RU2323957C2 - Process for thermofor-type cracking of oil residue - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: essence of invention is that oil residue is fed to powdered coke fluidised bed reactor, distinguishing itself by the fact that cracking heat is provided by supplying superheated steam through a tube furnace to the reactor. Superheated steam is produced during combustion of powdered coke discharged from the bottom part of the reactor in the fluidised bed steam generator, limestone or dolomite being charged into the steam generator. Cracking products from the reactor are condensed, and heavy fraction, which contains coke dust, is mixed with oil residue, heated in the tube furnace and supplied to the reactor.

EFFECT: lower capital costs, facilitated operation of the unit.

1 dwg

Description

The invention is intended for use in the refining industry.

For deep oil refining, coking processes are used. The raw materials for them are the remains of vacuum distillation of oil, catalytic cracking and other destructive processes. The most widespread is the process of semi-continuous (delayed) coking. The process of coking or thermal contact cracking (TCC) on pulverized coke is also used [1-3]. This process is continuous and high-performance, but rather complicated, since the heat for cracking is supplied with coke, which is heated in a separate apparatus by partially burning it. The industry uses the processes of Exxon, UOP, VNIINP. But these processes were not widely used due to the high investment in the technological installation and the complexity of its operation. In addition, the sour dusty coke obtained by this method has very limited demand. Therefore, the Exxon Flexicocking combined process, which includes the process of vapor-air gasification of coke with the production of low-calorie gas that requires purification from hydrogen sulfide, has found application, which further complicates the process unit. These shortcomings have led to the limited use of thermal contact cracking processes (coking on pulverized coke).

The closest analogue (prototype) of the claimed invention is the process "Flexicocking" company Exxon, since in it the obtained coke is used to produce synthesis gas.

In all TCC processes of the above companies, including the Flexicoking process, raw materials are cracked in a fluidized-bed (boiling) bed of coke-coolant. Coke from the reactor enters the heater and, after heating, is recycled to the reactor. Due to the heat of the circulating coke-heat carrier, the raw material is subjected to thermal cracking with the formation of cracked products in the vapor state and coke. The vaporous cracking products enter a scrubber, where they are cooled and partially condensed and then returned to the reactor without additional heating. Light fractions are removed from the top of the scrubber. In the Flexicoking process, the obtained coke is gasified by steam conversion of carbon (pulverized coke) in a separate reactor. The resulting synthesis gas is cooled and purified from sulfur compounds. The installation, including TCC, gasification of coke and purification of synthesis gas, is complicated and expensive [1-3].

The present invention eliminates these disadvantages. The essence of the invention lies in the fact that the heat is supplied for cracking reactions by heating the recycle and feeding superheated steam to the reactor, and pulverized coke is fed into the fluidized bed boiler without cooling. This achieves highly efficient energy use of coke and purification of flue gases from sulfur compounds.

Scheme TKK with the proposed heat supply is presented in the drawing. Raw materials (tar, asphaltite, bitumen, heavy resins) are mixed with recycling and fed into the tube furnace 1, where it is heated to 500-520 ° C. Heating to a higher temperature is not recommended due to the risk of coking of the furnace coil. In the same furnace or in a separate superheater, steam is heated to a temperature of 600-630 ° C. Part of the steam is fed into the lower part of the reactor 2 to create a fluidized bed of coke. In this case, the steam-coke mixture should have a temperature of 570-600 ° C, necessary for cracking and coking. Another part of the steam is mixed with the raw material, and a mixture with a temperature of about 580 ° C is fed in several streams into the reactor 2, operating under a pressure of 0.2-0.6 MPa. As a result of contact cracking, an additional layer of coke is deposited on the suspended particles. All other cracked products in the vapor state, together with coke dust, enter the scrubber 3, irrigated with a gas oil fraction. In this case, heavy fractions condense, and pairs of lighter fractions are washed from coke dust. The heavy fraction condensed with trapped coke dust is pumped out by pump 4 from the bottom blank scrubber plate and mixed with fresh raw materials into furnace 1. Dusty coke is discharged from the bottom of the reactor.

The usefulness of the invention lies in the fact that in connection with the supply of heat with steam, the capital costs of the process unit are reduced and its operation is greatly simplified. In addition, an important advantage is the technological compatibility of the coking process according to the proposed method and the process of burning coke in a fluidized-bed power boiler. And this relationship is shown in the drawing.

Pulverized coke is transported without cooling to a fluidized-bed steam generator (boiler) 5. Burning solid fuel in a fluidized (fluidized) bed is a progressive and efficient method of organizing fuel combustion. In addition to coke, limestone or dolomite is supplied to the steam generator 5, and the fluidized bed consists mainly of particles of these materials. The coke combustion process is carried out mainly on these particles at a temperature of 800-900 ° C. At this temperature, limestone is calcined to form calcium oxide CaO and lime Ca (OH) ₂ . As a result of the reactions of these alkaline compounds with SO ₂ , calcium sulfate CaSO _{4 is formed} , and SO ₂ emissions from flue gases can be reduced by 90-95% [4, 5]. In the boiler, high pressure steam is generated for the parameters set for the steam turbine installation (P _o = 12.8 MPa, t = 565 ° C). A small part of the steam is taken out and fed to the furnace 1 for overheating.

Using the proposed method of thermal contact cracking leads to a reduction in capital costs of the installation by 20-30% compared with the installation of VNIINP. Reducing energy costs when using coke in a fluidized-bed boiler is 10-12% with deep cleaning of flue gases from sulfur compounds.

LIST OF LINKS

1. Stepanov A.V., Goryunov B.C. Resource-saving oil refining technology. - K .: Naukova Dumka. 1993 .-- 270 p.

2. Kaminsky E.F., Khavkin V.A. Deep oil refining. M .: Technique. 2001 .-- 384 p.

3. Soskind D.M., Barsukov E.Ya. Thermal contact cracking of heavy oil residues. M .: TsNIITEneftekhim. 1983.

4. Stepanov A.V., Kuhar V.P. Achievements in energy and environmental protection. - K .: Naukova Dumka. 2004 .-- 206 p.

5. Ryabov GA, Shaposhpak D. A. The problem of creating boilers with a circulating fluidized bed for large power units. // Electric stations 2000. No. 9, p.6-12.

Claims (1)

Method for thermocontact cracking (coking) of oil residues by supplying oil residues to a pulverized-coke fluidized bed reactor, characterized in that the heat input for cracking is carried out by supplying superheated steam obtained from the bottom of the pulverized coke from the bottom through a tube furnace to the reactor the reactor in a fluidized bed steam generator, with limestone or dolomite being introduced into the steam generator, the cracked products obtained in the reactor are sent for condensation, while the condensed The fractions containing coke dust are mixed with oil residues, heated in a tube furnace and introduced into the reactor.