JPS63117092A - Method of demineralization of crude oil - Google Patents

Abstract

PURPOSE:To prepare a crude oil having improved demineralization and dehydration rates, by controlling the pH value of a waste water washing after demineralization prepd. by washing a crude oil contg. minerals. CONSTITUTION:A crude oil contg. minerals as an impurity is washed with a cleaning water or with a cleaning water having a demulsifier added thereto, thereby effecting separation into a demineralized crude oil layer having a decreased mineral content and a waste washing water layer contg. minerals. The pH value of this waste washing water is continuously monitored, and an acid substance or an alkali material is added to the crude oil or cleaning water in such an amt. that the pH value of the waste washing water is 5 or less when the inherent characteristic value dependent on the formulation of the crude oil (wt. ratio of the n-pentane insolubles to the n-butanol insolubles contained in the crude oil) is smaller than 1 and 8 or more when the characteristic value is 1 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Field of Application The present invention is a method for desalting crude oil, more specifically, as a preliminary treatment for crude oil distillation, to remove various salts that are impurities contained in crude oil (improved The present invention relates to a crude oil desalination method.

B. Conventional technology Crude oil generally contains various impurities such as salts such as NaC2, MfC12, and CaCtz, mud, and water.If it is distilled as is, the salt may cause corrosion in refining equipment, and the mud may cause fouling. The ring phenomenon occurs and causes fouling, resulting in serious consequences such as equipment operation and maintenance problems and reduced refined oil quality.

In order to solve these problems, the impurities that are emulsified and dispersed in the crude oil can be separated from the crude oil. Therefore, in the past, washing water and demulsifier (
A method is adopted in which a W10 type emulsion is formed by adding a desalting agent) and then sent to a desalter to separate oil and water.

However, with some types of crude oil, stable emulsions are formed, resulting in insufficient oil-water separation, and many impurities are entrained in the crude oil after desalting, which not only fails to fully achieve the original purpose of desalting. Oil often gets mixed into the washing wastewater after desalination, causing undesirable problems in water quality management.

The safety of the emulsion produced by stirring a mixture of crude oil and water mainly depends on the properties of the emulsion protective film created around the water particles by the surfactants (asphaltenes, resins, organic acids) present in the crude oil. do. Therefore, the types, amounts, and proportions of surfactants contained in different crude oil production areas (crude oil types) differ, so the stability of the emulsion produced varies greatly depending on the crude oil type, and depending on the crude oil type, the emulsion Even if a destroying agent is added or a voltage is applied, the stable emulsion is not destroyed, making oil/water separation difficult. In any case, a crude oil desalination method that can be efficiently applied to all types of crude oil has remained unresolved.

C.Object of the Invention An object of the present invention is to solve the problems associated with the above-mentioned prior art. In other words, the desalting rate and dewatering rate of crude oil and the oil removal rate of cleaning wastewater can be consistently maintained at a high level even if the characteristics of the crude oil source and, therefore, the crude oil type differ significantly.
There is a need to provide a cost-effective desalination method that is simple and safe to operate and can reduce operating costs including chemical costs, electricity costs, etc.

The present inventor focused on the stability and breakage mechanism of emulsions due to the composition of crude oil mentioned above, and as a result of extensive research based on theory and experiments, the present invention was conceived. In other words, in conventional technology, pH is
By adjusting the pH of washing wastewater after desalination, which is operated in a range of about 6 to 8, to an optimal value according to the characteristics of the crude oil type without being restricted to this range, The present invention was completed as a result of research focused on creating conditions advantageous for oil/water separation by weakening the surfactant ability of surfactants.

D. Structure of the Invention The present invention involves washing crude oil containing salts by adding washing water or washing water and a demulsifier, and converting the mixture into a layer of desalted crude oil with reduced salt content. In the conventional desalination method for removing or reducing the salts contained in crude oil, which consists of separation into a layer of washing wastewater containing salt, washing after desalination is performed according to unique characteristic values based on the composition of the crude oil. It is constructed by a method of controlling the pH of wastewater to a preset value.

The unique characteristic values based on the composition of the crude oil used in the present invention include the weight ratio between the N-pentane insoluble content and the N-butanol insoluble content (the ratio between the asphaltene content and the asphaltinox content). Weight ratio) has a strong correlation with pH, which is advantageous for oil-water separation, and is therefore one of the most suitable unique characteristic values. For crude oil where the weight ratio is less than 1, that is, the asphaltinox content is higher than the asphaltene content, the pH of the washing wastewater should be set to 5 or less, a reasonable value that does not adversely affect pH adjustment costs and the durability of related equipment. On the other hand, for crude oil in which the weight ratio exceeds 1, that is, the asphaltene content is greater than the asphaltix content, the pH of the washing wastewater should be controlled to a reasonable value of 8 or more. is desirable. In any case, by measuring the N-pentane insoluble content and the N-butanol insoluble content contained in the crude oil, and determining the ratio of the two, it is possible to determine the suitable pH of the washing wastewater for all crude oils. .

In the present invention, the pH of cleaning waste water is controlled by using acidic substances including mineral acids such as hydrochloric acid, sulfuric acid, and phosphoric acid and organic acids such as acetic acid and sulfonic acid, or alkaline substances including alkalis, ammonia, and amines such as NaOH-KoH. This can be easily done by adding it to crude oil or washing water, but due to economical and handling reasons, sulfuric acid and NaOH
is preferable, and it is very effective to add a commercially available product diluted to about 1 ml with water or the like. Since the effects of the present invention are not significantly affected by the type of acidic or alkaline substances added or the method of addition, a wide variety of pH control agents can be used.

