AU2013330776A1 - Method for unloading water-containing bulk material - Google Patents

Abstract

According to the present invention, after adding, as a liquid chemical, an agent having a polymer flocculant as the main ingredient to a water-containing bulk material on a belt conveyor, a bridge crane, or in a hopper on an unloader and producing water containing bulk material and suspended aggregates in water, aggregates are inevitably formed when unloading water-containing bulk material by way of transporting with a belt conveyor, and damage due to unloading on the belt conveyor can be eliminated by the slurry water.

Description

- 1 METHOD FOR UNLOADING WATER-CONTAINING BULK MATERIAL TECHNICAL FIELD [0001] The present invention relates to a method for unloading a 5 water-containing bulk material, which has been developed to resolve defective unloading on a belt conveyer caused by free water when unloading a water-containing bulk material such as ore or coal containing water from a carrier ship, a barge, or the like with use of a bucket of a bridge crane, unloader, or continuous unloader. 10 BACKGROUND [0002] Bulk materials such as ore and coal are mainly imported from foreign countries, and mostly transported by ship. Many of these bulk materials, especially ore and coal, in recent years are high in water content, and water 15 (free water) separates from the bulk material and accumulates at the bottom of the ship's hold during the transport process. Hence, in the middle or latter part of the unloading process using an unloader or the like, not only a free water suspension in which free water is turbid with a powder occurs and accumulates in a depression formed after grabbing by a grab bucket for 20 unloading, but also the free water suspension eventually becomes slurry. This causes a problem of defective unloading. The same problem arises in an unloading process using a bucket of a continuous unloader which includes a bucket conveyer and the like. [0003] Besides, for example when heavy rain falls during unloading from the 25 ship, the bulk material increases in water content and rain water accumulates at the bottom of the hold whether or not unloading is continued, leading to the same phenomenon of defective unloading. This occurs in any country with a rainy season. There is thus a problem in that, without a roof for covering the bridge crane or unloader 30 together with the ship, the bulk material being unloaded increases in water content and eventually becomes slurry as the unloading continues, causing defective unloading. [0004] In view of such problems, for example, a method whereby when free water occurs, the free water is drawn up by a drainage facility (suction 35 machine) and then unloading is resumed has been conventionally proposed, as disclosed in each of JP S60-204526 A (Patent Literature (PTL) 1) and JP P0133135-PCT-ZZ (1/22) -2 S50-13339 Y (PTL 2). CITATION LIST Patent Literatures 5 [0005] PTL 1: JP S60-204526 A PTL 2: JP S50-13339 Y PTL 3: JP S61-60784 A PTL 4: JP S61-164658 A 10 [0006] However, the drainage methods by drawing as proposed in PTLs 1 and 2 have a problem of long operation time as the ship needs to be moved to the location of the drainage (drawing) facility each time to draw up free water or the drainage (drawing) facility needs to be moved to draw up free water from the hold. 15 [0007] Since free water occurs in a depression formed after grabbing by a grab bucket during unloading, the free water drawing operation needs to be repeatedly performed in the above-mentioned drainage method by drawing. Repeatedly stopping and resuming the unloading operation is problematic in that the operation efficiency degreases significantly. 20 [0008] Particularly in recent years, such a problem is more evident because a lot of ore and coal are of poor quality, e.g. high in water content. When ore or coal to be unloaded has a high water content, the bulk material is fluid even before free water occurs. This hampers the conveyance by the belt conveyer during unloading. Thus, not only 25 conveyance troubles but also problems with the maintenance of the belt conveyer facility arise frequently. [0009] The conventional techniques proposed in PTLs 1 and 2 are based on the assumption that only free water is drawn up. However, a powder with a small particle diameter separated from the bulk material with a large particle 30 diameter flows into the depression formed after grabbing by the grab bucket, and mostly becomes slurry. The slurry liquid is difficult to be unloaded by a conventional drainage facility, and the operation efficiency declines each time free water occurs. If such a bulk material is unloaded, the unloaded bulk material tends to flow out of the belt conveyer because of its high fluidity as 35 mentioned above. This causes defective unloading, too. [0010] To address these problems, the inventors repeatedly performed P0133135-PCT-ZZ (2/22) -3 research based on the water content reduction methods proposed in JP S61-60784 A (PTL 3) and JP S61-164658 A (PTL 4). The inventors as a result learned that the methods described in PTLs 3 and 4 have a problem in that, since a water-absorbent resin which is solid is used, it is difficult to 5 bring the water-absorbent resin into uniform contact with the bulk material during unloading, and a problem in that the water-absorbent resin swells as a result of absorbing water and so tends to drop from the belt conveyer. The inventors also learned that, given that the water-absorbent resin needs to be eventually separated from the bulk material, it is very difficult to use the 10 water-absorbent resin when unloading the water-containing bulk material. [0011] The present invention has been developed in view of the above-mentioned circumstances, and has an object of proposing a method for unloading a water-containing bulk material for resolving defective unloading on a belt conveyer caused by slurry free water which inevitably occurs when 15 unloading a water-containing bulk material. SUMMARY [0012] Primary features of the present invention are as follows. 