CN1997726A - Fuel product and process - Google Patents

Abstract

A process for producing fuel pellets is described. The pellets are obtainable from a particulate carbon-based material and a binder, the process comprising the following steps: admixing the material and binder, and agglomerating the so-formed mixture by tumbling. The tumbling action, such as in a rotary drum, serves to agglomerate the particles and bind the mixture into the pellets, usually with a variable size distribution. No mechanical compression force is required, and with the binders used, the process can be carried out at ambient temperature. The process provides a simple but efficient process for using waste carbon-based materials, and forming a useable fuel product, which is easily transportable and efficiently combustible. Rotating drum or pan agglomerators are relatively low cost to build, and are capable of very high tonnage throughputs. Customised products can be produced and the process enhances the economics of ash and sulphur removal in coal upgrade plants.

Description

Fuel Products and Methods

technical field

The present invention relates to fuel products and methods for their manufacture.

Background technique

A persistent problem in many solid-based fuel extraction processes is the disposal of waste "fines" material. About 10% of mined coal ends up as fine (typically less than about 3 mm) or ultrafine (typically less than about 0.1 mm) coal dust. This pulverized coal is usually not suitable for final processing, even if its size is not problematic, but retains a large amount of water (10%-30%) making its transport and combustion "stubborn", difficult and inefficient.

One of the solutions is to form briquettes (briquettes). Briquettes can be formed by compressing fine particles under extremely high pressure to physically form the secondary fuel material. However, the high investment and operating costs of briquetting plants (forming plants) have prevented their use in countries other than some high-consuming countries. In many places, coal dust is usually only "dumped" near coal mines.

Another solution is to agglomerate carbonaceous fines using various methods, including pelletizing and extrusion. To this end, various binder (adhesive) materials have been proposed. In US 4219519 the main material of the binder is lime or related calcium compounds. US 3377146 lists various organic binders, while US 4357145 proposes tall oil pitch. US 4025596 describes a method of pelletizing the final separated mineral solids using latex optionally together with bentonite or starch.

However, all of these methods involve the need for some manipulation of the pellets after they have been formed, usually drying at high temperatures in order to provide the pellets in their final form. Consequently, all of these methods require some form of heat treatment, often in combination with one or more organic binders. More importantly, all of these methods have been in existence for more than 20 years, and none of them are known to be actually used, or used successfully.

Another problem is moisture weight. High moisture content in coal makes transport and combustion inefficient. Sub-bituminous coal, which comprises a large and valuable portion of the world's coal reserves, contains "chemically bound" moisture (as much as 20-30% moisture) in the coal structure. This "moisture" severely limits the use and value of sub-bituminous coal. For example, for every three truckloads of coal transported, 1 truckload of water has to be transported. Moisture also consumes (takes) energy from the flame (turning water into water vapor) from the flame when the coal is burned. Attempts to drive the moisture out by heating have proven unsuccessful, as the coal cracks as it dries and also becomes prone to spontaneous combustion. As a result, very little subbituminous coal is traded internationally.

Another industry that uses the briquetting process is the peat industry. To form a suitable crushable material, the peat must be efficiently dried (usually two or three times) and chopped and ground, which adds to the overall cost of forming the briquettes.

Contents of the invention

One of the objects of the present invention is to provide a more efficient fuel product and production method by reducing operating costs and capital requirements.

Therefore, according to one aspect of the present invention, there is provided a method of producing rigid fuel pellets from particulate carbon-based material and a binder, comprising the steps of:

mixing the material and binder, and agglomerating the mixture so formed by tumbling to form firm pellets;

wherein the binder is silicate-based and includes one or more surfactants, and the method is performed at ambient temperature.

The use of a silicate-based binder comprising one or more surfactants enables the process of the present invention to produce hard fuel pellets at ambient temperatures. Formation of solid fuel pellets at ambient temperature has not been achieved by any of the prior art methods.

The fuel pellets are "hard" in the sense that they are handleable and can be stored, stacked and/or shipped immediately without the need for any separate active curing step. That is, the pellets solidify without any assistance or further treatment, especially without heat and/or pressure treatment. Prior art methods require formation of fuel pellets by tumbling into agglomerates to effectively cure with heat and/or (forced air) pressure before these fuel pellets become hard and handleable. Thus, the fuel pellets of the present invention can be packaged and/or shipped immediately after formation.

