盐田饱和卤水直接进蒸发罐真空制盐工艺介绍模板.doc

盐田饱和卤水直接进蒸发罐真空制盐工艺介绍靳志玲（中盐制盐工程技术研究院，天津 300450）内容摘要：利用滩田饱和卤水直接进蒸发罐蒸发结晶制取氯化钠，在制盐过程中采取三次洗涤方法，除去钙镁离子，以取得纯度超出99.1%氯化钠和浓度较高制盐母液。关键词：滩田饱和卤水 真空 精制盐1 介绍现在，中国大部分井矿盐企业采取以井矿盐卤为原料，北方部分生产企业采取原盐化成饱和盐水再精制真空盐生产方法。 伴随中国“两碱”快速发展和人民生活水平提升，原盐供需矛盾已越来越突出。尤其是在海盐区，以原盐溶解成饱和卤水再生产精制盐，不仅增加了原盐消耗，而且降低了盐田面积使用效率，增加投资，生产成本高，不一样程度上影响了食用盐生产企业经济效益，造成很多食用盐定点生产企业减产、亏损，直接影响了百姓生活。而采取滩田饱和卤水直接进蒸发罐制盐，即能够节省结晶面积，其母液还能够为生产氯化钾、氯化镁等盐化工产品提供高质量原料苦卤，达成充足利用卤水中多种有效成份，实现零排放、无污染、循环经济目标。2. 工艺步骤简述卤水经滩田日晒蒸发，至饱和后引入一个卤水库中储存。卤水库作用，一是储存一定量饱和卤水，以备真空制盐生产需要；二是卤水在此有一定停留时间，能够使其中部分杂质颗粒沉淀下来，达成净化卤水目标。净化后饱和卤水从卤水库引出后，进入蒸发制盐车间精卤桶。采取预热后卤水进罐，顺流转料、末效排盐浆，集中排母液方法进行生产。I效蒸发罐盐箱中盐排到II效下循环管中，II效盐箱中盐排到III效下循环管中，III效盐箱中盐排到IV效下循环管中，最终集中在IV效盐箱；IV效排出盐浆，同时由IV效分离罐排出母液。工艺步骤简图见图1。3. 工艺优缺点利用该工艺已在中国北方建设了一个年产15万吨真空制盐生产线，相比再制盐生产工艺，其实施效果以下：本工艺采取饱和卤水制盐，不需要淡水化原盐，淡水消耗低，可节省淡水资源，依据生产情况，1t盐消耗淡水1.4-0.2m3，而再制盐生产工艺需要淡水3.5-4.53.73 m3，吨盐节省了2.1-4.3 m3淡水。2）节省日晒盐场土地，降低原盐消耗，提升了盐田利用率对再制盐生产线来说，通常生产1t精制盐需要消耗1.2t日晒原盐，年产15万t精制盐需要18万t原盐，需要结晶面积136.36公顷（按现在中国北方盐场有效结晶单产1650t/公顷，有效面积占80），采取饱和卤水直接进蒸发罐工艺，不需要饱和卤水进结晶池继续蒸发制盐，只需要建设一个约2公顷饱和卤库，所以，节省了土地面积134.36公顷，节省结晶面积可用于增加日晒盐产量8547t，按日晒盐销售价160元/t计算，日晒盐增加产值136.8万元。假如土地按3万元/亩计算，节省土地价值为6000多万元。3）采取三次洗涤方法洗涤盐浆以去除钙镁离子，使氯化钠含量超出99.4，精制盐达成优级盐质量。蒸发结晶过程中盐浆会夹带大量母液，母液中含有大量钙、镁杂质，所以，采取三次不一样洗涤方法洗涤盐浆，提升精制盐质量。4）用饱和卤水直接生产精制盐母液损失小，提升了母液利用率，实现盐化联产采取盐田饱和卤水直接生产优级真空精制盐工艺，每产1t精制盐副产母液约1.7m3，以年产15万t精制盐计算，整年可产生25.5万m3蒸发母液，且排出苦卤氯化钾含量达成了2430g/l，浓度为2934Be，钠镁比值为1.40.6，排出苦卤中氯化钾总含量为6589t，氯化镁总量为36540t，硫酸镁总量为18900t，氯化钠总量为37600t，溴总量510t。而年产18万t原盐，排出苦卤量通常只有18万m3，经过复晒、渗透损失、沟道输送进入化工厂后只有原来45左右，也就是说还有8.1万m3，这时氯化钾总含量为2036t，氯化镁总量为15280 t，硫酸镁总量为7727.4 t，氯化钠总量为11128 t，溴总量162t。所以，该工艺可为盐化工生产提供更多原料，提升了生产效率，降低了多种消耗，节省能源。该工艺排出制盐蒸发母液温度在55.04以上，可经过管道直接进入下步生产氯化钾工序，生产氯化钾产品，节省氯化钾生产过程中所需热量，折标煤1157吨/年5）因为滩田饱和卤水较化盐卤水氯化钠含量低，所以单位产品蒸发水量较高，吨盐产品电、蒸汽消耗量较大，能耗较高。6）蒸发设备换热面积较化盐溶解工艺稍高，所以设备投资相对较高，但因为节省大量盐田结晶面积，总体投资低。4. 和原盐溶解再制盐工艺技术经济指标比较中国海盐区生产真空盐工艺关键有滩田饱和卤水进罐蒸发制盐和原盐溶解制成饱和卤水蒸发制盐两种方法。原盐溶解制成饱和卤水蒸发制盐工艺优缺点有：（1）需建结晶池，工程总体投资较高；（2）单位产品蒸发水量小，设备投资稍低，（3）吨盐消耗电、蒸汽量较小；（4）水消耗较大，吨盐产品耗水2.4m3，（5）蒸发母液损失大。比较两种制盐方法技术经济指标如表。表 关键经济技术指标比较项 目再制盐生产饱和卤水直接进罐生产投资：结晶池投资550万元0蒸发设备投资9701080单位产品投资335元/吨306元/吨消耗指标：原煤0.23吨0.21吨原盐1.25吨1.15吨0.00吨卤水0.007.5m3白水3.5-4.5 m31.4-0.2 m3电50-70度50-70度两种工艺在投资和单位产品生产成本中有较大差异，饱和卤水法单位产品总投资低于原盐溶解法，单位产品成本低于原盐溶解法30。5. 结论对于北方海盐区生产精制盐企业来说，利用滩田饱和卤水直接进蒸发罐制取精制盐是一个很好生产工艺，节省投资，节省土地，尤其是将宝贵原盐溶解成饱和卤水再进行制盐是对土地资源浪费，再有其生产成本低，企业有较高利润空间；排出制盐母液综合利用生产钾、溴、镁等产品，使卤水全部吃干榨净，没有废物排放，降低了环境污染，有利于可连续发展。New technology of producing refined salt by adding salt field saturated brine into evaporator directly Jin zhiling Ge Jinyang (Salt Research Institute China Natural Salt Industry Corporation, TianJin 300450)Abstract: After Making saline saturated brine flow in evaporating pot, the sodium chloride is obtained by evaporative crystallization. Calcium and magnesium ions can be removed by washing salt three times in order to get the sodium chloride that the purity is over 99.1 percent and the mother liquor that have high concentration.Key words: saline saturated brine, vacuum, refine salt 1 BRIEF INTRODUCTIONAt present, the materials of making vacuum salt are using the well and rock salt in most of the well and rock salt corporations and the saturated brine got by dissolving crude salt. Along with the rapid development of caustic alkali and sodium carbonate and the growth in the peoples living standard, the contradiction of crude salt in supply and require is more and more stood out.Particularly in the sea salt areas, producting refine salt with saturated brine that is got by dissolving crude salt can increase the consumption of raw salt , reduce the availability factor of salt field, add investment and production cost. This willinfluence the economic efficiency of edible salt manufacturing enterprises , make them reduce output and affect peoples live.However, using the method of making saline saturated brine flow in evaporating pot and then obtaining sodium