Effective Reduction of Industrial GHG Emissions via Energy Integration and Biomass Utilization

Transcription

1 Effective Reduction of Industrial GHG Emissions via Energy Integration and Biomass Utilization Eva Lovelady and Mahmoud El-Halwagi Department of Chemical Engineering Texas A & M University 1 1

2 Motivation Raw Materials Fuel/Energy Material Utilities chips Dige ester white liquor white liquor clarifier pulp weak black liquor cond. mud washer Brown Stock Washing wash water wash water Multiple Effect Evaporators mud filter lime mud Gaseous Wastes Substantial quantities from energy utilities GHGs + Precursors for Ozone screening fluegas lime kiln O D E D E D concentrator salt cake wash water cond. SBL weak white liquor dregs washer & filter Recovery Boiler dust recycle dregs smelt ESP Flue Gas dissolving tank Products Byproducts Wastes causticizer grits slaker green liquor clarifier 2 2

3 Primary Responsibilities/ Goals of Process Engineers Faster, Better, Cheaper, Safer, & Greener Specific Objectives: Profitability Improvement Yield Enhancement Resource (mass and energy) Conservation Pollution Prevention/Waste Minimization Safety Improvement Quality Enhancement How? 3 3

4 Traditional Approaches to Process Development and Improvement Brainstorming among experienced engineers Heuristics based on experience-based rules Evolutionary techniques: Copy (or adapt) the last design we or someone else designed 4 4

5 Weaknesses/Limitations of Traditional Approaches Time and money intensive Cannot enumerate the infinite alternatives Not guaranteed to come close to optimum Does not shed light on global insights & key characteristics of the process Limited range of applicability Severely limits groundbreaking and novel ideas 5 5

6 Solution? Systematic, fundamental, & generally applicable techniques Process Synthesis Process Analysis Process Integration 6 6

7 Process Synthesis Process Analysis Process Integration Process Synthesis Process Inputs (Given) Process Structure & Parameters (Unknown) Process Outputs (Given) 7 7

8 Process Synthesis Process Analysis Process Integration Process Analysis/Simulation Process Inputs (Given) Process Structure & Parameters (Given) Process Outputs (Unknown) k 8 8

9 Process Integration Process Integration = Process Synthesis + Process Analysis + Process Optimization Process Synthesis Global Insights, Overall Interactions, Performance Targets, Major Structural Decisions Input/Output Relations, Performance vs. Design and Operating Conditions Process Analysis Process Optimization: Selection of the best solution from among the set of candidate solutions. Optimization derives the iteration between synthesis and analysis to an optimal closure. 9 9

10 Why Integration? Mass Integration Energy Integration A need exists for an integration framework: Guide/assist process synthesis Conserve process resources 10 10

11 MSA s (Lean Streams In) Waste (Rich) Streams (Sources) In R 1, G 1, y s 1 R 2, G 2, y s 2 R i, G i, y s i R NR, G NR, y s NR S 1 L 1? x 1 s S 2 L 2? x 2 s S j L j? j x s j S NS L NS? x NS t Mass Exchange Network y t 1 y t 2 y t i y t NR Waste (Rich) Streams (Sources) Out x t 1 x t 2 x t j x t NS MSA s (Lean Streams Out) Schematic Representation of the MEN Synthesis Problem 11 11

12 Mass Exchanged Mass Exchange Pinch Point Excess Capacity of Process MSAs Minimum Load For External MSAs Lean Composite Stream x s 1 El-Halwagi and Manousiouthakis, 1989 Rich Composite Stream Maximum Integrated Mass Exchange 1 x t 1 = ε 1 m1 y b x x2 = ε2 2 m 2 x 1 x s t 2 x y y b

13 DESIGN CHALLENGES Which mass-exchange technologies should be used? Which MSAs should be used? What is optimum flowrate of each MSA? Where should each MSA be used (stream pairing)? System configuration? 13 13

