The quality control of light diesel

Quality control of light diesel fuel mainly refers to the freezing point and, to a lesser extent, the flash point. The control of the freezing point is to ensure that the light diesel oil has good flowability under the requirements of use and different climatic conditions. And control the flash point is to ensure the safety of light diesel oil in the process of transportation, storage and use. The lower the flash point, the easier it is to flash fire, that is, prone to explosions and safety accidents.

1. Control of the freezing point of light diesel oil
The factors that affect the freezing point of diesel fuel are the nature of the feed and flow, reaction depth, fractionation tower top temperature and pressure, etc., a mid-cycle reflux, rich absorption oil flow and return tower temperature, etc., fractionation tower with heavy diesel fuel extraction, heavy diesel fuel extraction ratio will also affect the freezing point of diesel fuel.
Reaction processing volume increases, light diesel oil freezing point increases; reaction depth increases, diesel oil freezing point decreases, fractionation tower top temperature increases, light diesel oil freezing point increases; fractionation tower top pressure increases, light diesel oil freezing point decreases; a middle section of circulating oil return tower temperature decreases or return tower volume increases, light diesel oil freezing point decreases; stable post operation fluctuations, so that a middle section of circulating oil volume and return tower temperature fluctuations; rich absorption oil return tower volume increases or return tower The freezing point of light diesel oil decreases when the temperature of return tower is lowered; the freezing point of light diesel oil increases when the pumping temperature of light diesel oil increases.
In normal production, the freezing point of light diesel oil can be controlled by adjusting the pumping temperature of light diesel oil. When the diesel oil freezing point is high, lower the temperature of the middle return tower, increase the middle return flow rate and increase the amount of heavy diesel oil pumped out. When the middle section of the return tower temperature adjustment can not meet the requirements, can reduce the middle section of the return flow, control the middle temperature of the fractionation tower. If the heat extraction from the middle return is restricted, the middle return standby cooler can be activated in time or the heat extraction distribution of the fractionator can be changed.
The freezing point of heavy diesel fuel is often regulated by changing its extraction volume. When the pumping volume of heavy diesel oil is reduced, the return flow rate in the lower end increases, the heavy diesel oil becomes lighter and the freezing point is reduced.

2. Control of flash point of light diesel fuel
The low flash point of diesel fuel is because the diesel fuel contains a small amount of gasoline components, which not only affects the quality of diesel fuel, but also reduces the yield of gasoline. The main factors affecting the flash point of diesel fuel are the amount of vapour extraction, the level of the vapour extraction tower and the outflow of light diesel fuel, and the temperature of light diesel fuel extraction.
Steam tower steam flow increases, the flash point of light diesel fuel increases; steam tower level increases, the flash point of light diesel fuel decreases; light diesel fuel distillation volume is large, the flash point of light diesel fuel decreases; light diesel fuel extraction temperature decreases, the fractionation tower top temperature decreases, the flash point of light diesel fuel decreases.
During normal production, the flash point of light diesel fuel is controlled by changing the steam flow rate of the vapour extraction tower to qualify. When the flash point of light diesel oil is low, can be appropriate to increase the amount of steam, but should not be too large, too violent, to prevent the fractionation tower operation fluctuations. General steam for the amount of diesel fuel extraction of 2% to 3%, but also to reduce the level of steam tower, increase the vaporization space or residence time. If necessary, adjust the light diesel extraction temperature and fractionation tower top temperature.
Heavy oil catalytic cracking of diesel oil cetane value is low, sulphur, nitrogen and gum content is high, the oil colour is dark, poor stability, and easy to oxidation and precipitation, generally to carry out hydrogenation refining of diesel oil to improve the quality, when the heavy oil catalytic cracking of diesel oil flash point can be appropriately relaxed.