TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The radius difference between the outer ring and the inner ring of the annular cavity and the width of annular cavity is L equal to aW, where W is the width of the catalyst particles, which is 4-6 mm, and a is number of side-loaded catalyst, which is 4-6; the outer diameter of annular cavity R2 and inner diameter of the annular cavity R1, and the height H satisfies the following equation: A is equal to pH(R1+R2) is equal to (1.2-1.5) Q/KDT; V is equal to (1.05-1.3)V1 is equal to P(R22-R12)H/4, where Q is heat required for the steam reactor, Q is equal to nDH, where n is molar amount of natural gas required for reaction, DH is unit molar of natural gas and water vapor required for the reaction heat, K is the heat exchange coefficient, DT is reaction gas and flue gas logarithmic temperature difference, A is the heat exchange area of the reactor, V is volume of the reactor annular part, and V1 is catalyst loading volume. The nickel-based catalyst loading volume V1 is equal to F/n, where F is volumetric flow rate of natural gas, v is carbon air velocity of 500-1500/hour. The baffle plate is made of stainless steel, and is welded together with the outer ring of the reactor main body, where the height of the gap is 1/10 of the height of the reactor main body. The width of the arc-shaped channel is 1.5-3 cm. The diameter of the pre-heating pipe is 4-8 mm; the pre-heating pipe material is made of copper material. The natural gas preheating pipe and a water preheating pipe spiral structure winding number is 5-10 turns, mixing gas pre-heating pipe spiral structure winding number is 7-12 turns. The diameter of outer cylinder reactor R3 is equal to R2+(6-12) cm, and the length of reactor body is 20-30%; R2 is the outer diameter of the annular cavity. The upper end cover and the reactor outer cylinder are covered with heat insulating material. The heat insulating material is ceramic fiber, where the thickness of heat insulating material is more than 10 cm.