外文翻译能源利用效率和工业锅炉效率

外文翻译能源利用效率和工业锅炉效率 炉和公用事业锅炉是包括作为附录，以帮助帮助懂得多样化 的工业锅炉人.从EPA锅炉MACT数据库，从EPA锅炉MACT 数据库,用超过一千万Btus根据小时热投入有大约22,000 罗伯特•贝塞特，工业锅炉理事 台工业股票-商业和具有公共机构特征的锅炉. 会业主 新访.现有单位在调查工业锅炉效率考虑的细节之前,一旦锅 能源效率，为工业锅炉是一个特性锅炉高度的 炉设计,制造,和安装,它变得很困难和改进它的在设计之上特点。没有相同的两个锅炉。有两个相同的设计， 效率变得昂贵。另一方面，由于将讨论在燃油，负载，和运 相同的构造，在美国印第安纳州燃烧着同样燃料的 作方面的变化，，可以很容易的影响超过所有的工作效率。 司炉添加燃料的锅炉有着非常不同的特性技能。像 由于成能源本高昂，锅炉及相关系统，通常是购买的生活设 双胞胎少年，他们并不相同。为工业锅炉审议能源 施，充足的保证金为未来的增长和过程的变异。给予适当的 效率，往往不是用一刀切的办法简化和分类。正象 维修，锅炉寿命是无限期的。在大多数情况下，它将度过过 对待青少年，这是行不通的。而家长会想相信他们 程并完好，它o原本是被设计的，而不是设施。为了举例来的少年拥有很好的天赋，并在80%的人口之上，而 说，一个设施，这是生产八轨道录音带改变生产录音带，并 我们知道不一定如此。众所周知，对于锅炉，少年 正生产CD和DVD 。锅炉仍会在那里会适应新的 要求 对教师党员的评价套管和固井爆破片与爆破装置仓库管理基本要求三甲医院都需要复审吗 。 的平均值是不是代表的广泛多元化的人口。如果你 以今天的技术是有可能的设计锅炉，以处理各种各样的要 认为它是，可以询问任何家长与青少年或工业锅炉 求和的可能性。然而，在大多数情况下，这是生态系统是不 的经营者。当可变物与节能相关比那些有限与少年 可能的，如果一个过程，是生存在一个竞争激烈的世界。它 相关时，他们其中任一绝不被复杂化。 可以像建立一个新的首页与热泵和一炉的能力燃烧天然气和 有四个因素是至关重要的，在评估工业厂房的 一炉的能力烧伤荷兰石油，以支付暖气，空调，热水，和其 能源供应使产品对于顾客利益在一个高度竞争的 他家庭的需要。的成本，所有这种设备将打破预算。它是可 国际市场能源效率。他们是： 见，一个人平均大概可以自动对焦镜头福特只有一个，这些 1 、燃料类型， 设备。如果该人尝试购买所有三个，他们将无法负担内务。 2 、燃烧系统的局限性， 新单位购买与保证效率在最大连续评级（文礼利律师行） 3 、设备的设计，等， 为某一特定的设计燃料生产指明数量的蒸汽或热水在指定的 4 、蒸汽系统运作的要求。 TEM -温度和压力。任何的变化，这些炭- acteristics改变 此外，工业设施的复杂性，位置，和目标使他 经营效率。一瓜- antee一个更广泛的燃料，能力，和TEM - 们复杂化。不同的公用事业，能源是一个较小的部 温度和压力，在技术上是可行的。如何-以往任何时候都提到，分，它是工业的公司最终产品的价格是很重要的。 它可能不是经济合理的某一特定设施。在年底，一个新的单 然而，没有能量没有最终产品或服务。不用说，没 位可界定只能以一种是设计，购买和安装，但从来没有在运 有那里产品或服务是没有需要对于人完成工作。 行保证条件以外的其他通过accep -距离测试。在现实世界 这白皮书将论及影响工业锅炉和因素四个最 中几乎没有运作，在设计规格。 重要因素的和效率-有关的方面影响把合并热和力 平均每年比。文礼利律师行设计 量系统用在工业设施上.一份背景文件上的工业锅 如果您已开始从冷水您曾经watche需要多久才分歧之间的实际效率，平均每年，文礼利律师行可高达40 ％能得到它沸腾？我相信华本富兰克林谁说， “观或更多取决于设施。任何考虑工业锅炉的效率，必须考虑家 看了一锅neve归结起来“ 。它，但它需增加1,00庭综合系统- ferences之间的真正，实际，设计效率- 瓦每磅的水，才没有。之后，临屋区考虑到损失，ciencies 。 从茶壶，或锅炉，英国电信为仟卡，转换为蒸汽当的能力，某一特定过程中使用蒸汽有效地复杂化这个因素。 您使用它o失去它。在系统上有一个沉重的循环荷与蒸汽自动对焦镜头之三，这是制作您可以使用它，或松散。 载作用经营者可以启动或关闭次锅炉的需要（为一inefficien - cies固有的各种工艺因素，可作为重要，因 期持久的2至5侯每个单程）没有损失大部分的为效率低下与锅炉。 initi能源。不过，对于期长于thi如果并非所有 的初始1000 btus是洛杉矶在另一方面，经营者可燃料类型 以保持一压力，以确保快速反应supplyin足够的大自然是神奇。自然发生的-环燃料（天然气，石油，木材， 热量，以弥补损失，在石荫透射电镜。在这里，效煤和生物量）是可变能够的。该植物，动物，臭虫和其他 率是零，但初步1,00 btus得以维持。在这两种情critters形成了燃料经历了巨大的变化在不同地点和不同 况下有是在creased能量损失和无法满足o保持文的时间。元素成分付娥 [水分（ H2O ）的，碳（三） ，氢礼利律师行的效率。在设施，如一个协调法律上的（ h ）款，镍trogen （ n ）的，氯（氯离子） ，硫（ s ）校园，与热负荷，热需要每天早上，使学生将甲肝款，氧（海外）和灰分]可以不同，高达30 ％或更多从每年病毒温暖的班级去，热点骤雨后， u与，和热的平均的基础上取决于其固有的组成和程度的燃料精炼或准 食物在自助餐厅服务线，是更好地使锅炉热，失去备。任何变化，在燃料复合- tion从原来的制度设计西港岛 efficienc并保持学生，教授和家长高兴。在一个线直接影响锅炉效率。在大多数情况下，与锅炉设计这些天 大型医院performin在许多重大手术，每天使用消来，变化小于1或二％ ，从设计燃料的组成将有几乎没有任 毒炉吨消毒手术器械，应系统b设计来处理的最大何可察觉的影响，效率- ciency 。这种讨论，瓦每英镑加仑， 数量的苏恺geries预期或人数较少，因此limitin或立方米脚下的煤炭，石油或天然气分别- tively可能会更有多少人可以帮助在一一天？显然，系统必须好，但是超过简化的方式看它。 designe以满足最大容量的医院这里是不可能同时即使天然气可以各有不同， 900和1100仟卡/铜。英尺取决提供文礼利律师行电子疆界基金会ciency的条件于甲烷含量。多年来，技术，使气体的COM - panies混合气和最佳的病人servic也有一些相关的损失与低负体和控制其瓦和COM -的立场，以1左右的水平1000仟卡/荷作品所载将更为详细地讨论联合国明镜系统的铜。英尺（ +或-一个或两个％ ） ，平均每年和每小时的平 运作，下面一节。 均的基础上。这一点，连同其产能，易燃性和可控性是一个 每个设施的需求将有所不同。蒸汽负荷要求将良好的原因，天然气是用来作为一个主要的燃料家用取暖， 改变为不同的设施。离开文礼利律师行的条件将大医院和商业设施。非常高的氢含量（高氢碳比）天然气烧伤， 不相同取决于设施的过程中的需要。 subse - 形成的水消除了大量热从这个过程可以严重影响整体效率的 quently ，每年平均效率，并为一些，每小时的平锅炉相比，与其他燃料。原油是成品，以消除高度的价值-均效率将不少于该文礼利律师行工作效率的设计。能够部分工业原料为塑- TICS资本流动以及其他产品，汽油， 航空燃料和柴油燃料的运输，并为家用取暖油与非 木材和生物质固体燃料两种高氢碳和高水分含量（大于 常低的变异。那个变异每一个这些产品的保费可以40 ％ ） 。因为能源损失是由于水分从燃烧氢和转换的水分， 相等于或优于自然气体。工业燃料产品是剩菜从精以气相（ 1000瓦每英镑） ，这是很难获取的效率，无论是炼，并能增加variabil -性作为质量云从第2号文礼利律师行或每年平均-年龄，等于或接近这些自然煤气， 油1号6或高沥青质掩体C级油或道级沥青或石油别说油或煤。一个很好的年度平均效率为木材或生物量的单 焦。在这种情况下，变异的粘度（燃烧的东西一样，位可在 60 ％左右。而燃料财产的变化可能会优于煤，这些 “黑色肩带糖蜜”或炎热的枫糖浆为液体-焦炭是变化通常发生在水分含量与直接和重大的影响锅炉效率- 一个坚实的更象煤）可已严重影响了燃烧效率和整ciency 。 体锅炉效率。变化的燃料特色的每小时平均的基础燃料的特点确定设计了一个洞ticular单位。燃料的变上可能好于或等于说，天然气。如何-以往，不同化，特别是在氢和水分含量范围以外的一个或二％ ，天然气， 的燃料特性的比较出货量在过去一年可能会增加4时57 ％石油和10 ％的煤炭及其他固体燃料，将影响到效 一- nual平均变化在某个范围内五％ 。由于石油率，无论是文礼利律师行和每年的平均水平。当燃料切换， 具有较低的水电根内容（减少日益增加的职系）比相互作用的新燃料和锅炉，往往产生的负面影响，无论是负 天然气，整体锅炉效率的作为- sociated与燃烧载或锅炉效率。这些影响往往是上午plified因为遇到的限的燃油通常是较高的无论是在文礼利律师行和每制，在固相萃取- cific领域的锅炉，这些不利的跨行动发 年平均。油脂是非常良好的锅炉燃料。 生。一个很好的比喻，将是一个卡车来推上一条高速公路已 煤，我们最丰富的燃料，可以与雷区新技术和大桥清拆更适合汽车。当卡车办法的桥梁，它已放缓至恩确 选煤厂，以删除岩（污染物）中被俘的亲弗塞斯一保它可以通过下的地方，明确的之是足够的。这会导致交通 个加或减百分之十的自然变化能力在一个特定的动议慢因为公路的设计不符合卡车在铭记。 煤层。不过，不同的煤层不同，极大地从褐煤在 燃烧系统 4000瓦每英镑与七％ ，氢气和35 ％ ，水分，以 高效率的使用燃料的燃烧（燃烧） ，需要在-张力向整个无烟煤14000瓦每英镑与二％的氢气和三个含水燃烧器具。被-造成一些地区的问 题 快递公司问题件快递公司问题件货款处理关于圆的周长面积重点题型关于解方程组的题及答案关于南海问题 是共同的所有类型燃烧系 率。低氢含量（低氢碳比例） ，煤是马鞍山高效统，这些领域将是存款保险 计划 项目进度计划表范例计划下载计划下载计划下载课程教学计划下载 -了讨论，然后才检讨具体的率的能源来源，转换btus诠释可用的能源。 系统问题。 共混物的各种煤层和无法消除污染物，如果没 良好的燃烧是能力结构的空气和燃料，与小过剩空气尽 有准备植物，可导致燃油品质变化的10 ％ -或以量在足够高的温度，以维持过程中，完全烧伤燃料（完整的 上的就一小时的基础和20 ％至30 ％ -一分钱就碳转化率）最低环境的排放。良好的COM - bustion还包括一年度的基础上。燃煤系统，也没有- mally设计能力产生马克西-妈妈可用的能源与过程的需要，安全，经济。 处理多达1 Plus或架MI -新加坡国立大学10 ％这是一个复杂的过程，配套燃料的燃烧特性，免疫球蛋白- 的变异性，没有明显的degra - dation的表现。nition ，包括热解，燃烧和烧焦了重型液体和固体燃料，随 因为多样性煤的类型，位置和特征，家庭综合系统着时间的，温度切变及湍流，可从炉吸收的个人资料和燃烧 - ferent类型的燃烧系统主要是用于烧伤燃料和系统透射电镜能力设计。所有这一切，必须交流complished产生能量。以下秒-筹措将看看这方面的更多细节。 与安全的营办商及发cility人员的主意。 每一年，新闻媒体告知我们，锅炉前plosions如果它可用于成本效益，这是。讨论了一些，这些损失是包 杀死的人-无论是蒸汽拖拉机在一个县的公平或一括在附录C ，第4章： “锅炉”的cibo能源效率手册。 个工业或公用事业厂房在中心城市。一个典型的一 系统操作 十?点〇 〇万英镑每小时蒸汽锅炉大约需要1.25理想的情况将是能够运作锅炉或能源装置在设计文礼利 亿btus （ mmbtu ）燃料的投入，每一个小时。律师行。如果一切都是完美的，人们可以设计一个单位这将 这是大约相当于一千一加仑的汽油-线， 12.5万有一个较平坦的效率曲线在整个负荷范围。一切向燃烧锅炉 立方米。英尺的天然气和一小900多加仑的煤油。与摆式燃烧器，可以调整倾斜，以实现同时，出口气体温度 我们所是一个控制爆破的地方，我们采取了能源并与同一水平过剩空气和相同的燃烧效率在所有的作业负荷 把它用于有益的用途。有可问题与此有关。安全必（三个主要的测定- nants锅炉效率） 。不过，这类型单位须永远是我们的头号优先。 主要用于在公用事业行业就较大的锅炉。 燃烧系统，而他们可能似乎简单，是非常复杂cibo的能源效率手册指出，（在左下角的第26页，在的。包括在附录B是第3章， “燃烧”的cibo能第5章， “结论trols “下的氧气回路） ，即燃烧器的最源效率手册。在这里额外的细节每一天的关注，对重quire更多的过剩空气低负荷比在高因为有那么有效的燃 于优化和维护荷兰燃烧效率的介绍。 料空气混合。这是由于混合特性的流溪流和事实，即减去总 设备设计 的反应气体是现在，填补了炉容。空气渗透加剧了这种状况， 工业锅炉设备是为不同的作为产品- ucts和进因为渗入空气不与混合燃料在所有。这些因素事业的混合问 程服务。更好地理解荷兰的，这是由于在附录A ，题，也降低批量火焰温度，这反过来，放缓燃烧反应。因此， “分歧之间的工业和电站锅炉“ 。锅炉是的手段较高的前塞斯的空气在较低负荷的原因，减少了在锅炉效率， 之一提取能源，从控制燃料燃烧。有watertube ，由于额外的空气必须升温以堆叠的温度和用罄到大气中。天 水火，现场架设和包装车间组装单位从非常小到非然气的射击，这影响不算太坏。估计1 5 ％ -美分，效率下常大。概念是简单，就像一个茶壶。水煮沸，使蒸降，从满负荷到25 ％负载可能是合理的现代，紧包锅炉充 汽。不过，实际过程是复杂的。转折十点?万英镑分燃烧控制。在„之上另一方面， 1岁的斯托克没有空气管水（即的一万二千五加仑， 1250鱼缸或游泳池） ，制叶片气流的固定和下降，负荷降低-荷兰燃料的投入。在这以蒸汽每一个小时，带来许多并发症。 种情况下，可能会有更多的超过200 ％过剩空气低负荷造成 这是不可能捕捉每一个从瓦燃烧的锅炉。举例锅炉效率下降，从85 ％左右，在高负荷，以60 ％左右，在来说，有些得到客场的气氛。业界已制定的方法捕低负荷。 捉大部分的瓦的经济。作为一个岁的农民可能会问题一概而论的是，有这么多的因素，包括燃料类型， 说，他们捕获的一切，但该尖叫。当然，今天它也共收到条件的燃料，锅炉的类型，控制系统，金额漏风，维 有可能捕获这一张CD ，如果它有一个使用。这不修地位的单位，和更多的。较大的单位，往往受创较轻比规 是这样做可能不会做，因为它将更多的费用购买模较小的单位，因为他们有多个燃烧器集可以关闭，完全低 CD烧录机，并采取更大的能量，运行CD烧录机，负荷离开，其余燃烧器运行，如果他们在满负荷。此外，较 比价值该尖叫。同样的事情发生与能源。一些获得大的单位往往要更新，更好的控制系统，以调整的运作，从 距离和不同与锅炉，燃料，核电厂的要求- ments 。而减少损失，在外汇基金- ficiency相关较低的负荷。 在风险oversimplifying问题，如果我们假定元是值得多dol加拿大- lar ） 。此外，较高的温度瓦已更一个相对较新的单位，发射了煤，油，或气体，我多的价值比较低的温度下仟卡，因为它可以转换更有效地融 们可以使用以下范围： 入更多的价值-能够电器及机械能源。但是，双方电器及机械 能源必须亲诱导从一些其他的能源来源。 开始，燃料，工业完成协商版本燃烧的燃料和释放热量。 1引擎，然后转换成热能转化机械或电能。如果燃烧发生内 一引擎，它转换为热能，以机械能源，可用于驱动1水泵， 风机，压缩机，或电动发电机。排气离开引擎是热点。这排 气载有超过半数的btus期间释放初步燃烧的燃料，并且可以 超过1000楼如果没有排气热是用来，该装置被称为一个简单 的循环。如果是热从排气为额外的利用相结合的引擎和其他 装置被称为一联产系统或联合循环体系。 效率为简单的周期而异根据设计，大小和位置与EN - gine （燃气轮机，内燃机） 。这也转化为一系列的效率为 这是足以说，在正常的歌剧-要害效率低于保联合循环。作为与锅炉效率1尺寸不适合所有。例如效率转证效率- ciency的新的经营单位在文礼利律师行。换为电力，在简单和联合周期如下: 如何-以往任何时候都比较的原因，设计修改-筹措 或业务和燃料的变化，即时通讯- 协议 离婚协议模板下载合伙人协议 下载渠道分销协议免费下载敬业协议下载授课协议下载 文礼利律师 行的效率，应该有一个比例的影响，实际效率，该 设施是achiev -荷兰对，平均每年的基础上。 热电联产 理想的情况是，能源是使用最有效的当燃料燃 烧是在高温高压的TEM -温度btus被转换为电力 或我- chanical能源在燃气轮机，内部燃烧- tion 引擎，或背部的压力，汽轮机以下万维劳威尔通过 使用较低的温度，以btus满足的过程中需要通过 传热。 电力，机械能，热是家庭综合系统- ferent 形式的能源。科学家已经证明，不同形式的能源有 不同的素质基于后，有能力执行有用的工作。科学 一考试的发电外汇基金- 家告诉我们，电力和机械能源生产更有效地工作， ficiency表表明，当电力是 比热能源。在其他换言之，一仟卡，价值电器或机 只有产品，最高btus收回是 械能有更多的价值超过1瓦值得热能（类似钱凡美 40 ％左右，对于简单的周期和54 ％ - 为联合循环。增加效率- ciency为联合循环表明，只有 约25 ％的余热可协商 verted电力与现代科技。 之间的差额40 ％的转换 为简单循环和25 ％的额外 转换说明的差异，在价值之间的低温热和高温。 的概念，热电联产 提供了进一步的效率，改善生产，只有电力使用余 热直接在制造过程中。