14 What is Process Integration? A holistic approach to process design, retrofitting, and operation, which emphasizes the unity of the process. 1.) Task identification 2.) Targeting Involves: 3.) Generation of alternatives (Synthesis) 4.) Selection of alternatives (Synthesis) 5.) Analysis of selected alternatives 14 14

15 Targeting Identification of performance benchmarks for the whole process AHEAD of detailed design Specific Performance Targets: Profitability improvement (maximization) Yield enhancement (maximization) Resource (mass & energy) conservation (minimization) Pollution prevention/waste minimization (minimization) Safety improvement (maximization) 15 15

16 Categories of Process Integration Property Energy Mass Process Mass Integration + Energy Integration + Property Integration Process Integration 16 16

17 Research Theme Reduction of GHGs and ozone precursors from industrial sources via: 1. Energy integration energy conservation, cost savings, NO x & CO 2 reduction 2. Incorporation of biomass into utility systems (e.g., co-firing) Carbon recycling during growth (photosynthesis) Reduction in GHG emissions In-plant pollution prevention not end-of-pipe pollution control Environmental benefit + cost and energy savings: win-win 17 17

18 Problem Statement Consider a process with: A set of specific heating and cooling demands Steam demands for non-heating purposes such as tracing, blanketing, stripping, etc. A certain requirement of electric power A header system with steam generated by process operations and external fuel A set of fossil fuels and biomass streams that may be used as energy sources in the process The objective is to develop a systematic and generally applicable approach to target process cogeneration that effectively uses process sources and external biomass and biowaste streams while satisfying the process heating and non-heating steam demands, and to determine the GHG pricing options required to compete with fossil fuel cogeneration or electricity bought from external sources. Product & Byproduct Atmospheric Pollutants Raw Material PROCESS Water Steam UTILITIES Fuel Power Power Fuel Biomass Waste Heat Waste Waste 18 18

19 Research Questions What are the optimum quantities and levels of heating and cooling utilities? At what pressure level should steam from the external fuel be generated? Is there a potential for power cogeneration? What is the cogeneration target? What is the optimum scheme for recycling/reusing process sources for energy purposes? Can some of the combustible wastes be used instead of fresh fuel? To what extent? Where? What refrigeration technologies may be used (e.g., cooling towers, refrigeration cycles, absorptive refrigeration, etc.)? 19 19

20 Research Questions What are the necessary process modifications that are required to trade off the core-process units with the utility system? What cofiring ratio of biomass to fossil fuel should be used for external fuel steam generation? What is the benchmark for maximum cogeneration potential by utilization of biomass and biowaste streams and minimum usage of external thermal utilities? What is the benchmark for minimum emission of GHGs and ozone precursors (on a lifecycle basis) for the scenarios of using current technologies, new technologies, and incorporating biomass into the utility system? What are the sound policy recommendations that will enable market penetration of biomass-based cogeneration in the process industries? What are the corresponding technical and economic issues? What are the net reductions in ozone precursors and GHG emissions? 20 20

21 Project Objectives Develop a systematic and generally applicable approach to the optimization of design and operation process combined heat and power as well as integration with the core processing units Cost reduction + energy savings + reduction in GHGs and ozone precursors Determine the various feasible pathways and technologies for utilizing biomass in processing facilities, specially for cogeneration Provide an economic, energy and environmental evaluation of the prospects for biomass utilization in processing facilities Examine how potential GHG emission pricing alternatives might influence the relative efficiencies i i of alternative ti technologies and other strategies as well as the power generation market penetration of biomass. Examine the sensitivity of the findings in the face of a wide spectrum of possibilities for variables pertaining to processing characteristics, biomass availability, attributes and pricing, relative costs of power and heat, GHG trading markets and pricing, evolution of new environmental regulations, and technological advancements 21 21

22 Approach Process Cogeneration: energy integration, design, operation, and optimization i Biomass Utilization for Energy: integration, design, operation, and optimization Techno-Economic-Environmental Analysis and Policy Recommendations 22 22

