Pannir selvam's List: Escola de Biomassa para Econegocios e Produçao Mais Limpas

Rural DecentralizedEnergy Production from  Animal Waste BiogasPlant  : Evaluation of options  for  Water Minimization Using Process Simulation .

A Pannir Selvam , P.V, Santiago B. H.S Gilson.G.M and Melo Marcus .A

 Departamento de EngenhariaQuímica /CT.

Universidade Federal do Rio Grande doNorte, Natal-RN. 59078400. Brazil.

e-mail: pannirbr@gmail.com; www.biomass.eq.ufrn.br

Abstract

Producing Rural Energyon the Farm:Inthe past  farm waste did not pose a problem as the  manure made greatfertilizer so farmers simply spread it on their fields to help boost the nextyear's crop .  Today, many of the farms are specialized , very big andthese "farm machines" are designed to produce in bulk and the farmwaste problem began to mount.  So this huge amount of centralized  production began to runoff into nearbystream, rivers, and other water supplies not only in developed countries , butalso in the country like Brazil  and soonIndia too.In conjunction with these problems associated with farm waste , theseneed not considered to be waste  posingcontamination of water resource , but need to treated as the resource  for water and energy recovery .This is the objective of our research  work to   develop   ecologically sound  bios systems  design for   small community solid and bio wastes.  The anaerobic digestionof animal waste produces "biogas".  Biogas is typically made upof 70% methane and 30% carbon dioxide.  Since methane is easily combusted,it makes for a good source of energy. However the viable  and successful  process of producing biogas and eletrcityusing internalcombustion in  theintermediate scale in the semiarid the rural area of North East were reported in our ealier work..In this context  of   the  biogas based  on  wastes  from cow and chicken , water plays importanterole as much as the energy  for the integrated sustianable localdevelopment and was observed to be the limiting factor resource  for  future insataltions.?Good Quality?water is increasingly a scarce resource and wastewater treatment costs rise, theonce-through use of this  water isbecoming uneconomical and environmentally unacceptable , principly the semiarid region of the Northeast of Brazil. Instead, recovery and recycling of usedwastewater is becoming more attractive from both an economic and environmentalperspective. In this context  , the  water minimization and recycling  is ourother objective of this work  asthis  lead to  substantial savings through reduced wastewaterdisposal cost and rural  water requirements , as our   regionis  semiarid and  dry.. Further, it improves the environmentalaspact of  the surrounding communities. . To address the need forefficient design, evaluation, and operation of integrated wastewater treatmentand recycling processes,  our research  group   areevaluating and expanding the scope of a software tool called SuperProDesigner.  The use of computational modeling and dynamic simulation approachand the system design based on energy and environment concerns were  also used . The fundamental approaches inprocess analysis  (synthesis, modeling,and design) of energy and water recovery from animal waste  have particular attributes, require differenttypes of information and provide results applicable in several ways. The systemdesign for small scale energy production from wastes integrated with water conservation using reuse   treatments involve complex dynamic system design and operation. The focus of this paper is onmodeling of water recycling options as they apply to the smallscale biogasenergy gereation plant  using animal  wastes

Recently several processsimulation software were  reported  that can be applied to biomassutilization process, which also focus on the computer aids for engineeringeconomics. To use this one, several input data and mathematical model need tobe developed first for material balance, preliminary design and processeconomics. SuperPro , the process simultaor used in this work  features anintuitive graphical interface that enhances human-computer interaction andmakes the software easy to learn and simple to use, even for occasional userswith a limited process modeling and water treatment/recycling background. Tomodel a process, we  created several flow diagrams by putting togetherunit procedures, aerobics and anaerobic bioreactors and waste treatments ponds   andconnecting them with material streams. SuperPro design  tool was was used to both the  biological as well as physical treatment ofwastewater such as  filteration  .Besides water recycling applications. Thissystem is used for the evaluation of  diferent option for water  theconservation  and reuse at the small scale biogas  energy generationin the farm level. The main equipments used are anaerobic biodigester, compressed  biogas storage tanks , oxidation pond  for microalgae production  , hidrophonic biofiter system.    The firstcase study was  made the water consumptionrelated with  intermediate scale technology  of biogas production from animal wastes basedon the wastes from fruits and animal residuos.the second  case study was to evaluate water reuse option

Water Minimization Options 

Processing wastewater of biogasplant for reuse require that  the organicmatter in  this  used water    need to  be significantly reduced. This can be done ina number of different ways as intensively studied  recently by Brazilian , National Research Programof Sanitation(PROSAB)  :

• Aqua culture in Integrated  ponds for fish production : The water is left in ponds, where the organic matters are broken down by  algae , aerobic and anaerobic micro-organisms.
• Fertirrigation : The water is used for elephant grass protein production .
• Gravelbed hydrophonic filter: The water is filterd , where bacteria inth e consume the organic matter .

SuperPro softwere wasused to  evaluate these options  and performs material balances on individualcomponents and, based on stream composition and estimates Environmental/Aqueous characterization of streams.  .Recycling  the optium amount  was achived  after sevela  case studies  and process  optimization.This  was found to reduces the cost ofwaste disposal but results in increased equipment-dependent operating cost. Thecost of utilities also increases because of the additional power consumed by the recovery process.At a first case study , it appears that recycling ofwastewater is not an attractive process modification since it increases theunit cost of purified water . The investment is very significantly high to operate the plant .In addition to potential future financial benefits, themain selling point of wastewater recycling in such a facility is the reduceddependency on supply of city water and the improved  water supply for the surrounding communities.In the second case study , the role that processsimulation was founto play play in facilitating the undestanding of  the recycling and reuse of wastewater from small scale  biogas energyproduction  A water recycling effort  was analyzed using microalgaeproduction  and biofiler options by  developing a simulation modeland the potential benefits stemming from it. With a modest increase in the cost, a water recycling effort would become attractive even from an economic pointof view. Several tecnoeconomical parameter of the energy  fromwaste production integrated with  thebest reuse  option  to gother with effluent streamcharacteristics   made possible to makepossible the comparative evaluations. The aquaculture pond integrations wasobserved  to be more economical  and ecological for water waste  minimization of the semi arid region biogasbased decentralized  rural energyproduction

 Keywords:     Water purification, wastewater treatment, water recycling, computer-aidedprocess design, process modeling, process simulation, animal waste , Biogas ,rural energy

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