CN104098239B - sewage sludge treatment method - Google Patents

Abstract

The invention discloses a method for treating sewage sludge, which comprises the following steps: 1) continuously freezing the sludge in the sludge freezing container by a freeze-drying energy circulation system, and thawing the sludge after continuous freezing, and repeatedly freezing the sludge in this way Thawing; 2) Dewatering the sludge after freezing and thawing treatment in the filter press device, divided into a filter press stage and a press dehydration stage, so that the sludge is press filtered into a large mud cake sludge with a low moisture content; 3) Large pieces of mud cake sludge are crushed in the crushing device to form small sludge particles; 4) The crushed sludge particles are transported into the sludge drying device for drying, and are passed through the freeze-drying energy circulation system The condenser releases heat and transfers the heat to the air, and the hot air enters the sludge drying device to dry the sludge particles. The invention does not need to add chemical preparations to the sludge, and the treatment process does not increase the treatment capacity of the sludge, and the recycling of working medium energy greatly improves the freezing efficiency and heat utilization rate of the sludge.

Description

Sewage sludge treatment method

technical field

The invention relates to the field of sludge treatment, in particular to a sewage sludge treatment method.

Background technique

A large amount of sludge is produced in the process of sewage treatment, which accounts for about 0.3%-0.5% of the treated water volume. The investment and operation cost of sludge treatment are very huge, and the cost of sewage sludge treatment generally accounts for 10% of the operating cost of sewage treatment plants. 20%-50%, bringing a heavy burden to sewage treatment. Sludge dehydration is a very important link in sludge treatment and disposal, and is of great significance to subsequent drying, incineration, resource utilization, and landfill of sludge. The key to sludge dewatering is to improve the dewatering performance of sludge. The current traditional treatment method is to condition it first by adding flocculant, and then perform mechanical dehydration by filter press to form sludge with a moisture content of about 60% and transport it to landfill. , fermented fertilizer, etc. The pretreatment method of adding flocculant is to reduce the affinity between sludge and water through the flocculation of flocculant, change the existence form of water in sludge, neutralize the opposite charge in sewage, compress the electric double layer, and The destabilized coagulated particles play the role of adsorption and bridging, making them quickly form large flocs, so that the colloids can be destabilized and coagulated to achieve solid-liquid separation. The dosage of flocculant is calculated as a percentage of the dry weight of sludge solids, and the dosage of different flocculants will be different. Although the dewatering performance of sludge can be significantly improved by adding flocculants, due to the need for a large amount of flocculants, not only the cost of sewage sludge treatment will be increased, but also a large amount of flocculants will be added to the dewatered sludge, adding Large amount of sludge treatment. Other pretreatment methods, such as ultrasonic treatment, consume a lot of heat and need to add ultrasonic treatment devices; the use of biological methods and thermodynamic methods requires the consumption of biological agents and heat.

The freezing method is used to pre-treat the sludge. After the sludge is repeatedly frozen, it can destroy the binding force between the sludge and water and the structure of the colloid (similar to the built-in tofu after freezing), so that the colloid is destabilized and coagulated and the cell membrane is broken. The water inside the cells that is difficult to remove by mechanical means is dialyzed to form interstitial water that is easy to remove by mechanical means. The sludge particles settle rapidly, and the dehydration speed is dozens of times higher than that before freezing. Using the freezing method does not require adding chemicals, which can save the cost of chemicals. And it will not increase the amount of sewage sludge treatment in the later stage, and combined with the subsequent treatment method of sludge, the deep reduction treatment of sludge will be completed.

However, in the prior art, the freezing of sludge mainly relies on the natural environment, that is, placing the sludge outdoors in cold weather depends on the natural environment to cool down to about -10°C for freezing and thawing, but the efficiency is low and time-consuming, and if It cannot be operated in the southern region or in non-winter conditions, and the natural conditions are more demanding. In addition, in the prior art, using external force to freeze and thaw sludge requires dual energy for cooling and heating the sludge, and the cost is very high, so it is difficult to popularize and apply.