许多 制造过程需要热量在temperaoo 支出之间的250f和700f 。该btus亲vided由排 气从上述申请是在温度符合这些 温度要求。因此，通过转换 高温度，高品质的btus机械或电气能源和以较低 的 温度，质量较低的btus ，以满足过程中温度的需 要，能源的燃料可以 用最有效和高效率。带有 这种组合，从60 ％至85 ％的btus在燃料可以回 收和 有效的利用。 Energy Efficiency and Industrial Boiler Efficiency: An Industry Perspective on the Differences Between Industrial and Utility Boilers is included as an appendix to help un- Energy Efficiency and need for people to do the work. Industrial Boiler Efficiency: This white paper will address the efficiency-related An Industry Perspective aspects of the four primary factors Robert Bessette, Council of Industrial Boiler Owners affecting the industrial boiler and the factors Energy efficiency for industrial boilers is a affecting applica- highly tion of combined heat and power boiler-specific characteristic. No two boilers systems to in- are dustrial facilities. A copy of the alike. There are two identically designed, con- Background Paper structed side by side, stoker fired boilers in Indi- ana burning the same fuel that have very different performance characteristics. Like twin teenagers, they are not the same. Consideration of energy efficiency for industrial boilers, more often than not, is simplified and categorized to a one-size- fits-all approach. Just as when considering teen- agers, this does not work. While parents would like to believe their teenager is gifted and talented and in the 80th percentile of the population, we know that is not necessarily the case. We also know, as for boilers, the average teenager is not representative of a widely diversified population. If you think it is, ask any parent with teenagers or an industrial boiler operator. While the variables associated with energy efficiency are more limited than those associated with a teenager, they are in no way any less complicated. Four factors are critical for assessing energy effi- ciency in the industrial powerhouse supplying en- ergy to make products for the benefit of custom- ers in a highly competitive international market- place. These are: 1. fuel type, 2. combustion system limitations, 3. equipment design, and 4. steam system operation requirements. Furthermore, the industrial facility’s complexity, location, and objective complicate them. It is important for the industrial company to remem- ber, unlike the utility, that energy is a smaller por- tion of the final product price. However, without energy there is no final product or service. Need- less to say, without products or services there is no derstand the diversity of the industrial boiler competitive world. It could be like building a new population. From the EPA Boiler MACT Da- home with a heat pump and a furnace capable of tabase, there are about 22,000 industrial-com- burning natural gas and a furnace capable of burn- mercial and institutional boilers with greater ing oil to cover the heating, air conditioning, hot than ten million Btus per hour heat input. water, and other household needs. The cost of all of this equipment would break the budget. It is evident that an average person probably could af- NEW VS. EXISTING UNITS ford only one of these devices. If the person tried to buy all three, they would not be able to afford Before investigating specifics of industrial boiler the house. efficiency considerations, it is important to un- derstand that once a boiler is designed, con- New units are purchased with a guaranteed effi- structed, and installed, it can be difficult and costly ciency at a Maximum Continuous Rating (MCR) to improve its efficiency above the design. On for a specific design fuel producing a specified the other hand, as will be discussed below, changes quantity of steam or hot water at a specified tem- in fuel, load, and operation can easily impact over- perature and pressure. Any changes in these char- all efficiency. Because of the high cost of the en- acteristics change the operating efficiency. A guar- ergy plant, boilers and associated systems usually antee over a wider range of fuel, capacity, and tem- are purchased for the life of a facility with ample perature and pressure is technically possible. How- margin for future growth and process variability. ever, as mentioned, it may not be economically With proper maintenance, boiler life is indefinite. justifiable for a given facility. In the end, a new In most cases, it will outlive the process it origi- unit may be defined only as one that is designed, nally was designed for but not the facility. For example, a facility that was producing eight track tapes changed to produce cassette tapes and is now producing CDs and DVDs. The boiler will still be there meeting new demands. 5 With today’s technologies it is possible to design boilers to handle a wide range of requirements and possibilities. However, in most cases this is eco- nomically impossible if a process is to survive in a Energy Efficiency and Industrial Boiler Efficiency: An Industry Perspective the MCR efficiency of the design. Differences purchased and installed, but never run at the guarantee conditions other than to pass accep- tance tests. In the real world almost nothing operates at the design specifications. 6 ANNUAL AVERAGE VS. MCR DESIGN If you start from cold water have you ever watched how long it takes to get it boiling? I believe it was Ben Franklin who said, ―A watched pot never boils.‖ It does, but it takes the addition of 1,000 Btu per pound of water before it does. After that, considering losses from the teapot or boiler, Btu for Btu, is converted to steam where you use it or lose it. In systems that have a heavy cyclic load, the operator can either start up or shut down the boiler as needed (for a period lasting 2 to 5 hours each way) without the loss of much of the initial energy. However, for periods longer than this, much if not all of the initial 1,000 Btus are lost. On the other hand, the operator can keep it at pressure to ensure rapid response by supplying enough heat to compensate for losses in the sys- tem. Here, efficiency is zero, but the initial 1,000 Btus are maintained. In both cases there is in- creased energy loss and the inability to meet or maintain MCR efficiency. In facilities like a col- lege campus, with a heating load, where heat is needed every morning so the students will have warm classes to go to, hot showers to wake up with, and hot food in the cafeteria serving lines, it is better to keep the boiler hot, lose the efficiency, and keep the students, their professors and their parents happy. In a large hospital performing many major surgeries per day using autoclaves to sterilize surgical instruments, should a system be designed to handle the maximum number of sur- geries expected or a smaller number thus limiting the number of people that can be helped in any one day? Obviously, the system must be designed to meet the maximum capacity of the hospital. Here it is impossible to deliver both MCR effi- ciency conditions and optimum patient service. There also are losses associated with low load op- eration that will be discussed in greater detail un- der the Systems Operation section below. Each facility’s needs will be different. Steam load requirements will change for different facilities. Departures from MCR conditions will vary widely depending upon facility process needs. Subse- quently, the annual average efficiency, and for some, the hourly average efficiency will be less than Steam Digest 2002 between actual efficiency, an annual average, and MCR can be as much as 40 percent or more depending upon the facility. Any