FP07-0156-00 DESCRIPTION METHOD OF UTILIZING BY-PRODUCT WATER AND SYSTEM FOR UTILIZING BY-PRODUCT WATER Technical Field 5 [0001] The present invention relates to a reuse process of by-product water and to a reuse plant of by-product water. Background Art [0002] GTL (Gas to Liquids) is a known technology whereby hydrocarbon oils such as kerosene and gas oil are manufactured from 10 natural gas (hydrocarbon gas) by Fischer-Tropsch synthesis (hereinafter, "FT synthesis") reaction (for example, see Patent documents 1 and 2). GTL technology involves a synthetic gas production step in which oxygen, steam and carbon dioxide are introduced into natural gas composed mainly of methane to produce 15 synthetic gas containing hydrogen and carbon monoxide, an FT synthesis step in which the synthetic gas produced in the synthetic gas production step is subjected to FT synthesis reaction to produce FT synthetic oil composed mainly of normal paraffms, and a cracking/refining step in which the FT synthetic oil produced in the FT 20 synthesis step is cracked and refined to produce hydrocarbon oils such as naphtha, kerosene, gas oil and lubricating base oil. [Patent document 1] Japanese Unexamined Patent Publication HEI No. 7-62356 [Patent document 2] Japanese Unexamined Patent Publication No. 25 2006-22283 Disclosure of the Invention -2 Problems to be Solved by the Invention [0003] In the prior art, however, the by-product water resulting as a by product of the synthetic gas production step or FT synthesis step is released directly as waste water. With the increasing awareness of environmental 5 problems in recent years, it has been a goal to prevent pollution by waste water or to reutilize waste water. [0004] The present invention has been accomplished with the aim of solving the problems described above, and it seeks to provide a reuse process of by-product water and a reuse plant of by-product water for reduced 10 environmental burden. Means for Solving the Problems [0005] The reuse process of by-product water of a first aspect of the invention is a reuse process of by-product water which utilizes by-product water resulting as a by-product of a synthetic gas production step and/or 15 Fischer-Tropsch synthesis step, the reuse process of by-product water being characterized by: comprising a by-product water treatment step in which oxygen containing hydrocarbons in the by-product water are removed by membrane separation and an alcohol extraction step in which the alcohols are extracted 20 from the oxygen-containing hydrocarbons removed in the by-product water treatment step; and in that the treated water from which the oxygen-containing hydrocarbons have been removed by the by-product water treatment step is utilized as boiler feed water, process steam, heating steam, cooling water 25 and/or fire-fighting water. [0006] According to this reuse process of by-product water, since a by- -3 product water treatment step is provided in which oxygen-containing hydrocarbons are removed from by-product water produced by a synthetic gas production step and/or Fischer-Tropsch synthesis step, and the treated water from which the oxygen-containing hydrocarbons have been removed by the 5 by-product water treatment step is reutilized as boiler feed water, process steam, heating steam, cooling water and/or fire-fighting water, it is possible to reduce the waste water volume discharged out from the system into rivers and seas. It is also possible to reduce the amount of industrial water used. As a result, the burden on the environment can be alleviated. Moreover, 10 reutilization of the by-product water is facilitated because oxygen-containing hydrocarbons that tend to cause corrosion of equipment such as tanks and conduits is removed when the by-product water is reutilized. As examples of oxygen-containing hydrocarbons in by-product water there may be mentioned alcohols, aldehydes, carboxylic acids and the like. 15 [0007] In the by-product water treatment step, the oxygen-containing hydrocarbons are preferably removed so that alcohols are present at no greater than 100 ppm by weight in the treated water. This will reduce the alcohol concentration of the treated water to facilitate reutilization of the by-product water. 20 [0008] Also, boiler feed water preferably has a pH of 8.5-9.5, an electrical conductivity at 25*C of no greater than 0.05 mS/m, a hardness of below the measurement threshold value, as calculated from the lower limit of measurement by the calcium and magnesium test methods of JISB8224, a dissolved oxygen content of no greater than 100 pzg/l, an iron content of no 25 greater than 30 pig/l, a copper content of no greater than 10 pig/l and a hydrazine content of at least 0.01 mg/l. This can prevent damage to the boiler -4 to which the boiler feed water is supplied. [0009] The concentration of alcohols in the by-product water is preferably at least 1 wt%. [0010] The by-product water treatment step preferably includes at least 5 one selected from among a biological treatment step in which the oxygen containing hydrocarbons are decomposed by organisms, an adsorption step in which the oxygen-containing hydrocarbons are adsorbed for removal, a flocculating step in which the oxygen-containing hydrocarbons