chloride by evaporative crystallization can saving crystal area. Furthermore, the mother liquor can be used as material to produce chemically products such as potassium chloride, magnesium chloride etc. in order to make use of all kinds of effective constituents in the brine and achieve the objects of no discharge ,no pollution and circulating economy.2. INDICATION OF THE PROCESS FLOWAfter being solarized to saturation in beach field brine was inducted to brine tank and stored. On the one hand brine tank can store some saturated brine that is used to produce vacuum salt. On the other hand ,brine have some residence time here so some impurities can be deposited in order to make the brine be purified. After being drawouted from brine tank the cleaned saturated brine was pumped to fine brine tank in the manufacture salt plant. And production can be gone on by using the methods of preheating brine , transferring stuff in parallel flow, discharging salt slurry in the last effect and exporting mother liquor concentratedly. The salt in the first effect tank is discharged to the circulation pipe of the second effect, The salt in the second effect tank is discharged to the circulation pipe of the third effect, The salt in the third effect tank is discharged to the circulation pipe of the fourth effect. At last the salt is collected in the fourth effect tank where the salt slurry and the mother liquor are discharged. Fig. 1 is the diagram of the process flow. Figure.1 Diagram of the process flow3. RELATIVE MERITS OF THE PROCESSIn the north of China a production line has been built with this process, which can produce 1.5 million tons salt per year. Comparing with rework salt production process, the effect of this process is as follows:1）The saturated brine is used in this process take the place of dissolving crude salt with fresh water. Such can reduce the consumption of fresh water and save the resource. According to the produce conditions, producing 1 ton salt will consume 1.4-0.2 m3 fresh water. And that if use the reworking salt process 3.5-4.53 m3 fresh water will be used. That is to say 2.1-4.3 m3 fresh water can be saved corresponding to 1 ton salt .2) Saving the solar salt field, reduce the consumption of crude salt, increase the availability of the salt field. For the reworking salt production line, as a general rule producing 1 ton refine salt will consume 1.2 tons solar salt. Producing 1.5 million ton refine salt needs 1.8 million tons crude salt and 136.36 hectare crystal area(According to the experience that one hectare can produce 1650 ton crystal and the effective area is 80 percent). Using the process that the saturated brine is pumped to evaporating tank directly the brine need not evaporate in crystal pond but for a saturated brine storeroom of about 2 hectare. Such can save surface area of 134.36 hectare and this area can be used to increase 8547 ton output of solar salt. Hence the productive value of solar salt will increase 136.8 ten thousand yuan according to the market price of solar salt which is 160yuan/t. And land value of 60 million yuan can be saved if the land is 30,000 yuan per mou. 3）Adopting the method of washing salt three times in order to get rid of calcium and magnesium ions , make the purity of sodium chloride exceed 99.4% and make the refine salt reach first quality. In the process of evaporative crystallization much mother liquor will exist in salt slurry. The mother liquor contains a lot of impurity of calcium and magnesium. So salt slurry is washed in three different ways in order to improve the quality of refine salt.4）Using the saturated brine to produce refine salt can reduce the consume of mother liquors, enhance its availability and realize the production of salt and chemicals together. The process that producing excellent vacuum salt with salina saturated brine directly can