Tumbling action, such as in a rotating drum, is used to agglomerate the particles and bind the mixture into pellets, often with a variable size distribution. No mechanical stress (with associated low productivity and high cost) is required, and the method of the present invention can be performed at ambient temperature. Because the method can be carried out at ambient temperature, no additional equipment for any active second-stage processing, or the provision of elevated temperatures is required. This naturally obviates the need for energy sources to generate high temperatures, such as fuel to be burned, the effect of which is often a significant economic requirement of the production process.

The binder of the present invention allows the fuel pellets of the present invention to form and solidify in a "cold bonding" process. That is, pellets can form and solidify without any external heat input.

Furthermore, the present invention is particularly advantageous as it can be a "single stage" process, avoiding the need for any pre-mixing or handling of the components involved, and avoiding any post-formation handling (post -forming treatment). From an investment and economic point of view, the single stage process reduces the need to build a plant suitable for delivering the process of the invention and reduces operating costs by employing a single stage process operating at ambient temperature.

The use of inorganic binders in the present invention is also advantageous, in contrast to the usual use of organic materials as binders in prior art methods. The use of inorganic binders reduces process complexity and again reduces the need for any pretreatment or mixing of binder materials. The use of inorganic silicate based binders has two further advantages. Firstly, such binders do not affect the combustion qualities of carbonaceous materials (as they do not burn) compared to organic materials such as starch (which burn, thereby affecting the combustion qualities and calorific value of the material formed). Such binders also eliminate all environmental concerns (as they do not burn), again in contrast to organic binders.

Once hard fuel pellets are formed, they solidify to give the final shape of the fuel pellets. According to the invention, this curing can take place at ambient temperature and without any active and/or separate curing steps, especially the heat treatment steps used in the prior art. Hard fuel pellets will solidify over time without any external influence. Thus, they remain firm in place or place, for example, for a period of time, such as 1 to 10 days, while curing occurs after tumbling. As with concrete, curing may continue for a period of time, such as a few days, but the present invention provides rigid pellets with sufficient strength after tumbling so that they can be stored, stacked, transported, etc. immediately while curing.

The concept of curing as used herein includes any drying required to form a pellet, in addition to the chemical process that takes place at least on the surface of the pellet as it is formed, so as to preferably form a hard shell. As such, it is not an object of the present invention to provide any separate drying step or action (involving one or more liquid materials or substances, such as water, which evaporate from within the pellet as it is formed and solidified). Any such drying effect after pellet formation is considered to be secondary or insignificant compared to the effect of forming and curing the pellet.

Preferably, the method provides pellets with a hard exterior, skin, shell or shell. More preferably, the interior of the pellet is dry and has a small, preferably microscopic, airy or porous shape throughout or substantially. That is, the action of the surfactant to draw the silicate binder to the surface of the pellet creates cavitation and gas bubbles within the pellet as the pellet is formed, the benefits of which are discussed below.

In one embodiment of the invention, the water is part of the mixture of the material and the binder, or is added separately as part of the material, part of the binder, or any combination therebetween.

The amount of water required or desired for the process of the invention may depend on the nature of the particulate material and binder. For example, listed below are the various types of mined coal and the moisture content (m/c), heat content (h/c) and carbon content these coals typically have at the time of mining.

m/c h/c(mj/kg) carbon bituminous coal <20% 24～35 45%～86% anthracite <15% 26～33 86%～98% lignite <45% 10～20 25%～35% Subbituminous coal <30% 20～21 35%～45%

The heat content of coal is directly related to the moisture content. Thus, a high-grade anthracite with a moisture content of 15% has a caloric content of 26-33 mj/kg based on moist mineral-free matter. At the other end of the scale, lignite, the lowest rank coal, will have a moisture content of up to 45%, with a heat content of only 10-20 mj/kg on a moist, mineral-free basis.

In most power stations where coal is used, the coal is usually ground into a fine powder for spraying into the furnace. However, the energy used to pulverize coal with a moisture content of eg 25% is relatively high. As a result, half a million metric tons of "unusable coal" product is currently stacked annually at certain power stations because it is too wet, ie, its moisture content is too high to burn efficiently. As mentioned above, freshly mined bituminous coal can have a moisture content of up to 20%, low rank coal can have a moisture content of up to 30%, and lignite can have a moisture content of up to 45%. To drive off this level of moisture (by converting it to water vapour) prior to any combustion of the actual coal requires starting with so much energy that such coal cannot be used at all because it is not efficient. Grinding this coal to be more "combustible" is also inefficient, as the moisture-rich coal often clogs the grinder.