are flocculated for removal and a membrane separation treatment step in which 10 the oxygen-containing hydrocarbons are removed by membrane separation. [0011] In a second aspect of the invention there is provided a reuse plant of by-product water which utilizes by-product water resulting as a by-product of a synthetic gas production apparatus and/or Fischer-Tropsch synthesis apparatus, the reuse plant of by-product water being characterized by: 15 comprising a by-product water treatment apparatus in which oxygen containing hydrocarbons in the by-product water are removed by membrane separation and an alcohol extraction apparatus in which the alcohols are extracted from the oxygen-containing hydrocarbons removed in the by product water treatment apparatus; and 20 a by-product water utilizing installation wherein the treated water from which the oxygen-containing hydrocarbons have been removed by the by product water treatment apparatus is utilized as at least one type of water from among boiler feed water, process steam, heating steam, cooling water and fire-fighting water. 25 [0012] - 5 [0013] According to the reuse plant of by-product water, a by-product water treatment apparatus is provided in which oxygen-containing hydrocarbons are removed from by-product water produced by a synthetic gas production apparatus and/or Fischer-Tropsch synthesis apparatus, and it has a 5 by-product water utilizing installation wherein the treated water from which the oxygen-containing hydrocarbons have been removed by the by-product water treatment apparatus can be utilized as boiler feed water, process steam, heating steam, cooling water and/or fire-fighting water, so that it is possible to reduce the waste water volume discharged out from the system into rivers and 10 seas. It is also possible to reduce the amount of industrial water used. As a result, the burden on the environment can be alleviated. Effect of the Invention [0014] According to the reuse process of by-product water and reuse plant of by-product water of the invention, it is possible to reutilize by- C:\NRPonblDCC\NJL\379 41 1_ DOC-9/0/2u111 -6 product water and thereby reduce the environmental burden. Brief Description of the Drawings [0015] Fig. 1 is a process diagram for a hydrocarbon oil manufacturing system according to an embodiment of the invention. Fig. 2 is a graph 5 showing the oxygen-containing hydrocarbon content in by-product water produced by the FT synthesis apparatus in Fig. 1. Explanation of Symbols [0016] 1: Synthetic gas production apparatus, 2: FT synthesis apparatus, 3: cracking/refining apparatus, 4: by-product water treatment apparatus, 10 5: cooler, 6: boiler, 7: deaerating treatment apparatus, 8: fire-fighting installation, 9: alcohol extraction apparatus. Best Modes for Carrying Out the Invention [0017] A preferred embodiment of a hydrocarbon oil manufacturing system employing the reuse process of by-product water and reuse plant of 15 by-product water of the invention will now be explained with reference to the accompanying non-limiting drawings. Throughout the explanation of the drawings, identical or corresponding elements will be referred to by like reference numerals and will be explained only once. Fig. I is a process diagram for a hydrocarbon oil manufacturing system according to an 20 embodiment of the invention. [0018] The hydrocarbon oil manufacturing system of this embodiment is provided with a hydrocarbon oil manufacturing apparatus which uses GTL (Gas to Liquids) technology to manufacture hydrocarbon oils such as naphtha, kerosene, gas oil and lubricating base oil, from natural gas (hydrocarbon gas) 25 as the starting material, and the hydrocarbon oil manufacturing apparatus C:\NRPonbl\DCCNJL 7- _I I -DOC-9/u/2011 - 6A comprises a synthetic gas production apparatus 1 that produces synthetic gas (Syn Gas) composed mainly of hydrogen and carbon monoxide from natural gas, an FT synthesis apparatus 2 that produces a liquid reaction product containing FT synthetic oil (FT-L-Oil; light oil) composed mainly of normal 5 paraffins by FT synthesis reaction of the synthetic gas produced by the synthetic gas production apparatus 1, and a cracking/refining apparatus 3 that produces hydrocarbon oils as the products from the FT synthetic oil in the reaction product. [0019] The synthetic gas production apparatus 1 supplies oxygen, steam 10 (process steam) and carbon dioxide to the natural gas composed mainly of methane to produce a synthetic gas composed of hydrogen and carbon monoxide. The produced synthetic gas is fed to the FT synthesis apparatus 2. [0020] The FT synthesis apparatus 2 obtains a reaction product from FP07-0156-00 the synthetic gas by FT synthesis reaction. The reaction product contains FT synthetic oil consisting mainly of normal (straight-chain) paraffms (and) including olefms, by-product water and by-product oxygen-containing hydrocarbons. The FT synthetic oil from which 5 the by-product water and by-product oxygen-containing hydrocarbons have been removed is fed to the cracking/refining apparatus 3. [0021] The cracking/refining apparatus 3 carries out treatment such as cracking and refining of the FT synthetic oil, manufacturing products such as naphtha, kerosene, gas oil and lubricating base oil. 10 [0022] The hydrocarbon oil manufacturing apparatus is provided with a cooler 5 that cools the process fluids, a boiler 6 that generates steam, a deaerating treatment apparatus 7 for obtaining the boiler feed water and a fire-fighting installation 8 capable of discharging fire-fighting water during times of emergency. 