CN217103532U

CN217103532U - Energy-saving secondary sludge drying system

Info

Publication number: CN217103532U
Application number: CN202120942918.3U
Authority: CN
Inventors: 刘凌云; 杨祺; 朱明行
Original assignee: Beijing Yigao Renhe Engineering Equipment Co ltd
Current assignee: Beijing Yigao Renhe Engineering Equipment Co ltd
Priority date: 2021-05-06
Filing date: 2021-05-06
Publication date: 2022-08-02
Anticipated expiration: 2031-05-06

Abstract

The invention discloses an energy-saving secondary sludge drying system, which is characterized in that: 1) two dryers were operated in series. 2) An indirect drying machine: the sludge is subjected to primary drying in an indirect dryer to produce semi-dry sludge with the water content of 55-65%. In the indirect drier, the sludge and steam indirectly exchange heat, part of water in the sludge is changed into exhaust gas, and the steam is condensed into saturated water. 3) A direct drier: and (4) after the semi-dry sludge is made into a noodle shape, performing secondary drying in a direct dryer to produce dry sludge with the water content of 10-30%. In the direct drier, the sludge and hot air transfer mass and heat, part of water in the sludge is changed into water vapor to enter the hot air, and the hot air is discharged after the temperature of the hot air is reduced and the moisture content is increased. And the low-temperature and high-humidity outlet air is cooled, dehumidified, reheated and returned to the direct dryer for recycling. 4) The heat is obtained from the water vapor and the saturated water discharged by the indirect drying machine and is provided for the direct drying machine in the form of hot water, so that the overall energy consumption of the drying system is reduced.

Description

Energy-saving secondary sludge drying system

Technical Field

The invention relates to the technical field of sludge drying, in particular to an energy-saving secondary sludge drying system which comprises two forms of drying machines and particularly comprises a heat source which is used for recovering heat discharged by a primary drying machine and is used as a secondary drying machine.

Background

The sludge drying equipment is divided into indirect drying and direct drying. The indirect drying heat source is not in direct contact with the sludge, and the moisture in the sludge is removed in an indirect heat exchange mode. The heat source of the direct drying directly contacts with the sludge, and the water in the sludge is evaporated by the heat energy carried by the heat source.

The existing sludge drying mode and equipment mainly adopt primary drying, or indirect drying or direct drying, and the heat consumption is larger. When 1t of water is evaporated, the heat of 800-1140 kWh needs to be input, most of the heat is not recycled, and resources are wasted. Reference documents: PD-CEN-TR-15473-2007

When the indirect drying process is used independently, water in the sludge is evaporated into exhaust gas and then is separated from the sludge, and then is sprayed with water, cooled and condensed into water and then discharged, so that a large amount of cooling water is consumed, and heat in the exhaust gas is not utilized. The latent heat of saturated steam is fully utilized in the indirect drying machine, high-temperature saturated water or small-amplitude over-cooled water is discharged, the water temperature is far higher than the saturation temperature (100 ℃) at normal pressure, and the available heat is also available.

When the belt type drying process is used independently, an external heat source is needed to provide heat for the drying process, or the energy needed by the belt type drying machine is supplemented by consuming electric energy.

Disclosure of Invention

The invention aims to provide an energy-saving secondary sludge drying system for solving the defects in the existing sludge drying process technology, and the energy-saving secondary sludge drying system can minimize the consumption of heat required by sludge drying.

The invention relates to an energy-saving secondary sludge drying system which enables two drying machines to operate in series, recovers the heat of a first-stage drying machine, is used for a second-stage drying machine, and comprises the following components:

and the wet sludge is conveyed to the thin layer drying machine by the feed pump according to a given flow rate for primary drying. Wet sludge entering the thin-layer drier can be uniformly coated into a thin layer and conveyed forwards at a certain speed under the action of the rotation of the rotor and the scraper thereof, indirect heat exchange with saturated steam in a jacket of the thin-layer drier is realized in the conveying process, and a part of moisture in the wet sludge is evaporated. The flow direction of the evaporation tail gas is reverse to the conveying direction of the dry sludge, and the evaporation tail gas is finally pumped out of the thin-layer drier by a fan and enters a subsequent condensing system for spray condensation. And discharging the sludge subjected to the first-stage drying from an outlet of the thin-layer drying machine, extruding the sludge into noodle shapes by a forming machine, and performing second-stage drying. The first-stage dryer can also use other types of indirect dryers, such as a disc dryer, and only the moisture content of the sludge at the outlet is ensured to meet the requirement.

In the second-stage belt drier, noodle-shaped sludge is uniformly placed on a porous conveyer belt which runs slowly, hot air at 70-80 ℃ passes through the pores of the conveyer belt and is in direct contact with the sludge, moisture in the sludge is evaporated into the hot air, the humidity of the hot air is increased, the temperature is reduced, and the hot air becomes wet and cold exhaust air. The wet and cold exhaust air and the circulating cooling water exchange heat indirectly, and moisture carried in the air is condensed and discharged after the temperature is lower than the dew point. The low-temperature saturated air is heated by the hot water to become hot air, and the hot air returns to the belt drier again and repeatedly.

The exhaust gas discharged from the first-stage drying machine is atmospheric steam with the temperature of 100 ℃, and is mainly recovered heat. The latent heat of the fresh steam used for the heat source of the drier is utilized and then discharged out of the drier in the form of high-temperature high-saturated water, or the fresh steam can be flashed at normal temperature and then the heat of the flash steam is recovered, and only the saturated water under normal pressure is discharged. The recycling of the waste gas heat discharged by the first-stage drying machine is realized by combining a condenser and a heat exchanger; the recovery of the heat of the high-temperature saturated water is realized by combining a flash tank and a hot water tank.