consideration of industrial boiler efficiency must consider dif- ferences between real, actual, and design effi- ciencies. The ability of a particular process to use steam efficiently complicates this factor. With steam af- ter it is produced you use it or loose it. Inefficien- cies inherent for various process factors can be as important as the inefficiencies associated with the boiler. FUEL TYPE Mother Nature is miraculous. Naturally occur- ring fuel (gas, oil, wood, coal and biomass) is vari- able. The plants, animals, bugs and other critters that formed the fuel underwent tremendous change at different locations and over different time periods. Elemental compositions of fuel [moisture (HO), carbon (C), hydrogen (H), ni- 2 trogen (N), chlorine (Cl), sulfur (S), oxygen (O) and ash] can vary as much as 30 percent or more from an annual average basis depending upon their inherent composition and degree of fuel refining or preparation. Any variations in fuel composi- tion from the original design of the system will directly affect boiler efficiency. In most cases with boiler design these days, variations of less than one or two percent from the design fuel composition will have virtually no perceptible impact on effi- ciency. For this discussion, the Btu per pound, gallon, or cubic foot of the coal, oil, or gas respec- tively may be a better, however over simplified, way of looking at it. Even natural gas can vary between 900 and 1,100 Btu/cu. ft. depending upon the methane content. Over the years technology has allowed gas com- panies to blend gas and control its Btu and com- position to a level of around 1,000 Btu/cu. ft. (+ or – one or two percent) on an annual average and hourly average basis. This, along with its deliverability, ignitability and controllability is a good reason why natural gas is used as a primary fuel for home heating, hospitals and commercial installations. The very high hydrogen content (high hydrogen to carbon ratio) of natural gas that burns to form water removes a significant amount of heat from the process and can seriously impact the overall efficiency of the boiler as compared with other fuels. Energy Efficiency and Industrial Boiler Efficiency: An Industry Perspective Steam Digest 2002 Crude oil is refined to remove the highly valu- Wood and biomass are solid fuels with both high able portion for industrial feedstocks for plas- hydrogen to carbon and high moisture content tics and other products, for gasoline, aviation (greater than 40 percent). Because of energy fuel and diesel fuel for transportation, and for loss due to moisture from the combustion of home heating oil with very low variability. The hydrogen and conversion of moisture to vapor variability of each of these premium products (1,000 Btu per pound), it is very difficult to can be equal to or better than that of natural obtain efficiencies, either MCR or annual aver- gas. Industrial fuel products are the leftovers age, equal to or approaching those of natural from refining and can have increasing variabil- gas, never mind oil or coal. A very good annual ity as the quality goes from a No. 2 oil to a No. average efficiency for a wood or biomass unit 6 or high asphaltene Bunker C grade oil or road may be in the 60 percent range. While fuel grade asphalt or petroleum coke. In such cases, property variations may be better than coal, these variation in viscosity (burning something like variations usually occur in the moisture content ―black strap molasses‖ or hot maple syrup for with a direct and major impact on boiler effi- the liquids – coke is a solid more like coal) can ciency. have a serious impact on combustion efficiency and overall boiler efficiency. Variation in fuel Fuel characteristics determine the design of a par- characteristics on an hourly average basis may ticular unit. Fuel changes, especially in hydrogen be better or equal to that of natural gas. How- and moisture content outside the range of one or ever, variations in fuel characteristics between two percent for natural gas, three to five percent shipments over the year may increase the an- for oil and 10 percent for coal and other solid nual average variation to somewhere in the range fuels, will have an impact on efficiency, both MCR of five percent. Because oil has a lower hydro- and annual average. When fuels are switched, the gen content (decreasing with increasing grade) interaction of the new fuel and the boiler often than natural gas, the overall boiler efficiency as- produces negative impacts on either the load or sociated with burning fuel oils usually is higher the boiler efficiency. These effects often are am- both at MCR and annual average. Oils are very plified because of limitations encountered in spe- good boiler fuels. cific areas of the boiler where these adverse inter- actions occur. A good analogy would be a truck Coal, our most abundant fuel, can be mined with that comes onto a superhighway that has bridge new technologies and coal preparation plants to clearances more suitable for cars. When the truck remove rock (contaminants) captured in the pro- approaches a bridge, it has to slow down to en- cess to a plus or minus 10 percent natural vari- sure that it can pass under a place where the clear- ability within a given seam. However, different ance is adequate. This causes traffic to move slower coal seams vary tremendously from lignite at 4,000 because the highway was not designed with the Btu per pound with seven percent hydrogen and truck in mind. 35 percent moisture to anthracite with 14,000 Btu per pound with two percent hydrogen and three COMBUSTION SYSTEMS percent moisture. With low hydrogen contents (low hydrogen to carbon ratio), coal is the most Efficient fuel burning (combustion) requires at- efficient energy source for conversion of Btus into tention to the entire combustion apparatus. Be- usable energy. cause some problem areas are common to all types of combustion systems, those areas will be dis- Blends of various coal seams and the inability to cussed before reviewing specific system problems. remove contaminants, if there is no preparation plant, can lead to fuel quality variations of 10 Good combustion is the ability to mix air and fuel, per- with as little excess air as possible, at a high enough cent or more on an hourly basis and 20 to 30 temperature to sustain the process and completely per- burn the fuel (complete carbon conversion) with cent on an annual basis. Coal fired systems minimum environmental emissions. Good com- nor- bustion also includes the ability to generate maxi- mally are designed to handle up to a plus or mi- mum usable energy consistent with process needs, nus 10 percent variability without visible degra- safety, and economics. This is a complex process dation of performance. Because of the diversity of matching fuel combustion characteristics, ig- of coal types, locations, and characteristics, dif- nition, including pyrolysis, and char burn out ferent types of combustion systems are used to for heavy liquid and solid fuels, with the time, burn fuel and generate energy. The following sec- tions will look at this aspect in more detail. 