Municipal sludge drying system and process

Abstract

The invention discloses a municipal sludge drying system and process, the system 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 invention relates to a municipal sludge drying system and process, and belongs to the field of sludge treatment. Background Art

[0002] Urban sludge has a high water content, and its high content of organic matter is home to various bacteria, viruses and parasites. It also 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 dryer can process a large amount of sludge, it also produces a large amount of dust and pollutants, which seriously pollutes the environment. In addition, a large amount of dust also poses a safety hazard. At the same time, traditional sludge dryers use steam, kerosene, etc. as heat sources, which consumes a lot of energy. Therefore, how to develop a low-energy and high-efficiency urban sludge drying device that meets the theme of the era of low-carbon and environmental protection has become a research difficulty in this technical field. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a municipal sludge drying system and process, 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, which is beneficial to environmental protection. The use of this system also avoids the risk of dust explosion caused by excessive dust on site due to overheating of wet sludge.

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

[0006] A municipal sludge drying system comprises a dryer, a material collector, a waste heat recovery device, a condenser, a heat exchanger and a hot air furnace, wherein the dryer introduces high-temperature dry air to dry the municipal sludge to be treated, and the material collector collects the dried product, wherein:

[0007] The gas phase outlet of the material collector is connected to the waste heat recovery device, and the waste heat recovery device recovers the waste heat of the air 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, and 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 air furnace, and the hot air furnace is used to heat the 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, and the first medium outlet of the heat exchanger is connected to the dryer to provide it with the high-temperature dry air, thereby forming a circulating air circuit, and the circulating air is used to continuously supply heat to 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 treated wet urban sludge; the wet urban sludge is preheated in the waste heat recovery device using the waste heat of the airflow.

[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 to perform pretreatment such as screening, extrusion, and crushing on the preheated sludge.

[0010] In one embodiment, the heat exchanger is a fin-and-tube heat exchanger or a plate-and-sheet heat exchanger, which transfers heat through the wall surface, and the two fluid media are not in direct contact, so that high-temperature hot air and low-temperature dry air can exchange heat to form circulating air.

[0011] In one embodiment, the municipal sludge drying system further includes a waste gas treatment device, which is connected to the second medium outlet of the heat exchanger and treats the exhaust gas obtained after heat exchange with high-temperature hot air so as to meet emission standards.

[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 implemented by using the municipal sludge drying system, and the steps are as follows:

[0014] Use a hot air furnace to heat the air to obtain high-temperature hot air;

[0015] The dryer is used to dry the municipal sewage sludge to be treated by high-temperature dry air, and the dried sludge is sent to the material collector;

[0016] Use the material collector to separate gas and solid, collect the dried product, and discharge the high-temperature airflow;

[0017] Recovering the waste heat of the high-temperature airflow by a waste heat recovery device to obtain condensed water and low-temperature humid air;

[0018] Utilizing a condenser to condense the low-temperature humid air to obtain condensed water and low-temperature dry air;

[0019] The low-temperature dry air is heat-exchanged with the high-temperature hot air by using a heat exchanger to obtain high-temperature dry air and low-temperature tail gas. The high-temperature dry air is sent into the dryer to form a circulating air path to continuously supply heat to the dryer.

[0020] In one embodiment, the temperature of the high-temperature hot air is between 300°C and 350°C, the temperature range of the high-temperature dry air is between 290°C and 300°C, and no moisture is contained therein; the temperature of the low-temperature humid air is between 50°C and 60°C, containing 20% ​​to 30% moisture; the temperature of the low-temperature dry air is between 30°C and 40°C, and no moisture is contained; the moisture content of the urban sludge to be treated is 70% to 80%, and the moisture 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, and the wet municipal sludge to be treated is first sent to the waste heat recovery device to be preheated by the high-temperature airflow, and then sent to the dryer for drying.

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

[0023] Figure 1 It is a schematic diagram of the structure of the municipal sludge drying system of the present invention. DETAILED DESCRIPTION

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

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

[0026] The present invention connects the gas phase outlet of the material collector to a waste heat recovery device, utilizes the waste heat recovery device to recover the waste heat of the airflow discharged from the material collector, and processes to obtain condensed water and low-temperature humid air. The present invention connects the gas phase outlet of the waste heat recovery device to a condenser, utilizes the condenser to condense and process the low-temperature humid air, and obtains condensed water and low-temperature dry air. The present invention connects the gas phase outlet of the condenser to the first medium inlet of the heat exchanger, connects the second medium inlet of the heat exchanger to the gas phase outlet of the hot air furnace, uses high-temperature hot air as the second medium, and uses low-temperature dry air as the first medium, and obtains high-temperature dry air after heat exchange between the low-temperature dry air and the high-temperature hot air. The first medium outlet of the heat exchanger is connected to a dryer to provide it with high-temperature dry air, thereby forming a circulating air path, and the circulating air is used to continuously supply heat to the dryer.