A particular advantage of the present invention is that any type of "wet" or "dry" particulate carbon-based material can be used, although any wet material preferably has a maximum moisture content of 10-15%. This moisture content can be achieved by grinding with a drying effect (although the energy required thereby is much lower than that required to grind the coal into a powder form that can be burned immediately as described above). Such materials are also generally considered "wet" in the art, especially in contrast to processes such as briquetting, which require the material to be absolutely dry.

In some cases it is preferable to have dry particulate material. In other cases, the material can come from wet fuel sources, such as peat and coal tailing dams, and any reduction in the amount of drying required (compared to, for example, briquetting processes) reduces the need to form fuel products total energy input.

The method of the present invention can be used directly with moisture-rich pulverized coal and similar products because it allows any moisture content of the binder to be reduced in-line with the moisture content in the coal without affecting the process. Once the pellets are formed, their hardened shells completely or substantially terminate or significantly reduce moisture intrusion, especially when water repellent additives are used. Once fully cured, the pellets may have a moisture content of at least half that of the particulate starting material, and may be less than 5%, and thus be sufficiently dry to be immediately and easily ground to form a fuel product suitable for use in power stations.

The reduction in moisture also results in a direct increase in the calorific value of the products being combusted, thus increasing their efficiency and economic value. Shipping such products also has such economic benefits compared to the cost of shipping "wet" or moisture-enriched materials described above. In fact, the present invention provides a method which takes into account the type and amount of binder used, as well as process parameters, and can provide a combustible material or the like with a desired or predetermined combustibility value, which in particular Local economic conditions suitable for fuel sources. Different regions and countries mine different types and grades of coal, so they use them in different ways in order to try and maximize their economic value. The present invention provides a method which is particularly advantageous for what is currently considered waste material arising from the production process.

Thus, the present invention also results in a significant reduction in the moisture content of the fuel product, allowing the conversion of an inefficient fuel product into a highly efficient fuel product.

In a preferred embodiment of the invention, the amount of moisture used in the process is adjusted in the binder composition before the binder is mixed with the particulate material. The calculation of this binder and moisture adjustment depends on the moisture content of the granular material.

According to another embodiment of the invention, the particulate material has a maximum particle size or grade generally of 3 mm or less. Coal "dust" or "fines" can typically be sub-micron in size. Peat is a fuel material which is usually dried/chopped/dried/crushed prior to briquetting. Some peat material still needs to be chopped in order to provide a particulate material suitable for the present invention, but to a much lesser extent than is required for briquetting.

More preferably, the particulate material has a range of particle sizes or grades, preferably favoring finer or finer particle sizes.

Carbon-based particulate materials suitable for the present invention may be generally accepted wet or dry, and may be supplied from any type of coal-based fuel, including peat and lignite through to sub-bituminous coal, anthracite fines, petroleum coke (char) fines, etc. , as well as sewage waste, biowaste, animal waste and other hydrocarbon materials, which can all be used as fuel sources. The particulate material may also be a combination of two or more starting materials or "ingredients" (such as those mentioned above), without prior mixing, in order to provide "blended" fuel pellets.

Suitable materials also include low-grade or treated fuels, as well as hitherto "waste" products whose clean combustion contributes to lower overall pollution levels.

The present invention is not affected by high ash or sulfur content in the particulate material.

Any suitable silicate-based binder may be used in the present invention, which may be a homogeneous or heterogeneous material such as cement and similar calcium, sodium or potassium raw silicates.

The method may include adding one or more additional ingredients to the mixture, alone or with a binder. Such additional ingredients include lime, inorganic binders, cement, and waterproofing additives. As described below, the gel material may contribute to the green strength (green strength) of the pellet and may facilitate the formation of a harder outer surface or shell of the pellet.

The lime or cement helps stop sulfur emissions when the pellets so formed burn. A particular advantage of the present invention is the use of lime or other types of calcium hydroxide (which are known sulfur absorbents) mixed with the particulate carbon-based material. Increased mixing of such sulfur absorbents with sulfur-containing carbon-based materials reduces the need for current sulfur absorbing devices such as scrubbers used later in the fuel combustion process. In fact, it is believed that the present invention can achieve a reduction in sulfur emissions (typically in the form of sulfur dioxide) of 70% to 90%, or possibly more. In addition, this significantly reduces the demand on current power stations, thereby reducing costs.