Contents of the invention

In view of this, the present invention aims at the problems in the above-mentioned prior art that increasing the flocculant will increase the treatment capacity of sewage sludge, low freezing efficiency and high cost, and provides a treatment process that does not increase the treatment capacity of sewage sludge, freezing Sewage sludge treatment method with high efficiency and high energy utilization.

The technical solution of the present invention is to provide a sewage sludge treatment method with the following structure, based on a sludge treatment device, the sludge treatment device includes a sludge freezing container, a sludge drying device and a freeze-drying energy circulation system, The freeze-drying energy cycle system includes a compressor, a first evaporator, a condenser and a second evaporator arranged in a sludge freezing container, the outlet end of the compressor is connected to the condenser, and the condenser is connected to the condenser via a throttling element. The first evaporator is connected, and the first evaporator is connected to the intake end of the compressor through the second evaporator; the condenser is connected to the bottom of the sludge drying device through the gas pipeline, and the first evaporator is connected to the gas pipeline through the gas pipeline. The top of the sludge drying device is connected, and at the same time, the condenser is connected to the first evaporator through a gas pipeline;

Described sewage sludge processing method comprises the following steps:

1) The sludge in the sludge freezing container is continuously frozen by the freeze-drying energy circulation system, and the sludge is thawed after continuous freezing, so that the freezing and thawing is repeated many times;

2) In the filter press device, the sludge after freezing and thawing treatment is dehydrated, divided into a filter press stage and a press dehydration stage, so that the sludge is press filtered into a large mud cake sludge with a low moisture content;

3) Large pieces of mud cake sludge are crushed in the crushing device to form small sludge particles;

4) The crushed sludge particles are conveyed into the sludge drying device for drying, the freeze-drying energy circulation system releases heat through the condenser, and the heat is transferred to the air, and the hot air enters the sludge drying device to dry the sludge particles dry;

With the above structure, compared with the prior art, the present invention has the following advantages: by adopting the present invention, the freeze-drying energy circulation system is utilized, and at the same time, the freezing of the sludge in the sludge freezing container and the freezing of the sludge in the sludge drying device are realized. In the drying of sludge, the working medium is under the action of the compressor, and the high-temperature and high-pressure gaseous working medium is output. After passing through the condenser, the heat in the working medium is absorbed by the air, and the heat is transferred to the air. The temperature of the air rises, and the temperature of the working medium decreases. The air is passed into the sludge drying device to dry the material, the working fluid is condensed into a high-pressure liquid, and the high-pressure liquid working medium becomes a low-pressure liquid working medium after being depressurized by the throttling element, and the low-pressure liquid working medium enters the first evaporator , absorb the heat of the air in the first evaporator (the air coming out from the top of the material), and cool the air. After the saturated air cools down, the moisture it can hold decreases, and the excess moisture condenses into liquid water and passes through the accumulation of the first evaporator. The water pan is drained away, and the working medium changes from a low-pressure liquid to a low-pressure gas after absorbing heat (if the working medium does not absorb enough heat from the air, only part of the liquid working medium can be guaranteed to evaporate into a gaseous working medium, while the rest of the liquid working medium And the gaseous working fluid forms two-phase working fluid) enters the second evaporator, the working fluid absorbs the heat of the sludge in the second evaporator, and cools the sludge to the required freezing temperature -10℃～-15℃ (this temperature The range is better, but not limited to this numerical range), at this time, the liquid working medium is vaporized into a gaseous working medium, and the gaseous working medium enters the compressor. The sludge in the sludge freezing container has been frozen and thawed many times (thawing can be thawed naturally), which destroys the structure of the sludge, and the thawed sludge enters the filter press device, which presses the sludge into large cake-like sludge , and then sent to the crushing device for crushing to form sludge particles, and the sludge particles are dried in the sludge drying device to realize the staged treatment of sludge. Since there is no need to add chemicals to the sludge, the treatment process will not increase the amount of sewage sludge to be treated, and the recycling of working medium energy greatly improves the freezing efficiency of sludge; only by spending a small amount of compressor energy, the working medium can be The heat in the freezing container that is several times the energy consumption of the compressor is "transferred" to the drying box, and the sludge is frozen and dried at the same time, which not only solves the source of cold energy required for freezing, but also solves the source of heat required for drying, so that The cooling capacity and heat have reached a very good balance, greatly improving the heat application efficiency, and the energy saving effect is obvious.

