JPS5861184A - Manufacture of pellet of low-grade coal - Google Patents

Abstract

PURPOSE:To obtain coal pellets having excellent handleability and quality, by heating low-grade coal powder having a specific water content, pouring a suspension containing droplets of hydrocarbon oil to the powder to form granulation nuclei, forming the mixture to pellets, and coating and granulating the pellet with brown coal powder containing oil. CONSTITUTION:Low-grade powder dried to a water-content of <=35wt% by spontaneous drying, etc. is heated at 80-130 deg.C. An aqueous suspension of hydrocarbon oil droplets is poured slowly to the powder to form granulation nuclei containing <=47wt% water and 5-20wt% oil. The mixture is then pelletized with a rotary drum pelletizer, etc., and coated with 5-20wt% brown coal powder containing a hydrocarbon oil to obtain spherical pellets having diameter of <=30mm..

Description

【発明の詳細な説明】 本発明は粉体状の低品位炭を造粒して使用性並びに品質
の良好なベレット状の褐炭を製造する方法に関するもの
である。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing pellet-shaped brown coal with good usability and quality by granulating powdered low-rank coal.

褐炭等の低品位炭は採掘した状態では７０重量％前後の
水を含んでおり、これを脱水や粉砕の処理を行った場合
には自然放置、貯蔵あるいは輸送の際に自然発火を起こ
しやすい危険性があり、さらに輸送する際には嵩高であ
るためにほかの石炭類に比べて輸送費が高い状況にある
。しかし乍ら褐炭は火力発電、製鉄、化学産業等でボイ
ラー用あるいはその他のエネルギー源として直接燃料用
としたり、粉末にして重質油に混合してコロＸイド状の
燃料とすることのできる有望な資源である。Low-grade coal such as lignite contains approximately 70% water by weight when it is mined, and if it is dehydrated or pulverized, it is at risk of spontaneous combustion when left alone, stored, or transported. Due to its high volume and bulk, it costs more to transport than other coals. However, lignite has the potential to be used directly as a fuel for boilers or other energy sources in thermal power generation, iron and steel manufacturing, chemical industries, etc., or it can be powdered and mixed with heavy oil to produce colloidal fuel. It is a great resource.

また、褐炭はガス化や液化を行って燃料あるいは化学合
成用原料としてその用途が拡大、発展することが期待さ
れる。従って、上述のような褐炭の特性あるいは経済性
の欠点を補うための技術上の解決策が必要である。In addition, it is expected that the use of lignite will expand and develop as a fuel or a raw material for chemical synthesis by gasifying or liquefying it. Therefore, there is a need for a technical solution to compensate for the above-mentioned shortcomings in the characteristics or economy of lignite.

採掘した状態の塊状の褐炭は輸送、貯蔵、供給等の諸設
備で取り扱う際に破壊しやすく、特に乾燥するに従って
塊状を呈する形状の突起部で破壊しやすく、粉じんの発
生を伴うものであり、また粉砕処理を行った褐炭では同
様に粉じんの飛散による作業性の低下は免れ得ない。さ
らに粉体状の褐炭は空気との接触面積の増加によって発
煙、着火、粉じん爆発−等による著しい危険性が伴い、
加うるに単位重量当りの嵩（かさ）容積が大であるため
に輸送、貯蔵等の費用が大となる等種々の欠点がある。Lump-like lignite in the mined state is easily destroyed when handled in various facilities such as transportation, storage, and supply, and is particularly prone to breakage at protrusions that become lumpy as it dries, and is accompanied by the generation of dust. In addition, lignite that has been subjected to pulverization treatment similarly suffers from a decrease in workability due to the scattering of dust. Furthermore, powdered lignite has a significant risk of smoke generation, ignition, dust explosion, etc. due to the increased contact area with air.
In addition, since the bulk volume per unit weight is large, there are various drawbacks such as high costs for transportation, storage, etc.

本発明者は上述の事実に鑑み褐炭の固体形状についてこ
れをほぼ球形のベレットにすることにより上述のような
種々の欠点を排除しうろことに着目し鋭意研究の結果需
要者等にとって極めて有用で新規なベレット状褐炭を提
供することに成功した。In view of the above-mentioned facts, the present inventor focused on the solid shape of lignite and found that by making it into a nearly spherical pellet, the various drawbacks mentioned above could be eliminated, and as a result of intensive research, the present inventor found that the solid shape of lignite would be extremely useful for consumers. We succeeded in providing a new pellet-shaped lignite.

