LIME KILN APPARATUS FULLY RECYCLING CO2

Abstract

The present application provides a lime kiln apparatus recycling CO.sub.2 which includes a kiln body (100) and a heat-accumulating furnace set (20). The kiln body (100) defines no burner therein, and the heat-accumulating furnace set (20) provides hot CO.sub.2 (70) heated to a set temperature to the kiln body (100) for calcining mineral material, thereby finished lime is obtained. CO.sub.2 generated during the lime production is all recycled. After being dedusted, a part of the recycled CO.sub.2 is transported to the heat-accumulating furnace set (20) for heating, and is sent back to the kiln for calcining the mineral material after being heated to a temperature within a range of 800 C.-1200 C., and the other part of the recycled CO.sub.2 is recycled for use.

Claims

1. A lime kiln apparatus fully recycling CO.sub.2, wherein comprising a kiln body (100) and a heat-accumulating furnace set (20), the kiln body (100) defines no burner, the heat-accumulating furnace set (20) is configured to heat CO.sub.2 to a set temperature, and to send the heated CO.sub.2 to the kiln body (100) to calcinate a preheated mineral material; wherein CO.sub.2 generated during the calcination mixes with the CO.sub.2 heated by the heat-accumulating furnace set (20) to go upwards to preheat a mineral material at an upper part of the kiln body (100), and the mixed CO.sub.2 is pumped out of the upper part of the kiln body (100) to enter the heat-accumulating furnace set (20); the mixed CO.sub.2 is sent to the kiln body (100) after being heated to the set temperature by the heat-accumulating furnace set (20); and finished lime obtained by the calcination is discharged from a bottom of the kiln body (100) after being cooled.

2. The lime kiln apparatus fully recycling CO.sub.2 according to claim 1, wherein the kiln body (100) comprises a in-in-feeding device (30) and a out-in-feeding device (40); a working area of the kiln body (100) comprises a preheating section (110), a calcining section (120) and a cooling section (130) sequentially arranged from top to bottom; wherein the mineral material is fed to the kiln body (100) from the in-feeding device (30), and sequentially passes the preheating section (110) and the calcining section (120): the finished lime is discharged from the out-feeding (40) after being cooled by the cooling section (130); a side wall of the calcining section (120) defines an inlet of the heated CO.sub.2; a lower part of the cooling section (130) defines an inlet of cooling air (50); the cooling air (50) enters the kiln body (100) from the lower part of the cooling section (130) to cool the finished lime produced by the calcination, and the cooled finished lime is discharged out of the kiln body (100) through the out-feeding (40).

3. The lime kiln apparatus fully recycling CO.sub.2 according to claim 1, wherein the heat-accumulating furnace set (20) comprises two or three furnaces, each of the furnaces applying a ceramic burner or a metal burner, and comprising a heat-accumulating chamber filled with a regenerator, wherein, on condition that the heat-accumulating furnace set (20) comprises two furnaces, one of the two furnaces is configured to heat the regenerator with generated hot flue gas burnt by fuel with air, and the other furnace is configured to use the heated heat-accumulator to heat the CO.sub.2; on condition that the heat-accumulating furnace set (20) comprises three furnaces, two of the three furnaces are configured to generate the hot flue gas by burning the fuel with air to heat the regenerator, and the other furnace is configured to heat the CO.sub.2.

4. The lime kiln apparatus fully recycling CO.sub.2 according to claim 2, wherein the kiln body (100) defines an inner cylinder (AB), a material passage for delivering material is formed between an inner wall of the kiln body (100) and an outer wall of the inner cylinder (AB), a total width of cross section of the material passage defines a passing diameter, the inner cylinder (AB) defines an air inlet at an upper part of the cooling section (130), the cooling air (50) enters the material passage from the lower part of the kiln body (100) to cool the finished lime, then enters the inner cylinder (AB) from the air inlet of the inner cylinder (AB), and is pumped out of the kiln body (100) from a top of the kiln body (100).

