細(xì)菌氧化法處理金礦的工藝初步研究

1、細(xì)菌氧化法處理金礦的工藝初步研究摘要介紹了細(xì)菌氧化法處理金礦的工藝，細(xì)菌氧化冶金的原理、細(xì)菌氧化法金的回收、細(xì)菌氧化的影響因素、細(xì)菌氧化冶金的優(yōu)缺點(diǎn)，以及目前工藝中存在的問(wèn)題及對(duì)策。指出了細(xì)菌氧化法處理金礦工藝的發(fā)展方向以及在實(shí)際工業(yè)中重要作用。關(guān)鍵詞：金礦；細(xì)菌氧化；金回收率1前言細(xì)菌氧化是二十世紀(jì)下半葉冶金學(xué)領(lǐng)域十分活躍的學(xué)科之一。從本世紀(jì)七十年代末始，黃金資源就成為礦業(yè)界最熱門(mén)的開(kāi)發(fā)領(lǐng)域。近二十年，世界范圍內(nèi)黃金資源勘探、開(kāi)發(fā)程度的迅速提高直接促進(jìn)了選冶技術(shù)的革新和發(fā)展，用于金礦開(kāi)發(fā)的預(yù)處理技術(shù)也得到一定程度的利用。焙燒、加壓氧化和細(xì)菌氧化法成為當(dāng)今黃金選冶領(lǐng)域三大預(yù)處理技術(shù)。由于焙燒法

2、存在環(huán)保問(wèn)題、加壓氧化法投資高、技術(shù)難度大，人們便把更多的目光投向無(wú)污染、低成本的細(xì)菌氧化法，使之成為近幾年開(kāi)發(fā)速度最快的新興技術(shù)。2細(xì)菌氧化冶金細(xì)菌氧化冶金技術(shù)，又稱細(xì)菌浸出技術(shù)，通常指礦石的細(xì)菌氧化或生物氧化，由自然界存在的細(xì)菌進(jìn)行。這些細(xì)菌被稱作適溫細(xì)菌，大約有0.5-2.0微米長(zhǎng)、0.5微米寬，只能在顯微鏡下看到，靠無(wú)機(jī)物生存，對(duì)生命無(wú)害。這些細(xì)菌靠黃鐵礦、砷黃鐵礦和其他金屬硫化物如黃銅礦和銅鈾云母為生。在自然界，微生物在多種元素的循環(huán)當(dāng)中起著重要作用，地球上許多礦物的遷移和礦床的形成都和微生物的活動(dòng)有關(guān)。生物濕法冶金是一種很有前途的新工藝，它不產(chǎn)生二氧化硫，投資少，能耗低，試劑消耗少

3、，能經(jīng)濟(jì)地處理低品位、難處理的礦石。目前，這種方法仍處于發(fā)展之中，它還必須克服自身的一些局限性，如反應(yīng)速度慢、細(xì)菌對(duì)環(huán)境的適應(yīng)性差，超出了一定的溫度范圍細(xì)菌難以成活，經(jīng)不起攪拌，等等。為此，一些科學(xué)家建議應(yīng)從遺傳工程方面開(kāi)展工作，通過(guò)基因工程得到性能優(yōu)良的菌種。2.1細(xì)菌氧化冶金原理2.1.1細(xì)菌浸礦的作用方式關(guān)于細(xì)菌浸礦機(jī)理主要有直接作用和間接作用兩種。直接作用理論認(rèn)為細(xì)菌通過(guò)直接附著在礦物特定位點(diǎn)上，直接氧化礦物中的亞鐵和低價(jià)硫或砷。2FeS2+7O2+2H2O一2FeSO4+2H2SO42FeAs+7O2+H2SO4+2H202H3As04+Fe2(SO4)34FeSO4+O2+2H2S

4、O42Fe2(SO4)3+2H2O從而使金礦物的包裹層溶解。間接作用理論認(rèn)為細(xì)菌以溶液中的Fe2+為能量和電子供體生長(zhǎng)，形成的代謂產(chǎn)物Fe3+間接氧化礦物中的亞鐵和低價(jià)硫，構(gòu)成循環(huán)浸出。FeS2+7Fe2(SO4)3+8H2O一15FeSO4+8H2SO44FeSO4+O2+2H2SO42Fe2(SO4)3+2H2O但多數(shù)人認(rèn)為這兩種作用共同起作用，即常說(shuō)的聯(lián)合作用，具體到細(xì)菌催化的詳細(xì)步驟，是一個(gè)復(fù)雜的涉及NAD，F(xiàn)AD，NADP，ATP等生物大分子的酶系統(tǒng)，是一個(gè)有高效催化能力的電子傳遞鏈(已知的酶催化效率為普通化學(xué)催化劑的幾十至上千倍)。2.1.2反應(yīng)機(jī)理礦物的細(xì)菌氧化是靠一種天然的棒狀

