Shield slurry dehydration method

Abstract

The invention provides a shield slurry dehydration method, which comprises the following steps: carrying out flocculation treatment on shield slurry by using a quicklime-polydimethyldiallylammonium chloride solution as an inorganic-organic compound flocculant, concentrating by using a concentration tank, and carrying out filter pressing dehydration treatment to obtain a mud cake with the water content of 29.8-32.5%. According to the method, flocculation treatment is performed on the shield slurry in an adding mode of CaO-PDMDAAC, clay particles in the shield slurry can be promoted to be flocculated into floccules with larger particle sizes, the flocculation speed is higher, and a better flocculation effect is achieved. Besides, the inorganic-organic compound flocculant formed by the quick lime dry powder and the polydimethyldiallylammonium chloride solution can effectively reduce the specific resistance of the shield slurry and improve the efficiency of subsequent filter-pressing dehydration, and the filter-pressing efficiency can be improved by 60-70%. The method is simple, easy to operate and suitable for flocculation, concentration and dehydration of the high-viscosity shield slurry.

Description

Technical Field

[0001] The invention belongs to the technical field of shield mud treatment and relates to a shield mud dehydration method. Background Art

[0002] During the construction of shield tunnels in the silty clay layer in the lower reaches of the Yellow River, a large amount of waste shield mud will be generated. This shield mud generally contains a high clay content and water content. If it is piled up, a large number of yards are required, and on-site drying will also occupy a large amount of land resources; if it is transported out, it is very difficult to transport and causes great pollution to the environment.

[0003] In addition, since the clay particles in the shield mud have a special floc structure and high hydrophilicity, the water contained in the shield mud is difficult to remove, resulting in a huge volume of shield mud and difficulty in subsequent treatment. At the same time, the particles of the shield mud after pre-screening and cyclone are even finer, which brings great difficulties to its subsequent dehydration and reduction treatment. Summary of the invention

[0004] The purpose of the invention is to provide a shield mud dehydration method to solve the problem of high-clay shield mud treatment difficulty.

[0005] To achieve the above object, the present invention adopts the following technical solutions: The present application provides a shield mud dehydration method, the method comprising: S01: Add dry quicklime powder to the shield mud, stir for 10-20 minutes, then add polydimethyldiallyl ammonium chloride solution, mix and flocculate to form flocculated mud.

[0006] First, add quicklime powder to the shield mud and stir it with a stirrer for 10-20 minutes. The amount of quicklime powder added is 0.5-3.0% of the mass of the shield mud. The addition of quicklime powder can change the pore structure of clay particles in the shield mud, making it easier to discharge water from the shield mud during the filter pressing process and reducing the moisture content of the mud cake.

[0007] After adding the quicklime powder for 10-20 minutes, add the 0.3% polydimethyl diallyl ammonium chloride (PDMDAAC) solution, and use a stirrer to stir and dissolve at a speed of 20-200 rpm, so that the shield mud undergoes flocculation reaction to form flocculated mud. The amount of polydimethyl diallyl ammonium chloride solution added is 0.1-0.5% of the mass of the shield mud.

[0008] The inorganic-organic composite flocculant formed by quicklime powder and polydimethyldiallyl ammonium chloride solution can promote the flocculation of clay particles in shield mud into larger flocs, and the flocculation speed is faster, with better flocculation effect. In addition, the use of inorganic-organic composite flocculants can also effectively reduce the specific resistance of shield mud, improve the efficiency of subsequent filter press dehydration, and the filter press efficiency can be increased by 60-70%.

[0009] In addition, the polydimethyldiallyl ammonium chloride solution in the present application can be prepared using the overflow tail water of the concentration tank, and the flocculation efficiency can be increased by about 10%. This is because the overflow tail water contains residual polydimethyldiallyl ammonium chloride, and using the overflow tail water to prepare the polydimethyldiallyl ammonium chloride solution can increase the concentration of polydimethyldiallyl ammonium chloride, which is more conducive to flocculation and saves costs.

[0010] S02: The flocculated sludge enters the feed pipe of the concentration tank along the arc-shaped feed trough, and enters the concentration tank for concentration after being buffered by the conical distributor at the bottom of the feed pipe to form concentrated sludge.

[0011] The flocculated sludge is passed into the concentration tank for concentration to form concentrated sludge. The concentration treatment in the concentration tank before filter pressing can increase the specific gravity of the sludge before filter pressing, which is beneficial to improve the filter pressing dehydration efficiency.

