Method for high-precision and efficient desodium of high-sodium coal

Abstract

A method for accurately and efficiently desodium of high-sodium coal, comprising the following steps: detecting the moisture M of the high-sodium raw coal to be treated t , calculating the total sodium content M of the wet basis coal sample Na , converting the total sodium content M of the dry basis coal sample Na , determining the Na2O content in the ash of the high-sodium raw coal to be treated; selecting the key factors affecting the desodium rate; establishing the relationship model between the key factors and the actual desodium rate; according to the Na2O content in the ash and the requirements of the standard, the desodium rate of the high-sodium raw coal to be treated is converted, and the Re target value is obtained; the Re target value is brought into the relationship model, and the selection and value of the key factors of the high-sodium raw coal to be treated during desodium treatment are obtained respectively, and finally the actual leaching desodium of the high-sodium raw coal to be treated is carried out to obtain low-sodium coal meeting the requirements. The method can accurately desodium, reduce cost, energy consumption and corrosion and pollution generated in the production process, and has important significance for guiding large-scale application of high-sodium coal desodium.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of desodium of high-sodium coal, and particularly relates to a method for precisely and efficiently desodium of high-sodium coal. BACKGROUND

[0002] There are hundreds of billions of tons of coal resources in the eastern part of China, which has the characteristics of excellent environment, rich reserves, thick coal seam and simple mining. Due to its low ash content, low sulfur, low phosphorus, high volatile matter and high calorific value, it is a kind of natural clean coal and is widely used for power coal and coal chemical industry. However, due to the formation history of coal and the specific local natural and geographical environment, the content of Na2O in the ash of the eastern coal is usually more than 4%, and even up to 10% in some mining areas, which is much higher than the national standard of 2% for power coal combustion. Na in coal is usually converted into steam form during coal combustion, which causes problems such as boiler slagging, fouling, ash accumulation and corrosion, seriously affecting the safety of the boiler and the efficiency of coal utilization, and greatly hindering the effective utilization of the eastern coal. The removal of sodium is a necessary condition for the efficient, clean and safe utilization of the eastern coal. So far, acid leaching treatment is still an effective method for removing sodium from coal.

[0003] In practical application, the sodium content in high-sodium coal usually needs to be removed to below the national standard for combustion or utilization, but there is a phenomenon of excessive acid and excessive sodium removal in the acid leaching treatment of high-sodium coal. The addition of excessive acid not only corrodes the equipment and increases the cost, but also seriously pollutes the environment due to excessive acid wastewater. Since the sodium existing on the surface or in the large cracks of coal is easier to remove than the sodium existing in the interior of coal or in the minerals, excessive sodium removal often needs to remove more sodium existing in the interior of coal or on the minerals, which is more difficult to remove, which greatly increases the energy consumption and causes serious waste of resources. In summary, due to the lack of an industrial feasible precise desodium method, the current acid leaching desodium has not been widely used in industry. SUMMARY

[0004] The purpose of the present application is to provide a method for precisely and efficiently desodium of high-sodium coal, which can accurately remove sodium according to the actual utilization standard, reduce the addition amount of desodium reagent, reduce the cost and energy consumption, reduce the corrosion and pollution problems in the production process, and guide the large-scale application of desodium of high-sodium coal.

[0005] To achieve the above purpose, the technical scheme adopted by the present application is as follows: a method for precisely and efficiently desodium of high-sodium coal, comprising the following steps:

[0006] S1: take a small part of high-sodium raw coal to be treated, detect the moisture content of the high-sodium raw coal to be treated as M t , and measure the water-soluble sodium, ammonium acetate-soluble sodium, hydrochloric acid-soluble sodium and insoluble sodium of the wet basis coal sample by using a step-by-step extraction method, respectively as M water , M HCl With M Insoluble , the ammonium acetate soluble sodium and hydrochloric acid soluble sodium are collectively referred to as organic sodium M Organic , the sum of the contents of water-soluble sodium, ammonium acetate-soluble sodium, hydrochloric acid-soluble sodium, and insoluble sodium is referred to as total sodium M Na ; the total sodium content M Na ' of the dry basis coal sample is converted according to the formula M Na ' = M t / (1-M Na ); the Na2O content in the ash of the high-sodium raw coal to be treated is determined by XRF;

