Chlorine fixation method for co-carbonization process of chlorine-containing waste plastics and coking coal

Abstract

The invention relates to a chlorine fixation method for a co-carbonization process of chlorine-containing waste plastics and coking coal, which comprises the following steps: (1) mixing the chlorine-containing waste plastics, the coking coal, alkali metal strontium carbonate and an adhesive to prepare mixed coal; (2) carrying out cold pressing on the mixed coal obtained in the step (1) to prepare briquette coal; and (3) uniformly mixing the briquette coal and the bulk coal obtained in the step (2) according to a set proportion, and carrying out co-carbonization treatment in a coke oven carbonization chamber to obtain high-reactivity coke and low-chlorine coke oven gas. The chlorine element in the chlorine-containing waste plastic can be fixed in the solid product coke, the reactivity of the coke can be improved on the premise of ensuring the strength of the coke, and meanwhile, the use amount of coking coal is reduced; effective technical support is provided for chlorine-containing waste plastic treatment, and an important technical route is provided for multi-azimuth reduction of CO2 emission of a blast furnace.

Description

Technical Field

[0001] The present invention relates to the technical field of coking, and particularly relates to a method for fixing chlorine in the co-carbonization process of chlorine-containing waste plastics and coking coal. Background Art

[0002] Traditional waste plastic treatment methods mainly include landfill, incineration, and recycling. Among them, the landfill method not only occupies a large amount of land resources but may also cause soil and groundwater pollution; the incineration method generates a large amount of harmful gases (such as dioxins and hydrogen chloride, etc.), causing serious pollution to the atmospheric environment; although the recycling method is a relatively environmentally friendly treatment method, due to the wide variety and mixture of waste plastics, the recycling cost is high, and there are many difficulties in practical applications.

[0003] In order to alleviate the shortage of coking coal, researchers have begun to explore the use of waste plastics as substitutes for coking coal.

[0004] Waste plastics include polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polystyrene (PS), etc. Their softening range has a certain overlap with the plastic temperature range of coal and has a certain viscosity in the molten state, similar to the active components of coal (Master's Thesis of Liaoning University of Science and Technology in 2020, "Research on the Forming Performance and Co-carbonization of Coking Coal Added with Waste Plastics" by Shi Deqian). Therefore, adding waste plastics to coking coal can achieve the resource utilization of organic solid waste. For example, Bai Jie et al. have shown that when using 4% waste plastics to replace coking coal, the coke reactivity can be increased by one to three percentage points ([Experimental Study on Coke-making with Blended Coal Containing Waste Plastics], Master's Thesis of Liaoning University of Science and Technology in 2016), thereby reducing the coke reaction starting temperature, increasing the blast furnace utilization coefficient, reducing the coke ratio, and improving the blast furnace production efficiency. However, in the co-carbonization process, mainly chlorine-containing waste plastics such as chlorinated polyvinyl chloride (CPVC), chlorinated rubber (CR), and polyvinyl chloride (PVC) will generate hydrogen chloride gas, and their chlorine content is between 56% and 75%, resulting in a significant increase in the chlorine content in coke oven gas. Chlorine in coke oven gas will corrode equipment, affect production safety, lead to a decline in gas quality, and also cause environmental pollution (Ren Haohua et al., "Generation of HCl during PVC Pyrolysis and Its Influencing Factors", China Environmental Science, 2015, 35(08): 2460 - 2469). Therefore, how to effectively treat the chlorine element transferred to coke oven gas during the co-coking process of chlorine-containing waste plastics and coal has become an urgent problem to be solved.

