www.buffalo.edu

Project Overview

Motivation

Objective

Approach

Background

Process Flowsheet Overview

Preliminary Plant Design and Economic Analysis for Polylactic Acid ProductionWilliam Hilliard, Kaipin Huang, Min Wei, Qibiao Weng CE 408: Senior Design Project (Advisor: Dr. Johannes Nitsche)

Pre-polymer Reactor

Lactide Reactor

Distillation Column

Holding Tank

Flash Drum

Pump

Plant Layout

Department of Chemical and Biological Engineering, University at Buffalo (SUNY), Buffalo, NY 14260, USA

Economic Analysis

Pinch Analysis

Assessment of Success

Reference• Jamshidian, Majid, Elmira Arab Tehrany, and Muhammad Imran. "Poly-lactic Acid: Production,

Applications, Nanocomposites, and Release Studies." Comprehensive Reviews in Food Science and Food Safety 9 (2010): 552. Web. 8 Feb. 2015.

• Rahul M. Rasal , Amol V. Janorkar , Douglas E. Hirt, Poly(lactic acid) modifications. Progress in Polymer Science. 2010. Pages 339-348.

• Rejeev Mehta, Vineet Kumar, Haripada Bhunia S.N. Synthesis of Poly(Lactic Acid): A Review. Journal of Macromolecular Science, Part C: Polymer Reviews.

Different Design Approaches

Motivation•Polylactic acid can replace many plastics currently in use that are not biodegradable•It is worth studying whether or not mass production of polylactic acid is economically viable due to its versatility and a growing market for biodegradable materials

Objective•Design a chemical plant based on US Patent 6,326,458 that can produce 300,000,000lbs/year of high molecular weight polylactic acid

Approach•Use the patent for this process as a jumping off point•Design and optimize individual unit operations•Optimize overall process

Stream # Type CP(W/◦C) TS (◦C) Tt (◦C)Heat

Load(W)9 hot 4.75E+03 160 41.55 5.63E+053 hot 2.45E+04 130 41.55 2.17E+061 cold 5.96E+04 25 76.6 3.08E+06

Pinch Point(˚C) 35

Min Hot utility(W) 4.44E+05

Min Cold utility(W) 1.01E+05

Money save for Steam($) 5.71E+05

Money save for Cooling($) 9.58E+04

Total Money saved($) 6.67E+05

S(m2) 62.34a 28,000b 54n 1.2

Ce ($) 35,693.85435PED ($) 3.93E+04TCI ($) 2.33E+05

Equipment Ce($)Prepolymer

reactor/evaporator 9.30E+05Holding tank 6.20E+04

Lactide reactor 9.66E+05Flash drum 7.64E+03

Distillation column 9.98E+04 Pumps 1.35E+05

Total equipment cost 2.20E+06

FCI 1.22E+07 $WCI 2.15E+06 $TCI 1.44E+07 $MC 1.90E+08 $

Revenue 3.00E+08 $/year

Npave 4.00E+07 $/yearROI 278.62%  NPW 7.00E+08 $

• Tubes: 750• Diameter: 1in• Height: 5.7m• Conversion: 90% of entering lactic

acid• Stream 2 T=76.6°C, P=60mmHg Mass flowrate: 43,200kg/h Pipe: 12m, 3.01kW• Stream 4 T=130°C, P=60mmHg Mass flowrate: 22,260 kg/h Pipe: 21m, 1.67kW

• Diameter: 5.9m• Height: 5.9m• T=130°, P=60mmHg• Mass Flowrate: 22,260kg/h• Pipe: 19m, 0.0963kW• Line 4 pump design: 1¼ 1750RPM

pump with 9’’ impeller• Designed to hold a buildup of

liquid over 8 hoursC

• Reactor Type: Falling film evaporator• Conversion:80% of entering pre-polymer• P=60mmHg• Total heat transfer area: 386m2

• Pipe: 840 schedule 40 commercial steel 1 inch nominal diameter

• Stream 6 Mass flowrate: 26715 kJ/h T=148°C, P=60mmHg• Stream 7 Mass flowrate: 4452 kJ/h T=150°C, P=60mmHg• Flim thickness: 0.9mm to 1.7mm from

bottom to top• TLiquid film-gas interface : 172-178 °C

• Purpose: to separate water• Liquid outlet mass flowrate:

18,210kg/h, 12wt% lactic acid and 88wt% lactide

• T=150°C, P=60mmHg• Total volume: 1.22m3

• The cross-sectional area: 0.664m2

• Diameter: 0.9m• Height: 1.8m

• Feed: 18,210kg/h T=150°C, P=60mmHg• Distillate: 3,450 kg/h T=125°C, P=10mmHg, 95wt% lactic acid and 5wt% lactide• Bottom: 17,010 kg/h T=148°C, P=10mmHg, 99.99% lactide and 0.01wt% lactic acid• Reflux ratio: 2.88• Boil-up ratio: 1.7• Height: 13m• Diameter: 1.4m• Condenser: 97,000kg/h cooling water; 4.070,000kJ/h• Reboiler: 5,590kg/h stream;

11,140,000kJ/h

Table 1. Information for all Streams

Table 2. Summary Table for Pinch Analysis and Economic Analysis Table 3. Capital Investment of Heat Exchanger

Table 4. Summary Table for All Equipment Cost Table 5. Summary Table for Economic Analysis

• Pre-polymer Reactor Setting up VLE calculation using the UNIFAC method for the pre-polymer instead of approximating temperature by a rough estimate• Density and viscosity calculation for each stream assumes ideal mixtures• Improvement Set up the VLE calculations for the pre-polymer Splitting the pre-polymer reactor system into two separate units

General Information•Carothers discovered polylactic acid in 1932•Polylactic acid is a biodegradable plastic•Lactic acid is primary material used to make PLA•In 1930’s, low molecular weight of PLA was produced•Later on, high molecular weight of PLA was synthesized

Application•In textiles and non-woven industry Serve as binder fiber, filler for fiber•In medical Drug delivery, dissolvable sutures•In agricultural A substitute of material like PVC

Market•Worth $5,010.7 million by 2019•Annual growth rate of 20.8%

• Designed a pump for line 5 between pre-polymer reactor and holding tank

• 1 ¼ BC 1750RPM Bell & Gossett pump met the requirements

• Operating curve for valve positions 25% open to 100% open shown at right

• Efficiency: 56.7% when the valve is 75% open

• We were able to design an economically feasible process to mass produce high molecular weight polylactic acid, however some design mistakes and invalid assumptions may have been made that call the economic results into question

• We successfully designed the pre-polymer reactor, holding tank, lactide reactor, and distillation system in this process

• A detailed design of combined heat and mass transfer was achieved for the lactide reactor

• Pipelines for each stream were completely designed and a detailed pump design was completed for the line between the pre-polymer reactor and the holding tank

• We optimized the process by specifying reactor conversions and two recycle streams

• We also performed a pinch analysis to save money on utilities

Nature works INGEO PLA plant in Blair, Nebraska <http://greenchemicalsblog.blogspot.com/2013_09_

01_archive.html>

Operating curve for the chosen pump and valve system