Auxiliary cementitious material based on coal gasification fine ash and preparation method thereof

Abstract

The present invention discloses an auxiliary cementitious material based on coal gasification fine ash and a preparation method thereof. The preparation method of the auxiliary cementitious material based on coal gasification fine ash of the present invention comprises the following steps: 1) crushing and grading wet screening of blocky gasification fine ash to obtain high-carbon components and low-carbon components of gasification fine ash respectively; 2) making the high-carbon components of gasification fine ash into slurry, and then using a spiral gravity separator or a hydrocyclone separator to gravity grade and separate carbon and ash, and then mixing the ash with the low-carbon components of gasification fine ash and filtering to obtain mixed ash of gasification fine ash; 3) placing the mixed ash of gasification fine ash in an air atmosphere for microwave treatment, and then air cooling. The present invention prepares coal gasification fine ash into an auxiliary cementitious material, which has a simple preparation process, low energy consumption requirements, short time requirements, and high carbon removal and activation efficiency. It is suitable for large-scale promotion and application, and helps to realize large-scale resource utilization of coal gasification fine ash.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial solid waste resource utilization, and in particular to an auxiliary cementitious material based on coal gasification fine ash and a preparation method thereof. Background Art

[0002] Coal gasification fine ash is a solid waste generated during the gasification process, primarily composed of incompletely reacted residual carbon and inorganic minerals. Coal gasification is a technology that converts coal or other solid fuels into combustible gases, offering the advantages of high efficiency, cleanliness, and safety. Currently, emerging coal chemical industries, such as coal-to-liquids, coal-to-gas, and coal-to-ethylene glycol, centered around suspended fluidized beds, have been widely developed and applied in many areas rich in coal, poor in oil, and short of gas. However, with the expansion of coal gasification, the amount of fine ash generated has also increased year by year. Due to its ineffective utilization, fine ash accumulates in large quantities, occupying significant land resources while also polluting water resources and wasting energy and mineral resources.

[0003] Currently, the utilization of coal gasification fine ash is mainly concentrated in building materials, ecological restoration, residual carbon utilization, and the preparation of high-value composite materials. However, in general, the consumption and utilization of coal gasification fine ash by existing utilization methods are still relatively low, and they cannot fundamentally solve the problem of coal gasification fine ash treatment and disposal. The building materials industry is able to utilize solid waste on a large scale. Past examples have shown that solid wastes such as slag powder, fly ash, and desulfurized gypsum can be used in cement binders or cement active admixtures to improve the strength and durability of cement. However, because coal gasification fine ash contains a high level of residual carbon, its loss on ignition is far higher than the requirements of the usage standards, so it needs to be decarbonized first. Traditional decarbonization methods include gravity separation, reagent flotation, magnetic separation, hydrothermal decarbonization and direct calcination. Gravity separation has requirements for particle size, while reagent flotation and magnetic separation are liquid environments, and the carbon content of the treated gasified fine ash still does not meet the standards for use in the building materials industry. Hydrothermal decarbonization and direct calcination are more sufficient decarbonization, but the required reaction environment is more extreme. The former requires a high temperature and high pressure reaction environment, while the latter requires a high temperature reaction environment, and the decarbonization cost is higher.

[0004] In summary, how to truly realize large-scale resource utilization of coal gasification fine ash is still a major problem. Summary of the Invention

[0005] The object of the present invention is to provide an auxiliary cementitious material based on coal gasification fine ash and a preparation method thereof.

[0006] The technical solution adopted by the present invention is:

[0007] A method for preparing an auxiliary cementitious material based on coal gasification fine ash comprises the following steps:

[0008] 1) Crushing the blocky gasification fine ash discharged from coal chemical enterprises into granules in a filter press state, and then subjecting it to graded wet screening to obtain high carbon components and low carbon components of the gasification fine ash;

[0009] 2) The high carbon component of the gasified fine ash is made into a slurry, and then the carbon and ash are separated by gravity classification using a spiral gravity separator or a hydrocyclone separator. The ash is then mixed with the low carbon component of the gasified fine ash and filtered to obtain mixed gasified fine ash;

[0010] 3) The gasified fine ash mixed ash is placed in an air atmosphere for microwave treatment, and then air-cooled to obtain an auxiliary cementitious material based on the coal gasification fine ash.

