Method for in-furnace dechlorination of solid waste containing chlorine and incineration device

Abstract

The application discloses a method for in-furnace dechlorination of combustion of chlorine-containing solid waste and a combustion device. A Ca compound is put into a furnace chamber for in-furnace dechlorination, and a gas-solid mixture generated after combustion in the furnace chamber is separated by a cyclone separator. The separated solid substances are separated to a discharge channel, and at least part of the solid substances are discharged from a discharge port of the discharge channel to control the concentration of CaCl2 in the furnace chamber. The application can realize the target of no serious corrosion of a heating surface, greatly improve the reliability of operation of a boiler device, and prolong the continuous operation time to the standard of a first-class device.

Description

Technical Field

[0001] This invention relates to the technical field of solid waste treatment, and in particular to a method and incineration apparatus for incinerating chlorine-containing solid waste in a furnace. Background Technology

[0002] For a long time, circulating fluidized bed boilers have been widely used in the combustion treatment of high-chlorine solid waste. However, HCl is easily generated during the combustion process. Because HCl is highly corrosive, the heat exchange surface needs to have a certain degree of corrosion resistance, such as using duplex stainless steel alloys. However, even if such materials are used, they will still be corroded over time, and the general lifespan is 2-5 years.

[0003] In-furnace dechlorination is an effective measure to avoid furnace corrosion. Currently, the best method for in-furnace dechlorination is to use CaCO3. The CaCl2 produced after the reaction has a melting point of 772℃, while the furnace temperature is usually higher than the melting point of CaCl2, above 850℃. Therefore, CaCl2 will become molten. Molten CaCl2 has extremely strong adhesion. As the circulation process proceeds, the amount of molten CaCl2 adhering to the ash also increases. Some of the molten CaCl2 begins to adhere to the heating surfaces of various sections of the separator, such as the volute, central cylinder, return pipe, and superheater. The separation efficiency of the separator with adhered molten CaCl2 will decrease as the amount of adhering material increases. The efficiency of each section of the furnace decreases with the increase of adhering material, while the resistance of each section of the furnace heating surface and the flue increases with the increase of adhering material on the heating surface, until the induced draft fan cannot withstand the load and stops operating. Generally, a boiler can only operate for a maximum of ten days.

[0004] Due to the need to meet flue gas emission standards, the "external dechlorination" process, which has high investment costs, is often adopted. This includes dry dechlorination with NaHCO3 or semi-dry and wet dechlorination. Although external dechlorination solves the emission standard requirements, it cannot protect the corresponding heating surfaces, and the heating surfaces inside the furnace will still be severely corroded by chlorine. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by providing a method and incineration device for in-furnace dechlorination of chlorine-containing solid waste. By using in-furnace dechlorination to block the circulation, the molten CaCl2 is kept within a reasonable range, thus solving the problem that molten CaCl2 adheres to the cyclone separator, heating surface, and flue, preventing normal operation.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: The method of dechlorination in the furnace of chlorine-containing solid waste involves introducing Ca compounds into the furnace for in-furnace dechlorination. The gas-solid mixture generated after combustion in the furnace is separated by a cyclone separator. The separated solid material is discharged to the discharge channel, and at least part of the solid material is discharged from the discharge port at the discharge channel to control the concentration of CaCl2 in the furnace.

[0007] In the above technical solution, preferably, the discharge channel is designed not to be in fluid communication with the furnace, so that all solid materials are discharged from the discharge port and chlorine-containing materials are prevented from flowing back into the furnace.

[0008] In the above technical solution, preferably, the Ca compound is in powder or granular form.

[0009] In the above technical solution, the preferred Ca compound is CaCO3.

[0010] In the above technical solutions, preferably, additional substances that are chlorine-free or have low chlorine content and high melting point are added into the furnace to supplement the bed material.

[0011] In the above technical solution, the preferred additional substance is CaCO3.

[0012] In the above technical solutions, the preferred cyclone separator is a high-temperature cyclone separator.

[0013] Incineration equipment for dechlorination of chlorine-containing solid waste in a furnace, including The furnace chamber includes a hearth, a solid waste inlet, and a Ca compound inlet; A cyclone separator, which is in fluid communication with the furnace and connected to a flue for exhausting flue gas; and The discharge channel, which is in fluid communication with the cyclone separator, includes a discharge port for discharging solid materials.

