A method for heating a feed of natural gas, used as feed for a steam reformer of an ammonia production system, wherein the system comprises a steam reformer operably connected to a heat recovery unit comprising at least two heating coils (4, 5) maintained at a different temperature, wherein the feed of natural gas passes through the at least two heating coils (4, 5), comprising the steps of: a) recovering heat in the heat recovery unit from the ammonia production system; and b) exchanging at least part of the heat recovered in step a) with at least a portion of the feed of natural gas, thereby obtaining a heated feed of natural gas; wherein the feed of natural gas does not comprise steam; the method being characterised in that: - the heat recovered in step a) is heat recovered from flue gas produced in the steam reformer; - step b) comprises the consecutive steps of: b1) heating the feed of natural gas from a temperature ranging from 10 °C to 40 °C to a temperature ranging from 180 °C to 210 °C upon contacting the feed with a first heating coil of the heat recovery unit, thereby obtaining a pre-heated feed of natural gas; and b2) subsequently further heating the pre-heated feed of natural gas from step b1) to a temperature ranging from 360 °C to 380 °C upon contacting the feed with a second heating coil of the heat recovery unit, thereby obtaining the heated feed of natural gas; and-the method further comprises the step of: c) splitting the pre-heated feed of natural gas obtained in step b1) into a pre-heated feed stream fed to the second heating coil of the heat recovery unit and a gas stream having a temperature ranging from 180 °C to 210 °C used as fuel in the steam reformer, wherein the gas stream having a temperature ranging from 180 °C to 210 °C used as fuel in the steam reformer obtained from step c) is further mixed with natural gas. a) recovering heat in the heat recovery unit from the ammonia production system; and b) exchanging at least part of the heat recovered in step a) with at least a portion of the feed of natural gas, thereby obtaining a heated feed of natural gas; wherein the feed of natural gas does not comprise steam; the method being characterised in that: - the heat recovered in step a) is heat recovered from flue gas produced in the steam reformer; - step b) comprises the consecutive steps of: b1) heating the feed of natural gas from a temperature ranging from 10 °C to 40 °C to a temperature ranging from 180 °C to 210 °C upon contacting the feed with a first heating coil of the heat recovery unit, thereby obtaining a pre-heated feed of natural gas; and b2) subsequently further heating the pre-heated feed of natural gas from step b1) to a temperature ranging from 360 °C to 380 °C upon contacting the feed with a second heating coil of the heat recovery unit, thereby obtaining the heated feed of natural gas; and-the method further comprises the step of: wherein the feed of natural gas does not comprise steam; the method being characterised in that: - the heat recovered in step a) is heat recovered from flue gas produced in the steam reformer; - step b) comprises the consecutive steps of: b1) heating the feed of natural gas from a temperature ranging from 10 °C to 40 °C to a temperature ranging from 180 °C to 210 °C upon contacting the feed with a first heating coil of the heat recovery unit, thereby obtaining a pre-heated feed of natural gas; and b2) subsequently further heating the pre-heated feed of natural gas from step b1) to a temperature ranging from 360 °C to 380 °C upon contacting the feed with a second heating coil of the heat recovery unit, thereby obtaining the heated feed of natural gas; and-the method further comprises the step of: - the heat recovered in step a) is heat recovered from flue gas produced in the steam reformer; - step b) comprises the consecutive steps of: b1) heating the feed of natural gas from a temperature ranging from 10 °C to 40 °C to a temperature ranging from 180 °C to 210 °C upon contacting the feed with a first heating coil of the heat recovery unit, thereby obtaining a pre-heated feed of natural gas; and b2) subsequently further heating the pre-heated feed of natural gas from step b1) to a temperature ranging from 360 °C to 380 °C upon contacting the feed with a second heating coil of the heat recovery unit, thereby obtaining the heated feed of natural gas; and-the method further comprises the step of: b1) heating the feed of natural gas from a temperature ranging from 10 °C to 40 °C to a temperature ranging from 180 °C to 210 °C upon contacting the feed with a first heating coil of the heat recovery unit, thereby obtaining a pre-heated feed of natural gas; and b2) subsequently further heating the pre-heated feed of natural gas from step b1) to a temperature ranging from 360 °C to 380 °C upon contacting the feed with a second heating coil of the heat recovery unit, thereby obtaining the heated feed of natural gas; and-the method further comprises the step of: c) splitting the pre-heated feed of natural gas obtained in step b1) into a pre-heated feed stream fed to the second heating coil of the heat recovery unit and a gas stream having a temperature ranging from 180 °C to 210 °C used as fuel in the steam reformer, wherein the gas stream having a temperature ranging from 180 °C to 210 °C used as fuel in the steam reformer obtained from step c) is further mixed with natural gas.