[0005] To solve the above problems, taking chlorine-containing waste plastic PVC as an example, strontium carbonate and calcium oxide of alkali metals are added to the blended coal respectively. The alkali metals can react with the chlorine element in the waste plastic to fix the chlorine element in the coke, preventing it from transferring to the coke oven gas. The experimental results show that, compared with calcium oxide, strontium carbonate can better fix the chlorine element in the coke, significantly reducing the chlorine content in the coke oven gas. In addition, the addition of strontium carbonate of alkali metals can also improve the reactivity (CRI) of the coke. However, the addition of strontium carbonate will lead to a decrease in the coke strength after reaction (CSR), affecting the coke quality. To overcome this problem, the present invention adopts the process of blending formed coal for coking on the basis of adding strontium carbonate. The experimental results show that the process of blending formed coal for coking can effectively overcome the problem of the decrease in the coke strength after reaction caused by the addition of strontium carbonate, realizing the resource utilization of chlorine-containing waste plastics and ensuring the stability of the coke strength after reaction at the same time. Summary of the Invention

[0006] The present invention provides a method for fixing chlorine in the co-carbonization process of chlorine-containing waste plastics and coking coal, which can not only fix the chlorine element in the chlorine-containing waste plastics in the solid product coke, but also improve the reactivity of the coke on the premise of ensuring the coke strength, while reducing the consumption of coking coal; it provides effective technical support for the treatment of chlorine-containing waste plastics in China and also provides an important technical route for reducing the CO2 emissions of blast furnaces in multiple aspects.

[0007] To achieve the above object, the present invention is realized by adopting the following technical solutions:

[0008] A method for fixing chlorine in the co-carbonization process of chlorine-containing waste plastics and coking coal, in which the chlorine-containing waste plastics, coking coal and strontium carbonate of alkali metals are mixed to make blended coal, and the process of blending formed coal is adopted for co-carbonization coking; the specific steps are as follows:

[0009] (1) Mix the chlorine-containing waste plastics, coking coal, strontium carbonate of alkali metals and binder to make blended coal;

[0010] (2) Cold-press the blended coal obtained in step 1 to make formed coal;

[0011] (3) Uniformly mix the formed coal obtained in step 2 and slack coal according to a set ratio, and then place them in the coke oven carbonization chamber for co-carbonization treatment to obtain high-reactivity coke and low-chlorine coke oven gas.

[0012] In the step (1), by mass percentage, the addition amount of the binder is 1% - 5% of the blended coal; the addition amount of strontium carbonate of alkali metals is 0.2% - 1% of the total amount of the formed coal and slack coal, and the addition amount of the chlorine-containing waste plastics is 1% - 3% of the total amount of the formed coal and slack coal.

[0013] In the step (1), the coking coal is a mixed coking coal composed of gas coal, 1 / 3 coking coal, fat coal, coking coal and lean coal; and by mass percentage, gas coal: 3% - 8%, 1 / 3 coking coal: 10% - 30%, fat coal: 15% - 20%, coking coal: 40% - 50%, lean coal: 10% - 15%; the fineness of the mixed coking coal is 75% - 85%.

[0014] In the step (1), the chlorine-containing waste plastic is polyvinyl chloride, and the particle size of the polyvinyl chloride is 1 - 3 mm.

[0015] In the step (1), the binder is a coal tar binder and / or an asphalt binder.

[0016] In the step (1), the moisture content of the blended coal is 9% - 12%.

[0017] In the step (2), the equivalent diameter of the briquette is 10 - 30 mm.

[0018] In the step (3), the mass percentage of the briquette in the total of the briquette and the slack coal is 20% - 40%.

[0019] In the step (3), the slack coal is a mixed coking coal composed of gas coal, 1 / 3 coking coal, fat coal, coking coal and lean coal; and by mass percentage, gas coal: 3% - 8%, 1 / 3 coking coal: 10% - 30%, fat coal: 15% - 20%, coking coal: 40% - 50%, lean coal: 10% - 15%; the fineness of the mixed slack coal is 75% - 85%.

[0020] In the step (3), the coke reactivity index (CRI) of the highly reactive coke is > 34%, and the coke strength after reaction (CSR) is > 41%; the chlorine content in the low-chlorine coke oven gas is < 4%.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1) Aiming at the problem of difficult treatment of waste plastics, the prior art proposed a method of using waste plastics for coal blending coking. However, using this method will cause the chlorine element in the chlorine-containing waste plastics to transfer to the coke oven gas, resulting in the corrosion of subsequent gas purification equipment and affecting the subsequent processing of gas to synthesize products such as methanol and liquefied natural gas, and further causing problems such as environmental pollution and reduction of coking product quality. The present invention adds strontium carbonate to the chlorine-containing waste plastic coal blending process, which can effectively fix the chlorine element in the coke, thus preventing the occurrence of the above problems.

