The process of Crude Oil Storage Tank Cleaning is somewhat a challenge to many. It is a comprehensive activity involving the removal of the bottom crude oil sludge, treating the oil sludge and washing the receptacle . There is the conventional method of washing it and several scientific methods that come up every day as research goes on.
In the conventional method, the sludge is removed from storage chamber’s bottom, a process that can take between 90 to 120 days. This is done with experienced personnel and machines and with more operators, the stage can take less like 2 to 3 months. And when using receptacle cleaning machines that are remotely operated will take double the time as compared to human operators.
The removed sludge is then treated in the second step. It is separated into oil, solid wastes and water. The process is done right in the storage chamber before pumping it out of system.
The third stage is to wash the tank since the sludge has been removed. By the use of high pressure cleaners, the floor and walls of storage chamber are thoroughly cleaned and de-rusted by use of sand blasting. It can take around 50 days if one team is working on it or about 30 days for two teams working simultaneously. To clean the external wall by sand blasting, the operators will take another 30 to 60 days based on the number of teams working on it. Another more efficient alternative which is more expensive is to use ultra-high pressure cleaning which combines de-rusting and de-painting in one process.
There is also a one step tank cleaning technology in use. It is more efficient than the conventional method and takes relatively less time. Here, nozzles are fitted on top the storage chamber and diesel is pumped through them into the sludge. This washes the sludge after which the mixture of diesel and sludge is pumped out of the receptacle.
Even though this method is more efficient than the conventional one, some sludge will still remain solid and stuck to the tank base. This may take up to four months to dissolve then the mixture is pumped out into another tank. This means that an extra receptacle is required to store the mixture before it I separated.
A two step washing technology is also in use. This is an advanced method and is very different from the first two. It cleans oil tanks in a matter of weeks as compared to the 4 months for the other processes. The first step involves the use of submerged rotary jet mixer to dissolve the sludge into the oil solutions, a process called re-suspension. Around 90% of the hydrocarbons can be recovered using this process. This only takes 10 days, 7 days for equipment installation and 3 days for cleaning.
The second step can be skipped if the client feels so. But if there is a need, then the residual sludge is removed. And since it is only 10%, the process will take way less time. And after the thorough and violent mixing, the remaining sludge is quite soft and easy to handle as compared to when using the conventional method of Crude Oil Storage Tank Cleaning.
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