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利用玉米秸秆来提供热能和电能,以玉米乙醇工厂的技术经济分析

时间:2016-05-18 19:18来源:www.ukthesis.org 作者:英国论文网 点击联系客服: 客服:Damien
abstract 摘要
 
此文提出了玉米秸秆产生的一个典型的170经DAM3干磨乙醇厂供热供电。玉米乙醇厂需要5.6兆瓦的电力和52.3兆瓦的热过程,创造了高达140的GG每年秸秆的需求。玉米秸秆供应系统由采集、预处理、运输和现场燃料储存和制备生产乙醇厂热电。整个供水系统经济学使用集成的生物质供应物流进行了分析(IBSAL)仿真模型。玉米秸秆是三格式交付(方包,干排骨和颗粒)的热电联合厂。73美元用于包交付1毫克计算成本的生物质准备被烧毁,86美元和84美元为丸1毫克1毫克现场切量。三格式的秸秆供应系统中,交付成本颗粒生物量最高,由于制粒成本高。在各种形式的生物质颗粒散装运输可以在我们提供一个有前途的未来的生物质供应物流系统,如果造粒和运输成本最小化。Supply of corn stover to produce heat and power for a typical 170 dam3 dry mill ethanol plant is proposed. The corn ethanol plant requires 5.6 MW of electricity and 52.3 MW of process heat, which creates the annual stover demand of as much as 140 Gg. The corn stover supply system consists of collection, pre-processing, transportation and on-site fuel storage and preparation to produce heat and power for the ethanol plant. Economics of the entire supply system was conducted using the Integrated Biomass Supply Analysis and Logistics (IBSAL) simulation model. Corn stover was delivered in three formats (square bales, dry chops and pellets) to the combined heat and power plant. Delivered cost of biomass ready to be burned was calculated at 73 $ Mg 1 for bales, 86 $ Mg 1 for pellets and 84$ Mg 1 for field chopped biomass. Among the three formats of stover supply systems, delivered cost of pelleted biomass was the highest due to high pelleting cost. Bulk transport of biomass in the form of chops and pellets can provide a promising future biomass supply logistic system in the US, if the costs of pelleting and transport are minimized.
 
1. Introduction 介绍
 
DOI:10.1016 / j.biombioe.2009.10.001Ethanol plants in the US use corn grain as the feedstock for producing nearly 18 hm3 of ethanol [1]. Most of the ethanol produced is blended with gasoline. The ethanol represents roughly 1.5% of the current annual volume of petroleum consumption of 1.15 km3 [2]. National plans call for increasing ethanol production to levels that would offset at least 30% of the annual transportation fuel volume within the next 20– 30 years. It is forecasted that the current and projected increase in corn grain may support starch-based ethanol production up to 75 hm3 of ethanol. Lignocellulosic biomass feedstock can further support ethanol production beyond the75 hm3 from corn grain. Therefore, it is important to develop secure sources of biomass and supply infrastructure to support the projected growth of bioenergy. A typical ethanol plant requires 9.67 MJ of process heat and 0.288 kWh of electricity to produce 1 l of ethanol. Most of the existing ethanol plants in the US use natural gas as the source of process heat and electricity from the electric grid [1,2]. Prices for natural gas and electricity have increased in recent years making ethanol production economics less attractive. To offset this issue, some plants have or are planning to use coal [3] and that has created a negative impact on public acceptance of ethanol as a ‘‘green or clean fuel’’. The technology of producing process heat and electricity from direct 0961-9534/$ – see front matter a 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.
biomass and bioenergy 34 (2010) 75–81 combustion of biomass is now well developed [4,5]. Biomass can provide heat and power to the existing and future starch-based ethanol plants.