Preferably, there are multiple sludge freezing containers, and the second evaporator corresponds to the sludge freezing container one by one, and the two ends of the second evaporator in the multiple sludge freezing containers are connected to The first evaporator is connected to the compressor, the bottom of the sludge freezing container is provided with a filter structure, and the bottoms of multiple sludge freezing containers are connected to the filter press device through a liquid reversing valve and a liquid pipeline. In this way, when the sludge in a sludge freezing container is frozen, part of the sludge in the sludge freezing container is thawed naturally, and the thawed sludge is directly transported to the filter press device, thereby improving the treatment efficiency and enabling continuous Production.

As a preference, the sludge drying device includes a drying box and a sludge turning mechanism, the sludge turning mechanism is arranged horizontally at different vertical heights in the drying box, and the sludge turning mechanism The mechanisms are arranged in a staggered manner, and a sludge turning mechanism at the bottom layer protrudes out of the drying box. In this way, the sludge enters the sludge drying device after crushing, and first falls into the uppermost layer of the sludge turning mechanism. With the transmission of the sludge turning mechanism, the sludge falls on the sludge turning mechanism of the next layer, and the next step The sludge turnover mechanism on the first layer is then reversed and driven to the other end. This reciprocation can realize the contact between the hot air and the sludge up and down, left and right, and dry in all directions to improve the drying effect. When it falls to the sludge turnover mechanism on the bottom layer At this time, because it stretches out of the drying box, the sludge is transported to the outside of the drying box and enters the next step of processing.

Preferably, the filter press device is a plate and frame filter press, the plate and frame filter press includes a plurality of plate frames, and a plate pulling mechanism is provided under the plate frames, and the plate pulling mechanism includes a plurality of traction blocks and sliding plates A hinged link is provided between two adjacent traction blocks, and rollers are provided under each traction block. The multiple traction blocks are placed on the slide plate and are rotatably connected to the slide plate through the rollers. In this way, drawing and pulling of multiple plate frames can be achieved by pulling multiple plates, which solves the current problem that only one plate and frame can be pulled at the same time, shortens the plate pulling time, and improves the filter press efficiency of the filter press device.

As preferably, mechanical dehydration is carried out in the plate and frame filter press, and the filter press stage is carried out first, the filter press pressure is 1.0-1.2Mpa, the filter press time is 1.5-2 hours, and the sludge moisture content in the filter press stage is 65%- 70%, and then enter the stage of pressing and dehydration, the pressing pressure is 1.5Mpa, the pressing time is 1 hour, and the moisture content of the treated sludge is about 60%-65%.

Description of drawings

Fig. 1 is the schematic diagram of the used sludge treatment device of the present invention;

Fig. 2 is a structural schematic diagram of the plate pulling mechanism.

Fig. 3 is a flowchart of the method of the present invention.

As shown in the figure, 1. Filter press device, 1.1, plate frame, 1.2, traction block, 1.3, slide plate, 1.4, hinged connecting rod, 1.5, roller, 2, crushing device, 3, sludge drying device, 3.1, drying Box, 3.2, sludge turnover mechanism, 4, sludge freezing container, 5, compressor, 6, first evaporator, 7, condenser, 8, second evaporator, 9, throttling element, 10, gas Pipeline, 11, working medium reversing valve, 12, filter structure, 13, liquid reversing valve, 14, liquid pipeline, 15, rotor pump.

