Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Reexamination Certificate
2000-08-28
2002-10-29
Fortuna, Ana (Department: 1723)
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
C210S636000, C210S195200, C210S257200, C210S416100
Reexamination Certificate
active
06471869
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a crude oil processing apparatus for separating water from crude oil, and a crude oil processing method.
This application is based on Japanese Patent Applications (Japanese Patent Application No. Hei 10-48303and Japanese Patent Application No. Hei 10-48306) filed in Japan, the contents of which are incorporated herein as a part of this specification.
BACKGROUND ART
Crude oil contains as principal components paraffin, naphthene, aromatic and other hydrocarbons. The physical and chemical properties of the crude oil are determined by the proportion of various chemical compounds contained therein, and the properties of the crude also vary significantly from oil field to oil field, and from horizon to horizon.
It is an internationally accepted practice to represent the specific gravity of crude oil with API (American Petroleum Institute) gravity. API gravity is determined as follows.
API gravity=(141.5/G)−131.5
where G is the ratio of the mass of crude oil at 60° F.(15.6° C.) to the mass of water of the same volume at 60° F. Various types of crude oil are roughly classified as follows in terms of API gravity.
Bitumen API gravity:
Less than 10
Heavy oil
From 10 or more to below 22.3
Sub-heavy oil
15 to 25
Medium oil
24-39
Light oil
39-45
Ultra light oil
45 or higher
Crude oil is produced by, first, collecting the crude oil from various oil reservoirs in the ground through oil wells by flowing, pumping, water or gas injection, or other methods. The crude oil that has been collected is sent from a branch pipe, called the Christmas tree which is installed on the well head, through a pipeline embedded underground to an oil gathering station. The crude oil gathered at the oil gathering station is sent to a separator where gas and water are separated from the crude oil.
FIG. 8
shows an example of the separator. Separators are roughly classified into horizontal, vertical and spherical types. The example shown is of the horizontal type.
The separator
201
of the example comprises a closed tank that has a crude oil inlet
202
provided at a position a little above the center of the side wall on one end, a separated oil outlet
213
provided at a position a little below the center of the side wall on the other end, a separated water outlet
212
provided at the bottom on the other end, and a gas outlet
214
installed at the top. Provided in the separator
201
are a weir plate
203
installed near the crude oil inlet
202
to suppress billowing of the crude oil that has been introduced, and a partition wall
215
installed on the other end to allow only the supernatant (separated oil) of the liquid in the crude oil layer
204
to overflow into the separated oil layer
206
on the separated oil outlet
213
side.
To remove water from the crude oil using the separator
201
having such a constitution as described above, first, the crude oil sent from the production well is introduced rapidly through the crude oil inlet
202
into the separator
201
. After billowing has been quelled near the crude oil inlet
202
, the crude oil passes the weir plate
203
and into the crude oil layer
204
of the next section.
Gas that has escaped from the crude oil layer
204
is accumulated in a gas layer
205
located above in the separator
201
, and is occasionally discharged through a gas outlet
214
. The crude oil layer
204
separates over time into oil and water due to differences in specific gravity, and water is accumulated into a separate lower water layer
207
. The crude oil is heated to a temperature in a range from 40 to 60° C., thereby decreasing the viscosity of the crude oil, to improve the efficiency of separation. Water in the separated water layer
207
is occasionally discharged through a separated water outlet
212
by opening and closing a water level control valve
210
under the control of a water level controller
208
. The separated oil that is free of gas and water by separating from the crude oil layer
204
flows over the partition wall
215
into a separated oil layer
206
. The separated oil in the separated oil layer
206
is occasionally discharged through a separated oil outlet
213
by opening and closing an oil level control valve
211
under the control of an oil level controller
209
.
The method of separating water from the crude oil by making use of differences in specific gravity between oil and water using the separator
201
described above requires an increase in the scale of the facilities when the quantity of crude oil to be processed is increased, thus giving rise to such problems as the selection of site to build the facility, equipment investment cost for the facility and energy cost of the heating boiler. Moreover, such problems as the limitations to the processing rate and capacity and limitations to reduction of the water content make it difficult to increase the processing capacity by increasing the scale of the facility.
In the meantime, the separated oil from which gas and water are removed may still include a significant water content, with fine water particles and muddy matter uniformly dispersed therein depending on the nature of the crude oil. Such a dispersed state is called an emulsion. Such fine water particles would not be caused to aggregate into separable water simply by leaving the oil to stand still. This is because the surface tension of the fine water particles is strong and hinders the water particles from combining.
Also the muddy matter can corrode the processing facility after separation. The muddy matter may also have a composition that is not suited to refining and production, in which case that production yield may become lower.
Thus in order to decrease the water content in the separated oil, processes such as the following are employed: (1) to destroy the adsorption membrane of the water particles by using a surfactant thereby to cause the water particles in the emulsion to aggregate into separable water; and (2) to apply a high AC voltage of 10 kV to 20 kV to make an AC current flow through the emulsion thereby to reorient the adsorption membrane of the water particles under the effect of the electric field into such a state that the water particles collide with each other more frequently and also attract each other, thereby causing the water particles in the state of emulsion to aggregate into separable water.
However, the process (1) of adding the surfactant requires the choice of the surfactant best suited for the oil temperature, oil processing rate, components of the oil and the concentration of salt content in the oil, and makes it necessary to determine the surfactant adding condition. Also there has been the problem that the surfactant is subject to a strong limitation due to the concentration of salt content in the oil or water, and therefore the conditions of use must be studied and determined according to which location and horizon of the oil field the crude oil comes from.
Also the process (2) of applying a high AC voltage has the problems of the site to build the facility, equipment investment and cost of the facility, the possibility of fire caused by the high voltage, fire prevention measures and the method of supplying electric power.
Among the different types of crude oil described previously, bitumen and heavy oil have particularly high values of specific gravity, close to that of water, and therefore take a longer time to separate from water.
DISCLOSURE OF THE INVENTION
The first embodiment of the present invention provides a crude oil processing apparatus for separating and removing water contained in crude oil, comprising a processing tank having a water drainage port at the bottom, a membrane that selectively allows the oil content of the crude oil to pass therethrough installed in the processing tank, a means which pressurizes the crude oil and a removal pipe for removing dehydrated oil that has passed the membrane.
The first embodiment of the present invention also provides a crude oil processing method, which comprises immersing a membrane
Itakura Masanori
Kanno Michio
Uehara Masaru
Yanou Manabu
Fortuna Ana
Mitsubishi Rayon Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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