5、(長(zhǎng)0.5-2.0微米，寬0.5微米) 噬硫桿菌來(lái)完成的。噬硫桿菌的食物包括黃鐵礦、砷黃鐵礦、輝銅礦、黃銅礦、閃鋅礦和其它賤金屬硫化物。這些細(xì)菌需要從空氣中獲取氧氣和二氧化碳，以及少量氮和磷。噬硫桿菌和其它有關(guān)類型的細(xì)菌(如小螺旋菌和硫化裂片菌屬)，可以在酸性溫泉及其附近地區(qū)、火山活動(dòng)地區(qū)以及硫化物豐富地區(qū)找到。后兩種細(xì)菌一般在45-90 的溫度下繁殖。它們的生命力強(qiáng)，能在金屬離子高濃度和pH值低于2.5的硫酸環(huán)境下迅速繁殖。這些以巖石為食物的細(xì)菌將堅(jiān)硬的礦物分解成可溶于酸的硫、鐵及其它金屬，諸如砷、銅、鋅、鎳、鈷等?？扇荑F在氧化狀態(tài)下(三價(jià)鐵)是硫化礦物的強(qiáng)氧化荊。這些細(xì)菌能使鐵維持在三價(jià)狀

6、態(tài)下。因此，硫化礦物在化學(xué)和微生物的共同作用下進(jìn)行分解，使顯微和亞顯微金顆粒裸露出來(lái)。與在不含細(xì)菌的水和空氣中進(jìn)行氧化的方法相比，礦物細(xì)菌氧化的速度要快50-100萬(wàn)倍。在適當(dāng)條件下(酸性pH值和足夠的空氣)細(xì)菌的數(shù)量會(huì)急劇增長(zhǎng)，一直到每克礦石或精礦，或是1毫升酸性水中多達(dá)1億-100億個(gè)的驚人數(shù)字。在充氣攪拌槽及特殊構(gòu)筑的浸堆中，礦物的細(xì)菌氧化不僅迅速而且高效，例如，在4-5天的時(shí)間內(nèi)，可將難選的含金硫化礦精礦氧化，金回收率提高到90以上。但在此前，還不到3O。2.2細(xì)菌氧化法回收金2.2.1槽式細(xì)菌氧化法浮選精礦的細(xì)菌氧化過(guò)程，是把精礦同高濃度細(xì)菌懸浮液在較弱硫酸溶液中充氣攪拌的連續(xù)過(guò)程，

7、即先將懸浮在酸液中的浮選精礦送往第一槽，待大部分細(xì)菌氧化后，送入第二槽再次充氣攪拌。在通常情況下，細(xì)菌氧化裝置按三段串聯(lián)配置。第一段規(guī)格大，后兩段規(guī)格小。在第二段精礦停留時(shí)間較短。這種配置不僅為硫化礦的細(xì)菌分解提供了充裕的時(shí)間，而且消除了可能造成金回收率降低的礦漿短路現(xiàn)象。以下兩個(gè)參數(shù)對(duì)細(xì)菌氧化法回收金的經(jīng)濟(jì)效益有很大影響：（1）為獲得滿意的金回收率需用細(xì)菌分解的硫化礦數(shù)量。這一參數(shù)決定著所需的氧氣量和攪拌工作量，影響基建投資和生產(chǎn)成本。（2）細(xì)菌分解硫化礦物的速度。這一參數(shù)決定著每一段的處理能力和需要的段數(shù)，也影響基建投資。槽式細(xì)菌氧化法大都用于處理價(jià)值高的硫化礦精礦。這是因?yàn)閷?duì)細(xì)磨的礦物進(jìn)

