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The objective of this program was to develop a commercial process for producing ethanol from refinery waste gases. this report presents results from the development phases. The major focus of this work was the preparation of the prototype design which will demonstrate this technology in a 2.5 lb/hr ethanol production facility. Additional areas of focus included efforts in obtaining an industrial partner to help finance the prototype, and advanced engineering experiments concentrating on process optimization in various areas needing future development and optimization. The advanced engineering experiments were performed in the laboratory in these areas: treatment and use of recycle water from distillation back to fermentation; alternative methods of removing cells from the fermentation broth; the fermentation of streams containing CO{sub 2}/H{sub 2} alone, with little to no CO present; dealing with methanogen contaminants that are capable of fermenting CO{sub 2} and H{sub 2} to methane; and acetate tolerance by the culture. Results from the design, industrial partner search and the laboratory R&D efforts are discussed in this report.

Two aerobic microorganisms, Saccharomycopsis lipolytica and Brevibacterium lactofermentum, have been used in a study of mass transfer and oxygen uptake from a global perspective using a closed gas system. Oxygen concentrations in the gas and liquid were followed using oxygen electrodes, and the results allowed for easy calculation of in situ oxygen transport. The cell yields on oxygen for S. lipolytica and B. lactofermentum were 1.01 and 1.53 g/g respectively. The mass transfer coefficient was estimated as 10 h{sup {minus}1} at 500 rpm for both fermentations. The advantages with this method are noticeable since the use of model systems may be avoided, and the in situ measurements of oxygen demand assure reliable data for scale-up.

Refineries discharge large volumes of H2, CO, and CO 2 from cracking, coking, and hydrotreating operations. This RD III, engineering development; and IV, demonstration. Phase I, exploratory development, has been completed. The research effort has yielded two strains (Isolates O-52 and C-01) which are to be used in the pilot studies to produce ethanol from CO, CO2, and H2 in petroleum waste gas. Results from single continuous stirred tank reactor (CSTR) laboratory tests have shown that 20-25 g/L ethanol can be produced with < 5 g/L acetic acid byproduct. Laboratory studies with two CSTRs in series have yielded ethanol concentrations of 30-35 g/L with 2-4 g/L acetic acid byproduct. Water recycle from distillation back to the fermenter shows that filtration of the water before distillation eliminates the recycle of toxic materials back to the fermenter. Product recovery in the process will use direct distillation to the azeotrope, followed by adsorption to produce neat ethanol. This is less energy intensive than e.g. solvent extraction, azeotropic distillation, or pervaporation. Economic projections are quite attractive; the economics are refinery stream dependent and thus vary depending on refinery location and operation.

Oil refineries discharge large volumes of H{sub 2}, CO, and CO{sub 2} from cracking, coking, and hydrotreating operations. This program seeks to develop a biological process for converting these waste gases into ethanol, which can be blended with gasoline to reduce emissions. Production of ethanol from all 194 US refineries would save 450 billion BTU annually, would reduce crude oil imports by 110 million barrels/year and emissions by 19 million tons/year. Phase II efforts has yielded at least 3 cultures (Clostridium ljungdahlii, Isolate O-52, Isolate C-01) which are able to produce commercially viable concentrations of ethanol from CO, CO{sub 2}, and H{sub 2} in petroleum waste gas. Single continuous stirred tank reactor studies have shown that 15-20 g/L of ethanol can be produced, with less than 5 g/L acetic acid byproduct. Culture and reactor optimization in Phase III should yield even higher ethanol concentrations and minimal acetic acid. Product recovery studies showed that ethanol is best recovered in a multi-step process involving solvent extraction/distillation to azeotrope/azeotropic distillation or pervaporation, or direct distillation to the azeotrope/azeotropic distillation or pervaporation. Projections show that the ethanol facility for a typical refinery would require an investment of about $30 million, which would be returned in less than 2 years.

This report details the status of the Biological Conversion of Synthesis Gas Project. The following tasks are described as being completed: (1) the test plan, (2) culture development, and (3) the mass transfer/kinetic studies. The bioreactor studies (Task 4) are underway. The continuous stirred tank reactor system for the conversion of H{sub 2}S to elemental sulfur using Chlorobium thiosulfatophilum has been studied for varying light intensities. The system was also modified to include both sulfur recovery and cell recycle using ceramic membranes. Studies were also performed to observe the effects of cell recycle using a polysulfone hollow filter membrane module. Work on Task 5, limiting conditions/scale-up, includes a scale-up study with three different size reactors to establish the optimum operating conditions for hydrogen production from synthesis gas by the biological water-gas shift reaction using the photosynthetic bacterium Rhodospirillum rubrum. Finally, Task 6, an economic analysis, was performed for the H{sub 2} production system using R. rubrum. The analyses show that biological H{sub 2} production from syngas can be very economical if the light requirements for R. rubrum can be neglected.

