PELLET FLUE GAS CIRCULATION AND WASTE HEAT UTILIZATION PROCESS AND SYSTEM THEREOF

Abstract

The present application discloses a pellet flue gas circulation and waste heat utilization process and a system thereof, which relates to the technical field of flue gas treatment. The system includes a grate, a rotary kiln, an annular cooler, and ducts connecting each part. On the basis of not changing the existing process a flue gas circulation unit and intelligent control equipment are arranged additionally in the present application. The process is simple, and not only can ensure the parameter stability of the production system such as temperature, gas flow or gas pressure, but also can make full use of the low and medium temperature flue gas components and the waste heat, so as to achieve net zero waste gas discharging, energy saving and emission reduction.

Claims

1. A pellet flue gas circulation and waste heat utilization process, which is carried out based on a pellet flue gas circulation and waste heat utilization system; the pellet flue gas circulation and waste heat utilization system comprises a grate, a rotary kiln and an annular cooler; in the pellet feeding direction, the grate comprises a blast drying section, an extraction drying section, a first preheating section and a second preheating section in sequence, the annular cooler comprises a first annular cooling section, a second annular cooling section, a third annular cooling section and a fourth annular cooling section in sequence, and a head end of the rotary kiln is connected to the second preheating section of the grate, and a tail end of the rotary kiln is connected to the first annular cooling section of the annular cooler; an outlet of the first annular cooling section of the annular cooler is connected to an inlet of the rotary kiln through a duct, an outlet of the rotary kiln is connected to an inlet of the second preheating section of the grate through a duct, and an outlet of the second preheating section of the grate is connected to an inlet of the extraction drying section of the grate through a duct; an outlet of the second annular cooling section of the annular cooler is connected to an inlet of the first preheating section of the grate through a duct; an outlet of the third annular cooling section of the annular cooler is connected to inlets of the blast drying section and the extraction drying section of the grate through ducts, respectively; outlets of the extraction drying section and the first preheating section of the grate are connected to an inlet of the third annular cooling section of the annular cooler through ducts; an outlet of the blast drying section of the grate is connected to an inlet of the fourth annular cooling section of the annular cooler through a duct; an outlet of the fourth annular cooling section of the annular cooler is connected to inlets of the first annular cooling section and the second annular cooling section of the annular cooler through ducts, respectively; a continuous flue gas emission monitoring system and a control valve are arranged in the ducts between the blast drying section and the fourth annular cooling section, between the extraction drying section and the first preheating section and the third annular cooling section, and between the fourth annular cooling section and the first annular cooling section and the second annular cooling section; 50%-100% of the flue gas from the blast drying section is introduced into the fourth annular cooling section after dust removal; the flue gas introduced into the first annular cooling section and the flue gas introduced into the second annular cooling section from the fourth annular cooling section have a ratio of 0:1-1:0; the flue gas from the blast drying section after dust removal has a temperature of 80-150° C.; the flue gas from the extraction drying section and the first preheating section after desulfurization and denitrification has a temperature of 100-200° C.; the flue gas introduced into the first annular cooling section and the second annular cooling section from the fourth annular cooling section has a temperature of 100-200° C.; the flue gas introduced into the blast drying section and the extraction drying section from the third annular cooling section has a temperature of 250-350° C.; the flue gas from the blast drying section after dust removal has an oxygen content of 17-20%; the flue gas from the extraction drying section and the first preheating section after desulfurization and denitrification has an oxygen content of 12-18%; the flue gas introduced into the blast drying section and the extraction drying section from the third annular cooling section has an oxygen content of 17-20%; the flue gas introduced into the first annular cooling section and the second annular cooling section from the fourth annular cooling section has an oxygen content of 17-20%; dust removal equipment is further arranged between the blast drying section and the fourth annular cooling section; a desulfurization unit and a denitrification unit are further arranged in the duct from the extraction drying section and the first preheating section to the third annular cooling section; an SNCR system is further arranged on the top of the second preheating section or in an inlet duct of the second preheating section; an SCR system is arranged between the extraction drying section and the third annular cooling section.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in embodiments of the present application or in the prior art, the accompanying drawing used in the embodiments will be briefly described below. Apparently, the accompanying drawing below is only an embodiment of the present application, and other accompanying drawings may be obtained based on this one without creative efforts to those skilled in the art.