8、行充氣攪拌需要消耗動(dòng)力，另外，建造能耐硫酸和三價(jià)鐵混合物腐蝕的浸出槽，費(fèi)用高昂。2.2.2細(xì)菌堆浸法這一方法包括的作業(yè)有：破碎礦石，墊上筑堆、含菌(通常是噬硫桿菌和小螺旋菌)稀酸液噴淋。當(dāng)大量的硫化礦物被氧化，金裸露出來(lái)后，要用水洗滌礦物，以除去酸和其它金屬，再加石灰提高pH值，接著用氰化物溶液處理礦石。由于用堆浸法進(jìn)行細(xì)菌氧化的礦石顆粒粗，通常大于6.5毫米，所以，堆浸法生產(chǎn)，金的回收率低于充氣攪拌的浸出槽的回收率。鑒此，當(dāng)?shù)V石品位較低，用選礦法處理不經(jīng)濟(jì)，可考慮用細(xì)菌堆浸法。2.2.3賤金屬回收有價(jià)賤金屬(包括銅、鎳、鋅、鈷、鉬)常以硫化礦物(常夾有貴金屬)的形式賦存，也可用細(xì)菌分解，溶入

9、稀酸溶液的賤金屬可用傳統(tǒng)的冶煉方法回收。2.3細(xì)菌氧化的影響因素用細(xì)菌氧化法處理金礦時(shí)，會(huì)有許多的因素影響到金的產(chǎn)率，主要有細(xì)菌方面的因素、礦物學(xué)方面的因素、工藝方面的因素等等。2.3.1細(xì)菌方面的因素（）浸礦菌種浸礦細(xì)菌一般直接從要處理礦石的周圍環(huán)境中分離獲得。這些好氧的中溫菌大多生長(zhǎng)在酸熱環(huán)境中，從而形成以硫化礦為主要基質(zhì)的獨(dú)特的生理特征，具有對(duì)二價(jià)鐵、還原態(tài)硫的獨(dú)特的氧化能力。（）pH值對(duì)細(xì)菌生長(zhǎng)的影響影響培養(yǎng)基中有機(jī)化合物的電離，引起微生物表面(細(xì)胞膜)電荷變化，從而改變有機(jī)物質(zhì)滲入細(xì)胞的難易程度；pH有較大偏差時(shí)，由于氨基酸殘基離子化的改變和非共價(jià)相互作用的破壞，可導(dǎo)致酶的變性；pH

10、值太小，降低CO2在水中的溶解度，結(jié)果使得細(xì)菌的碳源物質(zhì)匱乏。只有在適宜的pH值下，細(xì)菌才能正常完成遲緩期內(nèi)的生理過(guò)程，促進(jìn)浸礦過(guò)程。2.3.2礦物學(xué)方面的因素礦石由礦物組成，礦物是細(xì)菌氧化的工作對(duì)象，它構(gòu)成了細(xì)菌浸礦工藝的內(nèi)因。在進(jìn)行細(xì)菌氧化時(shí)，首先應(yīng)查明礦石的化學(xué)成分和礦物成分。礦石的研究成為細(xì)菌氧化工藝研究的主體。（）礦石礦物組成礦石中金的賦存狀態(tài)、載金礦物的類型、硫化物的鑲嵌共生狀態(tài)必然影響金精礦中的顆粒在浸液中的電化學(xué)性質(zhì)，它們構(gòu)成了不同電位差的伽伐尼電池，使細(xì)菌對(duì)硫化物的氧化產(chǎn)生差異。（）礦石中硫化物的化學(xué)成分硫化物化學(xué)成分的復(fù)雜性，給細(xì)菌浸出帶來(lái)了一定的困難。世界上難浸金礦的分類

11、也主要根據(jù)礦石化學(xué)成分的差異來(lái)進(jìn)行分類的，有高砷微細(xì)粒金礦石、含碳金礦石、含碲金礦石、含多金屬金礦石。2.4細(xì)菌氧化冶金優(yōu)缺點(diǎn)細(xì)菌浸出技術(shù)的主要優(yōu)點(diǎn)有：（1）提高金的回收率；（2）從商業(yè)角度證實(shí)下游技術(shù)如溶劑萃取、電積法可用于經(jīng)生物技術(shù)處理過(guò)的溶液現(xiàn)物生產(chǎn)金（3）生產(chǎn)過(guò)程的簡(jiǎn)單化降低了前期投入和運(yùn)營(yíng)費(fèi)用，縮短了建設(shè)時(shí)間，維修簡(jiǎn)單方便；（4）生產(chǎn)在常壓和室溫（約為25攝氏度）條件下進(jìn)行，不用冷卻設(shè)備，節(jié)約了投資和運(yùn)營(yíng)資本；（5）細(xì)菌浸出的廢棄物為環(huán)境所接受，節(jié)約了處理廢棄物的成本，細(xì)菌浸出的廢棄物的預(yù)防措施也很少；（6）細(xì)菌易于培養(yǎng)，可承受生產(chǎn)條件的變化，對(duì)水的要求也很低，每百萬(wàn)水溶液中可溶解固

