GB2568293A - Liquid degasser - Google Patents

Abstract

A mass transfer device which may be a membrane contactor (1) is positioned upstream of a Venturi tube (2). An optional gas-release device (3) can be placed downstream of the Venturi tube. The liquid is fed through the membrane contactor, the Venturi tube, and the gas-release device, which generates a vacuum in the Venturi tube. The vacuum is applied to the membrane contactor via a vacuum line (4), driving dissolved gas separation in the membrane contactor. Separated gases travel along the vacuum line and are reintroduced to the liquid flow in the Venturi tube as bubbles. These bubbles exit the Venturi tube and are released to the atmosphere in the gas-release device. Liquid flow is induced by existing mains pressure or an existing non-dedicated pump. An objective is not to use chemical dosing, a dedicated external power source or using virtually no moving parts.

Description

This invention relates to a device for the separation of dissolved gases from liquids.

Dissolved gases impact upon the physical and chemical characteristics of a solution's liquid matrix and how it interacts with the external environment.

For example, water fed to domestic boilers is often saturated by dissolved air at the point of supply. Dissolved oxygen (DO) and dissolved carbon dioxide (CO₂) from air can chemically react upon contact with the internal surfaces of central heating systems. These chemical reactions corrode and damage critical components, e.g. heat exchangers, reducing their efficiency and lifetime whilst increasing maintenance demand. Corrosion also generates the black iron oxide sludge found inside radiators, causing cold spots and increasing natural gas consumption to compensate and achieve adequate heating.

In this example the invention effectively separates dissolved air from water before it is fed into the boiler, avoiding the problematic chemical interactions. This prevents corrosive damage in the boiler and stops black iron oxide sludge from being produced.

The invention will now be described solely by way of example and with reference to accompanying drawings in which:

Figure 1 shows the working arrangement of the invention's components.

Figure 2 shows an example for optional locations of the invention within a domestic water supply and central heating system.

In Figure 1 a mass transfer device (e.g. membrane contactor) (1) is positioned upstream of a Venturi tube (2). An optional gas-release device (3) can be placed downstream of 2. The liquid feed (i) is directed through 1, 2 and 3, which generates a vacuum pressure in 2. A vacuum line (4) applies the vacuum pressure to 1, which drives dissolved gas separation in 1. Separated gases travel along 4 and are reintroduced to the liquid flow in 2 as large gas bubbles. These bubbles exit 2 and are released to the atmosphere in 3, if present. Alternatively, liquid downstream of 1 can be used to feed appliances (ii) before being fed into 2. In this instance gas bubbles reintroduced in 2 may be allowed to re-dissolve, negating the need for 3, with liquid then exiting the invention (iii).

Figure 2 is an example of how the invention may be incorporated within a domestic central heating system. When positioned on the mains water feed (i) the invention removes bulk dissolved air from the entire water supply. This includes the central heating filling loop (iv) but also any other appliances not affiliated with the central heating (e.g. dishwashers, washing machines or boiling-water taps). In this instance water flow through the invention is induced by mains water pressure and water passes through the invention only once (single pass mode).

The invention can also be placed within the central heating system itself. An existing recirculation pump (5) is used to induce water flow through the invention, which is placed upstream of the critical components, i.e. heat exchanger (6). The water is then circulated through radiators (7) as normal, returned to 5 and the process repeated. In this instance water is circulated through the invention many times (multi pass mode).

In single pass mode, 1 must be sufficiently physically large to achieve targeted dissolved gas removal efficiency (e.g. >90% DO removal). For example, if 1 is a membrane contactor; sufficient membrane surface area must be provided to achieve >90% DO removal in a single pass of 1. By contrast, 1 in multi pass mode might be physically smaller because >90% DO removal may be achieved cumulatively by recirculation of a fixed liquid volume through the invention many times. This may be important, for example, in the scenario depicted by Figure 2, where a smaller physical size for 1 can allow incorporation within a conventional domestic boiler housing (8), making the invention logistically practical and more readily retrofitted. In this example it is plausible that both single pass and multi pass versions might be employed simultaneously or either in isolation, depending upon the degree of dissolved gas separation needed.

Claims (3)

Claims

1. A device for the separation of dissolved gases from liquids comprising a mass transfer device, to separate dissolved gases from liquid, a Venturi tube, to generate a vacuum pressure (via the Venturi effect) and a vacuum line, to apply vacuum pressure to the mass transfer device and drive gas separation.

2. A device for the separation of dissolved gases from liquids according to claim 1 but including a gasrelease device downstream to allow gas bubbles to escape from the liquid line.

3. The device achieves separation of dissolved gases from liquids without dosing of chemicals into the liquid, without using a dedicated external power source and without the use of moving parts (with the exception of any float used in the gas-release device).