[0007] S2: According to the actual sodium removal process, the key factors affecting the sodium removal rate (Re) are selected, Re = sodium removal amount / total sodium content;

[0008] S3: A relationship model between the key factors and the actual sodium removal rate is established, and when the correlation is above 0.95, the established relationship model meets the requirements, otherwise the interval value of the key factor needs to be replaced until the correlation of the established linear model reaches above 0.95;

[0009] S4: According to the Na2O content in the ash obtained in step S1 and the requirements of the standard, the sodium removal rate of the high-sodium raw coal to be treated is converted, and the Re target value is obtained; the Re target value is brought into the relationship model established in step S3 to obtain the selection and value of the key factors when the high-sodium raw coal to be treated is subjected to sodium removal treatment, and the selection and value are adjusted according to the actual situation;

[0010] S5: The relationship model between the key factors and the sodium removal rate established in step S4 is used to guide the actual leaching sodium removal of the high-sodium raw coal;

[0011] In the above steps, the specific process of sodium removal is as follows: the high-sodium coal to be treated is broken into fine particles of a certain size, then the fine particles are mixed with a sodium removal solution to form a coal slurry in a reaction container, and the coal slurry is treated under certain temperature and stirring time to obtain low-sodium coal meeting the use standard.

[0012] Preferably, in step S2, the key factors are sodium removal temperature, sodium removal leaching time, addition amount of sodium removal reagent, and type of sodium removal reagent.

[0013] Further, fixing a certain sodium removal reagent and addition amount and sodium removal leaching time, a relationship model between the sodium removal temperature and the actual sodium removal rate is obtained: Re Na,T = b T +a T *T.

[0014] Further, fixing a certain sodium removal reagent and addition amount and sodium removal temperature, a relationship model between the sodium removal leaching time and the actual sodium removal rate is obtained:

[0015]

[0016] Further, fixing a certain desodium agent, desodium temperature and desodium leaching time, the relationship model between the addition amount of the desodium agent and the actual desodium rate is obtained:

[0017] Re Na,A =b A +a A *A。

[0018] Further, based on the desodium rate Re Na of the wet base coal sample and the moisture detection value M t , the desodium rate Re Na,T ' of the dry base coal sample is converted according to the formula Re Na,T '=Re t / (1-M Na,h )、Re Na,h '=Re t / (1-M Na,A )、Re Na,A '=Re A / (1-M Na )。

[0019] Preferably, the desodium temperature is 20-80℃, and the desodium leaching time is 2min-24h.

[0020] Preferably, the desodium agent is one of hydrochloric acid, acetic acid, citric acid, benzoic acid and ammonium acetate.

[0021] Preferably, the high-sodium coal to be treated is broken into fine particle raw coal with a particle size of 5-2500μm.

[0022] Further, in step S1, the specific steps of the step-by-step extraction method are as follows: 4g of air-dried base coal sample with a particle size of less than 200 mesh is weighed and placed in a container, 100mL of deionized water is added, and constant temperature stirring is carried out at 80℃ and 200r / min for 24h; then the coal slurry is filtered and repeatedly washed, the filtrate is preserved after being preserved by a volumetric flask; 1mol / L ammonium acetate solution and 1mol / L hydrochloric acid solution are used to replace the deionized water in turn, and the above operation is repeated; the sodium content of all filtrates is detected; the last filter cake obtained after filtration is dried in an oven to obtain an air-dried base coal sample, and the sodium content in the coal is measured according to the standard DLT1713-2017; the sum of the measured sodium content in the filtrate and the measured sodium content in the filter cake is the total sodium content in the coal.

[0023] Compared with the prior art, the present application has the following advantages:

[0024] (1) The present application selects the factors related to the sodium leaching and desodium of high-sodium coal, such as desodium temperature, desodium leaching time, and desodium reagent addition amount, establishes the relationship model of desodium rate of high-sodium coal and the three factors, and realizes the precise and efficient leaching desodium of high-sodium coal through the simple condition adjustment of the desodium linear model to achieve the desodium rate target value; the present application can greatly reduce the desodium upgrading cost, realize the dynamic control of desodium cost, and has an important guiding role for large-scale application in factories.