[0023] 2) The addition of strontium carbonate can improve the reactivity (CRI) of the coke, which is beneficial to improving the quality of the coke.

[0024] 3) The present invention adopts the process of blending and forming coke, which can avoid the problem of the decline in the strength after reaction (CSR) of coke caused by the addition of alkali metal strontium carbonate. On the premise of ensuring that the strength of coke is maintained within a reasonable range and remains stable, the reactivity of coke is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a process flow diagram of a method for fixing chlorine in the co-carbonization process of chlorinated waste plastics and coking coal according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] The following further describes the specific embodiments of the present invention with reference to the drawings:

[0027] As Figure 1 shown, for a method for fixing chlorine in the co-carbonization process of chlorinated waste plastics and coking coal according to the present invention, the chlorinated waste plastics, coking coal and alkali metal strontium carbonate are mixed to form blended coal, and the co-carbonization coking is carried out by adopting the process of blending and forming briquettes; the specific steps are as follows:

[0028] (1) Mix the chlorinated waste plastics, coking coal, alkali metal strontium carbonate and binder to form blended coal;

[0029] (2) Cold-press the blended coal obtained in step 1 to obtain briquettes;

[0030] (3) After uniformly mixing the briquettes obtained in step 2 and slack coal in a set ratio, place them in the coking chamber of a coke oven for co-carbonization treatment to obtain high-reactivity coke and low-chlorine coke oven gas.

[0031] In the said step (1), by mass percentage, the addition amount of the binder is 1% - 5% of the blended coal; the addition amount of the alkali metal strontium carbonate is 0.2% - 1% of the total amount of the briquettes and the slack coal, and the addition amount of the chlorinated waste plastics is 1% - 3% of the total amount of the briquettes and the slack coal.

[0032] In the said step (1), the coking coal consists of a blended coking coal composed of gas coal, 1 / 3 coking coal, fat coal, coking coal and lean coal; and by mass percentage, gas coal: 3% - 8%, 1 / 3 coking coal: 10% - 30%, fat coal: 15% - 20%, coking coal: 40% - 50%, lean coal: 10% - 15%; the fineness of the blended coking coal (the percentage of coal with a particle size of 0 - 3mm in the total coal weight) is 75% - 85%.

[0033] In the said step (1), the chlorinated waste plastics are polyvinyl chloride, and the particle size of the polyvinyl chloride is 1 - 3mm.

[0034] In the said step (1), the binder is a coal tar binder and / or an asphalt binder.

[0035] In the said step (1), the moisture content of the blended coal is 9% - 12%.

[0036] In the step (2), the equivalent diameter of the briquettes is 10 - 30 mm.

[0037] In the step (3), the mass percentage of the briquettes in the sum of the briquettes and the slack coal is 20% - 40%.

[0038] In the step (3), the slack coal is a blended coking coal composed of gas coal, 1 / 3 coking coal, fat coal, coking coal and lean coal; and by mass percentage, gas coal: 3% - 8%, 1 / 3 coking coal: 10% - 30%, fat coal: 15% - 20%, coking coal: 40% - 50%, lean coal: 10% - 15%; the fineness after blending the slack coal is 75% - 85%.

[0039] In the step (3), the coke reactivity index (CRI) of the high-reactivity coke is > 34%, and the coke strength after reaction (CSR) is > 41%; the chlorine content in the low-chlorine coke oven gas is < 4%.

[0040] The object of the present invention is to solve the problems in the prior art that during the co-carbonization process of chlorine-containing waste plastics and coking coal, the corrosion of gas purification equipment caused by the transfer of chloride ions generated to the gas, the decline in gas quality affecting subsequent methanol synthesis, and environmental pollution.

[0041] The present invention fixes chlorine to a certain extent in coke by adding alkali metal strontium carbonate to the blended coal, which reacts with the chlorine element in the chlorine-containing waste plastics, significantly reducing the chlorine content in the gas. At the same time, the addition of strontium carbonate also improves the reactivity (CRI) of the coke. However, the addition of strontium carbonate will also affect the strength after reaction (CSR) of the coke. Therefore, the present invention further adopts the briquette coking process to restore and stabilize the strength after reaction of the coke.

