CN108611147B

CN108611147B - Formed coke and preparation method thereof

Info

Publication number: CN108611147B
Application number: CN201810495450.0A
Authority: CN
Inventors: 祖静茹; 李克忠; 刘雷; 刘元杰; 杨瑛
Original assignee: ENN Science and Technology Development Co Ltd
Current assignee: ENN Science and Technology Development Co Ltd
Priority date: 2018-05-22
Filing date: 2018-05-22
Publication date: 2020-07-14
Anticipated expiration: 2038-05-22
Also published as: CN108611147A

Abstract

The invention relates to the technical field of coal gasification, in particular to a formed coke and a preparation method thereof. The fly ash and the heavy tar are combined into high-calorific-value formed coke for gasification by modifying the fly ash and the heavy tar, so that the economic benefit can be improved. The embodiment of the invention provides a preparation method of formed coke, which comprises the following steps: modifying the fly ash to remove hydrophilic functional groups in the fly ash to obtain a hydrophobic carbon molecular porous skeleton; homogenizing heavy tar containing water and dust to obtain emulsified tar; and mixing the modified fly ash and the emulsified tar, stirring, separating water, and then pressurizing and molding a solid-phase product to obtain the formed coke. The embodiment of the invention is used for recycling the fly ash and the heavy tar.

Description

Formed coke and preparation method thereof

Technical Field

The invention relates to the technical field of coal gasification, in particular to a formed coke and a preparation method thereof.

Background

The fluidized bed coal gasification technology is an important way for clean and efficient utilization of coal, and various products such as crude gas, tar and the like are obtained by adopting air, water vapor and oxygen as fluidizing media under a certain temperature condition.

In the coal gasification process, a large proportion of fine-particle coal dust is contained in the gasification bed material due to abrasion and breakage of coal particles. In the prior art, the fly ash taken out of the gasification furnace is mainly subjected to gas-solid separation by a cyclone separation system and then returned to the gasification furnace for secondary gasification, but the fly ash capable of secondary gasification is very little and most of the fly ash can still be taken out by the product gas under the same gas speed, and the fly ash generated by some process devices is 10-20 times of the feeding treatment capacity, so that the reutilization difficulty is high, and the improvement of the coal gasification economic benefit is not facilitated.

Meanwhile, in the coal gasification process, the generated tar is usually separated by a water washing cooling mode, specifically, the tar in the product gas is cooled down by the water washing cooling, and then is separated into light tar (namely the tar with smaller molecular weight is positioned on the upper layer of water) and heavy tar (the tar with larger molecular weight is positioned on the lower layer of water) by standing and layering, the light tar has higher fluidity and good hydrophobicity, the separation and collection process is simple and reliable, the heavy tar has poorer fluidity and certain viscosity, a small amount of fly ash is adsorbed, an emulsified mixture is easily formed with water, and the separation and utilization are also difficult.

At present, the treatment and application of fly ash and heavy tar produced by coal gasification become bottlenecks which restrict the popularization of fluidized bed gasification.

Disclosure of Invention

The invention mainly aims to provide a method for preparing formed coke and the formed coke, wherein fly ash and heavy tar are modified to combine the fly ash and the heavy tar into the high-calorific-value formed coke for gasification, so that economic benefit can be improved.

In order to achieve the purpose, the invention adopts the following technical scheme:

in one aspect, an embodiment of the present invention provides a method for preparing formed coke, including: modifying the fly ash to remove hydrophilic functional groups in the fly ash to obtain a hydrophobic carbon molecular porous skeleton; homogenizing heavy tar containing water and dust to obtain emulsified tar; and mixing the modified fly ash and the emulsified tar, stirring, separating water, and then pressurizing and molding a solid-phase product to obtain the formed coke.

Optionally, the modification treatment of the fly ash specifically includes: and carrying out catalyst loading on the fly ash, and carrying out pyrolysis treatment on the fly ash subjected to catalyst loading by adopting a gasification agent containing water vapor to obtain a hydrophobic carbon molecular porous framework.

Optionally, the temperature of the pyrolysis treatment is 150-.

