CN112159067A

CN112159067A - Method and device for incinerating sludge

Info

Publication number: CN112159067A
Application number: CN202010974533.5A
Authority: CN
Inventors: 王小波; 赵增立; 黄振; 魏国强; 钟慧琼; 刘安琪; 李海滨
Original assignee: Guangzhou Institute of Energy Conversion of CAS
Current assignee: Guangzhou Institute of Energy Conversion of CAS
Priority date: 2020-09-16
Filing date: 2020-09-16
Publication date: 2021-01-01
Anticipated expiration: 2040-09-16
Also published as: CN112159067B

Abstract

The invention discloses a method and a device for incinerating sludge, wherein the method comprises the following steps: (1) drying the sludge; (2) separating volatile components from gas water; (3) sludge incineration; (4) gas-solid separation is carried out so as to burn the sludge; the device comprises an ascending bed, a descending bed in the ascending bed, a gas-solid separation device and a gas-water separation device. The invention is suitable for the incineration energy utilization of sludge generated by sewage treatment after low-heat-value drying; the utilization process is more flexible, and the incineration process is stable; the method is beneficial to solving the problem of difficult energy utilization of the sludge at present.

Description

Method and device for incinerating sludge

Technical Field

The invention relates to the technical field of environmental engineering, in particular to a method and a device for carrying out incineration energy utilization on sludge generated in a sewage treatment process.

Background

It is statistical that by the end of 2019, the urban sewage treatment capacity of our country is about 2.1 million tons/day, and some solid precipitated substances, which we generally refer to as sludge, are generated in urban sewage treatment. The municipal sludge production in China is expected to exceed 6000 million tons/year or 16 million tons/day in 2020. The discharge standard of pollutants for municipal wastewater treatment plants (GB 18918-. By the end of 2020, the harmless treatment rate of the municipal sludge of grade and above reaches 90%, and the harmless treatment rate of other cities reaches 75%; the county and city strive reaches 60%. In general, more than half of the sludge in China is still subjected to landfill treatment. Sludge incineration is used as a means for realizing the maximum reduction of sludge, can be used for carrying out single incineration or mixed incineration, is a disposal scheme for thoroughly realizing the harmlessness, reduction and energy regeneration of sludge, and is also one of the preferred schemes for carrying out sludge disposal by governments in various places at present. For example, the sludge treatment in Shanghai city is mainly drying incineration treatment, and the Foshan city will realize sludge 'zero landfill and full incineration' from 1 month and 1 day of 2020, and realize localized treatment. Before the planned 2020 years of Guangzhou city, the sludge drying and incinerating treatment capacity of the city basically meets the requirements, and after the sludge is dried and reduced in a factory, the city incineration treatment is basically realized.

However, because the heat value of the sludge is low, when the water content of the sludge is 80%, the low heat value of the sludge is usually a negative value, and when the sludge is dried to reach 40%, the low heat value of the sludge is usually only about 4000kJ/kg, and the sludge is difficult to be efficiently and stably incinerated by the traditional direct incineration method, so that the sludge reaches increasingly strict atmospheric emission standards. Patent CN 106949475B discloses a sludge incineration system, which comprises a rod making system and a bar stock incineration system. Wherein, system stick system includes system stick machine and bar drying system, and the mummification hollow bar export of system stick system and the feed unit intercommunication of bar burning system. Simultaneously, a sludge incineration method is also provided, which comprises the steps of mixing the materials with a combustion-supporting material after pre-dewatering the materials, and preparing a hollow bar material; and (4) feeding the hollow bar stock into a bar stock drying system for drying to obtain the dried hollow bar stock. The sludge is dried to prepare the hollow rod-shaped fuel, so that the contact area of the material and the combustion-supporting gas is increased. Patent CN 110513693A discloses a sludge incineration method, which comprises the steps of carrying out fuel treatment on dehydrated dry sludge to obtain fuel dry sludge particles, then sending the fuel dry sludge and coal powder to an incinerator together, carrying out incineration under the action of high-temperature primary air and secondary air, wherein steam generated by incineration is used for power generation, and flue gas can reach the emission standard after being purified.

None of the above patents relate to the efficient and stable incineration of low calorific value sludge using high temperature bed material circulation.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a method and a device for realizing high-efficiency and stable incineration of low-calorific-value and high-reactivity sludge.