12、體物2萬(wàn)份。細(xì)菌浸出技術(shù)的缺點(diǎn)是：（1）罐浸出的時(shí)間通常為46天，與焙燒和高壓氧化的幾小時(shí)相比，時(shí)間較長(zhǎng)；（2）難以處理堿性礦床和碳酸鹽型礦床。3存在問(wèn)題與發(fā)展對(duì)策從我國(guó)目前細(xì)菌氧化技術(shù)的開(kāi)發(fā)研究現(xiàn)狀來(lái)看，工業(yè)化進(jìn)程與理論研究、試驗(yàn)水平之間的差距較大，主要原因表現(xiàn)在技術(shù)本身存在某些障礙性因素，工程設(shè)計(jì)不完善，資金不足，科研力量無(wú)統(tǒng)一協(xié)調(diào)管理等，直接影響投資者信心與工業(yè)化實(shí)施。3.1技術(shù)問(wèn)題氧化周期長(zhǎng)是細(xì)菌氧化技術(shù)存在的最突出的恫題。一般金精粉氧化需要5lOd時(shí)間，原礦堆浸氧化則要60d以上，長(zhǎng)周期氧化作業(yè)直接影響著生產(chǎn)成本和經(jīng)濟(jì)效益。另外一個(gè)問(wèn)題就是處理難度很大的金精粉，礦漿濃度很低(小于l0

13、 )時(shí)，才能達(dá)到理想的氧化效果，這也是生產(chǎn)效率低的原因之一。因此，在細(xì)菌氧化技術(shù)應(yīng)用過(guò)程中，盡可能創(chuàng)造適合細(xì)菌作用的環(huán)境是提高氧化效率的措施外，培養(yǎng)氧化能力強(qiáng)、適應(yīng)范圍廣的高效菌種則可能是解決問(wèn)題的主要途徑。3.2設(shè)備問(wèn)題細(xì)菌氧化技術(shù)應(yīng)用于槽浸生產(chǎn)中，除遇到技術(shù)問(wèn)題外，還存在設(shè)備和機(jī)械材料問(wèn)題。為了要達(dá)到理想的氧化效果，一般都要采用降低礦漿濃度或延長(zhǎng)氧化時(shí)間來(lái)實(shí)現(xiàn)這樣則直接影響設(shè)備的設(shè)計(jì)規(guī)模及投資。另外，還有充氣方式、充氣量、葉輪結(jié)構(gòu)、轉(zhuǎn)速及散熱方式等設(shè)計(jì)參數(shù)，都會(huì)影響設(shè)備效率。因此，在細(xì)菌氧化技術(shù)的工業(yè)化應(yīng)用過(guò)程中，如何設(shè)計(jì)合理的設(shè)備規(guī)模與結(jié)構(gòu)、選擇合理的工程材料、降低工程造價(jià)都是提高技術(shù)實(shí)

14、用性與競(jìng)爭(zhēng)力的關(guān)鍵因素。從這一角度上講解決設(shè)備問(wèn)題比解決工藝問(wèn)題更重要。4細(xì)菌氧化冶金的應(yīng)用細(xì)菌氧化治金在經(jīng)濟(jì)可行性上可有效地與焙燒競(jìng)爭(zhēng)。故可以相信在不久的將來(lái)細(xì)菌氧化冶金技術(shù)可很好地應(yīng)用。采礦項(xiàng)目中環(huán)境因素占很大比重，這又可以加速細(xì)菌氧化冶金技術(shù)的應(yīng)用，因?yàn)樵摷夹g(shù)的產(chǎn)品或?yàn)槌恋砦锘驗(yàn)橄氆@得的金屬。細(xì)菌氧化浸出，充分利用了自然有機(jī)體在控制的條件下對(duì)硫化物的加速遞降分解。除了電積法過(guò)程有部分氧氣參與外，并無(wú)有害氣體和廢棄物直接進(jìn)入環(huán)境。該技術(shù)的環(huán)境優(yōu)勢(shì)可節(jié)省審批的時(shí)間，減少項(xiàng)目商業(yè)化從設(shè)計(jì)到投產(chǎn)的時(shí)間。礦業(yè)中日益增加的有利于環(huán)境清潔的加工技術(shù)要求是細(xì)菌氧化冶金技術(shù)商業(yè)化的強(qiáng)大動(dòng)力。長(zhǎng)期半工業(yè)化實(shí)