5. The lime kiln apparatus fully recycling CO.sub.2 according to claim 4, wherein the cooling air (50) forms a high-temperature waste cooling air during cooling the finished lime, and the high-temperature waste cooling air is pumped out of the kiln body (100) to enter a heat-accumulating heat exchanger of the heat-accumulating furnace set (20) for heating combustion-supporting air (22), wherein the heat-accumulating heat exchanger is a small heat-accumulating furnace without burner, and a dust collecting device is defined at a lower part of a heat accumulating chamber of the heat accumulating type heat exchanger.

6. The lime kiln apparatus fully recycling CO.sub.2 according to claim 2, wherein a steam inlet is defined in a side wall of the upper part of the cooling section (130) of the kiln body (100); on condition that the finished lime passes through the upper part of the cooling section (130) along the material passage, the finished lime is cooled for a first time by steam injected into the kiln body (100), the finished lime is cooled for a second time by cold CO.sub.2, wherein the cold CO.sub.2 is introduced into the cooling section (130) of the kiln body (100) from a bottom of the kiln body (100), goes upward to enter the calcining section (120) along with the steam, and is discharged out of the kiln body (100) from the top of the kiln body (100) together with the mixed CO.sub.2, obtaining a CO.sub.2 mixture which comprises the steam; the CO.sub.2 mixture is dedusted and dehydrated to obtain recycled CO.sub.2, a part of the recycled CO.sub.2 is introduced into a collecting device and the other part of the recycled CO.sub.2 is introduced into the furnace set for reuse.

7. The lime kiln apparatus fully recycling CO.sub.2 according to claim 2, wherein an inner diameter of the kiln body (100) at the lower part of the preheating section (110) and the middle part of the calcining section (120) is larger than an inner diameter of the kiln body (100) at the lower part of the calcining section (120), and an inner diameter of the kiln body (100) at the cooling section (130) increases after a transition section of the kiln body (100).

8. The lime kiln apparatus fully recycling CO.sub.2 according to claim 4, wherein a ratio of a maximum passing diameter of the material passage at the middle of the calcining section (120) to a minimum passing diameter of the material passage at the lower part of the calcining section (120) ranges within 2-3.5, and a ratio of a maximum passing diameter of the material passage at the cooling section (130) to a passing diameter of the material passage at the transition section ranges within 2-3.5.

9. The lime kiln apparatus fully recycling CO.sub.2 according to claim 4, wherein the inner cylinder (AB) defines a dedusting device at a lower part of the inner cylinder (AB), the upper part of the inner cylinder (AB) is connected with an air guiding pipe, wherein the air guiding pipe is configured for pumping the high-temperature waste cooling air out of the upper part of the kiln body (100) to heat the combustion-supporting gas.

10. A method for preparing industrial lime which totally recycles CO.sub.2, wherein the method comprises: heating CO.sub.2 to a set temperature; sending the heated CO.sub.2 into a kiln body (100) to calcine preheated mineral material; obtaining mixed CO.sub.2 by mixing CO.sub.2 generated during the calcination of the mineral material mixes with the heated CO.sub.2; preheating the mineral material at an upper part of the kiln body (100) by the mixed CO.sub.2 going upward; pumping the mixed CO.sub.2 out of the upper part of the kiln body (100) to obtain recycled CO.sub.2; sending a part of the recycled CO.sub.2 to a furnace set; heating the recycled CO.sub.2 to a set temperature and then sending back the heated recycled CO.sub.2 to the kiln body (100); and discharging finished lime produced by the calcination from a bottom of the kiln body (100) after the finished lime is cooled by air.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The present application will be further described with reference to the accompanying drawings.