1. A method for unloading a water-containing bulk material, wherein 20 in the case where, when unloading a water-containing bulk material including ore or coal from a cargo ship onto a belt conveyer using a grab bucket of a bridge crane or an unloader, a free water suspension in which a powder is suspended occurs and is contained in the water-containing bulk material and as a result the water-containing bulk material increases in water content, a 25 chemical agent mainly composed of a polymer flocculant is added, as a chemical solution, to the water-containing bulk material on the belt conveyer or in a hopper in the bridge crane or the unloader to form a floc of the water-containing bulk material and the free water suspension, and the floc is conveyed on the belt conveyer. 30 [0013] 2. The method for unloading a water-containing bulk material according to the foregoing 1, wherein an amount of the chemical solution added is in a range from 0.1 mass% to 1 mass% with respect to the water content of the bulk material. [0014] 3. The method for unloading a water-containing bulk material 35 according to the foregoing 1 or 2, wherein an amount of the chemical solution added is in a range from 0.15 mass% to 0.4 mass% with respect to the water P0133135-PCT-ZZ (3/22) -4 content of the bulk material. [0015] 4. The method for unloading a water-containing bulk material according to any one of the foregoing 1 to 3, wherein the bulk material, the free water, and the chemical agent in the floc of the water-containing bulk 5 material are further mixed together at a fall portion of a junction part of the belt conveyer. [0016] 5. The method for unloading a water-containing bulk material according to any one of the foregoing 1 to 4, wherein the addition of the chemical agent to the water-containing bulk material on the belt conveyer is 10 performed in spray form, and the chemical agent that has reached the belt conveyer after the spray is mixed again with the floc of the water-containing bulk material at a fall portion of a junction part of the belt conveyer. [0017] 6. The method for unloading a water-containing bulk material according to any one of the foregoing 1 to 4, wherein the addition of the 15 chemical agent to the water-containing bulk material on the belt conveyer is performed in mist spray form, and the chemical agent that has reached the belt conveyer after the mist spray is mixed again with the floc of the water-containing bulk material at a fall portion of a junction part of the belt conveyer. 20 [0018] 7. The method for unloading a water-containing bulk material according to any one of the foregoing 1 to 6, wherein the water content of the water-containing bulk material is restricted to 23 mass% or less. [0019] 8. The method for unloading a water-containing bulk material according to the foregoing 7, wherein a polymer absorbent is added to restrict 25 the water content of the water-containing bulk material. [0020] According to the present invention, even in the case where, during unloading of a bulk material in a cargo ship's hold, a free water suspension in which a powder is suspended occurs and is contained in the bulk material and the bulk material increases in water content, the bulk material can be 30 conveyed without the bulk material or the free water-derived contained water overflowing from the belt conveyer, with there being no need to perform the operation of drawing up the free water suspension. The unloading operation can be continuously performed without being stopped as in the conventional techniques, which contributes to improved unloading efficiency. 35 P0133135-PCT-ZZ (4/22) -5 BRIEF DESCRIPTION OF THE DRAWINGS [0021] The present invention will be further described below with reference to the accompanying drawings, wherein FIG. 1 is a diagram illustrating the situation where a bulk material in a 5 cargo ship is unloaded using a grab bucket of an unloader; FIG. 2(a) to (e) are a conceptual diagram illustrating the action when a polymer flocculant is added to a free water suspension; FIG. 3 is a conceptual diagram illustrating the state when a chemical solution (containing the polymer flocculant) is sprayed on the unloaded bulk 10 material in the form of a mist; FIG. 4 is a conceptual diagram illustrating the state when the chemical solution (containing the polymer flocculant) is sprayed on the unloaded bulk material in the form of a shower; FIG. 5 is a conceptual diagram illustrating a spray method for 15 facilitating the adhesion of the chemical solution when spraying the chemical solution (containing the polymer flocculant) on the unloaded bulk material in the form of a mist; FIG. 6 is a diagram illustrating a conveyance route by an ore carrier and belt conveyers after unloading; 20 FIG. 7A is a diagram illustrating the state of a pile of Carajis iron ore obtained according to each experimental condition (tests i to iii); FIG. 7B is a diagram illustrating the state of a pile of Carajis iron ore obtained according to each experimental condition (tests iv to vii); and FIG. 8 is a diagram illustrating photographing sites on the return side 25 of a belt conveyer and in the junction part at the end position of the belt conveyer. DETAILED DESCRIPTION [0022] The present invention is described in detail below. 