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> Innovative
 

Keeping a Pulsation
Column Running

Background

Bateman has over 80 years of experience in the application of mining, mineral processing and metallurgical know-how and state of the art solutions to the evaluation, development and beneficiation of mineral resources. They have extensive experience in the design and construction of Pulsed Column Technology across a wide range of industries and commodities. Pulsed Column applications include: Minerals (Copper, Uranium, Nickel / Colbalt, Zinc) Chemicals (Nitric Acid, Hydrochloric Acid, Phosphoric Acid, Inorganic Salts) Environment (Nitrate Removal, Heavy Metals Removal, Effluent Treatment).

 

Technology Description

The Pulsed Column consists of a large diameter vertical pipe, filled alternatively with disc and annular shaped (doughnuts) baffles which facilitate contact between the immiscible liquids passing through the column. The heavy phase enters through a disperser at the top of the column and the light phase enters through a similar device near the bottom. A settler at each end of the column permits the liquids to coalesce and be decanted separately. When the light phase is continued, the interface between the phases is in the lower settler and when the heavy phase is continued, it is in the upper settler. The advances of the Pulsed Column (PC) are significant particularly in processes with a fast rate of mass transfer.

 

The Application

The column is pulsed by blowing air or nitrogen into the pulse leg. The gas pressure is controlled to provide pulse of the required amplitude in the column while the frequency of the pulse is controlled by using special solenoid valves. The diameter of the column and the spacing between the discs and doughnuts are all calculated from the required process flowrate and optimal design flux as determined experimentally during pilot tests. Varying the pulsation rate controls the extent of dispersion of the phases, which governs the mass transfer rate. The flow rate creates a homogeneous medium, with drop size control. The system is required to operate over a large range of pressures and temperatures and is fully automated. Maintenance and operating costs must be kept low with no shutdowns for crude cleaning.

 

The Problem

The valve open-close operation had to follow a precise pulse ramp with an exact cycle time of no more than 2 seconds. The Cv required for the columns to pulse was calculated to 450. The original solenoid valves installed in the units were diverter globe valves with a Cv of 70. In order to maintain the flow rate and cycle time and to keep the pulsation rhythm steady, 7 automated valves were installed, each individually operated by solenoid valves and controlled with the same signal. The mission of keeping the pulsation steady became impossible had one valve, actuator or solenoid fail. After many shutdowns and failures to keep the columns working continuously 24 hours per day all year, Bateman called on Habonim for advise.

 

The Solution

After Habonim engineers met with Bateman engineers to study the critical issues, they came with a solution of a single automated valve that is working without flaw to this day after more than 1.5 years in service. To solve the problem of flow capacity, Habonim knew that the valve design had to be such that it will give the highest flow rate and will still cycle at the required 2 seconds. The idea behind the solution was to convince Bateman to change their piping layout so the valve will not be a diverter valve anymore, but a through flow 4-way valve. This meant redesign of the PC piping and installing one single valve instead of 7 individual valves working simultannuously. The valve size was 21/2" full port with special 3" flange connections with a Cv of 450. It was designed to fit in the existing 8" piping layout and the flow pattern was modified so there were no sharp bends and elbows. This unique adaption of a 4-way valve gave Bateman the required solution to their flow pattern and cycle time.