The implementation effect of the invention is as follows:

compared with the prior art, the energy-saving secondary sludge drying system combines two types of drying equipment, uses the secondary drying equipment in series, and recycles the heat of the first-stage drying machine to the second-stage drying machine. According to calculation, under the condition that the requirements of the water content of the sludge inlet and the sludge outlet are the same, compared with the single use of a drying machine, the fresh steam consumption can be reduced by 35-40%.

Drawings

FIG. 1 is a schematic flow diagram of an energy-saving secondary sludge drying system according to the present invention.

Detailed Description

The invention will be further described with reference to the drawings and examples, but the invention is not limited to the examples, and any modifications within the scope of the invention are intended to be within the scope of the invention without departing from the spirit thereof.

The feed pump 101 conveys wet sludge to the thin layer drier 102 for first-stage drying according to a given flow rate, and the moisture content of the wet sludge is usually 80-85%, and can be up to 90%. Wet sludge entering the thin-layer dryer can be uniformly coated into a thin layer and conveyed forwards at a certain speed under the action of the rotation of the rotor and the scraper thereof, indirect heat exchange with saturated steam in a jacket of the thin-layer dryer is realized in the conveying process, and a part of moisture in the wet sludge is evaporated. The flow direction of the evaporation tail gas is against the conveying direction of the dry sludge, and the evaporation tail gas is pumped out from the thin-layer drier by the fan 104 and enters the two-stage condensation system for spray condensation. The sludge after the first-stage drying is discharged from an outlet of the thin-layer drying machine, extruded into a noodle shape by a forming machine 201, and then subjected to second-stage drying.

In the second-stage belt drier 202, noodle-shaped sludge is uniformly placed on a porous conveyer belt which runs slowly, hot air at 70-80 ℃ passes through the pores of the conveyer belt and is in direct contact with the sludge, moisture in the sludge is evaporated into the hot air, the humidity of the hot air is increased, the temperature is reduced, and the hot air becomes wet and cold exhaust air. The wet and cold exhaust air and the circulating cooling water indirectly exchange heat in the first heat exchanger 203, and after the temperature is lower than the dew point, moisture carried in the air is condensed and discharged. The low-temperature saturated air is heated by the hot water in the second heat exchanger 204 to become hot air, and then is sent back to the belt drier by the circulating fan 205, and the process is repeated.

The exhaust gas discharged from the first-stage thin-layer drier is condensed into water in a first-stage condenser 301 by circulating spray water at about 70 ℃, the temperature of the circulating spray water is about 85 ℃ when the circulating spray water is discharged from the bottom of the condenser 301, the circulating spray water is pressurized by a circulating water pump 302, heat is transferred to circulating hot water required by the belt drier in a third heat exchanger 303, and the circulating hot water is returned to the condenser 301 as spray water after the temperature is reduced to 70 ℃. The 85 ℃ non-condensable gas and condensed water cooled by the primary condenser 301 are discharged into the secondary condenser 103, the same circulating spraying mode is adopted, the 45 ℃ non-condensable gas and condensed water are finally discharged out of the drying system, and the fourth heat exchanger 106 cools the circulating spray water by adopting external circulating cooling water.

The fresh steam used as the heat source for the thin layer dryer 102, after its latent heat has been utilized, exits the dryer as high temperature saturated water, which is at about 180 c if the steam pressure used is 0.9 MPaG. The high temperature saturated water is discharged through a trap to the flash tank 306 where it is flashed to steam and water at about 100 c under slight positive pressure. The steam is discharged from the top of the tank and then cooled in the coil of the hot water tank 304, and latent heat of the steam is transferred to circulating hot water required by the belt drier, so that the temperature of the circulating hot water is raised to about 85 ℃. No matter what quality of saturated steam is used by the thin-layer dryer, the temperature of the finally discharged steam condensate is about 100 ℃ normal-pressure saturated water, and the heat of the steam is used to the maximum extent.

Steam is used as a heat source to provide heat for the first-stage indirect drying machine, heat required by the second-stage direct drying machine is provided by hot water, and the heat of the hot water is recycled from the heat discharged by the first-stage drying machine, so that the consumption of fresh steam is saved to the maximum extent.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and concepts according to the present invention are equivalent to or changed within the technical scope of the present invention.

Claims

1. An energy-saving secondary sludge drying system is characterized by comprising the following components: the two forms of the indirect drying and the direct drying are connected in series to operate, steam is used as a heat source to input heat to the indirect drying, and the heat discharged by the indirect drying is recovered in a hot water form and is used as the heat source of the direct drying, so that the consumption of fresh steam is saved to the maximum extent.

2. The energy-saving secondary sludge drying system of claim 1, wherein: the first-stage indirect dryer is a thin-layer dryer or a disc dryer.

3. The energy-saving secondary sludge drying system of claim 1, wherein: the second-stage direct dryer is a belt dryer.

4. The energy-saving secondary sludge drying system of claim 1, wherein: steam is used as a heat source to provide heat for the first-stage indirect drying machine, the heat required by the second-stage direct drying machine is provided by hot water, and the heat of the hot water is recycled from the heat discharged by the first-stage drying machine.

5. The energy-saving secondary sludge drying system of claim 1, wherein: the waste gas heat discharged by the first-stage drying machine is recovered by combining a condenser and a heat exchanger.

6. The energy-saving secondary sludge drying system of claim 1, wherein: the heat of the steam condensate discharged by the first-stage drying machine is realized through the flash tank and the hot water tank together, and the condensate discharge temperature is about 100 ℃.

7. The energy-saving secondary sludge drying system of claim 1, wherein: the non-condensable gas and the wastewater of the first-stage drying machine are discharged after being cooled, so that the burden on subsequent treatment equipment is not caused.