The heat-pipe exchanger has high heat transmission efficiency. The equipment also has a compact structure, and small thermal side flow resistance. Its structure is safe, reliable, and better than the heat exchanger of other structures, and the damage of a single (or few) heat pipe will neither affect the overall performance of the equipment nor affect the plant production. The waterway is outside the flue, so it requires no shut down for replacement and overhaul. Design life is 10 years plus. This equipment is used in combination with the start-up pre-heater, which produces steam before cold start-up, external steam supply is no needed.   The recovery rate is 100kg sulfur burning generates 250kg steam. The first/second stage recovery of exhaust gas generates steam, and the third stage recovery produces hot water with efficiency of 36.5%, 44.2% and 67.3% respectively.