The invention is realized by the following technical scheme: a method for incinerating sludge comprises the following steps:

(1) sludge drying: the sludge after simple crushing treatment forms loose powdery sludge powder, the sludge powder enters the downer from the bottom of the downer, and is mixed with high-temperature bed materials circulated from the downer in the downer, and under the heating of the high-temperature bed materials, moisture and volatile substances in the sludge are separated out to form volatile components mainly comprising water vapor; the descending bed runs in a slow fluidization state, solid materials form a dense-phase area at the inner lower part of the descending bed, and a dilute-phase area at the inner upper part of the descending bed; the mixture of the dried sludge and the bed material and the volatile component are automatically separated in a dilute phase zone of a descending bed; the separated mixture of the dried sludge and the bed material enters an ascending bed;

(2) and (3) volatile gas-water separation: separating gas and water from volatile components generated by sludge drying, feeding non-condensable gas generated by separation into an ascending bed, and incinerating the non-condensable gas and dried sludge in the ascending bed;

(3) sludge incineration: in the ascending bed, the dried sludge is incinerated under the action of supplied oxidant, non-condensable gas and combustion-supporting fuel, and is further burnt out under the action of secondary air; the ascending bed runs in a fast fluidization state under the action of primary air; part of the solid generated by incineration is circulated to the descending bed as high-temperature bed material, and part of the solid is discharged from the ascending bed as bottom ash;

(4) gas-solid separation: and (3) carrying out gas-solid separation on the flue gas generated by burning the sludge in the ascending bed, and recovering the separated and collected solid products to the ascending bed for continuous burning.

The descending bed runs in a slow fluidization state, solid materials (sludge and bed materials) form a dense-phase area (more solid material areas) at the inner lower part of the descending bed, a dilute-phase area (less solid material areas) is formed at the upper part of the descending bed, and the dense-phase area and the dilute-phase area are obviously separated; in the slow fluidization state, the drying effect of the sludge can be controlled by controlling the bed material circulation amount, the feeding rate and the retention time (drying time) of the sludge powder in the downer. Through the drying process in the downer, the moisture in the sludge is basically and completely exerted to obtain the dried sludge, and most of the emitted gas is water vapor and a small amount of VOC in the sludge. The dry sludge is incinerated at high temperature together with the introduced non-condensable gas under the action of an oxidant (air), and when the incineration temperature cannot meet the requirement of the minimum incineration temperature, a certain amount of combustion-supporting fuel (heavy oil, coal, natural gas and the like) is introduced for auxiliary combustion. The flue gas generated by combustion is burnt out under the action of introduced secondary air, so that the content of pollutants such as CO, carbon black and the like in the flue gas is reduced. The circulating incineration can effectively improve the retention time of sludge powder in the ascending bed, improve the gasification efficiency and reduce the appropriate reduction rate of incineration ash.

The water content of the sludge is less than 40%. The sludge with the water content of less than 40 percent can be easily crushed into powder, meanwhile, the incineration process of the sludge with the lower calorific value is difficult to stabilize when the water content of the sludge is too high, and in addition, the energy consumption and the generation amount of volatile (mainly steam) in the sludge drying process of the downer with the too high water content of the sludge are too large/too high, so that the bed layer of the downer is easy to be unstable.

And the sludge drying temperature in the downer is 150-250 ℃.

The incineration temperature of the dried sludge in the ascending bed is 850-1000 ℃.

The oxidant is air, and the coefficient of the excess air in the system is 1.2-2.0.

The air volume ratio of the primary air to the secondary air is 70: 30-50: 50.

