A method for regulating aeration of a biological drying system based on sludge moisture content

Abstract

The application discloses a method for regulating aeration of a biological drying system based on sludge moisture content, and relates to the technical field of municipal sludge treatment. In the biological drying process, the application can regulate the aeration amount in real time according to the sludge moisture content, realizes appropriate supply of the aeration amount in different stages, maximally reduces heat loss generated by aerobic microbial metabolism, realizes rapid temperature rise of a pile body, further improves the maximum temperature of the pile body, prolongs the duration of the high-temperature period, and promotes rapid evaporation of the moisture of the material. Compared with the conventional intermittent aeration or continuous aeration sludge biological drying technology, the application improves the sludge biological drying efficiency, and shortens the time required for reducing the moisture content to below 40% to within 7 days.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of municipal sludge treatment, and particularly relates to a method for regulating aeration of a biological drying system based on sludge moisture content. BACKGROUND

[0002] In recent years, with the rapid improvement of sewage treatment capacity in China, the amount of sludge has also increased substantially, and it is estimated that it will exceed 90 million tons (calculated at 80% moisture content) in 2025. In order to reduce the negative impact of the huge amount of sludge and realize its resource utilization in the fields of incineration power generation, land and building materials, it needs to be dried. The traditional sludge drying method (thermal drying, solar drying, etc.) has the problems of high energy consumption or low efficiency, and the biological drying technology has been widely concerned in the field of sludge resource utilization due to its low pollution and low energy consumption.

[0003] Sludge biological drying is a sludge reduction technology that uses aerobic microorganisms to release heat during the metabolism of organic matter under aerobic conditions, so that the system maintains a high temperature, and the water in the sludge is evaporated, and the water is taken away by aeration. Aeration is a key factor affecting the efficiency of sludge biological drying. On the one hand, aeration can provide oxygen for the growth and metabolism of aerobic microorganisms, and on the other hand, water in the material can be taken out by aeration. Generally speaking, the greater the aeration rate, the faster the water removal rate, but in the biological drying process, too high aeration rate will take away a lot of heat from the heap, reducing the temperature of the heap, and affecting water evaporation, so it is necessary to find a suitable aeration control strategy to take away the water in the material and reduce the heat loss of the heap, improve the efficiency of sludge biological drying, and shorten the biological drying cycle.

[0004] The existing sludge biological drying aeration mode is mainly continuous aeration or intermittent aeration, and generally only a fixed aeration amount is set, which is difficult to meet the aeration needs of different stages of biological drying, and is prone to insufficient or excessive aeration. There are three forms of water in dewatered sludge, namely bound water, surface adsorbed water and interstitial water. During the biological drying process, different forms of water will transform and migrate each other and continue to decrease. This change will affect the binding energy between water and sludge, and further cause the aeration intensity required to take out water from the material to change; on the other hand, the change of surface adsorbed water content will also affect the contact between sludge particles and air, and affect the utilization of oxygen by microorganisms in the material. Therefore, based on the corresponding relationship between water content and water distribution rule in the process of sludge biological drying, the optimal aeration amount can be regulated according to the change of water content, and the efficiency of sludge biological drying can be further improved. SUMMARY

[0005] In order to overcome the deficiencies of the aeration method in the prior art, the present application provides a method for regulating aeration of a biological drying system based on sludge moisture content, which adjusts the aeration amount in real time according to the change of the moisture content of the sludge in the biological drying process, maintains continuous and rapid evaporation of water, and maximizes the reduction of heat loss of the pile, thereby shortening the biological drying cycle of the sludge.

[0006] The technical problems solved by the present application are solved by the following technical solutions:

[0007] A method for regulating aeration of a biological drying system based on sludge moisture content, which adopts a drum-type biological drying reactor configured with an online moisture content analyzer, and specifically includes the following steps:

[0008] (a) mixing municipal sludge and auxiliary materials and then adding them into the drum-type biological drying reactor;

[0009] (b) adding a sludge biological drying high-temperature bacterial agent into the drum-type biological drying reactor;

[0010] (c) setting the pile turning frequency and the air extraction and dehumidification parameters;

[0011] (d) operating the drum-type biological drying reactor while aerating the pile.

[0012] Further, the online moisture content analyzer includes but is not limited to a near-infrared online moisture content analyzer. In the present application, the online moisture content analyzer can realize real-time monitoring of the moisture content of the materials.