[0025] (2) The present application can determine the relationship between the addition amount of desodium reagent and the sodium content in coal according to the relationship model between the addition amount of desodium reagent and the actual desodium rate, so that the acidic solvent can be accurately added quantitatively, the reagent consumption can be reduced, the cost can be reduced, the added acidic solvent can completely participate in the desodium reaction, and there is almost no H + residue in the solution, which greatly reduces the corrosion of the reaction equipment in the desodium reaction process; at the same time, the wastewater generated in the leaching desodium is still neutral, so the treatment difficulty of the wastewater is reduced.

[0026] (3) The present application standardizes the control of coal moisture: the on-site sampling and moisture analysis are performed on each batch of coal samples, the moisture has a crucial influence on the accuracy of the sodium content in high-sodium coal, and the stable and effective desodium model is ensured through the accurate moisture conversion. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is the relationship model graph between the desodium temperature and the actual desodium rate in the embodiment.

[0028] Figure 2 It is the relationship model graph between the desodium leaching time and the actual desodium rate in the embodiment.

[0029] Figure 3 It is the relationship model graph between the addition amount of desodium reagent and the actual desodium rate in the embodiment.

[0030] Figure 4 It is the relationship model graph between different desodium reagents and the actual desodium rate in the embodiment. DETAILED DESCRIPTION

[0031] The present application will be further described in detail in combination with the drawings and specific embodiments.

[0032] A method for precise and efficient desodium of high-sodium coal, comprising the following steps:

[0033] S1: A small part of the Zhundong high-sodium raw coal to be treated is taken, and the moisture M t of the Zhundong high-sodium raw coal to be treated is detected, which is 10.52%, and the water-soluble sodium M water2148 μg / g, ammonium acetate soluble sodium 1915 μg / g, hydrochloric acid soluble sodium M HCl 39 μg / g, insoluble sodium M Insoluble 26 μg / g, organic sodium content M Organic 1954 μg / g, total sodium content M Na 4128 μg / g, according to the formula M Na = M Na ’ / (1-M t ) to convert the total sodium content M of the dry basis coal sample Na ’ is 4613 μg / g; the Na2O content in the Zhundong high sodium raw coal ash to be treated is 5.6% by XRF;

[0034] S2: According to the actual sodium removal process, the key factors affecting the sodium removal rate (Re) are selected (sodium removal temperature, sodium removal leaching time, sodium removal reagent addition amount, sodium removal reagent type), Re = sodium removal amount / total sodium content;

[0035] S3: Establish a relationship model between the key factors and the actual sodium removal rate, when the correlation is above 0.95, the established relationship model meets the requirements, otherwise the interval value of the key factor needs to be replaced until the correlation of the established linear model reaches above 0.95;

[0036] 1Establish a relationship model between the sodium removal temperature and the actual sodium removal rate

[0037] Take 4g of crushed fine particle raw coal and pour it into a 250ml flask, then add 100ml of deionized water and 0.001mol (0.25mmol / g) of hydrochloric acid solution (calculated by pure HCl) to prepare a coal slurry with a concentration of 40g / L. Put the flask in a constant temperature magnetic stirring pot, set different temperatures of 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃ for leaching treatment under the conditions of stirring speed 200r / min and stirring time 24h. After leaching, solid-liquid separation is carried out, the filter cake is repeatedly washed with deionized water, the mixed leaching liquid and washing liquid are collected, the sodium content of the mixed liquid is measured and the actual sodium removal rate of the coal sample is converted. As shown in Figure 1 , the relationship model between the sodium removal temperature and the actual sodium removal rate is: Re Na,T = 52.9+0.622*T (20≤T≤80), the correlation coefficient is 0.9691>0.95. When T=40℃, the theoretical Re Na,T is 77.78% by the relationship model, and the actual Re Na,T75.80%, and the relative error is only 2.61%. Since the total sodium in the above sodium removal relationship model is based on the wet basis, the relationship model between the sodium removal temperature converted to the dry basis and the actual sodium removal rate is the same as the wet basis, so Re Na,T = 52.9 + 0.622*T (20≤T≤80). When T = 40℃, the theoretical Re Na,T ' obtained by the dry basis relationship model is 77.78%, and the actual Re Na,T ' obtained by the experiment using the dry basis coal sample is 76.12%, the relative error is only 2.18%, and the model meets the requirements. From the above, it can be seen that when the temperature reaches 80℃, the highest sodium removal rate is 99.35%. Figure 1