一般に粉体を締め固めて一定の固体形状とする方法とし
ては粉体に湿分あるいは他の適性な結合剤を与えて混和
し、これを転動造粒機、押出成形機、圧縮成形機あるい
は混合機等にかけて造粒ないしは成形する方法が知られ
ている。しがし乍ら褐炭は粘土類、鉱石類、その他の無
機化合物、結晶性の有機化合物のような粉体と異なり、
水分を含んだ状態あるいは結合剤を添加したものを数秒
間で圧縮成形したり、あるいは数秒から数十秒の時間で
押出成形機のダイスで押出成形を行っても生成成形物が
膨張して破壊しやすく、十分使用に耐えるような強度を
もたせることが困難である。Generally, the method of compacting powder into a certain solid shape involves adding moisture or other suitable binders to the powder, mixing it, and then using a rolling granulator, extruder, compression molder, or A method of granulating or molding using a mixer or the like is known. However, lignite differs from powders such as clays, ores, other inorganic compounds, and crystalline organic compounds.
Even when compression molding is performed in a few seconds with moisture or a binder added, or extrusion molding is performed in a die of an extrusion molding machine for several seconds to tens of seconds, the molded product expands and breaks. It is difficult to provide sufficient strength to withstand use.

Ｉ−かし、粉粒状褐炭に添加する液状結合剤（バインダ
ー）の割合を塑性限界に相当する液状結合剤量の６５〜
８０重量％程度とした場合には押出成形機、圧縮成形機
等による褐炭成形物の膨張現象が著しく減少して破壊し
にくくなるが、液状結合剤の使用量が多くなるために大
量の成形処理には不向きである。゛また、回転皿型、回
転円筒型等の転勤造粒機に粉粒状褐炭を供給すると同時
に液状結合剤を添加しつつ造粒を行う方法では、水分を
含み、しかも嵩高である粉粒状褐炭に対して炭化水素系
油のような液状結合剤を添加しても充分に褐炭に浸透す
ることがな（、緻密な構造をもち。I-Kashi, the ratio of liquid binder (binder) added to powdered lignite is 65 to 65% of the amount of liquid binder that corresponds to the plasticity limit.
When it is about 80% by weight, the expansion phenomenon of lignite molded products by extrusion molding machines, compression molding machines, etc. is significantly reduced and it becomes difficult to break, but since the amount of liquid binder used is large, a large amount of molding processing is required. It is not suitable for゛In addition, in a method in which granular lignite is fed to a rotating plate type, rotating cylinder type, etc., and granulated while adding a liquid binder at the same time, the granular lignite contains moisture and is bulky. On the other hand, even if a liquid binder such as hydrocarbon oil is added, it does not penetrate sufficiently into lignite (which has a dense structure).

しかも使用に耐えるような強度をもつペレット状褐炭を
製造することが困難である。Moreover, it is difficult to produce pelletized lignite that has enough strength to withstand use.

本発明はベレット状褐炭の製造法において製品強度の保
持が極めて重要であることに鑑み、ベレットの製造工程
において粉粒状褐炭の粒度構成。In view of the fact that maintaining product strength is extremely important in the method for producing pellet-like lignite, the present invention aims to improve the particle size structure of powder-like lignite in the pellet production process.

この種の褐炭に対する炭化水素系油の混合方法、転勤造
粒機でのベレット化の方法等について検討し、作業性が
良好な品質の製品が得られるベレット状褐炭の製造方法
を提供することを目的とする。We have studied the method of mixing hydrocarbon oil with this type of lignite, the method of pelletizing it with a transfer granulator, etc., and have provided a method for producing pellet-shaped lignite that provides a product with good workability and quality. purpose.