7 Energy Efficiency and Industrial Boiler Efficiency: An Industry Perspective would cost more to buy a CD recorder and take more energy to run the CD recorder temperature and turbulence available from the than the value furnace absorption profile and combustion sys- of the squeal. The same thing tem capabilities design. All this has to be ac- happens with complished with the safety of operators and fa- energy. Some of it gets away cility personnel in mind. and that varies with the boiler, the fuel, and the Each year, the news media inform us of boiler plant require- ex- ments. If it can be used cost plosions that kill people – be it a steam tractor at effectively, it is. a county fair or an industrial or utility powerhouse in the center of a city. A typical 100,000 pounds per hour steam boiler requires about 125 million 8 Btus (MMBtu) of fuel input each hour. That is equivalent to approximately 1,100 gallons of gaso- line, 125,000 cu. ft. of natural gas, and a little more than 900 gallons of kerosene. What we have is a controlled explosion where we take energy out and use it for beneficial purposes. There can be problems with this. Safety must always be our number one priority. Combustion systems, while they may seem simple, are very complex. Included in Appendix B is Chapter 3, ―Combustion,‖ of the CIBO Energy Efficiency Handbook. Here additional details of day to day concerns for optimizing and maintain- ing combustion efficiency are presented. EQUIPMENT DESIGN Industrial boiler equipment is as varied as the prod- ucts and processes it serves. A better understand- ing of this is given in Appendix A, ―Differences Between Industrial and Utility Boilers.‖ Boilers are one means of extracting energy from controlled fuel combustion. There are watertube, firetube, field-erected, and packaged shop-assembled units from very small to very large. The concept is simple, like a teapot. Boil water to make steam. However, the actual process is complex. Turning 100,000 pounds of water (that’s 12,500 gallons, 1,250 fish tanks or a swimming pool) to steam each hour brings with it many complications. It is impossible to capture each and every Btu from combustion in the boiler. For example, some get away to the atmosphere. Industry has devised ways to capture most of the Btu’s economically. As an old farmer might say, they capture everything but the squeal. Of course, today it could be possible to capture that on a CD if it had a use. It is not done and probably will not be done because it Steam Digest 2002 A discussion of some of these losses is included in Appendix C, Chapter 4: ―Boilers‖ of the CIBO Energy Efficiency Handbook. SYSTEM OPERATIONS The ideal situation would be to be able to operate the boiler or energy device at the design MCR. If everything were perfect, one could design a unit that would have a relatively flat efficiency curve across the load range. A tangentially fired boiler with tilting burners could adjust tilts to achieve the same exit gas temperature with the same level of excess air and the same combustion efficiency at all operating loads (the three main determi- nants of boiler efficiency). However, this type unit is used primarily in the utility industry on larger boilers. CIBO’s Energy Efficiency Handbook points out (at the bottom left of page 26 in Chapter 5, ―Con- trols‖ under Oxygen Loop), that most burners re- quire more excess air at low loads than at high because there is less effective fuel to air mixing. This is due to mixing characteristics of flow streams and the fact that less total reacting gas is now filling the furnace volume. Air infiltration aggravates this condition because infiltrated air does not mix with the fuel at all. These factors cause mixing problems and also lower the bulk flame temperature, which, in turn, slows down combustion reactions. As a result, the higher ex- cess air at lower loads causes a decrease in boiler efficiency due to the additional air that must be warmed up to stack temperature and exhausted to the atmosphere. For natural gas firing, this impact is not too bad. An estimate of a five per- cent efficiency drop from full load to 25 percent load probably is reasonable for a modern, tight, package boiler with full combustion controls. On the other hand, an old stoker with no air controls leaves the airflow fixed and drops load by reduc- ing fuel input. In such cases there could be more than 200 percent excess air at low loads causing boiler efficiency to drop from about 85 percent at high load to around 60 percent at low load. The problem with generalizations is that there are so many factors including fuel type, as-received condition of the fuel, boiler type, control system, amount of air leakage, maintenance status of the unit, and more. Larger units tend to suffer less than smaller units because they have multiple burner sets that can be turned off completely at low loads leaving remaining burners to run as if they were at full load. Also, larger units tend Energy Efficiency and Industrial Boiler Efficiency: An Industry Perspective Steam Digest 2002 to be newer and have better control systems to curs inside an engine, it converts heat energy to adjust the operation thus reducing losses in ef- mechanical energy that can be used to drive a ficiency associated with lower loads. pump, fan, compressor, or electrical generator. Exhaust leaving the engine is hot. This exhaust At the risk of oversimplifying the problem, if contains over half of the Btus released during we assume a relatively new unit, firing coal, oil, initial combustion of the fuel and it can exceed or gas we can use the following ranges: 1,000 oF. If none of the exhaust heat is used, the device is known as a simple cycle. If heat is Table 1: Typical Efficiency For New Boilers recovered from the exhaust for the additional CFu ll load ef ifciency - Low load ef ifciency - utilization, the combination of the engine and oa85% 75% other devices is known as a cogeneration system l or a combined cycle system. Fu ll load ef ifciency - Low load ef ifciency - O li 80% 72% Efficiencies for simple cycles vary depending BioGaupon the design, size, and location of the en- Fu ll load ef ifciency - Low load ef ifciency - masgine (gas turbine, internal combustion engine). s s 75% 70% Fu ll load ef ifciency - Low load ef ifciency - 70% 60% It is sufficient to say that under normal opera- This also translates into a range of efficiencies tion, efficiency is lower than guaranteed effi- for combined cycles. As with boiler efficiencies ciency of the new unit operating at MCR. How- one size does not fit all. Example efficiencies for ever, for comparative reasons, design modifica- conversion to electricity in simple and combined tions or operational and fuel changes that im- cycles are as follows: pact MCR efficiency should have a proportional impact on actual efficiency the facility is achiev- Generatificiencies Typical on Ef Electric ing on an annual average basis. Low High Range Simple Range Cycle Applications Gas Turbines 25% Net HHV About 38% Net HHV COMBINED HEAT AND POWER ICE Engines 41% Net HHV 20% Net HHV Ideally, energy is used most efficiently when Coal Bo liers / About 40% Net HHV 25% Net HHV Steam Turbines fuel Wood Bo liers / 15% Net HHV 25% Net HHV is combusted at a high temperature and high Steam Turbines tem- Combined perature Btus are converted to electricity or me- Cycle chanical energy in a gas turbine, internal Application 57% Net HHV combus- 40% Net HHV Gas Turbines / tion engine, or back pressure steam turbine fol- HRSG Steam lowed by the use of the lower temperature Btus Turbine to HHV = 1 meet process needs through heat transfer. Electricity, mechanical energy, and heat are dif- ferent forms of energy. Scientists have shown that different forms of energy have different qualities able electrical and mechanical based upon the ability to perform useful