Drying and air purification in the production of food grade citric acid
Citric acid is an organic compound, white crystal powder, colorless crystals or particles, very easy to dissolve in water. Widely used in food, medicine, chemical industry, construction, energy and other industries. The production level of its products can be divided into food grade and industrial grade. The first annual output of # million! Food grade citric acid production plant using the original fermentation process, the introduction of foreign refining process, mainly the production of anhydrous citric acid ($%%) at the same time, according to the demand of the market, but also the production of citric acid monohydrate ($%&). Citric acid is extremely hygroscopic moisture under the normal temperature, strong corrosive. This paper focuses on the special requirements and design features of product drying and air purification in the production of food grade citric acid. Drying system with dry process! System deal with the air will go directly to the process system, and is in direct contact with the product and product design stage, the system not only to ensure that the indicators required for the process, the structure of the equipment and material selection should also have special consideration. "!! Heating system heating system for heating the outdoor fresh air into the filter, and is transported to the fluidized bed dryer, the citric acid crystals prepared by heating from the upper reaches of the centrifuge drying into powder. The citric acid crystal drying to complete in the specific conditions of temperature and humidity, low temperature or humidity are not dry citric acid crystals, but too high temperature or humidity is too small will cause compaction, a layer of hard clip formed in the citric acid crystal outside the wrap, the internal water can not be shed, too can not achieve the purpose of drying. In order to achieve food grade citric acid crystal drying, the drying process is as follows: (') taken in the design of hot dry air into the fluidized bed section of input, input parameters' section for air temperature and relative humidity) *, *,!; dry air after "are -*+, *,. The temperature gradually increased, while the relative humidity remained unchanged. The citric acid crystal is gradually heated, and the water is gradually evaporated. In order to ensure the quality of products, the air into the fluidized bed design considerations (filter, that is, the first, the efficiency of the filter and efficient filter. The composition of the equipment and materials of this system adopts anti pollution clean design, such as centrifugal fan, not to use the box structure commonly used, but the turbine entrance pipeline and fan connected directly to avoid pollution two motor and the driving mechanism of air blower. All of the material system including steam heating coil and fins, piping, humidifier nozzle, filter frame selection is not easy to corrosion and spalling of stainless steel material (* (* / (!!). #! "The cooling and drying conveying system for cooling and drying conveying system is the role of the heating and drying of citric acid powder cooling in the fluidized bed, and transported to a storage tank. The cooling medium air, the parameter requirements for temperature, absolute humidity) 0/10 *'. The cooling and drying design is divided into parts: one is the preparation of qualified cooling medium, the two is the citric acid powder cooling and drying. The design of the cooling air medium is abandoned to adopt the method of reducing the temperature of chilled water supply and return water. As shown in figure. The outdoor air through the primary, filter into the pre cooler, most water of high temperature and high humidity in the air through the frozen wet method to remove, and then through the dehumidifier, would have been in the low temperature water in the air again to remove the absolute humidity #$%&$. Through the rotary desiccant, the air temperature will be heated again to! "(or so, and then through the cooling coil cooling)" (in this process, the absolute humidity of the air is constant. Cooling cooling air flow drying and conveying medium qualified system is divided into two parts, one part of the high efficiency filter, is sent directly to the various stages of citric acid storage and screening, in order to ensure the proper temperature and humidity environments, avoid citric acid modification; the other part is conveyed to a cooling coil, cooling, again at constant humidity conditions filtered down to '(*. Subsequently, * "(the cold and dry air is again divided into parts, part) is transported to the fluidized bed!, rapid cooling of citric acid powder in a fluidized bed drying; the other part as a carrier gas delivery system, heating the citric acid powder dry from the fluidized bed and transported to the lemon acid ingredient storehouse.
Heating and drying system, composition of equipment and materials of this system using the anti pollution clean design, frame selection including frozen coil and fins, piping, filter frame, wheel is not easy to corrosion and spalling of stainless steel material ("" + "!"!). Air purification system packaging is the last operation of the production process, the air purification system has a certain requirement. ! "in the packaging product design stage # purification air, in order to ensure the product level, in the design of the HEPA air outlet increases, effective control into indoor air quality; in the construction, in strict accordance with the construction standard of clean plant requirements, to ensure that personnel, logistics equipment, clean, tidy and clean operation area to avoid a series of measures to the construction process of producing dust in the clean room etc.. "!! The temperature and humidity control design while ensuring the packaging process for air purification, control design of the packaging process of the temperature and humidity, temperature and humidity control respectively by using the return water temperature of chilled water for% to% / (to) get a larger dehumidifying ability.! "$equipment construction equipment structure also has a larger change, because of the ability, the common case of air conditioning manufacturers do not have the production of stainless steel coil so that the project of air conditioning in the tank is completely using similar method of cooling fan and industry, will split out air conditioning box, stainless steel single inlet centrifugal fan inlet the wind pipe is directly connected with the wind turbine entrance, mixing box and a filter box separately made, several parts connected by rubber sponge insulation directly attached to the surface of equipment and. The $design effect system after debug and operation months, various technical indicators have reached the design requirements: (*) yield and quality of the products meet the design requirements; ()) heating system and cooling drying and conveying system design is reasonable, normal operation, control and stability; (") reconstruction system equipment reached the expected purpose, normal operation.