Energy Conservation
If corn deep processing enterprises want to obtain a good energy-saving effect, the ranking of energy-saving measures is very important: combined heat and power, material heat exchange, waste heat recovery, energy migration, use new energy-saving equipment.
1. Combined Heat and Power:
The role of combined heat and power for enterprise energy conservation is very important. Pure power generation thermal power plants need to drive the steam turbine after power generation tail steam through the cooling tower condensation and then pressure back to the boiler, a large amount of energy is wasted, combined heat and power is based on the power generation of thermal power plants at a very low cost and meanwhile obtain the valuable steam.
Combined heat and power is very suitable for large production enterprises as energy supply centers，because the construction investment is large and difficult approval, generally not suitable for small and medium-sized enterprises.
2. Material Heat Exchange:
Material heat exchange refers to the low-temperature material in a certain process that needs steam heating, while the high-temperature material in another process needs cooling water to cool down. At this time, choose heat exchange equipment to let the two materials exchange heat, which not only saves the heating steam but also saves the cooling water. Whether it is 30℃ circulating cooling water or 7℃ circulating frozen water, the acquisition process both needs energy, saving cold source is also energy saving as saving steam.
In the design of material heat exchange, many people think that the temperature of cold material after heat transfer can not be higher than the temperature of hot material. In fact, with countercurrent heat exchange and a large enough heat exchange area, the temperature of the cold material after the material heat exchange may completely exceed the hot material and even close to the temperature before the heat exchange of the hot material. On many energy-saving occasions, excessive saving of heat exchanger area will seriously affect the energy-saving effect, so it is not recommended to choose a small heat exchanger area.
Most types of heat exchange equipment are well known, while heat pipe heat exchange technology is rarely known. It can be used for some occasions that ordinary heat exchange equipment cannot solve, such as heat exchange between dry tail air and fresh air.
3. Waste Heat Recovery:
Many processes in the use of steam at the same time, emit lots of waste steam, waste steam temperature is low and unable to return to this process cycle. But it can be considered to be recycled to the process without high-temperature steam to use, which can achieve a good energy-saving effect.
Many processes of corn processing enterprises can use waste heat to save energy, such as the dry exhaust of the dry gas in the starch production, which can be used as heating steam for corn syrup concentration, and the dry heat condensate can be used as the heating of the corn soak liquid. The liquid flash exhaust steam can be recycled into the sugar evaporator, and the 55℃ exhaust steam of the evaporator is used as a preheating of the dry wind. The exhaust about 55℃ steam of the fermentation factory’s evaporator and the evaporating crystallization tank can be used as the preheating of the dry wind, and the waste steam discharged from the fermenter can also be recycled into 90℃ circulating hot water and sent to various hot spots.
4. Energy Migration:
Energy migration, also known as heat pump technology, refers to the transfer of energy from low-temperature material to high-temperature material through a heat pump to achieve the purpose of energy-saving.
Heat pumps should be called energy pumps or energy pump units, that is, to promote energy transfer equipment or units. The concept of a heat pump is abstract, we can compare the characteristics of heat pump and centrifugal pump to understand the heat pump.
We know that in its natural state, water flows downwards. If we need water to flow upwards, we can use centrifugal pumps.
Similarly, in the state of nature, energy is always transmitted from a hot object to a cold object. If we want to transfer energy from a cold object to a hot object, we can do it through an energy pump called a heat pump.
Centrifugal pump is driven by electric energy to the impeller of the pump, convert mechanical energy into kinetic and potential energy, to achieve the transport of water from low to a high level.
And the heat pump includes three parts: low-temperature evaporation heat absorber (heat exchanger), gas compressor, and high-temperature condensation heat release. And the heat pump in the operation process also needs to add a heat conduction carrier or heat conduction agent. Heat conduction agent in the low-temperature environment of the evaporative heat sink, because of the low pressure or high vacuum, it still evaporates, from liquid to gas, so that through the heat exchanger from the low-temperature object energy will be sucked into the heat conduction agent; After the gas heat conductor is compressed to the high temperature condensing heat release by the gas compressor, the pressure increases or the vacuum degree decreases. Although in the high-temperature environment, it can still condense due to the high pressure or the vacuum degree decreases, and the energy in the heat conductor is released to the high-temperature object through the heat exchanger. After releasing the energy, the condensed heat conduction agent flows back to the low-temperature evaporation heat sink through the pressure reducing valve to complete a working cycle. The heat pump realizes the function of conducting the energy from the low-temperature object to the high-temperature object through the continuous circulation of the heat conduction agent.