[0012] In the present application, an arc-shaped feed trough is provided at the top of the concentration tank, a feed pipe is provided inside, and the tail of the arc-shaped feed trough is connected to the top of the feed pipe. The flocculated slurry enters the top of the feed pipe through the arc-shaped feed trough, and then enters the concentration tank. The arc-shaped feed trough is an arc-shaped structure, which can extend the flow path of the flocculated slurry, reduce the speed of the flocculated slurry, and achieve the purpose of buffering the flocculated slurry falling into the concentration tank. Preferably, the curvature of the arc-shaped feed trough is greater than the curvature of the concentration tank.

[0013] In addition, a conical distributor is provided at the bottom of the feed pipe. The flocculated mud that has slowed down the flow rate through the arc-shaped feed trough first falls on the conical distributor, and after the conical distributor buffers the speed again, it disperses to the surroundings and falls into the concentration tank, thus avoiding the phenomenon of the mud in the concentration tank flipping upward due to the too fast adding speed, achieving the effect of rapid sedimentation, and increasing the specific gravity of the concentrated mud from 1.1-1.3 to 1.35-1.45.

[0014] Furthermore, the bottom of the concentration tank is funnel-shaped, which can be beneficial to the accumulation of clay particles in the flocculated mud and the formation of supernatant, thereby facilitating the formation of concentrated mud.

[0015] S03: The concentrated mud is dehydrated by filter pressing to obtain a mud cake.

[0016] The concentrated slurry is passed into a plate and frame filter press or a belt filter press for filtration and dehydration to form a mud cake. After being concentrated in a concentration tank, the filtration efficiency is increased by 60-70% at the same filtration time, saving filtration time. In this application, the slurry feeding and filtration time are not less than 70 minutes, the feed pressure is 0.8Mpa, and the pressing pressure is 1.0Mpa.

[0017] The present invention has the following beneficial effects: (1) The use of dry quicklime powder can change the pore structure of clay particles in shield mud, making it easier to discharge water from the shield mud during the filter pressing process and reducing the moisture content of the mud cake.

[0018] (2) The flocculation treatment of shield mud by first adding quicklime powder and then adding polydimethyldiallyl ammonium chloride solution can promote the flocculation of clay particles in the shield mud into flocs with larger particle size, and the flocculation speed is faster, with better flocculation effect. In addition, the inorganic-organic composite flocculant formed by quicklime powder and polydimethyldiallyl ammonium chloride solution can also effectively reduce the specific resistance of shield mud and improve the efficiency of subsequent filter press dehydration, and the filter press efficiency can be increased by 60-70%.

[0019] (3) The polydimethyldiallyl ammonium chloride solution is prepared using the overflow tail water from the concentration tank, which can increase the flocculation efficiency by about 10% and save costs.

[0020] (4) Concentrating the slurry in a concentration tank before filter pressing and dehydration can increase the specific gravity of the slurry before filter pressing, which is beneficial to improving the dehydration efficiency of filter pressing.

[0021] (5) The setting of the arc-shaped feed trough on the top of the concentration tank can extend the flow distance of the flocculated mud, reduce the speed of the flocculated mud, and achieve the purpose of buffering the flocculated mud from falling into the concentration tank.

[0022] (6) The setting of the conical distributor at the bottom of the feed pipe enables the flocculated mud whose flow rate is slowed down by the arc-shaped feed trough to fall on the conical distributor first, and then after the speed is buffered again by the conical distributor, it is dispersed to the surroundings and falls into the concentration tank, thus avoiding the phenomenon of the mud in the concentration tank flipping upward due to the addition speed being too fast, achieving the effect of rapid sedimentation, and increasing the specific gravity of the concentrated mud from 1.1-1.3 to 1.35-1.45.

[0023] (7) This method is simple and easy to operate, and is suitable for flocculation, concentration and dehydration of high-clay shield mud. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 An application scenario diagram of the shield mud dehydration method provided in the embodiment of the present application; Figure 2 A top view of the concentration tank in the embodiment of the present application; Figure 3 This is a front cross-sectional view of the concentration tank in the embodiment of the present application; Figure 4 This is a comparison chart of the effects of the order of adding CaO and PDMDAAC in the examples of the present application. DETAILED DESCRIPTION

[0025] The present application provides a shield mud dehydration method, which uses quicklime-polydimethyldiallyl ammonium chloride solution as an inorganic-organic composite flocculant to flocculate the shield mud, and then performs filter pressing and dehydration treatment after concentration in a concentration tank to obtain a mud cake with a moisture content of 29.8-32.5%, wherein the application scene diagram of the shield mud dehydration method, the top view and the main cross-sectional view of the concentration tank are respectively as shown in the attached figure. Figure 1-3 The technical solution of the present invention is further explained and illustrated by specific embodiments below.