Detailed ways

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

As shown in Figures 1 and 2, a kind of sludge treatment device involved in the present invention includes a filter press device 1, a crushing device 2 and a sludge drying device 3, and the filter press device 1 carries out pressure filtration treatment on the sludge. The crushing device 2 performs crushing treatment, and after the sludge is crushed, it enters the sludge drying device 3 for drying treatment;

The sludge treatment device also includes a sludge freezing container 4 and a freeze-drying energy circulation system, and the freeze-drying energy circulation system includes a compressor 5, a first evaporator 6, a condenser 7, and a sludge freezing container. The second evaporator 8 in 4, the outlet end of the compressor 5 is connected to the condenser 6, the condenser 7 is connected to the first evaporator 6 through the throttling element 9, and the first evaporator 6 is connected to the compressor through the second evaporator 8 The inlet end of the machine 5 is connected; the condenser 7 communicates with the bottom of the sludge drying device 3 through the gas pipeline 10, and the first evaporator 6 communicates with the top of the sludge drying device 3 through the gas pipeline 10. The above-mentioned condenser 7 communicates with the first evaporator 6 through a gas pipeline 10 .

There are multiple sludge freezing containers 4, and the second evaporator 8 corresponds to the sludge freezing container 4 one by one. The valve 11 is connected with the first evaporator 6 and the compressor 5, the bottom of the sludge freezing container 4 is provided with a filter structure 12, and the bottoms of a plurality of sludge freezing containers 4 pass through the liquid reversing valve 13 and through the liquid pipeline 14 and press filter The device 1 is connected; the thawed sludge is pumped into the filter press device 1 from the sludge freezing container 4 through the rotor pump 15 .

The sludge drying device 3 includes a drying box 3.1 and a sludge turning mechanism 3.2. The sludge turning mechanism is arranged horizontally at different vertical heights in the drying box 3.1. The sludge turning mechanism The trigger mechanism 3.2 is arranged in a staggered manner, and a sludge turnover mechanism 3.2 at the bottom layer extends out of the drying box 3.1.

The filter press device 1 is a plate and frame filter press, and the plate and frame filter press includes a plurality of plate frames 1.1, and a plate pulling mechanism is provided below the plate frames 1.1, and the plate pulling mechanism includes a plurality of traction blocks 1.2 and Skateboard 1.3, hinged connecting rod 1.4 is provided between two adjacent traction blocks 1.2, and roller 1.5 is provided under each traction block 1.2, and the multiple traction blocks 1.2 are placed on the slide plate 1.3, and pass through the rollers 1.5 is slidably connected with slide plate 1.3.

Described sewage sludge processing method comprises the following steps:

1) The sludge in the sludge freezing container is continuously frozen by the freeze-drying energy circulation system, and then the sludge is thawed after continuous freezing, and the freezing and thawing is repeated several times; Repeated freezing within 1 hour; thawing between 20-40°C (ordinary temperature thawing can be used), and the thawing time is about 6 hours;

2) In the filter press device, the sludge after freezing and thawing treatment is dehydrated, divided into a filter press stage and a press dehydration stage, so that the sludge is press filtered into a large cake-like sludge with a low moisture content; Mechanical dehydration is carried out in the frame filter press, and the filter press stage is carried out first. The filter press pressure is 1.0-1.2Mpa, and the filter press time is 1.5-2 hours. The moisture content of the sludge after the filter press stage is 65%-70%, and then enters At the stage of pressing and dehydration, the pressing pressure is 1.5Mpa, the pressing time is 1 hour, and the moisture content of the treated sludge is about 60%-65%;

3) Large pieces of mud cake sludge are crushed in the crushing device to form small sludge particles; the size of sludge particles is generally about 20mm;

4) The crushed sludge particles are conveyed into the sludge drying device for drying, the freeze-drying energy circulation system releases heat through the condenser, and the heat is transferred to the air, and the hot air enters the sludge drying device to dry the sludge particles Drying; the sludge drying device is a multi-layer flap type, the drying time is 2 hours, the drying temperature is 50-60°C, and the moisture content of the sludge after drying is 10%-30%. At this time, the first evaporator provides cooling capacity for sludge freezer;

The above steps are only staged steps of sludge treatment. The sludge can also be incinerated after being dried, and the waste heat can be recovered, and the waste heat can be used for thawing the frozen sludge in the sludge freezing container. It should be noted that Figure 3 includes more complete treatment steps and methods, perfecting the energy cycle system (using the waste heat of combustion for sludge thawing), incinerating the dried sludge and reducing the waste generated by incineration. Waste heat is recycled.