work. energy. However, Scientists tell us that electricity and mechanical both electrical and mechanical energy must be pro- energy produce work more effectively than heat energy. In other words, a Btu worth of electrical duced from some other energy source. or mechanical energy has more value than a Btu worth of heat energy (similar to money where a Starting with fuels, industry U.S. dollar is worth more than a Canadian dol- lar). Furthermore, a higher temperature Btu accomplishes con- has version by burning the fuel and more value than a lower temperature Btu releasing heat. because An engine then converts heat energy it can be converted more efficiently into more valu- into me- An examination of the electricity generation ef- chanical or electrical energy. If combustion oc- ficiency table shows that when electricity is the only product, maximum Btus recovered are about 40 percent for simple cycles and 54 per- cent for combined cycles. The increased effi- ciency for the combined cycle shows that only about 25 percent of the exhaust heat can be con- verted to electricity with modern technology. The difference between 40 percent conversion for the simple cycle and 25 percent additional conversion illustrates the difference in value be- tween low temperature heat and high tempera- ture heat. The concept of combined heat and power pro- vides further efficiency improvements over pro- ducing only electricity using exhaust heat di- rectly in the manufacturing process. Many manufacturing processes require heat at tempera- ootures between 250F and 700F. The Btus pro- 9 Energy Efficiency and Industrial Boiler Efficiency: An Industry Perspective 10 vided by the exhaust from the above applica- tions are at temperatures that match these tem- perature requirements well. Hence, by convert- ing high temperature, high quality Btus to me- chanical or electrical energy and taking the lower temperature, lower quality Btus to meet pro- cess temperature needs, the energy in fuel can be used most effectively and efficiently. With this combination, from 60 percent to 85 per- cent of the Btus in the fuel can be recovered and used effectively. After comparing these efficiencies with boiler ef- ficiencies listed in Table 1, on the surface nothing seems to have been gained. However, the gain comes when one considers that for electricity gen- erated at a central plant or for mechanical energy to run a compressor, fan, or pump, from 60 per- cent to 75 percent of the Btus are lost. Under a conventional system, a boiler or other combus- tion device is still required to provide heat for the facility or manufacturing process. For those that may want a more technical discussion of combined heat and power and efficiency, the following should help provide additional insight. COMBINED HEAT AND POWER EFFICIENCY The most common expression of efficiency is a comparison of the desired output of a process to the input. Electrical power generation efficiency is a relatively simple concept because electrical power is the only desired output and fuel energy is the only input. Equation 1: =Efficiency = electrical generation Electrical Power Produced / Fuel Energy Input = Energy Desired / Purchased Energy A very common type of electrical generation sys- tem consists of a boiler and a steam turbine ar- rangement. In this arrangement the boiler serves to input fuel energy into water to produce steam. The steam exits the boiler with a very high energy content. As an example, the boiler may add 1,450 Btu of fuel energy to every pound of water pass- ing through the component. The steam turbine serves to convert this thermal steam energy into mechanical or shaft energy. The turbine is very effective at this conversion process; in fact, nearly 100 percent of the steam energy extracted by the turbine is converted into shaft energy. However, this excellent efficiency only applies to the ther- mal energy extracted by the turbine. The turbine Steam Digest 2002 actually leaves the vast majority of thermal en- ergy in the exhaust steam. As an example, a steam turbine may extract 450 Btus of thermal energy for every pound of steam passing through the turbine. This energy is readily converted into electrical energy with excellent efficiency, nearly 100 percent. However, recall the boiler input 1,450 Btus of thermal energy into every pound of steam. Therefore, 1,000 Btus remain in each pound of steam exiting the turbine. This steam exiting the turbine is not useful to the power generation system and is discarded from the sys- tem. The steam energy is discarded by cooling or condensing the steam. This gives rise to the description of this system as a ―condensing tur- bine‖ system. The desired output of this sys- tem is the 450 Btus of electrical energy and the input is the fuel-input energy (1,450 Btus of fuel energy). The efficiency of this system would be as follows. Equation 2: electrical generation = 450 Btu / 1,450 Btu = 31% Industrial systems utilizing combined heat and power arrangements have a need for the thermal energy discharged from the turbine. This provides the basis for the advantage of combining heat and power generation systems. If the 1,000 Btus in every pound of steam can be used in a productive manner the fuel utilization efficiency can dramati- cally increase. In a combined heat and power sys- tem there are two desired products, electricity and thermal energy. The fuel utilization efficiency equation will take the following form. Equation 3: CHP = Electrical Power Produced + Useful Thermal Energy / Fuel Energy Input In theory, this efficiency could reach 100 percent, in reality, inefficiencies result in maximum effi- ciencies approaching 70 percent. Note that this efficiency considers thermal energy equal in value to power. This may not be the case because power is normally more valuable (easily usable) than ther- mal energy, but thermal energy is valuable. Some common examples where steam could be more valuable than electricity are sterilizing hospital in- struments, making paper and steam tracing chemi- cal lines. Other mechanisms are utilized to pro- duce electrical power; however, current conven- tional mechanisms consuming fuel (combustion turbines and reciprocating internal combustion engines) result in very similar arrangements. Energy Efficiency and Industrial Boiler Efficiency: An Industry Perspective Steam Digest 2002 Condensing steam turbines with the ability to Natural gas is normally sold in cents per therm condense unneeded steam are often incorporated (100,000 Btu). Multiply this by 10 and we have into industrial combined heat and power sys- $/MMBtu. tems to allow the system to be balanced. In other words, if the demand for thermal energy dimin- For natural gas, if you pay 62 cents per therm, ishes and the demand for electrical energy in- you pay $0.62/therm x 10 therm/MMBtu = creases, steam can be passed through a condens- $6.20/MMBtu. ing steam turbine to produce the additional power while maintaining a more uniform and Electricity is normally sold in cents per Kilowatt efficient load and without venting the steam. (kW). Multiply this as dollars by 293 kW/MMBtu The fuel energy utilization efficiency of operat- gives dollars per MMBtu, something that is di- ing the condensing turbine returns to the low rectly comparable to the cost of other energy value described above (31 percent and even sources. much less) for that portion of the steam con- densed. In order for condensing power to be For electricity, if you pay 10 cents per kW, you cost effective, the