[0014] In the above technical solution, preferably, the discharge channel is not in fluid communication with the furnace.

[0015] In the above technical solution, preferably, the bottom of the furnace includes a slag discharge outlet.

[0016] The beneficial effects of this invention are: The technology described in this application can achieve the goal of preventing severe corrosion of the heating surface, significantly improve the reliability of boiler equipment operation, and increase the continuous operating time to the standard of Class I equipment issued by the Ministry. Attached Figure Description

[0017] Figure 1 This is a schematic diagram showing the complete blockage of the discharge channel and the furnace chamber in this invention.

[0018] Figure 2 This is a schematic diagram showing the partial obstruction between the discharge channel and the furnace chamber in this invention. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: For common circulating fluidized bed boilers, they typically include a furnace, a cyclone separator, and a circulation channel. For example, in the published patent document CN101952661B, the furnace includes a hearth, a waste inlet, and a dechlorination and desulfurization material inlet, with a slag outlet at the bottom of the furnace. The cyclone separator is in fluid communication with the furnace and is connected to a flue for venting flue gas, with various components following the flue. The circulation channel is used to return the solid material separated by the cyclone separator to the furnace (the circulation channel includes the entire section between the cyclone separator and the furnace).

[0020] Currently, the best method for dechlorination in the furnace is to use Ca compounds, such as CaCO3, as one option. Ca compounds can be in powder or granular form, such as CaCO3 powder or CaCO3 granules. Based on existing common circulating fluidized bed boilers, the furnace temperature is usually above 850℃. If CaCO3 is added, the resulting CaCl2 has a melting point of 772℃. Therefore, CaCl2 easily becomes molten. Molten CaCl2 has extremely strong binding properties. As the circulation process proceeds, the amount of molten CaCl2 adhering to the ash also increases. Some molten CaCl2 begins to adhere to the volute, central cylinder, return pipe, and superheater surfaces of the separator. The separator with adhered molten CaCl2 will experience a decrease in separation efficiency as the amount of adhering material increases. The efficiency of each section of the furnace will also decrease as the amount of adhering material increases, while the resistance of the heating surfaces and flue gas ducts will increase as the amount of adhering material increases, until the induced draft fan stops operating due to overload.

[0021] Therefore, it is necessary to solve the technical problem of slow or no increase in CaCl2 concentration. Based on this, this application designs the circulation channel as follows: Figure 1 The state shown is one where there is no fluid flow between the furnace and the interior, or as shown in the image. Figure 2 The diagram shows a small portion of the fluid connected. Figure 1 The completely disconnected state shown ensures that the CaCl2 concentration does not increase; Figure 2 The state of partial fluid connectivity shown can reduce the rate of increase in CaCl2 concentration.

[0022] In one embodiment, the furnace 1 retains the hearth, solid waste inlet, and Ca compound inlet; the cyclone separator 2 is fluidly connected to the furnace 1 and is connected to a flue 3 for venting flue gas. Various components after the flue 3 can refer to existing designs and will not be described in detail here; the existing circulation channel is replaced by a discharge channel 4, which is fluidly connected to the cyclone separator 2 and includes a discharge port 5 for discharging solid materials. The discharge channel is not fluidly connected to the furnace or only has a small channel fluidly connected to the furnace to ensure that most of the solid materials can be discharged through the discharge port, and the materials discharged from the discharge port can be further processed and utilized.

[0023] Specifically, a Ca compound (such as CaCO3) is introduced into the furnace for in-furnace dechlorination. The gas-solid mixture generated after combustion in the furnace is separated by a cyclone separator. The separated solid material is discharged to the discharge channel, and at least part of the solid material is discharged from the discharge port at the discharge channel to control the concentration of CaCl2 in the furnace.

[0024] When the discharge channel is not connected to the furnace fluid at all, all solid materials separated by the cyclone separator are discharged out through the discharge port; when the smaller channel 6 is connected to the furnace fluid, most of the solid materials separated by the cyclone separator can be discharged out through the discharge port, such as designing the diameter of the smaller channel connected to the furnace fluid to be one-third or less of the existing circulation channel.

