PROCESS TO PREPARE A GAS OIL PRODUCT

Abstract

The invention is directed to a process to prepare a gas oil product from a carbonaceous particles of a biomass source comprising the following steps: (a) pyrolysis of the carbonaceous particles to a gaseous mixture of hydrocarbons in the absence of oxygen, (b) quenching the gaseous mixture of hydrocarbons by contacting with a liquid quench mixture of hydrocarbons having a lower temperature than the gaseous mixture thereby obtaining a rich liquid quench mixture and a quenched gas, and (c) isolating from the quenched gas a gas oil product by means of vacuum distillation, wherein the liquid gas oil is partly supplied to the top of the vacuum distillation column as a distillation reflux, partly used as part of the liquid quench mixture in (b) and partly discharged as the gas oil product.

Claims

1. A process to prepare a gas oil product from a carbonaceous particles of a biomass source comprising the following steps: (a) pyrolysis of the carbonaceous particles to a gaseous mixture of hydrocarbons in the absence of oxygen; (b) quenching the gaseous mixture of hydrocarbons by contacting with a liquid quench mixture of hydrocarbons having a lower temperature than the gaseous mixture thereby obtaining a rich liquid quench mixture and a quenched gas; and (c) isolating from the quenched gas a gas oil product by means of vacuum distillation; wherein the liquid gas oil is partly supplied to the top of the vacuum distillation column as a distillation reflux, partly used as part of the liquid quench mixture in (b) and partly discharged as the gas oil product.

2. The process according to claim 1, wherein the liquid quench mixture comprises the gas oil product and hydrocarbons having a higher boiling point than the gas oil product.

3. The process according to claim 2, wherein part of the rich liquid quench liquid is discharged as a tar fraction and part of the rich liquid quench fluid is reused in step (b) in admixture with part of the gas oil product.

4. The process according to claim 3, wherein the temperature of the liquid quench mixture is at least 150° C. lower than the temperature of the rich liquid quench mixture.

5. The process according to claim 1, wherein the vacuum distillation is performed at a pressure of between 0.7 and 145 kPa.

6. The process according to claim 1, wherein step (b) and (c) are performed in the same distillation vessel; and wherein step (b) is performed at a lower end of the distillation vessel.

7. The process according to claim 1, wherein step (b) is performed in a packed bed or distillation trays including but not limited to bubble cap trays, sieve deck trays, dual flow trays, valve trays, or baffle trays.

8. The process according to claim 1, wherein in step (c) an overhead distillation fraction is partly condensed to obtain the liquid gas oil and a mixture of gaseous hydrocarbons boiling below the gas oil product; and wherein the liquid gas oil product is separated from the mixture of gaseous hydrocarbons by means of a gas-liquid separation.

9. The process according to claim 1, wherein the pyrolysis in step (a) is performed at a temperature of between 500 and 1300 C, at a pressure of between 0.7 kPa and 35 kPa and at a particle residence time of between 20 and 120 seconds.

10. The process according to claim 9, wherein the pyrolysis is performed in a bubbling fluidised bed of the carbonaceous particles of a biomass source.

11. The process according to claim 10, wherein from the bubbling fluidised bed a char product is discharged.

12. The process according to claim 1, wherein the carbonaceous particles of a biomass source are wood particles or fibrous biomass.

13. The process according to claim 1, wherein more than 90 wt % of the particles have a smallest dimension of above 0.3 and a largest dimension of smaller than 2.5 cm.

14. The process according to claim 13, wherein more than 90 wt % of the particles have a smallest dimension of above 0.5 cm and a largest dimension of smaller than 1.3 cm.

15. The process according to claim 1, wherein in step (c) a naphtha product is isolated.

Description

[0035] FIG. 1 shows a process scheme for performing the process according to this invention. Via flow (1) carbonaceous particles of a biomass source are provided to a lock hopper vessel (2). To this vessel (2) nitrogen is supplied via flow (3) to replace any air present in the particles. The carbonaceous particles are supplied to a fluidised bed reactor (5) via conduit (4). The fluidised bed (5) has a lower part (6) and an upper part (7) having a larger diameter than the lower part. In the lower part (6) a bubbling fluidised bed of particles is present. The wider diameter of the upper part (7) will avoid entrainment of particles with the gaseous mixture which is discharged from the bubbling bed of particles. A fluidising gas is supplied to the fluidised bed via a gas distribution pipe grid (9). The fluidising gas is heated in a furnace (10) using a fuel gas (11). The fuel gas (11) is preferably isolated from the gaseous overhead stream of the vacuum distillation column (20).

[0036] Char particles are discharged from the fluidised bed reactor (5) at a char particles outlet (14). The hot char particles are cooled in heat exchanger (15) against evaporating boiler feed water generating steam. Any entrained gasses are separated from the cooled char particles in two cyclones (16) wherein the char particles are collected in char collection vessel (17) and discharged as a separate char product (18). The separated gasses are combined with the gaseous overhead stream of the vacuum distillation column (20) via flow (19).

[0037] The gaseous mixture is discharged from the fluidised bed reactor (5) via two or more cyclones in series (5a) as present in the upper dome of the reactor vessel of the fluidised bed reactor (5). The separated particles are returned to the fluidised bed in the lower part (6). The gaseous mixture (21) depleted of any entrained particles is supplied to the lower end of a vacuum distillation column (20) which will be described in more detail in FIG. 2.

[0038] FIG. 2 shows the vacuum distillation column (20) of FIG. 1. To the lower end of the vacuum distillation column (20) the gaseous mixture (21) is supplied. The gaseous mixture will flow upwards and be subjected to a quenching step. The quenching step is performed in a packed bed (22) through which the gaseous mixture flows upwardly and a liquid quench mixture (26) flows counter-currently and thus downwardly. The resulting rich quenching liquid (26a) is cooled in heat exchanger (23) against evaporating boiler feed water and pumped by pump (25) to be partly used as the liquid quench mixture (26) and partly be discharged via flow (27) as a tar fraction to a tar storage vessel (28). In tar storage vessel the tar is heated to avoid solidification by means of indirect steam heater (29). The liquid tar may be discharged from the process via flow (30).

[0039] From the upper end of the vacuum distillation column (20) an overhead stream (31) is discharged and cooled in heat exchanger (32) wherein the gas oil fraction condenses. This liquid fraction is separated from the gaseous hydrocarbons boiling below the gas oil range in a gas-liquid separator (33). The overhead gas (34) as obtained and comprising hydrogen, fuel gas compounds and a naphtha fraction and a liquid gas oil fraction is compressed by compressor (35) and sent to a separation train (not shown). Part of the liquid gas oil fraction (36) is returned as a reflux stream to the vacuum distillation column (20) and part (37) of the liquid gas oil fraction is obtained as the gas oil product and part (39) is combined with part (27a) of the rich quenching liquid (26a) to be used as part of the liquid quench mixture (26). The valves shown in FIGS. 1 and 2 illustrate the many valves which may be present in such a process. The valves may be used to control the relative volumes of flows through the different conduits