A device for realizing sludge incineration comprises an ascending bed, a descending bed, a gas-solid separation device and a gas-water separation device, wherein the descending bed is positioned in the ascending bed; the upper end of the ascending bed is provided with a first gas outlet, the upper part of the ascending bed is provided with an ascending bed expansion section, the lower part of the ascending bed is provided with a first material return port, and the ascending bed is communicated with the descending bed through the first material return port; the bottom of the ascending bed is respectively provided with a second return port, an auxiliary fuel inlet, a primary air inlet for primary air to enter, an ash residue outlet and a secondary air inlet for secondary air to enter; when the device operates, the inner lower part of the downer forms a dense-phase area, and the inner upper part of the downer forms a dilute-phase area; a second gas outlet is formed in the upper part of the downer, and a third material returning port is formed in the middle of the downer; the bottom of the downer is respectively provided with a fourth material return port, a first gas inlet and a solid material inlet; the fourth material returning port is communicated with the first material returning port through the descending bed; the gas-solid separation device is provided with a second gas inlet, a solid outlet and a third gas outlet; the gas-water separation device is provided with a third gas inlet and a fourth gas outlet; the first gas outlet is communicated with the second gas inlet, the solid outlet is communicated with the fourth material returning port, and the second gas outlet is communicated with the third gas inlet; and the fourth gas outlet is respectively communicated with the first gas inlet and the primary air inlet.

Compared with the prior art, the invention has the advantages that: the invention is suitable for the incineration energy utilization of sludge generated by low-calorific-value dried municipal sewage treatment. Compared with the prior art, the sludge incineration technology (coal power plant blending combustion and garbage incineration plant blending combustion) is more flexible in utilization process and stable in incineration process. The method is beneficial to solving the problem of difficult energy utilization of the sludge at present.

Drawings

FIG. 1 is a front view of a sludge incineration apparatus according to an embodiment of the present invention;

FIG. 2 is a schematic view showing the state in which the sludge incineration apparatus operates its internal materials according to the embodiment of the present invention;

FIG. 3 is a schematic material flow diagram of a sludge incineration apparatus according to an embodiment of the present invention.

The reference numerals in the drawings mean: 1. an ascending bed; 11. a first gas outlet; 12. an ascending bed expansion section; 13. a first material returning port; 14. a second material returning port; 15. an auxiliary fuel inlet; 16. a primary air inlet; 17. an ash outlet; 18. a secondary air inlet; 2. a downer; 21. a second gas outlet; 22. a third material returning port; 23. a fourth material returning port; 24. a first gas inlet; 25. a solid material inlet; 3. a gas-solid separation device; 31. a second gas inlet; 32. a solids outlet; 33. a third gas outlet; 4. a gas-water separation device; 41. a third gas inlet; 42. a fourth gas outlet.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and detailed description.

Example 1

Referring to fig. 1 to 3, a method for sludge incineration includes the following steps:

(1) sludge drying: the method comprises the following steps that sludge with the water content of 30% is simply crushed to form loose powdery sludge powder, the sludge powder enters a descending bed 2 from the bottom of the descending bed 2, and is mixed with high-temperature bed materials circulated from an ascending bed 1 in the descending bed 2, and under the heating of the high-temperature bed materials, water and a small amount of volatile substances in the sludge are separated out to form volatile components mainly comprising water vapor; the descending bed 2 runs in a slow fluidization state, solid materials form a dense-phase area at the lower part in the descending bed 2, and a dilute-phase area at the upper part in the descending bed 2; the mixture of the dried sludge and the bed material and the volatile component are automatically separated in a dilute phase zone of the lower bed 2; the separated mixture of the dried sludge and the bed material enters an ascending bed 1;

(2) and (3) volatile gas-water separation: separating gas and water from volatile components generated by sludge drying, feeding non-condensable gas generated by separation into the ascending bed 1, and incinerating the non-condensable gas and dried sludge in the ascending bed 1;

(3) sludge incineration: in the ascending bed 1, the dried sludge is incinerated under the action of supplied oxidant, non-condensable gas and combustion-supporting fuel, and is further burnt out under the action of secondary air; the ascending bed 1 runs in a fast fluidization state under the action of primary air; part of the solid generated by incineration is circulated into the descending bed 2 as high-temperature bed material, and part of the solid is discharged out of the ascending bed 1 as bottom ash;

(4) gas-solid separation: the flue gas generated by the sludge incineration of the ascending bed 1 is subjected to gas-solid separation, and the separated and collected solid products are recycled to the ascending bed 1 for continuous incineration.

