Municipal sludge drying system

Abstract

The utility model discloses a municipal sludge drying system which comprises a dryer, a material collector, a waste heat recoverer, a condenser, a heat exchanger and a hot blast stove, high-temperature drying air is introduced into the dryer to dry municipal sludge to be treated, the material collector collects dried finished products, a gas phase outlet of the material collector is connected with the waste heat recoverer, and a gas phase outlet of the condenser is connected with the hot blast stove. The waste heat recoverer recovers waste heat of airflow to obtain condensate water and low-temperature moisture-containing air, a gas phase outlet of the waste heat recoverer is connected with the condenser, and the condenser condenses the low-temperature moisture-containing air to obtain condensate water and low-temperature dry air; a gas-phase outlet of the condenser is connected with a first medium inlet of the heat exchanger, and a second medium inlet of the heat exchanger is connected with a gas-phase outlet of the hot-blast stove which is used for heating air to obtain high-temperature hot air. And a first medium outlet of the heat exchanger is connected with the dryer to provide the high-temperature drying air for the dryer, so that a circulating air path is formed, and the circulating air is used for continuously supplying heat to the dryer.

Description

Technical Field

[0001] The present invention relates to an urban sludge drying system, belonging to the field of sludge treatment. Background Art

[0002] The moisture content of urban sludge is very high. High-content organic matter in it harbors various bacteria, viruses and parasites, and at the same time contains some toxic heavy metal compounds. The complexity of the sludge structure determines the difficulty of sludge drying treatment.

[0003] At present, sludge drying mostly uses dryers. Although the processing capacity of dryers for drying sludge is large, the dust generation amount and pollutant emission amount are also large, causing serious environmental pollution, and a large amount of dust also poses a safety hazard. At the same time, traditional sludge dryers use steam, kerosene, etc. as heat sources, consuming a large amount of energy. Therefore, how to develop a low-energy and high-efficiency urban sludge drying device, and to conform to the theme of the era of low-carbon environmental protection, has become a research difficulty in this technical field. Summary of the Invention

[0004] In order to overcome the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide an urban sludge drying system, aiming to reduce the energy consumption of sludge drying, which can not only save production costs, but also reduce the emission of toxic and harmful gases, is beneficial to environmental protection, and using this system to process also avoids the risk of dust explosion caused by excessive on-site dust due to overheating of wet sludge.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0006] An urban sludge drying system includes a dryer, a material collector, a waste heat recovery device, a condenser, a heat exchanger and a hot blast stove. The dryer passes high-temperature drying air to dry the urban sludge to be treated, and the material collector collects the dried products. Among them:

[0007] The gas phase outlet of the material collector is connected to the waste heat recovery device. The waste heat recovery device recovers the heat of the gas flow to obtain condensed water and low-temperature humid air. The gas phase outlet of the waste heat recovery device is connected to the condenser. The condenser condenses and processes the low-temperature humid air to obtain condensed water and low-temperature dry air; the gas phase outlet of the condenser is connected to the first medium inlet of the heat exchanger, and the second medium inlet of the heat exchanger is connected to the gas phase outlet of the hot blast stove. The hot blast stove is used to heat air to obtain high-temperature hot air; the low-temperature dry air exchanges heat with the high-temperature hot air to obtain high-temperature dry air. The first medium outlet of the heat exchanger is connected to the dryer to provide the high-temperature dry air for it, thereby forming a circulating air path, and using the circulating air to continuously heat the dryer.

[0008] In one embodiment, the waste heat recovery device has a gas phase inlet and a solid phase inlet. The gas phase inlet is connected to the gas phase outlet of the material collector, and the solid phase inlet receives the wet municipal sludge to be processed. The wet municipal sludge is preheated in the waste heat recovery device by using the waste heat of the gas flow.

[0009] In one embodiment, the municipal sludge drying system further includes a pretreatment device. The pretreatment device is connected to the solid phase outlet of the waste heat recovery device and pre-treats the preheated sludge by screening, squeezing, and crushing.

[0010] In one embodiment, the heat exchanger is a finned tube heat exchanger or a plate heat exchanger. The heat exchanger transfers heat through the wall surface, and the two fluid media do not come into direct contact, enabling the high-temperature hot air and the low-temperature drying air to exchange heat and form a circulating air flow.

[0011] In one embodiment, the municipal sludge drying system further includes an exhaust gas treatment device. The exhaust gas treatment device is connected to the second medium outlet of the heat exchanger and treats the tail gas obtained after the high-temperature hot air is heat-exchanged and discharges it up to the standard.