Optionally, the mass percentage of the water vapor in the gasifying agent is greater than or equal to 10%.

Optionally, the pyrolysis treatment time is 1-3 h.

Optionally, the catalyst is an alkali metal catalyst.

Optionally, the addition amount of the catalyst is 5-35% of the mass of carbon in the fly ash.

Optionally, before loading the catalyst on the fly ash, the method further comprises:

and treating the fly ash by using a strong acid solution so as to dissolve an ash framework in the fly ash.

Optionally, the addition amount of the strong acid solution is 2-4 times of the volume of the fly ash.

Optionally, the strong acid solution is a mixed solution of hydrochloric acid and nitric acid or a mixed solution of hydrochloric acid and hydrofluoric acid.

Optionally, an emulsifier and a stabilizer are added into the heavy tar containing water and dust, and the heavy tar containing water and dust is emulsified under stirring to homogenize the heavy tar containing water and dust.

Optionally, the adding amount of the stabilizer is not more than 5% of the mass of the heavy tar containing water and dust, and the adding amount of the emulsifier is not more than 8% of the mass of the heavy tar containing water and dust.

Optionally, the temperature of the homogenization treatment is 25-100 ℃, and the pressure is 0.5-3.0 MPa.

In another aspect, embodiments of the present invention provide a formed coke obtained by the preparation method as described above.

Optionally, the moisture content of the formed coke is less than 5% after the formed coke is exposed to air with a relative humidity in the range of 70% -80% for 5 days.

The embodiment of the invention provides a preparation method of formed coke and the formed coke, wherein fly ash is modified to remove hydrophilic functional groups in the fly ash to obtain a hydrophobic carbon molecular porous framework, heavy tar is homogenized to realize the transportation of the heavy tar, the modified fly ash and tar are conveniently and accurately metered when being mixed, the modified fly ash and the emulsified tar obtained after the homogenization treatment are mixed and stirred, the heavy tar has hydrophobicity and viscosity, the hydrophobic carbon molecular porous framework can be promoted to adsorb the heavy tar in the emulsified tar, the heavy tar is adsorbed to the surface and in the pore channels of the hydrophobic carbon molecular porous framework, the emulsified tar after the homogenization treatment has higher homogenization degree, the adsorption of the semicoke to the heavy tar is more uniform, and after water separation, the formed coke can be obtained through pressure forming and has higher hydrophobicity, The formed coke has uniform texture, high quality stability and higher activity and heat value, thereby improving the economic benefit.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without inventive efforts.

Fig. 1 is a schematic flow chart of a method for preparing formed coke according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it is to be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention. In the description of the present invention, "a plurality" means two or more unless otherwise specified.

The embodiment of the invention provides a preparation method of formed coke, which is shown in figure 1 and comprises the following steps:

step 1) performing modification treatment on the fly ash to remove hydrophilic functional groups in the fly ash to obtain a hydrophobic carbon molecular porous framework;

step 2) homogenizing heavy tar containing water and dust to obtain emulsified tar;

and 3) mixing the modified fly ash with the emulsified tar, stirring, separating water, and then pressurizing and molding a solid-phase product to obtain the formed coke.

The embodiment of the invention provides a preparation method of formed coke, which comprises the steps of modifying fly ash, removing hydrophilic functional groups in the fly ash to obtain a carbon molecular porous framework with higher hydrophobic function and adsorption property, homogenizing heavy tar to realize the transportation of the heavy tar, facilitating the accurate metering when the modified fly ash is mixed with tar, mixing and stirring the modified fly ash and emulsified tar obtained after the homogenization treatment, and enabling the hydrophobic carbon molecular porous framework to adsorb the heavy tar in the emulsified tar due to the hydrophobic property and the viscosity of the heavy tar and the higher adsorption property of the modified hydrophobic carbon molecular porous framework, so that the heavy tar is adsorbed to the surface and the pore channels of the hydrophobic carbon molecular porous framework, and the homogenized emulsified tar is higher in homogenization degree, the adsorption of the semicoke on the heavy tar is more uniform, and after water separation is carried out, the formed coke with higher hydrophobicity, uniform texture, high quality stability and higher activity and heat value can be obtained through pressure forming, so that the economic benefit can be improved.

