Regarding the fuel gas balance for the entire plant
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May I ask: How is the fuel gas balance across the entire plant generally managed? For example, what to do if there is an excess of fuel gas – should it be released? What to do if there is less fuel gas? What if the main supplier of fuel gas shuts down due to catalyst or coking issues? What will happen then with the gasification and liquefaction processes? We can discuss the equilibrium of steam and the equilibrium of hydrogen at the same time. Thank you all!
Regarding the fuel gas balance issue, under normal operation of various facilities, the amount of gas produced and the amount of gas consumed are roughly equal. The sum of the gas production amounts from each unit represents the amount of gas supplied as raw material, while the sum of the gas consumption amounts for each unit represents the amount used. The difference between these two values is the remaining amount of gas. If there is excess gas that can be reused, it may be recycled and sent to thermoelectric power plants for use, or else it will be burned in flares ； If there is a shortage, it is possible to reduce the output of the relevant equipment or suspend production, or supplement it with vaporized or liquefied gas.
Operating Condition, Device Name, Quantity, Unit, Subtotal, Balance, Remarks. Dry gas production volume: Two coking units – 10 t/h each, total 18 t/h; balance – 0.9 t/h; large circulation ratio. Three hydrogenation units – 3.5 t/h each; atmospheric and vacuum distillation unit – 0.5 t/h; catalytic unit – 4 t/h. Dry gas consumption: Two coking units – 4.9 t/h each, total 18.9 t/h; three hydrogenation units – 3.5 t/h each; hydrogen production unit – 7.5 t/h; make-up gas – 0.3 t/h; sulfur recovery unit – 0.5 t/h; atmospheric and vacuum distillation unit – 2.2 t/h. Dry gas production volume: Two coking units – 12 t/h each, total 20 t/h; balance – 1.1 t/h; small circulation ratio. Three hydrogenation units – 3.5 t/h each; atmospheric and vacuum distillation unit – 0.5 t/h; catalytic unit – 4 t/h. Dry gas consumption: Two coking units – 4.9 t/h each, total 18.9 t/h; three hydrogenation units – 3.5 t/h each; hydrogen production unit – 7.5 t/h; make-up gas – 0.3 t/h; atmospheric and vacuum distillation unit – 2.2 t/h; sulfur recovery unit – 0.5 t/h
The balance between gas production and gas consumption is relative, while imbalance is absolute. Our method is to use a gas flow rate higher than the amount of gas produced, compensating for the shortfall by vaporizing liquefied gas. It’s certainly not the liquefied gas produced by a catalytic unit, but rather the component that remains after propylene has been separated.
Isn’t there a gas holder? Normally, the gas production volume is balanced with the gas consumption volume, and gas holders are not used much for balancing.
Our plant has two coking units, three hydrogenation units, one reforming unit, two catalytic units, two atmospheric and vacuum distillation units, as well as systems for dry gas recovery and sulfur recovery. Generally, priority is given to meeting the fuel needs of the two dry gas hydrogen production units; after that, the needs of the coking units are met, followed by those of the reforming and hydrogenation units. Any remaining fuel is allocated to the two atmospheric and vacuum distillation units. If there is an excess of fuel, it is stored in gas tanks. In case of emergencies, each unit operates in self-protection mode. To date, liquefied gas from gas separation has not been used; basically, each heating furnace is equipped with fuel oil, allowing for operation using oil instead of gas
It’s unfortunate that you placed us at the very end of the gas system; reprocessing is a process that consumes a lot of energy! Hydrogen production at our plant has been shut down for a long time, so reforming has become the main source of energy consumption. The problem is that the scheduling system often sends large amounts of hydrogen-rich substances with low calorific value into the pipeline network, which is really annoying!
The fuel gas balance is indeed a major issue. Our company has to burn around 80,000 tons of liquefied gas each year due to an imbalance in the fuel gas supply. Next, we will look for alternative resources.
I work in oil refining design; although I’m not responsible for designing the overall balance of elements such as steam, fuel gas, and fuel oil across the entire plant, understanding these issues is very helpful for us as it enhances our knowledge of oil refining. Although these balances are certainly taken into account during the design phase, there are inevitably differences between the design and actual production; hence, as someone else mentioned above, imbalance is absolute. Therefore, there must be adjustment measures in the design. Let me share my understanding: For fuel gas, during production it is necessary to control the pressure in the entire plant’s fuel gas network; when the pressure reaches the set value, any excess fuel gas is released to the flare system where it is burned, or it is used to generate steam in the boilers. Of course, it depends on the specific circumstances. If a major fuel gas consumer in the plant, such as a reformer, has to shut down urgently, it would be a waste to send the fuel gas to the flare for an extended period of time; in such cases, it is necessary to consider using it to generate steam. If it’s for a short period of time, there’s no big problem going to the torch. When the pressure drops to the set value, liquefied gas may need to be vaporized for replenishment. Similarly, when a major supplier of fuel gas, such as a catalytic unit, shuts down, it has a significant impact on the overall balance of the plant; in such cases, other units must implement supplementary measures if they are to continue operating. Similarly, I think the steam balance works on the same principle. When the steam volume increases or decreases, corresponding adjustment measures are also required. For large companies, achieving this balance may be easier; for smaller companies, balancing steam and fuel gas is definitely a major challenge.
For a refinery, the overall fuel gas balance of the entire plant is of critical importance. Generally, refineries need to install fuel gas recovery facilities, namely gas tanks. The venting facility is the flare. Pressure replenishment points: 1. Natural gas; 2. LPG tank area. 3. Gas holder: Under normal conditions, the gas holder first stores a certain amount of fuel gas. Some refineries have natural gas available to be used as pressure compensation points for the pipeline network. In some cases, there is no other option but to use C4 or similar substances from the spherical tank area and then supplement the pipeline network after vaporization; the downside is that these substances tend to liquefy easily. Under normal circumstances, supply and demand are in balance. When the device is unbalanced, if the pressure in the pipeline network is high, steam is vented; if the pressure is low, pressure is restored using various pressure compensation points.
When there is a shortage of fuel gas, how do people obtain liquefied gas to replenish it? What does a carburetor look like? Could you explain in detail? QQ: 598819789 Thank you! !