[0012] In one embodiment, the municipal sludge drying system is a closed negative pressure system.

[0013] The present invention also provides a municipal sludge drying process, which is realized by using the municipal sludge drying system, and the steps are as follows:

[0014] Heat air by using a hot blast stove to obtain high-temperature hot air;

[0015] Use a dryer to dry the wet municipal sludge to be processed with high-temperature drying air, and send the dried sludge to a material collector;

[0016] Use a material collector to perform gas-solid separation, collect the dried product, and discharge the high-temperature gas flow;

[0017] Use a waste heat recovery device to recover the waste heat of the high-temperature gas flow to obtain condensed water and low-temperature wet air;

[0018] Use a condenser to condense and process the low-temperature wet air to obtain condensed water and low-temperature drying air;

[0019] Use a heat exchanger to exchange heat between the low-temperature drying air and the high-temperature hot air to obtain high-temperature drying air and low-temperature tail gas, and send the high-temperature drying air into the dryer to form a circulating air path and continuously supply heat to the dryer.

[0020] In one embodiment, the temperature of the high-temperature hot air is 300°C to 350°C, the temperature range of the high-temperature drying air is 290°C to 300°C, and it contains no moisture; the temperature of the low-temperature humid air is 50°C to 60°C, and it contains 20% to 30% moisture; the temperature of the low-temperature drying air is 30°C to 40°C, and it contains no moisture; the water content of the urban sludge to be treated is 70% to 80%, and the water content of the dried product is 1% to 10%.

[0021] In one embodiment, the waste heat recovery device is a solid-gas heat exchange device. The humid urban sludge to be treated is first sent to the waste heat recovery device to be preheated by the high-temperature gas flow, and then sent to the dryer for drying.

[0022] Compared with the prior art, the present invention can make full use of the heat in the system, effectively save energy, reduce energy consumption, and also reduce the emission of harmful exhaust gas, and is suitable for popularization and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of the urban sludge drying system of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] The embodiments of the present invention will be described in detail below with reference to the drawings and examples.

[0025] Reference Figure 1 As shown, the present invention is an urban sludge drying system, which mainly includes a dryer, a material collector, a waste heat recovery device, a condenser, a heat exchanger, a hot blast stove, etc. Among them, the dryer is used to introduce high-temperature drying air to dry the urban sludge to be treated, and the material collector is mainly used to collect the dried product. The hot blast stove is used to heat air to obtain high-temperature hot air, providing the initial heat source.

[0026] In the present invention, the gas phase outlet of the material collector is connected to the waste heat recovery device to recover the waste heat of the gas flow discharged from the material collector by the waste heat recovery device, and condensed water and low-temperature humid air are obtained. In the present invention, the gas phase outlet of the waste heat recovery device is connected to the condenser to condense and process the low-temperature humid air by the condenser to obtain condensed water and low-temperature drying air. In the present invention, the gas phase outlet of the condenser is connected to the first medium inlet of the heat exchanger, and the second medium inlet of the heat exchanger is connected to the gas phase outlet of the hot blast stove. The high-temperature hot air is used as the second medium, and the low-temperature drying air is used as the first medium. After the low-temperature drying air exchanges heat with the high-temperature hot air, high-temperature drying air is obtained. The first medium outlet of the heat exchanger is connected to the dryer to provide high-temperature drying air for it, thereby forming a circulating air path and continuously heating the dryer with the circulating air.

[0027] In an embodiment of the present invention, the waste heat recovery device has a gas phase inlet and a solid phase inlet. The gas phase inlet is connected to the gas phase outlet of the material collector, and the solid phase inlet is connected to the wet municipal sludge to be treated. The wet municipal sludge is preheated using the waste heat of the gas flow in the waste heat recovery device.

[0028] Further, a solid phase inlet is provided on one side of the waste heat recovery device for feeding the wet municipal sludge, and a gas phase inlet is provided on the other side for inputting the high-temperature gas flow discharged from the material collector. A gas phase outlet is provided in the upper middle part for discharging the low-temperature wet air, and a solid phase outlet and a liquid phase outlet are provided at the bottom for discharging the preheated sludge and condensed water respectively. The waste heat recovery device recovers the heat in the high-temperature drying process of the dryer and uses it as the heat source for the preheating process, improving the utilization rate of heat, reducing the difficulty of the drying process, and reducing the cost of wet sludge drying and disposal. For example, the waste heat recovery device can specifically be selected as a flue gas waste heat recovery device, which uses non-metallic materials to make heat exchange elements to recover and utilize the heat carried by the flue gas, and has the advantages of high efficiency and low energy consumption.

