Sludge hot filtration dehydration method

Abstract

The invention relates to a sludge hot filtration dehydration method. The method comprises the following specific steps: S1, preheating sludge; s2, adding the sludge preheated in the step S1 into a heat preservation filter; s3, pressurized air is introduced into the heat preservation filter containing the sludge in the step S2, the sludge is filtered after the pressure is stable, pressure relief is conducted after no filtrate is discharged till no gas escapes, and the dewatered sludge is obtained. Compared with the prior art, the method disclosed by the invention is simple and easy to implement, and the temperature rise can obviously reduce the sludge viscosity, weaken the water-solid affinity of the sludge and release bound water, so that the sludge dewatering efficiency is effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment, in particular to a sludge thermal filtration dewatering method. BACKGROUND

[0002] Sludge is the microbial residue and precipitate of pollutants transformation in the process of sewage treatment, which has the dual attributes of "pollution" and "resource". On the one hand, sludge carries more than 50% of the total amount of pollutants in the influent of sewage treatment plant, including various pathogenic bacteria, heavy metals and toxic organic pollutants; on the other hand, sludge contains rich resources and energy, including nutrients such as carbon, nitrogen and phosphorus, in addition, the sludge after deep dewatering (moisture content ≤40%) has a high combustion heat value, which can be effectively converted into heat energy through sludge incineration technology for power generation and heating. Therefore, the dual attributes of sludge should be fully considered, and the sludge should be properly treated and disposed to achieve the goal of "reduction, harmlessness and resource utilization".

[0003] The high water content characteristic of sludge is one of the key factors restricting its treatment and disposal efficiency. The "Technical Code for Sludge Treatment and Disposal of Municipal Sewage Treatment Plant" (CJJ 131-2009) has made specific technical requirements for sludge moisture content in the aspects of sludge transportation, pyrolysis, incineration, land use and other links of sewage treatment plant (moisture content of sanitary landfill sludge ≤60%, moisture content of land use sludge ≤45%, moisture content of building material utilization sludge ≤35%), therefore, dewatering is a common component in various treatment and disposal routes of sludge, and its core goal is to remove water in sludge through physical, chemical or biological methods, to convert the flow state sludge into semi-solid or solid sludge, to realize solid enrichment and volume reduction, and to create conditions for subsequent disposal. Therefore, efficiently and lowly reducing the moisture content of sludge and improving the heat value of sludge are important technical prerequisites for low-carbon, centralized and large-scale treatment and disposal of sludge in China.

[0004] However, sludge belongs to a highly organic-inorganic heterogeneous complex system, presents a stable colloidal flocculation state of water-solid infiltration distribution, and is extremely difficult to achieve efficient and low-cost deep dewatering. At present, the sludge deep dewatering process usually adopts a technical combination mode of "coagulation / flocculation conditioning + mechanical dewatering + thermal drying", but faces technical pain point problems such as high chemical consumption, low efficiency, and high energy consumption. Among them, coagulants and flocculants represented by polyaluminum chloride (PAC), polyferric chloride (PFC), and polyacrylamide (PAM) are still widely used sludge dewatering conditioners, which can change the surface electrical properties and aggregation state of sludge solid particles through electrical neutralization and adsorption bridging, and can reduce the interstitial water content of sludge to a certain extent and promote the removal of free water of sludge, but have no obvious advantage in removing surface attached water and bound water. Therefore, after using the above traditional conditioners, the sludge water content can only be reduced to about 80wt% during mechanical dewatering, and the large amount of chemical agents will also cause serious secondary pollution problems, greatly restricting the high-value utilization of dewatered sludge cake. In order to further achieve deep dewatering (sludge water content ≤40wt.%), it is necessary to use thermal drying process. However, the core working temperature of the traditional thermal drying process is 100℃-180℃, and the process energy consumption accounts for 50%-60% of the total energy consumption of the sludge treatment process, which has an adverse effect on energy saving and emission reduction of the whole sludge treatment process. Therefore, under the premise of balancing the environment, society and economic benefits, the sludge efficient deep dewatering technology without conditioning and at medium-low temperature has broad market application prospects and social environmental benefits. SUMMARY

[0005] The purpose of the present application is to solve the problems of chemical agent dependence and secondary pollution, low dewatering efficiency and high energy consumption in the prior art, and to provide a sludge thermal filtration dewatering method, which has the characteristics of no conditioning agent addition, medium-low temperature reaction conditions, and simple and easy-to-operate process.

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] A sludge thermal filtration dewatering method, the specific steps are as follows:

[0008] S1, preheating sludge;

[0009] S2, adding the preheated sludge in step S1 into a heat preservation filter;

[0010] S3, introducing pressurized air into the heat preservation filter containing sludge in step S2, filtering the sludge after the pressure is stabilized, and then unpressurizing after no filtrate is discharged, until no gas is emitted, to obtain dewatered sludge.