[0038] 2Establish the relationship model between sodium removal leaching time and actual sodium removal rate

[0039] Take 4g of crushed fine coal and pour it into a 250ml flask, then add 100ml of deionized water and 0.001mol (0.25mmol / g) of hydrochloric acid solution (calculated by pure HCl) to prepare a coal slurry with a concentration of 40g / L. Put the flask in a constant temperature magnetic stirring pot, set different times of 2min-24h under the conditions of stirring speed 200r / min and temperature 80℃, then separate the solid and liquid after leaching, wash the filter cake with deionized water repeatedly, collect the mixed leaching solution and washing solution, measure the sodium content of the mixed solution and convert the actual sodium removal rate of the coal sample. As shown in Figure 2 , the relationship model between sodium removal leaching time and actual sodium removal rate is: The correlation coefficient is 0.9932>0.95. When h = 1h, the theoretical Re Na,h ' obtained by the relationship model is 72.55%, and the actual Re Na,h ' obtained by the experiment is 75.55%, the relative error is only 3.97%, and the model meets the requirements. Since the total sodium in the above sodium removal relationship model is based on the wet basis, the relationship model between the sodium removal leaching time converted to the dry basis and the actual sodium removal rate is the same as the wet basis, so When h = 1h, the theoretical Re Na,h ' obtained by the relationship model is 72.55%, and the actual Re Na,h ' obtained by the experiment using the dry basis coal sample is 75.02%, the relative error is only 3.29%, and the model meets the requirements. From the above, it can be seen that when the temperature reaches 80℃, the highest sodium removal rate is 99.35%. Figure 2

[0040] 3Establish the relationship model between the addition amount of sodium removal reagent and the actual sodium removal rate

[0041] ​​Take 4 g of broken fine coal into a 250 ml flask, add 100 ml of deionized water to make a coal slurry with a concentration of 40 g / L, and place the flask in a constant temperature magnetic stirring pot. Under the conditions of stirring speed 200 r / min, temperature 80℃, and stirring time 24 h, add 0.15 mmol, 0.30 mmol, 0.45 mmol, 0.60 mmol, 0.75 mmol, 0.90 mmol, and 100 mmol of hydrochloric acid solution (calculated as pure HCl) for leaching treatment, respectively. After leaching, perform solid-liquid separation, wash the filter cake with deionized water repeatedly, collect the mixed leaching solution and washing solution, measure the sodium content of the mixed solution, and convert the actual desodium rate of the coal sample. As shown in Figure 3 , the relationship model between the addition amount of desodium reagent and the actual desodium rate is: Re Na,A = 54.4 + 311A (0≤A≤0.15), and the correlation coefficient is 0.9824>0.95. When A=0.075 mmol / g, the theoretical Re Na,A is 77.73%, and the actual Re Na,A is 78.16%, with a relative error of only 0.55%. Since the above desodium relationship model is based on wet basis, the relationship model between the addition amount of desodium reagent and the actual desodium rate based on dry basis is the same as that based on wet basis, so Re Na,A '= 54.4 + 311A (0≤A≤0.15). When A=0.075 mmol / g, the theoretical Re Na,A ' is 77.73%, and the actual Re Na,A ' obtained by experiment using dry coal sample is 78.11%, with a relative error of only 0.49%, meeting the requirements of the model. From Figure 3 , it can be seen that when the addition amount of hydrochloric acid reaches 0.15 mmol / g, it is the best addition amount, and the desodium rate is 98.34%.