[0011] Preferably, the blocky gasification fine ash in step 1) further comprises the following components in mass percentages, excluding carbon (excluding carbon), on a dry basis:

[0012] SiO2: 20% to 40%;

[0013] Al2O3: 10%~25%;

[0014] CaO: 10% to 15%;

[0015] Fe2O3: 8%~30%;

[0016] Na2O: 1% to 5%;

[0017] K2O: 0.5%~3%;

[0018] MgO: 0.2%~1.5%;

[0019] SO3: 1%~5%;

[0020] Other components: 0.1%~3.5%.

[0021] Preferably, the water content of the blocky gasification fine ash in step 1) is greater than 30%, the carbon content is 20% to 60%, and the specific surface area is 20m 2 / g~80m 2 / g. Note: Moisture content (%) = (M0-M1) / M1×100%, where M0 is the mass of lump gasification fine ash, and M1 is the mass of lump gasification fine ash after complete drying; Carbon content (%) = (m0-m1) / m0×100%, where m0 is the mass of lump gasification fine ash after complete drying, and m1 is the mass of lump gasification fine ash after complete drying and sufficient calcination.

[0022] Preferably, the specific operation of the graded wet screening in step 1) is: first pass through a 35-mesh sieve to remove impurities in the gasified fine ash, then pass through a 60-mesh sieve and crush the remaining portion, then pass through a 150-mesh sieve, the remaining portion is the high-carbon component of the gasified fine ash (particle size ≥ 0.1 mm), and screen out some low-carbon components of the gasified fine ash (particle size < 0.1 mm).

[0023] Preferably, the mass percentage concentration of the slurry in step 2) is 10% to 30%.

[0024] Preferably, the microwave treatment in step 3) is carried out under the conditions of a microwave output power of 800W to 1500W and a temperature of 550°C to 575°C, and the microwave treatment time is 30min to 80min. The microwave frequency commonly used in industry is fixed at 2450MHz. The industrial microwave output power required for gasification fine ash to reach the activation temperature is generally greater than 800W to ensure that the absorbing substances such as C and Fe contained in the gasification fine ash can raise the material temperature and maintain it at 550℃~575℃; when the temperature is lower than 550℃, the residual carbon attached to the gasification fine ash particles is difficult to fully remove because the ash-inactivation temperature point cannot be reached; when the temperature is higher than 600℃, since the microwave field can reduce the activation energy for mineral phase transformation, the active substances in the gasification fine ash undergo mineral phase transformation prematurely at this temperature, forming crystalline substances and losing some activity; therefore, based on energy consumption and activity, the temperature needs to be set in the range of 550℃~575℃ (after reaching the set temperature, the microwave source will reduce the power or temporarily shut down to control the temperature, which can ensure efficient heat treatment of gasification fine ash while significantly saving energy).

[0025] Preferably, the specific operation of the microwave treatment in step 3) is: putting the gasified fine ash and mixed ash into a container made of absorbing material and then placing it into a microwave push plate kiln for microwave activation.

[0026] Preferably, the absorbing material is one or more of silicon carbide, manganese dioxide, and ferrosoferric oxide.

[0027] Preferably, the specific operation of the air cooling in step 3) is: sending the gasified fine ash mixed ash after microwave treatment into the cooling chamber, blowing compressed air into the cooling chamber in parallel from one side of the cooling chamber, so that the gasified fine ash mixed ash is blown into the ash collecting net on the other side and falls into the ash collecting trough, and then collecting the fine ash in the ash collecting trough.

[0028] An auxiliary cementitious material based on coal gasification fine ash is prepared by the above preparation method.

[0029] A building material comprising the above-mentioned auxiliary cementitious material based on coal gasification fine ash.

[0030] The beneficial effects of the present invention are: the present invention prepares coal gasification fine ash into auxiliary cementitious material, the preparation process is simple, the energy consumption requirement is low, the time requirement is short, the carbon removal and activation efficiency is high, it is suitable for large-scale promotion and application, and helps to realize the large-scale resource utilization of coal gasification fine ash.

[0031] Specifically:

[0032] 1) The present invention fully utilizes the particle size distribution and composition characteristics of coal gasification fine ash, achieving the enrichment of active mineral components in the coal gasification fine ash through graded wet screening and spiral gravity or hydraulic classification (the spiral gravity separator and hydrocyclone separator can grade and separate the carbon and ash components in the coal gasification fine ash based on their different densities). Furthermore, based on the high humidity, high carbon content, and relatively high iron content of the coal gasification fine ash (which has the potential to serve as a good microwave absorbing medium), and utilizing the efficient heating and temperature rise of microwaves and the dual activation characteristics of the particles themselves, the present invention achieves energy-saving and efficient use of coal gasification fine ash to prepare auxiliary cementitious materials for building materials.