get 1.7 m3 mother liquor in relation to 1t refine salt. On the base of 150,000 ton refine salt, we can get 255,000 m3 evaporation mother liquor. In bitter brine whose concentration is 29340Bethe content of potassium chloride is 2430g/l and the ratio of sodium and magnesium is 1.40.6. And 6589t potassium chloride, 36540t magnesium chloride,18900t magnesium sulfate,37600t sodium chloride and 510t bromine are contained in the bitter brine.The bitter brine is about 180,000 m3 in relation to 180,000t crude salt. After being solarized repeatedly and consuming for filter the brine is left 45% when it is pumped to chemical plant. That is to say there are 81,000 m3 brine. By now there are 2036t potassium chloride, 15280t magnesium chloride, 7727.4t magnesium sulfate, 11128t sodium chloride and 162t bromine. So the process can provide more material for salt and chemicals plants, heighten production efficiency, reduce all kinds of consumption and save energy. The temperature of the mother liquor got from this process is over 55.04. So it can be pumped to the potassium chloride process with pipe to produce potassium chloride. Such will save the heat quantity in the process of producing potassium chloride. And the heat quantity is equal to 11578t/y standard coal.5) Because the content of sodium chloride in the beach saturated brine is lower than the content in the brine that is got by dissolving salt, the evaporated water of unit produce is higher, the electricity and steam consumption are more. That is to say the energy consumption is higher.6）The heat exchange area is a littler bigger than the process of dissolving salt, so the equipment investment is higher. But because of saving a lot of salina crystal area the total investment is lower.4. COMPARE THE ECONOMIC INDICATORS WITH THE PROCESS OF DISSOLVING CRUDE SALT AND THEN REMAKING SALT In China There are two main methods to producing vacuum salt in sea salt area. One is pumping the beach saturated brine into evaporating pot. The other is using the saturated brine got by dissolving crude salt. Comparing the second method with the first method the relative merits of the second method is as follows:（1）need to build crystal pond and the total investment is higher.(2)The evaporated water of unit product is smaller and the equipment investment is lower.(3)The consuming of electricity and steam is lower.(4)The consuming of water is more and 2.4 m3 water will be consumed in relation to 1 ton salt.(5)The loss of mother liquor is bigger. The economic indicators of the two methods are as follows:Comparison of the main economic and technical normsItemThe process by dissolving saltThe process by the saturated brine being pumped into evaporating pot directlyInvestmentEvaporating pot Crystal pond5,500,000yuan0Evaporating equipment9701080Unit product335 yuan/t306yuan/tConsuming indicatorTargetCrude fuel0.23t0.21tcrude salt1.25t1.15t0.00tBrine0.007.5m3Fresh water3.5-4.5 m31.4-0.2 m3Electricity50-70degree50-70 degreeBetween the two processes there is bigger difference in the investment and production cost of the unit product. The total investment of the unit product is lower and the cost of unit product is lower 30 than the method of dissolving crude salt.For the plant that producing refine salt in the sea salt area in north using the method of pumping beach saturated brine into evaporating pot and producing salt is a good production process. It can save investment and land. Particularly dissolving crude salt into saturated salt and then making salt is a kind of waste to land resource. Moreover, the production cost is lower. And corporations will get more profit. The mother liquor can be used to product potassium, bromine and magnesium etc. Brine will be utilized completely. No waste be discharged and it will reduce environment pollution. This is in favor of the sustainable development.