15 [0023] The hydrocarbon oil manufacturing apparatus of this embodiment is provided with a by-product water treatment apparatus 4 which removes the oxygen-containing hydrocarbons in the by-product water discharged from the synthetic gas production apparatus 1 and FT synthesis apparatus 2, and a by-product water utilizing installation for 20 reutilization of the treated water from which the oxygen-containing hydrocarbons have been removed by the by-product water treatment apparatus 4. As oxygen-containing hydrocarbons there may be mentioned alcohols, aldehydes, carboxylic acids and the like. The reuse plant of by-product water of the invention comprises the by 25 product water treatment apparatus 4 and the by-product water utilizing installation. 7 FP07-0156-00 [0024] Fig. 2 is a graph showing the oxygen-containing hydrocarbon content in by-product water produced by the FT synthesis apparatus 2, with the numbers of carbon atoms represented on the horizontal axis and the alcohol (R-OH) and carboxylic acid (R-COOH) mass 5 represented on the vertical axis. This graph shows that the C2 carboxylic acid content is greatest, followed by the C2 alcohol content. [0025] The by-product water treatment apparatus 4 removes the oxygen-containing hydrocarbons from the by-product water, and preferably it includes a denitrification step and a nitrification step, with 10 at least one function from among a biological treatment function whereby the oxygen-containing hydrocarbons are decomposed by organisms, an adsorbing function whereby the oxygen-containing hydrocarbons are adsorbed onto active carbon or the like, a flocculating function whereby a flocculating agent (for example, an inorganic 15 flocculating agent such as aluminum sulfate, a pH adjustor or a macromolecular flocculating agent) is supplied for flocculating removal of the oxygen-containing hydrocarbons, and a membrane separation function whereby the oxygen-containing hydrocarbons are membrane-separated using, for example, an RO membrane or UF 20 membrane, while it may also be constructed with a plurality of these functions. The concentration of alcohols in the by-product water fed to the by-product water treatment apparatus 4 is preferably at least 1 wt%. The oxygen-containing hydrocarbons are preferably removed to such a degree that the concentration of alcohols in the treated water is 25 no greater than 100 ppm by weight. [0026] The by-product water utilizing installation to which the treated 8 FP07-0156-00 water is supplied may be a cooler 5, boiler 6, deaerating treatment apparatus 7, fire-fighting installation 8 or the like, and the supplied treated water may be reutilized in a hydrocarbon oil manufacturing apparatus as cooling water, heating steam, process steam, boiler feed 5 water, fire-fighting water or the like. As process steam there may be mentioned feed steam that is injected into natural gas during synthetic gas production steps. Industrial water may also be supplied to the by product water utilizing installation. [0027] The deaerating treatment apparatus 7 is used to obtain boiler 10 feed water (BFW), and it is provided with a deaerator for removal of the dissolved oxygen in the treated water, a chemical dosing installation, and the like. As the properties of the boiler feed water treated by the deaerating treatment apparatus 7, it preferably has a pH of 8.5-9.5, an electrical conductivity at 25*C of no greater than 0.05 15 mS/m, a hardness of below the measurement threshold value, as calculated from the applied lower limit of measurement by the calcium and magnesium test methods of JISB8224, a dissolved oxygen content of no greater than 100 pg/l, an iron content of no greater than 30 pg/l, a copper content of no greater than 10 gg/l and a hydrazine content of at 20 least 0.01 mg/l. Supplying boiler feed water with these specifications can prevent damage to the boiler. [0028] The hydrocarbon oil manufacturing apparatus of this embodiment is also provided with an alcohol extraction apparatus 5 that extracts alcohols from the oxygen-containing hydrocarbons 25 removed by the by-product water treatment apparatus 4. This can yield alcohols as chemical products. 