The specific treatment method for modifying the fly ash is not limited, as long as the hydrophilic functional groups in the fly ash can be removed.

In an embodiment of the present invention, the modifying treatment of the fly ash specifically includes: and carrying out catalyst loading on the fly ash, and carrying out pyrolysis treatment on the fly ash after catalyst loading by adopting a gasification agent containing water vapor to obtain a hydrophobic carbon molecular porous framework.

In the embodiment of the invention, the fly ash is subjected to catalyst loading, and the fly ash subjected to catalyst loading is subjected to pyrolysis treatment by adopting water vapor, so that on one hand, water vapor molecules are smaller, and water molecules are more likely to react with activated carbon in the fly ash to generate more pore channel structures in the presence of a catalyst, and on the other hand, hydrophilic functional groups in the fly ash can be cut off through pyrolysis reaction to obtain a hydrophobic carbon molecule porous framework.

It should be noted that, when the modified fly ash is mixed with the emulsified tar and stirred, due to the hydrophilicity of the catalyst metal ions, the catalyst metal ions can also be dissociated from the fly ash particles to compete for water molecules in the emulsified tar, so that the modified fly ash has a good demulsification effect, the water phase and the oil phase are rapidly separated, and the hydrophobic carbon molecular porous skeleton can be promoted to be bonded with the heavy tar.

Wherein the fly ash and steam can be passed into a tubular furnace reactor for pyrolysis.

The catalyst may be an alkali metal catalyst or an alkaline earth metal catalyst. The alkali metal catalyst is usually a highly basic catalyst such as sodium hydroxide, potassium carbonate, or sodium carbonate, and the alkaline earth metal catalyst is usually calcium oxide or calcium hydroxide. Alkaline earth metal catalysts are less basic than alkali metal catalysts.

In the catalysis process, the fly ash is etched by utilizing the alkalinity of the catalyst, so that the pore channel structure in the fly ash particles is further enriched. Preferably, the catalyst is an alkali metal catalyst (e.g., potassium hydroxide, sodium hydroxide, potassium carbonate, etc.).

The amount of the catalyst to be added is not limited.

In order to improve the etching effect, it is preferable that the catalyst is added in an amount of 5% to 35% by mass of carbon in the fly ash.

The temperature and pressure of the pyrolysis treatment are not limited.

In a preferred embodiment of the present invention, the temperature of the pyrolysis treatment is 150-. Under the temperature and the pressure, metal ions can be easily dissociated from fly ash particles, which is favorable for promoting the hydrophobic carbon molecular porous skeleton to be quickly combined with the heavy tar.

The gasifying agent may be a mixed gas of steam and carbon monoxide.

Wherein the mass percentage of the steam in the gasifying agent is not limited.

In an embodiment of the present invention, the steam is contained in the gasifying agent in an amount of 10% by mass or more. More abundant pore channel structures can be formed in the fly ash particles.

In order to ensure that the fly ash has a developed pore channel structure, a large specific surface area and excellent adsorption performance after pyrolysis treatment. Preferably, the pyrolysis treatment time is 1 to 3 hours.

It should be noted that, the fly ash is small-particle coal powder carried out by a cyclone system in the coal gasification process, and the coal powder usually contains mineral salts or oxides containing elements such as Ca, Mg, K, Na, Si, P, S, Fe, Al, I, etc., which will combine with the catalyst to generate low-melting-point substances to deactivate the catalyst, so that before the fly ash is loaded with the catalyst, it is preferable that: the fly ash is treated with a strong acid solution to dissolve the ash framework in the fly ash. This also allows more channel structures to be created in the fly ash, exposing more carbon.

Wherein the fly ash can be mixed with the strong acid solution in any proportion as long as the fly ash can be subjected to ash framework dissolution treatment.

Since fly ash has a small particle size and a large volume of hydrogen by weight, it is preferable that the strong acid solution is added in an amount of 2 to 4 times the volume of the fly ash. The strong acid solution can be fully contacted with the fly ash to dissolve the ash framework in the fly ash.