fuel cost must be significantly pay $0.10/kW x 293 kW/MMBtu = $29.30/ less than the electricity cost. In fact, because MMBtu. the industrial facility will generate condensing power less efficiently than the large utility, in Thank goodness for heat pumps when the tem- the evaluation, to produce electricity through perature is in the proper range. Here they are about condensing, efficiency losses must balance 300 percent efficient and that lowers the heating against process needs, availability requirements, cost to about $9.80 per MMBtu. and alternative electricity purchasing costs or sales revenues. APPLICATION OF COMBINED HEAT AND Example: Consider an industrial facility requiring both POWER SYSTEMS ther- The discussion above explained advantages of mal energy and electricity. The facility currently combined heat and power systems using gas tur- purchases electricity from the local power bines, internal combustion (IC) engines, com- genera- bined with boilers to show how these systems use tor and fuel from the fuel supplier. The local power Btus released from fuel combustion more effi- generator purchases fuel from the same fuel sup- ciently. A common combined heat and power plier as the industrial customer. The local power system (perhaps the oldest for industrial applica- generator purchases 100 units of fuel and con- tions) consists of generating high temperature, verts this into 31 units of electrical energy. This high-pressure steam and running it through a back electrical energy is consumed in the industrial fa- pressure steam turbine to produce electricity. Hot cility. The industrial facility purchases 100 units exhaust from the turbine goes to the process to of fuel and converts it into 80 units of thermal use the lower temperature Btus. This section cov- energy. A combined heat and power system could ers applications of various combined heat and be operated at the industrial complex to supply power systems to show that selection of the opti- the same amount of electrical and thermal energy. mum system depends upon the resources and The combined heat and power system might re- needs of the facility. quire 143 units of fuel energy to supply the same thermal and electrical demands as the 200 units The main factors that determine the type of en- of fuel originally required. This is a 28 percent ergy supply system for a given facility are: reduction in fuel consumption. Fuel availability; To give you an idea of relative cost, comparison Proportion of plant energy needed in the form of the use of natural gas and electricity for home of electrical, mechanical and heat; heating may be beneficial. Assuming the same Extent and frequency in supply requirements amount of energy is needed to keep the home for steam; and warm on a very cold day (some temperature less Market for surplus electricity. than freezing outside), a simple calculation can help understand the differences. We can look at the energy costs in dollars per MMBtu delivered. 11 Energy Efficiency and Industrial Boiler Efficiency: An Industry Perspective power system may not be practical. Using the industrial examples, the following Fuel availability observations are Fuel availability depends upon the geographi- pertinent. If there is no need for cal location of the facility, products produced, thermal (heat) cost of various fuels, and compatibility of vari- ous fuels with plant processes. Some example industries that demonstrate this relationship are: pulp and paper, cane sugar processing, refiner- 12 ies, ammonia plants, and batch chemical plants. Contrary to popular opinion, there are areas in this country where natural gas is not available but where there are abundant supplies of coal or other fuels. Pulp and paper and cane sugar processing are ex- amples of industries that produce a fuel byproduct used for some or all of their energy supply. The pulp and paper industry burns bark and wood from trees that provide feedstock for making pulp and paper. It also burns pulp residue that other- wise would be wasted. The sugar industry burns bagasse, which is leftover material after sugar has been squeezed out of sugar cane. These fuels are solid biomass. The paper industry supplements fuels with coal, another solid fuel that is burned easily with biomass. Other biomass fuels include palm fronds, peanut shells, rice hulls, hog manure, and poultry litter. If it has Btu value, someone can use it, and probably is using it for a fuel to generate valuable energy and eliminating a poten- tially serious waste disposal problem. Refineries process crude oil, and use fuel byproducts (gas, heavy oil, and coke) for most of their energy requirements. These fuels are supple- mented with small quantities of natural gas. Ammonia plants use natural gas with some of their byproduct purge gas. Natural gas is both a fuel and the feedstock. Batch chemical plants use a variety of fuels (natu- ral gas, oil and coal) mainly depending upon the geographical location of the plant. Need for electrical, mechanical, and heat energy The proportion of energy in the forms of electric- ity, mechanical energy, and heat energy is impor- tant in determining the extent to which a com- bined heat and power system can be applied at a given facility. When there is little need for electri- cal or mechanical energy, a combined heat and Steam Digest 2002 or mechanical energy at a location, there is no possibility for a combined heat and power sys- tem. The pulp and paper industry needs heat in the form of steam to operate digesters that make pulp and to provide heat for drying paper. The industry needs electrical energy to run paper machines and mechanical or electrical energy to run debarking machines, pumps, and compres- sors. Due to these requirements, a pulp and paper mill often uses combined heat and power. Steam from boilers goes through backpressure turbines to make electricity; then exhaust steam goes to digesters and paper dryers to provide process heat. Due to fuel availability and steam and electric pro- cess requirements, use of gas turbines is not nor- mally practical in a combined heat and power ap- plication in this industry where energy efficiency maximization is of prime importance. Because the fuels contain high moisture levels, the ther- mal efficiency of the combined heat and power system within these facilities is inherently lower than in other applications. Refineries require both electricity and heat energy. Recently, many refineries have added gas turbines with heat recovery steam generators (waste heat boilers). Electricity runs pumps, fans, and com- pressors inside the refinery, and steam from the waste heat boilers provide heat for refinery opera- tions such as distillation units, reboilers, and other machinery that demand electricity and steam. Surplus electricity not used within the plant is sold to the electrical power grid. With available fuels, the combined heat and power system can attain very high efficiencies for refinery applications. Another form of cogeneration involves the use of petroleum coke that is burned in a circulating flu- idized bed boiler to generate steam. Steam goes to a backpressure turbine to make electricity and ex- haust steam goes to the refinery to provide heat for refinery operations. When discussing combined heat and power regu- lators, plant managers often concentrate on elec- tricity generation followed by the use of the re- sidual heat to produce steam. Although this is a typical combined heat and power scenario, it is not always the most