30 As illustrated in FIG. 1, the following phenomenon is typically known. When unloading ore or coal (hereafter also referred to as "ore(s)") called a water-containing bulk material 2 (hereafter also simply referred to as a "bulk material") housed in a cargo ship's hold (cargo chamber) 1 with use of a bucket of a bridge crane or unloader 5 or continuous unloader, a pool of free 35 water forms in the lower part of the ore deposit. When the unloading operation progresses and reaches the middle to lower parts of the ore deposit, P0133135-PCT-ZZ (5/22) -6 a depression 4 is formed in part of the water-containing bulk material deposit. A free water suspension 3 in which a powder separated from the ore mainly in gravel form is dispersed and suspended accumulates in the depression 4. In the drawing, reference sign 1 is the hold, 2 is the water-containing bulk 5 material, 3 is the free water suspension, 4 is the depression, 5 is the unloader, and 6 is the grab bucket. [0023] The free water suspension 3 that emerges in the deposit of the water-containing bulk material 2 in the hold 1 gradually becomes slurry as the unloading progresses, making the unloading by the grab bucket 6 of the 10 unloader 5 or the like difficult. This is because, once the slurry has formed, even if the slurry can be grabbed by the grab bucket 6, it flows out of a hopper (not illustrated) or a belt conveyer part (not illustrated) in the unloader, as a result of which the operation of the unloader cannot be continued. Particularly at the bottom of the hold 1, the free water suspension easily 15 becomes slurry, and the unloading operation needs to be frequently stopped to perform drainage. [0024] In view of this, in the present invention, when the bulk material has a high water content and degrades the cargo handling efficiency, a polymer flocculant is added to the bulk material charged into the hopper or unloaded 20 onto the belt conveyer in the unloader (which may be a continuous unloader), to cause particle coagulation and flocculation and induce granulation, i.e. form a floc. This enables the conveyance of the free water together with the bulk material, and improves the unloading efficiency by preventing interruptions of the unloading operation. Thus, according to the present 25 invention, the free water suspension 3, namely, the components of the free water suspension 3, is solidified (as a floc) together with the water-containing bulk material 2 such as ore, so as to be conveyable by the belt conveyer. Note that the water content (amount) in the present invention is the ratio of water to the water-containing bulk material. 30 [0025] [Principle for conveyability] FIG. 2(a) and (b) illustrate water Wm contained in a free water suspension that includes a powder P, and a polymer flocculant A to be added. When A is added to P + Wm, part of Wm and P coagulates as if caught by dendritic polymers B of molecular chains in the polymer flocculant A as 35 illustrated in FIG. 2(c), and forms some coagulated particles 7 small in particle diameter as illustrated in FIG. 2(d). After this, with mixture P0133135-PCT-ZZ (6/22) -7 (including mixture during falling at the junction part), a plurality of coagulated particles 7 eventually flocculate (cluster) and grow into a flocculated particle 8 large in particle diameter as illustrated in FIG. 2(e). Accordingly, the floc of the water-containing bulk material in the present 5 invention is made up of the above-mentioned flocculated particles and coagulated particles at any ratio (either of them may be 100%). Note that % in the present invention denotes mass% unless otherwise stated. [0026] In the stage illustrated in FIG. 2(e), Wm has been solidified and is in an adhesion state of adhering to the bulk material. In such a state, the bulk 10 material can be easily conveyed on the belt conveyer, and the free water suspension can be conveyed together with the bulk material without overflowing from the belt conveyer. As a result, the bulk material can be delivered to a raw material yard or the like without any trouble. Moreover, the components of the chemical solution in the present 15 invention, such as N, C, and H, are burned by a sintering machine in the next step and do not remain in the product, and so there is no need to separate the chemical solution. The present invention is thus advantageous in that a chemical solution separation step is unnecessary. [0027] As mentioned earlier, when the water or the bulk material overflows, 20 the water or powder adhering to the back of the belt conveyer not only hampers the conveyance of the bulk material and the like, but also causes a failure of the conveyer rollers and the drive system. According to the present invention, the water and the bulk material are kept from overflowing from the belt conveyer, so that these problems can be effectively prevented 25 even when conveying the bulk material with a high water content. [0028] FIG. 3 is a diagram illustrating the case of uniformly spraying the polymer flocculant on the surface of the bulk material unloaded on the belt conveyer, in the form of a mist. In this example, though the polymer flocculant adheres only to the surface of the mixture of the bulk material and 30 Wm, such adhesion is sufficient if the bulk material