CN114394722A

CN114394722A - Sludge in-situ solidification construction method

Info

Publication number: CN114394722A
Application number: CN202210038838.4A
Authority: CN
Inventors: 黄志亮; 郭晓静; 周欣; 陈辉; 蔡小平; 刘靖; 李北涛
Original assignee: Beijing Jingwei Environmental Technology Co ltd
Current assignee: Beijing Jingwei Environmental Technology Co ltd
Priority date: 2022-01-13
Filing date: 2022-01-13
Publication date: 2022-04-26
Anticipated expiration: 2042-01-13
Also published as: CN114394722B

Abstract

The invention relates to a sludge in-situ solidification construction method, which comprises the following steps: the method comprises the following steps: spreading ferrous sulfate on the surface of the sludge pit, stirring in situ, uniformly stirring, and standing for more than 5 hours; step two: spraying quicklime powder, stirring in situ, uniformly stirring, and standing for more than 2 hours; step three: spraying fly ash powder, and stirring in situ; step four: spraying cement and stirring in situ; step five: turning and stirring up and down; step six: performing in-situ natural maintenance, and performing in-situ turning and stirring for 1 time at intervals of more than 5 days; step seven: and (5) maintaining under natural conditions. The invention breaks the sludge cell wall, reduces the water content of the solidified sludge and improves the strength of the solidified sludge by controlling the adding sequence of the solidifying agent such as ferrous sulfate, quicklime powder, fly ash powder and cement and the reaction time of the solidifying agent and the sludge.

Description

Sludge in-situ solidification construction method

Technical Field

The invention relates to the technical field of sludge treatment, in particular to a sludge in-situ solidification construction method.

Background

Sludge pits formed by landfill of municipal sludge, fermented biogas residues and the like have high water content, the sludge is in a flow plastic and soft plastic state, and the field is in a marshland state and cannot be utilized. The existing sludge in-situ solidification construction utilizes a special stirring head to respectively add solidification agents into a sludge pit, and then the solidification agents are stirred with sludge, so that the sludge reacts with the solidification agents, and the purpose of sludge solidification is achieved. In the prior art, in-situ and ex-situ solidification construction is carried out through a turnover pit; in addition, the prior art provides a sludge in-situ stabilization and solidification construction process, which comprises the following steps: firstly, determining in-situ stabilization and solidification construction of sludge; carrying out in-situ stabilization, solidification and stirring construction on the sludge; maintaining the sludge after stabilizing and solidifying; the construction process is completed by sludge effect self-checking after stabilization and solidification and secondary dosing stabilization and solidification; there are also prior art references to sludge solidification by ex-situ stirring devices; in addition, the prior art mentions that a mechanical stirring head is adopted to carry out in-situ solidification on shallow sludge and high-pressure rotary spraying on deep sludge; the above prior art does not mention the addition sequence of the agents, the number of times of stirring, the reaction time after adding different curing agents and the overall stirring after curing to improve the conditions for the reaction of the curing agents and the sludge.

Disclosure of Invention

In view of the above, the main objective of the present invention is to provide a sludge in-situ solidification construction method, which aims to solve the technical problems of breaking sludge cell walls, reducing solidified sludge water content and improving solidified sludge strength by controlling the addition sequence of solidified reagents and the reaction time of the reagents and the sludge.

In order to achieve the purpose, the invention provides a sludge in-situ solidification construction method, which comprises the following steps:

the method comprises the following steps: spreading ferrous sulfate on the surface of the sludge pit, stirring in situ, uniformly stirring, and standing for more than 5 hours;

step two: spraying quicklime powder, stirring in situ, uniformly stirring, and standing for more than 2 hours;

step three: spraying fly ash powder, and stirring in situ;

step four: spraying cement and stirring in situ;

step five: turning and stirring up and down;

step six: performing in-situ natural maintenance, and performing in-situ turning and stirring for 1 time at intervals of more than 5 days;

step seven: and (5) maintaining under natural conditions.

Further, in the first step, the ferrous sulfate is crystal, wherein the content of anhydrous ferrous sulfate is more than 90 wt%.

Further, in the first step, the mass ratio of the ferrous sulfate to the sludge is (6-15): 100.

further, in the second step, the quicklime is powder which is sieved by a 200-mesh sieve, and the content of calcium oxide is more than 80 wt%.

