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Fouling and cleaning in the food and bioprocess industry: Key aspects in membrane plant operation

Lipnizki, Frank LU orcid and Jönsson, Ann-Sofi LU (2017) Engineering with Membranes 2017
Abstract
1. INTRODUCTION
From the early days of membrane technology fouling has been identified as the most important parameter for the slow integration of technology in the industry [1]. Since then significant progress has been achieved in the field of fouling and cleaning of membranes which are still both key aspects in membrane plant operation in the food and bioprocess industry with a significant impact on membrane plants capital (CAPEX) and operating expenditures (OPEX) and thus the sustainability of membrane processes. The aim of this presentation is to demonstrate the relationship between fouling, pre-treatment, operating conditions and cleaning and how on this background industrial membrane processes can be optimized from a... (More)
1. INTRODUCTION
From the early days of membrane technology fouling has been identified as the most important parameter for the slow integration of technology in the industry [1]. Since then significant progress has been achieved in the field of fouling and cleaning of membranes which are still both key aspects in membrane plant operation in the food and bioprocess industry with a significant impact on membrane plants capital (CAPEX) and operating expenditures (OPEX) and thus the sustainability of membrane processes. The aim of this presentation is to demonstrate the relationship between fouling, pre-treatment, operating conditions and cleaning and how on this background industrial membrane processes can be optimized from a techno-economical point of view. The first part of the presentation will introduce the challenges of cleaning and fouling in the food and bioprocess industry. The second part will demonstrate different approaches to reduce fouling and improve cleaning, while the final part will focus on an application study utilizing approaches to optimize fouling and cleaning and thus OPEX and CAPEX for industrial application in the starch-based sweetener industry.

2. FOULING AND CLEANING CHALLENGES
In the food and bioprocess industry cleaning is an integrated part of the daily plant operation and due to hygienic considerations one cleaning cycle per day will be often required. In many cases the selection of cleaning cycle length, number of cleaning steps and cleaning frequency is quite arbitrary in particular for new applications. Each cleaning cycle is combined with production downtime of either parts or the complete membrane plant and thus the plant design has to compensate for downtime, e.g. a 4-hour cleaning cycle per day requires 17% additional membrane area. Furthermore, each cleaning cycle consists typically of 3 – 4 chemical/enzymatic cleaning steps plus flushing steps in between and at least carried out once per day. Apart from the downtime aspect, each cleaning cycle is associated with costs for cleaning agents, water, heating and electricity. In addition, cleaning has a negative impact on membrane lifetime. Therefore optimizing plant design and operation together with cleaning cycle length, number of cleaning steps and cleaning frequency can improve both plant OPEX and CAPEX significantly.

3. APPROACHES TO MINIMISE FOULING AND CLEANING
The initial step to reduce fouling and thus the need of cleaning is to identify the fouling materials and sources. Based on this often optimizing the pre-treatment can lead to significant reductions in fouling, e.g. in the fruit juice industry membrane fouling can be significantly reduced by enzymatic degradation of starches and pectin before clarification of the juice, while in the fermentation industry sufficient pre-filtration with a self-cleaning strainer can reduce the risk of fouling and module blockage.
Apart from understanding of the fouling materials it is important to identify the fouling mechanisms. Depending on the fouling mechanism e.g. complete pore blockage, partial pore blockage or cake filtration remedies to minimize the fouling can be considered. Approaches to minimize fouling are e.g. constant transmembrane pressure operation for milk filtration, vibrating modules for recovery of beer from tank bottoms or rotating modules for white water recovery in the paper industry.
Since often fouling cannot be complete avoided despite best efforts or a hygienic requirement, cleaning is an inevitable part of plant operation. It is crucial that temperature, time, concentration and type of cleaning agents are adapted to the individual application and membranes used. One consideration to improve the cleaning process is to move from one comprehensive daily cleaning to two shorter cleanings. Using this approach for e.g. animal blood concentration reduces overall cleaning time and increases the overall plant capacity.

4. APPLICATION STUDY: STARCH-BASED SWEETENER INDUSTRY
In the starch-based sweetener production, the removal of impurities from the sweeteners after liquefaction and saccharification of the starch is a crucial step in the process. The impurity phase consists of retrograded starch, proteins and fat. In the past open tubular ceramic microfiltration modules and hybrid processes consisting of high speed separators and microfiltration have established themselves for the sweetener purification. Recently a new process consisting of a decanter and ultrafiltration spiral wound modules has been developed. Key aspects of this new process are a self-cleaning strainer before the ultrafiltration membranes to minimize fouling, the utilization of low fouling regenerated cellulose membranes to optimize membrane operations between cleaning cycles combined with an optimized cleaning method to maintain membrane performance. The overall concept resulted not only in higher sweetener quality but also in lower CAPEX and OPEX compared to established membrane based approaches.


