Laizhou Bay Salt Area in Shandong Province is the earliest area in China and even in the world to use this kind of underground brine resources, which has a history of thousands of years, but it was in the stage of spontaneous exploitation before 1980s. Except for shallow exploration in a small area of Shouguang Yangkou Salt Field in 1957, only the salt industry department has studied the technology of making salt from underground brine, but has not done geological research. Since the late 1970s, China's coastal economy has developed greatly, and the supply of raw salt is in short supply. In the past, the drying of beach salt with low concentration seawater always relied on expanding the area of salt pan to increase the output, but this was bound to be restricted by the area of beach. However, the technical transformation of the old saltworks has large investment, slow effect and low efficiency, which can not meet the needs of development.
Therefore, the road to the great development of salt industry has turned to "drying salt on the beach" with obvious advantages.
(1) Luchang Salt Area: Salt fields in Luchang Salt Area are mainly distributed in Laoting, Luannan, Tanghai, Hangu, Tanggu, Huanghua and Haixing counties. Its production scale (including salt field area, raw salt production capacity and salt industry output value, etc.). ) accounts for 25% ~ 35% of the national sea salt. 1988 crude salt output was 4 15000 tons, accounting for 50.2% of Bohai sea salt output. Judging from the development status of Luchang Salt Area, there is little room for expansion of Tianjin Binhai Tanggu and Hangu Salt Field. With the development of towns and port industries, there is still the possibility of further reduction, but Huanghua, Nanpu and Daqinghe saltworks still have considerable development potential.
(2) Liaodong Bay Salt Area: There are five salt fields in Liaodong Bay, including Fuzhou Bay, Yingkou, Jinzhou, Jinzhou and Lushun. The salt field area and crude salt production capacity account for more than 70% of Liaoning Salt Area, and the crude salt output 1988 reached 2.057 million tons, with an output value of 280 million yuan.
(3) Laizhou Bay Salt Area: This area is the main sea salt producing area in Shandong Province, including Yantai, Weifang, Dongying, Huimin and other places 17 salt field, with a total area of about 400 square kilometers and a sea salt output of 2.939 million tons 1988. From the level of technical equipment, product quality and economic benefits of enterprises, Laizhou Bay salt area is in a leading position among all salt areas in China. The comprehensive mechanization level of the main salt fields is over 60%, and the output per unit area is as high as 73 tons/hectare, ranking first in the northern sea salt area.
(4) Origin of Huai Salt: It is named after the Huaihe River crossing Jiangsu Salt Field. Jiangsu saltworks are distributed in the embroidered needle estuary at the junction of Sulu and Shandong in the north and the inclined long coastal zone at the Yangtze River estuary in the south, spanning Lianyungang, Yancheng, Huaiyin and Nantong 13 counties, covering an area of 653 square kilometers. Jiangsu coastal area is suitable for sea salt production, with the widest coastal beach in China and four totally different climatic conditions.
The raw material sources of salt are divided into four categories: sea salt, lake salt, well salt and mineral salt. The salt made by drying seawater is called sea salt; The salt produced by mining modern salt lake minerals is called lake salt; The salt made by extracting shallow surface or underground natural brine by open caisson method is called well salt; The salt produced by mining ancient rock salt deposits is called mineral salt. Because rock salt deposits sometimes coexist with natural brine salt deposits, and because of the advent of drilling water solution method for mining rock salt deposits, there is a general term for well salt and mineral salt-well salt (generally called mineral salt).
The salt used in the past dynasties mainly includes sea salt, pond salt (lake salt), well salt and rock salt (mineral salt). Sichuan well salt has a long history. According to literature records and expert research, the world-famous Zhuo Tong Jing in Daying County was founded in the Northern Song Dynasty and the Qing Dynasty, more than 800 years earlier than in the West. China's history of drilling technology, China's history of science and technology and China's history of well salt technology are all called "the father of oil drilling in the world" and "the first mechanical drilling".
People in ancient times did not regard natural salt as salt, but called it halogen. The earliest salt collected by ancient people may be sea salt. According to ancient records, when Emperor Yan (referring to Shennong), Su Sha was the first to make salt from seawater, which was called "Su Sha as edible salt" in history. Su Sha is just a legend. In fact, making salt with seawater should be created by ancient ancestors living by the sea after long-term exploration and practice. Perhaps Su Sha popularized the method of making salt, and later generations put the invention right of collecting sea salt on his head.
Lake salt, also known as pool salt, is an inland salt lake. Due to the influence of dry climate, crystalline salt can be naturally generated. The ancient Hedong Salt Pond in history naturally produces salt by wind, sun and evaporation, which is called "Xie Yan", "Luyan" or "Hedong Salt" in history. Hedong salt pond appeared in historical records very early, and the history of salt mining in salt pond may not be later than sea salt.