Further, in the second step, the mass ratio of the quicklime to the sludge is (6-15): 100.

further, in the third step, the fly ash is national standard second-level fly ash, the sieve residue of a 45-micron square-hole sieve is less than or equal to 25.0 percent, the water demand ratio is less than or equal to 105 percent, the loss on ignition is less than or equal to 8.0 percent, the water content is less than or equal to 1.0 percent, the sulfur trioxide is less than or equal to 3.0 percent, and the free calcium is less than or equal to 1.0 percent.

Further, in the third step, the mass ratio of the fly ash powder to the sludge is (5-10): 100.

further, in the fourth step, the mass ratio of the cement to the sludge is (8-15): 100.

further, in the fourth step, the cement is Portland cement 42.5.

Further, in the fifth step, the turning and stirring up and down specifically comprises: mixing and stirring the bottom sludge, the middle sludge and the surface sludge.

Further, in the sixth step, the in-situ turning and stirring times are at least 3.

Further, in the seventh step, the natural-condition curing is performed for more than 28 days from the beginning of the ferrous sulfate addition to the end of the curing.

By the technical scheme, the sludge in-situ solidification construction method at least has the following advantages:

1. the invention breaks the sludge cell wall, reduces the water content of the solidified sludge and improves the strength of the solidified sludge by controlling the adding sequence of the solidifying agent such as ferrous sulfate, quicklime powder, fly ash powder and cement and the reaction time of the solidifying agent and the sludge.

2. The invention adds the curing agent in several times and stirs the sludge to make the curing agent and the sludge mixed more evenly, so that the agent and the sludge react more fully.

3. According to the invention, the curing agent is stirred in an up-down turning manner and in a curing period, so that the agent can be uniformly stirred, and better curing conditions are created for hydration reaction, gas hardening reaction and water evaporation of the curing agent.

Detailed Description

To further illustrate the technical means and effects of the present invention for achieving the predetermined objects, the following detailed description will be given to the specific implementation, structure, features and effects of the sludge in-situ solidification construction method according to the present invention with reference to the preferred embodiments.

In the following examples of the present invention, unless otherwise specified, all the components referred to are commercially available products well known to those skilled in the art, and if not specified, all the methods referred to are conventional methods. Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs.

Some embodiments of the invention provide a sludge in-situ solidification construction method, which comprises the following steps:

the method comprises the following steps: spreading ferrous sulfate on the surface of the sludge pit, stirring in situ, uniformly stirring, and standing for more than 5 hours; wherein the ferrous sulfate can be scattered by adopting an excavator or a loader. The sludge pit is formed by burying municipal sludge, fermented biogas residues and the like, the water content is more than 80 wt%, the organic matter content is more than 20 wt%, and the sludge is in a flow plastic and soft plastic stateThe ground is in a marshland state. The in-situ stirring adopts a solidification stirring head for stirring, the solidification stirring head can be installed on an excavator with a proper tonnage, and the solidification stirring operation of the curing agent and the sludge in situ is carried out under the operation of a driver. The maximum processing depth of the stirring head is 8m, the stirring head is suitable for a hydraulic excavator with the self weight of more than 36 tons, the rotating speed is 1-100 rpm, and the working efficiency can reach 110m at most³H is used as the reference value. The ferrous sulfate is crystal, and the content of the anhydrous ferrous sulfate is more than 90 wt%. The spreading rate of the ferrous sulfate is 30t/h-40 t/h. The mass ratio of the ferrous sulfate to the sludge is (6-15): 100.

step two: spraying quicklime powder, stirring in situ, uniformly stirring, and standing for more than 2 hours; the quicklime is powder which is sieved by a 200-mesh sieve, and the content of calcium oxide is more than 80 wt%; the mass ratio of the powder quicklime to the sludge is (6-15): 100 and the injection rate is 30t/h-40 t/h. After being uniformly stirred, the standing sludge can reduce the water content of the solidified sludge and increase the shear strength of the solidified sludge, but the standing time is prolonged, so that the construction period is influenced.