has a water content of about several %. [0029] In a preferred embodiment of the present invention, the polymer flocculant is added in spray form to the bulk material with a high water content, when unloading the high water content bulk material before the 35 occurrence of the free water suspension and unloading the high water content bulk material upon and after the occurrence of the free water suspension. In P0133135-PCT-ZZ (7/22) -8 addition, the sprayed polymer flocculant that has reached the belt conveyer is discharged (re-sprayed) on the falling bulk material or free water at the fall portion of the belt conveyer junction part. This facilitates the above-mentioned coagulation action (which may include pseudo grains) and 5 flocculation action, and further enhances the unloading operation efficiency. [0030] In detail, as illustrated in FIG. 4, a chemical agent mainly composed of the polymer flocculant is sprayed directly as the chemical solution in the form of a shower so that the polymer flocculant supplied as a shower not only adheres to the surface of the bulk material but also passes through the bulk 10 material and reaches the surface of the belt conveyer. As a result of such spray, even if the adhesion of the polymer flocculant at the time of spray is not uniform in the width direction of the bulk material, once the bulk material is conveyed to the belt conveyer junction (fall port), the polymer flocculant remaining on the belt surface mixes again with the falling bulk material or 15 free water. This promotes the mixture of the polymer flocculant and the bulk material or the free water, and facilitates the action of forming the floc by mixing the bulk material, the free water, and the polymer flocculant, as compared with the case where the polymer flocculant is supplied in the form of a mist. 20 [0031] FIG. 5 illustrates another spray procedure. In this example, not only the polymer flocculant is sprayed in the form of a mist on the surface of the bulk material to adhere to the surface, but also the chemical agent mainly composed of the polymer flocculant is directly sprayed as the chemical solution in the form of a mist on the back (rear) of the bulk material upstream 25 of the belt conveyer junction part, and further the chemical agent mainly composed of the polymer flocculant is sprayed as the chemical solution in the form of a mist on the surface of the bulk material. With this spray method, the polymer flocculant mixes with the bulk material and the free water effectively. Hence, even when the polymer flocculant is supplied in the form 30 of a mist, the mixture with the polymer flocculant progresses to facilitate the flocculation action of the bulk material, the free water, and the polymer flocculant. [0032] [Polymer flocculant] In the present invention, the chemical agent mainly composed of the 35 polymer flocculant is used as the chemical solution. Alternatively, if the chemical agent is solid, the chemical agent is dispersed in a solution and used P0133135-PCT-ZZ (8/22) -9 as the chemical solution. The polymer flocculant may be any polymer flocculant that has an adsorption activity on a powder and induces an inter-powder crosslinking action by the electrostatic force or hydrogen bond of the polymer, and has the 5 effect of forming a solid granulated structure to generate coagulated particles (floc). For example, flocculants such as polyacrylamide (copolymer of acrylamide and sodium acrylate), polyvinyl amidine, and an amphoteric polymer, which are powdery, granular, or liquid organic flocculants, are preferable as they exhibit not only the coagulation action but also the 10 flocculation action. A well-known inorganic flocculant may also be mixed together. As the polymer flocculant, an acrylate cationic polymer, an acrylamide cationic polymer, a methacrylate polymer, a methacrylate amino ester cationic polymer, an amidine polymer, an anionic W/O emulsion polymer, 15 and the like are available, too. [0033] In the present invention, the chemical agent mainly composed of the polymer flocculant is a chemical agent that contains at least the amount of the polymer flocculant commonly recognized to have the flocculation effect, and is typically a chemical agent that contains about 40% or more the polymer 20 flocculant. The 100% polymer flocculant may be used as the chemical agent. In the case where the chemical agent is solid or is used in diluted state, the solution may be water or an organic solvent, the solute may be a polymer of C, H, N, and 0, and the solvent may be a hydrocarbon solvent (only C, H, and 0). 25 [0034] The addition amount of the chemical solution in the present invention is preferably about 0.1% to 1% with respect to the water content of the bulk material. When the addition amount is within this range, the fluidity due to excess water decreases, and the viscosity when the flocculant is excessively 30 added is suppressed, as confirmed in the below-mentioned test results. The addition amount is more preferably about 0.15% to 0.4% with respect to the water content of the bulk material. Note that the addition ratio (amount) of the chemical solution in the present invention is the ratio to the water content of the bulk material as mentioned above. 35 The addition speed of the chemical solution is not particularly limited, and may be set as appropriate depending on the facility and the like. As an P0133135-PCT-ZZ (9/22) - 10 example, the addition speed is about 2 L/min to 10 L/min. [0035] The following describes an experiment performed using a conveyance route illustrated in FIG. 6, to determine the working effects of the present invention. 