of a secondary separator, the bottom flow port of the secondary separator is connected to the inlet of the secondary wet ball mill, the overflow port of the secondary separator is connected to a limestone slurry box, and the limestone slurry box is connected to an absorption tower slurry pool through an absorption tower slurry supply pump.

[0008] The present invention is also characterized in that

[0009] The outlet of the secondary wet ball mill is connected to the inlet of the secondary separator through a slurry recirculation pump.

[0010] The distributor is also connected to a recirculation tank.

[0011] Another technical solution adopted by the present invention is a method for preparing limestone slurry, which adopts a limestone slurry preparation system and is specifically implemented according to the following steps:

[0012] Step 1, conveying limestone particles and water to a primary wet ball mill for grinding, and producing finished limestone slurry a after limestone slurry cyclone sorting;

[0013] Step 2: The limestone slurry a obtained after step 1 flows into the secondary separator by gravity, and the bottom sediment after separation enters the secondary wet ball mill for grinding again. The qualified limestone slurry is returned to the secondary separator through the slurry recycling pump to separate the coarse particles together with the newly added slurry, and the overflow in the secondary separator separates the limestone slurry b with good fineness. The mass concentration of the limestone slurry b is 25%; more than 90% of the particles in the limestone slurry b are less than 40 μm.

[0014] The beneficial effects of the present invention are that the limestone slurry preparation system of the present invention avoids the problem that limestone slurry with unqualified fineness quality is transported to the absorption tower slurry pool due to operating failure of the main slurry making system or blockage of the limestone slurry cyclone, resulting in sediment accumulation at the bottom thereof, thereby delaying equipment wear of the slurry circulation system; at the same time, the unit shutdown time is shortened; at the same time, the calcium-sulfur ratio of the desulfurization system operation is reduced, and the absorbent cost is saved; and a reasonable slurry residence time is better maintained. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The present invention is a structural schematic diagram of a limestone slurry preparation system.

[0016] In the figure, 1. primary wet ball mill, 2. recirculation box, 3. slurry circulation pump, 4. limestone slurry cyclone, 5. distributor, 6. secondary separator, 7. secondary wet ball mill, 8. slurry recirculation pump, 9. limestone slurry box, 10. absorption tower slurry supply pump, 11. absorption tower slurry pool. DETAILED DESCRIPTION

[0017] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0018] The present invention provides a limestone slurry preparation system, such as Figure 1 As shown, it includes a primary wet ball mill 1, through the inlet of the primary wet ball mill 1, limestone material and pulping water are supplemented, the outlet of the primary wet ball mill 1 is connected to the recycling box 2; the recycling box 2 is connected to the limestone slurry cyclone 4 through a slurry circulation pump 3, the bottom flow port of the limestone slurry cyclone 4 is connected to the inlet of the primary wet ball mill 1, the overflow port of the limestone slurry cyclone 4 is connected to the distributor 5, the distributor 5 is connected to the recycling box 2, the distributor 5 is also connected to the inlet of the secondary separator 6, the bottom flow port of the secondary separator 6 is connected to the inlet of the secondary wet ball mill 7, the outlet of the secondary wet ball mill 7 is connected to the inlet of the secondary separator 6 through the slurry recycling pump 8, the overflow port of the secondary separator 6 is connected to the limestone slurry box 9, and the limestone slurry box 9 is connected to the absorption tower slurry pool 11 through the absorption tower slurry supply pump 10.

[0019] The purpose of the distributor 5 is to divert part of the overflow slurry to the recirculation tank 2 to maintain the liquid level of the recirculation tank 2 and avoid idling of the slurry circulation pump 8; the overflow slurry can also be diverted to different limestone slurry tanks 9 for storage and standby.

[0020] The purpose of the recirculation box 2 is to continuously provide a stable flow of slurry to the slurry circulation pump 8 to prevent the slurry circulation pump 8 from idling.

[0021] The purpose of the slurry circulation pump 8 is to provide sufficient pressure for the cyclone at a set slurry flow rate to achieve centrifugal separation of coarse particles and fine particles in the limestone slurry.