In order to further improve the dissolution effect of the ash framework, the temperature for treating the fly ash by adopting the strong acid solution is preferably 40-80 ℃ and the time is preferably 30-120 min.

Wherein, the specific components of the strong acid solution are not limited. The strong acid mainly refers to permanganic acid, hydrochloric acid, sulfuric acid, nitric acid, perchloric acid, selenic acid, hydrobromic acid, hydroiodic acid and chloric acid, wherein the perchloric acid, the hydroiodic acid, the hydrobromic acid, the hydrochloric acid (hydrochloric acid), the sulfuric acid and the nitric acid are jointly called six inorganic strong acids. The strong acid herein refers to an acid capable of dissolving the ash framework in the fly ash.

Since ash content in fly ash is mostly silica, it is preferable that the strong acid solution is a mixed solution of hydrochloric acid and nitric acid or a mixed solution of hydrochloric acid and hydrofluoric acid. Among them, hydrofluoric acid is not a strong acid in the complete sense, but hydrofluoric acid has a very strong corrosivity to silica and can dissolve the ash framework in fly ash well.

Wherein, the homogenizing treatment process of the heavy tar containing water and dust is not limited as long as emulsified tar can be formed, the transportation of the heavy tar is convenient, and the fly ash can uniformly adsorb the heavy tar.

In one embodiment of the present invention, an emulsifier and a stabilizer are added to a heavy tar containing water and dust, and the heavy tar containing water and dust is emulsified with stirring to homogenize the heavy tar containing water and dust.

The emulsifier is used for mixing two immiscible liquids into a homogeneous system, the stabilizer can keep the homogeneous system stable, the emulsifier and the stabilizer are surfactants capable of promoting the two immiscible liquids to form stable emulsion, and the emulsifier and the stabilizer usually comprise hydrophilic groups and hydrophilic oil groups and can be adsorbed on the interface of heavy tar and water, so that the free energy between the interface of the heavy tar and the water can be remarkably reduced, and the heavy tar and the water can form uniform and stable emulsion.

The amount of the stabilizer and the emulsifier added is not limited, as long as the heavy tar containing water and dust can be emulsified to form emulsified tar.

In one embodiment of the present invention, the stabilizer is added in an amount of not more than 5% by mass of the heavy tar containing water and dust, and the emulsifier is added in an amount of not more than 8% by mass of the heavy tar containing water and dust.

In order to accelerate the emulsification process, the homogenization treatment is preferably carried out at a temperature of 25 to 100 ℃ and a pressure of 0.5 to 3.0 MPa.

Further preferably, the temperature of the homogenization treatment is 50 to 80 ℃ and the pressure is 1.0 to 2.0 MPa.

In order to enhance the emulsifying effect of the heavy tar, it is preferable that the stirring time is 0.5 to 5 hours.

More preferably, the stirring time is 1 to 3 hours.

Hereinafter, examples of the present invention will be described by way of comparative examples and examples. These examples are merely examples provided to specifically illustrate the present invention, and it will be understood by those skilled in the art that the scope of the present invention is not limited by these examples.

Comparative example

And mixing the semi-coke with a binding agent such as sodium hydroxide aqueous solution, starch and the like, and performing cold press molding to obtain the common formed coke.

The test shows that the heat value of the formed coke is 9200-³In the environment with the air relative humidity more than 70%, the average water content of the formed coke can reach more than 10% after being placed for 5 days, and the carbon conversion rate is less than 85% after 2 hours at the temperature of 800-900 ℃.