Centrifugal pumps do not change the amount of water in the process of consuming electricity to complete the transmission of water from low to high levels, so the process of power consumption is not associated with the change of the amount of water.
Similarly, a heat pump consumes electricity (Gas compressors consume electricity) to transfer energy from a low temperature to a high-temperature object without aiming to change the amount of energy transferred (although it does increase somewhat), so the amount of energy consumed is essentially independent of the amount of energy transferred. The principle of heat pump energy saving is to use a useless or low economic value of low-temperature energy, through the heat pump to the object of higher temperature, to replace or reduce the use of the valuable or high value of high-temperature energy to achieve the purpose of energy-saving.
When low water is cheap and readily available, the economic basis for using a centrifugal pump to move water from low to a high level is whether it is more economical to compare the cost of lifting the water than to obtain it from higher water by other means, rather than whether water can be produced during the operation of the centrifugal pump.
Similarly, when the low-temperature energy is cheap (such as the energy contained in the air are still free) or easy to obtain, to judge with the pump energy from low temperature to high-temperature object is based on comparing whether the cost of transporting energy is more economical than obtaining energy by other means (like burning steam in a boiler), it's not about how much heat a heat pump converts electrical energy into for use by a hot object.
Centrifugal pump in the same lifting height or lift, its electricity consumption is proportional to the amount of water transported.
The heat pump at the same inversion or temperature rise, its electricity consumption is proportional to the amount of energy transported.
Centrifugal pumps can accelerate the conveying speed of water in the process of conveying water from high to low levels, and the use of water energy to automatically flow from high to low can achieve hydroelectric power generation.
A heat pump can accelerate the transmission speed of energy in the process of conveying energy from high-temperature objects to low-temperature objects, and the use of energy can be automatically conducted from high-temperature objects to low-temperature objects to achieve temperature difference power generation.
When conveying the same amount of water, the power consumption of the centrifugal pump is directly proportional to the lift.
Centrifugal pump in the process of conveying water due to pipe block will cause a certain lift (pressure head) loss, the thicker the pipe, the less the lift loss. When choosing a centrifugal pump, considering the lift loss, a centrifugal pump with a slightly larger lift than the actual demand should be selected.
Heat pump in the process of energy transfer due to the heat conduction block of the heat exchanger will cause a certain loss of temperature rise, the larger the heat transfer area of the heat exchanger, the smaller the temperature rise loss. When choosing a heat pump, considering the loss of temperature rise, a heat pump with a slightly higher temperature rise than the actual demand should be selected.
The characteristics of heat pumps in addition to the above similarities with centrifugal pumps, there are also some differences:
1) The power consumption of the centrifugal pump is directly proportional to the pressure difference between the inlet and outlet (lift), It has little relation with actual pressures on imports or exports. A heat pump is not only proportional to the temperature rise but also has a certain relationship with the specific temperature of hot and cold objects, in some cases, the influence of temperature of hot and cold objects on power consumption even exceeds the influence of temperature rise on power consumption.
2) Centrifugal pumps deliver tangible water, heat pumps deliver energy that can't be seen or touched, this is why many people can not fully understand the heat pump technology. Although the energy conveyed by the heat pump can not be seen or touched, it can be felt and detected, so it does not affect its promotion and application, another difference is that heat pumps need heat conductors when they work, and the power consumption of heat pumps is directly related to what kind of heat conductors are used.
The most commonly used heat pump is the air conditioner that has a history of several decades and has entered into every home. When the air conditioner runs, the energy is transported from the indoor lower temperature to the outdoor higher temperature, to realize the indoor maintenance in the cool state of the lower temperature.
Through the air conditioning this common heat pump, from the understanding of the working principle of air conditioning to understand the working principle of heat pump, will greatly broaden the use of heat pump range, and in turn to promote the progress of air conditioning technology. Today's air conditioning from single cooling progress to cold and warm, from cold and warm progress to air water heater and refrigeration and heating water integrated machine, has changed the simple air conditioning to heating pump units. I believe that soon, the residents living with air conditioning must be the whole district of the cold and warm bath of central air conditioning (heat pump unit): in summer due to refrigeration from the residents home push out of the energy is not directly scattered into the atmosphere, but pushed to cold water for the generation of hot water for bath; In winter, the energy in the air is pushed into hot air to heat the residents, or pushed into cold water to heat into hot water for the residents to use in the bath.