In most coal-fired power stations, the coal is usually ground into a fine particulate material, which is then injected into the fuel furnace to provide power. The addition of the sulfur absorbent to the pellet formation process, followed by grinding of the pellets for subsequent use in fuel combustion units, provides two particular advantages. First, as noted above, the ability of the method of the present invention to provide overall or substantially "dry" pellets reduces the energy input required to grind the pellets prior to combustion, and second, grinding of the pellets increases The mixing of sulfur absorbents with carbon-based materials, thereby increasing the efficiency of sulfur absorption, thereby reducing sulfur emissions.

There is increasing legislation around the world to reduce sulfur emissions, especially from coal-fired power plants. The present invention facilitates these reductions without the need for additional or other physical and/or chemical sulfur absorbers or treatments such as scrubbers etc. (which also require periodic regeneration in order to be effective, which is another energy high energy process).

Accordingly, the method of the present invention may further comprise the step of grinding, pulverizing or otherwise reducing the pellets, preferably in a form ready for use in fuel fired power plants.

One or more other mineral additives such as zeolite or vermiculite may also be used as an additional ingredient to help bind any metal contaminants in the dust of the pellets, preventing any soluble metals from being released from the dust.

The particulate material and binder to be added, as well as any other individual agents or ingredients, may be mixed using any known method or device, including simple mixing. Since the next part of the method is the tumbling process, complete homogeneous mixing of the reagents or ingredients prior to tumbling is not necessary as the tumbling process can often facilitate the mixing process if necessary or desired. In some cases, mixing may occur at least partially during tumbling, so that the different processes of the invention may not be completely separated.

In one embodiment of the invention, the binder is applied to the particulate material. One method of application is to spray the adhesive onto the material.

In another embodiment of the invention, the particulate material is mobile and/or the material is in a dispersed state before or during mixing with the binder. One particularly suitable form is a falling curtain of granulated material, for example on a transport conveyor, within a granulation drum or pan, and from a stockpile unloading outlet or the like.

In another embodiment of the invention, the particulate material and the binder can be tumbled directly and/or immediately after contacting each other.

The tumbling action agglomerates the particulate material and binder mixture to form particles of increasing size, usually spherical or oval in shape. The size of the pellets thus formed can be adjusted according to the process conditions used for tumbling, such as rotational speed, moisture content, impact force and residence time. Pellets may also be screened and/or recycled during or after granulation in order to produce pellets of a desired (eg, narrower) particle size distribution.

One suitable device for providing the tumbling action is a rotating drum. Rotating drums are well known in the art. Their output can vary from a few tonnes per hour to hundreds of thousands of tonnes per hour depending on drum length, diameter, rotational speed and angle of installation.

Typical sizes and dimensions of granulator drums, such as pans, rotating drums, and conical drums, are known in the art, as are process variations to provide variations in the product formed. See for example British Patent No 787993.

Especially compared to briquetting equipment, the investment and operating costs of drums are low. They can even be provided in mobile form, so that the method of the invention can be set where desired or needed, e.g. moved and positioned to where it is currently stored or "dumped", rather than requiring significant movement (and thus cost) for moving The material is transported to a fixed processing location.

Agglomeration can be accomplished in one or more stages, which can be linked, for example by changing the tumbling conditions of the same drum, or feeding the material directly to another granulator. Alternatively, this effect can be separate. In one arrangement for multi-stage agglomeration, the tumbling conditions are variable or varied for each stage. The condition can be changed in a continuous manner or in action, or in a discrete manner.

When the process of the present invention involves tumbling the mixture in drums, one or more drums may be used for agglomeration, preferably in series.

Surfactants are used to pull the silicate based binder towards the surface of the forming pellets, so as they are forming and starting to solidify, the pellets will form and then proceed to have an outer portion that is harder than its interior , skin, shell or surface. Thus, the pellet has a variable density towards the core and a greater density at the surface. In practice, the "outer shell" layer or portion will generally have a high density compared to the low density of the "inner".

More preferably, the pellets are sufficiently rigid that, once formed, they can be handled, stacked and/or transported without any significant breakage.

Solidification of the pellets may begin during agglomeration or may be part of agglomeration.

The method of the invention may comprise one or more grading steps. That is, the pellets so formed are sized as desired or needed. This may include sorting out those pellets that are damaged or undersized, the pellet material of which can be recycled back into the process of the invention. When coal is mined, cleaned and transported, large quantities of fine coal (particles smaller than 5mm) are produced. The present invention makes it possible to form this pulverized coal into about 50 mm lumps with very low moisture content without any change in the coal chemistry. The pellets can then be handled, transported and used as normal lump coal.