Example 1

In the process of carrying out coal gasification reaction on lignite in a normal-pressure fluidized bed gasification furnace to produce tar and synthesis gas, collecting heavy tar containing water and dust generated by a synthesis gas separation system, adding 5% of emulsifier and 8% of stabilizer into the heavy tar, adding the heavy tar into a constant-temperature stirring tank, controlling the temperature of the constant-temperature stirring tank to be 80 ℃ and the pressure to be 2.0MPa, and stirring for 3 hours to obtain emulsified tar. Modifying the fly ash collected by the cyclone system, adding a certain volume of fly ash into a reaction kettle, simultaneously adding a mixed solution of concentrated hydrochloric acid-nitric acid (the volume ratio of hydrochloric acid to nitric acid is 2:1) with 2 times of the volume of the fly ash, keeping the temperature at 80 ℃ under ventilation conditions, taking out after 2 hours, and rinsing to be neutral. And adding sodium hydroxide accounting for 5% of the mass of the pickled fly ash into the pickled fly ash, uniformly mixing, putting into a tubular furnace reactor, and activating by adopting pure steam, wherein the temperature of the steam activation process is 150 ℃, the pressure is 0.1MPa, and the activation time is 3 h. Mixing the activated fly ash and the treated emulsified tar in a volume ratio of 1:4, and stirring for 1h to complete the tar adsorption of the activated fly ash. And then filtering and extruding and forming to obtain the high-quality formed coke with waterproof performance. Tests show that the formed coke has a heat value 20% higher than that of the formed coke obtained in the comparative example, the average water content of the formed coke is less than 5% after the formed coke is placed for 5 days in an environment with the relative air humidity of more than 70%, and the carbon conversion rate can reach more than 90% at 800-900 ℃ for 2 h.

Example 2

In the process of carrying out coal gasification reaction on subbituminous coal in a pressurized fluidized bed gasification furnace to produce tar and high-methane gas, 3% of emulsifier and 4% of stabilizer are added into heavy tar containing water and dust generated in a gas-water separation system, then the mixture is added into a constant-temperature stirring tank, the temperature of the constant-temperature stirring tank is controlled to be 50 ℃, the pressure is controlled to be 1.0MPa, and the mixture is stirred for 1 hour. Modifying the fly ash collected by the cyclone system, adding a certain volume of fly ash into a reaction kettle, simultaneously adding 3 times of the volume of the fly ash of mixed strong acid of hydrochloric acid-hydrofluoric acid mixture (the volume ratio of the hydrochloric acid to the hydrofluoric acid is 1:1), keeping the temperature at 40 ℃ under ventilation conditions, taking out after 2 hours, and rinsing to be neutral. Adding potassium carbonate accounting for 5% of the mass of the acid-washed fly ash into the acid-washed fly ash, uniformly mixing, putting into a tubular furnace reactor, and activating by using pure steam, wherein the process temperature of steam activation is 300 ℃, the pressure is normal, and the activation time is 2 h. Mixing the activated fly ash and the treated emulsified tar in a volume ratio of 1:1.3, and stirring for 0.4h to complete tar adsorption of the activated fly ash. And then filtering and extruding and forming to obtain the high-quality formed coke with waterproof performance. Tests show that the heat value of the formed coke is 18% higher than that of the formed coke obtained by the comparative example, the average water content of the formed coke is less than 4% after the formed coke is placed for 5 days in an environment with the relative air humidity of more than 60%, and the carbon conversion rate can reach more than 90% at 800-900 ℃ for 2 h.

Example 3

In the process of carrying out coal gasification reaction on bituminous coal in a pressurized fluidized bed gasification furnace to produce tar and high-temperature crude gas, 2% of emulsifier and 6% of stabilizer are added into heavy tar containing water and dust generated by a gas-water separation system, then the heavy tar is added into a constant-temperature stirring tank, the temperature of the constant-temperature stirring tank is controlled to be 70 ℃, the pressure is controlled to be 1.5MPa, and the mixture is stirred for 2 hours. Modifying fly ash collected by a cyclone system, adding fly ash with a certain volume into a reaction kettle, simultaneously adding a mixed solution of hydrochloric acid-hydrofluoric acid mixture (the volume ratio of hydrochloric acid to hydrofluoric acid is 1:1.5) with 4 times of the volume of fly ash, keeping the temperature at 60 ℃ under ventilation conditions, taking out after 30min, and rinsing to be neutral. Adding potassium hydroxide accounting for 35% of the mass of the acid-washed fly ash into the acid-washed fly ash, uniformly mixing, putting into a tubular furnace reactor, and activating by using boiler flue gas containing 10% of water vapor, wherein the temperature of the water vapor activation process is 400 ℃, the pressure is 3MPa, and the activation time is 1 h. Mixing the activated fly ash and the treated emulsified tar in a volume ratio of 1:1, and stirring for 0.7h to complete tar adsorption of the activated fly ash. And then filtering and extruding and forming to obtain the high-quality formed coke with waterproof performance. Tests show that the heat value of the formed coke is 25% higher than that of the formed coke obtained by the comparative example, the average water content of the formed coke is less than 5% after the formed coke is placed for 5 days in an environment with the relative air humidity of more than 80%, and the carbon conversion rate can reach more than 90% at 800-900 ℃ for 2 h.