[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 urban sludge to be treated. The wet urban sludge is preheated in the waste heat recovery device using the waste heat of the airflow.

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

[0029] In the embodiment of the present invention, the condenser condenses the low-temperature humid air, obtains the low-temperature dry air after dehydration, and the condensed water is discharged from the condensed water outlet. The high-temperature airflow discharged from the material collector of the present invention has a temperature drop during the process of passing through the waste heat recovery device and the condenser. In these two stages, part of the water vapor is liquefied and condensed into water, and the generated condensed waste water is sent to the wastewater treatment device for purification.

[0030] In an embodiment of the present invention, the urban sludge drying system also includes a pretreatment device; the pretreatment device is connected to the solid phase outlet of the waste heat recovery device, and the preheated sludge is screened, extruded, crushed and other pretreatments are performed, which can reduce the volume of the sludge, make the heating surface smoother, and increase the heating area. It also reduces the content of active substances in the sludge, improves the stability and durability of the sludge, and can greatly reduce the cost and risk of the sludge in subsequent treatment and disposal.

[0031] In the embodiment of the present invention, the heat exchanger is a conventional heat exchanger such as a fin-tube heat exchanger or a plate-type heat exchanger. The heat exchanger transfers heat through the wall surface and ensures that the two fluid media do not directly contact each other, so that the high-temperature hot air and the low-temperature dry air can achieve heat exchange and form circulating air. The circulating air dries the sludge in the subsequent dryer. The circulating air can be recycled repeatedly, avoiding the waste of heat energy. At the same time, harmful gas substances will not be discharged, reducing environmental pollution. Moreover, due to the lack of contact, no polluting waste gas will continue to be generated. No pollutants are discharged during the drying process, which is more environmentally friendly and energy-saving.

[0032] In an embodiment of the present invention, the municipal sludge drying system further comprises a waste gas treatment device, which is connected to the second medium outlet of the heat exchanger and treats the exhaust gas obtained after heat exchange with high-temperature hot air so as to meet the emission standards.

[0033] In the embodiment of the present invention, the municipal sludge drying system is a closed negative pressure system. The negative pressure comes from the system fan, which can generally be set 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 air tightness, simple system, and reliable operation, which can effectively prevent dust and odor from leaking into the surrounding environment during the drying sludge feeding process, causing pollution and safety risks.

[0034] The sludge drying system of the present invention forms a closed sludge drying environment and a circulating air path, thereby preventing sludge odor components from escaping into the external environment during the sludge drying process, and also preventing the corrosion of the machine by harmful substances in the sludge, thereby increasing the service life of the drying system.

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

[0036] The hot air is heated by a hot air furnace to obtain high temperature hot air in the range of 300℃~350℃. The high temperature hot air is passed into the heat exchanger instead of being directly sent into the dryer.

[0037] The dryer is used to dry the municipal sludge to be treated by high-temperature drying air at 290℃ to 300℃ without moisture. The high-temperature drying air takes away the moisture in the wet sludge to achieve the purpose of full drying. The dried sludge is sent to the material collector, in which the moisture content of the original municipal sludge is 70% to 80%;

[0038] Use the material collector to separate gas and solid, collect the dried product, and realize gas and solid separation, and discharge the high-temperature airflow to the next stage, wherein the moisture content of the dried product is 1% to 10%;

[0039] The waste heat of the high-temperature airflow is recovered by the waste heat recovery device to obtain condensed water and low-temperature humid air of about 50°C to 60°C, and the low-temperature humid air contains about 20% to 30% moisture; for example, the waste heat recovery device is a solid-gas heat exchange device, and the wet urban sludge to be treated is first sent to the waste heat recovery device for preheating with the high-temperature airflow, and then sent to 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 circular utilization;

[0040] The low-temperature humid air is condensed by a condenser to obtain condensed water and low-temperature dry air at about 30℃ to 40℃. After condensation, the low-temperature dry air no longer contains moisture.

