GB2473866A

GB2473866A - Rotating filter

Info

Publication number: GB2473866A
Application number: GB0916958A
Authority: GB
Inventors: Gary Tulie
Original assignee: ALGOIL Ltd
Current assignee: ALGOIL Ltd
Priority date: 2009-09-28
Filing date: 2009-09-28
Publication date: 2011-03-30
Also published as: GB0916958D0

Abstract

A rotating filter comprising a filter on a vertical axis for separating particles from a liquid. The filter may consist of a stack of conical settlement filters with circular concentric ridges 6 to collect algae from water. The water may enter the filter at one point 1 on its circumference, flow across the radius of the cone and drain off the filter leaving behind concentrated algae trapped by the ridges. Preferably a vacuum system 3 is used to suck up the algae which settle on the filter thereby collecting a small volume of concentrated algae which can be processed without centrifuging a huge volume of water. Advantageously the process has relatively modest capital cost and greatly reduces energy requirements and in this way, it seeks to speed up the process of utilizing algae as a major source of food, animal feed, fuel oil and fine chemicals.

Description

Rotating Algal Filtration System

Introduction

Algae is increasingly looked to as a partial solution to climate change, food shortages, and to the production of biofuels. In order for this to be cost effectively achieved, it is necessary that advances be made in dewatering algae, so the energy cost associated with centrifugation can be dramatically reduced.

This patent is for an invention which modifies existing filtration concepts to produce a simple, sophisticated, and clog free filter.

The System The filtration system consists of stacks of shallow inverted cones with a circular central cut out or otherwise, and covered with ridged plates (similar to an old style long playing record). Water trickles down ridged plates from the inside to the outside of the inverted funnel of the cone, leaving algae settled between the ridges to form a concentrated layer. There follows a "wet vac" stage in which the settled algae are lifted off the ridged plate using a vacuum (rather like washing a carpet). An alternative to vacuum collection is to brush or wipe the algae from the filter so that it flows out across the funnel and off the filter into a collection gutter. As an alternate to the ridges, a hard wearing carpet-like collector could be utilised, and constantly washed as described above.

In an alternate configuration, cones can be stacked right way up i.e. like funnels, directing water to the centre, with a scaffold framework to the outside and a vacuum collection system operating from inside the hole in the centre of the funnel.

Algae culture is introduced to an inner gutter on the filtration system through hoses at the centre of the stack, or in the alternate configuration gutters at the outer circumference and delivered at one point on the inner circle of the cone. Water flows down the ridged plates towards the outside of the circle. Water is also delivered to lower plates through hoses from the top gutter, attached to the inside of the top cone to each of the lower gutters which serve the other cones of the stack. The hoses to each of the lower cones are angled to keep each of the cones in phase with each of the others so allowing all the vacuum attachments to be positioned at the same point on the circumference. Water flows off the outer edge of the cones into a collecting tank to be returned to the cultivation system -with a small proportion of water replaced with fresh filtered sea water on each passage through the system to prevent an accumulation of salt, to replace the volume lost as algae are collected, and to replace nutrients removed from the water by the growing algae.

The cones are held in a stack joined together in the centre by a scaffold supporting each cone at suitable vertical separation from its neighbour.

The entire cone assembly slowly rotates whilst the hose position and the position of the vacuum system stay constant. In this way, as the cone rotates away from the point at which water is introduced, water progressively drains down leaving behind the collected algae. Just before the cone returns to its start position, and once again passes under the hose, the algae is lifted from the plates using a vacuum attachment. In this way, most of the algae is separated from most of the water producing a small volume of concentrated algae for centrifugation or other processing at substantially lower energy cost than traditional centrifugation methods. The feeder gutter system is separated into discrete wedges to deliver water to each segment in turn.

In the case of closed bioreactors, in order to maintain the integrity of the culture, filtration of air entering the room containing the filtration system is provided, as is positive pressure. In this way, contamination with wild algae is kept to a minimum and crop quality is maintained.

Given that the filtration system inherently involves a significant amount of evaporation, the system could form an evaporator within a greenhouse structure, lowering temperature and increasing relative humidity -so reducing irrigation requirements, or may be part of a system providing evaporative cooling to adjacent buildings.

In order to balance the weight of the conical stack around the whole of its circle of rotation in spite of an unbalanced water load, a slight displacement from the vertical axis is used, so placing the centre of gravity in the centre of the stack.

Parts / diagram labels Figures 1 & 2 1. Inlet hose from algal bioreactor 2. Circular gutter around each filter, separated into segments 3. Vacuum collector 4. Pipe to algal collection tank 5. Direction of rotation 6. Circular ridges going around the cone 7. Pipe allowing water to flow from each gutter to the one below.