[0046] FIG. 1 is a structure diagram of a pellet flue gas circulation and waste heat utilization system in Example 1 of the present application.

REFERENCE LIST

[0047] 1.1 blast drying section

[0048] 1.2 extraction drying section

[0049] 1.3 first preheating section

[0050] 1.4 second preheating section

[0051] 2 rotary kiln

[0052] 3.1 first annular cooling section

[0053] 3.2 second annular cooling section

[0054] 3.3 third annular cooling section

[0055] 3.4 fourth annular cooling section

DETAILED DESCRIPTION

[0056] Various exemplary embodiments of the present application will be described in detail, and this detailed description should not be regarded as a limitation of the present application, but a more detailed description of certain aspects, features and embodiments of the present application.

[0057] It is to be understood that the terms described in the present application are intended to describe particular embodiments only and are not intended to limit the present application. Additionally, with respect to the numerical range in the present application, it is to be understood that each value between the upper and lower limits of the range is specifically disclosed. Each listed value, each value within the listed range, and every smaller range between any other listed values or between any values within the listed range are all included in the present application. The upper and lower limits of these smaller ranges may be independently included or excluded from the scope.

[0058] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art. Although only preferred methods and materials are described in the present application, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present application. All documents referred to in this specification are incorporated by reference for disclosing and describing the methods and/or materials associated with said documents. In the case of conflict with any incorporated documents, the contents of this specification shall prevail.

[0059] Various improvements and variations may be made to specific embodiments of the specification of the present application without departing from the scope or spirit of the present application, which is apparent to those skilled in the art. Other embodiments obtained from the specification of the present application will be apparent to those skilled in the art. The specification and embodiments of the present application are exemplary only.

[0060] The terms “comprises”, “includes”, “has”, “contains”, etc., as used herein, are open-ended terms, which means “inclusive but not limited to”.

Example 1

[0061] A structure diagram of a pellet flue gas circulation and waste heat utilization system in an embodiment of the present application is shown in FIG. 1. The system includes a grate, a rotary kiln and an annular cooler; in the pellet feeding direction, the grate includes a blast drying section 1.1, an extraction drying section 1.2, a first preheating section 1.3 and a second preheating section 1.4 in sequence, the annular cooler includes a first annular cooling section 3.1, a second annular cooling section 3.2, a third annular cooling section 3.3 and a fourth annular cooling section 3.4 in sequence, and a head end of the rotary kiln 2 is connected to the second preheating section 1.4 of the grate, and a tail end of the rotary kiln 2 is connected to the first annular cooling section 3.1 of the annular cooler.

[0062] An outlet of the first annular cooling section 3.1 of the annular cooler is connected to an inlet of the rotary kiln 2 through a duct, an outlet of the rotary kiln 2 is connected to an inlet of the second preheating section 1.4 of the grate through a duct, and an outlet of the second preheating section 1.4 of the grate is connected to an inlet of the extraction drying section 1.2 of the grate through a duct.

[0063] An outlet of the second annular cooling section 3.2 of the annular cooler is connected to an inlet of the first preheating section 1.3 of the grate through a duct.

[0064] An outlet of the third annular cooling section 3.3 of the annular cooler is connected to inlets of the blast drying section 1.1 and the extraction drying section 1.2 of the grate through ducts, respectively.

[0065] Outlets of the extraction drying section 1.2 and the first preheating section 1.3 of the grate are connected to an inlet of the third annular cooling section 3.3 of the annular cooler through ducts.

[0066] An outlet of the blast drying section 1.1 of the grate is connected to an inlet of the fourth annular cooling section 3.4 of the annular cooler through a duct.

[0067] An outlet of the fourth annular cooling section 3.4 of the annular cooler is connected to inlets of the first annular cooling section 3.1 and the second annular cooling section 3.2 of the annular cooler through ducts, respectively.