[0044] FIG. 1 is a schematic structural diagram of an annular sleeve shaft kiln system in the prior art;

[0045] FIG. 2 is a schematic structural diagram of a concurrent heat-accumulating (Maerz kiln) and double-chamber lime shaft kiln in prior art;

[0046] FIG. 3 is a schematic structural diagram of a beam-type heat-accumulating lime kiln in prior art;

[0047] FIG. 4 is a schematic structural diagram of a concurrent heat-accumulating lime kiln in prior art:

[0048] FIG. 5 is a structural diagram of a lime kiln apparatus in example 1 of the present application;

[0049] FIG. 6 is a schematic diagram of the working principle of the lime kiln apparatus in example 1 of the present application;

[0050] FIG. 7 is a schematic diagram of the working principle of the heat-accumulating furnace in example 1 of the present application.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0051] The present application will be further described below with reference to the accompanying drawings and detailed description.

Example 1

[0052] FIG. 5 shows the structure and working principle of a lime kiln system fully recycling CO.sub.2, which includes: 100kiln body, 20furnace set, 21blast furnace gas, 22combustion-supporting air, 23combustion fan, 30in-in-feeding device, 40out-feeding, 50cooling air, 60CO.sub.2 recycling device, and 70hot CO.sub.2. The kiln body 100 includes a preheating section 110, a calcining section 120, and a cooling section 130.

[0053] As shown in FIG. 5, all current lime kiln technologies using gas fuel being compared, according to the lime kiln apparatus of the present application, hot CO.sub.2 having a constant temperature and no flame is used as a heat carrier to calcine mineral materials, which accelerates the decomposition of the mineral materials. Thereby, finished lime with a high quality may be obtained, and the calcination time is significantly reduced by using the lime kiln apparatus of the present application.

[0054] The mineral material enters the kiln body 100 from the in-in-feeding device 30, sequentially passes through the preheating section 110, the calcining section 120 and the cooling section 130, and the cooled finished lime is discharged from the lower out-feeding 40 of the kiln body 100. The mineral material is preheated and calcined by hot CO.sub.2, and the finished lime obtained by calcination is cooled by air.

[0055] The preheated mineral material is calcined by the hot CO.sub.2 entering the kiln body from the calcining section, then the hot CO.sub.2 combined with CO.sub.2 generated by decomposition of the mineral material goes up to enter the preheating section 110 at the upper part of the kiln body 100, and is pumped out of the upper part of the kiln body 100 after cooling down. The CO.sub.2 pumped out is introduced into the CO.sub.2 recycling device 60, and after the CO.sub.2 pumped out is dedusted, one part of the dedusted CO.sub.2 is recycled, the other part of the dedusted CO.sub.2 is introduced into the heat-accumulating furnace set to be heated and then returns to the calcining section 120 of the kiln body 100.

[0056] Preferably, the furnace set 20 consists of two heat-accumulating furnaces or three heat-accumulating furnaces. The furnace set 20 uses fuel such as blast furnace gas 21, coal powder, coal water slurry, natural gas or other gaseous fuels to heat the CO.sub.2 from the kiln body to a required temperature according to the process. The temperature is generally within a range of 800 C.-1250 C., and the preferred range is 850 C.-1150 C.

[0057] The finished lime obtained by the calcination enters the cooling section 130, and the cooling air 50 enters the cooling section 130 of the kiln body 100 from the lower part of the kiln body 100 to cool the finished lime. The cooled finished lime is then drawn out from the upper part of the cooling section 130 of the kiln body 100 and fed into the furnace set 20. The waste heat generated by the cooling air 50 during cooling the finished lime is used to heat the combustion-supporting air 22 via the heat-accumulating heat exchanger (two heat exchanger work alternately) in the furnace set 20.

[0058] The utilization of the waste heat generated by the cooling air 50 during cooling the finished lime may be realized by other mature process technologies in the field, such as heat exchangers made of materials resisting high temperature, or may be used for power generation by waste heat, in addition to the above-mentioned heat-accumulating heat exchangers.

