A method for preparing desulfurization and denitrification activated carbon using coking wastewater concentrated brine

Abstract

A method for preparing desulfurization and denitrification activated carbon using coking wastewater concentrated brine belongs to the field of activated carbon preparation and application technology, and can solve the problems of high cost, low performance and difficulty in treating coking wastewater concentrated brine in the prior art. The specific steps are: S1, sampling the coking wastewater concentrated brine and determining the Na + , Ca 2+ , Cl ‑ 、SO4 2‑ concentration; S2, crushing the raw coal for preparing activated carbon to more than 160 mesh; S3, mixing the coking wastewater concentrated brine with the raw coal in a certain proportion, wherein the addition ratio of the coking wastewater concentrated brine should not exceed 10% of the coal sample; S4, adding a binder to the mixed sample and then preparing the desulfurization and denitrification activated carbon through hot pressing, carbonization, and CO2 / steam activation. The present invention uses the coking wastewater concentrated brine to enhance the desulfurization and denitrification activity of activated carbon, which is conducive to promoting "reduction, recycling, and reuse" within the coking industry.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation and application of activated carbon, and specifically relates to a method for preparing desulfurization and denitrification activated carbon by utilizing coking wastewater concentrated brine. Background Art

[0002] Nitrogen oxides (NO x ) and sulfur oxides (SO x ) will cause acid rain, ozone layer depletion and other ecological and environmental problems. At the same time, my country has introduced strict ultra-low emission standards (NO x <50 mg•Nm -3 ;SO x <35 mg•Nm -3 ). However, due to the low temperature (<180℃) and complex flue gas composition of coke oven flue gas, the mature flue gas desulfurization and denitrification technology of thermal power plants cannot be extended to the coking industry. The integrated desulfurization and denitrification technology of activated carbon has been successfully applied to the field of low-temperature flue gas treatment such as coke ovens because of its advantages such as being able to remove multiple pollutants at the same time, basically no water consumption, and no secondary pollution. However, the relatively high cost and low performance of activated carbon have hindered its further promotion and application.

[0003] At the same time, a large amount of coking wastewater and concentrated brine will be discharged during the coking production process. The proposal and implementation of "zero discharge" of coking wastewater has increased the operating costs of coking plants. The traditional wet quenching process can absorb part of the coking wastewater and concentrated brine, but it will lead to problems such as reduced coke strength; and with the promotion of dry quenching technology, the coking wastewater and concentrated brine are more often treated by first concentrating and then crystallizing. This method has problems such as high equipment loss rate, high operating cost, and low resource recovery rate. Patent ZL200610056702.7 discloses a method of impregnating Na + The impregnated activated carbon is prepared by plasma method and used for purification of SO2 and NO2. Patent CN115171798A discloses that Na in coal can promote the desulfurization and / or denitrification activity of activated carbon. Coking wastewater brine contains a large amount of Na + Therefore, using coking wastewater concentrated brine to prepare activated carbon will inevitably optimize the physical and chemical structure of activated carbon and enhance the desulfurization and denitrification activity, thereby reducing the production cost of activated carbon. Summary of the invention

[0004] The above-mentioned activated carbon has the problems of high cost, low performance and great difficulty in treating the concentrated brine of coking wastewater. The present invention proposes a method for preparing desulfurization and denitrification activated carbon using concentrated brine of coking wastewater. The method has the advantages of simple steps, easy operation, and easy promotion and implementation in the coking industry, and is conducive to achieving "reduction, recycling and reuse" within the coking industry.

[0005] The present invention adopts the following technical solution:

[0006] A method for preparing desulfurization and denitrification activated carbon using coking wastewater concentrated brine, comprising the following steps:

[0007] S1, sample the concentrated brine of coking wastewater and determine the Na + , Ca 2+ , Cl - 、SO4 2- concentration;

[0008] S2, crushing the raw coal for preparing activated carbon to above 160 mesh;

[0009] S3, mixing the coking wastewater concentrated brine with the raw coal in proportion to obtain a mixed sample;

[0010] S4, adding a binder to the mixed sample, and then preparing activated carbon through hot pressing, carbonization, and CO2 / steam activation.

[0011] Furthermore, in step S2, at least three groups of coal samples are taken for preparing activated carbon.

[0012] Furthermore, in step S3, Na + The concentration is generally between 4 and 20 g / L, while Na + Excessive addition will lead to over-activation, causing the activated carbon pore structure to collapse and the adsorption performance to decrease. Therefore, the addition ratio of coking wastewater concentrated brine should not exceed 10% of the raw coal mass.

[0013] Furthermore, in step S4, the binder includes coal tar and / or asphalt, wherein the mass ratio of the mixed sample to the binder is 70~80:20~30; the hot pressing molding conditions are: pressure 25~35 MPa, temperature 75°C; carbonization temperature 450~750°C, carbonization time 40~100 min; activation temperature 800~950°C, activation time 20~60 min.

