1	CSChE 2002, Thermal Pinch Analysis Case Study TMP Pulp Mill Process Simulation and Pinch Analysis Results Chris Connaghan, P.Eng., Duncan Industrial Mike Van Aert, P. Eng., Quesnel River Pulp Gaétan Noël, M.Sc. Eng., Pragmathic
2	Quesnel River Pulp Mill Quesnel, BC Bleached TMP pulp mill 930 ADMT/D 3 lines of refining totalling 118,000 HP or 88 MW 3 flash dryers
3	Quesnel River Pulp Mill Quesnel, BC Thermal Energy System Description: Natural gas used for: Package Steam Boiler Glycol Boiler Pulp Flash Dryers Reboiler converts Refiner Dirty Steam to Clean Steam Glycol Heat Exchangers preheats Glycol using Dirty Steam Glycol heats Air Supply for Flash Dryers Effluent Heat Exchangers recover Waste Heat Fossil fuel: natural gas @ $5.00/GJ HHV
4	Mandate and Methodology Mandate: Reduce mill effluent temperature and volume Maximize energy savings with two year payback or less Methodology: Mill Wide Cadsim+ Computer Simulation Extensive Onsite Verification of Computer Simulation Identify Energy Conservation Opportunities to reduce effluent temperature and volume Pinch Analysis to Identify & Optimize additional ECO ’s
5	Mandate and Methodology (end) Study started fall 2000, completed spring 2001 Immediate Project Implementation by the mill with no delay Some projects even started during the study
6	Process Simulation (1) PreSteaming Bins, Impreg Tower Detailed balances done by Duncan Industrial using Cadsim+
7	Process Simulation (2) Refiners and Cyclone
8	Process Simulation (3) White Water Chests
9	Process Simulation (4) Major effort put on data collection, measurements and model validation Strong process knowledge and simulation expertise required to build the simulation correct choice of simulation building blocks and specifications to produce reliable predictions when modifications are evaluated Requires an experienced engineer understanding mill process and simulation Cadsim+ may look like but is not a computer game
10	Process Simulation (end) Computer Simulation Identified: Effluent cooling heat exchangers severly fouled 25% of design heat transfer, cleaned by the mill TMP reboiler capacity lost Severe shell-side tube fouling with no access for cleaning Retubed with 20% more heat exchange area 40% more clean steam production Therefore, less steam from gas package boiler Boiler feed water preheating Heat exchanger ordered immediately
11	Pinch Analysis: Data extraction Pinch analysis done by Pragmathic Stream data from the computer simulation
12	Pinch Analysis: Operating Scenarios
13	Pinch Analysis: Parameters for Cost Estimating
14	Pinch Analysis Energy targeting
15	Pinch Analysis Targets Reliable TARGETS, dTmin = 20°C Final solution designed for 26% savings in natural gas
16	Process Improvements Identified from Pinch Analysis Increase reboiler’s production: Increase size of blow lines, reduce quench water flowrate; From mill / simulation: reboiler maintenance/rebuilt Increase operating temperatures of: the glycol loop impregnator chips' washing system dewatering process temperature refiners’ dilution and shower water Replace the fresh water with clear white water: impregnators refiners’ dilution and shower water
17	Energy Saving Projects - 1
18	Energy Saving Projects - 2
19	Energy Saving Projects - 3
20	Energy Saving Project Summary
21	Action Plan Flexible road map Step 1: Implement Projects in any order as you wish: Maximum savings target = 13900 kW minus new additional reboiler’s capacity In fact, the rebuilt reboiler has a 40% larger production rate Flexible solution adaptable to the mill’s changing context Step 2: update energy balance and check actual results Step 3: update study and implement other projects if some potential is still there
22	Projects Implemented (1) Reboiler rebuilt Recover excess refiners’ steam for chips bins Impregnation fresh water displaced by ww (lines 1&2) Increased glycol loop heating with excess refiners atmospheric steam Capacity of existing atm. steam condensors has been increased Fan malfunction identified and repaired during the study course
23	Projects Implemented (end) One effluent HEX installed (part of P4B) Boiler feedwater preheater installed Not used with steam boiler shut-off normally Still generates profitable savings for the other operating scenarios During winter 2001, both steam and glycol boilers were off during normal production
24	Reboiler Modifications
25	Boiler Feedwater Preheating
26	Effluent Cooling Exchangers
27	Natural Gas Savings and Green House Gas Reduction
28	Fresh Water Savings
29	Economic Results to Date... Payback well below 1 year. Savings equal to 35% of the total gas bill
30	Conclusions Outstanding results in a short period of time as a consequence of: Rigorous and « precise » methodology Clear study recommendations Mill ’s personnel and management willingness Energy / Process integration using computer simulation and Pinch Analysis is the most cost-effective approach to maximize savings and beneficial environmental effects (GHG, fresh water usage) But needs experienced and practical engineers Very important to listen to the mill’s personnel and incorporate their ideas in the studying process