[0068] A continuous flue gas emission monitoring system CEMS and a flow control valve are arranged in the ducts between the blast drying section 1.1 and the fourth annular cooling section 3.4, between the extraction drying section 1.2 and the first preheating section 1.3 and the third annular cooling section 3.3, and between the fourth annular cooling section 3.4 and the first annular cooling section 3.1 and the second annular cooling section 3.2.

[0069] Dust removal equipment is further arranged between the blast drying section 1.1 and the fourth annular cooling section 3.4. The dust removal equipment is a cyclone dust collector.

[0070] A desulfurization unit and a denitrification unit are further arranged in the duct from the extraction drying section 1.2 and the first preheating section 1.3 to the third annular cooling section 3.3. The desulfurization unit is a circulating fluidized bed semi-dry desulfurization unit; the denitrification system is SCR denitrification.

[0071] An SNCR system is arranged on the top of the second preheating section 1.4.

[0072] The pellet flue gas circulation and waste heat utilization process is carried out based on the above system. The flue gas from the blast drying section 1.1 is introduced into the fourth annular cooling section 3.4 after dust removal; the net flue gas (with a high oxygen content) from the extraction drying section 1.2 and the first preheating section 1.3 after desulfurization and denitrification is introduced into the third annular cooling section 3.3, the flue gas from the third annular cooling section 3.3 is introduced into the blast drying section 1.1 and the extraction drying section 1.2, and the flue gas from the fourth annular cooling section 3.4 is introduced into the first annular cooling section 3.1 and the second annular cooling section 3.2 as blending gas.

[0073] When the grate is working, the blast drying section has a flue gas temperature range of 200-300° C., the extraction drying section has a flue gas temperature range of 300-400° C., the first preheating section has a flue gas temperature range of 550-650° C., and the second preheating section has a flue gas temperature range of 900-1000° C.; the rotary kiln has a roasting temperature of 1250-1350° C., the first annular cooling section is 1100° C., the second annular cooling section is 850° C., the third annular cooling section is 350° C., and the fourth annular cooling section is less than or equal to 180° C.; the temperature may have fluctuations depending on working conditions. The oxygen content is in the range of 14-21%.

[0074] 50%-100% of the flue gas from the blast drying section 1.1 is introduced into the fourth annular cooling section 3.4 after dust removal; the net flue gas from the extraction drying section 1.2 and the first preheating section 1.3 after desulfurization and denitrification has a ratio of 10-100%, i.e. 0.1:1-1:0; the gas flow introduced into the first annular cooling section 3.1 and the gas flow introduced into the second annular cooling section 3.2 from the fourth annular cooling section 3.4 have a ratio of 0-100%, i.e. 0:1-1:0.

[0075] The flue gas from the blast drying section 1.1 after dust removal has a temperature of 80-150° C.; the net flue gas from the extraction drying section 1.2 and the first preheating section 1.3 after desulfurization and denitrification has a temperature of 100-200° C.; the flue gas from the third annular cooling section 3.3 has a temperature of 250-350° C. when introduced into the blast drying section 1.1 and the extraction drying section 1.2; the exhaust gas introduced into the first annular cooling section 3.1 and the second annular cooling section 3.2 from the fourth annular cooling section 3.4 has a temperature of 100-200° C.

[0076] The flue gas from the blast drying section 1.1 after dust removal has an O.sub.2 content of 17-20%; the net flue gas (SO.sub.2: 35 mg/Nm.sup.3, NO.sub.x: 50 mg/Nm.sup.3, particulate: 10 mg/Nm.sup.3) from the extraction drying section 1.2 and the first preheating section 1.3 after desulfurization and denitrification has an O.sub.2 content of 12-18%; the flue gas from the third annular cooling section 3.3 has an O.sub.2 content of 17-20%; the exhaust gas introduced into the first annular cooling section 3.1 and the second annular cooling section 3.2 from the fourth annular cooling section 3.4 has an O.sub.2 content of 17-20%.

[0077] The above example is only the preferred embodiment of the present application and are not intended to limit the present application, and various variations and improvements, which can be made to the technical solutions of the present application by those skilled in the art without departing from the spirit of the present application, shall fall within the protection scope defined by the appended claims of the present application.