After any initial curing, the formed pellets are left for a period of time, which may be a number of days such as 3-7 days, to provide or allow curing to complete. Like other cured products, the pellets continue to cure to gain strength over time, eg, more days or weeks.

In another aspect, the present invention provides a method for making rigid fuel pellets at ambient temperature from a granular carbon-based material and a silicate-based binder comprising one or more surfactants, The method includes the following steps:

mix the material and binder, and

The mixture thus formed was agglomerated by tumbling to form hard fuel pellets.

According to another aspect of the present invention there is provided a rigid fuel pellet formable at ambient temperature by agglomeration of particulate carbon-based material and a silicate-based binder including one or more surfactants product.

According to another aspect of the present invention there is provided a fuel pellet product ready to be formed by the methods described herein.

The fuel pellet product of the present invention is an easily storable material. It is also easy to transport due to its variable diameter distribution. This increases the bulk density and also reduces attrition and the resulting breakdown of the pellets.

The product of the present invention can be advantageously used as fuel in many situations, for example domestic use such as domestic stoves, industrial use such as power plants and the like.

The product is made from currently "waste" materials, thus increasing the efficiency of current solid fuel mining and manufacturing.

The product preferably has a very high percent burn (possibly 100% burn) so that little or no combustible fuel remains in the ash.

Description of drawings

Specific embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a flow diagram of a method in a factory in the scope of material handling and manufacturing stages according to an embodiment of the invention;

Figure 2 is a front view of the tumbling action of agglomeration into pellets according to the present invention; and

Figure 3 is a view of a plurality of pellets according to another embodiment of the invention.

Detailed ways

Fine coal recovery systems are a common part of modern coal processing operations, but cost-effective high-tonnage solutions are required for handling wet coal fines produced by different beneficiation processes.

The high capital and operating costs of briquetting plants prevent multiple operations from maximizing their coal reserves. Briquetting is a method in which certain types of materials are compressed under high pressure. Compression of the material results in a rise in temperature which causes the raw material to release various viscous substances.

There are inexpensive hydraulic briquetting machines that are designed to be operated for only a few hours per day. Larger mechanical presses are used for large-scale installations producing hundreds of kilograms per hour, but require about 200kWh of energy input (for drying and processing) per metric ton of briquette material. In countries where coal prices are already low, the cost of the briquetting process is so expensive that coal dust is currently simply dumped in many countries around the world.

Similarly, existing methods of forming peat briquettes require initially drying mined peat to about 55% moisture, chopping, further drying to lower moisture content, followed by crushing, followed by high pressure briquetting. Each mechanical step requires a large energy input.

Other waste materials include petroleum coke (coke), a by-product of cracking oil, which is sold at low prices.

The method of the present invention allows all of these materials to be employed in a cost-effective manner to provide a beneficial fuel product.

FIG. 1 shows a flow chart of the method of the invention for use in the context of an industrial plant.

Prepare

Prepare fuel stock feed for agglomeration. Depending on its original state, some grinding, sieving or drying may advantageously be carried out. The finer the raw material feed, the more efficient the process. Preferably, but not limited to, the moisture content of the feed is at most 10% to 15% by weight.

Adjust the liquid feed to the appropriate level based on the moisture content and chemical characteristics of the fuel raw material feed. This will involve balancing the amount of moisture with the binders and surfactants used.

The above parameters can be determined during pre-testing of the process and plant. For agglomeration of coal fines, it has been found that between 20% and 25% liquid binder (relative to the weight of the raw material charge) is generally desired for efficient agglomeration. Generally, the wetter the raw material feed, the less water needs to be added at this stage.

In a group

The fuel feed continues and any dry reagents are added to the feed. It then falls off the end of the conveyor belt. The liquid binder is sprayed onto the flow curtain formed by the fine powder, which fall together into a drum, usually 1-5m (eg 3m) in diameter. As the mixture is tumbled while being sprayed with the binder and water mixture, small pellets are formed which agglomerate and grow to form hard pellets of the desired shape and size as shown in FIG. 2 .

The drum can be lined with a loosely fitted heavy duty rubber sheet to avoid material sticking to the sides of the drum. The drum is installed with a slope (eg 1%-3%) to facilitate the advancement of the pellets along it and to control the residence time within the drum. Finished pellets leave the opposite end of the drum and move onto another conveyor belt.

