Gas heater
A heating system and a process for heating a pressurized feed gas is provided, where the heat for the reaction is provided by resistance heating by means of electrical power.
1. A heating system for heating of a feed gas, said heating system comprising:
a supply of feed gas;
a structured body arranged for heating of said feed gas, said structured body comprising a macroscopic structure of electrically conductive material;
a pressure shell housing said structured body, said pressure shell comprising an inlet for letting in said feed gas and an outlet for letting out heated gas, wherein said inlet is positioned so that said feed gas enters said structured body in a first end of said structured body and said heated gas exits said structured body from a second end of said structured body;
a heat insulation layer between said structured body and said pressure shell;
at least two conductors electrically connected to said structured body and to an electrical power supply placed outside said pressure shell, wherein said electrical power supply is dimensioned to heat at least part of said structured body to a temperature of at least 400° C. by passing an electrical current through said macroscopic structure, wherein said at least two conductors are connected to the structured body at a position on the structured body closer to said first end of said structured body than to said second end of said structured body, and wherein the structured body is constructed to direct an electrical current to run from one conductor substantially to the second end of the structured body and return to a second of said at least two conductors; and,
an outlet for heated gas,
wherein the feed gas has essentially the same chemical composition at the inlet as at the outlet of the pressure shell housing.
2. The heating system according to claim 1 , wherein said electrical power supply is dimensioned to heat at least part of said structured body to a temperature of at least 700° C.
3. The heating system according to claim 1 , wherein the feed gas is selected from the group consisting of N 2 , H 2 , CO 2 , CH 4 , H 2 O, O 2 , and a mixture thereof.
4. The heating system according to claim 1 , wherein said macroscopic structure supports a ceramic coating.
5. The heating system according to claim 1 , wherein the resistivity of the electrically conductive material is between 10 −5 Ω·m and 10 −7 Ω·m.
6. The heating system according to claim 1 , where said at least two conductors are led through the pressure shell in a fitting so that the at least two conductors are electrically insulated from the pressure shell.
7. The heating system according to claim 1 , wherein said structured body has at least one electrically insulating part arranged to direct a current through said structured body in order to ensure that for at least 70% of the length of said structured body, a current density vector of the principal current path has a non-zero component value parallel to the length of said structured body.
8. The heating system according to claim 1 , wherein the material of the macroscopic structure is chosen as a material arranged to generate a heat flux of 500 to 50000 W/m 2 by resistance heating of the material.
9. The heating system according to claim 1 , wherein the structured body within said heating system has a ratio between the area equivalent diameter of a horizontal cross section through the structured body and the height of the structured body in the range from 0.1 to 2.0.
10. A process for heating a feed gas in a heating system, said heating system comprising:
a supply of feed gas;
a structured body arranged for heating of said feed gas, said structured body comprising a macroscopic structure of electrically conductive material;
a pressure shell housing said structured body, said pressure shell comprising an inlet for letting in said feed gas and an outlet for letting out heated gas, wherein said inlet is positioned so that said feed gas enters said structured body in a first end of said structured body and said heated gas exits said structured body from a second end of said structured body;
a heat insulation layer between said structured body and said pressure shell;
at least two conductors electrically connected to said structured body and to an electrical power supply placed outside said pressure shell, wherein said electrical power supply is dimensioned to heat at least part of said structured body to a temperature of at least 400° C. by passing an electrical current through said macroscopic structure, wherein said at least two conductors are connected to the structured body at a position on the structured body closer to said first end of said structured body than to said second end of said structured body, and wherein the structured body is constructed to direct an electrical current to run from one conductor substantially to the second end of the structured body and return to a second of said at least two conductors; and
an outlet for heated gas,
said process comprising the steps of:
pressurizing said feed gas,
supplying said pressurized feed gas to the heating system,
supplying electrical power via electrical conductors connecting an electrical power supply placed outside said pressure shell to said structured body, allowing an electrical current to run through said electrically conductive material, thereby heating at least part of the structured body,
heating the feed gas over the structured body and
outletting a heated gas from the heating system.
11. The process according to claim 10 , wherein at least part of the structured body is heated to a temperature of at least 700° C.
12. The process according to claim 10 , wherein the heated gas from the heating system is substantially pure CO 2 and is provided to an adiabatic post converter together with a synthesis gas; and in said adiabatic post converter, the heated gas reacts with the synthesis gas to thereby provide a second product gas, said second product gas being a CO rich synthesis gas stream.
13. A method for rapidly heating a feedstock in a heating system, from a first steady-state heating condition (A) to a second steady-state heating condition (B) or vice-versa;
said heating system comprising:
a supply of feed gas;
a structured body arranged for heating of said feed gas, said structured body comprising a macroscopic structure of electrically conductive material;
a pressure shell housing said structured body, said pressure shell comprising an inlet for letting in said feed gas and an outlet for letting out heated gas, wherein said inlet is positioned so that said feed gas enters said structured body in a first end of said structured body and said heated gas exits said structured body from a second end of said structured body;
a heat insulation layer between said structured body and said pressure shell;
at least two conductors electrically connected to said structured body and to an electrical power supply placed outside said pressure shell, wherein said electrical power supply is dimensioned to heat at least part of said structured body to a temperature of at least 400° C. by passing an electrical current through said macroscopic structure, wherein said at least two conductors are connected to the structured body at a position on the structured body closer to said first end of said structured body than to said second end of said structured body, and wherein the structured body is constructed to direct an electrical current to run from one conductor substantially to the second end of the structured body and return to a second of said at least two conductors; and
an outlet for heated gas,
said method comprising the steps of:
in said first steady-state heating condition (A):
supplying said feedstock to the heating system in a first total flow, and
supplying a first electrical power via electrical conductors connecting an electrical power supply placed outside said pressure shell to said structured body, thereby allowing a first electrical current to run through said electrically conductive material,
thereby heating at least part of the structured body to a first temperature at which said feedstock is heated over said structured body under said first steady-state heating conditions (A); and said first heated gas is outlet from the heating system;
and, in said second steady-state heating condition (B):
supplying said feedstock to the heating system in a second total flow,
supplying a second electrical power via electrical conductors connecting an electrical power supply placed outside said pressure shell to said structured body, thereby allowing a second electrical current to run through said electrically conductive material,
thereby heating at least part of the structured body to a second temperature; at which said feedstock is heated over said structured body under said second steady-state heating conditions (B); and said second heated gas is outlet from the heating system;
wherein said second electrical power is higher than said first electrical power; and/or said second total flow is higher than said first total flow.
14. The method according to claim 13 , wherein the ratio of total gas feed flow in said first heating condition A to said second heating condition B (A:B) is at least 1:10.
15. The method according to claim 13 , wherein the heated gas outlet temperature from the structured body in heating condition B is between 50° C. to 600° C. higher than the heated gas outlet temperature from the structured body in heating condition A.