to directly recover captured waste heat for use in an area that requires heat.
Te simplest approach to reusing baghouse heat energy is
the direct re-introduction of the exhausted-filtered air back into the plant. Tis is feasible if no additional gaseous waste pollutants are present in the waste air stream. Modern bag- houses and the advent of broken bag detection technology have eliminated the concern of reintroduction of particulates back into the workplace. Well run dust collection equipment regularly contains a lower particulate count than what may be experienced in the general work environment.
Air Handling Many metalcasting facilities’ air capture and baghouse
systems have not undergone significant redesign since their initial installation in the 1970s. Te average emissions system may consume 20 to 25% of the total energy usage in the plant. Many improvements in piping, engineering, compo- nents, baghouse design and bag materials can be incorpo- rated into an updated system. Heat leakage in heated ductwork in the winter months might be considered acceptable as a supplemental heat source, but in the summer, it adds to the plant temperature load and must be exhausted from the plant. Perform regular inspections on all ductwork and calculate the heat losses. Te value of insu- lating ductwork and piping will be recovered quickly.
Motors High-efficiency motors used in moldmaking can save
2-5% on operating energy. When considering the cost of high-efficiency motors, remember that the original purchase price will probably be no more than 5% of the operating cost of the motor over its lifespan. Te cost of electricity will be more than 95% of the cost of operation. In the case of re-winding motors, studies have shown that
rebuilding motors nearly always results in a motor that is not as efficient as the original purchased motor. If re-winding must be done, a carefully written set of
engineering instructions and procedures must be in place. Another consideration is using variable frequency motors
for operations that have widely varying loads throughout a cycle, such as in sand mulling.
Sub-Metering Many metalcasting facilities receive a single electric or gas bill
and don’t know specifically where the energy is being used. One U.S.-based gray iron facility installed sub-meters at multiple points throughout its operation to combat this problem. Te metalcaster installed meters on each furnace, compressor and bag house. Te process included computerized monitors to provide real-time electrical consumption for each piece of equip- ment and precise minute-by-minute KwH use. Te ferrous caster identified an excessive energy spike on a
single furnace and air compressor practices that led to waste. An $80,000 initial investment in the sub-meters and monitoring software resulted in a 10% energy reduction in the first year. ■
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废热再利用
废热再利用可以净节约能15%-20%，甚至更多。虽 然技术上可以把废热转换为电能，但有个简单又低成本 的方法是直接回收废热用在需要热量的地方。 回用布袋式除尘器热能的最简单的方法是直接把除尘 过滤后的空气引回到车间。如果在废气流中没有额外的 废气污染物存在，这是可行的。现代布袋式除尘器和破 袋检测技术的出现消除了微粒被带回到车间的问题。良 好运行的吸尘设备可以使空气中的颗粒比一般工作环境 的微粒还小。 空气调节
许多金属铸造厂的空气捕捉和布袋式除尘器自从上世 纪70年代初次安装后就没有进行重大的设计改进。车间 里粉尘处理系统平均消耗20%-25%的总能源利用。管 道、工程、零部件、布袋式除尘器设计和布袋材料等许 多方面的改进都可以纳入新系统中。
管道系统的散热损失在冬季可以被视为补充热源，但 是在夏天，它增加了车间的温度载荷，对于车间是无用 的。要对所有管道进行定期检查，计算热损失，绝热的 管道系统的价值是可以很快就会得到回报。 电动机
在模具制造采用高效率马达可节省运行能量2-5％。 考虑到高效电机的成本，最初的购买价格将可能不超过 其寿命内的运行成本5%。电力成本是运行成本的95% 以上。研究表明重绕改造电动机没有原购电动机高效。 如果必须进行重绕，必须有书面的工程说明和程序。 因为在整个周期中有普遍的变载荷运行的情况，例如混 砂，因此，还有一点就是考虑使用变频电机。 辅助计量
很多金属铸造厂接到单纯的电费或气费的账单，而不 明确知道这些能源具体消耗在哪里。一个美国灰铁铸造 厂在整个生产过程的多个地方中安装了辅助计量来解决 这个问题。该铸造厂在每个炉、压缩机和袋式除尘器上 都安装了仪表。这个方法包括计算机控制显示屏，该屏 幕提供设备每一部分的实时电力消耗和精确到每分钟的 耗电。
该铸铁铸造厂发现在一台炉子和空气压缩机中花费了 过多的能量，导致浪费。80000美元的辅助计量和监控 软件投资使第一年减少了10%的能源消耗。 ■
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FOUNDRY-PLANET.COM | MODERN CASTING | CHINA FOUNDRY ASSOCIATION Summer 2011
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