Table 1 lists the current and an estimated future number of ethanol plants in the US [1]. The list includes an estimate of the required grain (corn) as feedstock and the amount of process heat and electrical energy required to keep the plants running. An estimate of the required grain and stover and the amount of co-product, distillers dried grain (DDG) is also presented in Table 1. The last two rows are an estimate of net energy input to the plants for process heat and electricity. Assuming that 287 plants become operational in the next 5– 7 years, there will be a production of roughly 48 hm3 of ethanol from corn. Roughly 48 Tg of biomass is required to heat and power these plants if all these plants use biomass as a fuel source. Typical energy balance studies of corn ethanol show that the energy balance (defined in terms of renewable energy in the ethanol product over all non-renewable energy inputs from seed to product) ranges from 1.1 to 1.3 [4–7]. There are high energy demands in the provision of fertilizer and crop management as well as in the demand for heat and electricity in the process plant. Improvements in process plant efficiency, and the use of renewable energy inputs for electricity and heat could make the overall renewable energy balance >2. Morey et al. [4] proposed the use of DDG or corn stover for heat and electricity generation for the ethanol plants and found that there was a significant annual energy cost savings for the 170 dam3 ethanol plant. Use of DDG for power and heat generation may not be the best option due to its high nutritional value as a choice source of protein and fiber for animal feed (>80$ Mg 1). In order to compare and make corn stover competitive to the existing heating fuels, a techno-economic analysis of using biomass to supply heat and power systems should be investigated. Any biomass-based heat and power production system relies mainly on the continuous and cheap supply of biomass delivered to the plant. Our main objectives of this paper were to estimate the cost of supplying corn stover to the existing dry mill ethanol plants using the Integrated Biomass Supply Analysis and Logistics (IBSAL) model to produce heat and/or power and to calculate the cost of on-site fuel preparation for delivering it to the burner. 
 
2. Description of IBSAL model 描述ibsal模型
 
The Integrated Biomass Supply Analysis and Logistics (IBSAL) is a dynamic simulation model developed by Oak Ridge National Laboratory (ORNL) to estimate the delivered biomass cost, energy input and carbon emissions for various logistic options [8]. IBSAL consists of different sub-modules for harvesting, processing, pre-processing (grinding, pelleting), storage and transportation. Model input data include: local weather data; average net yield of biomass; crop harvest progress data (including start and end dates of harvest); dry matter loss with time in storage; moisture content of plant at the time of harvest; operating parameters of equipment; and cost of machinery in dollars per hour. The model was built on the EXTENDSIM  platform [9]. Main outputs of the model include: delivered cost of biomass ($ Mg 1); carbon emission (kg Mg 1) and energy consumption (GJ Mg 1). IBSAL also calculates dry matter losses of biomass using the limited data available for storing biomass bales and handling hay. Complete information about the model can be found in Sokhansanj et al. [10] and Sokhansanj and Mani [11]. The choices of particular size and operating conditions are based on three objectives: (1) the latest model of equipment that is commercially available for harvest, (2) the typical operational performance data that are available in the ASAE D497 standard [12] or from manufacturer’s literature, and Table 1 Overall ethanol production statistics in the US for the current, under construction, and planned corn starch-based ethanol plants [1,4]. Description Unit For a typical plant No. of current plants Under construction In planning stage Total Number of plants – 1 97 40 150 287 Volume of ethanol hm3 0.169 16.4 6.8 25.3 48.4 Mass of grain Tg 0.411 39.9 16.5 61.7 118.1 as feedstocka Mass of DDG co-product producedb Tg 0.129 12.5 5.2 19.3 37.0 Process heat PJ 1.632 158.3 65.3 244.8 468.3 inputc Electricity energy PJ 0.175 17.0 7.0 26.2 50.2 inputd Gross energy PJ 2.759 267.6 110.4 413.8 791.8 requiremente Natural gasf km3 0.073 7.1 2.9 11.0 20.8 Biomassg Tg 0.167 16.2 6.7 25.1 48.0 aAconversionefficiencyof0.41lofethanolperkgofcorn[4].b0.313kgofDDGperkgofcornprocessed.c9.67MJofprocessheatperliterofethanol.d0.288kWhofelectricityperliterofethanol.eConversionefficiencyofcombustiontoheatas80%andconversionefficiencytoelectricityas30%.fConversionfactorof38MJm 3fornaturalgas.gConversionfactorof16.5GJMg 1forstover. (责任编辑:anne)


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