本発明の方法の要点は３５重量％以下の水を含む褐炭を
８ｕ以下の粒子直径で、しがも細粒側と粗粒側に片寄っ
た二重の分布を示す粒度構成の粉粒状褐炭を原料とし、
これをジャケット式加熱部を有する混合機に仕込んで一
定の温度に保持するようにし、さらに水に炭化水素系油
の微小液滴を含む懸濁液を混合機内の粉粒状−褐炭に対
して徐々に注入して水分の蒸発のはやい細粒側の褐炭粒
子に油滴を付着させ、この油分を含んだ細粒側褐炭粒子
を媒体にして乾燥が遅れている籾粒側の褐炭粒子相互を
付着させて造粒核を生じたところで転勤造粒機にかけ、
こり造粒機内で転勤運動しつつ成長したベレットの表面
に１５重量％以下の炭化水素系油を含浸させた粉末状褐
炭を雪だるま式に被覆し、最後にこの被覆ベレットを振
動コンベア上に移送して振動作用で締め固めることによ
って強固なベレット状褐炭を製造する方法に存する。The key point of the method of the present invention is to use lignite containing 35% by weight or less of water with a particle diameter of 8u or less and a particle size structure that exhibits a double distribution, biased toward fine grains and coarse grains. As a raw material,
This is charged into a mixer with a jacket-type heating section to keep it at a constant temperature, and a suspension containing minute droplets of hydrocarbon oil in water is gradually added to the granular brown coal in the mixer. The oil droplets are injected into the lignite particles on the fine grain side, where moisture evaporates quickly, and the lignite particles on the fine grain side, which contain oil, are used as a medium to adhere the lignite grains on the rice grain side, where drying is delayed. When granulation nuclei are generated, it is passed through a transfer granulator,
Powdered lignite impregnated with 15% by weight or less of hydrocarbon oil is coated on the surface of the pellets that have grown while moving in a lump granulator in a snowballing manner, and finally the coated pellets are transferred onto a vibrating conveyor. The method consists in producing strong brown coal in the form of pellets by compacting it with vibration.

以下に本発明によるペレット状褐炭の製造方法を詳細に
説明する。The method for producing pelleted lignite according to the present invention will be explained in detail below.

使用する褐炭は通例の粉砕機によって二重に分けて製造
することが望ましく、褐炭全体の粒度分布は細粒側と粗
粒側に片寄った二重分布を示すような粒度構成とし、重
量頻度と粒子径の粒度分布曲線で細粒側の分布の最大重
量頻度に相当する粒子径が０．８　ａｕ程度、また同じ
く粗粒側の分布の最大重量頻度に相当する粒子径が３．
５藺程度で、最大粒子径が５Ｉ程度以下が適当である。It is desirable to manufacture the lignite used in two parts using a conventional crusher, and the particle size distribution of the entire lignite should be such that it shows a double distribution with one side biased towards fine particles and one towards coarse particles. In the particle size distribution curve, the particle size corresponding to the maximum weight frequency of the distribution on the fine particle side is about 0.8 au, and the particle size corresponding to the maximum weight frequency of the distribution on the coarse particle side is about 3.
Appropriately, the maximum particle diameter is about 5I or less.

又水分は３５重量％以下に脱水するのが適当である。こ
のような粒度構成で二重分布を有する粉粒状褐炭をジャ
ケット式混合機内で加熱しつつ水に炭化水素系油を含む
懸濁液を添加すると細粒側の方が粗粒側の褐炭に比べて
水分の蒸発が速やかに行われて懸濁液中の微小油滴の付
着が円滑であるため、この含油した細粒側の褐炭が架橋
媒体どなって粗粒側の褐炭粒子は相互に付着し合うよう
になり、混合機内での造粒核の成長を促進させて粘稠性
をおび、かつひき締った大きな造粒核が生成しゃすい。Further, it is appropriate to dehydrate the water to 35% by weight or less. When pulverulent lignite with such a particle size structure and double distribution is heated in a jacket mixer and a suspension containing hydrocarbon oil is added to water, the fine grained lignite becomes larger than the coarse grained lignite. As water evaporates quickly and the fine oil droplets in the suspension adhere smoothly, this oil-filled lignite on the fine grain side becomes a crosslinking medium, causing the lignite particles on the coarse grain side to adhere to each other. This promotes the growth of granulation nuclei within the mixer, resulting in the formation of large, viscous, and firm granulation nuclei.