[0059] For those auxiliary facilities and equipment not shown in FIG. 5 that are not related to the present application, it does not mean that these auxiliary facilities and equipment are not necessary for the realization of the present application. In order to realize the purpose of the present application, it is requested to configure necessary auxiliary facilities and equipment with mature technologies.

[0060] In order to explain the implementation method of the present application more clearly, FIGS. 6 and 7 further explain the working principles of the lime kiln and the heat-accumulating furnace set. FIG. 6 is a schematic diagram of the working principle of the lime kiln involved in the example, which illustrates the method of recycling CO.sub.2 from the lime kiln and calcining mineral materials by hot CO.sub.2. FIG. 7 is a schematic diagram of the working principle of the heat-accumulating furnace involve in the example of the present application, which illustrates the method of using the heat-accumulating fuel group to heat CO.sub.2 by using fuel with a low heating value and to heat combustion-supporting air by using the waste heat of cooling air.

[0061] According to FIG. 5, in terms of the kiln body of the lime kiln system, one of the keys to realize the present application is related to the technology of separating CO.sub.2 at the upper part of the kiln body from the cooling air at the lower part of the kiln body, and the technologies of dusting and waste heat utilization.

[0062] FIG. 6 is a typical example in which the lime kiln apparatus of the present application has a relatively simple structure and may effectively reduce CO.sub.2 emission.

[0063] The lime kiln apparatus includes: lime kiln body 100, inner cylinder AB, preheating section 110, calcining section 120, cooling section 130, in-feeding device 30, out-feeding 40, cooling air 50, CO.sub.2 recycling device 60, and hot CO.sub.2 70.

[0064] According to FIG. 6, the kiln body 100 is defined with an inner cylinder AB, and a material passage for delivering material is formed between the inner wall of the kiln body 100 and the outer wall of the inner cylinder AB. The material passage has different passing diameter at the preheating section, the calcining section and the cooling section. Mineral material enters the kiln body 100 from the top by the feeding system 30, passes through the preheating section 110 and the calcining section 120 along the material passage between the inner wall of the kiln body and the outer wall of the inner cylinder AB, and the finished product enters the cooling section 130. finally, the cooled finished lime is discharged through the discharging system 40.

[0065] The hot CO.sub.2 70 enters the kiln body 100 through three rows of air inlet nozzles arranged on the kiln body 100. Under the calcining section 120, a transition section is formed between the calcining section 120 and the cooling section 130, the material passage narrowing at the transition section. The transition section defines a material sealing layer between the calcining section and the cooling section. The main function of the material sealing layer of the transition section is to prevent the cooling air 50 from entering the calcining section 120.

[0066] In order to achieve the above purpose, the typical solution provided by the present application is as follows.

[0067] The kiln body 100 is in the form of a circular shaft kiln, preferably, is a drum waist shaft kiln with a larger inner diameter at the lower part of the preheating section 110 and the middle part of the calcining section 12, and a smaller inner diameter at the lower part of the calcining section 120. The kiln body 100 defines an inner cylinder AB therein, which is commonly in the form of a circular cylinder or a special-shaped cylinder. A material passage for delivering material is formed between the inner wall of the kiln body 100 and the outer wall of the inner cylinder AB. The total width of the cross section of the material passage defines a passing diameter. The passing diameter of the material passage is different in the preheating section, the calcining section and the cooling section. The passing diameter of the material passage in the middle of the calcining section 120 is larger, such as a1. The material passage has a transition section between the calcining section and the cooling section, and the passing diameter of the transition section is smaller, such as a. The ratio of the largest passing diameter of the material passage at the middle of the calcining section 120 to the smallest passing diameter at the lower part of the calcining section is within a range of 1-4, and preferably, 2-3.5.

[0068] Since the transition section of the material passage located at the lower part of the calcining section 120 has a smaller passing diameter, the material moves faster in the transition section with the smaller passing diameter, thus forming the material sealing layer of the transition section. Such structure may not only prevent the cooling air from entering the calcining section 120, but also is beneficial for improving the activity of the finished lime.

