TEP Energy Utilization and Process Integration in Industrial Plants, or for short: Energy and Process

Transcription

1 Department of Energy and Process Engineering - Energy Utilization and in Industrial Plants, or for short: Energy and Process The Objective is to convey Systems Thinking and Systematic Methods for: Analysis and Design (and partly Operation) of Processes and Utility Systems, with focus on Efficient Use of Energy while considering Economy, Operation and (to some extent) Environment Requirements to be able to join the Course None (meaning previous courses), but it is an advantage to have some basic knowledge about the following: heat exchangers, distillation columns, evaporators turbines, heat pumps and simple thermodynamics Fall 98: 100 students from 8 departments in 4 faculties!! From Spring 2009: Compulsory for the PuP Program Truls Gundersen Department of Energy and Process Engineering - Energy and Process The Course Content is primarily System based Strategyt for Design of integrated t Process Plants with corresponding Utility Systems Systematic Methods for Analysis and Design of Reactor Systems (very limited and not in depth) Thermally driven Separation Systems, such as (primarily) Distillation and (to a much less extent) Evaporation Heat Exchanger Networks and Correct Heat Integration Utility Systems (heating, cooling and power) The Thermodynamically based Pinch Analysis Brief Introduction to the use of Optimization Environmental Issues related to Energy Usage New Design and Retrofit of Existing Plants Truls Gundersen

2 Department of Energy and Process Engineering - Energy and Process The Curriculum for the Course is: R. Smith: Chemical Process Design and Integration, 2nd ed., John Wiley & Sons, January Alternative Text Book: I.C. Kemp: Pinch Analysis and, Elsevier, Butterworth Heinemann, December : Basic Concepts for Heat Recovery in Retrofit Design of Continuous Processes, Ch. 6 in A Primer, IEA, 2000 (18 pages). Lectures and Assignments. Assignments are Examination oriented (most are previous Ex Qs) Examination will test Understandingthrough Calculation Examples. This requires Training established by working with Assignments. Home Page: Truls Gundersen Department of Energy and Process Engineering - Plan for Assignments with Guidance Ass. Topic Supervised Deadline 1 Sequence of Distillation Columns Minimum Energy Requirements and Pinch Design of Heat Exchanger Networks (1) Optimization of Heat Exchanger Networks Retrofit Design of Heat Exchanger Networks Indirect Integration of Plants using Steam Integration of Distillation Columns Optimal Use of Heat Pump Area in Heat Exchanger Networks Heat Integration and Forbidden Matches Design of Heat Exchanger Networks (2) none Guidance: One Ph.D. Student, 4 Student Assistants and the Lecturer Truls Gundersen

3 Reactor System (R) What is expected by the Students on this topic Q: Chapter is part of the list describing what is curriculum from the text book by Robin Smith. Are we expected to be able to reproduce (or derive) the formulas here, or should we be able to use them? A: These Sections are listed with importance 1, meaning that this is Background material. No formulas need to be derived or used, these Sections are included (as 1 ) to provide background for the discussion about effects of T and p in the lectures Q - 01 Reactor Separator Interface (R/S) No questions so far Any Questions now? Relevance for the Exam? Lecturer to provide some wise words.. F F R R R F R R X P X S P B P y R = X S y P = X S (1+ ) Q - 02

4 Separation System (S) No Questions so far Any Questions now? Two Questions from 2009 is added (next slide) About Reboiler/Condenser and Hot/Cold Streams About mcp values for Condensers/Reboilers Q - 03 Separation System (S) Hot and Cold Streams in Distillation Columns Q: Why is the Reboiler identified as a Cold Stream, while the Condenser is identified as a Hot Stream, when the Reboiler has higher Temperature? A: A mixture is boiling in the Reboiler (liquid to vapor) and condensing in the condenser (vapor to liquid), thus heat must be supplied to the Reboiler and removed from the Condenser A: Hot/Cold refers to change in Thermodynamic State, not the absolute Temperature level of streams Q - 04

5 Separation System (S) mcp Values in Distillation Columns & Utilities Q: Why are mcp values of condensers and reboilers as well as utilities said to be infinity? A: Consider the following (use Blackboard) The slope of condensing/vaporizing streams in TQ diagrams Enthalpy change for sensible vs. latent heat A: Some Software Packages use T=1 C 1 Cfor condensing and vaporizing streams (results in very large mcp values, but not infinity ) Q - 05 Interface Separation System (S) and Heat Recovery System Distillation and Evaporation System (Exam 1 June, 2005, Task 2) Q: Can you explain the solution to this Task? A: Running out of time, but see Flow Sheets and Composite Curves on next Slide(s) Q - 06