粉粒状褐炭の結合剤として水中に炭化水素系油の油滴（
直径０．２　ｍａ以下）を含む懸濁液については、ジャ
ケット式混合機内で加熱状態の粉粒状褐炭に７４シて一
定の流量で注入する際に懸濁液中の油分の濃度が低いと
上述のような性状をもつ造粒核の成長が遅れる。また、
これとは逆に油分濃度の高い懸濁液を混合機内の粉粒状
褐炭に注入する場合には水分の蒸発が速く、かつ粗粉側
の褐炭にも油滴が付着するようになるために褐炭全体に
油分が分散されることとなって造粒核の生成が困難にな
り、そのためこのまま油分濃度の高い懸濁液を混合機内
に注入し続けると油分濃度の低い懸濁液に比べて余分の
懸濁液を注入する結果としてほぼ油分のみによる造粒核
の生成を促し、以後の転勤造粒機内においてこの造粒核
が形状の変化を伴わないまま付着し合って太き’ｔｌ団
塊を形成するために均質な構造をもつ強固なペレット状
褐炭の成長が抑制される。このように粉粒状褐炭に対す
る懸濁液の添加方法は混合機容量、混合機構、伝熱機構
等の装置特性とともに褐炭の粒度構成、初期水分、これ
に懸濁液中の油滴濃度油滴径等に依存−して変える必脣
があるが、一般に加熱式混合機内の粉と粒状の褐炭に対
する懸濁液の添加方法は結合剤として懸濁液を連続的に
供給し加熱温度を８０℃〜１３０℃の範囲に保持しつつ
水分の蒸発を制御し、最終的に塑性限界相当の油分と水
分を含む状態よりも６５〜８０重量％低めの油分と水分
を含めた状態で良好な褐炭造粒核とすることができ、こ
の造粒核に含まれる油分が５から２０重量％で、水分が
最大４７重量％にとることが望ましい。このような混合
工程で処理された褐炭の造粒核は通例の回転皿型あるい
は回転円筒型の転勤造粒機によって造粒処理を行うと数
ミリから数十ミリのペレット状褐炭が生成され、これに
１０から１５重ｔ％の炭化水素系油を含浸させた粉状褐
炭を５から２０重量％程度を添加して被覆（コーティン
グ）造粒を行い、ついでこのペレットを振動板上で振動
作用を与えると圧密によって締め固められ、直径６０襲
以下のより強固な球状褐炭ペレットが得られる。Droplets of hydrocarbon oil (
As mentioned above, when a suspension containing oil (with a diameter of 0.2 ma or less) is injected at a constant flow rate into heated granular lignite in a jacket mixer, the concentration of oil in the suspension is low. The growth of granulation nuclei with the following properties is delayed. Also,
On the other hand, when a suspension with a high oil content is injected into the powdered lignite in the mixer, the water evaporates quickly and oil droplets also adhere to the coarser lignite. The oil will be dispersed throughout, making it difficult to generate granulation nuclei. Therefore, if you continue to inject a suspension with a high oil content into the mixer, you will end up with excess oil compared to a suspension with a low oil content. As a result of injecting the suspension, the generation of granulation nuclei made almost entirely of oil is promoted, and in the subsequent transfer granulator, these granulation nuclei adhere to each other without changing their shape to form thick 'tl nodules. This suppresses the growth of solid pellet-like lignite with a homogeneous structure. In this way, the method of adding a suspension to granular lignite depends on the equipment characteristics such as mixer capacity, mixing mechanism, heat transfer mechanism, particle size composition of lignite, initial moisture content, oil droplet concentration and oil droplet diameter in the suspension. The method of adding a suspension to powder and granular lignite in a heating mixer is generally such that the suspension is continuously supplied as a binder and the heating temperature is set to 80℃~ By controlling the evaporation of moisture while maintaining the temperature within the range of 130℃, good lignite granulation is achieved with a final oil and moisture content that is 65 to 80% lower than the oil and moisture content equivalent to the plasticity limit. It is desirable that the granulated core contains 5 to 20% by weight of oil and 47% by weight of water at most. When the granulation nuclei of lignite treated in such a mixing process are granulated using a conventional rotating plate type or rotating cylindrical transfer granulator, pellet-like lignite from several millimeters to several tens of millimeters in size is produced. Approximately 5 to 20% by weight of powdered lignite impregnated with 10 to 15% by weight of hydrocarbon oil is added to this to perform coating and granulation, and then the pellets are placed on a diaphragm to vibrate. When given, the coal is compacted by consolidation, resulting in stronger spherical lignite pellets with a diameter of 60 or less.

以上説明した本発明によるペレット状褐炭製造工程を図
示すれば添付図面の如（なる。The process for producing pelleted lignite according to the present invention described above is illustrated in the accompanying drawings.

