Treatment of cold coker water and cut coker water in delayed coking units

In our factory, after oil removal, the liquid goes straight to the wastewater treatment plant; it seems that there’s little need for stripping

What are the common methods used for treating cold coker water and cut coke water in delayed coking units? Can the two streams of wastewater be mixed together, treated for oily waste, and then sent to the acidic water stripping unit? The treated water can subsequently be returned to the delayed coking unit to be used again as makeup water for cold quench water and coke cutting water First question: Cold coke water can be recycled. Does the treatment you mentioned refer to the removal of oil from cold coke water? ? ? Coke cutting water is the same as cold coke water; there is no distinction between the two, as it is water from the same storage tank. Second question: These two streams of water are originally from the same reservoir; it’s just that the filtration precision for cold coking water is lower, while a slightly higher filtration precision is required for coking removal water. All that’s needed is to install filters in front of the equipment before use. Regarding water treatment as you mentioned, I think it refers to the oil floating on the surface. For this oil, we have cyclone oil removal devices in the tank as well as overhead pipelines for removing oil from the surface. During major maintenance operations, unless the tank needs repair or extensive work is being carried out in the coking tank, this water can be stored in the tank for later use. Additionally, it can also be stored in the water storage tanks if those tanks are not cleaned or overhauled. If both the water storage tanks and reservoirs need to be overhauled at the same time, we can carry out the repairs separately. After completing the work on one of them, we can transfer the coking removal water and coke cutting water to these two facilities for storage, thereby avoiding significant waste.

Furthermore, if repairs are carried out simultaneously, the floating oil should be dealt with before shutting down the operation. This water does not need to go into the acidic water stripping unit of the sulfur plant; it can be discharged directly into the fresh water system for external disposal. However, care must be taken when discharging it to avoid the coke powder settled at the bottom from ending up in the rainwater drains and contaminating the environment.

Thank you for your reply. I still have the following questions: 1. I would like to ask whether the statement you made, that “cutting coke water is cold coke water,” is appropriate In fact, after coke is formed in the coke tower, it is first blown with steam; this serves to dislodge any oil and gas contained in the steam, while also reducing the temperature of the coke. This process is known as the \"blowing process\"” ； The coke is then cooled with water to further reduce its temperature; this is the “cold coke process,” and the water used at this stage is known as cold coke water ； After the temperature of the coke drops, high-pressure water is used to cut the coke off; the resulting coke pieces fall into the coke storage tank along with the cutting water. This is what is known as the \"coke cutting process\", or simply the use of cutting water. 2. Do you mean by “coking water” and “cold coking water” that there is no distinction between the two, and that it’s the same water from the same storage tank? Are you saying that the water generated in these two processes is mixed together for further treatment? If it is placed in a water storage tank, compared to a completely sealed treatment process, will some foul odors be emitted? Our goal is to minimize the release of such unpleasant smells as much as possible. 3. As for another point, if maintenance is carried out simultaneously, the floating oil should be treated before the shutdown; such water does not need to go into the acidic water stripping unit of the sulfur plant, and can be directly discharged into the fresh water system for external discharge. However, when discharging it, care must be taken to avoid the coke powder deposited at the bottom, so as to prevent it from reaching the rainwater drains and contaminating the environment. ”In this regard, if the feedstock processed by our delayed coking unit is vacuum residue and catalytic cracking slurry with high sulfur content, then wouldn’t the sulfur content in the cold coke water and cut coke water also be high? If this portion of water is not sent to the acidic water stripping unit in the sulfur plant, will the sulfur content in the cold coking water and cutting coking water increase? 4. Our idea is to send the cold coking water and cutting coking water to the acidic water stripping unit in the sulfur plant, and then reuse the treated water for use as cold coking water and cutting coking water, thereby minimizing the consumption of fresh water in the delayed coking unit.

If the sulfur content in the cold coker water and cut coker water is high, is it feasible to use such water for acidic water stripping in the sulfur recovery unit? Can it be considered feasible from a technical and economic perspective?

What methods do you use to remove oil from your cold coker water and cutting coker water? We have encountered this issue in petrochemical plants: the coarse gasoline and diesel products tend to emulsify heavily in such water, making it similar to milk in appearance; moreover, the content of coke powder is high. Prolonged circulation leads to a severe deterioration of the quality of this water. In such cases, the contaminated water can only be collected and disposed of. Do you have any effective solutions?

It feels like it’s been a long time since I’ve seen a post with such thoughtful questions and replies. In that case, I’ll get involved a little too. Firstly, the cold coke water system does produce foul-smelling gases; therefore, in current new designs, in addition to striving for maximum sealing, odor control facilities are also included, which is reflected in the principles of simultaneous implementation of environmental protection measures. Old installations also need to be modified, primarily by converting them into a closed system for cooling coke and a closed circulation system for the water used in cooling coke. Odor control facilities are not complex; amine-based desulfurization is sufficient (at least it is recognized by environmental protection authorities) ； Secondly, for dealing with floating oil, oil removal facilities are generally installed in the cold coke water tanks; centrifugal separation, floating separation, or fixed oil removal methods can all be used – the effectiveness depends only on the method chosen. There is no need to remove it every day in daily life. Look at the rank; if it’s high, make some adjustments. If there is no rank, perform the division every once in a while. Thirdly, no matter what it’s called—cold coking water or cut coking water—it’s not possible to allow it to be discharged directly! ! The oil and sulfur contents must be above the limits! If coke dust is carried along, it will also cause pollution and is difficult to wash away. It would be ideal to deaerate this water, but it’s not really necessary; it can be sent directly to the wastewater treatment plant in small amounts over time. Make sure to control the volume of water flowing in, and keep an eye on the operation of the wastewater flotation process at all times. Just avoid putting stress on the sewage treatment plant.