Now Chaerhan Salt Lake and Chaka Salt Lake in Qinghai Province are rich in this kind of pool salt. Pool salt has the characteristics of natural crystallization. The book "Luo Du Fu" written by the king of Jin Dynasty says that "Hedong Salt Pond is clean and fresh, but natural without cooking", which means that the salt in the pond can be obtained naturally without cooking with fire. Hedong salt pond is located in the Yellow River basin, so it can be seen that ancient ancestors living in the Yellow River basin should have been exposed to this natural pond salt very early.
It is difficult to determine which comes first, the discovery and consumption of pool salt and sea salt, because sea salt can also crystallize naturally by evaporation from the seawater in stagnant shoals. Ancient ancestors living by the sea also discovered and ate this natural sea salt produced by natural crystallization very early.
Naturally occurring pool salt and sea salt, as well as exposed rock salt on the surface, salt springs leaked by natural overflow and soil salt available everywhere, as long as there are human activities in the areas where these natural salts are produced, ancestors will always find them sooner or later. Just because of the long time, it is difficult to judge the time sequence of pond salt and sea salt discovery.
Well salt may have appeared a little later, and it first appeared in Bashu area during the Warring States Period according to literature records. "Huayang Guozhi" said that Li Bing, who is familiar with astronomy, geography and water veins, invented the technology of digging salt wells. While controlling water, libing surveyed the distribution of underground brine and dug a salt well. A number of portrait bricks of salt wells have been unearthed in Chengdu and other places, vividly reappearing the ancient well salt production.
In ancient China, sea salt, lake salt and well salt were mostly made of halogen, or boiled with firewood, or weathered by the sun and evaporated by water.
Before the Song Dynasty, the manufacture of sea salt was all fried. Sea salt is scraping the soil, drenching the brine, and burning the brine to cook the salt. There is no obvious difference in sea salt frying methods and utensils after the replacement of Yuan, Ming and Qing Dynasties. Laoshan green salt was twenty-seven years later than Guangxu (190 1) in Qing dynasty, and the salt was fried in the sun by the method of ditch and beach, thus ending the history of salt frying.
Stir-frying salt consumes a lot of wood and is labor intensive. Since the Northern Song Dynasty, the drying method of sea salt has appeared. Due to technical reasons, the effect is not very good, so fried salt is still more than dried salt. By the end of the Qing Dynasty, most sea salt producing areas were changed to sun drying, and the technology was gradually improved. Those woks and salt frying equipment set up along the coastline for thousands of years have naturally become a thing of the past.
South China, such as Hainan Island, is an ideal place for drying salt with abundant sunshine. The simplest method is to use the beach sediments dried by the sun, pour in seawater, filter to make high-salinity brine, and then store the brine in a pool and evaporate in the sun to form salt.
The production of well salt is divided into two steps: extracting brine and making salt. In ancient times, the methods of extracting natural brine were mostly salvage, but in modern times, there are gas lift method, oil pumping method and self-injection method. In rock salt-type mining areas, most of them adopt drilling solution mining method, some adopt single-well convection method, and some adopt double-well hydraulic fracturing method. In ancient times, well salt was fried, similar to sea salt frying.
Lake salt is primary salt and regenerated salt, which is mainly produced by mining or beach drying. Some salt lakes have been evaporated for a long time, and sodium chloride is deposited at the bottom of the lake, such as the salt lake in Qaidam Basin. After tens of millions of years of changes, dried lakes have been formed, and salt crystals are exposed on the surface, which can be directly excavated without processing. The beach drying method has a long history in lake salt production, which is different from the early sea salt production process.
Brine is extracted from the sea and land, fried in the sun and fire, boiled in the sea and boiled in waves, and brine becomes salt. Surprisingly, frying salt is so laborious, but this method has been used all the time in history. In some well salt areas in southwest China, cutting down the surrounding trees because of frying salt not only caused environmental damage, but also caused the salt wells to stop production due to lack of fuel. Of course, it was a last resort. There is little light in the salt producing area of the southwest well, so the salt workers can't think of letting the sun dry salt. However, there is no shortage of light in the eastern sea salt producing areas, but the time for drying salt is still very late, and it seems that it is not entirely a technical problem. The salt drying technology of pool salt appeared very early and developed very mature.