本発明による方法は前記の粉粒状褐炭を取り扱う際の自
然発火の防止、嵩高の粉粒状褐炭の高密度化による貯蔵
、供給、輸送等の効果的な取り扱いに寄与することが大
であり、更に粉粒状褐炭特有の発しんを防止して作業環
境の改善に役立つ。The method according to the present invention greatly contributes to the prevention of spontaneous combustion when handling the above-mentioned pulverulent lignite, and to the effective handling of bulky granular lignite in storage, supply, transportation, etc. by increasing its density. Helps improve the working environment by preventing the oozing that is characteristic of powdered lignite.

すなわち、炭化水素系油の微小油滴な含む懸濁液を結合
剤として粉粒状褐炭を造粒してペレット状褐炭にした効
果は圧壊強度、みかけ密度、着火点などの性状も向上し
■作業管理のうえで微粉末の飛散は作業環境の悪化、製
品損失、粉じん爆発、自然発火等の要因となるが、粉粒
状褐炭を凝集させたペレットではこれらを防ぐことがで
きる、■適当な大きさ、球形、高密度等の特性をもつペ
レットは供給、貯蔵、輸送等の自動化、連続化、省力化
等において著−い改善につながる、Φ装置、その他でペ
レットを充てん状態で使用する際には通気性がよくなり
、加熱、乾燥、化学反応等の操作で定量的に取り扱いや
すいなどの長所があげられる。In other words, the effect of granulating brown coal into pellets by using a suspension containing minute droplets of hydrocarbon oil as a binder improves properties such as crushing strength, apparent density, and ignition point. However, the scattering of fine powder can cause deterioration of the working environment, product loss, dust explosion, spontaneous combustion, etc., but pellets made by agglomerating powdery lignite can prevent these problems.■ Appropriate size, Pellets with characteristics such as spherical shape and high density lead to significant improvements in the automation, continuity, and labor saving of supply, storage, and transportation. Its advantages are that it has good properties and is easy to handle quantitatively through operations such as heating, drying, and chemical reactions.

以上の如く、本発明により比較的簡単な装置を用いて球
状の褐炭ペレットを製造することによって火災発生の要
因を取り除くことが可能になると同時に粉粒状褐炭の大
量処理を簡便なものとすることができる。As described above, by producing spherical lignite pellets using a relatively simple device, the present invention makes it possible to eliminate the causes of fire outbreaks, and at the same time, facilitates the mass processing of powdered lignite. can.

以下に示す実施例は本発明の適正な具体例を示すもので
あるが、云う迄もなく本発明はこれに限定されるもので
はない。The examples shown below show appropriate specific examples of the present invention, but it goes without saying that the present invention is not limited thereto.

実施例 木造核実験に用いた褐炭は表−１に示すような粒度分布
をもち、その含水率は３０重量−前後である。これが２
０日間の自然乾燥（夏期）後において１７重＠係の含水
率とな・つて、粒度分布での粗粒側の褐炭には細粒側の
褐炭が多小付着している形態である。この二重の粒度分
布を示す粉粒状褐炭は試料として５００ｙを加熱用ジャ
ケット付の混合機（容量１ｔ−）に入れ、混合機内壁面
の温度を１１０℃で、褐炭の温度を８０℃前後にして水
に炭化水素系油の微小油滴を含む懸濁液を徐々に注入す
ると、細粒側と粗粒側の褐炭の乾燥速度の差、ならびに
細粒側の褐炭の表面積が大なるために油分の多い細粒側
褐炭が粗粒側褐炭粒子間の架橋構造を形成せしめ、混合
機内での造粒核の形成する状態が良好となる。この造粒
核は最終的に水分４７重量％、油分５．６チとなって、
以後の造粒工程である回転ドラム型造粒機（ドラム直径
３８０ｍａ、長さｘｏｏＩｕ、回転速度４　ｏ　ｒ、ｐ
、ｍ−）によってペレット化を行った結果、直径１４乃
至２２ｔｕ程度の球状のペレットが得られ、更にこのペ
レットに対して１０メツシユ（タイラー標準篩以下で油
分１５重量％を含む粉状褐炭を１５重量％添加し、被覆
造粒を行うとひき締ったペレットが得られた。この場合
の生成ペレットの諸性状は表−２のとおりである。EXAMPLE The lignite used in the wooden core experiment had a particle size distribution as shown in Table 1, and its moisture content was around 30% by weight. This is 2
After 0 days of natural drying (summer), the moisture content is 17%, and the lignite on the coarse side of the grain size distribution has a small amount of lignite on the fine grain side attached to it. A sample of 500 y of this powdered lignite exhibiting a double particle size distribution was put into a mixer with a heating jacket (capacity 1 t), and the temperature of the inner wall of the mixer was set at 110°C, and the temperature of the lignite was set at around 80°C. When a suspension containing minute oil droplets of hydrocarbon oil is gradually injected into water, oil content increases due to the difference in the drying rate of lignite on the fine-grained side and the coarse-grained side, as well as the larger surface area of the lignite on the fine-grained side. The fine-grained lignite with a large amount of lignite forms a crosslinked structure between the coarse-grained lignite particles, and the state in which granulation nuclei are formed in the mixer becomes favorable. This granulation core finally has a moisture content of 47% by weight and an oil content of 5.6%,
The subsequent granulation process is a rotating drum type granulator (drum diameter 380 ma, length xooIu, rotation speed 4 o r, p
, m-), spherical pellets with a diameter of about 14 to 22 tu were obtained, and these pellets were further processed with 10 meshes of powdered lignite containing 15% by weight of oil using a Tyler standard sieve or less. When % by weight was added and coated granulation was performed, firm pellets were obtained.The properties of the pellets produced in this case are shown in Table 2.