Only operational drum adjustments (rotational speed, moisture content, and longitudinal drum angle, which directly affect residence time within the drum) can change pellet size. For example in current briquetting operations, costly tooling changes are not required to change the dimensions of the product.

Some formation and even some solidification may take place in another drum, similar to but having a larger diameter than the granulation drum. It may also have a larger diameter and be longer than the pelletizing drum. Here, the pellets travel slowly in the drum, allowing sufficient time for the pellets to initially cure or surface finish, thus allowing immediate handling and stacking. The residence time in this drum depends on the properties of the fuel and its use can be determined in pre-production tests.

Optional surface treatment additives may be added at this stage to increase the surface area of the pellet skin, prevent sticking, and/or prevent liquid leakage into the bag, etc.

Pellets have poor initial strength, and some additional binder or cement-like chemical may be added to rapidly speed up the curing process and thus provide a faster and stronger initial initial strength for handling, or processability etc. Cracked and undersized pellets can be removed using, for example, an open section of the drum or a vibrating screen at the drum outlet. Damaged and undersized pellets can then be returned to the pelletizing drum for reprocessing.

Final Grading (if required)

At this stage the pellets can be further fractionated to the desired cross-section if desired. Any damaged and undersized pellets can then be returned to the pelletizing drum for reprocessing.

Pellet fractions can even be designed and made according to the proposed use. The size of pellets can be adjusted by changing process conditions, equipment structure, and even reagent dosage.

The pellets can then be stored for curing. During this time, typically between 3 and 7 days for coal fines pellets, and depending on the ambient temperature, the pellets reach a strength that allows full handling. No heat or strong air drying is required. An example of pellet formation is shown in FIG. 3 .

The spherical shape of the pellets will allow air to move freely through the storage pile in order to facilitate the curing process and prevent heat buildup and the risk of spontaneous combustion. At this stage, the pellet surface is tightly sealed, preventing the ingress of air into the pellet, thus also slowing down any effect or possibility of spontaneous combustion. If there is still a problem of spontaneous combustion, an preventive agent can be added during the agglomeration process.

Shipping and Packaging

The agglomeration of tumbling and growth can result in a wide variation in final pellet size - as in natural lump coal. This has the advantage of reducing the coefficient of volume expansion of the spherical product, resulting in lower shipping costs.

The formed product is then bagged or stacked to allow continued curing at ambient temperature, with a curing time dependent on local humidity. In general, the higher the moisture content of the feed, the longer the pellets will need to cure at ambient temperature and humidity.

Processing speeds can be chosen, but production rates of between 10 and 100 metric tons per hour of coal material per drum are typical. Production speed can be scaled up with multiple processing units, or scaled down with smaller equipment.

Production costs depend on the production rate, the particle size distribution of the feed, and the properties of the granular material. However, the energy input has been measured to be approximately 0.5-2 kWh per metric ton of product, at least 100 times less than that required for briquetting.

In particular, the method of the present invention can be modified to handle high ash and/or high sulfur coals, since the pellets remain stable throughout the combustion process, allowing efficient combustion of even low rank coals.

Also suitable for fuel products that require ash and sulfur reduction in order to be salable, the method of the invention allows fine grinding to remove contaminants by gravity or flotation, resulting in a far higher quality fuel source. The method also provides a means of reforming the refined concentrate into a usable, stable, and valuable product shape.

Sulfur emissions, even from very poor quality coal, can be completely or substantially eliminated by simple adjustments to pelletizing additives, significantly reducing or possibly even eliminating any sulfur dioxide pollution that causes acid rain. The granulation process also simultaneously reduces fly ash through the inherent cohesion, silicification and stabilization of residual dust caused by the reagents used. In addition, the higher the product combustion temperature, the easier it is to produce due to the high gas transport velocity not only between the pellets but also between the particles inside the pellets, and can obtain more rapid and/or Or a more controlled burn.

Another advantage of the present invention is the very complete combustion of the fuel contained within the pellet due to the high gas transport velocity and the maintenance of the overall structure of the pellet until the completion of combustion. Retaining the hardened outer shell, skin, etc., causes a significant increase or intensification of the heat inside the pellet, causing a very high level of combustion, resulting in the completion of all predetermined chemical reactions of the pellet contents. Due to the dry and porous form of the contents, the "fine" character is usually still retained, and the immediate preheating is rapid, so that the contents burn completely. The pellets retain their shape even at white heat and exhibit very stable combustion characteristics.

