Electrodialysis problem

The mixing strength can be increased; the type of demulsifier can be changed, and it is necessary to check whether the method for analyzing salt content is accurate – currently, the Coulomb method is generally used.

After electrodialysis, the salt content is high, and the main reason for this is the moisture present after the process; the salt content measured through analytical tests refers to water-soluble salts. I’m not sure what level of desalination your plant uses. If it’s at the third stage, electricity can be applied at that stage without adding water or any other substances, using it solely as a sedimentation tank. The inlet for the third stage should not go through the mixer but rather via a bypass line, to see how effective that is.

Specialized manufacturers in electrodialysis may be able to help you solve this problem!

The factors that affect the efficiency of electrodialysis include the pressure and temperature in the electrodialysis tank, the type and dosage of the demulsifier, the amount of water injected, the mixing differential pressure (the differential pressure should not be too high, as this can lead to emulsification and increased salt content), whether backwashing is performed frequently, and the electrodialysis voltage. Checking each of these factors should help resolve the issues.

The general control target for the salt content after desalination is 3–5%. According to the poster, the properties of the crude oil fed into the electrodesalter often change; if the type of demulsifier isn’t adjusted accordingly in a timely manner, it seems that your operation is still quite good. The oil sources processed by local refineries vary greatly, resulting in poor compatibility with demulsifiers and suboptimal operation of electrode separators. Our facility adopted Qilu’s radio frequency demulsification technology during its renovation, and the results have been good.

The problem mentioned by the poster is something that many refineries encounter frequently. This situation occurs especially with crude oils that have a high asphaltene content. Generally, when the salt content in the crude oil is below 8 mg/L (sometimes around 5 mg/L), it becomes difficult to remove these salts. There is no connection between this and the level of salt content in the crude oil before processing; moreover, even if the water content in the crude oil after processing meets the standards, the salt content still doesn’t decrease. To address this phenomenon, two main approaches are taken. The first is to select a demulsifier; generally, it is difficult to remove emulsions using conventional demulsifiers, and there are currently no demulsifiers suitable for this type of crude oil. However, desalination aids with good desalination effects can be used in combination with demulsifiers. The second approach is to increase the mixing intensity (provided that the crude oil meets the dehydration requirements and there is no emulsification in the desalination tank). Additionally, the poster can go and inquire at the Luoyang Petrochemical Refinery; they currently use pulse-ultrasonic electrodeionization devices, which yield good results for the electrodeionization of heavy oil!

Now, the formulations of demulsifiers are more or less the same. Since the raw materials used in local refineries change quite frequently, constantly switching demulsifiers isn’t a viable solution; solutions must be found at the operational level instead.

I’d like to add one more thing: if making the usual adjustments doesn’t yield any results, it might be due to the high density, high viscosity of your raw materials, or a high content of heavy metals. You might consider diluting the raw materials or adding a certain amount of demetalizing agent to see if that helps. Also, check the quality of the water used for electro-deionization!

Electrodesalination is essentially a dehydration process; what happens is that emulsifiers are used to break the emulsion state of the oil-water mixture, allowing the salts in the oil to dissolve in water. Subsequent dehydration then removes those salts as well. I suggest you compare the dehydration efficiency of your system before and after this process – if there’s no significant change, it’s likely an issue with the mixing process; if there is a significant change, it’s probably a problem with other aspects of the system. My knowledge is limited, so please correct me if I’m wrong

I believe the addition of heavy metal removal agents should help reduce the salt content after removal. Currently, in China, calcium and nickel removal are the most common methods; the cost for such services is around 30,000 yuan. Imported products are also available on the domestic market, but their price is higher, at around 50,000 yuan.

Is the demulsifier water-soluble or oil-soluble, and what is its water separation performance? Perhaps the emulsion layer is too thick; it may be possible to increase the water injection volume or raise the temperature to 135 degrees and try again. The mixing intensity cannot be increased! Another option is to add a demulsifier along with a decalcifier, while keeping the amount of each additive unchanged! This post was last edited by Lianyou Sanji on 2008-7-2 at 17:17.]

The chapter on electrodialysis in this book seems to cover the topic quite comprehensively: http://bbs.hcbbs.com/thread-6641-1-1.html. There are quite a few people working in the field of vacuum distillation! Come to the front and report yourself!

What is the pH value of the water being injected? The pH value of the water used for injection should not be too high; it is best to keep it between 7 and 8. Adding a decalcifier should work. Decalcifiers are acids in themselves. Demetallization is possible, and the pH value of the injected water can be adjusted. But the amount added must be controlled. It is best to keep the pH value for controlling water cut between 5.5 and 6.5. We have used this method before, and it worked well.

I don’t know what kind of crude oil the original poster is processing. We process Tahe crude oil; its salt content before desalination is around 100. We use three-stage electrical desalination, and currently the salt content after desalination is roughly 4, though it’s not very stable – sometimes it can drop to 1–2 as well

Could you share your electro-deposition operation parameters and methods? When processing the Tahe crude oil, electrical dehydration is almost ineffective; if the value is 100 before dehydration, it can only be reduced to at most 70 after three stages of electrical dehydration. :handshake

I briefly mentioned it in another post about electrodialysis: We process crude oil from the Tahe region, and the quality of this crude oil is quite poor, with a viscosity level around 947. We use a three-stage electrodialysis process, and the overall desalination effect is fairly good, with the viscosity level remaining around 4. The operating conditions are as follows: (1) Demulsifier FJT-1 at a concentration of 25–30 PPM; (2) Water injection at around 7%, using fresh water in a three-stage injection process; (3) Voltage of 19 KV to 25 KV; (4) Mixing intensity of 30, 40, or 50, depending on the degree of emulsification and dehydration of the crude oil; (5) Operating pressures of 1.1, 1.0, and 0.9 respectively; (6) Temperatures of 130 °C, 125 °C, and 120 °C. Currently, in order to control the temperature of the residue leaving the processing unit, the temperature in the third stage is kept at around 113 °C. By the way, during a technical review conducted by the company some time ago, when the voltage was 13 KV, the current was 120 A. Now that the voltage has been increased to 19 KV, the current has decreased to 40 A. I believe this is due to an enhanced weak electric field effect in the electrodialysis process, which leads to a reduction in metal ions and water content, thereby increasing the resistance. I’m not sure if this is correct

Who are the manufacturers of desalination skids, and where should I purchase them?

Does anyone have a PPT presentation on electrodialysis? Thank you

Hello, could you tell me the parameters for your electric desalination process for Tahe oil?