[0042] 4. Establishing a relationship model between the type of desodium reagent and the actual desodium rate

[0043] Select hydrochloric acid, acetic acid, citric acid, benzoic acid, and ammonium acetate, respectively, and perform experiments according to the process of establishing the relationship model between the addition amount of desodium reagent and the actual desodium rate (due to the solubility of benzoic acid, its concentration is selected as 0.15 mmol, 0.30 mmol, 0.45 mmol, 0.60 mmol, 0.75 mmol, and 0.90 mmol). From Figure 4 , the relationship models between the different desodium reagents and the actual desodium rate under different addition amounts are Re Na,A,HCl = 54.4 + 311A, Re Na,A,醋酸铵 = 53.2 + 305A, and Re Na,A,乙酸= 55.0 + 216A, Re Na,A,苯甲酸 = 52.9 + 194A, Re Na,A,柠檬酸 = 55.0 + 192A. Thus, a A,HCl > 0.05 mmol / g A,醋酸铵 > 0.05 mmol / g A,乙酸 > 0.05 mmol / g A,苯甲酸 > 0.05 mmol / g A,柠檬酸 , the desodium efficiency of the desodium reagent from high to low is: HC1> ammonium acetate> acetic acid> benzoic acid> citric acid.

[0044] S4: According to the Na2O content in the coal ash obtained in step S1 and the requirement of burning standard Na2O≤2%, the desodium rate of the high-sodium raw coal to be treated is at least 65%, in order to ensure that the requirement can be met, the Re target value is set to 70%; the Re target value is substituted into the relationship model between the desodium temperature and the actual desodium rate, and the desodium theoretical temperature is obtained as 27.49℃, since the temperature is actually difficult to control, 28℃ is actually used, and the actual Re Na,T is 71.44%, at this time Na2O is 1.82%, and Re Na,T / Re 目标 = 1.02>1, so the temperature of 28℃ meets the coal burning requirement; the Re target value is substituted into the relationship model between the desodium leaching time and the actual desodium rate, and the desodium theoretical leaching time is obtained as 0.577h, since the time is actually difficult to control, 0.6h is actually used, and the actual Re Na,h is 73.38%, at this time Na2O is 1.77%, and Re Na,h / Re 目标 = 1.05>1, so the time of 0.6h meets the coal burning requirement; the Re target value is substituted into the relationship model between the addition amount of the desodium reagent and the actual desodium rate, and the addition amount of hydrochloric acid is obtained as 0.05mmol / g, and the actual Re Na,A is 71.58%, at this time Na2O is 1.80%, and Re Na,h / Re 目标 = 1.02>1, so the addition amount of hydrochloric acid of 0.05mmol / g meets the coal burning requirement.

[0045] S5: One of the three groups of key factors and values (① desodium temperature is 28℃, desodium leaching time is 24h, and desodium hydrochloric acid solution addition amount is 0.25mmol / g; ② desodium temperature is 80℃, desodium leaching time is 0.6h, and desodium hydrochloric acid solution addition amount is 0.25mmol / g; ③ desodium temperature is 80℃, desodium leaching time is 24h, and desodium hydrochloric acid solution addition amount is 0.05mmol / g) selected in step S4 is used to guide the actual leaching desodium of the high-sodium raw coal, so as to obtain low-sodium coal meeting the burning standard Na2O≤2%.

[0046] Therefore, if the above-mentioned ③ scheme is selected for industrial production, only 1.83 kg of hydrochloric acid (calculated as pure HCl) is needed to treat 1 t of the high-sodium coal to achieve a coal combustion standard of less than 2%, and the solution after sodium removal is neutral, indicating that the method is completely economically feasible for large-scale industrial production.