The specific working principle is as follows:

When the sludge enters the sludge freezing container, firstly, under the action of the second evaporator, the refrigerant enters the second evaporator, and the working fluid absorbs heat on the sludge, so that the freezing temperature of the sludge reaches the specified stability, and the sewage is in the -10℃～-15℃, freezing time 72 hours after repeated freezing, destroys the binding force of sludge and water and destroys the structure of the colloid, destabilizes the colloid and coagulates and ruptures the cell membrane, the sludge particles settle rapidly, and the dehydration performance is greatly improved. , the dehydration speed is dozens of times higher than before freezing, and the freezing is over. At this time, the working fluid reversing valve reverses the flow direction of the working fluid, and changes the flow direction of the working fluid to another sludge freezing container. At this time, air with a certain temperature is passed into the frozen sludge freezing container for thawing. The air temperature is between 20-40°C, and the thawing time is 6 hours.

After thawing, the sludge enters the rotor pump through the liquid pipeline. Under the pressure of the rotor pump, it enters the plate and frame machine (plate and frame filter press) to start pressure filtration for mechanical dehydration. After a period of pressure filtration, the plate and frame are pulled apart, The mud cake-like sludge falls into the material conveying device, and is transported to the crusher through the material conveying device. The crusher crushes the mud cake to form small sludge particles. The sludge increases the specific surface area of the sludge, which is beneficial to increase the contact area between the sludge and high-temperature air during drying, and improves the drying rate and effect.

Small sludge particles enter the upper flap in the dryer and fall from top to bottom layer by layer. During the falling process, the sludge will be turned over continuously, so that all surfaces are in full contact with the air. The dry air contacts the sludge from bottom to top. The air absorbs the moisture of the sludge and becomes moist air with high humidity. After passing through the first evaporator, it drops below the dew point and precipitates moisture. The precipitated moisture is discharged through the water storage pan, and the air After continuing to pass through the condenser, it is heated and enters the drying box to dry the sludge. After the sludge is heated and dried, it leaves the drying box after going through the bottom layer of flaps.

In order to better treat the sludge, after the above staged treatment, the sludge leaves the drying box and is transported to the incinerator through the material conveying device, and the primary air entering the combustion chamber is adjusted to make it in fluidized combustion under the action of the leveler. State, because the medium in the fluidized bed is in a suspended state, the gas and solid can be fully mixed and contacted, the temperature of the combustion section in the entire furnace is relatively uniform, and the exhaust gas generated after combustion is discharged into the waste heat boiler at about 850 °C. At the same time, the heat transfer oil in the waste heat boiler is heated from 220°C to 250°C. The heated heat transfer oil heats the air through the second heat exchanger, and the heated air enters the drying system and the thawing device to treat the sludge. Dry and thaw with heat. The gas purification device consists of two parts: acid gas removal and particle capture. Gas purification can be done by semi-dry method, spraying a certain amount of calcium oxide into the flue gas to make it react with the acidic substances in the flue gas, and pass through The spray device controls the moisture to reach the reaction process of spray drying. The deacidification reactant is basically a dry solid, and there will be no waste water discharge. The capture of particulate matter in the flue gas can be achieved through a filter combined with a cyclone separator or a cloth bag. A certain amount of activated carbon powder is sprayed before to absorb harmful substances such as heavy metals and dioxins in the flue gas. The purified gas can be discharged into the atmosphere with less pollution to the environment.

The above is only an illustration of the preferred embodiments of the present invention, but should not be construed as a limitation on the claims. The present invention is not limited to the above embodiments, and its specific structure is allowed to vary. In a word, all kinds of changes made within the protection scope of the independent claims of the present invention are within the protection scope of the present invention.