[0026] Example 1 The present application provides a shield mud dehydration method, the method comprising: S101: moisture content is 226.52%, density is 1.31g / cm 3 Add quicklime powder to the shield mud, where the amount of quicklime powder added is 0.5% of the shield mud mass. After stirring for 10 minutes, add 0.3% polydimethyldiallyl ammonium chloride solution, where the amount of polydimethyldiallyl ammonium chloride solution added is 0.1% of the shield mud mass. Use a stirrer to stir and dissolve at a speed of 20 rpm to form flocculated mud.

[0027] S102: The flocculated sludge enters the feed pipe of the concentration tank along the arc-shaped feed trough, and enters the concentration tank for concentration after being buffered by the conical distributor at the bottom of the feed pipe to form concentrated sludge.

[0028] S103: The concentrated mud is passed into a plate and frame filter press, and is filtered and dehydrated for 70 minutes at a feed pressure of 0.8 MPa and a pressing pressure of 1.0 MPa to form a mud cake.

[0029] Example 2 The present application provides a shield mud dehydration method, the method comprising: S201: Moisture content is 250%, density is 1.2g / cm 3Add quicklime powder to the shield mud, where the amount of quicklime powder added is 3.0% of the shield mud mass. After stirring for 20 minutes, add 0.3% polydimethyldiallyl ammonium chloride solution, where the amount of polydimethyldiallyl ammonium chloride solution added is 0.5% of the shield mud mass. Use a stirrer to stir and dissolve at a speed of 200 rpm to form flocculated mud.

[0030] S202: The flocculated sludge enters the feed pipe of the concentration tank along the arc-shaped feed trough, and enters the concentration tank for concentration after being buffered by the conical distributor at the bottom of the feed pipe to form concentrated sludge.

[0031] S203: The concentrated mud is passed into a belt filter press, and is filtered and dehydrated for 80 minutes at a feed pressure of 0.8 MPa and a pressing pressure of 1.0 MPa to form a mud cake.

[0032] Example 3 The present application provides a shield mud dehydration method, the method comprising: S301: moisture content is 236.2%, density is 1.25g / cm 3 Add quicklime powder to the shield mud, where the amount of quicklime powder added is 1.5% of the shield mud mass. After stirring for 15 minutes, add 0.3% polydimethyldiallyl ammonium chloride solution, where the amount of polydimethyldiallyl ammonium chloride solution added is 0.3% of the shield mud mass. Use a stirrer to stir and dissolve at a speed of 100 rpm to form flocculated mud.

[0033] S302: The flocculated sludge enters the feed pipe of the concentration tank along the arc-shaped feed trough, and enters the concentration tank for concentration after being buffered by the conical distributor at the bottom of the feed pipe to form concentrated sludge.

[0034] S303: The concentrated mud is passed into a plate and frame filter press, and is filtered and dehydrated for 75 minutes at a feed pressure of 0.8 MPa and a pressing pressure of 1.0 MPa to form a mud cake.

[0035] Comparative Example 1 The comparative example of the present application provides a shield mud dehydration method, the method comprising: D101: moisture content is 226.52%, density is 1.31g / cm 3 Add 0.3% polydimethyldiallyl ammonium chloride solution to the shield mud, wherein the amount of polydimethyldiallyl ammonium chloride solution added is 0.1% of the mass of the shield mud. Use a stirrer at a speed of 20-200 rpm to stir and dissolve to form flocculated mud.

[0036] D102: The flocculated slurry was passed into a plate and frame filter press, and filtered and dehydrated for 70 minutes at a feed pressure of 0.8 MPa and a pressing pressure of 1.0 MPa to form a mud cake.

[0037] Comparative Example 2 The comparative example of the present application provides a shield mud dehydration method, the method comprising: D201: Moisture content is 250%, density is 1.2g / cm 3 Add 0.3% polydimethyldiallyl ammonium chloride solution to the shield mud, wherein the amount of polydimethyldiallyl ammonium chloride solution added is 0.5% of the mass of the shield mud. Use a stirrer to stir and dissolve at a speed of 200 rpm to form flocculated mud.

[0038] D202: The flocculated slurry is passed into a belt filter press, and filtered and dehydrated for 80 minutes at a feed pressure of 0.8 MPa and a pressing pressure of 1.0 MPa to form a mud cake.

[0039] Comparative Example 3 The comparative example of the present application provides a shield mud dehydration method, the method comprising: D301: moisture content is 236.2%, density is 1.25g / cm 3 Add 0.3% polydimethyldiallyl ammonium chloride solution to the shield mud, wherein the amount of polydimethyldiallyl ammonium chloride solution added is 0.3% of the mass of the shield mud. Use a stirrer to stir and dissolve at a speed of 100 rpm to form flocculated mud.

