Simulation, integration, and economic analysis of gas-to-liquid processes

Gas-to-liquid (GTL) process involves the chemical conversion of natural gas (or other gas sources) into synthetic crude that can be upgraded and separated into different useful hydrocarbon fractions including liquid transportation fuels. A leading GTL technology is the Fischer Tropsch process. The objective of this work is to provide a techno-economic analysis of the GTL process and to identify optimization and integration opportunities for cost saving and reduction of energy usage and environmental impact. First, a basecase flowsheet is synthesized to include the key processing steps of the plant. Then, computer-aided process simulation is carried out to determine the key mass and energy flows, performance criteria, and equipment specifications. Next, energy and mass integration studies are performed to address the following items: (a) heating and cooling utilities, (b) combined heat and power (process cogeneration), (c) management of process water, (c) optimization of tail-gas allocation, and (d) recovery of catalystsupporting hydrocarbon solvents. Finally, an economic analysis is undertaken to determine the plant capacity needed to achieve the break-even point and to estimate the return on investment for the base-case study. After integration, 884 million $/yr is saved from heat integration, 246 million$/yr from heat cogeneration, and 22 million $/yr from water management. Based on 128,000 barrels per day (BPD) of products, at least 68,000 BPD capacity is needed to keep the process profitable, with the return on investment (ROI) of 5.1$/1000 SCF natural gas, 5 $/1000 SCF price can increase the ROI to 16.2%

Process Design and Optimization of Biorefining Pathways

Synthesis and screening of technology alternatives is a key process-development activity in the process industries. Recently, this has become particularly important for the conceptual design of biorefineries. A structural representation (referred to as the chemical species/conversion operator) is introduced. It is used to track individual chemicals while allowing for the processing of multiple chemicals in processing technologies. The representation is used to embed potential configurations of interest. An optimization approach is developed to screen and determine optimum network configurations for various technology pathways using simple data. The design of separation systems is an essential component in the design of biorefineries and hydrocarbon processing facilities. This work introduces methodical techniques for the synthesis and selection of separation networks. A shortcut method is developed for the separation of intermediates and products in biorefineries. The optimal allocation of conversion technologies and recycle design is determined in conjunction with the selection of the separation systems. The work also investigates the selection of separation systems for gas-to-liquid (GTL) technologies using supercritical Fischer-Tropsch synthesis. The task of the separation network is to exploit the pressure profile of the process, the availability of the solvent as a process product, and the techno-economic advantages of recovering and recycling the solvent. Case studies are solved to illustrate the effectiveness of the various techniques developed in this work. The result shows 1, the optimal pathway based on minimum payback period for cost efficiency is pathway through alcohol fermentation and oligomerized to gasoline as 11.7 years with 1620 tonne/day of feedstock. When the capacity is increased to 120,000 BPD of gasoline production, the payback period will be reduced to 3.4 years. 2, from the proposed separation configuration, the solvent is recovered 99% from the FT products, while not affecting the heavier components recovery and light gas recovery, and 99% of waster is recycled. The SCF-FT case is competitive with the traditional FT case with similar ROI 0.2. 3, The proposed process has comparable major parts cost with typical GTL process and the capital investment per BPD is within the range of existing GTL plant

Frequency of regulatory T-cells in the peripheral blood of patients with pulmonary tuberculosis from shanxi province, china.

BACKGROUND: Tuberculosis (TB) is a disease caused by the chronic and continuous infection of the pathogen Mycobacterium tuberculosis (M. tuberculosis). M. tuberculosis is an intracellular bacterial pathogen and is eliminated mainly through CD4(+) effector Th cells. M. tuberculosis induces regulatory T lymphocytes (Tregs) that mediate immune suppression by cell-to-cell contact or by secreting cytokines such as transforming growth factor-β (TGF-β). To understand the role of regulatory T-cells in the pathogenesis of TB, we have measured the in vivo frequency of regulatory T-cells and associated in vivo cytokine production in pulmonary tuberculosis patients. METHODOLOGY/PRINCIPAL FINDINGS: In this study, we analyzed blood samples from 3 different populations (Group 1: patients with active TB, Group 2: patients recovered from TB and Group 3: healthy controls). We measured natural regulatory T-cell expression in peripheral blood using flow cytometry, and levels of blood serum IFN-γ and TGF-β1 using ELISA. The in vivo function of inductive regulatory T cells was mainly indicated by the expression of IFN-γ, TGF-β1, etc. Frequencyof natural regulatory T cells and inductive regulatory T cells in the peripheral blood samples from Group 1 patients were all significantly higher (P<0.05) than those from Groups 2 and 3. CONCLUSION/SIGNIFICANCE: Our results indicate that frequency of natural regulatory T cells and inductive regulatory T cells are significantly higher in the peripheral blood of patients with active pulmonary tuberculosis. These findings have potential application in improving TB diagnostic methods

Regulatory T cells and the expression of related cytokines in different patient groups.

<p>1. Group 1 was compared with either Group 2 or Group 3, t  = 4.57, P<0.05 and t  = 4.89, P<0.05, respectively;</p><p>2. t  = 5.05, P<0.05 and t  = 7.72, P<0.05;</p><p>3. t  = 8.41, P<0.05 and t  = 11.08, P<0.05;</p><p>4. t  = 4.70, P<0.05 and t  = 9.18, P<0.05.</p

Differences in regulatory T cells and expression of related cytokines in sputum smear negative and positive patients.

<p>1. Sputum smear positive patients were compared with smear negative patients, t  = 2.51, P<0.05;</p><p>2. t  = 3.19, P<0.05;</p><p>3. t  = 3.07, P<0.05;</p><p>4. t  = 5.16, P<0.05.</p

Differences in regulatory T cells and expression of related cytokines in cavitary TB and non-cavitary TB patients.

<p>1. The cavitary TB group was compared with the non-cavitary TB group, t  = 2.99, P<0.05;</p><p>2. t  = 3.33, P<0.05;</p><p>3. t  = 6.78, P<0.05;</p><p>4. t  = 3.52, P<0.05.</p

Representative flow plots from a recovered TB patient labeled with anti-CD4, CD25 and Foxp3.

<p>Appropriate isotype controls were included to establish the positive gates. (I) FSC and SSC to identify lymphocytes. (II) CD4⁺ cells within the lymphocyte gate. (III) Cells were gated on the CD4⁺ cells shown in B and CD4⁺CD25⁺ cells were determined. (IV) Cells were gated on CD4⁺CD25⁺ cells and Foxp3 expression was determined.</p