[0069] The finished lime is cooled by using cooling air. The typical solution provided by the present application is as follow.

[0070] An inner cylinder AB is defined inside the kiln body 100, a dedusting device is defined inside the inner cylinder AB, a dust collecting device is defined at the lower part of the inner cylinder AB, and the upper part of the inner cylinder AB is connected with an air guiding pipe, the air guide pipe is configured for pumping the high-temperature cooling air 50 out of the upper part of the kiln body 100, and an air inlet is defined in the inner cylinder AB at the upper part of the cooling section 130. The cooling air 50 enters the material passage at the lower part of the cooling section 130, that is, the lower part of the kiln body 100, and is drawn into the inner cylinder AB through the air inlet of the inner cylinder AB at the upper part of the cooling section 130.

[0071] In the cooling section 130, the finished lime moves downward along the material passage, while the cooling air 50 flows inversely upward to cool the lime product. The passing diameter of the material passage at the middle and lower parts of the cooling section is larger, such as a2, and the ratio of the maximum passing diameter a2 of the material passage at the cooling section to the minimum passing diameter a of the material passage at the transition section above the cooling section is within a range of 1-4, preferably, 2-3.5. The finished lime enters the out-feeding 40 after being cooled. Under the suction by the air guiding pipe, the inner cylinder AB acquires negative pressure inside, and cooling air 50 is drawn into the inner cylinder AB from the air inlet at the upper part of the cooling section 130. After being dedusted by the inner cylinder AB, the cooling air 50 is drawn out of the kiln body 100 via the air guiding pipe.

[0072] In order to achieve the above objectives, other solutions different from the above typical solutions may also be adopted, but no matter which solution, efforts should be made to achieve 1) the cooling air being prevented from entering the calcining section; 2) the high-temperature cooling air being pumped out of the kiln body after preliminary dedusting.

[0073] FIG. 7 is a schematic diagram of the working principle of the heat-accumulating furnace set 20 according to the present application. The heat-accumulating furnace set 20 includes a heat-accumulating furnace 201, a heat-accumulating heat exchanger 202, a blast furnace gas 21, combustion-supporting air 22, a combustion fan 23, an air mixing chamber 24, a heat-accumulating heat exchanger reversing device 25, and heat-accumulating furnace flue gas 26.

[0074] And, three heat-accumulating furnaces 201 are preferably used to ensure continuous hot air supply to the lime kiln system. When one furnace is under maintenance, the other two furnaces may also keep the production.

[0075] The three heat-accumulating furnaces adopt the working mode of two burning and one delivery. The heat-accumulating furnace 201 uses blast furnace gas 21 and combustion-supporting air 22 when burning in the furnace. The cold dedusted CO.sub.2 collected from the lime kiln system is heated to 800 C.-1200 C. by the furnace 201, and then is sent back to the lime kiln 100 through the hot air nozzles annularly arranged.

[0076] The working principle of the furnace 201 is as follows. During one furnace burning period, blast furnace gas 21 and combustion-supporting air 22 enter the burner of the heat-accumulating furnace 201 for combustion to generate high-temperature flue gas of 1100 C.-1300 C., the flue gas is used for heat heat-accumulating materials in the furnace. During one air supply period, the burner is turned off, and cold CO.sub.2 is introduced which is a part of the CO.sub.2 collected and dedusted by the lime kiln 100. The CO.sub.2 is heated by the heat-accumulating materials of the furnace 201, and is sent back to the lime kiln 100 at a constant temperature within the range of 800 C.-1200 C. through the hot air nozzles annularly arranged. The furnace set has a working mode of two burning and one sending, i.e. two furnaces are configured for burning and one furnace is configured for supplying air at the same time.

[0077] A dust collecting device is defined at the lower part of the furnace 201 for collecting dust and convenience of cleaning the furnace during routine maintenance.