[0040] D302: The flocculated sludge is passed into a plate and frame filter press, and filtered and dehydrated for 75 minutes at a feed pressure of 0.8 MPa and a pressing pressure of 1.0 MPa to form a mud cake.

[0041] The moisture content of the mud cakes formed in Examples 1-3 and Comparative Examples 1-3 was tested respectively, and Table 1 was obtained. As can be seen from Table 1, the moisture content of the mud cakes in Examples 1-3 was 29.8%, 32.5% and 31.6%, respectively, and the moisture content of the mud cakes in Comparative Examples 1-3 was 46.5%, 51.2% and 49.6%, respectively, which were significantly higher than the moisture content of the mud cakes in Examples 1-3 of the present application. This shows that the shield mud dehydration method provided in the embodiments of the present application can effectively remove water from the shield mud, the filter press effect is good, and the moisture content of the filter press mud cake is low.

[0042] Table 1: Moisture content of mud cakes in Examples 1-3 and Comparative Examples 1-3 In addition, in order to verify that the effect of adding quicklime powder first and then PDMDAAC is better than that of adding PDMDAAC first and then quicklime powder, the present application conducted a flocculation sedimentation experiment. The specific experimental process is as follows: Take two groups of 500mL shield mud and place them in a beaker and stir them evenly. First add CaO to one group of shield mud and then add PDMDAAC to form a CaO-PDMDAAC group; first add PDMDAAC to the other group of shield mud and then add CaO to form a PDMDAAC-CaO group. After the two groups are fully mixed, let them settle naturally for 5 hours, and record the reading of the mud-water interface during the sedimentation process. The reading of the measuring cylinder is the scale of the mud-water interface, which reflects the effect of flocculation and sedimentation. The lower the reading, the better the effect. Draw a flocculation time-water content curve based on the sedimentation time and the measuring cylinder reading, and get the attached Figure 4 , where the amounts of CaO and PDMDAAC added to the two groups of shield muds were the same.

[0043] By the attached Figure 4 It can be seen that as the flocculation time increases, the water content of the CaO-PDMDAAC group is first lower than that of the PDMDAAC-CaO group. When the flocculation time is 20 minutes, the water content of the two is the same. Since the flocculation time in actual use is less than 20 minutes, and in the first 20 minutes, the water content of the CaO-PDMDAAC group is lower, and the flocculation and sedimentation effect is faster, the flocculation effect produced by the addition sequence of the CaO-PDMDAAC group is better than that of the PDMDAAC-CaO group. This is because after adding CaO first, CaO can change the pore structure of the clay particles in the shield mud, resulting in too many voids. After adding PDMDAAC, the clay particles can quickly flocculate into obvious flocs.

[0044] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A shield mud dehydration method, characterized in that: include: Add quicklime powder to the shield mud, stir for 10-20 minutes, then add polydimethyldiallyl ammonium chloride solution, mix and flocculate to form flocculated mud; The flocculated sludge enters the feed pipe of the concentration tank along the arc-shaped feed trough, and enters the concentration tank for concentration after being buffered by the conical distributor at the bottom of the feed pipe to form concentrated sludge; The concentrated mud is dehydrated by filter pressing to obtain a mud cake.

2. The shield slurry dehydration method according to claim 1, characterized in that: The added amount of the quicklime dry powder is 0.5-3.0% of the mass of the shield mud.

3. The shield slurry dehydration method according to claim 1, characterized in that: The amount of the polydimethyldiallyl ammonium chloride solution added is 0.1-0.5% of the mass of the shield mud.

4. The shield slurry dehydration method according to claim 1, characterized in that: The concentration of the polydimethyldiallylammonium chloride solution is 0.3%.

5. The shield slurry dehydration method according to claim 1, characterized in that: The polydimethyldiallyl ammonium chloride solution is prepared using the overflow tail water of the concentration tank.

6. The shield slurry dehydration method according to claim 1, characterized in that: The curvature of the arc-shaped feed trough is greater than the curvature of the concentration tank.

7. The shield slurry dehydration method according to claim 1, characterized in that: The rotation speed of the mixing and flocculation is 20-200 rpm.

8. The shield slurry dehydration method according to claim 1, characterized in that: The filter pressing dehydration adopts a plate and frame filter press or a belt filter press for dehydration, the slurry feeding and filter pressing time is 70 minutes in total, the feed pressure is 0.8 MPa, and the pressing pressure is 1.0 MPa.

9. The shield slurry dehydration method according to claim 1, characterized in that: The bottom of the concentration tank is funnel-shaped.

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