Simdean Envirotec Ltd  

Pollution solutions through Engineering Excellence

Chlorine Room Ventilation Multivent Scrubber System

With increasingly stringent regulations being applied to discharges of Chlorine from Chlorine storage facilities, the designers and operators of Water treatment works are having to consider the installation of pollution control equipment to the ventilation systems of Chlorine storage facilities.

Simdean Envirotec have developed the successful Multivent scrubber to provide an economic solution to the problem.

Key Features of the Scrubber

• Can be run dry for long periods without dirt clogging
• Inverter fan drive for reduced volume flowrate
• PLC control for automatic washing of the scrubber.

The Multivent scrubber is a gas liquid contactor comprising a matrix of elementary modules referred to as cell, in which gas and liquid circulate vertically under counter-current flow. Liquid is introduced at the top of the cell, gas flows vertically from the bottom between the cell walls. In each cell, placed in series, gases are successively washed by the mixing of the two phases.

A cell is formed by two rectangular sections, one convergent and one divergent, the intersection between the two forming the CELLNECK. Several cells placed in series form a FLOWCHANNEL.

The cell is characterised by its height, width, length and the width and the shape of the cellneck.

The diagram on the left shows the make up of one cell. When liquid is introduced into the cell at a given liquid/gas flowrate, intense mixing and turbulence is generated at the cell neck resulting in intimate contact between the scrubbing liquor and the contaminant gas-stream. It is this contact that produces the absorbing effect of the scrubber. The absorption efficiency of a cell depends on the scrubbing conditions and on the type of chemical reaction required. Typical absorption efficiency of a cell in the scrubber operating regime is from 55 to 65%. For five cells placed in series, the efficiency can reach 99.5%.

The gap between the modules at the cell neck is typically 8 –10 mm, thus the scrubber exhibits non-clogging characteristics during operation in particulate laden gas streams. (Compare this with the ability of either packed–bed or plate tower scrubbers to handle particulates). It also means that the scrubber can be run dry without dirt clogging the scrubber internals. In Chlorine storage facilities, this has the advantage of not having to operate scrubbing liquor pumps during periods when the ambient Chlorine concentrations within the building are well below alarm levels. Whilst there is an obvious saving due to reduced electricity costs, in areas where the cost of water is high there is a further saving through the reduced evaporation of water from the scrubber.

The scrubber system fan is fitted with an inverter thus, the volume flowrate through the scrubber can be varied. This allows the system to operate at reduced flowrate during periods when the ambient Chlorine concentration within the building are below alarm levels. This facility leads to a reduction in the amount of electricity required to operate the system.

The system is PLC controlled and is linked to the Chlorine sensors within the building. PLC control of the system allows the scrubber to be operated at a variety of flowrates dependent upon the level of Chlorine concentration present within the building. The scrubber can operate efficiently at a range of L/G ratios (liquid /gas flowrate) between 0.8 and 1.2. Thus the exhaust flowrate from the room can be set to increase with an increase in detected chlorine levels, up to a 50% increase in flowrate can be achieved without a reduction in scrubbing efficiency.

For storage facilities where there is a high degree of dust in the atmosphere the recirculation pumps on the scrubber can be set to operate automatically on a timed basis, say once a week or once a month, thus eliminating any possibility of the scrubber blocking due particulates.

Due to the ability to produce a rectangular tower for the scrubber the "footprint" area required for the unit is smaller than conventional circular scrubbers and thus can be housed more easily within the chlorine storage facility. If space is at a particular premium, then the unit can be housed external to the building.

All materials used in the construction of the scrubber are compatible for use in chlorine-laden gas streams, all electrical equipment and control panels are CE marked.

The major overall dimensions of the scrubber are given below for a range of flowrates . For more information on the use of the Multivent scrubber please contact us via e-mail at nick@simdean.co.uk