[0013] Further, the aeration stage of the pile is divided into a start-up period, a temperature rising period, a high-temperature period, and a temperature dropping period, the moisture content of the materials in the start-up period is 64-66%, and the regulated aeration amount is 0.8-1.0 L·h -1 ·kg -1 ; the moisture content of the materials in the temperature rising period is 62-64%, and the regulated aeration amount is 0.5-0.6 L·h -1 ·kg -1 ; the moisture content of the materials in the high-temperature period is 45-62%, and the regulated aeration amount is 0.4-0.5 L·h -1 ·kg -1 ; and the moisture content of the materials in the temperature dropping period is <45%, and the regulated aeration amount is 1.0-1.2 L·h -1 ·kg -1 , until the moisture content of the pile is lower than 40%. In the present application, the aeration amount is regulated in real time according to the change of the moisture content of the materials.

[0014] In some specific embodiments, the sludge is mixed with the auxiliary material to have a water content of about 65%, and the initial proportions of the three different forms of water in the total water are as follows: interstitial water 26-29%, surface adsorbed water 66-70%, and bound water 2-4%. The start-up period is 0-6h, during which the proportion of surface adsorbed water is the largest, and a large amount of aeration is required to promote the contact between the aerobic microorganisms in the pile and the air, so that the aerobic microorganisms can grow and metabolize rapidly, thereby accelerating the increase of the temperature of the pile and reducing the water content. The temperature rising period is 7-24h, during which part of the surface adsorbed water is converted into interstitial water, so the proportion of surface adsorbed water decreases and the proportion of interstitial water increases, and the space for the contact between the aerobic microorganisms in the material and the air gradually increases. During this period, the aeration amount is reduced, which can ensure the oxygen supply for the metabolism of the microorganisms while reducing the heat loss, further accelerating the temperature rise of the pile and increasing the evaporation rate of the water. The high-temperature period is 2-4d, during which the temperature is the main driving force for water removal. The high temperature causes the water in the material to evaporate rapidly, and a large amount of surface adsorbed water is converted into interstitial water, so that the proportion of surface adsorbed water further decreases and interstitial water gradually becomes the main form of water. The space for the contact between the microorganisms and the air further increases. During this period, the aeration amount is again reduced, which can maximize the reduction of heat loss under the condition of meeting the metabolic needs of the aerobic microorganisms, prolong the duration of the high-temperature period, and maintain the continuous and rapid evaporation of water. The temperature decreasing period is 5-6d, during which the temperature of the pile decreases, the content of organic matter in the sludge has been largely consumed, and the activity of the aerobic microorganisms decreases. The aeration amount becomes the main factor for water removal. At the same time, the proportion of interstitial water is more than 60% and the proportion of surface adsorbed water is less than 30%. Increasing the aeration amount is beneficial to water removal and shortening the biological drying cycle.

[0015] Further, the auxiliary material includes, but is not limited to, at least one of broken corn cob cores, sawdust, straw powder, and other agricultural wastes, and the particle size is generally controlled to be 1-2cm.

[0016] Further, the mass ratio of the sludge to the auxiliary material is controlled to be (3-5):1.

[0017] Further, the volume of the material obtained by mixing the sludge and the auxiliary material accounts for 50-80% of the total volume of the drum-type biological drying reactor.

[0018] Further, the initial water content of the drum-type biological drying reactor is controlled to be 60-70%, and the corresponding aeration stages can be appropriately prolonged or shortened according to the initial water content.

[0019] Further, the addition amount of the sludge biological drying high-temperature bacterial agent is 1-2%.

[0020] Further, the turning frequency is 1-4 times per day.

[0021] Further, the air extraction and dehumidification parameter is controlled according to the humidity in the reactor, and when the humidity is higher than 85%, the air extraction and dehumidification is started, and when the humidity is lower than 85%, the air extraction and dehumidification is stopped.

[0022] The present application has the advantages that the present application can regulate the aeration amount in real time according to the moisture content of sludge in the biological drying process, realizes the appropriate supply of aeration amount in different stages, maximally reduces the heat loss generated by the metabolism of aerobic microorganisms, realizes the rapid heating of the pile, further improves the maximum temperature of the pile, prolongs the duration of the high temperature period, and promotes the rapid evaporation of the material moisture. Compared with the conventional intermittent aeration or continuous aeration sludge biological drying technology, the present application improves the sludge biological drying efficiency, and shortens the time required for reducing the moisture content to below 40% to within 7 days. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The flowchart of Example 1 of the present application is shown. DETAILED DESCRIPTION

[0024] In order to make the technical means, creative features, purposes and effects realized by the present application easy to understand, the present application is further described below in combination with specific examples and drawings.