23 Energy Integration and Combined Heat and Power Energy conservation SCOPE Heat exchange networks Process cogeneration Optimization i of steam and utility systems 23 23

24 Motivation Product & Byproduct Gaseous Wastes (e.g., GHGs) Raw Material PROCESS Water Steam Power Fuel Waste Heat UTILITIES Fuel Power Water Waste Effluent & Gaseous Waste Wastewater & Solid Waste Optimize Process production and operation Fuel Power Steam (purchased & generated) Water Waste Gas (e.g., GHG) Discharge 24 24

25 Heat Integration Cold Streams In Hot Streams In Heat Exchange Network (HEN) Hot Streams Out Cold Streams Out Which heating/cooling utilities should be employed? What is the optimal heat load to be removed/added by each utility? How should the hot and cold streams be matched (i.e., stream pairings)? What is the optimal system configuration (e.g., how should the heat exchangers be arranged? Is there any stream splitting and mixing?) 25 25

26 Heat Exchanged Thermal Pinch Diagram Heat Exchange Pinch Point Minimum Heating Utility Minimum Cooling Utility Cold Composite Stream Hot Composite Stream Maximum It Integrated td Heat Exchange T t= T Δ T min 26 26

27 Grand Composite Curves Site-wide heat integration Targeting and selection of each utility Linnhoff, B., Townsend, D. W., Boland, D., Hewitt, G. F., Thomas, B. E. A., Guy, A. R., and Marsland, R. H. (1982). "User Guide on Process Integration for the Efficient Use of Energy," Warwickshire, UK

28 Cogeneration in a Chemical Plant In the chemical Plant s utility system, cogeneration can be implemented by: Cogenerating Power with heat Integrating heat/power requirements within the thermodynamic cycle 28 28

29 Cogenerating Power with Heat Power cogeneration with heat is utilized when expanding steam from a pressure level to another

30 Steam from a Fuel-FiredFired Boiler and/or Waste Heat Boiler (after material recycle) Process Heat Demand, Process Cooling Demand, Process Non-heating/cooling Demand, vent, losses Steam Headers and CHP BFW Generated Steam + Steam from Higher Pressure Level Let-Down Valve High Pressure Steam Header Back-pressure Multistage (Topping) Extraction Condensing Turbine Turbine Turbine Low Pressure Steam Header Process Heat Demand, Process Cooling Demand, Process Non-heating/cooling Demand, vent, losses Steam to lower Pressure Level To Reheating, BFW, or other Destination Condenser 30 30

31 Managing Steam Headers 31 31

32 Cogeneration Power Pinch Diagram Harell D., and El-Halwagi M., Design Techniques and Software Development for Cogeneration Targeting with Mass and Energy Integration, AIChE Spring Meeting, New Orleans, March

33 Biomass in Utility Systems Cost reduction, efficiency improvement, and NO x /CO 2 reduction through combined heat and power (CHP) in process industries Capturing power generation potential through pressure reduction in steam systems: cogeneration Utilization of biomass or biowaste for partial/total cogeneration Gaseous Waste Fossil Fuels Biomass VHP LP MP HP Process Steam Demands Process Steam Demands Process Steam Demands Process Steam Demands 33 33

34 Conclusions Systematic and generally-applicable procedures for the design and operation of optimum cogeneration and biomass utilization reduction in GHGs and ozone precursors (+ cost and energy savings) An integrated approach for analysis of technical, economic and environmental aspects of cogeneration and biomass utilization. In-process modifications leading to cost savings, energy conservation, and reduction in GHGs and ozone precursors. Strong interaction with industry. Dissemination via publications, workshops, monograph, and software. Insights on short- and long-term solutions and recommendations to policymakers

35 QUESTIONS? 35 35

36 Process Integration & Systems Optimization El Halwagi Research Group El-Halwagi Research Group Department of Chemical Engineering Texas A&M University