5 In this experiment, 700 t of Brazilian Carajais iron ore with a water content of 9.6% was used, and an unloader was used as unloading means. While ordinary ore has water retentivity, Carajis iron ore is low in water retentivity and, with a water content of about 8.0%, can possibly generate a free water suspension which hampers unloading. 10 [0036] Table 1 shows the experimental conditions of test 1. In the experiment, each 100 t Caraj is iron ore with a water content of 9.6% was used with a different chemical solution addition method, ore conveyance amount, and chemical solution addition speed and concentration. In the table, the flow time means the time during which the chemical agent was added. 15 The polymer flocculant in the chemical agent was a polymer such as an acrylate cationic polymer, an acrylamide cationic polymer, a methacrylate polymer, a methacrylate amino ester cationic polymer, an amidine polymer, an anionic W/O emulsion polymer, or the like, and the chemical agent itself was used as the chemical solution. 20 [0037] (Table 1) Table 1 Test i ii iii iv V Vi Vii Addition form - Mist Straight Straight Mist Straight Straight Ore amount (t) 100 100 100 100 100 100 100 Flow time (s) 780 420 360 230 330 420 240 Water content (%) 9.6 9.6 9.6 9.6 9.6 9.6 9.6 Chemical solution addition speed (L/min) - 3 3 6 6 4.9 4 Chemicalsolutionconcentration (%) - 0.22 0.19 0.24 0.34 0.36 0.17 Rating C C A B C B A [0038] Unloading from an ore carrier was performed using a grab bucket of the unloader, and a part of a second belt conveyer (OR-62) following a first 25 belt conveyer which runs along the pier was set as the chemical solution addition position for the experiment. In the drawing, the positions a to f in the dotted squares indicate belt conveyer junction parts. In this experiment, there were five belt conveyer junction parts, namely, the second belt conveyer (OR-62) end b, the third belt conveyer (OR-63S) end c, the fourth belt P0133135-PCT-ZZ (10/22) - 11 conveyer (OR-74R) end d, the fifth belt conveyer (OR-75) end e, and the sixth belt conveyer (OR-24) end f. The first belt conveyer (OR-61) is the top belt conveyer for unloading by the grab bucket. In actual equipment, the first belt conveyer may be the chemical 5 solution addition position. [0039] The experimental results are described below, with reference to FIG. 7 and Table 1. FIG. 7 illustrates, in photographs, piles of Carajis iron ore obtained according to the experimental conditions shown in Table 1 using 100 t ore 10 each, in the process of unloading from the ore carrier. In the case of experiment 1 (test i) not using the polymer flocculant, a part where the bulk material flowed out was observed at the foot of the pile. When the bulk material is conveyed on the belt conveyer, such a flow-out part is likely to adhere to the belt or overflow from the belt and adhere to the back of the belt 15 conveyer and hamper the conveyance, and also adhere to the conveyer rollers or the drive system and cause a failure, as mentioned above. A clogging accident due to the adhesion substance or the like is expected to occur at the belt conveyer junction parts. [0040] In the cases of experiment 2 (test ii) and experiment 5 (test v), the 20 chemical solution was added (mist spray addition) in the form of a mist at respective ratios of 0.22% and 0.34%. In the case of experiment 2 (test ii), no part where the bulk material flowed out was observed at the foot of the pile, but the adhesion substance to the belt was observed. This is probably due to an insufficient amount of the 25 polymer flocculant mixed with the bulk material and the free water in the mist addition. [0041] In the case of experiment 5 (test v), i.e. the example where the addition ratio of the chemical solution was increased, clumps of the powder were observed at the foot of the pile, while there was no adhesion substance to 30 the belt. Such clumps are expected to cause dropping from the belt conveyer. The powder clumps can be attributed to the uneven mixture of the polymer flocculant, and are assumed to have occurred in parts with a large amount of the chemical solution. These assumptions are based on the following: when the chemical 35 solution was added in a state where the ore was not present on the belt conveyer, a phenomenon of the high-viscosity chemical agent accumulating P0133135-PCT-ZZ (11/22) - 12 on the belt lower part in the cleaner portion of the tail (inversion part) of the belt took place. [0042] In the cases of experiment 3 (test iii), experiment 4 (test iv), experiment 6 (test vi), and experiment 7 (test vii), a different chemical 5 solution addition method was used to determine the difference between the mist spray method and the straight spray method. The chemical solution was added at respective ratios of 0.19%, 0.24%, 0.3 6%, and 0.17%, using the straight spray method, i.e. the method of spraying in the form of a shower over the unloaded bulk material on the belt conveyer. 