[0025] The sludge biological drying high-temperature bacterial agent in the following examples and comparative examples is a sludge biological drying JEM high-temperature bacterial agent made by Hefei Cement Research and Design Institute Co., Ltd.

[0026] Example 1

[0027] The present example provides a method for regulating the aeration of a biological drying system based on the moisture content of sludge, which uses a drum-type biological drying reactor configured with a near-infrared online moisture content analyzer, and specifically includes the following steps:

[0028] (a) After mixing the municipal sludge and crushed corn cob cores, the mixture is added to the drum-type biological drying reactor, and the mass ratio of the municipal sludge to the crushed corn cob cores is 3:1, and the moisture content of the feed is 65%.

[0029] (b) Then, 1% of the sludge biological drying high-temperature bacterial agent is added to the drum-type biological drying reactor.

[0030] (c) The reactor is set to be tumbled once every 12 hours, and when the humidity in the reactor is greater than 85%, the air extraction and dehumidification is started, and when the humidity is lower than 85%, the air extraction and dehumidification is stopped.

[0031] (d) The drum-type biological drying reactor is operated, and at the same time, the pile is aerated. The aeration stage of the pile is divided into a start-up period, a heating-up period, a high-temperature period and a cooling-down period, and the aeration amount is regulated according to the real-time monitoring of the change of the moisture content. The temperature and the moisture content of the pile are monitored during the biological drying process, as shown in Table 1.

[0032] Table 1

[0033]

[0034] Example 2

[0035] The present embodiment provides a method for regulating aeration of a biological drying system based on moisture content of sludge, using a drum-type biological drying reactor equipped with a near-infrared online moisture content analyzer, and specifically includes the following steps:

[0036] (a) After mixing municipal sludge and broken corn cob cores, the mixture is added to the drum-type biological drying reactor, and the mass ratio of municipal sludge to broken corn cob cores is 5:1, and the moisture content of the feed is 66%.

[0037] (b) 2% of a sludge biological drying high-temperature bacterial agent is further added to the drum-type biological drying reactor.

[0038] (c) The reactor is set to be turned over once every 12 hours, and when the humidity in the reactor is greater than 85%, the air draft dehumidification is started, and when the humidity is lower than 85%, the air draft dehumidification is stopped.

[0039] (d) The drum-type biological drying reactor is operated, and the pile is aerated at the same time. The aeration stage of the pile is divided into a start-up period, a temperature rising period, a high-temperature period, and a temperature decreasing period, and the aeration amount is regulated according to the change of the real-time monitored moisture content. The temperature and moisture content of the pile are monitored during the biological drying process, as shown in Table 2.

[0040] Table 2

[0041]

[0042] Example 3

[0043] The present embodiment provides a method for regulating aeration of a biological drying system based on moisture content of sludge, using a drum-type biological drying reactor equipped with a near-infrared online moisture content analyzer, and specifically includes the following steps:

[0044] (a) After mixing municipal sludge and broken corn cob cores, the mixture is added to the drum-type biological drying reactor, and the mass ratio of municipal sludge to broken corn cob cores is 5:1, and the moisture content of the feed is 66%.

[0045] (b) 2% of a sludge biological drying high-temperature bacterial agent is further added to the drum-type biological drying reactor.

[0046] (c) The reactor is set to be turned over once every 12 hours, and when the humidity in the reactor is greater than 85%, the air draft dehumidification is started, and when the humidity is lower than 85%, the air draft dehumidification is stopped.

[0047] (d) running the drum-type biological drying reactor while aerating the pile. The aeration stage of the pile is divided into a start-up period, a temperature rising period, a high temperature period and a temperature falling period, and the aeration amount is regulated according to the change of the real-time monitored moisture content. The temperature and moisture content of the pile are monitored during the biological drying process, as shown in Table 3.