表−１粉粒状褐炭の粒度分析 篩の目開き（藺）　　重量％　篩の目開き（藷）　　重
量％５．６６〜７．００　　　　８．５７　　　２．０
０〜２．５８　　　　　９，２０４．７６．５，６６　
　　　７，５３　　　１．６３〜２，００　　　　５．
１０４００〜４，７６　　　　７．７３　　　１．００
〜１６８　　　１７．５０３３６〜４．００　　　１０
．００　　　０．５９〜１．００　　　　　０１０２８
３〜３．３６　　　１８．１５　　　０．４２〜０．５
９　　　’　　　　０．４５２．３８〜２．８３　１１
３５　０．．４２以下　　　０．８５表−２褐炭ペレッ
トの諸性状 直径（代表）２０ｊ１１　　　　着火温度　　　３１０
〜？＋４０℃圧壊強度　　１８に９　　　みかけ密度　
　１．０５　ｆ　７ｃｍ３Table-1 Particle size analysis of powdered lignite Sieve opening (wt) Weight% Sieve opening (wt) Weight% 5.66-7.00 8.57 2.0
0~2.58 9,204.76.5,66
7,53 1.63-2,00 5.
10400～4,76 7.73 1.00
~168 17.50336~4.00 10
．． 00 0.59~1.00 01028
3-3.36 18.15 0.42-0.5
9' 0.452.38~2.83 11
35 0. ．． 42 or less 0.85 Table-2 Properties of lignite pellets Diameter (representative) 20j11 Ignition temperature 310
~? +40℃ crushing strength 18 to 9 apparent density
1.05 f 7cm3

【図面の簡単な説明】[Brief explanation of the drawing]

添付図面は本発明によるペレット状褐炭製造工程を示す
フローチャートである。The accompanying drawing is a flowchart showing the process for producing pelleted lignite according to the present invention.

Claims (1)

【特許請求の範囲】[Claims] ６５重量係以下の水分を含む粉粒状低品位炭を８０℃か
ら１３０℃の温度で加熱し、これに水に炭化水素系油の
微小油滴を含む懸濁液を徐々に注入しつつ最大４７重量
％の水分、ならびに５から２０重１ｆｔ％の油分を含む
造粒核を生じせしめた後、ペレット化を行ない、さらに
炭化水素系油を含む褐炭物を５から２０重量％添加して
被覆造粒処理を行って直径３０鰭以下の球形のベレット
を製造する方法。Powdered low-rank coal containing water of 65% by weight or less is heated at a temperature of 80°C to 130°C, and a suspension containing minute oil droplets of hydrocarbon oil is gradually injected into water to give a maximum of 47% by weight. After producing granulation nuclei containing 5 to 20 wt % of water and 1 ft % of oil by weight, pelletization is performed, and further 5 to 20 wt % of lignite containing hydrocarbon oil is added to form a coating. A method of producing spherical pellets with a diameter of 30 fins or less by performing grain processing.