Claims

Claims 1. A slowly rotating filtration system on a vertical axis for dewatering cultivated or wild crops of algae or cyanobacteria, or for separating similar small particles from a flow of water or other liquid.
2. The use of an inverted cone with central circular cut out or otherwise as a filter covered in circular ridges to catch algae I cyanobacteria or other small particulate matter -so separating them from water or any other liquid.
3. Use of a vacuum to lift algae / cyanobacteria or other particulate matter off conical filters on which they have settled, so collecting a concentrated algal / cyanobacterial / particulate matter harvest.
4. The alternate use of a brush or wiper to lift algae off the filter so that it flows across the filter into a collecting gutter.
5. Use of multiple inverted cones in a stack for filtration so allowing large filtration area in a small footprint.
6. Use of a central scaffold to join together a vertical stack of inverted conical filters.
7. In the alternate configuration in which cones slope down to the centre, scaffold to the circumference of the filter stack.
8. Use of concentric circular ridges to hold algae / cyanobacteria or other particles as they settle from a flow of water across the radius of a conical filter.
9. Use of an alternate "carpet" to hold algae / cyanobacteria or particulate matter in like manner from a flow of water or other liquid.
10. Use of filter rotation to first flow water across the radius of a conical filter from a fixed point, and then allow said water to drain, leaving behind its algal content on the filter for collection by vacuum, brushing or wiping before the dry section of the cone passes once more below the flow of water.
11. Use of a settlement filter as opposed to a flow through filter thereby making it impossible to clog.
12. Use of air filtration to minimise contamination with wild algae.
13. Use of positive air pressure in the filter room to minimise contamination with wild algae.
14. Use of a single hose to deliver water to a stack of filters.
15. Separation of the inlet gutters into discrete segments to ensure wetting of each segment of the cone in turn.
16. Use of angled hoses to deliver water to lower conical filters, so countering the spin of the filter and delivering water to the same segment of a stack of cones at one and the same time, enabling use of a vacuum, brushing or wiping system at the same point on each cone in the stack.
17. Evaporation from the filter system allows for the possibility of evaporative cooling and raised humidity for greenhouse cultivation.
18. Slight displacement of the axis of rotation from the vertical in order to balance the filter stack around its centre of gravity.Amendments to the claims have been filed as follows: Claims 1. A slowly rotating filtration device on a vertical axis for dewatering cultivated or wild crops of algae or cyanobacteria, or for separating similar small particles from a flow of water or other liquid.2. The device according to claim 1 consisting of a ridged or carpeted inverted or otherwise conical stack of filter units with central cut outs on a common scaffold, off the outside edges of which algae or other small particles settle.3. The device according to claims 1 and 2 with a vacuum, brush or wiper system to remove and harvest concentrated algae and forming part of a system which returns filtered water to the cultivation system.4. As in claim 2, a system of inverted cones with central circular cut out or otherwise used as a filter and covered with circular ridges to catch algae! cyanobacteria or other small particulate matter to separate them from water or any other liquid.5. As in claim 3, the use of a vacuum to lift algae / cyanobacteria or other particulate matter off conical filters on which they have settled, to collect a concentrated algal / cyanobacterial I particulate matter harvest.6. As an alternate to claim 5, the use of a brush or wiper to lift algae off the filter so that it flows across the filter into a collecting gutter.7. As in claim 2, the use of multiple inverted cones in a stack for filtration to allow large filtration area in a small footprint.8. As in claim 2, the use of a central scaffold to join together a vertical stack of I-inverted conical filters. 9. The device according to claims 1 and 2 in an alternate configuration in which cones slope down to the centre with scaffold to the circumference of the filter Q stack with water flowing off the cone into the central cut out. 10. Use of concentric circular ridges on the device in claim ito hold algae / Q cyanobacteria or other particles as they settle from a flow of water across the radius of a conical filter.ii. The use of "carpet" as an alternate to claim 3 to hold algae / cyanobacteria or particulate matter in like manner from a flow of water or other liquid.12. The device according to claim 1 with the use of filter rotation to first flow water across the radius of a conical filter from a fixed point, and then allow said water to drain, leaving behind its algal content on the filter for collection by vacuum, brushing or wiping before the dry section of the cone passes once more below the flow of water.13. The device according to claim 12 with the use of a settlement filter as opposed to a flow through filter thereby making it impossible to clog.14. Use of air filtration in the location where the device in claim 1 is situated as part of an overall system to minimise contamination with wild algae.15. Use of positive air pressure in the filter room where the device in claim 1 is located to minimise contamination with wild algae.16. The device according to claim 1 with the use of a single hose to deliver water to a stack of filters.17. Separation of the inlet gutters on the device in claim 1 into discrete segments to ensure wetting of each segment of the cone in turn.18. Use of angled hoses to deliver water to lower conical filters on the device according to claim 1, 50 countering the spin of the filter and delivering water to the same segment of a stack of cones at one and the same time, enabling use of a vacuum, brushing or wiping system at the same point on each cone in the stack.
19. The use of the filter system of which the device in claim 1 is part as a surface for evaporative cooling reducing the temperature of the cultivation water and raised humidity in the filter room where the device is located to provide cooled humidified air for greenhouse cultivation with reduced irrigation.
20. Slight displacement of the axis of rotation on the device according to claim 1 from the vertical in order to balance the filter stack around its centre of gravity. (\J (\J