A DIESEL PRODUCTION METHOD AND SYSTEM Technical Field

The present invention relates to diesel production methods and systems. Prior Art

Diesel fuels are subject to desulphurization process in refineries for decreasing sulphur dioxide emissions occurred as a result of the combustion and for increasing combustion quality. In diesel fuels, desulphurization process is a catalytic process. In said process, the intermediate product in diesel range reacts with hydrogen under high temperature and pressure, and organic sulphur and nitrogen compounds in the intermediate product are reduced under 10 ppm.

In the state of the art, desulphurization and denitrification reactions are performed in a fixed bed reactor under the 30 - 150 atmosphere pressure in the temperature range of 300°C - 400°C. The catalysts used in reactors are generally alumina (Al ₂ 0 ₃ ) based carriers, and cobalt molybdenum (Co - Mo) or nickel molybdenum (Ni - Mo) metals are distributed on the carrier materials. Besides said desulphurization and denitrification reactions, preferably a dewax reaction is performed by nickel-tungsten (Ni - W) metals which are distributed on the carriers based on silicon alumina in a second reactor. By said reaction, dewax in the diesel fuel is performed, thus low temperature performance of the fuel is increased.

In the desulphurization - denitrification and dewax process, after the intermediate product, which is to be distilled, is pressurized with the pump, the intermediate product is put in furnace by combining with hydrogen. The mixture heated in the furnace is delivered to the first reactor, and desulphurization and denitrification reactions are performed herein. The first reactor outlet is delivered to the second reactor in cold times (i.e. in winter months) and dewax process is performed; therefore low temperature performance of the diesel is improved. In hot conditions (i.e. in summer months), this reactor can be deactivated. The mixture received from the reactor is firstly cooled, and then products are obtained by providing liquid/gas separation. In present systems, during the denitrification and dewax of the diesel product , undesired partial conversion of diesel product to less valuable products such as liquefied petroleum gas (LPG) and naphta occurs. Said situation decreases economic income of the unit.

95% distillation point of diesel fuel produced in the denitrification unit should be maximum 360 °C according to the standards (TS 1232 EN ISO 3405/ASTM D86). By considering product usage, production process is performed such that this point is maximum 355 °C.

In denitrification units of the state of the art, while the denitrification process is performed, 95% distillation point of the mixture delivered to the unit is decreased about 10 °C. As a result, in order to maintain 95% distillation point of the produced diesel, a mixture whose 95% distillation point is maximum 365 °C is able to be delivered to the unit. The products (intermediate products whose 95% distillation point is higher than 365 °C) which are heavier than the mixture delivered to the unit cannot be used in the present units and damage the 95% distillation point property of the diesel. Therefore, the products which cannot be processed in the unit are sent to the conversion units such as hydrocracker and catalytic cracking depending on the refinery configuration; and in the event that said units are operated in full capacity, they are sent to the less valuable product pool.

In hydrocracker units, raw hydrocarbon is cracked with hydrogen under high temperature and pressure, and converted into valuable fuels such as diesel, gasoline, jet fuel, etc. Said conversion process is performed via catalyst used with hydrogen. Thanks to the type of used catalyst and process values, such as temperature and pressure, different products can be produced in the hydrocracker unit. Since the hydrocracker units change raw hydrocarbon compounds into valuable fuels such as diesel, gasoline, jet fuel, etc., high income is obtained by operating said units in high capacity (generally in full capacity) in refineries. However, even if hydrocracker units located in refineries are operated in full capacity, they cannot sometimes meet diesel production requirement. The patent document no CN1 171430A of the state of the art discloses a hydrocracker unit. In said hydrocracker unit, jet fuel and gasoline are produced from heavy oil at medium pressure. However, since production capacity of the unit is limited, this hydrocracker unit cannot meet production requirements of the refineries.

Brief Description of the Invention

Diesel production system of the present invention comprises a furnace in which hydrocarbon mixture heavier than diesel is fed and said mixture is heated; at least one desulphurization reactor in which mixture heated in the furnace is fed and which comprises at least one desulphurization catalyst for desulphurizing heated mixture; at least one modified dewax reactor which is connected to the output of the desulphurization reactor, in which clean mixture, whose sulphur content is cleaned, is fed, whose catalyst is replaced with at least one hydrocracker catalyst, which decreases the distillation point of the clean mixture to a desired value by cracking the hydrocarbons inside clean mixture, and which gives diesel from its output.

The diesel production method used in said diesel production system comprises the steps of pressurizing heavy hydrocarbon mixture; heating the mixture and hydrogen in said furnace; receiving heated mixture in the desulphurization reactor; desulphurizing heated mixture; and hydrocracking clean mixture whose sulphur content is cleaned. 95% distillation point is decreased in the diesel produced by the method. Objectives of the Invention

An aim of the invention is to develop a diesel production method and system.

The other aim of the invention is to develop a diesel production method and system in which a desulphurization unit is used. Another aim of the invention is to develop a diesel production method and system in which distillation point is reduced to desired value.

A further aim of the invention is to develop a diesel production method and system in which 95% distillation point is decreased.

Yet a further aim of the invention is to develop a diesel production method and system in which undesired conversion of the diesel to less valuable products is kept under control. Still a further aim of the invention is to develop a diesel production method and system by which economic profit of the unit is increased with respect to the system of the state of the art.