15、驗(yàn)工廠的研究和獨(dú)立的經(jīng)濟(jì)核算證明了該技術(shù)的技術(shù)可行性和經(jīng)濟(jì)可行性。大規(guī)模示范工廠的建立將證明這些發(fā)現(xiàn)，并將推動(dòng)細(xì)菌氧化冶金技術(shù)提取賤金屬精礦走向商業(yè)化。細(xì)菌氧化冶金技術(shù)在黃金領(lǐng)域中的主要應(yīng)用是作為預(yù)處理工藝用于難處理金礦資源的開(kāi)發(fā)上，細(xì)菌氧化提金技術(shù)。未來(lái)，細(xì)菌濕法冶金由于其利于環(huán)境保護(hù)、基建投資少、在某些情況下運(yùn)作成本低等優(yōu)越性，將獲得進(jìn)一步的發(fā)展。5結(jié)語(yǔ)細(xì)菌氧化技術(shù)不是處理金礦唯一可供選擇的技術(shù)方法，但在今后一段時(shí)間內(nèi)它是最具吸引力的，尤其是在處理難浸金礦石上。我國(guó)在此領(lǐng)域經(jīng)過(guò)十幾年的探索之后，已建立了較完整的試驗(yàn)體系，開(kāi)發(fā)研究能力相對(duì)提高，并且在難浸金精粉的槽浸細(xì)菌氧化和低品位難浸礦石堆

16、浸細(xì)菌氧化方面都有一定的工業(yè)償試。盡管在工業(yè)化進(jìn)程方面與發(fā)達(dá)國(guó)家有一定的差距，但急待開(kāi)發(fā)的難浸金礦資源與投資者日益高漲的投資興趣，都加大了這一技術(shù)的產(chǎn)業(yè)化力度，為大規(guī)模工業(yè)化生產(chǎn)提供了必要條件。隨著這一技術(shù)的廣泛應(yīng)用，將對(duì)我國(guó)黃金產(chǎn)業(yè)的健康穩(wěn)定發(fā)展產(chǎn)生積極影響。附錄BExtra-terrestrial Mineral Production: Multiple Aspects ofSustainabilityL. S. GertschRock Mechanics and Explosives Research Center, Missouri University of Science and

17、Technology, United StatesABSTRACT The production of minerals for human use at locations other than the Earth is expected to "advancehuman prosperity inways that do not compromise the potential prosperity and quality of life of future generations" (Brundtland, 1987); in other words, sustain

18、ably. This paper examines the interaction of extra-terrestrial mineral production (ETMP) with the following sustainability imperatives:·The sustainability of human activities on Earth;·The sustainability of human activities elsewhere;·Human survival in general, the ultimate sustainabi

19、lity goal Some of the consequences of mineral production on Earth are widely considered to decrease the future prosperity and quality of human life. Examples include noxious by-products or wastes andunsettling economic up- and downswings. Moving mineral production activities to extra-terrestrialloca

20、tions, where appropriate, will decrease many of its deleterious effects. Terrestrial mineral production presently is decreasing in some countries and increasing in others, moving from the cheaper and easier ores to more expensive, difficult materials. When the full costs of maintaining the terrestri

21、al environment in a sustainable manner are included, total mineral production costs must increase. The cost of extracting mineral products from extra-terrestrial sources will be substantially higher, especially in the initial phases, but as the full costs of terrestrial production increase, at some

22、point in the future (different points for different minerals), the curves will cross (Fig.1).This will occur at different points for different materials, a process whose prediction will be complicated by substitution of cheaper materials for some uses as prices of the original material rise. In summ

