Method of dewatering oil mud

A method of dewatering oil mud that occurs on board ships during the processing of heavy, diesel, and lubricating oils and consists of a mixture of water and mineral-oil residue that is intercepted on board and subjected to centrifuging. The liquids contaminated with mineral-oil residue that occur on board are collected in two separate containers. The liquids that contain heavy oil and diesel oil are conveyed to the first container and the liquids that contain lubricating oil are conveyed to the second container along with the water that occurs when the oils are processed. The contents of the containers are then conveyed sequentially to one and the same centrifuging device to concentrate the solids. The resulting liquid phases are subjected to separate further processing with on-board equipment, allowing complete disposal or further use of the liquids.

BACKGROUND OF THE INVENTION 
The invention concerns a method of dewatering oil mud that occurs on board 
ships during the processing of heavy, diesel, and lubricating oils and 
consists of a mixture of water and mineral-oil residue that is intercepted 
on board and subjected to centrifuging. 
"Oil mud" means the mixture of water, oil, and solids that occurs during 
separation and filtration. The oil muds can either be removed in the 
harbor by pumping them into waste-disposal ships, which is expensive, or 
processed on board the original vessel. 
A method of treating oil muds that involves collecting all the liquids in a 
buffer container and subsequently centrifuging them is known from German 
OS 2 438 602. The centrifugal separation of this mixture of various oils 
and water is not free of problems in that only relatively low throughputs 
can be attained and the separated phases are not satisfactorily pure. 
Since oil mud also contains waste water that in turn includes oil, 
considerable volumes of a material that can only be considered difficult 
to separate are involved. 
German AS 2 362 665 describes a method of processing large volumes of muddy 
and oily waste material. The mud is treated at temperatures of 500.degree. 
to 600.degree. C., requiring a considerable consumption of outside energy. 
The method is very complicated and is accordingly appropriate only for 
stationary plants. 
Using separate separators to process heavy oil and diesel oil is known from 
German OS 3 020 501. The resulting oil mud is collected in a mud tank and 
conveyed through a line to a mud burner. This method also requires 
considerable energy. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide a cost-effective method 
of dewatering oil mud on board a ship that will reduce the volume of the 
difficult-to-separate mixture while improving the quality of the resulting 
oil and water. 
This object is attained by the improvement wherein the liquids contaminated 
with mineral-oil residue that occur on board are collected in two separate 
containers, wherein the liquids that contain heavy oil and diesel oil are 
conveyed to the first container and the liquids that contain lubricating 
oil are conveyed to the second container along with the water that occurs 
when the oils are processed, wherein the contents of the containers are 
then conveyed sequentially to one and the same centrifuging device to . 
concentrate the solids, and wherein the resulting liquid phases are 
subjected to separate further processing with on-board equipment, allowing 
complete disposal or further use of the liquids. 
The result of this method is that the oil mud is separated into a 
difficult-to-break-down oil mud that contains heavy oil and diesel oil and 
very little water and an easy-to-break-down oil mud that contains 
lubricating oil. This approach eliminates the problem of the 
difficult-to-separate mixture in relation to the volume of the two 
different types of oil mud. The two types of oil mud are treated in a 
single centrifuging device, with the separated liquid phases varying 
widely in quality, one consisting mainly of water with traces of oil and 
the other of heavy oil with traces of water. These different streams of 
liquid can easily be treated with the equipment already on board for 
processing heavy oil, diesel oil, and lubricating oil to the extent that 
they can be completely removed. The recovered oil can be exploited as fuel 
to power the ship, and the separated water will be high enough in quality 
to be pumped overboard. 
The liquid phase resulting from centrifuging the contents of the first 
container can be conveyed to a settling tank and the liquid phase 
resulting from centrifuging the contents of the second container can be 
conveyed to an oil separator. 
The liquid phase resulting from centrifuging the contents of the first 
container can alternatively be conveyed, depending on how much oil it 
contains, either to a settling tank or to an oil separator. 
The centrifuging can be carried out with a solid-bowl helical centrifuge.

DETAILED DESCRIPTION OF THE INVENTION 
The system comprises a heavy-oil centrifuge 1, a diesel-oil centrifuge 2, 
and a lubricating-oil centrifuge 3. The solids outlets 4 and 5 from 
centrifuges 1 and 2 open into an oil-mud container 7 and the solids outlet 
6 from lubricating-oil centrifuge 3 opens into another oil-mud container 
8. The water separated in centrifuges 1, 2, and 3 travels through a line 9 
into second container 8. The water employed to automatically empty 
centrifuges 1, 2, and 3 also flows into second container 8 through another 
line 10. A line 12 that collects any heavy oil leaking out of the ship's 
main engine 11 leads to first container 7, and a line 13 that collects any 
lubricating oil that leaks out of the engine leads to second container 8. 
Containers 7 and 8 communicate by way of lines 14, 15, and 16 and a 
diversion valve 17 with the intake of a fourth centrifuge 18 that 
separates the mixture supplied to it into compact solids and a liquid 
phase. The solids leave fourth centrifuge 18 through an outlet 19, and the 
liquid phase is conveyed through a sensor 20, another diversion valve 21, 
and lines 22 and 23 to either an oil separator 24 or a settling tank 25. 
Fuel for powering the main engine is stored in a service tank 26. 
Dewatering lines 27 and 28 extend from tanks 25 and 26 to second container 
8 and mud lines 29 and 30 to first container 7. Service tank 26 
communicates by way of a line 31 with main engine 11. Another line 32 
leads from settling tank 25 to heavy-oil centrifuge 1. The oil separated 
out in oil separator 24 is conveyed by way of a line 33 and heavy-oil 
leakage line 12 into first container 7, and the water is pumped overboard. 
The residual oil from a heavy-oil filter 34 is conveyed into first 
container 7 and the residual oil from a lubricating-oil filter 35 into 
second container 8. 
The oil mud collecting in first container 7 consists of approximately 5% 
solids, 10% water, and 85% oil (heavy oil, diesel oil, and used oil). This 
mixture is heated to 80.degree. to 90.degree. C. and conveyed to fourth 
centrifuge 18. 
The oil mud in second container 8 consists of approximately 5% mud, 15% 
lubricating oil, and 80% water. This mixture is also heated to 80.degree. 
to 90.degree. C. and conveyed to fourth centrifuge 18. 
The liquid phase leaving the centrifuge originally consists of a mixture of 
liquids with a high content of water and only a little oil. As long as 
sensor 20 detects that the oil content is less than 10% for example, 
second diversion valve 21 will divert the liquid phase to oil separator 24 
by way of line 22. The water can, after being processed in oil separator 
24, be pumped overboard and the recovered oils and fuel can, after being 
purified in heavy-oil centrifuge 1, be conveyed in the form of fuel to 
main engine 11. If the oil content exceeds 10%, second diversion valve 21 
will divert the liquid phase to settling tank 25 by way of line 23, where 
the water will settle along with any particles of solids. Settling tank 25 
is dewatered manually by way of line 28 from time to time. 
It will be appreciated that the instant specifications and claims are set 
forth by way of illustration and not limitation, and that various 
modifications and changes may be made without departing from the spirit 
and scope of the present invention.