[0078] The waste flue gas of the furnace 201 generally needs to be continuously cooled, dedusted and discharged. There are many alternative technical solutions to cool the waste flue gas of the furnace 201. The preferred technical solution of the present application is to introduce the waste flue gas of the furnace 201 to the air mixing chamber 24 to adjust the temperature of combustion-supporting air from the heat-accumulating heat exchanger 202.

[0079] The shells of the two heat-accumulating heat exchangers 202 are made of metal structural steel and are provided with thermal insulation linings, the upper part of each heat-accumulating heat exchangers 202 is defined in an arched structure, the lower part of each heat-accumulating heat exchangers 202 is provided with a heat-accumulating chamber with heat-accumulating material defined inside, the heat-accumulating material is preferably in the form of checker bricks, a heat-resistant cast iron supporting device or a supporting structure made of refractory materials is defined at the lower part of the checker bricks. A waste gas outlet and a combustion-supporting air inlet are defined at the lower part of the heat-accumulating heat exchanger 202, a combustion-supporting air outlet is defined at the upper part of the checker bricks, and a dust collecting device is defined at the bottom of the heat-accumulating heat exchanger 202, an air inlet for high-temperature cooling air 50 is defined at the arched upper part, and the high-temperature cooling air 50 from the kiln body 100 enters the heat exchanger 202 from the arched upper part of the heat-accumulating heat exchanger 202 through an air guiding pipe.

[0080] The high-temperature cooling air 50 from the kiln body 100 is introduced into the heat exchanger from the arched top of a first heat-accumulating heat exchanger 202 through a pipeline to heat the heat-accumulating materials of the heat-accumulating chamber, and is discharged from the waste gas outlet after being cooled down, finally is emitted after being dedusted.

[0081] After the heat-accumulating material of the first heat exchanger is heated to a preset temperature, that is, after a cycle of heating is completed, the high-temperature cooling air 50 is introduced into a second heat-accumulating heat exchanger 202 through a pipeline by switching a valve to heat the heat-accumulating materials in the heat-accumulating chamber of the second heat exchanger. And, cold combustion-supporting air 22 is introduced into the first heat-accumulating heat exchanger 202 from the lower part and is discharged above the heat-accumulating material after being heated by the heat-accumulating materials in the heat-accumulating chamber to enter the air mixing chamber 24. The air mixing chamber is also introduced with cold combustion-supporting air and waste flue gas from the furnace 201 for adjusting the temperature of the combustion-supporting air 22. The combustion-supporting air 22 is introduced into the heat-accumulating furnace 201 from the air mixing chamber 24 at a constant temperature.

[0082] A small amount of dust carried by the high-temperature cooling air 50 is collected by a collecting device at the lower part of the heat exchanger 202, and is cleaned out of the heat-accumulating heat exchanger during routine maintenance.

[0083] The present application also provides a method for cooling the finished lime in the kiln, including the following operations: defining a steam inlet in the side wall of the upper part of the cooling section of the kiln body; spraying steam into the kiln to cool the finished lime for a first time, when the finished lime passes through the upper part of the cooling section along a material passage; cooling the finished lime for a second time by using cold CO.sub.2, wherein the cold CO.sub.2 is introduced into the cooling section of the kiln body from the bottom of the kiln, then goes upward with the steam to enter the calcining section, the steam and the cold CO.sub.2 mix with CO.sub.2 generated by the calcination to obtain CO.sub.2 mixture; discharging the CO.sub.2 mixture out of the kiln body from the top of the kiln; dedusting and dehydrating the CO.sub.2 mixture to obtain recycled CO.sub.2, part of the recycled CO.sub.2 being introduced a collecting device, and the other part of the recycled CO.sub.2 being introduced to the furnace set as circulating air.

[0084] For those skilled in the technical field, the inventive concept may be realized in different ways with the technology development. The embodiments of the present application are not limited to the examples described above, but may be varied within the scope of the claims.