Hydrogenation of gasoline and diesel

Catalytic cracking, coking and other secondary processing devices to get the product, containing a considerable amount of sulphur, nitrogen, oxygen and olefin substances, these magazines in the oil storage process is extremely unstable, gum increases quickly, the colour deepens sharply, seriously affect the storage stability and combustion performance of the oil. Therefore, the secondary processing of industrial oil, must be hydrogenated and refined to remove sulphur, nitrogen, oxygen compounds and unstable substances (such as olefins), to obtain the stability and quality of the better quality products. In the case of straight-run diesel, due to the increased sulphur content in crude oil and increasingly stringent environmental regulations, the city also requires hydrogenation and refining for the product to leave the factory. The market demand for diesel fuel quality is also increasing and it can no longer be shipped directly as a product, but also needs to undergo hydrogenation and refining.

The sulphides contained in diesel oil cause bad combustion performance, increased cylinder carbon, increased mechanical wear, corrosion of equipment and pollution of the atmosphere, and when present at the same time as diolefins, gums are also generated. Mercaptan is an oxidation initiator, generating sulfonic acid and metal corrosion of storage tanks, mercaptan can also directly react with metal to generate sulfites, further promote the oxidation of oil deterioration. Nitrides in diesel fuel, such as dimethylpyridine and alkylamines and other alkaline nitrides, can deteriorate the colour and stability of the oil, and when coexisting with thiols, can promote the oxidation of sulphuric acid and the decomposition of acid peroxides, thus deteriorating the colour and stability of the oil. The oxidation-sulphonic acid of thiols condenses with pyrrole to form a precipitate.

Coked gasoline, diesel or straight-run diesel from an atmospheric pressure reduction unit are mixed and then filtered through a feedstock filter to remove particles larger than 25um from the feedstock before entering the feedstock buffer tank. The raw oil from the feedstock buffer tank is pressurised by the hydrogenation feed pump and, after heat exchange with the refined diesel fuel, is mixed with the mixed hydrogen as a blend feed under flow control. To prevent and reduce scaling in the subsequent pipelines and equipment, a scale inhibitor is injected between the feedstock tank and the feedstock pump inlet pipeline.

The mixed feed is heated to the required temperature in the reaction feed heater and then enters the hydrofinishing reactor, where desulphurisation, denitrogenation, olefin saturation and aromatics saturation are carried out under the action of the catalyst. The reactor inlet temperature is controlled by adjusting the furnace fuel gas volume and the reactor is equipped with two catalyst beds with an emergency hydrogen injection facility between the beds.

The reaction effluent from the reactor is heated by a feed heat exchanger and then flashed into a hot high pressure separator. The hot high fraction gas coming out of the top is then cooled by a hot high fraction gas air cooler before entering the cold high pressure separator after the hot high fraction heat exchanger. In order to prevent ammonium salts in the reaction effluent from precipitating out at low temperatures, demineralised water is injected into the pipeline on the upstream side of the hot high fraction gas air cooler by means of a water injection pump, and the cooled hot high fraction gas is separated from oil, gas and water in the cold high pressure separator. The circulating hydrogen coming from the top of the cold high-pressure separator is divided by the liquid separation tank at the entrance of the circulating hydrogen desulphurisation tower and then enters the bottom of the circulating hydrogen desulphurisation tower. The circulating hydrogen after desulphurisation comes out from the top of the circulating hydrogen desulphurisation tower, is divided into two paths, one as the emergency path and the other as the emergency path. The hydrogen is then split into two paths, one as emergency cooled hydrogen to the reactor to control the temperature rise of the reactor bed and the other to mix with the new hydrogen from the outlet of the new hydrogen compressor to become mixed hydrogen.