1. I would like to ask whether the statement you made, that “cutting coke water is cold coke water,” is appropriate In fact, after coke is formed in the coke tower, it is first blown with steam; this serves to dislodge any oil and gas contained in the steam, while also reducing the temperature of the coke. This process is known as the \"blowing process\"” ； The coke is then cooled with water to further reduce its temperature; this is the “cold coke process,” and the water used at this stage is known as cold coke water ； After the temperature of the coke drops, high-pressure water is used to cut the coke off; the resulting coke pieces fall into the coke storage tank along with the cutting water. This is what is known as the \"coke cutting process\", or simply the use of cutting water. Yes, it’s exactly the situation you mentioned: after the cold coking process is completed, water is switched from being used for normal operations to being used for coking. 2. Do you mean by “coking water” and “cold coking water” that there is no distinction between the two, and that it’s the same water from the same storage tank? Are you saying that the water generated in these two processes is mixed together for further treatment? If it is placed in a water storage tank, compared to a completely sealed treatment process, will some foul odors be emitted? Our goal is to minimize the release of such unpleasant smells as much as possible. I haven’t seen any cold coking water systems that are enclosed; most of them are outdoors. Both cold coking water and coking removal water are stored in the same reservoir. 3. As for another point, if maintenance is carried out simultaneously, the floating oil should be treated before the shutdown; such water does not need to go into the acidic water stripping unit of the sulfur plant, and can be directly discharged into the fresh water system for external discharge. However, when discharging it, care must be taken to avoid the coke powder deposited at the bottom, so as to prevent it from reaching the rainwater drains and contaminating the environment. ”In this regard, if the feedstock processed by our delayed coking unit is vacuum residue and catalytic cracking slurry with high sulfur content, then wouldn’t the sulfur content in the cold coke water and cut coke water also be high? If this portion of water is not sent to the acidic water stripping unit in the sulfur plant, will the sulfur content in the cold coking water and cutting coking water increase? Water is continuously depleted in daily production, and replenishing it can fully meet the needs. 4. Our idea is to send the cold coking water and cutting coking water to the acidic water stripping unit in the sulfur plant, and then reuse the treated water for use as cold coking water and cutting coking water, thereby minimizing the consumption of fresh water in the delayed coking unit. A. Your idea is feasible; it’s best to send it to the sulfur removal unit and the acidic water stripping unit for treatment, as environmental regulations are quite strict ； B. In normal production, cold coking water and coking removal water do not require replacement; only regular top-up of water is needed. This kind of situation only arises during major maintenance. In such cases, it is entirely possible to manage the water by switching between storage tanks and reservoirs.

Sure, but we haven’t handled it this way here; it’s all done as mentioned before.

First of all, I am very grateful for your detailed response. Over the past period, I have reviewed a great deal of information and found that in our country, cold coking water and cutting coking water are still tended to be treated separately: cold coking water is processed through a closed-loop system, while cutting coking water is treated using multi-stage sedimentation tanks； In most foreign countries, the two types of water are mixed together for treatment (using a labyrinth system); in comparison, the process used in China is more complex, but it yields better results with less pollution ； Foreign methods are simple to operate, but they have a strong flavor! And is there such a tendency: that is, large-scale delayed coking units generally use a combined treatment of cut coke water and cold coke water? I see that this is the case at CNOOC Huiyan’s 4.2 million tons per year delayed coking unit; while for smaller and medium-sized delayed coking units, it seems better to treat these two types of water separately 1. There are two types of cold coke water: overflow cold coke water and foamed cold coke water. I would like to ask what method is used for handling cold coke in the delayed coking unit at your plant? Which of these two processing methods is more suitable? 2. The cold coke overflow method is used; there is a difference between the water resulting from the overflow of cold coke and the water released as waste from cold coke. The overflow water is considered to be \"dirtier\" and more difficult to treat, while the waste water contains more solid coke particles. Can the cold coking water, along with the water from the coking cutting process, be mixed together and fed into the coking cutting water treatment system (multi-stage sedimentation), while the overflow water continues to go through the cold coking water treatment process? 3. Cold coking water contains more contaminated oil and sulfides than cutting coking water. If it is not sent to other units for treatment and instead remains in circulation within the system, won’t there be an accumulation of sulfides, which in turn could cause corrosion to the equipment? What should be done at this point to deal with these wastewater streams with high sulfur and high pH levels? 4. Cold coking water and cutting coking water should be treated separately, and fresh water from outside the system is required for both types of water. How can the consumption of fresh water be minimized? Could you give one or two suggestions? Thank you! ! ! :):handshake:)