efficient or effective use of technology at a given facility. For example, am- monia plants require a lot of mechanical energy to compress gases to very high pressure. For Energy Efficiency and Industrial Boiler Efficiency: An Industry Perspective Steam Digest 2002 this case, it is better to use a gas turbine to drive temperatures and elevations above sea level. Co- the compressor(s) rather than use a large elec- generation applications that recover the maximum tric motor. The exhaust from the gas turbine amount of waste heat created by the generation of contains high levels of oxygen as well as high the electrical component of the plant achieve over- temperature. This exhaust can be used to fire all efficiencies in excess of 80 percent on a high more fuel in a furnace that produces hydrogen heating value (HHV) basis. Simple cycle ther- for the ammonia process. In this case, the mal efficiencies can exceed 41 percent on a HHV ―power‖ is mechanical energy and the residual basis, i.e., those when only electricity is being heat is converted directly to chemical energy andgenerated and no waste heat recovery is occur- steam in the furnace. Due to process require- ring. ments it is not wise to make electricity with the gas turbine and send it to an electric motor to Cogeneration applications favor gas turbine tech- drive the compressor. nology when the process requires a massive amount of high temperature steam. Gas turbines create Batch chemical plants have varying needs for elec- large quantities of high temperature exhaust gas, tricity, mechanical energy, and heat depending resulting in the need to generate large quantities upon the product produced. The suitability and of high temperature steam in order to achieve ac- selection of various combined power and heat and ceptable overall plant thermal efficiencies. If uses power systems may vary widely depending upon for the large quantity of high quality steam are process needs. available, then gas turbine technology usually is used. Extent and frequency in supply efficiency, which is the highest requirements for steam efficiency of com- Combined heat and power systems are less mercial technologies under real-world likely ambient to be practical in small plants where steam require- ments change rapidly. Many batch chemical plants have this characteristic. It is counterproductive to run a gas turbine or IC engine to produce elec- tricity and to throw Btus into the atmosphere in the form of vented surplus steam. Market for surplus electricity In some cases, the need for electricity or heat is out of balance. Electricity must be generated in surplus quantities to produce enough steam for process use. In these cases, electricity must be sal- able at a price that exceeds the money needed to build the combined heat and power unit at the facility. Industry operates at low profit margins and cannot afford to give free electricity to other users. However, there is one thing for certain, if there is a need for steam there is a possibility for combined heat and power. INTERNAL COMBUSTION ENGINES AND TURBINE CONSIDERATIONS WITH WASTE HEAT BOILERS OR HEAT RECOVERY STEAM GENERATORS Modern internal combustion (IC) engines used to generate electricity with either fired or unfired heat recovery boilers maintain their simple cycle In the other on-site situations requiring smaller efficiency varies with the time of year and the amounts of steam and higher quantities of pro- weather.) Recognizing this loss, boilers are rated cess hot water, modern IC engine technology pro- based on a higher heating value of the fuel. This vides the best economic returns for the owner and efficiency includes unrecovered heat from allow- is the technology of choice. ing water vapor to exit the boiler. As discussed previously, the reason that gas and Gas turbine advocates attempt to avoid this com- oil have lower boiler efficiencies than coal is be- plexity by referring to the lower heating value of cause these fuels have progressively higher hydro- the fuel and doing all of their calculations at ISO gen contents that generate water during combus- conditions (59?F and one bar and constant rela- tion. This water is boiled and heated up to stack tive humidity). In the real world, gas turbines temperature where it is emitted into the lose efficiency faster than steam turbines as load atmosphere. (The water in this instance is formed is decreased, and lose output particularly fast as as a vapor, as it contains the latent heat but does not pass through the boiling process in the com- bustion process). That moisture loss takes heat away from the energy available to boil the water 13 inside the tubes to make steam for productive use. If there is moisture present with the fuel, such as surface water or humidity, that water also is lost to the stack and causes an efficiency loss. (Yes, the Energy Efficiency and Industrial Boiler Efficiency: An Industry Perspective Steam system requirements often have signifi- cant adverse impacts on ambient temperatures and altitudes increase. achievable efficiencies Efficiencies presented in this white paper are all especially for potential combined based on the higher heating value to provide heat and power adequate comparisons. SUMMARY AND CONCLUSIONS Owners and operators of industrial facilities strive to operate at optimum efficiencies. However, 14 un- like the utility industry that produces a single prod- uct, industrial facilities are more complex. Boil- ers designed for such facilities are much more di- versified in order to meet widely differing require- ments. These different requirements naturally create optimal efficiencies that vary widely from industry to industry and from facility to facility. The one-size-fits-all approach often used by regu- lators to encourage increased energy efficiency sim- ply does not work because this approach does not consider the many specific factors that affect en- ergy efficiency. This white paper has discussed major factors that significantly affect achievable energy efficiencies within various industrial facilities. Fuel type and availability, combustion system limitations, equip- ment design, steam system operation require- ments, energy requirement mix, and outside mar- ket forces all affect the achievable efficiency of an industrial facility. Fuel type and availability has a major effect. Fu- els with high heating values, high carbon to hy- drogen ratios, and low moisture content can yield efficiencies up to 25 percent higher than fuels that have low heating values, low carbon to hydrogen ratios, and high moisture contents. A rule of thumb for the efficiency hierarchy in descending order is coal, heavy fuel oil, light fuel oil, natural gas, and biomass. From these rankings, it is obvi- ous that fuel availability plays a major role. Factors such as combustion system limitations and equipment design limit the types of fuels that rea- sonably can be used within a given boiler. Be- cause the design of older boilers is fixed, switch- ing fuels often leads to significant losses in effi- ciency or capacity. In some cases changing from one fuel to another, such as natural gas to fuel oil, may improve efficiency. Steam Digest 2002 applications. Widely different steam demands can lead to periods where the boiler is kept run- ning on ―idle‖ in certain industries. Because the boiler produces little or no steam under these conditions, its operating efficiency is close to zero. The alternative of shutting the boiler down to conserve energy in fact