[0042] The chlorine fixation method in the co-carbonization process of chlorine-containing waste plastics and coking coal according to the present invention can not only effectively fix the chlorine element in the chlorine-containing waste plastics (such as polyvinyl chloride, PVC) in the coke, but also improve the reactivity of the coke on the premise of ensuring that the coke strength is maintained within a reasonable range. It provides effective technical support for solving the problems of treating chlorine-containing waste plastics and the shortage of coking coal resources, and also provides a certain theoretical support for the low-carbon and high-efficiency production of blast furnaces.

[0043] The contents not specified in the present invention are all mass contents.

[0044] The following examples are implemented on the premise of the technical solution of the present invention, and the detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0045]

Example

[0046] Example 1 and Example 2 adopted the method described in the present invention to achieve chlorine fixation during the co-carbonization process of chlorine-containing waste plastics and coking coal. Comparative Example 1 adopted a conventional method, that is, coking coal and chlorine-containing waste plastics were mixed and co-carbonized; Comparative Example 2 co-carbonized coking coal with chlorine-containing waste plastics and alkali metal strontium carbonate, and did not adopt the process of forming briquettes compared with the method described in the present invention; Comparative Example 3 co-carbonized coking coal with chlorine-containing waste plastics and calcium oxide, and adopted the process of forming briquettes.

[0047] The properties of the coking coal (including briquettes and lump coal) used in each example and comparative example are shown in Table 1. The coal blending scheme, that is, the proportion of each single coal in the coking coal (including briquettes and lump coal), is shown in Table 2, and the particle size distribution of the blended coal is shown in Table 3.

[0048] Table 1 Properties of coking coal

[0049]

[0050] Table 2 Coal blending scheme

[0051]

[0052] Table 3 Particle size distribution of blended coal

[0053]

[0054] The comparison of the coke inspection results of each comparative example and example is shown in Table 4.

[0055] Through the comparison between Example 2 and Comparative Example 3, it can be found that compared with adding calcium oxide, adding strontium carbonate can better reduce the chlorine element content G in the gas cl , the chlorine content G in the gas cl is reduced from 3.593% to 2.716%

[0056] Through the comparison between Comparative Example 2 and Example 1 and Example 2, it can be found that adopting the process of forming briquettes can stabilize the coke reactivity after reaction CSR reduced due to the addition of strontium carbonate, and CSR is increased from 36.33% to 41.37% and 45.47% respectively.

[0057] Through the comparison between Comparative Example 1 and Example 2, it can be seen that adding strontium carbonate and adopting the process of forming briquettes can, on the premise of stabilizing the coke reactivity after reaction CSR, reduce the chlorine content G in the gas cl from 4.611% to 2.716%.

[0058] Table 4 Comparison of coke inspection results between comparative examples and examples

[0059] Example Coal blending plan CRI / % CSR / % <![CDATA[S cl / %]]> <![CDATA[G cl / %]]> <![CDATA[#S cl / %]]> <![CDATA[#G cl / %]]> Comparative example 1 Raw coal + 1% PVC 31.20 47.28 0.180 4.611 22.49 72.02 Comparative example 2 <![CDATA[Raw coal + 1% PVC + 0.2% SrCO3]]> 36.13 36.33 0.221 4.307 27.61 67.26 Comparative example 3 40% briquette + 60% raw coal + 1% PVC + 0.5% CaO 39.16 19.48 0.317 3.593 39.61 56.12 Example 1 <![CDATA[20% briquetted coal + 80% raw coal + 1% PVC + 0.2% SrCO3]]> 34.57 41.37 0.287 3.816 35.86 59.60 Example 2 <![CDATA[40% briquetted coal + 60% raw coal + 1% PVC + 0.5% SrCO3]]> 37.02 45.47 0.435 2.716 54.35 42.42

[0060] In the table: CRI - Coke Reactivity, %; CSR - Strength after Coke Reaction, %; S cl - Mass fraction of chlorine in coke, %; G cl - Mass fraction of chlorine in gas, %;

[0061] #S cl - Percentage of chlorine in coke accounting for the total chlorine in the raw material, %; #G cl - Percentage of chlorine in gas accounting for the total chlorine in the raw material, %.

