DE102017004049B4 - Modular device for temperature control of tubular microalgae photobioreactors - Google Patents

Abstract

The invention describes a modular device for controlling the temperature of tubular microalgae photobioreactors for cultivating microalgae, which improves the energy efficiency to such an extent that cost-effective operation, predominantly with renewable energies, is made possible all year round and also outside of greenhouse systems.

Description

[Description]

The invention relates to the heat exchange process of a modular device for temperature control of tubular microalgae photobioreactors for the industrial cultivation of microalgae using the infrared portion of sunlight, hereinafter referred to as tubular PBR, with a modular tubular PBR consisting of at least two identical modules coupled to one another.

The heat exchange process of a tubular PBR module is explained in more detail below. In order to achieve a large area exposed to sunlight, conventional tubular PBRs consist of a long, meandering, transparent tube that forms a closed circuit of an aqueous suspension of microalgae, which is driven by a pressure pump. In the device according to the invention for temperature control of tubular PBR, this tube is guided centered within another transparent tube, referred to below as the outer tube, with a space being created between the inner surface of the outer tube and the outer surface of the inner tube, which is permanently opened by means of a permanently connected, pressure-controlled vacuum pump a preset rough vacuum is evacuated. This rough vacuum has only a low thermal conductivity, so that the aqueous microalgae suspension flowing in the inner tube can largely accumulate the amount of heat contained in the infrared part of the sunlight and only a small amount of heat is lost towards the atmosphere.

If the accumulated amount of heat exceeds the heat requirement required for the growth of the microalgae, this must be dissipated so that the optimal growth temperature of the microalgae in the aqueous microalgae suspension is not exceeded. This is achieved by means of heat exchange in heat exchange tanks, through which the inner tube is routed in sections. The temperature control fluid of a closed temperature control circuit driven by a pressure pump flows through the heat exchange containers, with the aqueous microalgae suspension in the inner tube giving off the excess amount of heat to the temperature control fluid of the temperature control circuit due to heat exchange processes. A heat exchanger is integrated into the temperature control circuit, which is located inside an external tank for the temperature control fluid, with the excess amount of heat being given off to the temperature control fluid, which heats up in the process.

This amount of heat stored in the fluid can, if required, be returned to the aqueous microalgae suspension, also by means of heat exchange processes, with the heat exchange process taking place in the opposite direction to that in the case of an excess amount of heat. In this way, the process temperature required for microalgae growth in a tube PBR is usually ensured by the infrared portion of the sunlight, even in the case of low solar radiation or at night. If, for example, due to extremely dark weather conditions, both the solar radiation and the amount of heat stored in the fluid of the external fluid tank are not sufficient to generate the required process temperature for microalgae growth, thermal energy is supplied to the fluid tank by electrical resistance heating, with the possibility of cheap electricity being used Excess locations for renewable energies, such as wind energy, to use. In this case, the well-insulated fluid tank acts as an energy store for electricity from renewable energies. The entire temperature control process can be electronically sensor-controlled and applied to the optimal growth of the most diverse types of microalgae.

[State of the art]

In general, the modular device according to the invention for temperature control of tubular microalgae photobioreactors is based on the functional principle of vacuum tube collectors, which is often used in a number of design variants for generating process heat from solar radiation. These consist of evacuated glass tubes in which a tube with a layer that absorbs solar radiation is arranged concentrically, through which a heat transfer medium flows.

The Federal Statistical Office of Germany calculates an average annual yield of 120 watts/m ² for solar thermal collectors used to support heating (source: Solarthermie - Wikipedia), whereby times without solar radiation (night) and with little solar radiation (heavy clouds ) are included.

In central European latitudes, the main problem of industrial microalgae cultivation lies in the strong temperature fluctuations (summer-winter and day-night), which oppose the relatively narrow temperature window for optimal cultivation of many microalgae. The large, commercially used tubular PBR installed in a greenhouse in central European latitudes, Roquette Klötze GmbH, lacks the technical means to control the temperature of the microalgae suspension, both to cover the process heat requirement at low outside temperatures and for effective cooling at high sun intensity. The consequence of this is that operation in cold seasons for reasons of energy gy efficiency cannot be realized and cooling problems occur in summer with high greenhouse temperatures, which are reduced by manually hosing down the cultivation pipes with cold water, which is labor-intensive.

In DE102009045851A a tube photobioreactor is described, which is characterized in that a transparent or translucent tube is composed of an outer tube and a coaxial inner tube, with two separate chambers being created similar to the modular device according to the invention for temperature control of tube microalgae photobioreactors, from where one chamber is used to transport the microalgae suspension, the other chamber to transport a heat exchange medium for the purpose of tempering the suspension.

The main disadvantage of the tube photobioreactor compared to the modular device according to the invention for temperature control of tube microalgae photobioreactors is the energetic inefficiency, which is characterized by the fact that there is unhindered heat dissipation from the outer tube to the atmosphere, since there is no heat-insulating medium between the inner and outer tube .

[Object of the invention]

The object of the invention is to create a device that improves the energy efficiency of tubular PBR to such an extent that cost-effective operation, predominantly with renewable energies, is made possible all year round and also outside of greenhouse systems.

The object is achieved with the features of the first claim according to the invention. Advantageous further developments and refinements are the subject matter of the dependent claims.

The modular device for temperature control of tubular PBR is explained in more detail using drawings.