Step three: spraying fly ash powder, and stirring in situ; the fly ash is national standard second-grade fly ash, the fineness (the balance of a 45-micron square-hole sieve) of the fly ash is less than or equal to 25.0 percent, the water demand ratio is less than or equal to 105 percent, the ignition loss is less than or equal to 8.0 percent, the water content is less than or equal to 1.0 percent, the sulfur trioxide is less than or equal to 3.0 percent, and the free calcium is less than or equal to 1.0 percent; the mass ratio of the powdered coal ash to the sludge is (5-10): 100 and the injection rate is 30t/h-40 t/h.

Step four: spraying cement and stirring in situ; the cement is Portland cement 42.5; the mass ratio of the cement to the sludge is (8-15): 100 and the injection rate is 30t/h-40 t/h.

Step five: turning and stirring up and down; according to the depth selection of the sludge pit, a long-arm excavator is required to be used for mixing and stirring the sludge processed in the five steps with the sludge at the bottom, the middle and the surface layer to ensure that the medicament and the sludge are mixed more uniformly, wherein the depth of the sludge is more than 5 m.

Step six: standing at normal temperature and normal pressure, maintaining without disturbance, and stirring for at least 3 times at an interval of not less than 5 days. The in-situ natural curing specifically comprises: the ferrous sulfate, the quicklime powder, the fly ash powder and the cement are subjected to hydration reaction, volcanic ash reaction and other reactions with the sludge for a certain time, the in-situ solidification is carried out, after the medicament and the sludge are stirred, the maintenance is carried out under the natural condition, the sludge is not disturbed, and the standing is carried out for a period of time for natural reaction. The stirring time interval is increased, the water content and the shear strength of the solidified sludge are not greatly influenced, but the construction period is influenced. The increase of the stirring times can reduce the water content of the solidified sludge and increase the shear strength of the solidified sludge, but the construction period is influenced.

Step seven: and (4) naturally curing for more than 28 days from the beginning of adding the ferrous sulfate to the end of curing. The natural condition maintenance specifically comprises: standing at normal temperature and normal pressure without disturbance, and reacting the sludge with a medicament consisting of ferrous sulfate, quicklime powder, fly ash powder and cement. The curing time after the addition of the agent affects the moisture content and the shear strength of the cured sludge, the curing time is too long, the moisture content reduction rate and the shear strength improvement rate are not obviously affected, and the construction period is increased; the curing time is too short, the water content of the solidified sludge is increased and the shear strength is reduced.

The present invention is further illustrated by the following specific examples.

Example 1

The embodiment provides a sludge in-situ solidification construction method, which comprises the following steps:

the method comprises the following steps: in a sludge pit (the sludge amount is 1000 m)³The depth of the sludge is 7m, the water content of the sludge is 82.7 wt%, and the organic matter is 41.52 wt%), ferrous sulfate is spread on the surface, the stirring head is used for in-situ stirring, and the mixture is stirred uniformly and then stands for 5 hours. The ferrous sulfate is crystal, wherein the content of anhydrous ferrous sulfate is 90 wt%. The spreading rate of the ferrous sulfate is 35 t/h. The mass ratio of the ferrous sulfate to the sludge is 12: 100.

step two: spraying quicklime powder, stirring in situ by a stirring head, uniformly stirring, and standing for 2 hours; the quicklime is powder which is sieved by a 200-mesh sieve, and the content of calcium oxide is more than 80 wt%; the mass ratio of the quicklime to the sludge is 11: 100 and the injection rate is 35 t/h.

Step three: spraying fly ash powder, and stirring in situ by a stirring head; the fly ash is national standard second-grade fly ash, the fineness (the screen allowance of a 45-micron square-hole sieve) of the fly ash is 22.1 percent, the water demand ratio is 98.5 percent, the ignition loss is 6.2 percent, the water content is 1.0 percent, the sulfur trioxide is 2.4 percent, and the free calcium is 0.7 percent; the mass ratio of the fly ash to the sludge is 9: 100 and the injection rate is 35 t/h.

Step four: spraying cement, and stirring in situ by a stirring head; the cement may be portland cement 42.5; the mass ratio of the cement to the sludge is 13: 100 and the injection rate is 35 t/h.

Step five: the long-arm excavator is used for turning and stirring up and down, so that the added medicament and the sludge are mixed more uniformly.

Step six: standing at normal temperature and normal pressure, maintaining without disturbance, and stirring for 3 times at an interval of 5 days by in-situ turning and stirring for 1 time.