The purpose of the proposed research is to develop a technically and economically feasible process for biologically producing H{sub 2} from synthesis gas while, at the same time, removing harmful sulfur gas compounds. Six major tasks are being studied: culture development, where the best cultures are selected and conditions optimized for simultaneous hydrogen production and sulfur gas removal; mass transfer and kinetic studies in which equations necessary for process design are developed; bioreactor design studies, where the cultures chosen in Task 1 are utilized in continuous reaction vessels to demonstrate process feasibility and define operating conditions; evaluation of biological synthesis gas conversion under limiting conditions in preparation for industrial demonstration studies; process scale-up where laboratory data are scaled to larger-size units in preparation for process demonstration in a pilot-scale unit; and economic evaluation, where process simulations are used to project process economics and identify high cost areas during sensitivity analyses. The purpose of this report is to present economic evaluations for H{sub 2} production from synthesis gone by Rhodospirillum rubrum. Cases are presented with and without light requirements and in stirred tank and immobilized cell reactors. In addition, economic information is presented for isolate ERIH{sub 2} (from Engineering Resources, Inc.)more » in the two reactors with and without H{sub 2} recovery.« less

The purpose of the proposed research is to develop a technically and economically feasible process for biologically producing H{sub 2} from synthesis gas while, at the same time, removing harmful sulfur gas compounds. Six major tasks are being studied: culture development, where the best cultures are selected and conditions optimized for simultaneous hydrogen production and sulfur gas removal; mass transfer and kinetic studies in which equations necessary for process design are developed; bioreactor design studies, where the cultures chosen in Task 1 are utilized in continuous reaction vessels to demonstrate process feasibility and define operating conditions; evaluation of biological synthesis gas conversion under limiting conditions in preparation for industrial demonstration studies; process scale-up where laboratory data are scaled to larger-size units in preparation for process demonstration in a pilot-scale unit; and economic evaluation, where process simulations are used to project process economics and identify high cost areas during sensitivity analyses. The purpose of this report is to present results from bioreactor studies involving H{sub 2} production by water gas shift and H{sub 2}S removal to produce elemental sulfur. Many of the results for H{sub 2} production by Rhodospirillum rubrum have been presented during earlier contracts. Thus, this report concentrates mainlymore » on H{sub 2}S conversion to elemental sulfur by R. rubrum.« less

Based upon the results of this culture screening study, Rhodospirillum rubrum is recommended for biocatalysis of the water gas shift reaction and Chlorobium thiosulfatophilum is recommended for H{sub 2}S conversion to elemental sulfur. Both bacteria require tungsten light for growth and can be co-cultured together if H{sub 2}S conversion is not complete (required concentration of at least 1 ppM), thereby presenting H{sub 2} uptake by Chlorobium thiosulfatophilum. COS degradation may be accomplished by utilizing various CO-utilizing bacteria or by indirectly converting COS to elemental sulfur after the COS first undergoes reaction to H{sub 2} in water. The second alternative is probably preferred due to the low expected concentration of COS relative to H{sub 2}S. Mass transfer and kinetic studies were carried out for the Rhodospirillum rubrum and Chlorobium thiosulfatophilum bacterial systems. Rhodospirillum rubrum is a photosynthetic anaerobic bacterium which catalyzes the biological water gas shift reaction: CO + H{sub 2}O {yields} CO{sub 2} + H{sub 2}. Chlorobium thiosulfatophilum is also a photosynthetic anaerobic bacteria, and converts H{sub 2}S and COS to elemental sulfur.

Syngas is known to contain approximately 1 percent H{sub 2}S, along with CO{sub 2}, C0{sub 2}, H{sub 2} and CH{sub 4}. Similarly, the syngas may become contaminated with oxygen, particularly during reactor start-up and during maintenance. Previous studies with the water-gas shift bacterium Rhodospirillum rubrum have shown that the bacterium is tolerant of small quantities of oxygen, but the effects of oxygen on CO-consumption are unknown. Similarly, R. rubrum is known to be tolerant of H{sub 2}S, with high concentrations of H{sub 2}S negatively affecting CO-uptake. Batch experiments were thus carried out to determine the effects of H{sub 2}S and O{sub 2} on CO-uptake by R. rubrum. The results of these experiments were quantified by using Monod equations modified by adding terms for CO, H{sub 2}S and O{sub 2} inhibition. The techniques used in determining kinetic expressions previously shown for other gas-phase substrate bacterial systems including R. rubrum were utilized.

Overall mass transfer coefficients for CO have been determined in a continuous stirred-tank reactor at agitation rates of 300--700 rpm using a biological system with the photosynthetic bacterium Rhodospirillum rubrum. A non-steady state approach was employed in order to separate mass transfer and kinetic limited regions of the fermentation. As a result, a kinetic model could be developed for specific CO uptake by the culture including the apparent CO inhibition. The maximum specific CO uptake rate found matched the earlier results obtained in batch culture and by other investigators. CO inhibition was more predominant in CSTR culture than in batch culture, perhaps due to CO acclimation. The growth of the photosynthetic bacterium Chlorobium thiosulfatophilum on CO{sub 2} has been studied at light intensities ranging from 27-1723 lux in batch culture. Modeling results indicate that growth is dependent upon light intensity according to a Monod type relationship.