23、ary, mineral products from extra-terrestrial sources will tend to increase the sustainability of human civilization, once steady state has been reached.Keywords: Space mining; Moon; Mars; Asteroids; Comets; Extra-terrestrialINTRODUCTION The production of minerals for human use at locations other tha

24、n the Earth is expected to "advancehuman prosperity inways that do not compromise the potential prosperity and quality of life of future generations" (Brundtland, 1987); in other words, sustainably. This paper examines the interaction of extra-terrestrial mineral production (ETMP) with the

25、 following sustainability imperatives:·The sustainability of human activities on Earth;·The sustainability of human activities else- where;·Human survival in general, the ultimate sustainability goal.Some of the consequences of mineral production on Earth are widely considered to decr

26、ease the future prosperity and quality of human life. Examples include noxious by-products or wastes and unsettling economic up- and downswings. Moving mineral production activities to extra-terrestrial locations, where appropriate, will decrease many of its deleteriouseffects. Terrestrial mineral p

27、roduction presently is decreasing in some countries and increasing in others, moving from the cheaper and easier ores to more expensive, difficult materials. When the full costs of maintaining the terrestrial environment in a sustainable manner are included, total mineral production costs must incre

28、ase. The cost of extracting mineral products from extra-terrestrial sources will be substantially higher, especially in the initial phases, but as the full costs of terrestrial production increase, at some point in the future (different points for different minerals), the curves will cross. This wil

29、l occur at different points for different materials, a process whose prediction will be complicated by substitution of cheaper materials for some uses as prices of the original materialrise. This paper discusses the relationships between extra-terrestrial mineral production and the sustainability of

30、 human existence. This goes beyond the term "sustainable development, "which currently is taken to mean better integration of mineral production with local ecological and social issues. While the sustainability of human existence certainly must include these aspects, the full concept more

31、generally comprises the aggregate sustainability of all human activities. Furthermore, "human existence" is used here to mean a civilized quality of life beyond mere survival. Civilization fundamentally requires the extraction of mineral resources. To be sustainable,this extraction must sa

32、tisfy the equation:R-C=Bwhere R is revenue, C is cost, and B is benefit. Revenue is the immediate gain, usually economic, derived from the mineral extraction. Cost is all costs incurred thereby. Though commonly determined in economic units, both also contain aspects that are less easily quanti-fable

33、, such as maintainance of quality of life above a certain minimum threshold. Benefit is sometimes called profit, but just as revenue and cost cannot always be calculated in precise monetary units, benefit is not necessarily or immediately financial.SUSTAINABILITY ASPECTS OF MINERAL PRODUCTION The ot

34、her speakers in this Workshop have given far more comprehensive descriptions than are possible in this short space about current thought regarding the sustainability of modern mineral production practices on Earth. Instead, this section is devoted to the effects of mineral production on the survivab

35、ility of humans living and working in space, whether on other solar system bodies or in orbit. No space environment discovered to date or expected in future is inherently conducive to human existence in the manner that the Earth, our planetary home, is. Typical environmental hazards include no or no

36、xious atmospheres, micro-gravity, widely varying gravity fields, high-energy radiation, extreme temperatures, and extreme gradients of gravity, temperature, etc. The processes involved in creating usable commodities from natural geologic deposits also create waste materials, which can be in any stat

37、e. On Earth, many of these wastes create health and environmental hazards. This will also be true in space, especially in the engineered artificial environments in which humans must live. Extra-terrestrial humans will not have the large buffering effects of the planetary biosphere, geosphere, hydros

38、phere, and atmosphere to mitigate waste effects. Consequently, the life support systems will be much more sensitive to these effects than we are accustomed to. Some aspects of mineral production could serve to modify those environments, so they more nearly approximate human-survivable parameters. Ex

39、amples include soil compac-tion/excavation and the creation of greenhouse gases, heat, waste gases and other by-products. In addition, mineral exploration gathers data that is applicable also to environmental characterization and monitoring.EXTRA-TERRESTRIAL MINERAL PRODUCTIONSpace exploration Sever

40、al nations and groups of nations presently maintain access to space, and more nations are planning to join this group. The United States plans to re-establish human presence on the Moon by 2020, partly in preparation for sending humans onward to Mars a decade or two later, and partly for scientific

41、research. These activities will most likely be achieved by cooperation of the United States with the several other spacefaring nations. At present, the United States plans to launch a series of robotic missions to study the Moon beginning in October 2008, and the first crewed flight will occur befor