6 Inndamperanlegg CW Kondensat LP damp CW CW Destillasjonsanlegg HP damp Kondensat Produkt Føde HP damp Q - 07 T Kondensatorer i Kolonner Inndamper Duty Pinch Q H,min Kokere i Kolonner Q C,min Q Q - 08

7 Heat Recovery System (H) Stream Splitting (Exam 1 June 2005, Task 1.c): Q: Above Pinch, one of the cold streams (C2) has too low mcp to take any of the hot streams (H1 or H2) down to Pinch temperature. The other cold stream (C1) has larger mcp than both hot streams, but in the solution it is argued that C1 does not have large enough mcp to take both hot streams to Pinch. How can we see this? A: Good question; reflects an error done by many students during previous Exams (see next slide)!! Q - 09 Q C H1 180 C H2 180 C Pinch 120 C 120 C 100 C C1 60 C 100 C mcp Q C 30 C C C Remember: The mcp Rules apply to each Pinch Exchanger!! Q - 10

8 Heat Recovery System (H) More on Stream Splitting: Q: When splitting streams downstream of Pinch, it is possible to have different temperatures. How large can this difference be, and why are such temperature differences not allowed upstream of Pinch? A: Clarification needed, I would rather distinguish bt between streams entering or exiting the Pinch (see Examples on Blackboard) Q - 11 Heat Recovery System (H) Pinch Matches and mcp Rules (Exam 27 May 2004, Task 1.c): Q: There is a heat exchange above Pinch of 1200 kw between H1 (mcp=50) and C2 (mcp=30). This is against the mcp Rule above Pinch? A: This is the very heart of the Pinch Design Method and relates to the notion of Pinch Exchangers. The next Slide shows the actual MER Network from the proposed Solution to the Exam. Q - 12

9 182 C V IV 140 C I 158 C 100 C H1 150 C H2 133 C 160 C 160 C 1200 kw C C 900 kw H III 400 kw 120 C C1 800 kw 120 C 2000 kw Ca 500 kw II C Cb 300 kw 500 kw 90 C 120 C 110 C C2 20 C C3 mcp Q - 13 Heat Recovery System (H) Previous Exams and rather lengthy Solutions (Exam 27 May 2009, Task 1.d): Q: In this case, the Solution discusses design improvements over 4 pages. Is it expected that we should provide answers that are as good as in this proposed Solution? A: No, your answers should be even better!! A: That s a joke with some meaning. The Solutions are written to show the external examiner and later students how many alternatives even small cases can provide. More on the next Slide!! Q - 14

10 Heat Recovery System (H) Previous Exams and rather lengthy Solutions: A: In Grassroot Design, there are many combinations of Heat Load Loops and Paths that can be used to improve the Network, but make sure you demonstrate the mastering of the basic strategy and principles, and then look at alternatives if time allows. A: In Retrofits, there is no systematic method similar to PDM, and creativity i may be required. Here too, there are many alternatives, but make sure you show that the basic principles are understood (XP analysis, shifting, UA analysis and (??) Loops and Paths). Q - 15 Heat Recovery System (H) Forbidden Matches (Exam 27 May 2009, Task 3.a): Q: With forbidden matches (pairs of hot and cold streams that are not allowed to exchange heat for various reasons) there is a considerable probability that energy consumption related to external heating and cooling will increase compared to the situation when there are no such forbidden matches. The increase in energy consumption is caused by heat transfer across the process Pinch point. Mention what forms such heat transfer can take, and explain for each of these how something that will result in increased energy consumption can be taken advantage of and used to reduce the increased cost due to larger energy usage. Brief and precise answers will be awarded Q - 16

11 Penalty Heat Flow Diagram T Pinch QP C Hot Streams ST Cold Streams Hot Streams QP P QPH CW Cold Streams Q - 17 Interface between Utility System and Heat Recovery System (H/U) Steam Turbines (Exam 20 May 2006, Tasks 2.d+e): Q: Is the difference between backpressure and condensing steam turbines (operation and efficiency) relevant for us (i.e. during the Exam)? A: Yes, from a Systems point of view, such as what are the advantages and disadvantages of the different turbines, equipment efficiency vs. system efficiency. See next Slide as an illustration. Q - 18

12 Other Topics Changes in Curriculum Q: Previous Exams from 2004 to present are available at the Homepage. Has there been any significant changes in the Curriculum since then? A: The only minor changes have been reduced focus on Reactors and Reactor/Separator interface, and reduced focus on Mathematical Optimization. Q: Can you make more Exams available? A: 6 full sets of Exams w/solutions and relevant Assignments, so the answer is no (.English.) Q - 19