Step seven: standing at normal temperature and normal pressure, and maintaining for 28 days from the start of adding the agent to the end of curing.

Example 2

This example differs from example 1 in that the mixture is stirred uniformly in step one and then allowed to stand for 10 hours. The rest of the steps and parameters were the same as in example 1.

Example 3

This example differs from example 1 in that the mixture is stirred uniformly in step one and then allowed to stand for 15 hours. The rest of the steps and parameters were the same as in example 1.

Example 4

This example differs from example 1 in that the mixture is stirred uniformly in step two and then allowed to stand for 4 hours. The rest of the steps and parameters were the same as in example 1.

Example 5

This example differs from example 1 in that the mixture is stirred uniformly in step two and then allowed to stand for 6 hours. The rest of the steps and parameters were the same as in example 1.

Example 6

The difference between this example and example 1 is that in step six, 1 in-situ stirring is performed at intervals of 8 days, and the stirring times are 3 times. The rest of the steps and parameters were the same as in example 1.

Example 7

The difference between this example and example 1 is that in step six, 1 in-situ stirring is performed at intervals of 5 days, and the stirring times are 6 times. The rest of the steps and parameters were the same as in example 1.

Example 8

This example differs from example 1 in that the natural condition maintenance described in step seven was carried out for 35 days from the start of the addition of the chemical agent to the end of the maintenance. The rest of the steps and parameters were the same as in example 1.

Comparative example 1

This comparative example differs from example 1 in that the mixture is stirred uniformly in step one and then allowed to stand for 1 hour. The rest of the steps and parameters were the same as in example 1.

Comparative example 2

The comparative example differs from example 1 in that the mixture is stirred uniformly in step two and then allowed to stand for 1 hour. The rest of the steps and parameters were the same as in example 1.

Comparative example 3

The difference between the comparative example and the example 1 is that in the sixth step, 1 in-situ turning stirring is carried out at an interval of 3 days, and the stirring times are 3 times. The rest of the steps and parameters were the same as in example 1.

Comparative example 4

The difference between the comparative example and example 1 is that in step six, 1 in-situ turning and stirring is performed at intervals of 5 days, and the stirring frequency is 1. The rest of the steps and parameters were the same as in example 1.

Comparative example 5

The present comparative example differs from example 1 in that the natural-condition curing described in step seven, from the start of ferrous sulfate addition to the end of curing, takes 21 days or more. The rest of the steps and parameters were the same as in example 1.

Comparative example 6

This comparative example differs from example 1 in that it does not include steps five through seven. The rest of the steps and parameters were the same as in example 1.

Comparative example 7

This comparative example differs from example 1 in that the order of step one and step two is reversed. The rest of the steps and parameters were the same as in example 1.

Comparative example 8

This comparative example differs from example 1 in that the order of step one and step three is reversed. The rest of the steps and parameters were the same as in example 1.

Comparative example 9

This comparative example differs from example 1 in that the order of step one and step four is reversed. The rest of the steps and parameters were the same as in example 1.

Comparative example 10

This comparative example differs from example 1 in that the order of step two and step three is reversed. The rest of the steps and parameters were the same as in example 1.

Comparative example 11

This comparative example differs from example 1 in that the order of step two and step four is reversed. The rest of the steps and parameters were the same as in example 1.

Comparative example 12

This comparative example differs from example 1 in that the order of step three and step four is reversed. The rest of the steps and parameters were the same as in example 1.

Test example

Two experiments were carried out on 100g of municipal sludge (water content 85.5 wt%, organic matter 39.08 wt%) with one group containing 10g of ferrous sulfate and the other group containing no ferrous sulfate, and the two groups were stirred uniformly and allowed to stand for 5 hours under the same conditions. And respectively carrying out vacuum filtration, wherein the amount of sewage obtained after the sludge is added with the ferrous sulfate is 28.3g, and the amount of sewage obtained after the sludge is not added is 6.8 g.

3 points of the sludge obtained in the above examples 1 to 8 and comparative examples 1 to 12 were drilled in situ, and a sample obtained by solidifying the sludge at a depth of 6.5m was taken for detection, and the arithmetic mean of the detection results of each example is shown in table 1. Wherein the detection of the water content is based on a sludge detection method CJ/T221-2005 of an urban sewage treatment plant; the shear strength is measured according to geotechnical test method standard GB/T50123-2019.