Description of the Drawings

An exemplary embodiment of the diesel production method and system of the invention is shown in attached drawings wherein;

Figure 1 is flow chart of the method of the invention.

Figure 2 is a schematic view of the input-output currents of a diesel production system in which method of the invention is applied.

The parts in figures are individually enumerated and the corresponding terms of reference numbers are given as follows:

Diesel production system (A)

Furnace (F)

Mixture (1 )

Heated mixture (2)

Diesel (3)

Desulphurization reactor (4)

Modified dewax reactor (5) Hydrocracker catalyst (6) Desulphurization catalyst (7)

Clean mixture (8)

Pressurizing the mixture (101 )

Heating the mixture and hydrogen in the preheating furnace (102)

Receiving heated mixture in the desulphurization reactor (103)

Desulphurizing the mixture (104)

Hydrocracking the mixture (105) Description of the Invention

Diesel desulphurization unit comprises at least one desulphurization reactor wherein desulphurization process is performed and a dewax reactor wherein dewaxing of the product is performed. The present invention discloses a method and a system developed for providing diesel production in diesel desulphurization units.

The diesel production system (A) of the invention, a schematic view of the input-output currents of which is shown in figure 2, comprises a furnace (F) in which hydrocarbon mixture (1 ) heavier than diesel (characteristics such as intensity, boiling range and carbon number are higher than diesel) is fed and said mixture (1 ) is heated; at least one desulphurization reactor (4) in which mixture heated in the furnace (F) is fed, which comprises at least one desulphurization catalyst (7) for desulphurizing heated mixture (2); at least one modified dewax reactor (5) which is connected to the output of the desulphurization reactor (4), in which clean mixture (8), whose sulphur content is cleaned, is fed, whose catalyst is replaced with at least one hydrocracker catalyst (6), which decreases the distillation point of the clean mixture (8) to a desired value by cracking the hydrocarbons inside clean mixture (8), and which gives diesel (3) from its output. In other words, the diesel production system (A) of the present invention is a diesel production unit in which a dewax catalyst in the dewax reactor is replaced with at least one hydrocracker catalyst (6).

The diesel production method, a flow chart of which is shown in figure 1 , comprises following steps; pressurizing heavy hydrocarbon mixture (1 ) (101 );

heating the mixture (1 ) and hydrogen in said furnace (F) (102);

receiving heated mixture (2) in the desulphurization reactor (4) (103); - desulphurizing heated mixture (2) (104)

hydrocracking clean mixture (8), whose sulphur content is cleaned (105).

In the process of pressurizing the mixture (1 ) (101 ), after heavy hydrocarbon mixture (1 ) is pressurized by preferably a pump (not shown), the mixture (1 ) is put in a furnace by combining it with hydrogen gas. In the furnace (F), the process of heating the mixture and hydrogen to a certain temperature value is performed (102). Then, heated mixture (2) is received in the desulphurization reactor (4). Herein, the process of desulphurization (104) of the mixture (1 ) by the reaction of the diesel inside the mixture (1 ) with the desulphurization (hydrodesulphurization) catalyst (8) is performed by using hydrogen gas under high temperature and pressure. As a result of the catalytic processes performed in the desulphurization reactor (4), amounts of sulphur and nitrogen compounds inside the mixture (1 ) are decreased below 10 ppm. Said catalytic processes, are performed by desulphurization catalysts (8), for example in which cobalt molybdenum (Co - Mo) or nickel molybdenum (Ni - Mo) metals are distributed on the alumina (Al ₂ 0 ₃ ) based carrier materials at the temperature around 380 °C and under 65 atmosphere pressure.

Clean mixture (9) obtained at the output of the desulphurization reactor (4) is received in modified dewax reactor (5) which is loaded with hydrocracking catalyst (6) therefrom, and hydrocrackes the hydrocarbons therein (105). The aim of hydrocracking hydrocarbons (105) by hydrocracker catalyst is to convert hydrocarbon compounds having high boiling point to products which have relatively lower boiling points; in other words to decrease distillation point of the diesel. Said process is a catalytic process and is performed in a hydrogen enriched medium in the temperature preferably 390 °C and under 65 atmosphere pressure. The catalyst used as hydrocracker catalyst (6) comprises metals distributed on a carrier. Said catalyst (6) has two functions: cracking and hydrogenate. While the cracking function is ensured by an acidic carrier, the hydrogenation feature is provided by the metals. In a preferred embodiment of the invention, silica-alumina based zeolite carrier, on which at least one of nickel, tungsten and cobalt metals is distributed, is used as hydrocracker catalyst (6). In the diesel production method and system of the present invention, distillation point is decreased by cracking heavy hydrocarbons whose desired (preferably 95%) distillation point is heavier than the diesel. In an exemplary embodiment of the invention, a hydrocarbon mixture whose weight is increased at the rate of approximately 8% is delivered to the diesel production system (A). In said embodiment, the 95% distillation point which should be in compliance with the diesel standards (TS 1232 EN ISO 3405/ASTM D86) is provided at 383 °C in the mixture of desulphurization reactor (4) input and at 355 °C in the mixture of dewax reactor (5) output. Consequently, with the process of the invention a decrease of 28 °C at the 95% distillation point of the diesel (3) is ensured.