[0029] In an embodiment of the present invention, the condenser condenses and processes the low-temperature wet air, and low-temperature dry air is obtained after dehydration. The condensed water is discharged from the condensed water outlet. In the process of the high-temperature gas flow discharged from the material collector of the present invention passing through the waste heat recovery device and the condenser, the temperature drops. In these two stages, part of the water vapor liquefies and condenses into water, and the generated condensed wastewater is sent to the wastewater treatment device for purification treatment.

[0030] In an embodiment of the present invention, the municipal sludge drying system further includes a pretreatment device; the pretreatment device is connected to the solid phase outlet of the waste heat recovery device and performs pretreatment such as screening, extrusion, and crushing on the preheated sludge, which can reduce the volume of the sludge, make the heating surface flatter and have a larger heating area, and reduce the content of active substances in the sludge, improving the stability and durability of the sludge, and can greatly reduce the cost and risk in the subsequent treatment and disposal of the sludge.

[0031] In an embodiment of the present invention, the heat exchanger is a conventional heat exchanger such as a finned tube heat exchanger or a plate heat exchanger. The heat exchanger transfers heat through the wall surface and ensures that the two fluid media do not come into direct contact, enabling the high-temperature hot air and the low-temperature dry air to exchange heat and form a circulating air. This circulating air dries the sludge in the subsequent dryer. The circulating air can be recycled repeatedly, avoiding waste of heat energy. At the same time, harmful gas substances are not discharged, reducing environmental pollution. Moreover, since there is no contact, no polluting exhaust gas will be generated continuously, and there is no pollutant discharge during the drying process, which is relatively environmentally friendly and energy-saving.

[0032] In an embodiment of the present invention, the municipal sludge drying system further includes an exhaust gas treatment device, and the exhaust gas treatment device is connected to the second medium outlet of the heat exchanger to treat the tail gas obtained after heat exchange of the high-temperature hot air and discharge it up to standard.

[0033] In an embodiment of the present invention, the urban sludge drying system is a closed negative pressure system. The negative pressure comes from the system fan, which is generally arranged between the material collector and the waste heat recovery device. Under the negative pressure pneumatic conveying system, materials and dust will not fly out, ensuring the environmental protection and safety of the drying environment. The closed negative pressure system has the advantages of good airtightness, simple system, and reliable operation, which can effectively prevent dust and odor leakage during the feeding process of dried sludge into the surrounding environment, thus avoiding pollution and safety risks.

[0034] The sludge drying system of the present invention forms a closed sludge drying environment in cooperation with a circulating air path, avoiding the escape of sludge odor components into the external environment during the sludge drying process, and also avoiding the corrosion of machines by harmful substances in the sludge, thus improving the service life of the drying system.

[0035] According to the above system, the process steps of an urban sludge drying method of the present invention are as follows:

[0036] Use a hot blast stove to heat air to obtain high-temperature hot air in the range of 300°C to 350°C. The high-temperature hot air is introduced into the heat exchanger instead of being directly sent into the dryer;

[0037] Use a dryer to dry the urban sludge to be treated with high-temperature dry air without moisture at 290°C to 300°C. The high-temperature dry air takes away the moisture in the wet sludge to achieve the purpose of sufficient drying. The dried sludge is sent into the material collector, where the original moisture content of the urban sludge is 70% to 80%;

[0038] Use the material collector for gas-solid separation, collect the dried product, and achieve gas-solid separation, discharging the high-temperature gas flow to the next stage, where the moisture content of the dried product is 1% to 10%;

[0039] Use the waste heat recovery device to recover the waste heat of the high-temperature gas flow to obtain condensed water and low-temperature wet air at about 50°C to 60°C. The low-temperature wet air contains about 20% to 30% of moisture; for example, the waste heat recovery device is a solid-gas heat exchange device. The wet urban sludge to be treated is first sent into the waste heat recovery device to be preheated by the high-temperature gas flow, and then sent into the dryer for drying; based on this, the heat of the dryer is recovered by the waste heat recovery device for preheating the sludge, forming a cycle;

[0040] Use a condenser to condense the low-temperature wet air to obtain condensed water and low-temperature dry air at about 30°C to 40°C. After condensation treatment, the low-temperature dry air no longer contains moisture;

[0041] Use the heat exchanger to fully exchange heat between the low-temperature dry air and the high-temperature hot air to obtain high-temperature dry air and low-temperature tail gas. Send the high-temperature dry air into the dryer to supply heat for the drying process, and a circulating air path can be formed to continuously supply heat to the dryer.

