Production process and device of formaldehyde

The invention relates to a production process and device of formaldehyde, in particular to a production process and device of the formaldehyde, which can realize circulated recycling of unreacted methanol. The process comprises the following steps of: defogging after heated methanol and recycled diluting methanol form a mixed gas with air in an evaporator; then adding a small amount of saturated steam or not adding the saturated steam; and heating and filtering; introducing the mixed gas to a reactor filled with a silver catalyst for reacting to generate a formaldehyde gas; recycling the waste heat of the generated gas to produce steam; then introducing the steam to an absorbing tower for absorbing; carrying out dealcholization on the extracted finished product by utilizing a high-temperature generated gas; and extracting diluting methanol from the upper part of the absorbing tower back to the evaporator for recycling. The device comprises three kinds of main equipment, such as the evaporator, the reactor and the absorbing tower as well as auxiliary equipment, such as a fan, a pump, a heat exchanger, and the like. The invention has the advantages of simple process, low unit product energy consumption and material consumption, high product concentration methanol content close to zero.