9 FP07-0156-00 [0029] A process for manufacturing hydrocarbon oil by application of the reuse process of by-product water of the invention will now be explained. The hydrocarbon oil manufacturing process involves a hydrocarbon oil manufacturing step wherein hydrocarbon oils such as 5 naphtha, kerosene, gas oil and lubricating base oil are manufactured from natural gas (hydrocarbon gas) as the starting material, and the hydrocarbon oil manufacturing process comprises a synthetic gas production step in which synthetic gas composed mainly of hydrogen and carbon monoxide is produced from natural gas, an FT synthesis 10 step in which the synthetic gas produced in the synthetic gas production step is subjected to FT synthesis reaction to produce a liquid reaction product containing FT synthetic oil composed mainly of normal paraffms, and a product yielding step in which hydrocarbon oils are yielded as fished products from the FT synthetic oil in the reaction 15 product. [0030] First, the synthetic gas production step is carried out by the synthetic gas production apparatus 1, whereby oxygen, steam (feed steam) and carbon dioxide are fed to natural gas composed mainly of methane, and synthetic gas composed of hydrogen and carbon 20 monoxide is produced, after which the produced synthetic gas is fed to the FT synthesis step. [0031] Next, the FT synthesis step is carried out by the FT synthesis apparatus 2, whereby a reaction product is obtained by FT synthesis reaction from the synthetic gas. The reaction product contains FT 25 synthetic oil consisting mainly of normal (straight-chain) paraffms (and) including olefins, by-product water and by-product alcohols. 10 FP07-0156-00 The FT synthetic oil from which the by-product water and by-product alcohols have been removed is fed to the product yielding step. [0032] Next, the product yielding step is carried out by the cracking/refining apparatus 3, whereby the FT synthetic oil is subjected 5 to treatment including cracking and refining and collected into different products such as naphtha, kerosene, gas oil and lubricating base oil. [0033] The hydrocarbon oil manufacturing process of this embodiment is provided with a synthetic gas production step and a by product water treatment step wherein the oxygen-containing 10 hydrocarbons in the by-product water resulting as a by-product of the FT synthesis step are removed, and the treated water from which the oxygen-containing hydrocarbons have been removed by the by-product water treatment step is reutilized in the hydrocarbon oil manufacturing step (within the system). 15 [0034] The by-product water treatment step is carried out by the by product water treatment apparatus 4, and it preferably includes at least one selected from among a biological treatment step in which the oxygen-containing hydrocarbons are decomposed by organisms, an adsorption step in which the oxygen-containing hydrocarbons are 20 adsorbed onto active carbon or the like for removal, a flocculating step in which the oxygen-containing hydrocarbons are flocculated for removal and a membrane separation step in which the oxygen containing hydrocarbons are removed by membrane separation, and it may also include more than one of these steps. 25 [0035] Furthermore, the treated water treated in the by-product water treatment step is supplied to a cooler 5, boiler 6, deaerating treatment 11 FP07-0156-00 apparatus 7, fire-fighting installation 8 or the like, and reutilized in a hydrocarbon oil manufacturing apparatus as cooling water, heating steam, process steam, boiler feed water, fire-fighting water or the like. [0036] The hydrocarbon oil manufacturing process of this 5 embodiment is also provided with an alcohol extraction step wherein alcohols are extracted from the oxygen-containing hydrocarbons removed in the by-product water treatment step. The alcohol extraction step is carried out by the alcohol extraction apparatus 9, and this can yield alcohols as chemical products. 10 [0037] This embodiment includes a by-product water treatment step in which the oxygen-containing hydrocarbons in the by-product water produced in the hydrocarbon oil manufacturing step are removed, and the treated water from which the oxygen-containing hydrocarbons have been removed by the by-product water treatment step is reutilized as 15 process steam, heating steam, cooling water or fire-fighting water, thereby reducing the waste water volume discharged out from the system into rivers or seas. It is also possible to reduce the amount of industrial water used. As a result, it is possible to alleviate the environmental burden while also lowering cost. 20 [0038] Furthermore, since the treated water from which the oxygen containing hydrocarbons such as alcohols have been removed by the by-product water treatment step is reutilized, it is possible to reduce corrosion damage to equipment such as the cooler, boiler, fire-fighting installation and conduits to which the treated water is supplied. 25 [0039] In addition, providing an alcohol extraction step allows the alcohols to be extracted from the oxygen-containing hydrocarbons, and 12 C .\RPorbl\DCC\NJL\3798411_1 DOC-9/0/20 11 - 13 the extracted alcohols can be marketed as chemical products. The volume of alcohols discharged out of the system is also thereby reduced. [0040] The present invention has been explained above based on a preferred embodiment, but it is not limited to this embodiment. For the 5 embodiment described above, the by-product water resulting as a by-product from the synthetic gas production step (synthetic gas production apparatus) and FT synthesis step (FT synthesis apparatus) is reutilized, but alternatively by-product water discharged from either or both the synthetic gas production step and FT synthesis step may be reutilized. 10 [0041] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge. [0042] Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations 15 such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.