Driftsoptimering af pumpesystemer

Abstract

Dette projekt omhandler driftsoptimering af kloakpumpeledninger, som i kraft af centraliseringen af spildevandsrensningen udgør et vigtigt element i nutidens afløbssystem. Indenfor de seneste år er der udviklet en metode til overvågning af pumpesystemers helbredstilstand baseret på trykmålinger. Metoden er insipreret af elektrokardiografi, idet trykmålingerne omsættes til viden om pumpens og kloakledningens tilstand. På nuværende tidspunkt anvendes metoden til at nedbringe vedligeholdelsesomkostningerne, da den danner grundlaget for en behovsstyret vedligeholdelsesstrategi. I dette projekt udvides metodens anvendelsesområde til energioptimering af pumpesystemer. En analyse af potentialet for energibesparelser i to kloakpumpeledninger i Kongerslev og Tvis viser således, at der specielt i ledningen i Tvis er et potentiale for energibesparelser på op mod 60%, hvis ledningshastigheden reduceres til 0,5m/s. I projektet undersøges muligheden for at nedsætte ledningshastigheden uden en forøgelse af ledningens ruhed, hvis der samtidig implementeres en behovsstyret hydraulisk rensning, som baseres på overvågningen af pumpeledningens ruhed. En analyse af en regelmæssig hydraulisk rensning i en eksisterende pumpeledning viser imidlertid, at pumpesumpen typisk er for lille til at ledningen på effektiv vis kan skylles ren, og at energioptimeringen med hydraulisk rensning først kan blive implementeret ved nyanlæg, hvis den nuværende praksis for projektering af pumpesumpe ændres. I projektet undersøges desuden muligheden for at bekæmpe svovlbrintedannelse ved indblæsning af trykluft i kloakledninger. Analysen konkluderer, at luftindblæsning i nogle tilfælde er en omkostningseffektiv løsning, men at luftindblæsning ikke kan betragtes som et universelt virkemiddel, da luften på nogle ledningsstrækninger vil nedsætte kapaciteten af pumpesystemet markant. I projektets sidste del undersøges muligheden for at analysere og optimere pumpesumpes selvrensningsevne ved hjælp af kommercielle CFD-programmer. Det konkluderes, at CFD-simuleringer kan bidrage til optimering af pumpesumpes selvrensningsevne, og at simuleringerne specielt vil være anvendelige, hvis der implementeres en ny løsningsmetode, der muliggør simulering af varierende vandstand uden behov for at inddrage luftfasen i simuleringen.

This project deals with the challenge of optimizing the maintenance of pumped sewer systems. Recently, a method to monitor the health condition of a pump system based on pressure measurements has been developed. The method is inspired by electrocardiography, as the pressure measurements during transients are converted to knowledge about the condition of both the pump and the pipeline. Currently, the monitoring is used to reduce maintenance costs by enabling a demand-controlled maintenance program. In this project, the method is used to optimize the energy consumption of pump systems. An analysis of the current operation of two typical Danish pumped sewer mains in Kongerslev and Tvis, Denmark shows that it is possible to reduce the energy consumption by 60% in Tvis, if the flow velocity is reduced to 0,5m/s . However, normal engineering practice is to avoid such low velocities as they are associated with a risk of insuffcient self-cleaning. In the project, the possibility of reducing the flow velocity without increasing the roughness is investigated, when a hydraulic flushing of the pipeline is implemented. In such a pump operation, the pressure measurements serve as an indicator for the need for ?ushing. However, an analysis of the efficiency of a regular hydraulic flushing of a pipeline indicates that the typical pump sump is too small to facilitate an e?ective cleaning of the pipe. Therefore, hydraulic ?ushing can only be implemented in an energy optimization, if the current standards for pump system design are altered. Another widespread issue with the long pumped sewer systems is the formation of hydrogen sulfide. In this project, the effectiveness of adding pressurized air to the pipeline as a means for reducing hydrogen sulfide formation is investigated. The analysis concludes that air injection in certain pipelines is a cost-effective solution but cannot be considered a general means, as the air in some pipelines causes operational issues. In the last part of the project, commercial CFD-software is used to analyse and optimize the self-cleaning ability of two pump sumps. The use of CFD-software shows a potential to improve pump sump design. However, CFD-simulations will be particularly useful in the design of pump sumps if a new solution method is implemented. The method should enable the simulation of free surface ?ows without the current requirements to describe the air phase

A master thesis from Aalborg University

Driftsoptimering af pumpesystemer

[Maintenance Optimization of Pump Systems]