Claims

1. A method for high-precision and efficient desodium of high-sodium coal, characterized in that, Includes the following steps: S1: take a small part of the high-sodium raw coal to be treated, and detect the moisture of the high-sodium raw coal to be treated as M t , and use step-by-step extraction method to measure the water-soluble sodium, ammonium acetate-soluble sodium, hydrochloric acid-soluble sodium and insoluble sodium of the wet base coal sample as M water , M HCl and M Insoluble , wherein the ammonium acetate-soluble sodium and the hydrochloric acid-soluble sodium are collectively referred to as organic sodium M Organic , and the sum of the content of the water-soluble sodium, the ammonium acetate-soluble sodium, the hydrochloric acid-soluble sodium and the insoluble sodium is the total sodium M Na ; the total sodium content of the dry base coal sample M Na ' is converted according to the formula M Na ' = M t / (1-M Na ); the Na2O content in the ash of the high-sodium raw coal to be treated is determined by XRF; S2: Select the key factors affecting the sodium removal rate (Re) based on the actual sodium removal process. Re = Sodium removal amount / Total sodium content; S3: Establish a relationship model between the key factors and the actual sodium removal rate. The established relationship model is considered acceptable only when the correlation reaches 0.95 or higher. Otherwise, the interval values ​​of the key factors need to be changed until the correlation of the established model reaches 0.95 or higher. S4: Based on the Na2O content in the coal ash obtained in step S1 and the requirements of the standard, calculate the sodium removal rate of the high-sodium raw coal to be treated and obtain the Re target value; substitute the Re target value into the relational model established in step S3 to obtain the selection and value of key factors when the high-sodium raw coal to be treated is subjected to sodium removal treatment, and adjust them according to the actual situation. S5: The relationship model between key factors and sodium removal rate established in step S4 guides the actual leaching and sodium removal of high-sodium raw coal. In the above steps, the specific process of sodium removal is as follows: the high-sodium coal to be treated is crushed and ground into fine-grained raw coal of a certain size, and then the fine-grained raw coal and sodium removal solution are put into a reaction vessel to prepare coal slurry. After being treated under reaction conditions of a certain temperature and stirring time, low-sodium coal that meets the usage standards is obtained.

2. The method for high sodium coal accurate and efficient desodium according to claim 1, characterized in that, In step S2, the key factors are the desodiuming temperature, the desodiuming leaching time, the amount of desodiuming agent added, and the type of desodiuming agent.

3. The method for high sodium coal accurate and efficient desodium according to claim 2, characterized in that, Fixing a certain desodium agent and adding amount and desodium leaching time, the relationship model between desodium temperature and actual desodium rate is obtained: Re Na,T = b T + a T *T.

4. The method for high sodium coal accurate and efficient desodium according to claim 2, characterized in that, By fixing a specific sodium removal agent and its dosage, as well as the sodium removal temperature, a model relating sodium removal leaching time to the actual sodium removal rate is obtained:

5. The method for high sodium coal accurate and efficient desodium according to claim 2, characterized in that, By fixing a specific desodiumning agent, desodiumning temperature, and desodiumning leaching time, a model relating the amount of desodiumning agent added to the actual desodiumning rate is obtained: Re Na,A = b A + a A * A.

6. The method for high sodium coal accurate and efficient desodium according to claim 3 or 4 or 5, characterized in that, Based on the sodium removal rate Re of the wet coal sample Na and the moisture detection value M t , according to the formula Re Na,T ' = Re Na,T / (1-M t ), Re Na,h ' = Re Na,h / (1-M t ), Re Na,A ' = Re Na,A / (1-M A ), the sodium removal rate Re Na ' of the dry coal sample is converted.

7. The method for high sodium coal accurate and efficient desodium according to claim 2, characterized in that, The sodium removal temperature is 20-80℃, and the sodium removal leaching time is 2min-24h.

8. The method for high sodium coal accurate and efficient desodium according to claim 2, characterized in that, The sodium removal agent is one of the following: hydrochloric acid, acetic acid, citric acid, benzoic acid, or ammonium acetate.

9. The method for high sodium coal accurate and efficient desodium according to claim 1, characterized in that, The high-sodium coal to be processed is crushed and ground into fine-grained raw coal with a particle size of 5–2500 μm.

10. The method for high sodium coal accurate and efficient desodium according to claim 1, characterized in that, In step S1, the specific steps of the stepwise extraction method are as follows: Weigh 4g of air-dried coal sample (less than 200 mesh) and place it in a container. Add 100mL of deionized water and stir at 80℃ and 200r / min for 24h. Then filter and wash the coal slurry repeatedly. Dilute the filtrate to volume in a volumetric flask and store it. Repeat the above operation by replacing the deionized water with 1mol / L ammonium acetate solution and 1mol / L hydrochloric acid solution, and store the filtrate. Detect the sodium content of all filtrates. After filtration, dry the filter cake in an oven to obtain an air-dried coal sample. Measure the sodium content of the coal according to standard DLT1713-2017. The sum of the sodium content measured in the filtrate and the sodium content measured in the filter cake is the total sodium content of the coal.

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