Hydroquinone (HQ)

1. Material Overview

Hydroquinone is known as 1,4-hydroxyquinone with molecular formula C6H6O2 and molecular weight of 110.11. It is a colorless or white crystalline solid. It readily changes color upon exposure to light. Its aqueous solution oxidizes to brown in air, and oxidation is even faster in alkaline media.

Hydroquinone is primarily used as a photographic developer. Hydroquinone and its alkylates are widely used as polymerization inhibitors added during monomer storage and transportation, with a commonly used concentration of approximately 200 ppm. Hydroquinone monomethyl ether is an intermediate in the production of the edible oil antioxidant BHA. Hydroquinone dimethyl ether is an intermediate in dyes, organic pigments, and fragrances. Hydroquinone diethyl ether is an intermediate in photosensitive pigments and dyes. Hydroquinone is also used to produce N,N'-diphenyl-p-phenylenediamine, an antioxidant and deodorizing agent used in rubber and gasoline.

2. Process Introduction

The drying system adopts closed-loop circulation process with nitrogen protection. Hydroquinone (HQ) from the upstream process is fed into the fluid bed dryer (FBD). During the drying process, the nitrogen entering the FBD is effectively controlled, thus maintaining the stable fluidization state of the feedstock inside the FBD. Dried HQ feedstock continue to move forward into the cooling section of fluid bed dryer to exchange the heat with low-temperature nitrogen to reduce its temperature. Low-temperature nitrogen is pressurized by circulating fan and heated by heat exchanger to enter the fluid bed dryer after passing through the air chamber and air distribution plate. After cooling down, the dried HQ product is discharged by final product discharge valve into the vibrating screen after passing through the overflow weir plate. The final product is conveying into downstream section by final product conveyor.

3. Technical Advantages

1) Utilizing closed-loop nitrogen circulation system with inert, sealed atmosphere can completely isolates oxygen, effectively preventing material oxidation.

2) The nitrogen circulation along with waste heat recovery ensures that hot air and nitrogen are not discharged externally, resulting in high heat utilization. Only a small amount of nitrogen needs to make up, and media loss and energy consumption are far lower than with open-loop nitrogen drying.

4. Technical Benefit

1) More stable product quality

Due to the closed inert atmosphere isolating external interference, combined with uniform temperature-controlled drying, materials remain free from oxidation and deterioration, resulting in high consistency in moisture content and quality, and significantly improved finished product qualification rate.

2) Lower overall operating costs

Closed-loop nitrogen recycling and efficient waste heat utilization significantly reduce energy consumption and nitrogen consumption; furthermore, the equipment has a simple structure and low failure rate, reducing daily maintenance and media usage costs simultaneously.

3) Environmental friendly protection

Fully enclosed operation eliminates waste gas and dust emissions, requiring no additional exhaust gas treatment equipment;

Continuous and stable operation can ensure large-scale production, reaching environmental standard without additional rectification risks.