wastes energy and of- ten is not practical. When possible, the application of combined heat and power produces large improvements in effi- cient energy usage. Use of high temperature en- ergy to produce electrical or mechanical energy followed by the use of remaining lower tempera- ture energy to meet process heat requirements is the ideal. Industries such as the paper industry have utilized combined heat and power for more than a half century. The highest efficiencies are achieved by systems combining IC engines or gas turbines with boilers or process heaters. How- ever, these systems are not suitable for every facil- ity. Factors such as fuel availability, the facility’s relative needs for electrical, mechanical, and heat energy, steam demand and demand cycles and the market for surplus power have major effects on whether or how combined heat and power may be applied at a given facility. Even where com- bined heat and power is applied, one size does not fit all, and various applications can have widely different efficiencies. Energy Efficiency and Industrial Boiler Efficiency: An Industry Perspective Steam Digest 2002 dustries. Even at a single installation, applica- tion of steam from an industrial boiler can change Appendix A dramatically with the seasons, when steam or hot water is used for heating, as well as from hand, DIFFERENCES BETWEEN INDUSTRIAL AND have markedly different purposes in different in- UTILITY BOILERS Industrial and utility boilers are significantly different. Yet, because both generate steam, legislators and requlators tend to treat them the same. Major differences between industrial and utility boilers are in three principal areas: % boiler size % boiler steam application % boiler design Size The average new industrial boiler is a dwarf com- pared to the giant utility boiler. Today’s typical utility unit produces 3,500,000 pounds of steam an hour; the industrial boiler 100,000. In fact, most industrial boilers range in size from 10,000 to 1,200,000 pounds of steam per hour. The size of the utility boiler allows it to enjoy sig- nificant economies of scale, especially in the con- trol of emissions that simply are not available to the industrial unit. Smaller industrial boilers are more numerous and tailored to meet the unique needs and constraints of widely varying industrial processes. There are about 70,000 industrial boilers in use today com- pared to approximately 4,000 utility boilers. Yet, all the small industrial units combined produce only a fraction of the steam compared with large utility boilers. In addition, the nation’s utility boil- ers consume over 10 timeOs as much coal as the industrial boilers. Industrial units produce less than 10 percent of the emissions from the nation’s boiler population, but because of their smaller size and uniqueness must pay more than utilities to remove a given amount of emissions. Steam Application A utility boiler has one purpose—to generate steam at a constant rate to power turbines that produce electricity. Industrial boilers, on the other day to day and hour to hour, depending upon quires a high level of reliability from its boilers. industrial activities and processes underway at a Industrial boilers routinely operate with reliabil- given moment and their demand for steam. The ity factors of 98 percent. Any drop in reliability possibility of such widely fluctuating demand for an industrial system causes loss in production for steam in most industrial processes means that and related revenues. Combustion and add-on the industrial boiler does not, in the great ma- control technologies can interfere with system re- jority of cases, operate steadily at maximum ca- liability. pacity. In general, the industrial boiler will have a much lower annual operating load or capacity Design factor than a typical utility boiler. As a result, Utility boilers primarily are large field erected pul- any added control costs have a much greater af- verized coal, No. 6 oil or natural gas fired high fect on the final output steam cost. pressure high temperature boilers with relatively uniform design and similar fuel combustion tech- In contrast, a typical utility boiler, because of a nologies. Industrial boilers, on the other hand, constant demand for steam, operates continuously incorporate combustion systems including high at a steady-state rate close to maximum capacity. pressure and low pressure, large and small, field This basic difference in operation is reflected in erected and shop assembled package boilers de- proportionately lower operating costs than is the signed to burn just about anything that can be case for similarly equipped industrial boilers. Even burned alone or along with conventional fuels. In- when peaking units operate to meet utility load dustrial boilers use many different types of com- swings during the days or for seasonal peak de- bustion systems. Some of these different designs mands, the utility units’ load swings are more con- trolled and can be balanced over the complete elec- tric production and distribution grid. 15 In the event of unscheduled downtime for a given unit, utility electrical generating facilities have a variety of backup alternatives. Industry, on the other hand, rarely has a backup system for steam generation. Because of the desire to keep costs for steam production as low as possible, industry re- Energy Efficiency and Industrial Boiler Efficiency: An Industry Perspective include many different types of stokers, bub- bling and circulating fluidized bed combustion systems, and conventional coal, oil and gas com- bustion systems. In fact, the designs of indi- vidual industrial boilers regardless of fuel or com- bustion type can vary greatly, depending upon application of steam and space limitations in a particular plant. On the other hand, facilities at a utility plant are designed around the boilers and turbine(s) making application of emission controls significantly more cost effective. CONCLUSION Differences between industrial and utility boilers are major. These differences warrant separate de- velopment of laws and regulations that apply to each. Treating them both in the same fashion, simply because they both generate steam, inevita- bly results in unfair and inappropriate standards. Accordingly, the Council of Industrial Boiler Owners believes that government should recog- nize the basic differences between industrial and utility boilers and should tailor requirements to their individual natures and to the unique situa- tions within which each operates. COUNCIL OF INDUSTRIAL BOILER OWNERS The Council of Industrial Boiler Owners (CIBO) is a broad-based association of in- dustrial boiler owners, architect-engineers, related equipment manufacturers, and uni- versity affiliates consisting of over 100 mem- bers representing 20 major industrial sec- tors. CIBO members have facilities located in every region and state of the country; and, have a representative distribution of almost every type boiler and fuel combina- tion currently in operation. CIBO was formed in 1978 to promote the exchange of information within industry and between industry and government relating to energy and environmental equipment, technology, operations, policies, laws and regulations af- fecting industrial boilers. Since its for- mation, CIBO has taken an active interest and been very successful in the development of technically sound, reasonable, cost-effec- tive energy and environmental regulations for industrial boilers. 16 Steam Digest 2002