[0042] Figure 1 In the system shown, the optimized drying process and its principle can be described as follows:

[0043] The wet municipal sludge is put into the waste heat recovery device for preheating. The preheated sludge is discharged from the solid phase outlet of the waste heat recovery device and enters the pretreatment process. The pretreatment process increases the air permeability of the sludge, so that the drying effect of the sludge in the dryer is more uniform. The high-temperature drying air exchanges heat with the wet sludge, and the waste heat of the high-temperature gas flow is recovered by the waste heat recovery device. The heat of the waste heat recovery device can be reused for sludge drying, and the heat in the waste heat recovery device can be fully utilized. In the waste heat recovery device, the temperature of the saturated steam decreases and condensed water is condensed. These condensed waters can be discharged from the water outlet of the waste heat recovery device. The low-temperature wet air is discharged from the air outlet of the waste heat recovery device and enters the condenser. Condensed water is obtained again due to the temperature reduction and is discharged from the water outlet of the condenser. The condenser condenses and processes the low-temperature wet air and outputs low-temperature drying air. The low-temperature drying air exchanges heat with the high-temperature hot air heated by the heat source in the heat exchanger to obtain high-temperature drying air, and forms a closed loop of circulating air when input into the dryer.

[0044] In summary, the present invention has many advantages and application values. It has great improvements both in structure and function, and has remarkable progress in technology and good practical value.

[0045] The above examples are not an exhaustive list of the better inventions of the present invention, and there can be various forms of the equipment of the present invention.

[0046] The above are only the better examples of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed as above with the better examples, it is not used to limit the present invention. Any person skilled in the art of the present invention, within the scope of the technical solution of the invention, can make any minor changes or modifications into equivalent embodiments of equivalent changes by using the above-disclosed technical content. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. An urban sludge drying system, comprising a dryer, a material collector, a waste heat recovery device, a condenser, a heat exchanger and a hot blast stove. The dryer passes high-temperature drying air to dry the urban sludge to be treated. The material collector collects the dried finished products. It is characterized in that: The gas phase outlet of the material collector is connected to the waste heat recovery device. The waste heat recovery device recovers the waste heat of the air flow to obtain condensed water and low-temperature wet air. The gas phase outlet of the waste heat recovery device is connected to the condenser. The condenser condenses and processes the low-temperature wet air to obtain condensed water and low-temperature dry air. The gas phase outlet of the condenser is connected to the first medium inlet of the heat exchanger. The second medium inlet of the heat exchanger is connected to the gas phase outlet of the hot blast stove. The hot blast stove is used to heat air to obtain high-temperature hot air. The low-temperature dry air exchanges heat with the high-temperature hot air to obtain high-temperature dry air. The first medium outlet of the heat exchanger is connected to the dryer to provide the high-temperature dry air for it, thereby forming a circulating air path, and using the circulating air to continuously heat the dryer.

2. The urban sludge drying system according to claim 1, characterized in that: The waste heat recovery device has a gas phase inlet and a solid phase inlet. The gas phase inlet is connected to the gas phase outlet of the material collector. The solid phase inlet receives the wet urban sludge to be treated. The wet urban sludge is preheated by using the waste heat of the air flow in the waste heat recovery device.

3. The urban sludge drying system according to claim 2, characterized in that: The urban sludge drying system further comprises a pretreatment device. The pretreatment device is connected to the solid phase outlet of the waste heat recovery device and pre-treats the preheated sludge by screening, extruding and crushing.

4. The urban sludge drying system according to claim 1, characterized in that: The heat exchanger is a finned tube heat exchanger or a plate heat exchanger. The heat exchanger transfers heat through the wall surface, and the two fluid media do not directly contact, so that the high-temperature hot air and the low-temperature dry air realize heat exchange to form a circulating air.

5. The urban sludge drying system according to claim 1, characterized in that: The urban sludge drying system further comprises an exhaust gas treatment device. The exhaust gas treatment device is connected to the second medium outlet of the heat exchanger and discharges the tail gas obtained after the high-temperature hot air exchanges heat up to the standard after treatment.

6. The urban sludge drying system according to any one of claims 1 to 5, characterized in that: The urban sludge drying system is a closed negative pressure system.

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