[0011] Further, in step S1, the water content of the sludge is 80wt.%-90wt.%.

[0012] Further, in step S1, the method for preheating the sludge is an indirect heat exchange method.

[0013] Further, in step S1, the method for preheating the sludge is an indirect heat exchange method.

[0014] Further, in step S2, the heat preservation filter is a preheated heat preservation filter, and the specific steps are as follows: the heat preservation filter is heated to a predetermined temperature and kept constant.

[0015] Further, in step S2, the heat preservation filter is a preheated heat preservation filter, and the specific steps are as follows: the heat preservation filter is heated to a predetermined temperature and kept constant.

[0016] Further, in step S2, the heat preservation filter is a preheated heat preservation filter, and the specific steps are as follows: the heat preservation filter is heated to a predetermined temperature and kept constant.

[0017] Further, in step S3, the pressure of the pressurized air is 0.3-0.5MPa.

[0018] Further, in step S3, the pressure of the pressurized air is 0.3-0.5MPa.

[0019] Further, in step S3, the pressure of the pressurized air is 0.3-0.5MPa.

[0020] Compared with the prior art, the beneficial effects of the present application are as follows:

[0021] 1. The treatment method of the present application is simple and easy to operate. The present application first utilizes the viscosity sudden drop effect in the medium temperature zone (20.0℃-80.0℃), and only by changing the sludge temperature in the reactor and cooperating with the high-pressure filter pressing technology, the combined water is removed in a targeted manner, realizing efficient and deep dewatering of the sludge.

[0022] 2. The present application does not need other sludge industrial conditioner addition and sludge pretreatment process, and can overcome the shortcomings of high reagent addition amount and large sludge volume increase ratio before the traditional sludge mechanical dewatering process, greatly reducing the long-term operation cost caused by sludge conditioner addition and the possible secondary environmental pollution risk.

[0023] 3. The treatment process temperature of the present application is moderate, and only the conventional hot water circulation is needed to maintain the target temperature, which has significant advantages in economic benefit and social environmental benefit, and shows broad market application potential.

[0024] 4. The present application is simple and easy to operate, and the temperature rise can significantly reduce the sludge viscosity, weaken the water-solid affinity of the sludge, release the combined water, and thus effectively improve the sludge dewatering efficiency. DETAILED DESCRIPTION

[0025] The application will be described in detail below with specific examples. The examples are implemented on the premise of the technical solution of the application, and detailed implementation modes and specific operation processes are given, but the protection scope of the application is not limited to the examples below. Each of the following examples can be implemented individually, or any two or more of them can be combined.

[0026] Unless otherwise specified, the reagents, methods, instruments and equipment used in the application are conventional reagents, methods, instruments and equipment in the art. Unless otherwise specified, the reagents and materials used in the examples below are commercially available.

[0027] The above embodiments will be described in more detail below with specific examples. The sludge used in each example and comparative example is taken from a municipal sewage treatment plant in Shanghai. First, the sludge is concentrated to a water content of 80 wt.%.

[0028] Example 1

[0029] This example provides a sludge hot filtration dewatering method, and the specific steps are as follows:

[0030] (1) Heat the heat preservation filter and maintain the temperature at 20.0℃;

[0031] (2) After heating the sludge to 20.0℃, transfer it to the heat preservation filter while it is hot;

[0032] (3) Introduce pressurized air into the heat preservation filter to maintain the pressure at 0.4 MPa;

[0033] (4) After the pressure is stabilized, filter the sludge, record the filtrate mass corresponding to different filtration times, and then release the pressure after no filtrate is discharged from the heat preservation filter until no gas escapes, and the dewatered sludge is obtained.

[0034] Example 2

[0035] This example provides a sludge hot filtration dewatering method, and the specific steps are as follows:

[0036] (1) Heat the heat preservation filter and maintain the temperature at 40.0℃;

[0037] (2) After heating the sludge to 40.0℃, transfer it to the heat preservation filter while it is hot;

[0038] (3) Introduce pressurized air into the heat preservation filter to maintain the pressure at 0.4 MPa;

[0039] (4) After the pressure is stabilized, filter the sludge, record the filtrate mass corresponding to different filtration times, and then release the pressure after no filtrate is discharged from the heat preservation filter until no gas escapes, and the dewatered sludge is obtained.

[0040] Example 3

[0041] The embodiment provides a sludge hot filtration dewatering method, and specific steps are as follows:

[0042] (1) heating and keeping the filter, and maintaining the temperature at 60.0℃;

[0043] (2) after the sludge is heated to 60.0℃, the sludge is transferred into the heat preservation filter while being hot;

[0044] (3) the pressurized air is introduced into the heat preservation filter, so that the pressure is stably kept at 0.4MPa;

[0045] (4) after the pressure is kept constant, the sludge is filtered, the filtrate quality corresponding to different filtration times is recorded, the pressure is released after no filtrate is discharged from the heat preservation filter, until no gas is discharged, and then the dewatered sludge is obtained.