Claims (5)

1. A sewage sludge treatment method, based on sludge treatment device, described sludge treatment device comprises sludge freezing container (4), sludge drying device (3) and freeze-drying energy circulation system, described freezing The drying energy circulation system comprises a compressor (5), a first evaporator (6), a condenser (7) and a second evaporator (8) arranged in the sludge freezing container (4), and the compressor (5) The gas outlet is connected to the condenser (7), the condenser (7) is connected to the first evaporator (6) through the throttling element (9), and the first evaporator (6) is connected to the compressor through the second evaporator (8) (5) is connected to the inlet end; the condenser (7) is connected to the bottom of the sludge drying device (3) through the gas pipeline (10), and the first evaporator (6) is connected to the sludge drying device (3) through the gas pipeline (10). The top of the mud drying device (3) is connected, and the condenser (7) is connected with the first evaporator (6) through the gas pipeline (10) simultaneously; Described sewage sludge processing method comprises the following steps: 1) The sludge in the sludge freezing container is continuously frozen by the freeze-drying energy circulation system, and the sludge is thawed after continuous freezing, so that the freezing and thawing is repeated many times; 2) In the filter press device, the sludge after freezing and thawing treatment is dehydrated, divided into a filter press stage and a press dehydration stage, so that the sludge is press filtered into a large mud cake sludge with a low moisture content; 3) Large pieces of mud cake sludge are crushed in the crushing device to form small sludge particles; 4) The crushed sludge particles are conveyed into the sludge drying device for drying, the freeze-drying energy circulation system releases heat through the condenser, and the heat is transferred to the air, and the hot air enters the sludge drying device to dry the sludge particles dry. 2. The sewage sludge treatment method according to claim 1, characterized in that: there are multiple sludge freezing containers (4), and the second evaporator (8) is connected to the sludge freezing container (4) one by one. Correspondingly, the two ends of the second evaporator (8) in the plurality of sludge freezing containers (4) are respectively connected with the first evaporator (6) and the compressor (5) through the working fluid reversing valve (11), and the sludge The bottom of the sludge freezing container (4) is provided with a filter structure (12), and the bottoms of multiple sludge freezing containers (4) are connected to the filter press device (1) through the liquid reversing valve (13) and through the liquid pipeline (14). The thawed sludge is pumped into the filter press device (1) from the sludge freezing container (4) through the rotor pump (15). 3. The sewage sludge treatment method according to claim 1 or 2, characterized in that: the sludge drying device (3) comprises a drying box (3.1) and a sludge turnover mechanism (3.2), and the The sludge turnover mechanisms are arranged horizontally at different vertical heights in the drying box (3.1), the sludge turnover mechanisms (3.2) are arranged in a staggered manner, and a sludge turnover mechanism (3.2) at the bottom layer ) out of the drying box (3.1). 4. The sewage sludge treatment method according to claim 1 or 2, characterized in that: the filter press device (1) is a plate and frame filter press, and the plate and frame filter press includes a plurality of plate frames (1.1) , a plate pulling mechanism is provided below the plate frame (1.1), and the plate pulling mechanism includes a plurality of traction blocks (1.2) and slide plates (1.3), and a hinged link is arranged between two adjacent traction blocks (1.2) (1.4), and rollers (1.5) are provided under each traction block (1.2), and the multiple traction blocks (1.2) are placed on the slide plate (1.3), and pass through the rollers (1.5) and the slide plate (1.3) ) for scrollable connections. 5. The sewage sludge treatment method according to claim 4, characterized in that: mechanical dehydration is carried out in the plate and frame filter press, and the filter press stage is carried out first, the filter press pressure is 1.0-1.2Mpa, and the press filter time is 1.5 -2 hours, the water content of the sludge after the filter press stage is 65%-70%, and then enters the pressing dehydration stage, the pressing pressure is 1.5Mpa, the pressing time is 1 hour, the water content of the sludge after treatment is 60%-65% .