10 [0043] The results of the experiments show that advantageous effects were observed with a small addition amount in the straight method as compared with the mist (mist spray addition) method, with no adhesion substance to the belt. In the cases of experiments 4 and 6 in which the chemical solution was added at high ratios (respectively 0.24% and 0.36%), small clumps were 15 observed at the foot of the pile, but to such an extent that is expected to cause no dropping from the belt conveyer. This expectation is based on the fact that, when actually touching the clumps with hand, the surface was not viscous. [0044] The above-mentioned results are summarized as follows. As 20 described earlier with reference to FIG. 3, in the case of uniformly spraying the polymer flocculant on the surface of the bulk material in the form of a mist, the polymer flocculant adheres only to the surface of the mixture of the bulk material and Wm. When the bulk material and Wm are conveyed to the belt conveyer junction (fall port) in such a state, the adhesion of the bulk material 25 and Wm by the polymer flocculant is not facilitated because the polymer flocculant adheres only to the surface of the bulk material, and so the bulk material and Wm continue to be conveyed in a separate state. This leads to overflow from the belt conveyer, which causes various troubles (rating: B or C). 30 [0045] In the experiment, the rating levels A, B, and C in Table 1 are as follows. A: Improved overall, with no clumps and no sticky surface. B: Improved overall, but has some sticky (clumpy) part due to excessive chemical agent. 35 C: Has improved part and unimproved part, and also has part with excessive chemical agent (clumpy). P0133135-PCT-ZZ (12/22) - 13 [0046] In the case of using the straight spray method (see FIG. 4), the polymer flocculant passes through the bulk material and reaches the surface of the belt conveyer, as illustrated in FIG. 4. Accordingly, even if the amount of adhesion of the polymer flocculant on the surface of the bulk material is not 5 uniform upon spray, when the bulk material is conveyed to the belt conveyer junction (fall port), the polymer flocculant remaining on the belt surface mixes again with the falling bulk material and free water. This facilitates the mixture with the polymer flocculant as compared with the supply of the polymer flocculant in the form of a mist, thus contributing to the rating A. 10 [0047] (Example of experiment on addition range) The following experiment was performed using the chemical agent mainly composed of the polymer flocculant used in the present invention. The chemical agent used was Kurisat® (Kurita Water Industries Ltd.) in Table 2, and Hybrid Polymer-a@ (Technica Goudou Co., Ltd.) in Table 3. 15 Both chemical agents have been proposed as soil conditioners. Water was added to Carajis iron ore and the water content was adjusted, and then the chemical agent was directly added as the chemical solution. Whether or not the improvement is possible was determined while adjusting the stirring time. 20 [0048] Since Table 1 shows that the water content of 9.6% causes no problem according to the present invention, this experiment was performed to determine whether or not the improvement is possible without causing any problem in unloading as in the experimental results shown in Table 1 in the case where the water content exceeds 9.6%. The improvement means that 25 the bulk material can be conveyed on the belt conveyer. Whether or not the bulk material was able to be conveyed was used as the criterion for the improvement. [0049] As shown in Table 2, the experiment to determine the improvement of the bulk material was performed by using Kurisat as the chemical agent, 30 which itself was used as the chemical solution, and setting the water content of the bulk material to 12% or more, which exceeds 9.6%. In a first experiment, the addition amount of the chemical solution was 0.4%. In a second experiment, the addition amount of the chemical solution was increased to 1.0%. 35 P0133135-PCT-ZZ (13/22) - 14 [0050] (Table 2) Table 2 Test No. Concentration Water content Improvement Stirring time Remarks (mass%) masss) (s) 1 0.4 54 Not improved - Not solidified 2 0.4 24 Not improved - Not solidified 3 0.4 20 Improved 80 Solidified 4 0.4 17 Improved 60 Solidified 5 0.4 12 Improved 30 Solidified 6 1.0 54 Not improved - Not solidified 7 1.0 24 Not improved - Not solidified 8 1.0 20 Improved 60 Solidified 9 1.0 17 Improved 50 Solidified 10 1.0 12 Improved 50 Solidified [0051] As a result, the improvement of the bulk material was possible even 5 when the water content of the bulk material was 20% which exceeds 9.6%, but the improvement of the bulk material was difficult when the water content was 24% or more, as shown in Table 2. The second experiment was then performed with the addition concentration of the chemical solution being increased from 0.4% to 1.0%. 10 The improvement of the bulk material was difficult when the water content of the bulk material was 24% or more, as in the first experiment. [0052] Next, the experiment was performed by using Hybrid Polymer-a as the chemical agent, which itself was used as the chemical solution, and setting the water content of the bulk material to 11% or more, which exceeds 9.6%, as 15 shown in Table 3. Moreover, since the results shown in Table 2 demonstrate that the improvement of the bulk material is difficult when the water content of the bulk material is 24% or more, one of the water content test standards was changed from 24% to 23%. Meanwhile, the maximum water content was the same 54% as in the experiment shown in Table 2. 