[0041] The heat exchanger is used to fully exchange heat between low-temperature dry air and high-temperature hot air to obtain high-temperature dry air and low-temperature exhaust gas. The high-temperature dry air is sent to the dryer to provide 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:

[0043] The wet urban 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 air flow is recovered by the waste heat recovery device. The heat of the waste heat recovery device can be reused for sludge drying, which can make full use of the heat of the waste heat recovery device in the drying process. The temperature of the saturated hot steam in the waste heat recovery device is reduced, and condensed water is condensed. The condensed water can be discharged through the water outlet of the waste heat recovery device, and the low-temperature wet air is discharged from the air outlet of the waste heat recovery device into the condenser. Due to the temperature reduction, condensed water is obtained and discharged from the water outlet of the condenser. The condenser condenses the low-temperature wet air and outputs low-temperature dry air. The low-temperature dry air exchanges heat with the high-temperature hot air heated by the heat source in the heat exchanger to obtain high-temperature dry air, which is input into the dryer to form a closed loop of circulating air.

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

[0045] The above examples are not exhaustive of the preferred embodiments of the present invention, and the device of the present invention can also have many forms.

[0046] The above are only preferred examples of the present invention, and are not intended to limit the present invention in any form. Although the present invention has been disclosed as a preferred example as above, it is not intended to limit the present invention. Any technician familiar with the present invention can make any slight changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A municipal sludge drying system, comprising a dryer, a material collector, a waste heat recovery device, a condenser, a heat exchanger and a hot air furnace, wherein the dryer introduces high-temperature dry air to dry the municipal sludge to be treated, and the material collector collects the dried product, characterized in that: The gas phase outlet of the material collector is connected to the waste heat recovery device, and the waste heat recovery device recovers the waste heat of the air 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, and 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 air furnace, and the hot air furnace is used to heat the 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, and the first medium outlet of the heat exchanger is connected to the dryer to provide it with the high-temperature dry air, thereby forming a circulating air circuit, and the circulating air is used to continuously supply heat to the dryer.

2. The municipal 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, and the solid phase inlet receives the treated wet urban sludge. The wet urban sludge is preheated in the waste heat recovery device using the waste heat of the airflow.

3. The municipal sludge drying system according to claim 2, characterized in that: The municipal sludge drying system also includes a pretreatment device; the pretreatment device is connected to the solid phase outlet of the waste heat recovery device to perform pretreatment of screening, extrusion and crushing on the preheated sludge.

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

5. The municipal sludge drying system according to claim 1, characterized in that: The municipal sludge drying system also includes a waste gas treatment device, which is connected to the second medium outlet of the heat exchanger to treat the tail gas obtained after heat exchange with high-temperature hot air and then discharge it in compliance with the emission standards.

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

7. A municipal sludge drying process, implemented by using the municipal sludge drying system according to claim 1, characterized in that: Here are the steps: Use a hot air furnace to heat the air to obtain high-temperature hot air; The dryer is used to dry the municipal sewage sludge to be treated by high-temperature dry air, and the dried sludge is sent to the material collector; Use the material collector to separate gas and solid, collect the dried product, and discharge the high-temperature airflow; Recovering the waste heat of the high-temperature airflow by a waste heat recovery device to obtain condensed water and low-temperature humid air; Utilizing a condenser to condense the low-temperature humid air to obtain condensed water and low-temperature dry air; The low-temperature dry air is heat-exchanged with the high-temperature hot air by using a heat exchanger to obtain high-temperature dry air and low-temperature tail gas. The high-temperature dry air is sent into the dryer to form a circulating air path to continuously supply heat to the dryer.

8. The municipal sludge drying process according to claim 7, characterized in that: The temperature of the high-temperature hot air is between 300°C and 350°C, and the temperature of the high-temperature drying air is between 290°C and 300°C, and does not contain moisture; The temperature of the low-temperature humid wind is between 50°C and 60°C, containing 20% ​​to 30% moisture; the temperature of the low-temperature drying wind is between 30°C and 40°C, containing no moisture; the moisture content of the urban sludge to be treated is 70% to 80%, and the moisture content of the dried product is 1% to 10%.

9. The municipal sludge drying process according to claim 7, characterized in that: The waste heat recovery device is a solid-gas heat exchange device. The wet municipal sludge to be treated is first sent to the waste heat recovery device for preheating by the high-temperature airflow, and then sent to the dryer for drying.

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