Sichuan salt industry has a fine division of labor, complicated working procedures and large project cost and equipment investment from sinking wells, extracting brine, transporting brine to frying salt. It usually takes one or two to four or five years to open a well, at most ten or even decades; The investment in open caisson ranges from shallow 1200 yuan to deep 20,000 yuan, and some people even spend 30,000 to 42,000 yuan but can't see the works. Most business owners who run wells and stoves pool their capital and adopt a partnership system to make their capital strong. Take Furong production area as an example. Investors (called guests) and landlords in Zigong dig wells in the form of tenancy and partnership, which can be divided into "annual wells" (or "guest wells") and "descendants wells". Before Daoguang dynasty, most of them were "fixed-year wells", that is, after successful sinking, investors only enjoyed a certain number of years of shares and their income in proportion, and all wells and facilities were returned to the landlord free of charge; After the successful excavation of the "offspring well", investors and landlords will have ownership for a long time. With the improvement of sinking technology, the depth of well increases correspondingly, and the amount of capital advanced by investors continues to rise, which changes the original share ratio of investors and landlords in the share structure, and the "fixed-year well" gradually transitions to "future-generation well". In general, after the well is completed and put into production, the landlord holds one-sixth to one-fourth of the shares, which are called "main shares", "daily shares of the earth pulse" or "hukou of the earth pulse"; Most of the remaining shares belong to investors, which are called "working day share", "guest day share" or "boiling water"; If there is an undertaker (the sponsor or organizer of fund-raising sinking), it is necessary to draw a part of the daily share or pot mouth as a reward for the undertaker, which is called "dry day share", "first day share of the group" or "boiling water".
Mineral salt has been deposited underground for thousands of years, and the ancient industry was underdeveloped and the pollution was less, so the purity of mineral salt was good and the impurities were less. Sea salt comes from the sea, and human pollution has also affected the sea, and its purity is not as good as mineral salt. Salt is mined from strata and refined into salt, which is called rock salt, also called rock salt and mineral salt. There are seven places where rock salt is produced, such as Yuan Yong, and ancient submarine classics ... are also produced. Purple rock salt is produced in Wulan Dabusen Mountain, Tibet. There are not many records about rock salt in history books. The Biography of the Northern History and the Western Regions said: "Gaochang has white salt, which looks like a jade beam." That is, rock salt produced in Xinjiang.
After solar energy dries the sea water, crystalline sea salt is produced. After 600 million years of geological extrusion and underground high temperature, underground minerals and sea salt combined to form a "salt fossil"-mineral salt. Mineral salt can be said to have no pollution, and it is the cleanest and greenest of the three kinds of salt (mineral salt, sea salt and table salt). "
How is well salt mined and made into salt? Since salt mines are buried 280 to 500 meters underground, wells should be drilled first. After arriving at the location of the salt mine, water is injected into the pipeline to dissolve the salt mine into brine, and then the brine is pumped into the salt making device for evaporation, drying and a series of processes. Lu Jinhua said that simply speaking, the production process of well salt is the process of dissolution and recrystallization. "The whole process is relatively simple and there are few human intervention links, so,
Open the shaft and underground roadway to reach the coal seam, so that the underground and the ground form a complete transportation and ventilation system, and directly extract rock salt from the underground. There are three ways of mine development: vertical shaft, inclined shaft and adit.
If the rock salt obtained by dry mining is of high grade, it can be directly crushed and screened to obtain the finished product; If the grade is low, the ore will be dissolved in brine, purified and then evaporated and crystallized into salt.
Shaft development uses the shaft directly connected to the ground and the corresponding horizontal roadway to mine rock salt. It has strong adaptability to rock salt deposits with various geological conditions. It is especially suitable for deposits with large dip angle, deep burial depth, unstable surrounding rock and large output.
Inclined shaft uses inclined roadway and horizontal roadway directly connected with the ground to mine rock salt, which is suitable for deposits with small dip angle, shallow burial and stable surrounding rock.
In adit mining, the horizontal roadway, uphill and downhill roads directly connected with the ground are used for mining operations. It is suitable for rock salt deposits with deep and steep terrain cutting and some ore bodies buried below the horizontal erosion datum.
Salt lake production has a long history. The mode of production varies with resources: all salt lakes that have formed rock salt deposits and are rich in intercrystalline brine, such as most salt lakes in China and the Soviet Union, mainly mine rock salt directly; Salt lakes with no or little salt deposition, such as Great Salt Lake in Utah, Samba Salt Lake in India and Yuncheng Salt Lake in Shanxi Province of China, all need to build salt pans by the lake, introduce brine from the lake, and turn it into salt by sun. Dry salt lakes without intercrystalline brine, such as Lake McLaught in Australia, need water injection to dissolve saturated brine to dry salt or directly mine raw salt. Its principle and operation are basically the same as that of sea salt, but the concentration of brine in salt lake is higher, and the area of evaporation pool required is correspondingly smaller than that of sea salt.