[0048] Table 3

[0049]

[0050] Comparative Examples 1-2

[0051] Comparative Examples 1-2 differ from Example 1 in the aeration mode. Comparative Example 1 adopts an intermittent aeration mode (aeration for 10 min and stopping for 20 min every 30 min, and the aeration amount is 1.8 L·h -1 ·kg -1 ), and Comparative Example 2 adopts a continuous aeration mode (the aeration amount is 0.6 L·h -1 ·kg -1 ).

[0052] The sludge biological drying treatment effects of Example 1, Comparative Example 1 and Comparative Example 2 are compared, as shown in Table 4.

[0053] Table 4

[0054]

[0055] As can be seen from Table 4, in the whole biological drying process, the pile of the continuous aeration and the intermittent aeration has a slow temperature rising and a short high temperature period, which leads to a small amount of conversion and migration of the bound water and the surface adsorbed water in the sludge to the interstitial water, and a long biological drying period. The sludge biological drying aeration method provided by the present application can realize a rapid temperature rising of the pile (making the pile temperature exceed 50℃ within 24 h), and the maximum temperature of the pile reaches 80.8℃, which is much higher than that of the conventional intermittent aeration and continuous aeration. The high temperature promotes the conversion of the bound water and the surface adsorbed water in the sludge to the interstitial water, and accelerates the evaporation of the water, so that the moisture content of the material can be reduced to below 40% within 6 d. Therefore, the sludge biological drying aeration method provided by the present application can promote the temperature rising of the pile, shorten the sludge biological drying period, and improve the biological drying efficiency.

[0056] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. It should be understood by those skilled in the art that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for regulating aeration in a biological drying system based on sludge moisture content, characterized in that: The process employs a drum-type bio-drying reactor equipped with an online moisture content analyzer, specifically including the following steps: (a) The municipal sludge and auxiliary materials are mixed and then added to a drum-type biological drying reactor; (b) Add a high-temperature sludge biological drying agent to the drum-type biological drying reactor; (c) Set the turning frequency and ventilation / dehumidification parameters; (d) Operate the drum-type bio-drying reactor while aerating the pile; The aeration phase of the pile is divided into a start-up phase, a heating phase, a high-temperature phase, and a cooling phase. During the start-up phase, the material moisture content is 64-66%, and the aeration rate is adjusted to 0.8-1.0 L·h. -1 ·kg -1 The material moisture content during the heating period is 62-64%, and the aeration rate is adjusted to 0.5-0.6 L·h. -1 ·kg -1 The material moisture content during the high-temperature period is 45-62%, and the aeration rate is adjusted to 0.4-0.5 L·h. -1 ·kg -1 During the cooling period, the material moisture content is <45%, and the aeration rate is adjusted to 1.0~1.2 L·h. -1 ·kg -1 Continue until the moisture content of the pile is below 40%; The start-up period is 0-6 hours; the heating period is 7-24 hours; the high-temperature period is 2-4 days; and the cooling period is 5-6 days.

2. The method for regulating the aeration of a biological drying system based on sludge moisture content according to claim 1, characterized in that: The online moisture content analyzer is a near-infrared online moisture content analyzer.

3. The method for regulating aeration in a biological drying system based on sludge moisture content according to claim 1, characterized in that: The auxiliary material is at least one of crushed corn cobs, sawdust, and straw powder.

4. The method for regulating aeration in a biological drying system based on sludge moisture content according to claim 1, characterized in that: The mass ratio of sludge to auxiliary materials is (3~5):

1.

5. The method for regulating aeration in a biological drying system based on sludge moisture content according to claim 1, characterized in that: The volume of the material obtained after mixing the sludge with the auxiliary materials accounts for 50-80% of the total volume of the drum-type biological drying reactor.

6. The method for regulating aeration in a biological drying system based on sludge moisture content according to claim 1, characterized in that: The initial feed moisture content of the drum-type bio-drying reactor is controlled at 60-70%.

7. The method for regulating aeration in a biological drying system based on sludge moisture content according to claim 1, characterized in that: The amount of the high-temperature bacterial agent for sludge biological drying is 1-2%.

8. The method for regulating aeration in a biological drying system based on sludge moisture content according to claim 1, characterized in that: The turning frequency is 1 to 4 times per day; the ventilation and dehumidification parameters are controlled according to the humidity inside the reactor. Ventilation and dehumidification are turned on when the humidity is higher than 85% and stopped when the humidity is lower than 85%.

Images