[0033] 2) The blocky gasification fine ash in the filter-pressed state discharged by coal chemical enterprises contains a considerable amount of unburned residual carbon and iron-containing mineral phases, and contains a large amount of water. All three have large electrolyte losses, which determines that the coal gasification fine ash is a good microwave-absorbing medium material: the porous nature of the carbon component allows electromagnetic waves to be continuously scattered and emitted inside it, and the conductive iron will produce eddy currents under the microwave field, and the slightly magnetic iron-containing minerals in the coal gasification fine ash can also produce hysteresis loss and magnetic absorption. In addition, polar water molecules will undergo orientation polarization and electronic polarization under the action of the electric field. Based on their different dielectric loss mechanisms, the three components will undergo significant microwave energy loss under the microwave field, and microwave radiation will directly penetrate The diffused deposit covers the coal gasification fine ash particles, and the absorbing medium component converts microwave energy into thermal energy, performing uniform body heating from the inside out. Under the condition that the iron-containing mineral component acts as a catalyst, rapid dehydration and carbon removal (carbon ash separation and water evaporation) can be achieved. At the same time, the residual carbon releases heat and the iron-containing mineral is used as a heat source to thermally activate the active aluminosilicate minerals. The resulting activated coal gasification fine ash material has uniform quality (the traditional thermal calcination method requires the heating tube to continuously emit heat, evaporate water and transfer it step by step from the outside to the inside of the coal gasification fine ash. Due to the large specific heat capacity of water and the heat dissipation during the transfer process, this heating method results in extremely energy-consuming thermal calcination, low overall efficiency, and difficult to adopt and apply).

[0034] 3) The present invention activates coal gasification fine ash through microwaves. Under the action of microwaves, the carbon and iron elements in the coal gasification fine ash are rapidly heated by absorbing microwaves. On the one hand, the carbon source with a large specific surface area receives a large amount of microwave radiation energy per unit area, continuously providing an additional heat source during the ashing process. On the other hand, the iron-containing minerals inside the coal gasification fine ash particles serve as the inner core for heating. Under the dual internal and external thermal effects, the coal gasification fine ash particles themselves are rapidly heated to a suitable activation temperature (it can be seen from the implementation results of the embodiment and the comparative example that, without considering the water content in the coal gasification fine ash, the processing speed of the coal gasification fine ash treated with microwaves is 4 to 6 times faster than that of the same amount of coal gasification fine ash calcined in a traditional calcining furnace, and the required activation temperature is reduced from 650°C to 550°C, fully reflecting the characteristics of high efficiency and energy saving. This efficiency difference will be more obvious when there is water in the coal gasification fine ash).

[0035] 4) The present invention uses air cooling after microwave treatment of the gasified fine ash to achieve rapid cooling, which helps the amorphous or glassy aluminosilicate minerals in the gasified fine ash to convert unreleased thermal energy into chemical energy for storage, thereby increasing potential chemical activity and ensuring that the prepared active gasified fine ash has relatively high stability and reliability.

[0036] 5) The present invention processes the high-humidity and high-carbon typical difficult-to-treat solid waste coal gasification fine ash into an auxiliary cementitious material for building materials with reliable quality and stable performance. It can not only replace cement with high energy consumption characteristics, but also can be used to prepare new green building materials, greatly reducing carbon emissions and improving carbon neutrality capabilities. DETAILED DESCRIPTION

[0037] The present invention will be further explained and illustrated below with reference to specific embodiments.

[0038] Example 1:

[0039] An auxiliary cementitious material based on coal gasification fine ash, the preparation method of which comprises the following steps:

[0040] 1) The water content of coal chemical enterprises is 65%, the carbon content is 38.4%, and the specific surface area is 44.8m 2 / g of lump gasification fine ash in a filter press state (containing the following components by mass in addition to carbon on a dry basis: SiO2: 38.03%; Al2O3: 24.07%; CaO: 14.11%; Fe2O3: 12.70%; Na2O: 1.40%; K2O: 3.09%; MgO: 0.86%; SO3: 2.37%; other components: 3.37%) is added to a crusher and crushed into particles, then passed through a 35-mesh sieve to remove impurities in the gasification fine ash, then passed through a 60-mesh sieve and the remaining portion is crushed again, then passed through a 150-mesh sieve, the remaining portion being the high-carbon component of the gasification fine ash (particle size ≥ 0.1 mm), and a portion of the low-carbon component of the gasification fine ash (particle size < 0.1 mm) is sieved out;