20 P0133135-PCT-ZZ (14/22) - 15 [0053] (Table 3) Table 3 Test No. Concentration Water content Improvement Stirring time Remarks (mass%) (mass%) (s) 1 0.1 54 Not improved - Not solidified 2 0.1 23 Partially Improved 50 Slightly solidified 3 0.1 19 Improved 40 Solidified 4 0.1 16 Improved 40 Solidified 5 0.1 11 Improved 40 Solidified 6 0.2 54 Not improved - Not solidified 7 0.2 23 Improved 40 Solidified 8 0.2 19 Improved 40 Solidified 9 0.2 16 Improved 40 Solidified 10 0.2 11 Improved 40 Solidified [0054] A third experiment was performed by setting the addition 5 concentration of the chemical solution to 0.1%. As a result, the improvement of the bulk material was possible even when the water content of the bulk material was 20% which exceeds 9.6%. On the other hand, the following problem in the improvement was found in the case where the water content of the bulk material was 23%: the bulk material solidified only 10 slightly. To solve this problem, the experiment was performed again with the addition concentration of the chemical solution being changed from 0.1% to 0.2%. As a result, the above-mentioned problem in the condition of a water content of 23% was resolved by increasing the chemical solution concentration. 15 The present invention can thus be implemented in unloading of Carajds iron ore with a water content of 23% or less. [0055] In unloading of Carajds iron ore, in the case where the water content which is determined from the occurrence of the free water suspension, measured using an on-line measuring device such as a neutron moisture gauge, 20 or determined by simple water content measurement in an analysis center from a sample taken by an autosampler is 24% or more, the water content may be decreased to 23% or less in the following manner as an example: Carajds iron ore around the free water part, which is low in water content, is charged into P0133135-PCT-ZZ (15/22) - 16 the free water part high in water content using a grab bucket or a grab portion of a continuous unloader, and then the Carajis iron ore and the free water are unloaded simultaneously. The water content can also be restricted by adding a polymer absorbent (water-absorbent polymer). Such a procedure can 5 resolve the problem of excessive water content, and so is advantageous in actual operation. [0056] Although the present invention has been described above using Carajis iron ore as an example, other ores may also be used so long as they conform to the conditions of the present invention. In the case of using new 10 iron ore, the target value of the water content can be determined by subjecting the new iron ore to the experiments such as the first and second experiments mentioned above. EXAMPLES 15 [0057] The addition of the chemical solution was started when, during unloading of Carajis iron ore from the carrier ship, the water content reached the level of 9.6% or more, i.e. the excessive water level. The time at which the water content reached the level of 9.6% or more can be determined from the occurrence of the free water suspension in the 20 depression formed after grabbing by the grab bucket when unloading the Carajis iron ore from the carrier ship. In detail, the water content can be estimated from the amount of the free water suspension occurring after grabbing by the grab bucket and the capacity of the grab bucket. Alternatively, when unloading the Carajis iron ore from the carrier ship, upon 25 the first unloading operation the water content change of the Carajis iron ore may be measured by an on-line measuring device such as a neutron moisture gauge or analyzed by simple water content measurement in an analysis center from a sample taken by an autosampler so that whether or not the next unloading from the carrier ship reaches the water content level of 9.6% or 30 more is estimated from the relationship between the water content change and the amount of free water suspension (measured visually) occurring after grabbing by the grab bucket. To minimize the possibility that the free water-derived contained water overflows from the belt conveyer, it is safe to start adding the chemical 35 agent to the bulk material upon unloading when the water content level of 9.6% or more is reached. P0133135-PCT-ZZ (16/22) - 17 [0058] (Example 1) The following experiment was performed with the chemical agent addition position being set on the first belt conveyer in FIG. 6. Upon unloading Carajds iron ore with a water content of 7.9% to 23% 5 from the carrier ship, the chemical solution was added under each of the conditions where the improvement is possible from among the conditions shown in Tables 2 and 3. As the chemical solution, Kurisat C-333L and Hybrid Polymer-a were used. Kurisat C-333L and Hybrid Polymer-a are both liquids. 10 The effect of the addition was determined by photographing, after the unloading completion, the return side (I) of the belt conveyer and (II), (III), and (IV) of the junction part at the belt conveyer end position illustrated in FIG. 8. [0059] The determination results reveal that, while a slight adhesion 15 substance occurred at the positions a and b in FIG. 6, no adhesion substance occurred from the positon c onward (the return side (I) and (II), (III), and (IV) of the junction part at the belt conveyer end position illustrated in FIG. 8, from the third belt conveyer onward), and Carajis iron ore was successively unloaded. 