A special case of a heat pump is the current popular energy-saving evaporation equipment: MVR evaporator. As a special case of heat pump because of its direct use of evaporator continuously produce secondary steam as an agent of thermal conductivity, thermal conductivity after condensing agent directly discharge without reflux to the low-temperature evaporation heat absorber, so the heat exchanger of the low-temperature evaporation heat sink and the heat exchanger of the high-temperature condensation heat release can be combined into one heat exchanger, and borrowed the evaporator's heater to double as the combined heat exchanger. In this way, THE MVR evaporator is equivalent to a heat pump unit "The heat exchanger of the evaporator as the heat sink of low-temperature evaporation, a heat exchanger used in combination with high temperature condensing exotherms". The evaporation process of the evaporator does not consume energy. After the heating steam evaporates the material out of the secondary steam, a large amount of energy enters the secondary steam through natural conduction. Because the common evaporator can not reuse the energy (latent heat) in the secondary steam, it is forced to continuously add external steam to the heating chamber as the energy to maintain the evaporation operation. Due to the formation of a heat pump system, THE MVR evaporator can transfer the energy in the secondary steam back to the evaporator as the energy needed for the material to evaporate the secondary steam, so that the continuous operation of evaporation can be maintained without adding external steam. This is why an MVR evaporator can save energy, why not consume external steam.
· The basic purpose of industrial heat pump technology is to save energy, and it has a very broad application prospect in the corn deep processing industry. As we know, the normal temperature of corn into deep processing workshop, Starch sugar products or fermented products are produced at normal temperature, and the production process does not need energy or very small (60 hours saccharification process hardly cools down is the evidence), why our production line need to consume large amounts of foreign steam as an energy source? The answer is to meet the requirement of each process, and although we have done a lot of waste heat recovery work, we still need to keep to the production line filling energy, and these energies of filling are not into the product, but through the cooling tower and dry tail wind endless discharged into the atmosphere. Heat pump technology for our corn processing production provides such a possibility: All the energy in each production line will be recycled, the production line does not use external steam at all, no cooling tower, the dry tail wind drops to normal temperature. In this way, our enterprises are bound to reap both economic benefits and environmental friendliness.
Heat pump technology can be widely applied in the corn deep processing industry. For example, a heat pump can be used to transfer the energy in the waste steam with the final effect of corn syrup evaporation at about 55℃ to the starch drying air. The energy in 7℃ circulating frozen water and the energy in the waste steam with the final effect of syrup evaporation at about 55℃ can be transferred to starch sugar crystallization and drying air, and cancel the refrigeration unit for making 7℃ circulating frozen water. Some of the energy in the fermentation production line can also be transferred to the drying air of the finished crystal of the fermented product through a heat pump.
5. Use new energy-saving equipment
With the continuous progress of technology, a variety of energy-saving equipment continues to appear, timely, effective, and appropriate selection of new energy-saving equipment is also an important part of the work of energy conservation.
Drying of by-products in starch production, in recent years, a new type of rapid drying and frying tube bundle dryer has appeared, heat transfer efficiency is improved by using higher temperature heating steam, can save 10 ~ 15% steam consumption. MVR evaporator is used instead of multi-effect evaporator for evaporation and concentration, MVR evaporative crystallization tank is used instead of single effect evaporative crystallization tank, can achieve a very good energy-saving effect. As for drying, the most energy-saving is the combined fluid bed drying unit, especially suitable for starch, sugar, or fermentation product crystal drying. The unit consists of a cylindrical reverse mixing bed counter-current fixed fluid bed dryer, a vibrating fluid bed dryer, and a vibrating fluid bed cooler. Its working principle： the crystal granules drop into the cylindrical fixed fluid bed dryer by gravity, fluidized by the hot air from the bottom, due to good access to hot air, the water is evaporated rapidly and removed. Then the crystal granules are conveyed by automatic control rotary valve to the rectangular vibrating fluid bed dryer. Fluidized by the hot air from the bottom, the granules are then fully dried in the drying section of the rectangular vibrating fluid bed dryer, then will be cooled down in the cooling section and fed to a rectangular vibrating screen for big agglomerate granule removal. The advantage of this unit is that the drying process is divided into the pre-drying section and final drying section. For crystal granule drying, the closer to the end, the more difficult to remove the water further. G-Luckey uses two fluid bed dryers to separate the pre-drying and the final drying, so the crystal granule can be completely dried, meanwhile also can improve drying efficiency and save energy. The core equipment of the unit is the cylindrical fixed fluid bed dryer, it completes 90-95% drying, the drying process of hot air and sugar crystal is completely countercurrent. As the exhaust air humidity is very high, the energy consumption is only 35 ~ 40% of the full downstream drying.