Syngas is known to contain approximately 1 percent H[sub 2]S, along with CO[sub 2], C0[sub 2], H[sub 2] and CH[sub 4]. Similarly, the syngas may become contaminated with oxygen, particularly during reactor start-up and during maintenance. Previous studies with the water-gas shift bacterium Rhodospirillum rubrum have shown that the bacterium is tolerant of small quantities of oxygen, but the effects of oxygen on CO-consumption are unknown. Similarly, R. rubrum is known to be tolerant of H[sub 2]S, with high concentrations of H[sub 2]S negatively affecting CO-uptake. Batch experiments were thus carried out to determine the effects of H[sub 2]S and O[sub 2] on CO-uptake by R. rubrum. The results of these experiments were quantified by using Monod equations modified by adding terms for CO, H[sub 2]S and O[sub 2] inhibition. The techniques used in determining kinetic expressions previously shown for other gas-phase substrate bacterial systems including R. rubrum were utilized.

Research continues on the conversion of synthesis by shift reactions involving bacteria. Topics discussed here include: biological water gas shift, sulfur gas utilization, experimental screening procedures, water gas shift studies, H{sub 2}S removal studies, COS degradation by selected CO-utilizing bacteria, and indirect COS utilization by Chlorobia. (VC)

This paper presents the results of simultaneous overdesign and optimization of the contact sulfuric acid process. A stochastic optimization procedure is developed as described. Significant improvements in the economics of the process are achieved by optimization, and these improvements clearly justify the cost of such studies.

The sulfuric acid process is one of the oldest and most common in the chemical industry. Due to stricter pollution regulations, this process has recently received broader application to the production of sulfuric acid from SO2 in the waste gases from metallurgical roasting. Little work has been reported on the economic optimization of the sulfuric acid process, particularly for metallurgical operations. This paper presents a method for simulation and optimization of the sulfuric acid process using the PROPS simulation model and the adaptive random search algorithm. Optimal results are presented for plants to handle various SO2 gas strengths and to meet different pollution regulations. The effectiveness of the optimization is measured by comparing the cost of the simulation and optimization study with the improvement in annual earnings for older, near optimal, plants and modern facilities.

The overall objective of this three-year research project is to study the reaction kinetics of the anaerobic digestion process in both batch and continuous flow reactors. Anaerobic digestion of corn stover in continuous laboratory reactors has been found to follow first-order kinetics. A large number of microorganisms were screened for their ability to provide cellulolytic activity or produce methane intermediates. Clostridium butyricum was found to be the most promising. Batch studies involving culture enhancement with C. butyricum have shown a 42 percent increase in methane production. In continuous culture, enhancement with C. butyricum increases the first-order rate constant by 20 percent. These improvements in the reaction rate translate into significant reductions in capital cost for industrial processes. The design of a 3-ton-per-day demonstration unit to produce methane from corn stover has been completed. This design is based upon standard kinetics with two reactors in series. The capital cost for this unit is estimated to be $600,000 with annual operating cost of $200,000. Inoculation and agitation studies were conducted in the laboratory to determine the appropriate inoculation ratio for corn stover and the agitation requirements for batch farm scale systems. Agitation studies have shown that continuous agitation in batch laboratory reactorsmore » is unnecessary. Periodic agitation of only 10 minutes per day is necessary to prevent scum formation and promote mass transfer. The farm demonstration unit continued to operate to produce methane and electricity for farm use. The unit operated with 75 percent overall energy efficiency and can produce methane for $1.80 to $6.50 per 10/sup 6/ Btu, and electricity for $.04 to $.13 per kWh, depending upon the biomass and capital charges.« less

The farm energy system has been constructed in Drury, Missouri. The purpose of this unit is to demonstrate the feasibility of producing energy for farms (heat and electricity) from methane produced by anaerobic digestion of crop residues and other crop materials. The acid hydrolysis pre-treatment of corn stover studies utilize a two stage sulfuric acid contact. In the first stage, dilute sulfuric acid is used to hydrolyze the pentosan fraction of ground biomass. The second stage uses concentrated sulfuric acid for hexosan hydrolysis. The use of the two steps give high yields, possible with concentrated acid, without the problems of pentose decomposition.

Biomass is available on farms as agricultural residues or as energy crops. These materials can be converted into methane by anaerobic digestion. The methane can be used to heat farm buildings and to generate electricity for farm usage. This paper describes the design and operation of a system built by the University of Arkansas to produce heat and electricity from native grasses and corn stover. The system utilizes batch reactors to convert 40 tonne of biomass annually into 700 MJ per day. The operating performance and energy and economic analyses of this system are described and discussed.

About one quarter of the world's population lives in rural areas in remote regions of the world. Conventional forms of energy are usually not available in these areas. The use of alternative sources of energy is the only hope that these regions have of modernizing their societies. Agriculture is the primary means of support and agricultural residues are available as an energy resource. These residues can be converted into biogas by anaerobic digestion. Biogas can be used as a source of heat for cooking and also to generate electricity. This paper describes the design of biogas units for remote villages in Pakistan. Systems to supply energy for a population of about 500 cost around $200,000 and deliver biogas for about $5-8 per million BTU and electricity for $.03-.05 per kwh. Considering the increased income from irrigation of crop land, the cost of these systems could be recovered in about five years.