GB2106130A

GB2106130A - Gasification

Info

Publication number: GB2106130A
Application number: GB08225133A
Authority: GB
Inventors: Henry Thomas Wilson
Original assignee: Foster Wheeler (London) Ltd
Current assignee: Foster Wheeler (London) Ltd
Priority date: 1981-09-04
Filing date: 1982-09-03
Publication date: 1983-04-07
Also published as: GB2106130B

Abstract

This invention relates to a gasification process in which a particulate feedstock is fed to a cyclonic reactor (10) in a stream of reaction gas through an inlet (8). The reactor (10) allows the mixture to fully react while reducing the entrainment of particles to the product gas discharged through pipe (14) upwardly substantially along the cyclonic axis of the reactor (10). The product gas is further filtered in an ash cylone (16), and the heat utilized in a waste heat boiler (26). The solid end liquid residues from the reaction are collected and discharged at the base of the reactor (10). <IMAGE>

Description

SPECIFICATION Gasification process The invention relates to a gasification process and apparatus suitable particularly for coal or biomass. Such processes can produce a raw product gas suitable for conversion to, for example, Methanol.

The present invention utilises a cyclonic reactor in which a synthesis gas is produced.

We have found that the cyclone design ensures sufficient residence time to ensure good reaction and minimise carry over of particles in the gas discharged. A process according to the invention comprises passing a particulate feedstock and reaction gas to a cyclonic reactor; retaining the mixture of feedstock and reaction gas in the reactor while the feedstock and gas react to produce a raw product gas, and to separate entrained material therefrom; withdrawing the raw product gas; and collecting the discharging solid and liquid residues.

The gas produced may be discharged via a cyclone filter, from which ash may be recycled to the gasifier. Slag produced in the reactor can be removed from the base via a water quench and lock hopper.

Gasification apparatus according to the invention comprises a cyclonic reactor; means for delivering thereto a particulate feedstock and reaction gas; a collection and discharge device for solid and liquid products of the reaction in the reactor; and a conduit for withdrawing product gas from the reactor.

The reactor is normally oriented with its cyclonic axis vertical, and the feedstock and reaction gas delivered at an inlet to an upper part of and reaction gas delivered at an inlet to an upper part of reactor. The swirling mixture is forced downwards by the inlet and reaction pressure, and product gas discharged upwardly through a conduit substantially on the cyclonic axis of the reactor.

The reaction gas normally comprises at least one of steam and oxygen.

In preferred embodiments of the invention the particulate feedstock is mixed with reaction gas; e.g. a mixture of steam and oxygen just prior to entering the reactor. The particulate feedstock is carried to the reactor by being entrained in a stream of gas and the reaction gas, normally steam, may also be used as the transport medium for the feed stock as may recycled product gas. The gasification in the reactor will produce the gas at a high temperature and this heat may be utilised in a waste heat boiler in the discharge line.

The invention will now be described by way of example and with reference to the accompanying schematic drawing which iliustrates a preferred gasification process according thereto, and in which the hollow arrowheads indicate the flow path of gases, ana the solid arrowheads the flow path of solid (or liquid) matter.

In the process illustrated, finely divided feedstock material is delivered via a reception hopper 2 to an inlet transport line 4 to which steam and/or recycled product gas is fed at 6 to provide the transport medium. Further steam and oxygen are added at the inlet 8 to an entrained cyclonic reactor 10 via line 1 2.

In the cyclonic reactor 10 the entrained particulate feedstock will undergo an explosive pyrolysis/gasification, raw product or synthesis gas being discharged through pipe 14.

The reactor design can ensure sufficient residence time to minimize entrainment of particles in the discharged product gas, but any such entrained particles may be separated in a cyclone filter 1 6 and recycled to the reactor 10 as shown. This enhances efficiency by higher carbon utilisation. The heat generated in the reactor should be sufficient to cause slagging of inorganic particles which form a bath 1 8 at the base of the reactor 10 and are discharged via a water quench 20 and a lock hopper 22. Recycled product gas can be injected into the discharge pipe 14 at 24 to quench the generated gas.

The gas discharged through pipe 14 will be at an elevated temperature, and the available heat is utilised in a waste heat boiler 26 downstream of the cyclone filter 16. A typical operational temperature is around 2000"C (depending on the feedstock used) and thus, steam may also be generated in the shell 28 of the reactor. Water is delivered at 30 and circulated around the reactor before being discharged as steam at 32. The steam produced may be used as the transport medium or for the additionai steam supply (see above).

Any suitable water circulation system may be employed in the reactor shell compatible with the system pressures contemplated (up to 30 bars) and temperatures.

The use of an entrained cyclonic reactor 10 affords the principal advantage of providing a single route for the particulate feedstock which may be selected to give a high residence time under powerful gasifying conditions, without a long tubular arrangement being necessary as was the case with known gasification systems. Further, the cyclonic arrangement permits a certain variety of particle sizes, larger particles being retained in the reactor as a function of inertial forces. However, particle size will be critical to the performance of the system and 1 to 3 mm particles are preferred. The system is through adaptable to a wide variety of feedstocks and the operating parameters will of course vary according thereto.