In particular, the method of the invention may involve non-forced drying of the pellets, since the action of any surfactant used is optimized at ambient temperature. Also, when water is used, the surfactant causes the binder-containing moisture to migrate quickly to the surface of the pellet by capillary action, resulting in a harder surface and a softer interior due to the final heavy surface concentration of the binder. The eggshell effect". This results in a significantly increased skin strength, resulting in pellets that are very strong and low moisture content (about 5%), which also prevents the uptake of moisture from the air.

Yet another application of the method of the present invention is the reduction of feed moisture for pulverized coal fuels in power and heat generating stations, where coal fines or coal tailings are pelletized and allowed to fully solidify and dry prior to pulverization and combustion in furnaces. The average moisture content in current pulverized coal dumps typically ranges from 12% to 35%, making them very difficult to use or mix with other feeds.

As can be appreciated from the above, the method of the present invention overcomes or solves a number of financial and operational problems.

Once the "eggshell" effect is fully developed after curing, the pellet will retain its strength even during white hot burning. This enables high temperature reactions to take place inside the pellets, resulting in a much higher degree of combustion of the fuel, effective oxidation and sequestration of contained sulfur, and negligible levels of unburned carbon in the residual ash. The shell effect allows the pellets to retain their structure during combustion, resulting in less particulate emissions in the fuel gas.

The eggshell pelleting process can also be used on sulphide concentrates and iron ore to enable the manufacture of pre-melt furnace feed which can result in a "sulphur-free emission" furnace technology. This can be used cost-effectively in existing operations at high industrial tonnage production.

Compared with the prior art, the present invention has significant advantages, including:

• < 3mm coal/lignite fines can be pelletized dry or directly from filter units.

●The tonnage production capacity of each granulation production line can be from 10 metric tons/hour (common size) to 100 metric tons/hour.

●In the granulation process, a high level of automatic control can be used for precise control and reagent dosage.

●When using chemical "curing", the pellets need only be air-dried.

• Cured pellets can be shipped via bulk transport equipment, or alternatively "green pellets" bagged.

• Pellet size can be customized from 5mm to 150mm when necessary, depending on coal characteristics and process parameters.

●Specific heavy load reagents can be added in order to obtain higher strength, rapid curing, high temperature strength and increased water resistance.

• Pyrite removal can be reduced or eliminated due to gas transport to form _CaSO4 within the pellet due to various binder combinations to eliminate _SO2 .

●High ash pulverized coal will ignite and burn with high efficiency due to good combustion characteristics.

●Long-lasting burning, high percentage of carbon burning.

• Coal smaller than 20mm can be pulverized and pelletized with coal fines to obtain high value pellets.

• Contaminated coal or waste products such as sawdust, rice husks, garbage, animal waste, petroleum coke (char), or waste oil can be contained in these pellets.

• Residual ash has negligible residue of unburned fuel (eg coal) and is excellent for other industrial applications.

●Residual ashes can also be granulated with similar binders for concrete feed, aggregate mixtures and highly porous fillers.

• Lignite and peat can be treated with the same technology or blended with other fuel sources to produce blended pellet fuels with pre-engineered properties such as smokeless combustion.

The invention is applicable to all types of coal fines with varying amounts of moisture content and sulfur content. Generally, the diameter of the formed pellets is in the range of 5 to 50 mm, and the classified pellets are easy to handle, storeable, transportable, and then combustible, and, if necessary, used for Optimal shape and size for grinding.

The present invention provides a simple yet efficient method for using waste carbon-based materials and forming a usable fuel product that is easily transportable and burns efficiently. Drum or disc granulators have relatively low construction costs and can be produced in very high tonnages. Customized products can be produced and the invention improves the economics of ash and sulfur removal in coal upgrading plants.

Low-end technology applications in countries where there is little investment in high-efficiency coal processing plants can also easily utilize the present invention, thus, high efficiency, environmentally friendly and cost-effective processing plants can be obtained for manufacturing and operation. In these locations, any material that is not immediately usable is usually treated as waste and simply piled up in ever-larger waste heaps, increasing its environmental hazards.

Claims (40)

1. method of producing hard fuel spherolite by particulate carbon-based material and binding agent may further comprise the steps:

Described material and described binding agent are mixed, and make the mixture of such formation agglomerating so that form spherolite by lift-over,

Wherein, described binding agent be silicate-base and comprise and when described method is carried out at ambient temperature, can form hard fuel spherolite by one or more tensio-active agents.