[0041] 2) The high-carbon component of the gasified fine ash is made into a slurry with a mass percentage concentration of 18%, and then gravity-classified using a spiral gravity separator to separate the carbon component (low density) and the ash component (high density). The ash component is then mixed with the low-carbon component of the gasified fine ash and filtered until no water is exuded, thereby obtaining a gasified fine ash mixed ash;

[0042] 3) The gasified fine ash mixed ash is placed into a bowl-shaped container made of silicon carbide and then sent into a microwave push plate kiln, and then subjected to microwave treatment in an air atmosphere. The microwave parameters are set as follows: output power is 1000W, treatment time is 20 minutes to reach a set temperature of 550°C to 575°C, and then the temperature is kept at the set temperature for 10 minutes. The material is then sent into a cooling chamber equipped with an ash collection net and an ash collection trough for rapid air cooling to room temperature + 50°C, thereby obtaining an auxiliary cementitious material based on coal gasification fine ash.

[0043] Example 2:

[0044] An auxiliary cementitious material based on coal gasification fine ash is prepared in the same manner as in Example 1 except for different microwave treatment parameters (microwave parameters are set as follows: output power of 1000 W, treatment for 20 minutes to reach a set temperature of 550° C. to 575° C., and then keeping the temperature at the set temperature for 15 minutes).

[0045] Example 3:

[0046] An auxiliary cementitious material based on coal gasification fine ash is prepared in the same manner as in Example 1 except for different microwave treatment parameters (microwave parameters are set as follows: output power of 1000 W, treatment for 20 minutes to reach a set temperature of 550° C. to 575° C., and then keeping the temperature at the set temperature for 20 minutes).

[0047] Example 4:

[0048] An auxiliary cementitious material based on coal gasification fine ash is prepared in the same manner as in Example 1 except for different microwave treatment parameters (microwave parameters are set as follows: output power of 1000 W, treatment for 20 minutes to reach a set temperature of 550° C. to 575° C., and then keeping the temperature at the set temperature for 30 minutes).

[0049] Example 5:

[0050] An auxiliary cementitious material based on coal gasification fine ash is prepared in the same manner as in Example 1 except for different microwave treatment parameters (microwave parameters are set as follows: output power of 1000 W, treatment for 20 minutes to reach a set temperature of 550° C. to 575° C., and then keeping the temperature at the set temperature for 40 minutes).

[0051] Example 6:

[0052] An auxiliary cementitious material based on coal gasification fine ash is prepared in the same manner as in Example 1 except for different microwave treatment parameters (microwave parameters are set as follows: output power of 1000 W, treatment for 20 minutes to reach a set temperature of 550° C. to 575° C., and then keeping the temperature at the set temperature for 50 minutes).

[0053] Comparative Example:

[0054] An auxiliary cementitious material based on coal gasification fine ash is prepared in the same manner as in Example 1, except that microwave treatment is replaced by calcination in a calcination furnace (the calcination furnace parameters are set as follows: heating from room temperature to a set temperature of 650°C±25°C in 50 minutes, and then continuing calcination at the set temperature for 60 minutes).

[0055] Performance testing:

[0056] 1) The carbon removal rate test results in Examples 1 to 6 and the comparative example are shown in the following table:

[0057] Table 1 Carbon removal rate test results in Examples 1 to 6 and Comparative Examples

[0058]

[0059] Note:

[0060] Since a calciner is used in the comparative example, the presence of moisture in the coal gasification fine ash will cause greater disturbance to the calciner. In order to facilitate intuitive comparison, the mixed ash of gasification fine ash in the above embodiment and comparative example was dried and dehydrated before being sent to the microwave push plate kiln or calciner.

[0061] As shown in Table 1, compared with calcination in a traditional calcining furnace, the total time required to achieve a similar carbon removal rate is greatly shortened and the activation efficiency is much higher.

[0062] 2) The energy consumption of industrial microwave ovens (microwave push plate kilns) and industrial calciners with the same rated power for treating dry coal gasification fine ash is shown in the following table:

[0063] Table 2 Energy consumption

[0064]

[0065] Note: The actual working time of industrial microwave ovens and industrial calciners in the insulation stage accounts for 45.55% and 80.65% of the total working time.