42、e 2020. Japan and China plan to send human explorers to the Moon at about the same time, followed by the European Union, Russia, and India. Going onward to Mars will happen after that time, possibly 20302045.Robotic and/or human excursions to asteroids or comets that might impact the Earth will proc

43、eed on a separate, though related, timeline from lunar and martian exploration, a timeline that is controlled by parameters external to the Earth and its politics. At present, most of the effort being expended in this area is devoted to detection, identification, and orbit determination of objects g

44、reater than 1 kilometer in diameter, whose orbits intersect the orbit of Earth around the Sun. Once an object has been confirmed to be on a collision course with the Earth, several different approaches have been proposed for averting the impact, depending on how much time will elapse prior, and on d

45、etails of the relative trajectories of the body and of Earth. One proposed approach would be to mine the body in such a manner that its orbit is sufficiently modified to avert the impact. Another is to fragment the body into pieces too small to survive passage through Earth's atmosphere. The fir

46、st approach could generate useful products from the material of the body, depending on its constituents; if it is an asteroid, those products might include metals or oxygen. If it is a comet, they might instead be spacecraft propellants or explosive compounds. All would be potentially useful directl

47、y during the mining/fragmentation process, or could be used elsewhere in space.The development of ETMP Mineral production from extra-terrestrial resources will likely proceed in two main phases, that each will supply two different types of markets:·Support for the exploration and eventual colon

48、ization of space; in other words, the extra-terrestrial market. This will, over the course of time spent in space, eventually divide into submarkets: Local supply. In-space supply, especially spacecraft propellant manufacture. Export to other nonterrestrial locations.·The terrestrial market. Th

49、is includes materials and products for export to Earth.These two phases will overlap each other, but the first one will supply the extra-terrestrial market from Earth's Moon. The major value of mineral production from this source is to reduce the mass of material that must be lifted, at very hig

50、h energy cost, from the deep well of Earth's gravity to supply the materials needed for the return to space. This phase will grow and remain important, though its size may eventually be eclipsed by exports to other extra-terrestrial locations, as well as to Earth itself. The first terrestrial ma

51、rket may be power generation from nuclear fusion reactors using 3 He as fuel (Kulcinski and Schmitt, 1991). There will also be a novelty market for lunar materials, perhaps as jewelry or simple samples.The techniques of ETMP The mining and processing of materials from the Moon, Mars, asteroids, come

52、ts, and other bodies of the solar system will begin by adapting techniques first developed on Earth. People have been extracting materials from the ground for at least 300 thousand years and possibly 2.5 million years (Verri et al., 2004; and Leakey, 1994; respectively). As humans gain experience in

53、 space operations, the equipment and the approaches used will undoubtedly evolve from this starting point; in the meantime, however, the approach will comprise variations on currentart. Mining methods can be categorized in various ways, including whether access to the deposit is from the surface or

54、from underground. These categories can be further modified by incorporating the mode of energy dissipation inherent in the mining process, modified with traditional approaches. Methods that rely on unique terrestrial properties are not included, such as hydraulicking, which uses large-volume water j

55、ets for fragmentation, excavation, and transportation.EFFECTS ON SUSTAINABILITY In this paper, sustainability effects are grouped into those associated with the continuation of quality human existence on the Earth, human activities on other bodies, and survival of the human species in general, regar

56、dless of the location of individual members or groups.Human activities on Earth Energy availability is an important limiter of the human quality-of-life. A large fraction of the human population spends most of their time obtaining the energy needed for survival, both directly (fuel) and indirectly (

57、food). In addition, many aspects of mineral processing are energy-intensive. Presently all energy must be obtained from the same sources: the sun, with lesser contributions from terrestrial radioactive isotopes. This is true throughout the solar system, and in fact only two planets receive amounts o

58、f solar energy comparable to the Earth's share'. However, the amount of solar energy available in near-Earth space is enormous. According to the U.S. National Security Administration (2007), "Every 1 km-wide insolation band at GEOZ receives nearly as much energy per annum as the content

59、 of the entire 1.28T BBLs of recoverable oil remaining on Earth." As mentioned previously, hazardous waste from mining and mineral processing has widely recognized deleterious effects. Generating and mitigating these effects elsewhere than the single planet where humanity is adapted to live will enhance our future. Natural resource-based economic aspects are both positive and neg