20 [0060] (Example 2) The following experiment was performed with the chemical solution addition position being set on the belt conveyer downstream of the hopper of the first belt conveyer in FIG. 6. The same addition conditions and the chemical solution of the same 25 components as those in Example 1 were used. The effect of the addition was determined in the same way as in Example 1. [0061] The determination results reveal that, while a slight adhesion substance occurred at the position a in FIG. 6, no adhesion substance occurred from the positon b onward (the return side (I) and (II), (III), and (IV) of the 30 junction part at the belt conveyer end position illustrated in FIG. 8, from the second belt conveyer onward), and Carajis iron ore was successively unloaded. [0062] In conventional Carajds iron ore transport, a large amount of free water occur during unloading on land because Caraj is iron ore has a high 35 water content, as mentioned above. Accordingly, the iron ore is unloaded while intermittently performing a free water suspension removal (drainage) P0133135-PCT-ZZ (17/22) - 18 operation. Suppose the iron ore unloading efficiency when there is no free water is 100%. With the conventional unloading method that involves the drainage operation, the unloading efficiency decreased to 65%. In Example 2 5 described above, on the other hand, the unloading efficiency of about 92% was achieved by employing the unloading method that conforms to the present invention. [0063] The same applies to the case of unloading iron ore that has become excessive in water content as a result of continuing unloading by an unloader 10 during heavy rain. The unloading of iron ore by the grab bucket of the unloader was continued during heavy rain. When unloading, from the carrier ship, the iron ore in a state where free water caused by an increase in water content due to heavy rain started to be observed at the stage of reaching the lower part of the 15 iron ore in the latter half of the unloading as the unloading operation progressed, an acrylamide polymer flocculant was added at the chemical solution addition position set on the second belt conveyer in FIG. 6. Suppose the iron ore unloading efficiency when there is no free water due to heavy rain is 100%. With the conventional unloading method that 20 involves the drainage operation, the unloading efficiency decreased to 65% after the occurrence of free water. By employing the unloading method that conforms to the present invention, on the other hand, the unloading efficiency of about 90% was maintained even after the occurrence of free water due to heavy rain. 25 INDUSTRIAL APPLICABILITY [0064] The bulk material unloading technique according to the present invention described above can be applied to operations of unloading bulk materials that include not only water-containing ore or coal mentioned above 30 but also gravel, sand, grain, etc. REFERENCE SIGNS LIST [0065] 1 hold 2 bulk material 35 3 free water suspension 4 depression P0133135-PCT-ZZ (18/22) -19 5 unloader 6 grab bucket 7 small coagulated particle 8 large flocculated particle 5 A polymer flocculant B polymer P powder Wm water 10 P0133135-PCT-ZZ (19/22)

Claims (8)

1. A method for unloading a water-containing bulk material, wherein in the case where, when unloading a water-containing bulk 5 material including ore or coal from a cargo ship onto a belt conveyer using a grab bucket of a bridge crane or an unloader, a free water suspension in which a powder is suspended occurs and is contained in the water-containing bulk material and as a result the water-containing bulk material increases in water content, a chemical agent mainly composed of a polymer flocculant is added, 10 as a chemical solution, to the water-containing bulk material on the belt conveyer or in a hopper in the bridge crane or the unloader to form a floc of the water-containing bulk material and the free water suspension, and the floc is conveyed on the belt conveyer. 15

2. The method for unloading a water-containing bulk material according to claim 1, wherein an amount of the chemical solution added is in a range from 0.1 mass% to 1 mass% with respect to the water content of the water-containing bulk material. 20

3. The method for unloading a water-containing bulk material according to claim 1 or 2, wherein an amount of the chemical solution added is in a range from 0.15 mass% to 0.4 mass% with respect to the water content of the 25 water-containing bulk material.

4. The method for unloading a water-containing bulk material according to any one of claims 1 to 3, wherein the water-containing bulk material, the free water, and the 30 chemical agent in the floc are further mixed together at a fall portion of a junction part of the belt conveyer.

5. The method for unloading a water-containing bulk material according to any one of claims 1 to 4, 35 wherein the addition of the chemical agent to the water-containing P0133135-PCT-ZZ (20/22) -21 bulk material on the belt conveyer is performed in spray form, and the chemical agent that has reached the belt conveyer after the spray is mixed again with the floc of the water-containing bulk material at a fall portion of a junction part of the belt conveyer. 5

6. The method for unloading a water-containing bulk material according to any one of claims 1 to 4, wherein the addition of the chemical agent to the water-containing bulk material on the belt conveyer is performed in mist spray form, and the 10 chemical agent that has reached the belt conveyer after the mist spray is mixed again with the floc of the water-containing bulk material at a fall portion of a junction part of the belt conveyer.

7. The method for unloading a water-containing bulk material 15 according to any one of claims 1 to 6, wherein the water content of the water-containing bulk material is restricted to 23 mass% or less.

8. The method for unloading a water-containing bulk material 20 according to claim 7, wherein a polymer absorbent is added to restrict the water content of the water-containing bulk material. P0133135-PCT-ZZ (21/22)