• 1 den Längsschnitt durch das Rohr- in- Rohrsystem mit integrierter Vakuumpumpe
• 2 den Querschnitt durch das Rohr- in- Rohrsystem mit integrierter Vakuumpumpe und Abstandhaltern
• 3 den im transparenten Innenrohr fest angebrachten Verwirbler
• 4 das Prinzip des Wärmetauschs des Rohr- PBR- Moduls
• 5 die Rohrführung des Rohr- PBR- Moduls

Show it:

• 1 the longitudinal section through the pipe-in-pipe system with integrated vacuum pump
• 2 the cross-section through the pipe-in-pipe system with integrated vacuum pump and spacers
• 3 the swirler fixed in the transparent inner tube
• 4 the principle of heat exchange of tube PBR module
• 5 the pipe routing of the pipe PBR module

The 1 shows the longitudinal section through the pipe-in-pipe system, with a space 5 being created between the inner surface of the transparent outer pipe 3 and the outer surface of the transparent inner pipe 2, which is permanently evacuated to a preset rough vacuum by means of a permanently connected, pressure-controlled vacuum pump 6.

The 2 shows the cross section through the tube-in-tube system with integrated vacuum pump 6 and spacers 4, through which the transparent inner tube 2, through which the aqueous microalgae suspension 1 flows, is fixed centrally within the transparent outer tube 3.

The 3 shows a longitudinal section through the transparent inner tube 2 with a swirler 16 positioned in its interior, which consists of helically twisted flat material, for example stainless steel sheet, and which swirls the flowing aqueous microalgae suspension 1 in such a way that as many microalgae as possible get into the area of the wall of the transparent inner tube be moved and be able to participate in the sunlight. Several swirlers 16 can be positioned along the course of the transparent inner tube 2 .

The 4 shows the principle of heat exchange of the tube PBR module without means for filling, emptying, nutrient addition and flow generation. The tube bends of the transparent inner tube 2 are firmly attached within a heat exchange container 9, with a temperature control fluid 13 from a temperature control circuit 10 flowing around their outer surfaces, thus enabling heat exchange between the aqueous microalgae suspension 1, the transparent inner tube 2 and the temperature control fluid 13 from the temperature control circuit 10 and the amount of heat absorbed by solar radiation that exceeds the heat requirement of the aqueous microalgae suspension 1 is transferred via the temperature control fluid 13 of the temperature control circuit 10 driven by the pressure pump 11 by means of a heat exchanger 12 to the temperature control fluid 13 in an insulated fluid tank 14, where it is stored and when there is a heat requirement, the aqueous Microalgae suspension 1 is transferred back to this due to insufficient solar radiation by means of heat exchange in the reverse order, whereby the temperature of the aqueous microalgae suspension 1 is kept constant. The module is coupled within a module network of at least two identical modules via the inlet connection 18 and the outlet connection 19.

The 5 shows the pipe routing of the pipe PBR module. The vacuum pump 6 and the lei ducts for distributing the vacuum are not shown. The tube bends 20 of the transparent inner tube 2 are watertight within the at least two heat exchange containers 9, the transparent outer tubes 3 are fixed in a vacuum-tight manner. The module is coupled within a module network of identical modules via the inlet connection 18 and the outlet connection 19.

Reference List

1

aqueous microalgae suspension

2

transparent inner tube

3

transparent outer tube

4

spacers

5

Space

6

vacuum pump

9

heat exchange tank

10

temperature control circuit

11

pressure pump

12

heat exchanger

13

tempering fluid

14

insulated fluid tank

15

electrical resistance heating

16

swirler

18

inlet connection

19

drain connection

20

pipe bends

Claims (5)

Modular device for temperature control of tube microalgae photobioreactors, characterized in that an aqueous microalgae suspension (1) flows through a transparent inner tube (2) that is guided inside a likewise transparent outer tube (3), with at least one spacer (4) for centering the transparent inner tube (2), the space (5) between the outer surface of the transparent inner tube (2) and the inner surface of the transparent outer tube (3) is evacuated by means of a vacuum pump (6) and the transparent inner tube (2) passes through a heat exchange tank ( 9) in which the temperature control fluid (13) from a temperature control circuit (10) flows around the outer surface of the transparent inner tube (2) and heat is exchanged between the aqueous microalgae suspension (1), the transparent inner tube (2) and the Temperature control fluid (13) comes from the temperature control circuit (10), with the amount of heat absorbed by solar radiation, which exceeds the heat requirement of the aqueous microalgae suspension (1), being accumulated by the temperature control fluid (13) of the temperature control circuit (10) driven by the pressure pump (11), by means Heat exchanger (12) is transferred to the tempering fluid (13) in an insulated fluid tank (14), stored there and, when the aqueous microalgae suspension (1) requires heat due to insufficient solar radiation, is transferred back to it in the reverse order by means of heat exchange, whereby the temperature of the aqueous microalgae suspension ( 1) is kept constant. Modular device for temperature control of tubular microalgae photobioreactors claim 1 characterized in that by connecting the outlet connection (19) of the transparent inner tube (2) of the device for temperature control of tubular microalgae photobioreactors with the inlet connection (18) of the transparent inner tube (2) of an identical device, a tubular microalgae photobioreactor system is created on a modular basis , which comprises at least two modules and can be expanded at will. Modular device for temperature control of tubular microalgae photobioreactors claims 1 and 2 characterized in that within the insulated fluid tank (14) there is an electrical resistance heater (15) which can additionally heat the tempering fluid (13) of the fluid tank (14). Modular device for temperature control of tubular microalgae photobioreactors claims 1 until 3 characterized in that the inner surface of the transparent outer tube (3) is mirrored on one side, with the sunlight being focused on the transparent inner tube (2) and the light yield being increased by solar radiation on the microalgae suspension (1) in the transparent inner tube (2). Modular device for temperature control of tubular microalgae photobioreactors claims 1 until 4 characterized in that within the transparent inner tube (1) at least one swirler (16) made of flat material shaped like a screw is attached, through which the flowing microalgae suspension (1) is swirled, whereby a homogeneous light absorption of the microalgae suspension (1) takes place.

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