[0066] As shown in Table 2, the energy consumption required by the industrial microwave oven (microwave push plate kiln) to achieve the same carbon removal rate in the present invention is only about 1 / 14 of that in the industrial calcining furnace, which greatly reduces energy consumption.

[0067] 3) Modified coal gasification fine ash with a carbon content of less than 5% produced using an industrial microwave oven (microwave push plate kiln) and an industrial calcining furnace was used as a mineral admixture for cement building materials. The activity index of the modified coal gasification fine ash was tested according to the activity index determination method in "GB / T 1596-2017 Fly ash for cement and concrete". The test results are shown in the following table:

[0068] Table 3 Activity index test results of modified coal gasification fine ash

[0069]

[0070] It can be seen from Table 3 that the activity index of the modified coal gasification fine ash is significantly improved compared with the original coal gasification fine ash, especially the 28-day activity index.

[0071] In summary, the present invention fully utilizes the advantages of residual carbon and iron-containing minerals contained in coal gasification fine ash with a certain water content, and uses them as the main absorbing medium material to carry out activation and modification treatment of coal gasification fine ash under a microwave thermal field. By removing the residual carbon by ash removal, the influence of the residual carbon on the water content in cement and other cementitious materials is greatly reduced, thereby improving the reaction activity, and preparing auxiliary cementitious materials. Microwave heating also enhances the activity or content of amorphous silicate minerals inside it through thermal energy, further promoting the increase in activity.

[0072] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing an auxiliary cementitious material based on coal gasification fine ash, characterized in that: The following steps are involved: 1) Crushing the lumpy gasification fine ash discharged from coal chemical enterprises into granules in a filter press state, and then wet screening the granules to obtain high carbon components and low carbon components of the gasification fine ash; 2) The high carbon component of the gasified fine ash is made into a slurry, and then the carbon and ash are separated by gravity classification using a spiral gravity separator or a hydrocyclone separator. The ash is then mixed with the low carbon component of the gasified fine ash and filtered to obtain gasified fine ash mixed ash; 3) placing the gasified fine ash mixed ash in an air atmosphere for microwave treatment, and then air cooling to obtain an auxiliary cementitious material based on the coal gasification fine ash; Step 1) The water content of the blocky gasification fine ash is greater than 30%, the carbon content is 20% to 60%, and the specific surface area is 20m 2 / g~80m 2 / g; The specific operation of the graded wet screening in step 1) is as follows: first, the gasified fine ash is passed through a 35-mesh sieve to remove impurities, then passed through a 60-mesh sieve and the remaining portion is crushed again, and then passed through a 150-mesh sieve. The remaining portion is the high-carbon component of the gasified fine ash, and the sieved portion is the low-carbon component of the gasified fine ash; Step 3) The microwave treatment is carried out under the conditions of a microwave output power of 800W to 1500W and a temperature of 550°C to 575°C, and the microwave treatment time is 30min to 80min.

2. The preparation method according to claim 1, wherein: In step 1), the blocky gasification fine ash contains the following components by mass percentage in addition to carbon on a dry basis: SiO2: 20%~40%; Al2O3: 10%~25%; CaO: 10% to 15%; Fe2O3: 8%~30%; Na2O: 1% to 5%; K2O: 0.5%~3%; MgO: 0.2%~1.5%; SO3: 1%~5%; Other components: 0.1%~3.5%.

3. The preparation method according to claim 1, wherein: Step 2) The mass percentage concentration of the slurry is 10% to 30%.

4. The preparation method according to claim 1, wherein: The specific operation of step 3) the microwave treatment is as follows: the gasified fine ash and the mixed ash are placed in a container made of a microwave absorbing material and then placed in a microwave push plate kiln for microwave activation.

5. The preparation method according to claim 1, wherein: The specific operation of step 3) air cooling is as follows: the gasified fine ash mixed ash after microwave treatment is sent to the cooling chamber, and compressed air is blown into the cooling chamber from one side in parallel so that the gasified fine ash mixed ash is blown into the ash collecting net on the other side and falls into the ash collecting trough, and then the fine ash in the ash collecting trough is collected.

6. An auxiliary cementitious material based on coal gasification fine ash, characterized in that: Prepared by the preparation method according to any one of claims 1 to 5.

7. A building material, characterized in that: The auxiliary cementitious material comprising the coal gasification fine ash according to claim 6.

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