[0062] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes, shall be covered by the protection scope of the present invention.

Claims

1. A method for fixing chlorine in the process of co-carbonization of chlorine-containing waste plastics and coking coal, characterized in that: Chlorine-containing waste plastics, coking coal and alkali metal strontium carbonate are mixed to make blended coal, and the blended coal process is used for co-carbonization and coking; the specific steps are as follows: (1) mixing chlorine-containing waste plastics, coking coal, alkali metal strontium carbonate and a binder to prepare blended coal; (2) cold pressing the blended coal obtained in step 1 to obtain briquettes; (3) The briquette coal and loose coal obtained in step 2 are uniformly mixed according to a set ratio, and then placed in a coke oven carbonization chamber for co-carbonization treatment to obtain highly reactive coke and low-chlorine coke oven gas.

2. The method for fixing chlorine in the co-carbonization process of chlorine-containing waste plastics and coking coal according to claim 1, characterized in that: In the step (1), the amount of binder added is 1% to 5% of the mixed coal by mass percentage; the amount of alkali metal strontium carbonate added is 0.2% to 1% of the total amount of shaped coal and loose coal; and the amount of chlorine-containing waste plastic added is 1% to 3% of the total amount of shaped coal and loose coal.

3. The method for fixing chlorine in the co-carbonization process of chlorine-containing waste plastics and coking coal according to claim 1, characterized in that: In the step (1), the coking coal is a mixed coking coal consisting of gas coal, 1 / 3 coking coal, fat coal, coking coal and lean coal; and in terms of mass percentage, the gas coal is 3% to 8%, the 1 / 3 coking coal is 10% to 30%, the fat coal is 15% to 20%, the coking coal is 40% to 50%, and the lean coal is 10% to 15%; the fineness of the mixed coking coal is 75% to 85%.

4. The method for fixing chlorine in the co-carbonization process of chlorine-containing waste plastics and coking coal according to claim 1, characterized in that: In the step (1), the chlorine-containing waste plastic is polyvinyl chloride, and the particle size of the polyvinyl chloride is 1 to 3 mm.

5. The method for fixing chlorine in the co-carbonization process of chlorine-containing waste plastics and coking coal according to claim 1, characterized in that: In the step (1), the binder is a coal tar binder and / or an asphalt binder.

6. The method for fixing chlorine in the co-carbonization process of chlorine-containing waste plastics and coking coal according to claim 1, characterized in that: In the step (1), the moisture content of the blended coal is 9% to 12%.

7. The method for fixing chlorine in the co-carbonization process of chlorine-containing waste plastics and coking coal according to claim 1, characterized in that: In the step (2), the equivalent diameter of the coal briquettes is 10 to 30 mm.

8. The method for fixing chlorine in the co-carbonization process of chlorine-containing waste plastics and coking coal according to claim 1, characterized in that: In the step (3), the mass percentage of the shaped coal to the total mass of the shaped coal and the loose coal is 20% to 40%.

9. The method for fixing chlorine in the co-carbonization process of chlorine-containing waste plastics and coking coal according to claim 1, characterized in that: In the step (3), the loose coal is a mixed coking coal consisting of gas coal, 1 / 3 coking coal, fat coal, coking coal and lean coal; and in terms of mass percentage, the gas coal is 3% to 8%, the 1 / 3 coking coal is 10% to 30%, the fat coal is 15% to 20%, the coking coal is 40% to 50%, and the lean coal is 10% to 15%; the fineness of the mixed loose coal is 75% to 85%.

10. The method for fixing chlorine in the co-carbonization process of chlorine-containing waste plastics and coking coal according to claim 1, characterized in that: In the step (3), the coke reactivity CRI of the high-reactivity coke is greater than 34%, and the strength after reaction CSR is greater than 41%; and the chlorine content in the low-chlorine coke oven gas is less than 4%.

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