Assessment of an Power Generation Industrial Unit from Vinasse Treatment in Uasb Reactor

ASSESSMENT OF AN POWER GENERATION INDUSTRIAL UNIT FROM VINASSE TREATMENT IN UASB REACTOR

André Felipe de Melo Sales Santos1,2, Maurício Alves da Mota Sobrinho2, Adrianus Cornelius van Handel3

1Cetrel S.A.

2Environmental Process and Technology Group – DEQ – UFPE

3Department of Civil and Environmental Engineering - UFCG

The UASB reactors (upflow anaerobic sludge bed) represent the type most widely disseminated and applied in the world of high rate anaerobic system. They have the advantage of treating wastewater diluted or concentrated, dissolved or particulate material, and simple or complex, with high efficiency under conditions of relatively simplified operation.Are applicable to sanitary sewers and industrial effluents that have organic nature, biodegradable, with low concentrations of oil and grease, and toxic compounds. Their cost/benefit ratio make it attractive for industrial uses with advantages of high biomass retention, low sludge production, high efficiency and the biogas exploitation possibility.The anaerobic digestion of vinasse, particularly in the case of Brazil, represents great opportunities for expanding the national energy matrix,taking views of the large volumes produced alcohol. Each liter of alcohol produced can generate from 10 to 18 L of vinasse with a BOD of around 15,000 to 50,000 mg O2/L. Cetrel, from a research project in its program of Technological Innovation in 2009 startedthe project Energy appreciation of vinasse for the generation of decentralized electricity obtained from biogas through anaerobic biodegradation. The project has evolved from the laboratory scale, pilot reaching an industrial unit currently operating in the state of Pernambuco, in Vitória de Santo Antão. The project consists of a modified anaerobic UASB reactor for the treatment of vinasse, with capacity of 1000m3, with organic loading volume (COV) projected in the range from 16 to 20 kg COD/m3.d, and maximum flow rate of 60m3 / h of raw vinasse. The production of electricity is approximately 0.87 MWh using a power generator biogas GUASCOR, SFG-LD 480, which connects directly with the local utility.The plant started operation at the end of the year 2012, with the data presented in this article concerning the 2012-2013 and 2013-2014 harvests. At the beginning of the operation was necessary to inoculate anaerobic flocculent sludge originating from UASBused in urban sewage treatment, but this was not appropriate to the high organic loads applied, especially when applied loads above 4 kg COD/m3. In this case it was necessary to acquire industrial granular anaerobic sludge of high activity (0.44 kg COD/kg TSS.d) to increase the treatment capacity.The unit began operating with low VOC of approximately 1 kg COD / m3.d in increments of 0.5kg COD / m3.d to promote the process of acclimatization of the anaerobic biomass. The performance of the unit in the second harvest has exceeded expectations of project reaching about 91% in COD removal (daily average), reaching levels of 71% methane in biogas. However, when using the vinasseoriginated from the dilution of molasses, there was great difficulty in their treatment compared to vinasse coming directly from sugar cane juice.This problem was due to the presence of sulfatewith concentrations in the range of 700-900 mg / L, which may interfere with the microbiological equilibrium of the system. Sulfate is used in control of indigenous bacteria in the fermentation of the must, and when in an anaerobic environment, the sulfidogenesis competes with methanogenesis interfering with the balance of alkalinity and volatile fatty acids (ratio AT / AGV) leading to operating instability. The vinasse broth does not present as great challenges.Another drawback of the sulfate is your anaerobic degradation leads to H2S, which is highly toxic and corrosive. Were detected sulphate content of the order of 2000-5000 mg/L in the biogas removal system is required to prevent deterioration and shortening the life of equipment. The technology proved to be technically feasible even requiring optimization step.Challenges of economic viability also point to the energy market taking into view that this type of sustainable energy is not encouraged by the government, and the amounts paid by the MWh currently prohibitive to enable the business. However in other applications such as generating isolated systems or other applications can be economically viable.

Key-words: Biogas, Vinasse, UASB, Electric Power