1. A gasification process comprising passing a particulate feedstock and reaction gas to a cyclonic reactor; retaining the mixture of

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Gasification process The invention relates to a gasification process and apparatus suitable particularly for coal or biomass. Such processes can produce a raw product gas suitable for conversion to, for example, Methanol. The present invention utilises a cyclonic reactor in which a synthesis gas is produced. We have found that the cyclone design ensures sufficient residence time to ensure good reaction and minimise carry over of particles in the gas discharged. A process according to the invention comprises passing a particulate feedstock and reaction gas to a cyclonic reactor; retaining the mixture of feedstock and reaction gas in the reactor while the feedstock and gas react to produce a raw product gas, and to separate entrained material therefrom; withdrawing the raw product gas; and collecting the discharging solid and liquid residues. The gas produced may be discharged via a cyclone filter, from which ash may be recycled to the gasifier. Slag produced in the reactor can be removed from the base via a water quench and lock hopper. Gasification apparatus according to the invention comprises a cyclonic reactor; means for delivering thereto a particulate feedstock and reaction gas; a collection and discharge device for solid and liquid products of the reaction in the reactor; and a conduit for withdrawing product gas from the reactor. The reactor is normally oriented with its cyclonic axis vertical, and the feedstock and reaction gas delivered at an inlet to an upper part of and reaction gas delivered at an inlet to an upper part of reactor. The swirling mixture is forced downwards by the inlet and reaction pressure, and product gas discharged upwardly through a conduit substantially on the cyclonic axis of the reactor. The reaction gas normally comprises at least one of steam and oxygen. In preferred embodiments of the invention the particulate feedstock is mixed with reaction gas; e.g. a mixture of steam and oxygen just prior to entering the reactor. The particulate feedstock is carried to the reactor by being entrained in a stream of gas and the reaction gas, normally steam, may also be used as the transport medium for the feed stock as may recycled product gas. The gasification in the reactor will produce the gas at a high temperature and this heat may be utilised in a waste heat boiler in the discharge line. The invention will now be described by way of example and with reference to the accompanying schematic drawing which iliustrates a preferred gasification process according thereto, and in which the hollow arrowheads indicate the flow path of gases, ana the solid arrowheads the flow path of solid (or liquid) matter. In the process illustrated, finely divided feedstock material is delivered via a reception hopper 2 to an inlet transport line 4 to which steam and/or recycled product gas is fed at 6 to provide the transport medium. Further steam and oxygen are added at the inlet 8 to an entrained cyclonic reactor 10 via line 1 2. In the cyclonic reactor 10 the entrained particulate feedstock will undergo an explosive pyrolysis/gasification, raw product or synthesis gas being discharged through pipe 14. The reactor design can ensure sufficient residence time to minimize entrainment of particles in the discharged product gas, but any such entrained particles may be separated in a cyclone filter 1 6 and recycled to the reactor 10 as shown. This enhances efficiency by higher carbon utilisation. The heat generated in the reactor should be sufficient to cause slagging of inorganic particles which form a bath 1 8 at the base of the reactor 10 and are discharged via a water quench 20 and a lock hopper 22. Recycled product gas can be injected into the discharge pipe 14 at 24 to quench the generated gas. The gas discharged through pipe 14 will be at an elevated temperature, and the available heat is utilised in a waste heat boiler 26 downstream of the cyclone filter 16. A typical operational temperature is around 2000"C (depending on the feedstock used) and thus, steam may also be generated in the shell 28 of the reactor. Water is delivered at 30 and circulated around the reactor before being discharged as steam at 32. The steam produced may be used as the transport medium or for the additionai steam supply (see above). Any suitable water circulation system may be employed in the reactor shell compatible with the system pressures contemplated (up to 30 bars) and temperatures. The use of an entrained cyclonic reactor 10 affords the principal advantage of providing a single route for the particulate feedstock which may be selected to give a high residence time under powerful gasifying conditions, without a long tubular arrangement being necessary as was the case with known gasification systems. Further, the cyclonic arrangement permits a certain variety of particle sizes, larger particles being retained in the reactor as a function of inertial forces. However, particle size will be critical to the performance of the system and 1 to 3 mm particles are preferred. The system is through adaptable to a wide variety of feedstocks and the operating parameters will of course vary according thereto. CLAIMS

1. A gasification process comprising passing a particulate feedstock and reaction gas to a cyclonic reactor; retaining the mixture of feedstock and reaction gas in the reactor while the feedstock and gas react to produce a raw product gas, and to separate entrained material therefrom; withdrawing the raw product gas; and collecting and discharging solid and liquid residues.

2. A process according to Claim 1 wherein the reactor is arranged with its cyclonic axis substantially vertical; and wherein the mixture of feedstock and reaction gas is delivered to an upper part of the reactor, and the product gas withdrawn from a lower part thereof.

3. A process according to Claim 2 wherein the product gas is withdrawn upwardly through a pipe substantially on the cyclonic axis of the reactor.

4. A process according to any preceding claim wherein the particulate feedstock is carried to the reactor by being entrained in a stream of gas.

5. A process according to Claim 4 wherein said stream of gas comprises at least one of reaction gas and raw product gas.

6. A process according to Claim 4 or Claim 5 wherein reaction gas is fed to the stream of gas and entrained feedstock just prior to entry into the reactor.

7. A process according to any preceding claim wherein the reaction gas comprises at least one of steam and oxygen.

8. A process according to any preceding claim wherein the product gas is discharged through a cyclone filter, the residue therefrom being returned to the reactor.

9. A process according to any preceding claim wherein the product gas is discharged through a waste duct boiler.

1 0. A gasification process substantially as described herein with reference to the accompanying drawing.