[0022] The secondary separator 6 can be static natural separation such as overflow sedimentation tank, return sedimentation tank, mechanical centrifugal separation such as cyclone, mechanical filtration separation such as vibrating screen, etc.

[0023] The present invention provides a limestone slurry preparation system, and its specific working principle is:

[0024] Limestone particles and water are continuously conveyed to the primary wet ball mill 1 in a certain ratio for grinding, and the produced limestone slurry flows by gravity to the recycling box 2, and is conveyed to the limestone slurry cyclone 4 through the slurry circulation pump 3. The underflow of the limestone slurry cyclone 4 returns to the primary wet ball mill 1 for further grinding, and the overflow flows by gravity to the secondary separator 6 through the distributor 5. After natural or mechanical separation, the bottom sediment enters the secondary wet ball mill 7 for further grinding. The limestone slurry produced by the secondary wet ball mill 7 is conveyed to the secondary separator 6 again through the slurry recycling pump 8. The separated limestone slurry with good fineness and quality flows by gravity into the limestone slurry box 9, and is finally conveyed to the absorption tower slurry pool 11 through the absorption tower slurry supply pump 10.

[0025] The present invention provides a method for preparing limestone slurry, which is specifically implemented according to the following steps:

[0026] Step 1, conveying limestone particles and water to a primary wet ball mill 1 for grinding, and producing finished limestone slurry a after sorting by a limestone slurry cyclone 4;

[0027] Due to problems such as the operation adjustment of the main pulping system and equipment failure, the fineness of the limestone slurry does not meet the requirements;

[0028] Step 2, the limestone slurry a obtained after step 1 flows into the secondary separator 6 by gravity, and the bottom sediment after separation enters the secondary wet ball mill 7 for re-grinding, and the qualified limestone slurry is returned to the secondary separator 6 again through the slurry recycling pump 8 to separate the coarse particles together with the newly added slurry, and the overflow in the secondary separator 6 separates the limestone slurry b with good fineness and quality;

[0029] The mass concentration of limestone slurry b is 25%; more than 90% of the particles in limestone slurry b are smaller than 40 μm, which is even better than the requirement.

Claims

1. A limestone slurry preparation system, characterized in that: The invention comprises a primary wet ball mill (1), wherein the outlet of the primary wet ball mill (1) is connected to a recycling box (2); the recycling box (2) is connected to a limestone slurry cyclone (4) via a slurry circulation pump (3); the bottom flow outlet of the limestone slurry cyclone (4) is connected to the inlet of the primary wet ball mill (1); the overflow outlet of the limestone slurry cyclone (4) is connected to a distributor (5); the distributor (5) is connected to the inlet of a secondary separator (6); the bottom flow outlet of the secondary separator (6) is connected to the inlet of a secondary wet ball mill (7); the overflow outlet of the secondary separator (6) is connected to a limestone slurry box (9); the limestone slurry box (9) is connected to an absorption tower slurry tank (11) via an absorption tower slurry supply pump (10); the outlet of the secondary wet ball mill (7) is connected to the inlet of the secondary separator (6) via a slurry recycling pump (8); the distributor (5) is also connected to the recycling box (2).

2. A method for preparing limestone slurry, applied to the limestone slurry preparation system according to claim 1, characterized in that: Follow the steps below to implement it: Step 1, conveying limestone particles and water to a primary wet ball mill (1) for grinding, and producing finished limestone slurry a after sorting in a limestone slurry cyclone (4); Step 2, the limestone slurry a obtained after step 1 flows into the secondary separator (6) by gravity, and the bottom sediment after separation enters the secondary wet ball mill (7) for re-grinding, and the qualified limestone slurry is returned to the secondary separator (6) through the slurry recycling pump (8) to separate the coarse particles together with the newly added slurry, and the overflow in the secondary separator (6) is separated to obtain limestone slurry b with good fineness and quality.

3. The method for preparing limestone slurry according to claim 2, characterized in that: The mass concentration of the limestone slurry b is 25%; more than 90% of the particles in the limestone slurry b are smaller than 40 μm.

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