2. method according to claim 1, described method can be used as one-stage process and implement.

3. method according to claim 1 and 2, wherein, implementing described method does not need independent active curing schedule.

4. according to each described method in the claim 1 to 3, wherein, the hard spherolite of Xing Chenging solidifies after lift-over at ambient temperature like this.

5. according to the described method of aforementioned each claim, wherein, described spherolite forms hard shell.

6. according to the described method of aforementioned each claim, described method is suitable for providing the spherolite of variable size-grade distribution.

7. according to the described method of aforementioned each claim, wherein, described particulate material and/or binder mixtures comprise water.

8. method according to claim 8, wherein, described binding agent with comprise water before described particulate material mixes.

9. according to the described method of aforementioned each claim, wherein, overall dimension that described particulate material is common or grade are about 3mm or littler.

10. according to the described method of aforementioned each claim, wherein, described particulate material is coal dust or coal dust.

11. according to each described method in the claim 1 to 10, wherein, described particulate material is to be mud coal partly, mainly or fully.

12. method according to claim 11, wherein, described mud coal and coal dust combination.

13. according to the described method of aforementioned each claim, wherein, described particulate material is two or more raw-material compositions.

14. according to the described method of aforementioned each claim, wherein, described binding agent is partly, fully or mainly to be water glass or potassium silicate.

15. according to the described method of aforementioned each claim, wherein, described method comprises one or more other compositions of adding.

16. according to claim 15 described methods, wherein, described other composition or every kind of other composition are selected from the group that comprises lime, mineral binder bond, cement and waterproof additive.

17., wherein, described particulate material and binding agent are mixed by stirring at least in part according to the described method of aforementioned each claim.

18., wherein, described binding agent is sprayed onto on the described particulate material according to the described method of aforementioned each claim.

19. according to the described method of aforementioned each claim, wherein, described particulate material with before described binding agent mixes and/or during move.

20. according to the described method of aforementioned each claim, wherein, described spherolite is spherical or avette.

21., wherein, described spherolite is screened after lift-over according to the described method of aforementioned each claim.

22. according to the described method of aforementioned each claim, wherein, described lift-over is carried out in rotary drum.

23. according to the described method of aforementioned each claim, wherein, described method does not need any pre-treatment to described particulate carbon-based material.

24. according to the described method of aforementioned each claim, this method is used to reduce the moisture in the described carbon-based material, compares with the moisture weight in the particle carbon back parent material, preferably is reduced to less than 5%.

25., wherein, mix described particulate material and binding agent by lift-over according to the described method of aforementioned each claim.

26., also comprise the step of grinding the spherolite that forms according to the described method of aforementioned each claim.

27. a hard fuel sphere granule product, described fuel sphere granule product can be at ambient temperature by making particulate carbon-based material and the silicate-base binding agent is agglomerating forms, described silicate-base binding agent comprises one or more tensio-active agents.

28. a fuel sphere granule product, it forms by each described method in the claim 1～27.

29. according to claim 27 or 28 described fuel sphere granule products, it can be used for burning immediately.

30. according to each described fuel spherolite in the claim 27 to 29, wherein, described pellet product comprises one or more sulfur absorbing agents.

31. according to each described fuel spherolite in the claim 26 to 30, it is spherical, preferably is used for fuel combustion immediately.

32. according to each described fuel spherolite in the claim 27 to 31, it has hard shell.

33. according to each described fuel spherolite in the claim 27 to 32, it has the density of variation towards its core direction.

34. according to each described fuel spherolite in the claim 27 to 33, it has exsiccant inside.

35. according to each described fuel spherolite in the claim 27 to 34, it has enough hardness so that handle, pile up and/or transport and does not take place and anyly breaks significantly after lift-over.

36. according to each described fuel spherolite in the claim 27 to 35, it can burn fully or fully, so that almost or does not fully stay combustible fuel in ashes.

37. according to each described fuel spherolite in the claim 27 to 36, it is made by coal dust or coal dust.

38. according to each described fuel spherolite in the claim 27 to 37, it does not have sulphur emissions substantially in combustion processes, preferred sulphur emissions reduces by 70%～90% or more.

39. according to each described fuel spherolite in the claim 27 to 38, wherein, the moisture in described spherolite is little a lot of compared with the moisture in the beginning particulate material.

40. according to each described fuel spherolite in the claim 27 to 39, wherein, the moisture content of described spherolite is less than 5%.

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