The downer 2 runs in a slow fluidization state, solid materials (sludge and bed materials) form a dense-phase area (more solid material areas) at the lower part in the downer 2, a dilute-phase area (less solid material areas) is formed at the upper part of the downer 2, and the dense-phase area and the dilute-phase area are obviously demarcated; in the slow fluidization state, the drying effect of the sludge can be controlled by controlling the bed material circulation amount, the feeding rate and the retention time (drying time) of the sludge powder in the downer 2. Through the drying process in the downer 2, the moisture in the sludge is basically and completely utilized to obtain the dried sludge, and most of the emitted gas is water vapor and a small amount of VOC in the sludge. The dry sludge is incinerated at high temperature together with the introduced non-condensable gas under the action of an oxidant (air), and when the incineration temperature cannot meet the requirement of the minimum incineration temperature, a certain amount of combustion-supporting fuel (heavy oil, coal, natural gas and the like) is introduced for auxiliary combustion. The flue gas generated by combustion is burnt out under the action of introduced secondary air, so that the content of pollutants such as CO, carbon black and the like in the flue gas is reduced. The circulating incineration can effectively improve the retention time of sludge powder in the ascending bed 1, improve the gasification efficiency and reduce the appropriate reduction rate of incineration ash.

The water content of the sludge is less than 35%. The sludge with the water content of less than 35 percent can be easily crushed into powder, meanwhile, the incineration process of the sludge with the lower calorific value is difficult to stabilize when the water content of the sludge is too high, and in addition, the energy consumption and the generation amount of volatile (mainly steam) in the sludge drying process of the descending bed 2 with the too high water content of the sludge are too large/too high, so that the bed layer of the descending bed 2 is easy to be unstable.

The sludge drying temperature in the descending bed 2 is 150-250 ℃. In this embodiment, the sludge drying temperature in the downer 2 is 200 ℃.

The incineration temperature of the dried sludge in the ascending bed 1 is 850-1000 ℃. In the embodiment, the incineration temperature of the dried sludge in the travelling bed is 900 DEG C

The oxidant is air, and the coefficient of the excess air in the system is 1.2-2.0. In this example, the incineration excess air ratio in the system was selected to be 1.5.

The air volume ratio of the primary air to the secondary air is 70: 30-50: 50. In this embodiment, the ratio of the primary air to the secondary air is 60: 40.

A device for realizing sludge incineration comprises an ascending bed 1, a descending bed 2, a gas-solid separation device 3 and a gas-water separation device 4, wherein the descending bed 2 is positioned in the ascending bed 1; the upper end of the ascending bed 1 is provided with a first gas outlet 11, the upper part of the ascending bed 1 is provided with an ascending bed expansion section 12, the lower part of the ascending bed 1 is provided with a first material return port 13, and the ascending bed 1 is communicated with the descending bed 2 through the first material return port 13; the bottom of the ascending bed 1 is respectively provided with a second return port 14, an auxiliary fuel inlet 15, a primary air inlet 16 for primary air to enter, an ash outlet 17 and a secondary air inlet 18 for secondary air to enter; when in operation, the lower part in the downer 2 forms a dense phase region, and the upper part in the downer 2 forms a dilute phase region; the upper part of the downer 2 is provided with a second gas outlet 21, and the middle part of the downer 2 is provided with a third material return port 22; the bottom of the downer 2 is respectively provided with a fourth material return port 23, a first gas inlet 24 and a solid material inlet 25; the fourth return port 23 is communicated with the first return port 13 through the downer 2; the gas-solid separation device 3 is provided with a second gas inlet 31, a solid outlet 32 and a third gas outlet 33; the gas-water separation device 4 is provided with a third gas inlet 41 and a fourth gas outlet 42; the first gas outlet 11 is communicated with the second gas inlet 31, the solid outlet 32 is communicated with the fourth return port 23, and the second gas outlet 21 is communicated with the third gas inlet 41; the fourth gas outlet 42 is communicated with the first gas inlet 24 and the primary air inlet 16 respectively.

Referring to fig. 3, a is sludge, B is combustion-supporting fuel, C is ash, and D is oxidant; the solid arrows indicate the circulation path of the solid matter, and the open arrows indicate the circulation path of the gas.