5. OUTLOOK AND CONCLUSIONS
Overall this presentation will highlight the importance of fouling and cleaning and their impact on CAPEX and OPEX of membrane plants. The approaches proposed can help to optimize the performance of membrane processes and thus support the long-term sustainability of membrane processes in the different industries.
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Contribution to conference
publication status
published
subject
keywords
Membranes, Fouling, Cleaning, Food industry, Bioprocesses
conference name
Engineering with Membranes 2017
conference location
Singapore, Singapore
conference dates
2017-04-26 - 2017-04-28
language
English
LU publication?
yes
id
cb9b072f-7b57-41ff-bd4f-a5eb03a0bb50
date added to LUP
2018-10-05 10:36:12
date last changed
2019-03-08 02:29:57
@misc{cb9b072f-7b57-41ff-bd4f-a5eb03a0bb50,
  abstract     = {{1. INTRODUCTION<br/>From the early days of membrane technology fouling has been identified as the most important parameter for the slow integration of technology in the industry [1]. Since then significant progress has been achieved in the field of fouling and cleaning of membranes which are still both key aspects in membrane plant operation in the food and bioprocess industry with a significant impact on membrane plants capital (CAPEX) and operating expenditures (OPEX) and thus the sustainability of membrane processes. The aim of this presentation is to demonstrate the relationship between fouling, pre-treatment, operating conditions and cleaning and how on this background industrial membrane processes can be optimized from a techno-economical point of view. The first part of the presentation will introduce the challenges of cleaning and fouling in the food and bioprocess industry. The second part will demonstrate different approaches to reduce fouling and improve cleaning, while the final part will focus on an application study utilizing approaches to optimize fouling and cleaning and thus OPEX and CAPEX for industrial application in the starch-based sweetener industry. <br/><br/>2. FOULING AND CLEANING CHALLENGES<br/>In the food and bioprocess industry cleaning is an integrated part of the daily plant operation and due to hygienic considerations one cleaning cycle per day will be often required. In many cases the selection of cleaning cycle length, number of cleaning steps and cleaning frequency is quite arbitrary in particular for new applications. Each cleaning cycle is combined with production downtime of either parts or the complete membrane plant and thus the plant design has to compensate for downtime, e.g. a 4-hour cleaning cycle per day requires 17% additional membrane area. Furthermore, each cleaning cycle consists typically of 3 – 4 chemical/enzymatic cleaning steps plus flushing steps in between and at least carried out once per day. Apart from the downtime aspect, each cleaning cycle is associated with costs for cleaning agents, water, heating and electricity. In addition, cleaning has a negative impact on membrane lifetime. Therefore optimizing plant design and operation together with cleaning cycle length, number of cleaning steps and cleaning frequency can improve both plant OPEX and CAPEX significantly. <br/><br/>3. APPROACHES TO MINIMISE FOULING AND CLEANING <br/>The initial step to reduce fouling and thus the need of cleaning is to identify the fouling materials and sources. Based on this often optimizing the pre-treatment can lead to significant reductions in fouling, e.g. in the fruit juice industry membrane fouling can be significantly reduced by enzymatic degradation of starches and pectin before clarification of the juice, while in the fermentation industry sufficient pre-filtration with a  self-cleaning strainer can reduce the risk of fouling and module blockage.   <br/>Apart from understanding of the fouling materials it is important to identify the fouling mechanisms. Depending on the fouling mechanism e.g. complete pore blockage, partial pore blockage or cake filtration remedies to minimize the fouling can be considered. Approaches to minimize fouling are e.g. constant transmembrane pressure operation for milk filtration, vibrating modules for recovery of beer from tank bottoms or rotating modules for white water recovery in the paper industry. <br/>Since often fouling cannot be complete avoided despite best efforts or a hygienic requirement, cleaning is an inevitable part of plant operation. It is crucial that temperature, time, concentration and type of cleaning agents are adapted to the individual application and membranes used. One consideration to improve the cleaning process is to move from one comprehensive daily cleaning to two shorter cleanings. Using this approach for e.g. animal blood concentration reduces overall cleaning time and increases the overall plant capacity.  <br/><br/>4. APPLICATION STUDY: STARCH-BASED SWEETENER INDUSTRY<br/>In the starch-based sweetener production, the removal of impurities from the sweeteners after liquefaction and saccharification of the starch is a crucial step in the process. The impurity phase consists of retrograded starch, proteins and fat. In the past open tubular ceramic microfiltration modules and hybrid processes consisting of high speed separators and microfiltration have established themselves for the sweetener purification. Recently a new process consisting of a decanter and ultrafiltration spiral wound modules has been developed. Key aspects of this new process are a self-cleaning strainer before the ultrafiltration membranes to minimize fouling, the utilization of low fouling regenerated cellulose membranes to optimize membrane operations between cleaning cycles combined with an optimized cleaning method to maintain membrane performance. The overall concept resulted not only in higher sweetener quality but also in lower CAPEX and OPEX compared to established membrane based approaches.  <br/><br/><br/>5. OUTLOOK AND CONCLUSIONS<br/>Overall this presentation will highlight the importance of fouling and cleaning and their impact on CAPEX and OPEX of membrane plants. The approaches proposed can help to optimize the performance of membrane processes and thus support the long-term sustainability of membrane processes in the different industries.  <br/>}},
  author       = {{Lipnizki, Frank and Jönsson, Ann-Sofi}},
  keywords     = {{Membranes; Fouling; Cleaning; Food industry; Bioprocesses}},
  language     = {{eng}},
  title        = {{Fouling and cleaning in the food and bioprocess industry: Key aspects in membrane plant operation}},
  year         = {{2017}},
}