In summary, the fly ash is modified to remove the hydrophilic functional groups in the fly ash to obtain a hydrophobic carbon molecular porous skeleton, the heavy tar is homogenized to realize the transportation of the heavy tar, the modified fly ash and the tar are conveniently and accurately metered when being mixed, the modified fly ash and the emulsified tar obtained after the homogenization treatment are mixed and stirred, the hydrophobic carbon molecular porous skeleton can be promoted to adsorb the heavy tar in the emulsified tar due to the hydrophobicity and the viscosity of the heavy tar, the heavy tar is adsorbed to the surface and the pore channels of the hydrophobic carbon molecular porous skeleton, the emulsified tar after the homogenization treatment has higher homogenization degree, the adsorption of the semicoke to the heavy tar is more uniform, and after the water separation, the water separation is carried out to obtain higher hydrophobicity, uniform texture and high quality stability, the formed coke with higher activity and heat value can improve the economic benefit.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims

1. A method for preparing formed coke, which is characterized by comprising the following steps:

modifying the fly ash to remove hydrophilic functional groups in the fly ash to obtain a hydrophobic carbon molecular porous skeleton;

homogenizing heavy tar containing water and dust to obtain emulsified tar;

mixing the modified fly ash and the emulsified tar, stirring, separating water, and then pressurizing and molding a solid-phase product to obtain the formed coke;

wherein, the modification treatment of the fly ash specifically comprises the following steps:

carrying out catalyst loading on the fly ash, and carrying out pyrolysis treatment on the fly ash subjected to catalyst loading by adopting a gasification agent containing water vapor to obtain a hydrophobic carbon molecular porous framework;

the temperature of the pyrolysis treatment is 150-400 ℃, and the pressure is 0-3 MPa.

2. The production method according to claim 1,

the mass percentage of the water vapor in the gasifying agent is more than or equal to 10 percent.

3. The production method according to claim 1,

the time of the pyrolysis treatment is 1-3 h.

4. The production method according to claim 1,

the catalyst is an alkali metal catalyst.

5. The production method according to claim 1,

the adding amount of the catalyst is 5-35% of the mass of carbon in the fly ash.

6. The production method according to claim 1,

before the fly ash is loaded with the catalyst, the method further comprises the following steps:

7. The production method according to claim 6,

the addition amount of the strong acid solution is 2-4 times of the volume of the fly ash.

8. The production method according to claim 6,

the strong acid solution is a mixed solution of hydrochloric acid and nitric acid or a mixed solution of hydrochloric acid and hydrofluoric acid.

9. The production method according to claim 1,

adding an emulsifier and a stabilizer to a heavy tar containing water and dust, and emulsifying the heavy tar containing water and dust under stirring to homogenize the heavy tar containing water and dust.

10. The production method according to claim 9,

the addition amount of the stabilizer is not more than 5% of the mass of the heavy tar containing water and dust, and the addition amount of the emulsifier is not more than 8% of the mass of the heavy tar containing water and dust.

11. The production method according to claim 9,

the temperature of the homogenization treatment is 25-100 ℃, and the pressure is 0.5-3.0 MPa.

12. Formed coke obtained by the production method according to any one of claims 1 to 11.

13. The coke of claim 12, wherein the coke has a moisture content of less than 5% after exposure to air having a relative humidity in the range of 70% to 80% for 5 days.