The energy-saving of aerobic fermenters has also made some progress in recent years. The new concept holds that air distribution should not be solely based on high-intensity stirring, it should be about the distribution of the air, to greatly reduce the power consumption of stirring, and then reduce the height of the fermenter to reduce the power consumption of ventilation.
The improvement of germ extruders and fiber extruders in starch production is not reflected in their energy consumption, but a good extruder can dehydrate the material to lower water content, thus reducing the steam consumption in the subsequent drying process.
6. Other energy-saving measures
In addition to the above energy-saving measures, energy-saving measures for corn deep processing include process improvement, strengthening heat preservation, saving electricity, selecting large equipment, and maintaining stable and continuous production as far as possible.
At present, there is a debate on whether to use one jet liquefaction or two jet liquefaction for starch milk liquefaction, the steam consumption of two injection liquefaction is certainly higher than that of one injection, it is not necessary to use two - jet liquefaction of potato starch emulsion, for corn starch milk depends on what is the product. The main difference between two injections and one injection of corn starch milk is that the average DX of saccharification is about 0.2 ~ 0.3 higher, and the filtration speed of saccharification liquid and the finished product is faster. Therefore, the production of crystallized sugar, F55 fructose syrup, to use two injections is appropriate, especially for the production of medicinal glucose, two injections are necessary, a single injection is required for the production of invert syrup, malt syrup, F42 high fructose corn syrup, and fermentation syrup. When two injections are used, the waste steam of the liquefaction flash is generally recycled to the evaporator to drive the three-effect vacuum evaporation at the same time, so that the total steam consumption is only slightly increased than the first injection.
A low-temperature decolorization process should also be advocated, that is, the saccharification liquid is not heated or filtered through a vacuum drum, so that the temperature of the drum filtrate is between 53 ~ 56℃, directly without heating, add powder activated carbon for decolorization. Many books have introduced that the activated carbon is suitable between 75 ~ 80℃, and the adsorption capacity of activated carbon is higher. But we think that the decolorization rate of activated carbon is fast between 75 ~ 80℃, the low-temperature decolorization process between 53 ~ 56℃, only need to lengthen the mixing contact time between activated carbon and sugar solution, activated carbon can still fully absorb the pigment, will not increase the consumption of activated carbon. If the high-temperature decolorization process of 75 ~ 80℃ is used, not only the temperature of the drum filtrate needs to be raised, but also the decolorization solution needs to be fully cooled to remove ion exchange, countless energy is wasted.
The crystallization process also has a great impact on energy saving. If the final temperature of cooling crystallization can be raised as high as possible, the consumption of low-temperature circulating cooling water can be reduced to achieve the purpose of energy-saving. Many enterprises adopt multi-stage or multi-stage crystallization, sometimes too many crystallization segments do not help improve product quality but greatly increase energy consumption.
Put an end to the saccharification liquid to destroy enzymes, to use continuous elimination of bacteria, etc., can also save energy.
In addition to the saving of steam heat energy and cold source, the saving of electric energy should be considered in the production of corn deep processing. The main measures to save electricity are: The stirring of the storage tank should be promoted by the eccentric propeller as far as possible because the purpose of stirring is to mix rather than rotate, and should be determined according to the minimum requirements of the process, for example, for a 100 cubic mashing tank, 1.5KW of stirring is sufficient. And except for the feeding and later stages of discharging, just open it intermittently during saccharification. The manufacturers are generally equipped with large vacuum pumps for vacuum drums, it is best to have a small vacuum pump and a large hanging earth vacuum pump.
The brake feed system should be installed in the upper suspension centrifuge. The flow and lift of the pump should be matched appropriately, the diameter of the pipeline should be properly enlarged. Power equipment with variable load should be equipped with a frequency converter.