[0014] The beneficial effects of the present invention are as follows:

[0015] The present invention proposes a method for preparing desulfurization and denitrification activated carbon by using coking wastewater concentrated brine, and the preparation method has the advantages of simple steps, easy operation, and easy promotion in the coking industry. The present invention uses coking wastewater concentrated brine to enhance the desulfurization and denitrification activity of activated carbon. The present invention not only realizes the "resource" utilization of coking wastewater concentrated brine, but also reduces the preparation cost of activated carbon, and has a significant promoting effect on the clean production and sustainable development of the coking industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1This is the trend chart of denitrification rate of AC-40-xCW at 120℃;

[0017] Figure 2 This is the sulfur capacity variation trend of AC-20-xCW at 120°C. DETAILED DESCRIPTION

[0018] A method for preparing desulfurization and denitrification activated carbon using coking wastewater concentrated brine, comprising the following steps:

[0019] S1, sample the concentrated brine of coking wastewater and determine the Na + , Ca 2+ , Cl - 、SO4 2- concentration;

[0020] S2, crushing the raw coal for preparing activated carbon to above 160 mesh;

[0021] S3, mixing the coking wastewater concentrated brine with the raw coal in proportion to obtain a mixed sample;

[0022] S4, adding a binder to the mixed sample, and then preparing activated carbon through hot pressing, carbonization, and CO2 / steam activation.

[0023] Example 1

[0024] The present invention provides a method for preparing desulfurization and denitrification activated carbon by using coking wastewater concentrated brine, which specifically comprises the following steps:

[0025] 1. The coking wastewater concentrated brine is evenly mixed with coal;

[0026] 5wt.% of coking wastewater brine was added to the sub-bituminous coal from Fugu, Shaanxi. The main ion concentrations of the coking wastewater brine are shown in Table 1:

[0027] Table 1 Main ion concentrations in coking wastewater brine

[0028]

[0029] 2. Preparation of activated carbon;

[0030] The preparation method of the activated carbon is as follows: adding 23wt.% of a binder (a mixture of coal tar and asphalt, with the mass ratio of the two being 3:2) to the above-mentioned mixed sample and mixing them evenly, and hot pressing (constant temperature and pressure at 75°C and 25MPa for 5 minutes); carbonizing at 600°C for 1 hour to obtain a precursor; crushing the precursor to 20-40 meshes, taking 10g and activating it in a water vapor (water inlet: 0.06 mL / min•g, 900°C) atmosphere for 40 minutes to prepare desulfurization and denitrification activated carbon, named AC-b-xCW, wherein b is the activation time, and x is the addition ratio of concentrated brine of coking wastewater.

[0031] 3. Performance testing.

[0032] The denitrification performance of the prepared activated carbon was obtained by simulating the composition of coke oven flue gas. The simulated flue gas composition is: 5Vol.% O2, 450 ppm NO, 450 ppm NH3, N2 as the balance gas, the total gas flow rate is 100 mL / min, and the space velocity is 4000h -1 , the temperature is 120℃. The calculation formula of denitrification rate (Re) is as follows:

[0033] , where C in , C out are the inlet and outlet concentrations of NO, respectively.

[0034] Table 2 Changes in denitrification rate of AC-40-xCW

[0035]

[0036] Example 2

[0037] The preparation method of this activated carbon is basically the same as that of Implementation Case 1, except that: the addition ratio of coking wastewater brine in the mixed sample is 8 wt.%; the mass of the precursor during the activation process is 7g; the activation time is 20 min. The activated carbons prepared with / without the addition of coking wastewater brine were named AC-20-8CW and AC-20-0CW, respectively. Desulfurization tests were carried out under simulated flue gas atmosphere: 6 Vol.% O2, 10 Vol.% water vapor, 1400 ppm SO2, N2 as the balance gas, the total gas flow rate was 200mL / min, and the space velocity was 6000 h -1 , the temperature is 120℃. The saturated sulfur capacity (S) of activated carbon can be calculated by the following formula:

[0038] , where F is the total flow rate of simulated flue gas (mL / min); M is the mass of activated carbon (g); t q is the stoichiometric time of adsorption, which is 60 min in this experiment; Cin , C out are the inlet and outlet concentrations of SO2, respectively.

[0039] Table 3 Sulfur capacity change of AC-20-xCW

[0040]

[0041] Two examples are used in this paper to illustrate the principle and implementation of the present invention. The above examples are only used to help understand the core method and core idea of ​​the present invention. The above is a preferred implementation of the present invention. It should be pointed out that for those skilled in the art, the present invention can have various changes and variations.

[0042] Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention, or direct application of the concept and technical solution of the invention to other occasions without improvement, shall be deemed to be within the protection scope of the present invention.

Claims

1. A method for preparing desulfurization and denitrification activated carbon using coking wastewater concentrated brine, characterized in that: The steps include: Step a, pre-treating the coking wastewater brine and determining the ion content: + , Ca 2+ , Cl - 、SO4 2- The coking wastewater brine with Na ions was mixed with raw coal with a particle size of 160 mesh or more to obtain a mixed sample, wherein the addition ratio of the coking wastewater brine did not exceed 10% of the mass of the raw coal, and the Na + Concentration is 4-20 g / L; Step b, mixing the mixed sample with a binder in a mass ratio of 77:23, wherein the binder is a mixture of coal tar and asphalt in a mass ratio of 3:2, and hot pressing at a pressure of 25-35 MPa and a temperature of 75° C. for 5 minutes; Step c, carbonizing the hot pressed coal sample at a temperature of 450-750° C. for 40-100 minutes; Step d: The carbonized sample is crushed into 20-40 meshes, and activated with CO2 or water vapor at a temperature of 800-950°C for 20-60 minutes to obtain desulfurization and denitrification activated carbon.

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