In order to implement the method of the present invention in a practical plant, washing waste water is continuously discharged from the washing waste water layer at the bottom of the desalination tank, and its pH is continuously detected, and the concentration of acidic or alkaline substances and/or It is common to continuously and automatically control the pH of the washing wastewater to a preset value by continuously and automatically controlling the addition flow rate.

In the method of the present invention, when the pH of the washing wastewater is controlled to a preset value and a voltage is applied to the crude oil, the desalination rate and dewatering rate of the desalted crude oil are further improved. The applied voltage is 3,
A sufficient effect can be seen even at around 1,000 volts.

E Examples The configuration and effects of preferred embodiments of the present invention will be explained in more detail with the following examples.

Example-1 The N-pentane-insoluble content and N-butanol-insoluble content of various crude oils were measured to determine the weight ratio of the two, and at the same time, an oil-water separation test was conducted to determine the oil-water separation characteristics and the pH of cleaning wastewater. I sought the relationship between The oil/water separation test was conducted using 95V-% crude oil and 5% washing water.
After heating the mixture with v -% to a temperature of 70°C, it was stirred with a homogenizer to form an emulsion, which was placed in a pressure-resistant glass container and allowed to stand at a temperature of 120°C, and the amount of separated water was measured.

For pH adjustment, H2S04 or aqueous solutions with different NaOH concentrations were used as washing water.

The results are shown in Table-1. N-pentane insoluble matter and N-
Crude oil with a weight ratio of less than 1 and a high asphalteanox content to the butanol insoluble matter has a pH of less than 5, which is acidic, and a crude oil with a high asphaltene content has a pH of 5 or less. The oil-water separation property was good on the alkaline side with a pH of 8 or higher.

Example 2 An emulsion made using the same procedure as Example 1 for the boiled 7 crude oil of Example 1 was placed in a special desalting tester, and the temperature was 1.
After applying AC 3000V for 10 seconds at 20°C and leaving it for 20 minutes, the results obtained are shown in Table 2.

Blank space below Example 3 Table 3 shows the results of an experiment conducted using the same procedure as Example 2 for the &4 crude oil of Example 1.

Examples (Experiment No. 3.4)
and 7, 8) are significantly improved in oil-water separation properties (dehydration rate, desalination rate, and appearance of washing wastewater) compared to their respective comparative examples (experiment numbers 1.2 and 5, 6). Obviously, by applying a voltage of 3,000 V in the example.

Even if the amount of the demulsifier added is slightly reduced, better oil-water separation properties can be obtained.

F Effects of the Invention According to the method of the present invention, the desalination rate, dewatering rate, and oil removal rate of washing wastewater can be improved for all types of crude oil without modifying existing desalination equipment or using special chemical agents. Not only can it be maintained at a stable high level, operation is simple and safe, leading to reductions in operating costs such as chemical costs and electricity costs (as well as the operation and maintenance of subsequent crude oil refining equipment). It is expected that this will have a considerable effect on resolving management problems and ensuring safety.

Claims (1)

[Claims] 1. Crude oil containing salts as impurities is washed by adding washing water, or washing water and a demulsifier are added to wash the mixture, and the mixture is converted into desalted crude oil with reduced salt content. In a method for removing or reducing salts contained in crude oil, which consists of separating the salts into a layer of washing wastewater containing salt and a layer of washing wastewater containing salt, the washing wastewater after desalination is A method for desalting crude oil with improved desalination and dehydration rates, characterized by controlling the pH of the crude oil to a preset value. 2. The method according to claim 1, wherein the unique characteristic value based on the composition of the crude oil is the weight ratio of N-pentane-insoluble matter and N-butanol-insoluble matter contained in the crude oil. 3. The method according to claim 1 or 2, wherein the pH is controlled by adding an acidic substance or an alkaline substance to the crude oil or washing water. 4. For crude oil with a weight ratio of N-pentane insoluble content to N-butanol insoluble content of less than 1, the pH of washing waste water is controlled to 5 or less, and for crude oil with a weight ratio of more than 1, it is The method according to claim 2, wherein the pH of the washing wastewater is controlled to be 8 or higher. 5. The method according to claim 1 or 2, wherein the pH of the washing wastewater is continuously detected and the concentration and/or amount of addition of the acidic or alkaline substance is continuously and automatically controlled. 6. Crude oil containing salts as impurities is washed by adding washing water, or washing water and a demulsifier are added to wash the crude oil, and the mixture is formed into a layer of desalted crude oil with reduced salt content and a layer of desalted crude oil containing salt. In a method for removing or reducing salts contained in crude oil, which consists of separating the washing wastewater into a layer of washing wastewater, the pH of the washing wastewater after desalination is set in advance according to the unique characteristic value based on the composition of the crude oil. A method for desalting crude oil with improved desalination and dehydration rates, which comprises numerically controlling and applying a voltage to the crude oil. 7. The method according to claim 6, wherein the unique characteristic value based on the composition of the crude oil is the weight ratio of N-pentane-insoluble matter and N-butanol-insoluble matter contained in the crude oil. 8. The method according to claim 6 or 7, wherein the pH is controlled by adding an acidic substance or an alkaline substance to the crude oil or washing water. 9. For crude oil in which the weight ratio of N-pentane insoluble matter to N-butanol insoluble matter is less than 1, the pH of washing wastewater is controlled to 5 or less, and for crude oil in which the weight ratio exceeds 1, it is 8. The method according to claim 7, wherein the pH of the washing wastewater is controlled to be 8 or higher. 10. The method according to claim 6 or 7, wherein the pH of the washing wastewater is continuously detected and the concentration and/or amount of addition of the acidic or alkaline substance is continuously and automatically controlled.