[0046] Example 4

[0047] The embodiment provides a sludge hot filtration dewatering method, and specific steps are as follows:

[0048] (1) heating and keeping the filter, and maintaining the temperature at 60.0℃;

[0049] (2) after the sludge is heated to 80.0℃, the sludge is transferred into the heat preservation filter while being hot;

[0050] (3) the pressurized air is introduced into the heat preservation filter, so that the pressure is stably kept at 0.4MPa;

[0051] (4) after the pressure is kept constant, the sludge is filtered, the filtrate quality corresponding to different filtration times is recorded, the pressure is released after no filtrate is discharged from the heat preservation filter, until no gas is discharged, and then the dewatered sludge is obtained.

[0052] Comparative Example 1

[0053] The comparative example provides a sludge dewatering method, and specific steps are as follows:

[0054] (1) the sludge at room temperature is transferred into the heat preservation filter at room temperature, and the room temperature is 15.6℃;

[0055] (2) the pressurized air is introduced into the heat preservation filter, so that the pressure is stably kept at 0.4MPa;

[0056] (3) the sludge is filtered after the pressure is kept constant, the filtrate quality corresponding to different filtration times is recorded, the pressure is released after no filtrate is discharged from the heat preservation filter, until no gas is discharged, and then the dewatered sludge is obtained.

[0057] The data obtained by the sludge thermal filtration dewatering method in examples 1-4 and the sludge dewatering method in comparative example 1 are analyzed and calculated to obtain the specific resistance (r) of the sludge. The specific resistance of the sludge is the most commonly used index for characterizing the dewatering performance of the sludge, and is defined as follows: the resistance of a unit dry weight of filter cake on a unit filtration area under a certain pressure. The greater the specific resistance of the sludge, the worse the dewatering performance of the sludge, and vice versa. The specific test and calculation results are shown in Table 1.

[0058] Table 1: Test results of the dewatering performance of the sludge in examples 1-4 and comparative example 1

[0059] Filtration temperature (°C) Sludge specific resistance (cm / g) Comparative Example 1 15.6 2.99 x 10 12 ]] Example 1 20.0 2.60 x 10 12 ]] Example 2 40.0 1.69 x 10 12 ]] Example 3 60.0 1.21 x 10 12 ]] Example 4 80.0 9.20 x 10 11 ]]

[0060] As shown in Table 1, by adjusting the temperature of the sludge under a constant pressure, the specific resistance of the sludge is greatly reduced from the original 2.99x10 12 cm / g to 9.20x10 11 cm / g, a decrease of 69.2%, and the dewatering performance is significantly improved.

[0061] The above description of the examples is for the purpose of facilitating the understanding and use of the present application by those of ordinary skill in the art. Those skilled in the art can obviously make various modifications to the examples, and apply the general principles described herein to other examples without creative labor. Therefore, the present application is not limited to the above examples, and any improvements and modifications made by those skilled in the art based on the disclosure of the present application without departing from the scope of the present application should be within the scope of protection of the present application.

Claims

1. A sludge thermal filtration dewatering method characterized by, The specific steps are as follows: S1, preheating sludge; S2, adding the preheated sludge in step S1 into a heat preservation filter; S3, introducing pressurized air into the heat preservation filter containing sludge in step S2, filtering the sludge after the pressure is stabilized, and then depressurizing until no gas is emitted to obtain dewatered sludge.

2. The method of thermal filtration dewatering of sludge according to claim 1, characterized in that, In step S1, the moisture content of the sludge is 80wt.%-90wt.%.

3. The method of thermal filtration dewatering of sludge according to claim 1, characterized in that, In step S1, the method for preheating the sludge is indirect heat exchange.

4. The method of thermal filtration dewatering of sludge according to claim 3, characterized in that, The heating temperature of the sludge is 20.0℃-80.0℃.

5. The method of thermal filtration dewatering of sludge according to claim 1, characterized in that, In step S2, the heat preservation filter is a preheated heat preservation filter, and the specific steps are as follows: heating the heat preservation filter to a predetermined temperature and keeping the temperature constant.

6. The method of thermal filtration dewatering of sludge according to claim 5, characterized in that, The predetermined temperature is 20.0℃-80.0℃.

7. The method of thermal filtration dewatering of sludge according to claim 5, characterized in that, The accuracy of the preheating temperature of the heat preservation filter and the preheating temperature of the sludge is ±1.0℃.

8. The method of thermal filtration dewatering of sludge according to claim 1, characterized in that, In step S3, the pressure of the pressurized air introduced is 0.3-0.5MPa.

9. The method of thermal filtration dewatering of sludge according to claim 8, characterized in that, The pressure of the pressurized air introduced is 0.4MPa.

10. The method of thermal filtration dewatering of sludge according to claim 1, characterized in that, In step S3, the heat preservation filter is depressurized to the pressure of the gas in the heat preservation filter being consistent with the atmospheric pressure.