How is the material balance for the quench chamber and slag lockhopper calculated in the TEXACO process?

I’m not an expert in this field; I’m just sharing some casual thoughts. To cool the syngas from 1300 degrees to around 250 degrees, it’s first necessary to calculate the amount of water required – this is a theoretical value. Additionally, it’s important to consider how the water is distributed, ensuring that the downcomer isn’t exposed directly to the syngas; this is based on experience and should be a value higher than the theoretical one. I’m not sure if what I’m saying is correct

Adjusted according to load.. Last edited by Langtaosha on 2008-3-12 14:44 ]

First of all, thank you to the person above. The pressure in the quench chamber is about 41 bar. However, (1) why is it the case that the greater the amount of water used for cooling, the better? I think there must be a certain range; the syngas coming out of the cooling chamber contains saturated water, which means there should be a maximum amount of steam that can be carried away. Moreover, if too much water is used for cooling, how can the liquid level in the cooling chamber be maintained? (2) What I meant by flushing water was not accurate; what I want to ask is how the amount of water used to flush the slag into the slag lockhopper and to circulate between the slag lockhopper and the quenching chamber is determined

Actually, if it’s just a simple material balance, it’s relatively easy to calculate – all that’s needed is to determine the balance of materials entering and leaving. As for the drainage from the lock hoppers, it can be converted into an average flow rate. The issue related to adding water to the cooling ring can be calculated using the method described on the third floor. Additionally, the flow rate of the cooling water is determined by the flow velocity of the holes distributed within the cooling ring. The water flow rate should be considered with regard to the temperature dropping below 400 degrees within a range of 1 meter from the slag outlet; in some facilities, the material used in the lower part of the downcomer has been replaced with 316L material. I’m not sure if what I’m saying is correct.

As for determining the flow rate of the water used for flushing the lock hopper, it is also determined based on an empirical ratio related to the amount of slag discharged, as after all, the purpose of this water is to flush away the slag.

Please elaborate: On what empirical data regarding the slag discharge volume is the flow rate of the lock hopper flushing water determined, and how well is it related to the volume of the slag lock hopper? This post was last edited by ralph31 on 2008-3-12 17:21]

This post was last edited by GSP on 2009-6-30 at 15:46. I’ll give a brief answer. For the first question, it is true that the greater the amount of quench water used, the better – this represents the safest limit. However, this is an irresponsible statement; there is a certain maximum amount required, as otherwise the amount of water carried in the syngas would become uncontrolled. This amount varies depending on factors such as the type of coal, the type of furnace, and the output per unit time. For the second question, the flow rate of this circulating water is mainly determined by the volume of the slag tank. The answers are complete; I invite experts to offer their criticism and suggestions.

I would like to ask how often the water in the slag lock tank should be circulated, so as to determine an appropriate flow rate for the circulation pump

The flow rate of the quenching water is generally determined by the following factors: 1. Liquid level in the quenching chamber； 2. Temperature of process gas at exit ； 3. The need to protect the downcomer. Putting the water issue aside for now, if the flow rate of the quenching water is too high and drainage is insufficient, water will overflow the quenching ring, resulting in damage to the refractory bricks, which would be a costly mistake.

The function of the circulating water in the lock hopper is to flush out slag, as well as to maintain good fluidity of the slag water. It is recycled in order to save water and maintain a certain temperature gradient and heat balance. The amount of circulating water can be determined based on the slag content in the gasification furnace. It can be understood as follows: the solid content in the stream that enters the lock hopper from the bottom of the quenching chamber is about 20% (on a mass basis), including 50% from the ash of the coal and unreacted carbon; the remaining carbon is present in the black water and syngas. From this, the amount of water flowing out of the quenching chamber, q, can be calculated, while the amount of water pumped by the lock hopper circulation pump is q multiplied by 1.1. As for the amount of water required for quenching, I’m not sure how GE calculates it. Personally, I think it is related to the total calorific value of the stream coming out of the gasification chamber of the gasifier; therefore, it can be calculated based on the total calorific value of that outlet stream. The calculation is complex, and relevant literature can be consulted for more details. Roughly, about 2800 Kg of water is needed per MKcal (this is just an idea for reference only).

To answer briefly, it should be clear first that this pump operates continuously 24 hours a day! The pump outlet is equipped with a self-circulation pipeline, which serves two purposes: 1. It is used to calibrate the pump flow rate ； 2. Self-circulation pipeline during slag discharge. In a fluidized bed, slag is generally removed every about 30 minutes; it can be simply assumed that this water circulates once every half hour. The specific amount depends on the volume of the slag tank, and this amount should be easy to determine – there is no fixed value. Some experts suggest that it should be 1.5 times the volume of the slag tank, which seems reasonable. For your reference only; please feel free to point out any mistakes so that we can learn from each other and improve. This post was last edited by GSP on 2008-3-13 16:47]

Thank you all! For large slag lock tanks, the water inside circulates once every half hour; the pump flow rate should be 1.5 times the volume of the slag tank. It is reasonable for the water to circulate 1–2 times per slag discharge cycle. For smaller slag lock tanks, the number of water circulation cycles can be increased appropriately to enhance the mixing of slag and water, without causing issues with the equipment or energy consumption.

1. Based on the principle of energy balance, the theoretical amount of water required for the cycle can be calculated (what is said on the first floor is correct); multiplying the theoretical amount by 1.1–1.2 gives the actual amount of water needed. 2. It’s not the case that the greater the amount of cooling water, the better; the water volume should be adjusted according to the required temperature to ensure the proper operation of subsequent stages. This post was last edited by Langtaosha on 2008-10-9 at 17:53.]