[0025] This design reduces or prevents chlorine-containing substances from flowing back into the furnace. For example, if the circulation section is cut off to prevent further circulation, and the ratio of slag to ash is 40%:60%, with a cyclone separator efficiency of 90%, then the fly ash entering the tail flue will be only 6% of the total ash and slag, far lower than the original 60%. The fly ash separated by the cyclone separator (accounting for 54% of the total ash and slag) is discharged from the cut-off point (discharge port). After discharge, the temperature of the fly ash is lower than the melting point of CaCl2, and it is basically solid, with a significant reduction in viscosity, making it easier to handle. The large amount of calcium oxide contained in this part of the ash can also be further utilized.

[0026] It should be noted that continuous combustion does not accumulate CaCl2, as it is carried away by the ash. The problem only occurs when the amount is large. When CaCl2 and ash are mixed together, the overall viscosity will decrease after a certain degree of mixing. At the same time, the viscosity will also decrease due to the lower temperature at the end. Low viscosity will not cause the problem mentioned above. The main reason for the problem is that the circulation process will cause more and more CaCl2 to accumulate.

[0027] Because the circulating furnace needs to maintain heat exchange with bed material, after designing it as non-circulating, it is necessary to add additional substances that do not contain chlorine or have low chlorine content and high melting point into the furnace to supplement the bed material, such as increasing the amount of CaCO3 or increasing the amount of ash.

[0028] This application uses technical measures such as replacing circulating ash and keeping the CaCl2 concentration from increasing to solve the technical problem that circulating fluidized bed boilers that burn high-chlorine solid waste cannot maintain long-term operation.

[0029] The technology described in this application can achieve the goal of preventing severe corrosion of the heating surface, significantly improve the reliability of boiler operation, control the number of annual emergency repairs and minor repairs to within the standard of 2 times each, and increase the boiler thermal efficiency to over 87%. Continuous operating time can be increased to meet the standards for Class I equipment issued by the Ministry of Industry and Information Technology. The HCl concentration inside the furnace can be reduced to 10-100 mg / Nm³.

[0030] Compared with the external NaHCO3 deacidification process, the production cost can be reduced by more than 12 yuan per hour per ton of steam produced, and a 55t / h boiler can increase the annual profit by more than 6 million yuan.

[0031] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for in-furnace dechlorination of chlorine-containing solid waste by combustion, characterized in that: Ca compounds are introduced into the furnace for in-furnace dechlorination. The gas-solid mixture produced after combustion in the furnace is separated by a cyclone separator. The separated solids are discharged to the discharge channel, and at least part of the solids are discharged from the discharge port at the discharge channel to control the concentration of CaCl2 in the furnace.

2. The method for in-furnace dechlorination of chlorine-containing solid waste according to claim 1, characterized in that: The discharge channel is designed not to be in fluid communication with the furnace, so that all solid materials are discharged from the discharge port and chlorine-containing materials are prevented from flowing back into the furnace.

3. The method for in-furnace dechlorination of chlorine-containing solid waste according to claim 1, characterized in that: The Ca compound is in powder or granular form.

4. The method for in-furnace dechlorination of chlorine-containing solid waste according to claim 1 or 3, characterized in that: The compound of Ca is CaCO3.

5. The method for in-furnace dechlorination of chlorine-containing solid waste according to claim 1 or 2, characterized in that: Additional substances with no or low chlorine content and high melting point are added into the furnace to supplement the bed material.

6. The method for in-furnace dechlorination of chlorine-containing solid waste according to claim 5, characterized in that: The additional substance added was CaCO3.

7. The method for in-furnace dechlorination of chlorine-containing solid waste according to claim 1, characterized in that: The cyclone separator is a high-temperature cyclone separator.

8. An incineration device for dechlorination of chlorine-containing solid waste in a furnace, characterized in that: include The furnace chamber includes a hearth, a solid waste inlet, and a Ca compound inlet; Cyclone separator, which is in fluid communication with the furnace and connected to a flue for exhausting flue gas; as well as The discharge channel, which is in fluid communication with the cyclone separator, includes a discharge port for discharging solid materials.

9. The incineration apparatus for dechlorination of chlorine-containing solid waste in a furnace according to claim 8, characterized in that: The discharge channel is not in fluid communication with the furnace.

10. The incineration apparatus for dechlorination of chlorine-containing solid waste in a furnace according to claim 8, characterized in that: The bottom of the furnace includes a slag discharge outlet.

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