TABLE 1

As can be seen from the data in Table 1, the water content of the sludge after solidification in the embodiments 1-8 of the invention reaches 45.26-51.86%, and the shear strength reaches 25.28-28.43 kPa.

Comparing comparative examples 1 and 2 with example 1, it can be seen that the reduction of the standing time increases the moisture content of the solidified sludge and decreases the shear strength of the solidified sludge.

Comparing comparative example 3 with example 1, it can be seen that the shorter stirring interval time increases the moisture content of the solidified sludge and decreases the shear strength of the solidified sludge.

Comparing comparative example 4 with example 1, it can be seen that the smaller number of times of stirring increases the water content of the solidified sludge and decreases the shear strength of the solidified sludge.

Comparing comparative example 6 with example 1, it can be seen that the water content of the solidified sludge is obviously increased and the shear strength of the solidified sludge is reduced after fewer steps.

Comparing comparative examples 7 to 12 with example 1, it can be seen that the adjustment of the order increases the moisture content of the solidified sludge and decreases the shear strength of the solidified sludge.

In conclusion, according to the invention 1-8, ferrous sulfate is added to improve the sludge performance and increase the sludge dewatering property, then quicklime is added to further break the cell walls in the sludge under the alkali excitation condition, and then under the action of cement, quicklime and fly ash, the agent and water undergo hydration reaction, pozzolan reaction and the like to solidify the sludge, reduce the water content of the sludge and increase the strength of the solidified sludge. Meanwhile, through controlling the standing reaction time of the curing agent and the sludge, deep layer turnover, secondary stirring and other construction measures, the hydraulic material cement and the gas hard material quicklime can better react, and the strength of the cured sludge is improved.

In the description of the present invention, numerous specific details are set forth. It is understood, however, that embodiments of the invention may be practiced without these specific details. In some embodiments, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and any simple modification, equivalent change and modification made to the above embodiment according to the technical spirit of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. The sludge in-situ solidification construction method is characterized by comprising the following steps:

step three: spraying fly ash powder, and stirring in situ;

step four: spraying cement and stirring in situ;

step five: turning and stirring up and down;

step seven: and (5) maintaining under natural conditions.

2. The sludge in-situ solidification construction method as claimed in claim 1, wherein in the step one, the ferrous sulfate is crystal, and the content of anhydrous ferrous sulfate is more than 90 wt%.

3. The sludge in-situ solidification construction method according to claim 1, wherein in the first step, the mass ratio of the ferrous sulfate to the sludge is (6-15): 100.

4. the sludge in-situ solidification construction method as claimed in claim 1, wherein in the second step, the quicklime is powder passing through a 200-mesh sieve, and the content of calcium oxide is more than 80 wt%.

5. The sludge in-situ solidification construction method according to claim 1, wherein in the second step, the mass ratio of the quicklime to the sludge is (6-15): 100.

6. the sludge in-situ solidification construction method as claimed in claim 1, characterized in that in the third step, the fly ash is national standard second grade fly ash, the sieve residue percent of a 45-micron square-hole sieve is less than or equal to 25.0 percent, the water demand ratio is less than or equal to 105 percent, the ignition loss is less than or equal to 8.0 percent, the water content is less than or equal to 1.0 percent, the sulfur trioxide is less than or equal to 3.0 percent, and the free calcium is less than or equal to 1.0 percent; the mass ratio of the powdered coal ash to the sludge is (5-10): 100.

7. the sludge in-situ solidification construction method according to claim 1, wherein in the fourth step, the mass ratio of the cement to the sludge is (8-15): 100, respectively; the cement is Portland cement 42.5.

8. The sludge in-situ solidification construction method as claimed in claim 1, wherein in the fifth step, the up-down turning and stirring specifically comprises: mixing and stirring the bottom sludge, the middle sludge and the surface sludge.

9. The sludge in-situ solidification construction method as claimed in claim 1, wherein in the sixth step, the number of times of in-situ turning and stirring is at least 3.

10. The sludge in-situ solidification construction method as claimed in claim 1, wherein in the seventh step, the natural condition maintenance is carried out for more than 28 days from the beginning of the ferrous sulfate addition to the end of the maintenance.