The sludge enters the downer 2 from a solid material inlet 25 at the bottom of the downer 2, the primary air enters from a primary air inlet 16, the sludge A is mixed with high-temperature bed materials circulated from the uper 1 in the downer 2, and moisture and a small amount of volatile substances in the sludge A are separated out to form volatile components mainly comprising water vapor under the heating of the high-temperature bed materials; the mixture of the dried sludge A and the bed material and the volatile component are automatically separated in the dilute phase zone of the downer 2, and the separated mixture of the dried sludge A and the bed material enters the downer 2. The non-condensable gas and the dried sludge A are incinerated in the ascending bed 1 under the action of the supplied oxidant D (air) and combustion-supporting fuel B. Part of the solids burned enter the descending bed 2 from the first return port 13 to continue circulation, and the other part of the solids is discharged from the ash outlet 17 as bottom ash (ash C). The flue gas generated by burning the ascending bed 1 enters the gas-solid separation device 3 from the first gas outlet 11 for gas-solid separation, the gas enters the gas-water separation device 4 from the second gas outlet 21 through the third gas inlet 41 for gas-water separation, and the separated gas enters the ascending bed 1 from the first gas inlet 24 and the primary air inlet 16 for circulation.

Example 2

Referring to, as another method and apparatus for sludge incineration, example 2 is different from example 1 in that: the sludge adopted in the incineration process is sludge with the water content of 40 percent. The sludge drying temperature (drying temperature) in the downer 2 is 250 ℃. The dried sludge is incinerated together with the added heavy oil in the ascending bed 1, and the incineration temperature is 950 ℃. The excess air factor was 1.6. The ratio of the primary air to the secondary air is 70: 30.

The above detailed description is specific to possible embodiments of the present invention, and the embodiments are not intended to limit the scope of the present invention, and all equivalent implementations or modifications that do not depart from the scope of the present invention are intended to be included within the scope of the present invention.

Claims

1. A sludge incineration method is characterized by comprising the following steps:

(1) sludge drying: the sludge after simple crushing treatment forms loose powdery sludge powder, the sludge powder enters the downer from the bottom of the downer, and is mixed with high-temperature bed materials circulated from the downer in the downer, and under the heating of the high-temperature bed materials, moisture and volatile substances in the sludge are separated out to form volatile components mainly comprising water vapor; the downer is operated in a slow fluidization state; the mixture of the dried sludge and the bed material and the volatile component are automatically separated in a dilute phase zone of a descending bed; the separated mixture of the dried sludge and the bed material enters an ascending bed;

2. The method of sludge incineration of claim 1, characterized in that: the water content of the sludge is not more than 40%.

3. The method of sludge incineration of claim 1, characterized in that: and the sludge drying temperature in the downer is 150-250 ℃.

4. The method of sludge incineration of claim 1, characterized in that: the incineration temperature of the dried sludge in the ascending bed is 850-1000 ℃.

5. The method of sludge incineration of claim 1, characterized in that: the oxidant is air, and the coefficient of the excess air in the system is 1.2-2.0.

6. The apparatus for sludge incineration of claim 1, characterized in that: the air volume ratio of the primary air to the secondary air is 70: 30-50: 50.

7. An apparatus for implementing the sludge incineration method of claim 1, characterized in that: the device comprises an ascending bed, a descending bed, a gas-solid separation device and a gas-water separation device, wherein the descending bed is positioned in the ascending bed; the upper end of the ascending bed is provided with a first gas outlet, the upper part of the ascending bed is provided with an ascending bed expansion section, the lower part of the ascending bed is provided with a first material return port, and the ascending bed is communicated with the descending bed through the first material return port; the bottom of the ascending bed is respectively provided with a second return port, an auxiliary fuel inlet, a primary air inlet for primary air to enter, an ash residue outlet and a secondary air inlet for secondary air to enter; a second gas outlet is formed in the upper part of the downer, and a third material returning port is formed in the middle of the downer; the bottom of the downer is respectively provided with a fourth material return port, a first gas inlet and a solid material inlet; the fourth material returning port is communicated with the first material returning port through the descending bed; the gas-solid separation device is provided with a second gas inlet, a solid outlet and a third gas outlet; the gas-water separation device is provided with a third gas inlet and a fourth gas outlet; the first gas outlet is communicated with the second gas inlet, the solid outlet is communicated with the fourth material returning port, and the second gas outlet is communicated with the third gas inlet; and the fourth gas outlet is respectively communicated with the first gas inlet and the primary air inlet.